Modelling of PEMFC Cold Starts

Abstract

One challenge for the automotive application of polymer electrolyte fuel cells (PEMFC) is the start-up with sub-zero temperatures due to the reezing of water inside the cell. The temperature has to rise above 0 °C before the ice completely blocks the cathode pores and inhibits the oxygen reduction and species transportation. A transient 2D numerical model is presented to better understand the influence of start-up and design parameters and to propose efficient cold start strategies. This includes the drying of the membrane prior to shut-down as demonstrated with the simulation of a cycle of: normal operation, drying, cooling down, cold start, normal operation. Other beneficial factors for a successful cold start are thermal insulation and low cell voltage for the potentiostatic mode (Fig. 1). It is also shown that a temperature of 0 °C measured at the cathode bipolar plate might not be a sufficient criterion for a successful cold start due to the remaining ice in the cathode catalyst and microporous layer and the inhomogeneous temperature profile along the channel direction.