Control device, water electrolysis system, control method, and control program

Abstract

To appropriately cool circulating water in a water electrolysis system.SOLUTION: A control device (5) predicts a temperature change of circulating water that circulates between an electrolyzer (1), which electrolyzes water, and an oxygen gas-liquid separator (3), which separates oxygen and water generated in the electrolyzer (1), and controls a heat exchanger (82) that cools the circulating water based on the temperature prediction result.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to control of a water electrolysis system that electrolyzes water to generate oxygen and hydrogen. [Background technology]

[0002] In a conventional water electrolysis system that electrolyzes water to generate oxygen and hydrogen, the electrolytic cell is heated by heat generated during water electrolysis, so the electrolytic cell is cooled by cooling the circulating water that circulates between the electrolytic cell and an oxygen gas-liquid separator. Regarding this type of water electrolysis system, for example, Patent Document 1 discloses that a cooler that cools the circulating water is controlled based on the difference between a measured value (actual value) of the circulating water temperature and a specified value (threshold value). [Prior art documents] [Patent documents]

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

[0004] However, in a configuration in which the cooler is controlled based on the measured value of the circulating water temperature, if the temperature of the circulating water suddenly drops due to, for example, the supply (replenishment) of pure water or a decrease in the current of the electrolytic cell, the circulating water may be excessively cooled, resulting in a decrease in electrolysis efficiency. In particular, in large-scale water electrolysis systems, there has been a problem in that the responsiveness and tracking ability of the circulating water temperature control is poor, making it easy for the electrolysis efficiency to decrease.

[0005] An object of one aspect of the present disclosure is to appropriately cool circulating water in a water electrolysis system. [Means for solving the problem]

[0006] In order to solve the above problems, a control device according to one embodiment of the present disclosure is a control device for a water electrolysis system that electrolyzes water to generate oxygen and hydrogen, and includes: a temperature prediction unit that predicts a temperature change in circulating water circulating between an electrolytic cell that electrolyzes water and an oxygen-liquid separator that separates the oxygen generated in the electrolytic cell from the water; and an equipment control unit that controls a cooling device that cools the circulating water based on the temperature prediction result of the temperature prediction unit.

[0007] In order to solve the above problems, a control method according to one aspect of the present disclosure is a control method for a water electrolysis system that electrolyzes water to generate oxygen and hydrogen, and includes: a temperature prediction step of predicting a temperature change of circulating water circulating between an electrolytic cell that electrolyzes water and an oxygen-liquid separator that separates the oxygen generated in the electrolytic cell from the water; and an equipment control step of controlling a cooling device that cools the circulating water based on a temperature prediction result of the temperature prediction step. [Effects of the Invention]

[0008] According to one aspect of the present disclosure, it is possible to appropriately cool circulating water in a water electrolysis system. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating a schematic configuration of a water electrolysis system according to an embodiment of the present disclosure. FIG. [Figure 2] 2 is a functional block diagram showing an example of the configuration of a main part of the control device shown in FIG. 1. [Figure 3] 2 is a flowchart showing an example of control of the water electrolysis system shown in FIG. [Figure 4] 4 is a cross-sectional view of the oxygen gas-liquid separator shown in FIG. 1, illustrating an example of the water supply control shown in FIG. 3. [Figure 5] 10 is a graph showing an example of the transition of measured temperature values ​​when a heat exchanger is controlled based on the measured (actual) value of the circulating water temperature. [Figure 6] 10 is a graph showing an example of the transition of the measured temperature value of the circulating water when the heat exchanger is controlled based on the predicted temperature value of the circulating water temperature. [Figure 7] 2 is a graph showing the relationship between the voltage of the electrolytic cell shown in FIG. 1 and the temperature of the circulating water. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present disclosure will be described below with reference to Figures 1 to 7. However, the following description is an example of a control device according to the present disclosure, and the technical scope of the present disclosure is not limited to the illustrated example.

[0011] [Configuration of water electrolysis system 100] Fig. 1 is a schematic diagram showing the general configuration of a water electrolysis system 100 according to the present embodiment. As shown in Fig. 1, the water electrolysis system 100 includes an electrolytic cell 1, a hydrogen gas-liquid separator 2, an oxygen gas-liquid separator 3, a pure water tank 4, and a control device 5. The water electrolysis system 100 also includes a rectifier 6 that supplies power to the electrolytic cell 1, a pure water production device 7 that supplies feed water (pure water) to the pure water tank 4, and a water circulation line 8 that circulates circulating water between the electrolytic cell 1 and the oxygen gas-liquid separator 3. The water electrolysis system 100 generates oxygen and hydrogen by electrolyzing circulating water circulating through the water circulation line 8 in the electrolytic cell 1.

