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Calculation of the PV modules angular losses under field conditions by means of an analytical model
07 Alternative energy sources (solar energy) Excess electricity is utilized to produce hydrogen for storage through electrolysis of water. At the solar down time, the stored hydrogen can be used to produce high-quality steam in an aphodid burner to operate a turbine and with a field modulated generator to supplement electric power. Case studies are carried out on the optimum configuration of the hybrid system satisfying the energy demand. A numerical example based on the actual measured solar input is also included to demonstrate the design potential.
02/02075 Calculation of the PV modules angular losses under field conditions by means of an analytical model Martin, N. and Ruiz, J. M. Solar Energy Materials & Solar Cells, 2001, 70, (l), 25-38. Photovoltaic (PV) modules in real operation present angular losses in reference to their behaviour in standard test conditions, due to the angle of incidence of the incident radiation and the surface soil. Although these losses are not always negligible, they are commonly not taken into account when correcting the electrical characteristics of the PV module or estimating the energy production of PV systems. The main reason of this approximation is the lack of easy-to-use mathematical expressions for the angular losses calculation, This paper analyses these losses on PV modules and present an analytical model based on theoretical and experimental results. The proposed model fits monocrystalline as well as polycrystalline and amorphous silicon PV modules, and contemplates the existence of superficial dust. With it angular losses integrated over time periods of interest can be easily calculated. Monthly and annual losses have been calculated for 10 different European sites, having diverse climates and latitudes (ranging from 32 to 52°), and considering different module tilt angles.
02/02076 Empirical investigation of the energy payback time for photovoltaic modules Knapp, K. and Jester, T. Solar Energy, 2001, 71, (3), 165-172. Energy payback time is the energy analogue to financial payback, defined as the time necessary for a photovoltaic panel to generate the energy equivalent to that used to produce it. This research contributes to the growing literature on net benefits of renewable energy systems by conducting an empirical investigation of as-manufactured photovoltaic modules, evaluating both established and emerging products. Crystalline silicon modules achieve an energy break-even in 3 to 4 years. At the current R&D pilot production rate (8% of capacity) the energy payback time for thin film copper indium diselenide modules is between 9 and 12 years, and in full production is ~2 years. Over their lifetime, these solar panels generate 7-times the energy required to produce them. Energy content findings for the major materials and process steps are presented, and important implications for current research efforts and future prospects are discussed.
02/02077
Evolution of s p a c e solar cells
lies, P. A. Solar Energy Materials & Solar Cells, 2001, 68, (1), 1-13. The solar cells used in space for over 40 years are reviewed by discussing the semiconductor materials which have provided the best cells. Most emphasis was on high efficiency, combined with good tolerance to charged particle bombardment, and the steady increase in efficiency is discussed. The most important requirement is that the cells must be highly reliable, consistent in performance, and stable while operating in space. The need for highest reliability makes the costs less important. The progress to date has provided a good foundation for future applications for space cells.
02/02078
Limiting carrier effect in a-Si:H solar cells
Prentice, J. S. C. Solar Energy Materials & Solar Cells, 2001, 69, (1), 916. The limiting carrier effect in a-Si:H p-i-n and n-i-p solar cells has been investigated computationally, by adjusting the values of the carrier band mobilities. Using a realistic optical generation rate profile, it was found that the effect is significant in both types of cell, with the electron identified as the limiting carrier in the p-i-n cell, and the hole in the n-i-p cell. However, using a uniform generation rate profile in the simulation indicated that the limiting carrier effect was much less significant, and that device performance in both cells seemed to be slightly more sensitive to the hole transport properties that to the electron transport properties.
02/02079 Long-term stability of low-power dye-sensitised solar cells prepared by industrial methods Pettersson, H. and Gruszecki, T, Solar Energy Materials & Solar Cells, 2001, 70, (2), 203-212. Encapsulated dye-sensitized solar modules designed for low-power indoor applications have been prepared using industrial methods and equipment that can be applied to mass production. The modules have been tested for long-term stability. Especially, the influences of different illumination conditions, humidity, and operation conditions (e.g. short-circuit and open-circuit) have been evaluated. It is shown that the use of an inexpensive UV filter in combination with a novel
preparation technique and adequate module encapsulation can provide dye-photovoltaic (dye PV) devices that are stable enough for utilization in various low-power consumer applications.
02/02080 Network analysis of fault-tolerant solar photovoltaic arrays Gautam, N. K. and Kausbika, N. D. Solar Energy Materials & Solar Cells, 2001, 69, (1), 25-42. Large solar photovoltaic array networks have been investigated to find a configuration that is comparatively less susceptible to electrical mismatches due to manufacturer's tolerances in solar cell characteristics and shadow problems. Three network configurations have been selected for comparison: series-parallel, total-crossed-tied and bridgelinked. Explicit mathematical analysis based on randomly generated parameters of solar cell characteristics is presented. Series resistance of the constituent cells has been taken into account. The computation schemes for the array configurations of arbitrary size have been developed and implemented in numerical algorithms and computer programs. The illustrative numerical computations have shown that the bridge-linked array interconnection network under most conditions is superior to and never worse than the total-cross-tied and significantly superior to the series-parallel network in its fault-tolerance due to shadow effects and manufacturer's tolerances in cell characteristics.
