Water electrolysis system, water supply system, and water supply method

Abstract

To improve hydrogen generation efficiency while suppressing degradation of a water electrolysis apparatus.SOLUTION: A water electrolysis system comprises: a water electrolysis section that performs electrolysis of water; a tank that stores water supplied to the water electrolysis section; a supply section that supplies water to the tank; a water volume acquisition section that acquires the volume of water stored in the tank; a temperature acquisition section that acquires the temperature of the water stored in the tank; and a control section that controls the volume of water supplied from the supply section to the tank based on the volume and temperature of the water stored in the tank. The control unit supplies water from the supply unit to the tank until the water volume in the tank reaches a second water volume greater than a first water volume when the water volume in the tank is less than the first water volume. When the water volume in the tank is greater than or equal to the first water volume and the temperature of the water in the tank is higher than a reference temperature, the control unit supplies water from the supply unit to the tank until the water volume in the tank reaches a third water volume greater than the second water volume.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water electrolysis system, a water supply system, and a water supply method. [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 technique in which water supplied to a water electrolysis device that electrolyzes water is drained when the pH value drops so as to maintain the pH value, and pure water is supplied as water for electrolysis after drainage. Patent Document 2 describes a hydrogen and oxygen generation device that calculates the amount of electrolyzed water using the pressure and temperature of hydrogen and oxygen generated by the water electrolysis device and the power consumption of the water electrolysis device. In this device, the amount of raw water to be supplied to the water electrolysis system is determined based on the calculated amount of water. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-129265 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-198880 Summary of the Invention [Problem to be solved by the invention]

[0004] In water electrolysis, the higher the temperature of the water being decomposed, the more efficient the hydrogen production, so from the viewpoint of efficiency, it is preferable to maintain a high water temperature. On the other hand, an excessive rise in water temperature can lead to deterioration of the water electrolysis device, so it is preferable to manage the water temperature. The reaction temperature of water electrolysis is highly dependent on the temperature of the supplied water. Therefore, when pure water or the like is supplied to a tank that supplies water to a water electrolysis device, the water temperature in the tank changes, and as a result, the reaction temperature of water electrolysis also changes. Patent Documents 1 and 2 do not mention temperature management of the water supplied to the water electrolysis device. Therefore, there is room for improvement in improving hydrogen production efficiency.

[0005] The present invention has been made to solve at least part of the above-mentioned problems, and has an object to improve the hydrogen production efficiency and suppress deterioration of a water electrolysis device. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0007] (1) According to one aspect of the present invention, a water electrolysis system is provided, comprising: a water electrolysis unit that electrolyzes water; a tank that stores water to be supplied to the water electrolysis unit; a supply unit that supplies water to the tank; a water volume acquisition unit that acquires the amount of water stored in the tank; a temperature acquisition unit that acquires the temperature of the water stored in the tank; and a control unit that controls the amount of water supplied from the supply unit to the tank based on the amount of water stored in the tank and the water temperature, wherein, when the amount of water in the tank is less than a first water volume, the control unit supplies water from the supply unit until the amount of water in the tank reaches a second water volume that is greater than the first water volume; and when the amount of water in the tank is equal to or greater than the first water volume and the temperature of the water in the tank is higher than a reference temperature, the control unit supplies water from the supply unit until the amount of water in the tank reaches a third water volume that is greater than the second water volume.

[0008] According to this configuration, the amount of water and the temperature of the water in a tank that stores water as raw water to be supplied to the water electrolysis unit are acquired. In the water electrolysis unit, heat is generated as hydrogen is produced, causing the temperature of the water being electrolyzed to rise, and this rise in temperature also causes the water temperature in the tank to rise. An excessive rise in water temperature can cause deterioration of the water electrolysis unit, so control of the water temperature is necessary to suppress this deterioration. In this configuration, the temperature of the water in the tank and the temperature of the water being electrolyzed decrease as water is supplied from the supply unit to the tank. In particular, in this configuration, when the amount of water in the tank is small, less than the first water amount, water is supplied from the supply unit until the amount of water in the tank reaches a second water amount, so that sufficient raw water can be supplied from the tank to the water electrolysis unit. On the other hand, when the amount of water in the tank is equal to or greater than the first water amount but the water temperature in the tank is higher than the reference temperature, water is supplied from the supply unit until the amount of water in the tank reaches a third water amount. This decreases the water temperature in the tank, and when raw water is supplied from the tank to the water electrolysis unit, the temperature of the water electrolyzed in the water electrolysis unit can be reduced. As a result, by using this configuration, the temperature of the water electrolyzed in the water electrolysis unit can be controlled within a certain range, and the efficiency of hydrogen production can be improved while suppressing deterioration of the water electrolysis unit.

[0009] (2) The water electrolysis system of the above aspect may further include a flow path through which oxygen generated at the anode by water electrolysis in the water electrolysis unit and water used in the reaction are supplied to the tank, and the tank may have a gas-liquid separation function for separating oxygen from the water and oxygen supplied via the flow path. According to this configuration, water after the reaction at the anode of the water electrolysis unit is used as raw water to be supplied again to the water electrolysis unit via the flow path, thereby enabling effective use of pure water. Although the temperature of the water after the reaction is increased by electrolysis, in this configuration, the supply of water from the supply unit to the tank is controlled by comparing the water temperature in the tank with a reference temperature. This improves the efficiency of hydrogen production, suppresses the increase in the temperature of the water being electrolyzed, and suppresses deterioration of the water electrolysis unit.

