Water electrolysis system and control method of water electrolysis apparatus

Abstract

To realize high hydrogen generation efficiency while suppressing deterioration of a water electrolysis apparatus.SOLUTION: A water electrolysis system comprises: a water electrolysis unit for electrolysis of water; a power supply unit for supplying power to the water electrolysis unit; a current detection unit for detecting the magnitude of a current to be supplied to the water electrolysis unit from the power supply unit; a temperature acquisition unit for acquiring a water temperature, which is a temperature of water to be electrolyzed; and a control unit for controlling the power to be supplied to the water electrolysis unit from the power supply unit so that the acquired water temperature is at or below a preset upper limit temperature. The control unit decreases the upper limit temperature in accordance with an increase in the current detected by the current detection unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water electrolysis system and a method for controlling a water electrolysis device. [Background technology]

[0002] Techniques for obtaining hydrogen by electrolysis of water (water electrolysis) are known (see, for example, Patent Documents 1 and 2). Patent Document 1 describes a control device that detects the temperatures of water supplied to a water electrolysis device and water discharged from the water electrolysis device. This control device cools the water supplied to the water electrolysis device when the temperature of the discharged water exceeds a specified temperature. Patent Document 2 describes a current control method that, when starting up a water electrolysis device, reduces the current density below that during rated operation and starts up while monitoring the temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-203203 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-153965 Summary of the Invention [Problem to be solved by the invention]

[0004] In water electrolysis, the higher the temperature of the water being electrolyzed, the more efficient the hydrogen production. On the other hand, if the temperature is too high, the water electrolysis device will deteriorate. In order to improve production efficiency and suppress deterioration of the water electrolysis device, the technology described in Patent Document 1 estimates the heat generation amount of the water electrolysis device and controls the temperature of the supplied water so that the water discharged from the water electrolysis device does not exceed a specified temperature. However, this technology only suppresses deterioration of the water electrolysis device by controlling the temperature of the discharged water so that it does not exceed a specified temperature, and there is room for improvement in improving hydrogen production efficiency.

[0005] In the control method described in Patent Document 2, the current density is controlled by comparing the current density at the start-up of the water electrolysis device with the current density during rated operation. However, for example, when performing water electrolysis in response to fluctuations in renewable energy, operation at partial load as well as rated load is required. In other words, the technology described in Patent Document 2 does not take into consideration control of the water electrolysis device in response to multiple operating conditions. Furthermore, although temperature and other factors other than current density are also involved in the deterioration of the water electrolysis device, the impact of temperature changes on the deterioration of the water electrolysis device is not taken into consideration.

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and has an object to achieve high hydrogen generation efficiency while suppressing deterioration of a water electrolysis device. [Means for solving the problem]

[0007] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0008] (1) One aspect of the present invention provides a water electrolysis system comprising: a water electrolysis unit that electrolyzes water; a power supply unit that supplies power to the water electrolysis unit; a current detection unit that detects the magnitude of the current supplied from the power supply unit to the water electrolysis unit; a temperature acquisition unit that acquires the water temperature, which is the temperature of the water being electrolyzed; and a control unit that controls the power supplied from the power supply unit to the water electrolysis unit so that the acquired water temperature is equal to or lower than a predetermined upper limit temperature, and the control unit reduces the upper limit temperature in response to an increase in the current detected by the current detection unit.

[0009] According to this configuration, water is electrolyzed using power supplied from the power supply unit to the water electrolysis unit. During water electrolysis, the water being electrolyzed is heated by heat generated by the resistance of the water electrolysis unit, etc., and the water temperature increases. In this configuration, the power supplied to the water electrolysis unit is controlled by comparing the water temperature with the upper limit temperature, which changes depending on the detected current, which increases or decreases as the electrolysis progresses, rather than the upper limit temperature, which is a fixed value. In this configuration, the upper limit temperature is set high when the detected current is low, i.e., the degree of progress of electrolysis is not high. On the other hand, when the detected current is high, i.e., the degree of progress of electrolysis is high, the upper limit temperature is set low. By controlling the supplied power according to the variable upper limit temperature, high hydrogen generation efficiency can be achieved while suppressing deterioration of the water electrolysis unit.

[0010] (2) The water electrolysis system of the above aspect may further include a voltage acquisition unit that acquires a voltage applied to the water electrolysis unit, and when the acquired voltage exceeds an upper limit voltage, the control unit may reduce the power supplied to the water electrolysis unit so that the detected current is equal to or less than an upper limit current supplied to the water electrolysis unit when the upper limit voltage is applied to the water electrolysis unit. According to this configuration, when the resistance during electrolysis is high and the voltage applied to the water electrolysis unit is high even when the water temperature is equal to or lower than the upper limit temperature, the applied voltage is suppressed to equal to or lower than the upper limit voltage. This makes it possible to suppress the progression of deterioration of the water electrolysis unit, which would be caused by a high voltage exceeding the upper limit voltage being applied to the water electrolysis unit, even when the water temperature is equal to or lower than the upper limit temperature.

[0011] (3) In the water electrolysis system of the above aspect, the control unit may change the upper limit temperature based on a current-temperature relationship in which the detected current and the upper limit temperature are associated by a map or an equation. According to this configuration, the relationship between the detected current and the upper limit temperature is given by a map or an equation, so that the upper limit temperature is easily determined for the detected current, and the supplied power is easily controlled.

[0012] (4) In the water electrolysis system of the above aspect, the current-temperature relationship may include a first relationship in which the detected current and a first upper limit temperature as the upper limit temperature are associated by a map or an equation, and a second relationship in which the detected current and a second upper limit temperature higher than the first upper limit temperature are associated by a map or an equation, and the control unit may, when changing the upper limit temperature in response to the detected current based on the second relationship, change the upper limit temperature based on the detected current using the first relationship when the water temperature has remained at or above the first upper limit temperature for a predetermined time. According to this configuration, the power supply to the water electrolysis unit is controlled using parameters including two different temperatures, a first upper limit temperature and a second upper limit temperature, and time. Even when power is supplied to the water electrolysis unit at a temperature exceeding the first upper limit temperature, degradation of the water electrolysis unit may be limited and may be tolerated as long as the power is supplied within a predetermined time within a temperature range equal to or lower than a second upper limit temperature that exceeds the first upper limit temperature. In such cases, this configuration further improves the efficiency of hydrogen production by allowing the supply of power at a temperature exceeding the first upper limit temperature within a predetermined time.

