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; a storage tank (MH tank 16) having an opening 16A1 which is provided on the housing 16A and allows supply gas containing the produced hydrogen to go in and out of the side of the hydrogen production part; and an arithmetic control device 50 for calculating moisture concentration in the supply gas inside the storage tank, and sending the supply gas inside the storage tank to outside according to the calculated moisture concentration.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. Hydrogen in the supplied supply gas is stored in the hydrogen storage alloy by lowering the temperature of the hydrogen storage alloy.

[0003] Further, in Patent Document 1, a hydrogen utilization device is connected to the storage tank. 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 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 inventors focused on the fact 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 was 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 by focusing on the above-described problems, and provides a hydrogen storage system capable of suppressing the deterioration of an 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, and an opening provided in the housing through which a supply gas containing the hydrogen produced from the side of the hydrogen production unit enters and exits. An occlusion tank having, and an arithmetic control device that calculates the moisture concentration in the supply gas inside the occlusion tank and sends out the supply gas inside the occlusion tank to the outside according to the calculated moisture concentration.

[0009] In the first aspect, when hydrogen is occluded, it is possible to effectively suppress an increase in the concentration of moisture contained in the supply gas inside the occlusion tank. As a result, the deterioration of the occlusion alloy can be suppressed.

[0010] In the hydrogen storage system according to the second aspect, in the hydrogen storage system according to the first aspect, when the calculated moisture concentration exceeds a preset reference concentration, the arithmetic control device sends out the supply gas inside the occlusion tank to the outside.

[0011] In the second aspect, an increase in the moisture concentration can be more reliably suppressed.

[0012] In the hydrogen storage system according to the third aspect, in the hydrogen storage system according to the second aspect, the reference concentration is 300 ppm.

[0013] In the third aspect, deterioration of the occlusion alloy can be more reliably suppressed.

[0014] In the hydrogen storage system according to the fourth aspect, in the hydrogen storage system according to any one of the first to third aspects, the occlusion tank is provided with a heat circuit for raising the temperature of the occlusion alloy, and the arithmetic control device raises the temperature of the occlusion alloy by the heat circuit to release the hydrogen outside the occlusion tank, and uses the flow of the released hydrogen to send out the supply gas inside the occlusion tank to the outside.

[0015] In the fourth aspect, by raising the temperature of the occlusion alloy by the heat circuit, hydrogen is released outside the occlusion tank. Therefore, the supply gas inside the occlusion tank can be sent out to the outside using the flow of the released hydrogen.

[0016] In the hydrogen storage system according to the fifth aspect, in the hydrogen storage system according to the fourth aspect, the heat circuit includes a first heat circuit for raising the temperature of the first region of the occlusion alloy and a second heat circuit provided separately from the first heat circuit for raising the temperature of a second region different from the first region of the occlusion alloy, and each of the first heat circuit and the second heat circuit is connected to the arithmetic control device.

[0017] In the fifth aspect, it is not necessary to raise the temperature of the entire occlusion tank only to send out a part of the supply gas to the outside.

[0018] In the hydrogen storage system according to the sixth aspect, in the hydrogen storage system according to any one of the first to fifth aspects, the arithmetic control device calculates the oxygen concentration in the supply gas inside the occlusion tank, and sends out the supply gas inside the occlusion tank to the outside according to both the calculated moisture concentration and the calculated oxygen concentration.

[0019] In the hydrogen storage system according to the sixth aspect, in addition to the deterioration of the hydrogen storage alloy caused by moisture, the deterioration of the hydrogen storage alloy caused by oxygen can also be suppressed.

Effects of the Invention

[0020] According to the present disclosure, a hydrogen storage system capable of suppressing the deterioration of a hydrogen storage alloy can be provided.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Modes for Carrying Out the Invention

[0022] 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 embodiment is not limited to the configuration shown in the drawings. Also, the sizes of the members in each drawing are conceptual, and the relative relationships of the sizes between the members are not limited to this.

[0023] 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 portions where the dimensional relationships and ratios are different between the drawings. Also, unless otherwise specified in the specification, the number of each component of the present disclosure is not limited to one, and a plurality may exist.

