Hydrogen storage system

Abstract

To suppress changes in pressure in a hydrogen storage tank in which a hydrogen absorbing alloy is stored.SOLUTION: A hydrogen storage system 100 includes: a hydrogen storage tank 10 in which a hydrogen absorbing ally 11 is stored; a first hydrogen holder 73 and a second hydrogen holder 74 in which hydrogen can be stored; a first pressure sensor 57 for detecting a pressure in the hydrogen storage tank 10; and a controller 60 for controlling a communication state between the hydrogen storage tank 10 and the first hydrogen holder 73 and the second hydrogen holder 74. When the value detected by the first pressure sensor 57 is below a first threshold value, the controller 60 allows communication between the hydrogen storage tank 10 and the hydrogen holder higher in pressure than the hydrogen storage tank 10 of the first hydrogen holder 73 and the second hydrogen holder 74. When the value detected by the first pressure sensor 57 is above a second threshold value, the controller allows communication between the hydrogen storage tank 10 and the hydrogen holder lower in pressure than the hydrogen storage tank 10 of the first hydrogen holder 73 and the second hydrogen holder 74.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a hydrogen storage system including a hydrogen storage tank containing a hydrogen storage alloy that stores hydrogen, and a temperature adjustment unit capable of adjusting the temperature inside 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] Generally, the temperature of a hydrogen storage tank containing a hydrogen storage alloy changes depending on the temperature of the environment where the hydrogen storage system is installed. Such temperature changes cause pressure changes in the hydrogen storage tank. For example, when the environmental temperature drops, if the pressure in the hydrogen storage tank drops to a negative pressure, air may enter the hydrogen storage tank. Also, when the environmental temperature rises, if the pressure in the hydrogen storage tank exceeds the allowable pressure of the hydrogen storage tank, hydrogen may leak from the safety device of the hydrogen storage tank.

[0005] ​

[0006] An object of the present invention is to suppress a change in pressure of a hydrogen storage tank containing a hydrogen storage alloy without increasing the energy consumption of a hydrogen storage system.

Means for Solving the Problems

[0007] The present invention is a hydrogen storage system that stores hydrogen supplied from a hydrogen generator and supplies the stored hydrogen to a hydrogen utilization device, the hydrogen storage system including: a hydrogen storage tank containing a hydrogen storage alloy that absorbs hydrogen; a first hydrogen holder that is connected to be communicable with the hydrogen storage tank in a state where the pressure is controlled and that can store hydrogen; a second hydrogen holder that is connected to be communicable with the hydrogen storage tank in a state where the pressure is controlled and that can store hydrogen; a tank pressure detection unit that detects the pressure in the hydrogen storage tank; a first holder pressure detection unit that detects the pressure in the first hydrogen holder; a second holder pressure detection unit that detects the pressure in the second hydrogen holder; and a control unit that controls the communication state between the hydrogen storage tank and the first hydrogen holder and the communication state between the hydrogen storage tank and the second hydrogen holder in a state where the pressure is controlled based on detection values of the tank pressure detection unit, the first holder pressure detection unit, and the second holder pressure detection unit. The control unit, when the value detected by the tank pressure detection unit is lower than a first threshold value in a state where there is no inflow or outflow of hydrogen between the hydrogen storage system, the hydrogen generator, and the hydrogen utilization device, causes the hydrogen holder having a pressure higher than that of the hydrogen storage tank among the first hydrogen holder and the second hydrogen holder to communicate with the hydrogen storage tank in a state where the pressure is controlled; and when the value detected by the tank pressure detection unit exceeds a second threshold value higher than the first threshold value, causes the hydrogen holder having a pressure lower than that of the hydrogen storage tank among the first hydrogen holder and the second hydrogen holder to communicate with the hydrogen storage tank in a state where the pressure is controlled.

Advantages of the Invention

[0008] According to the present invention, it is possible to suppress a change in pressure of a hydrogen storage tank containing a hydrogen storage alloy without increasing the energy consumption of a hydrogen storage system.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011] The hydrogen storage system 100 supplies hydrogen to a generator or a drive source that uses hydrogen gas as fuel and is installed or mounted in a building or mobility, and absorbs or releases the hydrogen gas generated by the hydrogen generator P. First, with reference to FIG. 1, the hydrogen energy system S to which the hydrogen storage system 100 according to an embodiment of the present invention is applied will be briefly described.

[0012] As shown in FIG. 1, the hydrogen energy system S includes a hydrogen storage system 100, a hydrogen generator P that supplies hydrogen to the hydrogen storage system 100, and a hydrogen utilization device C that uses the hydrogen released from the hydrogen storage system 100.

[0013] The hydrogen generation device P generates hydrogen by electrolyzing water. The hydrogen generation device P includes a temperature adjustment device (not shown) that adjusts the temperature of the generated hydrogen, a dehumidification adjustment device (not shown) that adjusts the humidity of the generated hydrogen, and a pressure adjustment device (not shown) that adjusts the pressure of the generated hydrogen.

[0014] The hydrogen utilization device C is an energy generation source that creates energy through the chemical reaction of hydrogen released from the hydrogen storage system 100. Specifically, it is a fuel cell or a hydrogen engine. The fuel cell reacts hydrogen released from the hydrogen storage system 100 with oxygen to generate electrical energy, and the hydrogen engine burns hydrogen released from the hydrogen storage system 100 to generate rotational energy and the like. Note that heat, water, or water vapor is discharged from the fuel cell and the hydrogen engine.

[0015] The hydrogen storage system 100 includes a hydrogen storage alloy 11 that stores hydrogen, a hydrogen storage tank 10 that houses the hydrogen storage alloy 11, a circulation circuit 20 through which water (heat medium) that performs heat exchange with the hydrogen storage alloy 11 circulates, a cooling mechanism 30 that cools the water flowing in the circulation circuit 20, a heating mechanism 40 that heats the water flowing in the circulation circuit 20, and a controller (PLC: Programmable Logic Controller) 60 (control unit) that controls the circulation state of the water in the circulation circuit 20 and the operation of the heating mechanism 40, and controls the communication state between the hydrogen storage tank 10, the hydrogen generation device P, and the hydrogen utilization device C in a state where the pressure is controlled.

[0016] As shown in FIG. 1, the hydrogen storage tank 10 is connected to the hydrogen generation device P through a first flow path 51, and is also connected to the hydrogen utilization device C through a second flow path 54 having one end connected to the first flow path 51.

[0017] A first on-off valve 52 for opening or closing the first flow path 51 is provided in the first flow path 51 on the side of the hydrogen storage tank 10 rather than at the location where the second flow path 54 is connected to the first flow path 51, and a second on-off valve 53 for opening or closing the first flow path 51 is provided in the first flow path 51 on the side of the hydrogen generator P rather than at the location where the second flow path 54 is connected to the first flow path 51. Note that the second on-off valve 53 may be built into the hydrogen generator P.

[0018] Also, a third on-off valve 55 for opening or closing the second flow path 54 is provided in the second flow path 54. The opening and closing operations of these on-off valves 52, 53, 55 are controlled by a controller 60, and the communication state between the hydrogen storage system 100 and each of the devices P, C is controlled. Note that these on-off valves 52, 53, 55 may be control valves capable of adjusting the flow rate and pressure.

[0019] Specifically, in the hydrogen energy system S, when the first on-off valve 52 and the second on-off valve 53 are opened and the third on-off valve 55 is closed, the hydrogen generated by the hydrogen generator P can be supplied to the hydrogen storage tank 10 through the first flow path 51. When the first on-off valve 52 and the third on-off valve 55 are opened and the second on-off valve 53 is closed, the hydrogen in the hydrogen storage tank 10 can be supplied to the hydrogen utilization device C through the first flow path 51 and the second flow path 54. When the first on-off valve 52, the second on-off valve 53, and the third on-off valve 55 are closed, the inflow and outflow of hydrogen between the hydrogen storage system 100 and each of the devices P, C are blocked.

[0020] Also, a pressure reducing valve 56 for reducing the pressure of the hydrogen gas supplied to the hydrogen utilization device C through the second flow path 54 is provided in the second flow path 54 between the third on-off valve 55 and the hydrogen utilization device C. The pressure reducing valve 56 is a self-operated (spring type) pressure reducing valve that automatically adjusts the valve opening degree so that the pressure of the hydrogen gas supplied to the hydrogen utilization device C becomes a preset pressure (for example, about 0.15 MPaG (hereinafter, the pressure values shown in the description of this embodiment are gauge pressures based on atmospheric pressure)). That is, as long as hydrogen is not consumed in the hydrogen utilization device C, hydrogen does not flow through the first on-off valve 52 and the third on-off valve 55, and since the flow path for supplying hydrogen to the hydrogen utilization device C is filled with positive-pressure hydrogen, it is possible to prevent air from entering the second flow path 54 or the like from the outside. Therefore, the first on-off valve 52 and the third on-off valve 55 are held in an open state during standby (except in an emergency). Note that the set pressure of the pressure reducing valve 56 is not limited to being controlled according to the load of the spring, and may be controlled by the controller 60 or set manually.

[0021] The hydrogen storage tank 10 is composed of a pressure vessel, and a hydrogen storage alloy 11 is accommodated in the hydrogen storage tank 10. As the hydrogen storage alloy 11, AB5 type, AB2 type, A2B type, solid solution type (BCC alloy), etc. are used, and hydrogen is stored in the hydrogen storage tank 10 by adsorbing hydrogen to the hydrogen storage alloy 11 at a pressure of less than 1.0 MPaG.

[0022] A first pressure sensor 57 (tank pressure detection unit) is provided on the hydrogen storage tank 10 side of the first on-off valve 52 in the first flow path 51. The first pressure sensor 57 detects the pressure around the hydrogen storage alloy 11 (the pressure of hydrogen in the hydrogen storage tank 10). Note that the first pressure sensor 57 may be provided on the hydrogen storage tank 10. In addition, the hydrogen storage tank 10 is provided with a safety device (not shown) that releases hydrogen gas when the internal pressure exceeds a predetermined allowable pressure.

