Model validation and performance analysis of regenerative solid oxide cells for energy storage applications: Reversible operation

The need for electrical energy storage (EES) is being driven by the deployment of increasing amounts of intermittent renewable energy resources. In addition to their fuel flexibility, high efficiency, scalability, and long-term cost outlook, reversible (regenerative) solid oxide cell (rSOC) systems have the potential for round-trip efficiencies competitive with the other available energy storage technologies. Accordingly, the focus of the current study is to investigate modeling methods for high temperature rSOCs in order to facilitate future endeavors related to establishing optimal operating conditions and system designs. Previously developed solid oxide fuel cell (SOFC) and solid-oxide electrolytic cell (SOEC) models are integrated to form a general rSOC model. The model is first calibrated and validated based on the available experimental data in the extant literature. The validation results show that the fitting parameters extracted from the calibration study can precisely simulate the cell behavior under various operating conditions. The effects of key operating parameters, such as temperature, gas composition and fuel utilization, on the voltage-current density performance characteristic and thermoneutral voltage are then investigated. It is also observed that the total electrochemical losses of the cell can be significantly different in each operating mode (fuel cell and electrolyzing) under certain operating conditions. Advantages of pressurized operation on thermal management are also discussed.