Storage container and method

Abstract

A storage container (1) for storing a cryogen (H2), comprises an inner container (3) for receiving the cryogen (H2), a latent heat store (19) for receiving a phase-change material (N2), and a discharge line (22) for discharging the cryogen (H2) from the inner container (3), wherein the discharge line (22) is operatively connected to the latent heat store (19) in such a way that cryogen (H2) received in the discharge line (22) exchanges heat with the phase-change material (N2), and wherein the latent heat store (19) can be fluidically connected to an environment (23) of the storage container (1) exclusively with the aid of a blow-off line (24).

Description

[0001] Description

[0002] Storage tanks and processes

[0003] The invention relates to a storage container for storing a cryogen and a method for operating such a storage container.

[0004] The applicant is familiar with double-walled storage containers for liquid hydrogen, which comprise an outer container and an inner container arranged within the outer container for containing the liquid hydrogen. A gap provided between the inner container and the outer container is subjected to a vacuum. The gap can be filled, at least in sections, with an insulating material.

[0005] For use of such a storage vessel in a maritime environment, it may be necessary for the storage vessel to achieve a holding time of 15 days at maximum filling, based on operating pressure, in the event of an accident. This means that during this time, the maximum permissible pressure within the inner vessel must not be exceeded, and no hydrogen may escape from the storage vessel.

[0006] Currently, the storage vessel can only be filled to a certain extent with liquid hydrogen due to the holding time requirement, depending on the heat input and the thermodynamic equilibrium temperature of the stored liquid hydrogen. Under current typical conditions, sometimes only 70% to 80% of the geometric volume of the storage vessel can be used for liquid hydrogen storage. This needs to be improved.

[0007] Against this background, it is an object of the present invention to provide an improved storage container.

[0008] Accordingly, a storage container for storing a cryogen is proposed. The storage container comprises an inner container for receiving the cryogen, a latent heat storage device for receiving a phase-change material, and a withdrawal line for withdrawing the cryogen from the inner container. The withdrawal line is operatively connected to the latent heat storage device such that cryogen received in the withdrawal line is in heat exchange with the phase-change material, and the latent heat storage device is fluidically connectable to the environment of the storage container exclusively by means of a vent line.

[0009] By providing the latent heat storage, the phase change enthalpy of the phase-change material during a phase change from solid to liquid can be used, for example, to cool a shield surrounding the inner vessel or other components of the storage vessel. This can extend the holding time of the storage vessel for the cryogen. In particular, emergency cooling can be realized. Furthermore, a higher filling level of the inner vessel with cryogen can be achieved.

[0010] The storage container is particularly suitable for transporting the cryogen. Therefore, the storage container can also be referred to as a transport container. The storage container is preferably at least double-walled and, in addition to the inner container, comprises an outer container enclosing the inner container. The storage container can therefore also be referred to as a double-walled storage container. The storage container can be part of a vehicle, in particular a watercraft. In this case, the storage container is suitable for mobile applications. However, the storage container can also be used stationary, for example, in building services engineering.

[0011] The withdrawal line leads from the storage tank to a consumer, for example, a fuel cell. The consumer can, for example, power an electric motor that drives a ship's propeller. The liquid cryogen can be vaporized upstream of the consumer, so that gaseous cryogen is supplied to the consumer at a suitable supply pressure and temperature.

[0012] The cryogen can be liquid hydrogen. Since the storage container is preferably designed to hold liquid hydrogen, the storage container can also be referred to as a hydrogen storage container or hydrogen storage tank. The term "cryogen" can be replaced with the term "hydrogen" and vice versa. However, the cryogen can also be liquid helium, liquid neon, or the like.

[0013] The cryogen is contained in the inner container. As long as the cryogen is in the two-phase region, a gas zone with vaporized cryogen and a liquid zone with liquid cryogen can be provided in the inner container. After being filled into the inner container, the cryogen therefore has two phases with different states of aggregation, namely liquid and gaseous. This means that there is a phase boundary between the liquid cryogen and the gaseous cryogen in the inner container. Only the liquid cryogen is withdrawn from the inner container via the withdrawal line. One end of the withdrawal line located on or in the inner container is arranged in or at the lower part of the inner container in the direction of gravity. This end is preferably located in or at the lower third of the inner container, particularly preferably in or at the lower sixth of the inner container.Particularly preferably, this end of the extraction line is spaced up to 30 mm, more particularly preferably up to 20 mm, from the lowest point of the inner container in the direction of gravity.