[0013] (5) The water electrolysis system of the above aspect may further include a cooling unit that cools the water supplied to the water electrolysis unit, wherein the control unit may use the cooling unit to cool the water supplied to the water electrolysis unit when the water temperature exceeds the upper limit temperature. According to this configuration, the water supplied to the water electrolysis unit is cooled by the cooling unit, thereby decreasing the water temperature, which allows the water temperature to be quickly reduced to or below the upper limit temperature, thereby suppressing the progression of deterioration of the water electrolysis unit.

[0014] (6) In the water electrolysis system of the above aspect, when the control unit changes the upper limit temperature in accordance with the detected current using the second relationship, and the water temperature remains equal to or higher than the first upper limit temperature for a predetermined time, the control unit may use the cooling unit to cool the water supplied to the water electrolysis unit until the water temperature becomes equal to or lower than the first upper limit temperature. According to this configuration, when a predetermined time has elapsed at the first upper limit temperature and the water temperature needs to be reduced to equal to or lower than the first upper limit temperature, the power supply to the water electrolysis unit is reduced and cooling is performed by the cooling unit, thereby reducing the water temperature more quickly and suppressing the progression of deterioration in the water electrolysis unit compared to when only the power supply is reduced.

[0015] (7) The water electrolysis system of the above aspect may further include a heating unit that heats the water supplied to the water electrolysis unit, and the control unit may use the heating unit to heat the water supplied to the water electrolysis unit when the water temperature is lower than the upper limit temperature. According to this configuration, the water supplied to the water electrolysis unit is heated by the heating unit, thereby increasing the water temperature, which allows the water temperature to be increased within a range not exceeding the upper limit temperature, thereby quickly improving the efficiency of hydrogen production in the water electrolysis unit.

[0016] The present invention can be realized in various forms, such as a water electrolysis device, a water electrolysis system, a control device for a water electrolysis device, a water electrolysis method, a system including these devices, a computer program for executing these devices, a server device for distributing the computer program, and a non-transitory storage medium storing the computer program. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic block diagram of a water electrolysis system according to one embodiment of the present invention. [Figure 2] FIG. 10 is an explanatory diagram of an upper limit temperature determined according to a detected current and a detected temperature. [Figure 3] 3 is a flowchart of a control method for a water electrolysis apparatus according to the present embodiment. [Figure 4] FIG. 4 is a schematic block diagram of a water electrolysis system according to a second embodiment. [Figure 5] FIG. 10 is an explanatory diagram of an upper limit temperature and an upper limit current in the second embodiment. [Figure 6]FIG. 10 is an explanatory diagram of an upper limit temperature and an upper limit current in the second embodiment. [Figure 7] 10 is a flowchart of a control method for a water electrolysis apparatus according to a second embodiment. [Figure 8] FIG. 10 is a schematic block diagram of a water electrolysis system according to a third embodiment. [Figure 9] FIG. 11 is an explanatory diagram of a first upper limit temperature, a second upper limit temperature, and a third upper limit temperature as upper limit temperatures used in the third embodiment. [Figure 10] 10 is a flowchart of a control method for a water electrolysis apparatus according to a third embodiment. [Figure 11] 10 is a flowchart of a control method for a water electrolysis apparatus according to a third embodiment. [Figure 12] 10 is a flowchart of a control method for a water electrolysis apparatus according to a third embodiment. [Figure 13] 10 is a flowchart of a control method for a water electrolysis apparatus according to a third embodiment. [Figure 14] FIG. 10 is a schematic block diagram of a water electrolysis system according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0018] First Embodiment Figure 1 is a schematic block diagram of a water electrolysis system 10 according to one embodiment of the present invention. In the water electrolysis system 10 shown in Figure 1, the upper limit temperature used for control varies depending on the current supplied from a power source (power supply unit) 1 to a water electrolysis device (water electrolysis unit) 2. By controlling the temperature of the water electrolyzed in the water electrolysis device 2 (hereinafter also referred to as "water temperature") to a preset upper limit temperature or lower, hydrogen can be produced while suppressing deterioration of the water electrolysis device 2.

[0019] As shown in FIG. 1 , the water electrolysis system 10 includes a water electrolysis device 2 that electrolyzes water, a power supply 1 that supplies the water electrolysis device 2 with the power required for water electrolysis, a water supply unit 4 that supplies raw water to be electrolyzed to the water electrolysis device 2, a temperature sensor (temperature acquisition unit) 6 that detects the temperature of water discharged from the anode of the water electrolysis device 2, an ammeter (current detection unit) 5 that detects the magnitude of the current supplied from the power supply 1 to the water electrolysis device 2, a heater (heating unit) 8 that heats the raw water supplied from the water supply unit 4 to the water electrolysis device 2, a heat exchanger (cooling unit) 7 that cools the raw water supplied from the water supply unit 4 to the water electrolysis device 2, and a control unit 3 that controls each unit of the water electrolysis system 10.

[0020] The water electrolysis device 2 electrolyzes water as raw water supplied from a water supply unit 4 using power supplied from a power source 1. Hydrogen produced at the cathode by electrolysis is sent to a hydrogen tank not shown in FIG. 1 . Oxygen produced at the anode of the water electrolysis device 2 by electrolysis and the water after use in the reaction are discharged to the outside. A temperature sensor 6 detects the temperature of the water discharged from the anode of the water electrolysis device 2. In this embodiment, the temperature detected by the temperature sensor 6 is regarded as the water temperature of the water electrolyzed by the water electrolysis device 2.

[0021] The heater 8 externally heats the flow path FP1 through which raw water flows and is supplied from the water supply unit 4 to the water electrolysis device 2. The heat exchanger 7 is disposed downstream of the heater 8 along the flow direction of the raw water in the flow path FP1. The heat exchanger 7 exchanges heat between the flow path FP1 and a flow path FP2 through which cooling water, which has a lower temperature than the raw water, flows. The raw water flowing through the flow path FP1 is cooled by the heat exchange. A pump (not shown in FIG. 1 ) is driven under the control of the control unit 3 in the flow path FP2, thereby controlling the flow rate of the cooling water flowing through the flow path FP2.

