Experimental Study on Voltage Uniformity for Proton Exchange Membrane Fuel Cell Stack 2020-01-5130

Proton Exchange Membrane Fuel Cell (PEMFC) power system is an environmental-friendly energy conversion device and its operating life is determined by the single cell of worst output performance. Therefore, high stack voltage uniformity benefits to prolong its durability under the dynamic loading process. This work experimentally researches a stack voltage uniformity under the dynamic loading process from open-circuit state (28.6 V) to nominal voltage (18 V). Different dynamic loading strategies, namely constant loading rate strategy, decreasing loading rate strategy, and square increasing loading rate strategy, are elucidated and compared. The results reveal that constant loading rate strategy displays a slight fluctuation of Cv values compared to other strategies and effectively maintain the stack voltage uniformity for its instantaneous response process. Different influencing factors, including the stack temperature, inlet air mass flow and hydrogen pressure, are investigated by loading the constant loading rate strategy. The results show that rising the stack temperature and hydrogen pressure harms voltage uniformity while increasing the air mass flow is beneficial to the voltage uniformity during the open-circuit state. There is little difference in Cv values, which vary with fluctuation for the different stack temperature, hydrogen pressure and air mass flow during the voltage changing process. During the nominal voltage state, increasing the stack temperature, air mass flow supply, and hydrogen pressure themselves can increase the output current, and improve the voltage uniformity. However, increasing output current itself has a negative impact on voltage uniformity. So comprehensive effect exists on the stack voltage uniformity.