Electrochemical hydrogen pressure boosting system

Abstract

Provided is an electrochemical hydrogen pressure boosting system. The electrochemical hydrogen pressure boosting system (10) has a supply path (46) that communicates with an anode side of a single cell (28), a discharge path (72) that communicates with a cathode side of the single cell (28), a hydrogen backflow path (76) that guides high-pressure hydrogen from a position downstream of a gas-liquid separator (20) in the discharge path (72) to the supply path (46), and a control device (22). The control device (22) opens a hydrogen backflow valve (78) provided in the hydrogen backflow path (76) when an electrical value indicative of voltage or resistance of the hydrogen pressure boosting stack (24) exceeds a prescribed threshold value when the current of the hydrogen pressure boosting stack (24) is a prescribed value. Accordingly, the chemical reaction of oxygen and hydrogen can be suppressed.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrochemical hydrogen pressure boosting system. BACKGROUND

[0002] In recent years, in order to ensure that more people can obtain affordable, reliable, sustainable, and advanced energy, an electrochemical hydrogen pressure boosting system that contributes to energy efficiency is being researched and developed.

[0003] The electrochemical hydrogen pressure boosting system of Japanese Patent Laying-Open No. 2022-94891 includes an electrochemical hydrogen pressure boosting device that boosts the pressure of hydrogen. The electrochemical hydrogen pressure boosting device has a hydrogen pressure boosting stack (hydrogen pressure boosting section) and a power supply device (power source). The hydrogen pressure boosting stack has a unit cell including an electrolyte membrane, an anode power supply body, and a cathode power supply body. The power supply device supplies electric current to the hydrogen pressure boosting stack, and the hydrogen pressure boosting stack generates high-pressure hydrogen gas having a higher pressure than hydrogen gas supplied to the hydrogen pressure boosting stack.

[0004] A technology is disclosed in Japanese Patent Laying-Open No. 2022-94891 that restricts an exhaust port of the hydrogen pressure boosting stack for exhausting unreacted hydrogen gas, based on information about a wet state of the electrolyte membrane, and maintains a good wet state of the electrolyte membrane by retaining water vapor in the unit cell. SUMMARY

[0005] However, when electric current is supplied to the hydrogen pressure boosting stack, if the water content retained in the unit cell is large, there is a tendency for the water to be electrolyzed. In a case where oxygen gas generated by electrolysis is mixed with hydrogen gas supplied to the hydrogen pressure boosting stack, there is a technical problem that a chemical reaction occurs depending on the concentration of the oxygen gas.

[0006] An object of the present application is to solve the above-described technical problem.

[0007] The present application is an electrochemical hydrogen pressure boosting system including a hydrogen pressure boosting stack having a single cell including an electrolyte membrane, an anode electrode, and a cathode electrode, a power supply device that supplies a current to the single cell to cause high-pressure hydrogen gas having a higher pressure than hydrogen gas supplied to the anode side of the single cell to be generated on the cathode side of the single cell, and a hydrogen supply source that supplies the hydrogen gas to the hydrogen pressure boosting stack through a supply path. The electrochemical hydrogen pressure boosting system includes a gas-liquid separator provided in a discharge path that communicates with the cathode side of the single cell to separate moisture from the high-pressure hydrogen gas, a hydrogen backflow path that guides dry high-pressure hydrogen gas, from which the moisture has been separated, from a position on the downstream side of the gas-liquid separator in the discharge path to the supply path that communicates with the anode side of the single cell, a hydrogen backflow valve provided in the hydrogen backflow path, a detector that detects an electrical value indicative of a voltage or a resistance of the hydrogen pressure boosting stack, and a control device that controls the hydrogen backflow valve and the power supply device. The control device closes the hydrogen backflow valve when the electrical value at the time when the current is a prescribed value does not exceed a prescribed threshold value and opens the hydrogen backflow valve when the electrical value at the time when the current is the prescribed value exceeds the threshold value, and supplies the dry high-pressure hydrogen gas to the hydrogen pressure boosting stack through the supply path.

[0008] According to the above-described aspect, the amount of water remaining in the single cell when a current is supplied to the hydrogen pressure boosting stack can be reduced. Therefore, the amount of oxygen generated by electrolysis of water remaining in the single cell and mixed into hydrogen gas supplied to the hydrogen pressure boosting stack can be reduced. As a result, chemical reactions between oxygen and hydrogen gas can be suppressed.

[0009] The above objects, features, and advantages will be more apparent from the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a schematic diagram of an electrochemical hydrogen pressure boosting system.

[0011] Figure 2 is a flowchart showing steps of a water retention suppression process. DETAILED DESCRIPTION

[0012] Figure 1 is a schematic diagram of an electrochemical hydrogen pressure boosting system 10. The electrochemical hydrogen pressure boosting system 10 includes an electrochemical hydrogen pressure boosting device 12, a hydrogen supply source 14, a humidifier 16, a high-pressure hydrogen storage device 18, a gas-liquid separator 20, and a control device 22.

[0013] The electrochemical hydrogen pressure increasing device 12 is a device that electrochemically increases the pressure of hydrogen. The electrochemical hydrogen pressure increasing device 12 has a hydrogen pressure increasing stack 24 and a power supply device 26.

