Combined photovoltaic solar thermal systems (PVT) literature review: Difference between revisions

Latest revision as of 13:57, 23 February 2024

This page describes selected literature available on PVT[edit | edit source]

Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems [1][edit | edit source]

Abstract: In this work Author(s) present a study of the optoelectronic properties of nanocrystalline GaN (nc-GaN) and amorphous GaON (a‐GaON) grown by ion-assisted deposition. The two classes of film show very distinct photoconductive responses; the nc-GaN has a fast small response while the a‐GaON films have a much larger response which is persistent. To describe the observed intensity, wavelength, and temperature dependence of the photoconductivity in each class of film, Author(s) build a model which takes into account the role of a large density of localized states in the gap. The photoconductivity measurements are supplemented by thermally stimulated conductivity, measurement of the absorption coefficient, and determination of the Fermi level. Using the model to aid author(s) interpretation of this data set, Author(s) are able to characterize the density of states in the gap for the two materials.

First generation PV + CHP hybrids where the PV simply decreased some small fraction of the run time of the CHP, have been eclipsed by 2nd generation systems, where the PV is expanded and is completely backed up by CHP, usually with a diesel generator.
Additional complexity of a PV-CCHP system over a PV-CHP system creates system dynamics that require numerical simulation in order to optimize system design.
Electricity is generated by both the PV array and the CHP unit. In order to allow for more flexibility of matching thermal loads to electric loads, conversion and storage equipment for both electric and thermal loads are also incorporated.
Advantages of this design include better supply–demand correlation, maximized CHP fuel efficiency, and minimized CHP maintenance costs.
In the design and optimization of such a system, it is important that the load profile is representative of the annual onsumption and not subject to extreme anomalies that may lead to oversizing the system capabilities.
This paper overcame the limitations of available modeling techniques for hybrid systems that incapable of accounting for cooling loads by demonstrating a new simulation algorithm and dispatch strategy for the modeling of hybrid PV-CCHP systems.

A review on photovoltaic/thermal hybrid solar technology [2][edit | edit source]

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.

This article gives a review of the trend of development of the technology, starting from the early groundwork and placing more emphasis on the developments after year 2000.
A common PV module converts 4–17% of the incoming solar radiation into electricity, depending on the type of solar cells in use and the working conditions. In other words, more than 50% of the incident solar energy is converted as heat.
There can be two undesirable consequences: (i) a drop in cell efficiency (typically 0.4% per °C rise for c-Si cells) and (ii) a permanent structural damage of the module if the thermal stress remains for prolonged period.
Applications: Improved longwave absorption,High temperature applications,Autonomous applications,Commercial applications,The market potential.

Energy performance of water hybrid PV/T collectors applied to combisystems of Direct Solar Floor type [3][edit | edit source]

Abstract: The integration of photovoltaic (PV) modules in buildings allows one to consider a multifunctional frame and then to reduce the cost by substitution of components. In order to limit the rise of the cell operating temperature, a photovoltaics/thermal (PV/T) collector combines a solar water heating collector and PV cells. The recovered heat energy can be used for heating systems and domestic hot water. A combination with a Direct Solar Floor is studied. Its low operating temperature level is appropriate for the operating conditions of the mono- or poly-crystalline photovoltaic modules which are selected in that study. However, for a system including a glass covered collector and localised in Mâcon area in France, we show that the annual photovoltaic cell efficiency is 6.8% which represents a decrease of 28% in comparison with a conventional non-integrated PV module of 9.4% annual efficiency. This is obviously due to a temperature increase related to the cover. On the other hand, we show that without a glass cover, the efficiency is 10% which is 6% better than a standard module due to the cooling effect. Moreover, in the case of a glazed PV/T collector with a conventional control system for Direct Solar Floor, the maximum temperature reached at the level of the PV modules is higher than 100 °C. This is due to the oversize of the collectors during the summer when the heating needs are null, i.e. without a heated swimming pool for example. This temperature level does not allow the use of EVA resin (ethylene vinyl acetate) in PV modules due to strong risks of degradation. The current solution consists of using amorphous cells or, if we do not enhance the thermal production, uncovered PV/T collector. Further research led to water hybrid PV/T solar collectors as a one-piece component, both reliable and efficient, and including the thermal absorber, the heat exchanger and the photovoltaic functions.

The mono-crystalline (m-C) and poly-crystalline (PC) cells see their electric production decreasing when the temperature of the cell increases because of their negative temperature coefficient (approximately −0.5%/K).
The thermal efficiency of a PV/T collector is lower than for a traditional system because part of solar energy is converted into electricity, the optical factor is weaker and the global coefficient of the thermal losses is higher. On one hand, the presence of a glazed cover at the top of the collector increases the thermal efficiency. On the other hand, it deteriorates the electric efficiency by increasing both optical losses and temperature of PV cells. This decrease can be compensated by the installation of reflectors.
The hot water produced by the hybrid collector is used for domestic hot-water production and the Direct Solar Floor. The advantage of the DSF is that an additional solar tank is not used since collected solar energy is directly stored in the floor.
The dynamic behavior of the collector takes into account the heat capacity of each node. It is important because of the strong variations of flow rate related to control. The model of the wall (or roof) is defined with a model of type 3R4C.
The model, based on the electric diagram, is equivalent to a photovoltaic cell including a generator of current (photocurrent), a diode and a series resistance (Fig. 3). The photovoltaic module includes Nms modules in series and Nmp modules in parallel.

Reversible conductivity changes in discharge-produced amorphous Silicon [4][edit | edit source]

Abstract: A new reversible photoelectronic effect is reported for amorphous Si produced by glow discharge of SiH •. Long exposure to light decreases:'o.'both the photoconductivity and the dark conductivity, the latter by nearly four orders of magnitude. Annealing above 150·C reverses the process. A model involving optically induced changes in gap states is proposed. The results have strong implications for both the physical nature of the material and for its applications in thin-film solar cells. as well as the reproducibility of measurements on discharge-produced Si.

Both the photo-conductivity and the dark conductivity decrease with light exposure .
Dark conductivity as a function of temperature through this process the conductivity increases with increasing temperature following the expression a= ao exp(Ea/kT).
The hydrogen content, moreover,is stable at annealing temperatures below the deposition temperature.
The change in dark conductivity does not necessarily limit the performance because the bulk series resistance in an operating cell is determined by the photo-conductivity

DEVELOPMENT IN UNDERSTANDING AND CONTROLLING THE STAEBLER-WRONSKI EFFECT IN a-Si:H [5][edit | edit source]

Abstract: Hydrogenated amorphous silicon (a-Si:H) exhibits a metastable light induced degradation of its optoelectronic properties that is called the Staebler-Wronski effect, after its discoverers. This degradation effect is associated with the relatively high diffusion coefficient of hydrogen and the changes in local bonding coordination promoted by hydrogen. Reviewed are the fundamental aspects of the interplay between hydrogen and electronic energy states that form the basis of competing microscopic models for explaining the degradation effect. These models are tested against the latest experimental observations, and material and preparation parameters that reduce the Staebler-Wronski effect are discussed.

Dangling bond defects acting as recombination centers, decreased the photocarrier lifetime and, owing to their location near midgap shift EF, thereby decreased the dark conductivity.
Extended illumination appreciably degrading the optoelectronic properties of this material. This lightinduced degradation is called the Staebler-Wronski effect (SWE). Even though these defects anneal away between 150 and 200±C, the SWE seriously limits the use of a-Si:H in solar photovoltaic applications.
In crystalline Si, atomic motions that could produce coordination defects occur only near 1000±C. The low-anneal temperature of the light-induced coordination defects (dangling bonds) in a-Si:H is related to the diffusion of bonded hydrogen. Above TE » 200±C, hydrogen diffusion enables the equilibration of solid-state chemical reactions, which determine the concentration of coordination defects of silicon as well as of dopant atom.

Intrinsic and light induced gap states in a-Si:H materials and solar cells—effects of microstructure [6][edit | edit source]

Abstract: The effects of microstructure on the gap states of hydrogen diluted and undiluted hydrogenated amorphous silicon (a-Si:H) thin film materials and their solar cells have been investigated. In characterizing the films the commonly used methodology of relating just the magnitudes of photocurrents and subgap absorption, a(E), was expanded to take into account states other than those due to dangling bond defects. The electron mobility-lifetime products were characterized as a function of carrier generation rates and analysis was carried out of the entire a(E) spectra and their evolution with light induced degradation. Two distinctly different defect states at 1.0 and 1.2 eV from the conduction band and their contributions to carrier recombination were identified and their respective evolution under 1 sun illumination characterized. Direct correlations were obtained between the recombination in thin films with that of corresponding solar cells. The effects of the difference in microstructure on the changes in these two gap states in films and solar cells were also identified. It is found that improved stability of protocrystalline Si:H can in part be attributed to the reduction of the 1.2 eV defects. It is also shown that ignoring the presence of multiple defects leads to erroneous conclusions being drawn about the stability of a-Si:H and SWE.

Because as yet the nature and densities of the states are not known it is not possible to correlate them directly to those in the corresponding cells, but it is possible to relate them through their role as carrier recombination centers.
The distinct difference between the times taken to reach the 1 sun DSS with the cells having the protocrystalline and the undiluted a-Si:H i-layers can be attributed to a difference in the relative densities.
The same kinetics are observed for the cells and films where in the undiluted cell, there is an 'overshoot' in the recovery so-called 'fast' and 'slow' defect states.

