Storage vessel and cryogen supply system

Abstract

A storage container (1) for storing a cryogen (H2), comprising: an inner container (6) for receiving the cryogen (H2); an outer container (5) surrounding the inner container (6); and a heating device (19) disposed at least partially within the inner container (6) for introducing heat (Q) into the cryogen (H2), the heating device (19) having a heating element (30) for generating heat (Q) and an outer casing (21) liquid-tightly surrounding an interior space (22) of the heating device (19), the heating element (30) being housed within the interior space (22), the heating element (30) having a heating wire embedded in a metal oxide encapsulated by the casing housed within the interior space (22).

Description

[Technical field]

[0001] The present invention relates to a storage container for storing a cryogen and to a cryogen supply system having at least one such storage container.

[0002] The storage vessel for liquid hydrogen may, according to in-house know-how, have a pressure-generating vaporizer which makes it possible to increase the pressure in the storage vessel, so that gaseous hydrogen can be made available to a consumer, for example in the form of a fuel cell, at a stable supply pressure, for example between 1 and 2.5 bar. Such a storage vessel is substantially cylindrical or barrel-shaped. The pressure-generating vaporizer is configured to supply gaseous hydrogen to the storage vessel. Gaseous hydrogen can, for example, be obtained by vaporizing liquid hydrogen.

[0003] During operation of such storage vessels, for example in the marine sector (offshore use), movement of the storage vessel, for example due to swells, can make it very difficult to maintain stable operating conditions within the storage vessel so that the required supply pressure to the consumer can remain constant. When the storage vessel moves, the liquid hydrogen within the storage vessel sloshes back and forth uncontrollably. This back and forth movement of the liquid hydrogen when the storage vessel moves is referred to as "sloshing".

[0004] In a pressure generating vaporizer as described above, pressure in the storage vessel is generated by supplying gaseous hydrogen. As previously mentioned, gaseous hydrogen can be generated from liquid hydrogen using a pressure generating vaporizer. This increases the pressure in the gaseous region of the storage vessel. The gaseous region is located above the liquid region. A phase boundary is created between the gaseous region and the liquid region. The gaseous region is formed by the gaseous hydrogen. The gaseous hydrogen forms a gas phase. The liquid region is formed by the liquid hydrogen. The liquid hydrogen forms a liquid phase. A phase boundary is created between the liquid phase and the gas phase. The gas phase can change to a liquid phase and vice versa. During operation of the storage vessel, there is a continuous transport or exchange of heat between the gaseous and liquid phases and vice versa.

[0005] The transport of heat from the hot gas phase of hydrogen to the cold liquid phase is slow. This means that the liquid phase remains initially subcooled. In particular, in storage vessels for use in the marine sector, the hot gas phase condenses at the phase boundary due to heat exchange with the subcooled liquid phase, leading to uncontrolled pressure drops in the storage vessel due to sloshing of the subcooled liquid phase. This can lead to undesirable pressure fluctuations in the storage vessel. Such pressure fluctuations can complicate process control and can lead to undesirable shutdowns of hydrogen supply systems with such storage vessels. Hydrogen-powered fuel cells can be particularly sensitive to pressure fluctuations. As mentioned before, they require a constant supply of gaseous hydrogen at a given supply pressure.

[0006] It is desirable to saturate the gas and liquid phases of hydrogen to ensure that no pressure fluctuations occur in the storage vessel. On the one hand, the heat transfer from the hot gas phase to the subcooled liquid phase is much slower than if the liquid phase were directly heated, so that the use of known in-house pressure generation evaporators can result in long residence times in the storage vessel between the gas and liquid phases of hydrogen before saturation is reached. On the other hand, regulatory requirements for explosive cryogenic media such as hydrogen require a secondary barrier. Due to this secondary barrier, the heating of the liquid phase occurs very slowly, so that pressure generation by such pressure generation evaporators occurs slowly.

[0007] EP 0 997 682 describes an apparatus for increasing the pressure in a storage container for a cryogenic liquid, which has a housing with at least one inlet opening for the liquid, inside which is a heating device for evaporating the liquid and a vapor line arranged in the upper third of the housing for discharging vapor bubbles formed during evaporation, the cross section of the vapor line being sufficiently large so that during operation of the apparatus, more vapor than liquid is discharged through the vapor line.

[0008] Against this background, it is an object of the present invention to provide an improved storage tank.

[0009] Therefore, a storage container for storing a cryogen is proposed, the storage container comprising an inner container for receiving the cryogen, an outer container surrounding the inner container, and a heating device at least partially disposed within the inner container for introducing heat into the cryogen, the heating device having a heating element for generating heat and an outer casing liquid-tightly surrounding an interior space of the heating device, the heating element being housed within the interior space, the heating element having a heating wire embedded in a metal oxide encapsulated by the casing housed within the interior space.

[0010] Since the heating element is accommodated in the inner space of the outer casing, it is advantageously possible to create a separate pressure chamber for the heating element in the outer casing. The outer casing seals the heating element in a particularly liquid-tight manner from the atmosphere or surroundings of the storage container, from the vacuum space arranged between the inner container and the outer container, and from the cryogen. This avoids direct contact between the heating element and the cryogen in the inner container. Nevertheless, the heating device advantageously allows direct heating of the liquid phase of the cryogen.

[0011] The cryogen is preferably hydrogen. The terms "cryogen" and "hydrogen" are therefore interchangeable as desired. In principle, however, the cryogen may be any other cryogen. Examples of cryogenic fluids or liquids, or cryogen for short, are liquid helium, liquid nitrogen or liquid oxygen, in addition to the aforementioned hydrogen. "Cryogen" should therefore be understood in particular as a liquid. The cryogen may therefore also be referred to as a cryogenic liquid. The cryogen may be evaporated and thus converted into the gas phase. After evaporation, the cryogen may be a gas or may be referred to as a gaseous or vaporized cryogen. The term "cryogen" may therefore include both, i.e. the gas and liquid phases. As mentioned above, the liquid phase may also be referred to as a cryogenic liquid. Here, the term "vaporized cryogen" preferably refers only to the gas phase of the cryogen.