[0010] (3) The water electrolysis system of the above aspect may further include a power supply unit that supplies power to the water electrolysis unit; and a detection unit that detects at least one of the current and the power supplied from the power supply unit to the water electrolysis unit, wherein the control unit may decrease the reference temperature as the detection value of the detection unit increases. According to this configuration, the detection unit detects at least one of the power and current used in water electrolysis. Because water electrolysis is prone to deterioration at high power and high temperatures, when the power or current value is large, i.e., when the power is high, the reference temperature is lowered to lower the reaction temperature of the water electrolysis unit. This suppresses deterioration at high power, and at low power, hydrogen production efficiency can be improved by operating at a higher temperature than at high power.

[0011] (4) The water electrolysis system of the above aspect may further include a conductivity acquisition unit that acquires the electrical conductivity of the water in the tank, wherein the tank is capable of draining the stored water, and wherein, when the electrical conductivity is equal to or greater than a first conductivity, the control unit drains the water in the tank until the amount of water in the tank reaches the first water volume, and then supplies water from the supply unit until the amount of water in the tank reaches the third water volume; and when the electrical conductivity is less than the first conductivity and equal to or greater than a second conductivity that is lower than the first conductivity, the amount of water in the tank is equal to or greater than the third water volume, and the temperature of the water in the tank is higher than the reference temperature, the control unit drains the water in the tank until the amount of water in the tank reaches a fourth water volume that is greater than the first water volume and less than the third water volume, and then supplies water from the supply unit until the amount of water reaches the third water volume. According to this configuration, the amount of raw water supplied from the tank to the water electrolysis unit is controlled according to the electrical conductivity of the water in the tank. High electrical conductivity of the raw water facilitates deterioration of the water electrolysis. In this configuration, when the electrical conductivity of the water in the tank is high, at or above the first conductivity, the water in the tank is drained to a first water volume, and then water is supplied from the supply unit to the tank until the water volume reaches a third water volume. This reduces the electrical conductivity of the water in the tank and suppresses deterioration of the water electrolysis unit. Furthermore, when the electrical conductivity of the water in the tank is not as high as the first conductivity but is at or above the second conductivity and the water temperature in the tank is higher than the reference temperature, the water in the tank is drained to a fourth water volume, and then water is supplied from the supply unit to the tank until the water volume reaches the third water volume. Even if the electrical conductivity is not as high as the first conductivity, if the raw water temperature is high, water is drained and supplied to lower the water temperature and replaced with raw water with lower electrical conductivity. This suppresses deterioration of the water electrolysis unit.

[0012] The present invention can be realized in various forms, for example, a water electrolysis device, a water electrolysis system, a water supply device that supplies water to a water electrolysis device, a water supply method that supplies water to a water electrolysis device, 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 that stores the computer program. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic block diagram of a water electrolysis system according to one embodiment of the present invention. [Figure 2] FIG. 4 is an explanatory diagram showing the time transition of the power supplied to the water electrolysis device. [Figure 3] 4 is a flowchart of water supply control in the first embodiment. [Figure 4] FIG. 4 is a schematic block diagram of a water electrolysis system according to a second embodiment. [Figure 5] 10 is a flowchart of water supply control in the second embodiment. [Figure 6]FIG. 1 is a graph illustrating the relationship between the hydrogen production efficiency and the rate of deterioration of the water electrolysis device. [Figure 7] FIG. 10 is a schematic block diagram of a water electrolysis system according to a third embodiment. [Figure 8] 10 is a flowchart of water supply control according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] First Embodiment Fig. 1 is a schematic block diagram of a water electrolysis system 100 according to one embodiment of the present invention. In the water electrolysis system 100 shown in Fig. 1, raw water is supplied to a water electrolysis device (water electrolysis unit) 2, and the water electrolysis device 2 electrolyzes the raw water to generate hydrogen from the cathode. In the first embodiment, the supply of raw water from a tank 3 storing the raw water to the water electrolysis device 2 and the supply of pure water from a pure water production device (supply unit) 1 that produces pure water to the tank 3 are controlled based on the amount of water in the tank 3 and the temperature of the water in the tank 3. As a result, the temperature decrease due to the supply of pure water and the temperature increase due to water electrolysis are adjusted, thereby improving the hydrogen production efficiency of the water electrolysis device 2 and suppressing deterioration of the water electrolysis device 2.

[0015] As shown in FIG. 1 , the water electrolysis system 100 includes a water electrolysis device 2, a tank 3 for storing raw water to be supplied to the water electrolysis device 2, a raw water flow path FP2 connecting the tank 3 and the water electrolysis device 2 and through which the raw water flows, a raw water pump 4 for sending water in the tank 3 to the water electrolysis device 2 via the raw water flow path FP2, and a water volume W stored in the tank 3. n and a water volume sensor (water volume acquisition unit) 6 that acquires the temperature T of the raw water stored in the tank 3. n the temperature sensor (temperature acquisition unit) 5 that acquires the temperature, the pure water production apparatus 1 that produces pure water, a pure water flow path FP1 that connects the pure water production apparatus 1 and the tank 3 and through which the pure water flows, a valve 9 that opens and closes the pure water flow path FP1, a heat exchanger 7 that exchanges heat with the raw water sent from the raw water pump 4 to the water electrolysis apparatus 2, a cooling water pump 8 that sends cooling water to the heat exchanger 7, a reflux flow path (flow path) FP3 that connects the water electrolysis apparatus 2 and the tank 3, and a control unit 20 that controls each part of the water electrolysis system 100.

