CRYOGEN STORAGE SYSTEM

Description

Field of the invention

[0001] The present invention relates to a storage system for storing a cryogenic medium, in particular for storing hydrogen. State of the art

[0002] It is known that cryogenic media, i.e., extremely cold and at least partially liquid media, such as hydrogen or helium, can be stored in a storage container to transport energy, for example, to power a vehicle, ship, aircraft, or rocket. The medium is usually present partly in liquid form in the storage container and partly in gaseous form.

[0003] Cryogenic storage systems require a pressure buildup system during operation to compensate for the pressure drop that occurs during the gaseous or liquid withdrawal of, for example, hydrogen. This is usually achieved either by an internal tank heat exchanger (closed piping system) or by direct evaporation (open system). This type of pressure buildup requires both the withdrawal of hydrogen and a heat source (usually waste heat from the consumer). If no hydrogen is withdrawn and a higher pressure level is still required, this can be achieved with the help of electric heaters, so-called "blowers," or with cryogenic liquid pumps.

[0004] Modern mobile liquid hydrogen storage applications require pressure buildup systems that, on the one hand, enable pressure buildup without removing hydrogen and, on the other hand, require minimal space, are lightweight, and have low electrical power requirements. Electric heaters, blowers, and pumps cannot fulfill these requirements, or can only partially fulfill them, requiring significant technical complexity or high electrical power requirements, which represents a major disadvantage for mobile applications.

[0005] From DE 196 45 488 C5 a system for withdrawing cold gas from a cryogenic tank is known, comprising an insulated storage container for cryogenic, liquefied gas and a withdrawal line which leads from the storage container to a consumer, wherein an evaporation volume is connected to the withdrawal line, wherein liquefied gas passes through the withdrawal line into the evaporation volume, partially evaporates there and the evaporated gas flows at least partially back into the storage container via the withdrawal line, wherein the withdrawal line is the only means for compensating for a pressure drop when withdrawing cold gas from the cryogenic tank. Summary of the invention

[0006] It is an object of the invention to provide a cryogenic storage system which enables pressure build-up without removing hydrogen in a technically simple and cost-effective manner.

[0007] The object is achieved by a storage system for storing a cryogenic medium, in particular for storing hydrogen, having the features according to claim 1.

[0008] The storage system comprises a storage container for receiving the medium, wherein at least one pipe projects from outside the storage container into the storage container, wherein the pipe is closed at its end facing away from the storage container and is open at its end located in the storage container, wherein a shut-off valve is arranged on the pipe at a specific position, so that the interior of the pipe is fluidically connected to the interior of the storage container when the shut-off valve is open and the interior of the pipe is not fluidically connected to the interior of the storage container when the shut-off valve is closed.

[0009] According to the invention, a storage system, i.e. tank, for storing a cryogenic medium is designed such that a thin pipe protrudes from the outside into the tank - preferably into the liquid in the tank -, wherein the pipe is closed on the outside and the pipe has an open end on the inside of the tank and in this way the cryogenic medium can come into contact with the interior of the pipe.

[0010] The pipeline has a shut-off valve, which can be used to regulate / control the pressure in the tank or, when the valve is opened, to increase the pressure in the tank. The shut-off valve is preferably controllable by a control device, in particular, can be opened and closed.

[0011] The tube is designed to generate thermoacoustic vibrations so that when connected to a cryogenic medium, a pressure build-up occurs inside the tube based on the thermoacoustic effect.

[0012] This allows the pressure in the tank to be increased without the need to supply heat energy to the tank using additional heaters, as is usually the case.

[0013] A thermoacoustic pressure build-up system utilizes the effect of thermoacoustic oscillations (TAO) to increase the pressure in the tank system. The gas in the pipeline is caused to vibrate by heat transfer from the pipeline wall into the gas.

[0014] TAOs should be avoided for long-term storage of cryogenic media, especially hydrogen and helium, but can be used for the present case of the desired pressure build-up.

[0015] According to the invention, the components are limited to a shut-off valve and a thin pipe, which preferably provides a sufficiently large heat transfer surface on the warm side, for example, by forming pipe fins. At the warm end, i.e., outside the storage tank, the pipe is closed. The pipe is preferably completely closed outside the storage tank.

[0016] According to the invention, a liquid withdrawal line is arranged for withdrawing liquid medium from the storage tank.

