Location and Magnitude of Heat Sources in Solid Oxide Fuel Cells

The correct prediction of the temperature distribution is a prerequisite for the reliable determination of species and current distributions in any solid oxide fuel cell (SOFC) model. It is even more crucial if the model is intended for the analysis of thermo-mechanical stresses. This paper addresses the different mechanisms of heat generation and absorption in the fuel cell. Particular attention is paid to the heating associated with the oxidation of hydrogen, which is commonly assigned to the interface between electrolyte and anode in SOFC modeling. However, for a detailed determination of the temperature profile in the fuel cell solid components, the separate consideration of the cathodic and anodic half-reactions is required. A method for determining the specific entropy change of the half-reactions based on Seebeck-coefficient data is adopted from the literature and applied to the SOFC. In order to exemplarily demonstrate the contribution of the various heat sources to the overall heat generation as well as the influence of their location, a spatially discretized model of a tubular SOFC is used. Temperature profiles obtained with and without separate consideration of the electrode reactions are compared. The comparison shows that the spatially discretized reaction model is indeed necessary for the reliable assessment of temperature gradients in the ceramic SOFC components.