Experimental investigation on the impact of ambient temperature and current load rate on the cold start behavior of a short PEMFC stack

Abstract

Enhancing the cold start performance of short stacks at low temperatures, which is largely attributed to their significant end-plate effect, proves essential for advancing commercialization. The constant current control strategy remains the most prevalent approach during startup operations. In this study, a 12-cell short stack was employed to investigate experimentally the effects of ambient temperatures and current load rates on cold start behavior. Results demonstrate that decreasing ambient temperatures intensifies the end-plate effect, while implementing lower current load rates effectively prolongs cold-start duration. At elevated ambient temperatures, the generated heat predominates over potential freezing risks for successful rapid startups. The current-controlled cold start process can be divided into three stages: initial performance recovery, moderate membrane water adsorption, and icing onset, which are primarily associated with the hydration state of the membrane electrode assembly. Variations in high frequency resistance evolution and reverse polarity characteristics emerge across these stages. Membrane electrode assembly damage induced by reverse polarity and icing leads to substantial increases in both high frequency resistance and membrane resistance, accompanied by a marginal reduction in the roughness factor of catalyst layer. The protective voltage strategy sustains stable stack performance, demonstrating high consistency at −10 °C. However, significant performance degradation manifests below −20 °C, particularly near end-plates, emphasizing the critical requirement for maintaining internal thermal uniformity under extreme low-temperature conditions.