SOFC Modeling and Parameter Identification by Means of Impedance Spectroscopy

Abstract

A zero-dimensional stationary model for the I-U characteristics of anode-supported solid oxide fuel cells (SOFC) is presented. The different kinds of electrode polarization resistances are separated from experimental impedance data by means of a detailed equivalent circuit model specified for anode-supported cells. This has the big advantage that partial pressure and temperature dependency of electrode exchange current densities could be determined by a fit of semi-empirical power law model equations. For the first time, the exponents a and b for the pH2- and pH2O-dependency of the anodic exchange current density are obtained independently. Equally, the exponent m for the pO2-dependency of the cathodic exchange current density is derived. The anodic and cathodic gas diffusion polarization is calculated without the estimation of parameters such as tortuosity and porosity. Our approach is advantageous to separate anodic and cathodic activation and diffusion polarization and precisely predicts I-U characteristics for a wide operating range.