[0024] 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, and they 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.

[0025] 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.

[0026] 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.

[0027] 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, unless otherwise specified, the particle diameter of each component means a value for the mixture of the plurality of types of particles present in the composition.

[0028] 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 the layer or film is formed only in a part of the region.

[0029] <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.

[0030] 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. A 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.

[0031] 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 branch position of the branch pipe PB in the second pipe P2. The flow of the fluid flowing inside the second pipe P2 is controlled by the first valve 22. A second valve 24 for opening and closing the branch pipe PB is provided in the branch pipe PB. The flow of the fluid flowing inside the branch pipe PB is controlled by the second valve 24.

[0032] (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.

[0033] (MH Tank) The MH tank 16 corresponds to the storage tank of the present disclosure. In this 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 storage alloy 16B, and an opening 16A1. A thermal circuit 60 is provided in the MH tank 16. The thermal circuit 60 raises the temperature by heating the storage alloy 16B and lowers the temperature by cooling the storage alloy 16B.

[0034] (Housing) In this 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 storage alloy 16B is stored inside the housing 16A.

[0035] (Storage Alloy) The storage alloy 16B stores hydrogen. As the storage alloy 16B, for example, a lanthanum nickel (LaNi5)-based alloy can be adopted. In the present disclosure, the type of the storage alloy 16B is not limited to this and is arbitrary.

[0036] (Opening) The opening 16A1 is provided in the housing 16A. In the opening 16A1, the supply gas containing hydrogen produced from the side of the water electrolysis device 12 enters and exits. Also, the hydrogen released from the storage alloy 16B is sent out from the opening 16A1. The opening 16A1 of this embodiment is one opening that serves as both a gas inlet and a gas outlet. In the present disclosure, the number of the openings 16A1 is not limited to one and may be two or more. That is, the opening 16A1 as an inlet and the opening 16A1 as an outlet may be provided separately.

[0037] The number of the openings 16A1 functioning as inlets and the number of the openings 16A1 functioning as outlets can each be arbitrarily set to one or more. Further, when two openings 16A1 are provided, the two openings 16A1 may be provided separately at each of one end (the left end in FIG. 1) and the other end (the right end in FIG. 1) in the gas flow direction, or may be arranged side by side and closely disposed on the side of one end in the gas flow direction.

[0038] (Hydrogen utilization device) The hydrogen utilization device 30 is located outside the MH tank 16. Hydrogen is sent out from the opening 16A1 to the hydrogen utilization device 30. The hydrogen utilization device 30 is a device that utilizes the hydrogen sent out from the opening 16A1. 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 hydrogen utilization device 30, the heat circuit 60, the first valve 22, the second valve 24, and the heat circuit 60.

[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. 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) 51, 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 performs control of the above components and 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 the present embodiment, the ROM 52 or the storage 54 can store a concentration 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, a liquid crystal display having a touch panel that enables touch operations by the user, a voice input receiving unit that receives voice input by the user, and at least one of buttons that can be pressed by the user. The display unit of the present 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 device 50 to communicate with other devices. For example, standards such as Ethernet (registered trademark), FDDI, Wi-Fi (registered trademark) are used.

[0047] When executing the concentration control program of the present embodiment, the arithmetic control device 50 uses the above hardware resources to realize various functions. As a functional configuration realized by the arithmetic control device 50, the arithmetic control device 50 has 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 in the MH tank 16 and a preset allowable deterioration range. The reference concentration of the present 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 findings on the relationship between the increase in moisture concentration and the deterioration of the hydrogen storage alloy and the reference concentration in the present embodiment, a detailed description will be given 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 deterioration progresses when the moisture concentration is 300 ppm or more (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 a water electrolysis device, the supply gas containing the produced hydrogen contains moisture with an absolute humidity equivalent to the water electrolysis temperature. Therefore, generally, a system is used in which moisture is removed from the supply gas to a dew point temperature of about -70°C to -50°C using a dehumidifier, and then the hydrogen in the supply gas is occluded in the hydrogen storage alloy to suppress the deterioration of the hydrogen storage alloy.

