Yuya Tachikawa

Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are promising electrochemical devices that enable the highest fuel-to-electricity conversion efficiencies under high operating temperatures. The concept of multi-stage electrochemical oxidation using SOFCs has been proposed and studied over the past several decades for further improving the electrical efficiency. However, the improvement is limited by fuel dilution downstream of the fuel flow. Therefore, evolved technologies are required to achieve considerably higher electrical efficiencies. Here we present an innovative concept for a critically-high fuel-to-electricity conversion efficiency of up to 85% based on the lower heating value (LHV), in which a high-temperature multi-stage electrochemical oxidation is combined with a proton-conducting solid electrolyte. Switching a solid electrolyte material from a conventional oxide-ion conducting material to a proton-conducting material under the high-temperature multi-stage electrochemical oxidation mechanism has proven to be highly advantageous for the electrical efficiency. The DC efficiency of 85% (LHV) corresponds to a net AC efficiency of approximately 76% (LHV), where the net AC efficiency refers to the transmission-end AC efficiency. This evolved concept will yield a considerably higher efficiency with a much smaller generation capacity than the state-of-the-art several tens-of-MW-class most advanced combined cycle (MACC).

Exchange Current Density of Solid Oxide Fuel Cell Electrodes

It is desired to develop computational procedures to simulate internal current density, anode/cathode gas concentrations, and temperature distribution in solid oxide fuel cell (SOFC) systems. In this study, the influences of various operational conditions on the exchange current density, the essential parameter to simulate SOFC performance, are revealed and discussed. The anodic exchange current density depended strongly on the humidity of H2-based fuel gas, and it exhibited the highest value at around 40% H2O. The cathodic exchange current density was strongly affected by the operational temperature. Parameters necessary to describe dependencies of exchange current density on various operational parameters were determined by fitting measured exchange current density values with empirical equations.

Numerical Analysis of the Optimal Distribution of Hydrogen Filling Stations

This chapter describes possible numerical analysis for optimizing the distribution of hydrogen filling station. An algorithm is described to simulate the optimal geographical distribution of new hydrogen stations. A case study to specify possible locations of additional hydrogen filling stations in Japan is described, using statistical data on traffic flow, local employee numbers, and population in each region.