Estimation of heat generation rate in solid oxide fuel cell module from single cell performance and module performance based on impedance analysis

Abstract

Heat generation rate in SOFC module was estimated under various thermal self-sustained conditions. SOFC module and system was designed to evaluate power generation property and temperature of module. Single cell was also evaluated the performance and electrode overpotential by impedance analysis under the similar condition to module power generation state. We estimated the heat generation rate with enthalpy calculation based on the actual module performance, and also with entropy calculation based on the impedance analysis of single cell. It was found that the heat generation rate calculated by enthalpy is approximately corresponded with that calculated by entropy. There still contains small error between heat generation rate calculated by enthalpy and that calculated by entropy. It was considered that these errors are originated from distribution in stack temperature and reforming gas temperature in the module. According to impedance analysis, it was found that the ohmic resistance is varied under operating condition and related with the current distribution which is calculated with the current path length in the cell. It was suggested that power generation state of module is affected by the current path length in the cell (in another word, distribution of power density) and distribution of overpotential; these phenomena is dominated by gas composition and thermal self-sustainable temperature.