Combined photovoltaic solar thermal systems (PVT) - literature review
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 Photovoltaic Thermal Hybrid
There is a renewed interest in photovoltaic solar thermal (PVT) hybrid systems, which harvest solar energy for heat and electricity. Typically, a main focus of a PVT system is to cool the photovoltaic (PV) cells to improve the electrical performance. This works well; however, this causes the thermal component to under-perform compared to a solar thermal collector. Recently there has been very promising work, which utilized the low temperature coefficients of amorphous silicon (a-Si:H) PV which allow the PV cells to be operated at high temperatures, creating a more symbiotic PVT system. See: M.J.M. Pathak, J.M. Pearce and, S.J. Harrison, “Effects on Amorphous Silicon Photovoltaic Performance from High-temperature Annealing Pulses in Photovoltaic Thermal Hybrid Devices” Solar Energy Materials and Solar Cells, 100, pp. 199-203 (2012). arXiv. The fundamental challenge of a-Si:H PV is light-induced degradation known as the Staebler–Wronski effect (SWE). Fortunately, SWE is reversible and the a-Si:H PV efficiency can be returned to its initial state if the cell is annealed. Thus an opportunity exists to deposit a-Si:H directly on the solar thermal absorber plate where the cells could reach the high temperatures required for annealing.
 Related Appropedia articles
 IEA TASK 35 PV/T
The IEA (International Energy Association) is almost finished their study on PV/T.
They had five subtasks:
- Subtask A: Market and Commercialisation of PV/T
- Subtask B: Energy Analysis and Modelling
- Subtask C: Product and System Development, Tests and Evaluation
- Subtask D: Demonstration Projects
- Subtask E: Dissemination
They looked at 4 different types of PV/T set-ups in multiple countries.
- PV/T liquid collector
- PV/T air collector
- PV/T concentrator
- Ventilated PV with heat recovery
Canada is part of this TASK 35 and is studying Transpired Air PV/T collector at the National Solar Test Facility.
It started in 2005 and ended in 2008. Currently, they are reviewing the final draft. I have emailed the coordinators last week. See the following for contact information.
Everybody with the interest in PV/Thermal Solar Systems are invited to contact
Project Manager Jan Hansen, Esbensen Consulting Engineers A/S, firstname.lastname@example.org, +45 3326 7308
Operating Agent Henrik Sørensen, Esbensen Consulting Engineers A/S, email@example.com, +45 3326 7304,
The website is http://www.pv-t.org/
The canadian group is: Leader for Subtask B is Michael Collins, University of Waterloo, Canada, funded by Natural Resources Canada.
Here is the annual report of SHC (solar heating and cooling program) SHC Annual Report 2008
Here is another report from IEA SHC overview of current tasks IEA SHC Current Tasks Report
5mjmp 19:12, 1 June 2009 (UTC)
 Hybrid PV/Thermal Collectors 2000
This paper talks about the current PV/T systems, the future systems and what needs to be done. Isreal (Cromagen) has PV/T's since 1991 and the use water as the cooling medium. Germany has two companies as well; SolarWerk and SolarWatt. "Both systems use plat plate solar heat collectors with PV cells integrated on the absorber." Canada (Conserval Engineering) uses air as its medium.
"PV/T-technology is still very new and there is a strong need for R&D and demonstration efforts in the following areas:
- Maximization of heat transfer from the solar cell to the heat transfer medium and
maximization of the electrical yield from the solar cells for different temperaturelevels.
- Durability testing of collectors and solar cells, especially for laminated solutions and
solutions where the solar cells operate at a high temperature.
- A standardized method of assessing the energy performance of PV/T systems needs
to be defined and calculated, monitored and evaluated both for the commercial products and for the best solutions demonstrated as one-off systems in buildings."
H. SØRENSEN and D. MUNRO. Hybrid PV/Thermal Collectors. The 2nd World Solar Electric Buildings Conference: Sydney 8th-10th March 2000
 Commerically Available PVT Products 2006
- PVT air collectors
- Aidt Miljo / Grammer Solar / Conserval Engineering
- Ventilated PV with heat recovery
- Secco Sistemi
- PVT liquid collectors
- PVTWINS / Millennium Electric
- PVT concentrators
- Arontis / HelioDynamics / Menova
5mjmp 14:41, 3 June 2009 (UTC)
http://pv-t.org/ under documents
H.A. Zondag. Commerically Available PVT Products. Energy Research Center of the Netherlands. July 2006.
 PVT - Untapped Energy 2007
The article talks about the potential of PVT's. This article specifically deals with Canada's involvement with Task 35 with PVT's using Air has its heat transfer medium. The testing was done at Canada's National Solar Test Facility (NSTF) indoors under the STC set by the IEA Task 35 group. Several companies supplied some of their PV panels which were then fitted to a thermal system. Test were done and efficiencies were calculated. The total efficiencies (thermal and electric) ranged from 21-56 %. It was found that thermal was 150-400% more efficient than electric for crystalline and up to 800% more efficient for amorphous. However, tests did show that cooling PV panels is more efficient and that it does cool the PV panels making them work better. Up to 0.5%/C better.
5mjmp 14:12, 4 June 2009 (UTC)
J. Hollick and B. Barnes. PV Thermal Systems - Capturing the Untapped Energy. Conserval Engineering Inc. http://solarwall.com/media/images-articles/ASESPaper-PVThermalSystems-theUntappedEnergy175A3.pdf
 Review Journal Articles
 Evatuation of Flat-Plate Photovoltaic/Thermal Hybrid Systems 1980
The is a study on the economics of whether PV/T's are worth doing compared to PV, Thermal, PV and T (side by side). The study compared glazed and unglazed. The tests were done in Tampa, New York and LA. This study was done in 1980's and concluded that PV/T was not economcially feasible, however, now with better PV, PV/T has a second chance.
John W. Andrews
DEPARTMENT OF ENERGY AND ENVIRONMENT SO LAR TECH N 0 LOGY G RO U P BROOKHAVEN NATIONAL LABORATORY ASSOCIATED UNIVERSITIES, INC. UNDER CONTRACT NO. DE-AC02-76CH00016 WITH THE UNITED STATES DEPARTMENT OF ENERGY
BNL 51435 uc-59c (Heating and Cooling-Research and Development - TIC-4500
5mjmp 19:00, 1 June 2009 (UTC)
 Photovoltaic thermal (PV/T) collectors: A review 2007
Abstract: This paper presents a review of the available literature on PV/T collectors. The review is presented in a thematic way, in order to enable an easier comparison of the findings obtained by various researchers, especially on parameters affecting PV/T performance (electrical and thermal). The review covers the description of flat plate and concentrating, water and air PV/T collector types, analytical and numerical models, simulation and experimental work and qualitative evaluation of thermal/electrical output. The parameters affecting PV/T performance, such as covered versus uncovered PV/T collectors, optimum mass flow rate, absorber plate parameters (i.e. tube spacing, tube diameter, fin thickness), absorber to fluid thermal conductance and configuration design types are extensively discussed. Based on an exergy analysis, it was reported that the coverless PV/T collector produces the largest available total (electrical + thermal) exergy. From the literature review, it is clear that PV/T collectors are very promising devices and further work should be carried out aiming at improving their efficiency and reducing their cost, making them more competitive and thus aid towards global expansion and utilization of this environmentally friendly renewable energy device.
Photovoltaic thermal (PV/T) collectors: A review. P.G. Charalambous, G.G. Maidment, S.A. Kalogriou and K. Yiakoumetti. Applied Thermal Engineering 27 (2007) 275–286
5mjmp 16:38, 16 September 2009 (UTC)
09_09_16_Photovoltaic thermal (PV-T) collectors A review.pdf
 Flat-plate PV-Thermal collectors and systems: A review 2008
Abstract: Over the last 30 years, a large amount of research on PV-Thermal (PVT) collectors has been carried out. An overview of this research is presented, both in terms of an historic overview of research projects and in the form of a thematic overview, addressing the different research issues for PVT.
Flat-plate PV-Thermal collectors and systems: A review. H.A. Zondag. Renewable and Sustainable Energy Reviews 12 (2008) 891–959
5mjmp 18:08, 16 September 2009 (UTC)
09_09_16_Flat-plate PV-Thermal collectors and systems A review.pdf
 A review on photovoltaic/thermal hybrid solar technology 2009
Abstract: A significant amount of research and development work on the photovoltaic/thermal (PVT) technology has been done since the 1970s. Many innovative systems and products have been put forward and their quality evaluated by academics and professionals. A range of theoretical models has been introduced and their appropriateness validated by experimental data. Important design parameters are identified. Collaborations have been underway amongst institutions or countries, helping to sort out the suitable products and systems with the best marketing potential. This article gives a review of the trend of development of the technology, in particular the advancements in recent years and the future work required.
Chow TT. A review on photovoltaic/thermal hybrid solar technology. Appl Energy (2009), doi:10.1016/ j.apenergy.2009.06.037
5mjmp 20:29, 16 September 2009 (UTC)
09_09_08_a review on PVT (2009).pdf
 PV/T Journal Article Reviews Anything before the 1990's
 A Two Dimensional Thermal Analysis of a New High-Performance Tublar Solar Collector 1978
Does not involve PVT but just heat transfer of a solar collected. Useful equations but not really related.09_05_28_a two dimensional thermal analysis of a new high-performance tublar solar collector.pdf 5mjmp 19:54, 1 June 2009 (UTC)
A Two Dimensional Thermal Analysis of a New High-Performance Tublar Solar Collector. F.L. Lansing and C. S. Yung. DSN Engineering Section Report 42-49. 1978. http://tmo.jpl.nasa.gov/progress_report2/42-49/49P.PDF
 Testing Procedures for Solar Air Heaters, a Review 1988
This article does not relate to PVTs. However, it does talk about various methods to standardize testing for the thermal collector part. It suggest ways of making the test repeatable and to be able to reproduce outdoor conditions indoors. It also has heat transfer equations to create an analytical model of the solar air heater. As well as different designs to collect the heat better such as the normal flat plate, triangular duct and fins.
5mjmp 14:56, 26 July 2009 (UTC)
File:09 05 28 testing procedures for solar air heaters, a review.pdf 5mjmp 20:23, 1 June 2009 (UTC)
Energy Convers. Mgmt Vol. 32, No. 1, pp. 11-33, 1991. RAM CHANDRA and M. S. SODHA Testing Procedures for Solar Air Heaters, a Review. http://sfx.scholarsportal.info/queens?sid=google&auinit=R&aulast=Chandra&atitle=Testing+procedures+for+solar+air+heaters:+A+review.&title=Energy+conversion+and+management&volume=32&issue=1&date=1991&spage=11&issn=0196-8904
 PV/T Journal Article Reviews 1990's
 Experimental Study on a Hybrid Photovoltaic-Thermal Solar Water Heater and its Performance Predictions 1994
This article talks about the potential of PV/T's. The system that was tested as a thermosyphon ([]) water heater. Theorectical calculations were completed and they matched within error of the experimental data. They tested with and without a thermosyphon. It was found that the electrical and thermal efficiencies were 3.35% and 33.5%. A valid assumption is that the average cell temperature is the same as the average plate temperature.
Energy Convers. Mgmt Vol. 35, No. 7, pp 621-633, 1994. H. Garg, R. Agarwal and J. Joshi. http://sfx.scholarsportal.info/queens?sid=google&auinit=HP&aulast=Garg&atitle=Experimental+study+on+a+hybrid+photovoltaic-thermal+solar+water+heater+and+its+performance+predictions&title=Energy+conversion+and+management&volume=35&issue=7&date=1994&spage=621&issn=0196-8904
5mjmp 17:55, 8 June 2009 (UTC)
 The Effect of Collector Aspect Ratio on the Collector Efficiency of Flate-Plate Solar Air Heaters 1994
This article concluded that the collector efficiency increased with increasing the aspect ratio (L/B). The area of the collector remaind constant but the ratios changed. The ratios were 1/6, 2/3, 3/2 and 6/1. The best one was 6/1. In this paper they completed experimental and theoretical calculations. It was found that the experimental and theorectical values matched within reason expect for the 6/1 where the experimental efficiencies were found to be lower. This is believed to be the result of making the assumption that the loss coefficient Ub from the bottom and surface of the solar collector with respect to teh ambient is negligible. In this paper the reynolds, nussel number and other equations can be found for the theoretical calculations. The experimental procedure can also be found.
5mjmp 14:49, 28 July 2009 (UTC)
Energy Vol 20, No 10, pp 1041-1047, 1995. The Effect of Collector Aspect Ratio on the Collector Efficiency of Flate-Plate Solar Air Heaters. HO-MING YEH and TONG-TSHIEN LIN. http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/4027
 Recent Developments of Silicon Thin Film Solar Cells on Glass Substrates 1999
The thin film cells are placed on a transparent conductive oxide (TCO)/ glass substrate. The efficiency found was 8%. Although amorphous silicon cells efficiency is 5-7%, there is potential for a-Si to be cheaper than the thin film and with further research become a better cell than thin film. This paper explores some of the costs, TCO material options and how TCO substrates work with a nice diagram. This paper also only looks at p-i-n junctions rather than n-i-p junctions. a-Si have lower processing temperatures and are the thinnest cells.
"Features of the a-Si technology The interest in the a-Si technology is based on several attractive features, namely:
- Si-based technology, implying an abundant material
supply and non-toxic constituents,
- low process temperatures, facilitating low-cost substrate
materials, like oat-glass, moderate energy consumption, and short energy payback times,
- large-area deposition process by plasma-enhanced
chemical vapor deposition (PECVD),
- two-terminal stacked cell structures to allow for higher
voltage/lower current devices, and for the incorporation of different band gaps for extended spectral response (see Section 3.1),
- monolithic series connection of cells to modules, and
hence variability of output voltages (see Section 3.2),
- rear side encapsulation (see Section 3.2),
- low temperature coefficients of the photovoltaic data,
- substantial cost reduction potential, as indicated by a
recent study, funded by the European Commission under the APAS program  (see Section 5). For completeness some of the drawbacks of the a-Si technology are not to be ignored, in particular:
- the photostabilization effect (Staebler±Wronski effect
), and hence
- moderate stabilized ef®ciencies that for modules in
production currently are 5±7%, and for facilities presently coming on line are announced to be around 8%." -paper
5mjmp 16:03, 25 July 2009 (UTC)
09_05_28_recent developments of silicon thin film solar cells on glass substrates.pdf 5mjmp 20:23, 1 June 2009 (UTC)
Thin Solid Films 351 (1999) 241±246. C. Beneking, B. Rech, S. Wieder, O. Kluth, H. Wagner, W. Frammelsberger, R. Geyer, P. Lechner, H. RuÈbel and H. Schade. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TW0-3X9RXD3-1S&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=dbaadd05fff378ba65dbfe09f4cdafa2
 PV/T Journal Article Reviews 2000's
 Derivation of Efficiency and Loss Factors for Solar Air Heaters 1981
This article goes through the derivation of efficiency and loss factor using the Hottel-Whillier-Bliss equations. The derivations are for a flat and lee-congrated surface absorber. Flow under the absorber was also calculated. Furthermore, a triangular duct design was calculated too. A caution in the discussion warned the reader that this approximation wields larger errors for air type collectors rather than liquid since liquid usually exhibits smaller changes in temperature along the flow path.
solar Energy Vol. 26, pp. 27-32. DERIVATION OF EFFICIENCY AND LOSS FACTORS FOR SOLAR AIR HEATERS. BLAINE F. PARKER. 1981. http://adsabs.harvard.edu/abs/1979sun.....1..244P
5mjmp 18:33, 5 June 2009 (UTC)
 Comparative study of the performances of four photovoltaic-thermal solar air collectors 2000
This paper used hourly solar intensity and ambient temperature data and using it in simulations. Four common PVT models were used; air flow over the absorber (I), under the absorber (II), on both sides of the absorbers in a single pass (III) and double pass (IV). The efficiencies took into account everything such as the energy required to run the fan. It was found that the efficiencies of models II-IV were very similar and better than model I. However, the best model was III since it used the least amount of energy to run the fan to produce the same results as model II and IV. The overall efficiency of model III was 57.3%. Selective coatings were also tested but it was found that it did increase the overall efficiency since the thermal efficiency increased but the electrical efficiency did decrease which is the more useful product of the two.
09_06_16_Comparative study of the performances of four photovoltaic-thermal solar air collectors
Energy Conversion & Management 41 (2000) 861±881. Comparative study of the performances of four photovoltaic/thermal solar air collectors. Adel A. Hegazy. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2P-3Y6GXGH-6&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=ad93859b071bf8be1e6d5bf0ed5be620
5mjmp 20:46, 18 June 2009 (UTC)
 The DOE Office of Solar Energy Technologies' Vision for Advancing Solar Technologies in the New Millenium 2000
This journal article is not relavent at all. It talks about the US initative to adding solar (electricity, light and heat) to reducing the current loads. I feel very few of this goals and objectives have been reached. This paper just shows that solar is still in the beginning stages of becoming a energy source.
Solar Energy Vol. 69, No. 5, pp. 363–368, 2000. THE DOE OFFICE OF SOLAR ENERGY TECHNOLOGIES’ VISION FOR ADVANCING SOLAR TECHNOLOGIES IN THE NEW MILLENNIUM. JAMES RANNELS. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V50-41MHFG3-2&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=530364d05cabb7fba008b13049f0d083
 Development and application for PV Thermal 2002
The paper looks at many different combinations of PVTs and the efficiency. The PVTs were all built and tested.
Serveral concepts were analyzed:
- none, one, two top covers
- sheet-and-tube constructions vs channel construction
- adding a secondary absorber beneath the PV
Material choices could have been extended with other possiblities such as:
- type of PV; monocrystalline silicon, multicrystalline silicon, a-Si, CIS or other
- what cover material such as teflon instead of glass
- what collector medium (water, air,etc)
- what absorber medium (coper, plastic, etc)
With Sheet-and-Tube, one and no cover were tested adn it was foudn that the presences of the cover top increased the thermal efficiency but decreased the electrical efficiency.
Two absorber PVT collector where the PV-laminate was the primary absorber and a black copper was the secondary absorber which was located beneath the PV. To make this concept work, the primary absorber needs to be as transparent as possible.
Heat pumps were also used. It was found that the used a heat pump uses a fair bit of electricity but the simulations show that the PVT collector can produce more electricity than required by the heat pump. However, this does lower the electrical efficiency but it raises the thermal efficiency.
The best PV efficiency was an uncoverd collector with a heat pump.
09_06_16_Development and application for PV Thermal
Development and application for PV Thermal. H. Zondag, M. Jong and W. Helden. Energy research Centre of the Netherlands (ECN). http://www.ecn.nl/docs/library/report/2001/rx01025.pdf 5mjmp 14:22, 18 June 2009 (UTC)
 The Yield of different combined PV-Thermal Collector Designs 2003
The paper states that PVT are better than the side-by-side design previously used. The paper states that there are many advantages to using a PVT system; use less space than side-by-side, provide architectural uniformity and because it is one system there is a possible reduction in installation costs.
In this paper the thermal and electrical efficiency and the annual yield of 4 types of PVTs.
- Can have multiple top covers
- Greater than 2 creates very large reflection which reduces the electrical efficiency
- Can have multiple top covers
- Constraints - choice of collector fluid
- collector fluid affect the absorbtion of the PV - water decreased the electrical performance by 4%
- Need to make sure glass panel can withstand the water pressure
- Transparent PV laminates cost more
- Backside of PV laminate need to be water tight
- Constraints - choice of collector fluid
- Free Flow
- This design eliminates one glass layer
- Increased heat loss due to evaporation
- "Water seems like a natural choice, but, since its evaporation pressure is not very low, evaporation will be shown to create problems at higher temperatures" - Paper
- Efficiency could be improved by adding a transparent insulating layer between the primary and secondary channel to reduce teh heat loss
"High transparent plastics would probably give a small increase in optical efficiency, but their materials properties, such as sensitivity to UV or high temperatures as well as limited watertightness would problably limit thier application in PV-Thermal" -Paper
In this paper all the different types of PVTs were model and all the equations and steps can be found in the paper.
Since the single cover sheet-and-tube can be build from well known components and that were commerically avaible, it was chosen to do experimental tests on to compare to the experimental results. The results matched. It was found that the channel PVT had the best thermal efficiency of 65%.
09_06_16_The Yield of different combined PV-Thermal Collector Designs
Solar Energy 74 (2003) 253–269. T he yield of different combined PV-thermal collector designs. H.A. Zondag, D.W. de Vries, W.G.J. van Helden, R.J.C. van Zolingen and A.A. van Steenhoven. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V50-48GVJHW-6&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=3f51825c92679230619ac95fdb5123fe
5mjmp 20:48, 19 June 2009 (UTC)
 Dynamic Performance of Hybrid Photovoltaic-Thermal Collector Wall in Hong Kong 2003
In this paper, two different hybrid modules were simulated using hourly TRY (Test Reference Yearly) weather data from 1989. They simulated an EPV (thin cell) and a BPV (single silicon cell). The equations used are found in the paper and the flow chart of the FORTAN code as well. Theorectically PV/T total efficiency is supposed to range from 60-80%. In the simlation the PV/T was on the west wall of a building (facade integrations) and water was used as the coolant. A good quality PV should have an efficiency of 10% after all the loss factors are taken into account. It was found that the electrical efficiencies of EPV and BPV were 4.3% and 10.3% and the thermal efficiencies were 47.6% and 43.2%. However, the EPV system had 217 days compared to 195 days were the water reached 45 C. Also, compared to a normal concrete wall, the EPV and BPV systems' reduction of space heat gain reached 53% and 59.2%.
Building and Environment 38 (2003) 1327 – 1334. Dynamic performance of hybrid photovoltaic/thermal collector wall in Hong Kong. Jie Jia, Tin-Tai Chowb and Wei Hea. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V23-492029K-1&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=d35388b2dfe4bc352501612093350bee
5mjmp 14:51, 8 June 2009 (UTC)
 Field Experiments and Analysis on a Hybrid Solar Collector 2003
In this testing of the hybrid system, brine was used as the coolant. Single-junction crystalline silicon photovoltaic cells were used. The panels were tilted 30 degrees to optimize teh annual global irradiance. This was done at the Hokkaido Univeristy, Japan. The brine solution was propylene glycol (30 wt %) and the flow rate was 1 l/min. Throughout the experiment the brine temperature ranged from 10-40 C. The efficiencies found experimentally for thermal, electrical and hybrid energy production were 46.2%, 10.7% and 42.6%. Exergy analysis was done as well and the efficiencies were 4.4%, 11.2% and 13.3% for thermal, electrical and hybrid energy conversion. The hybrid system is predicted to reduce the panel area installation area by 27%.
Applied Thermal Engineering 23 (2003) 2089–2105. Field experiments and analyses on a hybrid solar collector. Hisashi Saitoh, Yasuhiro Hamada, Hideki Kubota, Makoto Nakamura, Kiyoshi Ochifuji, Shintaro Yokoyama and Katsunori Nagano. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1Y-49202TM-2&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=09b52035f6d395197dfc5db91cfc675c
5mjmp 15:24, 9 June 2009 (UTC)
 PVT System, PV Panels Supplying Renewable Electricity and Heat 2004
"The first systematic research into the possibilities of combining photovoltaic and solar thermal techniques was performed in the early 1980s by a group at MIT.4 In this comprehensive study, several PVT designs were made and tested, both air-type and water-type. The work was discontinued because of a change in government funding. The PVT research regained attention in the mid 1990s with, amongst others, the PhD work of De Vries at the Eindhoven University of Technology.5 He designed several PVT module concepts, of which one was realised and tested. A numerical model was developed calculating both electrical and thermal performance. The model predictions were found to agree with the experimental results.1 The work was continued with a development Figure 3. Prototype of a covered PVT collector programme at the Energy research Centre of the Netherlands ECN.6 In collaboration with industry and the EUT the thermal performance was further optimised and a production technology was developed.7 Bakker investigated another PVT concept, a two-absorber module, at ECN.8 In recent years, several other research groups worked on the topic of PVT. At the University of Patras in Greece, a broad range of PVT geometries for PVT panels were designed, built and tested.9 PhD research on a PVT design with a concentrating reflector is being performed in Sweden.10 In Norway, a concept is developed in which a plastic thermal absorber is used.11 Work on the application of thin-film PV in PVT concepts was carried out in Switzerland.12,13 From a more complete overview of the literature on PVT collectors14 it can be concluded that the research and development activities on PVT are widespread over the world and conducted in relatively small programs. Owing to this dispersion there was little attention for PVT from the PV R&D community. As a result the PVT development had to restrict itself to the application of market-ready PV technologies." - Paper
This paper does a very good job doing an overview of PVTs with their advantages, types, areas of improvement and what has been done in the past and currently. The different types discussed were air, water, double and single pass, combinations and multiple layering, covered or uncovered. The reason PVTs are a good idea is that they increase the overall efficiency (electrical and thermal), smaller energy and cost payback time and aesthetics.
- Emission of heat - losses from convection and radiation. Radiation losses can be reduced by adding a low emissivitive material (double glazed) but the problem is the traparency is reduced to 60-80% which is too low for the use in PVTs. Therefore new materials will need to be studied for the selective coatings
- Solar absorbtion - Ways to improve the absorbtion are to increase the active cell area and metallisation the cells and system (dope with metal). However, metallisation has a high reflection coefficent but there are ways two increase the absorption. Add suitable coatings and reduce the area that needs has the metallisation are ways to improve the absorption.
- Internal heat transfer - the system needs to have a good thermal conductivity to remove the heat from the system.
- PVT module reliablity - The PV panels need to be able to take high temperatures (~125 C) and the need to be able to take the stress of being hot and then cold quickly (once the colding medium is being used).
Another suggestion is making the PV cells transparent then a lower lower cell temperature can be achieved and maintained rather than geometries with heat and electricity generation in the single plane. An example of geometry is spacing the cells out to allow light to pass through and go directly to the absorber.
Prog. Photovolt: Res. Appl. 2004; 12:415–426 (DOI: 10.1002/pip.559). PV Thermal Systems: PV Panels Supplying Renewable Electricity and Heat. Wim G. J. van Helden1, Ronald J. Ch. van Zolingen and Herbert A. Zondag. http://www3.interscience.wiley.com/journal/109605024/abstract
5mjmp 15:54, 12 June 2009 (UTC)
 Development and application of solar-based thermoelectric technologies 2005
The paper is about a water-cooled PVT and it states that heat production, electicial production, material costs, production costs and installation costs. It also states that for all PVTs "Finding an elegant solution for reducing the size of the collector device, achieving better overall system-efficiency and sharing effectively the balance-of-system costs."-Paper
Extrude Aluminum alloy provides a highly effective heat transfer adn durability. TPT (Tedlar-polyester-tedlar) is a good electrical insulator and EVA (ethylene-vinyl acetate) is an adhesive material. "M/Ac is the mass of water in the thermosyphon system per unit collector surface area."-Paper The smaller the M/Ac the higher the final water temperature.
This PVT used Polycrystalline silicon solar cells and they only covered 50% of the thermal absorber surface. 4.6% of the solar energy was converted into electrical energy and the M/Ac was only 65.2 kg/m2 but the energy saving efficiency was 52% which is higher conventional solar hot water collectors.
09_06_16_Development and application of solar-based thermoelectric technologies
Renewable and Sustainable Energy Reviews 11 (2007) 923–936. Development and applications of solar-based thermoelectric technologies. Hongxia Xi�, Lingai Luo, Gilles Fraisse. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VMY-4GV9B68-1&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=233a7e690a7ce3441fc824a7d9519296
5mjmp 14:53, 19 June 2009 (UTC)
 Hybrid Solar Collector 2005
This article explores the practicality of hybrid solar collectors. Theoretical calculations were done with the following assumptions The collector is a flat solar one.
- The losses from heat conductivity are neglected since the
layers are very thin and the material they are made of has high thermal conductivity.
- The thermal losses in the photovoltaic cells are disregarded.
- The atmosphere radiates to the collector as an infinite absolutely
black surface with a temperature of the sky, Ts.
The calculations can be found in this paper. The results showed that hybrid collectors use half as much space as PV.
Journal of Materials Processing Technology 161 (2005) 229–233. Hybrid solar collector. V. Lazarov, Chr. Schaeffer, M. Shishkov and M. Ivanova. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TGJ-4DH2GK7-M&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=57a79e6e5285c69739b84b6c77ff0a94
5mjmp 18:25, 9 June 2009 (UTC)
 Potential of Applying Hybrid Solar Technology in Hong Kong 2005
This paper is about PVT with water as its heat transfer medium. c-Si cells have loss 0.4% / degree drop in efficiency compared to a-Si cells which has an efficiency drop of 0.1% / degree. Therefore, amorphous silicon cells are used in this experiment since they react to temperature rises. Water as a heat medium is suggested in warmer climates due to the better heat exchange. PVT panels were placed on the west and south walls since it was determined from simulations that they has the highest yearly intensities (west was the best). The proposed hybrid system design is described in the article. The efficiencies found were 33.6 % for thermal and 4.6% for electrical and for an amorphous silicon cell.
Potential of Applying Hybrid Solar Technology in Hong Kong. Potential of Applying Hybrid Solar Technology in Hong Kong. Potential of Applying Hybrid Solar Technology in Hong Kong. http://www.irbdirekt.de/daten/iconda/CIB9972.pdf
5mjmp 19:55, 11 June 2009 (UTC)
 Performance Evaluation of Photovoltaic Thermal Solar Air Collector for Composite Climate of India 2005
This paper studies the performance of PV panel with an air duct. It looks at natural convection, one fan and two fans. They also model using energy balance equations and the experimental results are similar to the predicted results. The results show that a flow rate of about 2m/s, a lenght of ~3 m and a duct depth of 0.03-0.06m produced the optimal efficiency.
Solar Energy Materials & Solar Cells 90 (2006) 175–189. Performance evaluation of photovoltaic thermal solar air collector for composite climate of India. Arvind Tiwari�, M.S. Sodha, Avinash Chandra and J.C. Joshi. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V51-4G1MD85-1&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=67943ffcccf337bf352831d4b64f4406
5mjmp 14:55, 5 June 2009 (UTC)
 Study of a New Concept of Photovoltaic-Thermal Hybrid Collector 2005
This article is about a 2D thermal model of a PVT/air and comparing to experiemntal results to study the thermal performance. The equations can be found in the paper. The paper looks at the difference between natural and forced airflow. The theory matched the experimental results and that force airflow as better.
