An efficient multi-point impedance method for real-time monitoring the working state of solid oxide fuel cells

Abstract

During the practical operation of commercial solid oxide fuel cells (SOFCs), it is significant and urgent to implement a non-destructive and timely diagnosis of performance degradation. However, the method, which can completely fulfill the above requirements, is still not available. This study presents a novel approach, the multi-point impedance (MPI) method, which enables in-situ and real-time monitoring of the operating state of commercial SOFCs. The method involves two critical steps: the determination of characteristic frequencies using the distribution of relaxation time (DRT) and the selection of reference frequencies for calculating impedances. The reliability of the MPI method is evaluated both theoretically and experimentally. The results of theoretical investigation reveal that the MPI method can accurately estimate the resistances of resistance-capacitance (RC) components. Subsequently, the MPI method is employed to monitor the working state of commercial microtubular SOFCs (MT-SOFCs) during the stability test. The experimental results show that by using the MPI method, the impact of different electrochemical processes on the durability of MT-SOFCs can be clearly clarified. Combining the theoretical and experimental studies, it demonstrates that the MPI method can serve as an efficient and simple diagnostic approach for real-time monitoring SOFCs.