Hydrogen storage device

Abstract

To provide a hydrogen storage device utilizing a hydrogen storage alloy capable of releasing hydrogen gas of higher pressure at lower temperature.SOLUTION: A hydrogen storage device includes first to third containers with a hydrogen storage alloy. The first container is connected to heating and cooling sections. Hydrogen gas can flow between the first and second containers. The second and third containers can transfer heat to each other. The third container is connected to a hydrogen supply source and a hydrogen supply target. A range of equilibrium pressure for hydrogen release in a first alloy overlaps with a range of equilibrium pressure for hydrogen storage in a second alloy. A range of equilibrium pressure for occlusion of the first alloy overlaps with a range of equilibrium pressure for release of the second alloy. An equilibrium pressure for the release of a third alloy at the highest temperature of the second alloy is higher than an equilibrium pressure at which the first alloy releases hydrogen by the heating section. A temperature range of the occlusion of the second alloy overlaps with a temperature range of the release of the third alloy. A temperature range of release of the second alloy overlaps with a temperature range of occlusion of the third alloy.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present disclosure relates to a hydrogen storage device.

Background Art

[0002] Conventionally, there has been a technique of lowering the temperature of a hydrogen storage alloy to store low-pressure hydrogen and raising the temperature of the hydrogen storage alloy to release high-pressure hydrogen. In the hydrogen storage system of Patent Document 1, a cooling medium is continuously introduced into and discharged from a heat exchanger. As a result, the hydrogen storage alloy is cooled by the heat exchanger, and the hydrogen storage alloy stores the hydrogen introduced through the hydrogen transfer pipe. Further, a heating medium is continuously introduced into and discharged from the heat exchanger. As a result, the hydrogen storage alloy is heated by the heat exchanger, and the hydrogen stored in the hydrogen storage alloy is released. Hydrogen moves through the hydrogen transfer pipe into the space in the hydrogen storage tank.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When attempting to release hydrogen gas having a certain degree of high pressure using the hydrogen storage system described in Patent Document 1, it is necessary to heat the hydrogen storage alloy to a high temperature corresponding to that pressure. For example, in order to release hydrogen gas for filling a hydrogen gas tank capable of storing hydrogen up to a pressure of about 40 MPa into the hydrogen storage system of Patent Document 1, it is necessary to heat the hydrogen storage alloy to a temperature exceeding 100°C. On the other hand, securing a heat source exceeding 100°C is not as easy as a heat source of 100°C or lower. For this reason, there is a demand for a hydrogen storage device using a hydrogen storage alloy that can release hydrogen gas at a higher pressure at a lower temperature.

Means for Solving the Problems

[0005] This disclosure can be implemented in the following forms:

[0006] (1) According to one embodiment of the present disclosure, a hydrogen storage device is provided. The hydrogen storage device comprises a first container containing a first hydrogen storage alloy, a second container containing a second hydrogen storage alloy, and a third container containing a third hydrogen storage alloy. The first container is connected to a heating section for heating the first hydrogen storage alloy and a cooling section for cooling the first hydrogen storage alloy, the first container and the second container are connected so that hydrogen gas can flow through their respective interiors, the second container and the third container are connected so that heat can be transferred between them, and the third container is connected to a hydrogen supply source for supplying hydrogen gas to the third container and to a hydrogen supply target for which hydrogen gas is supplied from the third container. The equilibrium pressure range in which the first hydrogen storage alloy releases hydrogen and the equilibrium pressure range in which the second hydrogen storage alloy absorbs hydrogen overlap, and the equilibrium pressure range in which the first hydrogen storage alloy absorbs hydrogen and the equilibrium pressure range in which the second hydrogen storage alloy releases hydrogen overlap, and at the highest temperature reached by the second hydrogen storage alloy during the operation of the hydrogen storage device, the equilibrium pressure in which the third hydrogen storage alloy releases hydrogen is higher than the equilibrium pressure in which the first hydrogen storage alloy releases hydrogen due to heating in the heating section, and the temperature range in which the second hydrogen storage alloy absorbs hydrogen and the temperature range in which the third hydrogen storage alloy releases hydrogen overlap, and the temperature range in which the second hydrogen storage alloy releases hydrogen and the temperature range in which the third hydrogen storage alloy absorbs hydrogen overlap. In this configuration, by heating the first hydrogen storage alloy in the heating section, the second hydrogen storage alloy can release reaction heat through the release of hydrogen from the first hydrogen storage alloy and the absorption of hydrogen from the first hydrogen storage alloy by the second hydrogen storage alloy. The reaction heat of the second hydrogen storage alloy can then heat the third hydrogen storage alloy via the second and third containers. As a result, hydrogen gas can be released from the third hydrogen storage alloy at a pressure higher than the pressure of hydrogen gas released by the heated first hydrogen storage alloy, and the pressure of hydrogen gas released by the third hydrogen storage alloy when it is heated to the temperature of the heated first hydrogen storage alloy. In other words, hydrogen gas at a higher pressure than when the third hydrogen storage alloy is heated in the heating section can be supplied to the hydrogen supply target. Furthermore, in this configuration, by cooling the first hydrogen storage alloy in the cooling section, the reaction heat can be absorbed by the second hydrogen storage alloy through the absorption of hydrogen by the first hydrogen storage alloy and the release of hydrogen to the first hydrogen storage alloy by the second hydrogen storage alloy. The reaction heat of the second hydrogen storage alloy can then be used to cool the third hydrogen storage alloy via the second and third containers. As a result, hydrogen gas can be absorbed into the third hydrogen storage alloy. (2) In the hydrogen storage apparatus of the above form, the second container may be arranged in contact with the outer circumference of the third container. In this configuration, the second and third containers can transfer heat to each other through the outer surface of the third container. Therefore, heat can be transferred to each other more efficiently compared to a configuration in which the second and third containers are arranged side by side with a heat transfer structure in between. (3) In the hydrogen storage apparatus of the above form, the first container may be arranged around the outer circumference of the second container. In this configuration, the hydrogen storage device can be made smaller compared to a configuration in which the first and second containers are arranged side by side with a hydrogen gas circulation device in between. (4) In the hydrogen storage device of the above configuration, at the lowest temperature reached by the second hydrogen storage alloy during operation of the hydrogen storage device, the equilibrium pressure at which the third hydrogen storage alloy absorbs hydrogen may be higher than the equilibrium pressure at which the first hydrogen storage alloy absorbs hydrogen due to cooling in the cooling section. In this embodiment, at the highest temperature reached by the second hydrogen storage alloy during operation of the hydrogen storage device, the equilibrium pressure at which the third hydrogen storage alloy releases hydrogen is higher than the equilibrium pressure at which the hydrogen storage alloy releases hydrogen due to heating by the heating section. Furthermore, at the lowest temperature reached by the second hydrogen storage alloy during operation of the hydrogen storage device, the equilibrium pressure at which the third hydrogen storage alloy absorbs hydrogen is higher than the equilibrium pressure at which the first hydrogen storage alloy absorbs hydrogen due to cooling by the cooling section. That is, in a graph with T as temperature and P as pressure, where 1 / T is on the horizontal axis and P on the vertical axis, both the characteristic straight line for the equilibrium pressure of release and the characteristic straight line for the equilibrium pressure of absorption of the third hydrogen storage alloy have gentle slopes. In other words, the decrease in P for an increase in 1 / T is small. The number of types of hydrogen storage alloys with such characteristics is large compared to the number of types of hydrogen storage alloys with steeply sloped characteristic straight lines. For this reason, an inexpensive hydrogen storage alloy can be selected to construct a hydrogen storage device at a low cost. This disclosure can also be implemented in various forms other than hydrogen storage devices. For example, it can be implemented in the form of a method for manufacturing a hydrogen storage device, a method for controlling a hydrogen storage device, a computer program for implementing the control method, or a non-temporary recording medium on which the computer program is stored. [Brief explanation of the drawing]

[0007] [Figure 1] This is a block diagram showing the configuration of the hydrogen storage device 10 and the operation of the hydrogen storage device 10 when releasing hydrogen. [Figure 2] This is a block diagram showing the configuration of the hydrogen storage device 10 and the operation of the hydrogen storage device 10 when storing hydrogen. [Figure 3] This is an explanatory diagram showing the schematic configuration of the internal structure of the hydrogen storage device 10. [Figure 4]This graph shows the hydrogen absorption and release characteristics of the first hydrogen storage alloy 120, the second hydrogen storage alloy 220, and the third hydrogen storage alloy 320. [Figure 5] This is an explanatory diagram showing the internal structure of the hydrogen storage device 12. [Figure 6] This is an explanatory diagram showing the hydrogen storage device 12 cut along the VI-VI section in Figure 5. [Figure 7] This is an explanatory diagram showing the hydrogen storage device 12 as it is cut along the VII-VII cross-section in Figure 5. [Figure 8] This graph shows the hydrogen absorption and release characteristics of the first hydrogen storage alloy 122, the second hydrogen storage alloy 222, and the third hydrogen storage alloy 322. [Modes for carrying out the invention]

[0008] A. First Embodiment: A1. Configuration of the hydrogen storage system: Figure 1 is a block diagram showing the configuration of the hydrogen storage device 10 in the first embodiment and the operation of the hydrogen storage device 10 when releasing hydrogen. Figure 2 is a block diagram showing the configuration of the hydrogen storage device 10 and the operation of the hydrogen storage device 10 when absorbing hydrogen.

