Hydrogen storage system

Abstract

To provide a hydrogen storage system capable of suppressing deterioration of a storage alloy.SOLUTION: A hydrogen storage system 10 includes: a hydrogen production part (water electrolysis apparatus 12) for producing hydrogen; a storage alloy 16B for storing hydrogen; a housing 16A for storing the storage alloy 16B therein; and a storage tank (MH tank 16) having a first opening 16A1 that is provided on the housing 16A and to which supply gas containing the produced hydrogen is sent from the side of the hydrogen production part, and a second opening 16A2 which is provided on the housing 16A separately from the first opening 16A1 and sends the supply gas to outside.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, as in Patent Document 1, there is known a hydrogen storage system that sends out hydrogen stored in a hydrogen storage alloy of a storage tank to a hydrogen utilization device at a predetermined timing. In Patent Document 1, a hydrogen production device is provided in front of the storage tank. The supply gas containing hydrogen produced by the hydrogen production device is sent into the inside of the storage tank through one opening provided in the storage tank. The hydrogen in the supplied supply gas is stored in the hydrogen storage alloy by lowering the temperature of the hydrogen storage alloy.

[0003] Also, in Patent Document 1, a hydrogen utilization device is connected to the storage tank. The hydrogen stored in the hydrogen storage alloy is released from the hydrogen storage alloy by raising the temperature of the hydrogen storage alloy. The hydrogen released from the hydrogen storage alloy is sent out to the hydrogen utilization device through the same opening. Hereinafter, in this specification, the hydrogen storage alloy may sometimes be simply referred to as the "storage alloy".

[0004] In a hydrogen storage system, when hydrogen is stored, it is known that the storage alloy deteriorates due to a small amount of moisture contained in the supply gas to the storage tank. As a means for suppressing the deterioration of the storage alloy, in Patent Document 1, a dehumidifier is provided in the hydrogen production device. That is, the dew point temperature (in other words, the dew point) of the supply gas is lowered by using a dehumidifier provided in front of the storage tank. And by reducing the moisture content of the supply gas, suppression of the deterioration of the storage alloy is achieved.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Here, the present disclosure inventors have noted that when hydrogen is occluded, the deterioration of the occlusion alloy progresses more as the concentration of moisture contained in the supply gas increases inside the occlusion tank. And, based on the new finding that the deterioration of the occlusion alloy is suppressed by suppressing the increase in the moisture concentration, the present disclosure has been devised. In this regard, Patent Document 1 does not disclose the technical idea of suppressing the deterioration of the occlusion alloy by suppressing the increase in the moisture concentration as in the present disclosure.

[0007] The present disclosure has been made paying attention to the above problems, and provides a hydrogen storage system capable of suppressing the deterioration of the occlusion alloy.

Means for Solving the Problems

[0008] The hydrogen storage system according to the first aspect includes a hydrogen production unit that produces hydrogen, an occlusion alloy that stores hydrogen, a housing in which the occlusion alloy is housed inside, a first opening provided in the housing through which a supply gas containing the hydrogen produced from the side of the hydrogen production unit is sent, and a second opening provided separately from the first opening in the housing through which the supply gas is sent out to the outside, and an occlusion tank having the second opening.

[0009] In the first aspect, a second opening for sending out the supply gas is provided in the occlusion tank separately from the first opening for sending in the supply gas. The supply gas sent in from the first opening at the inlet flows inside the housing of the occlusion tank and is sent out from the second opening at the outlet. That is, the first opening is an inlet of the supply gas containing hydrogen toward the occlusion alloy. The second opening is an outlet of the supply gas after flowing around the occlusion alloy.

[0010] Therefore, separately from the first opening, it becomes possible to send out the supply gas from the second opening to the outside of the housing. As a result, for example, compared with the case where only the first opening is provided without providing an outlet for the supply gas in the storage tank, it is possible to reduce the retention of the supply gas inside the housing during hydrogen storage. For this reason, since the concentration of moisture contained in the supply gas inside the storage tank due to hydrogen storage is alleviated, deterioration of the storage alloy can be suppressed.

[0011] In the hydrogen storage system according to the second aspect, in the hydrogen storage system according to the first aspect, the housing is cylindrical, the first opening is provided at one end in the axial direction of the cylindrical housing, and the second opening is provided at the other end in the axial direction.

[0012] In the second aspect, the first opening is provided at one end in the axial direction of the cylindrical housing, and the second opening is provided at the other end in the axial direction. That is, the inlet and the outlet are arranged apart from each other at both ends of the cylindrical storage tank. For this reason, for example, compared with the case where the first opening as the inlet and the second opening as the outlet are arranged side by side and close to each other on one end side of the housing, it is difficult for the supply gas to stay inside the housing.

