Characterizing SOFC Stack Electrochemical Performance at Elevated Pressure

Abstract

In this report, we present our work to characterize the electrochemical performance of solid-oxide fuel cell stacks under elevated-pressure operation. The effort is part of a five-year U.S. DoE ARPA-E INTEGRATE program to combine the high efficiency of solid-oxide fuel cells with the low-cost of reciprocating engines to demonstrate an advanced hybrid electric generator. Within this hybrid system, solid-oxide fuel cells (SOFCs) convert natural gas into electricity. Unconverted fuel leaving the SOFC stacks feeds a downstream natural-gas reciprocating engine that drives an electric generator. In this architecture, the stacks are hydraulically placed upstream of the engine, necessitating stack operation at elevated pressures of 2-5 barg. SOFC stack performance at elevated pressure has witnessed limited study. The team at the Colorado School of Mines is characterizing SOFC stack performance at elevated pressure through design and commissioning of the pressurized stack electrochemical test stand shown in the figure.Reactive gases are regulated using mass flow controllers to simulate the reformate stream produced by a natural gas fuel processor. Such a fuel processor will be incorporated into the stand at a later stage of the research program. Reactants flow through a preheat furnace and into a pressure vessel to reach the solid-oxide fuel cell stack. The pressure within this vessel is matched to the operating pressure of the SOFC stack, minimizing pressure differentials between the internal flow channels of the stack and the surrounding environment. Following electrochemical conversion, exhaust gases exit the stack and the pressure vessel, and are cooled through a series of heat exchangers. Back-pressure regulators near the end of the flow stream regulate stack and vessel operating pressure.The stand has been used to explore the impacts of elevated pressure operation on the electrochemical performance and degradation of Ceres SteelCell stacks. Additional parameters being explored include the effects of fuel composition, anode recycle, and internal fuel reforming. In this talk, we will present preliminary findings on the effects of these variables on stack performance, and their impact in achieving the aggressive performance targets of the SOFC-engine hybrid electric generator. Figure 1