- Email: [email protected]
06189 Absorptivity as a predictor of the photoluminescence spectra of silicon solar cells and photosynthesis
07
Alternative energy sources (geothermal energy)
Geothermal Energy Characterization of the geothermal system beneath 95D6182 the Northwest Geysers steam field, Callfornla, from relsmlclty and velocity patteina Romero, A. E. et al., Geothermics,Aug. 1995, 24, (4), 471-487. A high-resolution seismic network at the Coldwater Creek Steam Field (CCSF) in the Northwest Geyers tegion has provided data with which 10 estimate three-dimensional P- and S-wave velocity models and to relocate hypocentres. The seismicity distribution and resulting seismic velocity structure, coupled with the known geology! are used to characterize the geothermal reservoir. The velocity structure IS estimated usin the pro essive inversion technique of Thurber [J. Geophys. Res. 8i , 8226&36 (1983)] Hypocentres within the CCSF lie between depths of 1.5 and 2.5 km and appear to be associated with the steam production zone. A deeper cluster of events is located beneath an injection well. High-velocity nearsurface anomalies correspond lo mapped sections of Franciscan metagraywacke and greenstone. Development of a vapor-domlnated reaervolr with a 95108183 ‘high-temperature’ component Shook, G. M. Geothermics,Aug. 1995, 24, (4), 489-505. A conceptual model of The Geyers ‘High-Temperature Reservoir’ (HTR) has been developed that incorporates e+iFg field measurements and observations, including fluid inclusion sahrutles, core and cutting analyses, and the non-uniform depth to the top of the HTR. A numerIcal model based on the conceptual model successfully reproduces observed HTR characteristics. Results of the numerical model indicate that the HTR mav be a long-lived feature of the ‘normal’ vapor-dominated reservoir. Formation of the HTR is dependent on a spatial variation in petrophysical properties, a relatively rapid venting of a dgnificant fraction-of the mass in place, and the presence of a saline reservoir fluid. of Tattapanl Thermal Springs, 95108184 Geochemist Madhya Pradesh, India-fler d and experlmental lnveatlgatlona S_~irlrkharam, D. and Antu, M. C. Geothermics,Aug. 1995, 24, (4). The chemical composition of Tattapani thermal springs together with the experimental results on host rock-meteoric water interaciion al lOO’C,indicate dissolution of K-feldspars and albite during the initial stages of reaction. These phases control the chemical composition of the thermal springs. The estimated reservoir temperatures range from 205 lo 217°C. Assuming an average thermal gradient of 8O”C/km,the minimum depth of the reservoir is estimated 10 be around 3 km. 95108185 Nonalmllar aolutlona for mixed convection on a wedge embedded In a porous medlym Vargas, J. V. et al., Heat & Fluid Flow, Jun. 1995, 16, (3), 211-216. The problem of mixed convection on a wedge in a saturated porous medium is analyzed using the Darcy flow formulation and three different methods of sol&on. Nonsimilar soiutions are obtained for several wedge angles. The nonsimilarity technique is applied 10the boundary layer formulation, and the finite element method is used in both formulations. 95/08188 Numerlcal modelllng of the evolutlon of two-phase zones under a fractured caprock Yano. Y. and Ishido. T. Geothermics.AU 1995. 24. (41. 507-521. The conditions necessary for the evol&m%f twoiphakd zones in a eothermal reservoir located below a caprock that presents a permeable %racture were investigated. The two-dimensional reservoir model used in this numerical simulation study was based on data from the Ginyu reservoir of the Kirishima geothermal-field, Japan. The upper part of ihe reservoir is characterized by its vapor-static pressure distribution, and by the leakage of fluids to the surface. The reservoir can be represented as a two-phase permeable zone overlain by a fractured caprock. If the fracture in the caprock is highly transmissive, two-phase conditions may be found in the reservoir (a function of the rate of deep fluid recharge) but not necessarily a vapor-static pressure profile. If the fracture transmissivity and the rate of deep recharge are small enough, a vapor-static two-phase zone can develop. 98lOSi 87 A study of scale deposit1 n: An analogue of meaogr:e;;ermal ore formatlon In the vol8ano of Mlloa, Aegean Arc, Christanis, K. and St. Seymour, K. Geothermics,Aug. 1995, 24, (4), 541-552. The viability of boiling as a mechanism for meso- to epithermal ore formation has been tested in the Milos volcano, Aegean Island Arc, by investigating rates of deposition and composition of scale, and by drawing an analogy between the results and actual field occurrences on the island. Milos offers ideal conditions for such testing: it consists of predominantly felsic volcanic rocks with numerous latestage hydrovolcanic (phreatic) breccias.