[0009] The hydrogen storage device 10 supplies the stored hydrogen as hydrogen gas to the hydrogen-supplied HGT (see the middle right section of Figure 1). The hydrogen storage device 10 receives hydrogen gas from the hydrogen supply source HGS and stores that hydrogen (see the middle left and right sections of Figure 2). The pressure of the hydrogen gas supplied by the hydrogen storage device 10 to the hydrogen-supplied HGT is higher than the pressure of the hydrogen gas supplied to the hydrogen storage device 10 from the hydrogen supply source HGS. Specifically, the pressure of the hydrogen gas supplied to the hydrogen storage device 10 from the hydrogen supply source HGS is 10 MPa or less. The pressure of the hydrogen gas supplied by the hydrogen storage device 10 to the hydrogen-supplied HGT is 40 MPa or higher.

[0010] The hydrogen supply source HGS is, for example, a plant that electrolyzes water to produce hydrogen, an ironworks or a chemical plant that produces hydrogen as a by-product. The hydrogen supply target HGT is, for example, the hydrogen gas tank of a fuel cell vehicle that runs using hydrogen gas.

[0011] The hydrogen storage device 10 includes a first hydrogen storage device 100, a second hydrogen storage device 200, a third hydrogen storage device 300, a connecting pipe 400, and a temperature controller 500.

[0012] The first hydrogen storage device 100 is connected to a heating part HS and a cooling part CS (see the left parts of FIGS. 1 and 2). The heating part HS heats the first hydrogen storage device 100. The heating part HS is configured to be able to circulate a high-temperature fluid FL1 between the heating part HS and the first hydrogen storage device 100 (see the left part of FIG. 1). In this embodiment, the high-temperature fluid FL1 is water. The temperature Ths of the high-temperature fluid FL1 is 70°C or more and less than 100°C. The heating part HS makes the high-temperature fluid FL1 by imparting heat to the fluid circulated between the heating part HS and the first hydrogen storage device 100.

[0013] The cooling part CS cools the first hydrogen storage device 100. The cooling part CS is configured to be able to circulate a low-temperature fluid FL2 between the cooling part CS and the first hydrogen storage device 100 (see the left part of FIG. 2). In this embodiment, the low-temperature fluid FL2 is also water. In this embodiment, the temperature Tcs of the low-temperature fluid FL2 is from 0°C to 40°C. The cooling part CS makes the low-temperature fluid FL2 by taking heat away from the fluid circulated between the cooling part CS and the first hydrogen storage device 100.

[0014] The first hydrogen storage device 100 is connected to the hydrogen supply source HGS. The first hydrogen storage device 100 can be supplied with hydrogen gas HG1 from the hydrogen supply source HGS (see the left part of FIG. 2).

[0015] FIG. 3 is an explanatory diagram showing a schematic configuration of the internal structure of the hydrogen storage device 10. The first hydrogen storage device 100 includes a first outer shell 110 and a first hydrogen storage alloy 120 (see the left part of FIG. 3). The first outer shell 110 is a rectangular parallelepiped-shaped container made of a stainless steel plate. The first hydrogen storage device 100 houses the first hydrogen storage alloy 120 inside the first outer shell 110.

[0016] The first hydrogen storage alloy 120 is a hydrogen storage alloy in the form of powder having a particle size of several μm to several hundred μm. The first hydrogen storage alloy 120 is covered on the outer surface by a filter that allows hydrogen gas to flow through and does not allow the powder of the hydrogen storage alloy to flow through. As a result, the first hydrogen storage alloy 120 maintains a rectangular parallelepiped shape. The characteristics of the first hydrogen storage alloy 120 will be described later.

[0017] The first hydrogen storage device 100 is connected to a heating part HS and a cooling part CS (see the left part of FIG. 1 and the left part of FIG. 2). The first hydrogen storage device 100 is housed inside a temperature regulator 500. This structure enables the connection between the heating part HS and the cooling part CS of the first hydrogen storage device 100.

[0018] The temperature regulator 500 is supplied with a high-temperature fluid FL1 from the heating part HS by a pump provided in the heating part HS and circulates the fluid FL1 between the heating part HS. The temperature regulator 500 is supplied with a low-temperature fluid FL2 from the cooling part CS by a pump provided in the cooling part CS and circulates the fluid FL2 between the cooling part CS. The temperature regulator 500 is arranged around the first hydrogen storage device 100. The temperature regulator 500 includes an inner shell 530 and an outer shell 550.

[0019] The inner shell 530 has the same configuration as the first outer shell 110 of the first hydrogen storage device 100. That is, the first outer shell 110 of the first hydrogen storage device 100 functions as the inner shell 530 of the temperature regulator 500.

[0020] The outer shell 550 is a rectangular parallelepiped container made of stainless steel plate. The outer shell 550 surrounds the first outer shell 110 of the first hydrogen storage device 100. The outer shell 550 is positioned with a space between it and the first outer shell 110, i.e., the inner shell 530. A high-temperature fluid FL1 or a low-temperature fluid FL2 flows between the outer shell 550 and the inner shell 530.

[0021] The temperature controller 500 can switch between and circulate fluid FL1 from the heating section HS and fluid FL2 from the cooling section CS. The first hydrogen storage alloy 120 is heated by the heating section HS via fluid FL1 and the first outer shell 110. The first hydrogen storage alloy 120 is cooled by the cooling section CS via fluid FL2 and the first outer shell 110. In this specification, such a configuration is described as the first hydrogen storage unit 100 being connected to the heating section HS and the cooling section CS.

[0022] The third hydrogen storage container 300 comprises a third outer shell 310, a third hydrogen storage alloy 320, and a void 330 (see the right side of Figure 3). The third outer shell 310 is a cylindrical container made of stainless steel plate. The third hydrogen storage container 300 houses the third hydrogen storage alloy 320 within the third outer shell 310.

[0023] The third hydrogen storage alloy 320 is a hydrogen storage alloy in powder form with particle sizes ranging from a few micrometers to several hundred micrometers. The third hydrogen storage alloy 320 is covered on its outer surface by a filter that allows hydrogen gas to flow through but prevents the hydrogen storage alloy powder from flowing. As a result, the third hydrogen storage alloy 320 maintains a cylindrical shape. The shape of the void 330 in the center of the cylinder is maintained by a frame along with the filter. The third hydrogen storage alloy 320 receives hydrogen gas from the outside and supplies hydrogen gas to the outside through the central void 330. The properties of the third hydrogen storage alloy 320 will be described later.

[0024] The third hydrogen storage unit 300 is connected to the hydrogen supply source HGS and the hydrogen supply target HGT. The hydrogen supply source HGS supplies hydrogen gas HG1 to the third hydrogen storage unit 300 (see the right and left parts of Figure 2). The pressure of the hydrogen gas HG1 supplied by the hydrogen supply source HGS to the third hydrogen storage unit 300 is 10 MPa or less.

[0025] The hydrogen-supplied HGT is supplied with hydrogen gas HG2 from the third hydrogen storage unit 300 (see the right side of Figure 1). The pressure of the hydrogen gas HG1 supplied to the hydrogen-supplied HGT from the third hydrogen storage unit 300 is 40 MPa or higher.