[0022] The controller 3 acquires the detected temperature detected by the temperature sensor 6 and the detected current detected by the ammeter 5. The controller 3 controls the power supply from the power source 1 to the water electrolysis device 2 so that the acquired detected temperature is equal to or lower than the upper limit temperature as a threshold. The controller 3 lowers the upper limit temperature in response to an increase in the detected current.

[0023] FIG. 2 is an explanatory diagram of the upper limit temperature Tmax determined based on the detected current and the detected temperature. In FIG. 2, the upper limit temperature Tmax is shown as a broken line, with the detected current on the horizontal axis and the water temperature on the vertical axis. As shown in FIG. 2, the upper limit temperature Tmax decreases in a stepped manner as the detected current increases. In this embodiment, a map (current-temperature relationship) is provided in which each of the multiple temperature ranges shown in FIG. 2 is associated with the upper limit temperature Tmax as a predetermined temperature. The controller 3 controls the power supplied from the power source 1 to the water electrolysis device 2 so that the detected current falls within the hatched area shown in FIG. 2. In other words, the hatched area represents the range of use of the supplied current and detected temperature during water electrolysis by the water electrolysis device 2.

[0024] When the detected temperature exceeds the upper limit temperature Tmax, the controller 3 supplies cooling water to the heat exchanger 7 to cool the raw water supplied from the water supply unit 4 to the water electrolysis device 2. When the detected temperature is less than the upper limit temperature Tmax, the controller 3 controls the heater 8 to heat the water supplied from the water supply unit 4 to the water electrolysis device 2. Therefore, in this embodiment, the controller 3 controls the power supplied from the power source 1 to the water electrolysis device 2 so that the water temperature becomes the upper limit temperature Tmax.

[0025] Figure 3 is a flowchart of a control method for the water electrolysis apparatus 2 of this embodiment. The control flow shown in Figure 3 first performs a water supply step in which raw water is supplied from the water supply unit 4 to the water electrolysis apparatus 2 (step S1). Next, a power supply step in which power is supplied from the power source 1 to the water electrolysis apparatus 2 is performed (step S2). In the power supply step, the control unit 3 determines the power to be supplied to the water electrolysis apparatus 2 based on, for example, an externally requested amount of hydrogen production.

[0026] A current acquisition step is performed in which the control unit 3 acquires the detected current from the ammeter 5 (step S3). The control unit 3 determines the upper limit temperature Tmax using the acquired detected current and the map shown in FIG. 2 (step S4). The control unit 3 determines one temperature from the variable upper limit temperatures Tmax given as the map based on the value of the detected current as the upper limit temperature Tmax. Next, a temperature acquisition step is performed in which the control unit 3 acquires the detected temperature T from the temperature sensor 6 (step S5).

[0027] The control unit 3 determines whether the acquired detected temperature T is less than the upper limit temperature Tmax determined in step S4 (step S6). If it is determined that the detected temperature T is less than the upper limit temperature Tmax (step S6: YES), the control unit 3 uses the heater 8 to heat the raw water supplied to the water electrolysis device 2. If the raw water is being cooled using the heat exchanger 7 at this time, the control unit 3 stops the cooling by the heat exchanger 7.

[0028] If it is determined in step S6 that the detected temperature T is equal to or greater than the upper limit temperature Tmax (step S6: NO), and after step S7, the controller 3 determines whether the detected temperature T exceeds the upper limit temperature Tmax (step S8). If it is determined that the detected temperature T exceeds the upper limit temperature Tmax (step S8: YES), the controller 3 reduces the power supplied from the power source 1 to the water electrolysis device 2, and cools the raw water supplied to the water electrolysis device 2 using the heat exchanger 7 through which cooling water flows (step S9). If the raw water is being heated by the heater 8, the controller 3 stops the heating. Step S9 corresponds to a control step.

[0029] If it is determined in step S8 that the detected temperature T is equal to or lower than the upper limit temperature Tmax (step S8: NO), and after the processing of step S9, the control unit 3 determines whether or not to end the control flow (step S10). The determination of whether or not to end is based, for example, on whether or not a predetermined operation has been accepted. If it is determined not to end the control flow (step S10: NO), the processing from step S3 onward is repeated. If it is determined to end the control flow (step S10: YES), the control flow ends.

[0030] As described above, in the water electrolysis system 10 of this embodiment, the controller 3 controls the power supply from the power source 1 to the water electrolysis device 2 so that the detected temperature T is equal to or less than the upper limit temperature Tmax as a threshold value. The controller 3 decreases the upper limit temperature Tmax in response to an increase in the detected current I. In this embodiment, water is electrolyzed using the power supplied from the power source 1 to the water electrolysis device 2. During water electrolysis, the water being electrolyzed is heated by heat generated by the resistance of the water electrolysis device 2, resulting in an increase in the water temperature. In this embodiment, the power supply to the water electrolysis device 2 is controlled by comparing the upper limit temperature Tmax, which changes in response to the detected current I that increases or decreases as the electrolysis progresses, with the detected temperature T as the water temperature, rather than the temperature as a fixed value. In this embodiment, when the detected current I is low, i.e., when the degree of progress of electrolysis is not high, the upper limit temperature Tmax is set high. On the other hand, when the detected current I is high, i.e., when the degree of progress of electrolysis is high, the upper limit temperature Tmax is set low. Controlling the supply power in response to the variable upper limit temperature Tmax enables high hydrogen production efficiency while suppressing deterioration of the water electrolysis device 2.

[0031] 2, each of a plurality of temperature ranges is associated with an upper limit temperature Tmax as a predetermined temperature, and the map is provided. In the present embodiment, the relationship between the detected current I and the upper limit temperature Tmax is provided in the map, so the upper limit temperature Tmax can be easily determined for the detected current I, and the supplied power can be easily controlled.

