PNNL

Abstract

A "one-dimensional", steady-state model of an SOFC stack was needed to support the design of balance-of-plant components for a 5 kW mobile SOFC system. This "stack module" was required to predict appropriate stack voltage responses to changes in fuel composition, fuel flow rate, stack temperature and current demand, with response characteristics that were adjustable to changes in stack component materials and dimensions as well as to electrode porosity. The spreadsheet-based stack module was derived from the work by Kim, Virkar et al (see J. Electrochem. Soc. 146(1) 69-78 (1999)), with modifications suggested by Riess and Schoonman, p291 in CRC Handbook of Electrochemistry (1997) CRC Press. The usual overpotential terms account for ohmic resistance of the cell components, losses due to charge transfer at the electrodes, and losses due to diffusion of reactants into and products out of the porous electrodes. Response of the module is compared to published cell and stack data. After fitting adjustable parameters to match particular cell performance characteristics, the module responds reasonably well to changes in temperature and fuel concentration. The module is used to analyze the performance of anode-supported cells that were fabricated at PNNL (see abstract submitted by Stevenson, Meinhardt, Simner, Habeger and Canfield, "Fabrication and Testing of Anode-Supported SOFC").