[0014] The storage container is preferably constructed rotationally symmetrically to a symmetry or central axis. Accordingly, the inner container and the outer container can also be constructed rotationally symmetrically to the central axis. The storage container is preferably arranged such that the central axis runs perpendicular to a direction of gravity. This means that the storage container is arranged horizontally. However, the storage container can also be arranged vertically. In this case, the central axis is oriented parallel to the direction of gravity.

[0015] The inner container is preferably cylindrical. The inner container has, in particular, a tubular or cylindrical base section, which can be constructed rotationally symmetrically to the central axis. The base section of the inner container is closed at each end by two outwardly curved lid sections. However, this is not mandatory. The lid sections can also be designed differently. The inner container can also be referred to as an inner tank. The latent heat storage device can also be referred to as a phase change storage device or PCM storage device (Phase Change Material). In this context, a "latent heat storage device" is understood to mean, in particular, a special type of heat storage device that stores a large portion of the thermal energy added to it in the form of latent heat, for example, for a phase change from solid to liquid.

[0016] In particular, a phase change material is used which has a melting point that is above a storage and / or transport temperature of the cryogen contained in the inner container.

[0017] Nitrogen is preferably used as the phase change material. Therefore, the term "phase change material" can be replaced by the term "nitrogen 1 However, argon, for example, can also be used as a phase-change material.

[0018] The phase-change material can be part of the latent heat storage system and thus also part of the storage container. The phase-change material can undergo a phase transition from solid to liquid, as well as from liquid to gas, and vice versa.

[0019] Preferably, during normal operation of the storage vessel, during which cryogen is removed from the storage vessel, only a phase change between solid and liquid or between liquid and solid is provided. The phase-change material absorbs heat during the phase change from solid to liquid and releases heat during the phase change from liquid to solid. During the phase change from liquid to solid, the heat required for this can be extracted from a shield surrounding the inner vessel, which is thereby cooled. This shield can be part of the storage vessel.

[0020] The extraction line is connected to the latent heat storage device in a thermally conductive manner, so that the cryogen flowing through the extraction line can extract heat from the phase-change material, causing the phase-change material to undergo a phase change from liquid to solid. If, for example, no cryogen is extracted from the storage container for a short period of time, the phase-change material undergoes a phase change from solid to liquid. In doing so, the phase-change material absorbs heat, which can be used, in particular, to cool the inner container, for example, with the aid of the aforementioned shield. The extraction line can, for example, be connected to the latent heat storage device on the outside. However, the extraction line can also be routed directly through the latent heat storage device.In the present case, the fact that the extraction line is "actively connected" to the latent heat storage device is to be understood in particular to mean that the extraction line can be in heat exchange with the latent heat storage device in any manner, so that heat can be transferred from the latent heat storage device to the extraction line and vice versa.

[0021] During the aforementioned normal operation of the storage vessel, the latent heat storage system forms a closed system that is not connected to the environment. "Normal operation" in this context means that the cryogen is removed from the storage vessel and, if necessary, the cryogen removal is temporarily interrupted. If the cryogen removal is interrupted for an extended period, for example, in the event of a storage vessel malfunction, the latent heat storage system can be fluidly connected to the environment via the vent line, releasing gaseous phase-change material into the environment.

[0022] The fact that the latent heat storage device can be connected to the environment "exclusively" or "only" by means of the blow-off line means in this case that, apart from the blow-off line, no further fluidic connection exists or can be established between the latent heat storage device and the environment.

[0023] However, a fluidic connection between the latent heat storage device and the environment does not occur during normal operation of the latent heat storage device. Only in the event of a malfunction is the latent heat storage device fluidic connected to the environment via the vent line. In this context, the term "fluidic connection" between the latent heat storage device and the environment means, in particular, that the gaseous phase-change material from the latent heat storage device can be released to the environment via the vent line. For example, the vent line releases the gaseous phase-change material to the environment if a maximum permissible pressure in the latent heat storage device is exceeded. According to one embodiment, the extraction line is routed through the latent heat storage device.

[0024] The latent heat storage device can, for example, have a cylindrical shape. The extraction line can be routed through the latent heat storage device multiple times. For this purpose, the extraction line can be designed in a meandering pattern, for example. However, the extraction line can also be helical or screw-shaped. However, the extraction line can also be routed straight through the latent heat storage device. Alternatively, the extraction line can also be connected to the outside of the latent heat storage device.

[0025] According to a further embodiment, a heat exchanger is attached to the extraction line, which is arranged within the latent heat storage device.

[0026] The heat exchanger is preferably plate-shaped. The heat exchanger can, for example, be soldered or welded to the blow-off line. The heat exchanger is preferably made of a material with good heat conduction, such as aluminum or copper. The heat exchanger can have several heat exchanger plates positioned within the latent heat storage device.

