Hydrogen storage bed

Abstract

A hydrogen storage bed 10 for storing and releasing hydrogen, the hydrogen storage bed comprising: a hydrogen storage body 12; and a thermal transfer element 32 comprising a fin element 34, preferably a helical fin element, configured to allow the redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material.

Description

Field of the Invention

[0001] The present invention is directed towards a hydrogen storage bed for storing and releasing hydrogen. The present invention is also directed towards a method of assembling said hydrogen storage bed, a hydrogen storage bed system using said hydrogen storage bed, and methods of storing and providing hydrogen using said hydrogen storage bed. Background of the Invention

[0002] As countries try to move away from using fossil fuels for their energy grids, transport networks, industrial and domestic needs, there is a growing consensus that hydrogen may play a large-scale substituting role. Advantageously, hydrogen has a relatively high density of energy per unit mass and can be produced without the need for fossil fuels.

[0003] Whilst hydrogen has a lot of potential as a sustainable energy source, a major drawback is efficient storage, as hydrogen has a low volumetric energy density. Therefore, as hydrogen develops as an energy commodity, there is industrial and governmental interest in developing methods for efficient production, transport, storage, and utilisation of hydrogen.

[0004] Hydrogen is conventionally stored as either a compressed gas under higher pressure or as a cryogenic liquid. Neither of these storage solutions are currently conducive to large-scale application due to safety and efficiency issues: liquid hydrogen storage is costly and requires low storage temperatures; compressed hydrogen gas requires large storage tanks able to withhold significant internal pressure.

[0005] Hydrogen can also be stored in the solid-state, for example in metal hydride hydrogen storage reactors. However, there are still numerous technical problems with currently available metal hydride storage reactors. Currently available metal hydride storage reactors are relatively small scale and not suitable for storing large amounts of hydrogen to be useful as a sustainable energy source. Previous attempts to scale up currently available metal hydride storage reactors have been unsuccessful, primarily due to the difficulties in managing the heat flow into and out of the storage reactors required for loading and unloading of hydrogen, and the volumetric expansion of material in the reactor (hydrogen storage material) on uptake of hydrogen. Regarding management of heat flow, for example, metal hydrides often have extremely poor effective thermal conductivity, and this poor thermal conductivity means the heat released by the exothermic hydrogenation reaction, during the process of hydrogen storage, cannot be transferred or removed from the system in a timely and effective manner. This causes the internal temperature of the storage reactor to sharply rise over a short period of time, resulting in a sharp pressure increase, and a reduced or even non-existent hydrogen uptake rate. As a reactive material inside a hydrogen storage reactor takes up hydrogen, the hydride material (for example, the metal hydride) takes up significantly more volume than the precursor material. This volumetric expansion, if not well accommodated, can lead to structural weakness within the storage reactor. The volumetric expansion may also lead to increased material compression and stress generation within the storage reactor. This could result in internal deformation and / or bulging of the storage reactor. These issues are discussed in Kawamura (1982) and Masahiko (2012). The technical problems become increasingly difficult to address as the mass and size of the storage reactors increase. Conventional hydrogen storage systems, and their volumetric capacities can be found in Penzhorn (1990), Shmayda (2021) and Banos (2022). An overview of hydrogen storage technologies, and in particular, metal hydride hydrogen storage can be found in Yartys and Lototsky (2004). Safety concerns and boil-off issues of compressed and liquid hydrogen storage are discussed in Meng (2006), and Ramin and Growth (2019).

[0006] Whilst there are numerous different physical and chemical methods for storing hydrogen, it is important to develop a storage solution that is cost effective, safe, sustainable, reliable, has a smallfootprint, and addresses the problems of the prior art. Summary of the Invention

[0007] The present inventors have identified that a desirable hydrogen storage bed needs to: (1) adequately protect the reactive hydrogen storage material inside the bed; (2) effectively manage heat flow into and out of the bed to enable efficient loading and unloading of hydrogen; and (3) safely accommodate the volumetric change of the reactive material inside the bed as it takes up hydrogen. These are particularly important for a hydrogen storage bed containing metal hydride storage materials.

[0008] In a first aspect, the present invention provides a hydrogen storage bed for storing and releasing hydrogen, the hydrogen storage bed comprising: a hydrogen storage body; and a thermal transfer element comprising a fin element configured to allow the redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material.

[0009] The present inventors have surprisingly found that the use of a thermal transfer element according to the present invention is advantageous. The present inventors found that by providing a hydrogen storage bed comprising a thermal transfer element arranged within a hydrogen storage body as described herein, the thermal transfer element comprising at least one fin element configured to allow the redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material, allows for redistribution of the hydrogen storage material within the hydrogen storage body during expansion of the hydrogen storage material on uptake of hydrogen while also providing efficient transfer of thermal energy to and from the hydrogen storage material. Therefore, the hydrogen storage bed described herein provides for improved storage of hydrogen. The hydrogen storage bed described here can store greater amounts of hydrogen than the prior art while also avoiding localised strain build up against the hydrogen storage body due to the volumetric expansion upon hydriding of a hydrogen storage material as well as providing for efficient transfer of thermal energy as required during hydriding and dehydriding of the hydrogen storage material.

[0010] Deformation of a hydrogen storage body is a problem that has been observed for hydrogen storage beds that provide for strict compartmentalization of hydrogen storage material. Deformation has also been observed for hydrogen storage beds where the hydrogen storage material was initially loaded unevenly between two adjacent compartments. The present inventors surprisingly found that the provision of a thermal transfer element according to the present invention alleviates these problems by allowing for redistribution of the hydrogen storage material during hydriding and dehydriding without deforming the hydrogen storage body.

[0011] Furthermore, the present inventors surprisingly found that the invention allows for much larger amounts of hydrogen storage material to be utilised than previously shown. For example, the present inventors have found that the hydrogen storage beds described herein can store at least 10 times the amount of hydrogen compared to existing hydrogen storage beds / reactors. The hydrogen storage bed and methods described herein may also provide benefits in relation to improving the efficiency and reducing the production costs of the storage of hydrogen, mitigating health and safety issues when using expensive, rare, toxic or even radioactive hydrogen storage materials.

[0012] The present inventors have identified that not only have hydrogen storage beds of the prior art been difficult or impossible to provide at larger scale, but also that there are problems associated with releasing hydrogen quickly enough to be useful as a sustainable energy source. Therefore, the present inventors have identified that as well as providing a hydrogen storage bed which can accommodate increased volumes of hydrogen compared to existing hydrogen storage beds, it is desirable to provide an improved hydrogen storage bed which is able to transfer thermal energy quickly and efficiently to allow hydrogen to be released from a hydrogen storage material as quickly as possible. The present inventors have surprisingly found that the hydrogen storage bed described herein can be used to deliver large quantities of hydrogen as a sustainable energy source. In particular, due to the configuration of the hydrogen storage bed described herein allowing for redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material, it has been found to be possible to provide thermal energy to the hydrogen storage material in the hydrogen storage bed efficiently in order that hydrogen may be efficiently (and quickly) be unloaded from the hydrogen storage material.

[0013] In embodiments, the thermal transfer element comprises a single fin element. The fin element may extend along the longitudinal extent of the thermal transfer element in a continuous manner. Alternatively, a plurality of fin elements may be used in a continuous or discontinuous manner. The fin element(s) may be shaped to allow for the redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material.

[0014] In preferred embodiments, the fin element is a helical fin element, i.e., the fin element has a helical shape and is arranged along the thermal transfer element in a helical manner. In such embodiments, the helical shape of the fin element of the thermal transfer element allows for the redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material. The present inventors have found that providing a thermal transfer element with a helical fin element is advantageous in accommodating volumetric expansion of a hydrogen storage material while also providing for efficient thermal transfer.

[0015] The thermal transfer element allows for even distribution of a hydrogen storage material within the hydrogen storage body. The thermal transfer element may also loosely compartmentalise the hydrogen storage material in a beneficial manner. In some embodiments, the thermal transfer element comprises a fin element (for example, a single fin element) being arranged along the thermal transfer element in a helical manner. A helical shape may also allow for improved thermal transfer between the thermal transfer element and hydrogen storage material. A helical shape may also allow for improved distribution and / or redistribution of a hydrogen storage material within the hydrogen storage body. As such, a helical thermal transfer element may enhance heat distribution throughout the bed. The helical shape of the fin element may extend clockwise or anti-clockwise along the longitudinal extent of the thermal transfer element.

