An operating method is provided for a fuel cell system, in particular a fuel cell system in a motor vehicle. The system includes a cooling system via which waste heat of fuel cells of the fuel cell system is ultimately dissipated into the surrounding air, and a tank withstanding an internal pressure of the order of 150 bar and more. In the tank, fuel for the fuel cell system is stored in the cryogenic state, in particular as a cryogen, which tank has a heat exchanger in its storage volume, via which, in order to compensate for the pressure reduction resulting from the removal of fuel from the tank, heat can be supplied to the stored fuel in a controlled manner by way of a heat transfer medium. At operating points or in operating states of the fuel cell system in which the waste heat of the fuel cell system cannot be dissipated to the surroundings to the required extent, at least a portion of the waste heat from the fuel cells is supplied to the heat exchanger in the tank storing the fuel until a predefined limit value for the internal pressure in the tank is reached.

A fluid tank for a motor vehicle comprising a housing, wherein the housing has a housing base, a housing cover and at least one side wall. A through-passage is formed inside the side wall, wherein the through-passage extends from a first opening in the housing base in the direction of the housing cover. The through-passage is in fluidic connection with the interior of the fluid tank via a second opening.

A device for storing cryogenic fluid comprising a tank extending in a longitudinal direction and suitable for containing liquefied gas in equilibrium with a gas phase, a device for pressurizing the tank, the pressurization device comprising a pressurized gas generator and a rail for injecting the pressurized gas extending in the longitudinal direction in the upper portion of the tank, the injection rail comprising a plurality of gas outlet orifices spaced apart in the longitudinal direction, characterized in that at least one of the spacing between the orifices, the diameter of the orifices and the number of the orifices is different in the longitudinal direction between a first so end through which the gas enters the rail and an opposite second end of the rail and configured to render the flow rates leaving the orifices of the rail uniform in the longitudinal direction.