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01906 Preparation of carbon-supported PtRu nanoparticles for direct methanol fuel cell applications — a comparative study
14 Fuel science and technology (fuel cell technology) water and surrounding fluid properties on the mobility of the water droplets is addressed. The numerical solution is based on solving Navier-Stokes equations for Newtonian liquids. The study includes the effect of interfacial forces with constant surface tension. The volumeof-fluid method is used to keep track of the deformation of free surfaces. A comprehensive set of simulations is conducted covering a wide range of density ratios, viscosity ratios, Capillary numbers, Ca, and Reynolds numbers, Re. Deformation of water droplets and their motion is characterized based on the maximum distance between the droplet surface and the channel wall. This characteristic length has been used to compare systems with different droplet and surrounding fluid properties. Among the parameters affecting the mobility of water droplets in a PEM fuel cell, the surface tension is found to have the most important effect.
06•01900 cell
Experimental studies of a direct methanol fuel
Ge, J. and Liu, H. Journal of Power Sources, 2005, 142, (1-2), 56-69. Systematic experiments have been conducted to study the effects of various operating parameters on the performances of a direct methanol fuel cell (DMFC). The effects of cell operating temperature, methanol concentration, anode flow rate, air flow rate, and cathode humidification have been studied. The experimental results showed that all the studied operating parameters, except the cathode humidification, have significant effects on the DMFC cell performances, and the cathode humidification has almost negligible effect. The study revealed that the detrimental effect of methanol crossover can be alleviated by increasing cathode air flow rate or oxygen partial pressure. This result showed that the cathode structure and operating condition may play a very important role in DMFC design and operations. The experimental results are presented in both graphical and tabular forms.
photochemical etching method as the current collectors. Different conditioning methods for membrane electrode assembly (MEA) activation were discussed. With proper control of water crossover to the cathode, cathode flooding was avoided in the DMFC stack. Methanol crossover at open circuit voltage (OCV) in the air-breathing DMFC was measured. Further, it was found that flow maldistribution might occur in the parallel flow field of the stack, making carbon dioxide gas management at the anode necessary. Using humidified hydrogen in the anode with a high flow rate, the oxygen transport limiting current density was characterized and found to be sufficient in the air-breathing cathode. The stack produced a maximum output power of 1.33 W at 2.21 V at room temperature, corresponding to a power density of 33.3 m W cm 2.
06101904 On the consequences of methanol crossover in passive air-breathing direct methanol fuel cells Kho, B. K. et al. Journal of Power Sources, 2005. 142, (1 2), 50-55. Passive direct methanol fuel cells (DMFC) are under development for use in portable power applications due to their enhanced energy density in comparison with active DMFCs. This study has been carried out to understand the unique properties of passive DMFCs, focusing on the internal temperature and the open circuit voltage (OCV), which change as a consequence of the methanol crossover phenomenon. The changes found in the passive DMFCs were very different from active ones because of different reactants supplying conditions. Methanol concentration in the built-in reservoir attached to the anode changed with time on stream and the OCV and the temperature changed correspondingly. Various experiments were conducted to show the unique properties of passive DMFCs at controlled conditions and configurations of the cell.
06/01901 Genetic fuzzy control applied to the inverter of solid oxide fuel cell for power quality improvement
06/01905 Performance assessment of fuel cell microcogeneration systems for residential buildings
Jurado, F. and Valverde, M. Electric Power Systems Research, 2005, 76, (1 3), 93-105. The deregulation and unbundling of electricity markets in many countries worldwide bring new perspectives for fuel cells. The connection between the fuel cell and the load is through an inverter using pulse width modulation (PWM). This paper presents a new flux modulation approach for the closed-loop control of the output voltage of inverters for fuel cell power plants. A fuzzy logic control is proposed for this PWM converter and the fuzzy scaling factors are optimized by using genetic algorithms. The proposed control scheme can achieve fast transient responses and, at the same time, have low total harmonic distortion in output current during steady-state operation. This genetic fuzzy controller demonstrates improved response than conventional flux vector method.
