Combined photovoltaic solar thermal systems (PVT) literature review\Performance analysis of a hybrid photovoltaic\thermal (PV\T) collector with integrated CPC troughs

Performance analysis of a hybrid photovoltaic/thermal (PV/T) collector with integrated CPC troughs[1][1][1][1][1][11][11][21][21][31][31][41][41][edit | edit source]

Abstract: In the present investigation a theoretical analysis has been presented for the modelling of thermal and electrical processes of a hybrid PV/T air heating collector coupled with a compound parabolic concentrator (CPC). In this design, several CPC troughs are combined in a single PV/T collector panel. The absorber of the hybrid PV/T collector under investigation consists of an array of solar cells for generation of electricity, while collector fluid circulating past the absorber provides useful thermal energy as in a conventional flat plate collector. In the analysis, it is assumed that solar cell efficiency can be represented by a linear decreasing function of its temperature. Energy balance equations have been developed for the various components of the system. Based on the developed analysis, both thermal and electrical performance of the system as a function of system design parameters are presented and discussed. Results have been presented to compare the performance of hybrid PV/T collector coupled with and without CPC.

• The major applications of solar energy include solar collectors and solar photovoltaic systems. Solar collectors are designed to generate thermal energy; however, photovoltaic cell produces electricity directly from solar energy.
• Based on detailed heat transfer analysis the energy balance equations have been developed for each component of the system. Thermal and electrical performance of the system as a function of system design parameters are presented and discussed.
• After a certain point the system with CPC performs better. It implies that the integration of a CPC with PV/T system is appropriate for the application in the higher temperature range. For both the configurations, with and without CPC, the system performs better in the case of selective absorber.
• It has been observed that both the thermal and electric output decrease with an increase in duct depth for configurations with and without CPC.
• It is seen that the system performance increases with an increase in collector length; however, the percentage increase in performance output decrease for the larger values of collector length. This suggests that an optimum value of collector length can be obtained for fixed values of system and design parameters.
• It has been seen that increasing mass flow rate increases the thermal and electrical output for both the configurations. Higher mass flow rate results in a lower temperature of the absorber plate.It is also quite evident that the performance output of the system with CPC is quite higher than without CPC.
• The effect of packing fraction of solar cells on the performance of the system indicates that increasing the area covered by solar cells increases electrical output of the system quite rapidly. However, the thermal output remains more or less same. The system coupled with CPC shows better performance in terms of both the thermal and electrical output.

Experimental Study of a Novel Heat Pipe-Type Photovoltaic/Thermal System[2][2][2][2][2][12][12][22][22][32][32][42][42][edit | edit source]

Abstract: In order to solve the freezing problem associated with the traditional photovoltaic/thermal (PV/T) system, a novel heat pipe-type PV/T (HP-PV/T) system was designed and constructed in the present study. Outdoor tests were carried out from May to July, 2010. The performance of the system was also studied. The results showed that the average photothermal efficiency was 41.30% and the photoelectric efficiency was 9.42%. The average first law efficiency of the system was 48.52%, and the second law efficiency of 6.87%.

• PV cooling can increase the electrical efficiency of PV modules, increasing the total efficiency of the systems.
• Integration of a PV/T flat-plate collector and heat pipe were designed and constructed in this study.
• The photothermal efficiency had also a trend of increasing first and then decreasing, it was because the transmittance of glass increased with the solar altitude at the initial stage, so there was an efficiency increase at first; but the heat loss between the system and the ambient temperature also increased when the water temperature rose, thus decreasing efficiency.
• At the beginning water temperature was lower than the ambient temperature, so the exergy had a negative value, which was cold quantity exergy.
• Total efficiencies of the testing day show a trend of increasing at first and then decreasing gradually, as in the second law efficiency, the photoelectric exergy played a decisive role, so the second law efficiency showed a trend similar to that of the photoelectric efficiency.
• As in the second law efficiency, which is 6.87%, because the photoelectric exergy played a decisive role, the overall second law efficiency had a trend similar to that of photoelectric efficiency.