[0027] According to a further embodiment, the latent heat storage device is filled at least in sections with a heat-conducting, fluid-permeable material structure. This can be a woven, knitted, or warp-knitted fabric, which is preferably metallic. The material structure can comprise metal threads or metal wires. Preferably, it is metal wool. Alternatively, the material structure can also comprise smooth and / or structured metal plates and / or metal foils. The material structure can be made of aluminum, an aluminum alloy, copper, or a copper alloy.

[0028] In particular, the material structure can be connected to the heat exchanger. The material structure is impregnated with the phase-change material. This ensures particularly good contact between the phase-change material and the material structure, and thus also with the heat exchanger. The material structure can preferably be or comprise copper, copper alloy, aluminum, and / or aluminum alloy wool. The highly thermally conductive material structure ensures good heat transfer between the heat exchanger and the solid phase-change material.

[0029] According to a further embodiment, the blow-off line has a blow-off valve for blowing off the phase change material into the environment.

[0030] The release valve preferably opens at a specified pressure. For example, a maximum permissible pressure is specified for the latent heat storage system. As soon as this maximum permissible pressure is reached during evaporation of the phase-change material, the release valve opens and the gaseous phase-change material is released into the environment.

[0031] According to a further embodiment, the storage container further comprises a shield which encloses the inner container and the latent heat storage device, wherein the latent heat storage device is thermally conductively connected to the shield.

[0032] The latent heat accumulator can be part of the shield or vice versa. The shield is preferably made of a material with good thermal conductivity, such as aluminum or copper. The shield has, in particular, a tubular base section, which can be constructed rotationally symmetrically to the central axis. The shield is closed at its end by means of two cover sections. The cover sections can be curved outwards with respect to the base section. The inner container and the latent heat accumulator are arranged within this shield. The latent heat accumulator can be thermally conductively connected to the shield, for example, by means of one or more heat-conducting elements. The phase-change material can thus extract heat from the shield via the heat-conducting element(s), so that the shield is cooled.

[0033] According to a further embodiment, the latent heat storage device is arranged between a lid portion of the inner container and a lid portion of the shield.

[0034] As previously mentioned, the inner container has two lid sections, in particular a first lid section and a second lid section. Accordingly, the shield also has two lid sections, in particular a first lid section and a second lid section. The latent heat accumulator is particularly preferably arranged between the second lid section of the inner container and the second lid section of the shield, viewed along the central axis.

[0035] According to a further embodiment, the blow-off line is thermally conductively connected to the shield.

[0036] This improves heat transfer between the vent line and the shield. The cold, gaseous phase-change material can draw heat from the shield, further cooling it. For example, the vent line is soldered or welded to the shield. The vent line can be located inside or outside the shield. "Inside" the shield means facing the inner vessel. "Outside" the shield means facing away from the inner vessel.

[0037] According to a further embodiment, the blow-off line runs helically around the shield on the inside or outside.

[0038] This extends the blow-off line, improving the heat transfer from the blown-off gaseous phase change material to the shield.

[0039] According to a further embodiment, the storage container further comprises an outer container which encloses the shield.

[0040] The outer container has, in particular, a tubular base section, which can be constructed rotationally symmetrically to the central axis. The outer container is closed at its end face by means of two lid sections, in particular by means of a first lid section and a second lid section. The lid sections are preferably curved outwardly relative to the base section. The outer container encloses the shield, which in turn encloses the inner container and the latent heat storage device. The shield is thus arranged entirely within the outer container. According to a further embodiment, the storage container further has a multi-layer insulation element that at least partially fills a gap provided between the inner container and the outer container.

[0041] The insulation element can also be referred to as an insulating element. The insulation element serves to thermally insulate the inner container. In particular, the aforementioned shield is arranged in the gap. The gap can be completely filled with the insulation element and the shield. Alternatively, the gap can also be only partially filled with the insulation element. The insulation element preferably encloses both the base section and the lid sections of the inner container. The insulation element preferably comprises a plurality of plies or layers. In particular, the insulation element is a so-called multilayer insulation (MLI). The insulation element comprises several alternating layers or plies of perforated and / or embossed aluminum foil as a reflector and glass paper as a spacer between adjacent aluminum foils. The glass paper can be perforated and / or perforated.

[0042] According to a further embodiment, the shield is embedded in the insulation element.

[0043] This means, in particular, that layers of aluminum foil and glass paper can be provided inside and outside the shield. In particular, the shield is embedded in outer layers of the insulation element. "Outside" here is understood as in the area of ​​or toward the outer container.

