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03778 Technical large-scale test of cocombustion of biomass in a brown coal-fired power plant
07
Alternative
energy sources (solar energy)
compared with those of Dunaliellu ferriolecta; therefore, the energy inputs for cultivation and separation of E. braunii were calculated to be smaller than those of D. rerfiolecta. The energy input for fertilizers of B. braunii was also smaller than that of D. tertiolecfa. Based on these differences, the to produce net liquefaction process using B. braunii was suggested renewable energy, but not that with D. rertiolecta. If a 100 MW thermal plant using coal would be replaced by liquid fuelproduce,d from B. braunii, the quantity of COz mitigation could be 1.5 x l@ t year and 8.4 x 10’ ha of microalgal cultivation area could be necessary.
kerosene, liquid petroleum gas and electricity for cooking. Agricultural residues are used to start and support wood combustion; animal residues are not used as cooking fuels.
99103777 Reactivities of some biomass chars in air Di Blasi, C. D. et al. Carbon, 1999, 37, (8) 1227-1238. Biomass chars obtained using conventional pyrolysis were investigated with regard to their reactivities in air for applications in fixed-bed gasification. Biomasses considered are wheat straw, olive husks and grape residues. Char particles are spread to form a 150 /irn thick layer and are radiatively heated, to achieve a kinetically controlled conversion. Time-weight loss curves, determined under non-isothermal conditions (heating rates of 10 K/min and a final temperature of 873 K), indicate that the reactivity continuously increases with conversion. The olive husk chars present the highest value, whereas that of grape residue chars is the least. All biomass chars are also combusted at different heating rates, so that conversion consists of a dynamic stage, followed by an isothermal period. Again, grape residue chars are the least reactive. Furthermore, the reactivity first attains a maximum, decreases or remains almost constant and then increases again as a function of conversion. This behaviour can be explained by the different roles played by the reaction temperature, the development of surface area as combustion proceeds and the increase in the ratio of ashes to carbon. Finally, the weight loss curves are well interpreted by a one-step global reaction, whose rate presents a power law dependence on the solid conversion and activation energies in the range 75-94 kJ/mol.
99103782
99103778
Technical lar e-scale test of cocombustion of biomass in a brown coal- Plred power plant
Schmidt, W. and Dietl, R. L’GB Kraftwerkstech., 1999, 79, (4) 76-81. (In German) Co-combustion tests with biomass were conducted in the lignite-fired power plant Schwandorf, Germany, to investigate the influence of biomass on operational behaviour of the steam generator and fuel handling. The cocombustion of a biomass of up to 10% is technically feasible if various procedure-related basic conditions are taken into consideration. Major changes in the operating conditions were not revealed by the tests compared to an operation with lignite only. Emissions of dioxins and furans (PCDDIF) increased in the long-term test to a value slightly above detection limit. 99103779
Temperature effect on continuous gasification of microalgal biomass: theoretical yield of methanol production and its energy balance
Hirano, A. et al. Catal. Today, 1998, 45, (l-4) 399-404. Spirulina, a microalga, was partially oxidized at temperatures of 8SO”C, 950°C and 1000°C and the composition of produced gas was determined in order to evaluate the theoretical yield of methanol from the gas. Dependent on temperature, the gas composition at 1000°C gave the highest theoretical yield of 0.64 g methanol from 1 g of the biomass. Based on this yield, the total energy requirement for the whole process including the microalgal biomass production and conversion into methanol was obtained. Energy balance, which was defined as the ratio of the energy of methanol produced to the total required energy, was 1.1, which indicates that this process was plausible as an energy producing process. The greater part of the total required energy, almost four-fifths, was consumed with the microalgal biomass production, suggesting that more efficient production of microalgal biomass might greatly improve its energy balance.
Thermal analysis kinetics of bagasse and rice straw 99103780 Nassar, M. M. Energy Sources, 1998, 20, (9), 831-837. The author studied the role of added inorganic salt on the thermal degradation of lignin. The result was compared with the thermal analysis of two types of agricultural residues: rice straw with high silica content and bagasse with low silica. Thermal decomposition of such materials is faster than that of wood with a dual mechanism concept similar to wood. In general, the activation energy for rice straw is low, about 19.3 kcalimol, while that of bagasse is 33.4 kcabmol. This proves that the inorganic material, either inherited or added, changed the thermal activities of the lignocellulosic materials.
