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02228 Transient method for testing flat-plate solar collectors
07
The lost energy from the pond is a maximum However, increasing the extracted load increases solar radiation in the pond.
if no load is extracted. the amount of absorbed
Evaluation of parameters for anodic poiarisation curve from the experimentally measured U-l dependence for an electrochemical photovoltaic regenerative solar cell
9m2219
Rouar, I. et al. Solar Energy Materials and Solar Cells, 1998, 51, (2), 155169. At different values of the light intensity the cell voltage for an electrochemical photovoltaic regenerative solar cell with current leads located on opposite sides of a cell unit was measured. The light intensity examined was in the range 77-1360 W m-z. An empirical relation for anodic polarization curve with three parameters, namely the limiting current density, the formal exchange current density and open-circuit potential vs light intensity was formulated. The evaluation of these parameters is based on the chemical engineering description of a model cell. The transfer of the data to large modules for outdoor applications is enabled by this description.
Experimental and theoretical performance of a demonstration solar chimney model-part I: mathematical model development
90lO2220
Pasumarthi, N. and Sherif, S. A. Int. J. Energy Res., 1998, 22, (3), 277-288. The solar chimney is a natural draft device which uses solar radiation to provide upward momentum to the in-flowing air, thereby converting the thermal energy into kinetic energy. A study was undertaken to evaluate the performance characteristics of solar chimneys both theoretically and experimentally. In this paper, a mathematical model which was developed to study the effect of various parameters on the air temperature, air velocity, and power output of the solar chimney, is presented. Tests were conducted on a demonstration model which was designed and built for that purpose. The mathematical model presented here, was verified against experimental test results and the overall results were encouraging.
Improved fill-factor for the double-sided contact bifacial silicon solar cell
9am2221
buried-
Ghozati, S. B. et al. Solar Energy Materials and Solar Cells, 1998, 51, (2), 121-128. Buried-contact solar cells have met with commercial success, but the performance of early generations of these devices has been limited by an effective high rear-surface recombination velocity. The double-sided buried-contact bifacial (DSBCB) solar cells have demonstrated improved rear-surface passivation with corresponding improvements in current and voltage for a number of years. The fill factors of these devices have been significantly degraded in the past, however, due to shunting of the rear floating junction. Significantly higher sheet resistivities for the rear n-type layer have made it possible to overcome these limitations. Based on this new approach, experimental devices have achieved fill factors approaching 82% while simultaneously achieving open-circuit voltages in the vicinity of 670 mV. Float zone material have achieved efficiencies in the range 17-18% without texturing, anti-reflection coatings, any form of light trapping or even rear reflector. In-situ Kelvin probe and ellipsometry study of the doping of a-Si : H and a-SIC : H layers: correlation with solar cell parameters
9m2222
Hadjadj, A. et al. Solar Energy Materials and Solar Cells, 1998, 51, (2), 145153. The in-situ Kelvin probe technique was used to highlight the effects of boron doping on the photovoltaic characteristics of a-Si : H based p-i-n solar cells in order to determine the evolution of the contact potential at the SnOz/p interface in two series of solar cells. One had a p(a-Si : H) layer and the other had a p(a-SiC : H) layer plus a buffer a-Sic : H layer. In each series, the flow of diborane was varied between 0.5 and 7 seem. The in-situ Kelvin probe measurements on thick layers indicate that the doping efficiency is higher in a-Si : H than in a-Sic : H layers. In cells with a p(a-Si : H) layer an optimum in I’,, as a function of the diborane flow rate was observed. Below this optimum, the increase in k’,, is correlated to the increase of the contact potential measured by the Kelvin probe. Above the optimum value of the diborane flow, the further increase of the contact potential contrasts with the decrease of I’,,. In cells with a p(a-SiC : H), k’,, is independent of the diborane flow rate. This is interpreted in terms of the diffusion of impurities and changes in the p-layer induced by boron atoms.
Investigation storage system
98102223
Hamdan, Theoretical integrated galvanized collector performed was found angle of theoretical
of an inexpensive
Alternative
energy sources (wind energy)
Photothermal radiometry on nickel (pigmented aluminium oxide) selective solar absorbing surface coatings
98102224
Othonos, A. et al. Solar Energy Materials and Solar Cells, 1998, 51, (2) 171-179. Nickel-pigmented aluminium oxide solar absorbing coatings were characterized by photothermal radiometry (PTR). A modulated laser beam was used to heat the solar samples and the subsequent emission of thermal radiation was measured as a function of modulated frequency in the range of 10 Hz to 10 kHz. Allowing for the extraction of some thermal parameters for the solar absorbing coatings, a simple one-dimensional model is used to fit the experimental PTR results. A comparison of the emissivity measured by traditional technique and the photothermal radiometry was then made.
