Performance of MIEC cathodes in SOFC stacks evaluated by means of FEM modeling

摘要

In planar solid oxide fuel cell (SOFC) stacks, anode supported cells are connected in series and in parallel by metal interconnectors (MIC), which always goes to the cost of performance. Further insight was gained with the help of a 2D-FEM repeat unit model, accounting for ohmic and polarisation losses on stack level. Implemented physical processes are ⅰ) gas diffusion in the porous electrodes, ⅱ) electric/ionic conduction in the electrodes/electrolyte ⅲ) and electrochemical electrode reactions. Material and kinetic parameters have been determined experimentally and the model is validated against measured data over a broad range of operating conditions. The 2D-FEM repeat unit model calculates performance in dependence on cathode dimensions, microstructure and chemical composition versus MIC-flowfield design. The calculations show, that performance is mainly limited by the oxidant gas transport underneath the contact rib for a given flowfleld design. Thereby a well-chosen cathode thickness increases the overall power output of a planar SOFC stack most efficiently.