"Guiavarch (2003) proposed a modeling of a PV hybrid air collector, which can be integrated in roofs. Hollick (1999) reported the experimental study of a solar collector composed of metal perforated and corrugated sheet steel on which a solar panel is stuck. Then, Belusko (2004) proposed the analysis of a solar air collector with a metal corrugated plate by comparing it to an unglazed solar collector." -Paper
International Conference “Passive and Low Energy Cooling for the Built Environment”, May 2005, Santorini, Greece. Study of a new concept of photovoltaic-thermal hybrid collector. G. Fraisse, T. Lefebvre, Y.B. Assoa, C. Menezo and R. Yezou. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V50-4NPHJKC-1&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=fa8dd4b3c34444226a61e25695c261e1
5mjmp 20:17, 12 June 2009 (UTC)
 Hybrid photovoltaic and thermal solar-collector designed for natural circulation of water 2006
This article is about a pc-silicon PV module on a flat-box type aluminum alloy thermal absorber using water as the collant adn it was built and tested. It was found to have a total efficiency of 40% and that it could achieve the desired water tank temperature in one day of exposure. The electrical efficiency was on average 9.87% which was lower than expected of 14.5%. It was determined that the use of water as a collant is most suitable for warm/hot climates.
In this article the MPPT (maximum power point tracker) is more efficient than nothing.
Metal strips on PV panel reflect light and need to be improved. This is why don't have intense grid on PV...
5mjmp 15:21, 7 September 2009 (UTC)
09_06_16_Hybrid photovoltaic and thermal solar-collector designed for natural circulation of water http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1T-4GCWYPT-7&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=83b87287f0bb87d60889815d182d5698 5mjmp 18:59, 16 June 2009 (UTC)
 Hybrid PV/T solar systems for domestic hot water and electricity production 2006
Energy Conversion and Management 47 (2006) 3368–3382. Hybrid PV/T solar systems for domestic hot water and electricity production. S.A. Kalogirou and Y. Tripanagnostopoulos. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2P-4JJ2BCK-1&_user=1025668&_coverDate=11%2F30%2F2006&_alid=1014162511&_rdoc=5&_fmt=high&_orig=search&_cdi=5708&_sort=r&_st=5&_docanchor=&_ct=20&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=34c295e2fc144299f553050ada46da1d
5mjmp 17:48, 16 September 2009 (UTC) 09_09_16_Hybrid PVT solar systems for domestic hot water and electricity production.pdf
 Double-Pass Photovoltaic-Thermal Solar Air Collector with Compound Parabolic Concentrator and Fins 2006
In this article, the combined efficiency achieved was ~70% when the mass flow rate was greater than 0.1 kg/s. In the experiments the light intenisty was varied from 400-700 W/m2 from 23 halogen lights rated at 500 W. "Temperature rise is proportional to the radiation intensity at a specific mass flow rate." It was found that the higher the flow rate the better the efficiency was, however, the system shoudl function with a low pressure drop. Therefore, this is an opmitmization problem between energy production and maintaining a low pressure drop.
Double-Pass Photovoltaic-Thermal Solar Air Collector with Compound Parabolic Concentrator and Fins. M. Y. Othman, B. Yatim, K. Sopian, and M. N. A. Bakar. JOURNAL OF ENERGY ENGINEERING © ASCE / DECEMBER 2006. http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JLEED9000132000003000116000001&idtype=cvips&gifs=yes
5mjmp 19:33, 5 June 2009 (UTC)
 Performance, Cost and Life-Cycle Assessment Study of Hybrid PVT-Air Solar Systems 2006
The paper is about the research into improving PVT/AIR systems based on low-cost modifications. Areas of research include; improved air heat extraction by circulating air, reducing the PV module temperature and insulating the back surfaces and edges to reduct heat losses. Several different systems (with or without the following) were analyzed; diffuse reflectors, tilt, glazed thin film metalic sheet, just PV and combinations of the above. The test was done for 6 month and 12 months. The PVT-thin film metal sheet with a diffuse reflector produced the best results and was not the most expensive system eirther coming in at 29100 Euros. The energy payback, cost payback and CO2 payback were calculated. The lowest environmnental impact was the PVT with glaze and the best economic choice is the PVT/ thin film metal sheet. Note, both have reflectors added.
Prog. Photovolt: Res. Appl. 2006; 14:65–76. Performance, Cost and Life-cycle Assessment Study of Hybrid PVT/AIR Solar Systems. Y. Tripanagnostopoulos1,y, M. Souliotis, R. Battisti and A. Corrado. http://www3.interscience.wiley.com/journal/111081755/abstract?CRETRY=1&SRETRY=0
5mjmp 18:12, 11 June 2009 (UTC)
 Double-Pass Photovoltaic-Thermal Solar Collector 2006
In this experiement monocrystalline silicon cells were pasted on to the absorber plate with fins. It was found that the fill factor decrease as radiation intenisty increased with constant mass flow rate. The fill factor decreased from .48 to .27 when the light intensity increased from 400 to 700 W/m2. This experiment used halogen lights to create the light intensities. The theorectical calculations followed the same tread as the experimental results, however, the experiemental results produced slightly higher efficiencies for thermal but lower efficiencies for electrical.
JOURNAL OF ENERGY ENGINEERING © ASCE / DECEMBER 2006. Double-Pass Photovoltaic-Thermal Solar Collector. M. Y. Othman1, B. Yatim, K. Sopian, and M. N. A. Bakar. http://cedb.asce.org/cgi/WWWdisplay.cgi?0613063
5mjmp 20:23, 5 June 2009 (UTC)
 Energy performance of water hybrid PVT collectors applied to combisystems of Direct Solar type 2007
This article is about comparing several PVT system set ups and comparing it to the traditional PV + T system. It was concluded that due to the system heating up, the the PV panels produced less electricity when in a PVT system. The PV modules would get over 100 C (as much as 135 C) and at this temperature, one can not use Ethylene Vinyl Acetate (EVA) due to high degradation. The solution was to use Amorphous silicon or use an uncovered PVT system. Further research is required.
5mjmp 13:58, 8 September 2009 (UTC)
09_06_16_Energy performance of water hybrid PVT collectors applied to combisystems of Direct Solar type
Solar Energy 81 (2007) 1426–1438. Energy performance of water hybrid PV/T collectors applied to combisystems of Direct Solar Floor type. G. Fraisse, C. Me´ne´zo and K. Johannes. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V50-4N4YTKF-1&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=3b4311f17640d872eacc96f6d0c7e591 5mjmp 18:59, 16 June 2009 (UTC)
 Transient Mathematical Model of Both Side Single Pass Photovoltaic Thermal Air Collector 2007
"A number of theoretical as well as experimental studies have been made on (PV/T) systems with air and liquid as working fluid. Kern and Russell  are the first who give main concept of PV/T collector using water or air as the heat removal fluid. Hendrie and Raghuraman  have made a comparative experimental study on photovoltaic thermal collectors with liquid and air as working fluid. Raghuraman  presented numerical methods predicting the performance of liquid and air PV/T collector. Sopian et al.  have successfully demonstrated the improved performance of a steady state double pass collector over the single pass collector due to efficient cooling of the photovoltaic cell. Garg and Adhikari  reported the performance analysis of hybrid photovoltaic thermal collector with integrated compound parabolic concentrator (CPC) troughs; this case indicated that the total efficiency with CPC is higher than system without CPC. Zondag et al.  compared the efficiency of seven different design types of photovoltaic thermal collectors. Mohd.Y.Hj.Othman et al.  design a new model of double pass PV/T air collector with CPC and fins and they studied its performance over range of operating conditions." -paper
This paper explains the theorectical calculations for a single pass air PVT. It has a flow chart of how the FORTRAN code works and the equations it uses. The theorectical calculations state the higher the mass flow rate the better the electrical and thermal efficiency. The total efficiency ranged from 26.6 to 39.13% with mass flow rates of 0.0316 to 0.09 kg/s. These calculations have not been experimentally tested.
ARPN Journal of Engineering and Applied Sciences. VOL. 2, NO. 5, OCTOBER 2007. TRANSIENT MATHEMATICAL MODEL OF BOTH SIDE SINGLE PASS PHOTOVOLTAIC THERMAL AIR COLLECTOR. Ebrahim M. Ali Alfegi, Kamaruzzaman Sopian, Mohd Yusof Hj Othman and Baharudin Bin Yatim. http://arpnjournals.com/jeas/research_papers/rp_2007/jeas_1007_62.pdf
 Solar Hybrid Photovoltaic-Thermal Electricity 2007
"Most of these system configurations were based on the conventional flat-plate collectors with solar cells pasted on the absorber. Tripangnostopoulos et al.  have presented a summary on the work conducted by several researchers in the past in respect of PVT systems. Most of the research work and applications conducted earlier in this field  are converging on two alternate solutions: the first one, which is the most effective one, is to recover heat through natural or forced (mechanized) ventilation inside the panels; the second one, in which the heat can be transferred to another medium, such as water. The potential for architectural integration of this technology is considerable high and allows realizing a solar building envelope that produces energy to consume directly at the site. Applications of photovoltaic in built environment and its financial viability has been discussed by Bazilian et al. ." - Paper
The TIS (Integrated Solar Roof) was a tested PVT at the Politecnico di Milano. This PVT could be used on a wall or roof a building. In 2001 the CRF (Fait Research Centre) invested to add a PVT to their south wall which was financed under National Tetti fotovoltaici (Photovoltaic Roff) Programme. The PVT produced a 19.5 kWp and air was used as the coolant. The airflow as up ot 9000 m3/h and the temperature reached up to 60 C. The electrical efficiency of this system was about 9-10% and the thermal efficiency was ~30%. It was estimated that the PVT wall total primary energy savings were 185 MWh which corresponds to a CO2 reduction of 36 tons.
©2007 IEEE. Solar Hybrid Photovoltaic-Thermal (PVT) Façade for Heating, Cooling and Electricity Generation. F. Butera, R.S. Adhikari, N. Aste, and R. Bracco. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4272471
5mjmp 18:48, 12 June 2009 (UTC)
 Design, Development and Performance Monitoring of a Photovoltaic-Thermal Air Collector 2007
Written:2007 The research and development was completed at the Politecnico di Milano. The PV/T is made of a rectangle; bottom up: insulation then absorber plate then air gap for the air flow and then a glass top with checkered placed PV cells. Dimensions are included in article.
ηa = ηnkγkθkαkλ
- ηa actual efficiency
- ηn nominal efficiency (from lab testing STC)
- kγ Temperature correction factor
- kθ Optical correction factor
- kα Absorbtion correction factor
- kλ Spectrum correction factor
Seven sunny days were tested from march to august and the results show that the thermal efficiency was 20-40% and the electrical efficicency was 9-10%. Sunday days were chosen since there was not a way to correct for direct and diffused sunlight in this test.
In this article, there are equations to calculate the thermal balance of the PV cells, Thermal equilibrium of the glass (part of the sandwich without PV cells inside), Thermal equilibrium in the air gap, Thermal equilibrium of the absorber plate, PV thermal–spectral actual efficiency, Average temperature of the air in the gap and Thermal exchange coefficients.
The model and prototype were compared in this article and they were very similar.
Renewable Energy 33 (2008) 914–927. Design, development and performance monitoring of a photovoltaic-thermal (PVT) air collector. Niccolo` Aste�, Giancarlo Chiesa and Francesco Verri. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V4S-4PNF2KF-1&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=e411ef7879484c1bd205547f3c1fb8ac
5mjmp 20:07, 2 June 2009 (UTC)
 Performance Analysis of a Double Pass Thermoelectric Solar Air Collector 2008
"Over the last few years, different PVT systems, based on air and water as heat carrying fluid, have been studied, developed and reported in literature. For example, Kalogirou  has studied experimentally an unglazed hybrid PVT system under the force mode of operation for climatic condition of Cyprus. He observed an increase in the mean annual efficiency of a PV solar system from 2.8% to 7.7% with a thermal efficiency of 49%. Hagazy  and Sopian et al.  investigated a glazed PVT air system for a single and double-pass air heater for space heating and drying purposes. They have also developed a thermal model of each system. Thermal energy for the glazed PVT system is increased with lower electrical efficiency due to high operating temperature. However, there is another technology for combined electrical and thermal energies namely: thermoelectric (TE) technology. The term TE refers to solar thermal collectors that use TE devices as an integral part of the absorber plate. The system generates both thermal and electrical energy simultaneously. A TE device for power generation consists of n and p semiconductors connected electrically in series and thermally in parallel. Heat is supplied at one end of the TE, while the other end is maintained at a lower temperature with a heat sink . As a result of the temperature difference, a current flows through an external load resistance. TE has the advantage that it can operate from a low grade heat source such as waste heat energy. It is also attractive as a means of converting solar energy into electricity. A number of simulations as well as experimental studies have been reported on solar-driven TE power generators. Chen  derived a thermodynamic analysis of solar-driven TE power generator based on a well-insulated flat plate collector. A thermodynamic model including four irreversibilities is used to investigate the optimum performance of a solar-driven TE generator. The example discussed by Chen is based on an extremely well-insulated flat plate collector, which, in practice, may be difficult to achieve. Gunter et al.  constructed a prototype of a solar thermoelectric water heater. The hot side of TE module was heated by solar hot water. Meanwhile, the heat was released at the cold side of TE module via a heat sink. Three vacuum tubes with heat pipes, each with a 0.1m2 absorber area and with water as the heat pipe medium, were connected via a specially designed heat exchanger to a fluid circuit acting as a heat sink. Test result showed that the electrical efficiency reached a maximum value of 1.1% of the incoming solar radiation, which is around 2.8% of the transferred heat. Scherrer et al.  presented a series of mathematical models based on the optimal control theory to assess the electric performance of a skutterudites-based solar TE generator as a function of sunspacecraft distance, and optimized its design parameters (such as dimensions, weight and so on) when operating at a distance of 0.45 a.u. from the sun, for 400Welectrical output power and for a required load voltage of 30 VCD. The simulation results indicated that the skutterudites-based solar TE generator offered attractive performance features as primary or auxiliary power source for spacecraft in near-Sun missions. Maneewan et al.  studied a thermoelectric roof solar collector (TE-RSC) to reduce roof heat gain and improve indoor thermal comfort. Maneewan’s TE-RSC combined the advantages of a roof solar collector and TE to act as a power generator. The electric current produced by the TE modules was used to run a fan for cooling the modules and improve the indoor thermal conditions. The subsequent simulation results, using a real house configuration, showed that a TERSC unit with a 0.0525m2 surface area could generate about 1.2W under solar radiation intensity of about 800W/m2 and at ambient temperatures varying between 30 and 35 1C. The induced air change rate varied between 20 and 45 ACH (number of air changes per hour) and the corresponding ceiling heat transfer rate reduction was about 3–5W/m2. The electrical conversion efficiency of the proposed TE-RSC system is 1–4%." - Paper
This paper is about the testing and development of TE solar air heater to determine its performance in Thailand. The theoretical model and testing were within experimental error of each other. The results showed that with an air flow-rate of .123 kg/s the overall efficiency was 80.3% with the electrical efficiency of around 5.7%.
TE uses the same idea of thermocouples, ie. the higher the difference in temperture, the higher the voltage. So by cooling one side of the TE and collecting that warmer air, the thermal and electrical efficiency goes up. see thermoelectricity
& 2008 Elsevier B.V. All rights reserved. Performance analysis of a double-pass thermoelectric solar air collector. C. Lertsatitthanakorn, N. Khasee, S. Atthajariyakul and S. Soponronnarit. A. Therdyothin b, Ryosuke O. Suzukihttp://ci.nii.ac.jp/naid/120000947350/
5mjmp 19:06, 10 June 2009 (UTC)
 Performance Analysis of a Photovoltaic-Thermal Integrated System 2008
This is a very good paper going over PV/T's.
This paper is an overall summary of PV/T's and it talks about why PV/T's are more practical. PV/T's is designed to remove the unwanted heat from PV's and collect the excess heat, thus making them more efficient than PV's. You can not compare them to a thermal system since PV/T's produce heat and electricity which is more useful than just heat. The paper talks about the use of exergy efficiency as a means to determine the PV/T's efficiency since exergy takes more variables such as heat into the efficiency. Exergy help determine the magnitude, location and the sources of the thermodynamic inefficiencies in a system. This allows for the optimization of a system efficiency.
"The exergy efficiency can be defined to describe the quality difference between electricity and heat" - Paper
Exergy analysis is a tool that can help determine the amount of exergy required for a process and the avaible exergy which can then be used to utilize the exergy more efficiently. The exergy efficiency decreases with decreasing heat harvest (ie. heat transfer medium flow rate fast therefore medium isn't as hot and therefore heat harvest lower).
Many advantages to PV/T systems:
- "increase of the electric output power,
- improvement of conversion efficiency of solar cells,
- heat transfer from the module to the cooling medium" -Paper
"The exergy analysis of the hybrid system allows evaluating influence of every particular process on the efficiency of the system, eliminating the profitless components of the system, and identifying the maximum efficiency of the system." - Paper
80-952 Gdansk, POLAND, G. Narutowicza 11/12 e-mail: firstname.lastname@example.org, tel/fax +48 58 347 18 74 PERFORMANCE ANALYSIS OF A PHOTOVOLTAIC-THERMAL INTEGRATED SYSTEM. Ewa Radziemska. Chemical Faculty, Gdansk University of Technology. http://18.104.22.168/scholar?hl=en&lr=&q=cache:NJNQCrv6m98J:hindawi.com/RecentlyAcceptedArticlePDF.aspx%3Fjournal%3Dijp%26number%3D732093+Performance+Analysis+of+a+Photovoltaic-Thermal+Integrated+System+Ewa+Radziemska
5mjmp 20:26, 10 June 2009 (UTC)
 Nanodiagnostics of Concentrator Solar Cells with Vertical p-n-Junctions for PV/T Systems 2008
Not very useful. The following is the conclusion.
"Concentrator PV/T technologies are prospective alternative of traditional solar thermal collectors and PV modules. First results of diagnostic of solar cells with vertical p-n-junctions show high informative and useful data obtained with the help of modern methods of investigation of semiconductors. As for thickness of inter-layers connecting p-n- junction structures in developing SCs with vertical p-n junctions we have a definite reserve i.e. decreasing thickness of inter-layers it is possible to increase sensitive surface of SCs. It is necessary to improve quality of the surface on the cutting stage of bonded (soldered) structures for improving technology and quality of solar cells and potential using scanning capacitance microscopy for detailed study of carrier’s distribution." -Paper
5mjmp 18:53, 10 September 2009 (UTC)
489 - Nanodiagnostics of Concentrator Solar Cells with Vertical p-n- Junctions for PV/T Systems Corresponding Author, email@example.com 5mjmp 18:59, 16 June 2009 (UTC)
 Study on Thermal Performance of Hybrid Photovoltaic Thermal 2008
"Many researchers and institution have attempted to develop and evaluate the hybrid PV/T collector performance experimentally and analytically. Ito and Miura, experimentally and analytically studied the thermal performance of a PV/T collector that used a partially transparent PV module as a cover , . Ito and Miura also reported that the collector efficiency was slightly less while generating power than while not generating power . Othman et al. , studied theoretically and experimentally hybrid PV/T solar collector regarding its thermal and electrical performance, used air as a flowing fluid to extract heat from the photovoltaic cells and keep electrical efficiency of it a satisfactory level by the reduction of its operating temperature. The conclusion of this work this work is that is important to use fins as an integral part of the absorber surface in order to achieve meaningful efficiencies for both thermal and electrical output of the hybrid PV/T solar collector. Santbergen and Zolingen simulated various crystalline silicon solar cell configurations found that a standard untextured solar cell with a silver back contact has an absorption factor of only 74%. If a semi transparent solar cell is used in combination with second absorber the total absorption factor can increase to 87%, and if irradiance is absorbed in the back contact, the absorption factor can increase to 85%. They suggested to apply the rough interface in combination with a non standard metal as back contact ." - Paper
This paper experimentally tested whether having PV panels on a thermal collector greatly affected the thermal efficiencies. From the results, the PV panels do not reduce the efficiency significantly.
5mjmp 20:00, 10 September 2009 (UTC)
(PV/T) Collectors with and without Electricity Generation 041 - Study on Thermal Performance of Hybrid Photovoltaic Thermal (PV/T) Collectors with and without Electricity Generation *Corresponding Author, firstname.lastname@example.org 5mjmp 18:59, 16 June 2009 (UTC)
 Improvement of the performance of PVT Collectors 2008
This paper looks at the application of anti-reflective (AR) coatings adn low-emissivity (low-e) coatings. It was found that the AR coating improved the anual thermal and electrical efficiency by 10% and 5% relatively. The low-e coating reduces the electrical efficiency by 10% but increaes the thermal efficiency by 10%. Overall AR coating is much better than the low-e coating.
"In table 4 results are given for PVT collectors with amorphous silicon solar cells (with an efficiency of 6.3% at STC) in stead of crystalline silicon solar cells. In case a low-e coating is used, the drop in annual electrical efficiency is only 6.7% (5.02% versus 5.38%), because of the lower temperature coefficient of the efficiency of single junction amorphous silicon solar cells (-0.18%/ºC relative versus -0.45%/ ºC for crystalline silicon solar cells)." - Paper
09_06_16_Improvement of the performance of PVT Collectors
5th European Thermal-Sciences Conference, The Netherlands, 2008. IMPROVEMENT OF THE PERFORMANCE OF PVT COLLECTORS. R. Santbergen, C.C.M. Rindt and R.J.Ch. van Zolingen. http://www.eurotherm2008.tue.nl/Proceedings_Eurotherm2008/papers/Thermal_Solar_Energy/TSE_2.pdf 5mjmp 18:59, 16 June 2009 (UTC)
 Development and characterization of semitransparent double skin PV Façades 2008
"Some European funded projects have been actively supporting this work, PASSLINK, PV-HYBRIDPAS and IMPACT .Between 1999 and 2000, the Centre for Applied Research at the University of Applied Sciences Of Stuttgart [7,11] undertook the theoretical analysis and monitoring of the Mataro’s public library building, which had the first PV ventilated façade in Europe. More recently, the treatment of the induced flow and the heat transfer at the air gap and the surfaces of a natural ventilated double skin façade has been progressively refined by Brinkworth [3,4]. Concerning to the mathematical model to define the energy performance 2 of such façades, sophisticated models for double skin façades were developed by Saelens ." - Paper
"Although these detailed studies have lead to an increase in the knowledge of the heat transfer processes, there are still many unclear fields such as: the convective heat transfer coefficients definition; the evaluation of the direct solar radiation absorbed by the solid parts; the evaluation of the mass flow rate in non-developing turbulent flows and, the coupling with the HVAC systems." - Paper
This paper deals with Facades which are basically wall PVTs. In this paper it deals with air as the coolent with the air flowing from the bottom on the PVT (close to the ground facing the ground) and the exhaust air exits from the top which can then enter the building as a preheat. There are several Nussel equations and TRNSYS simulations. This paper deals more witht the convection heat transfer and simulations rather than the PV.
156 - Development and characterization of semitransparent double skin PV Façades. Eurosun 2008. J.Cipriano, C. Lodi, D.Chemisana, G.Houzeaux, O. Perpiñán. http://www.inive.org/members_area/medias/pdf/Inive%5CPalencAIVC2007%5CVolume1%5CPalencAIVC2007_043.pdf 5mjmp 18:59, 16 June 2009 (UTC)
 Multi Solar (PVT) Co-Generation Power Station 2008
Patent No 5522944
This power plant has a 85% solar efficiency (15% electrical and 70% thermal [35% hot water, 35% hot air]). Each square meter of the Multi Solar System (MSS) produce 150 W DC electricity from PV panels and 700 W of thermal energy. Using low pressure steam generators the thermal energy mass can be converted into electrical energy with a 20-25% efficiency. The temperature of the steam gets to 135 C. This is done by first using cold water to cold the PV panels and extracting that heat. The water exiting this array is about 55 C. Next this 55 C is further heated by solar thermal panels to 85 and then the second flow get the water to 135 C. This steam is then sent to a boiler and then to the turbine. This PVT/air technology has been developed for 16 years in a variety of projects in Isreal.
5mjmp 02:19, 22 July 2009 (UTC)
079 Multi Solar (PVT) Co-Generation Power Station http://www.ct-si.org/publications/proceedings/procs/Cleantech2009/2/10038 5mjmp 18:59, 16 June 2009 (UTC)
 PV Thermal Systems - Capturing the Untapped Energy 2008
Eurosun 2008 This is TASK 35 Canadian Results
It was found that it is possible to collect 2-3 times as much thermal energy as electrical energy. Typically, PV modules operate 50 C above ambient temperatures but with water/air coolants the temperature can be lowers and the electrical efficiency improved. Two problems that arise from the high temperatures is the stress that are produced on the PV panels and that the PV panel efficiency decreases. The total effiecient (thermal and electrical) ranged from 25-50% which is significantly higher than just the PV which had an efficiency of 6-12%. It was stated that covering a roof with just PV panels only utilizes 10-15% of solar potential. In this test air was used as a coolant. The testing was done indoors at Canada’s National Solar Test Facility in Mississauga and three different PV panels were used. The three companies were; BP Solar, Evergreen Solar and UniSolar.
- Evergreen supplied six of their new 170 Watt panels. Two rows of three panels covered 90% of the 10 m2 test panel.
- BP Solar supplied six of their 160 Watt panels which when placed onto the test panel covered
approximately 76% of the test panel surface leaving 24% of the transpired panel exposed to the sun.
- UniSolar supplied eight of their peel and stick 68 Watt modules which fit onto the test panel in a horizontal configuration and covered 90% of the test panel.
"It was decided to perform two sets of tests at two flow rates for each panel, one set at NOCT conditions and the other at the solar thermal conditions. The air flow heat removal rates selected were 36 m3/h. m2 (2 cfm/ft2) and 108 m3/h.m2 (6 cfm/ft2) of gross collector surface which represent low and medium air flows typical for heating ventilation air." - Paper
Four systems were tested for each companies PV panel: "System 1: SolarWall with two PV modules on top, variable flow (high) System 2: SolarWall with two PV modules on top, variable flow (low) System 3: SolarWall alone, variable flow (thermal reference) System 4: PV module alone, natural ventilation (electrical reference)" - Paper
"According to the SolarWall supplier, the additional cost for including the thermal component is about 25% of the cost of the PV system but the additional energy delivered is 150% to 400%." -paper
In conclusion, the Evergreen and BP PVT setup produce the highest electrical efficiency of 10.3% compared to Unisolar of 6.7%. However, because the Unisolar panel became hotter the thermal efficiency was the highest at 50% and therefore the overall highest efficiency goes to Unisolar. But looking at it from an exergy point of view, BP was the best since it had the second highest overall efficiency of 51.6%.
018 - PV Thermal Systems - Capturing the Untapped Energy http://solarwall.com/media/images-articles/ASESPaper-PVThermalSystems-theUntappedEnergy175A3.pdf 5mjmp 18:59, 16 June 2009 (UTC)
 Multi Solar (PVT) Air Conditioning System 2008
189 - Multi Solar (PVT) Air Conditioning System
This article is about the MSS (Multi Solar System) that combines PV panels cooled by air and water. (see another article on the details) This article is explains some of the technical notes of the MSS such as its use of lithium cloride as part of the heat exchanger. According to the article this material in environmental friendly. MSS is patented with it's number PATENT NO 5522944. The MSS claims to be 85% efficient and that it's the best PVT system currently. This MSS is designed for large scale electrical generation rather than for single homes.
5mjmp 17:14, 4 August 2009 (UTC)
http://www.nsti.org/procs/Nanotech2009v3/3/W63.115 5mjmp 18:59, 16 June 2009 (UTC)
 An Experimental Study of Air Flow and Heat Transfer in an inclined Rectangular Channel with Wood Strips on the Bottom Plate 2008
This article deals with thermal heat transfer using air as a medium and the testing of natural convenction with different inclines. It was found that the natural convection does not reduce the temperature reduction of the PV panels. A flat plate thermal collector had 24 thermal couples placed in 3 rows of 8 along it to record the temperatures. The heat transfer was also modelled and the equations used can be found in the article. The purpose of this research is to help improve BIPVT (Building Integrated PVT). PIV (Particle Image Velocity) system was used to understand the air flow within the system.
5mjmp 19:29, 4 August 2009 (UTC)
252 - An Experimental Study of Air Flow and Heat Transfer in an inclined Rectangular Channel with Wood Strips on the Bottom Plate Dr. Harrison 5mjmp 18:59, 16 June 2009 (UTC)
 The Active Solar Building – Overview of the SRA of the ESTTP and Synergy with other Technology Platforms 2008
This article talks about the steps required in reaching Europes 2030 goals to have 50% of their thermal energy produced from solar. According to the article, Europe plans to have its energy demands reduced by 20% and to have 20% of its energy demands renewable and that solar has a very good potential.
Areas that need further research to the 2030 goals are the following: "
- Selective coatings for absorbers
- Advanced collector production methods (e.g. laser welding)
- Advanced flat-plate collector technology
- High-quality vacuum tube collectors
- Process heat collectors
- Stratified hot water storage tanks
- Electronic controllers
- System technology (e.g. solar combined systems for domestic hot water and space heating, with a burner directly integrated into the storage unit)
- Large-scale ST systems combined with seasonal heat storage
- Advanced applications (cooling, combined systems and industrial applications)
Sweden, Austria, Denmark and Germany are the leading countries in low-energy building technology.
Areas which need to be improve on the manufacturing stages of the solar collectors are the following.
"Major efforts are needed in the following areas:
- More efficient ways to use conventional collector materials (metals, glass, insulation), especially with a view to developing multifunctional building components, which simultaneously act as an element of the building envelope and a solar collector.
- Evolution in the optical properties of collector components. In particular, a more systematic use of optical films to enhance heat/light transmission through glass covers and reduce this transmission during excessive exposure; and the use of colours in absorbers or covers to achieve more flexible integration concepts.
- Alternative materials for collector production: the use of polymers or plastics, the coating of absorbers optimised to resist stagnation temperatures and new materials to prevent deterioration resulting from UV exposure.
- Improvement in the recycling potential of collector components and materials in view of lifecycle cost reduction, and overall sustainability of materials.
- Special topics will include issues such as: The control of solar energy delivered by entire facades, in particular the aspects related to fault detection and the consequences of stagnation temperatures when a prolonged no-load situation coincides with peak solar radiation;
- New component testing and evaluation methods; and
- A dedicated concept for the automation of manufacturing processes and assembly techniques." -Paper
The paper also talks about different types of thermal storage; sensible, latent, sorption and thermochemical. Currently concrete, molten salt and pressurised liquid water are used for sensible storage. Latent storage (water) used for low temperature storage for small buildings. Sorption is still in the development stages. Thermochemical storage could be salts and hydrates combined together to produce a thermal storage capacity 8 to 10 times higher than water. However, further research is needed in all 4 fields to better improve the solar thermal systems.
