Hydrogen Storage and Compression Systems

Abstract

The hydrogen storage system (1) comprises a casing (2), a plurality of storage-compression vessels (6) forming at least one multi-container unit (4), and a metal hydride (MH) configured for hydrogen storage contained within each of the storage-compression vessels. The storage-compression vessels of the at least one multi-container unit are interconnected in direct fluid communication by gas flow tubes such that gas pressures within the plurality of vessels are substantially identical. The storage-compression vessels are mounted within a chamber (16) of the casing, the casing being configured to maintain a vacuum within the chamber for leak testing the at least one multi-container unit.

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for storing and compressing hydrogen using metal hydrides. [Background technology]

[0002] Hydrogen storage is an important tool in the transition away from fossil fuel technologies with renewable energy. Various storage methods have been considered, including gas compression, hydrogen liquefaction, and absorption into solid materials.

[0003] Metal hydrides are of great interest for the storage and compression of hydrogen because many metals and alloys can reversibly absorb large amounts of hydrogen and compress it by heating.

[0004] Before absorption, molecular hydrogen is dissociated at the surface of the metal hydride. After dissociation, the two H atoms then recombine to form H2. The hydrogen absorption reaction into the material is typically exothermic (generates heat), whereas the hydrogen dissociation reaction is endothermic (absorbs heat).

[0005] The metal hydride storage-compression system can be used as a storage-compressor unit to release and supply hydrogen isobarically and non-pulsatingly at the required high pressure level by adding the necessary heat for release.

[0006] To accommodate the storage-compression requirements of many applications, hydrogen storage-compression systems typically comprise multiple containers, which are interconnected by assembled joints and typically partitioned by valve mechanisms. Given the exothermic reactions during hydrogen absorption and endothermic reactions during hydrogen release, where the temperature inside the container affects the absorption and release rates and pressure, precise control of the process and a certain degree of complexity of the storage system are required to optimize the delivery and storage functions, but this latter may reduce the reliability of the system. Also, conventional metal hydride hydrogen storage tanks are often not ideal with regard to the heat transfer requirements during the heating phase, absorption, or release. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] PCT / EP2020 / 059860 Summary of the Invention [Problem to be solved by the invention]

[0008] One object of the present invention is to provide a hydrogen storage and compression system that is efficient, compact, safe and easy to use and maintain.

[0009] It would be advantageous to provide a hydrogen storage and compression system that is cost effective to manufacture and operate. [Means for solving the problem]

[0010] The object of the present invention is achieved by providing a hydrogen storage and compression system as claimed in claim 1.

[0011] Disclosed herein is a hydrogen storage-compression system comprising a casing, a plurality of storage-compression vessels forming at least one multi-container unit, and a metal hydride (MH) configured to store and compress hydrogen contained within each of the storage-compression vessels, the plurality of storage-compression vessels of the at least one multi-container unit being interconnected in direct fluid communication by gas flow tubing such that gas pressures within the plurality of vessels are substantially the same.

[0012] A plurality of storage-compression vessels are mounted within a chamber of a casing, the casing being configured to maintain a vacuum within the chamber for leak testing of the storage-compression vessels. The hydrogen storage-compression system further comprises a vacuum system comprising a vacuum pump coupled to the casing.

[0013] The vacuum pump may be configured to generate a vacuum inside the casing chamber during operation of the hydrogen storage-compression system, for example at least during a heating phase of the hydrogen storage-compression vessel.

[0014] In one embodiment, the hydrogen storage-compression system further comprises a heating system configured to heat each of the storage-compression vessels mounted within the casing.

[0015] In one advantageous embodiment, the heating system comprises an electric heating element mounted on the hydrogen storage and compression vessel.

[0016] In one advantageous embodiment, the heating system comprises an electric heating element mounted on or in the hydrogen storage and compression vessel.

[0017] In one advantageous embodiment, an electric heating element is attached to one end of the hydrogen storage-compression vessel and a heat transfer jacket or layer extends along and across the storage-compression vessel from the heating element to the other end of the storage-compression vessel.

[0018] In one embodiment, the heating system includes a heating fluid inlet to the casing configured to inject a heated fluid into the chamber of the casing.

[0019] In one advantageous embodiment, the heating fluid is steam.

[0020] In an advantageous embodiment, other heat transfer media, such as thermal oil or thermal water, may be used as the heating fluid.

[0021] In an advantageous embodiment, the hydrogen storage-compression system further comprises a cooling system configured to cool each of the storage-compression vessels mounted within the casing.

[0022] In one advantageous embodiment, the cooling system comprises a cooling fluid inlet to the casing configured to inject cooling fluid into the chamber of the casing.

[0023] In one embodiment, the cooling fluid is air.

[0024] In one embodiment, the cooling fluid is water.

[0025] In an advantageous embodiment, the tubular vessel of each storage-compression vessel has an outer diameter D in the range of 1.2 cm to 10 cm. Adjacent vessels of the plurality of storage-compression vessels of the module are spaced apart by a gap G in the range of distances corresponding to 0.02×D to 1×D, preferably in the range of 0.05×D to 0.5×D.

