Efficient thermal management strategies for cold starts of a proton exchange membrane fuel cell system

A fast, reliable and harmless cold start for proton exchange membrane fuel cell (PEMFC) systems is essential for transportation applications. This paper discusses an experimental study of different thermal management strategies of cold start for a PEMFC system. Our purpose is to identify an optimal thermal management strategy depending on the startup temperature, the startup time and energy efficiency of the system. A successful cold start requires the cells to warm up above 0 degrees C before all the cathode catalyst layer pores are plugged with ice. To achieve this, there are several thermal management strategies which can be classified into passive (using heat generated within the stack) or active (using external heat). Both strategies were investigated with numerous tests starting from 0 degrees C to -30 degrees C using a 4 kW PEMFC stack. The results showed cold starts at -30 degrees C were successful with a passive strategy. However, for quick cold starts with less ice formation, this strategy is only adequate at temperatures >= than -15 degrees C. Although the use of a heater requires extra energy, active strategies at-25 degrees C led to more favorable cold starts since avoid ice formation. In addition, at -25 degrees C using the heater only until -15 degrees C yielded to a quick and safe cold start, while improving the energy efficiency. Since at -15 degrees C, the heat was generated by the reaction in the cathode catalyst layer, which means less heat losses and better energy efficiency. This study provides guidelines to optimize cold start strategies.