[0012] In particular, a gaseous region in the inner vessel of the storage vessel and an underlying liquid region are formed in the storage vessel after or during the filling of the cryogen into the storage vessel. The storage vessel encloses an interior space, receiving space or cavity for receiving the cryogen. The gaseous region and the liquid region fill the interior space. In particular, the heating device is located at least partially in the interior space of the inner vessel. A phase boundary is created between the gaseous region and the liquid region. Thus, the cryogen preferably has two phases, i.e. a liquid phase and a gaseous phase, with different condensation states after entering the storage vessel. The liquid state phase can transition to the gaseous phase and vice versa. The liquid phase may be referred to as the liquid phase. The gaseous phase may be referred to as the gas phase. A purely liquid filling of the storage vessel is also possible.

[0013] The pressure prevailing in the storage vessel is preferably about 3.5 bar. The pressure prevailing in the storage vessel is in particular constant. The storage vessel is in particular suitable for supplying the gaseous or liquid phase of the cryogen to the consumer at a suitable supply pressure and at a suitable temperature. The consumer can be a fuel cell. In this case, "fuel cell" is understood to mean in particular a galvanic cell which converts the energy of a chemical reaction between a continuously supplied fuel (in this case hydrogen) and an oxidant (in this case oxygen) into electrical energy. The cryogen is supplied to the consumer itself, in particular in gaseous form. This means that, in the case of a gaseous phase supplied directly from the storage vessel, the cryogen is completely vaporized or heated before or upstream of the consumer. For example, the cryogen is supplied to the consumer at a supply pressure of 1 to 2.5 bar and at a temperature of +10°C to +25°C. The supply pressure can, however, be up to 6 bar.

[0014] The storage container is preferably assigned a central axis or an axis of symmetry, about which the storage container is constructed substantially rotationally symmetrically. In cross section, the storage container can therefore have a circular or annular cross section. In contrast to this, however, the storage container may also be oval or elliptical in cross section. In particular, the inner container and the outer container, respectively, are constructed rotationally symmetrically about the axis of symmetry. The inner container and the outer container, respectively, comprise a tubular base part that is rotationally symmetrical about the axis of symmetry. The inner container and the outer container, respectively, are sealed liquid-tight at the front part by means of a first cover part and a second cover part. The inner container and the outer container are in particular liquid-tight. The inner container and the outer container can be made, for example, of a metallic material, in particular stainless steel. The inner container is arranged completely inside the outer container. This in particular means that the outer container completely surrounds the inner container.

[0015] The heating device can be led from the periphery of the storage container through the outer container and the inner container into the inner container, in particular into the liquid region of the inner container. For this purpose, the heating device can for example pass through the first cover part of the inner container and the outer container, respectively. In particular, the heating device is placed below the phase boundary in the liquid region, so that the heating device is always surrounded or washed over by the liquid phase of the cryogen. The heating device is especially designed to introduce heat directly into the liquid phase of the cryogen. By introducing heat into the cryogen, the cryogen is at least partially vaporized, whereby a pressure increase can be achieved in the storage container, in particular in the inner container.

[0016] The heating element is preferably a heating wire or cable or includes a heating wire or cable. In particular, the heating element is an electric heating element. Preferably, the heating element converts electric energy into heat. The fact that the outer casing is "liquid-tight" means in this case in particular that no fluid, in particular liquid or gas, can escape from or enter the outer casing. The inner space is completely surrounded by the outer casing. The inner space may be partially located outside, i.e. around, the storage container, or partially inside the storage container, in particular inside the inner container. The outer casing is preferably made of a metallic material. For example, the outer casing can be made of stainless steel or an aluminum alloy.

[0017] Preferably, the heating device is operated in bubble-forming mode. This means, in particular, that the heating device is operated in such a way that bubbles of vaporized cryogen rise from the heating device immersed in the liquid phase and release heat to the liquid phase as they rise until they rise from the liquid phase to the gas phase. This can be done by suitable setting or adjustment of the heating power of the heating device. By operating in bubble-forming mode, film boiling around the heating device is avoided. No bubble formation occurs during film boiling. In this case, an undesirable layer of heated liquid phase can be formed around the heating device, which acts as an insulating liquid buffer. This can have a negative effect on the transfer of heat. By operating in bubble-forming mode, film boiling can be reliably prevented, which means that the transfer of heat from the heating device to the liquid phase is always ensured.

[0018] In contrast to the pressure generating vaporizers mentioned above, the heating device is designed so that the cryogen does not leave the outer casing in case of a leak in the latter. This makes it explosion-proof. An optional pressure monitoring system in the inner space can be used to detect leaks in the heating device. In this case, three different leak possibilities can be detected. It is always possible to reliably detect leaks to the surroundings, leaks to the vacuum space arranged between the inner and outer containers, and leaks to the inner container, especially in the liquid region. The heating device is explosion-proof. The heating device is also suitable for very low temperatures. The additional outer casing allows the cryogen and the heating element to be safely separated from each other. The heating element therefore does not come into direct contact with the cryogen, especially in the liquid phase.

[0019] The heating device is preferably assigned a central axis or axis of symmetry, about which the heating device is constructed substantially rotationally symmetrically. The heating device may be circular or cylindrical in cross section. However, this does not exclude that the heating device may be at least partially oval or elliptical in cross section. This means, in particular, that the heating device may have an oval cross section. In particular, the outer casing is rotationally symmetric about the axis of symmetry. With respect to the direction of gravity, the axis of symmetry of the heating device is placed below the axis of symmetry of the storage container. The axis of symmetry of the storage container is therefore arranged above the axis of symmetry of the heating device with respect to the direction of gravity. The axes of symmetry of the heating device and the axis of symmetry of the storage container are arranged parallel to each other and at a distance from each other.

[0020] Metal oxide powder is preferably used as the metal oxide. Aluminum oxide and / or magnesium oxide are examples of metal oxides used. The casing is in particular made of metal. The casing may therefore be referred to as a metal casing or metal casing. In particular, the casing is in particular non-conductive. The casing may therefore be referred to as a non-conductive or non-conductive casing, in particular a non-conductive or non-conductive metal casing. The casing may, for example, be a stainless steel casing. The heating device is therefore designed to be double-walled or double-enclosed with the help of an outer casing and a casing arranged within the outer casing. The heating device may therefore be referred to as a double-walled or double-enclosed heating device.