[0026] The second hydrogen absorber 200 is positioned in contact with the outer circumference of the third hydrogen absorber 300 (see the right side of Figure 3). The second hydrogen absorber 200 comprises a second outer shell 210, a second hydrogen absorber alloy 220, and a second inner shell 230 (see the right side of Figure 3). The second inner shell 230 has the same configuration as the third outer shell 310 of the third hydrogen absorber 300. That is, the third outer shell 310 of the third hydrogen absorber 300 functions as the second outer shell 210 of the second hydrogen absorber 200. As a result, the second hydrogen absorber 200 and the third hydrogen absorber 300 can transfer heat to each other. In this specification, this configuration is described as the second hydrogen absorber 200 and the third hydrogen absorber 300 being connected in such a way that they can transfer heat to each other.

[0027] In this embodiment, the second hydrogen absorber 200 and the third hydrogen absorber 300 can transfer heat to each other through the outer surface of the third outer shell 310 of the third hydrogen absorber 300. Therefore, compared to an embodiment in which the second hydrogen absorber 200 and the third hydrogen absorber 300 are arranged side by side with a heat transfer structure in between, the second hydrogen absorber 200 and the third hydrogen absorber 300 can efficiently transfer heat to each other.

[0028] The second outer shell 210 is a cylindrical container made of stainless steel plate. The second outer shell 210 shares the same central axis as the second inner shell 230 and surrounds the second inner shell 230. The second hydrogen storage container 200 houses the third hydrogen storage alloy 320 in the space between the second outer shell 210 and the second inner shell 230.

[0029] The second hydrogen storage alloy 220 is a hydrogen storage alloy in powder form with particle sizes ranging from a few micrometers to several hundred micrometers. The second hydrogen storage alloy 220 is covered on its outer surface by a filter that allows hydrogen gas to flow through but prevents the hydrogen storage alloy powder from flowing through. As a result, the second hydrogen storage alloy 220 maintains a cylindrical external shape. The second hydrogen storage alloy 220 is in contact with the third outer shell 310 via the filter. The second hydrogen storage alloy 220 heats or cools the third hydrogen storage alloy 320 via the filter and the third outer shell 310. The properties of the second hydrogen storage alloy 220 will be described later.

[0030] The connecting pipe 400 connects the first hydrogen storage unit 100 and the second hydrogen storage unit 200 so that the hydrogen gas HGi inside each unit can flow through them (see the center of Figure 3).

[0031] A2. Characteristics of hydrogen storage alloys for each hydrogen storage device: Figure 4 is a graph showing the hydrogen absorption and release characteristics of the first hydrogen storage alloy 120, the second hydrogen storage alloy 220, and the third hydrogen storage alloy 320. The horizontal axis of Figure 4 is 1 / temperature [1 / K]. The vertical axis of Figure 4 is pressure. On the horizontal axis of Figure 4, the position corresponding to room temperature, i.e., 20°C, is between 1 / Ths and 1 / T2min. The temperature T2min will be explained later.

[0032] In Figure 4, graph Go1 shows the equilibrium pressure of the first hydrogen storage alloy 120 during hydrogen storage. Graph Ge1 shows the equilibrium pressure of the first hydrogen storage alloy 120 during hydrogen release. Graph Go2 shows the equilibrium pressure of the second hydrogen storage alloy 220 during hydrogen storage. Graph Ge2 shows the equilibrium pressure of the second hydrogen storage alloy 220 during hydrogen release. Graph Go3 shows the equilibrium pressure of the third hydrogen storage alloy 320 during hydrogen storage. Graph Ge3 shows the equilibrium pressure of the third hydrogen storage alloy 320 during hydrogen release. In Figure 4, the equilibrium pressure of each hydrogen storage alloy during hydrogen storage is shown by a dashed line. In Figure 4, the equilibrium pressure of each hydrogen storage alloy during hydrogen release is shown by a dashed line. Note that each graph is approximated by a straight line.

[0033] As can be seen from graphs Go2 and Ge3, the temperature range To2 in which the second hydrogen storage alloy 220 absorbs hydrogen and the temperature range Te3 in which the third hydrogen storage alloy 320 releases hydrogen overlap (see lower part of Figure 4). As can be seen from graphs Ge2 and Go3, the temperature range Te2 in which the second hydrogen storage alloy 220 releases hydrogen and the temperature range To3 in which the third hydrogen storage alloy 320 absorbs hydrogen overlap (see lower part of Figure 4).

[0034] As can be seen from graphs Ge1 and Go2, the equilibrium pressure range Pe1 in which the first hydrogen storage alloy 120 releases hydrogen and the equilibrium pressure range Po2 in which the second hydrogen storage alloy 220 absorbs hydrogen overlap (see left side of Figure 4). As can be seen from graphs Go1 and Ge2, the equilibrium pressure range Po1 in which the first hydrogen storage alloy 120 absorbs hydrogen and the equilibrium pressure range Pe2 in which the second hydrogen storage alloy 220 releases hydrogen overlap (see left side of Figure 4).

[0035] During the operation of the hydrogen storage device 10, at the maximum temperature T2max reached by the second hydrogen storage alloy 220, the equilibrium pressure Pemax at which the third hydrogen storage alloy 320 releases hydrogen is higher than the equilibrium pressure Pe1ths at which the first hydrogen storage alloy 120 releases hydrogen when heated to temperature Ths by the heating section HS (see left side of Figure 4).

[0036] During the operation of the hydrogen storage device 10, at the lowest temperature T2min reached by the second hydrogen storage alloy 220, the equilibrium pressure Pomin at which the third hydrogen storage alloy 320 absorbs hydrogen is higher than the equilibrium pressure Po1tcs at which the first hydrogen storage alloy 120 absorbs hydrogen, due to cooling to temperature Tcs by the cooling unit CS (see left side of Figure 4). In Figure 4, T2 indicates the temperature range that the second hydrogen storage alloy 220 can take during the operation of the hydrogen storage device 10.

[0037] The third hydrogen storage alloy 320 that can achieve the characteristics shown in Figure 4 is specifically a BCC solid solution alloy. The second hydrogen storage alloy 220 that can achieve the characteristics shown in Figure 4 is specifically an AB-type titanium alloy. The first hydrogen storage alloy 120 that can achieve the characteristics shown in Figure 4 can be selected from any hydrogen storage alloy.

[0038] Along with the properties of the first hydrogen storage alloy 120, the second hydrogen storage alloy 220, and the third hydrogen storage alloy 320, the pressure of hydrogen gas HGi in the first hydrogen storage chamber 100 and the second hydrogen storage chamber 200, in other words, the amount of hydrogen gas HGi in the first hydrogen storage chamber 100 and the second hydrogen storage chamber 200 connected by the connecting pipe 400, is adjusted to achieve the operation described below.

[0039] A3. Operation of the hydrogen storage device: (1) Release of hydrogen gas from hydrogen storage devices: When hydrogen gas is released from the hydrogen storage device 10, the first hydrogen storage chamber 100 is heated by the heating unit HS (see the left side of Figure 1). As a result, the first hydrogen storage alloy 120 in the first hydrogen storage chamber 100 is heated to a temperature Ths. Temperature Ths is lower than 100°C. At this time, the pressure of the hydrogen gas HGi inside the first hydrogen storage chamber 100 is below the equilibrium pressure for hydrogen release from the first hydrogen storage alloy 120. Therefore, hydrogen gas HGi is released from the first hydrogen storage alloy 120 until the equilibrium pressure is reached. This state is shown at point S1 in Figure 4.

[0040] The second hydrogen storage chamber 200 is connected to the first hydrogen storage chamber 100 via a connecting pipe 400. Therefore, the pressure of hydrogen gas HGi in the second hydrogen storage chamber 200 is the same as the pressure of hydrogen gas HGi in the first hydrogen storage chamber 100. Due to the heating of the first hydrogen storage alloy 120 by the heating section HS, the pressure of hydrogen gas HGi in the second hydrogen storage chamber 200 is equal to or greater than the equilibrium pressure for hydrogen storage in the second hydrogen storage alloy 220 (see point S1 in Figure 4 and graph Go2). Therefore, the second hydrogen storage alloy 220 stores hydrogen gas HGi until the equilibrium pressure is reached.

[0041] In other words, inside the first hydrogen storage chamber 100 and the second hydrogen storage chamber 200, which are connected via a connecting pipe 400, the release of hydrogen gas HGi from the first hydrogen storage alloy 120 and the absorption of that hydrogen gas HGi by the second hydrogen storage alloy 220 occur continuously (see the center of Figure 1).