[0026] In an advantageous embodiment, the outer diameter D of the tubular vessel of each storage-compression vessel is in the range 2 cm to 8 cm, preferably in the range 3 cm to 6 cm, for example in the range 4 cm to 5 cm.

[0027] In an advantageous embodiment, the gap G between the storage-compression vessels is in the range of 0.1×D to 0.4×D.

[0028] The storage-compression vessel may have a length L in the range of 30 cm to 600 cm. In an advantageous embodiment, taking into account practicalities in manufacturing, installation, and maintenance, the storage-compression vessel has a length in the range of 60 cm to 200 cm, preferably in the range of 80 cm to 150 cm.

[0029] In one advantageous embodiment, the gas flow tube comprises a T-shaped connecting tube having a cap tube section extending substantially in an axial direction corresponding to the axis of the tubular vessel wall and a transverse tube section extending substantially perpendicular to said axial direction and welded to a first end of the cap tube section, the second end of the end cap tube section being welded to the inlet cap of the storage-compression vessel.

[0030] In one advantageous embodiment, the ends of the transverse tube sections are welded to the ends of the transverse tube sections of an adjacent or opposing storage-compression vessel.

[0031] In one advantageous embodiment, the storage-compression vessel at one end of the row is provided with an L-shaped or elbow-shaped connecting tube extending from the inlet cap to one end of the lateral tube section of the adjacent storage-compression vessel.

[0032] In one embodiment, the storage-compression vessels of a multi-container unit are arranged in a row, with the axes A of the vessels being parallel to one another.

[0033] In another embodiment, the storage-compression vessels of a multi-container unit are arranged in two parallel rows arranged in opposing relation such that the gas flow tube is positioned between the two rows, and the axes A of the vessels are parallel to each other.

[0034] In one advantageous embodiment, each multi-container unit includes a filter positioned on the inner side of the inlet cap covering the inlet / outlet, thereby preventing metal hydride particles from escaping the chamber through the inlet / outlet.

[0035] In one advantageous embodiment, the filter comprises or consists of a sintered metal disc welded at its periphery to the inlet cap.

[0036] In an advantageous embodiment, the vessel walls, inlet and end caps, and gas flow tubes are made from a hydrogen-, pressure-, and heat-resistant, and easily weldable metal, which can be stainless steel, modified carbon steel, aluminum alloy, or Cu-Ni alloy.

[0037] In one advantageous embodiment, a plurality of multi-container units are configured as a stack of multi-container units forming a storage-compression module configured to contain hydrogen gas at a common pressure.

[0038] In one advantageous embodiment, the multiple vessel units of the module are fluidly interconnected together and connected to valves for further connection to hydrogen consumption and generation systems.

[0039] In one advantageous embodiment, a number of said multi-container units are assembled in a stack within a support structure for connection to a common hydrogen production and consumption system or network.

[0040] In one embodiment, the hydrogen storage-compression system according to the present invention may be used as a near-isobaric and pulsation-free hydrogen supply system capable of absorbing and releasing hydrogen at high pressure, preferably above 50 bar, more preferably above 200 bar, and releasing hydrogen at substantially constant pressure with minimal temperature change, preferably with a temperature change of less than 40° C., more preferably with a temperature change in the range of 20° C. to 30° C.

[0041] In one embodiment, a hydrogen storage-compression system according to the present invention may be used to compress the hydrogen gas leakage stream from a labyrinth seal system to the suction pressure of a device such as, for example, a mechanical gas compressor or a cryopump.

[0042] In one application, the hydrogen storage-compression system may be advantageously used as a near-isobaric hydrogen supply system for absorbing and releasing hydrogen at high pressure, preferably above 50 bar, more preferably above 200 bar, and for releasing hydrogen at substantially constant pressure with minimal temperature change, preferably with a temperature change of less than 40° C., more preferably with a temperature change in the range of 20° C. to 30° C.

[0043] In one application, the hydrogen storage-compression system may be advantageously used to compress the hydrogen gas leakage stream from a labyrinth seal system to the suction pressure of an apparatus such as, for example, a mechanical gas compressor or a cryopump.

[0044] In one application, the hydrogen storage and compression system may be advantageously used to deliver hydrogen into a gas grid in a vibration- and pulsation-free manner.

[0045] Other objects and advantages of the present invention will become apparent from the appended claims, the following detailed description and the accompanying drawings.