[0052] On the other hand, inside a general storage tank as described above, basically only hydrogen in the supply gas is occluded. Therefore, when the hydrogen 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 hydrogen 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 the concentration of water vapor 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 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 per 1 m 3 of the hydrogen storage alloy 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 extremely large.

[0061] Also, 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 formed 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. 5 to 7.

[0063] In this embodiment, an example is illustratively described where the CPU of the arithmetic control device 50 reads and executes a program stored in a ROM or a 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, as shown in FIG. 6, supply gas is sent from the dehumidifier 14 toward the MH tank 16. Specifically, the supply gas is sent into the MH tank 16 in a state where the first valve 22 in FIG. 6 is opened and the second valve 24 is controlled to be closed. 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.

[0065] 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 in the same manner as the moisture concentration.

[0066] Also, 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 supply gas sent into the MH tank 16 can also be calculated based on the absorption reaction amount in the same manner as 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.

[0067] 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.

[0068] Specifically, for example, the sending unit of the arithmetic control device 50 raises the temperature of the occlusion alloy 16B by the heat circuit 60 to release hydrogen to the outside of the MH tank 16. The supply gas inside the MH tank 16 is sent to the outside using the flow of the released hydrogen. Note that in the present disclosure, the method of sending the supply gas to the outside is not limited to raising the temperature of the occlusion alloy 16B by the heat circuit 60, that is, releasing hydrogen from the occlusion alloy 16B.

[0069] In the present disclosure, for example, by providing an outlet opening different from the inlet opening 16A1 in the MH tank 16, a passage for sending the supply gas to the outside may be formed between the inlet and the outlet. Further, for example, a pressure boosting device such as a blower or a pump may be provided on the side of the hydrogen utilization device 30, and the flow of sending the gas to the outside of the MH tank 16 may be promoted by the provided pressure boosting device. The gas to be sent may include any of hydrogen released from the occlusion alloy 16B, supply gas containing hydrogen, and mixed gas of hydrogen and supply gas.

[0070] In FIG. 7, a case is illustrated in which a path is formed for the supply gas to move to the hydrogen utilization device 30 outside the MH tank 16 in a state where the first valve 22 is closed and the second valve 24 is controlled to be open. The sending of the supply gas to the outside of the MH tank 16 can be executed while adjusting the sending amount in a pulsed manner, that is, in a temporally pulsating manner. After sending 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.

[0071] On the other hand, in step S2, when the calculated moisture concentration is equal to or lower than 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.

[0072] In step S4, if the control is not continued, 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 is continued until the calculated moisture concentration reaches a reference concentration or less.

[0073] (Function and effect) The hydrogen storage system according to the present embodiment 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.

[0074] 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. For example, a dehumidifier 14 that realizes a dew point temperature of about -70°C to -60°C is unnecessary. Therefore, the load on the hydrogen storage system 10, that is, the energy consumed for dehumidification can be reduced. In addition, since it is possible to suppress the accumulation of water vapor in the voids inside the occlusion alloy 16B, it is difficult to generate a boundary film of water vapor on the occlusion alloy 16B, and as a result, a decrease in the occlusion rate can be suppressed.

[0075] Further, in the present embodiment, 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. Therefore, it is possible to more reliably suppress an increase in the moisture concentration.

[0076] Further, in the present embodiment, the reference concentration is 300 ppm. As described with reference to FIG. 3, by setting the reference concentration to 300 ppm which is an index of the start of deterioration, it is possible to more reliably suppress the deterioration of the occlusion alloy 16B.

[0077] Further, in the present embodiment, by raising the temperature of the hydrogen storage alloy 16B by the heat circuit 60, hydrogen is released to the outside of the MH tank 16. Therefore, the supply gas inside the MH tank 16 can be sent to the outside using the flow of the released hydrogen.

