- Email: [email protected]
The impact of optical and thermal properties on the performance of flat solar collectors
07 Alternative energy sources (solar energy) value of 4.2%. If a general linear relation UV=mG is considered, the square of coefficient of correlation r2 is always greater than 0.91 for Valencia and 0.97 for Cordoba. The UV hemispherical transmittance k,,, was modelled as a function of the total clearness index k,, and new correlations were determined permitting improvements in estimation and to reduce the local nature of the correlations. Also, the solar elevation was considered as an additional parameter in the correlation between k,, and k,, and it was proven that the coefficients of correlation improved for solar elevations over 55”. The k,,, index represented approximately 75% of the k, in Valencia and 71% in Cordoba.
;3&IrflcsThe
03/013W Revtew of solar and low energy cooling technologies for buildings
03/01305
Florides, G. A. et al. Renewable and Sustainable Energy Reviews. 2002, 6, (6), 557-572. The objective of this paper is to examine solar cooling and low energy cooling technologies. A brief review of various cooling systems is presented, including solar sorption cooling, solar-mechanical systems, solar related air conditioning, and other low energy cooling technologies. The relative efficiencies and applications of the various technologies are presented. These technologies can be utilized to reduce both the energy consumption and environmental impact of mechanical cooling systems.
03/01301 Simutatton and fabrication of flat-plate concentrator modutes
Yoshioka, K. et al. Solar Energy Materials and Solar Cells. 2003.75, (34), 373-380. A flat-plate concentrator (FPC) module has been proposed and developed for cost reduction of PV modules. The FPC has V-grooved rear reflectors on spaces between adjacent cells. To find appropriate design parameters, yearly optical performance is simulated by using meteorological data and introducing a performance index. As a result of the simulation, it is shown that the FPC module can reduce occupation area of solar cells to 75% compared with that of a conventional module, although its module area increases to 1.16 times. Several prototypes are fabricated and measured under a solar simulator. The measured results are somewhat lower than the simulated ones, but generally show the validity of the simulation.
03/01302
Space solar cells-tradeoff analysis
Reddy, M. R. Solar Energ.v Materials & Solar CeNs. 2003, 77, (2), 175% 208. This paper summarizes the study that had the objective to tradeoff space solar cells and solar array designs to determine the best choice of solar cell and array technology that would be more beneficial in terms of mass, area and cost for different types of space missions. Space solar cells, which are commercially now available in the market and to be available in the near future, were considered for this trade study. Four solar array designs: rigid, flexible, thin film flexible and concentrator solar arrays were considered for assessment. The performance of the solar cells along with solar array designs was studied for two types of space missions: geo synchronous orbit (CEO) and low earth orbit (LEO) spacecraft. The Solar array designs assumed were to provide 14 kW power for 15 years mission life in GE0 and 5 kW power for 5 years mission life in LEO altitudes. To perform tradeoff analysis a spread sheet model was developed that calculates the size, mass and estimates the cost of solar arrays based on different solar cell and array technologies for given set of mission requirements. Comparative performance metrics (W/kg, W/m2 kg/m*%/W) were calculated for all solar array studied and compared, at the solar arrays subsystem level and also at the spacecraft system level. The trade analysis results show that high-efficiency multijunction solar cells bring lot of cost advantages for both types of missions. The trade study also show that thin film solar cells with moderate efficiency with ultra lightweight flexible array design may become competitive with well-established single crystalline solar cell technologies in the future.
