The dynamic voltage uniformity of the commonly-controlled kW-class Air-cooled PEMFC

The existing kW-class air-cooled proton exchange membrane fuel cells (PEMFCs) are often controlled by tuning the purge valve, the cooling fan based on the purge interval and the optimum temperature curves recommended by the manufacturers. However, even if the fuel cell temperature can timely track the recommended curves, the individual cell voltage uniformity may be deteriorated while the voltage uniformity is an important factor reflecting and affecting the performance and the life of the fuel cell stack. Therefore, it is necessary to study the individual cell voltage uniformity under the existing kW-class air-cooled PEMFC control strategy. In this paper, the experiment study is conducted based on the self-built 2kW air-cooled PEMFC test platform. The voltage response and the uniformity of PEMFC stack during dynamic load were investigated with the step variable load working conditions. According to the experiment results, we found there were a larger overshoot or undershoot of stack voltage with a longer recovery time, a lower minimum voltage and a larger voltage volatility between the individual cells when a larger step current excitation appeared. Especially, the minimum individual cell voltage might be lower than the working voltage limit 0.5V and even the safety threshold voltage 0.4V, even if the stack voltage was not obviously abnormal. Meanwhile, the larger the initial currents, the smaller the effect of the same step current excitation on the voltage uniformity. Hence, it can be concluded that the individual cell voltage and voltage uniformity should be seriously considered for the commonly-controlled kW-class Air-cooled PEMFC under the dynamic working conditions.