Hydrogen tank, method for cooling a hydrogen tank, and hydrogen-powered vehicle with hydrogen tank

Description

[0001] The present invention relates to a hydrogen tank. Furthermore, the invention relates to a vehicle with a hydrogen drive and a hydrogen tank for supplying the hydrogen.

[0002] Hydrogen has a wide range of applications, particularly as an energy carrier in industry and technology. It is typically composed of ortho-hydrogen and para-hydrogen, whose molecules differ in the spin of their atomic nuclei. The equilibrium ratio that naturally develops over time is temperature-dependent: While the para-hydrogen content is almost 100% at temperatures up to the normal boiling point of around 20K, the ortho-hydrogen content increases with increasing temperature and is around 75% above a temperature of around 250K. The conversion of para-hydrogen to ortho-hydrogen is endothermic, while the reverse conversion is exothermic. Both conversions occur naturally slowly but can be accelerated by catalysts. Tanks typically store almost exclusively para-hydrogen.

[0003] However, as with other cryogenic liquids, the storage of liquid hydrogen in mobile as well as stationary tanks is problematic because heat input into the respective tank causes the liquid hydrogen to evaporate, thereby increasing the tank pressure.

[0004] This is usually partially prevented, in particular with various tank insulation measures; for example, the document DE 10 2019 118 323 A1 discloses a tank for storing liquid or gaseous substances, which comprises a fiber-reinforced plastic shell with an evacuable sandwich structure for thermal vacuum insulation.

[0005] In the automotive sector, catalysts for endothermic para-ortho conversion are used to reduce evaporation losses; such tank systems are known from US 2009 / 0199574 A1, US 2011 / 0302933 A1, the dissertation "Physical and technical aspects of the ortho-para conversion of hydrogen" by J. Essler (University of Dresden, 2013), the publication "Enhanced dormancy due to para-ortho hydrogen conversion in insulated cryogenic pressure vessels for automotive applications" by K. Peng and RK Ahluwalia (in: International Journal of Hydrogen Energy, 38, (2013)) and the article "Effect of para-ortho conversion on hydrogen storage system performance" by S. Ubaid et al. (in: International Journal of Hydrogen Energy, 39, (2014)). The catalysts can be installed in external cooling shields as additional lines of the venting system. In such applications, the tank pressure is usually well above the critical pressure of hydrogen.The hydrogen can be bound to porous inserts inside the tank by physisorption.

[0006] The use of cooling shields for propellant tanks is also known in the field of space travel. For example, the work "Parahydrogen-Orthohydrogen Conversion for Boil-Off Reduction from Space Stage Fuel Systems" by R.M. Bliesner (Master's Thesis, Washington State University, (2013)), the publication "Parahydrogen-Orthohydrogen Conversion for Enhanced Vapor-Cooled Shielding of Liquid Oxygen Tanks" by R.M. Bliesner, J.W., Leachman, and P.M. Adam (in: Journal of Thermophysics and Heat Transfer, 28 (4), (2014)), and the article "Parahydrogen-Orthohydrogen Conversion on Catalyst-Loaded Scrim for Vapor-Cooled Shielding of Cryogenic Storage Vessels" by B.P. Pedrow et al. (in: Journal of Thermophysics and Heat transfer, 35 (1), (2021)) Cooling shields for liquid oxygen tanks are described, which are fed with para-hydrogen gas and have a catalyst for the endothermic para-ortho conversion.In the publication "Space-based LH2 propellant storage system: subscale ground testing results" by MW Liggett (in: Cryogenics, 33 (4), (1993)) a cooling shield for a liquid hydrogen tank in the space sector is disclosed, which is realized by additional metallic lines.

[0007] US 9 777 889 B2 A discloses a cryogenic compatible composite pressure vessel that uses vapor cooled shielding (VCS) to minimize thermal gradients along support structures and reduce thermal loads on cryogenic systems.