[0014] The hydrogen pressure increasing stack 24 has an inlet port PT1, an outlet port PT2, and a high-pressure hydrogen port PT3. The inlet port PT1 is an interface for introducing hydrogen and communicates with the anode side of each of the single cells 28. The outlet port PT2 is an interface for discharging unreacted hydrogen and communicates with the anode side of each of the single cells 28. The high-pressure hydrogen port PT3 is an interface for discharging high-pressure hydrogen generated by the single cells 28 and communicates with the cathode side of each of the single cells 28.

[0015] The plurality of single cells 28 have the same structure. Each of the single cells 28 has an electrolyte membrane 30, an anode electrode 32 provided on one surface of the electrolyte membrane 30, and a cathode electrode 34 provided on the other surface of the electrolyte membrane 30.

[0016] The electrolyte membrane 30 is, for example, a solid polymer electrolyte membrane (a cation exchange membrane). The anode side of the electrolyte membrane 30 can be reinforced by a protective sheet (not shown) including a fibrous skeleton. In addition, the electrolyte membrane 30 can use an HC (hydrocarbon) type electrolyte in addition to a fluorine electrolyte. The electrolyte membrane 30 is sandwiched by the anode electrode 32 and the cathode electrode 34.

[0017] The anode electrode 32 includes an anode catalyst layer bonded to one surface of the electrolyte membrane 30 and an anode power supply body laminated to the anode catalyst layer. The cathode electrode 34 includes a cathode catalyst layer bonded to the other surface of the electrolyte membrane 30 and a cathode power supply body laminated to the cathode catalyst layer. The anode power supply body and the cathode power supply body are formed in a structure that allows hydrogen to flow therethrough.

[0018] When a current is supplied between the anode electrode 32 and the cathode electrode 34, a part of the hydrogen supplied to the anode electrode 32 from the inlet port PT1 is converted into protons (H + ions by a catalyst reaction. The converted protons are transported to the cathode electrode 34 through the electrolyte membrane 30. In the cathode electrode 34, high-pressure hydrogen is generated by an electrochemical reaction using the transported protons. The high-pressure hydrogen flows out from the high-pressure hydrogen port PT3. The hydrogen that is not reacted in the anode electrode 32 flows out from the outlet port PT2.

[0019] Hydrogen flowing out from the discharge port PT2 is supplied to the closed container 38 through a low-pressure discharge path 36, or is discharged through a discharge path 40 branched from the low-pressure discharge path 36. The discharge valve 42 and the pump 44 are provided on the low-pressure discharge path 36. The discharge valve 45 is provided on the discharge path 40. The discharge valve 42 and the discharge valve 45 are opened or closed in response to the control of the control device 22, respectively. The pump 44 is driven in response to the control of the control device 22, and applies a flow force from the upstream side to the downstream side to hydrogen.

[0020] The power supply device 26 supplies electric current to the hydrogen pressure-boosting stack 24. In accordance therewith, the hydrogen pressure-boosting stack 24 generates high-pressure hydrogen gas having a higher pressure than the supplied hydrogen gas.

[0021] The power supply device 26 applies a voltage to the anode electrode 32 and the cathode electrode 34 of each single cell 28, and supplies electric current to the single cell 28. The power supply device 26 is configured to be able to adjust the magnitude of the electric current supplied to each single cell 28 in response to the control of the control device 22. The greater the electric current supplied to the single cell 28 becomes, the greater the amount of the high-pressure hydrogen gas generated in the single cell 28 becomes.

[0022] The hydrogen supply source 14 is a device capable of supplying hydrogen gas. The hydrogen supply source 14 can be a cardle in which a plurality of gas cylinders storing hydrogen gas are gathered, or can be a storage tank storing hydrogen gas. The hydrogen supply source 14 supplies hydrogen gas to the hydrogen pressure-boosting stack 24 through a supply path 46.

[0023] The supply path 46 is a path through which hydrogen gas is introduced from the hydrogen supply source 14 to the hydrogen pressure-boosting stack 24. The upstream end of the supply path 46 is connected to an unillustrated output port of the hydrogen supply source 14. The downstream end of the supply path 46 is connected to the introduction port PT1 of the hydrogen pressure-boosting stack 24. On the supply path 46, a pressure-reducing valve 48, a hydrogen supply valve 50, and a flow rate adjusting valve 52 are provided in this order from the upstream side to the downstream side.

[0024] The pressure-reducing valve 48 is one in the Figure 1 above, but can be two or more. The hydrogen supply valve 50 is opened or closed in response to the control of the control device 22. The flow rate adjusting valve 52 adjusts the flow rate of hydrogen gas supplied to the hydrogen pressure-boosting stack 24 in response to the control of the control device 22.

[0025] The humidifier 16 is a device that humidifies hydrogen gas. The humidifier 16 has a closed container 38. The humidifier 16 vaporizes liquid water stored in the closed container 38. The humidifier 16 supplies water vapor to the supply path 46 through a lead-out path 54.

[0026] The discharge path 54 is a path that introduces water vapor from the humidifier 16 to the supply path 46. The upstream end of the discharge path 54 is disposed in the gas phase space of the closed container 38. The downstream end of the discharge path 54 is connected to the supply path 46 between the hydrogen supply valve 50 and the flow rate adjustment valve 52. A discharge valve 56 is provided on the discharge path 54. The discharge valve 56 is opened or closed in response to control by the control device 22.

