Comparison of finite volume SOFC models for the simulation of a planar cell geometry

This paper discusses the development of a finite volume model for a planar solid oxide fuel cell. Two different levels of detail for the definition of the basic cell elements are considered, the first with the assumption of isothermal behavior for a finite volume, defined by a portion of the cell PEN structure with pertinent air and fuel channels, and the second with a more refined element subdivision, capable of simulating temperature differences at a smaller scale. The model applies a detailed electrochemical and thermal analysis to a planar SOFC of a defined geometry (with co-flow, counter-flow or cross-flow configuration), material properties and input flows. Electrochemical modeling includes an evaluation of ohmic, activation and diffusion losses as well as a kinetic model of the hydrocarbon reactions involved. The model calculates internal profiles of temperature, flow composition, current density, and cell energy balances. Internal heat exchange coefficients are evaluated with a specific fluid-dynamic analysis. After a preliminary calibration of the model, a comparison of the simulation results generated by the two, models is presented and a parametric analysis to investigate the effects of different assumptions on a selection of key parameters (heat losses, air stoichiometric ratio and inlet temperatures) is carried out. The results show that the refined model developed here could significantly help in the design of efficient fuel cell stack projects and in the careful consideration of the influence of heat losses, air ratio the endothermic reforming reaction on cell temperature distribution and global performances.