[0016] In embodiments, the fin element is a helical fin element having a helix angle in the range of about 1° to about 80°, for example in the range of about 2° to about 70°, about 1° to about 60°, about 5° to about 50°, about 10° to about 40°, about 10° to about 30°, about 10° to about 25°, about 15° to about 25°, or in the range of about 20° to about 30°. In preferred embodiments, the fin element is a helical fin element having a helix angle in the range of about 5° to about 50°, for example in the range of about 10° to about 40°, about 10° to about 30°, about 10° to about 25°, about 15° to about 25°, or in the range of about 20° to about 30°. The helix angle is measured from the normal to the axis of the thermal transfer element.

[0017] In preferred embodiments, the fin element of the thermal transfer element is a continuous solid helical fin element.

[0018] In preferred embodiments, the fin element is formed from a thermally conductive material, for example a material exhibiting excellent thermal conductivity. The specifical material employed for the fin element is not particularly limited. Examples of suitable materials for construction of the fin element include copper and copper alloys. However, other thermally conducting material may be used, such as many different metals including titanium and palladium.

[0019] In alternative embodiments, the fin element may be arranged in a non-helical manner.

[0020] In preferred embodiments, the thermal transfer element is removable from the hydrogen storage body.

[0021] In some embodiments, the hydrogen storage body has an internal diameter, and the thermal transfer member has an outer most diameter, and the outer most diameter of the thermal transfer element is at least about 80% of the internal diameter of the hydrogen storage body, for example at least about 85%, at least about 90%, at least about 95%, or at least about 98% of the internal diameter of the hydrogen storage body. In some embodiments, the outer mostdiameter of the thermal transfer element is in the range of about 80% to about 100% of the internal diameter of the hydrogen storage body, for example in the range of about 90% to about 100% of the internal diameter of the hydrogen storage body. In some embodiments, the outer most diameter of the thermal transfer element is in the range of about 80% to about 99.9% of the internal diameter of the hydrogen storage body, for example in the range of about 90% to about 99.9% of the internal diameter of the hydrogen storage body, in the range of about 95% to about 99.9% of the internal diameter of the hydrogen storage body, or in the range of about 97% to about 99% of the internal diameter of the hydrogen storage body, or in the range of about 90% to about 98% of the internal diameter of the hydrogen storage body.

[0022] The thermal transfer element is fixable or fixed relative to the hydrogen storage body.

[0023] In some embodiments, the outer most diameter of the thermal transfer element being less than the internal diameter of the hydrogen storage body has been found to be useful to provide a volumetric expansion region between the thermal transfer element and the hydrogen storage body. In some embodiments, the provision of such a volumetric expansion region is not required. For example, in some embodiments, the thermal transfer member may contact, for example directly contact, the inner wall of the hydrogen storage body. The diameter of the hydrogen storage body may be tailored to the desired hydrogen storage material being used in the hydrogen storage bed. The outer most diameter of the thermal transfer element may also be tailored relative to the diameter of the hydrogen storage body. The outer most diameter of the thermal transfer element may also be tailored relative to the desired hydrogen storage material being used in the hydrogen storage bed.

[0024] The present inventors have found that the provision of a thermal transfer element as described herein allows for the prevention of pressure build up that can result from volumetric expansion of the hydrogen storage material upon hydriding. The thermal transfer element may also facilitate the redistribution of hydrogen storage material throughout the hydrogen storage body on hydriding and dehydriding of the hydrogen storage material. The diameter of the hydrogen storage body and / or the configuration of the thermal transfer element may be optimised for different hydrogen storage materials such that the hydrogen storage bed can safely accommodate the volumetric change of specific hydrogen storage materials.

[0025] In some embodiments, the hydrogen storage body may be described as comprising a first pressure vessel (e.g., a first vacuum pressure vessel) and a hydrogen diffusion liner. The hydrogen diffusion liner may be formed from a metal suitable for reducing hydrogen ingress into the wall of the first pressure vessel. Any material suitable for reducing or preventing hydrogen ingress may be used. Examples of suitable materials for reducing or preventing hydrogen ingress include metals comprising one or more elements selected from: copper, silver, gold and niobium.

[0026] Hydrogen ingress can lead to material failure, as hydrogen ingress may cause mechanical damage such as a loss in ductility and tensile strength. Hydrogen ingress is particularly problematic for steel. Therefore, when the hydrogen storage body comprises a steel pressure vessel, the provision of a hydrogen diffusion liner may be particularly beneficial.

[0027] A hydrogen diffusion liner may be formed on the internal surface of the hydrogen storage body by any suitable process, for example suitable processes include sweating, plasma spray coating and electrolytic coating.

[0028] As described herein, the hydrogen storage body may be used to accommodate a hydrogen storage material which may be hydrided to take up hydrogen and dehydrided to release hydrogen. In embodiments, the hydrogen storage bed may be described as comprising a hydrogen storage material.

[0029] In a preferred embodiment, the hydrogen storage material is a hydridable metal or metal alloy, i.e., a metal that can form a metal hydride. Examples of hydrogen storage materials include magnesium; magnesium alloys; lanthanum pentanickel (LaNi5); lanthanum alloys; zirconium cobalt (ZrCo); zirconium nickel (ZrNi); lithium; titanium; thorium; uranium, and rare earth elements such as Cerium. In some embodiments, the hydrogen storage material is depleted uranium. An advantage of employing depleted uranium as a hydrogen storage material is that a nuclear waste material may be made use of in the supply of a sustainable energy source.

[0030] The present inventors have surprisingly found that depleted uranium can be successfully used as a hydrogen storage material within the hydrogen storage bed described herein. Depleted uranium has previously been used in the fusion energy sector at a relatively small scale for storing deuterium and tritium - the heavy isotopes of hydrogen. However, there are difficulties in handling depleted uranium, such as the volumetric expansion during conditioning and phase transformations, as well as the thermal and pressure management during hydrogen absorption and desorption. The amount of depleted uranium able to be safely accommodated within a hydrogen storage bed has previously been shown to be problematic, and thus needed to be optimised to improve the range of applications and to ensure high loading and unloading kinetics of the hydrogen storage bed. However, the present inventors have found that the hydrogen storage bed described herein is able to address the problems of the prior art. In particular, the provision of the thermal transfer element accommodates the volumetric expansion of depleted uranium during hydriding, and allows for thermal management. If hydrogen is stored as uranium trihydride (UHj) using depleted uranium, the storage capacity per volume is about 2.1 times that of hydrogen in its liquid form. Practically, this means that depleted uranium can store more than twice as much hydrogen for the same volume as that of hydrogen when stored as liquid under cryogenic conditions. Furthermore, the use of an otherwise waste material is advantageous from a sustainability point of view. The inventors have also found that the present invention may use metal hydrides and / or other metallic hydrogen storage materials.

[0031] In some embodiments, the hydrogen storage bed comprises primary and secondary flanges configured to seal either end of the hydrogen storage body. In some embodiments, the hydrogen storage bed further comprises a capping plate configured to engage with the primary flange to seal an end of the hydrogen storage body. In embodiments, the capping plate supports the thermal transfer element. In some embodiments, the thermal transfer element may be formed as an integral part of the hydrogen storage body, for example using a sweating process, in such embodiments, the thermal transfer element may not be supported by the capping plate, as the support may be unnecessary.