5mjmp 23:28, 4 August 2009 (UTC)
313 - The Active Solar Building – Overview of the SRA of the ESTTP and Synergy with other Technology Platforms http://books.google.ca/books?hl=en&lr=&id=4SbqvDzIIw4C&oi=fnd&pg=PA175&dq=The+Active+Solar+Building+Wittwer&ots=lcYfm4XBlF&sig=Hm1jQ3T46GUYbkb9W-K6P9VLo44 5mjmp 18:59, 16 June 2009 (UTC)
 A COOLING SYSTEM FOR A HYBRID PV/THERMAL LINEAR CONCENTRATOR 2008
This article is about using a finite volume 3D numerical computations to study the thermal characteristics of a rectangular cross section aluminum pipe to determine the performance of a PVT collector using several laminar flow rates.
1981 Florschuetz  determined that due to air's low diffusivity and thermal capacity, air would not be a great coolant. He decided water would be a better choice. Even if water is used as the coolant, very few use the warm water.
Two systems that are currently being worked on:
- "CHAPS (Combined Heat And Power Solar), developed at the Australian National University. It
consists of a parabolic concentrator with a ratio of 37X which focuses radiation onto a PVT module. The module converts the radiation into thermal and electrical energy with efficiencies of 57% and 11% respectively. The prototype was initially designed as a photovoltaic system with active cooling, the idea later evolved to use the water to capture the thermal energy. Reference data of the thermal gain achieved by the collector is not mentioned in any of the reference publications for the system .
- BIFRES, developed at the University of Lleida, is a system which concentrates radiation by
Fresnel reflection to a concentration factor of 22X. The hybrid module operates with a nominal thermal efficiency of 59%, permitting the c-Si photovoltaic cells to operate at an optimum efficiency of 11.9% . "- Paper
Both achieve efficiencies greater than 50% but both are complicated systems... CHAPS uses an alumimum heat sink and BIFRES uses copper. BIFRES also uses furrowed tubes to improve convection of the liquid. Rectangle tubes are used for higher Nusselt numbers and greater heat exchange.
General Specs of the PVT system
"The configuration of the PVT module consists of a row of photovoltaic cells with a rectangular surface area of 1cm x 1m, placed at the top of the aluminium heat sink. The encapsulation can be divided into various elements. 1. In the surface at which concentrated radiation is received, an EVA film is applied to the cells, and high absorption glass with low iron content is used as an outer skin. This reduces deterioration of the cells and minimises the thermal losses through the top of the module.
- Between the cell and the heat sink a strip of electrical insulation is inserted using a double sided
adhesion (Chomerics Thermattach T404). This method considerably simplifies the adhesion process, as it simultaneously serves to insulate the cell and to fix it in right position.
- Finally, the lateral and underneath faces of the heat sink are thermally insulated with a plate of
temperature resistant polypropylene." -Paper
CONSIDER PRESSURE DROP ACROSS PIPES. The paper contains the pressure equations needed to determine the pumps power. Contains values and equations on the thermal resistance of the system.
"The heat exchange properties of the aluminium improve increasing the aspect ratio of its cross section, in addition the pressure drop or in consequence the pumping power is higher when the hydraulic diameter (which is directly related with the cross section) is lower. Nevertheless, a big aspect ratio implies a much more difficult mechanical procedures, suck as hydraulic connections, isolation. Moreover, is necessary to mention that the main aluminium factories don’t manufacture pipes of one centimetre width with aspect ratios higher than 2.43. Attending to this explanations, the pipe selected to be include in the PVT systems under concentration is with a cross section of 20x10cm2 (α = 2.43)." - Paper
5mjmp 19:03, 2 September 2009 (UTC)
174 - A COOLING SYSTEM FOR A HYBRID PV/THERMAL LINEAR CONCENTRATOR * Daniel Chemisana, email@example.com 5mjmp 18:59, 16 June 2009 (UTC)
 Modelling the Energy Contributions of a PVT System to a Low Energy House in Sydney 2008
084 - Modelling the Energy Contributions of a PVT System to a Low Energy House in Sydney * Corresponding Author, firstname.lastname@example.org 5mjmp 18:59, 16 June 2009 (UTC)
 Building Integrated Concentrating PV and PV/T Systems 2008
This paper looks at concentrated PV (CPV), PV/T and CPV/T and how they can be integrated into building designs / retro fitted.
"The performed works can be grouped in systems with V-trough reflectors [1-4], achieving concentration ratios up to two with east-west or north-south orientated reflectors, CPC (Compound Parabolic Concentrator) type reflectors [5-10], which are usually static and CR<2.5, refractive concentrators of 3D acrylic lens [11-13] and linear Fresnel lenses [14-16]. Comparison results give an idea about the benefits of concentrating photovoltaics and point-focus concentrating systems with a fixed flat plate PV module [17-19] show that the concentrating systems produces 37% greater electrical energy than the flat PV modules. In the University of Patras, research works on low concentration photovoltaics have been performed last years [20-25]." -Paper
5mjmp 13:18, 4 September 2009 (UTC)
241 - Building Integrated Concentrating PV and PV/T Systems Corresponding Author, email@example.com 5mjmp 18:59, 16 June 2009 (UTC)
 Modelling and Performance of a Solar Demonstration House with Integrated Storage and BIPV/T System 2008
This article deals with creating a zero net energy consumption house. The house was built in 2007 and uses a wide range of renewable sources / energy efficient building materials to reduce the energy consumption of the house. It uses a BIPV/T but does not go into the specifics of the make and materials.
5mjmp 13:44, 4 September 2009 (UTC)
288 - Modelling and Performance of a Solar Demonstration House with Integrated Storage and BIPV/T System *Corresponding Author: firstname.lastname@example.org 5mjmp 18:59, 16 June 2009 (UTC)
 Evaluation of a Parabolic Concentrating PVT System 2008
The article is nicely summarized in it's conclusion.
Solar8 is a PV/T system created by a Swedish company called Arontis. The tests were simulated using Sweden,Portugal and Zambia climates. The results are the following.
"With this study several conclusions can be taken not only for Solar8 but also perhaps to the general photovoltaic/thermal concentrating hybrids being developed:
- Solar8 can be replaced by a traditional side-by-side system using less space and producing the same electric and thermal output.
- Local diodes installed in each cell can be able to bypass the current over the poorest cells and help reducing the problem with uneven radiation.
- One axis tracking around North-South direction is considerably better than tracking around an axis placed on East-West direction.
- The global irradiation on a static surface is higher when compared with the beam irradiation towards a tracking concentrating surface.
- The ratio between electric and thermal output decreases when Solar8 is moved to the equator where the beam irradiation values are higher.
- This PV/T combination still present lower outputs when compared with the traditional side-by-side system for the same glazed area. It is possible to say that there is chain efficiency around the most important components in Solar8. If every part of this chain works accurately and perfectly integrated in the system, higher efficiencies can be achieved in future models." -Paper
5mjmp 14:39, 4 September 2009 (UTC)
321 – Evaluation of a Parabolic Concentrating PVT System Corresponding Author, Ricardo.Bernardo@ebd.lth.se 5mjmp 18:59, 16 June 2009 (UTC)
 Photovolatic-Thermal System for Stand-Alone Operation 2008
- Thermal systems have low costs and high efficiencies
- Solar panels have high costs and moderate efficiencies (long payback period)
- Thermocouples have low efficiencies and therefore combining them with thermal systems not a great way to get electicity
- Big issue with solar is roof area
This paper demostrates a PV/T stand alone system and tests it out. The theoretical calculations confirm the experimental results. This sytem uses Maximum power point tracking (MPPT) and pc-silicon panels.
5mjmp 15:59, 4 September 2009 (UTC)
09_06_16_Photovolatic-Thermal System for Stand-Alone Operation
Photovoltaic / Thermal System for Stand-Alone Operation. Rafael K. Jardan, Istvan Nagy, Angel Cid-Pastor, Ramon Leyva, Abdelali El Aroudi and Luis Martinez-Salamero ©2008 IEEE. http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=04592568 5mjmp 18:59, 16 June 2009 (UTC)
 Experimental Investigation of Single Pass, Double Duct Photovoltaic Thermal Air Collector with CPC and Fins 2008
This paper is the same as 09_05_23_the effect of flow rates on teh performance of finned single pass, double duct photovoltaic thermal solar air heaters and the conclusion is the same. 'Fins are crucial in the improvement of the efficiency of the PV/T.'
"A number of researches and development programs have been carried out to improve the applications of solar energy systems. Several design of photovoltaic thermal solar air collector has been proposed in the past. Among the first, Kern and Russel are the first who give main concept of photovoltaic thermal collector using water or air as the working fluid. Florschuetz has extended the Hottel-Willer model to analysis steady state combined photovoltaic/thermal collector with simple modification of the conventional parameters of the original model by assuming that a liner correlation between efficiency of solar cell array and its temperature over its operating temperature range. Hendrie and Raghuraman have been made a comparative experimental study in (pv/t) collectors with liquid and air as the heat removal fluid (working fluid). Cox and Raghuraman suggested air type photovoltaic thermal system by analysis the effect of various design variables on the performance of the system. Lalovic et al. fabricated photovoltaic thermal collector using amorphous Silicon pv cell and its performance was tested. Garg et al. presented the theoretical study of (pv/t) collector with reflectors; they found that the system is well suited for solar drying applications. Bharagava et al. and Prakash reported the effect of air mass flow rate, air channel depth and packing factor. Sopain have successfully demonstrated the improved performance of steady state double pass collector over the single pass collector due to efficient cooling of pv cells. Bergene and Lovvik found that the thermal efficiency may increase only by a factor of 0.1 if flow rate increase from 0.001 to 0.075 kg-1 s. Sopian et al. developed and tested a double pass photovoltaic collector suitable for solar drying applications and they comparison between theoretical and experimental results. Tripanagnotopoulos et al. built and tested various photovoltaic thermal collector models with both water and air as the working fluids. Zondag et al. compared the efficiency of seven different design types photovoltaic thermal collectors. Othman et al. investigate the performance of double pass (pv/t) air heater with fins fixed in the bottom of absorber, the system theoretically under steady state conditions and experimentally was studied. They conclude that it is important to use fins as integral part of the absorber surface in order to achieve meaningful efficiencies for both thermal and electrical output of photovoltaic solar collector. Y. B. Assoa developed simplified steady state 1-D mathematical model of (pv/t) bi-fluid (air and water) collector with a metal absorber. A Parametric study (numerically and experimentally) to determine the effect of various factors such as the water mass flow rate and thermal performance was studied. Simulation results were compared with the experimental results." -Paper
American Journal of Applied Sciences 5 (7): 866-871, 2008. Experimental Investigation of Single Pass, Double Duct Photovoltaic Thermal (PV/T) Air Collector with CPC and Fins. M. Ebrahim Ali Alfegi, Kamaruzzaman Sopian, Mohd Yusof Hj Othman and Baharudin Bin Yatim. http://scipub.org/fulltext/ajas/ajas57866-871.pdf
5mjmp 15:16, 8 June 2009 (UTC)
 Parametric Study of an Active and Passive Solar Distillation System: Energy and Exergy Analysis 2009
This article deals with solar stills instead of PVT however, it has some useful equations to help solve some of the heat problems. In this paper two models are looked at. One model assumes that the inner and outer walls of the glass cover are the same while the other does not. These models use mass and energy balance equations. The conclusion was that the temperature of the inner and outer glass does effect the yield of the solar stills.
Desalination 242 (2009) 1–18. Parametric study of an active and passive solar distillation system: Energy and exergy analysis. G.N. Tiwari, Vimal Dimri and Arvind Chel. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFX-4W3HPH2-3&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=7acf18855d8866aa699e11975ce5b025
5mjmp 20:18, 4 June 2009 (UTC)
 The Effect of Flow Rates on the Performance of finned single pass, double duct PVT solar air heaters 2009
In this article, the PV panels were pasted directly onto the absorber with fins attached to the back of the absorber. The solar radiation was set at 400-700 W/m2 from 23 halogen lights rated at 500 W. The flow rate was varied rom 0.0316-0.09 kg/s and it was found that the greater the flow rate, the higher the efficiencies. The total efficiencies ranged from 49.135%-62.823%. Air flows above and below the absorber plate. The fins were 0.025 cm high, 0.001 thick, density of 0.384 fin/ cm and there were 29 fins. The inlet air temperature varied from 30 - 35 C.
European Journal of Scientific Research ISSN 1450-216X Vol.25 No.2 (2009), pp.339-344. The Effect of Flow Rates on the Performance of Finned Single Pass, Double Duct Photovoltaic Thermal Solar Air Heaters. E. Ali Alfegi, K. Sopian, M. Othman and B. Yatim. http://www.eurojournals.com/ejsr_25_2_16.pdf
5mjmp 17:28, 5 June 2009 (UTC)
 Indoor Simulation and Testing of Photovoltaic Thermal Air Collectors 2009
"Several designs of hybrid PV/T solar air heater had been proposed in the past. Kern and Russed  were the first who gave the main concept of PV/T collector using water or air as the working fluid. Cox and Raghuraman  have performed computer simulation to optimize the design of flat plate PV/T solar air collector in order to increase the solar absorptance and reducing the infrared emittance (IR). Bhargava et al.  have analyzed a hybrid system which is a combination of an air heater and photovoltaic system parameters such as channel depth, length of the collector, and air mass flow rate. Garg et al.  have presented a theoretical study of PV/T collector using plane booster reflectors. The system consists of a flat plate solar air heater mounted with photovoltaic cells and two plan reflectors above and below the collector unit. Sopian et al.  have proposed at University of Miami a new design of double pass PV/T collector which can produce more heat, while simultaneously having a productive cooling effect on the cell. Garg and Adhikar  have developed a computer simulation model for predicting the transient performance of PV/T air heating collector with single and double glass configurations. Hagazy  has investigated glazed photovoltaic/ thermal air system for a single and a double pass air heater for space heating and the drying purposes. Kalogirou  has carried out monthly performance of an unglazed hybrid PV/T system under forced mode of operation for climatic condition of the Cyprus. Lee et al.  and Chow et al.  have described interesting modelling results on air cooled PV modules. They have found that the overall electrical efficiency of PV/T system in the year is around 10.2% and reduce the space heat gain by 48%. Tiwari et al.  have validated the theoretical and experimental results for photovoltaic (PV) module integrated with air duct for composite climate of India and concluded that an overall thermal efficiency of PV/T system is significantly increased (18%) due to utilization of thermal energy from PV module. Annual performance of building-integrated photovoltaic/ water-heating system for Hong Kong climates have presented by Chow et al.  and found that annual thermal and cell conversion efficiencies are 37.5% and 9.39%, respectively. Nayak and Tiwari  have presented performance of PV integrated greenhouse system for New Delhi climatic condition and reported that the exergy efficiency of the system is 4%. Dubey et al.  have derived the expression for temperature dependent electrical efficiency considering glass to glass and glass to tedlar type PV modules." - Paper
In this article a PVT system was set-up and tested under different operating conditions. 16 halogen lamps each rated at 500 W.
The following parameters were tested in the experiment:
- 1. Inlet air temperature.
- 2. Outlet air temperature for all the ducts.
- 3. Room temperature.
- 4. Solar cell temperature.
- 5. Air velocity.
- 6. Solar intensity.
- 7. Load current (IL) and load voltage (VL).
- 8. Short circuit current (Isc) and open circuit voltage (Voc).
In the theoretical model the following assumptions were made:
One dimensional heat conduction is good approximation for the present study.
- The glass cover is at uniform temperature due to no temperature
gradients along the thickness of glass.
- There is stream line flow of air through the duct at small flow
- The transmittivity of EVA is approximately 100% due to thickness
of EVA is less than 0.0003 m.
- The system is in quasi-steady state.
- The ohmic losses in the solar cell and PV module are negligible.
Solar Intensities (400-900 W/m2) and mass flow rates (0.01- 0.15 kg/s) were varied and results were graphed. The electrical, thermal and total efficiency found were 8.4%, 42% and 50%.
Future considerations suggested in the paper:
- Use of more halogen lamps of low capacities (or voltage) for uniform
insolation and temperature distribution, so that the each PV panel gets equal insolation and the output from the PV panels will be uniform.
- Automatic arrangement for varying the distance between lamps
and PV module. This will save the testing time and desired insolation can be obtained easily.
- Use of adhesive paste around PV/T air collector to further minimize
air leakage. This will helpful to get the optimum flow rate and uniform temperature can be obtained accurately.
Applied Energy 86 (2009) 2421–2428. Indoor simulation and testing of photovoltaic thermal (PV/T) air collectors. S.C. Solanki, Swapnil Dubey and Arvind Tiwari. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1T-4W207K3-3&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=150e40b6e74eb9a952595c14603cbeea
5mjmp 21:12, 9 June 2009 (UTC)
 Life Cycle Cost Analysis of Single Slope Hybrid (PVT) Active Solar Still 2009
"More than 80% of the solar radiation falling on photovoltaic (PV) cells is not converted to electricity, but either reflected or converted to thermal energy. In view of this, hybrid photovoltaic and thermal (PV/T) collectors are introduced to simultaneously generate electricity and thermal power . Chow  has analyzed the PV/T water collector with single glazing in transient conditions, consisting of tubes, in contact with the flat plate, reported an increase of electric efficiency by 2%, and obtained the thermal efficiency of 60% at 0.01 kg/s flow rate of water. Further, Zakharchenko et al.  have studied the unglazed hybrid (PV/T) system with suitable thermal contact between the PV module and the collector and reported that the area of module and collector in the PV/T system need not to be equal for higher overall efficiency. To operate the PV module at low temperature, the PV module should be fixed at lower temperature part of the collector (i.e. at the inlet of feed water). The parametric study of different configuration of hybrid (PV/T) air collector has also carried out by Tiwari and Sodha . Kumar and Tiwari  have reported that daily yield obtained from hybrid (PV/T) active solar still is 3.5 times of the passive solar still. Tiwari et al.  have validated the theoretical and experimental results for photovoltaic (PV) module integrated with air duct for composite climate of India and concluded that an overall thermal efficiency of PV/T system is significantly increased due to utilization of thermal energy from PV module. Recently, Dubey et al.  have reported the higher annual average efficiency of glass to glass type PV module with and without air duct as 10.41% and 9.75%, respectively." - Paper
This article is about the life-cycle analysis of passive and active PV/T solar stills. The purpose is to determine if which solar stills are better at producing potable water. It was found that the payback period for the passive and active solar stills were 1.1-6.2 years and 3.3-23.9 years. The active PV/T solar still is 2.8 the cost of the passive solar still. The paper also states the because of the continual development of the PV the PV/T active solar still will become feasible in the growing years.
Applied Energy 86 (2009) 1995–2004. Life cycle cost analysis of single slope hybrid (PV/T) active solar still. Shiv Kumar and G.N. Tiwari. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1T-4W034CH-3&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=0754dcf50bea79ad3103ff87311f7bf9
5mjmp 13:59, 10 June 2009 (UTC)
 Thin Film Silicon Photovoltaics, Architectural Perspectives and Technological Issues 2009
This article talks about thin film cells and their advantages. According to the article thin films can be integrated onto buildings such that they do not appear visible. Buildings in europe account for 40% of the energy consuming in Europe and the belief is that if the solar panels are added this will reduce the load. The other focus of this article is on the processing steps and how the thin films are made. It talks about transparent and conductive oxide (TCO) and thin film amorphous and microcrystalline silicon solar cells and the pros and cons with them. It has some technical and facts about the above. Useful if interested about thin films.
5mjmp 19:45, 31 July 2009 (UTC)
09_05_28_thin film silicon photovoltaics, architectural persepcitives and technological issues.pdf 5mjmp 20:23, 1 June 2009 (UTC)
Applied Energy 86 (2009) 1836–1844. Thin film silicon photovoltaics: Architectural perspectives and technological issues. Lucia Vittoria Mercaldo, Maria Luisa Addonizio, Marco Della Noce and Paola Delli Veneri, Alessandra Scognamiglio, Carlo Privato. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V1T-4VDSJRB-2&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=4e09fe1b4208f26a6bd1299bf2f1687d
 Amorphous Silicon PV/T
The Following are articles that deal with Amporphous Silicon panels in a PV/T system.
 Effects on Amorphous Silicon Photovoltaic Performance from High-temperature Annealing Pulses in Photovoltaic Thermal Hybrid Devices
There is a renewed interest in photovoltaic solar thermal (PVT) hybrid systems, which harvest solar energy for heat and electricity. Typically, a main focus of a PVT system is to cool the photovoltaic (PV) cells to improve the electrical performance; however, this causes the thermal component to under-perform compared to a solar thermal collector. The low temperature coefficients of amorphous silicon (a-Si:H) allow the PV cells to be operated at high temperatures, which are a potential candidate for a more symbiotic PVT system. The fundamental challenge of a-Si:H PV is light-induced degradation known as the Staebler–Wronski effect (SWE). Fortunately, SWE is reversible and the a-Si:H PV efficiency can be returned to its initial state if the cell is annealed. Thus an opportunity exists to deposit a-Si:H directly on the solar thermal absorber plate where the cells could reach the high temperatures required for annealing.
In this study, this opportunity is explored experimentally. First a-Si:H PV cells were annealed for 1 h at 100 °C on a 12 h cycle and for the remaining time the cells were degraded at 50 °C in order to simulate stagnation of a PVT system for 1 h once a day. It was found when comparing the cells after stabilization at normal 50 °C degradation that this annealing sequence resulted in a 10.6% energy gain when compared to a cell that was only degraded at 50 °C.
Source: M.J.M. Pathak, J.M. Pearce and, S.J. Harrison, “Effects on Amorphous Silicon Photovoltaic Performance from High-temperature Annealing Pulses in Photovoltaic Thermal Hybrid Devices” Solar Energy Materials and Solar Cells, 100, pp. 199-203 (2012). arXiv
 The Effect of Hybrid Photovoltaic Thermal Device Operating Conditions on Intrinsic Layer Thickness Optimization of Hydrogenated Amorphous Silicon Solar Cells
Historically, the design of hybrid solar photovoltaic thermal (PVT) systems has focused on cooling crystalline silicon (c-Si)-based photovoltaic (PV) devices to avoid temperature-related losses. This approach neglects the associated performance losses in the thermal system and leads to a decrease in the overall exergy of the system. Consequently, this paper explores the use of hydrogenated amorphous silicon (a-Si:H) as an absorber material for PVT in an effort to maintain higher and more favourable operating temperatures for the thermal system. Amorphous silicon not only has a smaller temperature coefficient than c-Si, but also can display improved PV performance over extended periods of higher temperatures by annealing out defect states from the Staebler-Wronski effect. In order to determine the potential improvements in a-Si:H PV performance associated with increased thicknesses of the i-layers made possible by higher operating temperatures, a-Si:H PV cells were tested under 1 sun illumination (AM1.5) at temperatures of 25oC (STC), 50oC (representative PV operating conditions), and 90oC (representative PVT operating conditions). PV cells with an i-layer thicknesses of 420, 630 and 840 nm were evaluated at each temperature. Results show that operating a-Si:H-based PV at 90oC, with thicker i-layers than the cells currently used in commercial production, provided a greater power output compared to the thinner cells operating at either PV or PVT operating temperatures. These results indicate that incorporating a-Si:H as the absorber material in a PVT system can improve the thermal performance, while simultaneously improving the electrical performance of a-Si:H-based PV.
M.J.M Pathak, K. Girotra, S.J. Harrison and J.M. Pearce, “The Effect of Hybrid Photovoltaic Thermal Device Operating Conditions on Intrinsic Layer Thickness Optimization of Hydrogenated Amorphous Silicon Solar Cells” Solar Energy (in press). DOI: http://dx.doi.org/10.1016/j.solener.2012.06.002 open access
 Review of the theory of amorphous semiconductors 1970
Abstract:The existing simple models of the electronic structure of disordered materials are reviewed. The focus is on the universal features of these models and their consequences for amorphous semiconductors. Simple plausibility arguments are given showing that continuous bands of extended states with tails of localized states associated with fluctuations within the disordered material can always be expected. Models for the mobility in which shoulders occur at the energies of transition from localized to extended states are reviewed. It is a mobility gap rather than a gap in the density of states which is responsible for the activated temperature dependence of the conductivity in amorphous semiconductors. Hopping conduction and the nature of the electronic motion in extended states near the mobility edges is discussed. The latter is likened to Brownian motion within certain limitations. Finally, the Anderson transition is discussed within the present models.
Morrel H. Cohen. Review of the theory of amorphous semiconductors. JOURNAL OF NON-CRYSTALLINE SOLIDS 4 (1970) 391409 © North-Holland Publishing Co., Amsterdam
5mjmp 19:38, 24 September 2009 (UTC)
 States in the gap and recombination in amorphous semiconductors 1975
Abstract: The paper examines states in the gap in amorphous silicon and chalcogenides and their effect on photoconductivity, luminescence and drift mobility. It is supposed that carriers in an ' ideal ' glassy semiconductor without defects would move by hopping at the band edge at low temperatures and by excitation to a mobility edge at high temperatures, and that the carriers do not form polarons; the results of Spear and co-workers (e.g. Spear 1974 a) for glow-discharge-deposited silicon and of Nagels, Callearts and Denayer (1974) for quenched As,Te, containing silicon are considered. The effectively zero value of the Hall coefficient in the hopping regime is discussed. States in the gap are supposed to be due to dangling bonds which may form pairs at divacancies; if the concentration is high, these may have a predominating effect on the conductivity and in this case polaron-type hopping could occur, both for chalcogenides and for silicon. For the chalcogenides (in contrast to silicon), it is proposed, adapting a model due to Anderson (1975), that all dangling bonds are positively or negatively charged due to a large distortion energy associated with the former state; the absence of Curie paramagnetism and variable-range hopping is thereby explained; a.c. conductivity is also discussed. The reason why chalcogenides differ in this respect from silicon and germanium lies in the differing natures of the upper parts of the valence bands, which in the former case arise from non-bonding lone-pair states. It is suggested that the same conclusions may be valid for oxide glasses. The recombination mechanisms active in photoconduction and photoluminescence are described; for non-radiative transitions we use a method due to Englman and Jortner (1970). It is emphasized that hydrogen can greatly accelerate multiphonon recombination.
Mott, N. F., Davis, E. A. and Street, R. A.(1975)'States in the gap and recombination in amorphous semiconductors',Philosophical Magazine,32:5,961 — 996. http://www.informaworld.com/smpp/19646066-11127800/content~db=all~content=a752754170
5mjmp 20:33, 16 September 2009 (UTC)
09_09_08_States in the gap and recombination in amorphous semiconductors.pdf
 Amorphous Semiconductor Superlattice 1983
Amorphous Semiconductor Superlattice. B. Abeles and T. Tiedje. Physical Review Letters. Vol 51, Num 21. (Nov 21, 1983)
5mjmp 19:09, 16 September 2009 (UTC)
09_09_16_Amorphous Semiconductor superlattices.pdf
 A Hybrid Amorphous Silicon Photovoltaic and Thermal Solar Collector 1985
a-Si amorphous silicon photovoltaic was used. The cells were deposited on glass panels which were attached to fins and a tube aluminum heat-exchange plate. Results showed that PV/T is possible.
The cells were produced commerically by Chronar Corporation. It made up of window glass, transparent tin oxide, p-i-n amorphous silicon and evaporated aluminum as the back layer. About 29% of the incident light is reflected back from the aluminum layer. Absorbtion is limited by the amorphous siliocn layer properties.
Two suggestions to improve the thermal performance, tin oxide layer could be textured causing the light to scatter and therefore increase the absorbtion of the amorphous layers. Or change the aluminum back electrode to indium tin oxide (ITO) which above 0.5 micrometers of the solar spectrum is transparent which would allow light to be absorbed by the heat exchange plate.
Results show that below 80 C for a short-circuit current is indpendent of temperature. At 80 C the power is reduced by about 15%. Due to Staebler-Wronski effect amorphous silicon is subject to degradation.
The efficiency of the cells is 4% and the thermal effeciency is 40%. At present best amorphous silicon has effeciencies of 8% but with multijunction they could reach 18%.
Solar Cells, 19 (1986 - 1987) 131 - 138. A HYBRID AMORPHOUS SILICON PHOTOVOLTAIC AND THERMAL SOLAR COLLECTOR. BRANISLAV LALOVIC. http://scholarsportal.info/science?_volkey=03796787%2319%23131%232
5mjmp 14:41, 3 June 2009 (UTC)
 A hybrid amorphous silicon photovoltaic and thermal solar collector 1987
Abstract: A hybrid amorphous silicon (a-Si) photovoltaic and thermal solar collector was developed and its performance tested. The solar cells, deposited on glass panels and having an average efficiency of 4% and a total area of 0.9 m 2, were bonded to the fin and tube aluminum heat-exchange plate using simple technology. This hybrid unit performed well as a thermal solar collector, heating water up to 65 °C, while the electric characteristics of the photovoltaic modules showed little change. In addition to saving space this integral unit substantially reduces the balance-of-system cost of the photovoltaic generator. The transmission of light through various layers of an a-Si cell was measured and, in order to improve the thermal efficiency, a novel transparent type of a-Si cell was developed and tested in the hybrid unit. The results obtained show that it is possible to construct simple and cheap hybrid systems having good photovoltaic as well as thermal efficiencies.
A hybrid amorphous silicon photovoltaic and thermal solar collector. B. Lalovic. Solar Cells, 19 (1986 - 1987) 131 - 138
Solar cells [0379-6787] Lalovic yr.1986 vol.19 iss.2 pg.131 http://sfx.scholarsportal.info/queens?sid=google&auinit=B&aulast=Lalovic&atitle=A+hybrid+amorphous+silicon+photovoltaic+and+thermal+solar+collector.&title=Solar+cells&volume=19&issue=2&date=1986&spage=131&issn=0379-6787
5mjmp 16:35, 16 September 2009 (UTC)
09_09_16_A hybrid amorphous silicon photovoltaic and thermal solar collector.pdf
 Amorphous Silicon Solar Cells 1989
IEEE Transactions on Electron Devices, Vol. 36, No. 12, December 1989. Amorphous Silicon Solar Cells. D Carlson. http://journals1.scholarsportal.info/tmp/7354344535286973519.pdf
09_09_24_Amorphous Silicon Solar Cells
5mjmp 19:35, 24 September 2009 (UTC)
 High-Efficiency a-Si/c-Si Heterojunction Solar Cell 1994
This article explains a bit about how HIT (Heterojunction with Intrinsic Thin-layer) are made and their efficiency and properties. They have a low backward current density of 10 − 8A / cm2. They have an intrinsic efficiency of 14.8% when the intrinsic layer is ~50 Armstrons. Simple structure and low temperature manufacturing (200 C)and simultaneous realization of surface passivation & p-n junction. The article states that these cells would have potential in the future.
