- Email: [email protected]
03250 An analysis of daylighting and solar heat for cooling-dominated office buildings
07
99103246 Chemical descri tion of spring waters from the Tutupaca and Rio Calientes PPeru) geothermal zones Barrag& R. M. et al. Int. J. Energy Res., 1999, 23, (2), 125-139. Chemical data from 34 spring samples, taken from the Tutupaca and Rio Calientes (Republic of Peru) geothermal zones, were analysed. The main objective of the work was to characterize geothermal resources to be exploited in the future. The investigated zones were: Tutupaca and Rio Calientes-Ancocollo-Challapalca. Thermal waters from Tutupaca showed low pH values and they were classified as sulfate type waters. Thermal springs from the Rio Calientes zone showed almost neutral pH values and they were classified as sodium chloride type waters with a probable geothermal origin. Reservoir temperatures were estimated and the results indicated that water-rock equilibrium in the hydrothermal system was not completely attained. Taking into account the chemical composition of some equilibrated or ‘mature’ waters from the Rio Calientes zone, reservoir temperatures in the range of 210-240°C were estimated. Mixing models based on silica, chloride and specific enthalpy of the samples were used to estimate the composition of the reservoir liquid. Isotopic data showed oxygen-18 shift for the waters from Rio Calientes-Ancocollo regarding the waters from Tutupaca zone which were found on the world meteoric line. Computational methods for planning and 99103247 evaluating geothermal energy projects Goumas, M. G. et al. Enqy Policy, 1999, 27, (3). 147-154. A number of technical, economic, social and environmental parameters should be considered when planning, designing and evaluating a geothermal energy project. The use of computational methods provides a rigorous analysis, improving the decision-making process. This article demonstrates the application of decision-making methods developed in operational research for the optimum exploitation of geothermal resources. Two characteristic problems are considered: (1) the economic evaluation of a geothermal energy project under uncertain conditions using a stochastic analysis approach and (2) the evaluation of alternative exploitation schemes for optimum development of a low enthalpy geothermal field using a multicriteria decision-making procedure. An expanded review and comparison of green99103246 house gas emissions from fossil fuel and geothermal electrical generating facilities Booth, R. B. and Neil, P. E. Proc., Annu. Meet. Air Waste Manage. Assoc., [computer optical disk], 1998, 91, RP10705/1-12. This review covers the greenhouse gas emissions due to fossil fuel and geothermal electric generation and the emissions of their respective support activities, including exploration, development and transportation aspects of the fuel source, including waste management. A single flash integrated gas turbine-geothermal 99103249 power plant with non condensable gas combustion Bidini, G. ei al. Geothermics, 1999, 28, (l), 131-150. In this work the possibility of improving the performance of the 20 MW standard geothermal power plant of ENEL (Italian Electric Power Company) has been studied. The conventional geothermal cycle was modified by adding a gas turbine, an organic Rankine cycle (ORC) and a flash separator. Exhaust heat from the gas turbine is recovered in a geothermal steam superheater and by the ORC. The results of thermodynamic analysis have been applied to a test case based on the Mt. Amiata geothermal field, where geothermal fluid has a water mass fraction ranging from 30 to 50% by weight and approximately 8% by weight of the steam fraction is non condensable gases (NCG). The non-condensable gases are a mixture of CO* (about 95% by weight), HzS, Hz, Hg, NH3 and CH+ Legislation on the emission of some of these substances into the atmosphere means that geothermal power plants are now equipped with gas clean-up devices but these increase the plant capital costs and reduce performance. Some of the components contained in the NCG, however, such as HzS, Hz and CHI, have an acceptable lower heating value (LHV) and can be considered as a source of energy. Hence, they could be burned to reduce their environmental impact while recovering energy that would otherwise be lost. In the power plant presented in this paper, NCG are mixed with inlet air in the gas turbine and burnt in the combustion chamber, thus helping to increase hybrid cycle performance.