Geothermal
Energy
Economic evaluation of geothermal power generation, heating, and cooling
Kanoglu, M. and Cengel, Y. A. Energy, 1999, 24, (6) 501-509. Economic analysis of a typical geothermal resource shows that potential revenues from geothermal heating or cooling can be much larger than those from power generation alone. Geothermal heating may generate up to about 3.1 times and geothermal absorption cooling 2.9 times as much revenue as power generation alone. Similarly, combined power generation and heating may generate about 2.1 times and combined power generation and cooling about 1.2 times as much revenue as power generation alone. Cost and payback period comparisons appear to favour power generation, followed by district heating.
Solar Energy 99103783
Approximate method for computation of glass cover temperature and top heat-loss coefficient of solar collectors with single glazing
Akhtar, N. and Mullick, S. C. Solar Energy, 1999, 66, (5), 349-354. An improved equation form for computing the glass cover temperature of flat-plate solar collectors with single glazing is developed. A semi-analytical correlation for the factor f, the ratio of inner to outer heat-transfer coefficients, as a function of collector parameters and atmospheric variables is obtained by regression analysis. This relation readily provides the glass (TJ The results are compared with those obtained by cover temperature numerical solution of heat balance equations. Computational errors in Tg and hence in the top heat loss coefficient ((I,) are reduced by a factor of five or more. With such low errors in computation of T& and U,, a numerical solution of heat balance equations is not required. The method is applicable over an extensive range of variables: the error in the computation of U, is within 2% with the range of air gap spacing 8 mm to 90 mm and the range of ambient temperature 0 to 45°C. In this extended range of variables the errors due to simplified method based on empirical relations for U, are substantially higher.
Assessment of uncertainty in solar collector modeling and testing
99103784
Mathioulakis, F. et al. Solar Energy, 1999, 66, (5) 337-348. The basic scope of solar collector testing is the determination of the collector efficiency by conducting measurements under specific conditions defined by international standards. The experimental results of testing lead to determination of the parameters of a more or less complex model, usually a 2- or 3-parameter single node steady-state model, which describes the collector behaviour. In the present study, a systematic analysis of the contribution of all the uncertainty components on the basis of the IS0 9806-l test procedure is carried out in order to determine the final uncertainty in the characteristic equation parameters and the instantaneous efficiency of the collector. A step-by-step methodology, based on specific statistical tools, for evaluation of the suitability of the collector models already in use, is proposed. This methodology not only allows an evaluation of the reliability of the testing procedure itself, but also a quantification of the goodness-of-fit. Furthermore, if the uncertainty in the characteristic equation parameters is known, the uncertainty in the collector instantaneous efficiency to be predicted can be assessed. This is essential for the reliability of the results of design tools, for which collector efficiency is a key parameter. 99103785 Catalyst application in solar thermochemistry Kirillov, V. A. Solar Energy, 1999, 66, (2), 143-149. A comprehensive survey on the current state of catalyst applications in the field of solar energy transformation and storage is presented.
99103787
Urban and rural fuelwood situation in the tropical rain-forest area of south-west Nigeria
99103788
Kersten, 1. et al. Energy, 1998, 23, (lo), 887-898. A survey comprising 1120 questionnaires was conducted in 1995 in the urban and rural rain-forests of Be-Ife, Osun State, Nigeria. The subject was the use of fuel for cooking. The biofuel burning in Africa was assessed, in particular, and in tropical countries, in general. Included are discussions of socio-economic conditions, descriptions of the types and numbers of stoves, fuel and combustion characteristics, specific fuel consumption in both the private and commercial sectors, fuel sources and their availability and health effects caused by cooking with firewood. Wood usage is greater for low-income groups than for better situated householders who utilize
Rothenberger, G. er al. Solar Energy Materials & Solar Cells, 1999, 58, (3) 321-336. The absorption of a large fraction of the incident solar radiation by the photoactive layer of dye-sensitized, liquid-junction photovoltaic cells is an important factor for achieving useful photoelectric conversion efficiencies. A model is presented that estimates the enhancement of optical absorption that can be obtained from light scattering in the porous nanocrystalline films used in these cells and from reflection at the back electrode. The model is applied to the optical characterization of two films, a transparent and a strongly scattering porous titania sample.
