AN EXPERIMENTAL STUDY ON PERFORMANCE DEGRADATION AND RECOVERY PROTOCOLS OF MODULE STACK PROTON EXCHANGE MEMBRANE FUEL CELL UNDER DYNAMIC LOAD

In this paper, the performance degradation of three-cell proton exchange membrane fuel cell (PEMFC) stacks was investigated in dynamic working conditions. A customized current cycle based on the World Harmonized Vehicle Cycle was developed as a test cycle. Long-term experiments, consisting of equal-duration test periods, were conducted at stack temperatures of 60 degrees C and 70 degrees C. The test cycle was repeated in each test period, followed by a recovery stage. To investigate the responses of PEMFC stacks during tests, the polarization curves were measured at the beginning and end of each test period, as well as after the recovery stages. Based on the degradation assessment, the more severe working temperature was selected as the test condition for assessing the recovery efficiency of the shutdown and the voltage cycling method. The experimental results indicated that the temperature of 70 degrees C resulted in a higher deterioration of stack voltage than the case of 60 degrees C. Specifically, the stack voltage measured at 0.5 A/cm2 in the case of 60 degrees C and 70 degrees C dropped by 1.75% and 3.59%, respectively, after 100 hours. Regarding the recovery effectiveness, the shutdown method was more efficient than the voltage cycling method as time progressed. At 0.8 A/cm2, for instance, the recovery efficiency of the shutdown method maintained at 77.25%, whereas the figure of the voltage cycling method decreased to 53.46% after 100 hours. The ohmic region had the highest recovery efficiency compared to the other regions with the shutdown approach. This study emphasized the recovery capability of the shutdown method and motivated further works to shorten its duration for practical conditions.