Durability Degradation in Proton Exchange Membrane Fuel Cell Stacks: The Scale Effect

The fuel cell products exhibit different power levels across various application scenarios or R&D stages. However, the performance exhibits a nonlinear mapping relationship across the material-single cell short stack-long stack hierarchy. This study constructs for the first time a model of ″identical core materials + identical test conditions + different power levels″, isolating the variables of materials and operating conditions, and conducted a comparative study on the 1000 h durability degradation behavior of three stacks (4 kW short stack, 45 kW medium stack, and 130 kW long stack). The results indicate that the long stack exhibited higher initial performance and better consistency than the medium stack, though its degradation rate was intermediate between the short and medium stacks. The results of linear fitting and the “beginning to the end” difference method are similar in evaluating the degradation rate, and both are applicable to the durability evaluation. Higher current densities lead to more severe degradation and increased inconsistency among individual cells. All stacks exhibit dynamic periodic fluctuations in performance, highlighting the non-negligible impact of reversible losses during long-term operation and providing an experimental basis for implementing regular maintenance. The conclusions offer practical engineering implications for stack design, process uniformity improvements, and lifetime prediction with multiple power levels.