Modeling and control of tubular solid-oxide fuel cell systems. I: Physical models and linear model reduction

This paper describes the development of a transient model of an anode-supported, tubular solid-oxide fuel cell (SOFC). Physically based conservation equations predict the coupled effects of fuel channel flow, porous-media transport, heat transfer, thermal chemistry, and electrochemistry on cell performance. The model outputs include spatial and temporal profiles of chemical composition, temperature, velocity, and current density. Mathematically the model forms a system of differential-algebraic equations (DAEs), which is solved computationally. The model is designed with process-control applications in mind, although it can certainly be applied more widely. Although the physical model is computationally efficient, it is still too costly for incorporation directly into real-time process control. Therefore, system-identification techniques are used to develop reduced-order, locally linear models that can be incorporated directly into advanced control methodologies, such as model predictive control (MPC). The paper illustrates the physical model and the reduced-order linear state-space model with examples.