[0016] The water electrolysis device 2 electrolyzes water supplied from the tank 3 using power supplied from an external power source (not shown in FIG. 1). Hydrogen generated at the cathode by electrolysis is sent to a hydrogen tank (not shown in FIG. 1). Oxygen generated at the anode of the water electrolysis device 2 by electrolysis and the water used in the reaction are sent to the tank 3 through the reflux flow path FP3. The tank 3 is a gas-liquid separator that has a gas-liquid separation function that separates oxygen from the water and oxygen supplied via the reflux flow path FP3. The oxygen separated by the tank 3 is released to the outside. The separated water is stored in the tank 3. As a result, in this embodiment, the raw water stored in the tank 3 is a mixture of the post-reaction water sent from the anode of the water electrolysis device 2 and the pure water supplied from the pure water manufacturing system 1. Note that, in this specification, pure water refers to water from which some of the inorganic matter, organic matter, particulate matter, microorganisms, and the like contained in tap water have been removed.

[0017] The water volume sensor 6 of this embodiment detects the liquid level of the raw water stored in the tank 3. The detected liquid level is used to calculate the amount of raw water W n is obtained. The pure water production system 1 produces pure water by removing impurities contained in the supplied tap water. The produced pure water is supplied to the tank 3 via a valve 9. Raw water supplied to the water electrolysis system 2 from the raw water pump 4 and cooling water sent from the cooling water pump 8 pass through the heat exchanger 7. Heat exchange occurs between the raw water and the cooling water via a partition wall. The temperature of the cooling water is set to be lower than the temperature of the raw water. Therefore, the temperature of the raw water decreases due to heat exchange by the heat exchanger 7. The temperature of the raw water supplied to the water electrolysis system 2 is adjusted by adjusting the flow rate and temperature of the cooling water supplied to the heat exchanger 7.

[0018] The control unit 20 controls the power supplied to the water electrolysis apparatus 2 for water electrolysis, the power for operating the raw water pump 4 and the cooling water pump 8, and the opening and closing of the valve 9. The control unit 20 determines the raw water to be supplied from the tank 3 to the water electrolysis apparatus 2 according to the amount of hydrogen production required of the water electrolysis apparatus 2. For example, the control unit 20 sets the supply flow rate to be several tens to several hundreds of times the amount of raw water required for the required hydrogen production (the amount of water to be electrolyzed). The control unit 20 controls the raw water pump 4 to supply the determined raw water to the water electrolysis apparatus 2.

[0019] FIG. 2 is an explanatory diagram illustrating the change over time in the power supplied to the water electrolysis device 2. In FIG. 2, the change in the power supplied to the water electrolysis device 2 is indicated by a broken line BL against the horizontal time axis. In this embodiment, the controller 20 changes the power supplied to the water electrolysis device 2 in a stepwise manner in accordance with the target hydrogen production amount at each time. Note that in other embodiments, the power supplied to the water electrolysis device 2 may change smoothly over time rather than in a stepwise manner. Alternatively, the power supplied to the water electrolysis device 2 may be controlled by controlling the current value.

[0020] The control unit 20 detects the water level in the tank 3 detected by the water level sensor 6 and the water temperature T n The control unit 20 acquires the water temperature T n For example, the control unit 20 controls the cooling water pump 8 based on the water temperature T n is equal to or greater than the threshold value, the cooling water pump 8 is operated to lower the temperature of the raw water supplied to the water electrolysis apparatus 2 through heat exchange by the heat exchanger 7. In another embodiment, the control unit 20 may increase the flow rate of the cooling water to lower the temperature of the raw water as the amount of hydrogen produced by water electrolysis increases.

[0021] The control unit 20 uses the liquid level in the tank 3 detected by the water level sensor 6 to calculate the amount of raw water W stored in the tank 3. n The control unit 20 calculates the calculated water volume W n and the water temperature T detected by the temperature sensor 5 nThe control unit 20 controls the opening and closing of the valve 9 using the above, thereby controlling the amount of pure water supplied from the pure water production apparatus 1 to the tank 3. Specifically, the control unit 20 controls the amount of water W n is the threshold value of the first water volume W L If the water volume in tank 3 is less than W n is the first water volume W L The second water volume W is greater than M The control unit 20 controls the amount of water in the tank 3 to be supplied with pure water from the pure water production device 1 until the amount of water in the tank 3 is W n is the first water volume W L Above, and the water temperature in tank 3 T n is the threshold value of the reference temperature T s If the water volume in tank 3 is higher than n is the second water volume W M The third water volume W is greater than H Pure water is supplied from the water purifier 1 until the temperature reaches 100°C.

[0022] 3 is a flow chart of the supply control of water from the pure water manufacturing system 1 of the first embodiment to the tank 3. In the supply control flow shown in FIG. 3, first, the water volume W n The water volume sensor 6 detects the water level in the tank 3. The control unit 20 calculates the water volume W in the tank 3 using the detected water level. n Next, calculate the water temperature T n The temperature sensor 5 acquires the temperature W (step S2). n and water temperature T n The acquisition will continue from then on.

