Managing transition of a fuel cell vehicle to a hot operating mode

A control system for a fuel cell vehicle comprising a fuel cell system comprising a fuel cell stack configured to generate power by electrochemical reaction, and a cooling system configured to circulate a coolant through the fuel cell system to dissipate heat generated by the fuel cell system,

• the control system comprising processing circuitry that is configured to control transition of the fuel cell vehicle from a normal operating mode to a hot operating mode comprising a fuel saving operating mode, wherein in the normal operating mode a coolant inlet temperature of the coolant at a coolant inlet of the fuel cell stack comprises a normal coolant temperature, and in the hot operating mode the coolant inlet temperature at the coolant inlet of the fuel cell stack comprises a hot coolant temperature, and wherein the hot coolant temperature is higher than the normal coolant temperature, the processing circuitry is configured to:
• determine a required value of a traction power from the fuel cell system for the fuel cell vehicle;
• determine a net electric power output value of the fuel cell system, wherein the net electric power output value is determined based on a fuel cell system power output and a cooling electrical power value indicative of a cooling electrical power required to be supplied by the fuel cell system to the cooling system for rejecting output heat that is generated at least by the fuel cell system when operating so as to produce the fuel cell system power output;
• when the fuel cell vehicle is operating in the normal operating mode, control the fuel cell vehicle to transition from the normal operating mode to the hot operating mode via a first transition mode or a second transition mode by:
• in the first transition mode, controlling the fuel cell vehicle to decrease the cooling electrical power thereby increasing a coolant inlet temperature at the coolant inlet of the fuel cell stack, and to adjust the fuel cell system power output and the cooling electrical power, until the coolant inlet temperature is equal to the hot coolant temperature;
• and
• in the second transition mode, controlling the fuel cell vehicle to decrease the cooling electrical power while maintaining the fuel cell system power output constant thereby increasing the coolant inlet temperature at the coolant inlet of the fuel cell stack, until the coolant inlet temperature is equal to the hot coolant temperature.