Annual analysis of heat pipe PV/T systems for domestic hot water and electricity production[3][3][3][3][3][13][13][23][23][33][33][43][43][edit | edit source]

Abstract: Heat-pipe photovoltaic/thermal (HP-PV/T) systems can simultaneously provide electrical and thermal energy. Compared with traditional water-type photovoltaic/thermal systems, HP-PV/T systems can be used in cold regions without being frozen with the aid of a carefully selected heat-pipe working fluid. The current research presents a detailed simulation model of the HP-PV/T system. Using this model, the annual electrical and thermal behavior of the HP-PV/T system used in three typical climate areas of China, namely, Hong Kong, Lhasa, and Beijing, are predicted and analyzed. Two HP-PV/T systems, with and without auxiliary heating equipment, are studied annually under four different kinds of hot-water load per unit collecting area (64.5, 77.4, 90.3, and 103.2 kg/m2).

• The HP-PV/T collector can be used in cold regions without freezing, and corrosion an be reduced as well.
• A low-iron tempered glass plate is used as the upper glaze for the collector, permitting sunlight passage but preventing thermal loss and the entry of dust particles and rain. A thermal insulation layer is placed behind the aluminum plate to prevent thermal loss.
• The water pump circulates the water between the water-storage tank and the collectors, such that the heat energy of the collectors is removed from the storage tank by the circulating water.
• Heat conduction along longitudinal direction of Al layer & the heat capacity the adhesive layer was neglected.
• HP-PV/T system with auxiliary heating equipment: when the daily solar energy is insufficient to cover the daily hot water load (in our simulation, a water temperature higher than 45 *C can be considered available), auxiliary energy is required to cover the hot water load.
• HP-PV/T system without auxiliary heating equipment: when a daily solar energy is insufficient to heat the water to reach the available temperature of 45 *C, the water is sequentially heated in the following day until the available temperature is reached.
• The system with small water storage capacity obtains less thermal energy than that with large water storage capacity.

Effect of colors of light on the PV/T system performance[4][4][4][4][4][14][14][24][24][34][34][44][44][edit | edit source]

Abstract: In this paper, a new approach is proposed to evaluate the effect of colors of light on the photovoltaic cell performance. Based on the energy and exergy analyses of a photovoltaic thermal (PV/T) system and by using the photonic theory, the energy available on the PV/T surface and the exergy of the PV/T system have been evaluated. A case study is conducted to experimentally validate the model by using solar radiation data for four different months, namely January, April, August and October for New Delhi, India. The results show that the present day PV technology is influenced by the red color of light. In other words, the energy available on the PV surface lies between the wavelengths of orange and red colors whereas the exergy of the system lies between yellow and green colors of light.

• A new approach to evaluate the exergetic performance of a solar cell based on photonic theory and compared it with the exergetic analysis using the fundamentals of second law efficiency and found some interesting results that the new photonic theory proposed is in good agreement with the exergy analysis based on thermodynamics.
• The energy of the measured incident solar radiation and the experimental exergy of the PV/T system are in accordance with the predicted energy and exergy levels of the different wavelengths of the visible spectrum by using photonic approach.
• Both, photonic and exergy-based methods give energy and exergy of the PV/T system close to each other. Hence, either can be used to evaluate the performance of photovoltaic systems.
• The energy of the solar radiation received on the PV surface has a fair agreement with the energy levels of red and orange colors of the visible spectrum. The specific color of the spectrum (that is, red) may influence the performance of the system as the present day PV technology works between the wavelengths of red color and/or infrared light.
• The exergy from the PV/T system has a fair agreement with the exergy level of yellow color in general and for higher thermal output it shifts towards the higher exergy levels that is, green (in August) and blue (in October) colors.

Thermal-photovoltaic solar hybrid system for efficient solar energy conversion Band-Gap Tuned Direct Absorption for a Hybrid Concentrating Solar Photovoltaic/Thermal System[5][5][5][5][5][15][15][25][25][35][35][45][45][edit | edit source]

Abstract: A hybrid solar system with high temperature stage is described. The system contains a radiation concentrator, a photovoltaic solar cell and a heat engine or thermoelectric generator. Two options are discussed, one with a special PV cell construction, which uses the heat energy from the part of solar spectrum not absorbed in the semiconductor material of the cell; the other with concentration of the whole solar radiation on the PV cell working at high temperature and coupled to the high temperature stage. The possibilities of using semiconductor materials with different band gap values are analyzed, as well as of the different thermoelectric materials. The calculations made show that the proposed hybrid system could be practical and efficient.

