The uniformity and consistency analysis of a fuel cell stack with multipoint voltage-monitoring method

The non-uniform internal status in one cell and the inconsistency between cells have significant impact on the performance and service life of commercial fuel cell stack. The identification of this phenomenon with in-situ method is the key technology for product development and optimization This paper presents the corresponding analysis and a practical in-situ method, i.e., the multipoint voltage-monitoring method, to identify the fuel cell stack uniformity and consistency. Cross plate current and voltage variation in bipolar plate can be therefore observed using the proposed method. In addition, an one-dimensional model has been developed to explain this phenomenon. A variable loading rate experiment has been conducted in a four-cell stack to explore the relationship between consistency and uniformity in multi-cell stack. When the loading rate increases from 20 mA/cm2.s to 40 mA/cm(2). s, the current concentrating in the cathode outlet also increases. Current non-uniformity is caused by gas distribution inconsistency between cells, which makes celll drier than the other cells. Voltage difference between the two monitors of celll is about 32mV, and it can be even larger in extreme conditions, like fuel starvation. It means the health condition estimation of fuel cell stack can be easily misdirected, when monitor is placed on different position. Experimental and simulation results show that the multipoint voltage monitoring method can avoid the 'voltage cheat' and therefore achieve the real consistency and uniformity performance. (C) 2019 The Authors. Published by Elsevier Ltd.