Modeling of light-induced degradation of amorphous silicon solar cells [7][edit | edit source]

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.

When two mobile hydrogen atoms 'collide', a metastable complex containing two Si–H bonds is formed together with two dangling-bond defects.
Recombination on weak bonds initiates the defect creation.
Computer simulation concluded that the dark-conductivity degradation was mainly determined by the shift in peak position of the positively charged/neutral defect-state peak of the DDOS and the photoconductivity by the total defect density.
Light soaking mainly leads to a change in the defect density of a-Si:H and the creation of defects is initiated by recombination events in the intrinsic layer of the device.
Light-soak the cells under both open- and short-circuit conditions with the objective to alter the recombination profile substantially in the cells.

Light-induced defect states in hydrogenated amorphous silicon centered around 1.0 and 1.2 eV from the conduction band edge [8][edit | edit source]

Abstract:To take into account the presence of multiple light-induced defect states in hydrogenated amorphous silicon (a-Si:H) the evolution of the entire spectra of photoconductive subgap absorption, a(hn ),has been analyzed. Using this approach two distinctly different light-induced defect states centered around 1.0 and 1.2 eV from the conduction band edge are clearly identified. Results are presented on their evolution and respective effects on carrier recombination that clearly point to the importance of these states in evaluating the stability of different a-Si:H solar cell materials, as well as elucidating the origin of the Staebler–Wronski effect.

LI degradationis associated with the creation of dangling bonds.
a(hn)is interpreted solely in terms of D0 defect states.However, results have also been reported that point to the introduction of other defect states and that a(hn ) cannot be interpreted in such a simple manner.
Two distinctly different light induced defect states centered around 1.0 and 1.2 eV from the conduction band ~CB! edge are clearly identified and their evolution found to be consistent with the corresponding changes in mt
It is shown that in the AS, the mt product of the R510 material is about five times higher than in the R50 material, as is generally expected for better quality materials.
At 25 °C, the protocrystalline material attains a DSS in approximately 100 h, whereas in the R50 material, the commonly reported kinetics with t21/3 extends for 400 h with no approach to DSS. When the temperature of degradation is raised to 75 °C, there is virtually no change in the kinetics of the 20 Å/s material, whereas the R510 reaches a DSS with a mt values that is two times higher than at 25 °C.
Any interpretation of a(hn ) in terms of the density and energy distribution of multiple defect states is complicated by the nature of photoconductive subgap absorption, which is determined by N(E),

PERFORMANCE TEST OF AMORPHOUS SILICON MODULES IN DIFFERENT CLIMATES – YEAR THREE: HIGHER MINIMUM OPERATING TEMPERATURES LEAD TO HIGHER PERFORMANCE LEVELS [9][edit | edit source]

Abstract:This paper presents third year results of a round robin exposure experiment designed to assess the performance of thin-film amorphous silicon (a-Si) solar modules operating in different climatic conditions. Three identical sets of commercially available a-Si PV modules from five different manufacturers were simultaneously deployed outdoors in three sites with distinct climates (Arizona – USA, Colorado – USA and Florianopolis – Brazil). Every year all PV module sets were sent to the National Renewable Energy Laboratory (NREL) for Standard Testing Conditions measurements under a SPIRE simulator. The fouryear experiment aims to determine the light-induced degradation and stabilization characteristics of a-Si regarding specific history of exposure, and to monitor and compare degradation rates in different climates. We present results from the first three years of measurements, showing that while most of the manufacturers underrate their products by 20 to 25% to account for the light-induced degradation, outdoor exposure temperature seems to be what will ultimately determine the stabilized performance level of a-Si.

After the first year of outdoor exposure, modules deployed at the site with the highest minimum operating temperature experienced the highest stabilized output level
Further reporting on the first and second years of this four-year experiment, indicated that there is barely any lifetime memory of the stabilized state in a-Si
In the first year of deployment outdoors, PV modules exposed at the coldest site underwent the largest amount of degradation, and outdoor exposure at the warmest site led to the smallest amount of degradation
In the second year, Set A went from the coldest site to the warmest site, which led to some recovery in output performance upon further light soaking, indicating that these modules do not seem to show a lifetime memory of the stabilized state.
In the third year, Set A was deployed outdoors at the year round- climate-intermediate site,and reached a new stabilized state, at a higher performance level than after the second year.

The potential of solar industrial process heat applications [10][edit | edit source]

Abstract:The temperature requirements of solar industrial process heat applications range from 60 °C to 260 °C. The characteristics of medium to medium-high temperature solar collectors are given and an overview of efficiency and cost of existing technologies is presented. Five collector types have been considered in this study varying from the simple stationary flat-plate to movable parabolic trough ones. Based on TRNSYS simulations, an estimation of the system efficiency of solar process heat plants operating in the Mediterranean climate are given for the different collector technologies. The annual energy gains of such systems are from 550 to 1100 kWh/m2 a. The resulting energy costs obtained for solar heat are from 0.015 to 0.028 C£/kWh depending on the collector type applied. The viabilities of the systems depend on their initial cost and the fuel price. None of these costs however is stable but change continuously depending on international market trends and oil production rates. The costs will turn out to be more favourable when the solar collectors become cheaper and subsidisation of fuel is removed. Therefore the optimisation procedure suggested in this paper should be followed in order to select the most appropriate system in each case.

The industrial heat-demand constitutes about 15% of the overall demand of final energy requirements in the southern European countries
Investment costs should be comparatively low, even if the costs for the collector are higher.One way to cause economically easy terms is to design systems without heat storage.
Solar thermal energy can be used for low-pressure steam generation at 100–110*C and for refrigeration of the wort, which can be accomplished with absorption cooling.
In a solar process heat system, interfacing of the collectors with conventional energy supplies must be done in a way compatible with the process. The easiest way to accomplish this is by using heat storage, which can also allow the system to work in periods of low irradiation and/or night time.
In the case of water preheating, higher efficiencies are obtained due to the low input-temperature to the solar system: thus low-technology collectors can work effectively and the required load supply temperature has no or little effect on the performance of the solar system.
The optimum collector area, storage tank volume, life-cycle savings and solar contribution of the various collector types and demand temperatures considered are investigated.
There are two major types of collectors that can be applied for industrial process-heat, non-tracking (stationary) collectors and one-axis sun-tracking parabolic trough collectors.

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Authors	Ankit Vora, Sanjay Debnath
License	CC-BY-SA-3.0
Organizations	MOST
Language	English (en)
Related	5 subpages, 4 pages link here
Impact	1,146 page views
Created	January 30, 2012 by Ankit Vora
Modified	February 23, 2024 by Felipe Schenone
Cite as	Ankit Vora, Sanjay Debnath (2012–2024). "Combined photovoltaic solar thermal systems (PVT) literature review". Appropedia. Retrieved April 26, 2024.
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↑ A. Nosrat and J. M. Pearce, "Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems," Applied Energy, vol. 88, no. 9, pp. 3270-3276, Sep. 2011.
↑ C. T.T., "A review on photovoltaic/thermal hybrid solar technology," Applied Energy, vol. 87, no. 2, pp. 365-379, Feb. 2010.
↑ "Energy performance of water hybrid PV/T collectors applied to combisystems of Direct Solar Floor type", Volume 81, Issue 11, November 2007, Pages 1426–1438
↑ "Reversible conductivity changes in discharge-produced amorphous Silicon ", Appl. Phys.Lett. 31,292 (1977);doi;10.1063/1.89674
↑ "DEVELOPMENT IN UNDERSTANDING AND CONTROLLING THE STAEBLER-WRONSKI EFFECT IN a-Si:H ", Energy Conversion Devices, Inc., Troy, Michigan 48084
↑ "Intrinsic and light induced gap states in a-Si:H materials and solar cells—effects of microstructure ", Thin Solid Films 451 –452 (2004) 470–475
↑ "Modeling of light-induced degradation of amorphous silicon solar cells ", Volume 92, Issue 1, January 2008, Pages 50–60
↑ "Light-induced defect states in hydrogenated amorphous silicon centered around 1.0 and 1.2 eV from the conduction band edge", Appl. Phys. Lett. 83, 3725 (2003); doi: 10.1063/1.1624637
↑ "PERFORMANCE TEST OF AMORPHOUS SILICON MODULES IN DIFFERENT CLIMATES – YEAR THREE: HIGHER MINIMUM OPERATING TEMPERATURES LEAD TO HIGHER PERFORMANCE LEVELS"
↑ "The potential of solar industrial process heat applications", Volume 76, Issue 4, December 2003, Pages 337–361

[A._Nosrat-1] A. Nosrat and J. M. Pearce, "Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems," Applied Energy, vol. 88, no. 9, pp. 3270-3276, Sep. 2011.

[C._T.T-2] C. T.T., "A review on photovoltaic/thermal hybrid solar technology," Applied Energy, vol. 87, no. 2, pp. 365-379, Feb. 2010.

