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01563 Fuel sensitivity tests in tubular solid oxide fuelcells
06 Electrical power supply and utilization (scientific, technical) 05•01561 Electrochemical characterization of activated carbon-ruthenium oxide nanoparticles composites for supercapacitors Chen, W.-C. et al. Journal of Power Sources, 2004, 125, (2), 292-298. The high specific capacitance of ruthenium oxide (denoted as RuO~) nanoparticles prepared by a modified sol-gel method with annealing in air for supercapacitors was demonstrated in this work. The specific capacitance of activated carbon (denoted as AC) measured at 5 mA/ cm is significantly increased from 26.8 to 38.7 F/g by the adsorption of RuOx nanoparticles with ultrasonic weltering in 1 M NaOH for 30 min. This method is a promising tool in improving the performance of carbon-based double-layer capacitors. The total specific capacitance of a composite composed of 90 wt% AC and 10 wt% RuO.~ measured at 25 mV/s is about 62.8 F/g, which is increased up to ca. l 11.7 F/g when RuOx has been previously annealed in air at 200°C for 2 h. The specific capacitance of RuO.~ nanoparticles was promoted from 470 to 980 F/g by annealing in air at 200°C for 2 h. The nanostructure of RuOx was examined from the transmission electron microscopic (TEM) morphology.
05/01562 Enhancing the electrical performance of a solid oxide fuel cell using multi-objective genetic algorithms Jurado, F. and Valverde, M. Renewable Energy, 2005, 30, (6), 881-902. Several technologies are being used in distributed generation applications with variable degree of success. Among those are: wind turbines, small-scale hydropower plants, biomass, micro-turbines, photovoltaic arrays, and fuel cells. A fuel cell is a device that converts the chemical energy of fuel to electric energy. New improvements in the fuel cell technology significantly meliorated the technical characteristics of this technology. Environmental friendliness, practically noise-free operation, and very high efficiency make fuel cells a challenger on the future electricity markets. The connection between the fuel cell and the load is through an inverter using Pulse Width Modulation. Subsequently, the fuel cell produces a significant amount of harmonics. This paper describes the use of multi-objective genetic algorithms in the design of a fuzzy logic control system for a solid oxide fuel cell.
05/01563 cells
Fuel sensitivity tests in tubular solid oxide fuel
Gopalan, S. and DiGiuseppe, G. Journal of Power Sources, 2004, 125, (2), 183-188. Fuel sensitivity experiments form an important feature of testing solid oxide fuel cell systems. In this paper a fuel sensitivity test and its relation to fuel utilization is described. The sensitivity of the measured terminal voltage of a tubular solid oxide fuel cell to the fuel utilization provides important information about 'leaks' through the cell. Such leaks could arise from pinholes in the electrolyte or from other sources. First a simple analytical model is presented which is then refined using a numerical simulation. Such tests also provide a methodology to quantify the leaks present in the cell which can ultimately have an effect on fuel cell efficiency.
05101564 Increased electrical yield via water flow over the front of photovoltaic panels Krauter, S. Solar Energy Materials and Solar Cells, 2004, 82, (1-2), 131-137. Reflection of the sun's irradiance typically reduces the electrical yield of PV modules by 8-15%. Facade applications located in the tropics may even experience a 42% drop in yield, due to flat incidence angles. Additionally, when a module's cell temperature is elevated there is 0.4%/K decrease in voltage and power for single- and multi-crystalline silicon solar cells: in reference to STC, that number may reach 20%. Numerous ideas to reduce reflection have been proposed, but most have drawbacks: anti-reflective-coatings are not durable and structured surfaces are expensive, accumulate dust and are difficult to clean. Yet water, with a refractive index of 1.3, is a viable intermediary between glass (nglass = 1.5) and air (hair = 1.0). In addition to help keeping the surface clean, water reduces reflection by 2-3.6%, decreases cell temperatures up to 22°C and the electrical yield can return a surplus of 10.3%; a net-gain of 8-9% can be achieved even when accounting for power needed to run the pump.