[0032] Many of the hydrogen storage materials that are likely to be used in the hydrogen storage bed of the present invention are air sensitive. Furthermore, the pyrophoricity and explosive behaviour of hydrogen gas in air (under sudden exposure) needs to be taken into account, alongside the potentially pyrophoric behaviour of any of the hydrogen storage materials. As such, it is beneficial to have a flange at either end of the hydrogen storage body to create a seal. Having a flange at either end may increase the ease of loading the hydrogen storage bed. The operational lifetime of the depleted uranium (DU) storage beds is mainly dependent on the degradation of the components of the bed, and degradation of the hydrogen storage material properties. Many hydrogen storage materials, such as uranium, have a strong affinity to air and oxygen. Therefore, many hydrogen storage materials will readily react with nitrogen, oxygen, and water to form nitrides, oxides, oxy-hydride and oxynitride phases. The rate of degradation will be reduced if the hydrogen storage bed is leak-tight. Therefore, the presence of a primary flange and a secondary flange may aid in extending the operational lifetime of the hydrogen storage bed. Additionally, the present invention may allow for maintenance of the hydrogen storage bed without exposing the hydrogen storage material to the atmosphere. This may be particularly beneficial as it may increase the ease of maintenance of the hydrogen storage bed, for example the ease of maintenance of the heating and cooling system.

[0033] In some embodiments, the hydrogen storage bed further comprising a secondary vessel, the hydrogen storage body positioned within the secondary vessel.

[0034] A length of the secondary vessel may be greater than a length of the hydrogen storage body so as to provide a primary thermal bridging reduction region.

[0035] An external diameter of the hydrogen storage body may be less than an internal diameter of the secondary vessel so as to provide a secondary thermal bridging reduction region.

[0036] The provision of a primary and / or secondary thermal bridging reduction region may be advantageous, as it reduces the direct physical contact between the hydrogen storage body and the secondary vessel, and thus thermal transfer. The thermal bridging reduction region allows for tolerance for thermal expansion of the hydrogen storage body during use. The thermal expansion bridging region may allow for the secondary vessel to remain at a lower temperature than the hydrogen storage body when in use. For example, the hydrogen storage body during hydrogen storage may reach temperatures of up to about 500 °C, whilst the secondary vessel may remain at a temperature of less than about 100 °C.

[0037] In some embodiments, a circumference of at least one of the primary flange and / or secondary flange may be covered in a thermal bridging limiter material.

[0038] In preferred embodiments, the hydrogen storage bed may further comprise a thermal bridging prevention plate connected to the primary and / or secondary flange.

[0039] In a second aspect, the present invention provides a method of storing hydrogen, the method comprising: providing a hydrogen storage bed as described herein; placing a hydrogen storage material in the hydrogen storage bed; exposing the hydrogen storage material to hydrogen; and sealing the hydrogen storage bed.

[0040] In a second aspect, the present invention provides a method of providing hydrogen, the method comprising: providing a hydrogen storage bed as described herein, the hydrogen storage bed comprising a hydrogen storage material which has been exposed to hydrogen; and releasing the hydrogen from the hydrogen storage material.

[0041] In some embodiments, releasing the hydrogen from the hydrogen storage material comprises heating the hydrogen storage material to release hydrogen. Brief Description of the Figures

[0042] The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which:

[0043] Figure 1 shows a side perspective view of a representative first embodiment of a hydrogen storage bed in accordance with the first aspect of the invention;

[0044] Figure 2 shows a side perspective view of a hydrogen storage body of the hydrogen storage bed of Figure 1;

[0045] Figure 3 shows a side perspective view of a secondary flange of the hydrogen storage bed of Figure 1;

[0046] Figure 4 shows a cross section view of the thermal transfer element of Figure 1;

[0047] Figure 5 shows a side perspective view of a thermal transfer element of the hydrogen storage bed of Figure 1;

[0048] Figure 6 shows a side perspective view of a capping plate of the hydrogen storage bed of Figure 1;

[0049] Figure 7 shows a method of assembly of the hydrogen storage bed of Figure 1;

[0050] Figure 8 shows a cross section view of a representative first embodiment of a hydrogen storage bed in accordance with the second aspect of the invention;

[0051] Figure 9 shows a side perspective view of a secondary vessel of the hydrogen storage bed of Figure 8;

[0052] Figure 10 a shows a back perspective view of a sealing flange of the secondary vessel of Figure 8; and

[0053] Figure 11a, 11b, 11c and lid show a method of assembly of the hydrogen storage bed of Figure 8. Detailed Description

[0054] The present invention provides a hydrogen storage bed for storing and releasing hydrogen. In embodiments, there is provided a hydrogen storage bed using depleted uranium as a hydrogen storage material within the hydrogen storage bed. However, as discussed above, other materials may be employed as a hydrogen storage material. Reference to the figures in the paragraphs that follow is provided in order to aid understanding of the following description and is not intended to be limiting.

[0055] Unless otherwise stated, any feature described herein can be combined with any aspect or any other feature described herein. Each of the features referred to with reference to the figures may be combined with other aspects or features referred to generally above or with reference to other figures.

[0056] Referring to Figure 1, there is indicated is a hydrogen storage bed, referenced globally at 10, which is suitable for storing and releasing hydrogen. The hydrogen storage bed 10 comprises a hydrogen storage body 12 and a thermal transfer element 14. The thermal transfer element 14 is positioned inside the hydrogen storage body 12.

[0057] The hydrogen storage body 12 in the depicted embodiment is tubular in shape. The hydrogen storage body 12 has primary flange 16 at one end, and a secondary flange 18 at the other end. The primary flange 16 is configured to allow for engagement with a capping plate 20. In embodiments, the capping plate 20 may be connected to the thermal transfer element 14. The capping plate 20, the primary flange 16 and the second flange 18 seal the hydrogen storage body 12.

[0058] The hydrogen storage body 12 is shown in more detail in Figure 2. The hydrogen storage body 12 is suitable for high vacuum application. The hydrogen storage body 12 is envisaged to be any length suitable for hydrogen storage and high vacuum application. In embodiments, the hydrogen storage body 12 may be at least about 100 mm in length, at least about 200 mm in length, at least about 300 mm in length, at least about 400 mm in length, or at least about 500 mm in length. Furthermore, the length of the hydrogen storage body 12 may be in the range of about 100 mm to about 1000 mm, for example in the range of about 200 mm to about 600 mm.

[0059] The hydrogen storage body 12 may be formed of any suitable material. In preferred embodiments, the hydrogen storage body is formed from stainless steel (preferably 316 L stainless steel due to this being a highly durable, corrosion and oxidation resistant material with high melting point (about 1454 °C), and a high tensile strength (about 621 MPa) or comprises a stainless steel pressure vessel.

[0060] The hydrogen storage body 12 has an inner diameter ID. For example, the inner diameter ID of the hydrogen storage body may be in the range of about 180 mm to about 210 mm, such as about 192.5mm, 195 mm, about 197.5 mm, or about 198 mm. The hydrogen storage body 12 has an outer diameter OD. For example, the outer diameter OD of the hydrogen storage body 12 may be in the range of about 190 to about 220 mm, such as about 195 mm, about 200 mm, about 205 mm, or about 210 mm. The thickness of a wall of the hydrogen storage body 12 may be in the range of about 1 mm to about 5 mm, for example about 2 mm to about 4 mm, or about 2.5 mm. It is envisaged that a larger-scale hydrogen storage body 12 may be provided, in such circumstances, it may be preferable to maintain the diameter ratio between the inner diameter ID of the hydrogen storage body 12 and the outer diameter OD of the hydrogen storage body 12.

[0061] In embodiments, the ratio of the inner diameter ID of the hydrogen storage body 12 and the outer diameter OD of the hydrogen storage body 12 is in the range of about 0.85:1 to about 1:1.25, for example, in the range of about 0.9:1 to about 1:1.22, in the range of about 0.95:1 to about 1:1.2, or in the range of about 1:05 to about 1:1.15. For example, the ratio of the inner diameter ID of the hydrogen storage body 12 and the outer diameter OD of the hydrogen storage body 12 may be about 0.9:1, or about 0.95:1, or about 1:1.05 or about 1:1.25.

[0062] In one embodiment, the ratio of the thickness of a wall of the hydrogen storage body 12 and the inner diameter ID of the hydrogen storage body 12 is in the range of about 1:36 to about 1:200, for example, in the range of about 1:40 to about 1:180, in the range of about 1:60 to about 1:150, or in the range of about 1:80 to about 1:125, for example the ratio of the thickness of a wall of the hydrogen storage body 12 and the inner diameter ID of the hydrogen storage body 12 may be about 1:36, or about 1:40, or about 1:180 or about 1:200.

