Bayerische Motoren Werke Aktiengesellschaft

Tobias Brunner

Manuel Tolosa

Thomas Hagler

Klaus Szoucsek

Gregor Fischer

Markus Amsz

Sylvain Bastian

Achim Baier

Oliver Kircher

Torsten Rech

An operating method is provided for a cryopressure tank in which cryogenic hydrogen for supplying a motor vehicle fuel cell can be stored under supercritical pressure at 13 bar or more. In order to compensate the pressure drop resulting from removal of hydrogen from the cryopressure tank, either a heat transfer medium is supplied to a heat exchanger provided in the cryopressure tank via a control valve over a period of time which significantly exceeds the cycle times of a conventional cycle valve or the heat transfer medium is not supplied to the heat exchanger. Depending on the fill level of the cryopressure tank, the control valve is actuated with respect to a desired temperature or a desired pressure of the hydrogen in the cryopressure tank. As long as there is a risk of liquefaction of the residual hydrogen in the cryopressure tank, as is the case when the temperature falls below the critical temperature of 33 K if the pressure drops below the critical pressure of approximately 13 bar, during the removal of cryogenic hydrogen from the cryopressure tank, the temperature is adjusted such that it does not drop below the critical temperature of 33 Kelvin. If the fill state in the cryopressure tank drops further, the pressure in the cryopressure tank is adjusted when there is no longer a risk of liquefaction such that the pressure does not drop below a minimum pressure value which the hydrogen that is removed from the cryopressure tank must have in order to be usable in the consumer without restricting the function thereof.

Operating method for a cryopressure tank

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.

Operating method for a fuel cell system

An operating method is provided for a cryo-compressed tank for supplying cryogenic hydrogen to a consumer of a motor vehicle under supercritical pressure at 13 bar or more. In order to compensate for pressure loss resulting from hydrogen removal, the removed hydrogen that has been heated in a heat exchanger is conveyed to a heat exchanger, provided in the cryo-compressed tank, by way of a tank pressure regulating valve and a branch line, which branches off of a supply line leading to the consumer. After flowing through the heat exchanger, it is introduced into the supply line downstream of the branching off of the branch line. Over a period of time that significantly exceeds the cycle times of a conventional frequency valve, either the removed amount of hydrogen is guided without limitation into the heat exchanger, provided in the cryo-compressed tank, the tank pressure regulating valve being completely open, or no return of the heated hydrogen into the heat exchanger occurs at all. Downstream of the branching off of the branch line, the supply line has a pressure regulating unit, which ensures that irrespective of the changes in the pressure in the supply line caused upstream of the pressure regulating unit by switching the tank pressure regulating valve, a sufficient and continuous supply of hydrogen to the consumer at the pressure required is guaranteed.

Operating method for a cryo-compressed tank

A system for cryogenic storage and delivery of fuel, particularly for supplying an internal-combustion engine driving a motor vehicle, includes at least a cryotank having an inner reservoir for receiving the cryogenic medium, which inner reservoir is held in a heat-insulated manner in an outer reservoir, a coolable cooling shield between the inner reservoir and the outer reservoir of the cryotank, and a heat sink. As a thermal-energy storage device, the heat sink is in heat-transmitting contact with the cooling shield. A filling and removal device has at least one pipe penetrating the outer reservoir and leading into the inner reservoir. At least for the filling with or for the removal of cryogenic medium, the heat sink is in heat-transmitting contact with the pipe for the cryogenic medium, in order to reduce the entry of heat from the environment into the inner reservoir while emitting heat. The inner reservoir has a recess in which at least the heat sink and the pipe for the cryogenic medium are housed such that they are situated essentially within the circumferential contour of the inner reservoir.

Growing community of inventors

Grasbrunn, Germany

Tobias Brunner