Towards a practical tool for online monitoring of solid oxide fuel cell operation: An experimental study and application of advanced data analysis approaches

An advanced approach, the distribution of relaxation time analysis of electrochemical impedance spectra is used to identify excitation frequencies altered by SOFC regulation or degradation effects. The technique used and results contained in this paper provide key information, which can be used in the development of a low cost and practical online monitoring hardware tailored specifically for SOFCs. The impacts of diverse operating parameters on an industrial sized SOFC cell performance are identified. Moreover, specific time constants for a practically relevant example stack degradation mode (carbon deposition) are determined. In a further step, the key frequencies for carbon deposition may be monitored online using the tool. A key finding of this work is that the processes can be successfully isolated via EIS excitation without using a reference electrode. This is of great importance for using the methods developed to isolate the key feedback frequencies in a practical experimental setup. Furthermore, this paper demonstrates why avoiding, and if necessary, the removal of carbon deposits, on the SOFC anode, are essential to understand and enact for reliable and durable SOFCs systems to break into and hold a market position.