[0012] In this water electrolysis system 100, the control device 5 predicts future (for example, several seconds from now) temperature changes of the circulating water and controls the circulating water temperature based on the temperature prediction results. This enables the control of the circulating water temperature to take into account the influence of various factors that cause temperature changes in the circulating water, thereby maintaining the circulating water within an appropriate temperature range.

[0013] The electrolytic cell 1 is, for example, an electrolytic cell stack in which a plurality of electrolytic cells are connected in series. The electrolytic cell 1 is supplied with the power (direct current) required for the electrolysis of water from a rectifier 6. The power supplied to the electrolytic cell 1 can be power from a commercial power source, or it can be renewable energy such as solar power or wind power, or surplus power thereof.

[0014] Hydrogen generated at the cathode of electrolytic cell 1 is sent in the form of a gas-liquid mixed water to hydrogen gas-liquid separator 2. Oxygen generated at the anode of electrolytic cell 1 is sent in the form of a gas-liquid mixed water to oxygen gas-liquid separator 3.

[0015] Electrolysis of circulating water (pure water) in the electrolytic cell 1 is carried out by applying a voltage and passing a current. The electrolytic cell 1 may be, for example, a solid polymer water electrolysis device that electrolyzes circulating water by applying a voltage to a solid polymer electrolyte membrane and passing a current through it to generate hydrogen and oxygen. However, the electrolytic cell 1 is not limited to a solid polymer water electrolysis device and may be, for example, an alkaline water electrolysis device or an anion exchange membrane water electrolysis device. The electrolytic cell 1 is equipped with a voltmeter 11 and an ammeter 12. The voltmeter 11 is a sensor that detects the voltage of the electrolytic cell 1 (for example, the voltage on both sides in the stacking direction of the electrolytic cell stack) and outputs a detection signal to the control device 5. The ammeter 12 is a sensor that detects the current flowing through the electrolytic cell 1 and outputs a detection signal to the control device 5. The ammeter 12 is installed in series with the electrolytic cell 1 and the rectifier 6.

[0016] The hydrogen-gas-liquid separator 2 separates the hydrogen and water generated in the electrolytic cell 1. The hydrogen-gas-liquid separator 2 is provided with a hydrogen level sensor 21. The hydrogen level sensor 21 detects the liquid level in the hydrogen-gas-liquid separator 2 and outputs a detection signal to the control device 5. The hydrogen separated in the hydrogen-gas-liquid separator 2 is supplied to a cooler, catalyst tower, dryer (dehumidifier), etc. (not shown), where oxygen and moisture are removed to produce product gas. Meanwhile, the water separated in the hydrogen-gas-liquid separator 2 is supplied to, for example, a pure water tank 4. The water separated in the hydrogen-gas-liquid separator 2 may be discharged outside the system during performance recovery operation of the water electrolysis system 100.

[0017] The oxygen-gas-liquid separator 3 separates the oxygen and water generated in the electrolytic cell 1. An oxygen level sensor 31 is installed in the oxygen-gas-liquid separator 3. The oxygen level sensor 31 is a sensor that detects the liquid level in the oxygen-gas-liquid separator 3 and outputs a detection signal to the control device 5. The oxygen separated in the oxygen-gas-liquid separator 3 is cooled, for example, by a cooler (not shown), and then discharged into the atmosphere. Meanwhile, the water separated in the oxygen-gas-liquid separator 3 is supplied again to the electrolytic cell 1 through the water circulation line 8.

[0018] The water circulation line 8 is a pipe for circulating the circulating water. A circulation pump 81 for circulating the circulating water and a heat exchanger (cooling device) 82 for cooling the circulating water are installed in this water circulation line 8. The circulating water is heated by heat generated in the electrolytic cell 1 during electrolysis, so the circulating water is cooled to a specified temperature (e.g., 80°C) in the heat exchanger 82 and supplied to the electrolytic cell 1. The heat exchanger 82 may be configured to cool the circulating water using, for example, cooling water, and includes a cooling water valve (flow rate adjustment valve) for adjusting the flow rate of the cooling water.

[0019] In the illustrated example, the heat exchanger 82 is installed downstream of the circulation pump 81. In other words, the heat exchanger 82 is installed between the circulation pump 81 and the electrolytic cell 1. By installing the heat exchanger 82 downstream of the circulation pump 81 in this way, the discharge pressure of the circulation pump 81 can be used to make it easier for the circulating water to pass through the heat exchanger 82.