[0046] The invention will now be described with reference to the accompanying drawings, which show, by way of example, embodiments of the invention. [Brief description of the drawings]

[0047] [Figure 1] FIG. 1 is a schematic cross-sectional view of a hydrogen storage-compression system according to one embodiment of the present invention, in which heating and cooling are achieved via a supply of a heat transfer medium. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a hydrogen storage and compression system according to another embodiment of the present invention in which the required heating power is provided by electrical resistance heating. [Diagram 3] FIG. 1 is a schematic cross-sectional view of a hydrogen storage and compression system according to another embodiment of the present invention, in which the required heating power is provided by electrical resistance heating, with an additional heat spreader system to ensure uniform temperature distribution. [Figure 4]FIG. 4 is a schematic cross-sectional view of a multi-container storage unit of the module of FIGS. 1 to 3. [Diagram 5] FIG. 5 is a schematic cross-sectional view of one storage-compression vessel of the unit of FIG. 4. [Figure 6a] 2 is a schematic diagram of a cross-sectional configuration of a container within a casing of a hydrogen storage system according to an embodiment of the present invention. FIG. [Figure 6b] 2 is a schematic diagram of a cross-sectional configuration of a container within a casing of a hydrogen storage system according to an embodiment of the present invention. FIG. [Figure 7] FIG. 1 is a graph of pressure (In P) versus inverse temperature (1000 / T) for a combination of multiple compression stages using different metal hydride materials to achieve high compression ratios with moderate temperature differences in accordance with an embodiment of the present invention. [Figure 8] FIG. 1 is a schematic diagram of a hydrogen storage and compression system according to an embodiment of the present invention coupled to an apparatus, such as a mechanical gas compressor or cryopump, in which a hydrogen leak stream from a labyrinth seal of the apparatus is compressed and returned to the suction pressure of the apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Referring to the figure, a hydrogen storage and compression system 1 according to an embodiment of the present invention comprises a pressure resistant casing 2 and one or more storage and compression modules 10 mounted within a chamber 16 defined by the casing. The storage and compression modules are for fluid connection to one or more hydrogen sources (not shown) and one or more hydrogen consumers (not shown). A support structure (not shown) may be provided for supporting the storage and compression modules within the casing. The storage and compression module 10 comprises a plurality of storage and compression vessels 6, each vessel 6 containing a metal hydride MH configured to store hydrogen as described in more detail below.

[0049] The hydrogen source may be, for example, an electrolyzer that utilizes renewable energy to produce hydrogen from water or other hydrogen-containing molecules. The hydrogen consumer may be, for example, a fuel cell for producing electricity from hydrogen gas, or in the form of compressed hydrogen storage tanks for mobile applications or other devices for further storage or consumption of hydrogen.

[0050] One example of the use of the hydrogen storage-compression system according to an embodiment of the present invention is to store and compress hydrogen produced by a hydrogen generation system converting solar energy generated by a photovoltaic panel into hydrogen gas. The hydrogen gas then serves as a fuel to store the harvested energy, which can be converted into electrical, mechanical, or thermal energy using various energy conversion systems including fuel cells, internal combustion engines, or gas turbines, among others. Additionally, other alternatives can be considered, including producing various gases, such as methane or ammonia, for easier handling and storage. Thus, the hydrogen storage system can act as both a buffer and a compressor in a single device.

[0051] Other examples of typical applications of the hydrogen storage and compression system according to an embodiment of the present invention are as follows. - Hydrogen storage and compression for hydrogen vehicle refueling. - For the same applications as above, but powered by another source (wind, hydro, etc.). - The storage and compression of hydrogen produced as a by-product of chemical processes and later used to generate electricity. - any of the above applications, where the hydrogen is then used for other purposes, such as, for example, as a precursor for chemical reactions or as a fuel for thermal energy production. - Compression and reinjection of hydrogen leakage streams in devices with labyrinth seals.

[0052] According to one aspect of the invention, the hydrogen storage system 1 comprises a vacuum system 18 connected to the casing 2. The vacuum system comprises a vacuum pump 19 connected to the casing chamber 16 via a vacuum pump connection line 3a, the vacuum pump 19 being configured to create a vacuum within the casing chamber 16.

[0053] The vacuum within the casing chamber may serve one or more purposes.

[0054] In one embodiment, the vacuum generation may be utilized to test for gas leaks from the hydrogen-containing storage and compression module 10. Such leaks may be detected and quantified by directly detecting the leaking gas in the exhaust stream of the vacuum system 18.

[0055] In some embodiments, this vacuum testing may be performed continuously or intermittently to test the integrity of the hydrogen storage system, and in some embodiments, these tests may be performed prior to first use of the hydrogen storage system and / or at specific intervals, such as, for example, a planned maintenance interval, or after a failure or repair.

[0056] The casing 2 is configured to withstand a vacuum pressure within the chamber 16, which is typically less than 0.1 mbar, in other words to withstand an external pressure on the casing of at least about 1 bar.

[0057] In some embodiments, the vacuum system 18 may further serve the purpose of reducing convective heat transfer from the surfaces of the hydrogen storage-compression vessel 6 to the casing 2. Thus, the thermal energy generated from the heating element 21 is used to heat the contents of the hydrogen vessel rather than the surroundings of the hydrogen vessel.

[0058] In such a system, the hydrogen storage-compression system 1 may include a heating system 20 that includes an electric heating element 21 coupled to each storage-compression vessel 6 for directly heating the storage-compression vessel 6 .

[0059] In one embodiment, for example as shown in FIG. 2, an electric heating element 21 may be mounted within the storage-compression vessel 6 .

[0060] In one embodiment, for example as shown in Figure 3, an electric heating element 21 may be attached to the exterior of the storage-compression vessel 6 and a heat conducting element 22 may be provided on the vessel wall to spread the generated heat and reduce the temperature gradient within the storage-compression vessel 6. The heat conducting element 22 may be made of a material with high thermal conductivity, for example copper or aluminum.