[0027] The humidifier 16 can be a bubbling type humidifier. Figure 1 An example in which the humidifier 16 is a bubbling type humidifier is shown. In this case, the humidifier 16 has a bubble generator 58. In the present embodiment, the bubble generator 58 is disposed in the liquid water inside the closed container 38. The bubble generator 58 releases hydrogen gas supplied from the supply path 46 through an introduction path 60 as bubbles into the liquid water. In this case, the hydrogen gas contains moisture (water vapor). The hydrogen gas containing moisture is supplied to the supply path 46 through the discharge path 54.

[0028] The introduction path 60 is a path that introduces a portion of the hydrogen gas flowing in the supply path 46 from the supply path 46 to the bubble generator 58. The upstream end of the introduction path 60 is connected to a position in the supply path 46 that is upstream of the connection position of the downstream end of the discharge path 54. The downstream end of the introduction path 60 is connected to the bubble generator 58. An introduction valve 62 is provided on the introduction path 60. The introduction valve 62 is opened or closed in response to control by the control device 22.

[0029] Further, a temperature adjustment device 64 that adjusts the temperature of the liquid water stored in the closed container 38 can also be provided. The temperature adjustment device 64 has a heat exchanger 66, a circulation path 68 that circulates between the heat exchanger 66 and the closed container 38, and a pump 70 provided to the circulation path 68. The temperature adjustment device 64 drives the pump 70, circulates the liquid water between the heat exchanger 66 and the closed container 38 through the circulation path 68, and adjusts the liquid water to a set temperature by heat exchange with the heat exchanger 66.

[0030] The high-pressure hydrogen storage device 18 is a device formed so as to be able to store high-pressure hydrogen gas. The high-pressure hydrogen storage device 18 can be a cylinder group in which a plurality of cylinders that store high-pressure hydrogen gas are gathered, or can be a storage tank that stores high-pressure hydrogen gas. The high-pressure hydrogen storage device 18 stores high-pressure hydrogen gas supplied from the hydrogen pressure-increasing electric pile 24 through a discharge path 72. The discharge path 72 is a path that guides the high-pressure hydrogen gas discharged from the hydrogen pressure-increasing electric pile 24. The upstream end of the discharge path 72 is connected to the high-pressure hydrogen port PT3 of the hydrogen pressure-increasing electric pile 24. The downstream end of the discharge path 72 is connected to an unillustrated input port of the high-pressure hydrogen storage device 18. A back pressure valve 74 is provided on the discharge path 72.

[0031] The gas-liquid separator 20 is provided in the discharge path 72 between the back pressure valve 74 and the hydrogen pressure-rising electric pile 24. The gas-liquid separator 20 separates moisture from high-pressure hydrogen gas. The high-pressure hydrogen gas from which moisture has been separated, i.e., dry high-pressure hydrogen gas, flows downstream of the discharge path 72. The dry high-pressure hydrogen gas is supplied to the high-pressure hydrogen storage device 18 through the discharge path 72 or to the supply path 46 through a hydrogen backflow path 76 branched from the discharge path 72.

[0032] The hydrogen backflow path 76 is a path that guides dry high-pressure hydrogen gas from a position in the discharge path 72 that is downstream of the gas-liquid separator 20 to the supply path 46. The upstream end of the hydrogen backflow path 76 is connected to the discharge path 72. In the present embodiment, the upstream end of the hydrogen backflow path 76 is connected to the discharge path 72 between the gas-liquid separator 20 and the back pressure valve 74. The downstream end of the hydrogen backflow path 76 is connected to the supply path 46. In the present embodiment, the downstream end of the hydrogen backflow path 76 is connected to the supply path 46 between the flow rate adjustment valve 52 and the hydrogen pressure-rising electric pile 24. A hydrogen backflow valve 78 is provided in the hydrogen backflow path 76. The hydrogen backflow valve 78 is opened or closed in response to control by the control device 22.

[0033] The moisture separated by the gas-liquid separator 20 is supplied to the humidifier 16 through a water supply path 80. The water supply path 80 is a path that supplies water from the gas-liquid separator 20 to the humidifier 16. The upstream end of the water supply path 80 is connected to a water discharge port of the gas-liquid separator 20, which is not shown. The downstream end of the water supply path 80 is connected to a water introduction port of the closed container 38 of the humidifier 16, which is not shown. A water supply valve 82 is provided in the water supply path 80. The water supply valve 82 is opened or closed in response to control by the control device 22.

[0034] The control device 22 is a computer that overall controls the electrochemical hydrogen pressure-rising system 10. The control device 22 includes one or more processors and a storage medium. The storage medium can be constituted by a volatile memory and a non-volatile memory. As the processor, a CPU, an MCU, or the like can be cited. As the volatile memory, a RAM or the like can be cited, for example. As the non-volatile memory, a ROM, a flash memory, or the like can be cited, for example.