Photovoltaic properties of WSep single-crystals 98102225 studied by photoelectron spectroscopy Klein, A. et al.
Solar Energy Materials and Solar Cells,1998, 51, (2).181-
191.
An investigation into the different surfaces and Schottky barriers of WSez single crystals has been performed using photoelectron spectroscopy with synchrotron radiation. The acceptor level with EA - Ev = 0.45 eV, an important defect level in WSez, was identified and attributed to the non-van der Waals planes. The photovoltages obtained for the Schottky barriers prepared on UHV-cleaved selenium grown p-WSeZ single crystals depend on the lateral conductivity of the surface which is a function of metal-film thickness and morphology. It is suggested that the crystal quality of WSez single crystals, and thus, achievable conversion efficiencies of WSez solar cells, relies on the transport agent used in chemical vapour transport growth.
Short-term thermal performance of a built-in solar storage for frost prevention In a greenhouse
98/02226
Kiirklii, A. Inc. .I. Energy Res., 1998, 22, (2), 169-174. An alternative to the traditional solar collectors is built-in solar storage. This paper explores the possibility of utilizing such solar stores for frost prevention in greenhouses. In the study, two identical NE-SW orientated greenhouses with 50 m2 ground area were erected. The total ground area and volume of the water stores used in the solar greenhouse were about 6.4 and 5.4% of the total ground area and volume of the greenhouse. The short-term results showed that at times when the air temperature in the control greenhouse dropped below 0°C it was about 3.5”C in the solar greenhouse. Sometimes this difference was as much as 4.5”C or more. The average fraction of solar energy storage by the stores was 0.26 for a four day period.
Solar radiation on tilted south oriented surfaces: validation of transfer-models
98lo2227
Behr, H. D. Solar Energy, 61, (6) 399-413. Tests were performed on three transfer-models in use for estimating solar radiation on tilted surfaces. There is available a 12-year series of hourly global, diffuse and reflected solar irradiation measured with horizontal pyranometers, as well as hourly global solar irradiation measured with tilted south oriented pyranometers. One model uses daily irradiation, the other two use hourly irradiation. The models converting hourly solar irradiation on a horizontal surface to a tilted surface yield better results than that using daily irradiation. The best results can be achieved with pairs of hourly global and diffuse solar irradiation. The root mean square errors exceed 10% only if the sky is covered by more than 85% with clouds or if the solar elevation angle is less than 10”.
98lO2228 tors
Transient method for testing fiat-plate solar collec-
Amer, E. H. et al. Energy Cowers. Mgmt, 1998, 39, (7), 549-558. To characterize the dynamic behaviour of flat-plate solar collectors, a transient test method has been developed. Based on a one-node model in which the heat capacity of the plate, the tubes and the fluid are lumped together in one node which is referred to the mean temperature of the working fluid. The method is both quicker and more simple. Test results are very close to those obtained from steady state tests based on the ASHRAE 93-86 standard. Also investigated were the effects of inlet temperature and incidence angle on collector parameters. Reasonable agreement was found between the theoretical predictions based on the parameters obtained from the transient test method and experimental observations.
Wind Energy
solar collector
M. A. Energy Cowers. Mgmt, 1998, 39, (516). 415-420. and experimental investigations were carried out on an rock bed and solar collector system. Consisting of an insulated iron box containing rocks, the apparatus may act as both a solar and a storage system. Furthermore, the measurements were at different values of tilt angle and mass flow rate of air. The bed to have a maximum storage efficiency of 46% when tilted at an 47”. Good agreement between the experimental results and predictions was discovered.