[0078] <Modification Example> As shown in FIG. 8, the hydrogen storage system 10A according to the modification example is different from the present embodiment in that it includes a reflux pipe PR and a third valve 26. The reflux pipe PR branches from a position between the branch position from the second pipe P2 and the second valve 24 in the branch pipe PB and extends toward the water electrolysis device 12.

[0079] A third valve 26 for opening and closing the reflux pipe PR is provided between the branch position of the reflux pipe PR from the branch pipe PB and the water electrolysis device 12. The flow of the fluid flowing inside the reflux pipe PR is controlled by the third valve 26. The third valve 26 is connected to the arithmetic control device 50.

[0080] Regarding the configurations of the other members in the hydrogen storage system 10A according to the modification example, excluding the reflux pipe PR and the third valve 26, they are the same as the members with the same names in the hydrogen storage system 10 according to the present embodiment, so redundant descriptions are omitted. Also, in the modification example, a series of control processes in FIG. 5 are executed. Therefore, hereinafter, redundant descriptions for the same processes as those described in the present embodiment are omitted, and mainly the differences from the present embodiment will be described.

[0081] As shown in FIG. 9, also in the modification, for example, when the supply gas is sent from the dehumidifier 14 toward the MH tank 16 with the first valve 22 open and both the second valve 24 and the third valve 26 controlled to be closed, the moisture concentration in the MH tank 16 increases. Therefore, when the calculated moisture concentration exceeds the reference concentration, as shown in step S3 in FIG. 5, the internal pressure of the MH tank 16 increases as the temperature of the hydrogen storage alloy 16B rises. FIG. 10 illustrates a case where a path is formed for the supply gas to return to the water electrolyzer 12 outside the MH tank 16 via the reflux pipe PR with the third valve 26 open and both the first valve 22 and the second valve 24 controlled to be closed.

[0082] Note that when sending out the supply gas via the reflux pipe PR, the opening degrees of the first valve 22 and the second valve 24 do not necessarily have to be fully closed and can be adjusted as appropriate. For example, the process of sending out the supply gas to the front stage 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.

[0083] Also in the hydrogen storage system 10A according to the modification, similar to the present embodiment, it is possible to effectively suppress an increase in the concentration of moisture contained in the supply gas inside the MH tank 16, and as a result, suppress the deterioration of the hydrogen storage alloy 16B. Further, in the modification, a part of the gas sent out to the outside of the MH tank 16 returns to the dehumidifier 14 via the reflux pipe PR. Therefore, different from the present embodiment, the state of storing hydrogen and the state of using hydrogen can be executed in a time - overlapping manner. Other operations in the modification are the same as those in the present embodiment.

[0084] (Another example of the thermal circuit) In the hydrogen storage system 10A according to the modified example illustrated in FIGS. 8 to 10, in order to send out a part of the supply gas to the outside, the entire MH tank 16 was heated using the heat circuit 60. However, as shown in FIG. 11, the heat circuit 60A may include a first heat circuit 60A1 that heats the first region of the occlusion alloy 16B and a second heat circuit 60A2 that is provided separately from the first heat circuit 60A1 and heats a second region different from the first region of the occlusion alloy 16B. Each of the first heat circuit 60A1 and the second heat circuit 60A2 is connected to the arithmetic control device 50.

[0085] That is, in the heat circuit 60A, two heat circuits 60 including the first heat circuit 60A1 and the second heat circuit 60A2 are provided separately. Therefore, only a part of the occlusion alloy 16B inside the MH tank 16 can be heated. As a result, it is not necessary to heat the entire MH tank 16 only to send out a part of the supply gas to the outside.

[0086] <Other Embodiments> Although the present disclosure has been described by the above-described disclosed embodiments, the description and the drawings that form a part of this disclosure should not be understood as limiting the present disclosure.

[0087] 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 by estimating the flow rate of the supply gas using the pressure difference before and after the first valve located between the dehumidifier 14 and the MH tank 16 and integrating the estimated flow rate in the time direction.

