The Shutdown Purge Strategy Used in Subzero Environmental Temperature for a Commercial 132kW Fuel Cell System Based on High-Frequency Resistance

PEMFC is considered more promising in NEV applications. The shutdown purging strategy is crucial in cold weather for its reliable operation. This paper focuses on the shutdown purge strategy for a commercial 132kW PEMFC system under subzero environmental temperature, in the purge process, the HFR was used to characterize the water content inside the stack. To obtain a definitely strategy, the role of stack operating temperature, pressure, gas flow and purge strategy was compared respectively. A 132kW PEMFC system was built to conduct the purging experiment, and the purging strategy was verified by cold start experiment under -30 °C in temperature chamber. For this system, increasing the air flow can help improve the purging process to some extent, however, it hardly can reach the target resistance needed for the cold startup when the stack temperature is lower than 60 °C because it reaches water-thermal equilibrium at lower resistance. Improving the stack operating temperature from 40 °C to 60 °C, the purging process is obviously accelerated. At stack temperature of 60 °C, it can reach the target resistance in 150s which is accepted by the equipment manufacturer. To help the air flow out more easily, the back pressure valve was opened completely in the purging process. Then the impedance can quickly reach the target value. Then a purging strategy was proposed in this paper, and the strategy was verified by different operating condition in temperature chamber, and the system successfully started under the environmental temperature of -30°C.