[0035] The detector 84 is connected to the control device 22. The control device 22 uses the detector 84 to acquire an electrical value of the hydrogen pressure increasing stack 24 at the time when the current of the hydrogen pressure increasing stack 24 is a prescribed value. The electrical value is a value indicating a voltage or a resistance. There is a relationship in which the more the voltage of the hydrogen pressure increasing stack 24 rises compared to a reference voltage that is appropriate for the operation of the hydrogen pressure increasing stack 24, the more the moisture that remains in the single cells 28 increases. Also, there is a relationship in which the more the resistance of the hydrogen pressure increasing stack 24 rises compared to a reference resistance that is appropriate for the operation of the hydrogen pressure increasing stack 24, the more the moisture that remains in the single cells 28 increases. Therefore, the control device 22 is able to grasp the moisture content that remains in the single cells 28 by acquiring the electrical value at the time when the current of the hydrogen pressure increasing stack 24 is a prescribed value.

[0036] The detector 84 is provided to the hydrogen pressure increasing stack 24. The detector 84 can be a voltage sensor. In this case, the control device 22 acquires, as the electrical value, a voltage value (detection voltage value) that is detected by the voltage sensor at the time when the current of the hydrogen pressure increasing stack 24 is a prescribed value. The detector 84 can also be a resistance sensor. In this case, the control device 22 acquires, as the electrical value, a resistance value (detection resistance value) that is detected by the resistance sensor at the time when the current of the hydrogen pressure increasing stack 24 is a prescribed value.

[0037] The voltage or the resistance can be calculated using Ohm's law. Therefore, the control device 22 can calculate the detection voltage value or the detection resistance value using the value that is detected by the detector 84.

[0038] The detection voltage value can be a voltage value that is applied across the plurality of single cells 28 that the hydrogen pressure increasing stack 24 has. Alternatively, the detection voltage value can also be a voltage value of one single cell 28 that is selected from among the plurality of single cells 28. Alternatively, the detection voltage value can also be a statistical value of the respective voltage values of the plurality of single cells 28. Alternatively, the detection voltage value can also be a statistical value of the voltage values of two or more single cells 28 that are selected from among the plurality of single cells 28. As the statistical value, for example, an average value, a median value, a total value, or the like can be cited.

[0039] Also, the detection resistance value can be a resistance value that is detected across the plurality of single cells 28 that the hydrogen pressure increasing stack 24 has. Alternatively, the detection resistance value can also be a resistance value of one single cell 28 that is selected from among the plurality of single cells 28. Alternatively, the detection resistance value can also be a statistical value of the respective resistance values of the plurality of single cells 28. Alternatively, the detection resistance value can also be a statistical value of the resistance values of two or more single cells 28 that are selected from among the plurality of single cells 28. As the statistical value, for example, an average value, a median value, a total value, or the like can be cited.

[0040] The control device 22 brings the hydrogen pressure-boosting stack 24 into an operating state when receiving an operation command. In this case, the control device 22 opens the hydrogen supply valve 50 to supply hydrogen gas from the hydrogen supply source 14 to the hydrogen pressure-boosting stack 24. In addition, the control device 22 controls the power supply device 26 to apply a prescribed voltage to the hydrogen pressure-boosting stack 24 and supply a current to the hydrogen pressure-boosting stack 24. In each of the unit cells 28 of the hydrogen pressure-boosting stack 24, an electrochemical reaction is performed based on the hydrogen gas supplied from the hydrogen supply source 14. Accordingly, high-pressure hydrogen gas is generated on the cathode side of each of the unit cells 28.

[0041] During operation of the hydrogen pressure-boosting stack 24, the control device 22 drives the pump 44, opens the discharge valve 42, and supplies hydrogen gas that has not reacted in the hydrogen pressure-boosting stack 24 to the closed container 38. In addition, the control device 22 opens the discharge valve 45 at an arbitrary timing to discharge the hydrogen gas.

[0042] During operation of the hydrogen pressure-boosting stack 24, the control device 22 controls the opening degree of the flow rate adjustment valve 52 in accordance with a target amount of generation of high-pressure hydrogen gas to adjust the flow rate of the hydrogen gas supplied to the hydrogen pressure-boosting stack 24.

[0043] During operation of the hydrogen pressure-boosting stack 24, the control device 22 compares the water level of the liquid water stored in the closed container 38 with a prescribed water level threshold at prescribed periods. The water level of the liquid water stored in the closed container 38 is detected by the water level sensor 86 provided to the closed container 38. In the case where the water level of the liquid water exceeds the water level threshold, the control device 22 closes the water supply valve 82. On the other hand, when the water level of the liquid water becomes lower than the water level threshold, the control device 22 opens the water supply valve 82. The control device 22 can open the water supply valve 82 until the water level of the liquid water exceeds the water level threshold. Alternatively, the control device 22 can open the water supply valve 82 until a prescribed period elapses from when the water level of the liquid water becomes lower than the water level threshold.

[0044] During operation of the hydrogen pressure-boosting stack 24, the control device 22 opens the introduction valve 62 and the discharge valve 56 to introduce water vapor into the supply path 46 together with the hydrogen gas. Accordingly, the control device 22 humidifies the hydrogen gas supplied to the hydrogen pressure-boosting stack 24. In this case, the control device 22 can control at least one of the opening degree of the hydrogen supply valve 50 and the opening degree of the introduction valve 62 to adjust the flow rate ratio of the hydrogen gas that has passed through the humidifier 16 to the hydrogen gas that has not passed through the humidifier 16.

