SOFC Cathode Design Optimization using the Finite Element Method

Abstract

Solid oxide fuel cells (SOFCs) are promising as an energy producing device, which at this stage of development will require extensive analysis and benefit from numerical modeling at different time- and length scales. A 3D model is developed based on the finite element method (FEM), using COMSOL Multiphysics, of a single SOFC operating at an intermediate temperature range. Ion, electron, heat, gas-phase species and momentum, transport equations are implemented and coupled to the kinetics of the electrochemical and internal reforming reactions. High current density spots were identified in our previous work, at positions where the electron transport distance is short and the oxygen concentration is high. The electron transport especially within the cathode is found to be limiting for the electrochemical reactions at positions far from the channel walls (interconnect). New cathode designs are proposed, for the cathode/air channel interface, to be able to reduce the maximum electron current density (decreasing the ohmic polarization due to electron transport), i.e., to increase the fuel utilization, with constant inlet conditions, compared to a standard approach. The two cases with a modified cathode structure presents 1 % higher average ion current density as well as 1 % higher fuel utilization, keeping the inlet conditions similar