05/01565 Morphology control of Ni-YSZ cermet anode for lower temperature operation of SOFCs Fukui, T. et al. Journal of Power Sources, 2004, 125, (1), 17-21. A NiO-YzO3 stabilized ZrO2 (YSZ) composite particles for solid oxide fuel cell (SOFC) anode was fabricated by advanced mechanical method in dry process. The processed powder achieved better homogeneity of NiO and YSZ particles, where snbmicron NiO particles were covered with finer YSZ particles. A Ni-YSZ cermet anode fabricated from the NiO-YSZ composite particles showed the porous structure in which Ni and YSZ grains of less than several hundred nano-meter as well as micron-size pores were uniformly dispersed. The cermet anode
234
Fuel and Energy Abstracts July 2005
achieved high electrical performance at low temperature operation (<800°C). It was led by larger electrochemical area successfully obtained by the excellent structure of the anode.
05/01566 Novel method for investigation of two-phase flow in liquid feed direct methanol fuel cells using an aqueous H202 solution Bewer, T. et al. Journal of Power Sources, 2004, 125, (1), 1-9. One major issue in the development of direct methanol fuel cells (DMFC) is the management of the evolving CO2 gas bubbles in the flow fields. These bubbles influence the flow distribution and therefore the power density of a cell. In this paper, a novel method for in situ production of bubbles in a test cell made of perspex is presented. The method is based on the decomposition of hydrogen peroxide solution (H2Oz) to oxygen and water in aqueous media at the presence of a catalyst. By using an appropriate H2Oz-eoncentration, the gas evolution rate can be set to same order of magnitude as in real direct methanol fuel cells. This approach allows the simulation of the flow distribution in DMFC by simple low-cost hardware. As no current conducting parts are needed, the whole dummy cell can be made of perspex to ensure a complete visibility of the flow. In a perspex flow cell with an active area of 600 em 2, the flow homogeneity as a function of gas evolution rate, flow field and manifold design was investigated. Experiments show that splayed manifolds have a superior performance concerning flow uniformity compared to other designs. The use of grid structures as a flow field gives good bubble transport at all investigated current densities.
05101567 Possible use of vanadium redox-flow batteries for energy storage in small grids and stand-alone photovoltaic systems Joerissen, L. et al. Journal of Power Sources, 2004, 127, (1-2), 98-104. The all-vanadium redox-flow battery is a promising candidate for load levelling and seasonal energy storage in small grids and stand-aloffe photovoltaic systems. The reversible cell voltage of 1.3 to 1.4 V in the charged state allows the use of inexpensive active and structural materials. In this work, studies on the performance of inexpensive active materials for use in vanadium redox-flow batteries are reported. Additionally, a cost analysis for a load levelling and a seasonal energy storage system is given based on a flow battery technology well established in Zn-flow batteries.
05•01568 Reduction of irreversible capacities of amorphous carbon materials for lithium ion battery anodes by Li~CO3 addition Mukai, S. R. et al. Carbon, 2004, 42, (4), 837-842. Amorphous carbon materials for lithium ion battery anodes which contain a small amount of Li2CO3 were prepared by three methods. The obtained materials were characterized using X-ray diffraction (XRD) analysis, Raman spectroscopy and COz adsorption experiments. Although the XRD profiles and Raman spectra of these materials were similar to those of carbon materials synthesized with no addition, the amount of CO2 adsorbed was largely decreased by Li2CO3 addition. These results suggest that the micro-pores in these materials were plugged and/or filled with LizCO3. Galvanostatic lithium charging and discharging experiments showed that the irreversible capacity of the material can be significantly decreased by Li2CO3 addition, which is thought to be due to the plugging of the pore inlets by Li2CO3. Moreover, it was also found that the reversible capacities of the materials can be increased by adjusting both the amount of Li2CO3 addition and carbonization temperature.
