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00872 Experimental testing of a box-type solar cooker using the standard procedure of cooking power
13 Altemative energy supplies (solar energy) order of m a g n i t u d e the power typically obtained from a conventional g e o t h e r m a l well in Iceland. The aim of the I D D P is to d e t e r m i n e w h e t h e r utilization of heat from such an unconventional g e o t h e r m a l resource at supercritical conditions will lead to increased productivity of wells at a competitive cost. If the I D D P is an economic success, this same approach could be applied in other h i g h - t e m p e r a t u r e volcanic g e o t h e r m a l systems elsewhere, an i m p o r t a n t step in e n h a n c i n g the g e o t h e r m a l industry worldwide.
06•00868 Thermodynamic analysis of a ground-source heat pump system for district heating Hepbasli, A. hzternational Journal of Energy Research, 2005, 29, (7), 671 687. This study deals with the t h e r m o d y n a m i c analysis of ground-source heat p u m p (GSHP) systems for district heating. The mass, energy, entropy and exergy balance relations are derived and applied to a G S H P system with a U - b e n d ground heat exchanger. The performance characteristics of this G S H P system are evaluated in terms of energetic and exergetic aspects. Based on the m e a s u r e m e n t s conducted on 7 J a n u a r y 2004, the heat extraction rate from the soil is found to be, on average, 61.4 W m 1 of bore depth, while the required borehole length in m e t e r per k W of heating capacity is obtained as 11.71. The entering w a t e r t e m p e r a t u r e to the unit is m e a s u r e d to be 15.3:C. The heating coefficient of performance of the heat p u m p (COPHe) is about 2.85, while that for the whole system is obtained to be 7.4%, lower than COPHp. The exergy efficiency values for the heat p u m p unit and whole system are found to be 66.8 and 66.6%,, respectively.
06•00871
Effect of relative humidity on solar potential
S6zen, A. and Arcaklioglu, E. Applied Energy, 2005, 82, (4), 345 367. In this study, the effect of relative humidity on solar potential is investigated using artificial neural-networks. Two different models are used to train the neural networks. Meteorological and geographical data (latitude, longitude, altitude, month, m e a n sunshine-duration, and m e a n t e m p e r a t u r e ) are used in the input layer of the network ( M o d e l 1). But, relative humidity values are added to one network in model (Model 2). In other words, the only difference between the models is relative humidity. New formulae based on meteorological and geographical data, have been developed to d e t e r m i n e the solar energy potential in Turkey using the networks' weights for both models. Scaled conjugate g r a d i e n t (SCG) and L e v e n b e r g - M a r q u a r d t (LM) learning algorithms and a logistic sigmoid transfer-function were used in the network. The best approach was obtained by the SCG algorithm with nine neurons for both models. Meteorological data for the four years, 2000 2003, for 18 cities spread over Turkey have been used as data in order to train the neural network. Solar radiation is in o u t p u t layer. One m o n t h for each city was used as test data, and these months have not been used for training. The m a x i m u m m e a n absolute p e r c e n t a g e errors ( M A P E s ) for Tosya are 2.770394%, and 2.8597%, for M o d e l s 1 and 2, respectively. The m i n i m u m M A P E s for Seydisehir are 1.055205%, and 1.041% with R 2 (99.9862%, 99.9842%) for M o d e l s 1 and 2, respectively, in the SCG a l g o r i t h m with nine neurons. The best value of R 2 for Models 1 and 2 are for Seydisehir. The m i n i m u m value o f R 2 for M o d e l 1 is 99.8855% for Tosya, and the value for M o d e l 2 is 99.9001% for Yenisehir. Results show that the humidity has only a negligible effect upon the prediction of solar potential using artificial neural-networks.
06•00872 Experimental testing of a box-type solar cooker using the standard procedure of cooking power
Solar energy 06•00869 Are new institutional economics enough? Promoting photovoltaics in India's agricultural sector Radulovic, V. Energy Policy, 2005, 33, (14), 1883 1899. Solar photovoltaic (PV) technology can bring emissions-free electricity to rural areas without access to the grid. Currently, policymakers are seeking ways to expand markets for off-grid PV from solar home systems to productive uses in order to enhance income generation and contribute to social development. This paper explores the role of the state in p r o m o t i n g such m a r k e t growth. As a start, the state must improve institutions, thus echoing popular r e c o m m e n d a t i o n s based in new institutional economic theory (NIE) that are currently touted by the W o r l d Bank and other large d e v e l o p m e n t agencies. Yet, N I E ' s framework may be insufficient because it fails to offer viable solutions to overcoming political barriers that contribute to technological path dependency. A case study in Punjab, India, where an agricultural PV water p u m p i n g p r o g r a m showed promising signs of successful m a r k e t p e n e t r a t i o n in its first 3 years of operation, illustrates how the N I E ' s shortcomings manifest themselves in practice. The program was b e g i n n i n g to p e n e t r a t e m a r k e t entry for P V p u m p s via competition between PV providers. However, the g o v e r n m e n t of I n d i a achieved this feat by providing subsidies to wealthy farmers, a move that is frowned upon by the N I E school. Based on findings from the case study, states should look beyond N I E ' s framework to expand and improve PV markets in productive uses by accounting for political constraints, assessing how PV technology can improve d e v e l o p m e n t goals, and cultivating locally a p p r o p r i a t e service delivery models.