[G._Fraissea-3] "Energy performance of water hybrid PV/T collectors applied to combisystems of Direct Solar Floor type", Volume 81, Issue 11, November 2007, Pages 1426–1438

[D._L._Staebler_and_C._R._Wronski-4] "Reversible conductivity changes in discharge-produced amorphous Silicon ", Appl. Phys.Lett. 31,292 (1977);doi;10.1063/1.89674

[Hellmut_Fritzsche-5] "DEVELOPMENT IN UNDERSTANDING AND CONTROLLING THE STAEBLER-WRONSKI EFFECT IN a-Si:H ", Energy Conversion Devices, Inc., Troy, Michigan 48084

[C.R._Wronski-6] "Intrinsic and light induced gap states in a-Si:H materials and solar cells—effects of microstructure ", Thin Solid Films 451 –452 (2004) 470–475

[#_A._Klaver,_R.A.C.M.M._van_Swaaij-7] "Modeling of light-induced degradation of amorphous silicon solar cells ", Volume 92, Issue 1, January 2008, Pages 50–60

[J._M._Pearce,-8] "Light-induced defect states in hydrogenated amorphous silicon centered around 1.0 and 1.2 eV from the conduction band edge", Appl. Phys. Lett. 83, 3725 (2003); doi: 10.1063/1.1624637

[R._Rüther,-9] "PERFORMANCE TEST OF AMORPHOUS SILICON MODULES IN DIFFERENT CLIMATES – YEAR THREE: HIGHER MINIMUM OPERATING TEMPERATURES LEAD TO HIGHER PERFORMANCE LEVELS"

[Soteris_Kalogirou-10] "The potential of solar industrial process heat applications", Volume 76, Issue 4, December 2003, Pages 337–361