[0045] When the amount of humidification of the hydrogen gas is increased, there is a tendency that moisture remains in the unit cells 28. There is a relationship that the more the moisture remains in the unit cells 28, the higher the voltage applied to the hydrogen pressure-boosting stack 24 is.

[0046] Therefore, in the present embodiment, when the operation of the hydrogen pressure increasing stack 24 is started, the control device 22 compares the electrical value at the time when the current of the hydrogen pressure increasing stack 24 is the prescribed value with the prescribed threshold value at prescribed periods after the hydrogen backflow valve 78 is closed. In the case where the electrical value at the time when the current of the hydrogen pressure increasing stack 24 is the prescribed value exceeds the threshold value, the control device 22 executes the process for suppressing the retention of moisture in the unit cells 28 (moisture retention suppression process).

[0047] The moisture retention suppression process can be prescribed by a program. Alternatively, the moisture retention suppression process can be realized by an integrated circuit such as an ASIC or an FPGA. Alternatively, the moisture retention suppression process can be realized by an electronic circuit including discrete devices. Figure 2 is a flowchart showing the steps of the moisture retention suppression process.

[0048] In step S1, the control device 22 shifts to step S2 after the introduction valve 62 and the discharge valve 56 are closed. When the introduction valve 62 and the discharge valve 56 are closed, the supply of the hydrogen gas containing moisture to the supply path 46 is stopped. Therefore, the hydrogen gas output from the hydrogen supply source 14 is not humidified by the humidifier 16 and is supplied to the hydrogen pressure increasing stack 24.

[0049] In step S2, the control device 22 shifts to step S3 after the hydrogen backflow valve 78 is opened. When the hydrogen backflow valve 78 is opened, the high-pressure hydrogen gas from which moisture is separated by the gas-liquid separator 20, that is, the dry high-pressure hydrogen gas is supplied from the discharge path 72 to the supply path 46 using the pressure difference between the discharge path 72 and the supply path 46. The dry high-pressure hydrogen gas supplied to the supply path 46 is supplied together with the hydrogen gas output from the hydrogen supply source 14 to the hydrogen pressure increasing stack 24.

[0050] In step S3, the control device 22 acquires the electrical value at the time when the current of the hydrogen pressure increasing stack 24 is the prescribed value using the detector 84 and compares it with the prescribed threshold value. In the case where the electrical value at the time when the current of the hydrogen pressure increasing stack 24 is the prescribed value still exceeds the prescribed threshold value, the control device 22 determines that moisture is still retained in the hydrogen pressure increasing stack 24. In this case, the control device 22 stays in step S3. On the other hand, in the case where the electrical value at the time when the current of the hydrogen pressure increasing stack 24 is the prescribed value is smaller than the prescribed threshold value, the control device 22 determines that there is almost no retained moisture in the hydrogen pressure increasing stack 24. In this case, the control device 22 shifts to step S4.

[0051] In step S4, the control device 22 closes the hydrogen backflow valve 78 and stops the supply of the dry high-pressure hydrogen gas to the hydrogen pressure increasing stack 24. Thereafter, the control device 22 shifts to step S5.

[0052] In step S5, the control device 22 opens the introduction valve 62 and the discharge valve 56, and resumes the supply of the hydrogen gas containing water vapor to the supply path 46. Thereafter, the control device 22 ends the water retention suppression processing.

[0053] As described above, in the present embodiment, the hydrogen backflow path 76 is provided between the discharge path 72 communicating with the cathode side of the unit cell 28 and the supply path 46 communicating with the anode side of the unit cell 28. The hydrogen backflow path 76 guides the dry high-pressure hydrogen gas from a position in the discharge path 72 downstream of the gas-liquid separator 20 to the supply path 46.

[0054] During the operation of the hydrogen pressure increasing stack 24, in a case where the electrical value at the time when the current of the hydrogen pressure increasing stack 24 is the prescribed value does not exceed the prescribed threshold value, the control device 22 closes the hydrogen backflow valve 78 provided in the hydrogen backflow path 76.

[0055] On the other hand, in a case where the electrical value at the time when the current of the hydrogen pressure increasing stack 24 is the prescribed value exceeds the prescribed threshold value, the control device 22 opens the hydrogen backflow valve 78, and supplies the dry high-pressure hydrogen gas from the discharge path 72 to the hydrogen pressure increasing stack 24 through the supply path 46.

[0056] Accordingly, the discharge path 72 communicates with the supply path 46, and the cathode side of the unit cell 28 is depressurized. Therefore, the dry high-pressure hydrogen gas can be supplied to the hydrogen pressure increasing stack 24 through the supply path 46 using the pressure difference between the discharge path 72 and the supply path 46. Thus, the water content remaining in the unit cell 28 can be moved to the cathode side of the unit cell 28. In addition, the water content remaining in the unit cell 28 can be discharged from the cathode side of the unit cell 28 to the discharge path 72 using the hydrogen gas supplied from the hydrogen supply source 14 to the hydrogen pressure increasing stack 24. Furthermore, since the dry high-pressure hydrogen gas separated from the water content by the gas-liquid separator 20 is supplied to the hydrogen pressure increasing stack 24, the water content remaining in the unit cell 28 can be discharged as soon as possible, and the hydrogen gas can be efficiently used. Therefore, the amount of oxygen gas generated by the electrolysis of water remaining in the unit cell 28 mixed into the hydrogen gas supplied to the hydrogen pressure increasing stack 24 can be reduced. As a result, the chemical reaction between the oxygen gas and the hydrogen gas can be suppressed.