0 1994 IEEE. New Materials Research Center, Sanyo Electric Co., Ltd. 1-1 8-13, Hashiridani, Hirakata, Osaka 573, Japan. HIGH-EFFICIENCY a-Si/c-Si HETEROJUNCTION SOLAR CELL. Toru Sawada, Norihiro Terada, Sadaji Tsuge, Toshiaki Baba, Tsuyoshi Takahama, Kenichiro Wakisaka, Shinya Tsuda and Shoichi Nakano. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=519952
5mjmp 17:07, 9 June 2009 (UTC)
 Model calculations on a flat-plate solar heat collector with integrated solar cells 1995
Abstract: detailed physical model of a hybrid photovoltaic/thermal system is proposed, and algorithms for making quantitative predictions regarding the performance of the system are presented. The motivation for the present work is that solar cells act as good heat collectors and are fairly good selective absorbers. Additionally, most solar cells increase their efficiency when heat is drawn from the cells. The model is based on an analysis of energy transfers due to conduction, convection and radiation and predicts the amount of heat that can be drawn from the system as well as the (temperature-dependent) power output. Special emphasis is laid on the dependence of the fin width to tube diameter ratio. We attribute values to the model parameters, and show that hybrid devices are interesting concerning system efficiency as is also confirmed by previous experiments. Possible applications of such systems are also proposed.
Model calculations on a flat-plate solar heat collector with integrated solar cells. TROND BERGENE and OLE MARTIN LOVVIK. Solar Energy Vol. 55, No. 6, pp. 453-462, 1995
5mjmp 17:32, 16 September 2009 (UTC)
09_09_16_Model calculations on a flat-plate solar heat collector with integrated solar cells.pdf
 Thermal recovery effect on light-induced degradation of amorphous silicon solar module under the sunlight 1997
Abstract: The thermal recovery effect from the light-induced degradation under the sunlight is experimentally investigated on the amorphous silicon photovoltaic module (a-Si PV module) for installing directly to the roof flames of wooden houses. To enhance the recovery effect, the heat-insulating material is attached to the back side of the module for increasing the module temperature under the sunlight: the heat-insulated module. The generated power from the heat-insulated module is compared with that from the normal module (without the heat-insulating material) for 2 yr, and it has been cleared that the generated power normalized at 25°C from the heat-insulated module is approximately 7.3% higher than that from the normal one with the average temperature increase of 4.2°C under the sunlight.
Thermal recovery effect on light-induced degradation of amorphous silicon solar module under the sunlight. T. Yamawaki, S. Mizukami, A. Yamazaki and H. Takahashi. Solar Energy Materials and Solar Cells 47 (1997) 125-134
5mjmp 16:45, 16 September 2009 (UTC)
09_09_16_Solar Energy Materials and Solar Cells.pdf
 Optimization of hydrogenated amorphous silicon p–i–n solar cells with two-step i layers guided by real-time spectroscopic ellipse 1998
Abstract: Hydrogenated amorphous silicon ~a-Si:H! p–i–n solar cell performance has been optimized using a two-step i-layer growth process. This effort has been guided by real-time spectroscopic ellipsometry ~RTSE! studies of the nucleation and growth of a-Si:H films by plasma-enhanced chemical vapor deposition at 200 °C using a variable H2-dilution gas flow ratio R5@H2#/@SiH4#. RTSE studies during film growth with R.15 reveal a transition from the amorphous to microcrystalline (a!mc) phase at a critical thickness that decreases with increasing R. From such results, the optimum two-step process was designed such that the initial stage of the i layer ~;200 Å! is deposited at much higher R than the bulk to ensure that the film remains within the amorphous side of the a!mc phase boundary, yet as close as possible to this boundary at low i-layer thicknesses.
Joohyun Koh, Yeeheng Lee, H. Fujiwara, C. R. Wronski, and R. W. Collins. Optimization of hydrogenated amorphous silicon p–i–n solar cells with two-step i layers guided by real-time spectroscopic ellipse. APPLIED PHYSICS LETTERS VOLUME 73, NUMBER 11 14 SEPTEMBER 1998
5mjmp 19:20, 24 September 2009 (UTC)
 Structural, defect, and device behavior of hydrogenated amorphous Si near and above the onset of microcrystallinity 1999
Abstract: High-hydrogen-diluted films of hydrogenated amorphous Si ~a-Si:H! 0.5 mm in thickness and optimized for solar cell efficiency and stability, are found to be partially microcrystalline (mc) if deposited directly on stainless steel ~SS! substrates but are fully amorphous if a thin n layer of a-Si:H or mc-Si:H is first deposited on the SS. In these latter cases, partial microcrystallinity develops as the films are grown thicker ~1.5–2.5 mm! and this is accompanied by sharp drops in solar cell open circuit voltage. For the fully amorphous films, x-ray diffraction ~XRD! shows improved medium-range order compared to undiluted films and this correlates with better light stability. Capacitance profiling shows a decrease in deep defect density as growth proceeds further from the substrate, consistent with the XRD evidence of improved order for thicker films.
S. Guha, J. Yang, D. L. Williamson, Y. Lubianiker, J. D. Cohen and A. H. Mahan. Structural, defect, and device behavior of hydrogenated amorphous Si near and above the onset of microcrystallinity. APPLIED PHYSICS LETTERS VOLUME 74, NUMBER 13 29 MARCH 1999
5mjmp 19:16, 24 September 2009 (UTC)
 Combined thermal and optical analysis of laser back-scribing for amorphous-silicon photovoltaic cells processing 1999
Abstract: The numerical and experimental analysis of laser back!scribing fabrication of a!Si photovoltaic cells\ made out of a multilayer thin _lm on a glass substrate\ is carried out[ The numerical study is performed by means of a rather simple combined optical and thermal model[ Experiments are carried out throughout the three phases of the manufacturing process[ The successive targets of the selective cut are a transparent conductive oxide thin _lm "TCO#\ a TCO:a!Si double layer and a TCO:a!Si:Al multilayer[ Experimental results and predictions from the numerical model are compared in terms of the cut energy ~ux values[ In the numerical study the cut energy ~ux is assumed to be the one which determines the melting of the material[ The predicted cut energy ~uxes are in good agreement with experimental results[
Combined thermal and optical analysis of laser back-scribing for amorphous-silicon photovoltaic cells processing. S. Avagliano, N. Bianco, O. Manca and V. Naso. International Journal of Heat and Mass Transfer 42 (1999) 645-656.
5mjmp 19:50, 16 September 2009 (UTC)
09_09_16_Combined thermal and optical analysis of laser back-scribing for amorphous-silicon photovoltaic cells processing.pdf
 Performance evaluation of solar photovoltaic/thermal systems 2001
Abstract: The major purpose of the present study is to understand the performance of an integrated photovoltaic and thermal solar system (IPVTS) as compared to a conventional solar water heater and to demonstrate the idea of an IPVTS design. A commercial polycrystalline PV module is used for making a PV/T collector. The PV/T collector is used to build an IPVTS. The test results show that the solar PV/T collector made from a corrugated polycarbonate panel can obtain a good thermal efficiency. The present study introduces the concept of primary-energy saving efficiency for the evaluation of a PV/T system. The primary-energy saving efficiency of the present IPVTS exceeds 0.60. This is higher than for a pure solar hot water heater or a pure PV system. The characteristic daily efficiency h* reaches 0.38 which is about 76% of s the value for a conventional solar hot water heater using glazed collectors (h* 50.50). The performance of a s PV/T collector can be improved if the heat-collecting plate, the PV cells and the glass cover are directly packed together to form a glazed collector. The manufacturing cost of the PV/T collector and the system cost of the IPVTS can also be reduced. The present study shows that the idea of IPVTS is economically feasible too.
Performance evaluation of solar photovoltaic/thermal systems. B.J. Huang, T.H.Lin, W.C. Hung and F. S. Sun. Solar Energy Vol. 70, No. 5, pp. 443–448, 2001 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V50-42G6KWJ-6&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1014104122&_rerunOrigin=scholar.google&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=47d291fbdd56427b1bb44d5fae32146d
5mjmp 16:30, 16 September 2009 (UTC) 09_09_16_Performance evaluation of solar photovoltaic-thermal systems.pdf
 Amorphous Silicon Alloy Solar Cells Near the Threshold of Amorphous-to-Microcrystalline Transition 2000
Abstract: A systematic study has been made of amorphous silicon (a-Si) alloy solar cells using various hydrogen dilutions during the growth of the intrinsic (i) layer. We find that the opencircuit voltage (Voc) of the cells increases as the dilution increases; it then reaches a maximum before it decreases dramatically. This sudden drop in Voc is attributed to the transition from amorphous silicon to microcrystalline inclusions in the i layer. We study i-layer thicknesses ranging from 1000 Å to 5000 Å and find that the transition occurs in all thicknesses investigated. Based on this study, a-Si alloy p i n solar cells suitable for use in the top cell of a high efficiency triple-junction structure are made. By selecting an appropriate dilution, cells with Voc greater than 1 V can be achieved readily. Solar cells made near the threshold not only exhibit higher initial characteristics but also better stability against light soaking. We have compared top cells made near the threshold with our previous best data, and found that both the initial and stable efficiencies are superior for the near-threshold cells. For an a-Si/a-Si double-junction device, a Voc value exceeding 2 V has been obtained using thin component cells. Thicker component cells give rise to an initial active-area efficiency of 11.9% for this tandem structure.
Member Price: $0; Non-Member Price: $25.00 Track ID: Paper #: A15.4 DOI:
5mjmp 19:00, 24 September 2009 (UTC)
 PROGRESS IN AMORPHOUS SILICON BASED SOLAR CELL TECHNOLOGY 2002
Abstract: As the negative environmental effects of the current use of non-renewable energy sources have become apparent, hydrogenated amorphous silicon (a-Si:H) solar cell technology has advanced to provide a means of powering a future sustainable society. Over the last 25 years, a-Si:H solar cell technology has matured to a stage where there is currently a production of 30 MWpeak/year; and this production capacity continues to increase. The progress is due to the continuous advances made in new materials, cell designs, and large area deposition techniques for mass production. The absence of long-range order result in not only characteristics which make a-Si:H excellent for thin film solar cells, but also provide great flexibility in the design of different solar cell structures and in the manufacturing of large area monolithic modules. A review is presented here of the progress in the development of a- Si:H based materials as well as the evolution of solar cell structures which led to the continuous improvement in their performance and stability.
Several hours at temperatures greater than 150 C will anneal defects out.
Hydrogen key role in eliminating the defects
"The quality of the a-Si based materials is determined by deposition parameters such as: substrate temperature, pressure, flow rate of the source gases, plasma frequency, power, electrode spacing, and dilution of the feedstock gases with hydrogen." -paper
"Such phase diagrams identify four separate growth regimes: 1) a-Si:H with a smooth surface and a stable roughness layer thickness, 2) a-Si:H with a rougher surface and an unstable roughness layer thickness, 3) mixed phase (a+c)-Si:H, and 4) fully coalesced (single phase) c-Si:H.Such phase diagrams identify four separate growth regimes: 1) a-Si:H with a smooth surface and a stable roughness layer thickness, 2) a-Si:H with a rougher surface and an unstable roughness layer thickness, 3) mixed phase (a+c)-Si:H, and 4) fully coalesced (single phase) c-Si:H."
" The challenge was to maximize the thickness of the i-layers for absorption of sunlight without loss in the ability to efficiently collect carriers so as to obtain fill factors. The acceptable thicknesses of such high performance cells were further limited by the SWE because of the decrease in carrier collection caused by light induced defects which leads to degradation of the FF. " -Paper
C. R. Wronski, J. M. Pearce, R. J. Koval, A. S. Ferlauto and R. W. Collins. PROGRESS IN AMORPHOUS SILICON BASED SOLAR CELL TECHNOLOGY. RIO 02 - World Climate & Energy Event, January 6-11, 2002
5mjmp 19:04, 24 September 2009 (UTC)
 A photovoltaic/thermal (PV/T) collector with a polymer absorber plate. Experimental study and analytical model 2002
Abstract: A polymer solar heat collector was combined with single-crystal silicon PV cells in a hybrid energy-generating unit that simultaneously produced low temperature heat and electricity. The PV/T unit was tested experimentally to determine its thermal and photovoltaic performance, in addition to the interaction mechanisms between the PV and thermal energy systems. Thermal efficiency measurements for different collector configurations are compared, and PV performance and temperature readings are presented and discussed. An analytical model for the PV/T system simulated the temperature development and the performance of both the thermal and photovoltaic units.
Solar panels brittle and therefore silicon was used to glue panels to solar thermal system
Angle of incident affects absorbtion since greater angle, greater
"A combined thermal and photovoltaic solar energy collector was successfully constructed by pasting single-crystal silicon cells onto a black, plastic, heat absorber. The adhesive was sufficiently elastic to absorb the difference in thermal expansion between the cells and the absorber.
A comparison of the PV/T absorber to a pure thermal absorber showed reduced thermal efficiency for the PV/T system which was attributed to:
• available solar energy for the thermal system reduced by the fraction of the incident energy converted to electricity by the PV cells;
• a lower optical absorption in the photovoltaic cells compared to the black absorber plate;
• increased heat transfer resistance introduced in the cell/absorber interface.
The PV/T system can on the other hand reduce heat loss from the collector as the solar cells act as selective absorbers. Heat loss was further reduced by an additional cover glass while at the same time increasing reflective losses.
Cooling of the PV cells was achieved by low-temperature operation of the heat collector which resulted in improved PV efficiency. The solar cell temperature correlated strongly to the system (inlet fluid) temperature and also to the collectors’ heat transport characteristics. The combined PV/T concept must therefore be associated with applications of sufficiently low temperature to give the desired cooling effect.
An analytical model of the PV/T system simulated the temperature development of the system, and photovoltaic and thermal performance. The simulation results were in agreement with the experimental data." - Paper
A PHOTOVOLTAIC/THERMAL (PV/T) COLLECTOR WITH A POLYMER ABSORBER PLATE. EXPERIMENTAL STUDY AND ANALYTICAL MODEL. BJØRNAR SANDNES and JOHN REKSTAD. Solar Energy Vol. 72, No. 1, pp. 63–73, 2002
5mjmp 16:43, 16 September 2009 (UTC)
09_09_16_A photovoltaic-thermal (PV-T) collector with a polymer absorber plate. Experimental study and analytical model.pdf
 Development of an approach to compare the ‘value’of electrical and thermal output from a domestic PV/thermal system 2003
Abstract: When considering the design of a PV/thermal system, determination of the ratio of the values of the electrical and thermal output from the system allows a rational approach to design optimisation via the minimization of ‘equivalent electrical levelised energy cost’. This paper focuses on methods that can be employed to develop a ratio between electrical and thermal output from a domestic style PV/thermal system. Methods discussed include thermodynamic analysis using exergy; market analysis for both an open market and a renewable energy market; and environmental analysis using avoided greenhouse gas emissions. Ratios are developed for each method based on real data. It is concluded that a renewable energy market approach seems most logical for such a system, and an indicative value of 4.24 is obtained. An example is given comparing a PV/thermal system that uses amorphous silicon cells with one that uses crystalline silicon cells. Levelised energy cost is plotted against the energy value ratio to show that there is a critical electrical-to-thermal energy value ratio below which a collector with a-Si cells is more cost effective than one with c-Si cells.
Talks in depth about Exergy as a way of comparing PV/T systems. Also want to look at market based methodology (levelised energy costs of both PV and thermal systems) and evironmental (greenhouse gass intensity gas intensity of conventional PV and thermal systems).
"Exergy (sometimes called availability) is defined as the maximum theoretical useful work obtainable from a system as it returns to equilibrium with the environment." -paper
Electricity --> = m(h2-h1) where m is the mass flow rate and h is specific enthalpy.
Theraml --> = m(h2-h1-T0(s2-s1) where s is the specific entropy and T0 is the environmental temperature.
Section 4.2 of the paper talks about life cyle emmissions and has a simple equation for teh ratio of electrical to thermal CO2 emissions based of a life cycle analysis.
"a-Si may have positive temperature coefficient for their stable efficiency due to a reduction in the solar degradation at higher temperatures over the long term." - paper
D evelopment of an approach to compare the ‘value’ of electrical and thermal output from a domestic PV/thermal system. J.S. Coventry and K. Lovegrove. Solar Energy 75 (2003) 63–72
Solar energy [0038-092X] Coventry yr.2003 vol.75 iss.1 pg.63 http://sfx.scholarsportal.info/queens?sid=google&auinit=JS&aulast=Coventry&atitle=Development+of+an+approach+to+compare+the+%E2%80%98value%E2%80%99of+electrical+and+thermal+output+from+a+domestic+PV/thermal+system&id=doi:10.1016/S0038-092X(03)00231-7&title=Solar+energy&volume=75&issue=1&date=2003&spage=63&issn=0038-092X
5mjmp 16:39, 16 September 2009 (UTC)
09_09_16_Development of an approach to compare the ‘value’of electrical and thermal output from a domestic PV-thermal system.pdf
Abstract: The influence ofthe operation temperature on the output properties ofsolar cells with hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous silicon germanium (a-SiGe:H) photovoltaic layers was investigated. The output power after longtime operation of an a-Si:H single junction, an a-Si:H/a-Si:H tandem, and an a-Si:H/a-SiGe:H tandem solar cell was calculated based on the experimental results oftwo types oftemperature dependence for both conversion efficiency and light-induced degradation. It was found that the a-Si:H/a- SiGe:H tandem solar cell maintained a higher output power than the others even after longtime operation during which a temperature range of25 �C to 80�C. These results confirm the advantages ofthe a-Si:H/a-SiGe:H tandem solar cell for practical use, especially in hightemperature regions.
In this paper they test the solar degradation (light-soaked) at temperatures between 25-80 C. It was found that at 80 C the degradation was faster at first but then remained constant at a higher normalized power output. This was for a-Si. GOOD COMPARISON FOR WHEN USING DEGRADATION STATION...
The influence ofoperation temperature on the output properties ofamorphous silicon-related solar cells. M. Shima, M. Isomura, K. Wakisaka, K. Murata and M. Tanaka. Solar Energy Materials & Solar Cells 85 (2005) 167–175
5mjmp 19:17, 16 September 2009 (UTC)
09_09_16_The influence of operation temperature on the output properties of amorphous silicon-related solar cells.pdf
 The Effect of Cell Thickness on Energy Production of Amorphous Silicon Solar Cells 2005
Abstract: Solar cells are currently evaluated under laboratory conditions and not under realistic operating conditions. Amorphous silicon (a-Si) devices exhibit a complicated dependence on operating conditions, with a major concern being the degradation of these devices in realistic operation. Optimising these devices for energy production of the stabilised state is dependent on many factors, with one of the main inputs being the overall thickness of the cell. In this paper, the effect of intrinsic layer (i-layer) thickness on the cell performance, the degradation and also the energy production under realistic conditions are investigated. It is apparent from the experiment that there has to be an optimisation of the i-layer thickness to maximise the light absorption and minimise the degradation, if higher performance and energy production is to be achieved.
- tested different thickness cells outside in "real" conditions
- monitored weather conditions every ten min
- found that thicker samples have higher initial I</sub>SC and efficiency
- thicker degrade more
- "Fantoni et al. (2002) reported a similar decrease in FF decreases with increasing thickness, making this a more general feature." - paper
- The paper has some degradation curve graphs plotting the results.
P. Vorasayan, T.R. Betts, R. Gottschalg, D.G. Infield and A.N. Tiwari. The Effect of Cell Thickness on Energy Production of Amorphous Silicon Solar Cells.
09_09_24_The Effect of Cell Thickness on Energy Production of Amorphous Silicon Solar Cell
5mjmp 18:57, 24 September 2009 (UTC)
 Amorphous-Silicon Photovoltaic-Thermal Solar Collector in Thailand 2005
This article talks about the use of a-silicon PV on aluminum absorber plate. The a-silicon panels absorb the visible light while the absorber collects the infrared. The collant is water which flows beneath the plate in coper tubes. The article explans that several locations have these systems to produce electricity and hot water. A 48 m^2 PVT produced 2.7 kW of electricity and 2500 litres of hot water. The performance of these systems was monitored by AHSRAE (93-77). The PV is stuck onto the plate by thermally expoxy.
5mjmp 17:49, 7 September 2009 (UTC)
09_06_16_Amorphous-Silicon Photovoltaic-Thermal Solar Collector in Thailand
National Science and Technology Development Agency,111 Paholyothin Rd., Klong 1, Klong Loung, Pathumtan i, 12120, Thailand E-Mail: email@example.com, firstname.lastname@example.org, email@example.com. Amorphous-Silicon Photovoltaic/Thermal Solar Collector in Thailand. Sirimongkhol Jaikla, Thipjak Nualboonrueng and Porponth Sichanutgrist. http://www.aseanenergy.info/search%20for%20energy-based/result_abstract.asp http://www.energy-based.nrct.go.th/Article/Ts-3%20amorphous-silicon%20photovoltaicthermal%20solar%20collector%20in%20thailand.pdf
5mjmp 18:59, 16 June 2009 (UTC)
 Hybrid PV/T solar systems for domestic hot water and electricity production 2006
Abstract: Hybrid photovoltaic/thermal (PV/T) solar systems can simultaneously provide electricity and heat, achieving a higher conversion rate of the absorbed solar radiation than standard PV modules. When properly designed, PV/T systems can extract heat from PV modules, heating water or air to reduce the operating temperature of the PV modules and keep the electrical efficiency at a sufficient level. In this paper, we present TRNSYS simulation results for hybrid PV/T solar systems for domestic hot water applications both passive (thermosyphonic) and active. Prototype models made from polycrystalline silicon (pc-Si) and amorphous silicon (a-Si) PV module types combined with water heat extraction units were tested with respect to their electrical and thermal efficiencies, and their performance characteristics were evaluated. The TRNSYS simulation results are based on these PV/T systems and were performed for three locations at different latitudes, Nicosia (35�), Athens (38�) and Madison (43�). In this study, we considered a domestic thermosyphonic system and a larger active system suitable for a block of flats or for small office buildings. The results show that a considerable amount of thermal and electrical energy is produced by the PV/T systems, and the economic viability of the systems is improved. Thus, the PVs have better chances of success especially when both electricity and hot water is required as in domestic applications.
Hybrid PV/T solar systems for domestic hot water and electricity production. S.A. Kalogirou and Y. Tripanagnostopoulos. Energy Conversion and Management 47 (2006) 3368–3382. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2P-4JJ2BCK-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1049597492&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=7147a09cec5b6da5c86f4d6b7c084ba5
 Hybrid photovoltaic and thermal solar-collector designed for natural circulation of water 2006
Abstract: The electricity conversion-efficiency of a solar cell for commercial application is about 6– 15%. More than 85% of the incoming solar energy is either reflected or absorbed as heat energy. Consequently, the working temperature of the solar cells increases considerably after prolonged operations and the cell�s efficiency drops significantly. The hybrid photovoltaic and thermal (PVT) collector technology using water as the coolant has been seen as a solution for improving the energy performance. Through good thermal-contact between the thermal absorber and the PV module, both the electrical efficiency and the thermal efficiency can be raised. Fin performance of the heat exchanger is one crucial factor in achieving a high overall energy yield. In this paper, the design developments of the PVT collectors are briefly reviewed. Our observation is that very few studies have been done on the PVT system adopting a flat-box absorber design. Accordingly, an aluminum-alloy flat-box type hybrid solar collector functioned as a thermosyphon system was constructed. While the system efficiencies did vary with the operating conditions, the test results indicated that the daily thermal efficiency could reach around 40% when the initial water-temperature in the system is the same as the daily mean ambient temperature.
Hybrid photovoltaic and thermal solar-collector designed for natural circulation of water. W. He, T.T. Chow, J. Ji, J. Lu, G. Pei and L. Chan. Applied Energy 83 (2006) 199–210
5mjmp 18:27, 16 September 2009 (UTC)
09_09_16_Hybrid photovoltaic and thermal solar-collector designed for natural circulation of water.pdf
 Aspects and improvements of hybrid photovoltaic/thermal solar energy systems 2007
Abstract: Hybrid photovoltaic/thermal (PV/T or PVT) solar systems consist of PV modules coupled to water or air heat extraction devices, which convert the absorbed solar radiation into electricity and heat. At the University of Patras, an extended research on PV/T systems has been performed aiming at the study of several modifications for system performance improvement. In this paper a new type of PV/T collector with dual heat extraction operation, either with water or with air circulation is presented. This system is simple and suitable for building integration, providing hot water or air depending on the season and the thermal needs of the building. Experiments with dual type PV/T models of alternative arrangement of the water and the air heat exchanging elements were performed. The most effective design was further studied, applying to it low cost modifications for the air heat extraction improvement. These modifications include a thin metallic sheet placed in the middle of the air channel, the mounting of fins on the opposite wall to PV rear surface of the air channel and the placement of the sheet combined with small ribs on the opposite air channel wall. The modified dual PV/T collectors were combined with booster diffuse reflectors, achieving a significant increase in system thermal and electrical energy output. The improved PV/T systems have aesthetic and energy advantages and could be used instead of separate installation of plain PV modules and thermal collectors, mainly if the available building surface is limited and the thermal needs are associated with low temperature water or air heating.
PVT/water useful for water heating but don't lower price of system. Have more limitations: " This is due to the necessary heat exchanger element, which should have good thermal contact with PV rear surface, while in PVT/air systems the air is heated directly from the front or/and the back surface of PV modules. But on the other hand the air heat extraction is less efficient than the water one, due to the low density of air and improvements are necessary to make PVT/air system efficient and attractive for real applications. In PV/T collectors the absorber element is less efficient compared to that of typical thermal collectors as it is of lower conductivity (glass or polymer substrate in PV modules) and also, there are limitations for PV module surface treatment to become selective in infrared emittance (low ε) and reducing heat radiation to operate effectively at higher temperatures." -Paper
PVT/dual (both air and water) for places that don't freeze... hopefully overcome limitations of water and air. Depending on the weater conditions water or air would be used as thee coolant. This system was designed and exerimentally tested and it was found to have a slightly higher efficiency than water or air. However, they are slightly more expensive.
Aspects and improvements of hybrid photovoltaic/thermal solar energy systems. Y. Tripanagnostopoulos. Solar Energy 81 (2007) 1117–1131
5mjmp 18:12, 16 September 2009 (UTC)
09_09_16_Aspects and improvements of hybrid photovoltaic-thermal solar energy systems.pdf
 Industrial application of PV/T solar energy systems 2007
Abstract: Hybrid photovoltaic/thermal (PV/T) systems consist of PV modules and heat extraction units mounted together. These systems can simultaneously provide electrical and thermal energy, thus achieving a higher energy conversion rate of the absorbed solar radiation than plain photovoltaics. Industries show high demand of energy for both heat and electricity and the hybrid PV/T systems could be used in order to meet this requirement. In this paper the application aspects in the industry of PV/T systems with water heat extraction is presented. The systems are analyzed with TRNSYS program for three locations Nicosia, Athens and Madison that are located at different latitudes. The system comprises 300 m2 of hybrid PV/T collectors producing both electricity and thermal energy and a 10 m3 water storage tank. The work includes the study of an industrial process heat system operated at two load supply temperatures of 60 �C and 80 �C. The results show that the electrical production of the system, employing polycrystalline solar cells, is more than the amorphous ones but the solar thermal contribution is slightly lower. A non-hybrid PV system produces about 25% more electrical energy but the present system covers also, depending on the location, a large percentage of the thermal energy requirement of the industry considered. The economic viability of the systems is proven, as positive life cycle savings are obtained in the case of hybrid systems and the savings are increased for higher load temperature applications. Additionally, although amorphous silicon panels are much less efficient than the polycrystalline ones, better economic figures are obtained due to their lower initial cost, i.e., they have better cost/benefit ratio.
This paper looks at the application of PVT systems in an industrial setting and comparing polycrystalline and amorphous silicon and the result is that the a-Si was better from a cost/benifit analysis stated in the paper.
Industrial application of PV/T solar energy systems. S.A. Kalogiru and Y. Tripanagnostopoulos. Applied Thermal Engineering 27 (2007) 1259–1270
5mjmp 18:05, 16 September 2009 (UTC)
09_09_16_Industrial application of PV-T solar energy systems.pdf
 A Comparison of Fill Factor and Recombination Losses in Amorphous Silicon Solar Cells on ZnO and SnO2 2007
It states that hydrogenated amorphous silicion p-i-n thin film most promising material since cheap. However solar degradation is a problem.
- low cost
- improve the conversion efficiency
- reduce radiation loss
- minimize resistance between p-layer and TCO
- plasma resistant
- 96-97% transmission
- Electrical performance poorer
- Tend to have low FF (fill factor) and VOC
- due to changes in the p/i junction recombination not contact
- low v (DC)
- Higher QM and modulated v
- chemically reduced by H or SiH4 plasma which causes a thin film of Sn to form lowering the transmission.
- Only 92-95% internal transmission over the visible spectrum
"Aim of the paper is to optimize the radiation and recombination losses by investigation two types of p-i-n solar cells which have the same a-si recipe and back contact ZnO and SnO2 TCO substrate materials." - paper
Renewable Energy 34 (2009) 1595–1599. A comparison of fill factor and recombination losses in amorphous silicon solar cells on ZnO and SnO2. A. Alkaya, R. Kaplan, H. Canbolat and S.S. Hegedus. http://scholarsportal.info/cgi-bin/sciserv.pl?collection=journals&journal=09601481&issue=v34i0006&article=1595_acoffascozas
5mjmp 15:15, 4 June 2009 (UTC)
 Determination of the thickness and optical constants of amorphous silicon 2008
Abstract: Over the last 30 years, a large amount of research on PV-Thermal (PVT) collectors has been carried out. An overview of this research is presented, both in terms of an historic overview of research projects and in the form of a thematic overview, addressing the different research issues for PVT.