[0063] In embodiments, the ratio of the inner diameter ID of the hydrogen storage body 12 and the outer diameter OD1 of the primary flange 16 is in the range of about 1:1.1 to about 1:1.5, for example, in the range of about 1:1.15 to about 1:1.45, in the range of about 1:1.25 to about 1:1:4, or in the range of about 1:3 to about 1:35, for example the ratio of the inner diameter ID of the hydrogen storage body 12 and the outer diameter OD1 of the primary flange 16 may be about 1:1.2, or about 1:1.3, or about 1:35 or about 1:1.5.

[0064] In embodiments, the ratio of the thickness of a wall of the hydrogen storage body 12 and the length of the hydrogen storage body 12 is in the range of about 1:20 to about 1:600, for example, in the range of about 1:20 to about 1:200, in the range of about 1:100 to about 1:600, in the range of about 1:100 to about 1:200, for example the ratio of the thickness of a wall of the hydrogen storage body 12 and the length of the hydrogen storage body 12 may be about 1:20, or about 1:100, or about 1:200 or about 1:600.

[0065] The thermal transfer element 14 shown in Figure 1 comprises a helical fin element 34. The present inventors have found that a helical fin element allows for the redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material. The present inventors have also found that the thermal transfer element 14 also allows for heat distribution. In embodiments the thermal transfer element 14 may comprise a core 32, for example a tubular core, for supporting and / or heating the fin element 34 of the thermal transfer element 14. In embodiments, the core 32 of the thermal transfer element 14 is hollow, for example, to allow for insertion of a heating element into the core 32.

[0066] In the embodiment shown in Figure 1, the primary flange 16 and secondary flange 18 may be arranged at either end of the hydrogen storage body 12 respectively. The primary flange 16 extends from the hydrogen storage body 12. The outer diameter OD1 of the primary flange 16 may be in the range of about 200 mm to about 300mm, for example about 240 mm to about 270 mm.

[0067] In the embodiment shown in Figure 1, the secondary flange 18 forms a seal flush with the hydrogen storage body 12. The outer diameter OD2 of the secondary flange 18, may be complementary to the outer diameter OD of the hydrogen storage body 12.

[0068] In the illustrated embodiment shown in Figure 2, an outer circumferential surface of the primary flange 16 is wrapped (for example, coated) in an insulating material 22a. Any material that would act to reduce thermal bridging may be used as the insulating material 22a. The insulating material 22a may be, for example, made from inorganic material, such as ceramic materials, one such ceramic material being silica, such as a silica weave. The insulating material 22a acts to limit thermal bridging.

[0069] In the depicted embodiment shown in Figure 2, the outer circumferential surface of the secondary flange 18 is coated in an insulating material 22b to limit thermal bridging. In such an embodiment, the outer diameter OD2a of the secondary flange 18 with the insulating material 22b is preferably the same, or substantially the same, as the outer diameter OD1 of the primary flange 16.

[0070] The insulating material 22a wrapped around the primary flange 16 may be the same material as the insulating material 22b wrapped around the secondary flange 18. Alternatively, the insulating material 22a wrapped around the primary flange 16 may be different to the insulating material 22b wrapped around the secondary flange 18. An embodiment where the primary flange 16 and / or secondary flange 18 are not wrapped in insulating material 22a, 22b is envisaged. For instance, an embodiment where only one of the primary flange 16 and / or the secondary flange 18 is wrapped in an insulating material 22a, 22b, and / or an embodiment where neither the primary flange 16 nor the secondary flange 18 is wrapped in an insulating material 22a, 22b.

[0071] An insulative plate 24 may be fitted to an outer surface of the secondary flange 18. The insulative plate 24 may be made from a material such as alumina ceramic or glass. Any material that is a suitable thermal insulator may be utilised as a material for the insulative plate 24.

[0072] In the depicted embodiment illustrated in Figure 2, the hydrogen storage body 12 (for example a hydrogen pressure vessel, which in examples may be a stainless steel pressure vessel) is lined with a hydrogen diffusion liner 26. The hydrogen diffusion liner 26 acts to prevent hydrogen ingress into the hydrogen storage body 12 material. In embodiments, the thickness of the hydrogen diffusion liner 26 is up to about 10mm, for example in the range of about 2 mm to about 5 mm.

[0073] In embodiments, the ratio of the thickness of a wall of the hydrogen storage body 12 and the thickness of the hydrogen diffusion liner 26 is in the range of about to about 1:1 to about 1:5, for example, in the range of about 1:1 to about 1:1.25, or in the range of about 1:15 to about 1:2, for example the ratio of the thickness of a wall of the hydrogen storage body 12 and the thickness of the hydrogen diffusion liner 26 may be about 1:1, or about 1:2, or about 1:25 or about 1:5.

[0074] The hydrogen diffusion liner 26 may be integrally formed with the hydrogen storage body 12. The hydrogen diffusion liner 26 may be formed by coating the wall of the hydrogen storage body 12. The coating may be achieved using a technique such as electroplating. Alternatively, the hydrogen diffusion liner 26 may not be integrally formed with the hydrogen storage body 12 and may be provided as a removable insert.

[0075] As best illustrated in Figure 3, the secondary flange 18 may comprise a blind hole 28 on an inner surface to support the thermal transfer element 14, or section of the thermal transfer element 14 (such as core 32 of the thermal transfer element 14). In the embodiment shown, the diameter of the blind hole 28 is complementary to the diameter of a central part of the thermal transfer element 14 (core 32). The secondary flange 18 may have a hydrogen diffusion liner 26 on the inner surface, as depicted in Figure 3. The hydrogen diffusion liner 26 preferably has an aperture 30 of a complementary size and dimension to the blind hole of the secondary flange 18.

[0076] The hydrogen diffusion liner 26 of the hydrogen storage body 12 and secondary flange 18 may be formed from any material that protects against hydrogen ingress. Examples of such materials include silver, gold, niobium and copper. Most preferably, copper is used as the hydrogen diffusion liner 26. The selection of a hydrogen diffusion liner 26 material may be governed by multiple criteria such as affordability, scarcity, and ability to prevent the hydrogen ingress. An embodiment without a hydrogen diffusion liner 26 on either the hydrogen storage body 12, secondary flange 18 and / or both, can be envisaged, however this is likely to be less preferable as hydrogen ingress is more likely to occur.

[0077] Figure 4 shows a lengthwise cross section through the thermal transfer element 14 shown in Figure 1. The length of the thermal transfer element 14 is complementary to the length of the hydrogen storage body 12. In embodiments, the thermal transfer element 14 extends from the capping plate 20 to the secondary flange 18.

[0078] In this embodiment, the thermal transfer element 14 has a tubular core 32. The tubular core 32 is preferably hollow. The tubular core 32 is preferably hollow to allow for insertion of a heating element. A dimension of the tubular core 32 is of a complementary size and dimension to the blind hole 28 in the secondary flange 18, and, if present, of complementary size and dimension to the aperture 30 in the hydrogen diffusion liner 26 of the secondary flange 18. This allows for complementary engagement of the thermal transfer element 14 into the blind hole 28, and thus allows for the thermal transfer element 14 to be supported at either end. The thermal transfer element 14 therefore does not need support from the wall of the hydrogen storage body 12.

[0079] The thermal transfer element 14 comprises fin element 34. In the embodiment shown, the fin element is a helical fin element comprising a solid and continuous helical fin extending longitudinally around an outer surface of the tubular core 32 to form a continuous spiral.

[0080] The diameter D of the outer most part of the thermal transfer element 14, is preferably at least about 80% of the internal diameter of the hydrogen storage body 12, for example at least about 85%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, at least about 98 % or at least about 99% of the internal diameter ID of the hydrogen storage body 12. In some embodiments, the outer most diameter of the thermal transfer element is in the range of about 80% to about 99.9% of the internal diameter of the hydrogen storage body, for example in the range of about 90% to about 99.9% of the internal diameter of the hydrogen storage body, in the range of about 95% to about 99.9% of the internal diameter of the hydrogen storage body, or in the range of about 97% to about 99% of the internal diameter of the hydrogen storage body.