[0044] Furthermore, a method for operating such a storage container for storing a cryogen is proposed. The method comprises the following steps: a) removing liquid cryogen from the storage container, wherein during step a) a phase-change material accommodated in a latent heat storage device of the storage container undergoes a phase transition from liquid to solid by transferring heat from the phase-change material to the liquid cryogen, or wherein the phase-change material remains solid during step a), b) ending step a), wherein the phase-change material undergoes a phase transition from solid to liquid, and c) fluidically separating the latent heat storage device from an environment of the storage container during steps a) and b).

[0045] In step a), in particular, a portion of the liquid cryogen is withdrawn from the storage vessel via the withdrawal line. During step a), the phase change material stored in the latent heat storage device undergoes a phase transition from liquid to solid by transferring heat from the phase change material to the cryogen. If the phase change material is already solid, the phase change material remains solid during step a). In this case, too, heat continues to be extracted from the phase change material. In step b), step a) is terminated. This means that, at least for a short time, no more cryogen flows through the withdrawal line. Step b) can be carried out until all of the phase change material has melted. In particular, step b) can be carried out until a maximum permissible pressure, as mentioned above, is reached in the latent heat storage device.During step b), the phase change material thus undergoes a phase transition from solid to liquid or remains in its solid state. Step c) is preferably carried out in parallel to steps a) and b). This means that during steps a) and b), the latent heat storage device is fluidically separated from the environment of the storage vessel according to step c). This means that the blow-off valve is always closed during steps a) to c). The fluidic separation of the latent heat storage device from the environment is only removed when the phase change material is at least partially gaseous and the maximum permissible pressure in the latent heat storage device is exceeded. This can occur, for example, during a storage vessel malfunction in which no cryogen is removed from the inner vessel for an extended period of time. The gaseous phase change material is then vented into the environment via the blow-off line and the blow-off valve.

[0046] According to one embodiment, during step b), heat required for the phase transition is extracted from a shield enclosing an inner container of the storage container.

[0047] In particular, during step b), the heat required for the phase transition from solid to liquid is extracted from the shield. This cools the shield. According to a further embodiment, steps a) to c) are carried out during normal operation of the storage vessel, with a vent valve of the storage vessel being opened only in the event of a storage vessel malfunction, thereby releasing gaseous phase-change material into the environment.

[0048] "Normal operation" of the storage vessel means that the liquid cryogen is being removed from it. However, normal operation can also involve a brief interruption in the removal of the liquid cryogen. A malfunction occurs when the phase-change material undergoes a phase transition from liquid to gaseous and the pressure in the latent heat storage rises above the maximum permissible pressure. This means that only in a malfunction is the latent heat storage connected to the environment via the vent valve to vent the gaseous phase-change material.

[0049] "One" in this case is not necessarily to be understood as limiting the number to exactly one element. Rather, multiple elements, such as two, three, or more, can also be considered. Any other counting term used here should also not be understood as requiring a precise limitation to the corresponding number of elements. Rather, numerical deviations upwards and downwards are possible.

[0050] The embodiments and features described for the storage container apply accordingly to the proposed method and vice versa.

[0051] Further possible implementations of the storage container and / or the method also include combinations of features or embodiments described above or below with respect to the exemplary embodiments that are not explicitly mentioned. In this case, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the storage container and / or the method.

[0052] Further advantageous embodiments of the storage container and / or the method are the subject of the dependent claims and the exemplary embodiments of the storage container and / or the method described below. The storage container and / or the method are explained in more detail below using preferred embodiments with reference to the accompanying figures.

[0053] Fig. 1 shows a schematic sectional view of an embodiment of a storage container;

[0054] Fig. 2 shows a schematic sectional view of an embodiment of a latent heat storage device for the storage container according to Fig. 1;

[0055] Fig. 3 shows the detailed view III according to Fig. 1; and

[0056] Fig. 4 shows a schematic block diagram of an embodiment of a method for operating the storage container according to Fig. 1.

[0057] In the figures, identical or functionally equivalent elements have been given the same reference numerals unless otherwise stated.

[0058] Fig. 1 shows a schematic sectional view of an embodiment of a storage container 1.

[0059] The storage container 1 can also be referred to as a storage tank. The storage container 1 is suitable for holding a cryogen H2. In this case, the cryogen H2 is hydrogen and is also referred to as hydrogen below. The storage container 1 is preferably suitable for holding liquid hydrogen H2 (boiling point: 1 bara: 20.268 K = -252.882 °C). Therefore, the storage container 1 can also be referred to as a hydrogen storage container or a hydrogen storage tank.

