Dynamic Processes of Mode Switching in Reversible Solid Oxide Fuel Cells

Abstract

With the development of distributed energy systems (DES), energy storage has attracted much attention in the research world. Reversible solid oxide fuel cells (RSOFCs) have shown potential as a promising means of electrical storage with high efficiency, especially for multienergy distributed systems coupling electricity and gas. RSOFCs have both a generation mode and a storage mode with a high fuel flexibility and in order to implement the frequent switch of generation and storage, a detailed dynamic behavior is needed in both the single mode and transitional process. However, few studies have been conducted investigating the complex dynamic processes of RSOFCs. In this study, a one-dimensional model is established to study the basic dynamic processes of RSOFCs, especially those involved in mode switching. The model is based on rich SOFC models and is first validated with experimental data and then employed to study the response of the primary characteristics of the cell, including current density, temperature, power density, and mole fraction of the voltage step input. The calculation results show that both the electrochemical and heat transfer greatly influence the transient process, but on different time scales. The reaction dynamics is another primary factor that determines the gas mole fraction. Furthermore, especially regarding the complex mode switching, three different modes are proposed and investigated to study the different switch processes and ultimately to provide a basic guide to control the RSOFC stacks.