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-{{MY5970}}
+{{MY5970 notice}}
-==This page describes selected literature available on PVT==
-====[http://www.sciencedirect.com/science/article/pii/S0306261911001632 Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems<ref name="A. Nosrat">A. Nosrat and J. M. Pearce, “Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems,” Applied Energy, vol. 88, no. 9, pp. 3270-3276, Sep. 2011.</ref>]====
+{{Literature review notice}}
-'''Abstract:''' In this work Author(s) present a study of the optoelectronic properties of nanocrystalline GaN (nc-GaN) and amorphous GaON (a‐GaON) grown by ion-assisted deposition. The two classes of film show very distinct photoconductive responses; the nc-GaN has a fast small response while the a‐GaON films have a much larger response which is persistent. To describe the observed intensity, wavelength, and temperature dependence of the photoconductivity in each class of film, Author(s) build a model which takes into account the role of a large density of localized states in the gap. The photoconductivity measurements are supplemented by thermally stimulated conductivity, measurement of the absorption coefficient, and determination of the Fermi level. Using the model to aid author(s) interpretation of this data set, Author(s) are able to characterize the density of states in the gap for the two materials.
+{{Subpages menu}}
-====[http://www.sciencedirect.com/science/article/pii/S0306261909002761 A review on photovoltaic/thermal hybrid solar technology<ref name="C. T.T">C. T.T., “A review on photovoltaic/thermal hybrid solar technology,” Applied Energy, vol. 87, no. 2, pp. 365-379, Feb. 2010.</ref>]====
+== This page describes selected literature available on PVT ==
-'''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.
+==== [http://www.sciencedirect.com/science/article/pii/S0306261911001632 Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems<ref name="A. Nosrat">A. Nosrat and J. M. Pearce, "Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems," Applied Energy, vol. 88, no. 9, pp. 3270-3276, Sep. 2011.</ref>] ====
-====[http://www.sciencedirect.com/science/article/pii/S1359431106002316 Photovoltaic thermal (PV/T) collectors: A review<ref name="P. G. Charalambous">P. G. Charalambous, G. G. Maidment, S. A. Kalogirou, and K. Yiakoumetti, “Photovoltaic thermal (PV/T) collectors: A review,” Applied Thermal Engineering, vol. 27, no. 2–3, pp. 275-286, Feb. 2007.</ref>]====
+'''Abstract:''' In this work Author(s) present a study of the optoelectronic properties of nanocrystalline GaN (nc-GaN) and amorphous GaON (a‐GaON) grown by ion-assisted deposition. The two classes of film show very distinct photoconductive responses; the nc-GaN has a fast small response while the a‐GaON films have a much larger response which is persistent. To describe the observed intensity, wavelength, and temperature dependence of the photoconductivity in each class of film, Author(s) build a model which takes into account the role of a large density of localized states in the gap. The photoconductivity measurements are supplemented by thermally stimulated conductivity, measurement of the absorption coefficient, and determination of the Fermi level. Using the model to aid author(s) interpretation of this data set, Author(s) are able to characterize the density of states in the gap for the two materials.
-'''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.
+* First generation PV + CHP hybrids where the PV simply decreased some small fraction of the run time of the CHP, have been eclipsed by 2nd generation systems, where the PV is expanded and is completely backed up by CHP, usually with a diesel generator.
+* Additional complexity of a PV-CCHP system over a PV-CHP system creates system dynamics that require numerical simulation in order to optimize system design.
+* Electricity is generated by both the PV array and the CHP unit. In order to allow for more flexibility of matching thermal loads to electric loads, conversion and storage equipment for both electric and thermal loads are also incorporated.
+* Advantages of this design include better supply–demand correlation, maximized CHP fuel efficiency, and minimized CHP maintenance costs.
+* In the design and optimization of such a system, it is important that the load profile is representative of the annual onsumption and not subject to extreme anomalies that may lead to oversizing the system capabilities.
+* This paper overcame the limitations of available modeling techniques for hybrid systems that incapable of accounting for cooling loads by demonstrating a new simulation algorithm and dispatch strategy for the modeling of hybrid PV-CCHP systems.
-====[http://qspace.library.queensu.ca/handle/1974/6870 Hydrogenated Amorphous Silicon PV an an Absorber Coating for Photovoltaic Thermal Systems]====
+==== [http://www.sciencedirect.com/science/article/pii/S0306261909002761 A review on photovoltaic/thermal hybrid solar technology<ref name="C. T.T">C. T.T., "A review on photovoltaic/thermal hybrid solar technology," Applied Energy, vol. 87, no. 2, pp. 365-379, Feb. 2010.</ref>] ====
-'''Abstract:''' Driven by the limitations of solar-optimized roof space and International Energy Association (IEA) Task 35, there is a renewed interest in photovoltaic solar thermal (PVT) hybrid systems. Current PVT systems focus on cooling the solar photovoltaic (PV) cells to improve the electrical performance. This however, causes the thermal component (T) to underperform. An exergetic study was completed comparing a PVT, PV + T and a PV only system in Detroit, Denver and Phoenix. It was found that the PVT system outperformed the PV + T system by 72% for each location and by 8, 8.6 and 9.9% for Detroit, Denver and Phoenix when compared to the PV only system. To further improve the PVT system, using hydrogenated amorphous silicon (a-Si:H) PV as the absorber layer of the solar thermal device was explored. The temperature coefficient and annealing properties of a-Si:H allow the thermal component to run more efficiently, while enabling the a-Si:H i-layers to be thicker resulting in more electricity production. It was found that running i-layer thicker cells (630nm and 840nm) stabilized at higher efficiencies at 90°C (potential PVT operating temperatures) than the thinner cell (420nm) by 2% and 0.5% respectively. In addition, spike annealing, which is a new concept of stagnating a PVT system to allow for the a-Si:H PV to anneal and return it to its original efficiencies was also investigated. It was found that over the lifetime of the system with the spike annealing occurring once a day 10.6% more electricity was produced than a system without stagnation.
+'''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.
-====[http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=519952&tag=1 High-efficiency a-Si/c-Si heterojunction solar cell<ref name="T. Sawada">T. Sawada et al., “High-efficiency a-Si/c-Si heterojunction solar cell,” in IEEE Photovoltaic Specialists Conference - 1994, 1994 IEEE First World Conference on Photovoltaic Energy Conversion, 1994., Conference Record of the Twenty Fourth, 1994, vol. 2, pp. 1219-1226 vol.2.</ref>]====
-'''Abstract:''' An aperture-area conversion efficiency of 20.0% (intrinsic efficiency: 21.0%) has been achieved for a 1.0 cm2 CZ n-type single crystalline silicon (c-Si) solar cell, by using the “HIT (heterojunction with intrinsic thin-layer)” structure on both sides of the cell. This is the world's highest value for a c-Si solar cell in which the junction is fabricated at a low temperature of below 200°C. In this paper, the junction fabrication technologies and features of the HIT structure are reviewed. The stability under light and thermal exposure, and the temperature dependence on performance of a high-efficiency HIT solar cell are also reported.
-====[http://www.sciencedirect.com/science/article/pii/S0306261905000462 Hybrid photovoltaic and thermal solar-collector designed for natural circulation of water<ref name="W. He">W. He, T.-T. Chow, J. Ji, J. Lu, G. Pei, and L.-shun Chan, “Hybrid photovoltaic and thermal solar-collector designed for natural circulation of water,” Applied Energy, vol. 83, no. 3, pp. 199-210, Mar. 2006.</ref>]====
-'''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. Author(s) 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.
-====[http://www.sciencedirect.com/science/article/pii/S0011916411004024 Design, fabrication and performance evaluation of a hybrid photovoltaic thermal (PVT) double slope active solar still<ref name="G. Singh">G. Singh, S. Kumar, and G. N. Tiwari, “Design, fabrication and performance evaluation of a hybrid photovoltaic thermal (PVT) double slope active solar still,” Desalination, vol. 277, no. 1–3, pp. 399-406, Aug. 2011.</ref>]====
-'''Abstract:''' A modified photovoltaic thermal (PVT) double slope active solar still was designed and fabricated for remote locations. The system has been installed at the campus of KIET, Ghaziabad (India) and its performance has been experimentally evaluated under field conditions in natural and forced circulation mode (series and parallel). Photovoltaic operated DC water pump has been used between solar still and photovoltaic (PV) integrated flat plate collector to re-circulate the water through the collectors and transfer it to the solar still. The production rate has been accelerated to 1.4 times than the single slope hybrid (PVT) active solar still and obtained highest (7.54 kg/day) for the parallel configuration in forced mode in the month of October, 2010. The daily average energy efficiency of the solar still is obtained as 17.4%. Comparative results have been predicted on annual basis with the single slope hybrid (PVT) active solar still accounting 250, 275 and 300 clear days in a year. Author(s) have found that energy payback time is significantly reduced by almost 30% in present design with less capital investment.
-====[http://www.sciencedirect.com/science/article/pii/S0038092X01000962 Hybrid photovoltaic/thermal solar systems<ref name="Y. Tripanagnostopoulos">Y. Tripanagnostopoulos, T. Nousia, M. Souliotis, and P. Yianoulis, “Hybrid photovoltaic/thermal solar systems,” Solar Energy, vol. 72, no. 3, pp. 217-234, Mar. 2002.</ref>]====
-'''Abstract:''' Author(s) present test results on hybrid solar systems, consisting of photovoltaic modules and thermal collectors (hybrid PV/T systems). The solar radiation increases the temperature of PV modules, resulting in a drop of their electrical efficiency. By proper circulation of a fluid with low inlet temperature, heat is extracted from the PV modules keeping the electrical efficiency at satisfactory values. The extracted thermal energy can be used in several ways, increasing the total energy output of the system. Hybrid PV/T systems can be applied mainly in buildings for the production of electricity and heat and are suitable for PV applications under high values of solar radiation and ambient temperature. Hybrid PV/T experimental models based on commercial PV modules of typical size are described and outdoor test results of the systems are presented and discussed. The results showed that PV cooling can increase the electrical efficiency of PV modules, increasing the total efficiency of the systems. Improvement of the system performance can be achieved by the use of an additional glazing to increase thermal output, a booster diffuse reflector to increase electrical and thermal output, or both, giving flexibility in system design.
-====[http://www.sciencedirect.com/science/article/pii/S0306261908002201 Analytical expression for electrical efficiency of PV/T hybrid air collector<ref name="S. Dubey">S. Dubey, G. S. Sandhu, and G. N. Tiwari, “Analytical expression for electrical efficiency of PV/T hybrid air collector,” Applied Energy, vol. 86, no. 5, pp. 697-705, May 2009.</ref>]====
-'''Abstract:''' The overall electrical efficiency of the photovoltaic (PV) module can be increased by reducing the temperature of the PV module by withdrawing the thermal energy associated with the PV module. In this communication an attempt has been made to develop analytical expression for electrical efficiency of PV module with and without flow as a function of climatic and design parameters. The four different configurations of PV modules are considered for the present study which are defined as; case A (Glass to glass PV module with duct), case B (Glass to glass PV module without duct), case C (Glass to tedlar PV module with duct), case D (Glass to tedlar PV module without duct). Further, experiments were carried out for all configurations under composite climate of New Delhi.
-It is found that the glass to glass PV modules with duct gives higher electrical efficiency as well as the higher outlet air temperature amongst the all four cases. The annual effect on electrical efficiency of glass to glass type PV module with and without duct is also evaluated. The annual average efficiency of glass to glass type PV module with and without duct is 10.41% and 9.75%, respectively.
-====[http://www.sciencedirect.com/science/article/pii/S0038092X00001535 Performance evaluation of solar photovoltaic/thermal systems<ref name="B. J. Huang">B. J. Huang, T. H. Lin, W. C. Hung, and F. S. Sun, “Performance evaluation of solar photovoltaic/thermal systems,” Solar Energy, vol. 70, no. 5, pp. 443-448, 2001.</ref>]====
-'''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 ηs* reaches 0.38 which is about 76% of the value for a conventional solar hot water heater using glazed collectors (ηs*=0.50). The performance of a 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.
-====[http://www.sciencedirect.com/science/article/pii/S0038092X07000813 Study of a new concept of photovoltaic–thermal hybrid collector<ref name="Y. B. Assoa">Y. B. Assoa, C. Menezo, G. Fraisse, R. Yezou, and J. Brau, “Study of a new concept of photovoltaic–thermal hybrid collector,” Solar Energy, vol. 81, no. 9, pp. 1132-1143, Sep. 2007.</ref>]====
-'''Abstract:''' This work represents the second step of the development of a new concept of photovoltaic/thermal (PV/T) collector. This type of collector combines preheating of the air and the production of hot water in addition to the classical electrical function of the solar cells. The alternate positioning of the thermal solar collector section and the PV section permits the production of water at higher mean temperatures than most of existing hybrid collectors. These higher temperatures will allow the coupling of components such as solar cooling devices during the summer and obviously a direct domestic hot water (DHW) system without the need for additional auxiliary heating systems. In this paper, a simplified steady-state two-dimensional mathematical model of a PV/T bi-fluid (air and water) collector with a metal absorber is developed. Then, a parametric study (numerically and experimentally) is undertaken to determine the effect of various factors such as the water mass flow rate on the solar collector thermal performances. Finally, the results from an experimental test bench and the first simulation results obtained on full scale experiments are compared.
-====[http://www.sciencedirect.com/science/article/pii/S0360544209003430 Expanding photovoltaic penetration with residential distributed generation from hybrid solar photovoltaic and combined heat and power systems<ref>P. J.M., “Expanding photovoltaic penetration with residential distributed generation from hybrid solar photovoltaic and combined heat and power systems,” Energy, vol. 34, no. 11, pp. 1947-1954, Nov. 2009.</ref>]====