[0008] The present invention is based on the object of providing a technology that can improve the storage of liquid hydrogen. The invention is also based on the object of improving a hydrogen-powered vehicle.

[0009] The objects are achieved by a hydrogen tank according to claim 1, a vehicle according to claim 6 and a method according to claim 7.

[0010] Advantageous embodiments are disclosed in the subclaims, the description and the figures.

[0011] A hydrogen tank according to the invention has a tank structure which at least partially delimits a tank space for hydrogen and comprises a region of lightweight construction in which a line system of a

[0012] A pressure relief system is designed to discharge gaseous hydrogen from the tank space. At least one para-ortho catalyst is arranged in the piping system to accelerate the conversion of para- to ortho-hydrogen.

[0013] Since heat is absorbed from the environment during such an endothermic transformation, the lightweight section of the tank structure comprising the piping system serves to cool its environment, which is why it is referred to below as a "cooling shield" of the tank structure.

[0014] Thanks to the piping system with para-ortho catalyst formed in the cooling shield, the present invention enables effective cooling of the tank structure by additionally utilizing the thermal energy contained therein for the endothermic para-ortho conversion and thus removing it from the tank structure. In this way, heat flow from the outside into the tank space can be minimized, thus keeping the amount of hydrogen required to be released from the hydrogen tank for necessary pressure relief relatively small. This minimizes evaporation losses.

[0015] In particular, the cooling shield of a hydrogen tank according to the invention thus has a thermally insulating effect.

[0016] According to advantageous embodiments of the present invention, the tank structure comprises at least one substructure in which at least one evacuable or evacuated hollow volume is formed for isolating the tank space. Preferably, a wall delimiting such a hollow volume withstands an internal pressure in the range of 0.0001 hPa to 0.01 hPa in the hollow volume. In particular, the at least one substructure can have a connection to a vacuum pump for evacuating the at least one hollow volume. The at least one substructure can be designed as a lightweight construction (like the cooling shield).

[0017] In particular, such a partial structure (having at least one evacuable or evacuated hollow volume) can be arranged at least in regions on a side facing the tank space (i.e. between the cooling shield and the tank space), and / or such a partial structure can be arranged at least in regions on a side of the cooling shield facing away from the tank space (i.e. between the cooling shield and an external environment of the hydrogen tank).

[0018] The lightweight construction of the cooling shield and / or (in corresponding embodiments) of the at least one partial structure can (in each case) be realized in particular at least partially in that the region or the partial structure is made at least partially from a foam material and / or in that the region or the partial structure comprises, for example, a plurality of (preferably force-absorbing) material layers which are at least partially spaced apart from one another, between which at least one cavity and / or a further material layer is arranged, the material of which has a lower density than at least one of its adjacent material layers; in corresponding embodiments, at least one such cavity can be / form the at least one evacuated or evacuable hollow volume mentioned above.

[0019] In such embodiments, one or more of the material layers can preferably be formed, at least in some regions, as a continuous sheet-like structure. According to the invention, the multiple material layers form a sandwich structure. The material layers can differ from one another at least partially in their material composition or can consist at least partially of the same materials. If they touch one another, they can be differentiated from one another in their contact region by an inhomogeneity in the material transition (so that the material layers are separate layers, i.e., not merely delimited from one another by an abstract boundary); in particular, they can be glued or welded to one another.

[0020] The cooling shield is preferably designed with an integrated support structure, thus, in addition to its cooling and insulation function, it also has a load-bearing function. This allows separate support structures to be at least partially dispensed with when used in a vehicle. Compared to other hydrogen tanks, such a design enables a reduction in structural mass and thus a minimization of fuel losses.

[0021] A vehicle according to the present invention has a hydrogen drive (i.e. a drive that uses hydrogen at least as a fuel component) and at least one hydrogen tank according to an embodiment of the present invention for supplying it with hydrogen.

[0022] A method according to the present invention serves to cool the tank structure of a hydrogen tank according to an embodiment of the present invention. It comprises passing gaseous hydrogen from the tank space of the hydrogen tank through the piping system and discharging the hydrogen into an environment of the hydrogen tank.