• Theoretical limits of photovoltaic conversion efficiency for a multi-junction cell predicts an efficiency of about 90%, but in practice not even half of that value has been obtained. On the other hand,the solar energy converters using a high temperature stage have promised very high efficiency but not proved to be practical yet.
• A non-traditional approach is developed based on the utilization of the thermal part of the solar spectrum. This could be done in two ways: one, by separating of the long wave length part of the spectrum (not absorbed in a semiconductor material of the cell) with its subsequent concentration and further conversion using a heat engine or a thermoelectric generator, and the other, by operating the cell at elevated temperatures, and use a heat engine of some kind to utilize the excess heat.
• For the first case total efficiency is the sum of thermal & electrical efficiency. in the case of a semiconductor with Eg = 1.75 eV, approximately 50% of solar radiation corresponds to the condition hm > Eg, and is suitable for photovoltaic conversion, and the other 50%, with hm < Eg, could be used as thermal energy.
• For the second case the cell is subjected to concentrated sunlight, which usually enhances its efficiency; the thermal flux through the cell is directed into the HTS by direct thermal contact, thus the working temperature of the cell is equal to the Th parameter of the HTS. Although the lifetime of the PV cell in question needs special study.
• A solar radiation concentration of approximately 50 times which is sufficient to achieve the cell temperature higher than 450 K. efficiency is 14.3% for single junction (SJ) cell, and 17.8% for multi-junction (mj) cell. Thus, practically 80% of solar radiation will be transformed into heat within the cell, and may be used for a heat-to-electric/mechanic energy conversion by the second stage of the hybrid system—a HTS
• The efficiency of TEG can be near to 90%. It works as a Carnot cycle.
• For higher TEG efficiency (Z = figure of merit) proper thermoelectric materials should be chosen. It is necessary to point out that Z for semiconductors depends on temperature, and the different kinds of semiconductor materials should be selected for different operating temperatures.

Hydrogenated Amorphous Silicon PV an an Absorber Coating for Photovoltaic Thermal Systems[6][6][6][6][6][16][16][26][26][36][36][46][46][edit | edit source]

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.

Investigation on a Novel PV/T Solar Collector[7][7][7][7][7][17][17][27][27][37][37][47][47][edit | edit source]

Abstract: A theoretical analysis of novel PV/T solar collector is presented in this paper. The collector is made of vacuum tube-PV sandwich and the heat extraction from PV panel by the water passing through u-shape cooper tube of the collector results in the reduction of the PV cells' working temperature. This also improves the electrical and thermal efficiencies of the PV cells. Based on energy balance of each parts of the vacuum-tube-PV sandwich, mathematical models are developed to evaluate the energy performance of the PV collector and analyze its affecting factors. The simulation results indicate that the thermal efficiency increases slightly while the electrical efficiency decreases slightly with the increasing radiation. Both the thermal and electrical efficiencies increase by 1.4% and 0.23% respectively with every 10 kg/h increase in water mass flow, and decrease by 3.8% and 0.6% respectively with every 10 ℃ increase in inlet water temperature.

Analysis of energy and exergy efficiencies for hybrid PV/T systems[8][8][8][8][8][18][18][28][28][38][38][48][48][edit | edit source]

Abstract: In this paper, Author(s) undertake a study to investigate the performance of hybrid photovoltaic thermal air collector systems through energy and exergy efficiencies and improvement potential factors and compare them for practical purposes. This will help identify the irreversibilities (exergy destructions) for performance improvement purposes. A case study is presented to highlight the importance of the efficiency modelings and compare them using some actual data. It is also aimed to find if there is room for improvement. It is found that the energy efficiency varies between 33 and 45% where as the variation in the exergy efficiency is from 11 to 16%, respectively. There is obviously a large scope for improvement in the existing system as about 11–16% of the exergy from the solar radiation is used.

