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01296 Optimal PWM-SHE switching on NPC inverter: a winning match for high power conversion
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Optimal PWM-SHE switching on NPC inverter: a 99101296 winning match for high power conversion Maswood, A. I. Electric Power Systems Research, 1998, 48, (1) 19-24. This paper provides a simple yet very effective method of real-time on-line solution for the pulsewidth modulation specific harmonic elimination (PWM-SHE) technique that readily accommodates the elimination of a particular set of harmonics. Piece-wise linear representations of PWM-SHE switching angles are utilized to formulate the on-line linear equations. A detailed analysis of linearization and on-line capability of an optimized PWM-SHE technique is described. A neutral point clamped (NPC) inverter configuration is chosen. For high power conversion, application of the PWM-SHE switching pattern to the NPC inverter yields substantially low switching losses with excellent output voltage/current waveform.
Optimal unit sizing of fuel cell cogeneration sys99101297 tems in consideration of performance degradation
Ito, K. et al. Energy Research, 1998, 22, (12), 1075-1089. A system’s economy is influenced by the life of a cell stack due to performance degradation. This paper explores this subject by investigating unit sizing of fuel cell co-generation systems. An optimal unit sizing method proposed by the authors is extended to this case so that it enables the life and performance degradation of the cell stack to be considered. Equipment capacities and maximum contract demands of utilities such as electricity and natural gas are determined so as to minimize the annual total cost levelled for a whole planning period based on the annualized costs method whilst considering operational strategies which change with performance degradation of the cell stack. Numerical studies were carried out for normally and highly pressurized phosphoric acid fuel cell co-generation systems installed in two urban areas. It was found that the life of the cell stack greatly influences system economics and equipment capacities.
Particle-size effect of carbon powders on the discharge capacity of lithium ion batteries
99101296
Sato, Y. et al. Journal of Power Sources, 1998, 75, (2), 271-277. A study has been made of the particle-size effect of carbon powder on discharge capacity in order to improve the performance of the negative electrodes for lithium-ion batteries. Also, the optimum mixing ratio between large (average diameter: 25.8 pm) and small (average diameter: 4.2 /Irn) powder particle size has been found. The largest capacity is obtained when the large particle size fraction is about 70 wt%. The smaller the particle size ratio, the larger the capacity, where the particle size ratio is the ratio of the average diameter of the smaller component to that of the larger one. The results obtained in this study indicate that discharge capacity is closely related to carbon powder packing.
Performance and life of lo-kW molten-carbonate 99101299 fuel cell stack using LilK and LilNa carbonates as the electrolyte Mugikura, Y. et al. Journal of Power Sources, 1998, 75, (l), 108-115. In molten carbonate fuel cells (MCFC), NiO cathode dissolution is a serious problem. The target life-time of such cells is 40,000 h, but shorting by NiO cathode dissolution markedly decreases cell performance. NiO cathode dissolution depends on the composition of the molten carbonate electrolyte. The electrolyte generally comprises a mixture of lithium carbonate and potassium carbonate. Since the solubility of NiO in a mixture of lithium carbonate and sodium carbonate is lower than in lithium and potassium carbonate, it is expected that shorting by NiO cathode dissolution will take longer in a mixture of lithium and sodium. Therefore, a mixture of lithium carbonate and sodium carbonate is a strong candidate for the electrolyte. A unique 10 kW class stack, which uses a mixture of lithium and potassium carbonate and mixture of lithium and sodium carbonate as the electrolyte, has been developed and tested. The basic performance and life time of both electrolyte cells of the stack are reported.
Performance of planar single cell lanthanum gallate based solid oxide fuel cells
99iO13QO
Maffei, N. and Kuriakose, A. K. Journal of Power Sources, 1998, 75, (l), 162-166. This paper describes a novel synthesis of high purity, single phase strontium-magnesium doped lanthanum gallate through a nitrate route. The prepared powder is formed into planar monolithic elements by uniaxial pressing followed by isostatic pressing and sintering. XRD analysis of the sintered elements reveal no detectable secondary phases. A report is given on the performance of the electrolyte in solid oxide fuel cells (SOFC) with three different anode/cathode combinations tested at 700°C with respect to the J-V and power density. The data show that the characteristics of this SOFC are strongly dependent on the particular anode/cathode system chosen.