[0023] The control unit 20 calculates the calculated water volume W in the tank 3. n is the third water volume W H It is determined whether the water volume W is equal to or greater than the water volume W (step S3). n is the third water volume W HIf it is determined that the amount is equal to or greater than this (step S3: YES), the control unit 20 waits for several seconds without supplying pure water from the pure water production apparatus 1 to the tank 3 (step S7), and then performs the process of step S9, which will be described later. In this embodiment, the waiting time in step S7 is set in advance, but in other embodiments, the waiting time may not be set.

[0024] In the process of step S3, the water volume W n is the third water volume W H If it is determined that the water volume W is less than the predetermined value (step S3: NO), the control unit 20 n is the first water volume W L It is determined whether the water volume W is less than the water volume W (step S4). n is the first water volume W L If it is determined that the amount of water in the tank 3 is less than W (step S4: YES), the control unit 20 n is the second water volume W M Pure water is supplied from the water purifying apparatus 1 to the tank 3 until the water reaches the predetermined level (step S8), and the process of step S9 described below is carried out. The processes of steps S4 and S8 correspond to a first water supply step.

[0025] In the process of step S4, the water volume W n is the first water volume W L If it is determined that the temperature is equal to or higher than the water temperature T n is the reference temperature T s (Step S5). n is the reference temperature T s If it is determined that the water temperature T is equal to or less than the predetermined value (step S5: NO), the process of step S7 is performed. n is the reference temperature T s If it is determined that the water volume W in the tank 3 is higher than n is the third water volume W H Pure water is supplied from the water purifying apparatus 1 to the tank 3 until the water reaches the predetermined concentration (step S6). The processes from steps S4 to S6 correspond to a second water supply step.

[0026] The control unit 20 determines whether to terminate the water supply control flow (step S9). The control unit 20 determines to terminate the supply control flow, for example, when a predetermined operation to terminate water electrolysis by the water electrolysis device 2 is received. If it is determined not to terminate the supply control flow (step S9: NO), the processing from step S3 onwards is repeated. If it is determined to terminate the supply control flow (step S9: YES), the control unit 20 terminates the supply control flow.

[0027] As described above, the water electrolysis system 100 of this embodiment can reduce the amount of water stored in the tank 3 by n and a water volume sensor 6 that acquires the temperature T of the raw water stored in the tank 3. n The control unit 20 is provided with a temperature sensor 5 for detecting the amount of water W n is the first water volume W L If the water volume in tank 3 is less than W n is the first water volume W L The second water volume W is greater than M The control unit 20 controls the amount of water in the tank 3 to be supplied with pure water from the pure water production device 1 until the amount of water in the tank 3 is W n is the first water volume W L Above, and the water temperature in tank 3 T n is the threshold value of the reference temperature T s If the water volume in tank 3 is higher than n is the second water volume W M The third water volume W is greater than H In the water electrolysis device 2 of this embodiment, heat is generated as hydrogen is produced, causing the water temperature to change. This causes the tank water temperature to rise. An excessive rise in water temperature will cause deterioration of the water electrolysis device 2, so it is necessary to control the water temperature to prevent this deterioration. In this embodiment, pure water is supplied from the pure water production device 1 to the tank 3, causing the water temperature T n In particular, in this embodiment, the amount of water W in the tank 3 is reduced. n is the first water volume W LWhen the amount of water in the tank 3 is less than 1000 W, in order to supply a sufficient amount of raw water from the tank 3 to the water electrolysis device 2, the amount of water in the tank 3 is set to W n is the second water volume W M The pure water is supplied from the pure water production system 1 until the water volume in the tank 3 reaches W n is the first water volume W L Although there is a certain amount of water above this, the water temperature T n is the reference temperature T s If it is higher than the water volume W in tank 3, n is the third water volume W H The pure water is supplied from the pure water production system 1 until the water temperature T n This reduces the temperature of the water electrolyzed in the water electrolysis device 2 when raw water is supplied from the tank 3 to the water electrolysis device 2. As a result, it becomes possible to control the temperature of the water electrolyzed in the water electrolysis device 2 within a certain range, thereby improving the hydrogen production efficiency while suppressing deterioration of the water electrolysis device 2.

[0028] In this embodiment, oxygen generated at the anode of the water electrolysis device 2 by electrolysis and the water used in the reaction are sent to the tank 3 through the reflux flow path FP3. The tank 3 is a gas-liquid separator having a gas-liquid separation function that separates oxygen from the water and oxygen supplied via the reflux flow path FP3. The oxygen separated by the tank 3 is released to the outside. The separated water is stored in the tank 3. With this configuration, the water generated after the reaction at the anode of the water electrolysis device 2 is used as raw water to be supplied again to the water electrolysis device 2 via the reflux flow path FP3, enabling effective use of pure water. Although the temperature of the water after the reaction is increased by electrolysis, in this embodiment, the water temperature T n and reference temperature T s The water supply from the pure water production system 1 to the tank 3 is controlled by comparing the above. This not only improves the efficiency of hydrogen production, but also suppresses an increase in the temperature of the water being electrolyzed, thereby suppressing deterioration of the water electrolysis system 2.