[0023] Also, between the first on-off valve 52 and the second on-off valve 53 in the first flow path 51, a second pressure sensor 58 is provided to monitor the pressure in the section that becomes a blocked flow path when the first on-off valve 52, the second on-off valve 53, and the third on-off valve 55 are closed. As described above, the first on-off valve 52 and the third on-off valve 55 may be held in an open state during standby (other than in an emergency).

[0024] The circulation circuit 20 circulates water, which is a heat medium, to perform heat exchange with the hydrogen storage alloy 11, the heating mechanism 40, and the cooling mechanism 30, and adjusts the temperature of the hydrogen storage alloy 11. As shown in FIG. 1, the circulation circuit 20 includes a pump 21 for circulating water in the circulation circuit 20, a first heat exchange section 22 that performs heat exchange with the heating mechanism 40, a second heat exchange section 23 that performs heat exchange with the hydrogen storage alloy 11, a bypass flow path 24 that bypasses the cooling mechanism 30, a control valve 25 that controls the distribution of the flow rate flowing to the cooling mechanism 30 and the bypass flow path 24, a first temperature sensor 26 that detects the water temperature on the inlet side of the second heat exchange section 23, and a second temperature sensor 27 that detects the water temperature on the outlet side of the second heat exchange section 23. Note that the heat medium circulating in the circulation circuit 20 is not limited to water, and may be other liquids such as antifreeze generally used as a heat medium.

[0025] The first heat exchange section 22 performs heat exchange with the heating mechanism 40 and heats the water circulating in the circulation circuit 20 by receiving heat from the heating mechanism 40. The second heat exchange section 23 adjusts the temperature of the hydrogen storage alloy 11 by performing heat exchange with the hydrogen storage alloy 11. By adjusting the temperature of the hydrogen storage alloy 11 in this way, as will be described later, the pressure in the hydrogen storage tank 10 is ultimately adjusted.

[0026] The control valve 25 distributes the water that has passed through the second heat exchange section 23 to the cooling mechanism 30 and the bypass flow path 24. Specifically, the control valve 25 is a three-way valve controlled by a controller 60 and controls the flow rate of the water distributed to the cooling mechanism 30 and the bypass flow path 24. Note that the control valve 25 may be constituted by two two-way valves.

[0027] The cooling mechanism 30 is composed of a chiller, a cooling tower, a radiator, etc. The cooling mechanism 30 may be any device as long as it has at least the function of a radiator that releases the heat of the water circulating in the circulation circuit 20 to the atmosphere.

[0028] The heating mechanism 40 transmits the heat generated in the hydrogen utilization device C to the circulation circuit 20 through water, which is a heat medium circulating inside. It includes a circulation circuit 41 through which water circulates, a pump 42 for circulating the water in the circulation circuit 41, a third heat exchange part 43 provided in the circulation circuit 41 for performing heat exchange with the first heat exchange part 22, a fourth heat exchange part 44 provided in the circulation circuit 41 for performing heat exchange with the hydrogen utilization device C, a bypass flow path 46 bypassing the third heat exchange part 43, a control valve 45 for controlling the distribution of the flow rate of the water flowing to the third heat exchange part 43 and the bypass flow path 46, a radiator 47 capable of dissipating the heat of the water circulating in the circulation circuit 41, and a temperature sensor 48 for detecting the temperature of the water that has passed through the radiator 47. Note that the heat medium circulating in the circulation circuit 41 is not limited to water, and other liquids such as antifreeze generally used as heat media may be used.

[0029] The control valve 45 is a three-way valve controlled by the controller 60, and controls the flow rate of the water distributed to the third heat exchange part 43 and the bypass flow path 46. Note that the control valve 45 may be composed of two two-way valves.

[0030] The third heat exchange part 43 performs heat exchange with the first heat exchange part 22, and heats the water circulating in the circulation circuit 20 with the heat of the water circulating in the circulation circuit 41. The fourth heat exchange part 44 performs heat exchange with the hydrogen utilization device C, and heats the water circulating in the circulation circuit 41 with the heat such as combustion heat and reaction heat generated when the hydrogen utilization device C is driven.

[0031] In addition, the surplus heat of the water that could not be completely transferred to the first heat exchanger 22 in the third heat exchanger 43 is removed by the radiator 47. The degree of cooling in the radiator 47, that is, the air volume of the cooling fan, is controlled according to the temperature detected by the temperature sensor 48 so that the temperature of the water supplied to the fourth heat exchanger 44 that performs heat exchange with the hydrogen utilization device C becomes equal to or lower than a predetermined temperature.

[0032] In this way, by heating the water circulating in the circulation circuit 20 with the heat generated when driving the hydrogen utilization device C via the heating mechanism 40, it is possible to increase the temperature of the hydrogen storage alloy 11 using the heat of the hydrogen utilization device C. In the example shown in FIG. 1, the flow of the heat medium in the first heat exchanger 22 and the flow of the heat medium in the third heat exchanger 43 are in parallel flow, but they may be in countercurrent flow.

[0033] Next, the adsorption and desorption of hydrogen in the hydrogen storage alloy 11 will be described with reference to FIG. 2. FIG. 2 is a graph showing the relationship between the pressure, temperature, and hydrogen storage amount of the hydrogen storage alloy 11 (hydrogen storage tank 10). The solid line in FIG. 2 indicates the characteristics during adsorption, and the broken line indicates the characteristics during desorption.

[0034] First, the adsorption of hydrogen to the hydrogen storage alloy 11 will be described.

[0035] The hydrogen generated by the hydrogen generator P is introduced into the hydrogen storage tank 10 through the first flow path 51 when the first on-off valve 52 and the second on-off valve 53 are open. The pressure of the hydrogen supplied from the hydrogen generator P is about 0.8 MPaG at maximum, and the hydrogen introduced into the hydrogen storage tank 10 is adsorbed by the hydrogen storage alloy 11. When the hydrogen storage alloy 11 adsorbs hydrogen, the temperature of the hydrogen storage alloy 11 rises due to the exothermic reaction. The actual hydrogen pressure supplied from the hydrogen generator P slightly varies depending on the specifications of the hydrogen generator P and the like.

[0036] As shown in FIG. 2, the hydrogen storage alloy 11 has a decreasing hydrogen storage amount as the temperature increases at the same pressure. Therefore, during adsorption, the pump 21 is driven to circulate the water in the circulation circuit 20 to cool the hydrogen storage alloy 11. Also, as described above, since the hydrogen storage alloy 11 undergoes an exothermic reaction when adsorbing hydrogen, it is necessary to cool the hydrogen storage alloy 11 in order to efficiently adsorb hydrogen.

[0037] Specifically, the water discharged from the pump 21 cools the hydrogen storage alloy 11 in the second heat exchange section 23. The water whose temperature has risen by exchanging heat with the hydrogen storage alloy 11 (the water that has passed through the second heat exchange section 23) is guided to the cooling mechanism 30 through the control valve 25. In the cooling mechanism 30, the heat of the passing water is removed, and the temperature of the water decreases. The water cooled by the cooling mechanism 30 is guided to the pump 21 and discharged from the pump 21 again.

[0038] By circulating the water in the circulation circuit 20 in this way, the heat generated by the hydrogen storage alloy 11 can be released to the outside. During adsorption, the pump 42 of the heating mechanism 40 is stopped, or the control valve 45 is controlled to stop the inflow of water to the third heat exchange section 43 so that the entire amount flows through the bypass flow path 46, so that heat exchange does not occur in the first heat exchange section 22. As a result, the water in the circulation circuit 20 is not heated.

[0039] Also, when hydrogen is adsorbed on the hydrogen storage alloy 11, the hydrogen pressure is controlled to be constant at about 0.8 MPaG.

[0040] Specifically, when the hydrogen pressure detected by the first pressure sensor 57 decreases, the controller 60 controls the control valve 25 to guide a part of the water that has passed through the second heat exchange section 23 to the bypass flow path 24 and the rest to the cooling mechanism 30. As a result, the water that has passed through the second heat exchange section 23 is not excessively cooled in the cooling mechanism 30, passes through the bypass flow path 24 and the cooling mechanism 30, then merges, and is discharged from the pump 21 again.

[0041] If the heat removal amount of the hydrogen storage alloy 11 is too large, that is, if the temperature of the water passing through the second heat exchange part 23 is too low, the temperature inside the hydrogen storage tank 10 will decrease. As a result, the pressure of hydrogen will decrease. Therefore, by guiding a part of the water passing through the second heat exchange part 23 to the bypass flow path 24 to bypass the cooling mechanism 30, the temperature of the water supplied to the second heat exchange part 23 is adjusted. In this way, in order to suppress the decrease in the pressure of hydrogen, the cooling of the hydrogen storage alloy 11 is suppressed.

[0042] This control is executed by adjusting the opening degree of the control valve 25 by feedback control such as PI control (proportional integral control) based on the pressure of hydrogen detected by the first pressure sensor 57. Note that the control may be performed using the first temperature sensor 26 and the second temperature sensor 27 provided in the circulation circuit 20, or the control may be performed by using the first pressure sensor 57 in combination with the first temperature sensor 26 and the second temperature sensor 27.

[0043] The adsorption of hydrogen by the hydrogen storage alloy 11 ends by closing the second on-off valve 53.

[0044] Next, the desorption of hydrogen from the hydrogen storage alloy 11 will be described.

[0045] The hydrogen in the hydrogen storage tank 10 is guided to the hydrogen utilization device C through the first flow path 51 and the second flow path 54 when the first on-off valve 52 and the third on-off valve 55 are in the open state.

[0046] When the hydrogen utilization device C starts, the controller 60 desorbs hydrogen from the hydrogen storage alloy 11 in order to supply hydrogen to the hydrogen utilization device C. Specifically, first, the controller 60 sets the first on-off valve 52 and the third on-off valve 55 to the open state. Thereby, hydrogen is supplied from the hydrogen storage tank 10 to the hydrogen utilization device C. Note that, as described above, the first on-off valve 52 and the third on-off valve 55 may be held in the open state.

[0047] The pressure of the hydrogen desorbed from the hydrogen storage alloy 11 is controlled to be constant at about 0.75 MPaG. The hydrogen utilization device C is supplied with hydrogen whose pressure is adjusted by the pressure reducing valve 56 to the set pressure (for example, 0.15 MPaG) necessary for operating the hydrogen utilization device C. That is, even if the pressure of the hydrogen desorbed from the hydrogen storage alloy 11 drops to about the set pressure of the pressure reducing valve 56, the hydrogen utilization device C can still operate.