03/01303 Structure of PECVD Si:H films for solar cell applications Edelman, F. et al. Solar Energy Mnterials & Solar Ceils. 2003. 77, (2), 125-143. The structure of undoped SiH films and solar cells deposited under different hydrogen concentration and substrate temperatures were studied. The characterization techniques used XRD, Raman spectroscopy, TEM, optical absorption, and hydrogen effusion. The high concentration films were amorphous in the as-deposited state but crystallized upon annealing at 70°C. Middle and low concentration films were nanocrystalline (nc) and remained nc up to 800°C annealing. A theoretical explanation is given for the stability of these films. Such films, on glass substrates, had optical absorption spectra close to those of amorphous material. The solar cell samples, showed some nc morphology in all-concentration states.
efficiency of solar cells immersed in liquid
Abrahamyan, Y. A. et al. Solar Energy Materials und Solar Cells, 2002, 73, (4), 367-315. The effect of an increase in the efficiency of solar cells (SCs) (in particular, common silicon SCs) by their immersion in. an isotropic liquid dielectric is described. The presence of a dielectric thin film results in an increase in the SCs efficiency by 40-60% from the reference value. The current-voltage characteristic, fill factor and other characteristics of SCs are analysed. The mechanisms of the increase in the efficiency of SCs are discussed.
The hybrid production system of solar fuel using solar thermal energy and biomass
Nishigami, Y. Taiyo Enerugi, 2002, 28, (2), 19-24. (In Japanese) A review of the title subject, mainly the global bio-methanol production via biomass gasification and Hr production by solar energy assisted hydrolysis. 03/01306 The impact of optical and thermal properties on the performance of flat plate solar collectors
Hellstrom, B. et al. Renewable Energy, 2003, 28, (3), 331-344. The impact of the optical properties on the annual performance of flat plate collectors in a Swedish climate has been estimated with the MINSUN program. The collector parameters were determined with a theoretically based calculation program verified from laboratory measurements. The importance of changes in solar absorptance and thermal emittance of the absorber, the addition of a teflon film or a teflon honeycomb, antireflection treatment of the cover glazing and combinations of these improvements were investigated. The results show that several improvements can be achieved for solar thermal absorbers. A combined increase in ahsorptance from 0.95 to 0.97 and a decrease in emittance from 0.10 to 0.05 increase the annual performance with 6.7% at 50°C operating temperature. The increase in performance by installing a teflon film as second glazing was estimated to 5.6% at 50°C. If instead a teflon honeycomb is installed, a twice as high performance increase is obtained, 12.1%. Antireflection treatment of the cover glazing increases the annual output with 6.5% at 50°C. A combination of absorber improvements together with a teflon honeycomb and an antireflection treated glazing results in a total increase of 24.6% at 50°C. Including external booster reflectors increases the expected annual output at 50°C to 19.9-29.4% depending on reflector material.
03/01307 crops
Thermal aspects of open sun drying of various
Jain, D. and Tiwari, G. N. Energy, 2003, 28, (I), 37-54. Open sun drying (OSD) is the most common method of crop drying in developing countries. Despite several disadvantages, it is widely practiced because it is a simple way of drying. Crop temperature, temperature around the crop, solair temperature, and rate of moisture evaporation are the important parameters in OSD. The thermal behaviour of OSD of green chillies, green pea, white gram (kabuli chana), onions, potatoes, and cauliflower was studied. The heat transfer analysis which is mainly dependent on the rate of moisture transfer has also been extended during drying process. A mathematical model has been developed to predict the crop temperature, rate of moisture removal, and solair temperature for a steady state condition. The rate of moisture transfer for potato slices and cauliflower was significantly higher than that in other crops. A fair agreement was observed between predicted and experimental results with coefficient of correlations ranging from 0.8936 to 0.7520, 0.9792-0.4172, and 0.9986-0.9942 for crop temperature, temperature above the crop surface, and rate of the moisture removal during drying, respectively except potato slices.
03/01308 Thermal performance evaluation of a latent heat storage unit for late evening cooking in a solar cooker having three reflectors Buddhi, D. Energy Conversion and Management. 2003.44, (6), 809-817. In this paper, a phase change material (PCM) storage unit for a solar cooker was designed and developed to store energy during sunshine hours. The stored energy was utilized to cook food in the late evening. Commercial grade acetanilide (melting point 118.9”C, latent heat of fusion 222 kJ/kg) was used as a latent heat storage material. Evening cooking experiments were conducted with different loads and loading times during the winter season. The experimental results showed that late evening cooking is possible in a solar cooker having three reflectors to enhance the incident solar radiation with the PCM storage unit.