[0061] Thus, if electrical heating is applied during the heating phase or during the endothermic process of hydrogen release, the vacuum prevents heat transfer to the casing by convection. In FIG. 2 an embodiment with direct electrical heating of the storage-compression vessel 6 during hydrogen release is shown. In this embodiment, cooling during the hydrogen absorption phase can be performed by a cooling system 24 using a cooling fluid, in particular air, injected into the casing chamber 16 via the cooling fluid connection 3c. The cooling fluid can be circulated inside the casing chamber by a ventilator or a gas pump to generate a fluid circulation for forced convection.

[0062] In another embodiment of the invention shown in FIG. 3, the electric heating element 21 may be supplemented with a heat conducting element 22 to ensure a uniform temperature distribution.

[0063] In another embodiment shown in FIG. 1, the heating system 20 comprises a heating fluid inlet connection 3b for allowing a heated fluid, such as steam, to be injected into the chamber 16 of the casing during the heat absorption phase. The steam can be discharged via a drain connection 3d controlled by a valve V. In the embodiment shown, the cooling system 24 can be realized by injecting a cooling fluid, for example water, into the chamber 16 of the casing via the cooling fluid connection 3c and discharging it via the drain connection 3d. However, it can be said that the connection for the heating fluid can also be used for the cooling fluid, in other words a single inlet can be provided, which can be switched, for example by a valve system between a heating fluid source and a cooling fluid source. There can also be a single outlet for the vacuum pump and the drain, connected by a valve system to the vacuum pump and the drain circuit, respectively.

[0064] The storage-compression module 10 may be coupled to an overpressure relief system 23, such as comprising a pressure relief valve, a burst disk, or other component configured to relieve pressure in the storage-compression vessel 6 at a predetermined safety threshold.

[0065] A plurality of storage-compression vessels 6 interconnected by gas flow tubes 5 may form a multi-container unit 4. Each storage-compression module 10 may comprise one or more multi-container units 4. The storage-compression vessels 6 of each multi-container unit 4 are fluidly connected to each other in direct fluid communication without valves or pressure isolation means between the vessels such that the vessels 6 are at substantially the same gas pressure and therefore operate in parallel in absorbing and releasing hydrogen. Each storage-compression vessel 6 has a chamber 13 therein that contains a metal hydride MH configured to store hydrogen as is known per se in the art. Various metal hydrides may be filled in these vessels, for example as described in PCT / EP2020 / 059860.

[0066] Splitting the hydrogen gas volume among multiple vessels, as opposed to using a single vessel, allows for small vessels with high surface area to volume ratios that can be separated from one another by a distance G that provides better heat transfer during exothermic and endothermic reactions. Furthermore, the storage volume of each multi-container unit 4 can be easily expanded by adding additional storage-compression vessels 6 without essentially changing the heat transfer properties and behavior of the multi-container unit 4. The multiple storage-compression vessels 6 of one multi-container unit 4 can be arranged essentially parallel to one another, preferably aligned in a two-dimensional directional row as shown in FIG. 4.

[0067] A number of multi-container units 4 forming a storage-compression module 10 may be stacked on top of one another and / or arranged adjacent to one another. Advantageously, the multi-container units 4 forming one or more storage-compression modules 10 may be arranged in a substantially square manner (when viewed in cross section) as shown in FIG. 6a so as to fit well within a substantially cylindrical casing 2. Also, without departing from the scope of the invention, the multi-container units of a storage-compression module may be arranged in various other geometrical ways to fill the casing chamber 16 with a smaller volume footprint than would be the case in a square arrangement, as shown diagrammatically in FIG. 6b. More generally, although the multi-container units 4 of the storage-compression vessel 6 arranged in rows as shown are advantageous, the hydrogen storage-compression vessels may be arranged and interconnected in various other geometrical ways without departing from the scope of the invention.

[0068] Each storage-compression vessel 6 comprises a tubular vessel wall 6a closed at one end by an end cap 6b and at the other end by an inlet cap 6c which comprises an inlet / outlet 7.

[0069] 5, the inlet / outlet 7 comprises a substantially centrally positioned orifice in an inlet cap welded to a T-shaped connecting tube 8 of the gas flow tube 5. The storage-compression vessel 6 at one end of the row of vessels in the multi-vessel unit 4 comprises an elbow-shaped or L-shaped connecting tube 8c, while all other storage-compression vessels 6 are substantially identical and comprise substantially identical T-shaped connecting tubes 8.

[0070] Each of the T-shaped connecting tubes 8 comprises a cap tube section 8a extending substantially axially from the inlet cap 6c in the direction of the axis A of the tubular container wall 6a, and a transverse tube section 8b welded to the end of the cap tube section 8a.

[0071] The gaps G between adjacent storage-compression vessels serve to allow for good heat transfer during endothermic or exothermic reactions by forced convection of fluid through the stack of multi-container units 4.