[0013] In the hydrogen storage system according to the third aspect, in the hydrogen storage system according to the first aspect or the second aspect, a dehumidifier is provided between the hydrogen production unit and the storage tank, and a reflux pipe for refluxing the supply gas sent out from the second opening to the dehumidifier is provided between the dehumidifier and the second opening.

[0014] In the third aspect, a reflux pipe for refluxing the supply gas sent out from the second opening to the dehumidifier is provided between the dehumidifier and the second opening. For this reason, hydrogen in the supply gas sent out from the second opening can be reused for storage.

[0015] The hydrogen storage system according to the fourth aspect is the hydrogen storage system according to any one of the first to third aspects, and includes an arithmetic control device that calculates the moisture concentration in the supply gas inside the storage tank and sends out the supply gas inside the storage tank to the outside according to the calculated moisture concentration.

[0016] In the fourth aspect, when hydrogen is stored, it is possible to effectively suppress an increase in the concentration of moisture contained in the supply gas inside the storage tank. As a result, deterioration of the hydrogen storage alloy can be suppressed.

Effect of the Invention

[0017] According to the present disclosure, it is possible to provide a hydrogen storage system that can suppress deterioration of a hydrogen storage alloy.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0019] Embodiments of the present disclosure will be described below. However, the present disclosure is not limited to the following embodiments. When describing embodiments with reference to the drawings in the present disclosure, the configuration of the embodiments is not limited to the configuration shown in the drawings. Also, the sizes of the members in each figure are conceptual, and the relative size relationships between the members are not limited to this.

[0020] In the following description of the drawings, the same parts are denoted by the same reference numerals. However, the drawings are schematic, and the relationship between the thickness and the planar dimensions, and the ratio of the thicknesses of each device and each member are different from the actual ones. Therefore, the specific thickness and dimensions should be determined with reference to the following description. Also, there are parts where the dimensional relationships and ratios between the drawings are different from each other. Also, unless otherwise specified in the specification, the number of each component of the present disclosure is not limited to one, and a plurality of components may exist.

[0021] In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present disclosure. In the numerical range indicated by "~" in the present disclosure, the numerical values described before and after "~" are included as the minimum value and the maximum value, respectively.

[0022] In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerically described range. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

[0023] In the present disclosure, when a component is included, each component may include a plurality of corresponding substances. When there are a plurality of substances corresponding to each component in the composition, the content rate or content of each component means the total content rate or content of the plurality of substances present in the composition, unless otherwise specified.

[0024] In the present disclosure, the particles corresponding to each component may include a plurality of types of particles. When there are a plurality of types of particles corresponding to each component in the composition, the particle diameter of each component means a value for the mixture of the plurality of types of particles present in the composition, unless otherwise specified.

[0025] In the present disclosure, the terms "layer" or "film" include not only the case where the layer or film is formed over the entire region when observing the region where the layer or film is present, but also the case where it is formed only in a part of the region.

[0026] <Hydrogen storage system> First, the hydrogen storage system 10 according to the present embodiment will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, the hydrogen storage system 10 according to the present embodiment includes a water electrolysis device 12, a dehumidifier 14, an MH tank 16, a hydrogen utilization device 30, and an arithmetic control device 50.

[0027] The dehumidifier 14 is provided between the water electrolysis device 12 and the MH tank 16. The water electrolysis device 12 and the dehumidifier 14 are connected by a first pipe P1. The dehumidifier 14 and the MH tank 16 are connected by a second pipe P2. The MH tank 16 and the hydrogen utilization device 30 are connected by a third pipe P3.

[0028] The reflux pipe PR is provided between the dehumidifier 14 and the second opening 16A2. Specifically, the reflux pipe PR branches from a position between the MH tank 16 and the hydrogen utilization device 30 in the third pipe P3 and extends toward the first pipe P1. That is, the reflux pipe PR connects the second opening 16A2 at the outlet of the MH tank 16 and the position in front of the dehumidifier 14. The reflux pipe PR refluxes the supply gas sent out from the second opening 16A2 to the dehumidifier 14.

[0029] In the second pipe P2, a first valve 22 for opening and closing the second pipe P2 is provided between the dehumidifier 14 and the MH tank 16. The flow of the fluid flowing inside the second pipe P2 is controlled by the first valve 22. In the third pipe P3, a second valve 24 for opening and closing the third pipe P3 is provided between the MH tank 16 and the hydrogen utilization device 30. The flow of the fluid flowing inside the third pipe P3 is controlled by the second valve 24.

