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EP-4735786-A1 - DEVICE FOR STORING CRYOGENIC HYDROGEN, AND MOTOR VEHICLE

EP4735786A1EP 4735786 A1EP4735786 A1EP 4735786A1EP-4735786-A1

Abstract

The invention relates to a device (1) for storing cryogenic hydrogen, having at least one container (2). The device (1) according to the invention is characterized in that the inner surface of the container (2) has, at least in part, projections (4) that project into the container interior; and/or is provided with a rough surface or with elements (5) having a rough surface in order, by way of the roughness of the surface, to prevent superheating.

Inventors

  • MANDRY, Nicolas
  • STANZEL, NICOLAS

Assignees

  • Daimler Truck AG

Dates

Publication Date
20260506
Application Date
20240626

Claims (10)

  1. 1. Device (1) for storing cryogenic hydrogen with at least one container (2), characterized in that the inner surface of the container (2) at least partially has projections (4) which protrude into the interior of the container; and/or is provided with a rough surface or with elements (4) with a rough surface in order to prevent boiling delay due to the roughness of the surface.
  2. 2. Device (1) according to claim 1, characterized by a tank heater (7) arranged in the container (2) for removing hydrogen, wherein the surface of the container (2) in the region of the tank heater (7) and the surface of the tank heater (7) have a lower surface roughness than the surrounding regions of the container (2).
  3. 3. Device (1) according to claim 2, characterized in that the tank heater (7) is arranged at the bottom in the direction of gravity (F g ) when the container (2) is used as intended.
  4. 4. Device (1) according to claim 1, 2 or 3, characterized in that the rough surface is produced by a coating or mechanical processing of the surface.
  5. 5. Device (1) according to one of claims 1 to 4, characterized in that the projections (4) are designed in the form of ribs or pins.
  6. 6. Device (1) according to one of claims 1 to 5, characterized in that the elements (5) are made of sintered metal and/or are designed as boiling stones.
  7. 7. Device (1) according to claim 6, characterized in that the elements (5) are held by a net in the region of the surface of the container (2).
  8. 8. Device (1) according to one of claims 1 to 7, characterized in that the projections (4) are provided with a rough surface, in particular are designed as sintered metal elements.
  9. 9. Device (1) according to one of claims 1 to 8, characterized in that the projections (4), the elements (5) and/or the rough surface are arranged downwards in the direction of gravity (F g ), at least when the container (2) is used as intended.
  10. 10. Motor vehicle with a device (1) according to one of claims 1 to 9, for storing hydrogen, in particular for a fuel cell drive system.

Description

Device for storing cryogenic hydrogen and motor vehicle The invention relates to a device for storing cryogenic hydrogen with at least one container. The invention further relates to a motor vehicle with such a device. The storage of liquid hydrogen, for example for use in motor vehicles, is well known in the art. The problem here is always that the liquid hydrogen is extremely cold, so the storage tanks have to be well insulated. Nevertheless, over time the hydrogen inevitably heats up and has to be released when it has reached its gas phase and exceeds a predetermined maximum pressure in the container. This so-called boil-off gas is then typically converted catalytically to prevent hydrogen emissions into the environment. Nevertheless, this gas is lost for the desired application. The unavoidable heating in the container for storing the cryogenic hydrogen also means that such hydrogen storage tanks have a relatively short storage life. After just a few days, conventional tanks can be empty or largely empty without the hydrogen stored in them being able to be used in the desired way. In order to counteract this problem, it is known, for example from DE 10 4342 210 02, to create a temperature-stratification-free storage facility for cryogenic liquids, such as hydrogen. The storage facility is divided into two storage areas, a main chamber and a secondary chamber. Liquid hydrogen from the main chamber is conveyed into the secondary chamber and from there is distributed over the surface of the hydrogen in the main chamber via a nozzle, over in which a gas cushion has collected. This leads to cooling and thus ultimately to a longer holding time. However, the structure is comparatively complex and requires additional energy to transport the liquid hydrogen from the main chamber to the secondary chamber. The object of the present invention is to provide an improved device for storing cryogenic hydrogen, which enables a longer holding time with a simple structure. According to the invention, this object is achieved by a device having the features in claim 1, and here in particular in the characterizing part of claim 1. Advantageous embodiments and further developments of the device according to the invention emerge from the dependent claims. A motor vehicle, in particular a commercial vehicle, with such a device for storing cryogenic hydrogen also achieves the object. According to the invention, it is now provided that the cryogenic hydrogen is stored in a container which has projections on its inner surface which protrude into the interior of the container and/or which is provided on its inner surface with a rough surface or with elements with a rough surface in order to prevent boiling delay due to the roughness of the surface. In the device according to the invention, the inner surface of the container is at least partially provided with projections and/or has a rough surface or elements with a rough surface. This makes use of two different mechanisms identified by the inventors to achieve the most homogeneous heating possible of the liquid phase of the stored cryogenic hydrogen. If more heat can be absorbed via the liquid phase, the pressure increase slows down. This results in the stored hydrogen being held in the container for a longer period of time. The projections protruding into the interior of the container, which can be designed in particular as ribs or pins, and which, in the case of typical container sizes, such as those used for storing cryogenic hydrogen in commercial vehicles, extend into the interior of the container in the range of a few millimetres to a few centimetres. The projections that can protrude from the inside of the container have three positive effects. They increase the surface area of the inner wall of the container and thus reduce the heat flow that has to be transferred from the outside to the inside of the container per area. The projections transport the heat flow, which cannot be completely avoided at the surface of the container, across the boundary layer between the container surface and the cryogenic hydrogen and comparatively far into the liquid hydrogen. This not only heats up the boundary layer, but also the hydrogen in an area that is somewhat further away from the container wall. Overall, this leads to a more homogeneous heating of the cryogenic hydrogen, which then, as explained above, is associated with a longer holding time. On the other hand, the projections - and this is particularly true when they are designed as ribs - impede the flow in the area of the boundary layer between the container wall and the cryogenic hydrogen. It is particularly advantageous if the ribs are designed transversely to gravity when used as intended in order to prevent the upward flow of warmer hydrogen and thus reduce boundary layer flow and at the same time the heat transfer between the liquid hydrogen and the container wall. In addition to or as an alternative to such projections, a