[0017] Preferably, the tube is designed for improved heat transfer at its end facing away from the storage tank, i.e. on the warm side, preferably by at least one heat transfer surface, for example by tube fins.

[0018] According to a not claimed embodiment, a heat exchanger is arranged at the end of the pipe facing away from the storage container, for transferring heat to the pipe, in particular heat from passing air and / or from a cooling liquid.

[0019] In a filled storage vessel, the cold, open end of the pipeline is immersed in the cryogenic liquid. The pipeline, which is preferably vacuum-insulated, runs through the vacuum space to the warm side, i.e. the outside of the vessel. The position of the pipeline's shut-off valve is preferably either in the vacuum region or just near the warm side of the vessel. The function of the shut-off valve is the targeted suppression of thermoacoustic oscillations, which are undesirable when the vessel is at rest. With an ideal system design, thermoacoustic resonance occurs, which enables pressure to build up within a very short time. A corresponding temperature gradient between the warm and cold ends of the pipeline is essential for its function. The ambient temperature preferably forms the warm end, and the cold end is cooled by a low-boiling liquid in the storage vessel, such as hydrogen or helium.

[0020] Preferably, the storage tank is double-walled, with an insulating vacuum space between the two walls of the storage tank. The end of the tube facing away from the storage tank lies outside the insulating vacuum space, and the tube passes through the vacuum space and opens into the storage tank. Furthermore, the ratio of tube length to tube diameter as well as the wall thickness of the tube play a significant role. The tube must be as long and as thin as possible, and the wall thickness as small as possible.

[0021] The inner diameter of the pipe is therefore small over the entire pipe length, or at least outside the storage tank, i.e. at the warm end, preferably a maximum of 20 mm or a maximum of 10 mm, particularly preferably a maximum of 6 mm.

[0022] The pipe outside the storage container preferably has a length of at least 50 mm, preferably at least 100 mm, particularly preferably at least 200 mm.

[0023] The pipe within the storage container preferably has a length of at least 500 mm, preferably at least 1000 mm, particularly preferably at least 2000 mm.

[0024] The tube preferably has a wall thickness of maximum 3 mm, preferably maximum 2 mm, particularly preferably maximum 1 mm.

[0025] The ratio of total length to inner diameter of the tube is preferably at least 100:1, preferably at least 400:1, particularly preferably at least 800:1.

[0026] A thermoacoustic pressure build-up system can be used as a standalone system or as a supplement to conventional pressure build-up systems.

[0027] To increase the performance of the system, several pipelines can be used, especially those arranged in parallel.

[0028] The storage system therefore preferably comprises several such pipes extending from outside the storage tank into the storage tank, with each pipe having its own shut-off valve or at least two pipes, preferably all pipes, being able to be opened and closed via shut-off valves in a common valve block. If several pipes are used in parallel, i.e., the system's capacity is multiplied by parallel arrangement, these pipes can be opened or closed via individual valves or a large "valve block."

[0029] To further increase the system's performance, additional heat can be introduced on the warm side of the pipe via a heat exchanger. This heat can be supplied, for example, from the passing air or from the waste heat of the consumer via a cooling fluid.

[0030] To further protect the cable(s) from external radiant heat during idle operation, they can be wrapped with insulation or radiation shields, such as multi-layer insulation (MLI). Depending on the variant, all or part of the cable length is then insulated in the vacuum chamber. The pipe can thus be thermally insulated over a section of the pipe in the vacuum chamber.

[0031] To further enhance the thermoacoustic effect, the geometry of the pipe end in the inner tank can be adapted, e.g., by reducing the open cross-section of the line or by continuously tapering the pipe end. Therefore, the pipe preferably has a smaller inner diameter over a pipe section inside the storage tank than over a pipe section outside the storage tank, in particular a reduced inner diameter or a continuous taper towards the end of the pipe located inside the storage tank.

[0032] A thermoacoustic pressure build-up system as described above can also be used as a supplement to state-of-the-art pressure build-up systems.