[0021] According to one embodiment, a storage container for storing a cryogen is proposed, the storage container comprising an inner container for receiving the cryogen, an outer container surrounding the inner container, and a heating device at least partially disposed within the inner container for introducing heat into the cryogen, the heating device having a heating element for generating heat and an outer casing liquid-tightly surrounding an interior space of the heating device, the heating element being accommodated within the interior space.

[0022] According to a further embodiment, the interior space is filled with a heat conducting medium.

[0023] The heat transfer medium may be a gas. The terms "medium" and "gas" are therefore interchangeable if necessary. Optionally, additional gases may be added. The heat transfer medium may be or may have a liquid. The heat transfer medium may have liquid, solid and gas phases. The heat transfer medium may be part of the heating device. The heat transfer medium is used to ensure heat transfer between the heating element and the outer casing of the heating device and thus between the heating element and the liquid phase of the cryogen. Suitable gases may be, for example, inert gases. The heat transfer medium or gas may be helium. In particular, the heat transfer medium should be selected such that no phase change of the heat transfer medium occurs over the entire operating temperature range of the storage container. In particular, the heat transfer medium must not freeze or freeze. Alternatively, a phase change of the heat transfer medium may be provided during operation of the heating device. This may be achieved by a suitable selection of the heat transfer medium. The filling pressure and the heat transfer medium are preferably selected such that at the lowest and highest temperatures that may occur during operation of the storage container, there is a difference between the surrounding ambient pressure and the operating pressure of the storage container. This aforementioned difference allows reliable detection of possible leaks between the liquid region and the inner space of the outer casing, between the vacuum space and the inner space of the outer casing, and / or between the surroundings and the interior of the outer casing. If the cryogen is hydrogen, the heat transfer medium is preferably helium. By using helium as the heat transfer medium, it is possible to reliably prevent the heat transfer medium from freezing when the storage vessel is operated with hydrogen. For example, any overpressure that allows leakage monitoring can be selected as the filling pressure of the inner space of the outer casing. Preferably, a pressure between 1.1 and 200 bar, in particular between 5 and 10 bar, is selected as the filling pressure. Monitoring the inner space thus allows safety-related leakage monitoring in order to meet the requirements for separation of the electrical system and the process system and from the surroundings in accordance with the relevant regulations. The heating element can extend along the longitudinal direction of the storage vessel oriented along the axis of symmetry.

[0024] According to a further embodiment, the heating device is guided from the periphery of the storage vessel through the outer vessel and the inner vessel into the liquid region surrounded by the inner vessel.

[0025] As mentioned above, in addition to the liquid region, a gas region is arranged in the inner container above the liquid region. The heating device can be arranged at least partially in the gas region or at least partially protrude into the gas region. The gas region and the liquid region together fill the above-mentioned internal space, receiving space or cavity of the inner container for containing the cryogen. In particular, the heating device extends into the internal space of the inner container. Preferably, the heating device is arranged so that it is always arranged or located in the liquid region. In particular, with respect to the axis of symmetry of the storage container, the heating device is arranged below this axis of symmetry. The heating device is in particular located in the floor or lower area of ​​the inner container.

[0026] According to a further embodiment, the outer casing is guided through the outer container and the inner container, the outer casing being connected to the outer container and the inner container with a material bond and / or a form fit.

[0027] Given an integrally joined connection, the connection partners are held together by atomic or molecular forces. A material bond is an undetachable connection that can only be separated by destroying the connection means and / or the connection partners. For example, the outer casing is soldered or welded into the outer container and / or the inner container. Brazing is particularly suitable as a soldering process. The outer casing can also be glued to the outer container and / or the inner container. In particular, the outer casing is guided through one of the cover parts, in particular the first cover part, of the outer container and through one of the cover parts, in particular the first cover part, of the inner container, and the outer casing is material-bonded to the corresponding cover part. Additionally or alternatively, a form fit can be provided. The form fit is brought about by at least two connection partners engaging with each other or behind each other. For example, a screw connection and / or a flange connection can be provided. Thus, the outer casing can be screwed and / or flanged to the outer container and the inner container.

[0028] According to a further embodiment, the outer casing has ends which protrude to the periphery and are closed in a liquid-tight manner by removable closing elements, the connecting lines of the heating element being led through the closing elements.

[0029] Preferably, the outer casing has a tubular base part with a first end at the end projecting to the periphery and a second end projecting into the inner container. The second end is, for example, a lid closing the front of the base part. The first end projects to the periphery and is sealed liquid-tight by a closure element. The closure element can be, for example, plate-shaped. The heating element can be, for example, pressed into the outer casing and pulled out of the outer casing while the closure element is removed. The heat conducting medium can in principle also be filled via the first end. The closure element can, for example, be screwed onto the first end. The closure element can have a hole or an opening through which the connecting cable of the heating element passes. Between the first end and the closure element a sealing element, in particular in the form of an O-ring, can be provided.

[0030] According to a further embodiment, the outer casing has a circumferentially protruding connection which is in fluid communication with the interior space, the connection being sealed liquid-tight.

[0031] For example, the heat conducting medium can be filled into the inner space of the outer casing via the connection. The connection can have a suitable valve for this purpose. This connection can also be used to monitor the pressure in the inner space. For this purpose, a sensor can be provided in the connection, in particular a pressure sensor. The connection can have a number of different sensors, such as a pressure sensor, a temperature sensor, an optical sensor, a sensor capable of detecting the cryogen and / or the heat conducting medium.

[0032] According to a further embodiment, at least one heat transfer layer is provided on the outer casing and attached to the outside of the outer casing.