[0048] When hydrogen is desorbed from the hydrogen storage alloy 11, the temperature of the hydrogen storage alloy 11 decreases due to the endothermic reaction. However, when the temperature of the hydrogen storage alloy 11 decreases, the pressure of the hydrogen desorbed from the hydrogen storage alloy 11 decreases and desorption stops. Therefore, the heating mechanism 40 is driven by receiving the heat of the hydrogen utilization device C, and the water circulating in the circulation circuit 20 is heated by the heating mechanism 40 to raise the temperature of the hydrogen storage alloy 11.

[0049] Specifically, the controller 60 drives the pump 42 and controls the control valve 45 so that the water gradually shifts from the state where the entire amount of water flows through the bypass passage 46 to the state where water flows into the third heat exchange section 43. As described above, the surplus heat of the water that could not be completely transferred to the first heat exchange section 22 in the third heat exchange section 43 is removed by the radiator 47. In addition, the controller 60 drives the pump 21 and controls the control valve 25 so that the entire amount of water circulating in the circulation circuit 20 flows through the bypass passage 24 and no water flows into the cooling mechanism 30. As a result, the water in the circulation circuit 41 circulates, and the water in the circulation circuit 20 circulates while bypassing the cooling mechanism 30. At this time, the controller 60 first adjusts the opening degree of either or both of the control valve 45 and the control valve 25 so that the temperature detected by the first temperature sensor 26 becomes about 45 degrees, and then adjusts the opening degree of either or both of the control valve 45 and the control valve 25 so that the pressure of the hydrogen storage tank 10 detected by the first pressure sensor 57 becomes a predetermined pressure.

[0050] The water circulating within the circulation circuit 41 is heated by the heat of the hydrogen utilization device C through heat exchange with the hydrogen utilization device C in the fourth heat exchanger 44. Then, when the water heated in the fourth heat exchanger 44 reaches the third heat exchanger 43, heat exchange occurs between the third heat exchanger 43 and the first heat exchanger 22, and the water circulating within the circulation circuit 20 is heated. By heating the water circulating within the circulation circuit 20 in this way, the hydrogen storage alloy 11 is heated via the second heat exchanger 23, and hydrogen is desorbed from the hydrogen storage alloy 11. By continuously desorbing hydrogen from the hydrogen storage alloy 11, hydrogen is stably supplied from the hydrogen storage tank 10 to the hydrogen utilization device C.

[0051] In this way, the circulation circuit 20 and the heating mechanism 40 function as a desorption promotion mechanism that utilizes the heat of the hydrogen utilization device C to heat the hydrogen storage alloy 11 accommodated in the hydrogen storage tank 10 and promotes the desorption of hydrogen from the hydrogen storage alloy 11.

[0052] On the other hand, if the temperature of the water circulating within the circulation circuit 20 becomes too high, the pressure of the hydrogen desorbed from the hydrogen storage alloy 11 will increase. In such a case, the controller 60 controls the control valve 45 to reduce the flow rate of the water passing through the third heat exchanger 43. As a result, since the amount of heat received from the third heat exchanger 43 in the first heat exchanger 22 can be reduced, the temperature rise of the water circulating within the circulation circuit 20 can be suppressed, and the increase in the pressure of the hydrogen desorbed from the hydrogen storage alloy 11 can be suppressed. This control is executed by performing feedback control based on the pressure detected by the first pressure sensor 57.

[0053] In addition, when the temperature of the water circulating within the circulation circuit 20 becomes too high, in addition to controlling the control valve 45, the control valve 25 may be controlled so that a part of the water circulating within the circulation circuit 20 passes through the cooling mechanism 30. The water that has passed through the cooling mechanism 30 is cooled by the cooling mechanism 30 and merges with the water that has passed through the bypass flow path 24. Thereby, the temperature of the water circulating within the circulation circuit 20 can be lowered.

[0054] In addition, although the hydrogen storage system 100 of the hydrogen energy system S shown in FIG. 1 includes only one hydrogen storage tank 10, the number of hydrogen storage tanks 10 may be two or more. For example, when two hydrogen storage tanks 10 are provided, when the hydrogen storage alloy 11 in one hydrogen storage tank 10 is desorbing hydrogen, hydrogen can be adsorbed in the hydrogen storage alloy 11 of the other hydrogen storage tank 10, so that hydrogen can be stably supplied to the hydrogen utilization device C.

[0055] Here, in a state where hydrogen is not supplied from the hydrogen generator P to the hydrogen storage system 100 and hydrogen is not supplied from the hydrogen storage system 100 to the hydrogen utilization device C, that is, in a state where the hydrogen generator P and the hydrogen utilization device C are not operating and there is no inflow or outflow of hydrogen between the hydrogen storage system 100 and the hydrogen generator P and the hydrogen utilization device C, the temperature of the hydrogen storage tank 10 containing the hydrogen storage alloy 11 changes according to the temperature of the environment where the hydrogen storage system 100 is installed.

[0056] Such a temperature change causes a pressure change in the hydrogen storage tank 10. For example, when the environmental temperature drops and the pressure of the hydrogen storage tank 10 drops to a negative pressure, air may enter the hydrogen storage tank 10. Also, if the pressure of the hydrogen storage tank 10 exceeds the allowable pressure of the hydrogen storage tank 10, hydrogen may leak from the safety device of the hydrogen storage tank 10.

[0057] To suppress such a pressure change in the hydrogen storage tank 10, it is conceivable to provide a temperature adjustment mechanism capable of adjusting the temperature of the hydrogen storage alloy 11 accommodated in the hydrogen storage tank 10. However, since energy such as electric power is separately required to operate the temperature adjustment mechanism, as a result, the energy consumption of the entire hydrogen energy system S and the hydrogen storage system 100 may increase.

[0058] In addition, it is conceivable to configure the hydrogen storage tank 10 with a pressure-resistant structure having an increased allowable pressure, for example, a structure capable of withstanding a high pressure of 1.0 MPaG or more. However, when handling hydrogen with a pressure exceeding 1.0 MPaG, it becomes subject to the High Pressure Gas Safety Act, which would increase the manufacturing cost and the management and operation cost of the entire hydrogen storage system 100. Therefore, it is desirable to avoid such applicability.

[0059] To solve such problems, the hydrogen storage system 100 of the present embodiment is configured to be able to maintain the pressure of the hydrogen storage tank 10 within a predetermined range without using energy such as electric power in a state where there is no inflow or outflow of hydrogen between the hydrogen storage system 100, the hydrogen generator P, and the hydrogen utilization device C.

[0060] Specifically, as shown in FIG. 1, the hydrogen storage system 100 further includes two hydrogen holders 73 and 74 that are connected in communication with the hydrogen storage tank 10 in a state where the pressure is stably controlled.

[0061] The hydrogen holders 73 and 74 are pressure vessels capable of storing hydrogen at less than 1.0 MPaG and are connected between the first on-off valve 52 and the second on-off valve 53 in the first flow path 51 via the connection flow path 71.

[0062] Of the two hydrogen holders 73 and 74, the first hydrogen holder 73 is connected to a first branch flow path 71a that branches from the connection flow path 71, and the second hydrogen holder 74 is connected to a second branch flow path 71b that branches from the connection flow path 71. The first hydrogen holder 73 is managed so that the pressure of the stored hydrogen is higher than that of the second hydrogen holder 74, and the second hydrogen holder 74 is managed so that the pressure of the stored hydrogen is lower than that of the first hydrogen holder 73, as will be described later.

[0063] The first branch flow path 71a is provided with a first flow rate and pressure control valve 76a capable of adjusting the flow rate and pressure of hydrogen entering and exiting the first hydrogen holder 73. A first holder pressure sensor 78a (first holder pressure detection unit) for detecting the pressure inside the first hydrogen holder 73 is provided between the first flow rate and pressure control valve 76a and the first hydrogen holder 73 in the first branch flow path 71a.

[0064] Further, the second branch flow path 71b is provided with a second flow rate and pressure control valve 76b capable of adjusting the flow rate and pressure of hydrogen entering and exiting the second hydrogen holder 74. A second holder pressure sensor 78b (second holder pressure detection unit) for detecting the pressure inside the second hydrogen holder 74 is provided between the second flow rate and pressure control valve 76b and the second hydrogen holder 74 in the second branch flow path 71b.

[0065] The opening degrees and opening / closing operations of these flow rate and pressure control valves 76a and 76b are controlled by the controller 60. As will be described later, based on the detection values of the first pressure sensor 57, the first holder pressure sensor 78a, and the second holder pressure sensor 78b, the controller 60 controls the communication state between the hydrogen storage tank 10 and the first hydrogen holder 73 and the communication state between the hydrogen storage tank 10 and the second hydrogen holder 74 in a state where the pressure is controlled.

[0066] Note that the holder pressure sensors 78a and 78b may be provided on the hydrogen holders 73 and 74. Further, each of the hydrogen holders 73 and 74 is provided with a safety device (not shown) that releases hydrogen gas when the internal pressure exceeds a predetermined allowable pressure.

[0067] Subsequently, with reference to the flowcharts shown in FIGS. 3 to 5, the control procedure for the absorption and release of hydrogen gas executed by the controller 60 in the hydrogen storage system 100 including the hydrogen holders 73 and 74 will be described.

[0068] First, in step S11, the controller 60 determines whether the hydrogen generator P and the hydrogen utilization device C are not operating and there is no inflow or outflow of hydrogen to and from the hydrogen storage tank 10, that is, whether hydrogen is being supplied from the hydrogen generator P to the hydrogen storage system 100 or from the hydrogen storage system 100 to the hydrogen utilization device C.

[0069] Specifically, when the second on-off valve 53 is closed, the hydrogen generator P is not operating, and the hydrogen utilization device C is also not operating, the controller 60 determines that there is no inflow or outflow of hydrogen to and from the hydrogen storage tank 10, that is, there is no inflow or outflow of hydrogen between the hydrogen storage system 100 and the hydrogen generator P and the hydrogen utilization device C, and proceeds to step S12 and subsequent steps, and executes control to maintain the pressure of the hydrogen storage tank 10 within a preset allowable range.

