Water electrolysis device

Abstract

To reduce the power consumption of a water electrolysis apparatus by adjusting a revolution speed of a circulation pump.SOLUTION: A water electrolysis apparatus (100) comprises an electrolyzer (20) that electrolyzes water, a circulation pump (27) installed in a water circulation line (23) that supplies water from an oxygen-gas-liquid separator (22) to the electrolyzer (20), an inverter (50) that supplies power to the circulation pump (27), and a controller (60) that controls the inverter (50) to change the circulating water flow rate in the water circulation line (23).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water electrolysis device that electrolyzes water to generate hydrogen and oxygen. [Background technology]

[0002] Water electrolysis devices that produce hydrogen using natural energy have been developed. As disclosed in Patent Document 1, this type of water electrolysis device is equipped with a circulation pump that circulates water by supplying it from an oxygen gas-liquid separator to an electrolytic cell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-173788 Summary of the Invention [Problem to be solved by the invention]

[0004] When using unstable natural energy with large power fluctuations, the electrolytic current in the electrolytic cell changes, so it is desirable to change the circulating water flow rate in accordance with the change in electrolytic current, etc. However, in the past, the rotation speed of the circulating pump was controlled to a constant value, which could cause the circulating water flow rate to become excessive during low-load operation, resulting in a decrease in overall energy efficiency.

[0005] One aspect of the present invention has been made in view of the above-described problems in the related art, and aims to reduce the power consumption of a water electrolysis device by adjusting the rotation speed of a circulation pump to change the flow rate of circulating water. [Means for solving the problem]

[0006] In order to solve the above problems, a water electrolysis device according to one aspect of the present invention includes an electrolytic cell that electrolyzes water, a gas-liquid separator that separates water from gas generated in the electrolytic cell, a circulation pump installed in a water circulation line that circulates water by supplying water from the gas-liquid separator to the electrolytic cell, an inverter connected to the circulation pump and supplying power to the circulation pump, and a controller that controls the inverter to change the flow rate of circulating water in the water circulation line. [Effects of the Invention]

[0007] According to one aspect of the present invention, the power consumption of the water electrolysis device can be reduced by adjusting the rotation speed of the circulation pump to change the flow rate of the circulating water. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of a water electrolysis device according to an embodiment of the present invention. [Figure 2] 4 is a flowchart illustrating an example of circulating water flow rate change control executed by the water electrolysis apparatus. [Figure 3] 3 is a graph showing an example of total power consumption calculated in step S5 shown in FIG. 2. [Figure 4] 3 is a graph showing an example of control in step S9 shown in FIG. 2. [Figure 5] 3 is a graph showing an example of control in step S10 shown in FIG. 2. [Figure 6] 3 is a graph showing an example of control in step S12 shown in FIG. 2. [Figure 7] 3 is a graph showing an example of control in step S13 shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Configuration of water electrolysis device 100] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the following description is an example of a water electrolysis device according to the present invention, and the technical scope of the present invention is not limited to the illustrated example.

[0010] (Configuration of water electrolysis device) First, a configuration example of a water electrolysis apparatus 100 according to one embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a configuration diagram showing a schematic configuration of the water electrolysis apparatus 100 according to this embodiment. The water electrolysis apparatus 100 according to this embodiment electrolyzes pure water in an electrolytic cell 20 to generate hydrogen (H2) and oxygen (O2).

[0011] 1 , the water electrolysis apparatus 100 includes an electrolytic cell 20, a hydrogen gas-liquid separator 21, an oxygen gas-liquid separator (gas-liquid separator) 22, a water circulation line 23, a first ion exchanger 24, a pure water tank 25, a branch line 41, and a second ion exchanger 43. The water electrolysis apparatus 100 also includes a circulation pump 27 installed in the water circulation line 23, an inverter 50 connected to the circulation pump 27, and a controller 60 that controls the operation of the entire water electrolysis apparatus 100, including the inverter 50. The controller 60 controls the inverter 50 to adjust the rotation speed of the circulation pump 27, thereby changing the flow rate of circulating water circulating through the water circulation line 23. In this way, the controller 60 optimizes the flow rate of circulating water, thereby reducing the power consumption of the water electrolysis apparatus 100.