[0033] The heat transfer layer may be made of copper. Aluminum alloys are also possible as suitable materials for the heat transfer layer. The heat transfer layer may be a copper sheet or a copper plate. For example, the heat transfer layer is wrapped around the outer casing. The heat transfer layer may be materially bonded to the outer casing. For example, the heat transfer layer is soldered onto the outer casing. The heat transfer layer may also be wrapped around the outer casing and not materially bonded to the outer casing, with the two ends of the heat transfer layer being clamped or screwed together to connect the heat transfer layer to the outer casing. The heat transfer layer ensures uniform heat transfer. A heat transfer plate may be molded onto the heat transfer layer. In this case, the heat transfer plate is formed with two ends of the heat transfer layer connected to each other. This means, in particular, that the first end and the second end abut each other and are connected to each other to form a heat transfer plate. The heat transfer plate may be a separate component connected to the outer casing or to the heat transfer layer. The heat transfer plate is preferably fin-shaped. For this reason, the heat transfer plate may be referred to as a heat transfer fin. A number of heat transfer plates may be provided on the outer casing or on the heat transfer layer. The heat transfer plate may be materially connected to the outer casing or on the heat transfer layer. For example, the heat transfer plate is soldered or welded to the outer casing or on the heat transfer layer. With the help of the heat transfer plate, the heat transfer surface of the heating device may be increased. Furthermore, the heat transfer plate also ensures that when the liquid level of the cryogen in the storage vessel is low, at least the heat transfer plate protrudes into the liquid phase of the cryogen and heat can be transferred to the liquid phase accordingly. Thus, the heat transfer plate is always wetted by or immersed in the liquid phase. This makes it possible to prevent local overheating. Preferably, at least one heat transfer plate is attached between the outer casing and the inner vessel. Any number of heat transfer plates may be provided. The heat transfer plate is preferably made of a metal material with good thermal conductivity, such as a copper or aluminum alloy.

[0034] According to a further embodiment, the heating device comprises a support element for supporting the heating element.

[0035] In particular, the support element is arranged completely inside the outer casing. The support element is preferably tubular. The support element may also be referred to as a support tube. Preferably, the support element is made of a thermally conductive material. For example, the support element may be made of a copper alloy or an aluminum alloy. Steel, in particular stainless steel, may also be used for the support element. Alternatively, the support element may be made of glass, glass ceramic or ceramic. In this case, the support element itself is not thermally conductive, or at least is not a good conductor of heat. If the support element is made of an electrically conductive material, the heating element may have an insulating element that electrically insulates the heating element from the support element. In this case, the heating element may for example have an electrically conductive heating wire surrounded by an insulating element. For example, the above-mentioned heating wire may be embedded in magnesium oxide powder enclosed by a non-conductive metal casing, for example a stainless steel casing. The term "heating element" in this case may therefore be understood to mean a metal-mineral insulated heating wire. The heating device may be attached to the support element such that the heating device extends linearly along the support tube or longitudinal direction. Alternatively, the heating element may be wrapped around a support element. The support element is optional. Alternatively, the heating element may be housed within the outer casing without a support element.

[0036] According to a further embodiment, the support element has an outer surface with a groove extending helically around the support element, in which the heating element is at least partially housed.

[0037] In this case, the heating element is wound on the support element. The heating element is in particular elastically deformable. This means that the heating element can be wound on the support element like a rope or wire without being damaged. The groove can also be described as helical or spiral. The groove may also be referred to as a retaining groove or a receiving groove. The groove is optional. This means that the heating element can be wound on the support element without a groove. The groove is at least partially cylindrical. The heating element has in particular a circular or round cross section. This ensures a flat contact between the heating element and the groove. This improves the transfer of heat from the heating element to the support element. The heating element and / or the support element transfer the heat to the heat conducting medium, which transfers the heat to the outer casing, which transfers the heat to the liquid phase of the cryogen to at least partially evaporate the liquid phase. The groove is optional. The heating element can also be wound on the support element without a groove.

[0038] According to a further embodiment, a circumferential gap is provided between the support element and the outer shell around the circumference of the support element.

[0039] The gap is in particular a part of the inner space of the outer casing. In particular, the gap is completely filled with a heat-conducting medium. In particular, the support element is placed in the center of the outer casing. For this purpose, for example, support legs can be provided which support the support element on the outer casing. The support legs are placed in the gap. The support legs are preferably poorly or not thermally conductive, whereby the heat from the heating element and / or the support element is preferably transferred to the outer casing only by means of the heat-conducting medium. This can prevent or at least reduce deviations in the temperature distribution on the outside of the outer casing. However, the support legs can be thermally conductive. In particular, the gap prevents direct contact between the support element and / or the heating element and the outer casing. This can prevent local overheating, which could otherwise result in damage to the heating device. In this context, "circumferential" means as seen along the circumferential direction of the heating device. The term "circumferential direction" is understood here to mean a rotational or spatial direction directed around the axis of symmetry of the heating device. A gap is optional. A gap may be necessary for design reasons, so that the support element with the wrapped heating element can be inserted into the outer casing. A heat conducting medium is required to ensure heat conduction to the outer casing. Alternatively, the support element may abut against the inside of the outer casing. This can improve heat transfer.

[0040] According to a further embodiment, the support element is tubular and has an inner surface with a cylindrical shape.

[0041] As mentioned above, the support element may also be referred to as a support tube. The inner surface can be realized, for example, by means of holes or cutouts extending through the entire support element. In particular, the support element has a cylindrical outer surface provided with a circumferential groove. The inner surface faces away from the outside of the support element.

[0042] According to a further embodiment, the heating device comprises at least one temperature sensor arranged in the support element.

[0043] The temperature sensor may also be referred to as a temperature pickup. The temperature sensor is in particular located inside the interior space of the outer casing. A number of temperature sensors may be provided. The temperature sensor is suitable for temperature monitoring and / or function control of the heating element. The temperature sensor may be used to prevent overheating of the heating element. Furthermore, the temperature sensor may also be used to detect and / or control the amount of heat introduced into the liquid phase of the cryogen.

[0044] According to a further embodiment, the heating device comprises a fastening element arranged in the support element for fastening the temperature sensor to the support element, the temperature sensor being inserted into the fastening element.

[0045] The fastening element is in particular tubular or sleeve-shaped. The fastening element may therefore also be referred to as a fastening tube or fastening sleeve. In particular, the fastening element has a cylindrical outer surface which can abut against a cylindrical inner surface of the support element. For example, the fastening element is pressed into the support element. The fastening element further comprises in particular a cylindrical inner surface facing away from the outer surface. The inner surface can for example be realised by a hole or a notch passing through the entire fastening element. The fastening element preferably has a receiving hole into which the temperature sensor is inserted. A number of receiving holes can be provided for a number of temperature sensors. The temperature sensor can be thermally coupled to the support element by means of a thermally conductive paste. The support element is preferably made of a thermally conductive material. For example, the support element is made of an aluminium or copper alloy. As the temperature sensor is arranged inside the support element, it is possible to reduce the installation space of the heating device. Compared to an arrangement in which the temperature sensor is provided outside the support element, interruptions of the contact surface between the support element and the heating element can advantageously be avoided. This can reliably prevent undesirable non-uniform temperature distribution along the heating element. The measurement of the temperature by the temperature sensor is preferably performed substantially only by thermal conduction. In other words, the temperature sensor is not directly adjacent to the heating element. To measure the temperature of the heating element, the fastening element is made of a highly thermally conductive material. The fastening element preferably fills the entire space between the support element supporting the heating element and the temperature sensor.

