Showing papers in "Progress in Photovoltaics in 2013"
TL;DR: In this paper, the degradation rates of flat-plate terrestrial modules and systems reported in published literature from field testing throughout the last 40 years have been analyzed, showing a median value of 0·5%/year.
Abstract: As photovoltaic penetration of the power grid increases, accurate predictions of return on investment require accurate prediction of decreased power output over time. Degradation rates must be known in order to predict power delivery. This article reviews degradation rates of flat-plate terrestrial modules and systems reported in published literature from field testing throughout the last 40 years. Nearly 2000 degradation rates, measured on individual modules or entire systems, have been assembled from the literature, showing a median value of 0·5%/year. The review consists of three parts: a brief historical outline, an analytical summary of degradation rates, and a detailed bibliography partitioned by technology. Copyright © 2011 John Wiley & Sons, Ltd.
1,202 citations
IBM1
TL;DR: In this paper, a vacuum process was used to construct a pure sulfide Cu2ZnSnS4 solar cell with 8.4% efficiency, a number independently certified by an external, accredited laboratory.
Abstract: Using vacuum process, we fabricated Cu2ZnSnS4 solar cells with 8.4% efficiency, a number independently certified by an external, accredited laboratory. This is the highest efficiency reported for pure sulfide Cu2ZnSnS4 prepared by any method. Consistent with literature, the optimal composition is Cu-poor and Zn-rich despite the precipitation of secondary phases (e.g., ZnS). Despite a very thin absorber thickness (~600 nm), a reasonably good short-circuit current was obtained. Time-resolved photoluminescence measurements suggest a minority carrier-diffusion length on the order of several hundreds of nanometers and relatively good collection of photo-carriers across the entire absorber thickness. Copyright © 2011 John Wiley & Sons, Ltd.
1,083 citations
789 citations
TL;DR: Consolidated tables showing an extensive listing of the highest independently measured photovoltaic cell and moduleencies for solar cells and modules are presented.
Abstract: Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells andmodules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January2013 are reviewed. Copyright © 2013 John Wiley & Sons, Ltd. KEYWORDSsolar cell efficiency; photovoltaic efficiency; energy conversion efficiency*CorrespondenceMartin A. Green, Australian Centre for Advanced Photovoltaics, University of New South Wales, Sydney, 2052, Australia.E-mail: m.green@unsw.edu.auReceived 6 June 2013; Accepted 6 June 2013 1. INTRODUCTION Since January 1993, ‘Progress in Photovoltaics’ haspublished six monthly listings of the highest confirmedefficiencies for a range of photovoltaic cell and moduletechnologies [1–3]. By providing guidelines for theinclusion of results into these tables, this not only allowsan authoritative summary of the current state of the artbut alsoencourages researchers to seek independent confir-mation of results and to report results on a standardisedbasis. In version 33 of these tables [2], results wereupdated to the new internationally accepted reference spec-trum (IEC 60904-3, Ed. 2, 2008), where this was possible.Themostimportantcriterionforinclusionofresultsintothe tables is that they must have been independentlymeasured by a recognised test centre listed elsewhere [1].A distinction is made between three different eligibledefinitions of cell area: total area, aperture area anddesignated illumination area, as also defined elsewhere[1]. ‘Active area’ efficiencies are not included. There arealso certain minimum values of the area sought for thedifferent device types (above 0.05cm
475 citations
IBM1
TL;DR: In this paper, a thin-film solar cell with solution-processed Cu(In,Ga)(S,Se)2 (CIGS) absorber was reported and the power conversion efficiency of 15.2% is the highest published value for a pure solution deposition technique for any photovoltaic absorber material.
Abstract: The remarkable potential for inexpensive upscale of solution processing technologies is expected to enable chalcogenide-based photovoltaic systems to become more widely adopted to meet worldwide energy needs. Here, we report a thin-film solar cell with solution-processed Cu(In,Ga)(S,Se)2 (CIGS) absorber. The power conversion efficiency of 15.2% is the highest published value for a pure solution deposition technique for any photovoltaic absorber material and is on par with the best nonvacuum-processed CIGS devices. We compare the performance of our cell with a world champion vacuum-deposited CIGS cell and perform detailed characterization, such as biased quantum efficiency, temperature-dependent electrical measurement, time-resolved photoluminescence, and capacitance spectroscopy. Copyright © 2012 John Wiley & Sons, Ltd.