[0057] In addition, the dry high-pressure hydrogen gas can be supplied to the hydrogen pressure increasing stack 24 through the supply path 46 using the pressure difference between the discharge path 72 and the supply path 46, and thus a pump can not be provided in the hydrogen backflow path 76 or the like. Therefore, the increase in the number of components of the electrochemical hydrogen pressure increasing system 10 can be suppressed, and the water content remaining in the unit cell 28 can be reduced.

[0058] Further, since the moisture of the unit cell 28 discharged from the cathode side to the discharge path 72 of the unit cell 28 can be separated by the gas-liquid separator 20, the moisture can be inhibited from returning again through the hydrogen backflow path 76.

[0059] In the present embodiment, in a case where the electrical value when the current of the hydrogen pressure-boosting stack 24 is a prescribed value exceeds a prescribed threshold value, the control device 22 closes the introduction valve 62 and the discharge valve 56, and stops the supply of the water vapor to the supply path 46. Thereby, compared to a case where the supply of the water vapor to the supply path 46 is not stopped, the amount of reduction of the moisture remaining in the unit cell 28 can be increased.

[0060] Further, in the present embodiment, there is a water supply path 80 that guides the moisture separated by the gas-liquid separator 20 from the gas-liquid separator 20 to the closed container 38 of the humidifier 16. Thereby, the utilization efficiency of the water can be achieved.

[0061] Further, in the present embodiment, in a case where the water level of the liquid water of the closed container 38 exceeds a water level threshold value, the control device 22 closes a water supply valve 82 provided to the water supply path 80. On the other hand, when the water level of the liquid water of the closed container 38 is lower than the water level threshold value, the control device 22 opens the water supply valve 82. Thereby, the water stored in the closed container 38 can be maintained at an amount or more. As a result, the humidification of the hydrogen gas flowing in the supply path 46 can be inhibited from becoming insufficient.

[0062] The above-described embodiments can be modified as follows.

[0063] (Modified Example 1)

[0064] The control device 22 can control at least one of the opening degree of the hydrogen backflow valve 78 and the magnitude of the current supplied to the unit cell 28, so that the supply amount of the dry high-pressure hydrogen gas is larger than the generation amount of the high-pressure hydrogen gas. Thereby, the pressure reduction speed of the cathode side of the unit cell 28 can be increased. Therefore, compared to a case where the pressure reduction speed of the cathode side of the unit cell 28 is not increased, the moisture remaining in the unit cell 28 can be discharged from the cathode side to the discharge path 72 of the unit cell 28 early.

[0065] The supply amount of the dry high-pressure hydrogen gas is the amount of the dry high-pressure hydrogen gas supplied per unit time from the hydrogen backflow valve 78 to the supply path 46. The generation amount of the high-pressure hydrogen gas is the amount of the high-pressure hydrogen gas generated per unit time in each of the unit cells 28 of the hydrogen pressure-boosting stack 24.

[0066] There is a relationship that the greater the opening degree of the hydrogen backflow valve 78 becomes, the greater the supply amount of the dry high-pressure hydrogen gas becomes. Also, there is a relationship that the greater the magnitude of the current supplied to the single cell 28 becomes, the greater the generation amount of the high-pressure hydrogen gas becomes. Therefore, the control device 22 can make the supply amount of the dry high-pressure hydrogen gas greater than the generation amount of the high-pressure hydrogen gas by making the opening degree of the hydrogen backflow valve 78 greater than the current value. Also, the control device 22 can make the supply amount of the dry high-pressure hydrogen gas greater than the generation amount of the high-pressure hydrogen gas by making the magnitude of the current supplied to the single cell 28 smaller than the current value.

[0067] For example, the control device 22 calculates the generation amount of the high-pressure hydrogen gas corresponding to the magnitude of the current currently supplied to the single cell 28. Thereafter, the control device 22 calculates the opening degree of the hydrogen backflow valve 78 that can supply more dry high-pressure hydrogen gas than the calculated generation amount of the high-pressure hydrogen gas, and controls the hydrogen backflow valve 78.

[0068] Also, for example, the control device 22 calculates the supply amount of the dry high-pressure hydrogen gas corresponding to the current opening degree of the hydrogen backflow valve 78. Thereafter, the control device 22 calculates the magnitude of the current that can generate less high-pressure hydrogen gas than the calculated supply amount of the dry high-pressure hydrogen gas, and controls the power supply device 26.

[0069] Further, the first table indicating the relationship between the opening degree of the hydrogen backflow valve 78 and the amount of the dry high-pressure hydrogen gas supplied from the hydrogen backflow valve 78 to the supply path 46 per unit time can be stored in the control device 22. Also, the second table indicating the relationship between the magnitude of the current supplied to the single cell 28 and the amount of the high-pressure hydrogen gas generated by the hydrogen pressure increasing stack 24 per unit time can be stored in the control device 22.