Doter, V. et al. Energy and Buildings. 2005, 37, (11), 1132 1146. The reduction of greenhouse gas emissions in the building sector to a sustainable level will require tremendous efforts to increase both energy efficiency and the share of renewable energies. Apart from the lowering of energy demand through better insulation and fenestration, small combined heat and power (micro-cogeneration) systems may help improve the situation on the supply side by cutting both the nonrenewable energy demand for residential buildings and peak loads in the electric grid. Though still on the brink of market entry, fuel cells are the focus of interest as the prime technology for such systems. In this study, a methodology for assessing the performance of such systems in terms of primary energy demand and the CO2 emissions by transient computer simulations is established, and demonstrated for a natural gas driven solid oxide fuel cell (SOFC) and, to a lesser extend, a polymer electrolyte fuel cell (PEFC) home fuel cell cogeneration system. The systems were evaluated for different grid electricity generation mix types and compared to traditional gas boiler systems. The interaction with hot water storage and solar thermal collectors, and the impact of storage size and predictive control was analysed. Typical heat and electricity demand load profiles for different types of residential buildings and occupancy were considered, and the sizing of the fuel cell system in relation to the heat demand of the building was analysed. Primary energy savings decline for cases with lower heat demand and for cases with solar thermal systems, and peak for fuel cell systems sized in accordance with the heat demand of the building. Future assessments of fuel cell systems will need a refined methodology, and depend on realistic performance characteristics and models that accurately consider dynamic conditions.
06/01902 Intelligent structure design of membrane cathode assembly for direct methanol fuel cell Furukawa, K. et al. International Journal of Energy Research, 2005, 29, (12), 1073 1082. The performance and the structural model of membrane electrode assembly (MEA) have been developed and experimentally verified with fundamental calculations of the direct methanol fuel cell (DMFC). The model provides information concerning the influence of the operating and structural parameters. The composition and performance optimization of M E A structure in DMFC has been investigated by including both electrochemical reaction and mass transport process. In the experimentation, the effect of Nation content and loading method in the catalyst layer of cathode for DMFC was investigated. For the spray method electrode (SME), the cell performance and cathode performance using a dynamic hydrogen electrode (DHE) as a reference electrode was improved in comparison with those of the PME electrode by decreasing cathode potential. From ac impedance measurements of the cathode, the adsorption resistance of the SME electrode was decreased compared with that of the PME electrode. The higher cell performance was mostly dependent on the adsorption resistance. In the modelling, the cathode overpotential was decreased with increasing ionomer content, due to increasing ionic conductivity for proton transfer and the larger reaction site. The resistance to oxygen transport was increased at the same time, and became dominant at higher ionomer loadings, leading to an increase in the voltage loss. The ratio of ionorner to void space in the cathode affected the cathode polarization, which had the lowest resistance of oxygen diffusion at the ratio of 0.1-0.2.
06/01903 stack
On mass transport in an air-breathing DMFC
Lu, G. Q. et al. International Journal of Energy Research, 2005, 29. (12), 1041 1050. An 8-cell air-breathin§ direct methanol fuel cell (DMFC) stack with the active area of 5 cm of each cell has been developed. Stainless steel plates of 500 ~tm thickness with flow channels were fabricated using
06/01906 Preparation of carbon-supported PtRu nanoparticles for direct methanol fuel cell applications a comparative study Deivaraj, T. C. and Lee, J. Y. Journal of Power Sources, 2005, 142, (12), 43-49. Carbon-supported PtRu nanoparticles were prepared by different methods that involve the simultaneous chemical reduction of H~PtC16 and RuC13 by NaBH4 at room temperature (PtRu-1), by ethanol under reflux (PtRu-2), and by the thermal decomposition of a single-source molecular precursor [(bipy)3Ru] (PtC16) (PtRu-3). Transmission electron microscopy (TEM) examinations show that the mean diameter of the PtRu nanoparticles is lowest for PtRu-1 followed by PtRu-2 and PtRu-3. Measurements of electrocatalytic properties, however, reveal a different trend, namely: PtRu-3 > PtRu-1 > PtRu-2. This is attributed to the formation of a more homogenous alloy nanoparticle system from the thermolysis of the single-source molecular precursor. All three catalysts are more active than commercially available E-TEK (20 wt%) Pt catalyst. PtRu-3 also displays the highest tolerance to carbon monoxide. Heat treatment of PtRu-1 and PtRu-2 only marginally affects their electrocatalytic performance, whereas the co-reduction of H2PtC16 and RuCI~ under alkaline conditions has more adverse outcomes.
