Electrochemical Simulation of Planar Solid Oxide Fuel Cells with Detailed Microstructural Modeling

Abstract

A quasi-two-dimensional physically-based model for the description of transport and reaction in planar solid oxide fuel cells (SOFC) is presented in this study. Electrochemistry and transport phenomena in the cell are locally described in 2D using mass conservation equations and well-established global electro-kinetics, coupled with the 1D representation of gas channels in both co-flow and counter-flow configurations. The key feature of the model consists in the numerical reconstruction, through packing algorithms, of the three-dimensional microstructure of each porous layer for an accurate evaluation of the effective properties. Coupling of a detailed microstructural modeling into the cell-level electrochemical model allows the prediction of the polarization behavior from the knowledge of operating conditions and powder characteristics, thus eliminating the need for empirical correlations and adjusted parameters, which is typically the weak point of existing cell-level models. The framework is used for the simulation of a short stack of anode-supported cells with LSM-based cathode and 1.5mm thick anode support, developed and tested by Forschungszentrum Jülich. The effective properties of each layer are calculated and compared with available experimental data. A good agreement is also reached when comparing simulated and experimental polarization curves under different operating conditions without fitting any parameter. Simulations show that at 800°C the activation resistance in the cathode functional layer is the main contribution to the cell overpotential. In addition, the model suggests that gas concentration effects at the anode play an important role on the global electrochemical response. The study shows that quantitative predictions can be obtained using this integrated approach, making it an attractive tool to assist the SOFC development.