[0070] Also, the opening degree of the hydrogen backflow valve 78 that the control device 22 can control includes a case where the opening degree is zero. In the case where the opening degree of the hydrogen backflow valve 78 is zero, it is indicated that the hydrogen backflow valve 78 is in a closed state. Further, the hydrogen backflow valve 78 provided to the hydrogen backflow path 76 can be constituted by a flow rate adjusting valve and a pressure reducing valve (an on-off valve) that is more downstream than the flow rate adjusting valve.

[0071] (Modified Example 2)

[0072] In a case where the electrical value of the current of the hydrogen pressure-boosting stack 24 at the time when the current is the prescribed value exceeds the prescribed threshold value, the control device 22 can not close the introduction valve 62 and the discharge valve 56. In this case, the control device 22 can control the opening degree of the introduction valve 62 and the discharge valve 56 so that the supply amount of the water vapor supplied from the humidifier 16 to the supply path 46 is reduced. For example, the control device 22 reduces the supply amount of the water vapor in a case where the electrical value of the current of the hydrogen pressure-boosting stack 24 at the time when the current is the prescribed value exceeds the prescribed threshold value, compared to a case where the electrical value is less than the threshold value. Thereby, compared to a case where the supply amount of the water vapor is not reduced, the amount of reduction of the moisture remaining in the single cells 28 can be increased.

[0073] (Modified Example 3)

[0074] The bubble generator 58, the introduction path 60, and the introduction valve 62 can be removed from the electrochemical hydrogen pressure-boosting system 10. Even if the bubble generator 58, the introduction path 60, and the introduction valve 62 are not provided, the hydrogen gas flowing in the supply path 46 can be humidified. Therefore, even if the bubble generator 58, the introduction path 60, and the introduction valve 62 are not provided, the same effects as those of the above-described embodiment can be obtained.

[0075] (Modified Example 4)

[0076] The gas-liquid separator 20 can be provided above the closed container 38. In this case, even if a pump is not provided on the water supply path 80 or the like, it is easy to supply water from the gas-liquid separator 20 to the closed container 38.

[0077] (Modified Example 5)

[0078] The hydrogen backflow valve 78 can be a three-way valve in a case where the opening degree of the hydrogen backflow valve 78 is not adjusted.

[0079] (Modified Example 6)

[0080] In a case where the capacity of the closed container 38 is large or a mechanism for discharging water from the closed container 38 is provided, or the like, the water supply valve 82 can not be provided. That is, the water supply valve 82 is not essential.

[0081] The following description can be understood based on the invention and effects described above.

[0082] (1) The present application is an electrochemical hydrogen pressure boosting system (10) having a hydrogen pressure boosting stack (24), a power supply device (26), and a hydrogen supply source (14), wherein the hydrogen pressure boosting stack has a single cell (28) including an electrolyte membrane (30), an anode electrode (32), and a cathode electrode (34); the power supply device supplies electric current to the single cell to cause high-pressure hydrogen gas, which has a higher pressure on the cathode side of the single cell than hydrogen gas supplied to the anode side of the single cell, to be generated on the cathode side of the single cell; and the hydrogen supply source supplies the hydrogen gas to the hydrogen pressure boosting stack through a supply path (46). The electrochemical hydrogen pressure boosting system has a gas-liquid separator (20), a hydrogen backflow path (76), a hydrogen backflow valve (78), a detector (84), and a control device (22), wherein the gas-liquid separator is provided in an exhaust path (72) that communicates with the cathode side of the single cell, for separating moisture from the high-pressure hydrogen gas; the hydrogen backflow path guides dry high-pressure hydrogen gas, which is the high-pressure hydrogen gas from which the moisture has been separated, from a position in the exhaust path that is downstream of the gas-liquid separator, to the supply path that communicates with the anode side of the single cell; the hydrogen backflow valve is provided in the hydrogen backflow path; the detector detects an electrical value that indicates a voltage or a resistance of the hydrogen pressure boosting stack; and the control device controls the hydrogen backflow valve and the power supply device. The control device closes the hydrogen backflow valve when the electrical value at the time when the electric current is a prescribed value does not exceed a prescribed threshold value, and opens the hydrogen backflow valve when the electrical value at the time when the electric current is the prescribed value exceeds the threshold value, to thereby supply the dry high-pressure hydrogen gas to the hydrogen pressure boosting stack through the supply path.

[0083] Accordingly, the cathode side of the single cell can be depressurized, and the dry high-pressure hydrogen gas can be supplied to the single cell from the anode side to the cathode side of the single cell. Therefore, the moisture remaining in the single cell can be discharged from the cathode side of the single cell to the exhaust path. As a result, the water content remaining in the single cell can be reduced while the electric current is being supplied to the hydrogen pressure boosting stack.

[0084] (2) In the electrochemical hydrogen pressure boosting system described in (1) above, the control device can control the opening degree of the hydrogen backflow valve so that the supply amount of the dry high-pressure hydrogen gas is greater than the generation amount of the high-pressure hydrogen gas. Accordingly, the depressurization speed of the cathode side of the single cell can be increased. The moisture remaining in the single cell can be discharged from the cathode side of the single cell to the exhaust path earlier than in the case where the depressurization speed of the cathode side of the single cell is not increased.