[0081] In embodiments, the ratio of the diameter D of the outer most part of the thermal transfer element 14 and the internal diameter of the hydrogen storage body 12 is in the range of about 0.8:1 to about 0.99:1, for example, in the range of about 0.9:1 to about 0.99:1, or in the range of about 0.95:1 to about 0.99:1. In some embodiments, the outer most diameter of the thermal transfer element being less than the internal diameter of the hydrogen storage body has been found to be useful to provide a volumetric expansion region between the thermal transfer element and the hydrogen storage body. However, the provision of such a volumetric expansion region may not be required. For example, in some embodiments, the thermal transfer member may contact, for example directly contact, the inner wall of the hydrogen storage body.

[0082] In the embodiment shown, the diameter D of the outer most part of the thermal transfer element 14 being smaller than the internal diameter ID of the hydrogen storage body 12 provides a volumetric expansion region therebetween. In such an embodiment, the thermal transfer element 14 is not in direct contact with the wall of the hydrogen storage body 12, this configuration is aided by the blind hole 28 in the secondary flange 18, as described above.

[0083] In embodiments in which a volumetric expansion region is provided, a gap is provided between the thermal transfer element 14 and the internal wall of the hydrogen storage body 12. In embodiments, the gap between the thermal transfer element 14 and the internal wall of the hydrogen storage body 12 may be in the range of about 0.1 mm to about 10 mm, for example, in the range of about 0.1 mm to about 5 mm.

[0084] In embodiments, the fin element 34 is a helical fin element having a helix angle in the range of about 1° to about 80°, for example in the range of about 2° to about 70°, about 1° to about 60°. In preferred embodiments, the fin element 34 is a helical fin element having a helix angle in the range of about 5° to about 50°, for example in the range of about 10° to about 40°, about 10° to about 30°, about 10° to about 25°, about 15° to about 25°, or in the range of about 20° to about 30°. The helix angle is measured from the normal to the axis of the thermal transfer element 14.

[0085] In alternative embodiments where a plurality of fin elements 34 are present, the plurality of fin elements 34 may be oriented at the same angle with respect to the longitudinal axis of the hydrogen storage body 12. Alternatively, at least one fin element 34 of the plurality of fin elements 34 may be at a different angle with respect to the longitudinal axis of the hydrogen storage body 12.

[0086] In alternative embodiments, the shape of the plurality of fin elements 34 may be uniform, this may result in a uniform volumetric expansion region. Alternatively, the shape of the plurality of fin elements 34 may vary. For example, at least one fin element 34 may have a smaller lateral extent than when compared to another at least one fin element 34. This may result in a non-uniform volumetric expansion region. A plurality of fin elements 34 of the thermal transfer element 14 may be evenly or unevenly distributed along the longitudinal extent of the tubular core 32.

[0087] In the embodiment shown in Figure 5, the thermal transfer element 14 is connected to an inner surface of the capping plate 20. In the depicted embodiment, at least one thermocouple guide tube 36 extends through the capping plate 20. The at least one thermocouple guide tube 36 ensures that a thermocouple aligns with the thermal transfer element 14 for increased accuracy of measurement. The at least one thermocouple guide tube 36 may be positioned in any configuration that allows for efficient thermal measurement.

[0088] A plurality of thermocouple guide tubes 36 may be fitted with a step increase in distance from the tubular core 32 to allow for better monitoring of the thermal profile of the hydrogen storage bed 10. The thermocouple guide tubes 36 are preferably of a complementary size and dimension to any thermocouples for use.

[0089] Although not depicted, a heating element may be inserted into the tubular core 32 of the thermal transfer element 14. The heating element allows for control of heating requirements during unloading / discharging of the bed. In a preferred embodiment, the heating element may be formed as a cartridge heater. In some embodiments, more than one heater element may be inserted into the tubular core 32. Also, although not depicted, at least one thermocouple may be placed into the at least one thermocouple guide to monitor the thermal profile of the hydrogen storage bed 10. The heating element may be controlled using a heater controller. The heater controller may accept multiple sensors and work as ON / OFF or PID control mode.

[0090] As best shown in Figure 6, in embodiments, the capping plate 20 has a heater insert aperture 38 to allow for the insertion of a heater into the tubular core 32 of the thermal transfer element 14. In embodiments, when the hydrogen storage body 12 is used in conjunction with a secondary vessel, the heater insert aperture 38 may have a ceramic insulator 40 to acts to inhibit thermal bridging. A ceramic insulator 40 may help to reduce heat loss from the hydrogen storage body 12 to the secondary vessel, and to the environment. The ceramic insulator 40 may also help to ensure safe operation of the supporting components and that no energy is lost during dehydriding when the hydrogen storage body is heated. Prevention of energy loss is key for improving the overall efficiency of the hydrogen storage solution.

[0091] In embodiments, the capping plate 20 may also have a gas port aperture 42. The gas port aperture 42 acts as the inlet / outlet gas port for hydrogen. The gas port aperture 42 may have a filter attached to prevent metal hydride particles from leaving the hydrogen storage bed 10. In embodiments, the gas port aperture 42 may have ceramic insulator break material to prevent thermal bridging.

[0092] A method of assembly of an embodiment of the hydrogen storage bed 10 is detailed in Figures 7a to 7c. As shown in Figure 7a, the hydrogen storage body 12 is assembled by attaching the secondary flange 18 to seal an end of the hydrogen storage body 12. Insulating material 22 is then wrapped around the outer circumferential surface of the secondary flange 18. An insulative plate 24 may then be fitted to an outer surface of the secondary flange 18. The thermal transfer element 14, connected to the capping plate 20, is then positioned inside the hydrogen storage body 12, as shown in Figure 7b. As shown in Figure 7c, the thermal transfer element 14 is fully inserted into the hydrogen storage body 12. The capping plate 20 is then connected to the primary flange 16 to seal the hydrogen storage bed 10.

[0093] Although not depicted, gaskets may be used to seal the flanges. Preferably the gaskets are copper.

[0094] Although not depicted in the drawings, the hydrogen storage bed 10 preferably comprises a hydrogen storage material. The hydrogen storage material may be inserted during assembly once the secondary flange 18 is sealed on end of the hydrogen storage body 12. The hydrogen storage material may be cut into appropriate dimensions and loaded evenly between the fin elements 34 of the thermal transfer element 14 whilst the thermal transfer element 14 is inserted into the hydrogen storage body 12.

[0095] The hydrogen storage material may be a metal hydride. For example, the hydrogen storage material may be uranium hydride.

[0096] In some embodiments, the hydrogen storage bed 10 also comprises filters. The filters are preferably metallic filters. The filters may be arranged within the hydrogen storage bed 10 to prevent powder / s and particulate / s from leaving the hydrogen storage bed 10.

[0097] Referring to Figure 8, there is indicated an embodiment of a hydrogen storage bed, which is suitable for storing and releasing hydrogen. The hydrogen storage bed comprises a hydrogen storage body and a secondary vessel 46.

[0098] In the depicted embodiment of Figure 8, a length of the secondary vessel 46 is greater than a length of the hydrogen storage body 12 so as to provide a primary thermal bridging reduction region 48. It is envisaged that the hydrogen storage bed would work without the primary thermal bridging reduction region 48, however it is thought to be less beneficial, as increased heat transfer, and as such heat loss, would occur.

[0099] A hydrogen storage bed as described herein may be provided and operated without a secondary vessel. However, in some embodiments the addition of a secondary vessel as described herein may be describable from a safety perspective.

[00100] In embodiments, the ratio of the length of the hydrogen storage body 12 and the length of the secondary vessel 46 is in the range of about 1:1.10 to about 1:10, for example, in the range of about 1:15 to about 1:7, in the range of about 1:2 to about 1:5, or in the range of about 1:3 to about 1:6.

[00101] In embodiments, the ratio of the outer diameter OD of the hydrogen storage body 12 and the inner diameter IDlof the secondary vessel 46 is in the range of about 1:1.05 to about 1:5 for example, in the range of about 1:10 to about 1:45, in the range of about 1:2 to about 1:4, in the range of about 1:25 to about 1:35, for example the ratio of the outer diameter OD of the hydrogen storage body 12 and the inner diameter ID1 of the secondary vessel 46 may be about 1:09, or about 1:26, or about 1:47 or about 1:5.