[0046] According to a further embodiment, the fastening element is fluid permeable.

[0047] This allows the heat conducting medium to pass through the support element. This reliably prevents the formation of different pressure chambers in the outer casing. The support element can preferably have a central hole as described above, which passes completely through the support element. Alternatively, a plurality of individual holes can be provided. With the help of the support element, a space-saving temperature measurement is possible in any desired area of ​​the heating element. Maximum heat transfer between the heating element and the temperature sensor is ensured. Furthermore, a defined and safe contact between the heating element and the temperature sensor is ensured. The formation of two separate volumes or pressure chambers in the inner space of the outer casing is prevented by the fact that the support element is fluid-permeable. Compensating holes can be provided for this purpose. Compared to the heating element, the fastening element is preferably designed with a minimum wall thickness. This means that the time delay in the temperature measurement can be kept small. The fastening element is manufactured to ensure good thermal contact with the support element. The fit between the fastening element and the support element is selected according to the minimum and maximum operating temperatures as well as the materials used, whereby sufficient pressure between the fastening element and the support element is ensured over the entire temperature range occurring during operation of the storage container. The fastening element can be equipped with an additional pretensioning device, in particular a screw tensioning device, to facilitate the installation of the fastening element. In the installed state, for example, the two parts of the fastening element can be loosely inserted into each other and aligned. The fastening element can be equipped with an additional internal clamping device that ensures contact pressure between the fastening element and the supporting element over a wide temperature range. The clamping device can be combined with the pretensioning device.

[0048] Furthermore, a cryogen supply system for supplying a cryogen to a consumer is proposed, the cryogen supply system comprising at least one storage container as previously described.

[0049] Alternatively, the cryogen supply system may comprise a plurality of storage containers. The cryogen supply system may be referred to as a hydrogen supply system. In particular, this means that the terms "cryogene supply system" and "hydrogen supply system" may be used interchangeably. The consumer may be a fuel cell as described above. The cryogen supply system may comprise an evaporator suitable for evaporating the liquid cryogen drawn from the storage container and supplying it to the consumer at a suitable supply pressure and at a suitable temperature. The consumer may be part of the cryogen supply system. The cryogen supply system may be part of a vehicle, in particular a land vehicle, a watercraft or an aircraft.

[0050] The embodiments and descriptions given for the storage container correspondingly apply to the cryogen supply system, and vice versa.

[0051] In this case, "a" should not necessarily be understood as limiting to exactly one element. Rather, several elements may be provided, such as two, three, or more. Any other number words used herein should also not be understood as limiting to the precise number of elements referenced. Rather, unless otherwise indicated, the number may deviate upwards or downwards.

[0052] Further possible implementations of the storage vessel and / or cryogen supply system also include combinations not expressly mentioned of the features or embodiments described above or below with respect to the exemplary embodiments. Those skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the storage vessel and / or cryogen supply system. [Brief description of the drawings]

[0053] Further advantageous embodiments and aspects of the storage vessel and / or the cryogen supply system are the subject of the dependent claims and of the embodiments of the storage vessel and / or the cryogen supply system described below, which are explained in more detail below on the basis of preferred embodiments and with reference to the attached drawings, in which: [Figure 1]1 is a schematic cross-sectional view of one embodiment of a storage vessel; [Diagram 2] Detail II according to FIG. 1 is shown. [Diagram 3] 3 shows a schematic cross-sectional view taken along line III-III in FIG. 2.

[0054] In the drawings, identical or functionally equivalent elements are labeled with the same reference numbers unless otherwise indicated.

[0055] Fig. 1 shows a schematic cross-sectional view of one embodiment of a storage container 1. Fig. 2 shows a detail II according to Fig. 1. Fig. 3 shows a schematic cross-sectional view according to the section line III-III in Fig. 2. In the following, Figs. 1 to 3 are simultaneously referred to.

[0056] The storage vessel 1 may be referred to as a storage tank. The storage vessel 1 is suitable for containing liquid hydrogen H2 (boiling point at 1 bar: 20.268 K = -252.882 ° C). The storage vessel 1 may therefore be referred to as a hydrogen storage vessel or hydrogen storage tank. However, the storage vessel 1 may also be used for other cryogenic liquids. Examples of cryogenic fluids or liquids, or cryogens for short, are liquid helium He, in addition to the aforementioned liquid hydrogen H2 (boiling point at 1 bar: 4.222 K = -268.928 ° C), liquid nitrogen N2 (boiling point at 1 bar: 77.35 K = -195.80 ° C) or liquid oxygen O2 (boiling point at 1 bar: 90.18 K = -182.97 ° C).

[0057] The storage vessel 1 is suitable for use in or on a vehicle (not shown). The vehicle may for example be a marine vessel, in particular a ship. The vehicle may be referred to as a marine vehicle. In particular, the vehicle may be a marine passenger ferry. Alternatively, the vehicle may be a land vehicle. However, in the following it is assumed that the vehicle is a vessel.

[0058] The vehicle may have a consumer 2, in particular a fuel cell. In this case, "fuel cell" is understood to mean a galvanic cell which converts the energy of a chemical reaction between a continuously supplied fuel, in this case hydrogen, and an oxidant, in this case oxygen, into electrical energy. The electrical energy obtained may, for example, power an electric motor (not shown), which drives a propeller of a vessel for propelling the vehicle. A storage vessel 1 is provided for supplying the consumer 2 with hydrogen H2.

[0059] The storage container 1 may be part of a cryogen supply system 3 suitable for supplying gaseous hydrogen H2 at a defined supply pressure and a defined supply temperature to a consumer 2, which in this case is preferably a fuel cell. For example, hydrogen H2 is supplied to the consumer 2 in gaseous form at a supply pressure of, for example, 1 to 2.5 bar and at a temperature of, for example, 0 to +70°C, in particular +10 to +25°C. However, the supply pressure may be up to 6 bar. The cryogen supply system 3 may be described as a hydrogen supply system. In addition to the storage container 1, the cryogen supply system 3 may comprise a vaporizer (not shown) suitable for vaporizing liquid hydrogen H2 and supplying it to the consumer 2.

