A Distributed Parameter Model for a Solid Oxide Fuel Cell: Simulating Realistic Operating Conditions

We present a detailed multiphysics model capable of simulating the dyn\ud amic behavior\ud of a solid oxide fuel cell (SOFC). This model includes a description of a\ud ll the important physical\ud and chemical processes in a fuel cell: fluid flow, mass and heat trans\ud fer, electronic and ionic\ud potential fields, as well as the chemical and electrochemical react\ud ions. The resulting highly\ud nonlinear, coupled system of differential equations is solved using a fi\ud nite volume discretization.\ud Our interest lies in simulating realistic operating conditions with the obj\ud ective of high efficiency\ud operation at high fuel utilization. While there are a number of studies\ud in the literature that\ud present multiphysics models for SOFCs, few have focused on simulat\ud ing operating conditions\ud that are necessary if SOFC systems are to realize their promise of h\ud igh efficiency conversion of\ud chemical energy to electrical energy. In this report we present s\ud imulation results at operating\ud conditions that approach the required ranges of power density an\ud d overall efficiency. Our results\ud include a) the temperature and composition profiles along a typical f\ud uel cell in a SOFC stack, b)\ud the dynamic response of the cell to step changes in the available inpu\ud t variables. Since models\ud such as the one presented here are fairly expensive computationa\ud lly and cannot be directly used\ud for online model predictive control, one generally looks to use simplifie\ud d reduced order models\ud for control. We briefly discuss the implications of our model results o\ud n the validity of using\ud reduced models for the control of SOFC stacks to show that avoid\ud ing operating regions where\ud well-known degradation modes are activated is non-trivial without u\ud sing detailed multiphysics\ud models