9am2229
One step ahead adaptive control technique for wind
systems
Dadone, A. et al. Energy Convers. Mgtnt, 1998, 39, (5/6), 399-413. An analysis is carried out on the control of a wind system considered as an isolated source of power and composed of a horizontal-axis wind-turbine connected to an induction generator. For both the horizontal-axis windturbine and the induction generator, mathematical models are used. The paper presents the one-step-ahead adaptive control technique, which is used to regulate the wind system. A sensitivity analysis of the induction generator performances with respect to control and disturbance variables is
Fuel and Energy Abstracts
May 1998 201
The lost energy from the pond is a maximum However, increasing the extracted load increases solar radiation in the pond.
if no load is extracted. the amount of absorbed
Evaluation of parameters for anodic poiarisation curve from the experimentally measured U-l dependence for an electrochemical photovoltaic regenerative solar cell
9m2219
Rouar, I. et al. Solar Energy Materials and Solar Cells, 1998, 51, (2), 155169. At different values of the light intensity the cell voltage for an electrochemical photovoltaic regenerative solar cell with current leads located on opposite sides of a cell unit was measured. The light intensity examined was in the range 77-1360 W m-z. An empirical relation for anodic polarization curve with three parameters, namely the limiting current density, the formal exchange current density and open-circuit potential vs light intensity was formulated. The evaluation of these parameters is based on the chemical engineering description of a model cell. The transfer of the data to large modules for outdoor applications is enabled by this description.
Experimental and theoretical performance of a demonstration solar chimney model-part I: mathematical model development
90lO2220
Pasumarthi, N. and Sherif, S. A. Int. J. Energy Res., 1998, 22, (3), 277-288. The solar chimney is a natural draft device which uses solar radiation to provide upward momentum to the in-flowing air, thereby converting the thermal energy into kinetic energy. A study was undertaken to evaluate the performance characteristics of solar chimneys both theoretically and experimentally. In this paper, a mathematical model which was developed to study the effect of various parameters on the air temperature, air velocity, and power output of the solar chimney, is presented. Tests were conducted on a demonstration model which was designed and built for that purpose. The mathematical model presented here, was verified against experimental test results and the overall results were encouraging.
Improved fill-factor for the double-sided contact bifacial silicon solar cell
9am2221
buried-
Ghozati, S. B. et al. Solar Energy Materials and Solar Cells, 1998, 51, (2), 121-128. Buried-contact solar cells have met with commercial success, but the performance of early generations of these devices has been limited by an effective high rear-surface recombination velocity. The double-sided buried-contact bifacial (DSBCB) solar cells have demonstrated improved rear-surface passivation with corresponding improvements in current and voltage for a number of years. The fill factors of these devices have been significantly degraded in the past, however, due to shunting of the rear floating junction. Significantly higher sheet resistivities for the rear n-type layer have made it possible to overcome these limitations. Based on this new approach, experimental devices have achieved fill factors approaching 82% while simultaneously achieving open-circuit voltages in the vicinity of 670 mV. Float zone material have achieved efficiencies in the range 17-18% without texturing, anti-reflection coatings, any form of light trapping or even rear reflector. In-situ Kelvin probe and ellipsometry study of the doping of a-Si : H and a-SIC : H layers: correlation with solar cell parameters
9m2222
Hadjadj, A. et al. Solar Energy Materials and Solar Cells, 1998, 51, (2), 145153. The in-situ Kelvin probe technique was used to highlight the effects of boron doping on the photovoltaic characteristics of a-Si : H based p-i-n solar cells in order to determine the evolution of the contact potential at the SnOz/p interface in two series of solar cells. One had a p(a-Si : H) layer and the other had a p(a-SiC : H) layer plus a buffer a-Sic : H layer. In each series, the flow of diborane was varied between 0.5 and 7 seem. The in-situ Kelvin probe measurements on thick layers indicate that the doping efficiency is higher in a-Si : H than in a-Sic : H layers. In cells with a p(a-Si : H) layer an optimum in I’,, as a function of the diborane flow rate was observed. Below this optimum, the increase in k’,, is correlated to the increase of the contact potential measured by the Kelvin probe. Above the optimum value of the diborane flow, the further increase of the contact potential contrasts with the decrease of I’,,. In cells with a p(a-SiC : H), k’,, is independent of the diborane flow rate. This is interpreted in terms of the diffusion of impurities and changes in the p-layer induced by boron atoms.
Investigation storage system
98102223
Hamdan, Theoretical integrated galvanized collector performed was found angle of theoretical
of an inexpensive
Alternative
energy sources (wind energy)
Photothermal radiometry on nickel (pigmented aluminium oxide) selective solar absorbing surface coatings
98102224
Othonos, A. et al. Solar Energy Materials and Solar Cells, 1998, 51, (2) 171-179. Nickel-pigmented aluminium oxide solar absorbing coatings were characterized by photothermal radiometry (PTR). A modulated laser beam was used to heat the solar samples and the subsequent emission of thermal radiation was measured as a function of modulated frequency in the range of 10 Hz to 10 kHz. Allowing for the extraction of some thermal parameters for the solar absorbing coatings, a simple one-dimensional model is used to fit the experimental PTR results. A comparison of the emissivity measured by traditional technique and the photothermal radiometry was then made.