[0012] The water circulation line 23 circulates water from the hydrogen gas-liquid separator 21 and the oxygen gas-liquid separator 22 to the electrolytic bath 20. The water circulation line 23 is equipped with a circulation pump 27 for circulating the water and a circulation water cooler (heat exchanger) 28 for cooling the circulation water before supplying it to the electrolytic bath 20. The illustrated example shows a configuration in which the circulation water cooler 28 is installed downstream of the circulation pump 27, i.e., a configuration in which the circulation water cooler 28 is installed between the electrolytic bath 20 and the circulation pump 27. Installing the circulation water cooler 28 downstream of the circulation pump 27 makes it easier for the circulation water to pass through the circulation water cooler 28 by utilizing the discharge pressure of the circulation pump 27. Furthermore, if the circulation water cooler 28 were installed upstream of the circulation pump 27, the pressure upstream of the circulation pump 27 would be low, potentially causing cavitation. To prevent this cavitation, it is preferable to install the circulation water cooler 28 downstream of the circulation pump 27. However, it is also possible to install the circulation water cooler 28 upstream of the circulation pump 27.

[0013] The branch line 41 is a line that extracts and treats a portion of the circulating water from the water circulation line 23 and sends the treated water to the pure water tank 25. The branch line 41 is provided with a blow water cooler 42 that cools the circulating water extracted from the water circulation line 23 and a second ion exchanger 43 that performs ion exchange on the cooled water. A blow water thermometer TT3 that detects the temperature of the blow water flowing through the branch line 41 is also provided between the blow water cooler 42 and the second ion exchanger 43. The downstream end of the branch line 41 is connected to the pure water tank 25. The upstream end of the branch line 41 is connected to the water circulation line 23 between the electrolytic cell 20 and the circulating water cooler 28. A blow valve 29 is provided upstream of the branch line 41. The opening and closing of the blow valve 29 is automatically controlled by the electrical conductivity of the circulating water obtained from an electrical conductivity controller 30 that is provided between the electrolytic cell 20 and the circulating water cooler 28 on the water circulation line 23.

[0014] The electrolytic cell 20 electrolyzes water, generating oxygen (O2) at the anode and hydrogen (H2) at the cathode. The electrolytic cell 20 is supplied with the power necessary for water electrolysis. The power supplied to the electrolytic cell 20 can be power from a commercial power source, or renewable energy such as solar power or wind power, or surplus power from such sources. The oxygen generated at the anode of the electrolytic cell 20 is sent to an oxygen gas-liquid separator 22. The hydrogen generated at the cathode of the electrolytic cell 20 is sent to a hydrogen gas-liquid separator 21.

[0015] An inlet thermometer TT1 is installed at the inlet side of the circulating water in the electrolytic cell 20 to detect the temperature of the circulating water supplied to the electrolytic cell 20. Furthermore, an outlet thermometer TT2 is installed at the outlet side of the circulating water in the electrolytic cell 20 to detect the temperature of the circulating water discharged from the electrolytic cell 20. Furthermore, a circulating water flow meter FT is installed upstream of the inlet thermometer TT1 to detect the flow rate of the circulating water circulating through the water circulation line 23.

[0016] The water electrolysis device 100 may be, for example, a solid polymer water electrolysis device that electrolyzes pure water to generate hydrogen and oxygen by applying a voltage to a solid polymer electrolyte membrane to pass a current through it. However, the water electrolysis device 100 is not limited to a solid polymer water electrolysis device, and may be, for example, an alkaline water electrolysis device, an anion exchange membrane water electrolysis device, or the like.

