Theoretical investigation of steady state multiplicities in solid oxide fuel cells

The nonlinear steady state behaviour of solid oxide fuel cells (SOFCs) is investigated. It is found that the temperature dependence of the electrolyte conductivity has a very strong influence on the occurrence of multiple steady states, instabilities and the formation of hot spots. Two correlations from the literature for the electrolyte conductivity are studied in a lumped model and in a 1D spatially distributed model of a SOFC. The cases of galvanostatic operation, potentiostatic operation, and operation under a constant ohmic load are considered. The lumped model possesses a unique steady state under galvanostatic operation and up to three steady states under potentiostatic operation or under constant load. In the distributed model, three steady states may coexist under galvanostatic operation and up to five under potentiostatic operation.