438
Fuel and Energy Abstracts November 1995
%Y 88
Water vapor adsorption on geothermal raarrvolr
Shang, S. et al., Geothermics,Aug. 1995, 24, (4), 523-540. The quantification of the amount of water retained in geothermal reservoir rocks allows a more realistic estimation of reserves for vapor-dominated geothermal reservoirs. If the measured desorption isotherm resembles the product.ion characteristics of a geothermal system, understandink of the adsorptlon/desorpcion hysteresis will aid the design of remjection processes. Adsorption/desorption isotherms of both nitro en and water vapor on Berea sandstone and a graywacke sample from 4 e Geyers well NEGU-17 were measured.
Solar Energy 95108189 Absor tlvlty as a predictor of the photolumlnercence spectra of aPllcon aolar cells and photoayntheala S;lTtad, G. P. SolarEnergy Materials& Solar Cells, Aug. 1995,38, (l), - . Experimental photoluminescence spectra obtained for silicon are compared lo predictions made using transmission and reflection data, as well as those using the action (or induced photo-product) spectrum. Although the absorptivity obtained from the optical measurements can be used lo predict much of the photoluminescence curve, the predicted values may deviate from measurements at long wavelengths. The photoluminescence spectrum for Si, and for photosynthesis found in green plants, may also be predicted from action sDectra. Both techniaues vield a reasonable fit IO the exoerimental spectral distribution and tie pr&icted chemical potentials and ;I$ages are consistent with electrical measurements. 95108190 Advances In solar energy - Volume 9 American Solar Energy Society, USA, 1994, $125.00, 495 pp. 95108191 Analytlcal aolutlona for the photocurrant and dark dlffualon current of preferentially doped polyalllcon solar cells Ben Arab, A. Solar Energy Materials& Solar Cells, Jul. 1995, 37, (3), 239-258. A two-dimensional physical model is used in (he analysis of the photovoltaic properties of a preferentially doped polycrystalline silicon solar cell along the grain boundaries. The cell is assumed to have an oriented columnar structure formed by a juxtaposition of silicon ains. A mathematical analysis, based on the superposition principle and t!re technique of separation of variables, is presented. The analysis has allowed the author to obtain analytical expressions for the photocurrents and dark diffusion currents of the horizontal junction and vertical junction of the base region. These expressions are valid for any arbitrary value of the recombination velocitv a1 the grain boundaries. _ 95108192 Band gap and refractive Index determination of Moblack coatings using several techniques :“s”;1”;9;. et al., Solar Energy Materials& Solar Cells, Jul. 1995, 37, (3), The optical energy gap of molybdenum black solar selective absorbing coatings has been estimated by various techniques and the results are compared. For thick absorbing coatings on metallic substrates the band gap has been estimated from reflectance spectra using the Kubelka-Munk function. The band gap of these coatings has also been estimated from transmission spectra obtained from a thin coating specially prepared on semitransparent aluminium coated glass substrates. 95108193 Charge transfer and charge trapplng In zeolltaa and almllar media k&, gg et al., Solar Energy Materials& Solar Cells, Aug. 1995, 38, (l),
-
.
Much work has been published on photo-induced charge transfer in homogeneous and colloidal solutions, and unique photo-systems of direct interest to ‘storage of energy’ have been developed. This paper describes the use of steady states as well as pulse laser photolysis, and pulse radiolysis techniques to investigate charge generation, charge separation, and charge stabilizationin zeolites and in porous silica gel. 95108194 Commsnt on thermodynamic aspects of photochsmlcal solar energy converalon h’;y$ A. J. Solar Energy Materials& Solar Cells, Aug. 1995, 38, (l), - . Two of the major issues discussed at a recent workshop on thermodynamits of photochemical solar energy conversion are summarized in this paper: (1) the effect of hot carrier processes on the thermodynamics of solar photon conversion; (2) the existence of a light-intensity threshold for photoconversion processes and the validity of quasi-Fermi levels.