[00102] As can be seen from Figure 8, the secondary vessel 46 may be sized and dimensioned so as to be complementary to the outer diameter OD1 of the primary flange 16 and outer diameter OD2, OD2a of the secondary flange 18. Therefore, a secondary thermal bridging reduction region 50 is formed due to the difference in diameter between the internal diameter ID1 of the secondary vessel 46 and the outer diameter OD of the hydrogen storage body 12.

[00103] The secondary vessel 46, as shown in Figure 9, has a gas inlet valve and a gas outlet valve 52a, 52b. The gas inlet and gas outlet valves 52a, 52b are configured to allow for cooling fluid, for example, nitrogen, to be introduced into the secondary thermal bridging reduction region.

[00104] As shown in the illustrated embodiment of Figure 9, the secondary vessel 46 has a tubular secondary vessel. The secondary vessel 46 has a secondary vessel flange 54 that extends from one end of the secondary vessel. An end plate 56 seals the secondary vessel flange 54. The secondary vessel 46 is suitable for high vacuum application. The secondary vessel is formed from stainless steel. Preferably the stainless steel is 316 L stainless steel. 316 L stainless steel is preferable for this application since it is a highly durable, corrosion and oxidation resistant material with a high melting point (about 1454 °C) and a high tensile strength (about 621 MPa). Alternative materials can be envisaged; however, these are likely to be less beneficial. The secondary vessel 46 is sealed at the end opposite to the secondary vessel flange 54.

[00105] In embodiments, the secondary vessel 46 preferably has a sampling tube 57 that extends through the secondary vessel. This may allow for monitoring of the temperature and pressure of the secondary thermal bridging reduction region. This is beneficial as it may allow a user to establish when more cooling fluid needs to be introduced into the secondary thermal bridging reduction region 50 by the gas inlet valve 52a.

[00106] The end plate 56 is best shown in Figure 10. The end plate 56 may have a heater insert flange 58. The heater insert flange 58 allows for the insertion of a heater into the tubular core 32 of the thermal transfer element 14. The heater insert flange 58 may be a Klein flange. The heater insert flange 58 may have a ceramic breaker 60 on the side of the heater insert flange 58 facing the hydrogen storage bed 10. A ceramic breaker 60 may help to reduce heat loss from hydrogen storage bed 10 to the secondary vessel 46 and the environment.

[00107] The end plate 56 may also have a thermocouple aperture 62 to allow for the insertion of at least one thermocouple into the hydrogen storage body 12, as shown in Figure 10. The end plate 56 also may have a gas inlet tube 64. The gas inlet tube 64 connects to the hydrogen storage body 12 via a stainless steel flexible tube 66.

[00108] A method of assembly of an embodiment of the hydrogen storage bed 10 is detailed in Figures 11a to lid. As shown in Figure 11a, the hydrogen storage body 12 is assembled by attaching the secondary flange 18 to seal an end of the hydrogen storage body 12. Insulating material is then wrapped around the outer circumferential surface of the secondary flange 18. An insulative plate may then be fitted to an outer surface of the secondary flange 18. The thermal transfer element 14, connected to the capping plate 20 is then positioned inside the hydrogen storage body 12, as shown in Figure lib. As shown in Figure lid, the thermal transfer element 14 is fully inserted into the hydrogen storage body 12. The capping plate 20 is connected to the primary flange 16 to seal the hydrogen storage body 12. The hydrogen storage body 12 is then inserted into the secondary vessel 46. The secondary vessel flange is sealed by attachment of the end plate. Examples

[00109] The following illustrates examples of the hydrogen storage bed and related aspects described herein. Thus, these examples should not be considered to restrict the present disclosure, but are merely in place to teach how to carry out the methods of the present disclosure. Example 1 - Hydrogen Storage Bed

[00110] In an example, a hydrogen storage bed was assembled. The example will be described in the context of Figures 7a - 9, with reference numerals used to aid understanding. The hydrogen storage bed 10 comprised a hydrogen storage body 12 of a half-nipple 316 L SS tube. The primary flange 16 had an outer diameter of 254 mm. The inner diameter of the hydrogen storage body 12 was 198.2 mm. The outer diameter of the hydrogen storage body 12 was 203.2 mm. The thickness of the wall of the hydrogen storage body 12 was 2.5 mm. The length of the hydrogen storage body 12 was 400 mm. A 3 mm thick copper hydrogen diffusion liner was used to line the inner surface of the hydrogen storage body 12. The presence of the copper hydrogen diffusion liner increased the thickness of the hydrogen storage body 12 wall to 5.5 mm, thus reducing the inner diameter of the hydrogen storage body to 192.2 mm. A GA-1000 copper gasket was used to seal the knife edge of the primary 16 and secondary flanges 18 at either end of the hydrogen storage body 12. The secondary flange 18 was made from stainless steel and brazed with copper. The secondary flange 18 had a blind hole of 50 mm formed in in diameter of the centre of the secondary flange 18, to accommodate a thermal transfer element 14. The hydrogen storage bed 10 comprised a secondary vessel 46 as shown in Figure 8 and 9, a 3 mm thick adhesive insulation material 22b made from silica was fitted across the circumference of the primary 16 and secondary flanges 18 to prevent thermal bridging. An alumina ceramic plate was fitted as an insulative plate 24 to the outer surface area of the secondary flange 18 to also prevent thermal bridging.

[00111] The capping plate 20 used was a 316 L stainless steel standard CF flange. A 43 mm Klein flange with a ceramic insulator break was used to form the heater insert aperture, to allow for insertion of a heater into the thermal transfer element 14. The capping plate 20 also had a gas port aperture. The gas port aperture was formed from a %-inch (1.91 cm) Swagelok male connection and a %-inch (1.91 cm male BSP thread on the inner side of the capping plate 20 facing towards the thermal transfer element 14. The %-inch (1.91 cm) male BSP thread allowed for the integration of a stainless steel cap filter. The stainless steel cap filter had a 5 pm pore size. The gas port aperture had ceramic insulator break material. Three stainless steel thermocouple guide tubes were welded to the inner side of the capping plate 20. Each stainless steel guide tube was 50 mm long and 3 mm in diameter. The inner side of the capping plate 20 was brazed with a 3 mm copper liner and sealed in place with a GA-1000 copper gasket.

[00112] A copper thermal transfer element 14 was used. The thermal transfer element 14 was formed of continuous copper fin elements in a clockwise helical configuration. The thermal transfer element 14 was fabricated using 3-D printing, but it is envisaged the thermal transfer element 14 may have been fabricated through machining a cylindrical copper block.

[00113] This copper thermal transfer element 14 configuration was used for effective heat transfer across the volume and to allow for redistribution of the material in the hydrogen storage bed 10. The copper thermal transfer element 14 comprised a hollow copper tubular core, with a length of 400 mm, an outer diameter of 48 mm, and a wall thickness of 2.5 mm. The copper fins were 3.5 mm thick. Each fin loosely compartmentalised the volume of the hydrogen storage bed 10 by allowing about 101 mm distance between each fin peak. The outer most diameter of the thermal transfer element 14 was 186 mm. A volumetric expansion region of 3 mm space was therefore formed between the thermal transfer element 14 and the hydrogen storage body 12.

[00114] The secondary vessel 46 comprised a half-nipple 316 L SS tube with a knife-edge seal mechanism fabricated by Kurt J Lesker. The outer diameter of the secondary vessel flange 54 is 336.55 mm. The secondary vessel had an outer diameter of 266 mm, and an inner diameter of 261 mm. The wall thickness of the secondary vessel was 2.5 mm. The secondary vessel was 508 mm long. Three welded stainless steel tubes were fitted to the secondary vessel. These welded stainless steel tubes included two one-inch (2.54 cm) stainless steel Swagelok tubes, combined with Swagelok SS 1-piece 40 series ball valves (part SS-45S8-1466) as the gas inlet valve 52a and a gas outlet 52b valve for cooling gas, and one 1 / 4-inch (6.35 mm) SS Swagelok sampling tube 57. The gas outlet 52b and gas inlet tubes 52a were welded at 132.5 and 397.5 mm distance from the end plate 56, respectively. The gas sampling port 57 was welded at 265 mm from the flange end down the length of the secondary vessel 46.