System analysis of a multifunctional PV/T hybrid solar window[9][9][9][9][9][19][19][29][29][39][39][49][49][edit | edit source]

Abstract: The work presented in this article aims to investigate a PV/T hybrid solar window on a system level. A PV/T hybrid is an absorber on which solar cells have been laminated. The solar window is a PV/T hybrid collector with tiltable insulated reflectors integrated into a window. It simultaneously replaces thermal collectors, PV-modules and sunshade. The building integration lowers the total price of the construction since the collector utilizes the frame and the glazing in the window. When it is placed in the window a complex interaction takes place. On the positive side is the reduction of the thermal losses due to the insulated reflectors. On the negative side is the blocking of solar radiation that would otherwise heat the building passively. This limits the performance of the solar window since a photon can only be used once. To investigate the sum of such complex interaction a system analysis has to be performed. In this paper results are presented from such a system analysis showing both benefits and problems with the product. The building system with individual solar energy components, i.e. solar collector and PV modules, of the same size as the solar window, uses 1100 kW h less auxiliary energy than the system with a solar window. However, the solar window system uses 600 kW h less auxiliary energy than a system with no solar collector.

Recent advances in flat plate photovoltaic/thermal (PV/T) solar collectors[10][10][10][10][10][20][20][30][30][40][40][50][50][edit | edit source]

Abstract: Flat plate photovoltaic/thermal (PV/T) solar collector produces both thermal energy and electricity simultaneously. This paper presents the state-of-the-art on flat plate PV/T collector classification, design and performance evaluation of water, air and combination of water and/or air based. This review also covers the future development of flat plate PV/T solar collector on building integrated photovoltaic (BIPV) and building integrated photovoltaic/thermal (BIPVT) applications. Different designs feature and performance of flat plate PV/T solar collectors have been compared and discussed. Future research and development (R&D) works have been elaborated. The tube and sheet design is the simplest and easiest to be manufactured, even though, the efficiency is 2% lower compared to other types of collectors such as, channel, free flow and two-absorber. It is clear from the review that for both air and water based PV/T solar collectors, the important key factors that influenced the efficiency of the system are the area where the collector covered, the number of passes and the gap between the absorber collector and solar cells. From the literature review, it is obvious that the flat plate PV/T solar collector is an alternative promising system for low-energy applications in residential, industrial and commercial buildings. Other possible areas for the future works of BIPVT are also mentioned.

A numerical and experimental study on a heat pipe PV/T system[11][11][11][11][11][21][21][31][31][41][41][51][51][edit | edit source]

Abstract: A novel heat-pipe photovoltaic/thermal system was designed and constructed by the authors. This system can simultaneously supply electrical and thermal energy. In addition, when compared with the traditional water-type photovoltaic/thermal system, this system can be used in cold regions without freezing. A dynamic model was developed to predict the performances of the heat-pipe photovoltaic/thermal system. Experiments were also conducted to validate results obtained for the simulation. A comparison between simulation values and experimental results demonstrated that the model was able to yield satisfactory predictions. Results indicated that the daily thermal and electrical efficiencies of the heat-pipe photovoltaic/thermal system were 41.9% and 9.4%, respectively, while the average heat and electrical gains were 276.9 and 62.3 W/m2, respectively. In addition, second-law efficiency, based on the second law of thermodynamics, is provided to analyze the total efficiency of the heat-pipe photovoltaic/thermal system, and the average total second-law efficiency of the system is 6.8%.

Advances in liquid based photovoltaic/thermal (PV/T) collectors[12][12][12][12][12][22][22][32][32][42][42][52][52][edit | edit source]

Abstract: In order to get more power and heat from PV/T system, it is necessary to cool the PV cell and decrease its temperature. This is not an easy task especially in hot and humid climate areas. There is a lack of an effective cooling strategy of PV/T panels. The liquid based photovoltaic thermal collector systems are practically more desirable and effective than air based systems. Temperature fluctuation in liquid based PV/T is much less than the air based PV/T collectors which subjected to variation in solar radiation levels. In this study a review of the available literature on PV/T collector systems which utilize water and refrigerant (working fluid) as heat removal medium for different applications has been conducted. Future direction of water-cooled and refrigerant hybrid photovoltaic thermal systems was presented. This study revealed that the direct expansion solar-assisted heat pump system achieved better cooling effect of the PV/T collector.