[0085] (3) The application can be, in the electrochemical hydrogen pressure boosting system described in (1) or (2) above, the control device controls the magnitude of the current supplied to the single cell, so that the supply amount of the dry high-pressure hydrogen gas is greater than the generation amount of the high-pressure hydrogen gas. Accordingly, the pressure reduction speed on the cathode side of the single cell can be increased. Compared with the case where the pressure reduction speed on the cathode side of the single cell is not increased, the water remaining in the single cell can be discharged from the cathode side of the single cell to the discharge path as early as possible.

[0086] (4) The application can be, in the electrochemical hydrogen pressure boosting system described in (1) above, further comprising a humidifier (16) and a discharge valve (56), wherein the humidifier supplies water vapor to the supply path through a discharge path (54); the discharge valve is provided in the discharge path and is controlled by the control device, and the control device controls the opening degree of the discharge valve in the case where the electrical value when the current is a prescribed value exceeds the threshold value, and reduces the supply amount of the water vapor supplied from the humidifier to the supply path compared with the case where the electrical value when the current is a prescribed value is less than the threshold value. Accordingly, compared with the case where the supply amount of the water vapor is not reduced, the reduction amount of the water remaining in the single cell can be increased.

[0087] (5) The application can be, in the electrochemical hydrogen pressure boosting system described in (1) above, further comprising a humidifier and a discharge valve, wherein the humidifier supplies water vapor to the supply path through a discharge path; the discharge valve is provided in the discharge path and is controlled by the control device, and the control device closes the discharge valve and stops the supply of the water vapor to the supply path in the case where the electrical value when the current of the hydrogen pressure boosting stack is a prescribed value exceeds the threshold value. Accordingly, compared with the case where the supply of the water vapor is not stopped, the reduction amount of the water remaining in the single cell can be increased.

[0088] (6) The application can be, in the electrochemical hydrogen pressure boosting system described in (4) or (5) above, further comprising a water supply path (80) that guides the water separated by the gas-liquid separator from the gas-liquid separator to the humidifier. Accordingly, the utilization efficiency of water can be improved.

[0089] In addition, the application is not limited to the technical solutions described above, and various structures can be adopted within the scope of the main idea of the application.

Claims

1. An electrochemical hydrogen booster system (10) comprising a hydrogen booster stack (24), a power supply unit (26), and a hydrogen supply source (14), wherein, The hydrogen booster stack has a single cell (28) comprising an electrolyte membrane (30), an anode electrode (32), and a cathode electrode (34); The power supply device supplies current to the individual battery, causing high-pressure hydrogen gas to be generated on the cathode side of the individual battery, which has a higher pressure than the hydrogen gas supplied to the anode side of the individual battery. The hydrogen supply source supplies hydrogen to the hydrogen booster stack via supply path (46). Its features are, The electrochemical hydrogen booster system includes a supply path, a discharge path (72), a gas-liquid separator (20), a hydrogen reflux path (76), a hydrogen reflux valve (78), a detector (84), and a control device (22), wherein, The supply path is used to supply hydrogen to the anode side of the single cell; The discharge path guides the high-pressure hydrogen gas generated on the cathode side of the single cell; The gas-liquid separator is disposed in the discharge path connected to the cathode side of the single cell, and is used to separate moisture from the high-pressure hydrogen. The hydrogen reflux path guides the high-pressure hydrogen after the water has been separated, i.e., dry high-pressure hydrogen, from the discharge path to the supply path, which is connected to the anode side of the single cell, at a position downstream of the gas-liquid separator. The hydrogen reflux valve is located in the hydrogen reflux path; The detector detects electrical values ​​representing the voltage or resistance of the hydrogen booster stack; The control device controls the hydrogen reflux valve and the power supply device. The control device closes the hydrogen reflux valve when the electrical value of the current at a specified value does not exceed a specified threshold, and opens the hydrogen reflux valve when the electrical value of the current at a specified value exceeds the threshold, supplying dry high-pressure hydrogen to the hydrogen booster stack through the supply path.

2. The electrochemical hydrogen booster system according to claim 1, characterized in that, The control device controls the opening of the hydrogen reflux valve so that the supply of dry high-pressure hydrogen is greater than the production of high-pressure hydrogen.

3. The electrochemical hydrogen booster system according to claim 1 or 2, characterized in that, The control device controls the magnitude of the current supplied to the individual battery cell, so that the supply of dry high-pressure hydrogen is greater than the production of high-pressure hydrogen.

4. The electrochemical hydrogen booster system according to claim 1, characterized in that, It also features a humidifier (16) and an outlet valve (56), wherein, The humidifier supplies water vapor to the supply path through the outlet path (54); The outlet valve is positioned in the outlet path and is controlled by the control device. The control device controls the opening of the outlet valve when the electrical value of the current at a specified value exceeds the threshold, thereby reducing the amount of water vapor supplied from the humidifier to the supply path compared to when the electrical value of the current at a specified value is less than the threshold.

5. The electrochemical hydrogen booster system according to claim 1, characterized in that, It also features a humidifier and an outlet valve, among which, The humidifier supplies water vapor to the supply path through the outlet path; The outlet valve is positioned in the outlet path and is controlled by the control device. When the electrical value exceeds the threshold when the current is at a predetermined value, the control device stops supplying water vapor to the supply path by closing the outlet valve.

6. The electrochemical hydrogen booster system according to claim 4 or 5, characterized in that, It also has a water supply path (80) that guides the water separated by the gas-liquid separator from the gas-liquid separator to the humidifier.

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