Model Based Characterization of Transient Response of a Solid Oxide Fuel Cell System

Abstract

In this paper we perform transient analysis of a Solid Oxide Fuel Cell (SOFC) system. We consider a steam reformer based SOFC system with anode recirculation and with methane as fuel. For the analysis, we develop a control-oriented model that captures the details of heat and mass transfer, chemical kinetics and electrochemistry of the SOFC system. The coupled dynamics of the steam reformer and the fuel cell anode control volumes are extracted and through coordinate transformations we derive closed-form expressions characterizing the steady-state and transient behaviors of two critical performance variables of reformer-based SOFC systems, namely utilization and steam-to-carbon balance. Our analysis is supported by simulations. Using the results derived, we address steady-state fuel optimization by posing it as a problem in linear programming. Our results can be applied in predicting system response to step changes in current and will be useful in designing control strategies for SOFC based power plants.