[A Review on Suitable Standards for Hybrid Photovoltaic∕Thermal Systems^[13]][edit | edit source]

Abstract: This paper will present an evaluation of the available standards and their considerations when using active‐cooled CPV systems, along with an initial assessment of the most appropriate tests, including additional test requirements, for hybrid Photovoltaic‐Thermal (PV‐T) systems in order to guarantee their long‐time electrical and thermal performance.

Performance evaluation of a solar photovoltaic thermal air collector using energy and exergy analysis[14][14][14][14][14][24][24][34][34][44][44][54][54][edit | edit source]

Abstract: In this article, a comparative study is carried out between two equations for the exergy efficiency of photovoltaic thermal (PV/T) air collectors; the first equation is based on net output exergy and the second equation is in terms of exergy losses. The exergy efficiency equation parametrically is dependent on thermal and electrical parameters of PV/T air collector; therefore, improved thermal and electrical models are used to calculate them. Developing an exergy balance for PV/T air collector system, the various exergy components in PV/T system are introduced and two equations for the exergy efficiency of PV/T air collector are derived. A computer simulation program is also developed which is based on the used improved thermal and electrical models. In order to validate the simulation results, a typical PV/T air collector has been built and some experiments have been carried out on it. The results of numerical simulation are in good agreement with the experimental results. Finally, parametric studies have been carried out and the effect of design and climatic parameters on two exergy efficiency equations has been investigated. It is observed that the improved exergy efficiency obtained in this paper is in good agreement with the one given by the previous literature and it is better because it shows the portion of each of exergy losses in the exergy efficiency equation, directly

Thermoelectric generators in photovoltaic hybrid systems[15][15][15][15][15][25][25][35][35][45][45][55][55][edit | edit source]

Abstract: The supply of distant electric devices that cannot be connected to the public electricity grid for reasons of cost, waiting time or due to the need of local flexibility has been a major problem. To date, the power supply of such stand-alone systems has been based mainly on battery-buffered fossil-fueled motor-generators. Apart from the consumption of limited fossil fuel reserves, the disadvantages of these systems include the creation of noise and exhaust gases, the constant need to obtain fuel and, most important, the high amount of maintenance and repairs. For these reasons, and due to the progress in regenerative energy conversion made in the last decade, battery-buffered PV power systems are used more and more often. Their advantages are high reliability and low cost of repairs. However, far away from the equator, where solar radiation is very low during the winter, large PV generators are needed to guarantee sufficient reliability. Therefore, system costs are high. Another disadvantage is that the battery lifetime in PV power systems is significantly reduced compared to its lifetime in fossil fueled systems. To avoid these disadvantages, the PV generator can be combined with fossil fueled power generators. In the medium power range, from 10 W up to several hundred W, thermoelectric generators appear to be particularly qualified because of their reliability and lifetime. In this paper, a (so called) "photovoltaic hybrid system" is compared to a purely PV power system on the basis of model calculations starting with the solar radiation situation on the Earth's surface.

Operational experience of a residential photovoltaic hybrid system[16][16][16][16][16][26][26][36][36][46][46][56][56][edit | edit source]

Abstract: This paper reports on the operational experience acquired with a photovoltaic (PV) hybrid system installed as a line extension alternative at a residence located in northern New York State. The system includes an 850 W PV array, 25 kWh worth of battery storage, and a 4 kW propane generator. The paper features a detailed analysis of the energy flows through the system and quantifies all losses caused by battery storage round-trip, rectifier and inverter conversions, and non-optimum operation of the generator and of the PV array. The paper also analyzes the evolution of end-use electricity consumption since the installation of the PV hybrid system.