398
Fuel
and
Energy
Abstracts
November 7999
A contribution to the optical design of dyesensitized nanocrystalline solar cells
Alternative
energy sources (solar energy)
compared with those of Dunaliellu ferriolecta; therefore, the energy inputs for cultivation and separation of E. braunii were calculated to be smaller than those of D. rerfiolecta. The energy input for fertilizers of B. braunii was also smaller than that of D. tertiolecfa. Based on these differences, the to produce net liquefaction process using B. braunii was suggested renewable energy, but not that with D. rertiolecta. If a 100 MW thermal plant using coal would be replaced by liquid fuelproduce,d from B. braunii, the quantity of COz mitigation could be 1.5 x l@ t year and 8.4 x 10’ ha of microalgal cultivation area could be necessary.
kerosene, liquid petroleum gas and electricity for cooking. Agricultural residues are used to start and support wood combustion; animal residues are not used as cooking fuels.
99103777 Reactivities of some biomass chars in air Di Blasi, C. D. et al. Carbon, 1999, 37, (8) 1227-1238. Biomass chars obtained using conventional pyrolysis were investigated with regard to their reactivities in air for applications in fixed-bed gasification. Biomasses considered are wheat straw, olive husks and grape residues. Char particles are spread to form a 150 /irn thick layer and are radiatively heated, to achieve a kinetically controlled conversion. Time-weight loss curves, determined under non-isothermal conditions (heating rates of 10 K/min and a final temperature of 873 K), indicate that the reactivity continuously increases with conversion. The olive husk chars present the highest value, whereas that of grape residue chars is the least. All biomass chars are also combusted at different heating rates, so that conversion consists of a dynamic stage, followed by an isothermal period. Again, grape residue chars are the least reactive. Furthermore, the reactivity first attains a maximum, decreases or remains almost constant and then increases again as a function of conversion. This behaviour can be explained by the different roles played by the reaction temperature, the development of surface area as combustion proceeds and the increase in the ratio of ashes to carbon. Finally, the weight loss curves are well interpreted by a one-step global reaction, whose rate presents a power law dependence on the solid conversion and activation energies in the range 75-94 kJ/mol.
99103782
99103778
Technical lar e-scale test of cocombustion of biomass in a brown coal- Plred power plant
Schmidt, W. and Dietl, R. L’GB Kraftwerkstech., 1999, 79, (4) 76-81. (In German) Co-combustion tests with biomass were conducted in the lignite-fired power plant Schwandorf, Germany, to investigate the influence of biomass on operational behaviour of the steam generator and fuel handling. The cocombustion of a biomass of up to 10% is technically feasible if various procedure-related basic conditions are taken into consideration. Major changes in the operating conditions were not revealed by the tests compared to an operation with lignite only. Emissions of dioxins and furans (PCDDIF) increased in the long-term test to a value slightly above detection limit. 99103779
Temperature effect on continuous gasification of microalgal biomass: theoretical yield of methanol production and its energy balance
Hirano, A. et al. Catal. Today, 1998, 45, (l-4) 399-404. Spirulina, a microalga, was partially oxidized at temperatures of 8SO”C, 950°C and 1000°C and the composition of produced gas was determined in order to evaluate the theoretical yield of methanol from the gas. Dependent on temperature, the gas composition at 1000°C gave the highest theoretical yield of 0.64 g methanol from 1 g of the biomass. Based on this yield, the total energy requirement for the whole process including the microalgal biomass production and conversion into methanol was obtained. Energy balance, which was defined as the ratio of the energy of methanol produced to the total required energy, was 1.1, which indicates that this process was plausible as an energy producing process. The greater part of the total required energy, almost four-fifths, was consumed with the microalgal biomass production, suggesting that more efficient production of microalgal biomass might greatly improve its energy balance.
Thermal analysis kinetics of bagasse and rice straw 99103780 Nassar, M. M. Energy Sources, 1998, 20, (9), 831-837. The author studied the role of added inorganic salt on the thermal degradation of lignin. The result was compared with the thermal analysis of two types of agricultural residues: rice straw with high silica content and bagasse with low silica. Thermal decomposition of such materials is faster than that of wood with a dual mechanism concept similar to wood. In general, the activation energy for rice straw is low, about 19.3 kcalimol, while that of bagasse is 33.4 kcabmol. This proves that the inorganic material, either inherited or added, changed the thermal activities of the lignocellulosic materials.
