Long-Term Testing of SOFC Stacks at Forschungszentrum Jülich†

Forschungszentrum Julich is performing long-term SOFC stack tests for more than 17 years. Within the European project Real-SOFC (2004–2008) durability tests operating at 700 °C were started with two short stacks which reached the first milestone of 10,000 h in November 2008. The operation of one stack, clearly showing progressive degradation over the last 5,000 h, was terminated after more than 2 years for inspection of the status of the components and interfaces. The second stack is now in operation for more than 5 years having reached 43,800 h in August 2012. The average voltage degradation over the full duration was about 1% per 1,000 h. Another short stack with plasma sprayed protective coatings on the air side of the interconnects is running for more than 14,000 h, showing about 0.12% voltage degradation per 1,000 h. A stack with a similar configuration but LSM cathodes, operated at a temperature of 800 °C, broke down after 2 years. As reason for the break-down manganese diffusion from the LSM cathode into the 8YSZ electrolyte could be determined by post-test analysis. All these short stacks have been tested with humidified hydrogen at a fuel utilization of 40% and with dry air. In the meantime a 2.6 kW stack was operated on internally reformed methane for 4,500 h showing about 0.3% voltage degradation per 1,000 h.