Multiphysical modelling of planar solid oxide fuel cell stack layers

Anode supported (ASC) and electrolyte supported cells (ESC) represent the most common cell concepts in solid oxide fuel cell (SOFC) technology. In ASCs, mechanical manageability is provided by a porous nickel/yttriastabilized zirconia (Ni/YSZ) substrate, whereas in ESCs a self-supporting dense YSZ electrolyte is applied. Naturally, the electrical loss contributions arising in ASCs and ESCs differ in quantity, leading to different temperature profiles within planar SOFC stacks. A two-dimensional, finite element method model was developed which considers the underlying chemical and physical processes, and calculates both the electrical performance and the thermal distribution of planar SOFC stack layers operated with reformate fuels. It was then validated by comparing simulation results with extensively measured (i) temperature profiles in SOFC stacks, (ii) gas composition changes along the fuel gas channel of planar ASCs, and (iii) current-voltage characteristics in a temperature range from 650 degrees C to 800 degrees C. The subsequent numerical study reveals (i) the different performances of ASC and ESC, (ii) the impact of operation conditions on performance and temperature profile and (iii) how the individual loss contributions generate temperature distributions in the stack layer.