[0060] However, storage vessel 1 can also be used for other cryogenic liquids. An example of a cryogenic fluid or liquid, or cryogen for short, in addition to the aforementioned hydrogen H2, is liquid helium He (boiling point at 1 bara: 4.222 K = -268.928 °C).

[0061] The storage container 1 can be a transport container. For example, the storage container 1 can be used to transport liquid hydrogen H2. The storage container 1 can be part of a vehicle, in particular a watercraft. In this case, the storage container 1 is suitable for mobile applications. However, the storage container 1 can also be used stationary, for example, in building technology.

[0062] For use of storage vessel 1 in a maritime environment, it is required that storage vessel 1, at maximum filling, achieves a holding time of 15 days based on the operating pressure in the event of an accident. This means that during this time, the maximum permissible pressure within the inner vessel 3 must not be exceeded, and no hydrogen H2 may escape from storage vessel 1.

[0063] Due to the holding time requirement, storage vessel 1 can currently only be partially filled with liquid hydrogen H2, depending on the heat input and the thermodynamic equilibrium temperature of the stored liquid hydrogen H2. Under current typical conditions, sometimes only 70% to 80% of the geometric volume of storage vessel 1 can be used for the storage of liquid hydrogen H2. This needs to be improved.

[0064] The storage container 1 is constructed rotationally symmetrically to a symmetry or central axis 2. The central axis 2 is oriented perpendicular to a direction of gravity g. The storage container 1 comprises a first container or inner container 3, which is also constructed rotationally symmetrically to the central axis 2. The inner container 3 comprises a tubular or cylindrical base section 4, which is also constructed rotationally symmetrically to the central axis 2. The base section 4 can have a circular or approximately circular geometry in cross-section.

[0065] The base section 4 is closed on both sides at the end by means of a lid section 5, 6. The lid sections 5, 6 are curved. A first lid section 5 and a second lid section 6 are curved in opposite directions, so that the lid sections 5, 6 are curved outwards with respect to the base section 4. The inner container 3 is fluid-tight, in particular gas-tight. The inner container 3 is made of stainless steel. The liquid hydrogen H2 is contained in the inner container 3. As long as the hydrogen H2 is in the two-phase region, a gas zone 7 with vaporized hydrogen H2 and a liquid zone 8 with liquid hydrogen H2 can be provided in the inner container 3. The hydrogen H2 therefore has two phases with different states of aggregation, namely liquid and gaseous, after being filled into the inner container 3.This means that in the inner container 3 there is a phase boundary 9 between the liquid hydrogen H2 and the gaseous hydrogen H2.

[0066] The inner container 3 is arranged entirely within a second container or outer container 10. The storage container 1 is thus double-walled. The outer container 10 is also constructed rotationally symmetrically to the central axis 2. The outer container 10, like the inner container 3, comprises a tubular or cylindrical base section 11, which is constructed rotationally symmetrically to the central axis 2. The base section 11 can have a circular or approximately circular geometry in cross-section.

[0067] The base section 11 is closed at each end by a lid section 12, 13. In particular, a first lid section 12 and a second lid section 13 are provided. The lid sections 12, 13 are curved in opposite directions, so that the lid sections 12, 13 are curved outward relative to the base section 11. The outer container 10 is fluid-tight, in particular gas-tight. The outer container 10 is also made of stainless steel.

[0068] A gap 14 is provided between the inner container 3 and the outer container 10, completely surrounding or enclosing the inner container 3. A vacuum is applied to the gap 14. A "vacuum" in this case is understood to mean, in particular, a pressure of less than 300 mbar, preferably less than 10 -3 mbar, more preferably less than 10 -7mbar. The storage container 1 is thus vacuum-insulated or vacuum-insulated. The fact that the gap 14 completely "encloses" or "envelops" the inner container 3 means, in this case, that the gap 14, on the one hand, completely runs circumferentially around the base section 4 and, on the other hand, is also provided between the two lid sections 5, 12 and between the two lid sections 6, 13. A screen or shield 15, in particular a so-called soft shield, is provided between the inner container 3 and the outer container 10. The shield 15 is thus placed in the gap 14. The shield 15 is made of a material with good thermal conductivity, such as copper or aluminum. The shield 15 is preferably fluid-permeable, in particular gas-permeable. The shield 15 has a cylindrical base section 16, which is rotationally symmetrical to the central axis 2.The base section 16 is closed at the front by means of a first cover section 17 and a second cover section 18.