[0032] Furthermore, when the detected temperature exceeds the upper limit temperature Tmax, the controller 3 of this embodiment supplies cooling water to the heat exchanger 7, thereby cooling the raw water supplied from the water supply unit 4 to the water electrolysis device 2. In this embodiment, the water supplied to the water electrolysis device 2 is cooled by the heat exchanger 7, thereby reducing the water temperature. This enables the water temperature to be quickly reduced to or below the upper limit temperature Tmax, and prevents deterioration of the water electrolysis device 2.

[0033] Furthermore, when the detected temperature T is less than the upper limit temperature Tmax, the controller 3 in this embodiment controls the heater 8 to heat the water supplied from the water supply unit 4 to the water electrolysis device 2. In this embodiment, the water supplied to the water electrolysis device 2 is heated by the heater 8, thereby increasing the water temperature. This enables the water temperature to be increased within a range that does not exceed the upper limit temperature Tmax, and the efficiency of hydrogen production in the water electrolysis device 2 is rapidly improved.

[0034] Second Embodiment 4 is a schematic block diagram of a water electrolysis system 10a according to the second embodiment. The water electrolysis system 10a differs significantly from the water electrolysis system 10 according to the first embodiment in that it further includes a voltmeter (voltage acquisition unit) 9 that detects the voltage applied to the water electrolysis device 2, and that the upper limit temperature Tmax is changed using the voltage V detected by the voltmeter 9. Therefore, in the second embodiment, only the configuration and control that are different from those in the first embodiment will be described, and descriptions of the configuration and control that are the same as those in the first embodiment will be omitted.

[0035] In the second embodiment, the controller 3a acquires the detected voltage V from the voltmeter 9. If the acquired detected voltage V exceeds an upper limit voltage Vmax, the controller 3a reduces the power supplied to the water electrolysis device 2 so that the detected current I from the ammeter 5 becomes equal to or less than the upper limit current Imax. The upper limit current Imax is the value of the current supplied to the water electrolysis device 2 when the upper limit voltage Vmax is applied to the water electrolysis device 2.

[0036] FIG. 5 and FIG. 6 are explanatory diagrams of the upper limit temperature Tmax and the upper limit current Imax in the second embodiment. In FIG. 5, the use region of the detection current I as the supply current of the water electrolysis device 2 and the detection temperature T as the water temperature when the detection voltage V is less than or equal to the upper limit voltage Vmax is shown as a hatched region. In FIG. 6, the use region of the water electrolysis device 2 when the detection voltage V exceeds the upper limit voltage Vmax is shown as a hatched region. The upper limit temperature Tmax of the second embodiment is given as a function in which the detection temperature T as the water temperature is associated with the detection current I.

[0037] When the detection voltage V exceeds the upper limit voltage Vmax, as shown in FIG. 6, the control unit 3a controls the power supplied to the water electrolysis device 2 so that the detection current I is less than or equal to the upper limit current Imax. Since the resistance during water electrolysis of the water electrolysis device 2 changes, the upper limit current Imax, as shown in FIG. 6, is not a constant current value but changes according to the detection temperature.

[0038] When the detection voltage V is less than or equal to the upper limit voltage Vmax, as shown in FIG. 5, the upper limit temperature Tmax when the detection current I is the current I1 is the temperature T2. The upper limit temperature Tmax when the detection current I is the current I2 (>I1) is the temperature T1 (<T2). When the detection voltage V exceeds the upper limit voltage Vmax, as shown in FIG. 6, the current I1 when the detection temperature T is T2 is less than or equal to the upper limit current Imax when the detection temperature T is T2. Therefore, the upper limit temperature Tmax when the detection temperature T is T2 is the current I1 as in the case shown in FIG. 5. On the other hand, the current I2 when the detection temperature T is T1 exceeds the upper limit current Imax when the detection temperature T is T2. Therefore, when the detection temperature T is less than T1, the control unit 3a controls the power supplied to the water electrolysis device 2 so that the detection current I is within the use region represented by the hatched region in FIG. 6 even if the temperature T1 is less than or equal to the upper limit temperature Tmax.

[0039] Figure 7 is a flowchart of a control method for a water electrolysis apparatus 2 according to a second embodiment. The control flow shown in Figure 7 differs from the control flow of the first embodiment shown in Figure 3 in that it further includes processes in steps S15 and S16, and in that it includes processes in steps S19 to S21 instead of the heating process in step S7. Therefore, the processes in steps S11 to S14, S17 to S18, and S22 to S24 in the control flow of Figure 7 are the same as the processes in steps S1 to S4, S5 to S6, and S8 to S10 in the first embodiment shown in Figure 3. In the second embodiment, the processes in steps S15, S16, and S19 to S21 that differ from those in the first embodiment will be described.

[0040] Once the upper limit temperature Tmax is determined in step S14 of Fig. 7, the controller 3a acquires the detected voltage V from the voltmeter 9 (step S15). The controller 3a compares the acquired detected voltage V with the upper limit voltage Vmax to determine the operating range of the water electrolysis device 2 (step S16). If the detected voltage V exceeds the upper limit voltage Vmax, the controller 3a controls the power supply to the water electrolysis device 2 so that the power falls within the operating range limited by the upper limit current Imax, which is indicated by hatching in Fig. 6. If the detected voltage V is equal to or less than the upper limit voltage Vmax, the controller 3a controls the power supply to the water electrolysis device 2 so that the power falls within the operating range, which is indicated by hatching in Fig. 5 and is not limited by the upper limit current Imax.

[0041] If it is determined in the process of step S18 that the detected temperature T is less than the upper limit temperature Tmax (step S18: YES), the controller 3a determines whether the detected temperature T and the detected current I are within the usage range (step S19). If it is determined that the detected temperature T and the detected current I are within the usage range (step S19: YES), the controller 3a heats the raw water using the heater 8 (step S21). If it is determined that the detected voltage V exceeds the upper limit voltage Vmax (step S19: NO), the controller 3a not only heats the water using the heater 8 but also reduces the power supplied to the water electrolysis device 2 so that the detected current I becomes equal to or less than the upper limit current Imax (step S20).