[0033] The operation of a device according to the invention is as follows: In the idle state, the valve in the pipe is closed to prevent thermoacoustic oscillations. If a pressure build-up is required, the valve is opened, a long section of pipe exposed to the ambient temperature is released and the critical length to diameter ratio is thus exceeded. The gas in the pipe begins to expand and contract again due to the heat transport across the pipe wall, i.e. to oscillate. With each oscillation, it expels gas from the end of the pipe that is in the liquid and sucks in liquid again, which then at least partially evaporates in the pipe. This repeats the effect or amplifies it further. Ideally, resonance occurs very quickly, whereby heat is continuously introduced into the system. Brief description of the drawings

[0034] The invention is described below by way of example with reference to the drawings. Fig. 1 is a schematic representation of a storage system not according to the invention. Fig. 2 is a schematic representation of a storage system not according to the invention in an alternative embodiment. Fig. 3 is a schematic representation of a storage system according to the invention. Fig. 4 is a schematic representation of a storage system according to the invention in an alternative embodiment. Fig. 5 is a schematic representation of a storage system according to the invention in an alternative embodiment. Fig. 6 is a schematic representation of a storage system according to the invention in an alternative embodiment. Fig. 7 is a schematic representation of a storage system not according to the invention in an alternative embodiment. Fig. 8 is a schematic representation of a storage system according to the invention in an alternative embodiment. Detailed description of the invention

[0035] In the Fig.1 a storage system not according to the invention for storing a cryogenic medium, in particular for storing hydrogen, is shown.

[0036] The storage system comprises a storage container 1 for holding the medium. The storage container 1 forms an inner container of a double-walled container, which additionally comprises an outer container 11. A vacuum is created between the outer container 11 and the inner container, i.e., storage container 1. Suspensions 13 are also arranged in sections between the outer container 11 and the inner container to position the two shells of the double-walled container relative to each other.

[0037] The cryogenic medium, in particular hydrogen, is located in the lower area of ​​the storage container 1, namely below the liquid surface shown as a wavy line in the figures as a liquid in the container, above the wavy liquid surface in a gaseous state.

[0038] A gas extraction line 2 is arranged to extract the gaseous medium from the storage tank 1, so that the free end of the gas extraction line 2 ends in the storage tank 1 above the liquid surface, near the ceiling of the storage tank 1.

[0039] A liquid withdrawal line 5 is arranged to withdraw the liquid medium from the storage tank 1, so that the free end of the liquid withdrawal line 5 ends in the storage tank 1 below the liquid surface, near the bottom of the storage tank 1.

[0040] The terms "ceiling" and "floor" refer to the usual installation position of the storage container, for example in a moving, floating or flying transport device, whereby gravity acts towards the floor of the storage container during normal operation of the transport device.

[0041] A first controllable line shut-off valve 6 is arranged in the gas extraction line 2 and a second controllable line shut-off valve 7 is arranged in the liquid extraction line 5. Both line shut-off valves are located outside the storage tank 1. In the Fig. 1 The line shut-off valves are also located outside the outer container 11.

[0042] In the alternative version of the storage system, the Fig. 2As shown, the two line shut-off valves are arranged within the outer container 11, i.e. between the inner container, storage container 1, and the outer container of the double-walled storage container, in particular in the vacuum space.

[0043] The line shut-off valves are controlled by a control device, which is also located in the vacuum chamber ( Fig.2 ) or outside the entire container ( Fig. 1 ) is arranged. The flow can be controlled not only by the line shut-off valves but also by the flow can be reduced.

[0044] The storage tank 1 can also be refueled from a refueling device 14 via the gas extraction line 2 and / or the liquid extraction line 5, preferably also via the first line shut-off valve 6 and / or the second line shut-off valve 7.

[0045] The gas extraction line 2 and the liquid extraction line 5 are combined into a common line downstream of the two line shut-off valves 6, 7. A rectifying valve, in particular a check valve 15, can be arranged in the gas extraction line 2, so that only the flow direction from the first line shut-off valve 6 to the first heat exchanger 3 is permitted, while the opposite direction is blocked.

[0046] The gas extraction line 2 and the liquid extraction line 5 are in the form of a common line with the outside of the storage tank 1, for example between storage tank 1 and outer tank 11 of the double-walled storage tank ( Fig. 2 ), arranged first heat exchanger 3 for heating the extracted medium.

[0047] Downstream of the first heat exchanger 3, an internal tank heat exchanger 4 is arranged within the storage tank 1 for heating the liquid medium in the storage tank 1. The heated medium drawn from the storage tank 1 flows through the internal tank heat exchanger 4. Due to the heating at the internal tank heat exchanger 4, the liquid medium in the storage tank 1 is partially heated and evaporated.