[0029] Second Embodiment 4 is a schematic block diagram of a water electrolysis system 100a according to the second embodiment. The water electrolysis system 100a according to the second embodiment differs from the water electrolysis system 100 according to the first embodiment in that it further includes a power supply (power supply unit) 11 that supplies power for the water electrolysis device 2 to perform water decomposition, an ammeter (detection unit) 10 that detects the current flowing during water electrolysis, and a control unit 20a that calculates a reference temperature T s Therefore, in the second embodiment, only the configuration and control that are different from those in the first embodiment will be described, and a description of the configuration and control that are the same as those in the first embodiment will be omitted.

[0030] The control unit 20a of the second embodiment acquires the current detected by the ammeter 10. As the detected current I of the ammeter 10 increases, the control unit 20a adjusts the reference temperature T s Specifically, the control unit 20a reduces the reference temperature T by using a function f that decreases as the detected current I increases and is defined as in the following equation (1): s Calculate. T s =f(I) (1)

[0031] Figure 5 is a flowchart of the supply control of water from the pure water manufacturing system 1 to the tank 3 according to the second embodiment. The supply control flow of the second embodiment differs from the supply control flow of the first embodiment shown in Figure 3 in that steps S15 and S16 have been newly added. Therefore, steps S11 to S14 and steps S17 to S21 in the supply control flow of the second embodiment are the same as steps S1 to S4 and steps S5 to S9 in the supply control flow of the first embodiment.

[0032] In the process of step S14 in the supply control flow shown in FIG. 5, the water volume W n is the first water volume W L If it is determined that the temperature is equal to or higher than the reference temperature T (step S14: NO), the control unit 20a acquires the detected current I detected by the ammeter 10 (step S15). s(Step S16). The control unit 20a determines the reference temperature T by substituting the value of the detected current I into the function f of the above formula (1). s After that, the control unit 20a calculates the water temperature T n The reference temperature T s It is determined whether the value is higher than (step S17), and the subsequent processing is carried out.

[0033] FIG. 6 is an explanatory diagram of the hydrogen production efficiency and the rate of deterioration of the water electrolysis device 2. FIG. 6 shows the hydrogen production efficiency and the rate of deterioration of the water electrolysis device 2 versus the temperature of the water being electrolyzed. In FIG. 6, the hydrogen production efficiency is indicated by a solid straight line L1, and the rate of deterioration is indicated by a dashed curve C1. As indicated by the straight line L1 in FIG. 6, the hydrogen production efficiency increases with an increase in the temperature of the water being electrolyzed. Meanwhile, the rate of deterioration also increases with an increase in the water temperature. In the second embodiment, the hydrogen production efficiency is increased relative to the reference temperature T s As the initial value of , 60 degrees Celsius (60°C) is set as shown by the dashed line in FIG.

[0034] As described above, the control unit 20a of the second embodiment uses the function f of the above formula (1) to calculate the reference temperature T s Since water electrolysis is prone to deterioration at high power and high temperature, when the power or current value is large, i.e., when the power is high, the reference temperature T s This reduces the temperature of the water electrolysis device 2, thereby suppressing deterioration in the case of high power output, and by operating at a higher temperature in the case of low power output compared to the case of high power output, it is possible to increase the efficiency of hydrogen production.

[0035] <Third embodiment> 7 is a schematic block diagram of a water electrolysis system 100b according to a third embodiment. The water electrolysis system 100b according to the third embodiment has a configuration in which the electrical conductivity E n The control unit 20b is provided with an electrical conductivity sensor 13 for detecting the electrical conductivity En The third embodiment is significantly different from the first embodiment in that raw water supplied from the tank 3 to the water electrolysis apparatus 2 and wastewater discharged from the tank 3 are controlled using a control valve. Therefore, in the third embodiment, only the configuration and control that are different from those in the first embodiment will be described, and a description of the configuration and control that are the same as those in the first embodiment will be omitted.

[0036] 7, the water electrolysis system 100b of the third embodiment further includes an electrical conductivity sensor 13 and a drain valve 12 that opens and closes a drain passage FP4 connected to the tank 3. The controller 20b detects the electrical conductivity E n The control unit 20b acquires the acquired electrical conductivity E n In response to the acquired electrical conductivity E n is the first conductivity E H In the above cases, open the drain valve 12 and increase the water volume W in the tank 3. n is the first water volume W L After that, the control unit 20b closes the drain valve 12 and controls the amount of water in the tank 3 to W n is the third water volume W H Pure water is supplied from the water purifier 1 to the tank 3 until the water reaches the temperature.

[0037] In addition, the control unit 20b determines the amount of water W in the tank 3 when the following two conditions are met: n is equal to or greater than the first water amount and less than the third water amount, HL (W L <W HL <W H ) and then drain the water to the third volume W H Pure water is supplied from the water purifier 1 to the tank 3 until the water reaches the temperature. Condition 1: Water volume in tank 3 W n is the third water volume W H End Condition 2: Electrical conductivity E n is the first conductivity E H Second conductivity E smaller than M Above 1st conductivity E H Less than (EM ≦E n <E H ) and the water temperature T n is the reference temperature T s higher than

[0038] Figure 8 is a flowchart of water supply control from the pure water manufacturing system 1 to the tank 3 according to the third embodiment. The supply control flow of the second embodiment differs from the supply control flow of the first embodiment shown in Figure 3 in that steps S33, S34, S39, S40, and S42 have been newly added. Therefore, steps S31 to S32 and steps S35 to S38, S41, S43, and S44 in the supply control flow of the third embodiment are the same as steps S1 to S2 and steps S3 to S9 in the supply control flow of the first embodiment.