[0030] In the reflux pipe PR, a pressure boosting device 18 is provided between the MH tank 16 and the dehumidifier 14. The pressure boosting device 18 can be constituted by, for example, a blower or a pump. The pressure boosting device sends out the gas to the outside of the MH tank 16 and promotes the reflux of the gas to the dehumidifier 14. The refluxing gas may contain any of hydrogen released by the hydrogen storage alloy 16B, a supply gas containing hydrogen, and a mixed gas of hydrogen and the supply gas.

[0031] (Water electrolysis device) The water electrolysis device 12 corresponds to the hydrogen production unit of the present disclosure. The water electrolysis device 12 produces hydrogen by electrolyzing water.

[0032] (MH tank) The MH tank 16 corresponds to the storage tank of the present disclosure. In the present embodiment, "MH" means a hydrogen storage alloy. The MH tank 16 functions as a hydrogen storage unit. The MH tank 16 has a housing 16A, a hydrogen storage alloy 16B, a first opening 16A1, and a second opening 16A2. A heat circuit (not shown) is provided in the MH tank 16. The heat circuit raises the temperature by heating the hydrogen storage alloy 16B and lowers the temperature by cooling the hydrogen storage alloy 16B.

[0033] (Housing) In the present embodiment, the housing 16A is cylindrical, but in the present disclosure, the shape of the housing (in other words, the tank shell) can be appropriately changed. The hydrogen storage alloy 16B is housed inside the housing 16A.

[0034] (Hydrogen storage alloy) The hydrogen storage alloy 16B stores hydrogen. As the hydrogen storage alloy 16B, for example, an alloy of the lanthanum nickel (LaNi5) series can be adopted. Note that in the present disclosure, the type of the hydrogen storage alloy 16B is not limited to this and is arbitrary.

[0035] (Opening) The first opening 16A1 is provided at one end (the left end in FIG. 1) in the axial direction of the cylindrical housing 16A. The second opening 16A2 is provided at the other end (the right end in FIG. 1) in the axial direction of the cylindrical housing 16A. The second opening 16A2 is provided separately from the first opening 16A1 in the housing 16A.

[0036] By connecting the second pipe P2 to the first opening 16A1, a supply gas containing hydrogen produced from the side of the water electrolysis device 12 is sent into the first opening 16A1. By connecting the third pipe P3 to the second opening 16A2, a supply gas containing hydrogen released from the hydrogen storage alloy 16B or hydrogen sent from the side of the water electrolysis device 12 is sent out to the outside from the second opening 16A2. That is, the first opening 16A1 of the present embodiment is a gas inlet. The second opening 16A2 of the present embodiment is a gas outlet.

[0037] The number of the first openings 16A1 functioning as inlets and the number of the first openings 16A1 functioning as outlets can each be arbitrarily set to one or more. Also, in the present embodiment, the first opening 16A1 and the second opening 16A2 are exemplified as being provided separately at one end (the left end in FIG. 1) and the other end (the right end in FIG. 1) in the gas flow direction, but the present disclosure is not limited to this. In the present embodiment, the arrangement position of the first opening 16A1 and the arrangement position of the second opening 16A2 may be arranged side by side and closely arranged, for example, on one end side in the gas flow direction.

[0038] (Hydrogen utilization equipment) The hydrogen utilization device 30 is located outside the MH tank 16. Hydrogen is sent out from the second opening 16A2 to the hydrogen utilization device 30. The hydrogen utilization device 30 is a device that utilizes the hydrogen sent out from the second opening 16A2. The hydrogen utilization device 30 of the present embodiment is, for example, a power generation device. Note that in the present disclosure, the type of the hydrogen utilization device is not limited to this and can be arbitrarily set.

[0039] (Arithmetic control device) The arithmetic control device 50 is connected to each of the water electrolysis device 12, the dehumidifier 14, the MH tank 16, the booster 18, the hydrogen utilization device 30, the first valve 22, the second valve 24, and a heat circuit (not shown).

[0040] (Concentration control) The arithmetic control device 50 calculates the moisture concentration in the supply gas inside the MH tank 16 (that is, inside the housing 16A). In other words, the arithmetic control device 50 predicts the moisture concentration inside the MH tank 16. A specific method for calculating the moisture concentration will be described later. Then, the arithmetic control device 50 sends out (that is, purges) the supply gas inside the MH tank 16 to the outside according to the calculated moisture concentration. By sending out the supply gas inside the MH tank 16 to the outside, the moisture concentration inside the MH tank 16 is controlled.

[0041] Specifically, when the calculated moisture concentration exceeds a preset reference concentration, the arithmetic control device 50 sends out the supply gas inside the MH tank 16 to the outside. Note that in the present disclosure, the condition for sending out the supply gas to the outside is not limited to the comparison between the calculated moisture concentration and the reference concentration. For example, the condition may be set using the average or change rate of a plurality of moisture concentrations calculated during a preset measurement time.

