The EU Integrated Project Real‐SOFC aims at improving the understanding of degradation in SOFC stacks, and extending the durability of planar SOFC stacks to degradation rates suitable for stationary application. As part of the Real‐SOFC project, three series of SOFC stacks, each with two or four planar anode‐supported cells, were operated for durations of 3,000 h up to 10,000 h under varying fuel and electrical load conditions. The durability tests on these short stacks were conducted galvanostatically at 800 and 700 °C in dependence of current‐density (0.3, 0.5 or 0.7 A cm–2), of fuel composition (hydrogen: H2 + 3–10% H2O or methane: CH4/H2O (S/C = 2)) and of fuel utilisation (8, 40, 60 or 75%). A pronounced difference in degradation behaviour was observed between the stacks operated at different current densities. The degradation behaviour was, however, not influenced by the choice of fuel (hydrogen or methane) and was hardly influenced by the fuel utilisation. Lowest degradation rates of about 20 mΩ cm2 kh–1 were determined for the tests of a short stack with cells with LSM cathodes operated at 800 °C and a current‐density of 0.3 A cm–2 and of a short stack with cells with LSCF cathodes operated at 700 °C and a current‐density of 0.5 A cm–2. Post‐test characterisation of the cathode with respect to chromium poisoning was performed on cells from several stacks. No clear relationship between the degradation rate of the stacks and amount of Cr incorporated in the cathode could be established. The major difference was a change in microstructure of the cathode in the region near the electrolyte interface; in the stacks operated at lower current densities, the structurally changed zone was clearly thinner than in those stacks operated at higher currents.

Forschungszentrum Jülich 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.

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