[0042] The hydrogen storage reaction in hydrogen storage alloys is an exothermic reaction. Therefore, the temperature of the second hydrogen storage alloy 220 rises with hydrogen storage. The temperature of the second hydrogen storage alloy 220 rises to T2max, as shown in graph Go2. Temperature T2max is higher than temperature Ths and 100°C. This state is shown at point S2 in Figure 4.

[0043] The heat from the second hydrogen storage alloy 220 is transferred to the third hydrogen storage alloy 320 via the second inner shell 230, i.e., the third outer shell 310 (see the right side of Figure 3). At temperature T2max, the third hydrogen storage alloy 320 releases hydrogen gas HG2 at equilibrium pressure Pemax. This state is shown at point S3 in Figure 4.

[0044] The hydrogen release reaction in hydrogen storage alloys is an endothermic reaction. The thermal energy released by the second hydrogen storage alloy 220 in the hydrogen gas HGi storage reaction is absorbed by the third hydrogen storage alloy 320. In other words, the thermal energy of the exothermic reaction in the second hydrogen storage alloy 220 is offset by the thermal energy of the endothermic reaction in the third hydrogen storage alloy 320 (see the lower right section of Figure 1).

[0045] As a result, at an equilibrium pressure Pemax, which is higher than the equilibrium pressure Pe1ths at which the first hydrogen storage alloy 120 releases hydrogen gas HGi at temperature Ths, the third hydrogen storage alloy 320 releases hydrogen gas HG2 (see S1 and S3 in Figure 4). The hydrogen gas HG2 released by the third hydrogen storage alloy 320 is supplied to the hydrogen supply target HGT (see the right side of Figure 1).

[0046] As described above, in the hydrogen storage device 10, by heating the first hydrogen storage alloy 120 at a temperature lower than 100°C using the heating unit HS, the second hydrogen storage alloy 220 can release reaction heat through the release of hydrogen by the first hydrogen storage alloy 120 (see S1 in Figure 4) and the absorption of hydrogen from the first hydrogen storage alloy 120 by the second hydrogen storage alloy 220 (see S2 in Figure 4). Then, the reaction heat of the second hydrogen storage alloy 220 can heat the third hydrogen storage alloy 320 to a temperature higher than 100°C via the second inner shell 230 of the second hydrogen storage container 200, i.e., the third outer shell 310 of the third hydrogen storage container 300 (see the right side of Figure 3). As a result, hydrogen gas HG2 can be released from the third hydrogen storage alloy 320 at a pressure Pemax that is higher than the pressure Pe1ths of the hydrogen gas HGi released from the first hydrogen storage alloy 120 heated in the heating section HS, and the pressure of the hydrogen gas released from the third hydrogen storage alloy 320 when the third hydrogen storage alloy 320 is heated to the temperature Ths of the heated first hydrogen storage alloy 120 (see S3 in Figure 4). In other words, hydrogen gas at a higher pressure can be supplied to the hydrogen supply target HGT than when the third hydrogen storage alloy 320 is heated in the heating section HS at a temperature lower than 100°C (see the right side of Figure 1).

[0047] (2) Hydrogen gas storage in hydrogen storage devices: When hydrogen gas is absorbed into the hydrogen storage device 10, the first hydrogen absorber 100 is cooled by the cooling unit CS (see the left side of Figure 2). As a result, the first hydrogen storage alloy 120 in the first hydrogen absorber 100 is cooled to temperature Tcs. At this time, the pressure of the hydrogen gas HGi inside the first hydrogen absorber 100 is greater than or equal to the equilibrium pressure for hydrogen absorption in the first hydrogen storage alloy 120. Therefore, hydrogen gas HGi is absorbed into the first hydrogen storage alloy 120 until the equilibrium pressure is reached. This state is shown as point S4 in Figure 4. At this time, additional hydrogen gas HG1 may be supplied to the first hydrogen absorber 100 from the hydrogen supply source HGS (see the left side of the middle section of Figure 2).

[0048] The second hydrogen storage chamber 200 is connected to the first hydrogen storage chamber 100 via a connecting pipe 400. Therefore, the pressure of hydrogen gas HGi in the second hydrogen storage chamber 200 is the same as the pressure of hydrogen gas HGi in the first hydrogen storage chamber 100. Cooling of the first hydrogen storage alloy 120 by the cooling section CS causes the pressure of hydrogen gas HGi in the second hydrogen storage chamber 200 to reach a pressure below the equilibrium pressure for hydrogen release from the second hydrogen storage alloy 220 (see point S4 in Figure 4 and graph Go1). As a result, the second hydrogen storage alloy 220 releases hydrogen gas HGi.

[0049] In other words, inside the first hydrogen storage unit 100 and the second hydrogen storage unit 200, which are connected via the connecting pipe 400, the release of hydrogen gas HGi from the second hydrogen storage alloy 220 and the absorption of that hydrogen gas HGi by the first hydrogen storage alloy 120 occur continuously (see the center of Figure 2).

[0050] The hydrogen release reaction in hydrogen storage alloys is an endothermic reaction. Therefore, the temperature of the second hydrogen storage alloy 220 decreases as hydrogen is released. The temperature of the second hydrogen storage alloy 220 decreases to T2min along the graph Ge2. This state is shown at point S5 in Figure 4.

[0051] The second hydrogen storage alloy 220 absorbs heat from the third hydrogen storage alloy 320 via the second inner shell 230, i.e., the third outer shell 310 (see the right side of Figure 3). At temperature T2min, the third hydrogen storage alloy 320 absorbs hydrogen gas HG1 at equilibrium pressure Pomin. This state is shown at point S6 in Figure 4.

[0052] The hydrogen storage reaction in hydrogen storage alloys is an exothermic reaction. The thermal energy released by the third hydrogen storage alloy 320 during the hydrogen gas HG1 storage reaction is absorbed by the second hydrogen storage alloy 220. In other words, the thermal energy of the exothermic reaction in the third hydrogen storage alloy 320 is offset by the thermal energy of the endothermic reaction in the second hydrogen storage alloy 220 (see the lower right section of Figure 2).

[0053] As a result, at an equilibrium pressure Pomin, which is higher than the equilibrium pressure Po1tcs at which the first hydrogen storage alloy 120 stores hydrogen at temperature Tcs, the third hydrogen storage alloy 320 stores hydrogen gas HG1 (see S4 and S6 in Figure 4). The hydrogen gas HG1 stored by the third hydrogen storage alloy 320 is supplied from the hydrogen supply source HGS (see the left side of Figure 2).

[0054] As described above, in the hydrogen storage device 10, by cooling the first hydrogen storage alloy 120 in the cooling section CS, the second hydrogen storage alloy 220 can absorb reaction heat through the release of hydrogen by the second hydrogen storage alloy 220 (see S5 in Figure 4) and the absorption of hydrogen from the second hydrogen storage alloy 220 by the first hydrogen storage alloy 120 (see S4 in Figure 4). Then, the reaction heat of the second hydrogen storage alloy 220 can cool the third hydrogen storage alloy 320 via the second inner shell 230 of the second hydrogen storage container 200, i.e., the third outer shell 310 of the third hydrogen storage container 300. As a result, hydrogen gas can be absorbed into the third hydrogen storage alloy 320 (see S6 in Figure 4 and the right side of Figure 2).

[0055] (3) Others: In this embodiment, at the highest temperature T2max reached by the second hydrogen storage alloy 220 during operation of the hydrogen storage device 10, the equilibrium pressure Pemax at which the third hydrogen storage alloy 320 releases hydrogen is higher than the equilibrium pressure Pe1ths at which the first hydrogen storage alloy 120 releases hydrogen due to heating by the heating unit HS. Furthermore, at the lowest temperature T2min reached by the second hydrogen storage alloy 220 during operation of the hydrogen storage device 10, the equilibrium pressure Pomin at which the third hydrogen storage alloy 320 absorbs hydrogen is higher than the equilibrium pressure Po1tcs at which the first hydrogen storage alloy 120 absorbs hydrogen due to cooling by the cooling unit CS. In other words, in the graph of Figure 4, both the characteristic straight line Ge3 for the equilibrium pressure of release of the third hydrogen storage alloy 320 and the characteristic straight line Go3 for the equilibrium pressure of absorption have gentle slopes. In other words, the decrease in equilibrium pressure P for an increase of 1 / T is small in both cases. The number of hydrogen storage alloys with such characteristics is greater than the number of hydrogen storage alloys with steeply sloped characteristic lines. Therefore, an inexpensive hydrogen storage alloy can be selected to construct the hydrogen storage device 10 at a low cost. Similarly, in the graph of Figure 4, the characteristic lines Ge1 and Ge2 for the equilibrium pressure of release, and the characteristic lines Go1 and Go2 for the equilibrium pressure of storage, for the first and second hydrogen storage alloys 120 and 220, have gentle slopes. Therefore, an inexpensive hydrogen storage alloy can be selected to construct the hydrogen storage device 10 at a low cost.