[0023] The tank contents of the tank space preferably include, in addition to gaseous hydrogen, liquid hydrogen with a para-hydrogen content (compared to ortho-hydrogen) of at least 90%, more preferably at least 95%. As the hydrogen flows through the piping system of the cooling shield of the tank structure, the para-ortho catalyst arranged in the piping system converts part of the para-hydrogen into ortho-hydrogen in an endothermic reaction. This removes heat from the cooling shield, thus cooling the tank structure.

[0024] When introduced into the piping system, the gaseous hydrogen preferably has a temperature in the range of 30K to 70K. Preferably, the gaseous hydrogen is passed through the piping system in the cooling shield until the hydrogen exiting the piping system has a temperature in the range of 50K to 200K (i.e., is heated to such a temperature). In this way, at least almost loss-free storage of liquid hydrogen at a temperature of approximately 20K in the tank space can be achieved.

[0025] In particular, a method according to the invention thus comprises depressurizing the hydrogen tank. This allows the gaseous hydrogen in the tank space to be repeatedly brought to a low level and stabilized there with minimal evaporation losses, despite external heat input to the hydrogen tank. The depressurization can be repeated several times during the operation of a hydrogen propulsion system powered by hydrogen from the hydrogen tank, or it can also be performed continuously.

[0026] Preferably, the cooling shield of a hydrogen tank according to the invention is configured to convert para-hydrogen by means of a catalyst, at least at cooling shield temperatures in the range from 50K to 200K, until a ratio V of ortho- to para-hydrogen is reached, which deviates from a respective equilibrium ratio G(T) (dependent on the respective temperature T) by at most 10% or by at most 5%. Similarly, the hydrogen discharged according to a method according to the invention preferably has a ratio V of ortho-hydrogen to para-hydrogen that deviates from a respective equilibrium ratio G(T) (dependent on the respective temperature T) by at most 10% or by at most 5%. In such embodiments, 0.9G(T) ≤ V and 0.95G(T) ≤ V respectively apply.

[0027] A hydrogen tank according to the invention can be configured, in particular, to be installed in a hydrogen-powered vehicle (e.g., an aircraft, spacecraft, ground vehicle, and / or watercraft) (which is therefore configured to use hydrogen at least as a fuel component), or it can already be installed in such a vehicle. A vehicle according to the invention can be configured, in particular, as an aircraft, spacecraft, ground vehicle, and / or watercraft.

[0028] According to advantageous embodiments, the tank space of a hydrogen tank according to the invention is designed to be substantially rotationally symmetrical about an (abstract) central axis. It can be bounded, for example, by a tank wall that is part of the tank structure and is formed along a prism or a circular cylinder, and / or by at least one rotationally symmetrical tank dome that is part of the tank structure and through which the central axis penetrates. In such embodiments, the cooling shield can at least partially encompass the tank wall and / or at least one such tank dome; in particular, the piping system can then be formed at least partially in the tank wall and / or the at least one tank dome.

[0029] The piping system serves to effectively guide the gaseous hydrogen, which acts as a coolant, within the tank structure. It can comprise one or more continuous (unbranched) cooling channels or form at least one branch. Because multiple material layers of the cooling shield (as mentioned above) form a sandwich structure, such a branched piping system can be formed by borders surrounding cells contained in the sandwich.

[0030] The para-ortho catalyst is preferably formed at least partially as an inner coating of at least one region of a boundary of the conduit system. It can, in particular, comprise iron oxide, nickel-silicon, chromium trioxide, and / or a porous magnetic material.

[0031] In relation to the material thickness of the cooling shield (in cross-section), the piping system can run at least partially through a central and / or an outer (i.e., facing away from the tank space) cross-sectional area of ​​the tank structure. This allows effective heat removal with minimal demand for exhaust gas and minimal demand for structural mass, thus particularly effectively reducing the heat input into the tank structure. In particular, at least part of the piping system can preferably run through a central cross-sectional area in embodiments with a prism-shaped or circular-cylindrical tank wall as mentioned above, and preferably through a central or outer cross-sectional area in embodiments with at least one rotationally or rotationally symmetrical tank dome pierced by a central axis.