Solar Energy 99lQ3250 An analysis of daylighting and solar heat for cooling-dominated office buildings Lam, J. C. and Li, D. H. W. Solar Energy, 1999, 65, (4), 251-262. In assessing the energy performance of a generic commercial office building in Hong Kong, computer simulation techniques were used. The simulation tool was DOE-2.lE. The thermal and energy performance of daylighting schemes were analysed in terms of the reduction in electric lighting requirement and the cooling penalty due to solar heat. Regression analysis was conducted to correlate the peak electricity demand and annual incremental electricity use with two fenestration variables, namely the solar aperture and the daylighting aperture. Contours of equal annual incremental electricity use were shown to be a function of the solar and
Alternative
energy sources (solar energy)
daylighting apertures. It is envisaged that these simple charts can be a useful design tool for architects and engineers to assess the relative energy performance of different fenestration designs, particularly during the initial design stage when different building design schemes and concepts are being considered and developed. Characterisation of high-temperature-resistant selective paints for solar absorbers Solar Energy Materials and Solar Cells, 1999, 57, (3), 291-301. Organically modified siloxane resin and inorganic pigment (FeMnCuO,P320) were used to prepare the spectrally selective paint coatings. In order to optimize the low-emittance properties, different thickness of paints were applied on high-reflecting aluminium foil by a draw bar coater. For all paints, optical and thermal properties were determined in addition to their adhesion resistance. Pigment to volume concentration ratio was 20% and, for thickness of about 1.7-2.0 g/m’, the solar absorptance for these samples were ar= 0.90-0.92 with corresponding thermal emittance of eT = 0.200.25. Temperature stability of these samples was followed by FT-IR spectroscopy at 300°C. The obtained results indicated good temperature stability of prepared paint coatings. 99103252 Characteristics of solar water pumping in Jordan Hammad, M. A. Energy, 1999, 24, (2), 85-92. Remote underground water wells were investigated and 13 such wells were chosen for this study. Photovoltaic (PV) generators were used to power pumping the water up to the surface tanks to be used. A design method was established and illustrated depending on a pumping factor (Fp) which is a function of the solar characteristics. A laboratory solar water pumping unit was constructed and year round results were analysed. Monthly F, values were calculated from the experimental results. 99103253 Comparative performances of ‘tower-top’ and ‘tower-reflector’ central solar receivers Segal, A. and Epstein, M. Solar Energy, 1999, 65, (4), 207-226. An analysis was conducted on the optics of various types of solar tower configurations and receivers. The power values that are finally available for the process, for a given field and different optical arrangements at specified operating temperatures (above 1100 K), are compared. At these temperatures the use of secondary concentrators placed in front of the receivers is peremptorily justified from optical and energetical points of view. Also presented is a model for calculating the efficiencies of central solar receivers with secondary concentrators. This model permits the optimization of these secondary concentrators taking into account the different losses of real devices. The effect of heliostat field density and the performance of ‘tower-top’ and ‘tower-reflector’ solar plants are discussed and a comparison is made. Construction and operational experience of a 6000 99103254 m2 solar pond at Kutch, India Kumar, A. and Kishore, V. V. N. Solar Energy, 1999, 65, (4), 237-249. In order to supply process heat and demonstrate the technical and economic viability of solar pond technology in the Indian context, a 6000 m* solar pond was constructed at Bhuj in India in the premises of a milk processing dairy plant. An inexpensive lining scheme, consisting of alternating layers of clay and LDPE (low density polyethylene) combination was used for lining the pond. The pond attained a maximum temperature of 99.8”C under stagnation in May 1991 but developed leakage soon after. A failure analysis that was carried out subsequently indicated that the leakage was caused by the combination of high stagnation temperature and large air pockets below the liner. The lining scheme was re-designed and the pond re-established in June 1993. Hot water supply to the dairy started in September 1993 and continued until April 1995. After an interruption of nearly one year, hot water was resumed in August 1996. The total cost of construction of the Bhuj Solar Pond was USS90,OOO (1997 prices), includin! heat exchanger and piping etc., corresponding to a unit cost of IJS$15 mm 99lO3255 Design of hybrid-photovoltaic power generator, with optimization of energy management Muselli, M. et al. Solar Energv, 1999, 65, (3), 143-157. A methodology is developed for calculating the correct size of a photovoltaic (PV)-hybrid system and for optimizing its management. The power for the hybrid system comes from PV panels and an engine-generator - that is, a gasoline or diesel engine driving an electrical generator. The combined system is a stand-alone or autonomous system, in the sense that no third energy source is brought in to meet the load. Two parameters were used to characterize the role of the engine-generator: denoted SDM and SAR, they are, respectively, the battery charge threshold at which it is started up and the storage capacity threshold at which it is stopped, both expressed as a percentage of the nominal battery storage capacity. The methodology developed is applied to designing a PV-hybrid system operating in Corsica, as a case study. Various sizing configurations were simulated and the optimal configuration that meets the autonomy constraint (no loss of load) was determined, by minimizing of the energy cost. The influence of the battery storage capacity on the solar contribution is also studied. The smallest energy cost per kWh was obtained for a system characterized by an SDM = 30% and an SAR = 70%. A study on the effects of component lifetimes on the economics of PV-hybrid and PV stand-alone systems has shown that battery size can be reduced by a factor of two in PV-hybrid systems, as compared to PV stand-alone systems.