[0069] A latent heat storage device 19 is located within the shield 15. In the orientation of Fig. 1, the latent heat storage device 19 is positioned next to the inner container 3. In particular, the latent heat storage device 19 is arranged between the lid sections 6, 18. The latent heat storage device 19 is filled at least in sections with a phase change material N2 (PCM), as will be explained below. In this case, the phase change material N2 is nitrogen. However, the phase change material N2 can also be argon, for example.

[0070] In the following, it is assumed that the phase-change material N2 is nitrogen. Therefore, the phase-change material N2 is referred to as nitrogen. The latent heat storage device 19 is connected to the shield 15, in particular to the base section 16 of the shield 15, via a heat-conducting element 20 extending around the central axis 2. The heat-conducting element 20 can be disc-shaped.

[0071] Within the latent heat storage 19 there is a heat exchanger or heat exchanger

[0072] 21. The heat exchanger 21 is thermally conductive with a withdrawal line

[0073] 22, which flows into the inner container 3 below the phase boundary 9, is guided through the latent heat storage 19 and is guided through the shield 15 and the outer container 10 into an environment 23 of the storage container 1.

[0074] The heat exchanger 21 is connected to the extraction line 22, so that the extraction line 22 can transfer heat to the heat exchanger 21 or vice versa. The heat exchanger 21 can be a metal plate, in particular an aluminum plate or a copper plate, welded or soldered to the extraction line 22. The heat exchanger 21 can also be constructed from several such metal plates.

[0075] A blow-off line 24 with a blow-off valve 25 discharges from the latent heat storage device 19. The blow-off line 24 can be routed inside the shield 15. The blow-off line 24 can be thermally connected to the shield 15. The blow-off line 24 can extend helically or helically around the central axis 2 and be attached to the inside or outside of the shield 15. The blow-off valve 25 can release vaporized nitrogen N2 into the environment 23.

[0076] Fig. 2 shows a schematic sectional view of an embodiment of a latent heat storage device 19 as mentioned above.

[0077] The latent heat storage unit 19 acts as a thermal buffer for the storage container 1. The latent heat storage unit 19 encloses an interior space 26 in which the heat exchanger 21 is accommodated, which is in contact with solid nitrogen N2. The latent heat storage unit 19 can be completely or partially filled with the solid nitrogen N2. The interior space 26 is at least partially or completely filled with a heat-conducting, fluid-permeable material structure, such as a knitted fabric 27 in this exemplary embodiment.

[0078] The knitted fabric 27 can be made of aluminum and / or copper threads. In particular, the knitted fabric 27 can be made of copper and / or aluminum wool. The knitted fabric 27 is connected to the heat exchanger 21 in a thermally conductive manner. The knitted fabric 27 is impregnated with nitrogen N2. The highly thermally conductive knitted fabric 27 ensures good heat transfer between the heat exchanger 21 and the solid nitrogen N2.

[0079] Fig. 3 shows the detailed view III of the storage container 1 according to Fig. 1.

[0080] A thermal insulation element or insulation element 28 is provided in the gap 14, completely enclosing or surrounding the inner container 3. This means that the insulation element 28 surrounds both the base section 4 and the lid sections 5, 6 of the inner container 3. The insulation element 28 serves for thermal insulation. The insulation element 28 is multi-layered. This means that the insulation element 28 comprises a plurality of layers.

[0081] Insulation element 28 can therefore also be referred to as a multi-layer insulation element or as a multi-layer thermal insulation element.

[0082] In particular, the insulation element 28 is a so-called multilayer insulation (MLI). The insulation element 28 comprises several alternating layers or plies of perforated and / or embossed aluminum foil 29 as a reflector and glass paper 30 as a spacer between adjacent aluminum foils 29. The glass paper 30 can be perforated and / or perforated.

[0083] In Fig. 3, only two layers of aluminum foil 29 and two layers of glass paper 30 are provided with a reference symbol. The glass paper 30 acts as a spacer between two adjacent aluminum foils 29, allowing the insulation element 28 to be exposed to the vacuum prevailing in the gap 14. The insulation element 28 rests against the outside of the inner container 3.

[0084] The insulation element 28 can partially or—as shown in Fig. 3—completely fill the gap 14. The shield 15 can be embedded in the insulation element 28. This means that layers of aluminum foil 29 and glass paper 30 can be provided inside and outside the shield 15. In particular, the shield 15 is embedded in outer layers of the insulation element 28. "Outside" here is understood to mean in the region of the outer container 10.

[0085] The functionality of storage tank 1 is explained below. During normal operation of storage tank 1, a substantially constant withdrawal of liquid hydrogen H2 from inner tank 3 occurs via withdrawal line 22. When the liquid hydrogen H2 is passed through latent heat storage 19, it extracts heat Q from the nitrogen N2 via heat exchanger 21 and fabric 27.