[0032] According to the invention, the conduit system is at least partially delimited by two or more (separate) material layers of the cooling shield, i.e., formed as a hollow space between the at least two material layers. In particular, at least one of the material layers can preferably have corrugations and / or surfaces angled relative to one another (in particular, extending along prisms), which at least partially delimit at least one region of the conduit system.

[0033] According to advantageous embodiments, the tank structure, in particular preferably its cooling shield, is made at least partially from a lightweight material, for example from plastic, fiber-reinforced composite, aluminum and / or at least one aluminum alloy.

[0034] The tank structure can therefore have a particularly low mass, so that its transport (especially in a vehicle with a hydrogen drive, which is supplied by the hydrogen tank) can be particularly energy-efficient.

[0035] In corresponding embodiments with multiple material layers, in particular at least one of the material layers may preferably consist at least partially of fiber-reinforced composite material; such a layer of fiber-reinforced composite material may in particular serve as a supporting structure and thus at least partially determine an advantageous load-bearing design of the cooling shield.

[0036] Preferred embodiments of the invention are explained in more detail below with reference to the drawings. It is understood that individual elements and components can also be combined differently than shown. Reference numerals for corresponding elements are used throughout the figures and may not be described again for each figure.

[0037] They show schematically: Fig. 1a: an exemplary embodiment of a hydrogen tank according to the invention as a tank of a spacecraft during a thrust phase in a longitudinal section; Fig. 1b: the hydrogen tank of the Figure 1a during a ballistic flight phase of the spacecraft; Fig. 1c: the hydrogen tank according to the invention of the Figures 1a, 1b in cross section; and Fig. 1d: an advantageous hydrogen tank according to an exemplary embodiment of the present invention in cross section.

[0038] The Figure 1aschematically shows a hydrogen tank 100 according to an embodiment of the present invention. The hydrogen tank has a tank structure 10 that surrounds and delimits a tank space T. The tank structure 10 comprises a cooling shield 11 in which a line system 21 of a pressure relief system 20 is formed. Through the inlet 22 of the cooling shield 11, gaseous hydrogen W g can flow from the tank space into the line system 21, then flow through the line system 21 and be discharged through an outlet 23 of the pressure relief system 20 into an area surrounding the hydrogen tank 100. A para-ortho catalyst (not visible in the figure) for accelerating the conversion of para- to ortho-hydrogen is arranged in the line system 21. The para-ortho catalyst is preferably formed as a coating of at least one region of a boundary of the line system 21 in the cooling shield 11.It can, in particular, comprise iron oxide, nickel silicon, chromium trioxide, and / or a porous magnetic material, and it ensures that para-hydrogen in the gaseous hydrogen W g flowing through the line system 21 is partially converted into ortho-hydrogen. Since the endothermic conversion removes heat from the cooling shield 11, the tank structure 10 is additionally cooled in this way, thus at least partially compensating for a heat flow Φ acting externally on the hydrogen tank 100. This allows pressure relief, which is necessary to regulate the tank pressure, to be used for effective cooling, so that evaporation losses can be minimized.

[0039] The tank space is rotationally symmetrical around an (abstract) central axis X, along which the hydrogen tank 100 is cut in the Figure 1a is shown.

[0040] The tank space T is delimited by a tank wall 12 and two tank domes 13a, 13b. The tank wall 12 is formed along a circular cylinder around the central axis X. The tank domes 13a, 13b are each shaped as spherical segments, which are penetrated by the central axis X. The inlet 22 of the pressure relief system 20 is arranged in the penetration area of ​​the central axis X through that tank dome 13a which, in an intended installation orientation of the hydrogen tank in a vehicle (not shown), is opposite a tank space area in which the liquid hydrogen W f collects under the influence of gravity or - if the vehicle is designed for space applications - under the influence of inertia during thrust: This situation is in the Figure 1a shown.

