Dynamic modeling of a solid oxide fuel cell system in Modelica

Abstract: In this study a dynamic model of a solid oxide fuel cell system has been developed. The work has been conducted in cooperation with Modelon AB using the Modelica language and the Dymola modeling and simulation tool. Modelica is an equation based, object oriented modeling language, which promotes flexibility and reuse of code. The objective of the study is to investigate the suitability of the Modelica language for dynamic fuel cell modeling. A cell electrolyte model including ohmic, activation and concentration irreversibilities is implemented and validated against simu- lations and experimental data presented in the open literature. A 1D solid oxide fuel cell model is created by integrating the electrolyte model and a 1D fuel flow model, which includes dynamic internal steam reforming of methane and water-gas shift reactions. Several cells are then placed with parallel flow paths and connected thermally and electrically in series. By introducing manifold pressure drop a stack model is created. The stack model is used in a complete system model including an autothermal re- former, a catalytic afterburner and heat recirculation. Four reactions are modeled in the autothermal reformer. Those are two types of methane steam reforming, the water-gas shift reaction and total combustion of methane. The simulation results have been compared with those in the literature and it can be concluded that the models are accurate and that Dymola and Modelica are tools well suited for simulations of the transient fuel cell system behaviour.