[0048] No controllable three-way valve is arranged in the gas extraction line 2 and in the liquid extraction line 5, so that the entire medium extracted through the gas extraction line 2 and / or through the liquid extraction line 5 and heated by the first heat exchanger 3 reaches the inner tank heat exchanger 4.

[0049] Since the pressure in the storage tank 1 is regulated by means of the first and second line shut-off valves 6, 7, no controllable three-way valve is required.

[0050] A control unit of the storage system is configured to control the pressure in the storage container 1 during the withdrawal of the medium by the control unit selectively opening the first line shut-off valve 6 and / or the second line shut-off valve 7, so that the medium is selectively withdrawn from the storage container 1 via the gas withdrawal line 2 and / or via the liquid withdrawal line 5.

[0051] Downstream of the inner tank heat exchanger 4 and outside the storage tank 1, outside ( Fig. 1 ) or within ( Fig. 2 ) of the outer container 11 of the double-walled container, a second heat exchanger 8 is arranged to heat the medium.

[0052] The medium withdrawn via the gas extraction line 2 and / or the liquid extraction line 5 is fed to a consumer 10, in particular a fuel cell, downstream of the inner tank heat exchanger 4. A third line shut-off valve 9 is arranged between the second heat exchanger 8 and the consumer 10.

[0053] The design of the Fig. 2 differs from the Fig. 1 that control-relevant components of the storage system, such as the first heat exchanger 3, the second heat exchanger 8, the first line shut-off valve 6 and the second line shut-off valve 8, as well as the check valve 15 are arranged inside the outer container 11, not outside the outer container 11 as in Fig. 1 , and are thus arranged in the space between the double-walled container, which forms a vacuum space.

[0054] In the Fig. 3a storage system according to the invention for storing a cryogenic medium, in particular for storing hydrogen, is shown.

[0055] The storage system according to the invention comprises a pipe 21 which projects from outside the storage container 1 into the storage container 1, the pipe 21 being closed at its end facing away from the storage container 1 and being open at its end located in the storage container 1, a shut-off valve 22 being arranged on the pipe 21 so that the interior of the pipe 21 is fluidically connected to the interior of the storage container 1 when the shut-off valve 22 is open, and the interior of the pipe 21 is not fluidically connected to the interior of the storage container 1 when the shut-off valve 22 is closed.

[0056] The storage system does not have an internal tank heat exchanger 4 for heating the liquid medium in the storage tank 1.

[0057] The pipe 21 is designed to generate thermoacoustic vibrations so that when connected to a cryogenic medium in the storage tank 1, with the shut-off valve 22 open, a thermoacoustic pressure build-up occurs inside the pipe 21.

[0058] The storage container 1 is double-walled, with an insulating vacuum space between the two walls 1, 11 of the storage container 1, wherein the end of the tube 21 facing away from the storage container 1 lies outside the insulating vacuum space and the end of the tube 21 located in the storage container 1 lies within the insulating vacuum space or the tube passes through the vacuum space and opens into the storage container 1.

[0059] The tube 21 can have a suitable geometry to accommodate a desired tube length in a smaller installation space, for example a meander or spiral shape.

[0060] The shut-off valve 22 of the pipe 21 is in Fig. 3outside the storage container 1 and outside the vacuum space, i.e. outside the outer container 11.

[0061] In the embodiment of the Fig. 4 is in contrast to Fig. 3 the shut-off valve 22 of the pipe 21 is arranged in the vacuum space, i.e. between the inner container of the storage container 1 and the outer container 11.

[0062] Fig. 5 shows that the storage system has several such tubes 21 for generating a higher power, which are designed to generate thermoacoustic oscillations and which therefore protrude from outside the storage tank 1 into the storage tank 1. In Fig. 5 A separate shut-off valve 22 is arranged on each pipe 21. This allows, for example, the heat output to be controlled by temporarily activating individual valves.

[0063] The design of the Fig. 6 differs from that of the Fig. 5only because all pipes 21 can be opened and closed together via shut-off valves 22 in a common valve block 24. This simplifies the actuation of the pressure buildup through the multiple pipes 21.