[0017] Oxygen generated at the anode of the electrolytic cell 20 is sent to an oxygen-gas-liquid separator 22. Hydrogen generated at the cathode of the electrolytic cell 20 is sent to a hydrogen-gas-liquid separator 21. The hydrogen-gas-liquid separator 21 separates the hydrogen generated at the cathode of the electrolytic cell 20 from water. The oxygen-gas-liquid separator 22 separates the oxygen generated at the anode of the electrolytic cell 20 from water. Most of the water discharged from the electrolytic cell 20 is sent to the oxygen-gas-liquid separator 22.

[0018] The liquid levels of the hydrogen gas-liquid separator 21 and the oxygen gas-liquid separator 22 are controlled independently. A hydrogen cooler 31 is installed in the hydrogen outlet path of the hydrogen gas-liquid separator 21, and an oxygen cooler 32 is installed in the oxygen outlet path of the oxygen gas-liquid separator 22. The water discharged from the oxygen gas-liquid separator 22 is resupplied to the electrolytic cell 20 via a water circulation line 23, and a portion of the water is sent to the pure water tank 25 via a branch line 41. The hydrogen gas-liquid separator 21 and the pure water tank 25 may be connected by a pipe, and the water discharged from the hydrogen gas-liquid separator 21 may be sent to the pure water tank 25 via this pipe.

[0019] The pure water tank 25 stores water to be electrolyzed in the electrolytic cell 20. The pure water tank 25 stores water obtained by treating supply water (city water, etc.) newly supplied to the electrolytic cell 20 using a first ion exchanger 24. The pure water tank 25 also stores water obtained by treating circulating water extracted from the water circulation line 23 via a branch line 41 using a second ion exchanger 43. A supply pump 26 is installed in the piping connecting the pure water tank 25 and the oxygen-gas-liquid separator 22 to send water from the pure water tank 25 to the oxygen-gas-liquid separator 22. The water temporarily stored in the pure water tank 25 is sent to the oxygen-gas-liquid separator 22 by the supply pump 26 in accordance with a preset level setting for the oxygen-gas-liquid separator 22.

[0020] The circulating water flowing through the water circulation line 23 is adjusted to a predetermined temperature (e.g., 65 to 70°C) by the circulating water cooler 28 and sent to the electrolytic cell 20 by the circulation pump 27. The set temperature of the circulating water for flowing through the branch line 41 is, for example, 1 μS / cm or less; if the temperature is higher than that, the blow valve 29 opens, and if the temperature is lower than that, the blow valve 29 closes. The circulating water taken out to the branch line 41 is cooled to room temperature by the blow water cooler 42 and supplied to the second ion exchanger 43, where it is treated to have an electrical conductivity of, for example, 0.5 μS / cm or less, and then supplied to the pure water tank 25. In this way, by taking a portion of the circulating water from the water circulation line 23 and treating it in the branch line 41, the impurity content in the circulating water can be reduced.

[0021] Circulation pump 27 circulates water by supplying circulating water in water circulation line 23 to electrolytic cell 20, and cools electrolytic cell 20 by supplying circulating water cooled in circulating water cooler 28 to electrolytic cell 20. In water electrolysis apparatus 100, an inverter 50 is connected to circulation pump 27. Electric power having a converted frequency is supplied from inverter 50 to circulation pump 27, thereby making it possible to adjust the rotation speed of circulation pump 27. Circulation pump 27 is driven at a rotation speed that corresponds to the frequency of the electric power supplied from inverter 50, and the flow rate of circulating water in water circulation line 23 increases or decreases depending on this rotation speed.

[0022] The inverter 50 is an electric circuit that supplies power with a converted frequency to the circulation pump 27. A control signal is input to the inverter 50 from the control unit 60. The inverter 50 outputs power of a frequency corresponding to the frequency designation signal (current value signal or voltage value signal) input by the control unit 60 to the circulation pump 27, and adjusts the rotation speed of the circulation pump 27.