03IO1309 Thermal performance of a trapezoidal-shaped solar collector/energy store Cruz, J. M. S. et al. Applied Energ?,, 2002, 73, (2). 195-212. Fuel and Energy Abstracts
July 2003
237
;3&IrflcsThe
03/013W Revtew of solar and low energy cooling technologies for buildings
03/01305
Florides, G. A. et al. Renewable and Sustainable Energy Reviews. 2002, 6, (6), 557-572. The objective of this paper is to examine solar cooling and low energy cooling technologies. A brief review of various cooling systems is presented, including solar sorption cooling, solar-mechanical systems, solar related air conditioning, and other low energy cooling technologies. The relative efficiencies and applications of the various technologies are presented. These technologies can be utilized to reduce both the energy consumption and environmental impact of mechanical cooling systems.
03/01301 Simutatton and fabrication of flat-plate concentrator modutes
Yoshioka, K. et al. Solar Energy Materials and Solar Cells. 2003.75, (34), 373-380. A flat-plate concentrator (FPC) module has been proposed and developed for cost reduction of PV modules. The FPC has V-grooved rear reflectors on spaces between adjacent cells. To find appropriate design parameters, yearly optical performance is simulated by using meteorological data and introducing a performance index. As a result of the simulation, it is shown that the FPC module can reduce occupation area of solar cells to 75% compared with that of a conventional module, although its module area increases to 1.16 times. Several prototypes are fabricated and measured under a solar simulator. The measured results are somewhat lower than the simulated ones, but generally show the validity of the simulation.
03/01302
Space solar cells-tradeoff analysis
Reddy, M. R. Solar Energ.v Materials & Solar CeNs. 2003, 77, (2), 175% 208. This paper summarizes the study that had the objective to tradeoff space solar cells and solar array designs to determine the best choice of solar cell and array technology that would be more beneficial in terms of mass, area and cost for different types of space missions. Space solar cells, which are commercially now available in the market and to be available in the near future, were considered for this trade study. Four solar array designs: rigid, flexible, thin film flexible and concentrator solar arrays were considered for assessment. The performance of the solar cells along with solar array designs was studied for two types of space missions: geo synchronous orbit (CEO) and low earth orbit (LEO) spacecraft. The Solar array designs assumed were to provide 14 kW power for 15 years mission life in GE0 and 5 kW power for 5 years mission life in LEO altitudes. To perform tradeoff analysis a spread sheet model was developed that calculates the size, mass and estimates the cost of solar arrays based on different solar cell and array technologies for given set of mission requirements. Comparative performance metrics (W/kg, W/m2 kg/m*%/W) were calculated for all solar array studied and compared, at the solar arrays subsystem level and also at the spacecraft system level. The trade analysis results show that high-efficiency multijunction solar cells bring lot of cost advantages for both types of missions. The trade study also show that thin film solar cells with moderate efficiency with ultra lightweight flexible array design may become competitive with well-established single crystalline solar cell technologies in the future.
03/01303 Structure of PECVD Si:H films for solar cell applications Edelman, F. et al. Solar Energy Mnterials & Solar Ceils. 2003. 77, (2), 125-143. The structure of undoped SiH films and solar cells deposited under different hydrogen concentration and substrate temperatures were studied. The characterization techniques used XRD, Raman spectroscopy, TEM, optical absorption, and hydrogen effusion. The high concentration films were amorphous in the as-deposited state but crystallized upon annealing at 70°C. Middle and low concentration films were nanocrystalline (nc) and remained nc up to 800°C annealing. A theoretical explanation is given for the stability of these films. Such films, on glass substrates, had optical absorption spectra close to those of amorphous material. The solar cell samples, showed some nc morphology in all-concentration states.
efficiency of solar cells immersed in liquid
Abrahamyan, Y. A. et al. Solar Energy Materials und Solar Cells, 2002, 73, (4), 367-315. The effect of an increase in the efficiency of solar cells (SCs) (in particular, common silicon SCs) by their immersion in. an isotropic liquid dielectric is described. The presence of a dielectric thin film results in an increase in the SCs efficiency by 40-60% from the reference value. The current-voltage characteristic, fill factor and other characteristics of SCs are analysed. The mechanisms of the increase in the efficiency of SCs are discussed.
