Solid oxide fuel cell development at Forschungszentrum Juelich

Solid Oxide Fuel Cells (SOFCs) are a promising power generation technology due to their high electrical efficiency, multi-fuel capability, potential role in carbon sequestration and possibilities for coupling with a gas turbine. SOFC development is, however, fraught with various problems of high-temperature operations, cost-effective materials and manufacturing processes etc. To solve these problems, we have assembled and tested around 150 SOFC stacks in the last 8 years. Our present design consists of thin electrolyte, planar anode substrate cells in stacks with metallic interconnects featuring internal manifolding with counterflow. The first in a series of large stacks was operated in 2002. All ferritic parts were made of commercial steel type X10CrAl 18 (Ferrotherm 4742). The 40-cell stack delivered 9.2 kW_el in hydrogen operation and 5.4 kW_el with methane as fuel. The average degradation rate of around 10% per 1 000h at 850°C is consistent with results published on characteristics of unprotected ferritic steel interconnects and our own laboratory experience. A new series of short stacks was assembled with interconnects manufactured from the modified ferritic steel Crofer22 APU. The new series of stack tests was operated up to 4 000 hours with degradation rates between 2 and 3% per 1 000 hours of operation, a marked improvement over earlier stacks. However, the target of development is directed towards 0.75%/ 1 000h for commercial operations.