Since FY 1981, R and D of solid oxide fuel cell (SOFC) and power generation system have continued in our laboratory as a program of Moon light project of Industrial Science and Technology of MITI. For the interim evaluations of the method of the fabrication and the performance of SOFC, the demonstration of 500W power generation test was executed with the gas conditions of hydrogen and air.
The power generation part was designed only under the rated condition of the operating cell voltage of 0.8V. The cylindrical 15-cell stacks were developed in phase I using the fabrication method with plasma and flame spray coating, and the typical performances were as follows: the output power at rated voltage of 12V was 28W, the maximum output power was 46W at voltage of 7.74V and the specific resistance was 1.2Ω•cm2.
The 500W power generation test was executed with 48 stacks, of which specifications were slightly changed for the mass production in phase II. At the test, the output power of 540W was generated at the rated load voltage of 12V, and 1, 200W was obtained as the maximum power. But the DC efficiency was low, because the current efficiency was not able to be increased due to the insufficient impermeability of cell stacks.
The rapid deterioration in the performance was observed due to the increase of the internal resistance coming from the separation of air electrodes from electrolyte because of large expansion coefficient of air electrodes.
Through these experiments, it is concluded that the impermeability of the stacks should be improved and the material of air electrode should be changed.