Investigation of the non-uniform distribution of current density in commercial-size proton exchange membrane fuel cells

Abstract

It is necessary to obtain the current density distribution in order to understand local reactions inside the proton exchange membrane (PEM) fuel cells. Enlarging the active area to commercial-size makes it difficult to maintain uniform assembly pressure, gas supply and heat dissipation inside the fuel cell stack. Existing studies for laboratory-level fuel cells cannot effectively guide the development of large-area fuel cells. In this study, current density distribution inside a 250 cm2 and 3 kW level fuel cell stack is measured and analyzed using the printed circuit board (PCB) technology. A four-layer PCB sensor plate covering 144 current collecting segments and shunt resistors for current measurement is well-designed. The in-house developed measurement system is proved with good function, and the accuracy of current density measurement is within 2%. Results show that the flow field configuration and stack assembly condition greatly affects the uniformity of local current densities. Higher current passes through the area with larger contact pressure, and the current density is low in the poor contact area. The local current density has larger deviations for higher output current, but the normalized current is more uniform. Effects of operating conditions including stoichiometric ratio and flow direction are investigated.