[0020] Furthermore, a circulating water thermometer 83 and a circulating water flow meter 84 are installed in the water circulation line 8. The circulating water thermometer 83 is a sensor that detects the temperature of the circulating water flowing through the water circulation line 8, and outputs a detection signal to the control device 5. The circulating water flow meter 84 is a sensor that detects the flow rate of the circulating water flowing through the water circulation line 8, and outputs a detection signal to the control device 5. In the illustrated example, the circulating water thermometer 83 and the circulating water flow meter 84 are arranged downstream of the heat exchanger 82. In other words, the circulating water thermometer 83 and the circulating water flow meter 84 are installed between the heat exchanger 82 and the electrolytic cell 1.

[0021] The pure water tank 4 is a water tank that stores feed water (pure water) to be supplied to the oxygen gas-liquid separator 3. The pure water tank 4 stores pure water obtained by treating tap water such as city water with a pure water production system 7. The pure water production system 7 may include, for example, an ion exchanger, and may produce pure water by treating tap water with the ion exchanger. The pure water tank 4 may also store water separated in the hydrogen gas-liquid separator 2.

[0022] A supply pump (supply device) 91 is installed in a water supply line 9 connecting the oxygen-gas-liquid separator 3 and the pure water tank 4 to send pure water from the pure water tank 4 to the oxygen-gas-liquid separator 3. In the water electrolysis system 100, circulating water is consumed by the electrolysis of water. Therefore, when the water level in the oxygen-gas-liquid separator 3 drops, the pure water stored in the pure water tank 4 is supplied to the oxygen-gas-liquid separator 3 by the supply pump 91.

[0023] The water electrolysis system 100 is also provided with an environmental thermometer 10. The environmental thermometer 10 is a sensor that detects, for example, the room temperature or the outside air temperature at the location where the water electrolysis system 100 is installed, and outputs a detection signal to the control device 5.

[0024] Note that the temperature of the tap water supplied to the pure water production apparatus 7 is approximately equal to the ambient temperature of the location where the water electrolysis system 100 is installed, and therefore the temperature of the pure water supplied from the pure water production apparatus 7 to the pure water tank 4 is also approximately equal to the ambient temperature. Therefore, the temperature of the pure water stored in the pure water tank 4 is approximately equal to the ambient temperature. Therefore, in the present disclosure, the ambient temperature detected by the environmental thermometer 10 is approximately synonymous with the temperature of the supply water supplied from the pure water tank 4 to the oxygen gas-liquid separator 3.

[0025] The control device 5 comprehensively controls the operation of the water electrolysis system 100. Fig. 2 is a functional block diagram showing an example of the configuration of the main parts of the control device 5 shown in Fig. 1. As shown in Fig. 2, the control device 5 includes a communication unit 51, a control unit 52, and a storage unit 53.

[0026] The communication unit 51 transmits and receives various signals via wired or wireless communication. For example, the communication unit 51 receives detection signals from various sensors in the water electrolysis system 100. The communication unit 51 also transmits control signals output from the control unit 52 to each component of the water electrolysis system 100.

[0027] The control unit 52 includes a temperature prediction unit 521 and an equipment control unit 522. The temperature prediction unit 521 predicts future temperature changes of the circulating water circulating between the electrolytic bath 1 and the oxygen gas-liquid separator 3. In this embodiment, the temperature prediction unit 521 predicts temperature changes of the circulating water at the inlet side of the electrolytic bath 1. The temperature prediction unit 521 may predict, for example, the amount of change in the circulating water temperature that will occur between the prediction execution time (present time) and a target prediction time (future time) after a certain time has elapsed (e.g., several seconds), i.e., the difference between the circulating water temperature at the prediction execution time and the circulating water temperature at the target prediction time. Alternatively, the temperature prediction unit 521 may predict the circulating water temperature at the target prediction time (predicted temperature value). The temperature prediction unit 521 outputs the circulating water temperature prediction result to the equipment control unit 522. A method for predicting temperature changes of the circulating water will be described later.