06•00870 Design consideration of low temperature differential double-acting Stirling engine for solar application Abdullah, S. et al. Renewable Energy, 2005, 30, (12), 1923 1941. This paper presents design considerations to be t a k e n in designing of a low t e m p e r a t u r e differential double-acting Stirling engine for solar application. The target power source will be a t h e r m o s i p h o n solar w a t e r heater with integrated storage system, which will supply a constant source t e m p e r a t u r e of 70:C. Hence, the system design is based on a t e m p e r a t u r e difference of 50:C, assuming that the sink is k e p t at 20:C. D u r i n g the preliminary design stage, the critical p a r a m e t e r s of the engine design are d e t e r m i n e d according to the Schmidt analysis, while the third order analysis was used during the design optimisation stage in order to establish a complete analytical m o d e l for the engine. The heat exchangers are designed to be of high effectiveness and low pressure-drop, and are m a d e from a 0.015 m tube, while the porosity of the steel wool of 0.722 is used for the r e g e n e r a t o r matrix. U p o n optimisation, the o p t i m a l engine speed is 120 rpm with the swept volume of 2.3 1, and thus the critical engine p a r a m e t e r s are found to be the bore d i a m e t e r of 0.20 m. In addition, the volumes of heater, cooler and regenerator are 1.3 1, 1.3 1 and 2.0 1 volumes, respectively.
128
Fuel and Energy Abstracts
March 2006
El-Sebaii, A. A. and Ibrahim, A. Renewable Energy, 2005, 30, (12), 1861 1871. A box-type solar cooker with one (Model I) or four (Model II) cooking pots was constructed and tested under T a n t a prevailing w e a t h e r conditions. Experiments were performed during July 2002 using the cooker with or w i t h o u t load. The obtained results were employed to calculate the two figures of merit, FI and F2, as well as the utilization efficiency qu and the specific t~ and characteristic tc boiling times. The obtained values of FI indicate that the cooker can be used twice a day for consecutive cooking. F2 was found to increase almost linearly with the mass of the cooking fluid Mr. The cooker is able to boil 1 kg of water in 15 rain when its aperture area equals 1 m 2. Furthermore, experiments also considered the requirements for the i n t e r n a t i o n a l standard test procedure for solar cookers. The cooking power P was correlated with the temperature difference ',T between the cooking fluid and the ambient air. Linear correlations between P and 3 T had correlation coefficients higher than 0.90 satisfying the standard. The obtained values of the initial cooking power, heat loss coefficient and the cooking power at a temperature difference of 50:C agree well with those obtained for small solar cookers. The present cooker is able to cook most kinds of food with an overall utilization efficiency of 26.7%.
06•00873 Further developments in CIS monograin layer solar cells technology Altosaar, M. et al. Solar Energy Materials and Solar Cells, 2005, 87, (1 4), 25 32. This paper reviews recent studies and technological developments on different materials and technologies for m o n o g r a i n layer (MGL) photovoltaics (PV) solar cells conducted at Tallinn University of Technology. It is shown that in spite of i m p r o v e m e n t s in technical p a r a m e t e r s of M G L solar cells resulting from research in adsorber layer materials and surface modification, several problems have to be solved before d e t e r m i n i n g the prospects of design.
06•00874 Heat-transfer enhancement in double-pass flatplate solar air heaters with recycle Ho, D. C. et al. Energy, 2005, 30, (15), 2796 2817. This work theoretically and experimentally investigates a device for inserting an absorbing plate into the double-pass channel in a flat-plate solar air heater with recycle. This m e t h o d substantially improves the collector efficiency by increasing the fluid velocity. The results are r e p r e s e n t e d graphically and c o m p a r e d with a downward-type singlepass solar air heater. Considerable i m p r o v e m e n t in heat transfer is obtainable by employing recycle-type double-pass devices instead of single-pass devices or a conventional double-pass heater with the same flow rate. The absorbing plate location influence on heat-transfer efficiency e n h a n c e m e n t and the hydraulic dissipated power i n c r e m e n t is also discussed.