05•01569 Solid oxide fuel cell architecture and system design for secure power on an unstable grid Krumdieck, S. et al. Journal of Power Sources, 2004, 125, (2), 189-198. In a power grid with significant components of distributed generation and insufficient spinning reserve, the quality of delivered power may not meet the requirements of advanced manufacturing. A system design for power quality security is described, which uses solid oxide fuel cell (SOFC) technology. Critical parameters for system performance are continuous supply voltage at the nominal voltage and frequency. The grid chosen for this study has significant voltage fluctuations and periodic voltage drops and surges, including total power loss. A supply of methane from a sewer sludge digester is scrubbed of CO2 and used for continuous standby operation, with excess stored to enable 8 h operation of an uninterruptible power supply (UPS). The system employs a modular, thermally coupled, SOFC architecture that includes steam reforming of the methane fuel, a rectifier, power controls, and control system. Continuous operation of a 125 kW tubular SOFC stack maintains operating temperature and steam for fuel reforming in a secondary SOFC stack, by exhausting through it before a gas turbine expands the exhaust to supply the plant air and fuel compression. Modelling of the energy balance of the
05/01562 Enhancing the electrical performance of a solid oxide fuel cell using multi-objective genetic algorithms Jurado, F. and Valverde, M. Renewable Energy, 2005, 30, (6), 881-902. Several technologies are being used in distributed generation applications with variable degree of success. Among those are: wind turbines, small-scale hydropower plants, biomass, micro-turbines, photovoltaic arrays, and fuel cells. A fuel cell is a device that converts the chemical energy of fuel to electric energy. New improvements in the fuel cell technology significantly meliorated the technical characteristics of this technology. Environmental friendliness, practically noise-free operation, and very high efficiency make fuel cells a challenger on the future electricity markets. The connection between the fuel cell and the load is through an inverter using Pulse Width Modulation. Subsequently, the fuel cell produces a significant amount of harmonics. This paper describes the use of multi-objective genetic algorithms in the design of a fuzzy logic control system for a solid oxide fuel cell.
05/01563 cells
Fuel sensitivity tests in tubular solid oxide fuel
Gopalan, S. and DiGiuseppe, G. Journal of Power Sources, 2004, 125, (2), 183-188. Fuel sensitivity experiments form an important feature of testing solid oxide fuel cell systems. In this paper a fuel sensitivity test and its relation to fuel utilization is described. The sensitivity of the measured terminal voltage of a tubular solid oxide fuel cell to the fuel utilization provides important information about 'leaks' through the cell. Such leaks could arise from pinholes in the electrolyte or from other sources. First a simple analytical model is presented which is then refined using a numerical simulation. Such tests also provide a methodology to quantify the leaks present in the cell which can ultimately have an effect on fuel cell efficiency.
05101564 Increased electrical yield via water flow over the front of photovoltaic panels Krauter, S. Solar Energy Materials and Solar Cells, 2004, 82, (1-2), 131-137. Reflection of the sun's irradiance typically reduces the electrical yield of PV modules by 8-15%. Facade applications located in the tropics may even experience a 42% drop in yield, due to flat incidence angles. Additionally, when a module's cell temperature is elevated there is 0.4%/K decrease in voltage and power for single- and multi-crystalline silicon solar cells: in reference to STC, that number may reach 20%. Numerous ideas to reduce reflection have been proposed, but most have drawbacks: anti-reflective-coatings are not durable and structured surfaces are expensive, accumulate dust and are difficult to clean. Yet water, with a refractive index of 1.3, is a viable intermediary between glass (nglass = 1.5) and air (hair = 1.0). In addition to help keeping the surface clean, water reduces reflection by 2-3.6%, decreases cell temperatures up to 22°C and the electrical yield can return a surplus of 10.3%; a net-gain of 8-9% can be achieved even when accounting for power needed to run the pump.
05/01565 Morphology control of Ni-YSZ cermet anode for lower temperature operation of SOFCs Fukui, T. et al. Journal of Power Sources, 2004, 125, (1), 17-21. A NiO-YzO3 stabilized ZrO2 (YSZ) composite particles for solid oxide fuel cell (SOFC) anode was fabricated by advanced mechanical method in dry process. The processed powder achieved better homogeneity of NiO and YSZ particles, where snbmicron NiO particles were covered with finer YSZ particles. A Ni-YSZ cermet anode fabricated from the NiO-YSZ composite particles showed the porous structure in which Ni and YSZ grains of less than several hundred nano-meter as well as micron-size pores were uniformly dispersed. The cermet anode
234
Fuel and Energy Abstracts July 2005
achieved high electrical performance at low temperature operation (<800°C). It was led by larger electrochemical area successfully obtained by the excellent structure of the anode.