[0056] The first hydrogen absorber 100 in this embodiment is also referred to as the "first container." The second hydrogen absorber 200 is also referred to as the "second container." The third hydrogen absorber 300 is also referred to as the "third container."

[0057] B. Second Embodiment: B1. Configuration of the hydrogen storage system: In the hydrogen storage device 12 of the second embodiment, the configurations of the first hydrogen absorber 102, the connecting channel 402, and the temperature controller 502 differ from the configurations of the first hydrogen absorber 100, the connecting pipe 400, and the temperature controller 500 in the corresponding hydrogen storage device 10 of the first embodiment. Other aspects of the hydrogen storage device 12 of the second embodiment are the same as those of the hydrogen storage device 10 of the first embodiment. For this reason, the block diagrams in Figures 1 and 2 can also be applied to the second embodiment.

[0058] Figure 5 is an explanatory diagram showing the internal structure of the hydrogen storage device 12. The hydrogen storage device 12 has a substantially cylindrical shape. The hydrogen storage device 12 comprises a first hydrogen absorber 102, a second hydrogen absorber 202, a third hydrogen absorber 302, a connecting channel 402, and a temperature controller 502. Among the components of the hydrogen storage device 12 of the second embodiment, components corresponding to the components of the hydrogen storage device 10 of the first embodiment are denoted by replacing the last digit 0 of the reference numerals used for the components of the hydrogen storage device 10 with 2.

[0059] The third hydrogen storage unit 302 comprises a third outer shell 312, a third hydrogen storage alloy 322, and a void 332. The configuration of the third hydrogen storage unit 302 is the same as that of the third hydrogen storage unit 300 of the hydrogen storage device 10.

[0060] The second hydrogen absorber 202 is positioned in contact with the outer circumference of the third hydrogen absorber 302. The second hydrogen absorber 202 comprises a second outer shell 212, a second hydrogen storage alloy 222, and a second inner shell 232. The configuration of the second hydrogen absorber 202 is the same as that of the second hydrogen absorber 200 of the hydrogen storage device 10, except for the configuration of the connection portion with the connecting channel 402.

[0061] The first hydrogen absorber 102 is positioned on the outer circumference of the second hydrogen absorber 202. The first hydrogen absorber 102 comprises a first outer shell 112, a first hydrogen absorber alloy 122, and a first inner shell 132.

[0062] The first inner shell 132 is a cylindrical container made of stainless steel plate. The first outer shell 112 is a cylindrical container made of stainless steel plate. The first outer shell 112 shares the same central axis as the first inner shell 132 and surrounds the first inner shell 132. The first hydrogen storage container 102 houses the first hydrogen storage alloy 122 in the space between the first outer shell 112 and the first inner shell 132.

[0063] The first hydrogen storage alloy 122 is a powdered hydrogen storage alloy. The outer surface of the first hydrogen storage alloy 122 is covered with a filter that allows hydrogen gas to flow through but prevents the hydrogen storage alloy powder from flowing through. As a result, the first hydrogen storage alloy 122 maintains a cylindrical outer shape. The first hydrogen storage alloy 122 is in contact with the first outer shell 112 and the first inner shell 132 via the filter.

[0064] By adopting this configuration, the hydrogen storage device 12 can be made smaller compared to the hydrogen storage device 10 (see Figure 3), in which the first hydrogen storage device 100 and the second hydrogen storage device 200 are arranged side by side with a connecting pipe 400 for circulating hydrogen gas HGi in between.

[0065] The temperature controller 502 is positioned around the second hydrogen absorber 202, with a space VP between it and the outer circumference of the second hydrogen absorber 202. The space VP is kept substantially under vacuum. The temperature controller 502 is positioned to sandwich the first hydrogen absorber 102 from the inside and outside. The temperature controller 502 comprises an outer shell 512, an inner shell 532, an inner shell 542, and an outer shell 552.

[0066] The outer shell 512 is a cylindrical container made of stainless steel plate. The outer shell 512 shares the same central axis as the second outer shell 212 of the second hydrogen storage container 202 and surrounds the second outer shell 212. The outer shell 512 is positioned with a space VP between it and the second outer shell 212. The outer shell 512 is also positioned with a space between it and the inner shell 532.

[0067] The inner shell 532 has the same configuration as the first inner shell 132 of the first hydrogen storage unit 102. That is, the first inner shell 132 of the first hydrogen storage unit 102 functions as the inner shell 532 of the temperature controller 502. A low-temperature fluid FL2 flows between the outer shell 512 and the inner shell 532. The configuration of the cooling unit CS that supplies the low-temperature fluid FL2 is the same as the configuration of the cooling unit CS in the first embodiment.

[0068] The inner shell 542 has the same configuration as the first outer shell 112 of the first hydrogen storage device 102. That is, the first outer shell 112 of the first hydrogen storage device 102 functions as the inner shell 542 of the temperature controller 502. The outer shell 552 is a cylindrical container made of stainless steel plate. The outer shell 552 shares the same central axis as the inner shell 542 and surrounds the inner shell 542. The outer shell 552 is positioned with a space between it and the inner shell 542. A high-temperature fluid FL1 flows between the outer shell 552 and the inner shell 542. The configuration of the heating unit HS that supplies the high-temperature fluid FL1 is the same as the configuration of the heating unit HS in the first embodiment.

[0069] Figure 6 is an explanatory diagram showing the hydrogen storage device 12 cut along the VI-VI cross-section in Figure 5. The portion of the hydrogen storage device 12 shown in Figure 5, above the central axis CA of the first hydrogen absorber 102, is shown in Figure 6.

[0070] The temperature controller 502 is supplied with high-temperature fluid FL1 from the heating section HS and circulates the fluid FL1 between itself and the heating section HS (see upper right of Figure 6). Within the temperature controller 502, the high-temperature fluid FL1 flows between the outer shell 552 and the inner shell 542. The temperature controller 502 is supplied with low-temperature fluid FL2 from the cooling section CS and circulates the fluid FL2 between itself and the cooling section CS (see lower right of Figure 6). Within the temperature controller 502, the low-temperature fluid FL2 flows between the inner shell 532 and the outer shell 512. In the temperature controller 502, the circulation path for the high-temperature fluid FL1, including the heating section HS, and the circulation path for the low-temperature fluid FL2, including the cooling section CS, are independent of each other. The temperature controller 502 can selectively perform the circulation of fluid FL1 between itself and the heating section HS and the circulation of fluid FL2 between itself and the cooling section CS by means of a valve (not shown).

[0071] The inner shell 542 of the temperature controller 502, i.e., the first hydrogen storage alloy 122 in contact with the first outer shell 112 of the first hydrogen storage unit 102, is heated by the heating unit HS via the fluid FL1 and the first outer shell 112 (see upper part of Figures 6 and 7). The inner shell 532 of the temperature controller 502, i.e., the first hydrogen storage alloy 122 in contact with the first inner shell 132 of the first hydrogen storage unit 102, is cooled by the cooling unit CS via the fluid FL2 and the first outer shell 112 (see middle part of Figures 6 and 7). In this specification, this configuration is described as the first hydrogen storage unit 102 being connected to the heating unit HS and the cooling unit CS.

[0072] Furthermore, the second hydrogen storage unit 202 is separated from the temperature controller 502 by a vacuum space VP (see Figures 5 and 6). Therefore, the second hydrogen storage unit 202 is substantially unaffected by the temperature of the temperature controller 502.

[0073] Figure 7 is an explanatory diagram showing the hydrogen storage device 12 cut along the VII-VII section in Figure 5. The portion of the hydrogen storage device 12 shown in Figure 5 to the right of the central axis CA of the first hydrogen absorber 102 is shown in Figure 6.

[0074] The connecting channel 402 connects the first hydrogen absorber 102 and the second hydrogen absorber 202 within the hydrogen storage device 12 so that the hydrogen gas HGi inside each can flow through them (see the middle right of Figure 7 and the middle of Figure 5).