[0070] On the other hand, when a signal from the outside, for example, an operation signal of the hydrogen generator P or an operation signal of the hydrogen utilization device C is received, and when the second on-off valve 53 is opened and the operation of the hydrogen generator P is confirmed, and when the operation of the hydrogen utilization device C is confirmed, the controller 60 determines that the inflow and outflow of hydrogen to and from the hydrogen storage tank 10 are in an allowed state, and proceeds to step S51 and subsequent steps. As described above, the first on-off valve 52 and the third on-off valve 55 are held in an open state.

[0071] In step S12, it is determined whether the pressure of the hydrogen storage tank 10 detected by the first pressure sensor 57 is less than a preset first threshold value (for example, 0.15 MPaG).

[0072] When the value detected by the first pressure sensor 57 is below the first threshold value, and since the pressure of the hydrogen storage tank 10 may further decrease to a negative pressure and air may enter the hydrogen storage tank 10, control for increasing the pressure of the hydrogen storage tank 10 is executed in step S13 and subsequent steps.

[0073] On the one hand, when the value detected by the first pressure sensor 57 is equal to or higher than the first threshold value, since it is unlikely that the pressure in the hydrogen storage tank 10 will immediately drop to a negative pressure, the process proceeds to step S31.

[0074] In step S13, when performing control to increase the pressure in the hydrogen storage tank 10, the pressure in the hydrogen storage tank 10 detected by the first pressure sensor 57, the pressure in the first hydrogen holder 73 detected by the first holder pressure sensor 78a, and the pressure in the second hydrogen holder 74 detected by the second holder pressure sensor 78b are compared.

[0075] If the result of the comparison performed in step S13 is the first result S13A where the pressure in the first hydrogen holder 73 is higher than the pressure in the hydrogen storage tank 10 and the pressure in the hydrogen storage tank 10 is higher than the pressure in the second hydrogen holder 74, the process proceeds to step S14 and subsequent steps. If the result is the second result S13B where the pressure in the first hydrogen holder 73 is higher than the pressure in the second hydrogen holder 74 and the pressure in the second hydrogen holder 74 is higher than the pressure in the hydrogen storage tank 10, the process proceeds to step S17 and subsequent steps.

[0076] As will be described later, since the first hydrogen holder 73 is managed to have a relatively high pressure (for example, 0.75 MPaG or higher), if the pressure in the first hydrogen holder 73 is lower than the pressure in the hydrogen storage tank 10 or the second hydrogen holder 74 in the result of the comparison performed in step S13, it may be determined that there is some abnormality in the first hydrogen holder 73 or the first holder pressure sensor 78a.

[0077] When proceeding to step S14, the controller 60 communicates the hydrogen storage tank 10 and the first hydrogen holder 73 in a state where the pressure is controlled.

[0078] Specifically, by adjusting the pressure of hydrogen flowing from the first hydrogen holder 73 to the hydrogen storage tank 10 with the first flow rate pressure control valve 76a, hydrogen is moved from the first hydrogen holder 73 with a higher pressure to the hydrogen storage tank 10 with a lower pressure in a state where the pressure is stably controlled.

[0079] The hydrogen introduced into the hydrogen storage tank 10 is adsorbed by the hydrogen storage alloy 11, and the temperature of the hydrogen storage alloy 11 rises due to the exothermic reaction during adsorption. As a result, as the temperature in the hydrogen storage tank 10 rises, hydrogen desorbs from the hydrogen storage alloy 11, causing the pressure in the hydrogen storage tank 10 to increase.

[0080] Therefore, after communicating the hydrogen storage tank 10 and the first hydrogen holder 73 in a state where the pressure is controlled, the controller 60 monitors the change in the pressure of the hydrogen storage tank 10 in step S15, and until the pressure of the hydrogen storage tank 10 detected by the first pressure sensor 57 becomes equal to or higher than a preset third threshold value, the communication between the hydrogen storage tank 10 and the first hydrogen holder 73 is continued in a state where the pressure is controlled, and hydrogen is moved from the first hydrogen holder 73 to the hydrogen storage tank 10.

[0081] The third threshold value is about 0.03 MPa larger than the first threshold value and is set to, for example, 0.18 MPaG.

[0082] In step S15, when the value detected by the first pressure sensor 57 becomes equal to or higher than the third threshold value, it is assumed that the possibility of the pressure in the hydrogen storage tank 10 dropping to a negative pressure is low, and the process proceeds to step S16. The controller 60 closes the first flow rate pressure control valve 76a to stop the inflow of hydrogen from the first hydrogen holder 73 to the hydrogen storage tank 10.

[0083] In this way, when it is confirmed that the pressure in the hydrogen storage tank 10 is equal to or higher than the third threshold value and higher than the first threshold value and within a preset allowable range, the control is terminated once. Note that since this control flow is repeatedly executed every predetermined time as described later, the pressure in the hydrogen storage tank 10 is continuously monitored, and it becomes possible to appropriately respond to changes in the pressure and temperature of the hydrogen storage tank 10 according to changes in the temperature of the environment where the hydrogen storage system 100 is installed.

[0084] On the other hand, when the result of the comparison performed in step S13 is the second result S13B and the process proceeds to step S17, the controller 60 first communicates the second hydrogen holder 74, whose pressure is lower than that of the first hydrogen holder 73 in the state where the pressure is controlled, with the hydrogen storage tank 10.

[0085] Specifically, by adjusting the pressure of hydrogen flowing from the second hydrogen holder 74 to the hydrogen storage tank 10 by the second flow rate pressure control valve 76b, hydrogen is moved from the second hydrogen holder 74 with a high pressure to the hydrogen storage tank 10 with a low pressure in a state where the pressure is stably controlled.

[0086] After communicating the hydrogen storage tank 10 with the second hydrogen holder 74 in the state where the pressure is controlled, in step S18, the controller 60 monitors the change in the pressure of the hydrogen storage tank 10. When the pressure of the hydrogen storage tank 10 detected by the first pressure sensor 57 becomes equal to or higher than the third threshold value, the process proceeds to step S19 on the assumption that the possibility of the pressure of the hydrogen storage tank 10 decreasing to a negative pressure has become low. The controller 60 closes the second flow rate pressure control valve 76b to stop the inflow of hydrogen from the second hydrogen holder 74 to the hydrogen storage tank 10.

[0087] In this way, once it is confirmed that the pressure in the hydrogen storage tank 10 is equal to or higher than the third threshold value, higher than the first threshold value, and within the preset allowable range, the control is terminated.

[0088] On the other hand, in step S18, when the pressure of the hydrogen storage tank 10 does not become equal to or higher than the third threshold value, the process proceeds to step S20 on the assumption that the inflow rate of hydrogen from the second hydrogen holder 74 to the hydrogen storage tank 10 is small and an exothermic reaction sufficient to raise the pressure in the hydrogen storage tank 10 cannot be obtained. The controller 60 closes the second flow rate pressure control valve 76b while keeping the first on-off valve 52 open, and then further moves hydrogen from the first hydrogen holder 73 with a high pressure to the hydrogen storage tank 10 with a low pressure in a state where the pressure is controlled by adjusting the pressure of hydrogen flowing from the first hydrogen holder 73 to the hydrogen storage tank 10 by the first flow rate pressure control valve 76a.

[0089] After communicating the hydrogen storage tank 10 and the first hydrogen holder 73 in a state where the pressure is controlled, in step S21, the controller 60 monitors the change in the pressure of the hydrogen storage tank 10 again, and until the pressure of the hydrogen storage tank 10 detected by the first pressure sensor 57 becomes equal to or higher than the third threshold value, the communication between the hydrogen storage tank 10 and the first hydrogen holder 73 is continued in the state where the pressure is controlled, and hydrogen is moved from the first hydrogen holder 73 to the hydrogen storage tank 10.

[0090] On the other hand, in step S21, when the value detected by the first pressure sensor 57 becomes equal to or higher than the third threshold value, it is assumed that the possibility of the pressure of the hydrogen storage tank 10 decreasing to a negative pressure is low, and the process proceeds to step S22. The controller 60 closes the first flow rate pressure control valve 76a and stops the inflow of hydrogen from the first hydrogen holder 73 to the hydrogen storage tank 10.

[0091] In this way, once it is confirmed that the pressure in the hydrogen storage tank 10 is equal to or higher than the third threshold value, higher than the first threshold value, and within the preset allowable range, the control is terminated.

[0092] As will be described later, the first hydrogen holder 73 is managed to have a relatively high pressure (for example, about 0.8 MPaG), and due to the desorption reaction accompanying the temperature rise when hydrogen is adsorbed on the hydrogen storage alloy 11, a sufficient amount of hydrogen is stored to promote the release of hydrogen from the hydrogen storage alloy 11 and increase the pressure in the hydrogen storage tank 10. Therefore, in steps S15 and S21 described above, for example, when the value detected by the first pressure sensor 57 does not become equal to or higher than the third threshold value, or when the value detected by the second pressure sensor 58 does not become equal to or higher than the third threshold value, or when the first flow rate pressure control valve 76a is fully open and the value detected by the first holder pressure sensor 78a does not become equal to or higher than the third threshold value, it may be determined that some abnormality has occurred in the flow path connecting the hydrogen storage tank 10 and the first hydrogen holder 73.

[0093] When it is determined that the pressure of the hydrogen storage tank 10 has decreased due to a decrease in the environmental temperature or the like, hydrogen is supplied from the first hydrogen holder 73 or the second hydrogen holder 74 into the hydrogen storage tank 10, and the exothermic reaction of the hydrogen storage alloy 11 when adsorbing hydrogen is utilized to increase the pressure of the hydrogen storage tank 10.

[0094] That is, in order to increase the pressure of the hydrogen storage tank 10, it is not necessary to supply energy such as electric power from the outside. Therefore, it is possible to suppress a decrease in the pressure of the hydrogen storage tank 10 without increasing the energy consumption of the hydrogen storage system 100.