-'''Abstract:''' The recent development of small scale combined heat and power (CHP) systems has provided the opportunity for in-house power backup of residential-scale photovoltaic (PV) arrays. This paper investigates the potential of deploying a distributed network of PV + CHP hybrid systems in order to increase the PV penetration level in the U.S. The temporal distribution of solar flux, electrical and heating requirements for representative U.S. single family residences were analyzed and the results clearly show that hybridizing CHP with PV can enable additional PV deployment above what is possible with a conventional centralized electric generation system. The technical evolution of such PV + CHP hybrid systems was developed from the present (near market) technology through four generations, which enable high utilization rates of both PV-generated electricity and CHP-generated heat. A method to determine the maximum percent of PV-generated electricity on the grid without energy storage was derived and applied to an example area. The results show that a PV + CHP hybrid system not only has the potential to radically reduce energy waste in the status quo electrical and heating systems, but it also enables the share of solar PV to be expanded by about a factor of five.
-====[http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5411247&tag=1 Optimizing design of household scale hybrid solar photovoltaic + combined heat and power systems for Ontario<ref>P. Derewonko and J. M. Pearce, “Optimizing design of household scale hybrid solar photovoltaic + combined heat and power systems for Ontario,” in 2009 34th IEEE Photovoltaic Specialists Conference (PVSC), 2009, pp. 001274-001279.</ref>]====
-'''Abstract:''' This paper investigates the feasibility of implementing a hybrid solar photovoltaic (PV) + combined heat and power (CHP) and battery bank system for a residential application to generate reliable base load power to the grid in Ontario. Deploying PV on a large-scale has a penetration level threshold due to the inherent power supply intermittency associated with the solar resource. By creating a hybrid PV+CHP system there is potential of increasing the PV penetration level. One year of one second resolution pyranometer data is analyzed for Kingston Ontario to determine the total amount of PV energy generation potential, the rate of change of PV power generation due to intermittent cloud cover, and the daily CHP run time required to supply reliable base load power to the grid using this hybrid system. This analysis found that the vast majority of solar energy fluctuations are small in magnitude and the worst case energy fluctuation can be accommodated by relatively inexpensive and simple storage with conventional lead-acid batteries. For systems where the PV power rating is identical to the CHP unit, the CHP unit must run for more than twenty hours a day for the system to meet the base load requirement during the winter months. This provides a fortunate supply of heat, which can be used for the needed home heating. This paper provides analysis for a preliminary base line system.
-====[http://www.sciencedirect.com/science/article/pii/S1364032107000020 Flat-plate PV-Thermal collectors and systems: A review<ref name="Z. H.A.">Z. H.A., “Flat-plate PV-Thermal collectors and systems: A review,” Renewable and Sustainable Energy Reviews, vol. 12, no. 4, pp. 891-959, May 2008.</ref>]====
-'''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.
-====[http://www.sciencedirect.com/science/article/pii/S0038092X97000285 A combined optimisation concet for the design and operation strategy of hybrid-PV energy systems<ref name="S.-H. G.C.">S.-H. G.C., “A combined optimisation concet for the design and operation strategy of hybrid-PV energy systems,” Solar Energy, vol. 61, no. 2, pp. 77-87, Aug. 1997.</ref>]====
-'''Abstract:''' This paper presents a method to jointly determine the sizing and operation control of hybrid-PV systems. Hybrid energy systems use different energy sources such as solar and wind energy and diesel gensets. They are an economical option in areas remote from the grid. In this context the correct and cost-effective system sizing as well as efficient system operation are important. The problem becomes complicated through uncertain renewable energy supplies and load demand, non-linear characteristics of some components, and the fact that optimum operation strategies and optimum sizing of hybrid system components are interdependent. The outlined approach finds an optimum operation strategy for a hybrid system by carrying out a search through possible options for the system operation control. The search is conducted over some time period using estimated weather and demand data and long-term system component characteristics. The costing of the operating strategies is evaluated and component sizes are changed by the designed algorithm according to optimum search rules. As a result an optimum system configuration is chosen by the algorithm together with an optimum operation strategy for a given site and application requirement.
-====[http://www.nature.com/nature/journal/v451/n7175/abs/nature06381.html Enhanced thermoelectric performance of rough silicon nanowires<ref anme="A. I. Hochbaum">A. I. Hochbaum, R. Chen, R. D. Delgado, W. Liang, E. C. Garnett, M. Najarian, A. Majumdar, and P. Yang, “Enhanced thermoelectric performance of rough silicon nanowires,” Nature, vol. 451, no. 7175, pp. 163–167, Jan. 2008.</ref>]====
-'''Abstract:''' Approximately 90 per cent of the world's power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30–40 per cent efficiency, such that roughly 15 terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT > 1, since the parameters of ZT are generally interdependent. While nanostructured thermoelectric materials can increase ZT > 1, the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here Author(s) report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20–300 nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50 nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.
-====[http://www.sciencedirect.com/science/article/pii/S0038092X11001265 Performance evaluation of low concentrating photovoltaic/thermal systems: A case study from Sweden]====
-'''Abstract:''' Some of the main bottlenecks for the development and commercialization of photovoltaic/thermal hybrids are the lack of an internationally recognized standard testing procedure as well as a method to compare different hybrids with each other and with conventional alternatives. A complete methodology to characterize, simulate and evaluate concentrating photovoltaic/thermal hybrids has been proposed and exemplified in a particular case study. By using the suggested testing method, the hybrid parameters were experimentally determined. These were used in a validated simulation model that estimates the hybrid outputs in different geographic locations. Furthermore, the method includes a comparison of the hybrid performance with conventional collectors and photovoltaic modules working side-by-side. The measurements show that the hybrid electrical efficiency is 6.4% while the optical efficiency is 0.45 and the U-value 1.9 W/m2 °C. These values are poor when compared with the parameters of standard PV modules and flat plate collectors. Also, the beam irradiation incident on a north–south axis tracking surface is 20–40% lower than the global irradiation incident on a fixed surface at optimal tilt. There is margin of improvement for the studied hybrid but this combination makes it difficult for concentrating hybrids to compete with conventional PV modules and flat plate collectors.
-====[http://www.sciencedirect.com/science/article/pii/S0038092X03002512 Performance analysis of photovoltaic-thermal collector by explicit dynamic model]====
-'''Abstract:''' Although the performance of hybrid photovoltaic-thermal (PV/T) collector had been studied both experimentally and numerically for some years, the thermal models developed in previous studies were mostly steady-state models for predicting the annual yields. The operation of a PV/T collector is inherently dynamic. A steady-state model is not suitable for predicting working temperatures of the PV module and the heat-removal fluid during periods of fluctuating irradiance or intermittent fluid flow. Based on the control-volume finite-difference approach, an explicit dynamic model was developed for a single-glazed flat-plate water-heating PV/T collector. A transport delay fluid flow model was incorporated. The proposed model is suitable for dynamic system simulation applications. It allows detailed analysis of the transient energy flow across various collector components and captures the instantaneous energy outputs.
-====[http://www.sciencedirect.com/science/article/pii/S0038092X0600288X Electrical and thermal characterization of a PV-CPC hybrid<ref name="J. Nilsson">J. Nilsson, H. Håkansson, and B. Karlsson, “Electrical and thermal characterization of a PV-CPC hybrid,” Solar Energy, vol. 81, no. 7, pp. 917–928, Jul. 2007.</ref>]====
-'''Abstract:''' Long term evaluation of an asymmetric CPC PV-thermal hybrid built for high latitudes, MaReCo (MaximumReflectorCollector), is performed in Lund, lat 55.7°, and this paper discusses output estimates and characteristics of the system. The output estimates are calculated using the MINSUN simulation program. To get the input for MINSUN, measurements were performed on two MaReCo prototypes. These measurements show that the front reflector collects most of the irradiation in the summer, and the back reflector in the spring and fall. Two different reflector materials were used, anodized aluminium and aluminium laminated steel. The steel based reflector was selected for its rigidness. The output estimates show no difference in yearly output between the two reflector materials, both back reflectors deliver 168 kW h/(m2 cell area) of electricity compared to 136 kW h/m2 cell area for cells without reflectors. The cells facing the front reflector deliver 205 kW h/(m2 cell area) of electricity. The estimated output of thermal energy was 145 kW h/(m2 glazed area) at 50 °C. The estimates show that the optimal placement of the photovoltaic cells is facing the front reflector, but having cells on both sides is in most cases the best option.
-====[http://www.sciencedirect.com/science/article/pii/S0306261910000462 Optimal design of orientation of PV/T collector with reflectors]====
-'''Abstract:''' Hybrid conversion of solar radiation implies simultaneous solar radiation conversion into thermal and electrical energy in the PV/Thermal collector. In order to get more thermal and electrical energy, flat solar radiation reflectors have been mounted on PV/T collector. To obtain higher solar radiation intensity on PV/T collector, position of reflectors has been changed and optimal position of reflectors has been determined by both experimental measurements and numerical calculation so as to obtain maximal concentration of solar radiation intensity. The calculated values have been found to be in good agreement with the measured ones, both yielding the optimal position of the flat reflector to be the lowest (5°) in December and the highest (38°) in June. In this paper, the thermal and electrical efficiency of PV/T collector without reflectors and with reflectors in optimal position have been calculated. Using these results, the total efficiency and energy-saving efficiency of PV/T collector have been determined. Energy-saving efficiency for PV/T collector without reflectors is 60.1%, which is above the conventional solar thermal collector, whereas the energy-saving efficiency for PV/T collector with reflectors in optimal position is 46.7%, which is almost equal to the values for conventional solar thermal collector. Though the energy-saving efficiency of PV/T collector decreases slightly with the solar radiation intensity concentration factor, i.e. the thermal and electrical efficiency of PV/T collector with reflectors are lower than those of PV/T collector without reflectors, the total thermal and electrical energy generated by PV/T collector with reflectors in optimal position are significantly higher than total thermal and electrical energy generated by PV/T collector without reflectors.
-====[http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4592568 Photovoltaic / Thermal System for Stand-Alone Operation]====
-'''Abstract:''' The growing demand for the utilization of clean energy resources requires consideration of more efficient and economical ways in the usage of available resources and technologies. In the field of solar energy both the efficiency and the economics, i.e. the payback times are crucial questions for a more widespread application of this resource in the future. A novel solution and system are proposed in the paper aimed at enhancing the amount of energy that can be harvested from solar radiation in the same area. The basis of the method presented is a special construction of combined Photovoltaic / Thermal panels that can generate heat power to produce hot water, while the photovoltaic part provides electric power for covering the electric power consumption of loads, to supply its own electronic control units and to operate pump drives etc. The theoretical predictions of the electric part of the system are confirmed by laboratory test results. The system and the overall control structure, including the MPPT control, are presented assuming stand-alone operation but parallel operation is also possible.
-====[http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4374983 Combined Photovoltaic / Thermal Energy System for Stand-alone Operation<ref name="R. K. Jardan">R. K. Jardan, I. Nagy, A. Cid-Pastor, R. Leyva, A. El Aroudi, and L. Martinez-Salamero, “Combined Photovoltaic / Thermal Energy System for Stand-alone Operation,” in IEEE International Symposium on Industrial Electronics, 2007. ISIE 2007, 2007, pp. 2403–2408.</ref>]====
+* This article gives a review of the trend of development of the technology, starting from the early groundwork and placing more emphasis on the developments after year 2000.
+* A common PV module converts 4–17% of the incoming solar radiation into electricity, depending on the type of solar cells in use and the working conditions. In other words, more than 50% of the incident solar energy is converted as heat.
+* There can be two undesirable consequences: (i) a drop in cell efficiency (typically 0.4% per °C rise for c-Si cells) and (ii) a permanent structural damage of the module if the thermal stress remains for prolonged period.
+* Applications: Improved longwave absorption,High temperature applications,Autonomous applications,Commercial applications,The market potential.