370 citations
TL;DR: In this article, a grid-parity model is presented, which is based on levelized cost of electricity (LCOE) coupled with the experience curve approach, and its key driving forces are discussed in detail.
Abstract: Grid-parity is a very important milestone for further photovoltaic (PV) diffusion. A grid-parity model is presented, which is based on levelized cost of electricity (LCOE) coupled with the experience curve approach. Relevant assumptions for the model are given, and its key driving forces are discussed in detail. Results of the analysis are shown for more than 150 countries and a total of 305 market segments all over the world, representing 98.0% of world population and 99.7% of global gross domestic product. High PV industry growth rates enable a fast reduction of LCOE. Depletion of fossil fuel resources and climate change mitigation forces societies to internalize these effects and pave the way for sustainable energy technologies. First grid-parity events occur right now. The 2010s are characterized by ongoing grid-parity events throughout the most regions in the world, reaching an addressable market of about 75–90% of total global electricity market. In consequence, new political frameworks for maximizing social benefits will be required. In parallel, PV industry tackle its next milestone, fuel-parity. In conclusion, PV is on the pathway to become a highly competitive energy technology. Copyright © 2012 John Wiley & Sons, Ltd.
325 citations
TL;DR: In this article, an improved ink formulation using alkanethiol as the solvent enables the ability to create uniform nanocrystal coatings over large areas using a simple knife coating technique.
Abstract: Solution phase deposition methods offer great potential for low-cost photovoltaic device fabrication. We have previously developed a method for copper indium gallium disulfoselenide (CIGSSe) device fabrication based on drop-casting copper indium gallium disulfide (CIGS) nanocrystals in a toluene or hexane-based ink followed by chalcogen exchange in elemental selenium vapor at 500 °C. By starting with the chalcopyrite or sphaelerite phase of CIGS nanocrystals with controlled stoichiometry, superior composition uniformity can be achieved inherently. Here, we present a dramatic improvement in ink formulation using alkanethiol as the solvent, which enables the ability to create uniform nanocrystal coatings over large areas using a simple knife coating technique. In addition, we show a major improvement in device performance by a simple and low-temperature method of incorporating sodium into the CIGSSe film based on soaking the films in aqueous NaCl solution. The addition of sodium plays an important role in improving the structural properties of the resulting CIGSSe films, where large and densely packed grain can be obtained. The improved film morphology significantly reduces recombination losses in the resulting device leading to a dramatically enhanced device performance. With the use of standard glass/Mo/CIGSSe/CdS/i-ZnO/ITO device structure, photovoltaic devices yield total area power conversion efficiency as high as 12.0% under AM1.5 illumination without an anti-reflection coating. Copyright © 2012 John Wiley & Sons, Ltd.
228 citations
TL;DR: In this article, hourly solar and photovoltaic (PV) forecasts for horizons between 0 and 48h ahead were developed using Environment Canada's Global Environmental Multiscale model.
Abstract: Hourly solar and photovoltaic (PV) forecasts for horizons between 0 and 48h ahead were developed using Environment Canada’s Global Environmental Multiscale model. The motivation for this research was to explore PV forecasting in Ontario, Canada, where feed-in tariffs are driving rapid growth in installed PV capacity. The solar and PV forecasts were compared with irradiance data from 10 North-American ground stations and with alternating current power data from three Canadian PV systems. A 1-year period was used to train the forecasts, and the following year was used for testing. Two post-processing methods were applied to the solar forecasts: spatial averaging and bias removal using a Kalman filter. On average, these two methods lead to a 43% reduction in root mean square error (RMSE) over a persistence forecast (skill score=0.67) and to a 15% reduction in RMSE over the Global Environmental Multiscale forecasts without post-processing (skill score=0.28). Bias removal was primarily useful when considering a “regional”forecast for the average irradiance of the 10 ground stations because bias was a more significant fraction of RMSE in this case. PV forecast accuracy was influenced mainly by the underlying (horizontal) solar forecast accuracy, with RMSE ranging from 6.4% to 9.2% of rated power for the individual PV systems. About 76% of the PV forecast errors were within � 5% of the rated power for the individual systems, but the largest errors reached up to 44% to 57% of rated power. © Her Majesty the Queen in Right of Canada 2011. Reproduced with the permission of the Minister of Natural Resources Canada.