02/02081 Performance evaluation of solar photovoltaic/ thermal systems Huang, B. J. et al. Solar Energy, 2001, 70, (5), 443-448. 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 and 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 77.* reaches 0.38 which is about 76% of the value for a conventional solar hot water heater using glazed collectors 'q.* = 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.
02/02082 Photovoltaic cogeneration in the built environment Bazilian, M. D. et al. Solar Energy, 2001, 71, (1), 57-69. Building integrated photovoltaic (BiPV) systems can form a cohesive design, construction, and energy solution for the build environment. The benefits of building integration are well documented and are gaining significant public recognition and government support. PV cells, however, convert only a small portion of the incoming insolation into electricity. The rest is either reflected or lost in the form of sensible heat and light. Various research projects have been conducted on the forms these by-products can take as cogeneration. The term cogeneration is usually associated with utility-scale fossil-fuel electrical generation using combined heat and power production. It is used here in the same spirit in the evaluation of waste heat and by-products in the production of PV electricity. It is important to have a proper synthesis between BiPV cogeneration products, building design, and other HVAC systems in order to avoid overheating or redundancy. Thus, this paper looks at the state-of-the-art in PV cogen from a whole building perspective. Both built examples and research will be reviewed. By taking a holistic approach to the research and products already available, the tools for a more effective building integrated system can be devised. This should increase net system efficiency and lower installed cost per unit area. An evaluation method is also presented that examines the energy and economic performances of PV/T systems. The performed evaluation shows that applications that most efficiently use the low quality thermal energy produced will be the most suitable niche markets in the short- and mid-term.
02/02083 Preparation and characterization of CulnS2 thin films solar cells with large grain Onuma, Y. et al. Solar Energy Materials & Solar Cells, 2001, 69, (3), 261-269. The CulnS2 films with maximum thickness of about 9 #m and a maximum atomic Cu/In ratio (as-deposited precursor) of 3.0 were prepared, and, to prevent peeling from substrate, were heat treated during Cu/In evaporation and/or intercalated with very thin Pt or Pd (between Mo and CulnS2 layers). Thus, we could prepare the films with very large grain. It is also worth noting that the large grain films
Fuel and Energy Abstracts July 2002
269
02/02075 Calculation of the PV modules angular losses under field conditions by means of an analytical model Martin, N. and Ruiz, J. M. Solar Energy Materials & Solar Cells, 2001, 70, (l), 25-38. Photovoltaic (PV) modules in real operation present angular losses in reference to their behaviour in standard test conditions, due to the angle of incidence of the incident radiation and the surface soil. Although these losses are not always negligible, they are commonly not taken into account when correcting the electrical characteristics of the PV module or estimating the energy production of PV systems. The main reason of this approximation is the lack of easy-to-use mathematical expressions for the angular losses calculation, This paper analyses these losses on PV modules and present an analytical model based on theoretical and experimental results. The proposed model fits monocrystalline as well as polycrystalline and amorphous silicon PV modules, and contemplates the existence of superficial dust. With it angular losses integrated over time periods of interest can be easily calculated. Monthly and annual losses have been calculated for 10 different European sites, having diverse climates and latitudes (ranging from 32 to 52°), and considering different module tilt angles.
02/02076 Empirical investigation of the energy payback time for photovoltaic modules Knapp, K. and Jester, T. Solar Energy, 2001, 71, (3), 165-172. Energy payback time is the energy analogue to financial payback, defined as the time necessary for a photovoltaic panel to generate the energy equivalent to that used to produce it. This research contributes to the growing literature on net benefits of renewable energy systems by conducting an empirical investigation of as-manufactured photovoltaic modules, evaluating both established and emerging products. Crystalline silicon modules achieve an energy break-even in 3 to 4 years. At the current R&D pilot production rate (8% of capacity) the energy payback time for thin film copper indium diselenide modules is between 9 and 12 years, and in full production is ~2 years. Over their lifetime, these solar panels generate 7-times the energy required to produce them. Energy content findings for the major materials and process steps are presented, and important implications for current research efforts and future prospects are discussed.
02/02077
Evolution of s p a c e solar cells
lies, P. A. Solar Energy Materials & Solar Cells, 2001, 68, (1), 1-13. The solar cells used in space for over 40 years are reviewed by discussing the semiconductor materials which have provided the best cells. Most emphasis was on high efficiency, combined with good tolerance to charged particle bombardment, and the steady increase in efficiency is discussed. The most important requirement is that the cells must be highly reliable, consistent in performance, and stable while operating in space. The need for highest reliability makes the costs less important. The progress to date has provided a good foundation for future applications for space cells.
