Modelling, validation and analysis of preheating strategy of fuel cell vehicle during Subzero cold start

The rapid cold start capability of fuel cell vehicles in low-temperature environments is one of the key factors restricting their commercialization. Reasonable and effective strategies are crucial to improving the lowtemperature cold start capability of fuel cell vehicles. In this paper, a cold start model of fuel cell system is established, and the model is verified based on the cold start experiment of a hybrid fuel cell vehicle. The necessity of the coolant preheating strategy in the cold start is analyzed, and the important role of the coolant preheating strategy in helping the fuel cell system to start quickly at -10 degrees C and below is demonstrated. Furthermore, the effects of air inlet temperature, air inlet flow rate, and external heater power on the cold start performance are investigated. The results show that when the air inlet temperature rises from -13 degrees C to 65 degrees C, the start time is shortened from 279 s to 234 s (reduced by 16.13 %). And at low air inlet temperatures, the lower flow rate of air can significantly reduce the temperature difference and maintain uniformity of temperature inside the stack, while at a higher temperature, the higher air flow rate causes the temperature of the cell stack to rise rapidly. For heating power, the start time is shortened from 421 s to 126 s (reduced by 70.07 %) when the heating power is increased from 3 kW to 11 kW. However, it will cause a larger temperature difference between the inlet and outlet of the coolant, which is not conducive to the uniform distribution of the temperature inside the stack. Thus, the start time can be shortened by increasing the air inlet temperature, air inlet flow rate, and heating power with the consideration of the temperature difference that the stack can withstand. The model developed by this study provides an effective way to analyze the fuel cell system during cold start, which is useful for the development of control strategies in the future.