[0095] Next, in step S12 described above, the case where it is determined that the pressure of the hydrogen storage tank 10 is equal to or higher than the first threshold value will be described with reference to the flowchart of FIG. 4.

[0096] In step S12, when it is determined that the pressure of the hydrogen storage tank 10 is equal to or higher than the first threshold value, the process proceeds to step S31.

[0097] In step S31, it is determined whether the pressure of the hydrogen storage tank 10 detected by the first pressure sensor 57 is higher than a preset second threshold value (for example, 0.9 MPaG).

[0098] When the value detected by the first pressure sensor 57 exceeds the second threshold value, since the pressure of the hydrogen storage tank 10 further increases and exceeds the allowable pressure of the hydrogen storage tank 10, and there is a risk of hydrogen leakage from the safety device, control for reducing the pressure of the hydrogen storage tank 10 is executed after step S32.

[0099] On the other hand, when the value detected by the first pressure sensor 57 is equal to or less than the second threshold value, it is highly unlikely that the pressure in the hydrogen storage tank 10 will immediately exceed the allowable pressure of the hydrogen storage tank 10. Also, since it has already been determined in step S12 that it is highly unlikely that the pressure in the hydrogen storage tank 10 will immediately drop to a negative pressure, the control is terminated once. Note that since this control flow is repeatedly executed every predetermined time as described later, the pressure in the hydrogen storage tank 10 will be continuously monitored, and it will be possible to appropriately respond to changes in the pressure and temperature of the hydrogen storage tank 10 according to changes in the temperature of the environment in which the hydrogen storage system 100 is installed.

[0100] In step S32, when executing the control to reduce the pressure in the hydrogen storage tank 10, the pressure in the hydrogen storage tank 10 detected by the first pressure sensor 57, the pressure in the first hydrogen holder 73 detected by the first holder pressure sensor 78a, and the pressure in the second hydrogen holder 74 detected by the second holder pressure sensor 78b are compared.

[0101] If the result of the comparison performed in step S32 is the first result S32A in which the pressure in the first hydrogen holder 73 is higher than the pressure in the hydrogen storage tank 10 and the pressure in the hydrogen storage tank 10 is higher than the pressure in the second hydrogen holder 74, the process proceeds to step S33 and subsequent steps. If the result is the second result S32B in which the pressure in the hydrogen storage tank 10 is higher than the pressure in the first hydrogen holder 73 and the pressure in the first hydrogen holder 73 is higher than the pressure in the second hydrogen holder 74, the process proceeds to step S36 and subsequent steps.

[0102] Note that as described later, since the second hydrogen holder 74 is managed so as to have a relatively low pressure (for example, about 0.15 to 0.2 MPaG), if the pressure in the second hydrogen holder 74 is higher than the pressure in the hydrogen storage tank 10 or the first hydrogen holder 73 in the result of the comparison performed in step S32, it may be determined that there is some abnormality in the second hydrogen holder 74 or the second holder pressure sensor 78b.

[0103] When proceeding to step S33, the controller 60 communicates the hydrogen storage tank 10 with the second hydrogen holder 74 in a state where the pressure is controlled.

[0104] Specifically, by adjusting the pressure of hydrogen flowing from the hydrogen storage tank 10 to the second hydrogen holder 74 with the second flow rate pressure control valve 76b, hydrogen is moved from the hydrogen storage tank 10 with a higher pressure to the second hydrogen holder 74 with a lower pressure in a state where the pressure is controlled.

[0105] When hydrogen is released from the hydrogen storage tank 10, the temperature of the hydrogen storage alloy 11 decreases due to the endothermic reaction that occurs when hydrogen desorbs from the hydrogen storage alloy 11, and as a result, the pressure inside the hydrogen storage tank 10 decreases.

[0106] Therefore, after communicating the hydrogen storage tank 10 with the second hydrogen holder 74 in a state where the pressure is controlled, the controller 60 monitors the change in the pressure of the hydrogen storage tank 10 in step S34, and continues the communication between the hydrogen storage tank 10 and the second hydrogen holder 74 in a state where the pressure is controlled until the pressure of the hydrogen storage tank 10 detected by the first pressure sensor 57 becomes equal to or less than a preset fourth threshold value, and releases hydrogen from the hydrogen storage tank 10 to the second hydrogen holder 74.

[0107] The fourth threshold value is set to be about 0.03 MPa lower than the second threshold value, for example, 0.87 MPaG.

[0108] In addition, when the pressure of the second hydrogen holder 74 detected by the second holder pressure sensor 78b exceeds a preset allowable pressure, an alarm may be issued assuming that it has become impossible to move hydrogen from the hydrogen storage tank 10 to the second hydrogen holder 74.

[0109] In step S34, when the value detected by the first pressure sensor 57 becomes equal to or less than the fourth threshold value, it is assumed that the possibility that the pressure of the hydrogen storage tank 10 exceeds the allowable pressure of the hydrogen storage tank 10 has decreased, and the process proceeds to step S35. The controller 60 closes the second flow rate pressure control valve 76b to stop the release of hydrogen from the hydrogen storage tank 10 to the second hydrogen holder 74.

[0110] In this way, once it is confirmed that the pressure in the hydrogen storage tank 10 is equal to or less than the fourth threshold value, less than the second threshold value, and within a preset allowable range, the control is terminated once.

[0111] On the other hand, when the result of the comparison performed in step S32 is the second result S32B and the process proceeds to step S36, the controller 60 first connects the first hydrogen holder 73, whose pressure is higher than that of the second hydrogen holder 74 in the state where the pressure is controlled, to the hydrogen storage tank 10.

[0112] Specifically, by adjusting the pressure of hydrogen flowing from the hydrogen storage tank 10 to the first hydrogen holder 73 by the first flow rate pressure control valve 76a, hydrogen is moved from the hydrogen storage tank 10 with a high pressure to the first hydrogen holder 73 with a low pressure in a state where the pressure is stably controlled.

[0113] After connecting the hydrogen storage tank 10 and the first hydrogen holder 73 in a state where the pressure is controlled, in step S37, the controller 60 monitors the change in the pressure of the hydrogen storage tank 10. When the pressure of the hydrogen storage tank 10 detected by the first pressure sensor 57 becomes equal to or less than the fourth threshold value, it is assumed that the possibility that the pressure of the hydrogen storage tank 10 exceeds the allowable pressure of the hydrogen storage tank 10 has decreased, and the process proceeds to step S38. The controller 60 closes the first flow rate pressure control valve 76a to stop the release of hydrogen from the hydrogen storage tank 10 to the second hydrogen holder 74.

[0114] In this way, once it is confirmed that the pressure in the hydrogen storage tank 10 is equal to or less than the fourth threshold value, less than the second threshold value, and within a preset allowable range, the control is terminated once.

[0115] On the other hand, in step S37, if the pressure in the hydrogen storage tank 10 does not become equal to or lower than the fourth threshold value, the amount of hydrogen released from the hydrogen storage tank 10 to the first hydrogen holder 73 is small, and it is assumed that an endothermic reaction sufficient to sufficiently reduce the pressure in the hydrogen storage tank 10 cannot be obtained, and the process proceeds to step S39. The controller 60 closes the first flow rate pressure control valve 76a in a state where the first on-off valve 52 is opened, and then adjusts the pressure of hydrogen flowing from the hydrogen storage tank 10 to the second hydrogen holder 74 by the second flow rate pressure control valve 76b, so as to further move hydrogen from the hydrogen storage tank 10 with a higher pressure to the second hydrogen holder 74 with a lower pressure in a state where the pressure is controlled.

[0116] After communicating the hydrogen storage tank 10 and the second hydrogen holder 74 in a state where the pressure is controlled, in step S40, the controller 60 monitors the change in the pressure of the hydrogen storage tank 10 again, and continues to communicate the hydrogen storage tank 10 and the second hydrogen holder 74 in a state where the pressure is controlled until the pressure of the hydrogen storage tank 10 detected by the first pressure sensor 57 becomes equal to or lower than the fourth threshold value, and releases hydrogen from the hydrogen storage tank 10 to the second hydrogen holder 74.

[0117] On the other hand, in step S40, when the value detected by the first pressure sensor 57 becomes equal to or lower than the fourth threshold value, it is assumed that the possibility that the pressure in the hydrogen storage tank 10 exceeds the allowable pressure of the hydrogen storage tank 10 is low, and the process proceeds to step S41. The controller 60 closes the second flow rate pressure control valve 76b and stops the release of hydrogen from the hydrogen storage tank 10 to the second hydrogen holder 74.

[0118] In this way, once it is confirmed that the pressure in the hydrogen storage tank 10 is equal to or lower than the fourth threshold value, smaller than the second threshold value, and within a preset allowable range, the control is terminated once.

[0119] Note that, as described later, the second hydrogen holder 74 is controlled to have a relatively low pressure (for example, about 0.15 MPaG), and since it is in a state where it can receive a sufficient amount of hydrogen to lower the pressure in the hydrogen storage tank 10 by the endothermic reaction when hydrogen is desorbed from the hydrogen storage alloy 11, in the above-described steps S34 and S40, if the value detected by the first pressure sensor 57 does not become equal to or less than the fourth threshold value, it may be determined that some abnormality has occurred in the hydrogen storage tank 10, the first pressure sensor 57, or the second hydrogen holder 74.

[0120] When it is determined that the pressure in the hydrogen storage tank 10 has increased due to an increase in the ambient temperature or the like in this way, hydrogen is released from the hydrogen storage tank 10 to the first hydrogen holder 73 or the second hydrogen holder 74, and the pressure in the hydrogen storage tank 10 is reduced by utilizing the endothermic reaction of the hydrogen storage alloy 11 when hydrogen is desorbed.

[0121] That is, since it is not necessary to supply thermal energy produced from external power or the like to reduce the pressure in the hydrogen storage tank 10, an increase in the pressure in the hydrogen storage tank 10 can be suppressed without increasing the energy consumption of the hydrogen storage system 100.

[0122] Note that the process from the above-described step S13 to step S22 and the process from the above-described step S32 to step S41 are constructed so as not to proceed simultaneously.

