Investigation of the interaction mechanism between power and heat of a reversible solid oxide cell during a mode switching cycle

Abstract

Chemical energy and electrical power can be converted bi-directionally with unrivaled efficiency by the mode switching of reversible solid oxide cell (RSOC) stacks. Mode switching can lead to temperature fluctuations in RSOC stacks, which will significantly affect the mechanical stability of stacks. To investigate the transient performance of the RSOC, a 1D dynamic model of a single repeating unit (SRU) is established and validated against experimental data. The interaction mechanisms between the thermodynamic and electrochemical parameters of the RSOC during transients are elucidated elaborately. Two indicators, i.e., temperature variation rate and temperature gradient, are used for the quantification analysis. The effects of current density, hydrogen fraction, and inlet gas temperatures on the temperature distribution along the SRU are investigated. In the simulation scenarios, the maximal temperature variation rate can achieve 1.49 and 1.495 K min−1 in co- and counter-flow configuration, and the maximal temperature gradient can achieve 5.6 and 4.6 K cm−1, respectively. The hydrogen fraction has a significant influence on the temperature. Increasing the hydrogen fraction from 0.4 to 0.7, the maximal temperature variation rate decreases by 12.8 % and 12.1 % in the co- and counter-flow SRU, and the maximal temperature gradient reduces by 10.6 % and 14.2 %, respectively.