[0042] Next, the internal structure of the arithmetic control device 50 will be described with reference to FIG. 2. As shown in FIG. 2, the arithmetic control device 50 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, a storage 54, a user interface 55, and a communication interface 56. Each component is communicably connected to each other via a bus 57.

[0043] The CPU 51 is a central processing unit that executes various programs and controls each part. That is, the CPU 51 reads a program from the ROM 52 or the storage 54 and executes the program using the RAM 53 as a work area. The CPU 51 controls the above components and performs various arithmetic processes according to the program recorded in the ROM 52 or the storage 54. The arithmetic control device 50 has at least one processor. In this embodiment, the ROM 52 or the storage 54 can store a density control program.

[0044] The ROM 52 stores various programs and various data. The RAM 53 temporarily stores a program or data as a work area. The storage 54 is composed of an HDD (Hard Disk Drive) or an SSD (Solid State Drive) and stores various programs including an operating system and various data.

[0045] The user interface 55 is an interface when the user uses the arithmetic control device 50. The user interface 55 may include, for example, at least one of a liquid crystal display provided with a touch panel that enables a touch operation by the user, a voice input reception unit that receives voice input by the user, and buttons that can be pressed by the user. The display unit of this embodiment is an example of the user interface 55. Note that the user interface 55 is not essential.

[0046] The communication interface 56 is an interface for the arithmetic control unit 50 to communicate with other devices. For example, standards such as Ethernet (registered trademark), FDDI, Wi-Fi (registered trademark), etc. are used.

[0047] When executing the concentration control program of this embodiment, the arithmetic control unit 50 realizes various functions by using the above-mentioned hardware resources. As a functional configuration realized by the arithmetic control unit 50, the arithmetic control unit 50 includes a calculation unit, a comparison unit, and a transmission unit. Each functional configuration is realized by the CPU 51 reading and executing the concentration control program stored in the ROM 52 or the storage 54.

[0048] (Reference concentration) The reference concentration is determined in consideration of the type of metal of the MH tank 16 and a preset allowable deterioration range. The reference concentration of this embodiment is 300 ppm. Note that in the present disclosure, the reference concentration is not limited to this and can be changed as appropriate.

[0049] Next, regarding the knowledge about the relationship between the increase in moisture concentration and the deterioration of the hydrogen storage alloy and the reference concentration in this embodiment, it will be described in detail with reference to FIGS. 3 and 4. First, it is known that the hydrogen storage alloy deteriorates (in other words, corrodes) according to the cycle of absorption and release. As a specific mode of deterioration, there are modes such as oxidation of the surface of the hydrogen storage alloy by water vapor and a reaction by hydroxylation.

[0050] Regarding the mode of deterioration, for example, in the papers of G.D. Sandrock and P.D. Goodell, in the case of LaNi5-based hydrogen storage alloys, it has been reported that when the moisture concentration is 300 ppm or more, deterioration progresses (the paper "Surface poisoning of LaNi5, FeTi and (Fe,Mn)Ti by O2, Co and H2O." (G.D. Sandrock and P.D. Goodell, Journal of the Less Common Metals, Volume 73, Issue 1, 1 September 1980, Pages 161-168)). That is, a moisture concentration of 300 ppm is an indicator of deterioration.

[0051] Here, when the hydrogen supplied to the storage tank is mainly produced by electrolysis using an electrolyzer, the supply gas containing the produced hydrogen contains moisture with an absolute humidity equivalent to the electrolysis temperature of water. For this reason, generally, after removing moisture from the supply gas to a dew point temperature of about -70°C to -50°C using a dehumidifier, a system that suppresses the deterioration of the storage alloy by occluding the hydrogen in the supply gas into the storage alloy is used.

[0052] On the other hand, inside the above-mentioned general storage tank, basically, only hydrogen in the supply gas is occluded. For this reason, when the storage alloy occludes hydrogen, the trace amount of water vapor, which is the remaining component other than hydrogen in the supply gas, is concentrated, and as a result, the moisture concentration in the supply gas increases.

[0053] Figure 3 is a graph showing the relationship between the dew point temperature of the supply gas and the purity of hydrogen, which is disclosed in the above-mentioned papers of G.D. Sandrock and P.D. Goodell. The storage alloy used for the measurement is LaNi5. All impurities other than hydrogen in the supply gas containing hydrogen are assumed to be water vapor. Also, the pressure of the supply gas is 0.9 MPa. In the graph of Figure 3, the saturation region A and the deterioration region B are each illustrated by a bidirectional arrow extending along the left-right direction.

[0054] The saturation region A is a range of dew point temperatures with respect to the purity of hydrogen in which the supply gas is stored from 0% to 100% inside the storage tank, and when water vapor concentration occurs with hydrogen storage, the void inside the storage tank is filled with saturated vapor pressure at 50°C. The void inside the storage tank is set to a value of 50% of the total volume of the portion inside the housing excluding the storage alloy.