[0075] B2. Characteristics of hydrogen storage alloys for each hydrogen storage device: Figure 8 is a graph showing the hydrogen absorption and release characteristics of the first hydrogen storage alloy 122, the second hydrogen storage alloy 222, and the third hydrogen storage alloy 322. The horizontal axis of Figure 8 is 1 / temperature [1 / K]. The vertical axis of Figure 8 is pressure. On the horizontal axis of Figure 8, the position corresponding to room temperature, i.e., 20°C, is between 1 / Ths and 1 / T2min. Figure 8 corresponds to Figure 4 in the first embodiment.

[0076] In Figure 8, graph Go12 shows the equilibrium pressure of the first hydrogen storage alloy 122 during hydrogen storage. Graph Ge12 shows the equilibrium pressure of the first hydrogen storage alloy 122 during hydrogen release. Graph Go22 shows the equilibrium pressure of the second hydrogen storage alloy 222 during hydrogen storage. Graph Ge22 shows the equilibrium pressure of the second hydrogen storage alloy 222 during hydrogen release. Graph Go32 shows the equilibrium pressure of the third hydrogen storage alloy 322 during hydrogen storage. Graph Ge32 shows the equilibrium pressure of the third hydrogen storage alloy 322 during hydrogen release. Note that each graph is approximated by a straight line.

[0077] Graph Go12 is the same graph as Graph Go1. Graph Ge12 is the same graph as Graph Ge1. Graph Go22 is the same graph as Graph Go2. Graph Ge22 is the same graph as Graph Ge2.

[0078] The decrease in equilibrium pressure P for an increase in 1 / T in graph Go32 is greater than the decrease in equilibrium pressure P for an increase in 1 / T in graph Go3 in the first embodiment. The decrease in equilibrium pressure P for an increase in 1 / T in graph Ge32 is greater than the decrease in equilibrium pressure P for an increase in 1 / T in graph Ge3 in the first embodiment. Both graphs Go32 and Ge32 intersect with graphs Go12, Ge12, Go22, and Ge22.

[0079] During the operation of the hydrogen storage device 12, at the highest temperature T2max reached by the second hydrogen storage alloy 222, the equilibrium pressure Pemax at which the third hydrogen storage alloy 322 releases hydrogen is higher than the equilibrium pressure Pe1ths at which the first hydrogen storage alloy 122 releases hydrogen when heated to temperature Ths by the heating section HS (see left side of Figure 8).

[0080] During the operation of the hydrogen storage device 10, at the lowest temperature T2min reached by the second hydrogen storage alloy 222, the equilibrium pressure Pomin at which the third hydrogen storage alloy 322 absorbs hydrogen is approximately equal to the equilibrium pressure Po1tcs at which the first hydrogen storage alloy 122 absorbs hydrogen after being cooled to temperature Tcs by the cooling unit CS (see left side of Figure 8).

[0081] Along with the properties of the first hydrogen storage alloy 122, the second hydrogen storage alloy 222, and the third hydrogen storage alloy 322, the pressure of hydrogen gas HGi in the first hydrogen storage chamber 102 and the second hydrogen storage chamber 202, in other words, the amount of hydrogen gas HGi in the first hydrogen storage chamber 102 and the second hydrogen storage chamber 202 connected by the connecting channel 402, is adjusted to achieve the operation described below.

[0082] B3. Operation of the hydrogen storage system: (1) Release of hydrogen gas from hydrogen storage devices: When hydrogen gas is released from the hydrogen storage device 12, the first hydrogen absorber 102 is heated by the heating unit HS (see left side of Figure 1). As a result, hydrogen gas HGi is released from the first hydrogen storage alloy 122 (see S1 in Figure 8), and the hydrogen gas HGi is absorbed into the second hydrogen storage alloy 222 (see S2 in Figure 8). Consequently, the reaction heat of the second hydrogen storage alloy 222 heats the third hydrogen storage alloy 320. The third hydrogen storage alloy 320 releases hydrogen gas HG2 at an equilibrium pressure Pemax at a temperature T2max (see S3 in Figure 8). The operation of the hydrogen storage device 12 when releasing hydrogen gas is the same as the operation of the hydrogen storage device 10 when releasing hydrogen gas.

[0083] According to the hydrogen storage device 12, by heating the first hydrogen storage alloy 120 at a temperature lower than 100°C in the heating unit HS, hydrogen gas at a higher pressure can be supplied to the hydrogen supply target HGT than when the third hydrogen storage alloy 320 is heated at the same temperature in the heating unit HS (see the right side of Figure 1).

[0084] (2) Hydrogen gas storage in hydrogen storage devices: When hydrogen gas is absorbed into the hydrogen storage device 12, the first hydrogen absorber 102 is cooled by the cooling unit CS (see the left side of Figure 2). As a result, the first hydrogen storage alloy 122 of the first hydrogen absorber 102 is cooled to a temperature Tcs. The temperature Tcs is between 0°C and 40°C. At this time, the pressure of the hydrogen gas HGi inside the first hydrogen absorber 102 is greater than or equal to the equilibrium pressure for hydrogen absorption in the first hydrogen storage alloy 122. Therefore, hydrogen gas HGi is absorbed into the first hydrogen storage alloy 122 until the equilibrium pressure is reached. This state is shown as point S42 in Figure 8. At this time, additional hydrogen gas HG1 may be supplied to the first hydrogen absorber 102 from the hydrogen supply source HGS (see the left side of the middle section of Figure 2).

[0085] The second hydrogen storage chamber 202 is connected to the first hydrogen storage chamber 102 via a connecting channel 402. Therefore, the pressure of hydrogen gas HGi in the second hydrogen storage chamber 202 is the same as the pressure of hydrogen gas HGi in the first hydrogen storage chamber 102. Cooling of the first hydrogen storage alloy 122 by the cooling section CS causes the pressure of hydrogen gas HGi in the second hydrogen storage chamber 202 to reach a pressure below the equilibrium pressure for hydrogen release from the second hydrogen storage alloy 222. Therefore, the second hydrogen storage alloy 222 releases hydrogen gas HGi until it reaches the equilibrium pressure.

[0086] In other words, inside the first hydrogen storage chamber 102 and the second hydrogen storage chamber 202, which are connected via the connecting channel 402, the release of hydrogen gas HGi from the second hydrogen storage alloy 222 and the absorption of that hydrogen gas HGi by the first hydrogen storage alloy 122 occur continuously (see the center of Figure 2).

[0087] The hydrogen release reaction in hydrogen storage alloys is an endothermic reaction. Therefore, the temperature of the second hydrogen storage alloy 222 decreases as hydrogen is released. The temperature of the second hydrogen storage alloy 222 decreases to T2min, following the line of graph Go2. This state is shown at point S52 in Figure 8.

[0088] The second hydrogen storage alloy 222 absorbs heat from the third hydrogen storage alloy 322 via the second inner shell 232, i.e., the third outer shell 312 (see Figure 5). At temperature T2min, the third hydrogen storage alloy 322 absorbs hydrogen gas HG1 at equilibrium pressure Pomin. This state is shown at point S62 in Figure 8. The graph Go32 of the equilibrium pressure for hydrogen storage of the third hydrogen storage alloy 322 has a larger negative slope compared to the graph Go3 of the equilibrium pressure for hydrogen storage of the third hydrogen storage alloy 320 in the first embodiment (see Go3 in Figure 4 and Go32 in Figure 8). Therefore, the equilibrium pressure Pomin at which the third hydrogen storage alloy 322 absorbs hydrogen is approximately the same as the equilibrium pressure Po1tcs at which the first hydrogen storage alloy 122 absorbs hydrogen.

[0089] As a result, at an equilibrium pressure Pomin, which is approximately equal to the equilibrium pressure Po1tc at which the first hydrogen storage alloy 122 stores hydrogen at temperature Tcs, the third hydrogen storage alloy 322 stores hydrogen gas HG1 (see S42 and S62 in Figure 8). The hydrogen gas HG1 stored by the third hydrogen storage alloy 322 is supplied from the hydrogen supply source HGS (see the left side of Figure 2).

[0090] As described above, in the hydrogen storage device 12, by cooling the first hydrogen storage alloy 122 in the cooling section CS, the second hydrogen storage alloy 222 can absorb reaction heat through the release of hydrogen by the second hydrogen storage alloy 222 (see S52 in Figure 8) and the absorption of hydrogen from the second hydrogen storage alloy 222 by the first hydrogen storage alloy 122 (see S42 in Figure 8). Then, the reaction heat of the second hydrogen storage alloy 222 can cool the third hydrogen storage alloy 322 via the second inner shell 232 of the second hydrogen storage container 202, i.e., the third outer shell 312 of the third hydrogen storage container 302. As a result, hydrogen gas can be absorbed into the third hydrogen storage alloy 322 (see S62 in Figure 8 and the right side of Figure 2).