[0064] In the non-inventive embodiment of the Fig. 7 At the end of the tube 21 facing away from the storage tank 1, a heat exchanger 23 is arranged for transferring heat to the tube 21, in particular heat from passing air and / or from a cooling liquid.

[0065] The inventive embodiment of the Fig. 8Finally, in addition to the thermoacoustic pressure build-up system by means of pipe 21, a classic pressure build-up system is provided, namely, downstream of the first heat exchanger 3, an inner tank heat exchanger 4 arranged within the storage tank 1 for heating the liquid medium in the storage tank 1, through which the medium taken from the storage tank 1 flows. Due to the heating at the inner tank heat exchanger 4, the liquid medium in the storage tank 1 is partially heated and evaporated. The classic pressure build-up system of the Fig. 8 thus essentially corresponds to that of the Fig. 1 and 2 . The pressure build-up can be controlled via a partial flow control valve 25.

[0066] Please note that the figures are purely schematic and do not necessarily reflect the actual size and length ratios. List of reference symbols

[0067] 1Storage tank 2Gas extraction line 3First heat exchanger 4Inner tank heat exchanger 5Liquid extraction line 6First controllable line shut-off valve 7Second controllable line shut-off valve 8Second heat exchanger 9Third controllable line shut-off valve 10Consumer 11Outer tank 13Suspension 14Fueling device 15Check valve 21Pipe 22Shut-off valve 23Heat exchanger 24Valve block 25Partial flow control valve

Claims

1. Storage system for storing a cryogenic medium, in particular for storing hydrogen, comprising a storage container (1) for receiving the medium, wherein at least one pipe (21) projects from outside the storage container (1) into the storage container (1), wherein the pipe (21) is closed at the end thereof directed away from the storage container (1) and is open at the end thereof located in the storage container (1), wherein a shut-off valve (22) is arranged on the pipe (21) so that the inner space of the pipe (21) is connected to the inner space of the storage container (1) in a fluid-conducting manner when the shut-off valve (22) is opened and the inner space of the pipe (21) is not connected to the inner space of the storage container (1) in a fluid-conducting manner when the shut-off valve (22) is closed, wherein the external diameter of the pipe (21) is small over the entire pipe length, wherein the pipe (21) is configured to form thermo-acoustic oscillations and is thus part of a thermo-acoustic pressure build-up system, wherein the components of the thermo-acoustic pressure build-up system are limited to a thin pipeline of the pipe (21) and the shut-off valve (22), wherein a liquid removal line (5) is adapted to remove liquid medium from the storage container (1).

2. Storage system according to Claim 1, characterized in that the storage container (1) is constructed with double walls, with an insulating vacuum space between the two walls of the storage container (1), wherein the end of the pipe (21) directed away from the storage container (1) is located outside the insulating vacuum space and the pipe (21) extends through the vacuum space and opens into the storage container (1).

3. Storage system according to at least one of the preceding claims, characterized in that the pipe (21) is constructed at the end thereof directed away from the storage container (1) for improved heat transfer, preferably by at least one heat transfer area, for example, by pipe ribs.

4. Storage system according to at least one of the preceding claims, characterized in that the internal diameter of the pipe (21), over the entire pipe length, is a maximum of 20 mm, preferably a maximum of 10 mm, particularly preferably a maximum of 6 mm.

5. Storage system according to at least one of the preceding claims, characterized in that the pipe (21) has outside the storage container (1) a length of at least 50 mm, preferably at least 100 mm, particularly preferably at least 200 mm and / or in that the ratio of the total length to the internal diameter of the pipe (21) is at least 100:1, preferably at least 400:1, particularly preferably at least 800:1.

6. Storage system according to at least one of the preceding claims, characterized in that the storage system has a plurality of such pipes (21) which project from outside the storage container (1) into the storage container (1), wherein an individual shut-off valve (22) is arranged on each pipe (21) or wherein at least two pipes (21), preferably all the pipes (21), can be opened and closed via shut-off valves (22) in a common valve block (24).

7. Storage system according to at least one of the preceding claims, characterized in that the pipe (21) is constructed in a thermally insulated manner via a pipe portion in the vacuum space.

8. Storage system according to at least one of the preceding claims, characterized in that the pipe (21) has over a pipe portion inside the storage container a smaller internal diameter than over a pipe portion outside the storage container, in particular a reduced internal diameter or a continuous tapering towards the end of the pipe located in the storage container.