[0086] The nitrogen N2, if it is liquid, undergoes a phase transition from liquid to solid. If the nitrogen N2 is already solid, it is maintained in the solid state. This means that the nitrogen N2 stored in the latent heat storage unit 19 is solid during normal operation of the storage tank 1. The latent heat storage unit 19 is at least partially thermally separated from the inner tank 3.

[0087] If there is no longer any withdrawal of liquid hydrogen H2 for a short time, the solid nitrogen N2 melts with a moderate increase in pressure in the latent heat storage 19. As the solid nitrogen N2 melts, it extracts heat Q from the shield 15 via the heat conducting element 20. Because the latent heat storage 19 is connected to the shield 15 via the heat conducting element 20, the shield 15 is cooled down.

[0088] If the withdrawal of liquid hydrogen H2 is subsequently resumed, a reverse phase transition of the nitrogen N2 from liquid to solid occurs, since the liquid hydrogen H2 flowing through the withdrawal line 22 extracts heat Q from the liquid nitrogen N2. Thus, during normal operation of the storage tank 1, it is a closed system.

[0089] If no more liquid hydrogen H2 is removed for an extended period, the solid nitrogen N2 melts, begins to boil, and eventually evaporates. The gaseous nitrogen N2 can then be vented into the environment 23 via the vent line 24 and the vent valve 25. As previously mentioned, the vent line 24 can helically encircle the shield 15, with the cold, gaseous nitrogen N2 continuing to extract heat Q from the shield 15.

[0090] During normal operation, the phase transition of nitrogen N2 from solid to liquid and vice versa prevents a loss of nitrogen N2 via the vent line 24 and the vent valve 25 and / or prevents an excessively high maximum permissible pressure within the latent heat storage device 19. The heat input into the inner vessel 3 is significantly reduced during a malfunction by the shield 15, which is cooled by nitrogen N2. This increases the retention time of the hydrogen H2.

[0091] During normal operation of the storage tank 1, the latent heat storage unit 19, together with the heat exchanger 21, thus forms a closed system in which a phase transition from solid to liquid occurs alternately. Only in the event of a malfunction—that is, when no liquid hydrogen H2 is extracted for an extended period—does the nitrogen N2 evaporate and is released into the environment 23.

[0092] The filling level of the storage vessel 1 with liquid hydrogen H2 can be significantly increased compared to a storage vessel without such a latent heat storage device 19, so that a larger mass of hydrogen H2 can be stored within the same footprint for the storage vessel 1. The resulting compact design of the storage vessel 1 can be particularly advantageous for use on ships retrofitted with a system for liquid hydrogen H2. The latent heat storage device 19 enables, in particular, emergency cooling of the shield 15 and thus also of the storage vessel 1.

[0093] Fig. 4 shows a schematic block diagram of an embodiment of a method for operating the storage container 1.

[0094] In the method, in a step S1, a portion of the liquid hydrogen H2 is withdrawn from the storage tank 1 via the withdrawal line 22. During step S1, the nitrogen N2 stored in the latent heat storage 19 undergoes a phase transition from liquid to solid by transferring heat Q from the nitrogen N2 to the hydrogen H2. If the nitrogen N2 is already solid, the nitrogen N2 remains solid during step S1.

[0095] In step S2, step S1 is terminated. This means that no more hydrogen H2 flows through the extraction line 22. Step S2 can be continued until all of the nitrogen N2 has melted. During step S2, the nitrogen N2 thus undergoes a phase transition from solid to liquid.

[0096] In a step S3, which is preferably carried out in parallel to steps S1, S2, the latent heat accumulator 19 is fluidically separated from the environment 23 of the storage container 1. The fluidic separation of the latent heat accumulator 19 from the environment 23 is only removed when the nitrogen N2 is at least partially gaseous and excessive pressure builds up in the latent heat accumulator 19. This can occur during a malfunction. When the maximum permissible pressure within the latent heat accumulator 19 is reached, the gaseous nitrogen N2 is then vented into the environment 23 via the vent line 24 and the vent valve 25. During step S2, the heat Q required for the phase transition of the nitrogen N2 from solid to liquid is extracted from the shield 15 surrounding the inner container 3 of the storage container 1. This cools the shield 15.

[0097] In particular, steps S1 to S3 are only carried out during normal operation of the storage tank 1, whereby the blow-off valve 25 of the storage tank 1 is opened only in the event of a malfunction of the storage tank, whereby gaseous nitrogen N2 is blown off into the environment 23.