05/01566 Novel method for investigation of two-phase flow in liquid feed direct methanol fuel cells using an aqueous H202 solution Bewer, T. et al. Journal of Power Sources, 2004, 125, (1), 1-9. One major issue in the development of direct methanol fuel cells (DMFC) is the management of the evolving CO2 gas bubbles in the flow fields. These bubbles influence the flow distribution and therefore the power density of a cell. In this paper, a novel method for in situ production of bubbles in a test cell made of perspex is presented. The method is based on the decomposition of hydrogen peroxide solution (H2Oz) to oxygen and water in aqueous media at the presence of a catalyst. By using an appropriate H2Oz-eoncentration, the gas evolution rate can be set to same order of magnitude as in real direct methanol fuel cells. This approach allows the simulation of the flow distribution in DMFC by simple low-cost hardware. As no current conducting parts are needed, the whole dummy cell can be made of perspex to ensure a complete visibility of the flow. In a perspex flow cell with an active area of 600 em 2, the flow homogeneity as a function of gas evolution rate, flow field and manifold design was investigated. Experiments show that splayed manifolds have a superior performance concerning flow uniformity compared to other designs. The use of grid structures as a flow field gives good bubble transport at all investigated current densities.
05101567 Possible use of vanadium redox-flow batteries for energy storage in small grids and stand-alone photovoltaic systems Joerissen, L. et al. Journal of Power Sources, 2004, 127, (1-2), 98-104. The all-vanadium redox-flow battery is a promising candidate for load levelling and seasonal energy storage in small grids and stand-aloffe photovoltaic systems. The reversible cell voltage of 1.3 to 1.4 V in the charged state allows the use of inexpensive active and structural materials. In this work, studies on the performance of inexpensive active materials for use in vanadium redox-flow batteries are reported. Additionally, a cost analysis for a load levelling and a seasonal energy storage system is given based on a flow battery technology well established in Zn-flow batteries.
05•01568 Reduction of irreversible capacities of amorphous carbon materials for lithium ion battery anodes by Li~CO3 addition Mukai, S. R. et al. Carbon, 2004, 42, (4), 837-842. Amorphous carbon materials for lithium ion battery anodes which contain a small amount of Li2CO3 were prepared by three methods. The obtained materials were characterized using X-ray diffraction (XRD) analysis, Raman spectroscopy and COz adsorption experiments. Although the XRD profiles and Raman spectra of these materials were similar to those of carbon materials synthesized with no addition, the amount of CO2 adsorbed was largely decreased by Li2CO3 addition. These results suggest that the micro-pores in these materials were plugged and/or filled with LizCO3. Galvanostatic lithium charging and discharging experiments showed that the irreversible capacity of the material can be significantly decreased by Li2CO3 addition, which is thought to be due to the plugging of the pore inlets by Li2CO3. Moreover, it was also found that the reversible capacities of the materials can be increased by adjusting both the amount of Li2CO3 addition and carbonization temperature.
05•01569 Solid oxide fuel cell architecture and system design for secure power on an unstable grid Krumdieck, S. et al. Journal of Power Sources, 2004, 125, (2), 189-198. In a power grid with significant components of distributed generation and insufficient spinning reserve, the quality of delivered power may not meet the requirements of advanced manufacturing. A system design for power quality security is described, which uses solid oxide fuel cell (SOFC) technology. Critical parameters for system performance are continuous supply voltage at the nominal voltage and frequency. The grid chosen for this study has significant voltage fluctuations and periodic voltage drops and surges, including total power loss. A supply of methane from a sewer sludge digester is scrubbed of CO2 and used for continuous standby operation, with excess stored to enable 8 h operation of an uninterruptible power supply (UPS). The system employs a modular, thermally coupled, SOFC architecture that includes steam reforming of the methane fuel, a rectifier, power controls, and control system. Continuous operation of a 125 kW tubular SOFC stack maintains operating temperature and steam for fuel reforming in a secondary SOFC stack, by exhausting through it before a gas turbine expands the exhaust to supply the plant air and fuel compression. Modelling of the energy balance of the