[0023] The control unit 60 comprehensively controls the operation of the water electrolysis apparatus 100. The control unit 60 is configured by, for example, a processor such as a CPU (Central Processing Unit), a logic circuit formed in an integrated circuit (IC chip), or the like.

[0024] The control unit 60 controls the operation of the electrolytic cell 20, for example, by controlling the power supply to the electrolytic cell 20. The control unit 60 also changes the flow rate of circulating water in the water circulation line 23, for example, by controlling the inverter 50 to adjust the rotation speed of the circulation pump 27. During the electrolytic operation of the electrolytic cell 20, the control unit 60 also stores various values ​​such as the flow rate of circulating water, the temperature of the electrolytic cell 20, and the power consumption of the circulation pump 27 in a memory (not shown) as past history information.

[0025] 1 shows a configuration example in which the oxygen gas-liquid separator 22 is installed as the gas-liquid separator in the water circulation line 23. However, instead of the oxygen gas-liquid separator 22, the hydrogen gas-liquid separator 21 may be installed in the water circulation line 23, or both the hydrogen gas-liquid separator 21 and the oxygen gas-liquid separator 22 may be installed in the water circulation line 23.

[0026] (Control of water electrolysis device 100) Next, control of the water electrolysis apparatus 100 will be described with reference to Figures 2 to 7. As an example of a method for controlling the water electrolysis apparatus 100, circulating water flow rate change control for changing the circulating water flow rate in the water circulation line 23 will be described below.

[0027] Figure 2 is a flowchart showing an example of circulating water flow rate change control executed by the water electrolysis apparatus 100. After the electrolysis operation of the electrolytic bath 20 starts, the control unit 60 repeatedly executes the control flow shown in Figure 2 at intervals of, for example, a few tenths of a second to a few seconds. The following description will be given taking as an example the circulating water flow rate change control executed the kth time (k is a natural number equal to or greater than 2) since the electrolysis operation of the electrolytic bath 20 starts.

[0028] In the circulating water flow rate change control, the control unit 60 controls the heat generation amount P E For example, the control unit 60 calculates the heat generation amount P (k) of the electrolytic cell 20 based on the values ​​of the current and voltage of the electrolytic cell 20 (power consumption of the electrolytic cell 20) and the amount of hydrogen generated at the cathode of the electrolytic cell 20 (energy generated). E (k) may be calculated.

[0029] Next, the control unit 60 detects whether the outlet temperature of the circulating water of the electrolytic bath 20 is a threshold temperature T m (for example, 80°C) (step S2). Generally, an upper limit is set for the temperature of the electrolytic bath 20, and if the outlet temperature of the circulating water in the electrolytic bath 20 is higher than the threshold temperature T m The control unit 60 adjusts the outlet temperature of the electrolytic bath 20 to be less than the threshold temperature T mThe flow rate of the circulating water is adjusted based on the result of the determination, thereby enabling optimal control of the flow rate of the circulating water according to the outlet temperature.

[0030] The outlet temperature of the electrolytic cell 20 is the threshold temperature T m If it is equal to or less than the specific heat of water (No in step S2), the control unit 60 calculates the circulating water flow rate based on the specific heat of water and the heat generation amount of the electrolytic cell 20 (step S3). H2O , the heat generation amount P of the electrolytic cell 20 E , the upper limit of the temperature difference between the inlet temperature and the outlet temperature of the circulating water in the electrolytic cell 20 (the set value of the inlet / outlet temperature difference) ΔT m , the set value of the circulating water flow rate N S If 、 The control unit 60 calculates the set value N of the circulating water flow rate using the following formula: S may be calculated.

number

[0031] On the other hand, the outlet temperature of the electrolytic cell 20 is the threshold temperature T m If it is higher (Yes in step S2), the control unit 60 determines whether the power consumption P PThe control unit 60 measures the power consumption P of the circulation pump 27 using, for example, a power meter (not shown) connected to the circulation pump 27. P The control unit 60 may also calculate the power consumption of the circulation pump 27 based on the output current and output voltage of the inverter 50 connected to the circulation pump 27, for example.