[0042] As described above, in the second embodiment, when the acquired detected voltage V exceeds the upper limit voltage Vmax, the controller 3a reduces the power supplied to the water electrolysis device 2 so that the detected current I of the ammeter 5 becomes equal to or less than the upper limit current Imax. In this embodiment, when the resistance during electrolysis is high and the voltage applied to the water electrolysis device 2 is high even if the detected temperature T is equal to or less than the upper limit temperature Tmax, the applied voltage is suppressed to equal to or less than the upper limit voltage Vmax. This makes it possible to suppress the progression of deterioration of the water electrolysis device 2, which would be caused by a high voltage exceeding the upper limit voltage Vmax being applied to the water electrolysis device 2, even if the detected temperature T is equal to or less than the upper limit temperature Tmax.

[0043] <Third embodiment> 8 is a schematic block diagram of a water electrolysis system 10b according to a third embodiment. The water electrolysis system 10b according to the third embodiment differs from the water electrolysis system 10 according to the first embodiment in that it does not include a heater 8 or a heat exchanger 7 and controls the supply power using multiple upper limit temperatures Tmax1 to Tmax3 and elapsed time. Therefore, in the third embodiment, only the configuration and control that are different from those in the first embodiment will be described, and descriptions of the configuration and control that are the same as those in the first embodiment will be omitted.

[0044] Because the water electrolysis system 10b of the third embodiment does not include the heater 8 or the heat exchanger 7, the controller 3b controls the power supply to the water electrolysis device 2, thereby controlling the water temperature of the water electrolysis device 2. The controller 3b controls the power supply to the water electrolysis device 2 using three different upper limit temperatures: a first upper limit temperature Tmax1, a second upper limit temperature Tmax2, and a third upper limit temperature Tmax3, as well as the elapsed time since power was supplied to the water electrolysis device 2.

[0045] FIG. 9 is an explanatory diagram of the first, second, and third upper limit temperatures Tmax1, Tmax2, and Tmax3 used as upper limit temperatures in the third embodiment. As shown in FIG. 9, the first upper limit temperature Tmax1 is lower than the second upper limit temperature Tmax2, and the second upper limit temperature Tmax2 is lower than the third upper limit temperature Tmax3. The controller 3b in the third embodiment controls the power supplied to the water electrolysis device 2 using the elapsed time in one of the following usage regions: a first usage region AR1 equal to or lower than the first upper limit temperature Tmax1; a second usage region AR2 higher than the first upper limit temperature Tmax1 and equal to or lower than the second upper limit temperature Tmax2; or a third usage region AR3 higher than the second upper limit temperature Tmax2 and equal to or lower than the third upper limit temperature Tmax3. The relationship between the second upper limit temperature Tmax2 and the detected current I corresponds to the first relationship, and the relationship between the third upper limit temperature Tmax3 and the detected current I corresponds to the second relationship.

[0046] The control unit 3b detects the period t p The controller 3b controls the power supply to the water electrolysis device 2 so that the temperature T detected by the temperature sensor 6 is equal to or lower than the third upper limit temperature Tmax3. A third elapsed time t c,3 In other words, the controller 3b controls the power supply to the water electrolysis apparatus 2 so that the third elapsed time t c,3 is allowed up to the third threshold t3. c,3 exceeds the third threshold value t3, the controller 3b reduces the power supply to the water electrolysis device 2 so that the detected temperature T becomes equal to or lower than the second upper limit temperature Tmax2.

[0047] The detected temperature T is equal to or lower than the second upper limit temperature Tmax2, and the detected temperature T and the detected current I are included in the second use range AR2 within a second elapsed time t c,2 The power supplied to the water electrolysis device 2 is controlled so that the second elapsed time t is equal to or less than the second threshold value t2. c,2 exceeds the second threshold value t2, the controller 3b reduces the power supply to the water electrolysis device 2 so that the detected temperature T becomes equal to or lower than the first upper limit temperature Tmax1.c,2 is the second reset threshold t cr,2 In the above cases, the third elapsed time t c,3 is reset to zero, i.e., the second elapsed time t c,2 is the second reset threshold t cr,2 When the temperature reaches the second upper limit temperature Tmax2, the battery becomes usable again within the third usable range AR3 above the second upper limit temperature Tmax2.

[0048] The control unit 3b determines whether the detected temperature T and the detected current I are within the first use region AR1 within a first elapsed time t c,1 is the first reset threshold t cr,1 In the above cases, the second elapsed time t c,2 is reset to zero, i.e., the first elapsed time t c,1 is the first reset threshold t cr,1 When the temperature reaches the first upper limit temperature Tmax1, the battery becomes usable again within the second usable range AR2 above the first upper limit temperature Tmax1.

[0049] 10 to 13 are flowcharts of a control method for the water electrolysis apparatus 2 according to the third embodiment. In the control flow according to the third embodiment, the control unit 3b performs a water supply step of supplying raw water to the water electrolysis apparatus 2 (step S31). The control unit 3b performs a power supply step of supplying power to the water electrolysis apparatus 2 (step S32). The control unit 3b starts counting the elapsed time during which power is supplied to the water electrolysis apparatus 2 (step S33). In this embodiment, the elapsed time is counted in cycles t p The control unit 3b performs a current acquisition step of acquiring the detected current I of the ammeter 5 (step S34). The control unit 3b determines each of the upper limit temperatures Tmax1 to Tmax3 and each of the usage ranges AR1 to AR3 shown in Fig. 9. The control unit 3b performs a temperature acquisition step of acquiring the detected temperature T of the temperature sensor 6 (step S36).

[0050] The control unit 3b determines whether the detected temperature T is greater than the first upper limit temperature Tmax1 (step S37). If it is determined that the detected temperature T is equal to or less than the first upper limit temperature Tmax1 (step S37: NO), the control unit 3b determines whether the detected temperature T and the detected current I are within the first use range AR1. c,1period t p (step S42), and the process of step S53 (FIG. 11) described later is performed.