[00115] The secondary vessel end plate 56 was a modified flange with CF fitting based part no. FN-1325. Five penetration points were machined through its surface. A bellows flexible Klein heater insert flange was provided, to allow for insertion of a heater through the end plate of the secondary vessel into the thermal transfer element of the hydrogen storage bed. The heater insert flange included a ceramic breaker (to prevent thermal bridging). The Klein flanges was sealed using a CF flange connection (HN-0275). A %-inch (1.91 cm) Swagelok male connection for both the inner and outer surface of the secondary vessel end plate was also present, as well as a %-inch (1.91 cm) female stainless Swagelok flexible hose. The female stainless Swagelok flexible hose was used to connect the hydrogen storage bed and secondary vessel and act as the inlet / outlet of the hydrogen gas. Three thermocouple apertures with a 1 inch (2.54 cm) stainless steel port fitting on the outer surface of end plate we also present. Flexible thermocouples were fitted through the thermocouple apertures of the end plate into the thermocouple guide tubes of the hydrogen storage bed and sealed in place on the surface of the end plate. This way the thermocouples were easily retrieved / maintained or replaced without opening the hydrogen storage bed. Finally, a pair of 1 / 4-inch (6.35 mm) Swagelok female connections were welded to the end plate to be used as sampling ports for pressure measurement or gas composition in the inter-chamber space. The secondary vessel 46 was sealed using a GA-1325 copper gasket.

[00116] The flexible, and hydrogen ready hose used was a 316 L Stainless steel FL Hose with two %-inch (1.91 cm) female ends and a 38.1 cm length (part number SS-FL12TA12TA12-15). The extended length allows the hose to move and bed down to a radius of 6.4 inch (1 inch = 2.54 cm).

[00117] Cartridge heater elements were inserted to the tubular core of the thermal transfer element for the heating requirements of the hydrogen storage bed during unloading / discharging. Stainless steel-enclosed, cylindrically shaped heaters were used which had an outer diameter of 15 mm and were 400 mm length. The cartridge heaters also had an additional 500 mm glass fibre lead. Four heater elements were fitted into the central tube. Thermocouples with a 200 mm probe length were used for the hydrogen storage bed. Example 2 - LaNi5

[00118] The hydrogen storage bed according to the present invention can be used alongside a hydrogen storage material for the storage and release of hydrogen. One suitable hydrogen storage material is depleted uranium (DU). For DU, the volume expansion associated with phase transition from uranium (U) to DU (UH3) is 75 %, which is only valid for the material in its crystalline form. When finely divided and porous UH3 powder is formed during hydrogen charging, the expanded material can take-up 460 % of the initial volume, exhibiting a density as low as 3.4 g cm'3. As discussed above, the present inventors have identified that a desirable hydrogen storage bed needs to safely accommodate the volumetric change of the reactive material inside the bed as it takes up hydrogen. The following Example shows the hydrogen storage bed according to the present invention is capable of accommodating said volumetric expansion.

[00119] LaNi5was used in the following Example to serve as a surrogate to DU. LaNi5 exhibits similar volumetric expansion during conversion to metal hydride (volume expansion to its polycrystalline form is 50 % for LaNis and 75 % for DU) and similar average particle size during powderisation.

[00120] The hydrogen storage bed was loaded with 190 g of LaNi5. The hydrogen storage bed of the Example comprised a thermal transfer element. The thermal transfer element was in a helical copper configuration and arranged within the hydrogen storage body such than a 1 mm volumetric expansion region was provided. The thermal transfer element was found to allow the redistribution of expanding LaNis material. The thermal transfer element also acted as an efficient heat exchanger allowing homogeneous heat dissipation.

[00121] The hydrogen storage bed was evacuated to Ultra High Vacuum and cooled down to liquid nitrogen temperature which is the hydrogenation temperature for LaNi5. Once the temperature had stabilized to cryogenic conditions, the material was exposed to a constant H2 pressure of 1 MPa until the measured consumption of hydrogen was minimal. Before the reaction was stopped, the total consumption of H2 was 0.09 moles. Subsequently, the sample system was sealed while maintaining a headspace hydrogen pressure of 0.5 MPa and allowed to stabilize to room temperature.

[00122] During preparation, the hydrogen storage bed was subjected to considerable agitation. In the next step, the sample was connected to a scroll pump and left at room temperature overnight to allow for dehydriding of the material.

[00123] The sample was characterized using neutron radiography and neutron tomography. The radiograph and tomograph data collected during the absorption and desorption of hydrogen showed that the thermal transfer element, alongside the volumetric expansion region, reduced stress in the hydrogen storage bed caused from compression of the expanded material as it converted into powder. As such, the hydrogen storage bed was able to accommodate the volumetric expansion of LaNi5. Furthermore, the provision of the thermal transfer element comprising a fin element configured to allow the redistribution and expansion of a hydrogen storage material was shown to facilitate even distribution, and reduce compaction, of LaNi5in the hydrogen storage bed in both the hydrided and dehydrided state. This is advantageous as even distribution allows for homogeneous heat transfer across the bed walls and reduction of thermal gradients and hot-spot formation during these processes.

[00124] In this Example it is demonstrated that the hydrogen storage bed design of the present invention allows for efficient hydriding / dehydriding. The present inventors found that the hydrogen storage bed of the present invention accommodated the volumetric expansion and subsequent desirable redistribution of the hydrogen storage material. The present inventors have also found that, if desired, volumetric expansion of the thermal transfer element itself can also be accommodated. The hydrogen storage bed was found to adequately protect the reactive hydrogen storage material inside the bed, effectively manage heat flow into and out of the bed to enable efficient loading and unloading of hydrogen, and safely accommodate the volumetric change of the reactive material inside the bed as it takes up hydrogen.

[00125] The inventors expect depleted uranium hydride to behave in a very similar manner to LaNi5, and as such expect the DU can be successfully used as hydrogen storage material in the hydrogen storage bed of the present invention.

[00126] DUH3 formation leads to an about 77 % volume expansion when compared to the parent metal and an approximate 5.6x increase in volume if the material is allowed to expand freely as a porous powder. The present inventors have found that volumetric considerations for the hydrogen storage body and mass of hydrogen storage material are important since they greatly affect both the loading and unloading rate of the hydrogen storage bed. Since the present inventors found that the hydrogen storage bed of the present invention accommodated volumetric expansion, it is envisaged be suitable for use with DU.

[00127] The rates of hydrogen loading / unloading of a depleted uranium bed are mainly governed by the heat (thermal conductivity) and mass transfer (gas conductance) within the system. Thus, characteristics of the bed design such as heat-enhancing components, degree of hydride powder compaction, etc. play a pivotal role in the kinetics of the system. For example, if the heat transfer coefficient of the bed is poor, the increase in temperature during to exothermic loading will result in an increase in the equilibrium hydrogen pressure. Hence, even though the kinetics will initially accelerate with temperature, as the equilibrium pressure approaches the hydrogen charging pressure the kinetics of the system will decelerate. The thermal transfer element of the present invention was found to the allow for efficient hydriding / dehydriding of LaNi5, and so it is thought that DU may be successfully used as hydrogen storage material in the hydrogen storage bed of the present invention. Example 4 - UH3 Powder Preparation

[00128] The formation of a metallic uranium powder from a precursor metallic coupon was examined by the inventors. Powderisation was achieved by repeated cycles of hydride (UH3) formation and then hydride thermal decomposition; termed as 'hydriding and dehydriding'. After each cycle a small mass of particulate material was extracted for electron microscopy analysis to understand how the size and morphology of the arising powder changed from one cycle to the next.

[00129] Particulate uranium was produced in-situ on the gas rig by performing a series of hydriding and dehydriding cycles on a piece of uranium metal. The procedure was the same whether hydrogen or deuterium was used as the reacting gas, and the term 'hydriding' is used as the catch all term for both unless otherwise stated.