06•00875 Minority carrier lifetime in plasma-textured silicon wafers for solar cells Kumaravelu, G. et al. Solar Energy 3laterials and Solar Cells, 2005, 87, (1 4), 99 106.
06•00868 Thermodynamic analysis of a ground-source heat pump system for district heating Hepbasli, A. hzternational Journal of Energy Research, 2005, 29, (7), 671 687. This study deals with the t h e r m o d y n a m i c analysis of ground-source heat p u m p (GSHP) systems for district heating. The mass, energy, entropy and exergy balance relations are derived and applied to a G S H P system with a U - b e n d ground heat exchanger. The performance characteristics of this G S H P system are evaluated in terms of energetic and exergetic aspects. Based on the m e a s u r e m e n t s conducted on 7 J a n u a r y 2004, the heat extraction rate from the soil is found to be, on average, 61.4 W m 1 of bore depth, while the required borehole length in m e t e r per k W of heating capacity is obtained as 11.71. The entering w a t e r t e m p e r a t u r e to the unit is m e a s u r e d to be 15.3:C. The heating coefficient of performance of the heat p u m p (COPHe) is about 2.85, while that for the whole system is obtained to be 7.4%, lower than COPHp. The exergy efficiency values for the heat p u m p unit and whole system are found to be 66.8 and 66.6%,, respectively.
06•00871
Effect of relative humidity on solar potential
S6zen, A. and Arcaklioglu, E. Applied Energy, 2005, 82, (4), 345 367. In this study, the effect of relative humidity on solar potential is investigated using artificial neural-networks. Two different models are used to train the neural networks. Meteorological and geographical data (latitude, longitude, altitude, month, m e a n sunshine-duration, and m e a n t e m p e r a t u r e ) are used in the input layer of the network ( M o d e l 1). But, relative humidity values are added to one network in model (Model 2). In other words, the only difference between the models is relative humidity. New formulae based on meteorological and geographical data, have been developed to d e t e r m i n e the solar energy potential in Turkey using the networks' weights for both models. Scaled conjugate g r a d i e n t (SCG) and L e v e n b e r g - M a r q u a r d t (LM) learning algorithms and a logistic sigmoid transfer-function were used in the network. The best approach was obtained by the SCG algorithm with nine neurons for both models. Meteorological data for the four years, 2000 2003, for 18 cities spread over Turkey have been used as data in order to train the neural network. Solar radiation is in o u t p u t layer. One m o n t h for each city was used as test data, and these months have not been used for training. The m a x i m u m m e a n absolute p e r c e n t a g e errors ( M A P E s ) for Tosya are 2.770394%, and 2.8597%, for M o d e l s 1 and 2, respectively. The m i n i m u m M A P E s for Seydisehir are 1.055205%, and 1.041% with R 2 (99.9862%, 99.9842%) for M o d e l s 1 and 2, respectively, in the SCG a l g o r i t h m with nine neurons. The best value of R 2 for Models 1 and 2 are for Seydisehir. The m i n i m u m value o f R 2 for M o d e l 1 is 99.8855% for Tosya, and the value for M o d e l 2 is 99.9001% for Yenisehir. Results show that the humidity has only a negligible effect upon the prediction of solar potential using artificial neural-networks.
06•00872 Experimental testing of a box-type solar cooker using the standard procedure of cooking power
Solar energy 06•00869 Are new institutional economics enough? Promoting photovoltaics in India's agricultural sector Radulovic, V. Energy Policy, 2005, 33, (14), 1883 1899. Solar photovoltaic (PV) technology can bring emissions-free electricity to rural areas without access to the grid. Currently, policymakers are seeking ways to expand markets for off-grid PV from solar home systems to productive uses in order to enhance income generation and contribute to social development. This paper explores the role of the state in p r o m o t i n g such m a r k e t growth. As a start, the state must improve institutions, thus echoing popular r e c o m m e n d a t i o n s based in new institutional economic theory (NIE) that are currently touted by the W o r l d Bank and other large d e v e l o p m e n t agencies. Yet, N I E ' s framework may be insufficient because it fails to offer viable solutions to overcoming political barriers that contribute to technological path dependency. A case study in Punjab, India, where an agricultural PV water p u m p i n g p r o g r a m showed promising signs of successful m a r k e t p e n e t r a t i o n in its first 3 years of operation, illustrates how the N I E ' s shortcomings manifest themselves in practice. The program was b e g i n n i n g to p e n e t r a t e m a r k e t entry for P V p u m p s via competition between PV providers. However, the g o v e r n m e n t of I n d i a achieved this feat by providing subsidies to wealthy farmers, a move that is frowned upon by the N I E school. Based on findings from the case study, states should look beyond N I E ' s framework to expand and improve PV markets in productive uses by accounting for political constraints, assessing how PV technology can improve d e v e l o p m e n t goals, and cultivating locally a p p r o p r i a t e service delivery models.