[0032] Next, the control unit 60 calculates the power consumption P of the circulation pump 27 calculated in step S4. P (k) and the heat generation amount P of the electrolytic cell 20 obtained in step S1 E (k) and the total power consumption P SUM (k) is calculated (step S5).

[0033] FIG. 3 shows the total power consumption P SUM 3 is a graph showing an example of the power consumption P P As (k) increases, the rotation speed increases, and the circulating water flow rate increases accordingly. Normally, the power consumption of the circulating pump 27 is proportional to the cube of the circulating water flow rate (rotation speed). Furthermore, as the circulating water flow rate increases, the increase in the outlet temperature of the electrolytic cell 20 is suppressed, and the temperature difference between the inlet and outlet of the electrolytic cell 20 decreases. There is an upper limit to the temperature of the electrolytic cell 20 during electrolysis operation (upper limit of the electrolytic cell temperature). Taking this upper limit of the electrolytic cell temperature into consideration, the smaller the temperature difference between the inlet and outlet, the higher the inlet temperature can be, so the power consumption of the electrolytic cell 20 decreases (i.e., the conversion efficiency increases). Therefore, as the circulating water flow rate increases, the heat generation amount P E (k) decreases.

[0034] The control unit 60 calculates the power consumption P P (k) and the heat generation amount P of the electrolytic cell 20 E (k) and (k) to obtain the total power consumption P SUM Calculate (k). Total power consumption P SUM (k) is a curve that is convex downward, and its vertex is the total power consumption P SUM The control unit 60 calculates the total power consumption P SUM(k) is recorded in memory.

[0035] Next, the control unit 60 calculates the total power consumption P SUM (k-1) is read from the memory, and the total power consumption P calculated in step S5 is calculated. SUM (k) and the previous total power consumption P SUM (k-1) is the same value (step S6). When the operation cycle of the circulating water flow rate change control is relatively short (for example, when the operation cycle is 0.5 seconds), the past total power consumption P SUM The value of the previous total power consumption P SUM Instead of (k-1), the total power consumption of the previous time P SUM It is also possible to use (k-2) etc.

[0036] There may be a slight time lag between when the control unit 60 controls the inverter 50 to adjust the rotation speed of the circulation pump 27 and when a change in the circulating water flow rate is actually confirmed. SUM (k) and the previous total power consumption P SUM (k-1) is the same value (Yes in step S6), that is, the total power consumption P SUM If the value has not yet changed, the control unit 60 may take into account the time lag, etc., terminate the circulating water flow rate change control without changing the circulating water flow rate, and control the circulating water flow rate change control to change the circulating water flow rate from the next time onwards.

[0037] On the other hand, the total power consumption P SUM (k) and the previous (past) total power consumption P SUM If (k-1) is not the same value (No in step S6), the control unit 60 calculates the total power consumption P SUM (k) is the total power consumption of the previous SUM It is determined whether the number has increased from (k-1) (step S7).

[0038] In step S7, the total power consumption P SUM (k) is the total power consumption of the previous SUMIf it is less than (k-1) (No in step S7), the control unit 60 reads from memory the circulating water flow rate N(k-1) at the time of the previous (k-1) circulating water flow rate change control, and determines whether the circulating water flow rate N(k) has increased from the previous circulating water flow rate N(k-1) (step S8).

[0039] If the circulating water flow rate N(k) is higher than the previous circulating water flow rate N(k-1) (Yes in step S8), the control unit 60 controls the inverter 50 so that the circulating water flow rate N(k) increases (step S9).