This paper goes through the equations required to calculated the refractice index, absorbtion coefficient and the thickness of the sample using transmission spectrum data. These equations are simple enough to be used in a programmable calculator.
Flat-plate PV-Thermal collectors and systems: A review. H.A. Zondag. Renewable and Sustainable Energy Reviews 12 (2008) 891–959
5mjmp 19:03, 16 September 2009 (UTC)
09_09_16_Determination of the thickness and optical constants of amorphous silicon.pdf
 Energy metrics analysis of hybrid – photovoltaic (PV) modules 2009
Abstract: In this paper, energy metrics (energy pay back time, electricity production factor and life cycle conversion efficiency) of hybrid photovoltaic (PV) modules have been analyzed and presented for the composite climate of New Delhi, India. For this purpose, it is necessary to calculate (1) the energy consumption in making different components of the PV modules and (2) the annual energy (electrical and thermal) available from the hybrid-PV modules. A set of mathematical relations have been reformulated for computation of the energy metrics. The manufacturing energy, material production energy, energy use and distribution energy of the system have been taken into account, to determine the embodied energy for the hybrid-PV modules. The embodied energy and annual energy outputs have been used for evaluation of the energy metrics. For hybrid PV module, it has been observed that the EPBT gets significantly reduced by taking into account the increase in annual energy availability of the thermal energy in addition to the electrical energy. The values of EPF and LCCE of hybrid PV module become higher as expected.
Energy metrics analysis of hybrid – photovoltaic (PV) modules. A. Tiwari, P. Barnwal, G.S. Sandhu and M.S. Sodha. Applied Energy 86 (2009) 2615–2625
5mjmp 17:39, 16 September 2009 (UTC)
09_09_16_Energy metrics analysis of hybrid – photovoltaic (PV) mod.pdf
 Analysis of the temperature history of amorphous silicon photovoltaic module outdoors 2009
Abstract: Toanalyzetheeffectsofthemoduletemperatureandirradianceonphotovoltaic(PV)modulesoutdoors, contour graphsweremadefortheperformanceratio(PR)ofsingle-crystallineSi(sc-Si)andamorphous Si (a-Si)PVmodules.TheresultshowsthatthePRofthesc-SiPVmoduledecreaseswithincreasein module temperature.Incontrast,thePRofthea-SiPVmoduleshowsuniquetemperaturedependence influencedbytemperaturehistory.DependenceofenvironmentalfactorsofthePRofthea-SiPVmodule wasanalyzedinalmostthesametemperatureseasons,i.e.,SpringandFall.ThePRinFallwashigher than thatinSpring.TheresultshowsthattherecoveredperformanceinsummermaycontinueforFall. The contourgraphofremainderofPRinFallandSpringwasmade.Theenvironmentalconditionthat the PRinFallwashigherwasclarified.
Analysisofthetemperaturehistoryofamorphoussiliconphotovoltaic module outdoors. S. Fukushige, K. Ichida, T. Minemoto and H. Takura. Solar Energy Materials & Solar Cells 93(2009)926–931
5mjmp 19:21, 16 September 2009 (UTC)
09_09_16_Analysis of the temperature history of amorphous silicon photovoltaic module outdoors.pdf
 UofT Amorphous Silicon Papers
Note: Stefan Zukotynski is a retired professor.
 An effective-mass model of hydrogenated amorphous silicon: A tail state analysis 1992
Abstract:An effective-mass model of hydrogenated amorphous silicon (a-Si:H) is proposed. This model focuses upon the impact of hydrogen on the electronic structure of the tail states. Tail state density-of-states calculations are performed in the high hydrogen concentration limit, and the results are found to be in general agreement with present experimental data. These results are shown to be quite robust to variations in the modeling parameters.
Stephen K. O'Leary and Stefan Zukotynski, John M. Perz. J. Appl. Phys. 72, 2272 (1992); doi:10.1063/1.351568. An effective-mass model of hydrogenated amorphous silicon: A tail state analysis. http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JAPIAU000072000006002272000001&idtype=cvips&gifs=yes
10_01_19_An effective-mass model of hydrogenated amorphous silicon A tail state analysis
 Hydrogen-induced quantum confinement in amorphous silicon 1995
Abstract:We study how hydrogen-induced quantum confinement in hydrogenated amorphous silicon influences the distribution of tail states. To do this, the potential structure of this semiconductor is treated as being comprised of an ensemble of potential wells, these wells corresponding to unhydrogenated regions enveloped by hydrogenated regions. To evaluate the distribution of states, we determine the ground state associated with each well, and then average over the distribution of wells. We find that our calculated distribution of tail states exhibits an essentially exponential functional dependence, over several decades, and that this tail of states shifts toward the band edge as the hydrogen content is increased. This shift toward the band edge is suggested to be one of the factors responsible for the observed increase in energy gap with higher hydrogen content.
Stephen K. O'Leary and Stefan Zukotynski, John M. Perz. Hydrogen-induced quantum confinement in amorphous silicon. J. Appl. Phys. 78, 4282 (1995); doi:10.1063/1.359828. http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JAPIAU000078000006004282000001&idtype=cvips&gifs=yes
10_01_19_Hydrogen-induced quantum confinement in amorphous silicon
 Optical absorption in amorphous semiconductors 1995
Abstract:We use the joint density-of-states function to study the optical-absorption spectrum of amorphous semiconductors. To determine the overall joint density of states, we average a local joint density of states over spatially correlated Gaussian distributions of conduction-band and valence-band potential fluctuations. Our results span the transition from below to above the energy gap and both analytical and numerical results are obtained. Spatial correlations are found to play a dramatic role in influencing the shape of the optical-absorption spectrum. We apply this formalism to the case of hydrogenated amorphous silicon and several other amorphous semiconductors of interest, and find that our results are consistent with those of experiment.
Stephen K. O’Leary and Stefan Zukotynski, John M. Perz. Phys. Rev. B 52, 7795–7797 http://prb.aps.org/abstract/PRB/v52/i11/p7795_1
10_01_19_Optical absorption in amorphous semiconductors.pdf
 Semiclassical density-of-states and optical-absorption analysis of amorphous semiconductors 1995
Abstract:A semiclassical analysis of amorphous semiconductors is presented. This analysis, cast within an effective-mass setting, provides for the overall density-of-states by averaging a local density-of-states over a distribution of potential fluctuations. Our density-of-states results span the transition from the tail states to the band states, and both analytical and numerical results are obtained. We then determine the functional form of the optical-absorption coefficient, and show that both subgap and Tauc absorption edges are captured within this analytical framework. Finally, we apply this formalism to the case of hydrogenated amorphous silicon, and find that our results are consistent with those of experiment.
Stephen K. O’Leary and Stefan Zukotynski,John M. Perz. Phys. Rev. B 51, 4143–4149. http://prb.aps.org/abstract/PRB/v51/i7/p4143_1
10_01_19_Semiclassical density-of-states and optical-absorption analysis of amorphous semiconductors.pdf
 RECOMBINATION IN TRITIATED AMORPHOUS SILICON 2000
Abstract:Tritiated amorphous silicon was used for the intrinsic layer of a p-i-n hydrogenated amorphous silicon diode. Current versus voltage measurements were carried out on the diode over time under dark and illuminated conditions. There was a decrease in the forward characteristic of the diode when measured under dark conditions and there was a decrease in photovoltaic power. These changes can be explained by the creation of dangling bonds when bonded tritium atoms decay. By annealing the diode at 125 °C, most of its photovoltaic properties could be recovered. It was also found that luminescence could be recovered in tritiated amorphous silicon by thermal annealing.
Tome Kosteski, Franco Gaspari, David Hum, Stefan Costea, Stefan Zukotynski, Nazir P. Kherani, and Walter T. Shmayda. Mat. Res. Soc. Symp. Proc. Vol. 609 © 2000 Materials Research Society.
10_01_14_RECOMBINATION IN TRITIATED AMORPHOUS SILICON.pdf
 1/f noise in p-type amorphous silicon 2000
Abstract:We have measured conductance fluctuations in four samples of p-type hydrogenated amorphous silicon, two doped at 10–4 and the other two at 5×10–2, at temperatures between 22 and 200 °C. The noise power density varies for the most part as 1/f in the frequency range 2 Hz to 1 kHz, although deviations from a strict power law are observed. In all samples, the magnitude of the noise trends higher with temperature typically increasing by a factor of 5 over the temperature range. also increases with temperature from near unity to over 1.4. The magnitude of the noise decreases as the Fermi level moves toward the valence band with increased doping. The dependence on doping and temperature is inconsistent with generation-recombination noise. Above 180 °C for the 10–4 doped samples, the noise fails to scale as the square of the bias current at low frequencies.
Robert E. Johanson and S. O. Kasap, Franco Gaspari, Davit Yeghikyan, and Stefan Zukotynski. J. Vac. Sci. Technol. A Volume 18, Issue 2, pp. 661-664. 1/f noise in p-type amorphous silicon. http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JVTAD6000018000002000661000001&idtype=cvips&gifs=yes
10_01_19_1 over f noise in p-type amorphous silicon
 Tritiated Amorphous Silicon Films and Devices 2001
It's a Thesis.
10_01_14_Tritiated Amorphous Silicon Films and Devices THESIS
 PROMOTING GRID-TIED SOLAR ELECTRICITY ON BUILDINGS IN CANADA 2003
Abstract:A recent study by the Photovoltaics and Hybrid Systems Program at CANMET Energy Technology Centre-Varennes examined the benefits of on-site generation of electricity using grid-tied photovoltaic technology on buildings in Canada. The study focused on the grid-connect segment of the PV market, which has been experiencing the strongest growth. It showed that while costs of PV worldwide have been falling at about 5% per year in real terms over the past twenty years following a well-established learning curve, there remain several barriers to be addressed before greater inroads can be made in this sector of photovoltaics in Canada. There are many challenges to grid-tied PV in Canada. CETC-Varennes has been addressing these challenges through their RD&D programactivities. These activities range from removing interconnection barriers to the grid, providing assistance to Canadian industry by championing climate change TEAM projects, accelerating the development of adequate policies, and providing quality information to Canadians. The outcomes of these efforts are elucidated in this paper. CETC-Varennes is committed to continuing building alliances with the private sector and with other federal, provincial and municipal levels of government to mainstream grid-tied PV in Canada. It will continue to seek out technology investment opportunities, such as those provided by TEAM, in order to share the RD&D risk and to demonstrate the benefits of linking private sector business strategies and technology capabilities with global business opportunities. PV projects show how GHG reduction and economic benefits can be achieved together, along with environmental and social co-benefits.
J. Ayoub, L. Dignard-Bailey, and W. Richardson. SESCI 2003 CONFERENCE. Queen’s University. Kingston, Ontario, Canada. August 18 to 20, 2003
10_01_14_PROMOTING GRID-TIED SOLAR ELECTRICITY ON BUILDINGS IN CANADA.pdf
 MODELING OF DC SADDLE FIELD PECVD USING THE DIRECT MONTE CARLO METHOD 2004
Abstract:Enhancements in rates of ionization, dissociation, and current in the DC saddle field (DCSF) glow discharge are studied using the direct Monte Carlo method (DMCM). The DCSF consists of a planar semitransparent anode positioned between two planar cathodes, producing a symmetric electric field that serves to lengthen the path of electrons. Simulations of current versus anode transparency of a N2 discharge agree very well with experimental results reported previously. Numerical results of the DCSF SiH4 discharge are also presented. At typical operating conditions (600V, 5cm cathode-anode spacing, anode transparency of 0.8), DMCM predicts a significant increase in the dissociation rate at pressures below 100mTorr in comparison to the DC diode. In consideration of its use for plasma enhanced chemical vapour deposition, the efficiency with which the DCSF operates at low pressures makes it attractive for the production of thin films whose qualities are sensitive to gas phase reactions.
Johnson Wong, Nazir P. Kherani, Stefan Zukotynski. Canadian Solar Buildings Conference. Montreal, August 20-24, 2004. Refereed Paper.
10_01_14_MODELING OF DC SADDLE FIELD PECVD USING
 Density of states in tritiated amorphous silicon obtained with the constant photocurrent method 2005
Abstract: The constant photocurrent method was implemented to determine the density of states in tritiated hydrogenated amorphous silicon below the Fermi level. The tritiated hydrogenated amorphous silicon samples were grown using a mixture of silane and tritium gases in the dc saddle-field deposition system. Over time the tritium incorporated in the amorphous silicon undergoes beta decay and transmutation into helium. The transmutation leads to an increase in the density of states in the energy gap of the material. These states are linked to silicon dangling-bond defects. Given its well-characterized decay process, tritium can be used as an experimental tool to study the behavior of hydrogenated amorphous silicon thin films as a function of their defect state density. The density-of-states information in this work indicates a dominant peak of doubly occupied dangling bonds (D–) positioned 1.24 eV below the conduction band. The defect density was monitored in time showing an increase of more than two orders of magnitude over a period of 20 days and a decrease of similar magnitude upon thermal annealing.
Simone Pisana,Stefan Costea, Tome Kosteski, Walter T. Shmayda,Nazir P. Kherani, and Stefan Zukotynski. JOURNAL OF APPLIED PHYSICS 98, 093705 2005
10_01_14_Density of states in tritiated amorphous silicon obtained with the constant photocurrent method.pdf
 Tritiation of amorphous and crystalline silicon using T2 gas 2006
Abstract:Incorporation of tritium in hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) at 250 °C using tritium (T2) gas at pressures of up to 120 atm is reported. The tritium is stored in a surface layer which is approximately 150 and 10 nm for a-Si:H and c-Si, respectively. The concentration of tritium occluded in planar and textured c-Si is linearly dependent on the total surface area. The tritium is stable and the dominant tritium evolution occurs at temperatures above 300 °C. The concentration of tritium locked in a-Si:H and c-Si was 20 and 4 at. %, respectively. Self-catalysis appears to be important in the tritiation process.
Baojun Liu and Kevin P. Chena,Nazir P. Kherani, Tome Kosteski, Stefan Costea, and Stefan Zukotynski, Armando B. Antoniazzi. APPLIED PHYSICS LETTERS 89, 044104 2006
10_01_14_Tritiation of amorphous and crystalline silicon using T2 gas
 Raman scattering characterization of SF-PECVD-grown hydrogenated microcrystalline silicon thin films using growth surface electrical bias 2006
Abstract:A series of hydrogenated microcrystalline films were grown by a novel thin film deposition method using the Saddle Field Plasma Enhanced Chemical Vapour Deposition system. We show that the surface potential during growth strongly affects the microcrystalline character of the films, as quantified by Raman scattering. This effect can be reproduced on both conductive and non-conductive substrates. Films grown close to the threshold for microcrystalline growth exhibit laser-induced crystallization at low laser intensities.
Erik V. Johnson Æ Nazir P. Kherani, Stefan Zukotynski. J Mater Sci: Mater Electron (2006) 17:801–813.
10_01_14_Raman scattering characterization of SF-PECVD-grown hydrogenated microcrystalline silicon thin films using growth surface electrical bias.pdf
 Density of States in Tritiated Amorphous Silicon Measured Using CPM
Abstract: The constant photocurrent method has been used to obtain the density of occupied electronic states of tritiated amorphous silicon thin films. The analyses showed a peak of defects located 1.24 eV below the conduction band edge, suggesting that the main type of defect present in the films was a doubly occupied dangling bond. The concentration of defect states increases as a result of tritium decay by about two orders of magnitude over a period of 500 hours. The defect density in the tritiated amorphous silicon samples could be reduced by thermal annealing, after which it increased once more.
Simone Pisana†, Stefan Costea, Tome Kosteski, Nazir P. Kherani, Stefan Zukotynski and Walter T. Shmayda
10_01_14_Density of States in Tritiated Amorphous Silicon Measured Using CPM
 Use of Tritium in the Study of Defects in Amorphous Silicon 2006
Abstract:Hydrogen is known to strongly affect the physical properties of amorphous semiconductors. Indeed hydrogen is introduced during the growth of amorphous silicon films, used in active matrix displays and solar cells, to passivate silicon dangling bonds and to relax the lattice thereby reducing the density of states in the energy gap by several orders of magnitude and giving rise to device grade material. Ideally, hydrogenated amorphous silicon (a-Si:H) is a continuous covalently bonded random network of silicon-silicon and silicon-hydrogen atoms, with the predominant nearest neighbour environment similar to that of crystalline silicon. a-Si:H typically contains about 10 atomic percent hydrogen.Tritium can readily substitute for hydrogen in a-Si:H without altering the physicochemical properties of the material. Tritium decay leads to a change in the local bond structure of the material as helium detaches from bonds leaving behind dangling bonds. The decay rate of tritium and therefore the rate of dangling bond formation is determined by the half-life of tritium. Hence, tritium provides a unique avenue to dynamically study the effect of dangling bonds on the density of states in the energy gap and therefore on the optoelectronic properties of a-Si:H. Tritiated hydrogenated amorphous silicon (a-Si:H:T) was deposited using mixtures of tritium and silane gases in a dc saddle-field glow-discharge deposition system. The amount of tritium in the films was controlled by adjusting the relative flow of tritium and silane gases into the deposition chamber.Photoluminescence, isothermal capacitive transient spectroscopy and constant photocurrent spectroscopy were used to measure defect concentration as a function of time in the films. The defect concentration was found to increase between 1 and 2 orders of magnitude, in about 300 hours. Thermal annealing decreased the defect concentration. It was found that tritium permits a study of the change in the density of defect states due to dangling bond formation in a-Si:H without the uncertainties introduced by the use of multiple samples.
Journal Name: Fusion Science and Technology; Journal Volume: 48; Journal Issue: 1; Other Information: Copyright (c) 2006 American Nuclear Society (ANS), United States, All rights reserved. http://epubs.ans.org/; Country of input: International Atomic Energy Agency (IAEA)
 Time evolution of charged defect states in tritiated amorphous silicon 2007
Abstract:Tritiated hydrogenated amorphous silicon (a-Si:H:T) thin films were deposited on crystalline silicon and high resistivity glass substrates. The time evolution of the density of defect states in these films was studied using the constant photocurrent method (CPM) and isothermal capacitance transient spectroscopy (ICTS). The density of defect states was found to change with time and to recover upon thermal annealing. The ICTS results revealed that, following thermal annealing, in a sample with approximately 1 at. % tritium, the concentration of positively charged dangling bonds (D+) decreased by more than an order of magnitude over a period of 300 h. The CPM results showed that, over the same period of time, the concentration of negatively charged dangling bonds (D−) increased by over two orders of magnitude. The D+ and D− concentrations followed exponential functions of time, but the rate was different than that of tritium decay. At the same time, the Urbach energy was found to decrease with time to about 1/2 of its postanneal value. The change in the D+ and D− concentrations is primarily the result of capture of the beta particle generated electrons in dangling bonds and weak bonds, with steady state achieved through the development of a balance between carrier generation and carrier capture processes. The role of excess carriers was confirmed by CPM experiments under electrical bias.
Stefan Costea, Nazir P. Kherani,and Stefan Zukotynski. JOURNAL OF APPLIED PHYSICS 102, 103715 2007.
10_01_14_Time evolution of charged defect states in tritiated amorphous silicon
 Photocarrier Radiometric Lifetime Measurements of Intrinsic Amorphous-Crystalline Silicon Heterostructure
Abstract: Intrinsic hydrogenated amorphous silicon films were deposited by the DC saddle field system on crystalline silicon wafers. The substrate temperature of the amorphous film, crystalline silicon surface cleaning schemes, and the native oxide etchant were varied. The transport parameters of the amorphous-crystalline silicon heterostructures were evaluated by Photocarrier Radiometric (PCR) lifetime measurements. PCR bulk lifetime estimates were obtained using the quinhydrone in methanol solution to passivate the crystalline silicon surface. We present the effectiveness of the PCR system in evaluating different surface passivation schemes
 HYDROGENATED AMORPHOUS CARBON AS A SPECTRALLY SELECTIVE COATING FOR PHOTOVOLTAIC-THERMAL PANELS *
Abstract:Photovoltaic (PV) panels utilize only a small fraction of incident solar radiation. Typical PV panels convert only about 10-20% of incident solar radiation into electricity, while approximately 10% is reflected, and the remaining 70-80% is dissipated as thermal energy. In photovoltaic-thermal (PV/T) panels, the thermal energy is stored and utilized as a water or air heating source. Thus PV/T panels are able to make use of a much higher percentage of incident solar radiation. While there is a clear advantage for the use of PV/T, key technical challenges have yet to be overcome. One of the primary obstacles with PV/T is the fact that due to the high emissivity of the PV cells, PV/T panels have a lower thermal yield than stand-alone solar thermal collectors. In this paper, spectrally selective, low-emissive, hydrogenated amorphous carbon (a-C:H) coatings are investigated for application to PV/T panels. These coatings have the properties of being highly transparent in the solar region (300nm-900nm) and reflective in the mid-infrared (5μm-25μm). An evaluation of these a- C:H coatings and how they relate to the current stateof- the-art in spectrally selective coatings will be given. In addition, a discussion of the application of these a- C:H coatings to thin-film hydrogenated amorphous silicon (a-Si:H) PV/T cells will be presented.
This article states that a-C:H is amenable to a-Si:H for a highly transparent low-E coating. It deals with some of the basic physics to explain what one would want to create a perfect PVT system. It also talks about a Transparent Heat Mirror which is created by placing a thin metallic layer between a dielectric stack, usually silver. However, adding one of these (or more) adds complexity to manufacturing the PVT and therefore makes it more expensive. However, the THM talked about in this paper were designed at room temperature...
Pratish Mahtani, Nazir P. Kherani, and Stefan Zukotynski
10_01_14_HYDROGENATED AMORPHOUS CARBON AS A SPECTRALLY.pdf
 THE USE OF AMORPHOUS SILICON IN FABRICATING A PHOTOVOLTAIC-THERMAL SYSTEM 2007
Abstract: In this paper, a PV/T system based on directly depositing hydrogenated amorphous silicon photovoltaic devices on the surface of a heat exchanger will be presented. This system has the potential of overcoming the drawbacks of current PV/T systems. A background on amorphous silicon related to its application to PV/T systems will be given. In addition, an overview of current experimental work as well as future research goals will discussed.
This paper deals with my my thesis is about and hopefully I will be working with them.
"There are three major road blocks that are preventing PV/T systems from penetrating the commercial market:
- lower PV efficiency due to high temperature operation of the thermal system;
- lower thermal performance due to high emissivity of PV module; and
- PV/T systems do not provide any manufacturing cost savings over separately manufacturing PV and STC modules.
As temperature is increased, there are two major effects in typical PV cell operation. First, the dark saturation current of the PV cell increases which leads to a decrease in open circuit voltage. Second, the bandgap of the photovoltaic material decreases which leads to an increase in photocurrent. The first effect is more dominant than the second effect and thus there is a net decrease in the solar conversion efficiency with increasing temperature [Nelson, 2003]. Nelson, J. 2003. The Physics of Solar Cells (Properties of Semiconductor Materials), London: Imperial College Press
The positive temperature coefficient of a-Si:H was demonstrated in a module by Hof et. al, showing that after several months an a-Si:H PV module kept at an average temperature of 60ºC during daylight hours produces 20% more power than when the same module is kept at an average temperature of 35 ºC during daylight hours [Hof et al, 1996]. Hof, C., Ludii, M., Goetz, M., Fischer, D., Shah, A., 1996. “Long term behaviour of passively heated or cooled a-Si:H modules”, Proceedings of 25th Photovoltaic Specialists Conference, pp. 1057.
Future Work Following the investigation into diffusion barriers and demonstration of an integrated PV/T system using a-Si:H, research on optical coatings amenable to maximizing absorption and minimizing IR emissivity will be pursued. In addition, an investigation into integrating thermally conductive and electrically insulative materials such as Al2O3 will be performed. These materials will be necessary in order to monolithically interconnect the a-Si:H PV cells in series. Also, the potential of using tandem cells such as a-SiGe/a-Si:H and nc-Si/a-Si:H in order to increase the combined electrical-thermal efficiency of the system will be carried out." - paper
2nd Canadian Solar Buildings Conference Calgary, June 10 - 14, 2007. THE USE OF AMORPHOUS SILICON IN FABRICATING A PHOTOVOLTAIC-THERMAL SYSTEM. Pratish Mahtani, Davit Yeghikyan, Nazir P. Kherani and Stefan Zukotynski. http://www.solarbuildings.ca/c/sbn/file_db/The%20use%20of%20amorphous%20silicon%20in%20fabricating%20a%20photovoltaic.pdf
5mjmp 18:38, 16 September 2009 (UTC)
09_09_16_The use of amorphous silicon in fabricating a PVT system.pdf
 A comparison between defects created by light soaking and tritium decay in amorphous silicon 2007
Abstract:We compare two ways to create defects in a-Si:H, namely decay of bonded tritium and irradiation with visible light. Tritium decays to He^3, emitting a beta particle and an antineutrino. In tritium doped a-Si:H samples each beta decay of tritium bonded to silicon will create a defect by converting a bonded tritium to an interstitial helium, leaving behind a silicon dangling bond. We track these defects using electron spin resonance (ESR). We have kept the sample in liquid nitrogen for two years. After two years the defect density increases without saturation to a value of 7x10^19/cm^3. In the second experiment, we have kept the sample in liquid nitrogen irradiated with white light of intensity about 100mW/cm^2. After about 6 months, the spin density increased to about 9x10^17/cm^3 with no evidence of saturation. In the tritiated sample the increase in the defect density is proportional to the time, t, while in the light-soaked sample the increase is approximately proportional to t^1/3. This difference in behavior will be discussed.
can't get the article http://adsabs.harvard.edu/abs/2007APS..MARY31014J
 Infrared Ellipsometry Investigation of Hydrogenated Amorphous Silicon
Abstract:Hydrogenated amorphous silicon (a-Si:H) has been extensively investigated experimentally in the infrared spectral region via techniques such as Fourier Transform Infrared (FTIR) and Raman spectroscopy. Although spectroscopic ellipsometry has been proven to be an important tool for the determination of several parameters of a-Si:H films, including dielectric constant, surface roughness, doping concentration and layer thickness, the spectral range used in these studies has rarely covered the infrared region below 0.6 eV, and never over the complete spectral region of interest (0.04 – 0.3 eV). We have measured for the first time the dielectric function of a-Si:H films grown by the saddle field glow discharge technique by spectroscopic ellipsometry in the energy range from 0.04 eV to 6.5 eV, thus extending the analysis into the far infrared region. The a-Si:H films were deposited on germanium substrates for the ellipsometry studies, and on crystalline silicon substrates for the comparative FTIR analysis. Preparation parameters were chosen to obtain films with different hydrogen content. In this paper, we present the results of the ellipsometry analysis, evaluate different fitting techniques, and compare the results with the corresponding FTIR spectra. The similarities and differences between the spectra are discussed in terms of the a-Si:H properties.
Have to buy it...
 Metastable defects in tritiated amorphous silicon 2007
Abstract:We have observed the growth of defects caused by tritium decay in tritiated a-Si: H instead of inducing defects optically. We kept the samples in liquid nitrogen for two years. After two years the ESR signal reached ～1019 cm-3 with no evidence of saturation. However, the density is still less than the density of tritium that has decayed. We step-wise annealed (isochronally annealed) one sample up to 200 ºC, where all of the defects were annealed out. Another sample was isothermally annealed at 300 K for several months. At this temperature, the defects anneal slowly.
T. Jua, J. Whitakerb, S. Zukotynskic N. Kheranic, P.C. Taylord, P. Stradinse. Mater.Res.Soc.Symp.Proc. (2007). Article 0989-A02-04
10_01_14_Metastable defects in tritiated amorphous silicon
 Electrical properties of a-Si:H thin films as a function of bonding configuration 2008
Abstract: Hydrogenated amorphous silicon (a-Si:H) thin films were fabricated by Radio Frequency (RF) magnetron sputtering. For solar-cell applications, a-Si:H layers are required to show low dark conductivity and high photoconductivity and, thus, high photosensitivity. Hydrogen flow ratio and working pressure were mainly adjusted to control bonding configurations and hydrogen concentration in the films. At a high working pressure of 12 mTorr, all of the prepared amorphous and microcrystalline silicon films showed a dominant IR absorption peak at 2100 cm−1, which indicates a Si–H2 stretching mode, grain boundaries and microvoids. When the working pressure was decreased to as low as 3 mTorr with a hydrogen flow ratio of 0.1, the bonding configuration of the films was mainly Si–H as determined by the dominant IR absorption peak at 2000 cm−1, and the photosensitivity of the films was maximized to 760.
Do Yun Kim,In Soo Kim,Se Young Choi. 0927-0248/$-see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.solmat.2008.10.003
10_01_14_Electrical properties of a-Si-H thin films as a function of bonding configuration
 Quantum Efficiency
Has an interesting interaction graph which allows you to change the emitter and base collection properties to change the Jsc quantum efficiency. http://pvcdrom.pveducation.org/CELLOPER/QUANTUM.HTM
The following 65 Papers were found using the link below.
 Electroluminescence in amorphous silicon 1976
Abstract:Electroluminescence has been obtained in forward-biased p-i-n diodes, and also in Schottky barrier diodes fabricated from discharge-produced amorphous Si. The emission at 78 °K in both electroluminescence and photoluminescence peaks at 1.28±0.08 eV in a 0.2-eV broad band with an external quantum efficiency of ~10−3.
Pankove, J.I. (RCA Labs., Princeton, NJ, USA); Carlson, D.E. Source: Applied Physics Letters, v 29, n 9, p 620-22, 1 Nov. 1976 http://scitation.aip.org.proxy.queensu.ca/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000029000009000620000001&idtype=cvips&gifs=yes
10_01_22_Electroluminescence in amorphous silicon
 Photoluminescence in sputtered amorphous silicon-hydrogen alloys 1980
Deep hole traps in high efficiency Schottky barrier solar cells on sputtered amorphous silicon as evidenced by spectral response and thermally stimulated current measurements
 Field-dependent quantum efficiency in hydrogenated amorphous silicon 1980
Abstract:A model calculation of the electric field dependence of the quantum efficiency for electron-hole pair production in hydrogenated amorphous silicon is presented and compared with recent measurements of the electric field dependence of the solar-cell collection efficiency. The theory, based on electric field reduction of geminate recombination of the excited electron-hole pair, agrees well with experiment.