227 citations
TL;DR: In this article, a multi-dimensional model for comprehensive simulations of solar cells (SCs), considering both electromagnetic and electronic properties, is presented, which provides complete spectral and spatial information of typical optical and electronic behavior.
Abstract: We present a multi-dimensional model for comprehensive simulations of solar cells (SCs), considering both electromagnetic and electronic properties. Typical homojunction and heterojunction gallium arsenide SCs were simulated in different spatial dimensions. When considering one-dimensional problems, the model performs carrier transport calculations following a Beer–Lambert optical absorption approximation. We show that the results of such simulations exhibit excellent agreement with the standard PC1D one-dimensional photovoltaic simulation. Photonic and plasmonic attempts to enhance SC efficiency demand comprehensive electromagnetic calculations to be undertaken in order to acquire accurate carrier generation profiles in two and three-dimensional systems. Our model provides complete spectral and spatial information of typical optical and electronic behavior. Furthermore, our approach permits the detailed investigation of complex systems, including plasmonic SCs, which cannot be simulated using low-dimensional modeling tools. We present the results of numerical simulations of an optically thin plasmonic gallium arsenide SC and observe improved device performance arising from the application of plasmonic nanostructures, which agree well with previous experimental findings. Copyright © 2012 John Wiley & Sons, Ltd.
127 citations
TL;DR: In this article, an indoor method is presented for quantification of the current-matching ratio of a multijunction cell within a concentrator under arbitrary spectral irradiance conditions, where the cell current is measured across a very large spectral sweep to force the relevant subcells into a limiting condition.
Abstract: An indoor method is presented for the quantification of the current-matching ratio of a multijunction cell within a concentrator under arbitrary spectral irradiance conditions. The cell current is measured across a very large spectral sweep to force the relevant subcells into a limiting condition. The light spectrum is monitored using component cells to avoid the need for a spectroradiometer and spectral response measurements. The method also provides an estimation of the current losses beyond the overall current mismatch, for example, losses produced in concentrators with chromatic aberration by the non-uniformity of the incident spectrum across the cell. The method has been applied to a pair of refractive point-focus concentrator systems; first, a 300X single-stage Fresnel lens over a lattice-matched GaInP/Ga(In)As/Ge triple-junction cell and second, a 1000X two-stage system with the same Fresnel lens over a homogenizing secondary lens that encapsulates a triple-junction cell of the same kind but smaller. The experiment demonstrates that the single-stage concentrator exhibits a higher sensitivity of the current mismatch to variations in the focal distance. Copyright © 2012 John Wiley & Sons, Ltd.
119 citations
TL;DR: In this paper, the authors report on the evolution of metal plating techniques, from their use in early silicon solar cells, to current light-induced plating processes, and review relevant recently-developed dielectric patterning methods.
Abstract: Increasing silver prices and reducing silicon wafer thicknesses provide incentives for silicon solar cell manufacturing to develop new metallisation strategies that do not rely on screen printing and preferably reduce silver usage. Recently, metal plating has re-emerged as a metallisation process that may address these future requirements. This paper reports on the evolution of metal plating techniques, from their use in early silicon solar cells, to current light-induced plating processes. Unlike screen-printed metallisation, metal plating typically requires an initial patterning step to create openings in a masking layer for the subsequent self-aligned metallisation. Consequently, relevant recently-developed dielectric patterning methods are also reviewed because, in many cases, the plating process must be adapted to the properties of the patterning method used. The potential of new light-induced plating processes to form cost-effective copper metallisation is supported by the recent activity in the development of metal plating tools for commercial silicon solar cell manufacture. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, the growth mechanism for chalcopyrite-type thin films when varying the Cu content during a multi-stage deposition process is studied, and the film structure and morphology are studied by X-ray diffraction and scanning electron microscopy.
