Optimization of contact resistance with better gasketing for a unitized regenerative fuel cell

Abstract

Unitized regenerative fuel cells, as being able to use and regenerate the hydrogen, seem to be compact solution for the standalone systems. The cells with smaller active areas (<50 cm2) have better contact between electrode and bipolar plate due to their smaller sizes. It therefore results in very low resistance at the interface owing to high performance. However, the power produced by the cells is not generally observed to linearly follow the changes in the size of electrodes. Such losses in the performance for scaled up cells is due to the high interfacial contact resistance incurred at the interface. Such resistance could be lowered using optimized gaskets as well as applied torque. The present study evaluates different gaskets for a scaled-up version of the cell (300 cm2) as a measure of increased contact resistance when operated at high pressures during electrolysis mode of operation. The cell is modelled structurally and simulated for most available gasket materials i.e. silicon and Teflon. Average contact pressure at the interface of electrode and bipolar plate is considered as the parameter to estimate the interfacial contact resistance. Silicon is evaluated better material than Teflon and is observed to hold almost 4.5 bar of gas in electrolysis mode when clamped with 8 Nm of torque. The cell is observed to perform close to state of art system and delivered 125 A at 0.5 V during fuel cell mode and generate 500 and 250 mL/min of hydrogen and oxygen during electrolysis mode of operation.