[0055] That is, the void filled with saturated vapor pressure at 50°C is assumed to be half the volume of the total volume of the portion inside the housing excluding the storage alloy as the dead volume of the storage tank. Also, the deterioration region B is a range of dew point temperatures with respect to the purity of hydrogen in which a moisture concentration of 300 ppm or more as an index of deterioration is formed.

[0056] For example, in the supply gas with a dew point temperature of -50°C containing hydrogen after passing through a dehumidifier, 0.0590 [g / m 3 of moisture is contained. Also, when 0.9 MPa of hydrogen is stored, the molar storage amount of the stored hydrogen is 370 [mol / m 3 . Also, when the storage alloy is LaNi5, the molar storage amount of hydrogen by the hydrogen storage alloy per 1 m 3 is 46500 [mol / m 3 . In this case, when the maximum amount of hydrogen is stored in the LaNi5 storage alloy, the moisture concentration of the water vapor remaining in the supply gas may be concentrated to about 7.41 [g / m 3 . The moisture concentration of 7.41 [g / m 3 corresponds to approximately 44°C at the dew point temperature.

[0057] Also, as described above, when the void (i.e., the dead volume of the storage tank) filled with saturated vapor pressure at 50°C is set to half of the total volume of the portion inside the housing excluding the storage alloy, the moisture concentration is calculated to be about 14.82 [g / m 3 , which is twice that of 7.41 [g / m 3 . Assuming the temperature at this time is 50°C, about 2000 Pa of water vapor accumulates inside the storage tank.

[0058] That is, even when the dew point temperature of the supply gas is -50°C, due to the concentration of water vapor inside the storage tank, a water vapor pressure of about 2000 Pa is generated inside, and as a result, it can be seen that the moisture concentration greatly exceeds 300 ppm.

[0059] Further, FIG. 4 shows the pressure when condensation is assumed not to occur when water vapor concentration occurs. Assuming that the temperature inside the storage tank during storage is 50°C, water vapor with a dew point temperature of -33°C condenses at a pressure of approximately 12 kPa. Therefore, when water vapor with a dew point temperature below -33°C enters the inside of the storage tank, the concern of condensation increases as the internal water vapor pressure increases.

[0060] Considering such concentration, in the case of the structure of a conventional general storage tank, in order to suppress the deterioration of the storage alloy, it is necessary to achieve a dew point temperature of about -70°C to -60°C by removing moisture using, for example, a dehumidifier. For this reason, the load on the hydrogen storage system, that is, the energy consumed for dehumidification, becomes very large.

[0061] In addition, when water vapor accumulates inside the storage tank, the voids inside the storage alloy are filled with water vapor, so a boundary film of water vapor is generated on the storage alloy, and as a result, there is also a problem that the storage rate decreases. Based on the above findings, in this embodiment, the deterioration of the storage alloy is suppressed by suppressing the increase in the moisture concentration, and the reference concentration is set to 300 ppm, which is an index of deterioration.

[0062] <Method for Controlling Moisture Concentration> Next, a method for controlling the moisture concentration using the hydrogen storage system 10 according to this embodiment will be described with reference to FIGS. 1 and 5.

[0063] In this embodiment, an example is illustratively described in which the CPU of the arithmetic control device 50 reads and executes a program stored in the ROM or the storage, and the concentration control process is executed. In the present disclosure, the user may execute a series of concentration control processes illustrated in FIG. 5 by using the arithmetic control device 50.

[0064] In this embodiment, first, supply gas is sent from the dehumidifier 14 toward the MH tank 16. Specifically, for example, the supply gas is sent into the MH tank 16 in a state where the first valve 22 in FIG. 1 is opened and the second valve 24 is controlled to be closed.

[0065] Note that the arithmetic control device 50 may perform in parallel the feeding of the supply gas into the MH tank 16 through the first opening 16A1 and the sending out of hydrogen to the hydrogen utilization device 30 through the second opening 16A2 in a state where the first valve 22 in FIG. 1 is opened and the second valve 24 is controlled to be opened. Next, as shown in step S1 in FIG. 5, the calculation unit of the arithmetic control device 50 calculates the moisture concentration in the supply gas.

[0066] The moisture concentration can be calculated, for example, by estimating the flow rate of the supply gas using the pressure difference before and after the first valve 22 located between the dehumidifier 14 and the MH tank 16 and integrating the estimated flow rate in the time direction. Note that the hydrogen storage amount can also be calculated using the pressure difference, similar to the moisture concentration.

