NOVELTY - Fuel cell system includes an air supply system comprising: (i) a blower for driving the air to a fuel cell stack and a humidifier to humidify the air supplied to the stack; and (ii) a coolant circulation system supplying a low temperature coolant to the fuel cell stack and comprising a coolant reservoir, a pump driving the circulation of the coolant, a radiator to convert high to low temperature coolant, and a heat exchanger.    USE - The fuel cell system is used for generating electrical power energy e.g. for electric vehicle.    ADVANTAGE - The liquid cooling device and air humidifying device ensure high performance of the fuel cell stack.    DETAILED DESCRIPTION - Fuel cell system comprises:    (a) a fuel cell stack;    (b) an air supply system supplying an air flow to the fuel cell stack and comprising a blower for driving the air to the stack and a humidifier for humidifying the air supplied to the fuel cell stack;    (c) a hydrogen supply system supplying hydrogen to the fuel cell stack and comprising a hydrogen storage zone in which hydrogen is stored and from which a hydrogen flow is supplied to the fuel cell stack, and a pressure regulating device for regulating the hydrogen flow, a hydrogen recirculator for receiving excess hydrogen from the fuel cell stack and forcing it back into the stack to induce a hydrogen flow inside the stack;    (d) a coolant circulation system supplying a low temperature coolant to the fuel cell stack for absorbing heat from the stack and becoming high temperature coolant, and comprising a coolant reservoir in which the coolant is stored, a pump driving the circulation of the coolant, and a radiator for removing heat from the high temperature coolant and converting the high temperature coolant into the low temperature coolant; and    (e) a control circuit electrically controlling the flow and pressure regulating device, the blower, the pump and the fan.    The coolant reservoir comprises a ventilation device for removing air bubbles from the coolant. The coolant circulation system further comprises a heat exchanger for transferring heat from the high temperature coolant to the hydrogen storage. The radiator comprises a fan for generating an air flow through it to remove heat from the coolant.    DESCRIPTION OF DRAWING(S) - The figure is a system block diagram of a fuel cell system.