Fuel and Energy Abstracts
September
1999
341
99103246 Chemical descri tion of spring waters from the Tutupaca and Rio Calientes PPeru) geothermal zones Barrag& R. M. et al. Int. J. Energy Res., 1999, 23, (2), 125-139. Chemical data from 34 spring samples, taken from the Tutupaca and Rio Calientes (Republic of Peru) geothermal zones, were analysed. The main objective of the work was to characterize geothermal resources to be exploited in the future. The investigated zones were: Tutupaca and Rio Calientes-Ancocollo-Challapalca. Thermal waters from Tutupaca showed low pH values and they were classified as sulfate type waters. Thermal springs from the Rio Calientes zone showed almost neutral pH values and they were classified as sodium chloride type waters with a probable geothermal origin. Reservoir temperatures were estimated and the results indicated that water-rock equilibrium in the hydrothermal system was not completely attained. Taking into account the chemical composition of some equilibrated or ‘mature’ waters from the Rio Calientes zone, reservoir temperatures in the range of 210-240°C were estimated. Mixing models based on silica, chloride and specific enthalpy of the samples were used to estimate the composition of the reservoir liquid. Isotopic data showed oxygen-18 shift for the waters from Rio Calientes-Ancocollo regarding the waters from Tutupaca zone which were found on the world meteoric line. Computational methods for planning and 99103247 evaluating geothermal energy projects Goumas, M. G. et al. Enqy Policy, 1999, 27, (3). 147-154. A number of technical, economic, social and environmental parameters should be considered when planning, designing and evaluating a geothermal energy project. The use of computational methods provides a rigorous analysis, improving the decision-making process. This article demonstrates the application of decision-making methods developed in operational research for the optimum exploitation of geothermal resources. Two characteristic problems are considered: (1) the economic evaluation of a geothermal energy project under uncertain conditions using a stochastic analysis approach and (2) the evaluation of alternative exploitation schemes for optimum development of a low enthalpy geothermal field using a multicriteria decision-making procedure. An expanded review and comparison of green99103246 house gas emissions from fossil fuel and geothermal electrical generating facilities Booth, R. B. and Neil, P. E. Proc., Annu. Meet. Air Waste Manage. Assoc., [computer optical disk], 1998, 91, RP10705/1-12. This review covers the greenhouse gas emissions due to fossil fuel and geothermal electric generation and the emissions of their respective support activities, including exploration, development and transportation aspects of the fuel source, including waste management. A single flash integrated gas turbine-geothermal 99103249 power plant with non condensable gas combustion Bidini, G. ei al. Geothermics, 1999, 28, (l), 131-150. In this work the possibility of improving the performance of the 20 MW standard geothermal power plant of ENEL (Italian Electric Power Company) has been studied. The conventional geothermal cycle was modified by adding a gas turbine, an organic Rankine cycle (ORC) and a flash separator. Exhaust heat from the gas turbine is recovered in a geothermal steam superheater and by the ORC. The results of thermodynamic analysis have been applied to a test case based on the Mt. Amiata geothermal field, where geothermal fluid has a water mass fraction ranging from 30 to 50% by weight and approximately 8% by weight of the steam fraction is non condensable gases (NCG). The non-condensable gases are a mixture of CO* (about 95% by weight), HzS, Hz, Hg, NH3 and CH+ Legislation on the emission of some of these substances into the atmosphere means that geothermal power plants are now equipped with gas clean-up devices but these increase the plant capital costs and reduce performance. Some of the components contained in the NCG, however, such as HzS, Hz and CHI, have an acceptable lower heating value (LHV) and can be considered as a source of energy. Hence, they could be burned to reduce their environmental impact while recovering energy that would otherwise be lost. In the power plant presented in this paper, NCG are mixed with inlet air in the gas turbine and burnt in the combustion chamber, thus helping to increase hybrid cycle performance.