-'''Abstract:''' The utilization of solar energy can be made by photovoltaic (PV) cells to generate electric power directly and solar thermal (T) panels can be applied to generate heat power. When the utilization of the solar energy is necessary to generate electric power, the option of using T panels in combination with some heat / electric power conversion technology can be a viable solution. The power generated by utilizing the solar energy absorbed by a given area of solar panel can be increased if the two technologies, PV and T cells, are combined in such a way that the resulting unit will be capable of co-generation of heat and electric power. In the present paper combined Photovoltaic / Thermal panels are suggested to generate heat power to produce hot water, while the photovoltaic part is used to obtain electric power mainly for covering the electric power consumption of the system, to supply the electronic control units and to operate pump drives etc. Ac and dc supplies are provided by converters for covering self-consumption and possibly the need of some household appliances. The development and design of the system is made by extensive use of modeling and simulation techniques. In the paper a part of the simulation studies, carried out to determine the energy balance in the electric energy conversion section of the system and the control structure, assuming stand-alone operation is presented.
+==== [http://www.sciencedirect.com/science/article/pii/S0038092X07000266 Energy performance of water hybrid PV/T collectors applied to combisystems of Direct Solar Floor type<ref name="G. Fraissea">"Energy performance of water hybrid PV/T collectors applied to combisystems of Direct Solar Floor type", Volume 81, Issue 11, November 2007, Pages 1426–1438</ref>] ====
-====[http://www.ecn.nl/fileadmin/ecn/units/egon/pvt/pdf/ises03_lca.pdf Application Aspects Of Hybrid PV/T Solar Systems]====
+'''Abstract:''' The integration of photovoltaic (PV) modules in buildings allows one to consider a multifunctional frame and then to reduce the cost by substitution of components. In order to limit the rise of the cell operating temperature, a photovoltaics/thermal (PV/T) collector combines a solar water heating collector and PV cells. The recovered heat energy can be used for heating systems and domestic hot water. A combination with a Direct Solar Floor is studied. Its low operating temperature level is appropriate for the operating conditions of the mono- or poly-crystalline photovoltaic modules which are selected in that study. However, for a system including a glass covered collector and localised in Mâcon area in France, we show that the annual photovoltaic cell efficiency is 6.8% which represents a decrease of 28% in comparison with a conventional non-integrated PV module of 9.4% annual efficiency. This is obviously due to a temperature increase related to the cover. On the other hand, we show that without a glass cover, the efficiency is 10% which is 6% better than a standard module due to the cooling effect.
+Moreover, in the case of a glazed PV/T collector with a conventional control system for Direct Solar Floor, the maximum temperature reached at the level of the PV modules is higher than 100 °C. This is due to the oversize of the collectors during the summer when the heating needs are null, i.e. without a heated swimming pool for example. This temperature level does not allow the use of EVA resin (ethylene vinyl acetate) in PV modules due to strong risks of degradation. The current solution consists of using amorphous cells or, if we do not enhance the thermal production, uncovered PV/T collector. Further research led to water hybrid PV/T solar collectors as a one-piece component, both reliable and efficient, and including the thermal absorber, the heat exchanger and the photovoltaic functions.
-'''Abstract:''' PV modules show temperature increase during their operation due to the absorption of solar radiation, as most of it is converted into heat and not into electricity. Hybrid Photovoltaic/Thermal (PV/T) solar systems combine a simultaneous conversion of solar radiation in electricity and heat. These devices consist of PV modules and heat extraction units mounted together, by which a circulating fluid of lower temperature than that of PV modules is heated by cooling them. An extensive study on water and air cooled PV/T solar systems has been conducted at the University of Patras, where hybrid prototypes have been experimentally studied. The water cooled PV/T systems consist of metallic heat exchanger placed at PV module rear surface, by which water circulating through pipes is heated. The methodology of Life Cycle Assessment (LCA) has been used to do an energetic and environmental assessment of the heat recovery system. The goal of this study, carried out at the University of Rome “ La Sapienza”, was to verify the benefits of heat recovery, implemented by a specific software for LCA, SimaPro 5.0. In this work Author(s) present the design, performance and aspects of improved PV/T systems based on the LCA results, giving guidelines for their application.
+* The mono-crystalline (m-C) and poly-crystalline (PC) cells see their electric production decreasing when the temperature of the cell increases because of their negative temperature coefficient (approximately −0.5%/K).
+* The thermal efficiency of a PV/T collector is lower than for a traditional system because part of solar energy is converted into electricity, the optical factor is weaker and the global coefficient of the thermal losses is higher. On one hand, the presence of a glazed cover at the top of the collector increases the thermal efficiency. On the other hand, it deteriorates the electric efficiency by increasing both optical losses and temperature of PV cells. This decrease can be compensated by the installation of reflectors.
+* The hot water produced by the hybrid collector is used for domestic hot-water production and the Direct Solar Floor. The advantage of the DSF is that an additional solar tank is not used since collected solar energy is directly stored in the floor.
+* The dynamic behavior of the collector takes into account the heat capacity of each node. It is important because of the strong variations of flow rate related to control. The model of the wall (or roof) is defined with a model of type 3R4C.
+* The model, based on the electric diagram, is equivalent to a photovoltaic cell including a generator of current (photocurrent), a diode and a series resistance (Fig. 3). The photovoltaic module includes Nms modules in series and Nmp modules in parallel.
-====[http://www.hindawi.com/journals/ijp/2009/732093/ Performance Analysis of a Photovoltaic-Thermal  Integrated System]====
+==== [http://apl.aip.org/resource/1/applab/v31/i4/p292_s1 Reversible conductivity changes in discharge-produced amorphous Silicon<ref name="D. L. Staebler and C. R. Wronski" >"Reversible conductivity changes in discharge-produced amorphous Silicon ", Appl. Phys.Lett. 31,292 (1977);doi;10.1063/1.89674</ref>] ====
-'''Abstract:'''The present commercial photovoltaic solar cells (PV) converts solar energy into electricity with a relatively low efficiency, less than 20%. More than 80% of the absorbed solar energy is dumped to the surroundings again after photovoltaic conversion. Hybrid PV/T systems consist of PV modules coupled with the heat extraction devices. The PV/T collectors generate electric power and heat simultaneously. Stabilizing temperature of photovoltaic modules at low level is higly desirable to obtain efficiency increase. The total efficiency of 60–80% can be achieved with the whole PV/T system provided that the T system is operated near ambient temperature. The value of the low-T heat energy is typically much smaller than the value of the PV electricity. The PV/T systems can exist in many designs, but the most common models are with the use of water or air as a working fuid. Efficiency is the most valuable parameter for the economic analysis. It has substantial meaning in the case of installations with great nominal power, as air-cooled Building Integrated Photovoltaic Systems (BIPV).
+'''Abstract:''' A new reversible photoelectronic effect is reported for amorphous Si produced by glow discharge of SiH •.
-In this paper the performance analysis of a hybrid PV/T system is presented: an energetic analysis as well as an exergetic analysis. Exergy is always destroyed when a process involves a temperature change. This destruction is proportional to the entropy increase of the system together with its surroundings—the destroyed exergy has been called anergy. Exergy analysis identifies the location, the magnitude, and the sources of thermodynamic inefficiences in a system. This information, which cannot be provided by other means (e.g., an energy analysis), is very useful for the improvement and cost-effictiveness of the system. Calculations were carried out for the tested water-cooled ASE-100-DGL-SM Solarwatt module.
+Long exposure to light decreases:'o.'both the photoconductivity and the dark conductivity, the latter by
+nearly four orders of magnitude. Annealing above 150·C reverses the process. A model involving
+optically induced changes in gap states is proposed. The results have strong implications for both the
+physical nature of the material and for its applications in thin-film solar cells. as well as the
+reproducibility of measurements on discharge-produced Si.
-====[http://www.hindawi.com/journals/ijp/2012/630692/ Design of Novel Compound Fresnel Lens for High-Performance Photovoltaic Concentrator]====
+* Both the photo-conductivity and the dark conductivity decrease with light exposure .
+* Dark conductivity as a function of temperature through this process the conductivity increases with increasing temperature following the expression a= ao exp(Ea/kT).
+* The hydrogen content, moreover,is stable at annealing temperatures below the deposition temperature.
+* The change in dark conductivity does not necessarily limit the performance because the bulk series resistance in an operating cell is determined by the photo-conductivity
-'''Abstract:'''We present a new design of compound Fresnel-R concentrator which is composed of two lenses: a primary lens (Fresnel lens) that works by total internal reflection at outer sawteeth but refraction at inner sawteeth, and a ringed secondary lens that works by refraction. In contrast to previous Fresnel lens concentrators, this design increases the acceptance angle, improves the irradiance uniformity on the solar cell, and reduces the aspect ratio significantly. Meanwhile several sawteeth of the primary Fresnel lens can correspond to a same ring of secondary lens, which will efficiently lower the complexity of designing and manufacturing. Moreover, in order to reduce the influence of manufacturing tolerances and to increase the optical efficiency further, the central part of the bottom of the secondary lens which directly adhered to the solar cell is designed as a cone-shaped prism to collect the sunlight that does not reach the solar cell. Finally, we provide simulations and analyses of the design method an optical efficiency more than 80% and an aspect ratio smaller than 0.5 can be achieved.
+==== [http://www.annualreviews.org/doi/pdf/10.1146/annurev.matsci.31.1.47 DEVELOPMENT IN UNDERSTANDING AND CONTROLLING THE STAEBLER-WRONSKI EFFECT IN a-Si:H<ref name="Hellmut Fritzsche" >"DEVELOPMENT IN UNDERSTANDING AND CONTROLLING THE STAEBLER-WRONSKI EFFECT IN a-Si:H ", Energy Conversion Devices, Inc., Troy, Michigan 48084</ref>] ====
+'''Abstract:''' Hydrogenated amorphous silicon (a-Si:H) exhibits a metastable light induced degradation of its optoelectronic properties that is called the Staebler-Wronski effect, after its discoverers. This degradation effect is associated with the relatively high diffusion coefficient of hydrogen and the changes in local bonding coordination promoted by hydrogen. Reviewed are the fundamental aspects of the interplay between hydrogen and electronic energy states that form the basis of competing microscopic
+models for explaining the degradation effect. These models are tested against the latest experimental observations, and material and preparation parameters that reduce the Staebler-Wronski effect are discussed.
-====[http://www.irec.cmerp.net/irec09/papers/HE/IREC09-HE-07.pdf A dynamic model of hybrid photovoltaic/thermal panel]====
+* Dangling bond defects acting as recombination centers, decreased the photocarrier lifetime and, owing to their location near midgap shift EF, thereby decreased the dark conductivity.
+* Extended illumination appreciably degrading the optoelectronic properties of this material. This lightinduced degradation is called the Staebler-Wronski effect (SWE). Even though these defects anneal away between 150 and 200±C, the SWE seriously limits the use of a-Si:H in solar photovoltaic applications.
+* In crystalline Si, atomic motions that could produce coordination defects occur only near 1000±C. The low-anneal temperature of the light-induced coordination defects (dangling bonds) in a-Si:H is related to the diffusion of bonded hydrogen. Above TE » 200±C, hydrogen diffusion enables the equilibration of solid-state chemical reactions, which determine the concentration of coordination defects of silicon as well as of dopant atom.
-'''Abstract:'''In this paper a dynamic simulation model of a photovoltaic and water heating system (PV/T) is developed. The model consists of a set of mathematical equations governing the main components of the system; namely: transparent cover, solar cell, absorber plate, operating fluid and storage tank. The model is based on the analysis of the energy balance which includes the photo electric conversion and the thermal conduction, convection and radiation. The model gathers all components equations so as to reflect the electrical and thermal behaviour of the PV/T system. It delivers the state equation of the system function of the climatic parameters and the fluid flow rate. The investigation of the effect of water mass flow rate through the collector on PV/T outputs have been carried out.
+==== [http://www.sciencedirect.com/science/article/pii/S0040609003015293 Intrinsic and light induced gap states in a-Si:H materials and solar cells—effects of microstructure<ref name="C.R. Wronski" >"Intrinsic and light induced gap states in a-Si:H materials and solar cells—effects of microstructure ", Thin Solid Films 451 –452 (2004) 470–475</ref>] ====
+'''Abstract:''' The effects of microstructure on the gap states of hydrogen diluted and undiluted hydrogenated amorphous silicon (a-Si:H) thin film materials and their solar cells have been investigated. In characterizing the films the commonly used methodology of relating just the magnitudes of photocurrents and subgap absorption, a(E), was expanded to take into account states other than those due to dangling bond defects. The electron mobility-lifetime products were characterized as a function of carrier generation rates and analysis was carried out of the entire a(E) spectra and their evolution with light induced degradation. Two distinctly different defect states at 1.0 and 1.2 eV from the conduction band and their contributions to carrier recombination were identified and their respective evolution under 1 sun illumination characterized. Direct correlations were obtained between the recombination in thin films with that of corresponding solar cells. The effects of the difference in microstructure on the changes in these two gap states in films and solar cells were also identified. It is found that improved stability of protocrystalline Si:H can in part be attributed to the reduction of the 1.2 eV defects. It is also shown that ignoring the presence of multiple defects leads to erroneous conclusions being drawn about the stability of a-Si:H and SWE.
+* Because as yet the nature and densities of the states are not known it is not possible to correlate them directly to those in the corresponding cells, but it is possible to relate them through their role as carrier recombination centers.