[0060] The storage container 1 is rotationally symmetrical about a central axis or axis of symmetry 4. The axis of symmetry 4 may be oriented perpendicular to the direction of gravity g. This means that the storage container 1 is in a lying or horizontal position. Alternatively, the axis of symmetry 4 may be oriented parallel to the direction of gravity g. That is, the storage container 1 may also be positioned upright or vertically.

[0061] A coordinate system is assigned to the storage container 1 with a first spatial direction, a longitudinal or x-direction x, a second spatial direction, a height or y-direction y, and a third spatial direction, a depth or z-direction z. The directions x, y, z are oriented perpendicular to one another. The axis of symmetry 4 lies parallel to the x-direction x. The storage container 1 is assigned a longitudinal direction L that may coincide with the x-direction x.

[0062] The storage container 1 comprises an outer container 5 which is rotationally symmetrical with respect to an axis of symmetry and an inner container 6 which is rotationally symmetrical with respect to an axis of symmetry 4. The inner container 6 is arranged completely inside the outer container 5. Between the outer container 5 and the inner container 6 a vacuum space 7 is provided, which is at least partially designed as a gap. A negative pressure prevails in the vacuum space 7 compared to the surroundings 8 of the storage container 1. The surroundings 8 may also be referred to as atmosphere. This means that the terms "surroundings" and "atmosphere" may be used interchangeably. In the vacuum space 7 an insulating element may be provided which fills the vacuum space 7 at least partially or completely. The insulating element may have or be designed as a multilayer insulation layer (MLI). The outer container 5 and / or the inner container 6 may be made, for example, of stainless steel.

[0063] The outer container 5 comprises a tubular or cylindrical base part 9 which may have a rotationally symmetrical design relative to the axis of symmetry 4. The base part 9 is closed at both end faces by a first cover part 10 and a second cover part 11. In cross section, the base part 9 may have a circular or approximately circular geometric shape. The cover parts 10, 11 are dome-shaped. The cover parts 10, 11 are dome-shaped in opposite directions such that the first cover part 10 and the second cover part 11 are dome-shaped outwardly relative to the base part 9. The outer container 5 is liquid-tight, in particular gas-tight. The longitudinal direction L runs from the first cover part 10 towards the second cover part 11.

[0064] The inner container 6, like the outer container 5, comprises a tubular or cylindrical base part 12 which is rotationally symmetrical with respect to the axis of symmetry 4. The base part 12 is closed on both sides by a first cover part 13 and a second cover part 14. In cross section, the base part 12 can have a circular or approximately circular geometric shape. The cover parts 13, 14 are dome-shaped. In particular, the first cover part 13 and the second cover part 14 are dome-shaped in opposite directions such that the first cover part 13 and the second cover part 14 are dome-shaped outwardly with respect to the base part 12. The outer container 6 is liquid-tight, in particular gas-tight. The outer container 5 and / or the inner container 6 can have a blow-off valve (not shown). The longitudinal direction L runs from the first cover part 13 towards the second cover part 14.

[0065] Liquid hydrogen H2 is contained in the inner vessel 6. The inner vessel 6 surrounds an internal space 15 in which the liquid hydrogen H2 is stored. As long as the hydrogen H2 is in a two-phase region, a gas region 16 having vaporized hydrogen H2 and a liquid region 17 having liquid hydrogen H2 can be provided in the inner vessel 6 or internal space 15. Thus, after filling the inner vessel 6 or internal space 15, the hydrogen H2 has two phases with different condensation states, namely liquid and gas. That is, in the inner vessel 6 or internal space 15, a phase boundary 18 exists between the liquid hydrogen H2 and the gaseous hydrogen H2. The gas region 16 and the liquid region 17 together fill the internal space 15. The internal space 15 may be referred to as the vessel internal space.

[0066] The storage vessel 1 comprises a heating device 19. The heating device 19 is shown in cross section in Fig. 2 and Fig. 3. The heating device 19 is designed to introduce heat Q into the liquid hydrogen H2. The heating device 19 is electrically operated. The heating device 19 may therefore be referred to as an electric heating device or heater, in particular an electric heater. The heating device 19 protrudes through the first cover part 10, 13 from the periphery 8 into the inner vessel 6, in particular into the liquid region 17. The part of the heating device 19 protruding into the inner vessel 6 or into the interior space 15 is preferably flushed by the liquid hydrogen H2 of the liquid region 17.

[0067] The heating device 19 is rotationally symmetrical with respect to a central axis or axis of symmetry 20. The axis of symmetry 20 may be oriented parallel to the axis of symmetry 4. The axis of symmetry 20 is placed below the axis of symmetry 4 with respect to the y-direction y or the direction of gravity g, and the heating device 19 is also assigned a radial direction R. The radial direction R is perpendicular to the axis of symmetry 20 and is oriented away from the axis of symmetry 20.

[0068] The heating device 19 comprises a liquid-tight outer casing 21. The outer casing 21 is tubular and may therefore be referred to as an outer tube. The outer casing 21 is preferably made of a metallic material, preferably stainless steel. The outer casing 21 is preferably made of a material that conducts heat well. The outer casing 21 is guided through the first two cover parts 10, 13 into the liquid region 17. This means that the outer casing 21 extends partly into the surroundings 8 and partly into the inner container 6, in particular into the liquid region 17. The outer casing 21 can be soldered or welded to the first cover parts 10, 13. The outer casing 21 can also be made of a copper alloy, an aluminum alloy, glass, glass ceramic or ceramic.

[0069] The outer casing 21 is rotationally symmetrical with respect to the axis of symmetry 20. The outer casing 21 may be circular in cross section. Alternatively, the outer casing 21 may be slightly oval or elliptical in cross section. Viewed in the circumferential direction U, the outer casing 21 extends completely around the axis of symmetry 20. The outer casing 21 is therefore closed in the circumferential direction. The circumferential direction U is oriented along the outer casing 21, around the axis of symmetry 20. The outer casing 21 surrounds an interior space 22. The interior space 22 may be referred to as the interior space of the outer casing 21 or the interior space of the heating device 19. The interior space 22 may be referred to as the heating interior space. The interior space 22 is filled with a heat conducting medium. The heat conducting medium is preferably a gas, in particular helium He. The outer casing 21 is liquid-tight.