02/02078
Limiting carrier effect in a-Si:H solar cells
Prentice, J. S. C. Solar Energy Materials & Solar Cells, 2001, 69, (1), 916. The limiting carrier effect in a-Si:H p-i-n and n-i-p solar cells has been investigated computationally, by adjusting the values of the carrier band mobilities. Using a realistic optical generation rate profile, it was found that the effect is significant in both types of cell, with the electron identified as the limiting carrier in the p-i-n cell, and the hole in the n-i-p cell. However, using a uniform generation rate profile in the simulation indicated that the limiting carrier effect was much less significant, and that device performance in both cells seemed to be slightly more sensitive to the hole transport properties that to the electron transport properties.
02/02079 Long-term stability of low-power dye-sensitised solar cells prepared by industrial methods Pettersson, H. and Gruszecki, T, Solar Energy Materials & Solar Cells, 2001, 70, (2), 203-212. Encapsulated dye-sensitized solar modules designed for low-power indoor applications have been prepared using industrial methods and equipment that can be applied to mass production. The modules have been tested for long-term stability. Especially, the influences of different illumination conditions, humidity, and operation conditions (e.g. short-circuit and open-circuit) have been evaluated. It is shown that the use of an inexpensive UV filter in combination with a novel
preparation technique and adequate module encapsulation can provide dye-photovoltaic (dye PV) devices that are stable enough for utilization in various low-power consumer applications.
02/02080 Network analysis of fault-tolerant solar photovoltaic arrays Gautam, N. K. and Kausbika, N. D. Solar Energy Materials & Solar Cells, 2001, 69, (1), 25-42. Large solar photovoltaic array networks have been investigated to find a configuration that is comparatively less susceptible to electrical mismatches due to manufacturer's tolerances in solar cell characteristics and shadow problems. Three network configurations have been selected for comparison: series-parallel, total-crossed-tied and bridgelinked. Explicit mathematical analysis based on randomly generated parameters of solar cell characteristics is presented. Series resistance of the constituent cells has been taken into account. The computation schemes for the array configurations of arbitrary size have been developed and implemented in numerical algorithms and computer programs. The illustrative numerical computations have shown that the bridge-linked array interconnection network under most conditions is superior to and never worse than the total-cross-tied and significantly superior to the series-parallel network in its fault-tolerance due to shadow effects and manufacturer's tolerances in cell characteristics.
02/02081 Performance evaluation of solar photovoltaic/ thermal systems Huang, B. J. et al. Solar Energy, 2001, 70, (5), 443-448. 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 and 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 77.* reaches 0.38 which is about 76% of the value for a conventional solar hot water heater using glazed collectors 'q.* = 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.
02/02082 Photovoltaic cogeneration in the built environment Bazilian, M. D. et al. Solar Energy, 2001, 71, (1), 57-69. Building integrated photovoltaic (BiPV) systems can form a cohesive design, construction, and energy solution for the build environment. The benefits of building integration are well documented and are gaining significant public recognition and government support. PV cells, however, convert only a small portion of the incoming insolation into electricity. The rest is either reflected or lost in the form of sensible heat and light. Various research projects have been conducted on the forms these by-products can take as cogeneration. The term cogeneration is usually associated with utility-scale fossil-fuel electrical generation using combined heat and power production. It is used here in the same spirit in the evaluation of waste heat and by-products in the production of PV electricity. It is important to have a proper synthesis between BiPV cogeneration products, building design, and other HVAC systems in order to avoid overheating or redundancy. Thus, this paper looks at the state-of-the-art in PV cogen from a whole building perspective. Both built examples and research will be reviewed. By taking a holistic approach to the research and products already available, the tools for a more effective building integrated system can be devised. This should increase net system efficiency and lower installed cost per unit area. An evaluation method is also presented that examines the energy and economic performances of PV/T systems. The performed evaluation shows that applications that most efficiently use the low quality thermal energy produced will be the most suitable niche markets in the short- and mid-term.
02/02083 Preparation and characterization of CulnS2 thin films solar cells with large grain Onuma, Y. et al. Solar Energy Materials & Solar Cells, 2001, 69, (3), 261-269. The CulnS2 films with maximum thickness of about 9 #m and a maximum atomic Cu/In ratio (as-deposited precursor) of 3.0 were prepared, and, to prevent peeling from substrate, were heat treated during Cu/In evaporation and/or intercalated with very thin Pt or Pd (between Mo and CulnS2 layers). Thus, we could prepare the films with very large grain. It is also worth noting that the large grain films
Fuel and Energy Abstracts July 2002
269