[0123] Subsequently, regarding the case where it is determined in the above-described step S11 that either the hydrogen generator P or the hydrogen utilization device C is operating, that is, the state where there is no inflow or outflow of hydrogen to the hydrogen storage tank 10 is not established, it will be described with reference to the flowchart of FIG. 5.

[0124] In step S11, if it is determined that either the hydrogen generator P or the hydrogen utilization device C is operating and the hydrogen storage tank 10 is not in a state where there is no inflow or outflow of hydrogen, the process proceeds to step S51, and it is determined whether the system is in a state where hydrogen is supplied from the hydrogen generator P to the hydrogen storage system 100 (first result S51A) or a state where hydrogen is supplied from the hydrogen storage system 100 to the hydrogen utilization device C (second result S51B).

[0125] Specifically, when the controller 60 opens the second on-off valve 53 in response to an operation signal of the hydrogen generator P from the outside, it determines that the system is in a state where hydrogen is supplied from the hydrogen generator P to the hydrogen storage system 100 (first result S51A). When the start of the operation of the hydrogen utilization device C is confirmed in response to an operation signal of the hydrogen utilization device C from the outside, the controller 60 determines that the system is in a state where hydrogen is supplied from the hydrogen storage system 100 to the hydrogen utilization device C (second result S51B).

[0126] When the first result S51A occurs, the process proceeds to step S52. The controller 60 closes the first on-off valve 52 and then opens the first flow rate and pressure control valve 76a, and in a state where the pressure is controlled, the hydrogen generator P is communicated with the first hydrogen holder 73, that is, the hydrogen generated by the hydrogen generator P is made to flow into the first hydrogen holder 73 instead of the hydrogen storage tank 10.

[0127] After communicating the hydrogen generator P and the first hydrogen holder 73 in a state where the pressure is controlled, in step S53, the controller 60 monitors the change in the pressure of the first hydrogen holder 73, and continues the communication between the hydrogen generator P and the first hydrogen holder 73 in a state where the pressure is controlled until the pressure of the first hydrogen holder 73 detected by the first holder pressure sensor 78a exceeds a preset fifth threshold value, and makes the hydrogen generated by the hydrogen generator P flow into the first hydrogen holder 73.

[0128] The fifth threshold value is set to be of the same magnitude as the pressure of the hydrogen supplied from the hydrogen generator P, for example, 0.75 to 0.9 MPaG. That is, the fifth threshold value is set according to the hydrogen pumping capacity from the hydrogen generator P.

[0129] By filling the first hydrogen holder 73 with hydrogen every time the hydrogen generator P operates in this way, the first hydrogen holder 73 is managed so that the internal pressure becomes a relatively high pressure corresponding to the fifth threshold value. For this reason, in the above-described step S14 and step S20, it becomes possible to reliably allow hydrogen to flow from the first hydrogen holder 73 into the hydrogen storage tank 10.

[0130] In step S53, when it is determined that the pressure of the first hydrogen holder 73 has exceeded the fifth threshold value, the process proceeds to step S54. The controller 60 opens the second on-off valve 53 and opens the first flow rate pressure control valve 76a, and allows the hydrogen generated by the hydrogen generator P to flow into the hydrogen storage tank 10 while the pressure is controlled by the first on-off valve 52 so that the pressure detected by the second pressure sensor 58 maintains a certain pressure near the fifth threshold value.

[0131] Thereafter, when the pressure detected by the second pressure sensor 58 stabilizes near the fifth threshold value, the first flow rate pressure control valve 76a is gradually closed, and the hydrogen generated by the hydrogen generator P flows only into the hydrogen storage tank 10. In this way, the filling of hydrogen into the hydrogen storage tank 10 is performed after the filling of hydrogen into the first hydrogen holder 73 is completed. In addition, in order to enable the hydrogen storage tank 10 to smoothly receive the hydrogen generated by the hydrogen generator P, a standby operation for adjusting the pressure of the hydrogen storage tank 10 by the circulation circuit 20 in advance may be performed. Further, even after the pressure detected by the second pressure sensor 58 stabilizes near the fifth threshold value, the first flow rate pressure control valve 76a may be left open. In this case, since the pressure of the first hydrogen holder 73 exceeds the fifth threshold value, the hydrogen generated by the hydrogen generator P flows only into the hydrogen storage tank 10, and since the hydrogen generator P and the first hydrogen holder 73 are in communication, when the pressure of the hydrogen generated by the hydrogen generator P fluctuates, the first hydrogen holder 73 can absorb this pressure fluctuation. Also, the filling of hydrogen into the hydrogen storage tank 10 may be performed not after the filling of hydrogen into the first hydrogen holder 73 is completed, but simultaneously with the filling of hydrogen into the first hydrogen holder 73. In this case, when the pressure detected by the first holder pressure sensor 78a exceeds the fifth threshold value, the first flow rate pressure control valve 76a is closed and the filling of hydrogen into the first hydrogen holder 73 ends, while the filling of hydrogen into the hydrogen storage tank 10 continues.

[0132] The communication between the hydrogen generator P and the hydrogen storage tank 10 in a state where the pressure is controlled continues until the generation of hydrogen in the hydrogen generator P ends, for example, when the amount (pressure) of hydrogen stored in the hydrogen storage tank 10 reaches a predetermined threshold value or when the power supply to the hydrogen generator P is stopped (step S55).

[0133] In step S55, when it is determined that the supply of hydrogen from the hydrogen generator P has ended, the controller 60 closes the second on-off valve 53 to cut off the communication between the hydrogen generator P and the hydrogen storage tank 10 in a state where the pressure is controlled (step S56). If the first flow rate and pressure control valve 76a remains open, the controller 60 gradually closes the first flow rate and pressure control valve 76a before closing the second on-off valve 53.

[0134] When the hydrogen generator P stops in this way and the supply of hydrogen from the hydrogen generator P to the hydrogen storage tank 10 is cut off, the control is once terminated.

[0135] On the other hand, when the determination result in step S51 is the second result S51B, the process proceeds to step S57. The controller 60 closes the first on-off valve 52 and then opens the second flow rate and pressure control valve 76b to put the hydrogen utilization device C and the second hydrogen holder 74 in communication with each other in a state where the pressure is controlled, that is, to supply hydrogen to the hydrogen utilization device C from the second hydrogen holder 74 instead of from the hydrogen storage tank 10.

[0136] After putting the hydrogen utilization device C and the second hydrogen holder 74 in communication with each other in a state where the pressure is controlled, in step S58, the controller 60 monitors the change in the pressure of the second hydrogen holder 74 and continues the communication between the hydrogen utilization device C and the second hydrogen holder 74 in a state where the pressure is controlled until the pressure of the second hydrogen holder 74 detected by the second holder pressure sensor 78b falls below a preset sixth threshold value, and supplies hydrogen from the second hydrogen holder 74 to the hydrogen utilization device C.

[0137] The sixth threshold value is a pressure equivalent to the pressure of the hydrogen finally supplied to the hydrogen utilization device C, and is set to, for example, 0.15 to 0.2 MPaG. That is, the sixth threshold value is set to a pressure slightly higher than the pressure after being reduced by the pressure reducing valve 56 (the pressure required when the hydrogen utilization device C is operating).

[0138] Each time the hydrogen utilization device C operates, hydrogen is supplied from the second hydrogen holder 74 to the hydrogen utilization device C, so that the second hydrogen holder 74 is managed such that its internal pressure becomes a relatively low pressure corresponding to the sixth threshold value. Therefore, in the above-described step S33 and step S39, it becomes possible to reliably release hydrogen from the hydrogen storage tank 10 to the second hydrogen holder 74.

[0139] Also, when starting the hydrogen utilization device C, hydrogen is supplied from the second hydrogen holder 74 instead of the hydrogen storage tank 10. Therefore, when starting the hydrogen utilization device C, for example, it is not necessary to heat the hydrogen storage alloy 11 in the hydrogen storage tank 10 by receiving energy such as electric power from the outside and desorb hydrogen. Furthermore, by using the heat of the hydrogen utilization device C started by the hydrogen supplied from the second hydrogen holder 74, as described above, it becomes possible to execute the normal control of heating the hydrogen storage alloy 11 in the hydrogen storage tank 10 via the circulation circuit 20 and desorbing hydrogen.

[0140] In addition, when the pressure of the second hydrogen holder 74 is so low that the hydrogen utilization device C cannot be started, hydrogen may be supplied from the first hydrogen holder 73 to the hydrogen utilization device C. When supplying hydrogen from the first hydrogen holder 73 to the hydrogen utilization device C, the first flow rate pressure control valve 76a is controlled such that the detected pressure of the second pressure sensor 58 is slightly higher than the pressure after being reduced by the pressure reducing valve 56, that is, the supply pressure to the hydrogen utilization device C (equivalent to the sixth threshold value). When supplying hydrogen from the first hydrogen holder 73 to the hydrogen utilization device C, as described above, by using the heat of the hydrogen utilization device C to heat the hydrogen storage alloy 11 in the hydrogen storage tank 10 via the circulation circuit 20, when a pressure sufficient to supply a sufficient amount of hydrogen from the hydrogen storage tank 10 to the hydrogen utilization device C is secured, for example, when the detected pressure of the first pressure sensor 57 exceeds the detected pressure of the second pressure sensor 58, the first on-off valve 52 is opened. Note that when the detected pressure of the first pressure sensor 57, that is, the pressure in the hydrogen storage tank 10 exceeds the pressure of the hydrogen supplied from the first hydrogen holder 73 adjusted by the first flow rate pressure control valve 76a (equivalent to the sixth threshold value), the outflow of hydrogen from the first hydrogen holder 73 stops due to the pressure difference, and the first hydrogen holder 73 is in a state where neither hydrogen flows out nor flows in.

[0141] Even after the first on-off valve 52 is opened, when the pressure in the hydrogen storage tank 10 becomes stable due to the continued heating of the hydrogen storage tank 10 using the circulation circuit 20, if the pressure of the first hydrogen holder 73 is below the fifth threshold value and it is possible to fill hydrogen, when the detected pressure of the second pressure sensor 58 becomes equal to or higher than the detected pressure of the first holder pressure sensor 78a, the first flow rate pressure control valve 76a is fully opened, hydrogen is supplied from the hydrogen storage tank 10 to the hydrogen utilization device C, and at the same time, the hydrogen storage tank 10 fills the first hydrogen holder 73 with hydrogen. Note that even when the pressure of the first hydrogen holder 73 exceeds the fifth threshold value, the first flow rate pressure control valve 76a may be controlled according to the detected pressure of the second pressure sensor 58 to fill the first hydrogen holder 73 with hydrogen from the hydrogen storage tank 10.

