Experimental study on the dynamic performance of a power system with dual air-cooled PEMFC stacks

• Gas purging improved performance and consistency under high current density. • Dynamic performance of dual air-cooled PEMFC stacks was studied experimentally. • Different current loading ranges, loading times and air flow rates were considered. • Performance evolution, temperature evolution and voltage consistency were focused. • Temperature and membrane hydration had a greater influence than stoichiometry. • Gas purging improved performance and consistency under high current density. Air-cooled proton exchange membrane fuel cell (PEMFC) system with simplified system composition, low energy consumption and high efficiency is regarded as a reliable power source for the backup and emergency power. Dual air-cooled PEMFC stacks with a rated power of 7.5 kW are used in the experiment to investigate the dynamic response under different current loading rates of 0–20 A and 20–40 A. The experimental results show that stacks perform better under low air flow rate due to the greater influence of the temperature and membrane hydration than stoichiometry on the performance. Similarly, dual air-cooled PEMFC stacks show superior performance under a rapid loading process with the same air flow rate because of higher stack temperature and short-term gas sweeping. The maximum temperature, voltage variance and voltage fluctuation rate of the dual-stacks system increase significantly from 50 ℃, 0.00015 and 1.85 % under current loading of 0–20 A to 57 ℃, 0.00092 and 4.52 % under current loading of 20-40 A, indicating more stringent requirements of thermal management, water management and flow distribution at high current densities. Furthermore, periodic hydrogen purging under current loading of 20–40 A has been proven to improve the performance and consistency of the stacks.