Review of R&D progress and practical application of the solar photovoltaic/thermal (PV/T) technologies[17][17][17][17][17][27][27][37][37][47][47][57][57][edit | edit source]

Abstract: In this paper, the global market potential of solar thermal, photovoltaic (PV) and combined photovoltaic/thermal (PV/T) technologies in current time and near future was discussed. The concept of the PV/T and the theory behind the PV/T operation were briefly introduced, and standards for evaluating technical, economic and environmental performance of the PV/T systems were addressed. A comprehensive literature review into R&D works and practical application of the PV/T technology was illustrated and the review results were critically analysed in terms of PV/T type and research methodology used. The major features, current status, research focuses and existing difficulties/barriers related to the various types of PV/T were identified. The research methods, including theoretical analyses and computer simulation, experimental and combined experimental/theoretical investigation, demonstration and feasibility study, as well as economic and environmental analyses, applied into the PV/T technology were individually discussed, and the achievement and problems remaining in each research method category were described. Finally, opportunities for further work to carry on PV/T study were identified. The review research indicated that air/water-based PV/T systems are the commonly used technologies but their thermal removal effectiveness is lower. Refrigerant/heat-pipe-based PV/Ts, although still in research/laboratory stage, could achieve much higher solar conversion efficiencies over the air/water-based systems. However, these systems were found a few technical challenges in practice which require further resolutions. The review research suggested that further works could be undertaken to (1) develop new feasible, economic and energy efficient PV/T systems; (2) optimise the structural/geometrical configurations of the existing PV/T systems; (3) study long term dynamic performance of the PV/T systems; (4) demonstrate the PV/T systems in real buildings and conduct the feasibility study; and (5) carry on advanced economic and environmental analyses. This review research helps finding the questions remaining in PV/T technology, identify new research topics/directions to further improve the performance of the PV/T, remove the barriers in PV/T practical application, establish the standards/regulations related to PV/T design and installation, and promote its market penetration throughout the world.

Modeling and optimization of hybrid solar thermoelectric systems with thermosyphons[18][18][18][18][18][28][28][38][38][48][48][58][58][edit | edit source]

Abstract: Author(s) present the modeling and optimization of a new hybrid solar thermoelectric (HSTE) system which uses a thermosyphon to passively transfer heat to a bottoming cycle for various applications. A parabolic trough mirror concentrates solar energy onto a selective surface coated thermoelectric to produce electrical power. Meanwhile, a thermosyphon adjacent to the back side of the thermoelectric maintains the temperature of the cold junction and carries the remaining thermal energy to a bottoming cycle. Bismuth telluride, lead telluride, and silicon germanium thermoelectrics were studied with copper–water, stainless steel–mercury, and nickel–liquid potassium thermosyphon-working fluid combinations. An energy-based model of the HSTE system with a thermal resistance network was developed to determine overall performance. In addition, the HSTE system efficiency was investigated for temperatures of 300–1200 K, solar concentrations of 1–100 suns, and different thermosyphon and thermoelectric materials with a geometry resembling an evacuated tube solar collector. Optimizations of the HSTE show ideal system efficiencies as high as 52.6% can be achieved at solar concentrations of 100 suns and bottoming cycle temperatures of 776 K. For solar concentrations less than 4 suns, systems with thermosyphon wall thermal conductivities as low as 1.2 W/mK have comparable efficiencies to that of high conductivity material thermosyphons, i.e. copper, which suggests that lower cost materials including glass can be used. This work provides guidelines for the design, as well as the optimization and selection of thermoelectric and thermosyphon components for future high performance HSTE systems.

Light-induced recovery of a-Si solar cells[19][19][19][19][19][29][29][39][39][49][49][59][59][edit | edit source]

Abstract:The light-induced recovery in efficiency of amorphous silicon (a-Si) solar cells has been studied. The recovery of solar cells degraded by a concentrated light-soaking was accelerated under 1 sun illumination as compared with that in the dark. A similar phenomenon has been observed under current injection. The kinetics of light-induced annealing has been discussed on the basis of a series of the experiments.

Development and characterization of high-efficiency Ga0.5In0.5P/GaAs/Ge dual- and triple-junction solar cells[20][20][20][20][20][30][30][40][40][50][50][60][60][edit | edit source]

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

References[edit | edit source]