Impact of antifreeze shut-down strategy on performance degradation and freeze start of a proton exchange membrane fuel cell system

Abstract

Proton exchange membrane fuel cell (PEMFC) systems for heavy-duty applications must operate in cold environments and guarantee durability. This work investigates the influence of methanol solution on performance degradation and freeze-start behavior of a 4 kW PEMFC system. Antifreeze and gas purging shut-down strategies are tested, starting from +3 °C to −20 °C, using 25 and 40 vol % methanol and two stacks with different performance degradation. Results show that methanol has a washing effect on the cells, regenerating performance and leading to negative degradation rates after multiple freeze starts. Moreover, methanol prevents ice formation during subzero storage and ensures reliable freeze starts; the lower the temperature and the higher the methanol concentration, the slower the start-up. Although gas purging yields faster freeze starts, antifreeze start-up time can be optimized, e.g., by oxygen enrichment. This study introduces a novel method to extend PEMFC lifetime while enabling efficient and reliable freeze starts from −40 °C.