Fuel and Energy Abstracts
July 2006
287
06•01900 cell
Experimental studies of a direct methanol fuel
Ge, J. and Liu, H. Journal of Power Sources, 2005, 142, (1-2), 56-69. Systematic experiments have been conducted to study the effects of various operating parameters on the performances of a direct methanol fuel cell (DMFC). The effects of cell operating temperature, methanol concentration, anode flow rate, air flow rate, and cathode humidification have been studied. The experimental results showed that all the studied operating parameters, except the cathode humidification, have significant effects on the DMFC cell performances, and the cathode humidification has almost negligible effect. The study revealed that the detrimental effect of methanol crossover can be alleviated by increasing cathode air flow rate or oxygen partial pressure. This result showed that the cathode structure and operating condition may play a very important role in DMFC design and operations. The experimental results are presented in both graphical and tabular forms.
photochemical etching method as the current collectors. Different conditioning methods for membrane electrode assembly (MEA) activation were discussed. With proper control of water crossover to the cathode, cathode flooding was avoided in the DMFC stack. Methanol crossover at open circuit voltage (OCV) in the air-breathing DMFC was measured. Further, it was found that flow maldistribution might occur in the parallel flow field of the stack, making carbon dioxide gas management at the anode necessary. Using humidified hydrogen in the anode with a high flow rate, the oxygen transport limiting current density was characterized and found to be sufficient in the air-breathing cathode. The stack produced a maximum output power of 1.33 W at 2.21 V at room temperature, corresponding to a power density of 33.3 m W cm 2.
06101904 On the consequences of methanol crossover in passive air-breathing direct methanol fuel cells Kho, B. K. et al. Journal of Power Sources, 2005. 142, (1 2), 50-55. Passive direct methanol fuel cells (DMFC) are under development for use in portable power applications due to their enhanced energy density in comparison with active DMFCs. This study has been carried out to understand the unique properties of passive DMFCs, focusing on the internal temperature and the open circuit voltage (OCV), which change as a consequence of the methanol crossover phenomenon. The changes found in the passive DMFCs were very different from active ones because of different reactants supplying conditions. Methanol concentration in the built-in reservoir attached to the anode changed with time on stream and the OCV and the temperature changed correspondingly. Various experiments were conducted to show the unique properties of passive DMFCs at controlled conditions and configurations of the cell.
06/01901 Genetic fuzzy control applied to the inverter of solid oxide fuel cell for power quality improvement
06/01905 Performance assessment of fuel cell microcogeneration systems for residential buildings
Jurado, F. and Valverde, M. Electric Power Systems Research, 2005, 76, (1 3), 93-105. The deregulation and unbundling of electricity markets in many countries worldwide bring new perspectives for fuel cells. The connection between the fuel cell and the load is through an inverter using pulse width modulation (PWM). This paper presents a new flux modulation approach for the closed-loop control of the output voltage of inverters for fuel cell power plants. A fuzzy logic control is proposed for this PWM converter and the fuzzy scaling factors are optimized by using genetic algorithms. The proposed control scheme can achieve fast transient responses and, at the same time, have low total harmonic distortion in output current during steady-state operation. This genetic fuzzy controller demonstrates improved response than conventional flux vector method.
