Energy dense storage using intermediate temperature reversible solid oxide cell systems

The development of high efficiency electrical energy storage of power produced from intermittent renewable energy sources increases the potential for their integration into the electric grid. The focus of the present study is to examine an intermediate temperature reversible solid oxide cell system (ReSOC) of distributed generation capacity (100 kW), which has been identified as a promising technology for electrical energy storage applications. Conceptualized ReSOC systems often store syngas in fixed volume tanks that can be rich in hydrogen, but have low volumetric energy density. The aim of this study is to increase syngas volumetric energy density by integrating a methanation reactor downstream of the electrolysis cell, which will thereby increase the methane content produced during charging mode and significantly raise the volumetric energy storage density of the system. It is found that integration of a methanation reactor into the system can improve volumetric energy storage density by 60% and the overall system round-trip efficiency, albeit at the expense of increased plant complexity and heat exchanger surface area requirements.