Alternative energy sources (geothermal energy)
Geothermal Energy Characterization of the geothermal system beneath 95D6182 the Northwest Geysers steam field, Callfornla, from relsmlclty and velocity patteina Romero, A. E. et al., Geothermics,Aug. 1995, 24, (4), 471-487. A high-resolution seismic network at the Coldwater Creek Steam Field (CCSF) in the Northwest Geyers tegion has provided data with which 10 estimate three-dimensional P- and S-wave velocity models and to relocate hypocentres. The seismicity distribution and resulting seismic velocity structure, coupled with the known geology! are used to characterize the geothermal reservoir. The velocity structure IS estimated usin the pro essive inversion technique of Thurber [J. Geophys. Res. 8i , 8226&36 (1983)] Hypocentres within the CCSF lie between depths of 1.5 and 2.5 km and appear to be associated with the steam production zone. A deeper cluster of events is located beneath an injection well. High-velocity nearsurface anomalies correspond lo mapped sections of Franciscan metagraywacke and greenstone. Development of a vapor-domlnated reaervolr with a 95108183 ‘high-temperature’ component Shook, G. M. Geothermics,Aug. 1995, 24, (4), 489-505. A conceptual model of The Geyers ‘High-Temperature Reservoir’ (HTR) has been developed that incorporates e+iFg field measurements and observations, including fluid inclusion sahrutles, core and cutting analyses, and the non-uniform depth to the top of the HTR. A numerIcal model based on the conceptual model successfully reproduces observed HTR characteristics. Results of the numerical model indicate that the HTR mav be a long-lived feature of the ‘normal’ vapor-dominated reservoir. Formation of the HTR is dependent on a spatial variation in petrophysical properties, a relatively rapid venting of a dgnificant fraction-of the mass in place, and the presence of a saline reservoir fluid. of Tattapanl Thermal Springs, 95108184 Geochemist Madhya Pradesh, India-fler d and experlmental lnveatlgatlona S_~irlrkharam, D. and Antu, M. C. Geothermics,Aug. 1995, 24, (4). The chemical composition of Tattapani thermal springs together with the experimental results on host rock-meteoric water interaciion al lOO’C,indicate dissolution of K-feldspars and albite during the initial stages of reaction. These phases control the chemical composition of the thermal springs. The estimated reservoir temperatures range from 205 lo 217°C. Assuming an average thermal gradient of 8O”C/km,the minimum depth of the reservoir is estimated 10 be around 3 km. 95108185 Nonalmllar aolutlona for mixed convection on a wedge embedded In a porous medlym Vargas, J. V. et al., Heat & Fluid Flow, Jun. 1995, 16, (3), 211-216. The problem of mixed convection on a wedge in a saturated porous medium is analyzed using the Darcy flow formulation and three different methods of sol&on. Nonsimilar soiutions are obtained for several wedge angles. The nonsimilarity technique is applied 10the boundary layer formulation, and the finite element method is used in both formulations. 95/08188 Numerlcal modelllng of the evolutlon of two-phase zones under a fractured caprock Yano. Y. and Ishido. T. Geothermics.AU 1995. 24. (41. 507-521. The conditions necessary for the evol&m%f twoiphakd zones in a eothermal reservoir located below a caprock that presents a permeable %racture were investigated. The two-dimensional reservoir model used in this numerical simulation study was based on data from the Ginyu reservoir of the Kirishima geothermal-field, Japan. The upper part of ihe reservoir is characterized by its vapor-static pressure distribution, and by the leakage of fluids to the surface. The reservoir can be represented as a two-phase permeable zone overlain by a fractured caprock. If the fracture in the caprock is highly transmissive, two-phase conditions may be found in the reservoir (a function of the rate of deep fluid recharge) but not necessarily a vapor-static pressure profile. If the fracture transmissivity and the rate of deep recharge are small enough, a vapor-static two-phase zone can develop. 98lOSi 87 A study of scale deposit1 n: An analogue of meaogr:e;;ermal ore formatlon In the vol8ano of Mlloa, Aegean Arc, Christanis, K. and St. Seymour, K. Geothermics,Aug. 1995, 24, (4), 541-552. The viability of boiling as a mechanism for meso- to epithermal ore formation has been tested in the Milos volcano, Aegean Island Arc, by investigating rates of deposition and composition of scale, and by drawing an analogy between the results and actual field occurrences on the island. Milos offers ideal conditions for such testing: it consists of predominantly felsic volcanic rocks with numerous latestage hydrovolcanic (phreatic) breccias.