[0067] Further, the moisture concentration can be calculated by estimating the hydrogen absorption reaction amount using the heat exchange amount measured during hydrogen storage in the MH tank 16 and based on the estimated absorption reaction amount. Note that the amount of the supply gas sent into the MH tank 16 can also be calculated based on the absorption reaction amount, similar to the moisture concentration. The calculation of the moisture concentration is continuously executed in time during the execution of the control process. That is, a plurality of moisture concentrations are calculated during the execution of the control process.

[0068] Next, as shown in step S2 in FIG. 5, the comparison unit of the arithmetic control device 50 compares the calculated moisture concentration with the reference concentration. When the calculated moisture concentration exceeds the reference concentration, the process proceeds to step S3 in FIG. 5. Then, in step S3, the sending unit of the arithmetic control device 50 sends out the supply gas inside the MH tank 16 to the outside.

[0069] Specifically, for example, the sending unit of the arithmetic control device 50 sends out the supply gas to the outside of the MH tank 16 using the passage formed between the first opening 16A1 and the second opening 16A2 at the inlet of the MH tank 16. Further, the sending unit promotes the flow of sending out the supply gas to the outside by the pressure boosting device 18. The supply gas refluxes to the upstream of the dehumidifier 14 outside the MH tank 16 via the reflux pipe PR.

[0070] Note that in the present disclosure, the method of promoting the flow when sending out the supply gas to the outside is not limited to using the pressure boosting device 18. In the present disclosure, for example, the hydrogen storage alloy 16B may be heated by a heat circuit (not shown) provided in the MH tank 16 to release hydrogen to the outside of the MH tank 16. The supply gas inside the MH tank 16 is sent out to the outside using the flow of the released hydrogen.

[0071] Note that when sending out the supply gas via the reflux pipe PR, the opening degree of the first valve 22 and the opening degree of the second valve 24 do not necessarily need to be fully closed, respectively, and can be adjusted as appropriate. For example, the process of sending the supply gas into the MH tank 16 from the side of the dehumidifier 14 and the process of sending out the mixed gas of hydrogen and the supply gas to the upstream of the dehumidifier 14 via the reflux pipe PR may be executed in parallel. Further, for example, the process of sending out the mixed gas of hydrogen and the supply gas to the upstream of the dehumidifier 14 via the reflux pipe PR and the process of sending out the mixed gas of hydrogen and the supply gas to the hydrogen utilization device 30 may be executed in parallel.

[0072] The delivery of the supply gas to the outside of the MH tank 16 via the reflux pipe PR can be performed in a pulsed manner, that is, while adjusting the delivery amount so as to pulsate temporally. After delivering the supply gas inside the MH tank 16 to the outside, the process returns to step S1. Then, the processes after step S2 are repeated.

[0073] On the other hand, in step S2, when the calculated moisture concentration is less than or equal to the reference concentration, the process proceeds to step S4. As shown in step S4 in FIG. 5, when the control continues, the process returns to step S1. Then, the processes after step S2 are repeated.

[0074] In step S4, when the control does not continue, the control process according to the present embodiment ends. By the above series of processes, the moisture concentration control method according to the present embodiment is configured. In the present embodiment, the control process continues until the calculated moisture concentration reaches less than or equal to the reference concentration.

[0075] (Comparative Example) On the other hand, as shown in FIG. 6, the MH tank 16 of the hydrogen storage system 10Z according to the comparative example is not provided with a second opening. Specifically, the MH tank 16 of the comparative example has only one first opening 16A1 that serves as both the gas inlet and outlet.

[0076] Also, the branch pipe PB branches from a position between the first valve 22 and the MH tank 16 in the second pipe P2 and extends toward the hydrogen utilization device 30. That is, the branch pipe PB connects a position between the first valve 22 and the MH tank 16 in the second pipe P2 and the hydrogen utilization device 30. In the comparative example, the second valve 24 is provided in the branch pipe PB and opens and closes the branch pipe PB. The flow of the fluid flowing inside the branch pipe PB is controlled by the second valve 24.

[0077] The MH tank 16 of the hydrogen storage system 10Z according to the comparative example has only one first opening 16A1 that serves as both the gas inlet and outlet. Therefore, compared with this embodiment, when hydrogen is absorbed, the supply gas is likely to stay inside the housing. For this reason, when the moisture contained in the supply gas is concentrated as hydrogen is absorbed inside the storage tank, the degree of deterioration of the storage alloy becomes greater than in this embodiment.

[0078] (Function and effect) In the hydrogen storage system 10 according to this embodiment, a second opening 16A2 for sending out the supply gas is provided in the MH tank 16, separate from the first opening 16A1 for sending in the supply gas. The supply gas sent in from the first opening 16A1 at the inlet flows inside the housing 16A of the MH tank 16 and is sent out from the second opening 16A2 at the outlet. That is, the first opening 16A1 is the inlet of the supply gas containing hydrogen directed toward the storage alloy. The second opening 16A2 is the outlet of the supply gas after flowing around the storage alloy.