[0051] If it is determined that the detected temperature T is greater than the first upper limit temperature Tmax1 (step S37 in FIG. 10: YES), the controller 3b determines whether the detected temperature T is greater than the second upper limit temperature Tmax2 (step S38). If it is determined that the detected temperature T is greater than the second upper limit temperature Tmax2 (step S38: YES), the controller 3b determines whether the detected temperature T is greater than the third upper limit temperature Tmax3 (step S39). If it is determined that the detected temperature T is greater than the third upper limit temperature Tmax3 (step S39: YES), the controller 3b reduces the current supplied to the water electrolysis device 2 so that the detected temperature T is equal to or less than the third upper limit temperature Tmax3 (step S40).

[0052] The control unit 3b determines whether the detected temperature T after current suppression has fallen to or below the third upper limit temperature Tmax3 (step S41). If it is determined that the detected temperature T has not fallen to or below the third upper limit temperature Tmax3 (step S41: NO), the process of step S40 continues. If it is determined that the detected temperature T has fallen to or below the third upper limit temperature Tmax3 (step S41: YES), the process of step S53 (FIG. 11) described below is performed.

[0053] In the process of step S38 of FIG. 10, when it is determined that the detected temperature T is equal to or lower than the second upper limit temperature Tmax2 (step S38: NO), the control unit 3b determines whether the detected temperature T and the detected current I are within the second use range AR2 or not within the second elapsed time t c,2 period t p (Step S43 in FIG. 12). After that, the control unit 3b adds the period t p The second elapsed time t c,2 It is determined whether the second elapsed time t exceeds the second threshold value t2 (step S44). c,2 If it is determined that the second elapsed time t is equal to or less than the second threshold value t2 (step S44: NO), the process of step S53 in FIG. 11, which will be described later, is performed. c,2is determined to be greater than the second threshold value t2 (step S44 in FIG. 12: YES), the controller 3b reduces the current supplied to the water electrolysis device 2 so that the detected temperature T becomes equal to or less than the first upper limit temperature Tmax1 (step S45).

[0054] The control unit 3b determines whether the detected temperature T after the current suppression has fallen to or below the first upper limit temperature Tmax1 (step S46). If it is determined that the detected temperature T has not fallen to or below the first upper limit temperature Tmax1 (step S46: NO), the process of step S45 continues. If it is determined that the detected temperature T has fallen to or below the first upper limit temperature Tmax1 (step S46: YES), the control unit 3b determines whether the detected temperature T and the detected current I are within the first use region AR1 during the first elapsed time t c,1 period t p (step S47), and the process of step S53 (FIG. 11) described later is performed.

[0055] In the process of step S39 of FIG. 10, when it is determined that the detected temperature T is equal to or lower than the third upper limit temperature Tmax3 (step S39: NO), the control unit 3b determines whether the detected temperature T and the detected current I are within the third use range AR3, and whether the third elapsed time t c,3 period t p (Step S48 in FIG. 13). After that, the control unit 3b adds the period t p The third elapsed time t c,3 It is determined whether the third elapsed time t exceeds the third threshold value t3 (step S49). c,3 If it is determined that the third elapsed time t is equal to or less than the third threshold value t3 (step S49: NO), the process of step S53 in FIG. 11, which will be described later, is performed. c,3 is determined to be greater than the third threshold value t3 (step S49 in FIG. 13: YES), the controller 3b reduces the current supplied to the water electrolysis device 2 so that the detected temperature T becomes equal to or less than the second upper limit temperature Tmax2 (step S50).

[0056] The control unit 3b determines whether the detected temperature T after the current suppression has fallen to or below the second upper limit temperature Tmax2 (step S51). If it is determined that the detected temperature T has not fallen to or below the second upper limit temperature Tmax2 (step S51: NO), the process of step S50 continues. If it is determined that the detected temperature T has fallen to or below the second upper limit temperature Tmax2 (step S51: YES), the control unit 3b determines whether ... process of step S50 continues. c,2 period t p (step S52), and the process of step S53 (FIG. 11) described later is performed.

[0057] In the process of step S53 in FIG. 11, the control unit 3b determines whether the second elapsed time t c,2 is the second reset threshold t cr,2 It is determined whether the second elapsed time t c,2 is the second reset threshold t cr,2 If it is determined that the third elapsed time t c,3 and the second elapsed time t c,2 and are reset to zero (step S54). c,2 is the second reset threshold t cr,2 If it is less than the first elapsed time t (step S53: YES), and after the process of step S54, the control unit 3b c,1 is the first reset threshold t cr,1 It is determined whether the first elapsed time t c,1 is the first reset threshold t cr,1 If it is determined that the first elapsed time t c,1 and the second elapsed time t c,2 and the third elapsed time t c,3 and are reset to zero (step S56). c,1 is the first reset threshold t cr,1If it is less than 1 / 2 (step S55: YES), and after the process of step S56, the controller 3b determines whether or not to terminate the control flow of the water electrolysis device 2 (step S57). If it is determined not to terminate the control flow (step S57: NO), the process from step S34 onwards in Fig. 11 is repeated. If it is determined to terminate the control flow (step S57: YES), the control flow terminates.

[0058] As described above, the controller 3b of the third embodiment controls the power supply to the water electrolysis device 2 so that the temperature T detected by the temperature sensor 6 is equal to or lower than the third upper limit temperature Tmax3. When the detected temperature T is equal to or lower than the third upper limit temperature Tmax3 and the detected temperature T and the detected current I are within the third use range AR3, the third elapsed time t c,3 The power supplied to the water electrolysis device 2 is controlled so that the third elapsed time t is equal to or less than the third threshold value t3. c,3 exceeds the third threshold value t3, the controller 3b reduces the power supply to the water electrolysis device 2 so that the water temperature becomes equal to or lower than the second upper limit temperature Tmax2. c,1 ~t c,3 The power supply to the water electrolysis device 2 is controlled based on the parameters above. Even when power is supplied to the water electrolysis device 2 at a temperature exceeding the second upper limit temperature Tmax2, degradation of the water electrolysis device 2 may be limited and permitted as long as the power is supplied within the second threshold value t2 and in a temperature range equal to or lower than a third upper limit temperature Tmax3 that exceeds the second upper limit temperature Tmax2. In this embodiment, in such a case, the hydrogen production efficiency is further improved by permitting the supply of power at a temperature exceeding the second upper limit temperature Tmax2 while limiting the time to within the second threshold value t2.