[0088] Also, similar to the moisture concentration, the oxygen concentration can be used to estimate the amount of hydrogen storage reaction by using the amount of heat exchange measured during hydrogen storage in the MH tank 16, and can also be calculated based on the estimated storage 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 hydrogen storage alloy 16B due to oxygen as well as deterioration of the hydrogen storage alloy 16B due to moisture can be suppressed.

[0089] In addition, in the present disclosure, not only simply purging the supply gas, but also 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.

[0090] 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 scope of claims appropriate from the above description.

[0091] (Appendix 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, and an opening provided in the housing through which the supply gas containing the hydrogen produced from the side of the hydrogen production unit enters and exits, and a hydrogen storage tank having the same, 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, A hydrogen storage system comprising the same.

[0092] (Appendix 2) When the calculated moisture concentration exceeds a preset reference concentration, the arithmetic control device sends out the supply gas inside the storage tank to the outside. The hydrogen storage system according to Supplementary Note 1.

[0093] (Supplementary Note 3) The reference concentration is 300 ppm. The hydrogen storage system according to Supplementary Note 2.

[0094] (Supplementary Note 4) A thermal circuit for raising the temperature of the storage alloy is provided in the storage tank. The arithmetic control device releases the hydrogen to the outside of the storage tank by raising the temperature of the storage alloy by the thermal circuit, and uses the flow of the released hydrogen to send out the supply gas inside the storage tank to the outside. The hydrogen storage system according to any one of Supplementary Notes 1 to 3.

[0095] (Supplementary Note 5) The thermal circuit includes a first thermal circuit for raising the temperature of the first region of the storage alloy and a second thermal circuit that is provided separately from the first thermal circuit and raises the temperature of a second region of the storage alloy different from the first region of the storage alloy. Each of the first thermal circuit and the second thermal circuit is connected to the arithmetic control device. The hydrogen storage system according to Supplementary Note 4.

[0096] (Supplementary Note 6) The arithmetic control device calculates the oxygen concentration in the supply gas inside the storage tank, and sends out the supply gas inside the storage tank to the outside according to both the calculated moisture concentration and the calculated oxygen concentration. The hydrogen storage system according to any one of Supplementary Notes 1 to 5.

Explanation of Signs

[0097] 10, 10A Hydrogen storage system 12 Water electrolysis device (hydrogen production unit) 14 Dehumidifier 16 MH Tank (Storage Tank) 16A1 Opening 16A Housing 16B Storage Alloy 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 60 Thermal Circuit 60A Thermal Circuit 60A1 First Thermal Circuit 60A2 Second Thermal Circuit A Saturation Region B Degradation Region P1 First Pipe P2 Second 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, and an opening provided in the housing through which a supply gas containing the hydrogen produced from the side of the hydrogen production unit enters and exits, and a hydrogen storage tank having the same, 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, A hydrogen storage system comprising the same.

2. When the calculated moisture concentration exceeds a preset reference concentration, the arithmetic control device sends out the supply gas inside the hydrogen storage tank to the outside, The hydrogen storage system according to Claim 1.

3. The reference concentration is 300 ppm, The hydrogen storage system according to Claim 2.

4. The hydrogen storage tank is provided with a thermal circuit for raising the temperature of the hydrogen storage alloy, The arithmetic control device releases the hydrogen to the outside of the hydrogen storage tank by raising the temperature of the hydrogen storage alloy by the thermal circuit, and sends out the supply gas inside the hydrogen storage tank to the outside by using the flow of the released hydrogen, The hydrogen storage system according to any one of Claims 1 to 3.

5. The thermal circuit includes a first thermal circuit for raising the temperature of a first region of the hydrogen storage alloy, A second thermal circuit provided separately from the first thermal circuit and for raising the temperature of a second region of the hydrogen storage alloy different from the first region, Each of the first thermal circuit and the second thermal circuit is connected to the arithmetic control device, The hydrogen storage system according to Claim 4.

6. The arithmetic control device calculates the oxygen concentration in the supply gas inside the storage tank, and sends out the supply gas inside the storage tank to the outside according to both the calculated moisture concentration and the calculated oxygen concentration. The hydrogen storage system according to any one of claims 1 to 3.

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