[0039] After the temperature acquisition process of step S32 in the supply control flow shown in FIG. 8 is performed, the control unit 20b acquires the electrical conductivity E n (Step S33). n The acquisition will continue thereafter.

[0040] The control unit 20b determines the obtained electrical conductivity E n is the first conductivity E H It is determined whether the electrical conductivity E is equal to or greater than the predetermined value (step S34). n is the first conductivity E H If it is determined that the amount of water in the tank 3 is equal to or greater than the predetermined amount (step S34: YES), the control unit 20b n is the first water volume W L Drain until the third water volume W H Water is supplied from the water purifying apparatus 1 to the tank 3 until the electrical conductivity E n is the first conductivity E H If it is determined that the amount of water in the tank 3 is less than W (step S34: NO), the control unit 20b n is the third water volume W H It is determined whether or not it is equal to or greater than this (step S35).

[0041] Water volume in tank 3 W n is the third water volume W H If it is determined that the amount of water in the tank 3 is equal to or greater than the amount of water in the tank 3 (step S35: YES), the control unit 20b determines whether both of the above-mentioned two conditions 1 and 2 are satisfied, or whether at least one of them is not satisfied (step S39). If it is determined that both of the two conditions are satisfied (step S39: YES), the control unit 20b n The fourth water volume W HL Drain until the third water volume W H Water is supplied from the water purifying apparatus 1 to the tank 3 until the electrical conductivity E n is the second conductivity E M In the above cases, the electrical conductivity E n is the first conductivity E H Since it is determined that the electrical conductivity is less than E n is the second conductivity E M Above 1st conductivity E H It will be less than.

[0042] As described above, the control unit 20b of the third embodiment controls the electrical conductivity E n is the first conductivity E H In the above case, the amount of water in tank 3 is W n is the first water volume W L After that, the control unit 20b controls the amount of water in the tank 3 to n is the third water volume W H The control unit 20b supplies pure water from the pure water production apparatus 1 to the tank 3 until the amount of water W in the tank 3 is n is equal to or greater than the first water amount and less than the third water amount, HL (W L <W HL <W H ) and then drain the water to the third volume W H Pure water is supplied from the water purifier 1 to the tank 3 until the water reaches the temperature. Condition 1: Water volume in tank 3 Wn is the third water volume W H End Condition 2: Electrical conductivity E n is the first conductivity E H Second conductivity E smaller than M Above 1st conductivity E H Less than (E M ≦E n <E H ) and the water temperature T n is the reference temperature T s higher than

[0043] Electrical conductivity E of raw water n In this embodiment, the electrical conductivity E of the water in the tank 3 is high, which leads to the deterioration of the water electrolysis. n is the first conductivity E H When the water level in tank 3 is higher than the first water level W L After the water is discharged up to the third volume W H Water is supplied from the pure water production system 1 into the tank 3 until the electrical conductivity of the water in the tank 3 becomes E n This reduces the electrical conductivity E of the water in the tank 3, thereby preventing an excessive rise in the temperature of the water being electrolyzed in the water electrolysis device 2. n is the first conductivity E H Although not as high as the second conductivity E M or more, and the water temperature T n is the reference temperature T s If the water volume in tank 3 is higher than n The fourth water volume W HL After draining to the third water volume W H Water is supplied from the pure water production system 1 to the tank 3 until the electrical conductivity E n is the first conductivity E H The water temperature T n If the electrical conductivity is high, the water temperature is lowered by draining and supplying water, and raw water with lower electrical conductivity is replaced. This prevents deterioration of the water electrolysis device 2.

[0044] <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.

[0045] <Variation 1> The water electrolysis systems 100, 100a, 100b of the first to third embodiments are merely examples, and the control units 20, 20a, 20b are configured to control the amount of water W n and water temperature T n and can be modified within the scope of controlling the amount of water supplied from the pure water production system 1 to the tank 3. A supply unit other than the pure water production system 1 may be used to supply water to the tank 3; for example, tap water may be supplied to the tank 3. Furthermore, the pure water flow path FP1 through which the water supplied to the tank 3 flows may be regarded as the water supply unit. The water flowing through the pure water flow path FP1 may be something other than pure water.

[0046] In the first embodiment, the tank 3 is a gas-liquid separator that separates the oxygen produced at the anode of the water electrolysis device 2 and supplied via the reflux flow path FP3 from the water used in the reaction. However, the tank may simply store water without having a gas-liquid separation function. In this case, the water electrolysis system 100 may not include the reflux flow path FP3, and the oxygen produced at the anode of the water electrolysis device 2 and the water used in the reaction may be discharged to the outside. The amount of water W in the tank 3 may be n Although the method of obtaining is calculated from the detection of the liquid level in the tank 3 by the water level sensor 6, well-known techniques may also be applied.

[0047] In the supply control flow of the first embodiment shown in Fig. 3, the end of the process is determined in step S9 as the final process, but the end of the process may be determined by receiving an end operation during each process. The timing of the end determination may be any time, as in the second and third embodiments.