Crandall, R. (RCA Labs., Princeton, NJ, USA) Source: Applied Physics Letters, v 36, n 7, p 607-8, 1 April 1980 Database: Inspec http://scitation.aip.org.proxy.queensu.ca/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000036000007000607000001&idtype=cvips&gifs=yes
10_01_22_Field-dependent quantum efficiency in hydrogenated amorphous silicon
 Development of amorphous silicon stacked cells 1980
Hanak, J.J. (RCA Labs., Princeton, NJ, USA); Faughnan, B.; Korsun, V.; Pellicane, J.P. Source: Fourteenth IEEE Photovoltaic Specialists Conference 1980, p 1209-13, 1980
 On the computation of Onsager quantum efficiency 1981
Abstract:A new method of computing the Onsager quantum efficiency of photogeneration is presented. This method is shown to be much faster than and as accurate as the series method used previously. Results applicable to a-Si (dielectric constant=11.5) are given as an example.
Kwok-leung Yip (Joseph C. Wilson Center for Technol., Xerox Corp., Webster, NY, USA); Li, L.S.; Chen, I. Source: Journal of Chemical Physics, v 74, n 1, p 751-3, 1 Jan. 1981 http://scitation.aip.org.proxy.queensu.ca/getabs/servlet/GetabsServlet?prog=normal&id=JCPSA6000074000001000751000001&idtype=cvips&gifs=yes 10_01_22_On the computation of Onsager quantum efficiency
 Computer model of amorphous silicon solar cell 1982
Abstract:A computer model to simulate a n+ip+ amorphous silicon solar cell was developed. This model is based on the computer simulations of solar cells by T. Chappell and the Read diode by Scharfetter and Gummel. The model is used to generate field plots, band diagrams, quantum efficiency curves, I-V characteristics, carrier density distribution plots, carrier generation, and carrier recombination plots. The simulated values of short circuit current density, open circuit voltage, fill factor, efficiency, junction quality factor, quantum efficiency, junction quality factor, quantum efficiency, slope of I-V curves at V = 0 and V = Voc are in good agreement with the measured cell values. Computer simulation shows that a major loss mechanism is the back diffusion of holes into the n+ layer which is diminished by a strong electric field provided by a high concentration of ionized donors in the n+ layer. Projection of cell performance based on the production of n+ and p+ contact layers with ionized donor and ionized acceptor concentrations in the 2×1020 cm−3 range indicates cell efficiencies greater than 10%.
Swartz, G.A. (RCA Labs., Princeton, NJ, USA) Source: Journal of Applied Physics, v 53, n 1, p 712-19, Jan. 1982 http://scitation.aip.org.proxy.queensu.ca/getabs/servlet/GetabsServlet?prog=normal&id=JAPIAU000053000001000712000001&idtype=cvips&gifs=yes 10_01_22_Computer model of amorphous silicon solar cell
 Observation of electroluminescence from amorphous silicon solar cells at room temperature 1982
Abstract:Electroluminescence from a-Si pin, pi(B-doped)n, and nip solar cells was observed at room temperature (300 K) for the first time. The electroluminescence spectrum of the nip cell showed very broad with a peak at 1.31 eV or slightly less. The external quantum efficiency of the nip cell was 10-5% at 300 K. Electroluminescence intensity from this cell was stronger than that from the pin cell. It became clear that this can be attributed to the difference in the current transport mechanism of the nip and pin cells. A pin cell whose i-layer was slightly boron doped, the pi(B)n cell, gave a stronger electroluminescence intensity than a usual pin cell.
Lim, K.S. (Tokyo Inst. of Technol., Tokyo, Japan); Konagai, M.; Takahashi, K. Source: Japanese Journal of Applied Physics, Part 2 (Letters), v 21, n 8, p L473-5, Aug. 1982 http://jjap.ipap.jp.proxy.queensu.ca/link?JJAP/21/L473/
10_01_22_Observation of Electroluminescence from Amorphous Silicon Solar Cells at Room Temperature
 The absolute luminescence quantum efficiency in hydrogenated amorphous silicon 1983
Jackson, W.B. (Xerox Palo Alto Res. Center, Palo Alto, CA, USA); Nemanich, R.J. Source: Journal of Non-Crystalline Solids, v 59-60, pt.1, p 353-6, Dec. 1983 Database: Inspec
 Photovoltaically active p layers of amorphous silicon 1983
Abstract:Studies on amorphous silicon p-n diodes have shown that the p layers are photovoltaically active. Jsc of up to 3.4 mA/cm2 and Voc of 780 mV have been observed. Detailed quantum efficiency measurements were performed as a function of bias voltage, p-layer thickness, and boron doping. The data fit a simple depletion width model in which all photogenerated carriers created inside the depletion region are collected. An additional ``reverse barrier depletion width is assumed at the interface between the front transparent oxide electrode and the p layer to explain the results. A 10-nm-thick p layer typically used in p-i-n cells could collect up to 1 mA/cm2 if the electric field in the p layer is greater than 105 V/cm.
Faughnan, B.W. (RCA Labs., Princeton, NJ, USA); Hanak, J.J. Source: Journal of Non-Crystalline Solids, v 59-60, pt.2, p 1127-30, Dec. 1983 http://scitation.aip.org.proxy.queensu.ca/getpdf/servlet/GetPDFServlet?filetype=pdf&id=APPLAB000042000008000722000001&idtype=cvips&prog=normal 10_01_22_Photovoltaically active p layers of amorphous silicon
 High quantum efficiency a-Si:H picosecond transit-time limited Schottky barrier photodetectors 1984
Abstract:Amorphous silicon films have previously been utilized to make high speed photoconductive detectors with response times ranging from 4–200 psec in microstrip transmission line structures. However, in typical devices, the low carrier mobilities resulted in poor carrier collection efficiencies resulting in quantum efficiencies in the range 0.001–0.3%. We have demonstrated photogenerated carrier sweep-out in Schottky barrier photodetectors with internal quantum efficiencies of 36% (0.18 A/W) and sampling oscilloscope limited response times of 40 psec (FWHM) using 100 nm-thick films of rf-glow discharge deposited a-Si:H in a new transmission line structure. The estimated deconvolved response time was 27 psec. These a-Si:H detectors are compared in speed and sensitivity to high mobility crystalline detectors.
Johnson, A.M. (AT&T Bell Labs., Holmdel, NJ, USA); Glass, A.M.; Olson, D.H.; Simpson, W.M.; Harbison, J.P. Source: Journal of Non-Crystalline Solids, v 66, n 1-2, p 381-6, July 1984 http://www.sciencedirect.com.proxy.queensu.ca/science?_ob=ArticleURL&_udi=B6TXM-48CXV8T-39G&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=a88acc135efb81d2bd2e56431adda4d3 10_01_22_High quantum efficiency a-SiH picosecond transit-time limited Schottky barrier photodetectors
 High quantum efficiency amorphous silicon photodetectors with picosecond response times 1984
Abstract:Amorphous silicon Schottky barrier photodetectors with internal quantum efficiencies of 36% and sampling oscilloscope limited response times of 40 ps (full width at half-maximum) have been fabricated. Utilizing ultrathin films of rf glow discharge deposited hydrogenated amorphous silicon, carrier sweep-out was achieved in a new microstrip transmission line structure. The performance of these devices, for picosecond pulse detection, is now comparable to that of crystalline semiconductor detectors
Johnson, A.M. (Bell Labs., Holmdel, NJ, USA); Glass, A.M.; Olson, D.H.; Simpson, W.M.; Harbison, J.P. Source: Applied Physics Letters, v 44, n 4, p 450-2, 15 Feb. 1984 http://scitation.aip.org.proxy.queensu.ca/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000044000004000450000001&idtype=cvips&gifs=yes 10_01_22_High quantum efficiency amorphous silicon photodetectors with picosecond response times
 Experimental observation of light trapping in hydrogenated amorphous silicon solar cells 1985
Abstract:Experimental evidence for light trapping in glass/conductive transparent oxide/p-i-n/metal hydrogenated amorphous silicon solar cell structures is presented. A short-circuit current of 17.8 mA/cm2 has previously been reported for a cell made with this structure. The light trapping is treated by a modification of the Yablonovitch–Cody (YC) statistical theory of light trapping in textured layers [E. Yablonovitch and G. D. Cody, IEEE Trans. Electron. Devices ED-29, 300 (1982)]. Reflection measurements show that 80% of the incident light is trapped. Quantum efficiency measurements made on cells with back electrode metals of different reflectivity are shown to be in agreement with the predictions of the YC theory.
Faughnan, B.W. (RCA Labs., Princeton, NJ, USA) Source: Journal of Applied Physics, v 58, n 7, p 2746-50, 1 Oct. 1985 http://scitation.aip.org.proxy.queensu.ca/getpdf/servlet/GetPDFServlet?filetype=pdf&id=JAPIAU000058000007002746000001&idtype=cvips&prog=normal 10_01_22_Experimental observation of light trapping in hydrogenated amorphous silicon solar cells
 Optical properties and quantum efficiency of a-Si1-xCx:H/a-Si:H solar cells 1985
Abstract:The optical properties of all components of heterojunction solar cells based on hydrogenated amorphous silicon (a‐Si:H) have been measured individually. By combining these data with knowledge of the cell geometry, an envelope quantum efficiency curve is generated, being simply the fraction of incident photons absorbed in the i layer of the p‐i‐n cell. Resultant curves for typical cell dimensions are seen to agree remarkably well with observed values for cells with long minority‐carrier collection lengths. The model is then used as a diagnostic tool, and finally is demonstrated to have predictive value in the quest for further optimization of solar‐cell performance.
Schade, H. (RCA Labs., Princeton, NJ, USA); Smith, Z.E. Source: Journal of Applied Physics, v 57, n 2, p 568-74, 15 Jan. 1985 http://ieeexplore.ieee.org.proxy.queensu.ca/Xplore/defdeny.jsp?url=http://ieeexplore.ieee.org/stamp/stamp.jsp%3Ftp%3D%26arnumber%3D5115155&denyReason=-133&arnumber=5115155&productsMatched=null 10_01_22_Optical properties and quantum efficiency of a-Si1−xCxH a-SiH solar cells
 Determination of the mobility gap in amorphous silicon from a low temperature photoconductivity measurement 1985
Abstract:Measurement of the spectral dependence of photoconductivity and quantum efficiency at liquid helium temperature is presented. The mobility gap value was found to be quite close to the Tauc optical gap value for undoped good quality material.
Vanecek, M. (Inst. of Phys., Czechoslovak Acad. of Sci., Prague, Czechoslovakia); Stuchlik, J.; Kocka, J.; Triska, A. Source: Journal of Non-Crystalline Solids, v 77-78, pt.1, p 299-302, 11 Dec. 1985 http://www.sciencedirect.com.proxy.queensu.ca/science?_ob=ArticleURL&_udi=B6TXM-48N5J8B-G9&_user=1025668&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050549&_version=1&_urlVersion=0&_userid=1025668&md5=35adac45ad89416aa83987dba3f13cb7 10_01_22_Determination of the mobility gap in amorphous silicon from a low temperature photoconductivity measurement
 Optical properties of hydrogenated amorphous silicon based solar cells 1986
Ellis, F.B., Jr. (Chronar Corp., Lawrenceville, NJ, USA); Delahoy, A.E. Source: Solar Energy Materials, v 13, n 2, p 109-32, Feb.-March 1986
 Status of fluorinated amorphous silicon-germanium alloys and multijunction devices 1987
Ross, R. (Energy Conversion Devices Inc., Troy, MI, USA); Mohr, R.; Fournier, J.; Yang, J. Source: Conference Record of the Nineteenth IEEE Photovoltaic Specialists Conference - 1987 (Cat. No.87CH2400-0), p 327-30, 1987 Database: Inspec
 High efficiency multi-junction solar cells using amorphous silicon and amorphous silicon-germanium alloys 1988
Abstract: We have incorporated a new c e l l design and achieved a 13.7% conversion efficiency using amorphous s i l i c o n and amorphous silicon-germanium alloys i n a three-cell stacked-junction configuration. This i s the highest efficiency reported t o date f o r t h i n - f i l m solar cells. The efficiency value was measured using a t r i p l e - source solar simulator adjusted f o r global AM1.5 test conditions. This t r i p l e device has a structure of stainless steel/textured s i l v e r / zinc oxide/ni lp/ni p/ni 3p/ITO/grid. We have used an amorphous s?licon-germanium alloy with the new design i n the il layer, and amorphous s i l i c o n alloys i n the i2 and i layers The 3-V characteristic shows Jsc = 7?66 mA/cm*, VOC = 2.55 Volts, FF = 0.70, with an active area of 0.25 cm2. The quantum efficiency measurement of t h i s device shows 60% c o l l e c t i o n a t 400 nm, 93% at the peak, 55% at 800 nm, and 21% at 850 nm. The t o t a l photocurrent density obtained by integrating the quantum efficiency enyelope with the global AM1.5 spectrum i s 23.5 mA/cm .
Yang, J. (Energy Conversion Devices Inc., Troy, MI, USA); Ross, R.; Glatfelter, T.; Mohr, R.; Hammond, G.; Bernotaitis, C.; Chen, E.; Burdick, J.; Hopson, M.; Guha, S. Source: Conference Record of the Twentieth IEEE Photovoltaic Specialists Conference - 1988 (Cat. No.88CH2527-0), p 241-6 vol.1, 1988
10_01_25_HIGH EFFICIENCY MULTI-JUNCTION SOLAR CELLS USING AMORPHOUS SILICON
 Performance of silicon solar cells under hot and dusty environmental conditions 1988
Bajpai, S.C. (Sokoto Energy Res. Centre, Sokoto Univ., Nigeria); Gupta, R.C. Source: Indian Journal of Pure and Applied Physics, v 26, n 5, p 364-9, May 1988
 On mobility-lifetime problem and on quantum efficiency of photogeneration in amorphous silicon 1989
Abstract:Discrepancy in the value of mobility-lifetime (μ τ) product measured under different experimental conditions is elucidated with the help of steady-state and transient demarcation level concept. Experimental data on the quantum efficiency of photogeneration of free carriers presented as a function of electric field (5×103−2×105V/cm) and temperature (300-14K). For sufficiently high electric fields, η approaches unity even at very low temperature.
Vanecek, M. (Inst. of Phys., Czechoslovak Acad. of Sci., Praha, Czechoslovakia); Kocka, J.; Sipek, E.; Triska, A. Source: Journal of Non-Crystalline Solids, v 114, pt.2, p 447-9, 1989 Database: Inspec
10_01_25_On mobility - lifetime problem and on quantum efficiency of photogeneration in amorphous silicon
 The effect of water vapor and oxygen in the processing environment on the properties of sputtered a-Si:H films 1989
Abstract: We show that the addition of small amounts of water vapor, or O2 into the processing ambient leads to significant improvements in the properties of a-Si:H films deposited by reactive magnetron sputtering at substrate temperatures <150°C. The relative fraction of polyhydride bonding, and defect densities are both reduced; the films show increased stability against light-soaking induced defects; while levels of oxygen in the films remain below 5×1018/cm3.
Cheng Wang (Dept. of Phys., North Carolina State Univ., Raleigh, NC, USA); Parsons, G.N.; Lucovsky, G. Source: Amorphous Silicon Technology-1989 Symposium, p 75-80, 1989
10_01_25_Effects of gas additives on the properties of a-SiH films
 Effect of light soaking on the short-wavelength photoresponse in hydrogenated amorphous silicon 1990
Abstract:The spectrum of the values of µ, the product of quantum efficiency, lifetime, and mobility of photogenerated carriers, has been obtained in the wavelength range 300–900 nm, before and after light soaking. It has been shown that in the annealed state, these values are nearly independent of wavelength as well as film thickness. The values of µhave been found to decrease more drastically in the short-wavelength region after light soaking, similarly to that observed after moisture adsorption. Changes in band bending are not likely to be the cause of the decrease in response as the dark conductivity does not change on light soaking. The implications of the result are discussed.
Ghosh, S. (Energy Res. Unit, Indian Assoc. for the Cultivation of Sci., Calcutta, India); Ganguly, G. Source: Journal of Applied Physics, v 68, n 11, p 5896-8, 1 Dec. 1990
10_01_25_Effect of light soaking on the short-wavelength photoresponse in hydrogenated amorphous silicon
 Effect of light induced defects on the quantum efficiency of amorphous silicon Schottky barrier solar cell structures 1991
Abstract: Changes in internal quantum efficiency (QE) of n-i- Pt Schottky barrier solar cells are directly correlated with light induced defects in the bulk a-Si:H. These short circuit QE’s measured on cells 0.84 to 3.4pm thick in the annealed state and after open circuit degradation up to 650 hours with 100 mW/cm2 ENH white light were analyzed using a detailed numerical model to obtain the corresponding densities of mid-gap states and capture cross sections. The self consistent results obtained for the different thickness cell structures correlate light-induced, metastable defect creation with the degradation of the short circuit currents.
Malone, C.T. (Center for Electron. Mater. & Process., Pennsylvania State Univ., University Park, PA, USA); Nicque, J.L.; Fonash, S.J.; Wronski, C.R.; Bennett, M. Source: Conference Record of the Twenty Second IEEE Photovoltaic Specialists Conference - 1991 (Cat. No.91CH2953-8), p 1219-24 vol.2, 1991 Database: Inspec
10_01_25_Effect of light induced defects on the quantum efficiency of amorphous silicon Schottky barrier solar cell structures
 Hydrogen content and the goal of stable efficient amorphous-silicon-based solar cells 1991
Fortmann, C.M. (Inst. of Energy Conversion, Delaware Univ., Newark, DE, USA); Hegedus, S.S.; Zhou, T.X.; Baron, B.N. Source: Solar Cells, v 30, n 1-4, p 255-60, May 1991
 An experimental observation of photo-induced carrier multiplication in hydrogenated amorphous silicon 1991
Abstract:A photo-induced carrier multiplication in a hydrogenated amorphous silicon has been observed. A careful measurement of photo-carrier generation has been done with amorphous silicon Schottky barrier structure junctions as a function of incident photon energy in the range between 1.55eV and 6.2eV. The quantum efficiency is estimated to be multiplied by a factor of two in higher photon energy region than 5.4eV. This multiplication can be explained by an interband carrier ionization due to the energy given by a high energy photo-carrier.
Sugawa, S. (Canon Inc., Semicond. Dev. Center, Kanagawa, Japan); Ohmi, K.; Yamanobe, M.; Osada, Y. Source: Solid State Communications, v 80, n 6, p 373-6, Nov. 1991
10_01_25_ experimental observation of photo-induced carrier multiplication in hydrogenated amorphous silicon
 Quantum efficiency of textured a-Si:H p-i-n solar cells after high intensity light-soaking 1992
Li, X.R. (Dept. of Electr. Eng., Princeton Univ., NJ, USA); Wagner, S.; Bennett, M.; Fonash, S.J. Source: Amorphous Silicon Technology - 1992, Symposium, p 929-33, 1992
 Photocurrent multiplication in a hydrogenated amorphous silicon-based p-i-n junction with an a-SiN:H layer 1992
Abstract:Photocurrent multiplication has been observed in a hydrogenated amorphous silicon-based p-i/a-SiN:H/i-n structure junction under a reverse biased condition. A systematic investigation on the photocurrent characteristics in this junction system has been carried out. It has been shown from the analysis of the results that multiplication arises from the interband tunneling injection of valence band ``electron through the a-SiN:H barrier layer. A device modeling on the basis of the experimental data permits us to design the device structure for achieving better performances. As a preliminary optimization of device structure, an external quantum efficiency exceeding 70 has been obtained under the operation voltage 30 V in the heterojunction photodiode having an a-SiN:H (thickness of 40 nm with optical energy gap 2.1 eV) at the p a-SiC:H/i a-Si:H interface. The proposed highly sensitive photomultiplier device might have a wide variety of application fields such as a solid-state imager for high-definition televisions, etc.
Yoshimi, M. (Fac. of Eng. Sci., Osaka Univ., Toyonaka, Japan); Ishiko, T.; Hattori, K.; Okamoto, H.; Hamakawa, Y. Source: Journal of Applied Physics, v 72, n 7, p 3186-93, 1 Oct. 1992
10_01_25_Photocurrent multiplication in a hydrogenated amorphous silicon-based p-i-n junction with an a-SiNH layer
 Mobility, recombination kinetics, and solar cell performance 1993
Abstract:In order to optimize the amorphous silicon structure for improved stabilized performance it is necessary to understand a great number of material parameters as they exist in the solar cell under operating conditions. Towards the goal of using the solar cells themselves for quantitative defect analysis we show that the short wavelength quantum efficiency measurement is a means to determine the total density of charged and uncharged dangling bonds in the i-layer as a function of light soaking time. The compound effect that dangling bond defects have on solar cell performance, consisting of the redistribution of the electric fields and decreased lifetimes are considered. The magnitude of the short wavelength response can be directly linked to the number of bulk defects in the solar cells. Also it is not possible to directly determine the electron mobility from solar cell characterization due to the diffusive carrier transport found in amorphous materials. Surprisingly, we do expect the electron mobility to be directly linked to the stability of the solar cells.
Fortmann, C.M. (Inst. de Microtechnol., Neuchatel Univ., Switzerland); Fischer, D. Source: Conference Record of the Twenty Third IEEE Photovoltaic Specialists Conference - 1993 (Cat. No.93CH3283-9), p 966-70, 1993
10_01_25_MOBILITY, RECOMBINATION KINETICS, AND SOLAR CELL PERFORMANCE
 Measurement of the quantum efficiency of CsI, amorphous silicon and organometallic reflective photocathodes 1994
Measurement of the quantum efficiency of CsI, amorphous silicon and organometallic reflective photocathodes Malamud, G. (Lab de Phys. Nucl. et des Hautes Energies, Ecole Polytech., Palaiseau, France); Mine, Ph.; Vartsky, D.; Equer, B.; Besson, P.; Bourgeois, P.; Breskin, A.; Chechik, R. Source: Nuclear Instruments & Methods in Physics Research, Section A (Accelerators, Spectrometers, Detectors and Associated Equipment), v 348, n 2-3, p 275-9, 1 Sept. 1994 Database: Inspec
 Fabrication of more stable materials and devices in amorphous silicon 1994
Abstract:We discuss two approaches for improving the stability of a-Si:H devices. The first approach relies on improving the stability of the material by controlling the growth chemistry. We show that when the film is subjected to a strong H atom flux during growth, its microstructure becomes very robust, with few polysilane-type chains and its stability is significantly improved. The stability is further enhanced by sub-ppm doping by diborane during growth. We speculate that diborane compensates the native oxygen donors, and changes the localized bonding environment, thereby improving stability. We have been able to obtain a very low mid-gap defect density after prolonged illumination under 10× sun intensity using the combination of H etching and compensation. We have also made devices in these materials. The devices were made on standard textured tin oxide substrates and had simple Al back reflectors. We had to use high C buffer layers to block the diffusion of B from the p into the i layer at these temperatures. The best device efficiency to-date for a device made at 375 C is 7.8%. The quantum efficiency data on the devices indicate very good µ products for holes in our materials. Stability experiments on these devices are in progress.
Dalal, V.L. (Dept. of Electr. & Comput. Eng., Iowa State Univ., Ames, IA, USA); Baldwin, G.; Ping, E.X.; Leonard, M.; Bhan, M. Source: AIP Conference Proceedings, n 303, p 460-7, 1994
couldn't dl file
 Significant improvements in stability of amorphous silicon solar cells by using ECR deposition 1996
Abstract: The fabrication and stability of p-i-n amorphous Si(a-Si:H) solar cells using low pressure electron-cyclotron-resonance (ECR) discharge are reported. The cells are fabricated at high temperatures (325 to 375°C) on tin oxide substrates using a Hydrogen-ECR discharge. Problems relating to diffusion of B from the p-layer at these temperatures are solved using unique diffusion barriers. High fill factors (68%) have been achieved in these cells using 350 nm thick i-layers in a p-i-n structure. Quantum efficiency (QE) measurements show that the i-layers in these cells have low defect densities and Urbach energies. The ECR cells and companion glow discharge cells with similar initial device parameters were subjected to 200 mW/cm2 of xenon illumination for 160 h. The tests show that the ECR cells degrade significantly less than comparable glow discharge cells. Detailed measurements of quantum efficiency before and after light soaking show that the improved stability of the ECR cells is due to the more stable i-layer in these cells.
Dalal, V.L. (Microelectron. Res. Center, Iowa State Univ., Ames, IA, USA); Kaushal, S.; Knox, R.; Han, K.; Martin, F. Source: Journal of Non-Crystalline Solids, v 198-200, pt.2, p 1101-4, May 1996
10_01_25_Significant improvements in stability of amorphous silicon solar cells by using ECR deposition
 An amorphous silicon alloy triple-junction solar cell with 14.6% initial and 13.0% stable efficiencies 1997
Abstract:We have achieved 14.6% initial and 13.0% stable conversion efficiencies using an amorphous silicon-based alloy in a spectrum-splitting, triple-junction structure. These efficiencies have been confirmed independently by the National Renewable Energy Laboratory. Key factors leading to this major advance include improvements made in the low band-gap amorphous silicon–germanium alloy cell, the pn tunnel junction between the component cells, and the top conducting oxide.
Yang, J. (United Solar Syst. Corp., Troy, MI, USA); Banerjee, A.; Guha, S. Source: Amorphous and Microcrystalline Silicon Technology - 1997 Symposium, p 693-8, 1997
10_01_25_Triple-junction amorphous silicon alloy solar cell with 14.6% initial and 13.0% stable conversion efficiencies
 A model for quantum efficiency and detectivity of n+p and n+n−p Hg1−xCdxTe photodiodes 1997
Abstract:In this paper a model for calculating the quantum efficiency � and the specific detectivity D� of both n+p and n+n−p photodiodes, considering both frontand backside illuminated configurations, is presented. The n+n−p diode is analysed by assuming a step model for the concentration profile. The effects of the surface recombination velocities at different surfaces/interfaces of the diode, the minority carrier lifetimes and the carrier concentrations are considered. It is pointed out that the parameter to be optimized for a photodiode is D� and not the zero-bias resistance–area product R0A, although the latter combines with the quantum efficiency to determine the behaviour of D�. Based on our calculations, it is observed that the values of different parameters that maximize R0A are different from those that are optimal for high quantum efficiency. For sufficiently high R0A, � dominates D�; otherwise, both factors affect D�. The calculation of D� done here refers to the long-wavelength IR region where often R0A is low, with the result that the injection efficiency into the CCD multiplexer is decreased, which has been taken into account.
This paper has equations to model the quantum efficiency. Might be useful but I believe that the equations deal with this specific semiconductor set-up.
V Dhar and R Ashokan Solid State Physics Laboratory, Lucknow Road, Delhi 110054, India Received 9 October 1996, accepted for publication 17 January 1997 Semicond. Sci. Technol. 12 (1997) 580–588. Printed in the UK PII: S0268-1242(97)78522-5
10_01_27_A model for quantum efficiency and detectivity of n+p and n+n−p Hg1−xCdxTe photodiodes
 Widegap a-Si:H films prepared at low substrate temperature 1997
Abstract:Wide bandgap hydrogenated amorphous silicon (a-Si:H) films have been prepared by the PECVD method at a low substrate temperature (80°C) controlling the incorporation of hydrogen (bonded with silicon) into the film. Optimizing the deposition parameters viz. hydrogen dilution, rf power, a-Si:H film with Eg 1.90 eV and σph ≥ 10−4 Scm−1 has been developed. This film exhibited better optoelectronic properties compared to a-SiC:H of similar optical gap. The quantum efficiency measurement on the Schottky barrier solar cell structure showed a definite enhancement of blue response. Surface reaction as well as structural relaxation under suitable deposition condition have been claimed to be responsible for the development of such material.
Saha, S.C. (Energy Res. Unit, Indian Assoc. for the Cultivation of Sci., Calcutta, India); Ghosh, S.; Ray, S. Source: Solar Energy Materials and Solar Cells, v 45, n 2, p 115-26, 25 Jan. 1997
10_01_25_Widegap a-SiH films prepared at low substrate temperature
 Interfaces in a-Si:H solar cell structures 1997
Abstract:The performance of amorphous silicon based solar cells depends on the tailored properties of the various layer materials making up the cell structure as well as on the properties and on the design of the interface regions between the layers. The electronic properties related to the various interfaces are markedly influenced by the Fermi level position within these regions, and by structural properties and chemical compositions resulting from the preparation conditions. Results are presented for the p/i and the TCO/p interfaces and discussed with respect to device performance. Further examples of interface effects are described which are related to chemical reactions and hydrogen diffusion in the course of sample preparation.
Stiebig, H. (Inst. fur Schicht- und Ionentech., Forschungszentrum Julich GmbH, Germany); Siebke, F.; Beyer, W.; Beneking, C.; Rech, B.; Wagner, H. Source: Solar Energy Materials and Solar Cells, v 48, n 1-4, p 351-63, Nov. 1997
10_01_25_Interfaces in a-SiH solar cell structures
 Signal, noise, and detective quantum efficiency of a-Si:H flat-panel imagers 1998
Abstract:Flat-panel imagers based upon the technology of thin-film amorphous silicon transistors and photodiodes are under investigation for a wide variety of medical imaging applications. This thesis presents quantitative empirical and theoretical investigations of the imaging performance of such imaging systems. Performance was evaluated in terms of imager signal size, spatial resolution, noise characteristics, and signal-to-noise ratio for a wide variety of imaging system configurations and exposure conditions relevant to medical imaging. A theoretical model based upon cascaded systems analysis allowed prediction of imager signal, noise, and detective quantum efficiency (DQE), and theoretical results were found to agree well with empirical measurements. The empirical and theoretical analyses yielded quantification of the performance of existing imager designs, allowed investigation of the potential performance of future flat-panel imaging systems, and provided a methodology for identifying optimal imager configurations for various applications and imaging tasks. There is every indication that flat-panel imagers could provide performance superior to that of existing clinical imaging technologies. For example, in general x-ray radiography, mammography, and radiotherapy portal imaging, such systems could provide DQE exceeding 60%, 80%, and 1.5%, respectively, approximately twice that of film-based systems. However, for applications involving very low exposures per image, e.g., real-time fluoroscopy, flat-panel imagers may suffer from reduced signal-to-noise ratio. The analyses developed in this thesis provide a general description of imager signal and noise as well as a means of identifying strategies for improved imager performance
Siewerdsen, J.H. (Dept. of Radiat. Oncology, University of Michigan, Ann Arbor, MI, USA) Source: Medical Physics, v 25, n 11, p 2250, Nov. 1998
can't dl full article
 Degradation and annealing of amorphous silicon solar cells by current injection experiment and modeling 1999
Abstract:In this paper we report in detail on the effect of current injection in amorphous silicon solar cells. A set of devices has been degraded and then annealed at different current intensities. Device performances during the whole experiment have been monitored by current–voltage characteristics and quantum efficiency curves. It has been found that annealing rate increases with current intensity, while stabilized photovoltaic parameters decrease. Time evolution of efficiency and short-circuit current during degradation has been reproduced by a numerical device modeling, resulting in a pronounced increase of defects near the p–i interface. The model also demonstrated that annealing results are not well reproduced if current-induced annealing is not energy selective.
