Startup optimization of an automotive polymer electrolyte membrane fuel cell system with dynamic hydrogen reference electrodes

Efficient polymer electrolyte membrane fuel cell (PEM-FC) systems with minimal degradation are indispensable for automotive applications. A decisive measure to achieve this goal is the optimization of the startup procedure as part of the system operating strategy. This applies in particular to startups where the anode is partly or completely filled with ambient air after long downtimes. When displacing the air in the anode with hydrogen, damage to the cathode is inevitable and should be minimized. Basic approaches for this optimization are known from literature but are mainly derived from single cell and short stack experiments. In this paper, we optimize a full PEM-FC system by utilizing Dynamic Hydrogen Electrodes and show how gas replacement speed and half cell voltage evolution can be improved to mitigate degradation. The experimental results show that a homogeneous flow of the hydrogen/air front across the stack is to prioritize over its speed as only this enables additional upper voltage control in large stacks. The system optimum is achieved by maximizing startup pressure and purge valve flow, adapting the anode recirculation rate and precise voltage clipping. This study thus forms a procedural template for the optimization of the SUSD procedure in automotive fuel cell systems.