Mitsuyuki Nagahama

Analysis of Current Distribution at PEFCs Using Measured Membrane Properties and Comparison with Measured Current Distribution

In order to properly understand the power generation performance of polymer electrolyte fuel cells (PEFCs), it is necessary to have accurate data on water management, such as the diffusion coefficient of water through the membrane electrode assembly (MEA) and gas diffusion layer (GDL), electro-osmotic coefficient through MEA, and power loss data such as the activation and resistance overpotentials. In this study we measured these data with the aim of analyzing our experimental results from PEFC power generation tests done using our two-dimensional simulation code. Our code simultaneously solves mass, charge, and energy conservation equations, and the equivalent electric-circuit for PEFC to obtain numerical distributions of hydrogen/oxygen concentrations, cell potential, current density, and gas/cell-component temperatures. The current density distributions calculated with our simulation code were compared with the distribution measured using a segmented electrode cell. The distributions measured under various operating conditions agreed well with the calculated ones, demonstrating that our code is reliable. The concentration overpotential through GDL was also estimated with the parallel fine-pore model, but the estimated concentration overpotential was very small. Also, the cathode flooding is discussed with the calculated distribution of saturation degree along the channel flow, in comparison with experimental stability.

Cycle Analysis of Low and High H2 Utilization SOFC/Gas Turbine Combined Cycle for CO2 Recovery

A major factor in global warming is CO2 emission from thermal power plants, which burn fossil fuels. One technology proposed to prevent global warming is CO2 recovery from combustion flue gas and the sequestration of CO2 underground or near the ocean bed. Solid oxide fuel cell (SOFC) can produce highly concentrated CO2 , because the reformed fuel gas reacts with oxygen electrochemically without being mixed with air in the SOFC. We therefore propose to operate multi-staged SOFCs with high utilization of reformed fuel to obtain highly concentrated CO2 . In this study, we estimated the performance of multi-staged SOFCs considering H2 diffusion and the combined cycle efficiency of a multistage SOFC / gas turbine / CO2 recovery power plant. The power generation efficiency of our CO2 recovery combined cycle is 68.5%, whereas the efficiency of a conventional SOFC/GT cycle with the CO2 recovery amine process is 57.8%.Copyright