[0079] Therefore, it becomes possible to send out the supply gas from the second opening 16A2 to the outside of the housing 16A, separate from the first opening 16A1. As a result, compared with the case where only the first opening 16A1 is provided without providing an outlet for the supply gas in the MH tank 16, for example, when hydrogen is absorbed, the retention of the supply gas inside the housing 16A can be reduced. For this reason, since the concentration of the moisture contained in the supply gas as hydrogen is absorbed inside the MH tank 16 is alleviated, deterioration of the storage alloy can be suppressed.

[0080] Also, in this embodiment, the first opening 16A1 is provided at one end in the axial direction of the cylindrical housing 16A. The second opening 16A2 is provided at the other end in the axial direction of the cylindrical housing 16A, that is, the inlet and outlet are arranged apart from each other at both ends of the cylindrical MH tank 16. For this reason, the supply gas is less likely to stay inside the housing 16A compared with the case where, for example, the first opening 16A1 at the inlet and the second opening 16A2 at the outlet are arranged side by side and close to each other on one side of the housing 16A.

[0081] Further, in the present embodiment, a reflux pipe PR for refluxing the supply gas sent out from the second opening 16A2 to the dehumidifier 14 is provided between the dehumidifier 14 and the second opening 16A2. Therefore, hydrogen in the supply gas sent out from the second opening 16A2 can be reused for occlusion.

[0082] The hydrogen storage system 10 according to the present embodiment further includes an arithmetic control device 50 that calculates the moisture concentration of the supply gas inside the MH tank 16 and sends out the supply gas inside the MH tank 16 to the outside according to the calculated moisture concentration. Therefore, when hydrogen is occluded, it is possible to effectively suppress an increase in the concentration of moisture contained in the supply gas inside the MH tank 16. As a result, deterioration of the occlusion alloy 16B can be suppressed.

[0083] Further, by sending out the supply gas inside the MH tank 16 to the outside according to the calculated moisture concentration, the moisture concentration inside the MH tank 16 is controlled. Therefore, for example, a dehumidifier 14 that realizes a dew point temperature of about -70°C to -60°C is unnecessary. As a result, the load on the hydrogen storage system 10, that is, the energy consumed for dehumidification can be reduced. In addition, since the accumulation of water vapor in the voids inside the occlusion alloy 16B is suppressed, it is difficult to form a boundary film of water vapor on the occlusion alloy 16B, and as a result, a decrease in the occlusion rate can be suppressed.

[0084] (Another example of the occlusion tank) The cylindrical MH tank 16 illustrated in FIG. 1 has a longer side length measured along the left-right direction in FIG. 1 than the diameter of the bottom measured along the up-down direction in FIG. 1. However, the shape of the occlusion tank of the present disclosure is not limited thereto.

[0085] The cylindrical MH tank 17 illustrated in FIG. 7 has a maximum diameter D measured along the radial direction of the MH tank 17 (i.e., the vertical direction in FIG. 7) that is longer than the maximum length L measured along the axial direction of the MH tank 17 (i.e., the flow direction of the supply gas parallel to the left-right direction in FIG. 7). In other words, the shape of the MH tank 17 is flat. In this specification, "the storage tank (MH tank 17) is flat" means that the aspect ratio L / D is 1 or less.

[0086] In the MH tank 17 illustrated in FIG. 7, a first opening 17A1 is provided on the side of one bottom surface (the left side in FIG. 7) in the axial direction of the cylindrical MH tank 17, and a second opening 17A2 is provided on the side of the other bottom surface (the right side in FIG. 7) in the axial direction.

[0087] Note that in the present disclosure, the shape of the cylindrical storage tank is not limited to a straight cylindrical shape in which the side surface appears as a strictly rectangular shape as in the cylindrical MH tank 16 illustrated in FIG. 1 and the MH tank 17 illustrated in FIG. 7. Protrusions or depressions may be formed on each of the bottom surface and the side surface. In the present disclosure, for example, the shape of the cylindrical storage tank may be not only a cylindrical shape but also a square tube shape. Also, the corners between the bottom surface and the side surface in the cylindrical storage tank may be rounded, or a taper may be provided at the corners.

[0088] In the MH tank 17 illustrated in FIG. 7, for example, the residence time of moisture inside the MH tank 17 can be further reduced compared to an MH tank having a common maximum diameter D and an aspect ratio L / D greater than 1. Therefore, deterioration of the storage alloy can be more suppressed.

[0089] <Other Embodiments> Although the present disclosure has been described by the above-described disclosed embodiments, the discourse and drawings that form a part of this disclosure should not be understood as limiting the present disclosure.