[0142] The filling of hydrogen from the hydrogen storage tank 10 to the first hydrogen holder 73 ends when the detected pressure of the first holder pressure sensor 78a exceeds the fifth threshold value, and at this time, hydrogen no longer flows into the first hydrogen holder 73 through the first flow rate pressure control valve 76a. After that, the heating of the hydrogen storage tank 10 using the circulation circuit 20 is performed within a range where sufficient hydrogen can be supplied from the hydrogen storage tank 10 to the hydrogen utilization device C. Note that the first flow rate pressure control valve 76a is closed before the heating of the hydrogen storage tank 10 using the circulation circuit 20 stops as the hydrogen utilization device C stops. By thus restoring the pressure of the first hydrogen holder 73 to a relatively high pressure corresponding to the fifth threshold value, it becomes possible to surely make hydrogen flow from the first hydrogen holder 73 into the hydrogen storage tank 10 in the above-described step S14 and step S20. Note that the supply of hydrogen from the first hydrogen holder 73 to the hydrogen utilization device C may be stopped when a pressure capable of supplying a sufficient amount of hydrogen from the hydrogen storage tank 10 to the hydrogen utilization device C is secured.

[0143] In step S58, when it is determined that the pressure of the second hydrogen holder 74 is lower than the sixth threshold value, the process proceeds to step S59. The controller 60 controls the pressure of the hydrogen discharged from the first hydrogen holder 73 by the first flow rate pressure control valve 76a to supply hydrogen from the first hydrogen holder 73 to the hydrogen utilization device C while closing the second flow rate pressure control valve 76b with the third on-off valve 55 open, and also supplies the hydrogen stored in the hydrogen storage tank 10 to the hydrogen utilization device C. Note that the supply of hydrogen from the first hydrogen holder 73 to the hydrogen utilization device C ends when the state where hydrogen is filled from the hydrogen storage tank 10 to the first hydrogen holder 73 is reached as described above. The first flow rate pressure control valve 76a may be closed when the detected pressure of the first holder pressure sensor 78a exceeds the fifth threshold value.

[0144] Note that, before it is determined in step S58 that the pressure of the second hydrogen holder 74 has fallen below the sixth threshold value, if it becomes possible to supply a sufficient amount of hydrogen from the hydrogen storage tank 10 to the hydrogen utilization device C by heating the hydrogen storage alloy 11 in the hydrogen storage tank 10 using the heat of the hydrogen utilization device C via the circulation circuit 20 and the heating mechanism 40 (desorption promotion mechanism), specifically, when the detected pressure of the first pressure sensor 57 becomes slightly higher than the pressure after being reduced by the pressure reducing valve 56 (equivalent to the sixth threshold value), at that time, the second flow rate pressure control valve 76b is closed, and only the first on-off valve 52 is opened without opening the first flow rate pressure control valve 76a, so that the communication destination of the hydrogen utilization device C is switched from the second hydrogen holder 74 to the hydrogen storage tank 10 in a state where the pressure is controlled, and hydrogen may be supplied from only the hydrogen storage tank 10 to the hydrogen utilization device C.

[0145] The communication between the hydrogen utilization device C and the hydrogen storage tank 10 continues, for example, until the amount of hydrogen stored in the hydrogen storage tank 10 becomes equal to or less than a predetermined pressure (amount), until the operation of the hydrogen utilization device C stops, or until the energy generated by the hydrogen utilization device C is no longer required (step S60).

[0146] In step S60, when it is determined that the supply of hydrogen to the hydrogen utilization device C has ended, the controller 60 keeps the first on-off valve 52 and the third on-off valve 55 in the open state and continues the communication between the hydrogen utilization device C and the hydrogen storage tank 10 in a state where the pressure is controlled (step S61). Note that, when the detected pressure of the first holder pressure sensor 78a has not reached the fifth threshold value, the first flow rate pressure control valve 76a may be opened, and hydrogen may be filled from the hydrogen storage tank 10 to the first hydrogen holder 73 until the detected pressure of the first holder pressure sensor 78a exceeds the fifth threshold value, and then the operation of the hydrogen utilization device C may be stopped.

[0147] When the operation of the hydrogen utilization device C stops in this way and the supply of hydrogen from the hydrogen storage tank 10 to the hydrogen utilization device C stops, the control is once terminated.

[0148] The control flow consisting of the above steps is repeatedly executed by the controller 60 at predetermined time intervals while the hydrogen energy system S is operating. Therefore, the pressure in the hydrogen storage tank 10 is continuously monitored, and it becomes possible to appropriately respond to changes in the pressure and temperature of the hydrogen storage tank 10 according to changes in the temperature of the environment where the hydrogen storage system 100 is installed. Note that the control flow consisting of the above steps may be executed not at predetermined time intervals but when it is predicted that changes will occur in the pressure and temperature of the hydrogen storage tank 10 based on changes in the temperature of the environment where the hydrogen storage system 100 is installed.

[0149] According to the hydrogen storage system 100 configured as described above, the following operational effects are achieved.

[0150] According to the hydrogen storage system 100 of the present embodiment, when it is determined that the pressure of the hydrogen storage tank 10 has decreased due to a change in the environmental temperature or the like, hydrogen is supplied from the first hydrogen holder 73 or the second hydrogen holder 74 into the hydrogen storage tank 10, and the exothermic reaction of the hydrogen storage alloy 11 when adsorbing hydrogen is utilized to increase the pressure of the hydrogen storage tank 10. When it is determined that the pressure of the hydrogen storage tank 10 has increased, hydrogen is released from the hydrogen storage tank 10 to the first hydrogen holder 73 or the second hydrogen holder 74, and the endothermic reaction of the hydrogen storage alloy 11 when desorbing hydrogen is utilized to decrease the pressure of the hydrogen storage tank 10.

[0151] In this way, in a state where the pressure is controlled, by communicating either the first hydrogen holder 73 or the second hydrogen holder 74 with the hydrogen storage tank 10 to cause an exothermic reaction or an endothermic reaction in the hydrogen storage alloy 11, it is possible to increase or decrease the pressure of the hydrogen storage tank 10 in which the hydrogen storage alloy 11 is accommodated. Therefore, it is not necessary to supply energy such as electric power from the outside to maintain the pressure of the hydrogen storage tank 10 within a predetermined range. Therefore, it is possible to suppress changes in the pressure of the hydrogen storage tank 10 caused by changes in the environmental temperature or the like without increasing the total energy consumption of the hydrogen storage system 100.

[0152] Further, since the first hydrogen holder 73 is controlled so that the internal pressure becomes higher than that of the second hydrogen holder 74, hydrogen can be reliably made to flow from the first hydrogen holder 73 into the hydrogen storage tank 10. As a result, the exothermic reaction of the hydrogen storage alloy 11 when adsorbing hydrogen is likely to occur, and the pressure of the hydrogen storage tank 10 can be relatively easily increased.

[0153] Also, since the second hydrogen holder 74 is controlled so that the internal pressure becomes lower than that of the first hydrogen holder 73, hydrogen can be reliably released from the hydrogen storage tank 10 into the second hydrogen holder 74. As a result, the endothermic reaction of the hydrogen storage alloy 11 when desorbing hydrogen is likely to occur, and the pressure of the hydrogen storage tank 10 can be relatively easily decreased.

[0154] Note that the following modifications are also within the scope of the present invention, and it is also possible to combine the configurations shown in the modifications with the configurations described in the above-described embodiments, or to combine the configurations described in the following different modifications with each other.

[0155] In the above-described embodiment, when performing the control to increase the pressure of the hydrogen storage tank 10 and the control to decrease the pressure of the hydrogen storage tank 10, the pressure of the hydrogen storage tank 10, the pressure of the first hydrogen holder 73, and the pressure of the second hydrogen holder 74 are compared (steps S13 and S32). Instead of this, as in the modified example shown in FIG. 6, when it is determined in step S12 that the pressure of the hydrogen storage tank 10 is lower than the first threshold value, without comparing the pressure of the hydrogen storage tank 10, the pressure of the first hydrogen holder 73, and the pressure of the second hydrogen holder 74, the first hydrogen holder 73, which is managed so that the internal pressure becomes a relatively high pressure, and the hydrogen storage tank 10 are communicated with each other in a state where the pressure is controlled (step S113). When it is determined in step S31 that the pressure of the hydrogen storage tank 10 exceeds the second threshold value, without comparing the pressure of the hydrogen storage tank 10, the pressure of the first hydrogen holder 73, and the pressure of the second hydrogen holder 74, the second hydrogen holder 74, which is managed so that the internal pressure becomes a relatively low pressure, and the hydrogen storage tank 10 are communicated with each other in a state where the pressure is controlled (step S132).

[0156] In the modified example shown in FIG. 6, after communicating the first hydrogen holder 73 and the hydrogen storage tank 10 in a state where the pressure is controlled in step S113, the first on-off valve 52 and the first flow rate pressure control valve 76a are controlled (steps S114 and S115) in the same manner as steps S15 and S16 described above. After communicating the second hydrogen holder 74 and the hydrogen storage tank 10 in a state where the pressure is controlled in step S132, the first on-off valve 52 and the second flow rate pressure control valve 76b are controlled (steps S133 and S134) in the same manner as steps S34 and S35 described above.

[0157] Therefore, also in the modification shown in FIG. 6, similar to the above-described embodiment, in a state where the pressure is controlled, the first hydrogen holder 73 and the hydrogen storage tank 10 are communicated with each other to cause an exothermic reaction in the hydrogen storage alloy 11, thereby increasing the pressure of the hydrogen storage tank 10 in which the hydrogen storage alloy 11 is accommodated. In a state where the pressure is controlled, the second hydrogen holder 74 and the hydrogen storage tank 10 are communicated with each other to cause an endothermic reaction in the hydrogen storage alloy 11, thereby making it possible to decrease the pressure of the hydrogen storage tank 10 in which the hydrogen storage alloy 11 is accommodated.