[0072] Also, the length of the storage-compression vessel, in particular the tubular vessel wall 6a, can be easily set as needed to increase or decrease the volume of each multi-container unit 4, without substantially changing the heat transfer characteristics here. Thus, the thermal behavior of the multi-container unit can be substantially independent of the storage volume of the system.

[0073] An optimal heat transfer process for storage and compression of hydrogen using metal hydrides, taking into consideration weight, practicality in manufacturing, and economy, may be achieved by using storage-compression vessels 6 each having a diameter D in the range of 1.2 cm to 10 cm, preferably in the range of 2 cm to 6 cm, e.g., about 4.5 cm.

[0074] Taking into consideration practicality in manufacturing, installation, and maintenance, the practical length L of each storage-compression vessel may be in the range of 50 cm to 600 cm, but is preferably in the range of 80 cm to 200 cm, for example, in the range of 60 cm to 150 cm.

[0075] Preferably, the vessel wall material is made of stainless steel or other hydrogen resistant steel, such as modified carbon steel, aluminum alloy, or Cu-Ni alloy, and the end caps 6b, 6c are welded to both ends of the tubular vessel wall 6a, such as by orbital welding process (TiG welding). In the manufacturing process, the end cap 6b can be first welded to one end of the tubular vessel wall 6a, then metal hydride particles can be filled through the other end to about 70%-100% of the internal volume of the vessel 6, and then the inlet cap 6c can be welded to the other end of the tubular vessel wall 6a.

[0076] The vessel walls, end caps, and gas flow tubes are preferably made from stainless steel, but may be made from other weldable metals, such as modified carbon steels, aluminum alloys, or Cu-Ni alloys, etc. Composite materials may also be used for the vessel walls, end caps, and gas flow tubes without departing from the scope of the invention.

[0077] The inlet cap 6c is welded to the T-shaped manifold tube 8 before being welded to the tubular vessel wall 6a. The inlet cap may further comprise a filter 9 that is mounted inside the inlet cap over the inlet / outlet 7 and configured to prevent metal hydride particles from entering the gas flow tube 5 while allowing hydrogen to pass into the gas flow tube 5.

[0078] In one advantageous embodiment, the filter 9 is made from a sintered stainless steel disk, which can be welded at its outer periphery 9a to the inner side of the inlet cap 6c. The similarity of the materials makes the weld easy to perform. Furthermore, because similar or identical materials are used for the inlet cap 6c and the filter 9, the welded connection is robust and does not experience high thermal expansion forces due to similar thermal expansion coefficients.

[0079] Thus, each storage-compression vessel 6 with its inlet cap welded to the T-shaped connecting tube constitutes an integral component during the manufacturing process, which is connected together by welding together the ends 15 of the lateral tube sections 8b of adjacent storage-compression vessels to form a welded connection 11. The gas flow tubes 5 may also be made from stainless steel or other hydrogen resistant steels of the same or similar composition and the same or similar grade as used for the inlet caps 6c and end caps 6b and tubular vessel wall 6a. Because these gas flow tubes 5 are welded together at the ends 15 of the lateral tube sections 8b, further storage-compression vessels 6 can be easily added depending on the total storage volume desired in a cost-effective yet highly reliable and safe configuration during the manufacturing process.

[0080] The inlet cap 6c and the end cap 6b can be formed substantially by a stamping process, including machining a circular edge that forms a welding surface with the tubular vessel wall 6a, and this makes it possible to ensure a particularly robust structure that is economical to manufacture while being resistant to high pressures, and that offers a high degree of flexibility in terms of the volume that may be required for the desired application.

[0081] Thus, the multi-container unit 4 has a single inlet / outlet for the storage-compression vessels 6 when the storage-compression vessels 6 are welded together, which in turn is connected to the other multi-container units 4 via one or more valves V, and the multi-container units 4 are in a stack with gaps between them similar in size to the gaps G between the vessels of a unit, thereby providing natural or forced convection around each vessel of the system 2 for heat transfer during endothermic and exothermic reactions.

[0082] The storage-compression vessels 6 of multiple vessel units 4 in multiple layers, e.g., two, three or four layers, can be interconnected to form a single fluidly interconnected storage unit with a single common inlet and outlet to the valves. A number of these units may then be stacked or positioned adjacent to one another, or both stacked and positioned relative to one another, to form modules of a hydrogen storage system in which each unit may be individually filled and consumed in a desired sequence, as described, for example, in PCT / EP2020 / 059860. Also, different metal hydrides can be used for low and high pressure operation in different units or modules, as described in the above patent applications.

[0083] Process Description-Quality Control The casing 2 allows for leak testing under vacuum without the need for separate testing equipment. This leak testing can be performed before or during the first use of the hydrogen storage and compression system 1. Before the first use, helium can be filled inside the hydrogen storage and compression vessel 6 to at least the maximum operating pressure (i.e., the "design pressure") based on the design of the hydrogen storage and compression vessel. In some instances, higher pressures are required to comply with local codes and regulations (e.g., 10%, 25%, 50%, or even 100% of the design pressure). The reason for using helium rather than hydrogen is to prevent activation of the metal hydride material until qualification testing is completed. This is the first step of the integral pressure and leak testing, which confirms the structural integrity of the system at the design pressure.

