A fuel cell electric vehicle (FCEV) comprising a cooling system (20, 20', 20", 20′′′), wherein the cooling system comprises: - a coolant circuit circulating a coolant, - a heat exchanger for cooling the circulating coolant, - a positive displacement device for removing thermal energy from the heat exchanger to the environment, - a first chamber (32, 32', 32") configured to contain relatively hot fluid, - a second chamber (34, 34', 34") configured to contain relatively cold fluid, - characterized in that the FCEV comprises a control unit configured to monitor the ratio of cooling power/fan power of the positive displacement device and configured to control thermal energy transfer between the coolant and said chambers based on said ratio, wherein when the FCEV is operating at a point where said ratio is above a pre-defined value or value range, then thermal energy from the first chamber is provided to the coolant in the coolant circuit and is passed into the heat exchanger, after which part of the thermal energy of the cooled coolant leaving the heat exchanger is provided to and stored in the second chamber, and when the FCEV is operating at a point where said ratio is below said pre-defined value or value range, then stored cold thermal energy from the second chamber is provided to the coolant in the coolant circuit to reduce the temperature of the coolant before it is passed to the fuel cells of the FCEV, after which part of the thermal energy of the heated coolant leaving the fuel cells is provided to and stored in the first chamber. - a coolant circuit circulating a coolant, - a heat exchanger for cooling the circulating coolant, - a positive displacement device for removing thermal energy from the heat exchanger to the environment, - a first chamber (32, 32', 32") configured to contain relatively hot fluid, - a second chamber (34, 34', 34") configured to contain relatively cold fluid, - characterized in that the FCEV comprises a control unit configured to monitor the ratio of cooling power/fan power of the positive displacement device and configured to control thermal energy transfer between the coolant and said chambers based on said ratio, wherein when the FCEV is operating at a point where said ratio is above a pre-defined value or value range, then thermal energy from the first chamber is provided to the coolant in the coolant circuit and is passed into the heat exchanger, after which part of the thermal energy of the cooled coolant leaving the heat exchanger is provided to and stored in the second chamber, and when the FCEV is operating at a point where said ratio is below said pre-defined value or value range, then stored cold thermal energy from the second chamber is provided to the coolant in the coolant circuit to reduce the temperature of the coolant before it is passed to the fuel cells of the FCEV, after which part of the thermal energy of the heated coolant leaving the fuel cells is provided to and stored in the first chamber. when the FCEV is operating at a point where said ratio is above a pre-defined value or value range, then thermal energy from the first chamber is provided to the coolant in the coolant circuit and is passed into the heat exchanger, after which part of the thermal energy of the cooled coolant leaving the heat exchanger is provided to and stored in the second chamber, and when the FCEV is operating at a point where said ratio is below said pre-defined value or value range, then stored cold thermal energy from the second chamber is provided to the coolant in the coolant circuit to reduce the temperature of the coolant before it is passed to the fuel cells of the FCEV, after which part of the thermal energy of the heated coolant leaving the fuel cells is provided to and stored in the first chamber.