Geothermal
Energy
Economic evaluation of geothermal power generation, heating, and cooling
Kanoglu, M. and Cengel, Y. A. Energy, 1999, 24, (6) 501-509. Economic analysis of a typical geothermal resource shows that potential revenues from geothermal heating or cooling can be much larger than those from power generation alone. Geothermal heating may generate up to about 3.1 times and geothermal absorption cooling 2.9 times as much revenue as power generation alone. Similarly, combined power generation and heating may generate about 2.1 times and combined power generation and cooling about 1.2 times as much revenue as power generation alone. Cost and payback period comparisons appear to favour power generation, followed by district heating.
Solar Energy 99103783
Approximate method for computation of glass cover temperature and top heat-loss coefficient of solar collectors with single glazing
Akhtar, N. and Mullick, S. C. Solar Energy, 1999, 66, (5), 349-354. An improved equation form for computing the glass cover temperature of flat-plate solar collectors with single glazing is developed. A semi-analytical correlation for the factor f, the ratio of inner to outer heat-transfer coefficients, as a function of collector parameters and atmospheric variables is obtained by regression analysis. This relation readily provides the glass (TJ The results are compared with those obtained by cover temperature numerical solution of heat balance equations. Computational errors in Tg and hence in the top heat loss coefficient ((I,) are reduced by a factor of five or more. With such low errors in computation of T& and U,, a numerical solution of heat balance equations is not required. The method is applicable over an extensive range of variables: the error in the computation of U, is within 2% with the range of air gap spacing 8 mm to 90 mm and the range of ambient temperature 0 to 45°C. In this extended range of variables the errors due to simplified method based on empirical relations for U, are substantially higher.
Assessment of uncertainty in solar collector modeling and testing
99103784
Mathioulakis, F. et al. Solar Energy, 1999, 66, (5) 337-348. The basic scope of solar collector testing is the determination of the collector efficiency by conducting measurements under specific conditions defined by international standards. The experimental results of testing lead to determination of the parameters of a more or less complex model, usually a 2- or 3-parameter single node steady-state model, which describes the collector behaviour. In the present study, a systematic analysis of the contribution of all the uncertainty components on the basis of the IS0 9806-l test procedure is carried out in order to determine the final uncertainty in the characteristic equation parameters and the instantaneous efficiency of the collector. A step-by-step methodology, based on specific statistical tools, for evaluation of the suitability of the collector models already in use, is proposed. This methodology not only allows an evaluation of the reliability of the testing procedure itself, but also a quantification of the goodness-of-fit. Furthermore, if the uncertainty in the characteristic equation parameters is known, the uncertainty in the collector instantaneous efficiency to be predicted can be assessed. This is essential for the reliability of the results of design tools, for which collector efficiency is a key parameter. 99103785 Catalyst application in solar thermochemistry Kirillov, V. A. Solar Energy, 1999, 66, (2), 143-149. A comprehensive survey on the current state of catalyst applications in the field of solar energy transformation and storage is presented.
99103787
Urban and rural fuelwood situation in the tropical rain-forest area of south-west Nigeria
99103788
Kersten, 1. et al. Energy, 1998, 23, (lo), 887-898. A survey comprising 1120 questionnaires was conducted in 1995 in the urban and rural rain-forests of Be-Ife, Osun State, Nigeria. The subject was the use of fuel for cooking. The biofuel burning in Africa was assessed, in particular, and in tropical countries, in general. Included are discussions of socio-economic conditions, descriptions of the types and numbers of stoves, fuel and combustion characteristics, specific fuel consumption in both the private and commercial sectors, fuel sources and their availability and health effects caused by cooking with firewood. Wood usage is greater for low-income groups than for better situated householders who utilize
Rothenberger, G. er al. Solar Energy Materials & Solar Cells, 1999, 58, (3) 321-336. The absorption of a large fraction of the incident solar radiation by the photoactive layer of dye-sensitized, liquid-junction photovoltaic cells is an important factor for achieving useful photoelectric conversion efficiencies. A model is presented that estimates the enhancement of optical absorption that can be obtained from light scattering in the porous nanocrystalline films used in these cells and from reflection at the back electrode. The model is applied to the optical characterization of two films, a transparent and a strongly scattering porous titania sample.
398
Fuel
and
Energy
Abstracts
November 7999
A contribution to the optical design of dyesensitized nanocrystalline solar cells