[0070] The outer casing 21 comprises a tubular base part 23 which is rotationally symmetrical about the axis of symmetry 20. In addition to the base part 23, the outer casing 21 comprises a first end part 24 which projects to the periphery 8 and is liquid-tight closed by means of a plate-shaped closing element 25. A second end part 26 is provided facing away from the first end part 24, is lid-shaped and liquid-tightly closes the base part 23 at the front. The second end part 26 is located in the liquid region 17.

[0071] At least one heat transfer plate 27 may be provided on the outer casing 21, in particular on the base 23, and extends in the radial direction R away from the base 23. The heat transfer plate 27 serves to enlarge the surface so that the transfer of heat Q from the heating device 19 to the hydrogen H2 is improved. The heat transfer plate 27 is fin-shaped and may therefore be referred to as a heat transfer fin. A plurality of heat transfer plates 27 may be provided.

[0072] Outside the outer vessel 5, the outer casing 21 has a connection 28 which can be closed liquid-tight. By means of the connection 28, for example, the interior space 22 can be filled with helium He. Furthermore, the connection 28 can also be used to monitor the heating device 19. Via the connection 28, for example, a pressure drop or a pressure increase in the interior space 22 can be detected. The connection 28 is placed on the outside periphery 8 of the storage vessel 1.

[0073] In addition to the outer casing 21, the heating device 19 has a tubular support element 29 which carries a wire-shaped heating element 30. The support element 29 may also be called a support tube. The support element 29 is rotationally symmetrical about the axis of symmetry 20. The support element 29 is made of a material which conducts heat well. For example, the support element 29 is made of a metallic material, in particular a copper alloy or an aluminum alloy. However, the support element 29 may also be made of glass, glass ceramic or ceramic.

[0074] The support element 29 may be a one-piece component, in particular a materially one-piece component. "One-piece" or "one piece" means that the support element 29 is a single component that is not made up of multiple subassemblies or components. In this case, "materially one-piece" means in particular that the support element 29 is made entirely of the same material. Alternatively, the support element 29 may be multi-part or multi-piece. In this case, the support element 29 is built up from multiple subassemblies or components.

[0075] The support element 29 extends in the longitudinal direction L in the inner vessel 6. The support element 29 is preferably arranged completely in the outer vessel 5. Viewed in the circumferential direction U, the entire circumference of the support element 29 is closed. The support element 29 is accommodated in the outer casing 21. This means, in particular, that the support element 29 is placed in the interior space 22. Preferably, the support element 29 is centered with respect to the axis of symmetry 20, so that in the circumferential direction U a gap 31 filled with helium He is provided, which gap 31 extends completely around the support element 29. The gap 31 can have a gap width of 0.5 to 1 millimeter. The gap width is selected to be as small as possible and as large as necessary to allow the support element 29 with the heating element 30 to be inserted in the outer casing 21. The gap 31 is part of the interior space 22. The gap 31 is optional. Alternatively, the support element 29 can be placed inside the outer casing 21. This can improve heat transfer.

[0076] The cylindrical outer surface 32 of the support element 29 faces the outer casing 21. A gap 31 is provided between the outer surface 32 and the outer casing 21. The outer surface 32 is provided with a groove 33, which runs helically around the support element 29 in the circumferential direction U and accommodates the heating element 30. The heating element 30 is preferably a heating wire wound around the support element 29. If the support element 29 is made of an electrically conductive material, the heating element 30 can have an electrical insulator that electrically insulates the heating element 30 from the support element 29. For example, the above-mentioned heating wire can be embedded in magnesium oxide powder enclosed by a non-conductive metal casing, for example a stainless steel casing. The term "heating element" can therefore be understood in this case to mean a metal-mineral insulated heating wire. The groove 33 is optional. The heating element 30 can also be wound around the support element 29 without the groove 33.

[0077] The cylindrical inner side 34 of the support element 29 faces away from the outer side 32. The inner side 34 extends in a circumferential direction U around the axis of symmetry 20. The inner side 34 can be realized by a hole leading through the center of the support element 29. The heating element 30 has electrical connection lines 35, 36, which are led via the closure element 25 to an open-loop and closed-loop control device 37. The open-loop and closed-loop control device 37 can supply an electric current to the heating element 30 and thus control the amount of heat Q introduced into the hydrogen H2. The open-loop and closed-loop control device 37 can be part of the storage vessel 1 and / or the cryogen supply system 3.

[0078] The heating device 19 has at least one temperature sensor 38 coupled to the open-loop and closed-loop control device 37 by a sensor line 39. The temperature sensor 38 makes it possible to detect the temperature of the heating device 19. The temperature sensor 38 may be part of a control circuit comprising the heating element 30, the open-loop and closed-loop control device 37 and the temperature sensor 38. The temperature sensor 38 comprises a fastening tab 40. Alternatively to the fastening tab 40, it is also possible to provide another fastening type, for example clamping, screwing, soldering or plugging.

[0079] The temperature sensor 38 is held or fastened by means of a fastening element 41. The fastening element 41 is made of a material with good thermal conductivity, for example a copper alloy or an aluminum alloy. The fastening element 41 is tubular. The fastening element 41 is arranged in the support element 29. For example, the fastening element 41 is press-fitted into the support element 29. The fastening element 41 can be a one-piece component, in particular a materially one-piece component. Alternatively, the fastening element 41 can be several parts or several pieces.

[0080] The fastening element 41 is rotationally symmetrical with respect to the axis of symmetry 20. It comprises a cylindrical outer side 42 which abuts against the inner side 34 of the support element 29. It further comprises a cylindrical inner side 43, which is realized for example by a hole provided in the center of the fastening element 41. Helium He can therefore flow through the fastening element 41.

[0081] For each temperature sensor 38, the fastening element 41 has a receiving hole 44 into which the respective temperature sensor 38 is inserted. The receiving hole 44 is provided on the front side of the fastening element 41 and extends along the longitudinal direction L or along the x-direction x into the fastening element 41. The receiving hole 44 extends parallel to the axis of symmetry 20. The receiving hole 44 may be a blind hole. Viewed along the radial direction R, the receiving hole 44 is located directly below the outer side 42.