[0158] In addition, as in the above-described embodiment, when the pressure of the first hydrogen holder 73 is higher than the pressure of the second hydrogen holder 74 and the pressure of the second hydrogen holder 74 is higher than the pressure of the hydrogen storage tank 10 (second result S13B), in a state where the pressure is controlled, by first communicating the second hydrogen holder 74 having a pressure lower than that of the first hydrogen holder 73 with the hydrogen storage tank 10, it may be possible to sufficiently increase the pressure of the hydrogen storage tank 10. Also, when the pressure of the hydrogen storage tank 10 is higher than the pressure of the first hydrogen holder 73 and the pressure of the first hydrogen holder 73 is higher than the pressure of the second hydrogen holder 74 (second result S32B), in a state where the pressure is controlled, by first communicating the first hydrogen holder 73 having a pressure higher than that of the second hydrogen holder 74 with the hydrogen storage tank 10, it may be possible to sufficiently decrease the pressure of the hydrogen storage tank 10. Therefore, it is preferable to provide a step (steps S13 and S32) of comparing the pressure of the hydrogen storage tank 10, the pressure of the first hydrogen holder 73, and the pressure of the second hydrogen holder 74.

[0159] Further, in the above embodiment, the first hydrogen holder 73 is managed such that the internal pressure becomes a relatively high pressure, while the second hydrogen holder 74 is managed such that the internal pressure becomes a relatively low pressure. Instead of this, which of the first hydrogen holder 73 and the second hydrogen holder 74 is managed to have a relatively high pressure or a relatively low pressure may be changed at any time. Specifically, in step S52 described above, the hydrogen generator P and the first hydrogen holder 73 are in communication with each other in a state where the pressure is controlled. However, among the first hydrogen holder 73 and the second hydrogen holder 74, the hydrogen holder with the higher pressure at this time is put into communication with the hydrogen generator P in a state where the pressure is controlled, and the hydrogen holder that is put into communication with the hydrogen generator P in the state where the pressure is controlled in step S52 may be used as the hydrogen holder whose internal pressure is managed to be a relatively high pressure hereafter. Also, in step S57 described above, the hydrogen utilization device C and the second hydrogen holder 74 are in communication with each other in a state where the pressure is controlled. However, among the first hydrogen holder 73 and the second hydrogen holder 74, the hydrogen holder with the lower pressure at this time is put into communication with the hydrogen utilization device C in a state where the pressure is controlled, and the hydrogen holder that is put into communication with the hydrogen utilization device C in the state where the pressure is controlled in step S57 may be used as the hydrogen holder whose internal pressure is managed to be a relatively low pressure hereafter.

[0160] Also, in the above embodiment, the hydrogen holder is composed of two, namely the first hydrogen holder 73 and the second hydrogen holder 74, but it may be composed of three or more.

[0161] Further, since the first threshold value, the third threshold value, and the sixth threshold value in the above embodiment depend on the performance and specifications of the hydrogen utilization device C, these values are appropriately changed according to the performance and the like of the hydrogen utilization device C connected to the hydrogen storage system 100. Also, since the second threshold value, the fourth threshold value, and the fifth threshold value in the above embodiment depend on the performance and specifications of the hydrogen generator P, these values are appropriately changed according to the performance and the like of the hydrogen generator P connected to the hydrogen storage system 100.

[0162] Further, in the above embodiment, as the heating mechanism 40, a configuration in which water flowing through the circulation circuit 41 is heated using the heat from the hydrogen utilization device C has been described as an example. However, the present invention is not limited to this, and the heating mechanism 40 may be a heater that directly heats the water circulating in the circulation circuit 20. Further, when a chiller or the like that can heat and cool the water circulating in the circulation circuit 20 is provided, the heating mechanism 40 may not be provided. From the viewpoint of energy conservation, it is desirable to adopt the heating mechanism 40 that utilizes the heat generated by the hydrogen utilization device C as in the above embodiment.

[0163] Further, in the above embodiment, as the hydrogen generation device P, an electrolysis device that generates hydrogen by electrolyzing water has been described as an example. However, the hydrogen generation device P is not limited to a fixed type such as an electrolysis device, and may be a mobile type such as a hydrogen trailer, for example.

[0164] Further, in the above embodiment, the first heat exchange unit 22 that exchanges heat with the third heat exchange unit 43 of the heating mechanism 40 is disposed between the pump 21 and the second heat exchange unit 23. Instead of this, the first heat exchange unit 22 may be disposed between the second temperature sensor 27 and the control valve 25.

[0165] As described above, the embodiments of the present invention have been described. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

Explanation of Reference Numerals

[0166] 100 ··· Hydrogen storage system 10 ··· Hydrogen storage tank 11 ··· Hydrogen storage alloy 20 ··· Circulation circuit (desorption promotion mechanism) 40 ··· Heating mechanism (desorption promotion mechanism) 57 ··· First pressure sensor (tank pressure detection unit) 60 ··· Controller (control unit) 73 ··· First hydrogen holder (hydrogen holder) 74 ··· Second hydrogen holder (hydrogen holder) 78a ··· First Holder Pressure Sensor (First Holder Pressure Detection Unit) 78b ··· Second Holder Pressure Sensor (Second Holder Pressure Detection Unit) S ··· Hydrogen Energy System P ··· Hydrogen Generator C ··· Hydrogen Utilization Device

Claims

1. A hydrogen storage system that stores hydrogen supplied from a hydrogen generator and supplies the stored hydrogen to a hydrogen utilization device, comprising: a hydrogen storage tank containing a hydrogen storage alloy that absorbs hydrogen; a first hydrogen holder that is connected to be communicable with the hydrogen storage tank in a state where the pressure is controlled and can store hydrogen; a second hydrogen holder that is connected to be communicable with the hydrogen storage tank in a state where the pressure is controlled and can store hydrogen; a tank pressure detector that detects the pressure in the hydrogen storage tank; a first holder pressure detector that detects the pressure in the first hydrogen holder; a second holder pressure detector that detects the pressure in the second hydrogen holder; a control unit that controls the communication state between the hydrogen storage tank and the first hydrogen holder and the communication state between the hydrogen storage tank and the second hydrogen holder in a state where the pressure is controlled based on the detection values of the tank pressure detector, the first holder pressure detector, and the second holder pressure detector; the control unit: in a state where there is no inflow or outflow of hydrogen between the hydrogen storage system, the hydrogen generator, and the hydrogen utilization device, when the value detected by the tank pressure detector is lower than a first threshold value, the hydrogen holder having a higher pressure than the hydrogen storage tank among the first hydrogen holder and the second hydrogen holder is communicated with the hydrogen storage tank in a state where the pressure is controlled; when the value detected by the tank pressure detector exceeds a second threshold value higher than the first threshold value, the hydrogen holder having a lower pressure than the hydrogen storage tank among the first hydrogen holder and the second hydrogen holder is communicated with the hydrogen storage tank in a state where the pressure is controlled; a hydrogen storage system.

2. the control unit: in a state where there is no inflow or outflow of hydrogen between the hydrogen storage system, the hydrogen generator, and the hydrogen utilization device, When the value detected by the tank pressure detector is lower than the first threshold value, if the pressures of both the first hydrogen holder and the second hydrogen holder are higher than that of the hydrogen storage tank, the one with the lower pressure among the first hydrogen holder and the second hydrogen holder is preferentially communicated with the hydrogen storage tank in a state where the pressure is controlled. When the value detected by the tank pressure detector exceeds the second threshold value, if the pressures of both the first hydrogen holder and the second hydrogen holder are lower than that of the hydrogen storage tank, the one with the higher pressure among the first hydrogen holder and the second hydrogen holder is preferentially communicated with the hydrogen storage tank in a state where the pressure is controlled. The hydrogen storage system according to claim 1.

3. The first hydrogen holder is managed to be in a state where the pressure is higher than that of the second hydrogen holder. The control unit In a state where there is no inflow or outflow of hydrogen between the hydrogen storage system, the hydrogen generator, and the hydrogen utilization device, When the value detected by the tank pressure detector is lower than the first threshold value, the first hydrogen holder is communicated with the hydrogen storage tank in a state where the pressure is controlled so that the pressure of hydrogen flowing from the first hydrogen holder to the hydrogen storage tank exceeds a third threshold value that is larger than the first threshold value. When the value detected by the tank pressure detector exceeds the second threshold value, the second hydrogen holder is communicated with the hydrogen storage tank in a state where the pressure is controlled so that the pressure of hydrogen flowing from the hydrogen storage tank to the second hydrogen holder is lower than a fourth threshold value that is smaller than the second threshold value. The hydrogen storage system according to claim 1.

4. When hydrogen is supplied from the hydrogen generator to the hydrogen storage system, The control unit communicates the hydrogen generator with the one having the higher pressure among the first hydrogen holder and the second hydrogen holder in a state where the pressure is controlled, prior to the hydrogen storage tank. The hydrogen storage system according to claim 1 or 2.

5. When hydrogen is supplied from the hydrogen storage system to the hydrogen utilization device, The control unit communicates the hydrogen utilization device with the one having the lower pressure among the first hydrogen holder and the second hydrogen holder in a state where the pressure is controlled, prior to the hydrogen storage tank. The hydrogen storage system according to claim 1 or 2.

6. The hydrogen storage alloy is heated by using the heat of the hydrogen utilization device, and a desorption promotion mechanism for promoting desorption of hydrogen from the hydrogen storage alloy is further provided. When desorption of hydrogen from the hydrogen storage alloy is promoted by the desorption promotion mechanism and hydrogen can be supplied from the hydrogen storage tank to the hydrogen utilization device, the control unit switches the communication destination of the hydrogen utilization device to the hydrogen storage tank. The hydrogen storage system according to claim 5.

7. When switching the communication destination of the hydrogen utilization device to the hydrogen storage tank, the control unit communicates the hydrogen utilization device with the one having a higher pressure among the first hydrogen holder and the second hydrogen holder in a state where the pressure is controlled. The hydrogen storage system according to claim 6.

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