Caputo, D. (Dept. of Electron. Eng., Tor Vergata Univ., Rome, Italy) Source: Solar Energy Materials and Solar Cells, v 59, n 3, p 289-98, Oct. 1999
10_01_25_Degradation and annealing of amorphous silicon solar cells by current injection experiment and modeling
 Simulation of quantum efficiency spectroscopy for amorphous silicon p-i-n junctions 1999
Estwick, R. (Dept. of Electr. Eng. & Comput. Eng., Iowa State Univ., Ames, IA, USA); Dalal, V.L. Source: Amorphous and Heterogeneous Silicon Thin Films: Fundamentals to Devices - 1999. Symposium. (Materials Research Society Symposium Proceedings Vol.557), p 37-42, 1999 Database: Inspec
 Thermally enhanced quantum efficiency in hydrogenated amorphous silicon p-i-n photodiodes studied by intensity-modulated photocurrent spectroscopy 1999
Abstract: is shown that at zero bias or slightly reverse bias the photocurrent quantum yield of hydrogenated amorphous Si (a-Si : H) p+-i-n+ photodiodes increases with decreasing absorbed photon flux. The quantum yield can exceed unity. The dynamics of photogenerated charge carriers in the intrinsic layer of a-Si : H were studied by intensity-modulated photocurrent spectroscopy (IMPS). A model is proposed, which accounts for the enhanced quantum yield at low light intensities. Basically, the increase in the quantum yield is explained by thermal generation of charge carriers mediated by a one-electron defect state formed under illumination. The model is supported by the results of IMPS measurements.
Vanmaekelbergh, D. (Debye Inst., Utrecht Univ., Netherlands); van de Lagemaat, J.; Schropp, R.E.I.; Cardon, F. Source: Philosophical Magazine B (Physics of Condensed Matter: Statistical Mechanics, Electronic, Optical and Magnetic Properties, v 79, n 2, p 291-318, Feb. 1999 Database: Inspec
10_01_25_Thermally enhanced quantum efficiency in hydrogenated amorphous silicon p-i-n photodiodes studied by intensity- modulated photocurrent spectroscopy
 Minority carrier properties of single- and polycrystalline silicon films formed by aluminium-induced crystallisation [solar cells] 2000
Abstract:The aluminium-induced crystallisation (AIC) of amorphous silicon is a simple low-temperature method for the growth of thin (5 0.5 pm), ptype ( - 2 ~ 1 0 '~~m -s~ing)le - and polycrystalline Si films on Si wafers and foreign substrates, respectively. While previous work has shown that such Si films can be used as thin emitters of p+-n Si wafer cells, this paper investigates the minority carrier diffusion length L, of AIC-grown Si and thus determines whether these films can be used as absorber layer (i.e. base region) of c-Si solar cells. The AIC-grown Si films are made at 460°C on single-crystal n-Si wafers and glass, respectively. By means of current-voltage and quantum efficiency measurements, we show that L, in our AICgrown p'-Si films is only about 100 nm. This is far too low to enable the use of these AIC films as absorber layers in thin-film c-Si solar cells. However, as shown in a companion paper (Harder et a/.), these AIC films are excellent seeding layers on glass that can epitaxially be thickened by suitable Si deposition methods.
Neuhaus, D.H. (Photovoltaics Special Res. Centre, New South Wales Univ., Sydney, NSW, Australia); Bardos, R.; Feitknecht, L.; Puzzer, T.; Keevers, M.J.; Aberle, A.G. Source: Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference - 2000 (Cat. No.00CH37036), p 65-8, 2000
10_01_25_MINORITY CARRIER PROPERTIES OF SINGLE- AND POLYCRYSTALLINE
 Recombination mechanisms in amorphous silicon/crystalline silicon heterojunction solar cells 2000
Abstract:This article investigates limitations to the open circuit voltage of n-type amorphous silicon/p-type crystalline silicon heterojunction solar cells. The analysis of quantum efficiency and temperature dependent current/voltage characteristics identifies the dominant recombination mechanism. Depending on the electronic quality of the crystalline silicon absorber, either recombination in the neutral bulk or recombination in the space charge region prevails; recombination at the heterointerface is not relevant. Although interface recombination does not limit the open circuit voltage, recombination of photogenerated charge carriers at the heterointerface or in the amorphous silicon emitter diminishes the short circuit current of the solar cells.
Jensen, N. (Inst. fur Phys. Elektronik, Stuttgart Univ., Germany); Rau, U.; Hausner, R.M.; Uppal, S.; Oberbeck, L.; Bergmann, R.B.; Werner, J.H. Source: Journal of Applied Physics, v 87, n 5, p 2639-45, 1 March 2000 Database: Inspec
10_01_25_Recombination mechanisms in amorphous silicon crystalline silicon heterojunction solar cells
 Silicon-based materials for optoelectronics: visible photoluminescence and electroluminescence from amorphous silicon 2000
Abstract:Room temperature visible photoluminescence (PL) and electroluminescence (EL) of wide band gap hydrogenated amorphous silicon thin films prepared in SiH4 microwave plasma strongly diluted with He is reported. The emission spectra are peaked at approximately 1.5 eV. Films were characterized by means of optical and IR absorption and hydrogen thermal desorption. The band gap of a-Si:H films varies within the interval 2.0-2.2 eV. The strong evidence for two distinct types of PL processes is presented: one being linked with oligosilanes and the second one attributed to electron-hole recombination in tail states. EL has been investigated in p-i-n and p + -p-n-n + structures with CrNi/ITO contacts. The EL occurs after initial forming in reverse bias only and its external quantum efficiency is approximately 10-5 percent. The shape and spectral position of EL spectra suggest that the light emission in this case is probably due to simultaneous excitation of the oligosilane units and impact ionization by hot electrons.
Dian, J. (Fac. of Math. & Phys., Charles Univ., Prague, Czech Republic); Valenta, J.; Poruba, A.; Horvath, P.; Luterova, K.; Fojtik, P.; Pelant, I. Source: Proceedings of the SPIE - The International Society for Optical Engineering, v 4016, p 472-7, 2000
10_01_25_Silicon based materials for optoelectronics visible photoluminescence and electroluminescence from amorphous silicon
 Hole diffusion at the recombination junction of thin film tandem solar cells and its effect on the illuminated current-voltage characteristic 2000
Abstract:Computer simulation of experimental current density–voltage (J–V) and quantum efficiency characteristics of thin film p1-i1-n1-p2 structures and of double junction solar cells (p1-i1-n1-p2-i2-n2), has been used to understand the hole transport mechanisms near the np "tunnel" junction between two subcells of a multijunction structure. Two different types of p layers at the junction have been studied: (i) hydrogenated microcrystalline silicon (µc-Si:H) and (ii) hydrogenated amorphous silicon carbide (a-SiC:H). There is a striking difference between the experimental J–V characteristics for the p1-i1-n1-p2 structures, with case (i) having a fairly high fill factor (FF) and conversion efficiency (), as against a very low FF and in case (ii). Although the difference is much smaller for double junction cells employing these two types of materials as the p layer at the junction, the fill factor of the cell employing µc-Si:H is about 8% higher. Analysis of transport properties as a function of position by computer modeling reveals that the main difference in behavior between the two cases is due to the much higher free hole population in the p layer at the junction when it is microcrystalline; which in turn, is a direct consequence of the lower activation energy for this case. We also learn that not only tunneling and the electric field in the bottom subcell, but also diffusion, plays a major role in pushing the holes produced in it by the incident light towards the recombination layer at the junction; and thereby helps improve cell performance, especially its fill factor. We conclude that the p layer at the junction should have a high free hole density (low activation energy in the device), to attain an overall high fill factor and conversion efficiency. Another interesting inference is the fact that tunneling as transport mechanism for holes towards the junction is more important when the p layer at the junction is a-SiC:H than when it is microcrystalline, while diffusion plays a more prominent role in propelling holes towards the junction in the latter case.
Palit, N. (Energy Res. Unit, Indian Assoc. for the Cultivation of Sci., Calcutta, India); Dasgupta, A.; Ray, S.; Chatterjee, P. Source: Journal of Applied Physics, v 88, n 5, p 2853-61, 1 Sept. 2000
10_01_25_Hole diffusion at the recombination junction of thin film tandem solar cells and its effect on the illuminated current–voltage characteristic
 Optical modeling of a-Si:H solar cells with rough interfaces: Effect of back contact and interface roughness 2000
Abstract:An approach to study the optical behavior of hydrogenated amorphous silicon solar cells with rough interfaces using computer modeling is presented. In this approach the descriptive haze parameters of a light scattering interface are related to the root mean square roughness of the interface. Using this approach we investigated the effect of front window contact roughness and back contact material on the optical properties of a single junction a-Si:H superstrate solar cell. The simulation results for a-Si:H solar cells with SnO2:F as a front contact and ideal Ag, ZnO/Ag, and Al/Ag as a back contact are shown. For cells with an absorber layer thickness of 150–600 nm the simulations demonstrate that the gain in photogenerated current density due to the use of a textured superstrate is around 2.3 mA cm–2 in comparison to solar cells with flat interfaces. The effect of the front and back contact roughness on the external quantum efficiency (QE) of the solar cell for different parts of the light spectrum was determined. The choice of the back contact strongly influences the QE and the absorption in the nonactive layers for the wavelengths above 650 nm. A practical Ag back contact can be successfully simulated by introducing a thin buffer layer between the n-type a-Si:H and Ag back contact, which has optical properties similar to Al, indicating that the actual reflection at the n-type a-Si:H/Ag interface is smaller than what is expected from the respective bulk optical parameters. In comparison to the practical Ag contact the QE of the cell can be strongly improved by using a ZnO layer at the Ag back contact or an ideal Ag contact. The photogenerated current densities for a solar cell with a 450 nm thick intrinsic a-Si:H layer with ZnO/Ag and ideal Ag are 16.7 and 17.3 mA cm–2, respectively, compared to 14.4 mA cm–2 for the practical Ag back contact. The effect of increasing the roughness of the contact interfaces was investigated for both superstrate and substrate types of solar cells. Increasing the roughness of the carrier electrode, i.e., the rough electrode on which the silicon cell structure is deposited, up to 35 nm leads to a strong increase in the photogenerated current density; for higher values of the interface roughness the photogenerated current density tends to saturate.
Zeman, M. (Lab. of Electron. Components, Technol. & Mater., Delft Univ. of Technol., Netherlands); van Swaaij, R.A.C.M.M.; Metselaar, J.W.; Schropp, R.E.I. Source: Journal of Applied Physics, v 88, n 11, p 6436-43, 1 Dec. 2000
10_01_25_Optical modeling of a-SiH solar cells with rough interfaces Effect of back contact and interface roughness
 Detective quantum efficiency of an X-ray image intensifier chain as a benchmark for amorphous silicon flat panel detectors 2001
Abstract:Amorphous silicon flat panel x-ray detectors (A-Si FXD) are expected eventually to replace traditional x-ray image intensifier systems (XRII) in medical radiography in the long term. The advantages of FXD's are their large detection area, no distortion, no sensitivity to magnetic fields, low weight and compactness. However, they do not provide the high sensitivity of specific optimized systems based on image intensifiers, which approach the sensitivity of single x-ray photon counting in an appropriate configuration whereas the noise equivalent number of photons for an a-Si imager is typically several photons at medical energies. That is, the detective quantum efficiency of an XRII at low dose is expected to be higher.
Koch, A. (Thales Electron Devices, Moirans, France); Macherel, J.M.; Wirth, T.; de Groot, P.; Ducourant, T.; Couder, D.; Moy, J.P.; Calais, E. Source: Proceedings of the SPIE - The International Society for Optical Engineering, v 4320, p 115-20, 2001 Database: Inspec
10_01_25_Detective quantum efficiency of an x-ray image intensifier chain as a benchmark for amorphous silicon flat-panal detectors
 Development of highly efficient thin film silicon solar cells on texture-etched zinc oxide-coated glass substrates 2001
Abstract:ZnO films prepared by magnetron sputtering on glass substrates and textured by post-deposition chemical etching are applied as substrates for p–i–n solar cells. Using both rf and dc sputtering, similar surface textures can be achieved upon etching. Excellent light trapping is demonstrated by high quantum efficiencies at long wavelengths for microcrystalline silicon solar cells. Applying an optimized microcrystalline/amorphous p-layer design, stacked solar cells with amorphous silicon top cells yield similarly high stabilized efficiencies on ZnO as on state-of-the-art SnO2 (9.2% for a-Si/a-Si). The efficiencies are significantly higher than on SnO2-coated float glass as used for module production.
Muller, J. (Inst. of Photovoltaics, Forschungszentrum Julich GmbH, Germany); Kluth, O.; Wieder, S.; Siekmann, H.; Schope, G.; Reetz, W.; Vetterl, O.; Lundszien, D.; Lambertz, A.; Finger, F.; Rech, B.; Wagner, H. Source: Solar Energy Materials and Solar Cells, v 66, n 1-4, p 275-81, Feb. 2001
10_01_25_Development of highly efficient thin film silicon solar cells on texture-etched zinc oxide-coated glass substrates
 Modeling the optical quantum efficiency of thin film amorphous silicon solar cells 2001
Abstract:The optical quantum efficiency and spectral response of p-i-n thin film amorphous silicon (a-Si:H) solar cells have been modeled using software based on optical admittance analysis. The optical constants of a-Si:H and Indium Tin Oxide (ITO) thin film layers have been measured by Variable Angle Spectroscopic Ellipsometry (VASE) and used as inputs into the optical admittance analysis program in order to model cells constructed from these films. Amorphous silicon thin films and p-i-n assemblies have been deposited by glow discharge and reactive sputtering techniques. The optical constants of doped and intrinsic a-Si:H thin films were determined by VASE, and the film thickness verified by Scanning Electron Microscopy studies. The optical constants of commercially available transparent conducting oxide (TCO) coated substrates have also been determined by VASE. The experimental transmission spectra of p-i-n assemblies are compared with transmission spectra that have been modeled using the measured optical constants. Results of modeling different a-Si:H solar cell structures using these materials are presented, including a study of the optimal TCO layer thickness for p-i-n a-Si:H solar cells. This work shows that optical admittance modeling gives a good prediction of the optical behavior of p-i-n assemblies, but that accurate measurements of the optical constants of the component films are required in order to model effectively the optical quantum efficiency and photocurrent.
Rowlands, S.F. (Electr. & Electron. Eng., Univ. of Western Australia, Perth, WA, Australia); Livingstone, J.; Lund, C.P. Source: Amorphous and Heterogeneous Silicon Thin Films - 2000. Symposium (Materials Research Society Symposium Proceedings Vol.609), p A30.7.1-6, 2001 Database: Inspec
 Optical modelling of thin film solar cells with textured interfaces using the effective medium approximation
Abstract:Simple methods for increasing the maximum achievable current density of amorphous silicon (a-Si:H) solar cells include bandgap and layer thickness optimisation, and light confinement strategies. The goal of the optical modelling work presented here has been to examine the nature and potential of these effects, in particular the optical enhancement resulting from the use of finely textured transparent conducting oxides. A computer program that combines coherent and incoherent optical theory has been used as a flexible tool for simulating the performance of any general thin film solar cell structure. An effective medium approximation has been used to model the optical effects of microroughness (texturing with correlation lengths smaller than the wavelength of light). This work suggests that effective interface grading due to microroughness does have a significant effect on the optical performance of a-Si:H solar cells, and that both enhancement and deterioration in the maximum achievable current density can be the outcome. Where both effective interface grading (microroughness) and larger scale texturing (macroroughness) are fully exploited, optical yields may be increased beyond their current level. This work emphasises the importance of characterising and controlling the interface morphology to optimise the short circuit current and maintain the open circuit voltage.
10_01_25_Optical modelling of thin film solar cells with textured interfaces using the effective medium approximation
 Performance of a-Si:H photodiode technology-based advanced CMOS active pixel sensor imagers 2001
Abstract:Amorphous silicon photodiode technology is a very attractive option for image array integrated circuits because it enables large die-size reduction and higher light collection efficiency than c-Si arrays. The concept behind the technology is to place the photosensing element directly above the rest of the circuit, thus eliminating the need to make areal tradeoffs between photodiode and pixel circuit. We have developed an photodiode array technology that is fully compatible with a 0.35 um CMOS process to produce image sensors arrays with 10-bit dynamic range that are 30% smaller than comparable c-Si photodiode arrays. The work presented here will discuss performance issues and solutions to lend itself to cost-effective high-volume manufacturing. The various methods of interconnection of the diode to the array and their advantages will be presented. The effect of doped layer thickness and concentration on quantum efficiency, and the effect of a-Si:H defect concentration on diode performance will be discussed. The photodiode dark leakage current density is about 80 pA/cm2, and its absolute quantum efficiency peaks about 85% at 550 nm. These sensors have 50% higher sensitivity, and 2x lower dark current when compared to bulk silicon sensors of the same design. The cell utilizes a 3 FET design, but allows for 100% photodiode area due to the elevated nature of the design. The VGA (640 X 480), array demonstrated here uses common intrinsic and p-type contact layers, and makes reliable contact to those layers by use of a monolithic transparent conductor strap tied to vias in the interconnect.
Theil, J.A. (Imaging Electron. Div., Agilent Technol., Santa Clara, CA, USA); Haddad, H.; Snyder, R.D.; Zelman, M.; Hula, D.; Lindahl, K.A. Source: Proceedings of the SPIE - The International Society for Optical Engineering, v 4435, p 206-13, 2001
10_01_26_Performance of a-SiH photodiode technology-based advanced CMOS active pixel sensor imagers
 Thin-film UV detectors based on hydrogenated amorphous silicon and its alloys 2001
Abstract:Thin film ultraviolet detectors based on hydrogenated amorphous silicon alloys are realized with different diode structures (PIN, NIP, PN, and NP). The PIN and NIP detectors exhibit higher sensitivity in the ultraviolet spectrum and a significant lower dark current in comparison to the PN or NP structures. The best detector performance was achieved with a 33 nm thick PIN diode. This detector shows a maximum of quantum efficiency of 36.3% at a wavelength of 310 nm. By varying the thickness of the semi-transparent Ag front contact the selectivity of the detectors with the quantum efficiency peak at 320 nm can be adjusted. Thus, the spectral sensitivity of the detector shifts from a broad UV to a selective UV-B spectrum.
Krause, M. (Inst. fur Photovoltaik, Forschungszentrum Julich GmbH, Germany); Topic, M.; Stiebig, H.; Wagner, H. Source: Physica Status Solidi A, v 185, n 1, p 121-7, 16 May 2001
10_01_26_Thin-Film UV Detectors Based on Hydrogenated Amorphous Silicon and Its Alloys
 Design considerations for a hybrid amorphous silicon/photoelectrochemical multijunction cell for hydrogen production 2003
Abstract:Triple-junction amorphous silicon (a-Si) solar cells demonstrating photovoltaic (PV) efficiencies up to 12.7% and open-circuit voltages up to 2.3V have recently been deposited onto stainless-steel foil substrates by the University of Toledo for photoelectrochemical (PEC) tests conducted by the University of Hawaii. The fundamental design strategy for producing such high efficiency in multijunction amorphous silicon devices involves careful current matching in each of the junctions by adjustment of the absorption spectra through bandgap tailoring. Integrated electrical/optical models are frequently used to aid in the optimization procedure, as well documented in the PV literature. Typically, the top nip junction in an a-Si triple-junction cell is designed to absorb most strongly in the 350-500nm range. In principle, this top cell could be replaced by a PEC junction with strong absorption in a similar range to form a water-splitting photoelectrode for hydrogen production. This photoelectrode could be fabricated on SS with the back surface catalyzed for the hydrogen evolution reaction, and the front surface deposited with an a-Si:nipnip/ITO/SC structure. The top layer semiconductor (SC), which forms the PEC junction with an electrolyte, must have appropriate conduction band alignment for the oxygen evolution reaction, and the junction must be strongly absorbing in the 350-500nm region for current matching. Possible candidate SC materials include dye-sensitized titanium dioxide (TiO2), tungsten trioxide (WO3), and iron oxide (Fe2O3). This paper discusses the specific design considerations for high solar-to-hydrogen conversion efficiency in a hybrid solid-state/PEC photoelectrode, and describes the use of integrated electrical/electrochemical/optical models developed at the University of Hawaii for the analysis of such hybrid structures. Important issues include the bias-voltage and current-matching requirements in the solid-state and electrochemical junctions, as well as fundamental quantum efficiency considerations.
Miller, E.L. (Sch. of Ocean & Earth Sci. & Technol., Hawaii Univ., Honolulu, HI, USA); Rocheleau, R.E.; Deng, X.M. Source: International Journal of Hydrogen Energy, v 28, n 6, p 615-23, June 2003
10_01_26_Design considerations for a hybrid amorphous silicon photoelectrochemical multijunction cell for hydrogen production
 Quantum Efficiency
Abstract:Quantum efficiency (QE) is a figure-of-merit of a photon detector. QE is equal to the percentage of incident photons that are converted by the detector into electrons that constitute a measurable signal. QE applies to detectors spanning a wavelength range from the far infrared (IR) to gamma rays because these are all photons. A detector's QE is affected by many variables: wavelength (of radiation), surface reflectance(s), absorption coefficient(s), layer thickness(es), frequency response, bulk and surface recombination, doping level(s), device configuration, etc.
Early detectors, which were based on the photoelectric effect in metals, required a lot of energy (> workfunction) for a photon to release an electron to vacuum. The advent of semiconductors reduced the energy needed to create photoexcited charge carriers (electrons and holes) because the electrons were only excited from the valence to the conduction band. Initially, silicon (because of its high bandgap energy) allowed operation from the near ultraviolet (UV) to the near infrared (NIR). Later, new low bandgap materials enabled longer wavelength operation, out to the far infrared, and also a wide variety of detectors. Modern detectors fall into three classes: photoconductive (PC) (intrinsic, extrinsic, or quantum well), photovoltaic (PV) diodes (p-n, p-i-n, Schottky barrier, avalanche, and heterojunction), and external photoeffect (photoemissive) photocathodes.
Usually, single element detectors are used for simple detection. For imaging purposes, linear or area arrays of small detectors (size < diffusion length Ldiff) are used. Large single element detectors (size > Ldiff) are effectively infinite, and described by one-dimensional models of QE; small detectors in arrays are finite and require three-dimensional, numerical models for the QE.
This paper is quite good in explaining QE and it gives different cases such as photoconductors, schottky barrier diodes, external photoeffect diodes and quantum well infared detectors. This paper talks about ideal QE devices and how to calculated the QE for devices. However it does not explain what each part of the QE graph tells you.
TY - GEN BT - Encyclopedia of Optical Engineering PB - Taylor & Francis AU - Dhar, Vikram TI - Quantum Efficiency SN - 978-0-8247-0940-2 PY - 2003 SP - 2197 EP - 2218 UR - http://www.informaworld.com/10.1081/E-EOE-120009873
 Effect of surface roughness of ZnO:Al films on light scattering in hydrogenated amorphous silicon solar cells 2003
Abstract:Experimental investigation combined with computer modeling is used for analysis of light scattering process in hydrogenated amorphous silicon (a-Si:H) solar cells deposited on textured glass/ZnO:Al substrates. Descriptive scattering parameters—haze and angular distribution functions (ADFs)—for the textured ZnO:Al films with different surface roughness are determined. The haze parameters of all internal interfaces in the a-Si:H solar cells are calculated using equations of scalar scattering theory calibrated on the measurements of the substrates. The ADFs determined for the substrates are modified and applied to the internal interfaces. The scattering parameters are incorporated in our optical model and used to simulate the effect of the ZnO:Al surface roughness on the quantum efficiency (QE) of the solar cells. The simulations reproduce the measured QE of all solar cells with different roughness of the substrate very well.
Krc, J. (Fac. of Electr. Eng., Ljubljana Univ., Slovenia); Zeman, M.; Kluth, O.; Smole, F.; Topic, M. Source: Thin Solid Films, v 426, n 1-2, p 296-304, 24 Feb. 2003
10_01_26_Effect of surface roughness of ZnOAl films on light scattering in hydrogenated amorphous silicon solar cells
 3-dimensional optical model for thin film silicon solar cells 2003
Abstract:This paper addresses optical effects in small area thin film silicon p-i-n solar cells deposited on a glass/TCO substrate. An existing one-dimensional model was extended to three dimensions to include the effect of substrate glass thickness and lateral solar cell area. With its help we can model real laboratory cells where the cell dimensions are comparable to the glass thickness. For a quantitative evaluation we compare the external quantum efficiency of an infinitely large solar cell with small area cells. Here the modeling results show increasing differences with increasing glass thickness, decreasing cell area and improving light scattering properties of the TCO. This is explained by internal light trapping in the glass substrate, which causes loss or gain of light intensity absorbed in the cell area. Neglecting such effects can lead to about 11% error in short circuit current density calculated from quantum efficiency measurements.
Springer, J. (Inst. of Phys., Acad. of Sci. of the Czech Republic, Prague, Czech Republic); Poruba, A.; Mullerova, L.; Vanecek, M.; Reetz, W.; Muller, J. Source: Proceedings of 3rd World Conference on Photovoltaic Energy Conversion (IEEE Cat. No.03CH37497), p 1827-30 Vol.2, 2003
10_01_26_3-dimensional optical model for thin film silicon solar cells
 Analysis of light scattering in amorphous Si:H solar cells by a one-dimensional semi-coherent optical model 2003
Abstract:A one-dimensional semi-coherent optical model for thin-film solar cells is presented. The optical circumstances at flat interfaces are addressed and the situation at rough interfaces in the model is described for the case of direct (coherent) incident and scattered (incoherent) incident light. After the model has been experimentally verified, analysis of the light scattering process in hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells is carried out. The influence of the interface root-mean-square roughness and the effect of different angular distribution functions of diffused light on quantum efficiency and short-circuit current are investigated by the optical model.
Krc, J. (Fac. of Electr. Eng., Ljubljana Univ., Slovenia); Smole, F.; Topic, M. Source: Progress in Photovoltaics: Research and Applications, v 11, n 1, p 15-26, Jan. 2003
10_01_26_Analysis of light scattering in amorphous SiH solar cells by a one-dimensional semi-coherent optical model
 Characterization of a 14" × 17" flat panel detector based on ion shower doped a-Si:H PIN diodes 2003
Abstract:In recent years it has become technically and economically feasible to use solid-state detector technology to display, store, and transfer x-ray images. In this paper we report the performance of a 33 x 41 cm2 amorphous silicon flat panel detector based on an ion shower doped P-I-N photodiode/TFT array. The p-layer of diode is formed by an ion shower doping method instead of the conventional Plasma Enhanced Chemical Vapor Deposition method. Measurements of x-ray imaging performances are reported with respect to the general imaging metrics, such as modulation transfer function, noise power spectrum, and detective quantum efficiency.
Hee Joon Kim; Gyuseong Cho Source: 2002 IEEE Nuclear Science Symposium Conference Record (IEEE Cat. No.02CH37399), p 931-5 vol.2, 2003
10_01_26_Characterization of a 14” x 17” Flat Panel
 Optical modelling of thin-film silicon solar cells deposited on textured substrates 2004
Abstract:Optical modelling is used to investigate effects of light scattering in amorphous silicon and microcrystalline silicon solar cells. The role of enhanced haze parameter and different angular distribution function of scattered light is analyzed. Results of optical simulation show that enhanced haze parameter compared to that of Asahi U-type SnO2:F does not improve external quantum efficiency and short-circuit current density of amorphous silicon solar cell significantly, whereas for microcrystalline silicon solar cell the improvement is larger. Angular distribution function affects the external quantum efficiency and the short-circuit current density significantly.
Krc, J. (Fac. of Electr. Eng., Ljubljana Univ., Slovenia); Zeman, M.; Smole, F.; Topic, M. Source: Thin Solid Films, v 451-452, p 298-302, 22 March 2004
10_01_26_Optical modelling of thin-film silicon solar cells deposited on textured substrates
 Improved back reflector for high efficiency hydrogenated amorphous and nanocrystalline silicon based solar cells 2005
Baojie Yan (United Solar Ovonic Corp., Troy, MI, USA); Owens, J.M.; Chun-Sheng Jiang; Yang, J.; Guha, S. Source: Amorphous and Nanocrystalline Silicon Science and Technology-2005. Symposium (Materials Research Society Symposium Proceedings Vol.862), p 603-8, 2005
 Light induced degradation of microcrystalline silicon solar cells 2006
Abstract:Microcrystalline silicon solar cells with different crystalline volume fractions (Xc) of intrinsic layer were used to perform light soaking experiments under different light sources. Results showed that the higher Xc of microcrystalline silicon of intrinsic layer is, the less light induced degradation produced in solar cell. According to quantum efficiency (QE) results, the degradation only occurred in the short wavelength range which corresponds to amorphous silicon absorption. A Stabler–Wronski (SW)-like effect associated with the amorphous silicon fraction in microcrystalline silicon is responsible for this degradation.
Yan Wang (Inst. of Photo-Electron. Thin Film Devices & Technique, Nankai Univ., Tianjin, China); Xiaoyan Han; Feng Zhu; Guofu Hou; Huizhi Ren; Kunde Zhang; Junming Xue; Jian Sun; Ying Zhao; Xinhua Geng Source: Journal of Non-Crystalline Solids, v 352, n 9-20, p 1909-12, 15 June 2006
10_01_26_Light induced degradation of microcrystalline silicon solar cells
 High performance hydrogenated amorphous silicon n-i-p photo-diodes on glass and plastic substrates by low-temperature fabrication process 2007
Kyung Ho Kim (Univ. of Waterloo, Waterloo, Canada); Vygranenko, Y.; Bedzyk, M.; Jeff Hsin Chang; Tsu Chiang Chuang; Striakhilev, D.; Nathan, A.; Heiler, G.; Tredwell, T. Source: Amorphous and Polycrystalline Thin-Film Silicon Science and Technology - 2007, p 481-6, 2007
 Internal Quantum Efficiency for Solar Cells 2007
Abstract:The total internal quantum efficiency (IQE) of a flat-band p–n homojunction silicon solar cell and contributions of the three regions to it are numerically evaluated. It is found that both the spatial widths of the cell and the surface recombination velocities have significant impacts on the IQEs. By a linear transformation and a proper approximation, the differential equation of the minority carrier density in a textured cell becomes the same form as for the flat cell. What makes differences is that texturization slightly enhances the IQEs for photons with longer wavelengths while notably increasing external quantum efficiency. Hence it plays a good role for getting a better performance of a solar cell. It is considered that the results in the present are of universal technical importance both in designing solar cells and their surface structures.