[0090] For example, the arithmetic control device 50 of the hydrogen storage system may be configured to calculate the oxygen concentration in the supply gas inside the MH tank 16. Similar to the moisture concentration, the oxygen concentration can be calculated, for example, by using the pressure difference before and after the first valve located between the dehumidifier 14 and the MH tank 16 to estimate the flow rate of the supply gas and integrating the estimated flow rate in the time direction.

[0091] Also, similar to the moisture concentration, the oxygen concentration can be calculated by using the heat exchange amount measured during hydrogen occlusion in the MH tank 16 to estimate the hydrogen occlusion reaction amount and calculating based on the estimated occlusion reaction amount. Then, the arithmetic control device 50 may be configured to send out the supply gas inside the MH tank 16 to the outside according to both the calculated moisture concentration and the calculated oxygen concentration. Since the supply gas inside the MH tank 16 is sent out to the outside according to both the moisture concentration and the oxygen concentration in the supply gas, deterioration of the occlusion alloy 16B caused by oxygen as well as deterioration of the occlusion alloy 16B caused by moisture can be suppressed.

[0092] In addition, in the present disclosure, not only the supply gas is simply purged, but the purge timing may be determined by combining the hydrogen storage system and an Energy Management System (EMS). The combination of the hydrogen storage system and the EMS is effective in that it can optimize the energy of the entire system.

[0093] In addition, the present disclosure can also be configured by partially combining the configurations illustrated in the plurality of attached drawings. As described above, the present disclosure includes various embodiments not described above, and the technical scope of the present disclosure is determined by the invention specific matters of the valid patent claims from the above description.

[0094] (Appendix 1) A hydrogen production unit that produces hydrogen, An occlusion alloy that stores hydrogen, A housing in which the occlusion alloy is housed inside, A first opening provided in the housing into which a supply gas containing hydrogen produced from the side of the hydrogen production unit is fed; A storage tank having, separately from the first opening, a second opening provided in the housing for sending out the supply gas to the outside; A hydrogen storage system comprising the same.

[0095] (Appendix 2) The housing is cylindrical; The first opening is provided at one end in the axial direction of the cylindrical housing; The second opening is provided at the other end in the axial direction. The hydrogen storage system according to Appendix 1.

[0096] (Appendix 3) A dehumidifier is provided between the hydrogen production unit and the storage tank; A reflux pipe for refluxing the supply gas sent out from the second opening to the dehumidifier is provided between the dehumidifier and the second opening. The hydrogen storage system according to Appendix 1 or 2.

[0097] (Appendix 4) An arithmetic control device is provided for calculating the moisture concentration in the supply gas inside the storage tank and sending out the supply gas inside the storage tank to the outside according to the calculated moisture concentration. The hydrogen storage system according to any one of Appendices 1 to 3.

Explanation of Reference Numerals

[0098] 10, 10Z Hydrogen storage system 12 Water electrolysis device (hydrogen production unit) 14 Dehumidifier 16 MH tank (storage tank) 16A1 First opening 16A2 Second opening 16A Housing 16B Hydrogen storage alloy 17 MH tank (storage tank) 17A1 First opening 17A2 Second Opening 18 Boosting Device 22 First Valve 24 Second Valve 26 Third Valve 30 Hydrogen Utilization Equipment 50 Arithmetic Control Unit 54 Storage 55 User Interface 56 Communication Interface 57 Bus A Saturation Region B Degradation Region P1 First Pipe P2 Second Pipe P3 Third Pipe PB Branch Pipe PR Return Pipe

Claims

1. A hydrogen production unit for producing hydrogen, A hydrogen storage alloy for storing hydrogen, A housing in which the hydrogen storage alloy is housed inside, A first opening provided in the housing and into which a supply gas containing the hydrogen produced from the side of the hydrogen production unit is fed, A hydrogen storage tank having a second opening provided in the housing separately from the first opening and sending out the supply gas to the outside, A hydrogen storage system comprising the above.

2. The housing is cylindrical, The first opening is provided at one end in the axial direction of the cylindrical housing, The second opening is provided at the other end in the axial direction, The hydrogen storage system according to Claim 1.

3. A dehumidifier is provided between the hydrogen production unit and the hydrogen storage tank, A reflux pipe for refluxing the supply gas sent out from the second opening to the dehumidifier is provided between the dehumidifier and the second opening, The hydrogen storage system according to Claim 1 or 2.

4. It comprises an arithmetic control device that calculates the moisture concentration in the supply gas inside the hydrogen storage tank and sends out the supply gas inside the hydrogen storage tank to the outside according to the calculated moisture concentration, The hydrogen storage system according to Claim 1 or 2.

Images