Fault Monitoring in PEFC Stacks by Evaluation of Local Performance and Cell Impedance Analysis

Abstract

PEMFC stack performance is characterized by gradients in various parameters, material inhomogeneity, and uneven flow distribution between the single cells. Local starvation, flooding, or dry-out phenomena can occur due to increasing or lowering the parameter gradients within the individual cells. The presented work is aimed to analyze the nature of these phenomena in stacks operating under system relevant conditions. The impact of different operating conditions on the performance was identified for individual single cells within a 10-cell PEMFC stack from ZSW. The homogeneity of local current density across the active area at the cell level was determined using the patented printed circuit board technology (PCB) by DLR. Three PCBs were used to investigate effects caused by cell positioning within the stack. Electrochemical impedance spectroscopy (EIS) was used for operando fault monitoring. Combined studies of local current density measurements and EIS for all single cells in the stack will be presented. Though these studies we will highlight the occurring links between the EIS response and the local effects within the cells. The presented work is realized in the COALA project (control algorithm and controller for increasing the efficiency of hybrid PEMFC systems in different applications) in the framework of the Polish-German Sustainability Research Call (STAIR II). The funding for this research was received from The National Center For Research and Development (NCBR, Poland) and the Federal Ministry of Education and Research (BMBF, Germany) with the Grant No.: STAIR/6/2016 and 01LX1601, respectively.