99lO1301 0 system
Phase stability of the mixed-conducting Sr-Fe-Co-
Ma, B. et al. Mater. Res. Sot. Symp. Proc., 1998, 496, 167-172. In high-temperature electrochemical applications (such as solid oxide fuel cells, batteries, sensors and oxygen-permeable membranes), mixed-conducting ceramic oxides have potential uses. The strontium-iron-cobaltoxygen system combines high electronic/ionic conductivity with appreciable oxygen permeability at elevated temperatures. Dense ceramic membranes made from this material can be used to separate high-purity oxygen from air without the need for external electric circuitry, or to partially oxidize methane to produce syngas. Samples of Sr,Fes_,Co,O, (with x = 0, 0.6, 1.0
Electrical power supply and utilization (scientific, technical)
and 1.4) were prepared by solid-state reaction method in atmospheres with various oxygen partial pressures (~0~) and were characterized by X-ray diffraction, SEM and electric conductivity testing. Phase components of the sample were dependent pOz and cobalt concentration. Electric conductivity increases with increasing temperature and cobalt content in the material. 99101302 Polymer-oxide anode materials Kerr, T. A. et al. Mater. Res. Sot. Symp. Proc., 1998, 496, 499-504. the amino derivative form of the conductive polymer poly(p-phenylene) (PPPNHz) was inserted within the van der Waals gap of molybdenum trioxide by exploiting its adaptable layer structure. Two polymer insertion routes were designed that yield novel PPPNHz-Moos materials of different compositions. Characterization of these materials using powder X-ray diffraction (XRD), thermal analysis and Fourier transfer infrared spectroscopy (FTIR) showed insertion of the polymer had occurred. The properties of the nanocomposites for low potential electrochemical lithium insertion were compared to those of the sodium molybdenum bronze using the materials as cathodes in conventional lithium cells. Initial results indicate the specific charge capacity and irreversibility during the first charge are effected by polymer content whereas polarization is not.
99101303 Probabilistic production simulation including combined heat and power plants
Larsen, H. V. et al. Electric Power Systems Research, 1998, 48, (l), 45-56. Simulation tools for estimating key indicators for decision making are required for expansion planning of combined heat and power (CHP) systems. Probability production simulation techniques have been used extensively for power systems. These techniques have been extended to include CHP systems with a single heat area and back-pressure type CHP units. This paper extends existing simulation methods for CHP to include extraction power plants. Further, the case of multiple heat areas is addressed and three different simulation strategies are presented for such systems. The results show that an assumption of perfectly correlated heat demands in all heat areas gives results that are very similar to a general case, whereas working with a system with all heat areas aggregated into one gives rather poor results. This paper shows that it is possible to use the traditional concepts and methods for power-only analysis on a CHP system. Additional concepts are presented, depending on the heat criterion applied. Probabilistic production simulation including CHP units can be performed with reasonable effort and accuracy.
Procedure and system for removal of leakage gas from coke-oven batteries
99101304
Moessner, F. and Toll, H. Ger. Offen. DE 19,700,768 (Cl. ClOB27/00). 16 Jul 1998, Appl. 19,700,768, 11 Jan 1997, 4 pp. (In German) The procedure for the removal of gases, especially leakage gases, withdrawn from coke-oven batteries is discussed. The gases are subjected to dust removal, compression, mixing with atmospheric air, fine dust removal and recompression. This results in a cold blast which is fed into a heater heated by blast-furnace gases. The resulting hot blast is then charged into a metallurgical blast furnace.