[0040] 4 is a graph showing an example of the control in step S9. As shown in FIG. SUM (k) is the total power consumption of the previous SUM If the circulating water flow rate N(k) is decreased from (k-1) (arrow A in the figure) and is increasing (arrow B in the figure), by further increasing the circulating water flow rate N(k) (arrow C in the figure), the total power consumption P SUM It is estimated that (k) will decrease further (arrow D in the figure). Therefore, in step S9, the control unit 60 controls the inverter 50 to increase the circulating water flow rate N(k). In the illustrated example, the control unit 60 controls the inverter 50 to increase the circulating water flow rate N(k) so that it approaches 380 [L / min], which is the circulating water flow rate for the minimum power consumption P. As a result, the total power consumption P SUM Since (k) can be made to approach the minimum power consumption P, the power consumption of the water electrolysis apparatus 100 can be reduced.

[0041] On the other hand, if the circulating water flow rate N(k) is less than or equal to the previous circulating water flow rate N(k-1) (No in step S8), the control unit 60 controls the inverter 50 to reduce the circulating water flow rate N(k) (step S10).

[0042] 5 is a graph showing an example of the control in step S10. As shown in FIG. 5, the total power consumption P SUM (k) is the total power consumption of the previous SUMIf the circulating water flow rate is reduced from (k-1) (arrow A in the figure) and is also reduced (arrow B in the figure), the total power consumption P SUM Therefore, in step S10, the control unit 60 controls the inverter 50 to reduce the circulating water flow rate N(k). As a result, the total power consumption P SUM Since (k) can be made to approach the minimum power consumption P, the power consumption of the water electrolysis apparatus 100 can be reduced.

[0043] In step S7, the total power consumption P SUM (k) is the total power consumption of the previous SUM If the circulating water flow rate N(k-1) has increased compared to the previous (k-1) circulating water flow rate change control (Yes in step S7), the control unit 60 reads from memory the circulating water flow rate N(k-1) at the time of the previous (k-1) circulating water flow rate change control, and determines whether the circulating water flow rate N(k) has increased compared to the previous circulating water flow rate N(k-1) (step S11).

[0044] If the circulating water flow rate N(k) is higher than the previous circulating water flow rate N(k-1) (Yes in step S11), the control unit 60 controls the inverter 50 to decrease the circulating water flow rate N(k) (step S12).

[0045] 6 is a graph showing an example of the control in step S12. As shown in FIG. SUM (k) is the total power consumption of the previous SUM If the power consumption is higher than (k-1) (arrow A in the figure) and the circulating water flow rate is increasing (arrow B in the figure), the total power consumption P SUM Therefore, in step S12, the control unit 60 controls the inverter 50 to reduce the circulating water flow rate N(k). As a result, the total power consumption P SUM Since (k) can be made to approach the minimum power consumption P, the power consumption of the water electrolysis apparatus 100 can be reduced.

[0046] On the other hand, if the circulating water flow rate N(k) is less than or equal to the previous circulating water flow rate N(k-1) (No in step S11), the control unit 60 controls the inverter 50 to increase the circulating water flow rate N(k) (step S13).

[0047] 7 is a graph showing an example of the control in step S13. As shown in FIG. 7, the total power consumption P SUM (k) is the total power consumption of the previous SUM If the total power consumption P SUM Therefore, in step S13, the control unit 60 controls the inverter 50 to increase the circulating water flow rate N(k). As a result, the total power consumption P SUM Since (k) can be made to approach the minimum power consumption P, the power consumption of the water electrolysis apparatus 100 can be reduced.

[0048] [Effects of the water electrolysis device 100] As described above, the water electrolysis apparatus 100 according to the present embodiment comprises the electrolytic cell 20 that electrolyzes water, the oxygen-gas-liquid separator 22 that separates water from oxygen generated in the electrolytic cell 20, the circulation pump 27 installed in the water circulation line 23 that circulates water by supplying water from the oxygen-gas-liquid separator 22 to the electrolytic cell 20, the inverter 50 connected to the circulation pump 27 and supplying power to the circulation pump 27, and the control unit 60 that controls the inverter 50 to change the flow rate of circulating water in the water circulation line 23.