[0041] In contrast, the Figure 1bthe hydrogen tank 100 installed in the intended installation orientation in a spacecraft (not shown) in a situation in which the spacecraft rotates about the central axis X during a ballistic phase: In this situation, the liquid hydrogen W f is forced radially outwards with respect to the central axis X and thus against the tank wall 12 due to the centrifugal force.

[0042] In both situations, the liquid hydrogen W f is spaced from the inlet 22 of the pressure relief system 20 into the piping system 21 so that its penetration into the piping system is prevented.

[0043] The tank structure 10 is in the Figures 1a and 1bEach is shown in simplified form with two flat material layers 14a, 14b, between which at least one intermediate space Z is formed. This enables a lightweight construction of the tank structure. Preferably, at least one of the flat material layers consists at least partially of a lightweight material such as plastic, fiber-reinforced composite, aluminum, and / or at least one aluminum alloy. At least one of the material layers can preferably impart a load-bearing function to the cooling shield.

[0044] As continued in the Figures 1a and 1b As can be seen, the intermediate space Z in the embodiment shown forms at least part of the line system 21.

[0045] In the Figure 1cthe hydrogen tank 100 is shown schematically perpendicular to the central axis X and in section in the region of the tank wall 12 (and with modified dimensions to clarify the structure). In this illustration, it can be seen that a corrugated material layer 14c is arranged between the material layers 14a and 14b as a further material layer, the corrugations of which, in contact with the material layer 14a located further outwards, even delimit a plurality of intermediate spaces Z, of which only two are provided with reference numerals in Figure 2 for the sake of clarity. In contact with the material layer 14b arranged further inwards (relative to the tank space T or the central axis X), the corrugated material layer 14c delimits further intermediate spaces Z i .

[0046] In this case, the respective outer spaces Z form at least a portion of the conduit system 21 with the para-ortho catalyst (not shown). When gaseous para-hydrogen is passed through the conduit system 21, the outer material layer 14b in particular is cooled, thus at least partially compensating for a heat flow Φ from the outside. Alternatively or additionally, the further spaces Z i can form a portion of the conduit system 21 with the para-ortho catalyst (not shown in the figure).

[0047] In particular, the para-ortho catalyst may comprise one or more regions in which it is formed as a respective coating of at least a part of one or more respective walls of the interspaces Z and / or the interspaces Z i.

[0048] As an alternative to the wave shape, the material layer 14c could comprise sections angled relative to one another, in particular be jagged (not shown).

[0049] The Figure 1d schematically illustrates a particularly advantageous hydrogen tank 100' according to a further embodiment of the present invention in a cross-section. The hydrogen tank 100' can, in particular, be spherical or have a circular-cylindrical tank wall; the cross-section shown here is taken perpendicular to its central axis X.

[0050] The hydrogen tank 100' has a tank structure 10' which has a cooling shield 11 which is analogous to the cooling shield 11 of the Figure 1c shown tank structure 100 and is therefore also designated here and will not be described again.

[0051] In addition, the tank structure 10' of the hydrogen tank 100' comprises material layers 15a and 15b, each on a side of the cooling shield 11 facing the tank compartment T (i.e., between the tank compartment T and the cooling shield 11) as well as material layers 17a and 17b on a side of the cooling shield 11 facing away from the tank compartment (i.e., further out than the cooling shield 11 with respect to the tank compartment).

[0052] The material layers 15a and 17b are each corrugated in the present case, so that in contact with the respective adjacent material layers 14a, 15b and 14b, 17a and together with these respective material layers they delimit cavities H a , H i , of which in the Figure 1dFor the sake of clarity, only two are provided with reference numerals. The tank structure 10' thus has (relative to the tank space T) a partial structure 16 and 18 inside and outside the cooling shield 11, respectively, which is designed in a lightweight construction like the cooling shield 11. In particular, the Figure 1d The tank structure 10' shown here has three wave plate cores, of which the middle one in cross section forms the cooling shield 11.