Doter, V. et al. Energy and Buildings. 2005, 37, (11), 1132 1146. The reduction of greenhouse gas emissions in the building sector to a sustainable level will require tremendous efforts to increase both energy efficiency and the share of renewable energies. Apart from the lowering of energy demand through better insulation and fenestration, small combined heat and power (micro-cogeneration) systems may help improve the situation on the supply side by cutting both the nonrenewable energy demand for residential buildings and peak loads in the electric grid. Though still on the brink of market entry, fuel cells are the focus of interest as the prime technology for such systems. In this study, a methodology for assessing the performance of such systems in terms of primary energy demand and the CO2 emissions by transient computer simulations is established, and demonstrated for a natural gas driven solid oxide fuel cell (SOFC) and, to a lesser extend, a polymer electrolyte fuel cell (PEFC) home fuel cell cogeneration system. The systems were evaluated for different grid electricity generation mix types and compared to traditional gas boiler systems. The interaction with hot water storage and solar thermal collectors, and the impact of storage size and predictive control was analysed. Typical heat and electricity demand load profiles for different types of residential buildings and occupancy were considered, and the sizing of the fuel cell system in relation to the heat demand of the building was analysed. Primary energy savings decline for cases with lower heat demand and for cases with solar thermal systems, and peak for fuel cell systems sized in accordance with the heat demand of the building. Future assessments of fuel cell systems will need a refined methodology, and depend on realistic performance characteristics and models that accurately consider dynamic conditions.
06/01902 Intelligent structure design of membrane cathode assembly for direct methanol fuel cell Furukawa, K. et al. International Journal of Energy Research, 2005, 29, (12), 1073 1082. The performance and the structural model of membrane electrode assembly (MEA) have been developed and experimentally verified with fundamental calculations of the direct methanol fuel cell (DMFC). The model provides information concerning the influence of the operating and structural parameters. The composition and performance optimization of M E A structure in DMFC has been investigated by including both electrochemical reaction and mass transport process. In the experimentation, the effect of Nation content and loading method in the catalyst layer of cathode for DMFC was investigated. For the spray method electrode (SME), the cell performance and cathode performance using a dynamic hydrogen electrode (DHE) as a reference electrode was improved in comparison with those of the PME electrode by decreasing cathode potential. From ac impedance measurements of the cathode, the adsorption resistance of the SME electrode was decreased compared with that of the PME electrode. The higher cell performance was mostly dependent on the adsorption resistance. In the modelling, the cathode overpotential was decreased with increasing ionomer content, due to increasing ionic conductivity for proton transfer and the larger reaction site. The resistance to oxygen transport was increased at the same time, and became dominant at higher ionomer loadings, leading to an increase in the voltage loss. The ratio of ionorner to void space in the cathode affected the cathode polarization, which had the lowest resistance of oxygen diffusion at the ratio of 0.1-0.2.
06/01903 stack
On mass transport in an air-breathing DMFC
Lu, G. Q. et al. International Journal of Energy Research, 2005, 29. (12), 1041 1050. An 8-cell air-breathin§ direct methanol fuel cell (DMFC) stack with the active area of 5 cm of each cell has been developed. Stainless steel plates of 500 ~tm thickness with flow channels were fabricated using
06/01906 Preparation of carbon-supported PtRu nanoparticles for direct methanol fuel cell applications a comparative study Deivaraj, T. C. and Lee, J. Y. Journal of Power Sources, 2005, 142, (12), 43-49. Carbon-supported PtRu nanoparticles were prepared by different methods that involve the simultaneous chemical reduction of H~PtC16 and RuC13 by NaBH4 at room temperature (PtRu-1), by ethanol under reflux (PtRu-2), and by the thermal decomposition of a single-source molecular precursor [(bipy)3Ru] (PtC16) (PtRu-3). Transmission electron microscopy (TEM) examinations show that the mean diameter of the PtRu nanoparticles is lowest for PtRu-1 followed by PtRu-2 and PtRu-3. Measurements of electrocatalytic properties, however, reveal a different trend, namely: PtRu-3 > PtRu-1 > PtRu-2. This is attributed to the formation of a more homogenous alloy nanoparticle system from the thermolysis of the single-source molecular precursor. All three catalysts are more active than commercially available E-TEK (20 wt%) Pt catalyst. PtRu-3 also displays the highest tolerance to carbon monoxide. Heat treatment of PtRu-1 and PtRu-2 only marginally affects their electrocatalytic performance, whereas the co-reduction of H2PtC16 and RuCI~ under alkaline conditions has more adverse outcomes.
Fuel and Energy Abstracts
July 2006
287