Durability improvement of segmented-in-series cell stacks for small scale SOFCs

SOFC cells-stacks called "flat-tube segmented-in-series cells-stacks operable at intermediate temperatures" have been developed by a joint work of Tokyo Gas and Kyocera. The cells-stack is composed of multiple single-cells (electrolyte, anode, and cathode) and ceramic interconnects, placed on both sides of a flat-tubular substrate made of insulating material. Ceramic interconnects make the cells-stack more durable than other types of cellsstacks with alloy interconnects. The single-cells are electrically connected in-series on the substrate, so that a high-voltage is easily achievable. Durability tests under several conditions in electric furnaces were conducted in order to clarify the accelerating factors of deterioration. In the conditions, a particular test parameter was set to severe value. In the real system environment, the degree of variation of the parameters is larger than that in the standard condition in electric furnace. Therefore in order to estimate the degradation phenomenon in the real system, the durability tests were conducted also in the simulated system condition in the furnace with temperature distribution of 120°C and reformed methane as a fuel. Then the cell-stacks were modified successfully to improve the durability with lower degradation rates under the several conditions.