Analysis and optimization of dynamic response during the startup process of proton exchange membrane fuel cell

Abstract

Proton Exchange Membrane Fuel Cell (PEMFC) is a prominent application of hydrogen energy in fields such as mobile devices, vehicles and small-scale energy systems. This study experimentally investigates transient response of the automotive PEMFC when starting with different load under various operating conditions, which significantly influences durability. The key finding is that dynamic behavior follows a “two-stage” response mode under drier conditions. The first stage is related to the diffusion processes of cathode gas and the second stage is determined by the membrane rehydration process. Under wetter conditions, dynamic behavior exhibits a “three-stage” response mode with a larger voltage fluctuation and longer startup time. The contributors to the first two stages are the same as the “two-stage” response mode and the third stage is determined by the degree of cathode flooding. Results indicate that increasing cathode stoichiometry, cathode humidity, and temperature obviously enables PEMFC to startup more stable and faster and with a higher load. Besides, a step loading strategy with a gradually reducing magnitude achieves an optimal balance between response time and voltage fluctuation at the target load, with a moderate startup time of 9.6 s and minimal voltage fluctuation of 0.009 V.