+* The distinct difference between the times taken to reach the 1 sun DSS with the cells having the protocrystalline and the undiluted a-Si:H i-layers can be attributed to a difference in the relative densities.
+* The same kinetics are observed for the cells and films where in the undiluted cell, there is an 'overshoot' in the recovery so-called 'fast' and 'slow' defect states.
-====[http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=792006&tag=1 Development and characterization of high-efficiency Ga0.5In0.5P/GaAs/Ge dual- and triple-junction solar cells]====
+==== [http://www.sciencedirect.com/science/article/pii/S0927024807003406 Modeling of light-induced degradation of amorphous silicon solar cells<ref name="# A. Klaver, R.A.C.M.M. van Swaaij " >"Modeling of light-induced degradation of amorphous silicon solar cells ", Volume 92, Issue 1, January 2008, Pages 50–60</ref>] ====
-'''Abstract:'''This paper describes recent progress in the characterization, analysis, and development of high-efficiency, radiation-resistant Ga0.5In0.5P/GaAs/Ge dual-junction (DJ) and triple-junction (TJ) solar cells. DJ cells have rapidly transitioned from the laboratory to full-scale (325 kW/year) production at Spectrolab. Performance data for over 470000 large-area (26.94 cm2 ), thin (140 μm) DJ solar cells grown on low-cost, high-strength Ge substrates are shown. Advances in next-generation triple-junction Ga0.5In0.5P/GaAs/Ge cells with an active Ge component cell are discussed, giving efficiencies up to 26.7% (21.65-cm2 area), AM0, at 28°C. Final-to-initial power ratios P/P0 of 0.83 were measured for these n-on-p DJ and TJ cells after irradiation with 1015 1-MeV electrons/cm2 . Time-resolved photoluminescence measurements are applied to double heterostructures grown with semiconductor layers and interfaces relevant to these multijunction solar cells, to characterize surface and bulk recombination and guide further device improvements. Dual- and triple-junction Ga0.5In0.5P/GaAs/Ge cells are compared to competing space photovoltaic technologies, and found to offer 60-75% more end-of-life power than high-efficiency Si cells at a nominal array temperature of 60°C
+'''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.
-====[http://digitalcommons.lmu.edu/mech_fac/10/ Parametric analysis of a coupled photovoltaic/thermal concentrating solar collector for electricity generation]====
+* When two mobile hydrogen atoms 'collide', a metastable complex containing two Si–H bonds is formed together with two dangling-bond defects.
+* Recombination on weak bonds initiates the defect creation.
+* Computer simulation concluded that the dark-conductivity degradation was mainly determined by the shift in peak position of the positively charged/neutral defect-state peak of the DDOS and the photoconductivity by the total defect density.
+* Light soaking mainly leads to a change in the defect density of a-Si:H and the creation of defects is initiated by recombination events in the intrinsic layer of the device.
+* Light-soak the cells under both open- and short-circuit conditions with the objective to alter the recombination profile substantially in the cells.
-'''Abstract:'''The analysis of the combined efficiencies in a coupled photovoltaic PV/thermal concentrating
+==== [http://apl.aip.org/resource/1/applab/v83/i18/p3725_s1 Light-induced defect states in hydrogenated amorphous silicon centered around 1.0 and 1.2 eV from the conduction band edge<ref name="J. M. Pearce," >"Light-induced defect states in hydrogenated amorphous silicon centered around 1.0 and 1.2 eV from the conduction band edge", Appl. Phys. Lett. 83, 3725 (2003); doi: 10.1063/1.1624637</ref>] ====
-solar collector are presented based on a coupled electrical/thermal model. The calculations take into
-account the drop in efficiency that accompanies the operation of PV cells at elevated temperatures
-along with a detailed analysis of the thermal system including losses. An iterative numerical scheme
-is described that involves a coupled electrothermal simulation of the solar energy conversion
-process. In the proposed configuration losses in the PV cell due to reduced efficiencies at elevated
-temperatures and the incident solar energy below the PV bandgap are both harnessed as heat. This
-thermal energy is then used to drive a thermodynamic power cycle. The simulations show that it is
-possible to optimize the overall efficiency of the system by variation in key factors such as the solar
-concentration factor, the band gap of the PV material, and the system thermal design configuration,
-leading to a maximum combined efficiency of 32.3% for solar concentrations between 10–50 and
-a band-gap around 1.5–2.0 eV. © 2010 American Institute of Physics.
-====[http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JSEEDO000128000002000258000001&idtype=cvips&gifs=yes Analysis of Potential Conversion Efficiency of a Solar Hybrid System With High-Temperature Stage]====
+'''Abstract:'''To take into account the presence of multiple light-induced defect states in hydrogenated amorphous silicon (a-Si:H) the evolution of the entire spectra of photoconductive subgap absorption, a(hn ),has been analyzed. Using this approach two distinctly different light-induced defect states centered around 1.0 and 1.2 eV from the conduction band edge are clearly identified. Results are presented
+on their evolution and respective effects on carrier recombination that clearly point to the importance of these states in evaluating the stability of different a-Si:H solar cell materials, as well
+as elucidating the origin of the Staebler–Wronski effect.
-'''Abstract:'''The analysis is given of hybrid system of solar energy conversion having a stage operating at high temperature. The system contains a radiation concentrator, a photovoltaic solar cell, and a thermal generator, which could be thermoelectric one or a heat engine. Two options are discussed, one (a) with concentration of the whole solar radiation on the PV cell working at high temperature and coupled to the high-temperature stage, and another (b) with a special PV cell construction, which allows the use of the part of solar spectrum not absorbed in the semiconductor material of the cell ("thermal energy") to drive the high-temperature stage while the cell is working at ambient temperature. The possibilities of using different semiconductor materials are analyzed. It is shown that the demands to the cell material are different in the two cases examined: in system (a) with high temperature of cell operation, the materials providing minimum temperature dependence of the conversion efficiency are necessary, for another system (b) the materials with the larger band gap are profitable. The efficiency of thermal generator is assumed to be proportional to that of the Carnot engine. The optical and thermal energy losses are taken into account, including the losses by convection and radiation in the high-temperature stage. The radiation losses impose restrictions upon the working temperature of the thermal generator in the system (b), thus defining the highest possible concentration ratio. The calculations made show that the hybrid system proposed could be both efficient and practical, promising the total conversion efficiency around 25–30  % for system (a), and 30–40  % for system (b).
+* LI degradationis associated with the creation of dangling bonds.
+* a(hn)is interpreted solely in terms of D0 defect states.However, results have also been reported that point to the introduction of other defect states and that a(hn ) cannot be interpreted in such a simple manner.
+* Two distinctly different light induced defect states centered around 1.0 and 1.2 eV from the conduction band ~CB! edge are clearly identified and their evolution found to be consistent with the corresponding changes in mt
+* It is shown that in the AS, the mt product of the R510 material is about five times higher than in the R50 material, as is generally expected for better quality materials.
+* At 25 °C, the protocrystalline material attains a DSS in approximately 100 h, whereas in the R50 material, the commonly reported kinetics with t21/3 extends for 400 h with no approach to DSS. When the temperature of degradation is raised to 75 °C, there is virtually no change in the kinetics of the 20 Å/s material, whereas the R510 reaches a DSS with a mt values that is two times higher than at 25 °C.
+* Any interpretation of a(hn ) in terms of the density and energy distribution of multiple defect states is complicated by the nature of photoconductive subgap absorption, which is determined by N(E),
+==== [http://www.public.asu.edu/~jkwawu/PTL/rd/docs/IEEEPVSC%20of%20Jan05-Final.pdf PERFORMANCE TEST OF AMORPHOUS SILICON MODULES IN DIFFERENT CLIMATES – YEAR THREE: HIGHER MINIMUM OPERATING TEMPERATURES LEAD TO HIGHER PERFORMANCE LEVELS<ref name="R. Rüther," >"PERFORMANCE TEST OF AMORPHOUS SILICON MODULES IN DIFFERENT CLIMATES – YEAR THREE: HIGHER MINIMUM OPERATING TEMPERATURES LEAD TO HIGHER PERFORMANCE LEVELS"</ref>] ====
-====[http://www.sciencedirect.com/science/article/pii/S0927024898001998 Limiting efficiency of coupled thermal and photovoltaic converters   <ref name=" * Antonio LuqueCorresponding author contact information,* Antonio Martı́"> * Antonio LuqueCorresponding author contact information, * Antonio Martı́ * Instituto de Energı́a Solar, Universidad Politécnica de Madrid, Ciudad Universitaria, 28040 Madrid, Spain * Received 27 May 1998. Accepted 20 October 1998. Available online 21 June 1999. </ref>]====
+'''Abstract:'''This paper presents third year results of a round robin exposure experiment designed to assess the performance of thin-film amorphous silicon (a-Si) solar modules operating in different climatic conditions. Three identical sets of commercially available a-Si PV modules from five different manufacturers were simultaneously deployed outdoors in three sites with distinct climates (Arizona – USA, Colorado – USA and Florianopolis – Brazil). Every year all PV module sets were sent to the National Renewable Energy Laboratory (NREL) for Standard Testing Conditions measurements under a SPIRE simulator. The fouryear experiment aims to determine the light-induced degradation and stabilization characteristics of a-Si regarding specific history of exposure, and to monitor and compare degradation rates in different climates. We present results from the first three years of measurements, showing that while most of the manufacturers underrate their products by 20 to 25% to account for the light-induced degradation, outdoor exposure temperature seems to be what will ultimately determine the stabilized performance level of a-Si.
-'''Abstract:''' This paper presents a general energetic and entropic analysis of ideal photovoltaic and solar-thermal converters. Its purpose is to determine the efficiency limit when both types of converters operate together (hybrid converters). It has been found that, while in practical cases hybrid converters may give very high efficiency (61.7% vs. 40.0% of the solar thermal at 500 K and 40.7% of the photovoltaic at 300 K), in the limiting case of a system formed by an infinite number of band gaps, the efficiency of hybrid converters, 86.8%, is strictly equivalent to photovoltaic or solar thermal converters. Conversely, hybrid systems operating with one gap give an efficiency of 86.7%, very close to the previous one and higher than the top efficiency achievable with a single temperature solar thermal, 85.4%.
+* After the first year of outdoor exposure, modules deployed at the site with the highest minimum operating temperature experienced the highest stabilized output level
+* Further reporting on the first and second years of this four-year experiment, indicated that there is barely any lifetime memory of the stabilized state in a-Si
+* In the first year of deployment outdoors, PV modules exposed at the coldest site underwent the largest amount of degradation, and outdoor exposure at the warmest site led to the smallest amount of degradation
+* In the second year, Set A went from the coldest site to the warmest site, which led to some recovery in output performance upon further light soaking, indicating that these modules do not seem to show a lifetime memory of the stabilized state.
+* In the third year, Set A was deployed outdoors at the year round- climate-intermediate site,and reached a new stabilized state, at a higher performance level than after the second year.
+==== [http://www.sciencedirect.com/science/article/pii/S0306261902001769 The potential of solar industrial process heat applications<ref name="Soteris Kalogirou" >"The potential of solar industrial process heat applications", Volume 76, Issue 4, December 2003, Pages 337–361</ref>] ====
+'''Abstract:'''The temperature requirements of solar industrial process heat applications range from 60 °C to 260 °C. The characteristics of medium to medium-high temperature solar collectors are given and an overview of efficiency and cost of existing technologies is presented. Five collector types have been considered in this study varying from the simple stationary flat-plate to movable parabolic trough ones. Based on TRNSYS simulations, an estimation of the system efficiency of solar process heat plants operating in the Mediterranean climate are given for the different collector technologies. The annual energy gains of such systems are from 550 to 1100 kWh/m2 a. The resulting energy costs obtained for solar heat are from 0.015 to 0.028 C£/kWh depending on the collector type applied. The viabilities of the systems depend on their initial cost and the fuel price. None of these costs however is stable but change continuously depending on international market trends and oil production rates. The costs will turn out to be more favourable when the solar collectors become cheaper and subsidisation of fuel is removed. Therefore the optimisation procedure suggested in this paper should be followed in order to select the most appropriate system in each case.
-== References ==
+* The industrial heat-demand constitutes about 15% of the overall demand of final energy requirements in the southern European countries
-<references/>
+* Investment costs should be comparatively low, even if the costs for the collector are higher.One way to cause economically easy terms is to design systems without heat storage.
+* Solar thermal energy can be used for low-pressure steam generation at 100–110*C and for refrigeration of the wort, which can be accomplished with absorption cooling.
+* In a solar process heat system, interfacing of the collectors with conventional energy supplies must be done in a way compatible with the process. The easiest way to accomplish this is by using heat storage, which can also allow the system to work in periods of low irradiation and/or night time.
+* In the case of water preheating, higher efficiencies are obtained due to the low input-temperature to the solar system: thus low-technology collectors can work effectively and the required load supply temperature has no or little effect on the performance of the solar system.
+* The optimum collector area, storage tank volume, life-cycle savings and solar contribution of the various collector types and demand temperatures considered are investigated.
+* There are two major types of collectors that can be applied for industrial process-heat, non-tracking (stationary) collectors and one-axis sun-tracking parabolic trough collectors.
-[[Category:MOST literature reviews]]
+{{Page data
+| authors = User:Ankitvora, User:S.Debnath
+| organizations = MOST
+}}