[0098] Although the present invention has been described using exemplary embodiments, it can be modified in many ways.

[0099] Reference symbols used

[0100] 1 storage tank

[0101] 2 central axis

[0102] 3 inner containers

[0103] 4 Basic section

[0104] 5 Lid section

[0105] 6 Lid section

[0106] 7 Gas Zone

[0107] 8 Liquid zone

[0108] 9 Phase boundary

[0109] 10 outer containers

[0110] 11 Base section

[0111] 12 Lid section

[0112] 13 Lid section

[0113] 14 gap

[0114] 15 Shield

[0115] 16 Base section

[0116] 17 Lid section

[0117] 18 Lid section

[0118] 19 latent heat storage

[0119] 20 Heat conducting element

[0120] 21 heat exchangers

[0121] 22 Withdrawal line

[0122] 23 Surroundings

[0123] 24 Blow-off line

[0124] 25 Blow-off valve

[0125] 26 Interior

[0126] 27 knitted fabrics

[0127] 28 Insulation element

[0128] 29 aluminum foil

[0129] 30 glass paper g gravity direction

[0130] H2 Hydrogen / Cryogen N2 Nitrogen / Phase change material

[0131] Q Heat

[0132] 51 steps

[0133] 52 Step S3 Step

Claims

Patent claims 1. Storage container (1) for storing a cryogen (H2), with an inner container (3) for receiving the cryogen (H2), a latent heat accumulator (19) for receiving a phase change material (N2), and a withdrawal line (22) for withdrawing only the liquid phase of the cryogen (H2) from the inner container (3), wherein the withdrawal line (22) is operatively connected to the latent heat accumulator (19) in such a way that liquid cryogen (H2) received in the withdrawal line (22) is in heat exchange with the phase change material (N2), and wherein the latent heat accumulator (19) is fluidically connectable to an environment (23) of the storage container (1) exclusively with the aid of a vent line (24).

2. Storage container according to claim 1, wherein the extraction line (22) is passed through the latent heat storage device (19).

3. Storage tank according to claim 1 or 2, wherein a heat exchanger (21) is attached to the extraction line (22) and is arranged within the latent heat storage device (19).

4. Storage container according to one of claims 1 - 3, wherein the latent heat accumulator (19) is at least partially filled with a heat-conducting, fluid-permeable material structure, in particular a knitted fabric (27).

5. Storage container according to one of claims 1 - 4, wherein the blow-off line (24) has a blow-off valve (25) for blowing off the phase change material (N2) into the environment (23).

6. Storage container according to one of claims 1 - 5, further comprising a shield (15) which encloses the inner container (3) and the latent heat accumulator (19), wherein the latent heat accumulator (19) is thermally conductively connected to the shield (15).

7. Storage container according to claim 6, wherein the latent heat storage device (19) is arranged between a lid portion (6) of the inner container (3) and a lid portion (18) of the shield (15).

8. Storage container according to claim 6 or 7, wherein the blow-off line (24) is thermally conductively connected to the shield (15).

9. Storage container according to claim 8, wherein the blow-off line (24) runs helically around the shield (15) on the inside or outside.

10. Storage container according to one of claims 6 - 9, further comprising an outer container (10) enclosing the shield (15).

11. Storage container according to claim 10, further comprising a multi-layer insulation element (28) which at least partially fills a gap (14) provided between the inner container (3) and the outer container (10).

12. Storage container according to claim 11, wherein the shield (15) is embedded in the insulation element (28).

13. A method for operating a storage container (1) according to one of claims 1-12 for storing a cryogen (H2), comprising the following steps: a) removing (S1) liquid cryogen (H2) from the storage container (1), wherein during step a) a phase change material (N2) accommodated in a latent heat storage device (19) of the storage container (1) undergoes a phase transition from liquid to solid by means of a transfer of heat (Q) from the phase change material (N2) to the liquid cryogen (H2), or wherein the phase change material (N2) remains solid during step a), b) terminating (S2) step a), wherein the phase change material (N2) undergoes a phase transition from solid to liquid, and c) fluidically separating (S3) the latent heat storage device (19) from an environment (23) of the storage container (1) during steps a) and b).

14. The method according to claim 13, wherein during step b) heat (Q) required for the phase transition is extracted from a shield (15) surrounding an inner container (3) of the storage container (1).

15. The method according to claim 13 or 14, wherein steps a) to c) are carried out in a Normal operation of the storage tank (1) is carried out, and only in the event of a malfunction of the storage tank (1) is a blow-off valve (25) of the storage tank (1) opened, whereby gaseous phase change material (N2) is blown off into the environment (23).

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