Photovoltaic properties of WSep single-crystals 98102225 studied by photoelectron spectroscopy Klein, A. et al.
Solar Energy Materials and Solar Cells,1998, 51, (2).181-
191.
An investigation into the different surfaces and Schottky barriers of WSez single crystals has been performed using photoelectron spectroscopy with synchrotron radiation. The acceptor level with EA - Ev = 0.45 eV, an important defect level in WSez, was identified and attributed to the non-van der Waals planes. The photovoltages obtained for the Schottky barriers prepared on UHV-cleaved selenium grown p-WSeZ single crystals depend on the lateral conductivity of the surface which is a function of metal-film thickness and morphology. It is suggested that the crystal quality of WSez single crystals, and thus, achievable conversion efficiencies of WSez solar cells, relies on the transport agent used in chemical vapour transport growth.
Short-term thermal performance of a built-in solar storage for frost prevention In a greenhouse
98/02226
Kiirklii, A. Inc. .I. Energy Res., 1998, 22, (2), 169-174. An alternative to the traditional solar collectors is built-in solar storage. This paper explores the possibility of utilizing such solar stores for frost prevention in greenhouses. In the study, two identical NE-SW orientated greenhouses with 50 m2 ground area were erected. The total ground area and volume of the water stores used in the solar greenhouse were about 6.4 and 5.4% of the total ground area and volume of the greenhouse. The short-term results showed that at times when the air temperature in the control greenhouse dropped below 0°C it was about 3.5”C in the solar greenhouse. Sometimes this difference was as much as 4.5”C or more. The average fraction of solar energy storage by the stores was 0.26 for a four day period.
Solar radiation on tilted south oriented surfaces: validation of transfer-models
98lo2227
Behr, H. D. Solar Energy, 61, (6) 399-413. Tests were performed on three transfer-models in use for estimating solar radiation on tilted surfaces. There is available a 12-year series of hourly global, diffuse and reflected solar irradiation measured with horizontal pyranometers, as well as hourly global solar irradiation measured with tilted south oriented pyranometers. One model uses daily irradiation, the other two use hourly irradiation. The models converting hourly solar irradiation on a horizontal surface to a tilted surface yield better results than that using daily irradiation. The best results can be achieved with pairs of hourly global and diffuse solar irradiation. The root mean square errors exceed 10% only if the sky is covered by more than 85% with clouds or if the solar elevation angle is less than 10”.
98lO2228 tors
Transient method for testing fiat-plate solar collec-
Amer, E. H. et al. Energy Cowers. Mgmt, 1998, 39, (7), 549-558. To characterize the dynamic behaviour of flat-plate solar collectors, a transient test method has been developed. Based on a one-node model in which the heat capacity of the plate, the tubes and the fluid are lumped together in one node which is referred to the mean temperature of the working fluid. The method is both quicker and more simple. Test results are very close to those obtained from steady state tests based on the ASHRAE 93-86 standard. Also investigated were the effects of inlet temperature and incidence angle on collector parameters. Reasonable agreement was found between the theoretical predictions based on the parameters obtained from the transient test method and experimental observations.
Wind Energy
solar collector
M. A. Energy Cowers. Mgmt, 1998, 39, (516). 415-420. and experimental investigations were carried out on an rock bed and solar collector system. Consisting of an insulated iron box containing rocks, the apparatus may act as both a solar and a storage system. Furthermore, the measurements were at different values of tilt angle and mass flow rate of air. The bed to have a maximum storage efficiency of 46% when tilted at an 47”. Good agreement between the experimental results and predictions was discovered.
9am2229
One step ahead adaptive control technique for wind
systems
Dadone, A. et al. Energy Convers. Mgtnt, 1998, 39, (5/6), 399-413. An analysis is carried out on the control of a wind system considered as an isolated source of power and composed of a horizontal-axis wind-turbine connected to an induction generator. For both the horizontal-axis windturbine and the induction generator, mathematical models are used. The paper presents the one-step-ahead adaptive control technique, which is used to regulate the wind system. A sensitivity analysis of the induction generator performances with respect to control and disturbance variables is
Fuel and Energy Abstracts
May 1998 201