[0049] According to this embodiment, the rotation speed of the circulation pump 27 is adjusted to optimize the flow rate of circulating water, thereby reducing the power consumption of the water electrolysis apparatus 100. Furthermore, according to this embodiment, the power consumption of the water electrolysis apparatus 100 can be reduced, which contributes to achieving, for example, Goal 7 of the Sustainable Development Goals (SDGs) advocated by the United Nations, "Ensure access to affordable, reliable, sustainable and modern energy for all (renewable energy, etc.)."

[0050] [Modification] In the above description, the control unit 60 calculates the total power consumption P SUM The above description concerns a control example in which the circulating water flow rate is changed so that (k) approaches the minimum power consumption P. Instead of this control, the control unit 60 can also change the circulating water flow rate by the following control.

[0051] (Variation 1) The control unit 60 may change the circulating water flow rate based on past history information. For example, the control unit 60 may change the circulating water flow rate based on history information such as the past circulating water flow rate, the past heat generation amount of the electrolytic bath 20, and the past power consumption of the circulating pump 27. Table 1 shows an example of history information stored in the memory. [Table 1] As shown in Table 1, the historical information includes the past power consumption of circulating pump 27, the past heat generation amount of electrolytic bath 20, the past total power consumption, and the past circulating water flow rate. When changing the circulating water flow rate, control unit 60 may extract from the historical information the combination of the power consumption of circulating pump 27 and the heat generation amount of electrolytic bath 20 that minimizes the total power consumption (No. 1 in the table), and change the circulating water flow rate to approach the circulating water flow rate for the extracted combination. In this way, by optimizing the circulating water flow rate based on the past historical information, the processing load of control unit 60 in circulating water flow rate change control can be reduced.

[0052] (Variation 2) Furthermore, the control unit 60 may change the circulating water flow rate based on the differential value of a function that expresses the calculated total power consumption in terms of the circulating water flow rate. When the total power consumption is expressed as a function P=F(N) of the circulating water flow rate, the differential value P'=f'(N) at N is the total power consumption P shown in FIG. SUMThis represents the slope of the curve (k). Therefore, when the differential value P' is positive (+), increasing the circulating water flow rate increases the total power consumption. Therefore, when the differential value P' is positive, the control unit 60 controls the inverter 50 to decrease the circulating water flow rate. On the other hand, when the differential value P' is negative (-), increasing the circulating water flow rate decreases the total power consumption. Therefore, when the differential value P' is negative, the control unit 60 controls the inverter 50 to increase the circulating water flow rate. When the absolute value of this differential value P' is large, the slope of the curve becomes steeper. Therefore, the amount of change in the circulating water flow rate increases, and the total power consumption can quickly approach the minimum power consumption P.

[0053] For example, if C is a negative constant and N(k) is the current circulating water flow rate, the circulating water flow rate N(k+1) that minimizes the total power consumption can be determined using the following equation.

number

[0054] 〔summary〕 A water electrolysis device according to a first aspect of the present invention includes an electrolytic cell that electrolyzes water, a gas-liquid separator that separates water from gas generated in the electrolytic cell, a circulation pump installed in a water circulation line that circulates water by supplying water from the gas-liquid separator to the electrolytic cell, an inverter connected to the circulation pump and supplying power to the circulation pump, and a controller that controls the inverter to change the flow rate of circulating water in the water circulation line.

[0055] In addition, in the water electrolysis apparatus according to a second aspect of the present invention, in the first aspect, the control unit may change the circulating water flow rate based on the power consumption of the circulating pump and the heat generation amount of the electrolytic cell.

[0056] In addition, in a water electrolysis apparatus according to a third aspect of the present invention, in accordance with the first aspect, the control unit may change the flow rate of the circulating water based on a heat generation amount of the electrolytic cell and a set value of a temperature difference between an inlet and an outlet of the circulating water in the electrolytic cell.

