Definition of optimal working conditions for a solid oxide fuel cell

Electrochemical characterizations were performed on commercial electrolyte-supported cells (ESCs) (InDEC Ltd.) to determine optimal conditions of power density, electrical efficiency, and lifetime. We determined the properties of these cells in different hydrogen and air flows, at 850° and 900°C, under dry or wet hydrogen. We showed that increasing the hydrogen flow improves power density and reduces hydrogen utilization and electricity efficiency. No variation in performance was obtained as a function of air flow at the cathode. No improvement in power density was measured using wet hydrogen instead of dry hydrogen. Decreasing operating temperature from 900° to 850°C resulted in 20% loss of power density. We observed a 3% irreversible degradation of cell performance in 90 hr. However, at 80% of maximum power density, no loss was observed after more than 360 hr. To control the degradation kinetics of SOFCs, we would need to work at 80 to 90% of maximum power density. We also observed some differences in the performance of the three ESCs tested that was correlated to electrolyte thickness. To compare electrochemical performance of several SOFC cells in different operating conditions, electrical efficiency is required.