Process concepts for the direct use of methanol in fuel-cell systems
99101305
Menzer, R. et al. Ber. Forschungszent. Juelich, 1998, l-50. (In German) In using methanol as fuel in low-temperature fuel-cell systems there are two different procedures. On the one hand, methanol can be reformed to a hydrogen-rich synthesis gas before the generation of electricity via an electrochemical reaction in a fuel cell; on the other hand, methanol can also be used directly for electricity generation inside the fuel cell. This kind of direct methanol oxidation differs extremely from the indirect oxidation of methanol via hydrogen in terms of electrochemical basic reactions and process engineering units. This study includes the analyses of different concepts with liquid and gaseous methanol as energy input for fuel-cell systems. The operating requirements for specific procedures can be identified as a function of both operating conditions and the respective yield of electricity, based on simulation calculations.
99101306 Production of crude hydrogen and electric energy Kummann, P. et al. Ger. Offen. DE 19,651,282 (Cl. F02C3/28), 18 Jun 1998, Appl. 19,651,282, 10 Dee 1996, 6 pp. (In German) Electric energy and crude hydrogen are produced from a hydrocarbon charge and/or coal in the integrated gasification combined cycle process using a gas turbine and involving gasification of the hydrocarbon charge and/or coal to give a synthesis gas, scrubbing of the synthesis gas with water and shift conversion of a (partial) stream of the quenched synthesis gas. During shift conversion of the entire synthesis gas, the shifted synthesis gas is divided into two physical washes or the shifted gas and not-shifted gas are subjected to separate physical washes. After removal of HzS and COz during purification, pure hydrogen is suitable for hydrogenation in petroleum refining or in the manufacture of ammonia. b Roles of alkaline elements in sulfur retention by ashes from Chinese coals used for electric power generation
99101307
Sheng, C. and Xu, Y. Ranshao Kexue Yu Jisho, 1998, 4, (l), 99-103. (In Chinese) In coal, a part of the total sulfur will be retained in ash as solid compounds during combustion. In the present paper, the role of alkaline elements in sulfur retention by ashes of Chinese coals both in laboratory ashing
Fuel and Energy Abstracts
March 1999
131
Optimal PWM-SHE switching on NPC inverter: a 99101296 winning match for high power conversion Maswood, A. I. Electric Power Systems Research, 1998, 48, (1) 19-24. This paper provides a simple yet very effective method of real-time on-line solution for the pulsewidth modulation specific harmonic elimination (PWM-SHE) technique that readily accommodates the elimination of a particular set of harmonics. Piece-wise linear representations of PWM-SHE switching angles are utilized to formulate the on-line linear equations. A detailed analysis of linearization and on-line capability of an optimized PWM-SHE technique is described. A neutral point clamped (NPC) inverter configuration is chosen. For high power conversion, application of the PWM-SHE switching pattern to the NPC inverter yields substantially low switching losses with excellent output voltage/current waveform.
Optimal unit sizing of fuel cell cogeneration sys99101297 tems in consideration of performance degradation
Ito, K. et al. Energy Research, 1998, 22, (12), 1075-1089. A system’s economy is influenced by the life of a cell stack due to performance degradation. This paper explores this subject by investigating unit sizing of fuel cell co-generation systems. An optimal unit sizing method proposed by the authors is extended to this case so that it enables the life and performance degradation of the cell stack to be considered. Equipment capacities and maximum contract demands of utilities such as electricity and natural gas are determined so as to minimize the annual total cost levelled for a whole planning period based on the annualized costs method whilst considering operational strategies which change with performance degradation of the cell stack. Numerical studies were carried out for normally and highly pressurized phosphoric acid fuel cell co-generation systems installed in two urban areas. It was found that the life of the cell stack greatly influences system economics and equipment capacities.
