Numerical Modeling of SOFC Based on Mixed Conductive Electrolyte

Abstract

As one of the possible electrolyte materials for intermediate temperature SOFCs that works around 500 to 800°C, we focus on Gadolinia Doped Ceria (GDC). This ceramic material shows reasonable ion conductivity even at 600°C. It, however, is a mixed conductive material having non-negligible electronic conductivity. In this study, the fundamental performance of a simple planar SOFC with GDC electrolyte is numerically investigated. The effects of electrical leakage on the cell performance are the main focus of discussion. The electrolyte thickness is varied in a range from 50 to 200μm. Both air and fuel flows are assumed to be steady and laminar. Governing equations are the continuity, momentum, energy and mass transfer equations. They are solved numerically by the control volume method. It is found that the leakage of electricity becomes larger for the smaller electrolyte thickness cases, and is more prominent for an electrolyte thickness of less than 80μm. Under such conditions, output power and energy conversion efficiency decrease dramatically. On the other hand, energy conversion efficiency also decreases for an electrolyte thickness that is too large because of the increase of ohmic overpotential of the electrolyte. Consequently, there seems to be an adequate thickness for the electrolyte that gives preferable output power and energy conversion efficiency.