Combined photovoltaic solar thermal systems (PVT) literature review: Difference between revisions

Latest revision as of 13:57, 23 February 2024

This page describes selected literature available on PVT[edit | edit source]

Dispatch strategy and model for hybrid photovoltaic and trigeneration power systems[1][edit | edit source]

A review on photovoltaic/thermal hybrid solar technology[2][edit | edit source]

Energy performance of water hybrid PV/T collectors applied to combisystems of Direct Solar Floor type[3][edit | edit source]

Reversible conductivity changes in discharge-produced amorphous Silicon[4][edit | edit source]

DEVELOPMENT IN UNDERSTANDING AND CONTROLLING THE STAEBLER-WRONSKI EFFECT IN a-Si:H[5][edit | edit source]

Intrinsic and light induced gap states in a-Si:H materials and solar cells—effects of microstructure[6][edit | edit source]

Modeling of light-induced degradation of amorphous silicon solar cells[7][edit | edit source]

Light-induced defect states in hydrogenated amorphous silicon centered around 1.0 and 1.2 eV from the conduction band edge[8][edit | edit source]

PERFORMANCE TEST OF AMORPHOUS SILICON MODULES IN DIFFERENT CLIMATES – YEAR THREE: HIGHER MINIMUM OPERATING TEMPERATURES LEAD TO HIGHER PERFORMANCE LEVELS[9][edit | edit source]

The potential of solar industrial process heat applications[10][edit | edit source]