[0053] As an alternative to the wave shape, one or more of the material layers 14c, 15a, 17b could comprise sections angled relative to one another, in particular be jagged (not shown).

[0054] According to advantageous embodiments, one or more of the cavities H a and / or one or more of the cavities H i is / are connected to a vacuum pump, thus forming an evacuable hollow volume. This allows for a particularly good thermal insulation effect to be achieved.

[0055] Disclosed is a hydrogen tank 100 having a tank structure 10 that at least partially defines a tank space T and comprises a lightweight cooling shield 11. A line system 21 of a pressure relief system 20, connected to the tank space T, is formed in the cooling shield 11 for discharging gaseous hydrogen W g from the tank space T. At least one para-ortho catalyst for accelerating the conversion of para- to ortho-hydrogen is arranged in the line system.

[0056] Furthermore, a vehicle with a hydrogen drive and such a hydrogen tank 100 as well as a method for cooling the tank structure of such a hydrogen tank are disclosed. Reference symbol

[0057] 10Tank structure 11Cooling shield 12Tank wall 13a, 13bTank dome 14a, 14b, 14cMaterial layer 15a, 15bMaterial layer 16Partial structure on the side of the cooling shield facing the tank compartment T 11 17a, 17bMaterial layer 18Partial structure on the side of the cooling shield facing away from the tank compartment T 11 20Pressure relief system 21Pipe system 22Inlet 23Outlet 100 hydrogen tanks ΦHeat flow H i , H a cavity W f liquid hydrogen W g gaseous hydrogen TTank space Xcentral axis Zinterspace Z i inner interspace

Claims

1. A hydrogen tank (100) with a tank structure (10) which at least partially delimits a tank chamber (T) and which comprises a region (11) designed using lightweight construction methods, hereinafter designated a cooling shield, in which a conduit system (21) of a pressure relief system (20) which is connected to the tank chamber (T) is formed for discharging gaseous hydrogen (Wg) from the tank chamber (T), wherein at least one para-ortho catalyst for the accelerated conversion of parahydrogen into orthohydrogen is disposed in the conduit system, characterized in that the cooling shield (11) has at least two separate layers of material (14a, 14b, 14c) which form a sandwich structure, between which layers at least one hollow intermediate space (Z), which forms at least a portion of the conduit system (21), is formed.

2. The hydrogen tank as claimed in claim 1, wherein the para-ortho catalyst is at least partially formed as an internal coating of at least a portion of a boundary of the conduit system (21).

3. The hydrogen tank as claimed in one of claims 1 or 2, wherein at least one of the layers of material (14c) has corrugations and / or surfaces which are angled with respect to each other, which at least partially delimit the at least one intermediate space (Z).

4. The hydrogen tank as claimed in one of the preceding claims, wherein the tank structure (10, 10') additionally has a substructure (16, 18) in which at least one hollow volume which can be or is evacuated is formed for the thermal insulation of the tank chamber.

5. The hydrogen tank as claimed in one of the preceding claims, wherein the tank structure is at least partially fabricated from plastic, fibre-reinforced composite, aluminium and / or at least one aluminium alloy.

6. A vehicle with a hydrogen drive, which comprises at least one hydrogen tank (100) as claimed in one of the preceding claims for supplying the hydrogen drive.

7. A method for cooling the tank structure of a hydrogen tank (100) as claimed in one of claims 1 to 5, wherein the method comprises passing gaseous hydrogen (Wg) out of the tank chamber (T) of the hydrogen tank (T) through the conduit system (20) containing the at least one para-ortho catalyst, as well as discharging the hydrogen into an environment of the hydrogen tank (100).

8. The method as claimed in claim 7, wherein the gaseous hydrogen (Wg) is fed out of the tank chamber into the conduit system (20) at a temperature in the range from 30K to 70K.