Optimization of annealing cycles for electric output in outdoor conditions for amorphous silicon photovoltaic–thermal systems[edit | edit source]
- Joseph Rozario and Joshua M. Pearce, Optimization of annealing cycles for electric output in outdoor conditions for amorphous silicon photovoltaic–thermal systems. Applied Energy, 148, pp. 134–141 (2015). DOI: http://dx.doi.org/10.1016/j.apenergy.2015.03.073 open access preprint
Abstract[edit | edit source]
Previous studies with fixed operating temperatures have shown that hydrogenated amorphous silicon (a-Si:H) was a promising absorber layer for solar photovoltaic–thermal (PVT) systems because of (a) a low temperature coefficient and (b) the opportunity to reverse light induced degradation with thermal annealing. This study further refined the simulation of the optimal dispatch strategy for a-Si:H based PVT by studying annealing cycles and analysis of the degradation at other operating temperatures controlled by the varying ambient temperatures. Four representative case studies were evaluated for the combinations of high and low solar flux and high and low average ambient temperature. Electrically-optimized dispatch strategies are found for a range of PVT thermal insulating effectivenesses. The results showed significantly more electricity generation in all the case study representative regions except for areas dominated by low temperatures and low solar fluxes. These results indicate that a-Si:H PV performance can be improved in most populated regions in the world by integrating it into a PVT device and using spike annealing to reverse light-induced degradation effects. The model presented in this paper uses publicly-available data to implement suitable dispatch strategies and execute virtual performance analysis of PVT for any geographic location in the world.
Review of the theory of amorphous semiconductors 1970[edit | edit source]
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[edit | edit source]
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[edit | edit source]
Amorphous Semiconductor Superlattice. B. Abeles and T. Tiedje. Physical Review Letters. Vol 51, Num 21. (Nov 21, 1983)
http://prola.aps.org/pdf/PRL/v51/i21/p2003_1
5mjmp 19:09, 16 September 2009 (UTC)
09_09_16_Amorphous Semiconductor superlattices.pdf
A Hybrid Amorphous Silicon Photovoltaic and Thermal Solar Collector 1985[edit | edit source]
Written: 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%.
File:09 05 28 a hybrid amorphous silicon photovoltaic and thermal solar collector.pdf
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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
Written: 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 . 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.
File:09 05 28 high-efficiency a-Si-c-Si heterojunction solar cell.pdf
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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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:
http://www.mrs.org/s_mrs/sec_subscribe.asp?CID=2351&DID=180479&action=detail
5mjmp 19:00, 24 September 2009 (UTC)
PROGRESS IN AMORPHOUS SILICON BASED SOLAR CELL TECHNOLOGY 2002[edit | edit source]
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
http://www.rio02.com/proceedings/pdf/067_Wronski.pdf
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[edit | edit source]
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[edit | edit source]
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
Exergy equation:
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
[edit | edit source]
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[edit | edit source]
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 ISC 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[edit | edit source]
Written 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: sirimongkhol@nstda.or.th, thipjak@nstda.or.th, porponth@nstda.or.th. Amorphous-Silicon Photovoltaic/Thermal Solar Collector in Thailand. Sirimongkhol Jaikla, Thipjak Nualboonrueng and Porponth Sichanutgrist. 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[edit | edit source]
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[edit | edit source]
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[edit | edit source]
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