[0048] The control unit 20 of the first embodiment is configured to detect the amount of water W in the tank 3. n is the first water volume W L If it is less than the second water volume W M The process of supplying water up to the amount W in the tank 3 (step S8) n is the first water volume W L (Step S4: NO) or more and the water temperature T n is the reference temperature T s If it is higher than (step S5: YES), the third water volume W H Therefore, for example, in step S7 of FIG. 3, the control unit 20 may supply water up to the third water volume W H Water may be supplied to the extent that it does not reach the first water volume W L , 2nd water volume W M , 3rd water volume W H , and the fourth water volume W HL The magnitude relationship in the third embodiment may be set to, for example, 80%, 30%, 20%, and 70% when the capacity of the tank 3 is 100%. L ~4th water volume W HL The setting of the fourth water volume W HL is the first water volume W L The third water volume W is larger than H The second water volume W M It may be smaller than

[0049] <Variation 2> The control unit 20a of the second embodiment calculates the reference temperature T using the detected current I detected by the ammeter 10 as in the above formula (1). s However, the power supplied to the water electrolysis device 2 was detected instead of the ammeter 10, and the control unit 20a used the detected power to calculate the reference temperature T s The reference temperature T sAlthough the function f shown in the above formula (1) decreases with an increase in the detected current I, a map or the like other than the function f may be used. For example, the detected current I may be divided into several ranges of values, and the reference temperature T s may be set.

[0050] In the supply control flow of the second embodiment shown in FIG. 5, the detected current I is acquired in step S15, but it may be acquired earlier. For example, the detected current I may be acquired after the temperature acquisition step (step S12) of step S12, or before the water volume acquisition step (step S11), as long as detection continues thereafter. In FIG. 6, the relationship between the hydrogen production efficiency and the rate of deterioration of the water electrolysis device 2 is explained using 60°C as a reference temperature, as an example. However, the reference temperature T may be changed depending on the performance of the water electrolysis device 2, etc. s The initial value may be other than 60°C.

[0051] The water electrolysis system 100a of the second embodiment shown in Fig. 4 includes the power supply 11 as the power supply unit for the water electrolysis apparatus 2, but the power supply unit can be modified. For example, as in the first embodiment (Fig. 1), the power supply 11 may exist as an external power source, and the electric wire through which the current flows may be regarded as the power supply unit.

[0052] 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.

[0053] The present invention can also be realized in the following forms. [Application example 1] A water electrolysis system, a water electrolysis unit that electrolyzes water; a tank for storing water to be supplied to the water electrolysis unit; a supply unit that supplies water to the tank; a water volume acquisition unit that acquires the amount of water stored in the tank; a temperature acquisition unit that acquires the temperature of the water stored in the tank; a control unit that controls the amount of water supplied from the supply unit to the tank in accordance with the amount of water stored in the tank and the temperature of the water; Equipped with The control unit When the amount of water in the tank is less than a first water amount, water is supplied from the supply unit until the amount of water in the tank reaches a second water amount that is greater than the first water amount; a water electrolysis system in which, when the amount of water in the tank is equal to or greater than the first water amount and the temperature of the water in the tank is higher than a reference temperature, water is supplied from the supply unit until the amount of water in the tank reaches a third water amount that is greater than the second water amount. [Application example 2] The water electrolysis system according to Application Example 1, further comprising: a flow path for supplying oxygen generated at an anode by water electrolysis in the water electrolysis unit and water used in the reaction to the tank; The water electrolysis system, wherein the tank has a gas-liquid separation function for separating oxygen from water and oxygen supplied via the flow path. [Application example 3] The water electrolysis system according to Application Example 1 or Application Example 2, further comprising: a power supply unit that supplies power to the water electrolysis unit; a detection unit that detects at least one of the current and the power supplied from the power supply unit to the water electrolysis unit; Equipped with The control unit reduces the reference temperature as the detected value of the detection unit increases. [Application example 4] The water electrolysis system according to any one of Application Examples 1 to 3, further comprising: a conductivity acquisition unit that acquires the electrical conductivity of the water in the tank; The tank is capable of draining the stored water, The control unit When the electrical conductivity is equal to or higher than a first conductivity, the water in the tank is drained until the amount of water in the tank reaches the first water amount, and then water is supplied from the supply unit until the amount of water in the tank reaches the third water amount; a water electrolysis system which, when the electrical conductivity is less than the first conductivity and equal to or greater than a second conductivity lower than the first conductivity, the amount of water in the tank is equal to or greater than the third water volume, and the temperature of the water in the tank is higher than the reference temperature, drains water from the tank until the amount of water in the tank reaches a fourth water volume that is greater than the first water volume and less than the third water volume, and then supplies water from the supply unit until the amount reaches the third water volume. [Application example 5] A water supply system for supplying water to a water electrolysis device, a tank for storing water to be supplied to the water electrolysis device; a supply unit that supplies water to the tank; a water volume acquisition unit that acquires the amount of water stored in the tank; a temperature acquisition unit that acquires the temperature of the water stored in the tank; a control unit that controls the amount of water supplied to the tank in accordance with the amount of water stored in the tank and the temperature of the water; Equipped with The control unit When the amount of water in the tank is less than a first amount of water, water is supplied until the amount of water in the tank reaches a second amount of water that is greater than the first amount of water; A water supply system that supplies water until the amount of water in the tank reaches a third amount that is greater than the second amount, when the amount of water in the tank is equal to or greater than the first amount and the temperature of the water in the tank is higher than a reference temperature. [Application Example 6] A water supply method for supplying water to a water electrolysis device, comprising: a water volume acquiring step of acquiring a water volume in a tank that stores water to be supplied to the water electrolysis device; a first water supply step of supplying water to the tank when the amount of water in the tank is less than a first water amount until the amount of water in the tank reaches a second water amount that is greater than the first water amount; a temperature acquisition step of acquiring the temperature of the water in the tank; a second water supply process of supplying water to the tank until the amount of water in the tank reaches a third water amount that is greater than the second water amount, when the amount of water in the tank is equal to or greater than the first water amount and the temperature of the water in the tank is higher than a reference temperature; Implementing a water supply method. [Explanation of symbols]

