Understanding the Transient Behavior and Consistency Evolution of PEMFC from the Perspective of Temperature

The temperature of proton exchange membrane fuel cell (PEMFC) is the key factor restricting fuel cell’s performance. A deep understanding of temperature on stack voltage consistency and transient characteristics is necessary for improving the output performance of fuel cell. In this paper, the variation trend of consistency and transient characteristics of 20kW PEMFC stack at different temperatures is studied by experiment. In consistency, the amplitude of voltage changes and voltage difference (voltage coefficient variation σV) under different thermal loading conditions is examined. In transient characteristics, discussing the trends of transient voltage at different thermal loading. As the result, once the stack temperature increases from 65 °C to 70 °C, the stack performance and dynamic response are significantly improved, which may be caused by the rise in temperature promoting the establishment of the internal quality transmission channel. While, as the temperature further increases to 75 °C, the voltage coefficient variation σV rises from 0.029 to 0.031 at 1.0 A·cm^-2, and the average voltage of single-cell decreased from 0.625v to 0.618v. This shows that the further increase of temperature will not lead to the increase of PEMFC stack performance. The results make known that temperature has two sides to the performance of the stack. The higher temperature improves the catalytic activity, aggravates the nonuniformity of water and heat distribution in the stack, but also leads to local hot spots and mass transfer loss, and reduces the consistency and transient characteristics of the PEMFC. These works provide a deep insight into the dynamic behaviors of the PEMFC and can help thermal management system controller design.