Koji Hoshino

Development of a Low Temperature Operation Solid Oxide Fuel Cell

Lowering operation temperature of the solid oxide fuel cell (SOFC) would promote the commercialization of a power-generation module in terms of the manufacturing cost, lifetime, reliability, etc. Mitsubishi Materials Corporation and Oita University have been jointly developing a planar-type SOFC which could operate at a temperature of about 700°C. As an electrolyte, lanthanum gallate (LaGaO 3 ) with substitution of Sr for the La site and Mg and Co for the Ga site was used at this temperature. So far we have established a technique for large-seale cell production, and currently we are examining the performance of a commercial-size cell as large as 154 mm in diam. The obtained cell attained an output power of 31 W with an effective electrode area of 177 cm - at 650°C. Furthermore, a stack of two cells has been tested and the use of stainless steel for the separator was found to be possible during the examined time period at this temperature. The internal CH 4 reforming on the cell has been examined, and the cell output performance using methane [steam/carbon ratio (S/C) = 2] was about 93% of the power density of the cell using hydrogen.

Development of Intermediate-Temperature SOFC Module Using Doped Lanthanum Gallate

An intermediate temperature solid oxide fuel cell (SOFC) module was developed using electrochemically active cells composed of (La, Sr)(Ga, Mg, Co)O 3 electrolyte, Ni-(Ce, Sm)O 2 anode, and (Sm, Sr)CoO 3 cathode. Seal-less planar type stack design was employed. The first generation module successfully provided the output power of I kW with thermal self-sustainability below 800°C. Maximum electrical efficiency obtained with this module was 43%[LHV] together with the corresponding fuel utilization of 78%. Dynamic performance tests demonstrated the capability of output power alteration from 0.6 to 1 kW while maintaining a high electrical conversion efficiency. Further testing and modification of the module for methane fuel utilization are in progress.