[0054] 1...Pure water production equipment (supply section) 2...Water electrolysis device (water electrolysis section) 3. Tank 4...Raw water pump 5...Temperature sensor (temperature acquisition part) 6...Water volume sensor (water volume acquisition unit) 7...Heat exchanger 8...Cooling water pump 9...Valve 10…Ammeter 11…Power supply (power supply section) 12...Drain valve 13...Electrical conductivity sensor (conductivity acquisition unit) 20, 20a, 20b...Control section 100, 100a, 100b...Water electrolysis system E n …electrical conductivity of water in the tank E H …1st conductivity E M …2nd conductivity FP1…Pure water flow path FP2…Raw water flow path FP3…reflux flow path (flow path) FP4…Drainage channel I: Detected current T n …Water temperature in the tank T s …Reference temperature W n …water volume in the tank W L …1st water volume W M …Second water volume W H …3rd water volume W HL …4th water volume

Claims

1. A water electrolysis system, a water electrolysis unit that performs electrolysis of water; a tank for storing water to be supplied to the water electrolysis unit; a supply unit that supplies water to the tank; a water volume acquisition unit that acquires the amount of water stored in the tank; a temperature acquisition unit that acquires the temperature of the water stored in the tank; a control unit that controls the amount of water supplied from the supply unit to the tank in accordance with the amount of water stored in the tank and the temperature of the water; Equipped with The control unit When the amount of water in the tank is less than a first water amount, water is supplied from the supply unit until the amount of water in the tank reaches a second water amount that is greater than the first water amount; and, when the amount of water in the tank is equal to or greater than the first water amount and the temperature of the water in the tank is higher than a reference temperature, supplying water from the supply unit until the amount of water in the tank reaches a third water amount that is greater than the second water amount.

2. The water electrolysis system according to claim 1, further comprising: a flow path for supplying oxygen generated at an anode by water electrolysis in the water electrolysis unit and water used in the reaction to the tank; The water electrolysis system, wherein the tank has a gas-liquid separation function for separating oxygen from water and oxygen supplied via the flow path.

3. The water electrolysis system according to claim 1, further comprising: a power supply unit that supplies power to the water electrolysis unit; a detection unit that detects at least one of the current and the power supplied from the power supply unit to the water electrolysis unit; Equipped with The control unit reduces the reference temperature as the detected value of the detection unit increases.

4. The water electrolysis system according to any one of claims 1 to 3, further comprising: a conductivity acquisition unit that acquires the electrical conductivity of the water in the tank; The tank is capable of draining the stored water, The control unit When the electrical conductivity is equal to or higher than a first conductivity, the water in the tank is drained until the amount of water in the tank reaches the first water amount, and then water is supplied from the supply unit until the amount of water in the tank reaches the third water amount; a water electrolysis system comprising: a water supply unit that supplies water from the tank until the amount of water in the tank reaches a fourth water volume that is greater than the first water volume and less than the third water volume, and a water conductivity that is less than the first conductivity and greater than a second water volume that is lower than the first conductivity; a water volume that is greater than the third water volume and a water temperature that is higher than the reference temperature;

5. A water supply system for supplying water to a water electrolysis device, a tank for storing water to be supplied to the water electrolysis device; a supply unit that supplies water to the tank; a water volume acquisition unit that acquires the amount of water stored in the tank; a temperature acquisition unit that acquires the temperature of the water stored in the tank; a control unit that controls the amount of water supplied to the tank in accordance with the amount of water stored in the tank and the temperature of the water; Equipped with The control unit When the amount of water in the tank is less than a first amount, water is supplied until the amount of water in the tank reaches a second amount that is greater than the first amount of water; A water supply system that supplies water until the amount of water in the tank reaches a third amount that is greater than the second amount when the amount of water in the tank is equal to or greater than the first amount and the temperature of the water in the tank is higher than a reference temperature.

6. A water supply method for supplying water to a water electrolysis device, comprising: a water volume acquiring step of acquiring a water volume in a tank that stores water to be supplied to the water electrolysis device; a first water supply step of supplying water to the tank when the amount of water in the tank is less than a first water amount until the amount of water in the tank reaches a second water amount that is greater than the first water amount; a temperature acquisition step of acquiring the temperature of the water in the tank; a second water supply step of supplying water to the tank until the amount of water in the tank reaches a third water amount that is greater than the second water amount, when the amount of water in the tank is equal to or greater than the first water amount and the temperature of the water in the tank is higher than a reference temperature; Implementing a water supply method.

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