A rapid start-up strategy of polymer electrolyte fuel cells from subzero to normal operating temperatures via controlling operating current density

In a previous study, we numerically showed three distinct stages of ice evolution during cold-start of polymer electrolyte fuel cells (PEFCs), i.e. freezing, undersaturated, and melting stages. Based on the numerical observation, we propose efficient cold start-up strategy for achieving rapid cell temperature rise and simultaneously mitigating the rate of ice accumulation inside a cell. The key of the cold-start strategy is to raise operating current of PEFCs at the undersaturated stage, which can accelerate cell temperature rise without further ice accumulation. Using a three-dimensional, transient cold start model, we numerically demonstrate that rising cell current at the undersaturated stage is indeed effective, significantly improving cold-start behavior of PEFCs. In contrast, the rising cell current during the freezing stage has a negative impact on PEFC cold-start, leading to the faster ice growth due to higher water production rate by oxygen reduction reaction (ORR), which finally results in cold-start failure and deterioration in MEA structure. This study clearly illustrates that optimization of cold-start operation holds the key to obtaining better cold-start performance and the important roles played by cold-start PEFC modeling and simulations to search for optimum cold-start strategy.