Abstract: In order to transfer the potential for the high efficiencies seen for Cu(In,Ga)Se2 (CIGSe) thin films from co-evaporation processes to cheaper large-scale deposition techniques, a more intricate understanding of the CIGSe growth process for high-quality material is required. Hence, the growth mechanism for chalcopyrite-type thin films when varying the Cu content during a multi-stage deposition process is studied. Break-off experiments help to understand the intermediate growth stages of the thin-film formation. The film structure and morphology are studied by X-ray diffraction and scanning electron microscopy. The different phases at the film surface are identified by Raman spectroscopy. Depth-resolved compositional analysis is carried out via glow discharge optical emission spectrometry. The experimental results imply an affinity of Na for material phases with a Cu-poor composition, affirming a possible interaction of sodium with Cu vacancies mainly via In(Ga)Cu antisite defects. An efficiency of 12.7% for vacancy compound-based devices is obtained. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this paper, a new world record efficiency was achieved for single-junction microcrystalline silicon solar cells, with a conversion efficiency of 10.69%, independently confirmed at ISE CalLab PV Cells.
Abstract: This short communication highlights our latest results towards high-efficiency microcrystalline silicon single-junction solar cells. By combining adequate cell design with high-quality material, a new world record efficiency was achieved for single-junction microcrystalline silicon solar cell, with a conversion efficiency of 10.69%, independently confirmed at ISE CalLab PV Cells. Such significant conversion efficiency could be achieved with only 1.8 µm of Si.
TL;DR: In this article, the effect of spatial and spectral non-uniform irradiance distribution on multi-junctio n solar cell performance was analyzed using an integrated approach using ray-tracing simulation and direct imaging at a range of cell-to-lens distances.
Abstract: The irradiance and spectral distribution cast on the cell by a concentrating photovoltaic system, typically made up of a pri mary Fresnel lens and a secondary stage optical element, is dependent on many factors, and these distributions in turn in fluence the electrical performance of the cell. In this paper, the effect of spatial and spectral non-uniform irradiance distribution on multi-junctio n solar cell performance was analyzed using an integrated approach. Irradiance and spectral distributions were obtained by means of ray-tracing simulation and by direct imaging at a range of cell-to-lens distances. At the same positions, I-V curves were measured and compared in order to evaluate non-uniformity effects on cell perfor mance. The procedure was applied to three different optical systems comprised a Fresnel lens with a secondary optical element consisting of either a pyramid, a dome, or a bare cell. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this paper, the influence in the power and the efficiency of concentrator photovoltaic systems technology under real conditions to understand, different modules from different manufacturers were measured in a new research center in Jaen.
Abstract: For the behavior of concentrator photovoltaic systems technology under real conditions to be understood, different modules from different manufacturers were measured in a new research center in Jaen. The influence in the power and the efficiency of irradiation levels, air temperature, and the influence of air mass were under study for 6 months. Pmax shows a linear behavior with direct normal irradiance, and efficiency was constant to a first approximation for a wide range of irradiance levels. The effect of air temperature was negligible for the temperatures under study. At the same time, efficiency shows a maximum around AM1.5 and decreases aside this point. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this paper, an effective rigorous 3-D optical modeling of thin-film silicon solar cells based on finite element method (FEM) is presented, which is used to validate a commercial FEM-based package, the High Frequency Structure Simulator (HFSS).