[0059] <Modifications of the embodiment> The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the present invention, including, for example, the following modifications: In the above-described embodiment, part of the configuration realized by hardware may be replaced by software, and conversely, part of the configuration realized by software may be replaced by hardware.

[0060] <Variation 1> In the first to third embodiments, examples of the water electrolysis systems 10, 10a, and 10b have been described. However, the water electrolysis system can be modified as long as the controller reduces the upper limit temperatures Tmax, Tmax1 to Tmax3 in response to an increase in the detected current I. The reduction in the upper limit temperature Tmax does not necessarily have to be in response to an increase in the detected current I, and also includes a mode in which the upper limit temperature Tmax reduces in a stepwise manner when the increase in the detected current I reaches a certain level, as shown in FIG. 2. The relationship between the detected current I and the upper limit temperature Tmax may be represented by the map shown in FIG. 2, or the upper limit temperatures Tmax, Tmax1 to Tmax3 may be expressed by a function that varies with the detected current I, as shown in FIGS. 5 and 9, or may be related in a manner other than a map or a function.

[0061] In the first embodiment, the power supply 1 functions as the power supply unit. However, the water electrolysis system 10 may not include the power supply 1, and the electric wire through which the supplied power flows may simply be regarded as the power supply unit. Similarly, the water electrolysis system 10 may not include the water supply unit 4, and the flow path FP1 through which the raw water flows may be regarded as the water supply unit. Furthermore, raw water may be supplied to the water electrolysis device 2 from an external device other than the water electrolysis system 10. In the above embodiment, the temperature sensor 6 detects the detected temperature T of the post-reaction water discharged from the anode of the water electrolysis device 2 as the temperature of the water electrolyzed by the water electrolysis device 2. However, other temperatures may also be detected. For example, the temperature near the anode or cathode of the water electrolysis device 2 may be detected as the water temperature. The water electrolysis system 10 of the first embodiment includes the heater 8 that heats the raw water and the heat exchanger 7 that cools the raw water. However, the water electrolysis system 10 may include either the heater 8 or the heat exchanger 7, or neither. In the process of step S9 of FIG. 3 , the supply power may be reduced, and the raw water may not be cooled. In the process of step S20 in Fig. 7, heating may not be performed and only power reduction may be performed. Instead of heater 8 for heating raw water, a well-known technique may be applied as a method for heating raw water. Instead of heat exchanger 7 for cooling raw water, a well-known technique may be applied as a method for cooling raw water. The raw water supplied to water electrolysis apparatus 2 may be, for example, pure water from which impurities have been removed using a water purifier, or simply tap water.

[0062] In the first embodiment, the water temperature is controlled by the heat exchanger 7 to be equal to or lower than the upper limit temperature Tmax, and by the heater 8 to be equal to or higher than the upper limit temperature Tmax. However, the temperature control by the heat exchanger 7 and the heater 8 may be performed within a certain temperature range. For example, the water temperature may be controlled by the heat exchanger 7 to be equal to or lower than the upper limit temperature Tmax, and by the heater 8 to be equal to or higher than the upper limit temperature (Tmax-ΔT (ΔT>0)).

[0063] 3, 7, 10 to 13, the determination of termination is executed as the final process, but termination may be determined by receiving a termination operation during each process, and the timing of the termination determination may be any. In the above embodiment, the upper limit temperature Tmax is set using the detected current I detected by the ammeter 5, but the ammeter 5 can be modified within a range that detects the magnitude of the current. Instead of the detected current I, the current density may be detected by the current detection unit, and the detected current density may be used to perform various controls.

[0064] <Variation 2> In the third embodiment, three different upper limit temperatures Tmax1 to Tmax3 and an elapsed time t c,1 ~t c,3 The power supply to the water electrolysis device 2 was controlled using the two upper limit temperatures Tmax2 and Tmax3 and the elapsed time t c,2 ,t c,3 In this case, the second use area AR2 shown in Fig. 9 may be set as an area that includes the first use area AR1.

[0065] FIG. 14 is a schematic block diagram of a water electrolysis system 10c according to a modified example. The water electrolysis system 10c shown in FIG. 14 differs from the water electrolysis system 10b according to the third embodiment in that it includes a heat exchanger 7 for cooling raw water and in that the raw water is cooled by the heat exchanger 7 when the supply power is reduced. In the control flow shown in FIGS. 10 to 13 , the controller 3c of the water electrolysis system 10c cools the raw water using the heat exchanger 7 during the process of reducing the current supplied to the water electrolysis device 2 in steps S40, S45, and S50. In this modified example, when the detected temperature T needs to be reduced to or below the upper limit temperatures Tmax1 to Tmax3, the controller 3c reduces the power supplied to the water electrolysis device 2 and performs cooling by the heat exchanger 7. This allows the water temperature to decrease more quickly than when the supply power is reduced alone, thereby suppressing deterioration of the water electrolysis device 2.