[0084] As a next step, the vacuum pump 19 is operated to evacuate the air in the casing chamber 16. The pressure is reduced, typically to less than 0.1 mbar (absolute). A helium detector is positioned in the exhaust flow of the casing chamber to measure the helium concentration. The helium detector may be mass spectrometer based. The leakage flow rate from the hydrogen storage-compression vessel 6 to the casing chamber 16 can be directly measured based on the helium concentration. The leakage flow rate needs to be below a certain quality threshold, which is typically set at 2.0E-6 mbar*l / s.

[0085] A further advantage of this feature, for example in an embodiment using direct electrical heating as shown in FIG. 1, is that the casing chamber 16 is maintained under vacuum at all times, allowing continuous monitoring of the leakage flow rate during compression operations. In such an example, the vacuum system 18 allows for continuous monitoring of potential leakage, eliminating the need for manual inspection. The leak detector can monitor not only helium but also hydrogen, which is common in the case of mass spectrometers. Thus, this example provides increased certainty and safety when compared to other hydrogen storage options where the storage-compression vessel is directly exposed to the ambient environment.

[0086] Description of the operating process - embodiment with direct electrical heating In one exemplary advantageous configuration, a single storage-compression module 10 may be used, consisting of several multi-vessel units 4 connected in parallel to increase the flow rate of compressed hydrogen or to ensure a continuous flow of compressed hydrogen. The complete cycle of compression is carried out in single or multi-stage compression, from an initial supply pressure (typically 10-50 bar) to a delivery pressure (typically 50-950 bar). In the following paragraphs, the complete cycle of compression is described, including the following phases: (i) heating, (ii) discharge, (iii) cooling, and (iv) absorption. The exemplary values ​​given hereinafter are valid for a typical compression cycle from 35 bar (inlet) to 350 bar (outlet) in single stage and batch configurations (discontinuous hydrogen compression).

[0087] Heating and Ejection Phases At the start of the heating phase, hydrogen is present in the hydrogen-absorbing metal hydride material of the hydrogen storage-compression vessel 6 at a temperature of, for example, about 30° C. and a pressure of, for example, about 35 bar. The electrical heating systems 20, 21 are activated to provide the heat output required to increase the system temperature and, as a result, the system pressure.

[0088] In the exemplary embodiment of Figure 3, heat is conducted to the metal hydride through a heat spreader made of a highly thermally conductive material (e.g., copper), which allows for rapid heat conduction and reduced temperature differentials in the axial and radial directions. Radial heat conduction proceeds significantly more quickly toward the center of each hydrogen storage-compression vessel 6 than in the surrounding environment. This can be achieved by using a vacuum inside the chamber 16 of the casing 2 in which the hydrogen storage-compression vessel 6 is enclosed, thereby minimizing heat loss to the environment.

[0089] The hydrogen storage and compression vessel 6 is heated, for example, from p1=35 bar and T1=30° C., respectively, to p2=350 bar and T2=ca. 150° C. The process can continue to release hydrogen at substantially constant pressure (for example, p2=circa (ca.) 350 bar) and at approximately constant temperature (for example, T2=ca. 150° C.). Because the release reaction is endothermic, the system requires a heat supply until the metal hydride has released most of the hydrogen.

[0090] Cooling and Absorption Phase At the end of the release cycle, the hydrogen storage-compression vessel 6 is cooled, for example, from T2=ca. 150°C to T1=ca. 30°C. During this cooling phase, the hydrogen pressure is reduced, for example, from p2=350 bar to p1<35 bar. The vacuum chamber is filled with a cooling fluid, for example air, by opening the valve V on the cooling fluid connection line 3c. Cooling of the hydrogen storage-compression vessel is achieved by flowing this cooling fluid, the fluid flow rate and the resulting cooling capacity can be regulated by a fan or a gas compressor. The heat dissipation efficiency on the surface of the hydrogen storage-compression vessel 6 is further enhanced by a highly thermally conductive layer 22.

[0091] At the end of the cooling phase, the hydrogen supply is opened to allow hydrogen to flow at a lower operating pressure, e.g. p1 = 35 bar. Since the absorption is exothermic, heat rejection is required so that the temperature and pressure remain substantially constant. This is achieved by a cooling fluid (e.g. air) flow through the cooling fluid connection line 3c.

[0092] Description of the Operating Process - an embodiment including heating with a heating fluid (e.g. steam) and cooling with a cooling fluid (e.g. water) In an exemplary advantageous configuration, a single storage-compression module 10 may be used with several multi-container units 4 connected in parallel to increase the flow rate of compressed hydrogen or to ensure a continuous flow of compressed hydrogen. The complete compression cycle is carried out in a single stage or in multiple stages, from an initial supply pressure (e.g. typically 10-50 bar) to a delivery pressure (e.g. typically 50-950 bar). In the following paragraphs, the complete compression cycle is described, including the following phases: (i) charging, (ii) heating, (iii) discharging, and (iv) cooling. The values ​​given below are valid for a typical compression cycle from about 35 bar (inlet) to 350 bar (outlet) in single stage and batch configurations (discontinuous hydrogen compression). This embodiment can be extended to multiple stages and / or continuous operation, which allows lowering the required temperature and providing a continuous hydrogen supply.

