Browse Publications Technical Papers 2021-01-0731

Experimental Research on Voltage Uniformity of a PEMFC Stack under Dynamic Step Loading 2021-01-0731

Proton exchange membrane fuel cell (PEMFC) stack has been a promising electricity conversion device because of its high efficiency, environment-friendly, and fast dynamic response. The durability of a stack is mainly determined by the weakest single cell. Thus, keeping high single-cell voltage uniformity under a dynamic operating process is of great importance for enhancing stack working life. This work experimentally researches the voltage output responses under different dynamic operating conditions and the single-cell voltage uniformity, characterized as voltage coefficient variation Cv. Under the condition of the same initial current (70A) and different step loading amplitudes, with the increase of loading amplitude, i.e., from 20A to 110A, the variation of maximum value Cv values increases from 2.15% to 11.12% and a longer time is needed for voltage to return stable. For different initial current and the same step current amplitude (70A) conditions, the maximum Cv values range from 6.75% to 8.99% with the increase of initial current. In comparison, the influence of the different initial current with the same step amplitude on Cv value is not as evident as the condition that the same initial current with different loading size. For overall experiments, the single-cell minimum voltage is larger than 0.5V, which meets the stack's requirement during the operating process. Under the condition of different operating steady state, the voltage uniformity decreases with the increase of loading current. For various air mass flow supplement, it is found that increasing air supply can significantly improve the stack output performance at high loading current. Simultaneously, the maximum Cv values drop from 7.55% to 6.93%, which benefits to enhance the single-cell voltage uniformity in the step loading process.


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