Solar Energy 99lQ3250 An analysis of daylighting and solar heat for cooling-dominated office buildings Lam, J. C. and Li, D. H. W. Solar Energy, 1999, 65, (4), 251-262. In assessing the energy performance of a generic commercial office building in Hong Kong, computer simulation techniques were used. The simulation tool was DOE-2.lE. The thermal and energy performance of daylighting schemes were analysed in terms of the reduction in electric lighting requirement and the cooling penalty due to solar heat. Regression analysis was conducted to correlate the peak electricity demand and annual incremental electricity use with two fenestration variables, namely the solar aperture and the daylighting aperture. Contours of equal annual incremental electricity use were shown to be a function of the solar and
Alternative
energy sources (solar energy)
daylighting apertures. It is envisaged that these simple charts can be a useful design tool for architects and engineers to assess the relative energy performance of different fenestration designs, particularly during the initial design stage when different building design schemes and concepts are being considered and developed. Characterisation of high-temperature-resistant selective paints for solar absorbers Solar Energy Materials and Solar Cells, 1999, 57, (3), 291-301. Organically modified siloxane resin and inorganic pigment (FeMnCuO,P320) were used to prepare the spectrally selective paint coatings. In order to optimize the low-emittance properties, different thickness of paints were applied on high-reflecting aluminium foil by a draw bar coater. For all paints, optical and thermal properties were determined in addition to their adhesion resistance. Pigment to volume concentration ratio was 20% and, for thickness of about 1.7-2.0 g/m’, the solar absorptance for these samples were ar= 0.90-0.92 with corresponding thermal emittance of eT = 0.200.25. Temperature stability of these samples was followed by FT-IR spectroscopy at 300°C. The obtained results indicated good temperature stability of prepared paint coatings. 99103252 Characteristics of solar water pumping in Jordan Hammad, M. A. Energy, 1999, 24, (2), 85-92. Remote underground water wells were investigated and 13 such wells were chosen for this study. Photovoltaic (PV) generators were used to power pumping the water up to the surface tanks to be used. A design method was established and illustrated depending on a pumping factor (Fp) which is a function of the solar characteristics. A laboratory solar water pumping unit was constructed and year round results were analysed. Monthly F, values were calculated from the experimental results. 99103253 Comparative performances of ‘tower-top’ and ‘tower-reflector’ central solar receivers Segal, A. and Epstein, M. Solar Energy, 1999, 65, (4), 207-226. An analysis was conducted on the optics of various types of solar tower configurations and receivers. The power values that are finally available for the process, for a given field and different optical arrangements at specified operating temperatures (above 1100 K), are compared. At these temperatures the use of secondary concentrators placed in front of the receivers is peremptorily justified from optical and energetical points of view. Also presented is a model for calculating the efficiencies of central solar receivers with secondary concentrators. This model permits the optimization of these secondary concentrators taking into account the different losses of real devices. The effect of heliostat field density and the performance of ‘tower-top’ and ‘tower-reflector’ solar plants are discussed and a comparison is made. Construction and operational experience of a 6000 99103254 m2 solar pond at Kutch, India Kumar, A. and Kishore, V. V. N. Solar Energy, 1999, 65, (4), 237-249. In order to supply process heat and demonstrate the technical and economic viability of solar pond technology in the Indian context, a 6000 m* solar pond was constructed at Bhuj in India in the premises of a milk processing dairy plant. An inexpensive lining scheme, consisting of alternating layers of clay and LDPE (low density polyethylene) combination was used for lining the pond. The pond attained a maximum temperature of 99.8”C under stagnation in May 1991 but developed leakage soon after. A failure analysis that was carried out subsequently indicated that the leakage was caused by the combination of high stagnation temperature and large air pockets below the liner. The lining scheme was re-designed and the pond re-established in June 1993. Hot water supply to the dairy started in September 1993 and continued until April 1995. After an interruption of nearly one year, hot water was resumed in August 1996. The total cost of construction of the Bhuj Solar Pond was USS90,OOO (1997 prices), includin! heat exchanger and piping etc., corresponding to a unit cost of IJS$15 mm 99lO3255 Design of hybrid-photovoltaic power generator, with optimization of energy management Muselli, M. et al. Solar Energv, 1999, 65, (3), 143-157. A methodology is developed for calculating the correct size of a photovoltaic (PV)-hybrid system and for optimizing its management. The power for the hybrid system comes from PV panels and an engine-generator - that is, a gasoline or diesel engine driving an electrical generator. The combined system is a stand-alone or autonomous system, in the sense that no third energy source is brought in to meet the load. Two parameters were used to characterize the role of the engine-generator: denoted SDM and SAR, they are, respectively, the battery charge threshold at which it is started up and the storage capacity threshold at which it is stopped, both expressed as a percentage of the nominal battery storage capacity. The methodology developed is applied to designing a PV-hybrid system operating in Corsica, as a case study. Various sizing configurations were simulated and the optimal configuration that meets the autonomy constraint (no loss of load) was determined, by minimizing of the energy cost. The influence of the battery storage capacity on the solar contribution is also studied. The smallest energy cost per kWh was obtained for a system characterized by an SDM = 30% and an SAR = 70%. A study on the effects of component lifetimes on the economics of PV-hybrid and PV stand-alone systems has shown that battery size can be reduced by a factor of two in PV-hybrid systems, as compared to PV stand-alone systems.
Fuel and Energy Abstracts
September
1999
341