[0091] The first hydrogen absorber 102 in this embodiment is also referred to as the "first container." The second hydrogen absorber 202 is also referred to as the "second container." The third hydrogen absorber 302 is also referred to as the "third container."

[0092] C. Other embodiments: C1. Other Embodiments 1: (1) In the first embodiment described above, the second hydrogen storage alloy 220 is an AB-type titanium alloy, and the third hydrogen storage alloy 320 is a BCC solid solution alloy. However, the combination of the second hydrogen storage alloy and the third hydrogen storage alloy can be, for example, the following combinations. (i) AB2 type Raves phase alloy and AB2 type Raves phase alloy. (ii) AB2 type Raves phase alloys and AB5 type rare earth alloys. (iii) AB5 type rare earth alloys and AB2 type Rabes phase alloys. (iv) AB type titanium alloy and AB2 type Raves phase alloy. (v) AB-type titanium alloys and AB5-type rare earth alloys.

[0093] Any hydrogen storage alloy can be used as the first hydrogen storage alloy. However, it is preferable that the first and second hydrogen storage alloys have the following characteristics in a graph with the horizontal axis as 1 / temperature [1 / K] and the vertical axis as pressure: The equilibrium pressure line of the first hydrogen storage alloy during hydrogen storage intersects with the equilibrium pressure line of the second hydrogen storage alloy during hydrogen release (see Go1, Ge2 in Figure 4). The equilibrium pressure line of the first hydrogen storage alloy during hydrogen release intersects with the equilibrium pressure line of the second hydrogen storage alloy during hydrogen storage (see Ge1, Go2 in Figure 4). By having such characteristics, a device combining a first hydrogen storage unit equipped with the first hydrogen storage alloy and a second hydrogen storage unit equipped with the second hydrogen storage alloy can be made to function as a heat pump by heating and cooling.

[0094] (2) In the first embodiment described above, the first hydrogen storage alloy 120 is covered on its outer surface by a filter that allows hydrogen gas to flow but prevents the hydrogen storage alloy powder from flowing (see Figure 3). However, the opening connecting the internal space of the first hydrogen storage chamber 100 and the connecting pipe 400 may be covered by a filter that allows hydrogen gas to flow but prevents the hydrogen storage alloy powder from flowing, and the hydrogen storage alloy powder may be present in the internal space of the first hydrogen storage chamber 100 without being covered by a filter or the like.

[0095] In the first embodiment described above, the second hydrogen storage alloy 220 is covered on its outer surface by a filter that allows hydrogen gas to flow but prevents the hydrogen storage alloy powder from flowing (see Figure 3). However, the opening connecting the internal space of the second hydrogen storage chamber 200 to the connecting pipe 400 may be covered by a filter that allows hydrogen gas to flow but prevents the hydrogen storage alloy powder from flowing, and the hydrogen storage alloy powder may be present in the internal space of the second hydrogen storage chamber 200 without being covered by a filter or the like.

[0096] In the second embodiment described above, the first hydrogen storage alloy 122 is covered on its outer surface by a filter that allows hydrogen gas to flow but prevents the hydrogen storage alloy powder from flowing (see Figure 5). However, the opening connecting the internal space of the first hydrogen storage chamber 102 and the connecting channel 402 may be covered by a filter that allows hydrogen gas to flow but prevents the hydrogen storage alloy powder from flowing, and the hydrogen storage alloy powder may be present in the internal space of the first hydrogen storage chamber 102 without being covered by a filter or the like.

[0097] In the second embodiment described above, the second hydrogen storage alloy 222 is covered on its outer surface by a filter that allows hydrogen gas to flow but prevents the hydrogen storage alloy powder from flowing (see Figure 5). However, the opening connecting the internal space of the second hydrogen storage chamber 202 and the connecting channel 402 may be covered by a filter that allows hydrogen gas to flow but prevents the hydrogen storage alloy powder from flowing, and the hydrogen storage alloy powder may be present in the internal space of the second hydrogen storage chamber 202 without being covered by a filter or the like.

[0098] (3) In the first embodiment described above, the first hydrogen absorber 100 is connected to the hydrogen supply source HGS (see left side of Figure 2). It has been explained that when hydrogen gas is absorbed into the hydrogen storage device 10, additional hydrogen gas HG1 may be supplied to the first hydrogen absorber 100 from the hydrogen supply source HGS. However, the hydrogen storage device can also be configured such that its component, the second hydrogen absorber, is connected to the hydrogen supply source HGS.

[0099] Furthermore, the hydrogen storage device can be configured such that its components, the first hydrogen storage unit and the second hydrogen storage unit, are not connected to the hydrogen supply source HGS. In such a configuration, the amount of hydrogen gas HGi in the first hydrogen storage unit 100 and the second hydrogen storage unit 200, which are connected by a connecting pipe 400, is constant.

[0100] (4) In the first embodiment described above, the heating unit HS circulates a high-temperature fluid FL1 with the first hydrogen storage unit 100 (see Figure 1). The cooling unit CS circulates a low-temperature fluid FL2 with the first hydrogen storage unit 100 (see Figure 2). However, the high-temperature fluid FL1 may be supplied from the heating unit HS to the first hydrogen storage unit 100 and then discharged outside the system without returning to the heating unit HS. The low-temperature fluid FL2 may be supplied from the cooling unit CS to the first hydrogen storage unit 100 and then discharged outside the system without returning to the cooling unit CS.

[0101] (5) In the first embodiment described above, the high-temperature fluid FL1 supplied from the heating unit HS to the first hydrogen storage unit 100 is water. The low-temperature fluid FL2 supplied from the cooling unit CS to the first hydrogen storage unit 100 is also water. However, the medium for heating or cooling the first hydrogen storage unit is not limited to water, but may be other fluids such as oil. Furthermore, the first hydrogen storage unit may also be heated or cooled via a heat transfer member made of a material having greater heat transfer properties than the material constituting the outer shell of the first hydrogen storage unit.

[0102] (6) In the first embodiment described above, in order to facilitate understanding of the technology, the second hydrogen storage alloy 220 was described as reaching T2max when releasing hydrogen gas HG2. However, when releasing hydrogen gas, the hydrogen storage device 10 may be operated in an operating state where the temperature of the second hydrogen storage alloy 220 is lower than T2max.

[0103] In the first embodiment described above, for the sake of ease of understanding the technology, the second hydrogen storage alloy 220 was described as reaching T2min during hydrogen gas HG1 storage. However, when storing hydrogen gas, the hydrogen storage device 10 may be operated under operating conditions where the temperature of the second hydrogen storage alloy 220 is higher than T2min.

[0104] C2. Other Embodiments 2: In the first embodiment described above, the second hydrogen absorber 200 is arranged in contact with the outer circumference of the third hydrogen absorber 300 (see the right side of Figure 3). However, the second hydrogen absorber and the third hydrogen absorber may be arranged adjacent to each other, for example, and share an outer wall separating them so that heat exchange can occur. Alternatively, the second hydrogen absorber and the third hydrogen absorber may be arranged so that heat exchange can occur by circulating a heat-transferring fluid between them. In other words, the second hydrogen absorber and the third hydrogen absorber should be arranged so that heat from the second hydrogen absorber is transferred to the third hydrogen absorber, and heat from the third hydrogen absorber is transferred to the third hydrogen absorber.

[0105] C3. Other Embodiments 3: In the second embodiment described above, the first hydrogen absorber 102 is arranged on the outer circumference of the second hydrogen absorber 202 (see Figure 6). However, the first hydrogen absorber and the second hydrogen absorber can also be arranged in a configuration where the first hydrogen absorber 100 and the second hydrogen absorber 200 are arranged side by side with a connecting pipe 400 for circulating hydrogen gas HGi in between, as in the hydrogen storage device 10 of the first embodiment (see Figure 3). In other words, the first hydrogen absorber and the second hydrogen absorber only need to be connected so that the hydrogen gas inside each can circulate.