The hybrid production system of solar fuel using solar thermal energy and biomass
Nishigami, Y. Taiyo Enerugi, 2002, 28, (2), 19-24. (In Japanese) A review of the title subject, mainly the global bio-methanol production via biomass gasification and Hr production by solar energy assisted hydrolysis. 03/01306 The impact of optical and thermal properties on the performance of flat plate solar collectors
Hellstrom, B. et al. Renewable Energy, 2003, 28, (3), 331-344. The impact of the optical properties on the annual performance of flat plate collectors in a Swedish climate has been estimated with the MINSUN program. The collector parameters were determined with a theoretically based calculation program verified from laboratory measurements. The importance of changes in solar absorptance and thermal emittance of the absorber, the addition of a teflon film or a teflon honeycomb, antireflection treatment of the cover glazing and combinations of these improvements were investigated. The results show that several improvements can be achieved for solar thermal absorbers. A combined increase in ahsorptance from 0.95 to 0.97 and a decrease in emittance from 0.10 to 0.05 increase the annual performance with 6.7% at 50°C operating temperature. The increase in performance by installing a teflon film as second glazing was estimated to 5.6% at 50°C. If instead a teflon honeycomb is installed, a twice as high performance increase is obtained, 12.1%. Antireflection treatment of the cover glazing increases the annual output with 6.5% at 50°C. A combination of absorber improvements together with a teflon honeycomb and an antireflection treated glazing results in a total increase of 24.6% at 50°C. Including external booster reflectors increases the expected annual output at 50°C to 19.9-29.4% depending on reflector material.
03/01307 crops
Thermal aspects of open sun drying of various
Jain, D. and Tiwari, G. N. Energy, 2003, 28, (I), 37-54. Open sun drying (OSD) is the most common method of crop drying in developing countries. Despite several disadvantages, it is widely practiced because it is a simple way of drying. Crop temperature, temperature around the crop, solair temperature, and rate of moisture evaporation are the important parameters in OSD. The thermal behaviour of OSD of green chillies, green pea, white gram (kabuli chana), onions, potatoes, and cauliflower was studied. The heat transfer analysis which is mainly dependent on the rate of moisture transfer has also been extended during drying process. A mathematical model has been developed to predict the crop temperature, rate of moisture removal, and solair temperature for a steady state condition. The rate of moisture transfer for potato slices and cauliflower was significantly higher than that in other crops. A fair agreement was observed between predicted and experimental results with coefficient of correlations ranging from 0.8936 to 0.7520, 0.9792-0.4172, and 0.9986-0.9942 for crop temperature, temperature above the crop surface, and rate of the moisture removal during drying, respectively except potato slices.
03/01308 Thermal performance evaluation of a latent heat storage unit for late evening cooking in a solar cooker having three reflectors Buddhi, D. Energy Conversion and Management. 2003.44, (6), 809-817. In this paper, a phase change material (PCM) storage unit for a solar cooker was designed and developed to store energy during sunshine hours. The stored energy was utilized to cook food in the late evening. Commercial grade acetanilide (melting point 118.9”C, latent heat of fusion 222 kJ/kg) was used as a latent heat storage material. Evening cooking experiments were conducted with different loads and loading times during the winter season. The experimental results showed that late evening cooking is possible in a solar cooker having three reflectors to enhance the incident solar radiation with the PCM storage unit.
03IO1309 Thermal performance of a trapezoidal-shaped solar collector/energy store Cruz, J. M. S. et al. Applied Energ?,, 2002, 73, (2). 195-212. Fuel and Energy Abstracts
July 2003
237