Particle-size effect of carbon powders on the discharge capacity of lithium ion batteries
99101296
Sato, Y. et al. Journal of Power Sources, 1998, 75, (2), 271-277. A study has been made of the particle-size effect of carbon powder on discharge capacity in order to improve the performance of the negative electrodes for lithium-ion batteries. Also, the optimum mixing ratio between large (average diameter: 25.8 pm) and small (average diameter: 4.2 /Irn) powder particle size has been found. The largest capacity is obtained when the large particle size fraction is about 70 wt%. The smaller the particle size ratio, the larger the capacity, where the particle size ratio is the ratio of the average diameter of the smaller component to that of the larger one. The results obtained in this study indicate that discharge capacity is closely related to carbon powder packing.
Performance and life of lo-kW molten-carbonate 99101299 fuel cell stack using LilK and LilNa carbonates as the electrolyte Mugikura, Y. et al. Journal of Power Sources, 1998, 75, (l), 108-115. In molten carbonate fuel cells (MCFC), NiO cathode dissolution is a serious problem. The target life-time of such cells is 40,000 h, but shorting by NiO cathode dissolution markedly decreases cell performance. NiO cathode dissolution depends on the composition of the molten carbonate electrolyte. The electrolyte generally comprises a mixture of lithium carbonate and potassium carbonate. Since the solubility of NiO in a mixture of lithium carbonate and sodium carbonate is lower than in lithium and potassium carbonate, it is expected that shorting by NiO cathode dissolution will take longer in a mixture of lithium and sodium. Therefore, a mixture of lithium carbonate and sodium carbonate is a strong candidate for the electrolyte. A unique 10 kW class stack, which uses a mixture of lithium and potassium carbonate and mixture of lithium and sodium carbonate as the electrolyte, has been developed and tested. The basic performance and life time of both electrolyte cells of the stack are reported.
Performance of planar single cell lanthanum gallate based solid oxide fuel cells
99iO13QO
Maffei, N. and Kuriakose, A. K. Journal of Power Sources, 1998, 75, (l), 162-166. This paper describes a novel synthesis of high purity, single phase strontium-magnesium doped lanthanum gallate through a nitrate route. The prepared powder is formed into planar monolithic elements by uniaxial pressing followed by isostatic pressing and sintering. XRD analysis of the sintered elements reveal no detectable secondary phases. A report is given on the performance of the electrolyte in solid oxide fuel cells (SOFC) with three different anode/cathode combinations tested at 700°C with respect to the J-V and power density. The data show that the characteristics of this SOFC are strongly dependent on the particular anode/cathode system chosen.
99lO1301 0 system
Phase stability of the mixed-conducting Sr-Fe-Co-
Ma, B. et al. Mater. Res. Sot. Symp. Proc., 1998, 496, 167-172. In high-temperature electrochemical applications (such as solid oxide fuel cells, batteries, sensors and oxygen-permeable membranes), mixed-conducting ceramic oxides have potential uses. The strontium-iron-cobaltoxygen system combines high electronic/ionic conductivity with appreciable oxygen permeability at elevated temperatures. Dense ceramic membranes made from this material can be used to separate high-purity oxygen from air without the need for external electric circuitry, or to partially oxidize methane to produce syngas. Samples of Sr,Fes_,Co,O, (with x = 0, 0.6, 1.0
Electrical power supply and utilization (scientific, technical)
and 1.4) were prepared by solid-state reaction method in atmospheres with various oxygen partial pressures (~0~) and were characterized by X-ray diffraction, SEM and electric conductivity testing. Phase components of the sample were dependent pOz and cobalt concentration. Electric conductivity increases with increasing temperature and cobalt content in the material. 99101302 Polymer-oxide anode materials Kerr, T. A. et al. Mater. Res. Sot. Symp. Proc., 1998, 496, 499-504. the amino derivative form of the conductive polymer poly(p-phenylene) (PPPNHz) was inserted within the van der Waals gap of molybdenum trioxide by exploiting its adaptable layer structure. Two polymer insertion routes were designed that yield novel PPPNHz-Moos materials of different compositions. Characterization of these materials using powder X-ray diffraction (XRD), thermal analysis and Fourier transfer infrared spectroscopy (FTIR) showed insertion of the polymer had occurred. The properties of the nanocomposites for low potential electrochemical lithium insertion were compared to those of the sodium molybdenum bronze using the materials as cathodes in conventional lithium cells. Initial results indicate the specific charge capacity and irreversibility during the first charge are effected by polymer content whereas polarization is not.
