PNNL

Abstract

This paper examines the electrochemical and on-cell steam-methane reforming performance of the solid oxide fuel cell when subjected to pressurization. Pressurized operation boosts the Nernst potential and decreases the activation polarization, both of which serve to increase cell voltage and power while lowering the heat load and operating temperature. A model considering the activation polarization in both the fuel and air electrodes was adopted to address this effect on the electrochemical performance. Both the increase in methane conversion kinetics and the increase in equilibrium methane concentration, which are competing effects of pressurization on steam-methane reforming, are considered in a new rate expression. The models were then applied in simulations to preview how the distributions of reforming rate, temperature, and current density can potentially be changed within stacks operating at elevated pressure. A generic 10 cm counter-flow stack model was created and used for the simulations of pressurized operation. The predictions showed improved thermal and electrical performance with increased operating pressure. The average and maximum cell temperatures decreased by 3% while the cell voltage increased by 9% as the operating pressure was increased from 1 to 10 atmospheres.