06•00870 Design consideration of low temperature differential double-acting Stirling engine for solar application Abdullah, S. et al. Renewable Energy, 2005, 30, (12), 1923 1941. This paper presents design considerations to be t a k e n in designing of a low t e m p e r a t u r e differential double-acting Stirling engine for solar application. The target power source will be a t h e r m o s i p h o n solar w a t e r heater with integrated storage system, which will supply a constant source t e m p e r a t u r e of 70:C. Hence, the system design is based on a t e m p e r a t u r e difference of 50:C, assuming that the sink is k e p t at 20:C. D u r i n g the preliminary design stage, the critical p a r a m e t e r s of the engine design are d e t e r m i n e d according to the Schmidt analysis, while the third order analysis was used during the design optimisation stage in order to establish a complete analytical m o d e l for the engine. The heat exchangers are designed to be of high effectiveness and low pressure-drop, and are m a d e from a 0.015 m tube, while the porosity of the steel wool of 0.722 is used for the r e g e n e r a t o r matrix. U p o n optimisation, the o p t i m a l engine speed is 120 rpm with the swept volume of 2.3 1, and thus the critical engine p a r a m e t e r s are found to be the bore d i a m e t e r of 0.20 m. In addition, the volumes of heater, cooler and regenerator are 1.3 1, 1.3 1 and 2.0 1 volumes, respectively.
128
Fuel and Energy Abstracts
March 2006
El-Sebaii, A. A. and Ibrahim, A. Renewable Energy, 2005, 30, (12), 1861 1871. A box-type solar cooker with one (Model I) or four (Model II) cooking pots was constructed and tested under T a n t a prevailing w e a t h e r conditions. Experiments were performed during July 2002 using the cooker with or w i t h o u t load. The obtained results were employed to calculate the two figures of merit, FI and F2, as well as the utilization efficiency qu and the specific t~ and characteristic tc boiling times. The obtained values of FI indicate that the cooker can be used twice a day for consecutive cooking. F2 was found to increase almost linearly with the mass of the cooking fluid Mr. The cooker is able to boil 1 kg of water in 15 rain when its aperture area equals 1 m 2. Furthermore, experiments also considered the requirements for the i n t e r n a t i o n a l standard test procedure for solar cookers. The cooking power P was correlated with the temperature difference ',T between the cooking fluid and the ambient air. Linear correlations between P and 3 T had correlation coefficients higher than 0.90 satisfying the standard. The obtained values of the initial cooking power, heat loss coefficient and the cooking power at a temperature difference of 50:C agree well with those obtained for small solar cookers. The present cooker is able to cook most kinds of food with an overall utilization efficiency of 26.7%.
06•00873 Further developments in CIS monograin layer solar cells technology Altosaar, M. et al. Solar Energy Materials and Solar Cells, 2005, 87, (1 4), 25 32. This paper reviews recent studies and technological developments on different materials and technologies for m o n o g r a i n layer (MGL) photovoltaics (PV) solar cells conducted at Tallinn University of Technology. It is shown that in spite of i m p r o v e m e n t s in technical p a r a m e t e r s of M G L solar cells resulting from research in adsorber layer materials and surface modification, several problems have to be solved before d e t e r m i n i n g the prospects of design.
06•00874 Heat-transfer enhancement in double-pass flatplate solar air heaters with recycle Ho, D. C. et al. Energy, 2005, 30, (15), 2796 2817. This work theoretically and experimentally investigates a device for inserting an absorbing plate into the double-pass channel in a flat-plate solar air heater with recycle. This m e t h o d substantially improves the collector efficiency by increasing the fluid velocity. The results are r e p r e s e n t e d graphically and c o m p a r e d with a downward-type singlepass solar air heater. Considerable i m p r o v e m e n t in heat transfer is obtainable by employing recycle-type double-pass devices instead of single-pass devices or a conventional double-pass heater with the same flow rate. The absorbing plate location influence on heat-transfer efficiency e n h a n c e m e n t and the hydraulic dissipated power i n c r e m e n t is also discussed.
06•00875 Minority carrier lifetime in plasma-textured silicon wafers for solar cells Kumaravelu, G. et al. Solar Energy 3laterials and Solar Cells, 2005, 87, (1 4), 99 106.