99101303 Probabilistic production simulation including combined heat and power plants
Larsen, H. V. et al. Electric Power Systems Research, 1998, 48, (l), 45-56. Simulation tools for estimating key indicators for decision making are required for expansion planning of combined heat and power (CHP) systems. Probability production simulation techniques have been used extensively for power systems. These techniques have been extended to include CHP systems with a single heat area and back-pressure type CHP units. This paper extends existing simulation methods for CHP to include extraction power plants. Further, the case of multiple heat areas is addressed and three different simulation strategies are presented for such systems. The results show that an assumption of perfectly correlated heat demands in all heat areas gives results that are very similar to a general case, whereas working with a system with all heat areas aggregated into one gives rather poor results. This paper shows that it is possible to use the traditional concepts and methods for power-only analysis on a CHP system. Additional concepts are presented, depending on the heat criterion applied. Probabilistic production simulation including CHP units can be performed with reasonable effort and accuracy.
Procedure and system for removal of leakage gas from coke-oven batteries
99101304
Moessner, F. and Toll, H. Ger. Offen. DE 19,700,768 (Cl. ClOB27/00). 16 Jul 1998, Appl. 19,700,768, 11 Jan 1997, 4 pp. (In German) The procedure for the removal of gases, especially leakage gases, withdrawn from coke-oven batteries is discussed. The gases are subjected to dust removal, compression, mixing with atmospheric air, fine dust removal and recompression. This results in a cold blast which is fed into a heater heated by blast-furnace gases. The resulting hot blast is then charged into a metallurgical blast furnace.
Process concepts for the direct use of methanol in fuel-cell systems
99101305
Menzer, R. et al. Ber. Forschungszent. Juelich, 1998, l-50. (In German) In using methanol as fuel in low-temperature fuel-cell systems there are two different procedures. On the one hand, methanol can be reformed to a hydrogen-rich synthesis gas before the generation of electricity via an electrochemical reaction in a fuel cell; on the other hand, methanol can also be used directly for electricity generation inside the fuel cell. This kind of direct methanol oxidation differs extremely from the indirect oxidation of methanol via hydrogen in terms of electrochemical basic reactions and process engineering units. This study includes the analyses of different concepts with liquid and gaseous methanol as energy input for fuel-cell systems. The operating requirements for specific procedures can be identified as a function of both operating conditions and the respective yield of electricity, based on simulation calculations.
99101306 Production of crude hydrogen and electric energy Kummann, P. et al. Ger. Offen. DE 19,651,282 (Cl. F02C3/28), 18 Jun 1998, Appl. 19,651,282, 10 Dee 1996, 6 pp. (In German) Electric energy and crude hydrogen are produced from a hydrocarbon charge and/or coal in the integrated gasification combined cycle process using a gas turbine and involving gasification of the hydrocarbon charge and/or coal to give a synthesis gas, scrubbing of the synthesis gas with water and shift conversion of a (partial) stream of the quenched synthesis gas. During shift conversion of the entire synthesis gas, the shifted synthesis gas is divided into two physical washes or the shifted gas and not-shifted gas are subjected to separate physical washes. After removal of HzS and COz during purification, pure hydrogen is suitable for hydrogenation in petroleum refining or in the manufacture of ammonia. b Roles of alkaline elements in sulfur retention by ashes from Chinese coals used for electric power generation
99101307
Sheng, C. and Xu, Y. Ranshao Kexue Yu Jisho, 1998, 4, (l), 99-103. (In Chinese) In coal, a part of the total sulfur will be retained in ash as solid compounds during combustion. In the present paper, the role of alkaline elements in sulfur retention by ashes of Chinese coals both in laboratory ashing
Fuel and Energy Abstracts
March 1999
131