Abstract: An effective rigorous 3-D optical modeling of thin-film silicon solar cells based on finite element method (FEM) is presented. The simulation of a flat single junction thin-film silicon solar cell on thick glass (i.e., superstrate configuration) is used to validate a commercial FEM-based package, the High Frequency Structure Simulator (HFSS). The results are compared with those of the reference software, Advanced Semiconductor Analysis (ASA) program, proving that the HFSS is capable of correctly handling glass as an incident material within very timely, short, and numerically stable calculations. By using the HFSS, we simulated single junction thin-film silicon solar cells on glass substrates textured with one-dimensional (1-D) and two-dimensional (2-D) trapezoid-shaped diffraction gratings. The correctness of the computed results, with respect to an actual device, is discussed, and the impact of different polarizations on spectral response and optical losses is examined. From the simulations carried out, optimal combinations for period and height in both 1-D and 2-D grating configurations can be indicated, leading to short-circuit current percentage increase with respect to a flat cell of, respectively, 25.46% and 32.53%. With very limited computer memory usage and computational time in the order of tens of minutes for a single simulation, we promote the usage of 3-D FEM as a rigorous and efficient way to simulate thin-film silicon solar cells. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, the life cycle embodied energy for 15 new materials encompassing a variety of donor, acceptor, and interface compounds showing the most promise in organic electronics was calculated with the use of new inventory data.
Abstract: Organic photovoltaics (OPVs) are expected to be a low cost, environmentally friendly energy solution with advantageous properties such as flexibility and light weight that enable their use in new applications. Considerable progress in power conversion efficiencies has brought OPV technology closer to commercialization. However, little consideration has been given to potential environmental impact associated with their production. Although environmental life cycle studies of OPV exist, their scope is narrow or too reliant on outdated technologies. Some of the most significant recent improvements are the result of new semiconductors materials, which have not yet been assessed from a life cycle perspective. Therefore, this study calculates life cycle embodied energy for 15 new materials encompassing a variety of donor, acceptor, and interface compounds showing the most promise in organic electronics. With the use of new inventory data, life cycle energy impact associated with production of both single junction and multi-junction architectures has been calculated including bulk heterojunction polymer, planar small molecule, and planar-mixed small molecule devices. The cumulative energy demand (CED) required to fabricate small molecule and polymer photovoltaics were found to be similar from 2.9 to 5.7 MJ/Wp. This CED is on average of 50% less than for conventional inorganic photovoltaics, motivating the continued development of both technologies. The use of fullerenes was shown to have a dramatic impact on polymer solar cells, comprising 18–30% of the CED, despite only being present in small quantities. Increases in device efficiency are shown to marginally reduce CED for both small molecule and polymer designs. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, the authors present the results of a study carried out at the University of Malaga to quantify radiation losses caused by soiling on the surface of photovoltaic modules.
Abstract: The accumulation of dust on the surface of a photovoltaic module decreases the radiation reaching the solar cell and produces losses in the generated power. Dust not only reduces the incoming radiation on the solar cell but also changes the dependence on the angle of incidence of such radiation. This work presents the results of a study carried out at the University of Malaga to quantify radiation losses caused by soiling on the surface of photovoltaic modules. Our results show that the mean of the daily irradiation losses in a year caused by dust deposited on the surface of a photovoltaic module is around 4%. After long periods without rain, daily irradiation losses can be higher than 20%. In addition, the irradiance losses are not constant throughout the day, and they are strongly dependent on the angle of incidence and the ratio between diffuse and direct radiations. The irradiance losses as a function of solar time are symmetric with respect to noon, where they reach the minimum value. We also propose a simple theoretical model that describes the qualitative behaviour of the irradiance losses during the day. This model takes into account the percentage of dirty surface and the diffuse/direct irradiance ratio. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this paper, the influence of the thickness of atomic layer deposited Zn1−xSnxOy buffer layers and the presence of an intrinsic ZnO layer on the performance of Cu(In,Ga)Se2 solar cells is investigated.
Abstract: The influence of the thickness of atomic layer deposited Zn1−xSnxOy buffer layers and the presence of an intrinsic ZnO layer on the performance of Cu(In,Ga)Se2 solar cells are investigated. The amo ...
TL;DR: The authors envision possible formal results, opportunities and challenges, for the use of PV in Z EBs, as well as new research issues for the future relationships between PV and ZEBs from the architecture and landscape design point of view.