438
Fuel and Energy Abstracts November 1995
%Y 88
Water vapor adsorption on geothermal raarrvolr
Shang, S. et al., Geothermics,Aug. 1995, 24, (4), 523-540. The quantification of the amount of water retained in geothermal reservoir rocks allows a more realistic estimation of reserves for vapor-dominated geothermal reservoirs. If the measured desorption isotherm resembles the product.ion characteristics of a geothermal system, understandink of the adsorptlon/desorpcion hysteresis will aid the design of remjection processes. Adsorption/desorption isotherms of both nitro en and water vapor on Berea sandstone and a graywacke sample from 4 e Geyers well NEGU-17 were measured.
Solar Energy 95108189 Absor tlvlty as a predictor of the photolumlnercence spectra of aPllcon aolar cells and photoayntheala S;lTtad, G. P. SolarEnergy Materials& Solar Cells, Aug. 1995,38, (l), - . Experimental photoluminescence spectra obtained for silicon are compared lo predictions made using transmission and reflection data, as well as those using the action (or induced photo-product) spectrum. Although the absorptivity obtained from the optical measurements can be used lo predict much of the photoluminescence curve, the predicted values may deviate from measurements at long wavelengths. The photoluminescence spectrum for Si, and for photosynthesis found in green plants, may also be predicted from action sDectra. Both techniaues vield a reasonable fit IO the exoerimental spectral distribution and tie pr&icted chemical potentials and ;I$ages are consistent with electrical measurements. 95108190 Advances In solar energy - Volume 9 American Solar Energy Society, USA, 1994, $125.00, 495 pp. 95108191 Analytlcal aolutlona for the photocurrant and dark dlffualon current of preferentially doped polyalllcon solar cells Ben Arab, A. Solar Energy Materials& Solar Cells, Jul. 1995, 37, (3), 239-258. A two-dimensional physical model is used in (he analysis of the photovoltaic properties of a preferentially doped polycrystalline silicon solar cell along the grain boundaries. The cell is assumed to have an oriented columnar structure formed by a juxtaposition of silicon ains. A mathematical analysis, based on the superposition principle and t!re technique of separation of variables, is presented. The analysis has allowed the author to obtain analytical expressions for the photocurrents and dark diffusion currents of the horizontal junction and vertical junction of the base region. These expressions are valid for any arbitrary value of the recombination velocitv a1 the grain boundaries. _ 95108192 Band gap and refractive Index determination of Moblack coatings using several techniques :“s”;1”;9;. et al., Solar Energy Materials& Solar Cells, Jul. 1995, 37, (3), The optical energy gap of molybdenum black solar selective absorbing coatings has been estimated by various techniques and the results are compared. For thick absorbing coatings on metallic substrates the band gap has been estimated from reflectance spectra using the Kubelka-Munk function. The band gap of these coatings has also been estimated from transmission spectra obtained from a thin coating specially prepared on semitransparent aluminium coated glass substrates. 95108193 Charge transfer and charge trapplng In zeolltaa and almllar media k&, gg et al., Solar Energy Materials& Solar Cells, Aug. 1995, 38, (l),
-
.
Much work has been published on photo-induced charge transfer in homogeneous and colloidal solutions, and unique photo-systems of direct interest to ‘storage of energy’ have been developed. This paper describes the use of steady states as well as pulse laser photolysis, and pulse radiolysis techniques to investigate charge generation, charge separation, and charge stabilizationin zeolites and in porous silica gel. 95108194 Commsnt on thermodynamic aspects of photochsmlcal solar energy converalon h’;y$ A. J. Solar Energy Materials& Solar Cells, Aug. 1995, 38, (l), - . Two of the major issues discussed at a recent workshop on thermodynamits of photochemical solar energy conversion are summarized in this paper: (1) the effect of hot carrier processes on the thermodynamics of solar photon conversion; (2) the existence of a light-intensity threshold for photoconversion processes and the validity of quasi-Fermi levels.