Modeling and analysis of short-period transient response of a single, planar, anode supported, solid oxide fuel cell during load variations

Abstract

The main motivation for this study was to analyze transient responses of a solid oxide fuel cell (SOFC) during load variations, which can possibly cause fuel starvation within porous anode active layer and, consequently, accelerate the degradation rate of the SOFC. Simulation approach was taken into consideration. For this purpose, three-dimensional (3-D) dynamic model of a single, planar, anode supported SOFC was built. The model is also briefly presented in this paper. The paper focuses on detailed transient analysis of current density (J), power density (P), fuel utilization (FU) and electrical conversion efficiency (η) after a step change of voltage (load). The simulation results also give us valuable data about local mass fractions of fuel species that cannot be measured in realistic devices. It is shown that fuel starvation occurs when the J (load) is increased by approximately 100% and FU is above 0.85 at final value of J (when steady state is assumed). Moreover, the time-dependent profile of FU give us guideline for setting appropriate inlet flow rate of fuel to prevent fuel starvation. The results show that a SOFC with very thin (ds = 0.1 mm) porous anode support layer is prone to fuel starvation during large load variation. Using a thicker porous anode support layer (ds = 0.5 mm) is proposed to avoid fuel starvation and, consequently, mitigate the degradation of a realistic SOFC. The P and η of modeled SOFC are also analyzed during large load variations. The η increases with increasing the ds from 0.1 mm to 1.0 mm. The results indicate the improvement of η by appropriate design and control of a realistic SOFC.