[0093] Filling of hydrogen storage-compression module Hydrogen is delivered from the supply line at a pressure of, for example, about 35 bar and a temperature of, for example, about 30° C. In order to maintain a constant pressure and temperature, the hydrogen storage-compression vessel 6 needs to be continuously cooled during this phase since the absorption reaction is exothermic. Cooling of the hydrogen storage-compression vessel 6 is achieved by direct contact of the vessel wall with a cooling fluid, for example water, thereby achieving efficient heat transfer. The temperature of the hydrogen storage-compression module can be controlled by the cooling fluid (for example water) flow, which is preferably regulated by a variable speed pump or a control valve. Once the filling process is completed, the cooling fluid (for example water) is discharged from the casing chamber 16 via a drain connection 3d, for example arranged at the bottom of the casing 2.

[0094] heating The process then continues by heating the hydrogen storage-compression module 10, for example from about 30° C. to 150° C., with a corresponding pressure increase, for example from about 35 bar to 350 bar. This heating is achieved by injecting a flow of a heating fluid, for example advantageously compressed steam, into the chamber 16 of the casing 2 and flowing it across the hydrogen storage-compression vessel 6. This makes use of the concentration enthalpy of water and makes it possible to maintain a large temperature difference between the steam and the walls of the hydrogen storage-compression vessel during the heating process. An efficient control of the heating capacity can be achieved by regulating the steam pressure.

[0095] Emission: The module is then heated so that hydrogen is released at the required pressure, for example about 350 bar. Similarly as for the previous phase, compressed steam may advantageously be used for this process.

[0096] cooling: The process continues with cooling of the hydrogen storage and compression vessel 6. This reduces the temperature from a temperature such as about 150°C to a starting temperature such as about 30°C.

[0097] Examples of Hydrogen Storage and Compression Systems for Certain Applications (I) In many industrial applications, hydrogen gas is trapped in a certain volume by the use of so-called labyrinth seals. In such instances, there is always hydrogen leakage from the trapped volume. A metal hydride hydrogen compressor can be used to compress this leakage flow and pump it back into the system at high suction pressure. One typical application of this system is for example in a labyrinth seal reciprocating piston compressor 26 or possibly a labyrinth seal turbo compressor. Such a typical application is shown in FIG. 8. The hydrogen flow from the labyrinth seal 25 is absorbed in the metal hydride hydrogen storage and compression system 1 and then compressed to the suction pressure so that it is re-injected isobarically and pulsation-free into the suction flow of the piston compressor 26. The metal hydride hydrogen storage and compression system 1 can potentially be used for any hydrogen compressor using a labyrinth seal system.

[0098] Examples of Hydrogen Storage and Compression Systems for Certain Applications (II) Another application of the described hydrogen storage and compression system can be the injection of hydrogen into existing natural gas infrastructure or compressed hydrogen storage systems. Currently, conventional reciprocating piston or diaphragm compressors are used. However, these devices induce vibrations and pulses that are harmful to gas pipelines. The described metal hydride hydrogen storage and compression system can be used to compress hydrogen and deliver it isobarically, pulsation-free and vibration-free into existing natural gas grids. [Explanation of symbols]

[0099] 1 Hydrogen storage and compression system 2 Casing 16 Casing chamber 3 Inlet / Exit 3a Vacuum pump connection 3b Heated fluid connection heating medium 3c Cooling fluid connection cooling medium 3d drain connection 18 Vacuum System 19 Vacuum Pump 20 Heating System 21 Electric heating element 22 Heat Transfer Elements heated fluid inlet 24 Cooling System cooling fluid 10 Storage-Compression Module 4. Multi-container units 6 Storage - Compression Vessels 6a Tubular container wall 6b End cap 6c Inlet cap 7 Inlet / Exit 9 Filters 9a Outer periphery 13 Storage-Compression Vessel Chamber MH Metal hydride 5 Gas flow tube 8 T-shaped connecting tube 8a Cap Tube Section 8b Transverse tube section 15 End 11 Welded joints 23 Overpressure Relief System V-Valve 12 Support structure Control System P Pressure Sensor T Temperature Sensor V-Valve Automatic Valve Control 26 Labyrinth seal reciprocating piston compressor 25 Labyrinth Seal D Storage-compression vessel diameter G Gap distance between adjacent containers L Container length

Claims

1. 1. A hydrogen storage and compression system (1) comprising a casing (2), a plurality of storage and compression vessels (6) forming at least one multi-container unit (4), and a metal hydride (MH) configured to store and compress hydrogen contained in each of the storage and compression vessels, the plurality of storage and compression vessels of the at least one multi-container unit being interconnected in direct fluid communication by a gas flow tube such that gas pressures within the plurality of vessels are substantially identical, the plurality of storage and compression vessels being mounted within a chamber (16) of the casing, the casing being configured to maintain a vacuum within the chamber for leak testing the at least one multi-container unit, the hydrogen storage and compression system (1) further comprising a vacuum system (18) comprising a vacuum pump (19) coupled to the casing.