"On the other hand, the photo-generated current strongly relates to the quantum efficiency (QE). To enhance the conversion efficiency one has to raise the QE. From theoretical aspect, the QE corresponds to the spectral response (SR) which determines the spectral distribution of the short circuit current ISC. By calculating the QE, both the SR and the contributions to the ISC of different wavelengths can be determined, helping one analyze quantum yields from the different cell regions." -paper
doi:10.1016/j.solener.2007.07.010 | How to Cite or Link Using DOI Copyright © 2007 Elsevier Ltd All rights reserved. W.J. Yang, a, , Z.Q. Maa, X. Tanga, C.B. Fenga, W.G. Zhaoa and P.P. Shia
aMicroelectronic Group, Department of Physics, Shanghai University, Shanghai 200444, PR China Received 1 September 2006; revised 10 December 2006; accepted 20 July 2007. Communicated by: Associate Editor T.M. Razykov. Available online 5 September 2007.
10_02_02_Internal Quantum Efficiency for Solar Cells
 Optimization of amorphous silicon oxide buffer layer for high-efficiency p-type hydrogenated microcrystalline silicon oxide/n-type crystalline silicon heterojunction solar cells 2008
Abstract:Intrinsic hydrogenated amorphous silicon oxide (i-a-SiO:H) films deposited by very high frequency plasma-enhanced chemical vapor deposition (60MHz VHF-PECVD) at a low substrate temperature of approximately 200 �C were used as a front buffer layer in p-type hydrogenated microcrystalline silicon oxide/n-type crystalline silicon (p-mc-SiO:H/n-c-Si) heterojunction solar cells. We found that the oxygen concentration in the i-a-SiO:H buffer layer strongly affected the solar cell performance and that the short wavelength response in quantum efficiency (QE) was improved by oxygen addition. Employing a p-mc-SiO:H/i-a-SiO:H/n-Si [Czochralski (CZ), 200 mm, (100)]/i-a-Si:H/n-a-Si:H/Ag/Al configuration, we achieved an efficiency of 17.9% with Voc of 671 mV.
Sritharathikhun, J. (Dept. of Phys. Electron., Tokyo Inst. of Technol., Tokyo, Japan); Yamamoto, H.; Miyajima, S.; Yamada, A.; Konagai, M. Source: Japanese Journal of Applied Physics, v 47, n 11, p 8452-5, Nov. 2008
10_01_26_ Optimization of amorphous silicon oxide buffer layer for high-efficiency p-type hydrogenated microcrystalline silicon oxide n-type crystalline silicon heterojunction solar cells
 Modeling of light-induced degradation of amorphous silicon solar cells 2008
Abstract:Light-induced degradation of hydrogenated amorphous silicon (a-Si:H) solar cells has been modeled using computer simulations. In the computer model, the creation of light-induced defects as a function of position in the solar cell was calculated using the recombination profile. In this way, a new defect profile in the solar cell was obtained and the performance was calculated again. The results of computer simulations were compared to experimental results obtained on a-Si:H solar cell with different intrinsic layer thickness. These experimental solar cells were degraded under both open- and short-circuit conditions, because the recombination profile in the solar cells could then be altered significantly. A reasonable match was obtained between the experimental and simulation results if only the mid-gap defect density was increased. To our knowledge, it is the first time that light-induced degradation of the performance and the quantum efficiency of a thickness series of a-Si:H solar cells has been modeled at once using computer simulations.
Klaver, A. (Delft Univ. of Technol., Delft, Netherlands); van Swaaij, R.A.C.M.M. Source: Solar Energy Materials and Solar Cells, v 92, n 1, p 50-60, Jan. 2008
10_01_26_Modeling of light-induced degradation of amorphous silicon solar cells
 Substrate engineering for high efficiency thin film solar cells 2008
Abstract:The design considerations for a spectra modifying, light scattering layer for amorphous silicon solar cells were investigated. Efficient commercially available phosphors absorb one near IR photon and one near UV photon and emit one photon in the visible spectrum. Thereby such phosphors offer the possibility to convert two poorly utilized portions of the solar spectrum to photons that are converted to electric energy with high quantum efficiency in amorphous silicon-based solar cells. Large band gap, conductive, a-SiC:H and a-SiN:H are attractive matrices for phosphors as scattered light and emitted photons are thereby directed towards the underlying solar cell structure.
Mawyin, J.A. (Stony Brook Univ., Stony Brook, USA); Chawda, S.G.; Halada, G.P.; Clayton, C.R.; Tonucci, R.J.; Fortmann, C.M. Source: Journal of Non-Crystalline Solids, v 354, n 19-25, p 2492-4, 1 May 2008
10_01_26_Substrate engineering for high efficiency thin film solar cells
 A comparison of fill factor and recombination losses in amorphous silicon solar cells on ZnO and SnO2 2009
Abstract:Effects of ZnO and SnO2 TCO (Transparent Conductive Oxide) substrate materials on hydrogenated amorphous silicon (a-Si:H) p-i-n solar cell performances and recombination kinetics have been investigated. DC and Frequency-resolved photocurrent measurements in a-Si:H p-i-n solar cells of 6 have been carried out experimentally. In particular, the I–V characteristics in the dark and light, the quantum efficiency spectra, the intensity-, bias voltage- and frequency-dependence of photocurrent were obtained. Fill factor (FF) values were determined from I–V characteristics for both types of substrate cells under various illumination levels. The exponent v in the power–law relationship, Iph α Gv, between generating flux density and photocurrent were determined at different bias voltages (DC) and modulation frequencies. High values of Voc (open-circuit voltage), FF, and DC exponent v for the a-Si:H p-i-n solar cell with SnO2 were obtained, but the integrated QE (quantum efficiency), the modulated exponent v were found to be low compared to cells prepared on ZnO substrates. Our results show that these parameters are sensitive to the ZnO and SnO2 substrate materials which act as a window layer allowing most of the incident light to pass into the i-layer of p-i-n cells.
Alkaya, A. (Dept. of Electr.-Electron. Eng., Univ. of Mersin, Mersin, Turkey); Kaplan, R.; Canbolat, H.; Hegedus, S.S. Source: Renewable Energy, v 34, n 6, p 1595-9, June 2009
10_01_26_A comparison of fill factor and recombination losses in amorphous silicon solar cells on ZnO and SnO2
 2D modeling of silicon based thin film dual and triple junction solar cells 2009
Abstract:Based on Crosslight APSYS, thin film amorphous Si (a-Si:H)/microcrystalline (µc-Si) dual-junction (DJ) and a- Si:H/amorphous SiGe:H (a-SiGe:H)/µc-Si triple-junction (TJ) solar cells are modeled. Basic physical quantities like band diagrams, optical absorption and generation are obtained. Quantum efficiency and I-V curves for individual junctions are presented for current matching analyses. The whole DJ and TJ cell I-V curves are also presented and the results are discussed with respect to the top surface ZnO:Al TCO layer affinity. The interface texture effect is modeled with FDTD (finite difference time domain) module and results for top junction are presented. The modeling results give possible clues to achieve high efficiency for DJ and TJ thin film solar cells.
Xiao, Y.G. (Crosslight Software Inc., Burnaby, BC, Canada); Uehara, K.; Lestrade, M.; Li, Z.Q.; Li, Z.M.S. Source: Proceedings of the SPIE - The International Society for Optical Engineering, v 7409, p 74090F (8 pp.), 2009
10_01_26_2D modeling of silicon based thin film dual and triple junction solar cells
 Quantum efficiency of light-induced defect creation in hydrogenated amorphous silicon and amorphous As2Se3 2004
Abstract:The quantum efficiency (QE) of light-induced metastable defect creation in hydrogenated amorphous silicon (a-Si : H) and amorphous As2Se3 (a-As2Se3) by bandgap and subgap illumination has been deduced from photocurrent measurements. The QE decreases with increasing number of absorbed photons. A higher QE for a-As2Se3 than for a-Si : H has been observed and this is interpreted in terms of the higher structural flexibility of a-As2Se3. We have also found that, for both materials, subgap illumination yields a higher QE than does bandgap illumination.
Shimakawa, K. (Dept. of Electr. & Electron. Eng., Gifu Univ., Japan); Meherun-Nessa; Ishida, H.; Ganjoo, A. Source: Philosophical Magazine, v 84, n 1, p 81-9, 1 Jan. 2004 Database: Inspec
10_01_26_Quantum efficiency of light-induced defect creation in hydrogenated amorphous silicon and amorphous As2Se3
 Annual exergy evaluation on photovoltaic-thermal hybrid collector 1997
Abstract: In this study, we designed and constructed a photovoltaic-thermal hybrid collector on our campus. The collector consisted of a liquid heating fiat-plate solar collector with mono-Si PV cells on substrate of non-selective aluminum absorber plate, The collector area was 1.3 x 0.5 m . Since electrical and thermal energy are different in nature, it is necessary to take into account the nature of the energy in evaluating or comparing them. For this, we adopted concepts based on the exergy theory. From our annual experimental evaluation based on exergy, we are concluding that the PV/T collector can produce higher output density than a unit PV module or liquid heating fiat-plate solar collector.
 Exergy Efficient Production, Storage and Distribution of Solar Energy 2003 THESIS
Abstract: Effective energy management must not only consider how much energy is needed to perform a certain task, but also what type of energy is actually required. The energy demand by application area in residential buildings in the EU countries is shown in Figure 1.1 (European Commission, 2000). Space heating and hot water represent the largest demand, and the required energy is “low quality” heat characterized by obtaining temperature differences in the range of 10 – 50 °C. In the industrialized world this demand for low temperature heat is usually covered by consuming “high quality” resources such as fossil fuels, which are both limited in abundance and have a negative effect on the global environment. Our future energy system must to a larger extent be based on renewable and clean energy resources and carriers, and, since the access to high quality energy is limited, these resources must be reserved for applications where high quality energy is actually required. Demands for low quality, low temperature heat on the other hand, can successfully be covered by utilizing correspondingly low quality energy resources.
The work presented in this thesis represents a small contribution to the ongoing research aiming to develop effective ways of utilizing thermal energy, solar heat in particular, thereby replacing the consumption of high quality resources for low quality purposes. More specifically, the thesis addresses the effectiveness at which exergy is managed through the stages of solar heat production, storage, and distribution, and investigates the integration of new technologies in an exergy efficient low temperature heating system. Exergy is a measure of the quality associated with a particular source of energy, or how much work can be withdrawn in a reversible process. A second main topic is long term storage of thermal energy as latent heat in supercooled liquids. Supercooled substances in thermal equilibrium with the surroundings experiences no further heat loss, and the stored latent heat can be retrieved on demand at a later time. A limited amount of previous work has been documented on this topic. The thesis therefore gives an overview over important factors for potential supercooling heat storage applications, while probing deeper into the issues of quantifying the heat storage capacity and also how the crystallization of a supercooled liquid can be triggered in a controlled manner.
10_04_28_Exergy Efficient Production, Storage and Distribution of solar energy.pdf
 Performance of a concentrating photovoltaic/thermal solar collector 2005
Abstract: The performance of a parabolic trough photovoltaic/thermal collector with a geometric concentration ratio of 37· is described. Measured results under typical operating conditions show thermal efficiency around 58% and electrical efficiency around 11%, therefore a combined efficiency of 69%. The impact of non-uniform illumination on the solar cells is investigated using purpose built equipment that moves a calibrated solar cell along the line of the receiver and measures short circuit current. The measured illumination flux profile along the length shows significant variation, despite the mirror shape error being less than 1 mm for most of the mirror area. The impact of the illumination nonuniformities due to the shape error, receiver support post shading and gaps between the mirrors is shown to have a significant effect on the overall electrical performance. The flux profile transverse to the receiver length is also investigated. Peak flux intensities are shown to be around 100 suns. The impact on efficiency due to open circuit voltage reduction is discussed.
 Performance evaluation of photovoltaic thermal solar air collector for composite climate in India 2005
Abstract:The objective of present study is to evaluate the performance of the photovoltaic (PV) module integrated with air duct for composite climate of India. In this case, thermal energy is produced along with electrical energy generated by a PV module with higher efficiency. An analytical expression for an overall efficiency (electrical and thermal) has been derived by using energy balance equation for each component. Experimental validation of thermal model of hybrid photovoltaic/thermal (PV/T) system has also been carried out. It has been observed that there is a fair agreement between theoretical and experimental observations. Further it is concluded that an overall thermal efficiency of PV/T system is significantly increased due to utilization of thermal energy in PV module.
10_04_28_Performance evaluation of photovoltaic thermal solar air collector for composite climate of India.pdf
 Energy and exergy efficiencies of a hybrid photovoltaic–thermal air collector 2006
Abstract:In this communication, an attempt has been made to evaluate exergy analysis of a hybrid photovoltaic–thermal (PV/T) parallel plate air collector for cold climatic condition of India (Srinagar). The climatic data of Srinagar for the period of four years (1998–2001) has been obtained from Indian Metrological Department (IMD), Pune, India. Based on the data four climatic conditions have been defined. The performance of a hybrid PV/T parallel plate air collector has been studied for four climatic conditions and then exergy efficiencies have been carried out. It is observed that an instantaneous energy and exergy efficiency of PV/T air heater varies between 55–65 and 12–15%, respectively. These results are very close to the results predicted by Bosanac et al. [Photovoltaic/thermal solar collectors and their potential in Denmark. Final Report, EFP Project, 2003, 1713/00-0014, www.solenergi.dk/rapporter/pvtpotentialindenmark.pdf].
10_04_28_Energy and exergy efficiencies of a hybrid photovoltaic–thermal air collector.pdf
 Quantifying global exergy resources 2006
Abstract:Exergy is used as a common currency to assess and compare the reservoirs of theoretically extractable work we call energy resources. Resources consist of matter or energy with properties different from the predominant conditions in the environment. These differences can be classified as physical, chemical, or nuclear exergy. This paper identifies the primary exergy reservoirs that supply exergy to the biosphere and quantifies the intensive and extensive exergy of their derivative secondary reservoirs, or resources. The interconnecting accumulations and flows among these reservoirs are illustrated to show the path of exergy through the terrestrial system from input to its eventual natural or anthropogenic destruction. The results are intended to assist in evaluation of current resource utilization, help guide fundamental research to enable promising new energy technologies, and provide a basis for comparing the resource potential of future energy options that is independent of technology and cost.
 Energy, exergy, and Second Law performance criteria 2007
Abstract: Performance criteria, such as efficiencies and coefficients of performance, for energy systems, are commonly used but often without sufficient understanding and consistence. The situation becomes particularly incoherent when simultaneous energy interactions of different types, such as work, heating and cooling, take place with a system. Also, the distinction between exergy and Second Law efficiencies is not clearly recognized by many. It is attempted here to clarify the definitions and use of energy and exergy based performance criteria, and of the Second Law efficiency, with an aim at the advancement of international standardization of these important concepts.
 Industrial application of PV/T solar energy systems 2007
Abstract: Hybrid photovoltaic/thermal (PV/T) systems consist of PV modules and heat extraction units mounted together. These systems can simultaneously provide electrical and thermal energy, thus achieving a higher energy conversion rate of the absorbed solar radiation than plain photovoltaics. Industries show high demand of energy for both heat and electricity and the hybrid PV/T systems could be used in order to meet this requirement. In this paper the application aspects in the industry of PV/T systems with water heat extraction is presented. The systems are analyzed with TRNSYS program for three locations Nicosia, Athens and Madison that are located at different latitudes. The system comprises 300 m2 of hybrid PV/T collectors producing both electricity and thermal energy and a 10 m3 water storage tank. The work includes the study of an industrial process heat system operated at two load supply temperatures of 60 �C and 80 �C. The results show that the electrical production of the system, employing polycrystalline solar cells, is more than the amorphous ones but the solar thermal contribution is slightly lower. A non-hybrid PV system produces about 25% more electrical energy but the present system covers also, depending on the location, a large percentage of the thermal energy requirement of the industry considered. The economic viability of the systems is proven, as positive life cycle savings are obtained in the case of hybrid systems and the savings are increased for higher load temperature applications. Additionally, although amorphous silicon panels are much less efficient than the polycrystalline ones, better economic figures are obtained due to their lower initial cost, i.e., they have better cost/benefit ratio.
 Performance evaluation of a hybrid photovoltaic thermal (glass to glass) system 2008
Abstract:In this paper, an attempt is made to evaluate the thermal performance of a hybrid photovoltaic thermal (PV/T) air collector system. The two type of photovoltaic (PV) module namely PV module with glass-to-tedlar and glass-to-glass are considered for performance comparison. The results of both PV modules are compared for composite climate of New Delhi. Analytical expression for solar cell, back surface, outlet air temperatures and an overall thermal efficiency are derived for both cases. It is observed that hybrid air collector with PV module glass-to-glass gives better performance in terms of overall thermal efficiency. Parametric studies are also carried out.
10_04_28_Performance evaluation of a hybrid photovoltaic thermal (glass-to-glass) system.pdf
 An experimental study on energy generation with a photovoltaic (PV)– solar thermal hybrid system 2008
Abstract: A hybrid system, composed of a photovoltaic (PV) module and a solar thermal collector is constructed and tested for energy collection at a geographic location of Cyprus. Normally, it is required to install a PV system occupying an area of about 10m2 in order to produce electrical energy; 7 kWh/day, required by a typical household. In this experimental study, we used only two PV modules of area approximately 0.6m2 (i.e., 1.3�0.47m2) each. PV modules absorb a considerable amount of solar radiation that generate undesirable heat. This thermal energy, however, may be utilized in water pre-heating applications. The proposed hybrid system produces about 2.8kWh thermal energy daily. Various attachments that are placed over the hybrid modules lead to a total of 11.5% loss in electrical energy generation. This loss, however, represents only 1% of the 7kWh energy that is consumed by a typical household in northern Cyprus. The pay-back period for the modification is less than 2 years. The low investment cost and the relatively short pay-back period make this hybrid system economically attractive.
 Performance characteristics and energy–exergy analysis of solar-assisted heat pump system 2008
Abstract: In this study solar-assisted heat pump (SAHP) system with flat plate collectors was investigated experimentally and tested for domestic space heating. SAHP system was located in a test room with 60m2 floor area in Firat University, Elazig (38,411N, 39,141E) Turkey. The experiments were performed in heating season of January 2003. The coefficient of performance of the SAHP system was calculated. The system COP of the SAHP was obtained as 3.08 while the exergy loss of the solar collector was found to be 1.92 kW. The second law efficiency of the compressor, condenser, evaporator and solar heat exchanger in SAHP system were evaluated 42.1%, 83.7%, 43.2% and 9.4%, respectively. The first law efficiency and exergetic efficiency of the whole system are found to be 65.6%, 30.8%, respectively. Consequently the energy and exergy loss analysis results show that the COP increase when the exergy loss of evaporator decrease.
 An improved thermal and electrical model for a solar photovoltaic thermal air collector 2009
Abstract:In this paper, an attempt is made to investigate the thermal and electrical performance of a solar photovoltaic thermal (PV/T) air collector. A detailed thermal and electrical model is developed to calculate the thermal and electrical parameters of a typical PV/T air collector. The thermal and electrical parameters of a PV/T air collector include solar cell temperature, back surface temperature, outlet air temperature, open-circuit voltage, short-circuit current, maximum power point voltage, maximum power point current, etc. Some corrections are done on heat loss coefficients in order to improve the thermal model of a PV/T air collector. A better electrical model is used to increase the calculations precision of PV/T air collector electrical parameters. Unlike the conventional electrical models used in the previous literature, the electrical model presented in this paper can estimate the electrical parameters of a PV/T air collector such as open-circuit voltage, short-circuit current, maximum power point voltage, and maximum power point current. Further, an analytical expression for the overall energy efficiency of a PV/T air collector is derived in terms of thermal, electrical, design and climatic parameters. A computer simulation program is developed in order to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, parametric studies have been carried out. Since some corrections have been down on thermal and electrical models, it is observed that the thermal and electrical simulation results obtained in this paper is more precise than the one given by the previous literature. It is also found that the thermal efficiency, electrical efficiency and overall energy efficiency of PV/T air collector is about 17.18%, 10.01% and 45%, respectively, for a sample climatic, operating and design parameters.
10_04_28_An improved thermal and electrical model for a solar photovoltaic thermal air collector.pdf
 How much exergy one can obtain from incident solar radiation? 2009
Abstract:A thermodynamic model is proposed to study the exergetic content of incident solar radiation reaching on the Earth’s surface which can be used to produce work through a dually cascaded thermodynamic cycle. The “topping” cycle is an ad hoc engine created by nature that connects the outer shell of the terrestrial atmosphere �which is in equilibrium with the extraterrestrial solar radiation� to the collector of a solar heat engine operating on the Earth’s surface. The work produced by the topping cycle is dissipated in form of scattering, absorption, heat, movement of air masses �wind�, etc. The “bottoming” cycle is a heat engine operating between the collector and surrounding temperatures, and delivers useful work. It is shown that the maximum work extractable from this system as exergy is obtained when both cycles operate reversibly. An expression for this maximum work, which represents the exergy of incident solar radiation on the Earth’s surface, is proposed. The application of the present model is illustrated and validated by calculating the exergy of solar radiation based on some measurements. The results obtained by the present model are compared to the ones obtained through other models available in the open literature.
10_04_28_How much exergy one can obtain from incident solar radiation.pdf
 Analysis of terrestrial solar radiation exergy 2009
Abstract: Based on Candau’s definition of radiative exergy, the exergy of the extraterrestrial and the terrestrial solar radiation are computed and compared by using the solar spectral radiation databank developed by Gueymard. The results show that within the spectrum region from 0.28 to 4.0 lm, the total energy quality factor (i.e., the exergy-to-energy ratio) of extraterrestrial solar radiation is about 0.9292, and that of the global terrestrial solar radiation is about 0.9171 under US standard atmosphere condition and zero solar zenith angle. The terrestrial solar spectral radiation exergy flux is large in the near ultraviolet and the visible light region. The reference radiation exergy spectra are obtained under atmospheric conditions consistent with ASTM standard G173-03. The effect of tilt angle on the terrestrial solar radiative exergy for inclined surface, and the effect of air mass on total energy quality factor of the terrestrial solar radiation for horizontal surface are analyzed. With the increase of tilt angle, the terrestrial solar spectral radiation exergy flux initially increases and then decreases, the total energy quality factor of the diffuse part decreases monotonically, while that of the direct part is invariant. The total energy quality factor of the direct, the diffuse and the global terrestrial solar radiation all decrease with the increase of air mass.
 Energy and exergy analysis of photovoltaic–thermal collector with and without glass cover 2009
Abtract: In photovoltaic–thermal (PV/T) technology, the use of glass cover on the flat-plate hybrid solar collector is favorable to the photothermic process but not to the photovoltaic process. Because of the difference in the usefulness of electricity and thermal energy, there is often no straight forward answer on whether a glazed or unglazed collector system is more suitable for a specific application. This glazing issue was tackled in this paper from the viewpoint of thermodynamics. Based on experimental data and validated numerical models, a study of the appropriateness of glass cover on a thermosyphon-based water-heating PV/T system was carried out. The influences of six selected operating parameters were evaluated. From the first law point of view, a glazed PV/T system is found always suitable if we are to maximize the quantity of either the thermal or the overall energy output. From the exergy analysis point of view however, the increase of PV cell efficiency, packing factor, water mass to collector area ratio, and wind velocity are found favorable to go for an unglazed system, whereas the increase of on-site solar radiation and ambient temperature are favorable for a glazed system.
 Exergy analysis of integrated photovoltaic thermal solar water heater under constant flow rate and constant collection temperature modes 2009
Abtract: In this communication, an analytical expression for the water temperature of an integrated photovoltaic thermal solar (IPVTS) water heater under constant flow rate hot water withdrawal has been obtained. Analysis is based on basic energy balance for hybrid flat plate collector and storage tank, respectively, in the terms of design and climatic parameters. Further, an analysis has also been extended for hot water withdrawal at constant collection temperature. Numerical computations have been carried out for the design and climatic parameters of the system used by Huang et al. [Huang BJ, Lin TH, Hung WC, Sun FS. Performance evaluation of solar photovoltaic/thermal systems. Sol Energy 2001; 70(5): 443–8]. It is observed that the daily overall thermal efficiency of IPVTS system increases with increase constant flow rate and decrease with increase of constant collection temperature. The exergy analysis of IPVTS system has also been carried out. It is further to be noted that the overall exergy and thermal efficiency of an integrated photovoltaic thermal solar system (IPVTS) is maximum at the hot water withdrawal flow rate of 0.006 kg/s. The hourly net electrical power available from the system has also been evaluated.
 Performance analysis of photovoltaic systems: A review 2009
Abstract: In this paper, a thorough review of photovoltaic and photovoltaic thermal systems is done on the basis of its performance based on electrical as well as thermal output. Photovoltaic systems are classified according to their use, i.e., electricity production and thermal applications along with the electricity production. The application of various photovoltaic systems is also discussed in detail. The performance analysis including all aspects, e.g., electrical, thermal, energy, and exergy efficiency are also discussed. A case study for PV and PV/T system based on exergetic analysis is presented.
 Thermodynamic assessment of photovoltaic systems 2009
Abstract: In this paper, an attempt is made to investigate the performance characteristics of a photovoltaic (PV) and photovoltaic-thermal (PV/ T) system based on energy and exergy efficiencies, respectively. The PV system converts solar energy into DC electrical energy where as, the PV/T system also utilizes the thermal energy of the solar radiation along with electrical energy generation. Exergy efficiency for PV and PV/T systems is developed that is useful in studying the PV and PV/T performance and possible improvements. Exergy analysis is applied to a PV system and its components, in order to evaluate the exergy flow, losses and various efficiencies namely energy, exergy and power conversion efficiency. Energy efficiency of the system is calculated based on the first law of thermodynamics and the exergy efficiency, which incorporates the second law of thermodynamics and solar irradiation exergy values, is also calculated and found that the latter is lower for the electricity generation using the considered PV system. The values of ‘‘fill factor” are also determined for the system and the effect of the fill factor on the efficiencies is also evaluated. The experimental data for a typical day of March (27th March 2006) for New Delhi are used for the calculation of the energy and exergy efficiencies of the PV and PV/T systems. It is found that the energy efficiency varies from a minimum of 33% to a maximum of 45% respectively, the corresponding exergy efficiency (PV/T) varies from a minimum of 11.3% to a maximum of 16% and exergy efficiency (PV) varies from a minimum of 7.8% to a maximum of 13.8%, respectively.
 A review on photovoltaic/thermal hybrid solar technology 2010
Abstract:A significant amount of research and development work on the photovoltaic/thermal (PVT) technology has been done since the 1970s. Many innovative systems and products have been put forward and their quality evaluated by academics and professionals. A range of theoretical models has been introduced and their appropriateness validated by experimental data. Important design parameters are identified. Collaborations have been underway amongst institutions or countries, helping to sort out the suitable products and systems with the best marketing potential. This article gives a review of the trend of development of the technology, in particular the advancements in recent years and the future work required.
 Enhancing the performance of building integrated photovoltaics 2010
Abstract:Recent research in Building Integrated Photovoltaics (BIPV) is reviewed with the emphases on a range of key systems whose improvement would be likely to lead to improved solar energy conversion efficiency and/or economic viability. These include invertors, concentrators and thermal management systems. Advances in techniques for specific aspects of systems design, installation and operation are also discussed.
 Optimizing the energy and exergy of building integrated photovoltaic thermal (BIPVT) systems under cold climatic conditions 2010
Abtract: Building integrated photovoltaic thermal (BIPVT) system has the potential to become a major source of renewable energy in the urban environment. In this paper, the system has been used as the roof top of a building to generate higher electrical energy per unit area and to produce necessary thermal energy required for space heating. One-dimensional transient model has been developed using basic heat transfer equations. On the basis of this model, an analysis has been carried in order to select an appropriate BIPVT system suitable for the cold climatic conditions of India. The PV performances, net energy gain and exergy of the building are determined. The results show that for a constant mass flow rate of air the system connected in series gives a better performance whereas for a constant velocity of air flow the system connected in parallel gives a better performance. The BIPVT system, fitted on the rooftop in an effective area of 65 m2, is capable of annually producing the net electrical and thermal exergies of 16,209 kW h and 1531 kW h, respectively, at an overall thermal efficiency of 53.7%.
 Photovoltaic thermal module concepts and their performance analysis: A review 2010
Abstract: This paper presents a review of the available literature covering the latest module aspects of different photovoltaic/thermal (PV/T) collectors and their performances in terms of electrical as well as thermal output. The review covers detailed description of flat-plate and concentrating PV/T systems, using liquid or air as the working fluid, numerical model analysis, experimental work and qualitative evaluation of thermal and electrical output. Also an in-depth review on the performance parameters such as, optimum mass flow rate, PV/T dimensions, air channel geometry is presented in this study. Based on the thorough review, it is clear that PV/T modules are very promising devices and there exists lot of scope to further improve their performances. Appropriate recommendations are made which will aid PV/T systems to improve their efficiency and reducing their cost, making them more competitive in the present market.
 Thermal radiation and the second law 2010
Abstract: The purpose of this paper is to collect and interrelate the fundamental concepts about second law analysis of thermal radiation. This heat transfer mode plays a leading role in solar energy utilization and in high-temperature devices, representing a significant contribution to irreversibility that is frequently omitted in engineering analysis. Entropy and exergy of thermal radiation are reviewed first. Radiative transfer processes are reviewed next, including exchange between surfaces, the presence of a participative medium, and the analysis of combined heat transfer modes. Emphasis is put on grey body radiation when treating with non-black body radiation, due to its relevance in engineering applications. The mathematical formulation of second law analysis of thermal radiation is complex, which limits its use in conventional heat transfer analysis. For this reason, numerical approaches reported to date deal with quite simple cases, leaving an open promising field of research.
Staebler-Wronski effect: When light interacts with the amorphous silicon cell, the light changes the cell's properties by light induced metaphase changes. The damage can be reversed if the cell is heated above 150 C.