Performance analysis of a reversible solid oxide cell system based on multi-scale hierarchical solid oxide cell modelling

The increasing penetration of intermittent renewable energy into power grids calls for energy storage means to balance the electricity production and consumption. The reversible solid oxide cell is a promising technology for distributed renewable energy storage. A system-level model is a useful tool for system design and efficiency optimization. In this study, a reversible solid oxide cell system model was developed in gPROMS ModelBuilder for distributed energy storage applications by integrating a multi-scale hierarchical three-dimensional solid oxide cell stack model with zero-dimensional balance of plant components models. The hierarchical rSOC stack model considers the electrochemical reactions at the electrodes, the one-dimensional + one-dimensional thermo-fluidic transport along the thickness and the flow direction at repeating unit level, and the three-dimensional heat transfer at stack level. The proposed system model enables the simultaneous investigations on both the total system performance and detailed stack temperature distributions. The roundtrip stack efficiency and roundtrip system efficiency reached 72.3% and 58.3% respectively at base case operation conditions. The effects of excess air ratio and fuel utilization on the system efficiency as well as the temperature uniformity of the reversible solid oxide cell stack were investigated. While increasing the excess air ratio decreases stack temperature gradients, it also decreases both the stack and system roundtrip efficiency. However, improved fuel utilization decreases stack temperature gradients without affecting the stack and system roundtrip efficiency.