2. 10. The hydrogen storage-compression system of claim 1, further comprising a heating system (20) configured to heat each of the storage-compression vessels mounted within the casing.

3. 3. The hydrogen storage and compression system of claim 2, wherein the heating system comprises an electric heating element (21) mounted on or in the hydrogen storage and compression vessel.

4. 4. The hydrogen storage-compression system of claim 3, wherein the electric heating element (21) is attached to one end of the hydrogen storage-compression vessel and a heat transfer jacket or layer (22) extends along and across the storage-compression vessel from the heating element to the other end of the storage-compression vessel.

5. 3. The hydrogen storage and compression system of claim 2, wherein the heating system comprises a heated fluid inlet (3b) to the casing configured to inject a heated fluid into the chamber of the casing.

6. 6. The hydrogen storage and compression system of claim 5, wherein the heated fluid is a vapor.

7. 10. The hydrogen storage-compression system of claim 1, further comprising a cooling system (24) configured to cool each of the storage-compression vessels mounted within the casing.

8. 8. The hydrogen storage and compression system of claim 7, wherein the cooling system comprises a cooling fluid inlet (3a) to the casing configured to inject a cooling fluid into the chamber of the casing.

9. 9. The hydrogen storage and compression system of claim 8, wherein the cooling fluid is air or water.

10. 2. The hydrogen storage-compression system of claim 1, wherein each storage-compression vessel comprises a tubular vessel wall (6a) and end caps (6b, 6c) closing both ends of the tubular vessel wall, the tubular vessel wall of each storage-compression vessel having a diameter D in the range of 1.5 cm to 10 cm, and adjacent vessels among the plurality of storage-compression vessels of the at least one multi-container unit (4) are separated by a gap (G) having a length in the range of 0.02×D to 1×D.

11. A hydrogen storage and compression system according to claim 10, wherein the diameter D of the tubular vessel wall of each storage and compression vessel is in the range of 2 cm to 8 cm, preferably in the range of 3 cm to 6 cm.

12. 11. The hydrogen storage-compression system of claim 10, wherein the gap (G) between the storage-compression vessels is in the range of 0.1×D to 0.5×D.

13. 11. The hydrogen storage and compression system of claim 10, wherein the storage and compression vessel has a length in the range of 60 cm to 200 cm, preferably in the range of 80 cm to 150 cm.

14. 11. The hydrogen storage and compression system of claim 10, wherein the gas flow tube (5) comprises a T-shaped connecting tube (8) having a cap tube section (8a) extending substantially in an axial direction corresponding to an axis of the tubular vessel wall and a transverse tube section (8b) extending substantially perpendicular to the axial direction and welded to a first end of the cap tube section (8a), and a second end of the end cap tube section (8a) is welded to an inlet cap (6a) of the storage and compression vessel.

15. 15. The hydrogen storage-compression system of claim 14, wherein the ends of the lateral tube sections (8b) are welded to the ends of the lateral tube sections of adjacent or opposing storage-compression vessels.

16. 16. The hydrogen storage and compression system of claim 15, wherein the storage and compression vessel at one end of the train is provided with an "L" or elbow shaped connecting tube (8c) extending from the inlet cap to one end of the lateral tube section of an adjacent storage and compression vessel.

17. 2. The hydrogen storage-compression system of claim 1, wherein the storage-compression vessels of the at least one multi-container unit are arranged in a row, with the axes (A) of the vessels being parallel to one another.

18. 2. The hydrogen storage and compression system of claim 1, wherein each multi-container unit comprises a filter (9) positioned on an inner side of the inlet cap covering the inlet / outlet (7) to prevent metal hydride particles from escaping from the chamber through the inlet / outlet.

19. 20. The hydrogen storage and compression system of claim 18, wherein the filter (9) comprises or consists of a sintered metal disk welded at its periphery to the inlet cap.

20. 10. The hydrogen storage and compression system of claim 1, wherein said multi-container unit and said gas flow tubes are made from stainless steel or other hydrogen resistant material.

21. 2. The hydrogen storage-compression system of claim 1, wherein a plurality of the multi-container units (4) are configured as a stack of multi-container units forming a storage-compression module (10) configured to contain hydrogen gas at a common pressure.

22. 2. The hydrogen storage and compression system of claim 1 for use as a near-isobaric hydrogen supply system for absorbing and releasing hydrogen at high pressure, preferably above 50 bar, more preferably above 200 bar, and for releasing said hydrogen at substantially constant pressure with minimal temperature change, preferably with a temperature change of less than 40° C., more preferably with a temperature change in the range of 20° C. to 30° C.

23. 13. The hydrogen storage and compression system of claim 1, used to compress a hydrogen gas leakage stream from a labyrinth seal system to the suction pressure of a device such as a mechanical gas compressor or a cryopump.

24. 13. The hydrogen storage-compression system of claim 1, used to deliver hydrogen in a vibration- and pulsation-free manner into a gas network or into a compressed hydrogen storage system.

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