Abstract: Starting from the end of2020, allnew buildings will havetobe NearlyZero EnergyBuildings (NearlyZEBs—ED2010/31/EU recast). This new ‘energy paradigm’ might be a revolution for architecture and for Photovoltaics (PV) too, but there are both cultural and technical obstacles to overcome. There is a need tore-think the way buildings are designed (integrating renewables for being ZE). There isa need tore-think the way PVisdesigned inbuildings. PV will be gaining an increasing relevance inthe ZEBs design, thanks to its features and potentialities (suitability for any kind of energy demand of the building, easiness of building integration, cost). In a ZEB scenario, PV is very suitable for generating energy, ‘on site’ and ‘at site’; this enlarges the perspective of use of PV from the architectural scale to a wider scale, including the space close to the building or even to the urban and landscape scale. In such a new context, the existing research on the relationships between PV and architecture, focusing mainly on the way the PV components are used in relation to the envelope (Building-integrated PV/Building-added (Attached) PV), is no longer sufficient. The authors envision possible formal results, opportunities and challenges, for the use of PV in ZEBs, as well as new research issues for the future relationships between PV and ZEBs from the architecture and landscape design point of view. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, the authors present a review of the distributed nature of series resistance and commonly applied methods to measure series resistance of a solar cell and discuss the multi-light method (MLM) where series resistance in both the light and dark can be measured as a function of current by extracting Rs from a set of currentvoltage (J-V) curves attained at different illumination intensities.
Abstract: The series resistance (Rs) of a solar cell is commonly represented as a constant resistance value. However, because of the distributed nature of series resistance, the effective lumped Rs vary with current density and illumination intensity. Treating Rs as a constant is usually insufficient for an accurate analysis of its J–V curve. This work first presents a review of the distributed nature of series resistance and commonly applied methods to measure Rs. Particular attention is given to the multi-light method (MLM) and it is discussed in detail, where Rs in both the light and dark can be measured as a function of current by extracting Rs from a set of current–voltage (J–V) curves attained at different illumination intensities. The principle behind this method is discussed, and the results are then compared with those of other known methods of Rs measurement. The accurate measurement of Rs(J) attained with the MLM permits the extraction of an Rs-corrected J–V curve, which is theoretically more accurate than that attained by alternative methods because of negligible error from injection dependence and spectral mismatch. With the solar cell equation modified to include Rs(J), we attain a much better fit to experimental data, finding a significant reduction in error compared with using a constant Rs. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this paper, the material and energy inventories in the life cycle of high-concentration PV systems, and, based on measured field-performances, evaluates their energy payback times, life cycle greenhouse gas emissions, and usage of land and water.
Abstract: The environmental profiles of photovoltaic (PV) systems are becoming better as materials are used more efficiently in their production, and overall system performance improves. Our analysis details the material and energy inventories in the life cycle of high-concentration PV systems, and, based on measured field-performances, evaluates their energy payback times, life cycle greenhouse gas emissions, and usage of land and water. Although operating high-concentration PV systems require considerable maintenance, their life cycle environmental burden is much lower than that of the flat-plate c-Si systems operating in the same high-insolation regions. The estimated energy payback times of the Amonix 7700 PV system in operation at Phoenix, AZ, is only 0.9 year, and its estimated greenhouse gas emissions are 27 g CO2-eq./kWh over 30 years, or approximately 16 g CO2-eq./kWh over 50 years. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, the effects of the microstructures of molybdenum (Mo) back contacts on sodium diffusion from sodalime glass into a Cu(In,Ga)Se2 (CIGS) absorber as a function of the sputter deposition pressure during preparation of the Mo contact layer was investigated.
Abstract: We investigated the effects of the microstructures of molybdenum (Mo) back contacts on sodium (Na) diffusion from sodalime glass into a Cu(In,Ga)Se2 (CIGS) absorber as a function of the sputter deposition pressure during preparation of the Mo contact layer. The surface characteristics of the Mo layers more significantly affected the diffusion of Na ions into the CIGS compared with the Mo bulk. The Na ion diffusion depended strongly on the amount of oxygen adsorbed onto the Mo layer surfaces. Secondary ion mass spectroscopy results showed that Na accumulated in a layer (Na–O compound) on the Mo surface (the CIGS/Mo interface), and this layer served as a primary source of Na ions diffusing into the CIGS. A trilayered Mo back contact structure was prepared in an effort to decouple the functions of electrical conductance and Na diffusion. The ability of this surface to control the Na concentration in a CIGS absorber is discussed. Copyright © 2012 John Wiley & Sons, Ltd.
