Dynamic control of stack temperature prevents abnormal flooding in 60 kW PEM fuel Cells: Modeling and 2000h road validation

Water content inside the stack affects durability of the proton exchange membrane fuel cell in vehicle. Gas temperature and relative humidity at stack inlet are important factors affecting the water content. This paper proposes a model-based dynamic control of stack temperature to prevent abnormal flooding in a 60 kW PEM fuel cell stack with experiment validation. To be specific, a hydrothermal dynamic model of air supply subsystem including gas-gas humidifier is established by taking into consideration heat exchange between air supply subsystem and environment, heat capacity of humidifier and influence of liquid water at stack outlet on exchange of heat and water in humidifier. Simulation result shows that during load change, liquid water at stack outlet and thermal response of parts of air supply subsystem (particularly the humidifier) dominate large latency and multi-stage dynamic response of gas temperature and relative humidity at stack inlet. Experiment is performed on a 60 kW fuel cell system. During load increase, gas temperature at stack inlet rises in four stages, which is consistent with simulation result. During load decrease, average high frequency impedance, air temperature at stack inlet and average cell voltage of the stack are gradually decreased and reach stable state in about 2000s. Experiment result validates the dynamic model and discovers abnormal phenomenon of flooding for the stack at 87A. Accordingly, a control strategy for water management by adjusting stack temperature is further developed to adapt to variable environment condition. Finally, road test indicates that the water management strategy effectively reduces degradation rate of cell voltage to −2.18μV/h within 2000h from winter to autumn.