[0106] C4. Other Embodiments 4: In the first embodiment described above, at the lowest temperature T2min reached by the second hydrogen storage alloy 220 during the operation of the hydrogen storage device 10, the equilibrium pressure Pomin at which the third hydrogen storage alloy 320 absorbs hydrogen is higher than the equilibrium pressure Po1tcs at which the first hydrogen storage alloy 120 absorbs hydrogen due to cooling to temperature Tcs by the cooling unit CS (see left side of Figure 4). However, as shown in the second embodiment, the equilibrium pressure Pomin at which the third hydrogen storage alloy 320 absorbs hydrogen at temperature T2min may be substantially equal to the equilibrium pressure Po1tcs at which the first hydrogen storage alloy 120 absorbs hydrogen at temperature Tcs (see Figure 8). Furthermore, the equilibrium pressure Pomin at which the third hydrogen storage alloy 320 absorbs hydrogen at temperature T2min may be lower than the equilibrium pressure Po1tcs at which the first hydrogen storage alloy 120 absorbs hydrogen at temperature Tcs.

[0107] Furthermore, the technology of this disclosure can also be provided in the following embodiments. In the operation of the hydrogen storage device, at the highest temperature reached by the second hydrogen storage alloy, the equilibrium pressure at which the third hydrogen storage alloy absorbs hydrogen may be higher than the equilibrium pressure at which the first hydrogen storage alloy releases hydrogen due to heating in the heating section. And, in the operation of the hydrogen storage device, at the lowest temperature reached by the second hydrogen storage alloy, the equilibrium pressure at which the third hydrogen storage alloy absorbs hydrogen and the equilibrium pressure at which the third hydrogen storage alloy releases hydrogen may be higher than or equal to the equilibrium pressure at which the first hydrogen storage alloy absorbs hydrogen due to cooling in the cooling section.

[0108] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features of the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]

[0109] 10...Hydrogen storage device, 12...Hydrogen storage device, 100...First hydrogen absorber, 102...First hydrogen absorber, 110...First outer shell, 112...First outer shell, 120...First hydrogen storage alloy, 122...First hydrogen storage alloy, 132...First inner shell, 200...Second hydrogen absorber, 202...Second hydrogen absorber, 210...Second outer shell, 212...Second outer shell, 220...Second hydrogen storage alloy, 222...Second hydrogen storage alloy, 230...Second inner shell, 232...Second inner shell, 300...Third hydrogen absorber, 302...Third hydrogen absorber, 310...Third outer shell, 312...Third outer shell, 320...Third hydrogen storage alloy, 322...Third Hydrogen storage alloy, 330...void, 332...void, 400...connecting tube, 402...connecting channel, 500...temperature controller, 502...temperature controller, 512...outer shell, 530...inner shell, 532...inner shell, 542...inner shell, 550...outer shell, 552...outer shell, CA...central axis of the first hydrogen storage chamber, CS...cooling section, FL1...fluid, FL2...fluid, Ge1...graph of equilibrium pressure during hydrogen release of the first hydrogen storage alloy, Ge2...graph of equilibrium pressure during hydrogen release of the second hydrogen storage alloy, Ge3...graph of equilibrium pressure during hydrogen release of the third hydrogen storage alloy, Go1...equilibrium pressure during hydrogen storage of the first hydrogen storage alloy Graphs: Go2... Equilibrium pressure graph during hydrogen storage of the second hydrogen storage alloy, Go3... Equilibrium pressure graph during hydrogen storage of the third hydrogen storage alloy, Ge12... Equilibrium pressure graph during hydrogen release of the first hydrogen storage alloy, Ge22... Equilibrium pressure graph during hydrogen release of the second hydrogen storage alloy, Ge32... Equilibrium pressure graph during hydrogen release of the third hydrogen storage alloy, Go12... Equilibrium pressure graph during hydrogen storage of the first hydrogen storage alloy, Go22... Equilibrium pressure graph during hydrogen storage of the second hydrogen storage alloy, Go32... Equilibrium pressure graph during hydrogen storage of the third hydrogen storage alloy, HG1... Hydrogen storage device HG2...Hydrogen gas received by the hydrogen storage device, HGi...Hydrogen gas absorbed and released within the hydrogen storage device, HGS...Hydrogen supply source, HGT...Hydrogen supply target, HS...Heating section, Pe1...Equilibrium pressure range when hydrogen is released from the first hydrogen storage alloy, Pe2...Equilibrium pressure range when hydrogen is released from the second hydrogen storage alloy, Pe3...Equilibrium pressure range when hydrogen is released from the third hydrogen storage alloy, Pemax...Equilibrium pressure when hydrogen is released from the hydrogen storage device, Pe1ths...Equilibrium pressure when hydrogen is released from the first hydrogen storage alloy, Po1tcs...Equilibrium pressure when hydrogen is absorbed from the first hydrogen storage alloy,Po1…Equilibrium pressure range during hydrogen storage of the first hydrogen storage alloy, Po2…Equilibrium pressure range during hydrogen storage of the second hydrogen storage alloy, Po3…Equilibrium pressure range during hydrogen storage of the third hydrogen storage alloy, Pomin…Equilibrium pressure during hydrogen storage of the hydrogen storage device, S1…Point representing the state of the first hydrogen storage alloy, S2…Point representing the state of the second hydrogen storage alloy, S3…Point representing the state of the third hydrogen storage alloy, S4…Point representing the state of the first hydrogen storage alloy, S42…Point representing the state of the first hydrogen storage alloy, S5…Point representing the state of the second hydrogen storage alloy, S52…Point representing the state of the second hydrogen storage alloy, S6…Third hydrogen storage alloy S62…Point representing the state of the third hydrogen storage alloy, T2max…Maximum temperature reached by the second hydrogen storage alloy, T2min…Minimum temperature reached by the second hydrogen storage alloy, Tcs…Temperature of the low-temperature fluid, Te1…Temperature range when hydrogen is released by the first hydrogen storage alloy, Te2…Temperature range when hydrogen is released by the second hydrogen storage alloy, Te3…Temperature range when hydrogen is released by the third hydrogen storage alloy, Ths…Temperature of the high-temperature fluid, To1…Temperature range when hydrogen is absorbed by the first hydrogen storage alloy, To2…Temperature range when hydrogen is absorbed by the second hydrogen storage alloy, To3…Temperature range when hydrogen is absorbed by the third hydrogen storage alloy, VP…Space,

Claims

1. A hydrogen storage device, A first container containing the first hydrogen storage alloy, A second container containing a second hydrogen storage alloy, The system comprises a third container containing a third hydrogen storage alloy, The first container is connected to a heating section for heating the first hydrogen storage alloy and a cooling section for cooling the first hydrogen storage alloy. The first container and the second container are connected so that the hydrogen gas inside each can circulate. The second container and the third container are connected so that heat can be transferred between them. The third container is connected to a hydrogen supply source that supplies hydrogen gas to the third container, and to a hydrogen supply target that receives hydrogen gas from the third container. The equilibrium pressure range in which the first hydrogen storage alloy releases hydrogen and the equilibrium pressure range in which the second hydrogen storage alloy absorbs hydrogen overlap. The equilibrium pressure range in which the first hydrogen storage alloy absorbs hydrogen and the equilibrium pressure range in which the second hydrogen storage alloy releases hydrogen overlap. In the operation of the hydrogen storage device, at the highest temperature reached by the second hydrogen storage alloy, the equilibrium pressure at which the third hydrogen storage alloy releases hydrogen is higher than the equilibrium pressure at which the first hydrogen storage alloy releases hydrogen due to heating in the heating section. The temperature range in which the second hydrogen storage alloy absorbs hydrogen and the temperature range in which the third hydrogen storage alloy releases hydrogen overlap. A hydrogen storage device in which the temperature range in which the second hydrogen storage alloy releases hydrogen and the temperature range in which the third hydrogen storage alloy absorbs hydrogen overlap.

2. A hydrogen storage device according to claim 1, The second container is a hydrogen storage device arranged in contact with the outer circumference of the third container.

3. A hydrogen storage device according to claim 1 or 2, The first container is a hydrogen storage device arranged around the outer circumference of the second container.

4. A hydrogen storage device according to any one of claims 1 to 3, A hydrogen storage device in which, during operation of the hydrogen storage device, at the lowest temperature reached by the second hydrogen storage alloy, the equilibrium pressure at which the third hydrogen storage alloy absorbs hydrogen is higher than the equilibrium pressure at which the first hydrogen storage alloy absorbs hydrogen due to cooling in the cooling section.

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