[0066] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0067] The present invention can also be realized in the following forms. [Application example 1] A water electrolysis system, a water electrolysis unit that performs electrolysis of water; a power supply unit that supplies power to the water electrolysis unit; a current detection unit that detects the magnitude of the current supplied from the power supply unit to the water electrolysis unit; a temperature acquisition unit that acquires the water temperature, which is the temperature of the water to be electrolyzed; a control unit that controls the power supplied from the power supply unit to the water electrolysis unit so that the acquired water temperature is equal to or lower than a preset upper limit temperature; Equipped with The control unit reduces the upper limit temperature in response to an increase in the current detected by the current detection unit. [Application example 2] The water electrolysis system according to Application Example 1, further comprising: a voltage acquisition unit that acquires a voltage applied to the water electrolysis unit; The control unit and when the acquired voltage exceeds an upper limit voltage, the power supplied to the water electrolysis unit is reduced so that the detected current is equal to or less than an upper limit current supplied to the water electrolysis unit when the upper limit voltage is applied to the water electrolysis unit. [Application example 3] The water electrolysis system according to Application Example 1 or Application Example 2, the control unit changes the upper limit temperature based on a current-temperature relationship in which the detected current and the upper limit temperature are associated by a map or an equation. [Application example 4] The water electrolysis system according to any one of Application Examples 1 to 3, The current-temperature relationship is a first relationship in which the detected current and a first upper limit temperature as the upper limit temperature are associated by a map or an equation; a second relationship in which the detected current and a second upper limit temperature higher than the first upper limit temperature are associated by a map or an equation; and wherein, when the upper limit temperature is changed in response to the detected current based on the second relationship, and the water temperature has remained at or above the first upper limit temperature for a predetermined time period, the controller changes the upper limit temperature based on the detected current using the first relationship. [Application example 5] The water electrolysis system according to any one of Application Examples 1 to 4, further comprising: a cooling unit that cools the water to be supplied to the water electrolysis unit, the control unit, when the water temperature exceeds the upper limit temperature, cools the water supplied to the water electrolysis unit using the cooling unit. [Application Example 6] The water electrolysis system according to any one of Application Examples 1 to 5, wherein, when the control unit changes the upper limit temperature in accordance with the detected current using the second relationship, and when the water temperature has remained at or above the first upper limit temperature for a predetermined time, the control unit cools the water supplied to the water electrolysis unit using the cooling unit until the water temperature becomes equal to or lower than the first upper limit temperature. [Application Example 7] The water electrolysis system according to any one of Application Examples 1 to 6, further comprising: a heating unit that heats the water to be supplied to the water electrolysis unit, the control unit, when the water temperature is lower than the upper limit temperature, uses the heating unit to heat the water supplied to the water electrolysis unit. [Application Example 8] A method for controlling a water electrolysis device that electrolyzes water, comprising: a power supply step of supplying power to the water electrolysis device; a current detection step of detecting a magnitude of a current supplied to the water electrolysis device; a temperature acquisition step of acquiring a water temperature, which is the temperature of the water to be electrolyzed; a control step of controlling the power supplied to the water electrolysis device so that the acquired water temperature is equal to or lower than a preset upper limit temperature; Run In the control step, the upper limit temperature is decreased in response to an increase in the detected current. [Explanation of symbols]

[0068] 1...Power supply (power supply section) 2...Water electrolysis device (water electrolysis section) 3,3a,3b,3c...Control unit 4...Water supply section 5…Ammeter (current acquisition section) 6...Temperature sensor (temperature acquisition part) 7...Heat exchanger (cooling section) 8...Heater (heating part) 9...Voltmeter (voltage acquisition section) 10, 10a, 10b...Water electrolysis system AR1…1st usage area AR2…Second usage area AR3…Third usage area FP1, FP2...flow path I: Detected current I1,I2…Current Imax…Upper limit current T: Detected temperature T1,T2…Temperature Tmax…Upper limit temperature Tmax1…1st upper limit temperature Tmax2…Second upper limit temperature Tmax3...Third upper limit temperature Ts…Reference temperature V: Detection voltage Vmax: Upper limit voltage t2: Second threshold t3...Third threshold t c,1 …First elapsed time t c,2 …Second elapsed time t c,3 ...Third elapsed time t cr,1 …First reset threshold t cr,2 …Second reset threshold t p …period

Claims

1. A water electrolysis system, a water electrolysis unit that electrolyzes water; a power supply unit that supplies power to the water electrolysis unit; a current detection unit that detects the magnitude of the current supplied from the power supply unit to the water electrolysis unit; a temperature acquisition unit that acquires the water temperature, which is the temperature of the water to be electrolyzed; a control unit that controls the power supplied from the power supply unit to the water electrolysis unit so that the acquired water temperature is equal to or lower than a preset upper limit temperature; Equipped with The control unit reduces the upper limit temperature in response to an increase in the current detected by the current detection unit.

2. The water electrolysis system according to claim 1, further comprising: a voltage acquisition unit that acquires a voltage applied to the water electrolysis unit; The control unit and when the acquired voltage exceeds an upper limit voltage, the power supplied to the water electrolysis unit is reduced so that the detected current is equal to or less than an upper limit current supplied to the water electrolysis unit when the upper limit voltage is applied to the water electrolysis unit.

3. The water electrolysis system according to claim 1, the control unit changes the upper limit temperature based on a current-temperature relationship in which the detected current and the upper limit temperature are associated by a map or an equation.

4. The water electrolysis system according to claim 3, The current-temperature relationship is a first relationship in which the detected current and a first upper limit temperature as the upper limit temperature are associated by a map or an equation; a second relationship in which the detected current and a second upper limit temperature higher than the first upper limit temperature are associated by a map or an equation; and wherein, when the upper limit temperature is changed in response to the detected current based on the second relationship, and the water temperature has remained at or above the first upper limit temperature for a predetermined time period, the control unit changes the upper limit temperature based on the detected current using the first relationship.

5. The water electrolysis system according to claim 4, further comprising: a cooling unit that cools the water to be supplied to the water electrolysis unit, the control unit uses the cooling unit to cool the water supplied to the water electrolysis unit when the water temperature exceeds the upper limit temperature.

6. The water electrolysis system according to claim 5, wherein, when the control unit changes the upper limit temperature in accordance with the detected current using the second relationship, and when the water temperature has remained equal to or higher than the first upper limit temperature for a predetermined time, the control unit cools the water supplied to the water electrolysis unit using the cooling unit until the water temperature becomes equal to or lower than the first upper limit temperature.

7. The water electrolysis system according to any one of claims 1 to 6, further comprising: a heating unit that heats the water to be supplied to the water electrolysis unit, the control unit, when the water temperature is lower than the upper limit temperature, uses the heating unit to heat the water supplied to the water electrolysis unit.

8. A method for controlling a water electrolysis device that electrolyzes water, comprising: a power supply step of supplying power to the water electrolysis device; a current detection step of detecting a magnitude of a current supplied to the water electrolysis device; a temperature acquisition step of acquiring a water temperature, which is the temperature of the water to be electrolyzed; a control step of controlling the power supplied to the water electrolysis device so that the acquired water temperature is equal to or lower than a preset upper limit temperature; Run In the control step, the upper limit temperature is decreased in response to an increase in the detected current.

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