Validation and Application of a CFD-Based Model for Solid Oxide Fuel Cells and Stacks

Abstract

The National Energy Technology Laboratory (NETL) has developed a solid oxide fuel cell (SOFC) model based on commercial computational fluid dynamics (CFD) software. This new tool is being used to support the US DOE Solid State Energy Conversion Alliance Fuel Cell Program, which will require advanced fuel cell designs in order to meet the program goal of reaching $400/kW for small (∼5kW) systems. The NETL model combines a special SOFC electrochemical model with an electrical potential field model in the finite-volume commercial CFD code from Fluent Incorporated (Lebanon NH). Mass and energy sources and sinks resulting from the electrochemical reactions and electrical current flow are coupled to the fluid flow, chemical species transport, heat transfer, porous media flow, and gas phase chemistry capabilities available in the base CFD model. The NETL SOFC model has also been recently extended to model SOFC stacks with cells connected in electrical series. The model is able to predict detailed, spatially resolved current flow through the electrolyte and through all conducting media in three-dimensional SOFC cells and cell stacks. In conjunction with the SOFC model development program, NETL has an experimental facility in place to generate data for validation of the SOFC model. The experimental program includes collaboration with the University of Utah, a supplier of test specimens and preliminary cell performance data. Well-characterized SOFC test specimens are being tested in the NETL fuel cell test stands for single cell and short-stack arrangements. Anode-supported cells with controlled electrode microstructures, electrode thickness, and electrolyte thickness are being tested. Operating data from the test stands includes cell and stack polarization curves, temperature data, and chemical composition of reactant streams. Using NETL and University of Utah data, an extensive validation program is now underway for the NETL SOFC model. The model is being tested using a simple button-cell configuration. A parametric study of varying operating conditions, cell geometries and cell properties is being performed. Good agreement between predicted and measured cell performance has been observed and is presented. The model has also been applied to planar single cell and cell stack configurations to help in the design of NETL experimental test facilities.