TL;DR: In this article, a model is developed for the diffusion of moisture into a solar module package and subsequent degradation of copper indium gallium di-selenide (CIGS) solar cells.
Abstract: A model is developed for the diffusion of moisture into a solar module package and the subsequent degradation of copper indium gallium di-selenide (CIGS) solar cells. It is based on time-dependent mass and energy balances governing module temperature and the diffusion of water through a module package subjected to weather conditions. The moisture ingress calculations are coupled to an experimentally determined degradation model for CIGS solar cells, where the degradation rate is proportional to the encapsulant degree of saturation. Extensive results are presented for module conditions of temperature and relative humidity for four benchmark climates. Detailed predictions are presented for moisture ingress, module degradation and life as functions of the climate, mounting, packaging materials, configuration, and the kinetics of cell degradation. The results clearly show how the moisture ingress and degradation scale with the climate and the characteristic package diffusion half-time. This time constant determines the rate at which the module approaches the environment's average humidity. In order to keep enough of the moisture out of the package to significantly slow the degradation for a target number of years, diffusion half-times approximately equal to the target years must be achieved, which typically translates into moisture barriers of 10−4 g/m2 day or better at 25°C—a formidable challenge. In the diffusion-controlled regime, the life depends on the square root of package permeability and cell degradation rate. Estimated acceleration factors for damp heat (85°C/85% RH) versus Miami are nonlinear and range from 10X to 700X, depending on the package and cell degradation kinetics. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this paper, phase change materials (PCMs) are investigated as an option to regulate photovoltaic module temperature and thereby reduce its electrical efficiency decrease, and a simplified heat balance model is used to calculate the extra energy gain; such a PV/PCM system can bring on an annual basis.
Abstract: The performance of photovoltaic (PV) module outdoors suffers from attained high module temperatures due to irradiation as a result of the negative temperature coefficient of their efficiency. Phase change materials (PCMs) are investigated as an option to regulate photovoltaic module temperature and thereby reduce its electrical efficiency decrease. In this study, a simplified heat balance model is used to calculate the extra energy gain; such a PV/PCM system can bring on an annual basis. With present day commercially available PCM materials, a moderate increase of up to 3% of the total energy output can be expected. When taking into account the additional PCM material cost, a PV/PCM module presently is not economically viable. For an acceptable payback period of 10–20 years to be reached, the heat storage capacity of a PCM would require an increase of about one order of magnitude, which is presently not realistic. Nevertheless, a combination with building climate control in which the PCM plays a double role controlling both the PV temperature as well as the inside climate temperature may be feasible. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: In this paper, the behavior of a 20-cell InGaP/In0.01GaAs/Ge multi-junction concentrator system was simulated in 5-min intervals over an entire year, accounting for changes in direct normal irradiance, humidity, temperature and aerosol optical depth.
Abstract: III–V concentrator photovoltaic systems attain high efficiency through the use of series connected multi-junction solar cells. As these solar cells absorb over distinct bands over the solar spectrum, they have a more complex response to real illumination conditions than conventional silicon solar cells. Estimates for annual energy yield made assuming fixed reference spectra can vary by up to 15% depending on the assumptions made. Using a detailed computer simulation, the behaviour of a 20-cell InGaP/In0.01GaAs/Ge multi-junction concentrator system was simulated in 5-min intervals over an entire year, accounting for changes in direct normal irradiance, humidity, temperature and aerosol optical depth. The simulation was compared with concentrator system monitoring data taken over the same period and excellent agreement (within 2%) in the annual energy yield was obtained. Air mass, aerosol optical depth and precipitable water have been identified as atmospheric parameters with the largest impact on system efficiency. Copyright © 2012 John Wiley & Sons, Ltd.