[00130] Metal preparation: The uranium coupons used were relatively large (about 3 g). Therefore, inside a glovebox these were cut to 0.3 g samples to reduce the quantity of material used.

[00131] The metal was cleaned of its surface oxide by submerging it for one minute in 10% nitric acid diluted with deionised water. This was then washed in ethanol, dried, weighed and then gasket sealed in a reaction cell (with thermocouple attachment). The reaction cell ('bed') was placed in a clam-shell furnace, attached to the gas control rig and evacuated ready for H2 / D2 exposure.

[00132] Gases: The gas used was either: H2,99.9997% supplied by Air Products or; D2 99.8% supplied by Isotec.

[00133] Hydriding-dehydriding: With the sample under vacuum, the furnace was then set to 240 °C to maintain a pressure of about 55000 Pa in the reaction cell from a fixed volume of H2 in the reservoir lines. From monitoring of the reservoir pressure, it could be seen that hydriding was complete when the pressure no longer decreased. The pressure controller was closed, the cell evacuated and sealed, and the furnace set to 600 °C. Dehydriding was observed to have begun when gas pressure in the cell started to rise and to have completed when the pressure had plateaued. The cell was then reevacuated, sealed to check for any further pressure increase indicative of any unreleased hydrogen, reopened to the vacuum and the furnace switched off. This cycle was repeated up to 10 times to ensure the complete comminution of the sample.

[00134] As described the starting material was solid coupons that then went through numerous hydriding and dehydriding cycles to produce a fine uranium particulate. It is considered that for uranium storage beds used for larger-scale hydrogen storage, a similar conditioning process should be used to prepare each 'bed' module for operation. By starting with precursor pellets of solid-uranium metal bed preparation is rapid and can be performed safely in a glove box or even air due to the low surface area of the uranium metal.

[00135] Once bed powderisation is completed, the resulting powder material was found to be very volatile. Characterisation of powders had to occur post reaction.

[00136] Comparison of particulates produced from increasing numbers of hydriding-dehydriding cycles indicated that after seven cycles the characteristics of the residual powders remained effectively the same in terms of particle size, morphology and surface area. This is an important conclusion for hydrogen storage application as it demonstrates an effective 'conditioning' sequence for uranium hydrogen storage beds, when starting from solid uranium metal pellets. Conclusions

[00137] This study presents a new approach to hydrogen storage, offering improved hydrogen storage efficiency, with improved volumetric expansion capabilities, hydrogen storage material redistribution, pressure, which could be particularly advantageous for use in larger scale applications.

[00138] The present inventors surprisingly found that a hydrogen storage bed according to the present invention accommodated the volumetric expansion of the hydrogen storage material and allowed for the redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material. The hydrogen storage bed was found to adequately protect the reactive hydrogen storage material inside the bed, effectively manage heat flow into and out of the bed to enable efficient loading and unloading of hydrogen, and safely accommodate the volumetric change of the reactive material inside the bed as it takes up hydrogen.

[00139] The present inventors have surprisingly found that the hydrogen storage bed described herein can be used to deliver large quantities of hydrogen as a sustainable energy source. In particular, due to the configuration of the hydrogen storage bed described herein allowing for redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material, it has been found to be possible to provide thermal energy to the hydrogen storage material in the hydrogen storage bed efficiently in order that hydrogen may be efficiently (and quickly) be unloaded from the hydrogen storage material.

[00140] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[00141] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[00142] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[00143] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[00144] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word "comprise" and "include", and variations such as "comprises", "comprising", and "including" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[00145] It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent "about," it will be understood that the particular value forms another embodiment. The term "about" in relation to a numerical value is optional and means for example + / -10%. References Okumura (2012) - Okumura, Masahiko, et al. "Investigation of wall stress development and packing ratio distribution in the metal hydride reactor." International journal of hydrogen energy 37.8 (2012): 6686-6693. Kawamure (1982) - Kawamura, M., S. Ono, and Y. Mizuno. "Stress induced in metal hydrogen powder bed by hydriding reaction." Metal-Hydrogen Systems. Pergamon, 1982. 489-500 Penzhorn (1990) - R.-D. Penzhorn, M. Sirch, Evaluation of ZrCo and other getters for tritium handling and storage, Journal of Nuclear Materials 170 (1990) 217-231. Shmayda (2021) - W. Shmayda, Fundamentals of Tritium handling, Presentation at Transversal Actions for Tritium (TRANSAT) - 2nd Tritium School, (2021). Banos (2022) - Validating the Nuclear Option for Hydrogen Storage - A Banos, TB Scott WM2022 Conference, March 6- 10, 2022, Phoenix, Arizona, USA2022 Yartys and Lototsky (2004) - Overview of hydrogen storage technologies with final concentration on metal hydride storage: An Overview of Hydrogen Storage Methods V. A. Yartys &M. V. Lototsky -Hydrogen Materials Science and Chemistry of Carbon Nanomaterials, 75-104 - Conference paper. Meng (2006) - Ni, Meng. "An overview of hydrogen storage technologies." Energy exploration &exploitation 24.3 (2006): 197-209. Ramin and Growth (2019) - Hydrogen storage and delivery: Review of the state of the art technologies and risk and reliability analysis." International Journal of Hydrogen Energy 44.23 (2019): 12254-12269.

Claims

1. A hydrogen storage bed for storing and releasing hydrogen, the hydrogen storage bed comprising:a hydrogen storage body; anda thermal transfer element comprising a fin element configured to allow the redistribution and expansion of a hydrogen storage material within the hydrogen storage body during hydrogen loading and unloading of the hydrogen storage material.

2. A hydrogen storage bed according to claim 1, wherein the fin element is a helical fin element.

3. A hydrogen storage bed according to claim 2, wherein the helical fin element has a helix angle in the range of about 10° to about 40°.

4. A hydrogen storage bed according to any of the preceding claims, wherein the hydrogen storage body is lined with a hydrogen diffusion liner, the hydrogen diffusion liner formed from a material suitable for preventing hydrogen ingress into the hydrogen storage body.

5. A hydrogen storage bed according to any of the preceding claims further comprising a hydrogen storage material.

6. A hydrogen storage bed according to claim 5, wherein the hydrogen storage material is depleted uranium.

7. A hydrogen storage body according to any of the preceding claims, wherein the thermal transfer element is removable from the hydrogen storage body.

8. A hydrogen storage bed according to any of the preceding claims, wherein the hydrogen storage body has an internal diameter, and the thermal transfer member has an outer most diameter, andwherein the outer most diameter of the thermal transfer element is at least about 80% of the internal diameter of the hydrogen storage body, for example at least about 90% of the internal diameter of the hydrogen storage body, or at least about 95% of the internal diameter of the hydrogen storage body.

9. A hydrogen storage bed according to any of the preceding claims, wherein the hydrogen storage body has an internal diameter, and the thermal transfer member has an outer most diameter, andwherein the outer most diameter of the thermal transfer element is in the range of about 80% to about 99.9% of the internal diameter of the hydrogen storage body, for example in the range of about 90% to about 98% of the internal diameter of the hydrogen storage body.

10. A hydrogen storage bed according to any of the preceding claims further comprising a primary and a secondary flange, wherein the primary flange and the secondary flange are configured to seal the hydrogen storage body.

11. A hydrogen storage bed according to any of the preceding claims further comprising a secondary vessel, the hydrogen storage body positioned within the secondary vessel.

12. A hydrogen storage bed according to claim 11, wherein the hydrogen storage body is connected to the secondary vessel via a thermal bridging limiting material.

13. A method of storing hydrogen, the method comprising:providing a hydrogen storage bed according to any of the preceding claims;placing a hydrogen storage material in the hydrogen storage bed; exposing the hydrogen storage material to hydrogen; and sealing the hydrogen storage bed.

14. A method of providing hydrogen, the method comprising:providing a hydrogen storage bed according to any of claims 1-12, the hydrogen storage bed comprising a hydrogen storage material which has been exposed to hydrogen; andreleasing the hydrogen from the hydrogen storage material.

15. A method of providing hydrogen according to claim 14, wherein releasing hydrogen from the hydrogen storage material comprises heating the hydrogen storage material.31

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