[0082] The heat transfer layer 45 is provided on the outer casing 21 and attached to the outside of the outer casing 21. The heat transfer layer 45 can be made of copper. A suitable material for the heat transfer layer 45 can also be an aluminum alloy. The heat transfer layer 45 can be a copper sheet or a copper plate. The heat transfer layer 45 is, for example, wrapped around the outer casing 21. The heat transfer layer 45 can be materially bonded to the outer casing 21. For example, the heat transfer layer 45 is soldered onto the outer casing 21.

[0083] The heat transfer layer 45 may also be merely wound on the outer casing 21 and not physically connected to the outer casing 21, and the two ends 46, 47 of the heat transfer layer 45 are clamped or screwed together to connect the heat transfer layer 45 to the outer casing 21. The first end 46 and the second end 47 abut each other and are connected to each other. The heat transfer layer 45 ensures uniform heat transfer. The aforementioned heat transfer plate 27 may be molded on the heat transfer layer 45. In this case, the heat transfer plate 27 is formed by the two interconnected ends 46, 47 of the heat transfer layer 45.

[0084] However, the heat transfer plate 27 may also be a separate component connected to the outer casing 21 or the heat transfer layer 45. A plurality of such heat transfer plates 27 may be provided on the outer casing 21 or the heat transfer layer 45. The heat transfer plate 27 may be materially joined to the outer casing 21 or the heat transfer layer 45. For example, the heat transfer plate 27 is soldered or welded to the outer casing 21 or the heat transfer layer 45.

[0085] The heat transfer plate 27 ensures that when the liquid level of hydrogen H2 in the storage vessel 1 is low, at least the heat transfer plate 27 protrudes into the liquid region 17 of hydrogen H2 and is therefore able to transfer heat Q to the hydrogen H2. Preferably, at least one heat transfer plate 27 is mounted between the outer casing 21 and the inner vessel 6. Any number of heat transfer plates 27 may be provided. The heat transfer plate 27 is preferably made of a metal material with good thermal conductivity, such as a copper alloy or an aluminum alloy.

[0086] Although the invention has been described with reference to exemplary embodiments, the invention can be modified in many ways within the scope of the claims. [Explanation of symbols]

[0087] 1. Storage container 2 Consumers 3. Cryogen supply system 4 Axis of Symmetry 5 Outer container 6 Inner container 7 Vacuum space 8. Periphery 9 Base 10 Cover part 11 Cover part 12 Base section 13 Cover part 14 Cover part 15. Interior Space 16 Gas Region 17 Liquid area 18 phase boundary 19 Heating Devices 20 Axis of Symmetry 21 Outer casing 22 Interior Space 23 Base 24 End 25 Closure elements 26 End 27 Heat transfer plate 28 Connection 29 Supporting Elements 30 heating elements 31 Gap 32 External surface 33 Groove 34 Inner surface 35 Connection Lines 36 Connection Lines 37 Open-loop and closed-loop control devices 38 Temperature Sensor 39 Sensor Line 40 Fastening tab 41 Fastening elements 42 External surface 43 Inner surface 44 Receiving hole 45 Heat Transfer Layer 46 End 47 End g direction of gravity He Helium / medium H2 Hydrogen / Cryogen L Longitudinal Q Fever R Radial direction U circumferential direction xx direction yy direction zz direction

Claims

1. A storage container (1) for storing a cryogen (H2), comprising: an inner container (6) for receiving the cryogen (H2); an outer container (5) surrounding the inner container (6); and a heating device (19) disposed at least partially within the inner container (6) for introducing heat (Q) into the cryogen (H2), the heating device (19) comprising a heating element (30) for generating the heat (Q) and an outer casing (21) fluid-tightly surrounding an interior space (22) of the heating device (19), the heating element (30) being housed within the interior space (22), the heating element (30) having a heating wire embedded in a metal oxide encapsulated by a casing housed within the interior space (22).

2. 2. The storage container (1) according to claim 1, wherein the interior space (22) is filled with a heat conducting medium (He).

3. 2. The storage container according to claim 1, wherein the heating device (19) is guided from the periphery (8) of the storage container (1), through the outer container (5) and the inner container (6), into the liquid area (17) surrounded by the inner container (6).

4. 4. The storage container according to claim 3, wherein the outer casing (21) is guided through the outer container (5) and the inner container (6), and the outer casing (21) is connected to the outer container (5) and the inner container (6) by a material bond and / or a form fit.

5. 4. The storage container according to claim 3, wherein the outer casing (21) has an end (24) that protrudes into the periphery (8) and is closed in a liquid-tight manner by a removable closing element (25), and the connecting lines (35, 36) of the heating element (30) are led through the closing element (25).

6. 4. The storage container according to claim 3, wherein the outer casing (21) has a connection (28) that protrudes into the periphery (8) and is in fluid communication with the interior space (22), the connection (28) being sealed in a liquid-tight manner.

7. 2. The storage vessel of claim 1, wherein a heat transfer layer (45) is provided on the outer casing (21) and attached to the outside of the outer casing (21).

8. 2. A storage vessel according to claim 1, wherein the heating device (19) comprises a support element (29) carrying the heating element (30).

9. 9. The storage container of claim 8, wherein the support element (29) has an outer surface (32) with a groove (33) extending spirally around the support element (29) in which the heating element (30) is at least partially housed.

10. 9. A storage vessel according to claim 8, wherein a gap (31) is provided between the support element (29) and the outer casing (21) and extends circumferentially around the support element (29).

11. 9. A storage vessel according to claim 8, wherein the support element (29) is tubular and has an inner surface (34) of cylindrical shape.

12. 9. The storage container according to claim 8, wherein the heating device (19) comprises at least one temperature sensor (38) arranged in the support element (29).

13. 13. The storage container of claim 12, wherein the heating device (19) has a fastening element (41) arranged in the support element (29) for fastening the temperature sensor (38) to the support element (29), and the temperature sensor (38) is inserted into the fastening element (41).

14. 14. The storage container according to claim 13, wherein the fastening element (41) is fluid permeable.

15. A cryogen supply system (3) for supplying cryogen (H2) to a consumer (2), comprising at least one storage container (1) according to any one of claims 1 to 14.

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