[0057] In addition, in a water electrolysis apparatus according to a fourth aspect of the present invention, in the second aspect, the control unit may calculate a total power consumption of the circulation pump and the electrolytic cell, and change the flow rate of the circulating water so as to reduce the total power consumption.

[0058] In addition, in a water electrolysis apparatus according to a fifth aspect of the present invention, in the fourth aspect, the control unit may compare the calculated total power consumption with the past total power consumption, and change the circulating water flow rate when the calculated total power consumption differs from the past total power consumption.

[0059] In addition, in a water electrolysis apparatus according to a sixth aspect of the present invention, in any one of the first to fifth aspects, the controller may determine whether an outlet temperature of the circulating water in the electrolytic cell is higher than a threshold temperature, and change the flow rate of the circulating water based on the determination result.

[0060] In a water electrolysis apparatus according to a seventh aspect of the present invention, in accordance with the fourth aspect, the control unit may change the circulating water flow rate based on history information of the past circulating water flow rate, the past heat generation amount of the electrolytic cell, and the past power consumption of the circulating pump.

[0061] In addition, in a water electrolysis apparatus according to an eighth aspect of the present invention, in accordance with the fourth aspect, the control unit may change the circulating water flow rate based on a derivative of a function that expresses the calculated total power consumption in terms of the circulating water flow rate.

[0062] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0063] 20: Electrolytic cell 22: Oxygen gas-liquid separator (gas-liquid separator) 23: Water circulation line 27: Circulation pump 50: Inverter 60: Control unit 100: Water electrolysis device

Claims

1. An electrolytic cell for electrolyzing water; a gas-liquid separator that separates the gas and water generated in the electrolytic cell; a circulation pump installed in a water circulation line that circulates water by supplying water from the gas-liquid separator to the electrolytic cell; an inverter connected to the circulation pump and supplying power to the circulation pump; a control unit that controls the inverter to change the flow rate of circulating water in the water circulation line; Equipped with The control unit changes the flow rate of the circulating water based on the power consumption of the circulating pump and the heat generation amount of the electrolytic cell.

2. An electrolytic cell for electrolyzing water; a gas-liquid separator that separates the gas and water generated in the electrolytic cell; a circulation pump installed in a water circulation line that circulates water by supplying water from the gas-liquid separator to the electrolytic cell; an inverter connected to the circulation pump and supplying power to the circulation pump; a control unit that controls the inverter to change the flow rate of circulating water in the water circulation line; Equipped with The control unit changes the flow rate of the circulating water based on a heat generation amount of the electrolytic cell and a set value of a temperature difference between an inlet and an outlet of the circulating water in the electrolytic cell.

3. An electrolytic cell for electrolyzing water; a gas-liquid separator that separates the gas and water generated in the electrolytic cell; a circulation pump installed in a water circulation line that circulates water by supplying water from the gas-liquid separator to the electrolytic cell; an inverter connected to the circulation pump and supplying power to the circulation pump; a control unit that controls the inverter to change the flow rate of circulating water in the water circulation line; Equipped with The control unit determines whether an outlet temperature of the circulating water in the electrolytic cell is higher than a threshold temperature, and changes the flow rate of the circulating water based on a result of the determination.

4. The water electrolysis apparatus according to claim 1 , wherein the control unit calculates a total power consumption of the circulation pump and the electrolytic cell, and changes the flow rate of the circulating water so as to reduce the total power consumption.

5. 5. The water electrolysis apparatus according to claim 4, wherein the control unit compares the calculated total power consumption with the past total power consumption, and changes the flow rate of the circulating water when the calculated total power consumption differs from the past total power consumption.

6. 5. The water electrolysis apparatus according to claim 4, wherein the control unit changes the circulating water flow rate based on history information of the past circulating water flow rate, the past heat generation amount of the electrolytic cell, and the past power consumption of the circulating pump.

7. The water electrolysis apparatus according to claim 4 , wherein the control unit changes the circulating water flow rate based on a differential value of a function that expresses the calculated total power consumption in terms of the circulating water flow rate.

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