[0028] The equipment control unit 522 controls each unit of the water electrolysis system 100. For example, the equipment control unit 522 controls the rectifier 6 to perform power supply control, which controls the power supply to the electrolytic cell 1. Furthermore, the control device 5 controls the supply pump 91 based on the temperature prediction result obtained from the temperature prediction unit 521 to perform water supply control, which controls the amount of water supplied from the pure water tank 4 to the oxygen-gas-liquid separator 3. Furthermore, the equipment control unit 522 adjusts the aperture of the cooling water valve of the heat exchanger 82 based on the temperature prediction result obtained from the temperature prediction unit 521 to perform temperature control, which adjusts (cools) the temperature of the circulating water.

[0029] The storage unit 53 stores various data used by the control device 5. For example, the storage unit 53 stores operating data used to control each part of the water electrolysis system 100, model data used to predict the temperature of the circulating water, etc.

[0030] [Method for predicting temperature changes] Next, a prediction method for predicting a change in the temperature of the circulating water will be described. However, the following description is an example of a prediction method, and the prediction method of the present disclosure is not limited to the following method.

[0031] (Prediction model) The temperature prediction unit 521 may predict the circulating water temperature change amount ΔTw, which is the amount of temperature change of the circulating water per unit time, using, for example, the following prediction model. This prediction model is stored in, for example, the storage unit 53.

number

[0032] The electrolytic cell heat generation amount ΔPe is the amount of heat generated per unit time by the electrolytic cell 1. This electrolytic cell heat generation amount ΔPe can be calculated, for example, based on the voltage value detected by the voltmeter 11 and the current value detected by the ammeter 12. The electrolytic cell heat generation amount ΔPe may also be calculated using the voltage value obtained by subtracting the thermal neutral voltage value (e.g., 1.48 V) from the voltage value detected by the voltmeter 11. This allows the electrolytic cell heat generation amount ΔPe to be calculated excluding the heat consumed in the electrolysis of water, thereby improving the accuracy of predicting the circulating water temperature change amount ΔTw.

[0033] The circulating water volume Qw ​​is the total volume of circulating water circulating through the water circulation line 8. The circulating water volume Qw ​​is the total volume of circulating water circulating between the electrolytic cell 1 and the oxygen-gas-liquid separator 3, and is, for example, the sum of the volume of circulating water in the oxygen-gas-liquid separator 3, the volume of circulating water on the oxygen side in the electrolytic cell 1, and the volume of circulating water flowing through the water circulation line 8. This circulating water volume Qw ​​can be calculated based on the flow rate detected by a circulating water flow meter 84 installed in the water circulation line 8, for example.

[0034] The circulating water temperature Tw is the temperature of the circulating water circulating through the water circulation line 8. This circulating water temperature Tw can be determined based on the temperature value detected by a circulating water thermometer 83 installed in the water circulation line 8, for example.

[0035] The circulating water specific heat Cw is the amount of heat required to raise the temperature of the circulating water by 1 degree per unit, and is essentially synonymous with the specific heat of pure water in this disclosure. Therefore, the specific heat of pure water (water) may be used as the circulating water specific heat Cw.

[0036] The ambient temperature Te is, for example, the ambient temperature of the location where the water electrolysis system 100 is installed, and in the present disclosure is substantially synonymous with the temperature of tap water supplied to the pure water production system 7, i.e., the temperature of water supplied to the oxygen gas-liquid separator 3. The ambient temperature Te can be determined based on the temperature value detected by, for example, the ambient thermometer 10.

[0037] The water supply amount ΔQs is the amount of water supplied per unit time from the pure water tank 4 to the oxygen-gas-liquid separator 3. This water supply amount ΔQs can be determined based on the liquid level detected by the oxygen water level sensor 31 installed in the oxygen-gas-liquid separator 3, for example.

[0038] The coefficients α and β are constants determined depending on the configuration, performance, scale, etc. of the water electrolysis system 100. For example, the coefficients α and β may be determined so as to minimize the sum of squares of the prediction errors as an objective function.

[0039] In this manner, the temperature prediction unit 521 may predict the amount of change in circulating water temperature ΔTw based on input values ​​based on detection signals from various sensors in the water electrolysis system 100 and a prediction model.

[0040] As shown in the prediction model, the temperature prediction unit 521 may predict the temperature change of the circulating water (the amount of circulating water temperature change ΔTw) based on the amount of temperature increase of the circulating water due to self-heating of the electrolytic cell 1 and the amount of temperature decrease of the circulating water due to heat radiation from the water circulation line (circulating water piping) 8 through which the circulating water flows. For example, the temperature prediction unit 521 can predict the temperature change of the circulating water based on the difference between the amount of temperature increase of the circulating water due to self-heating of the electrolytic cell 1 and the amount of temperature decrease of the circulating water due to heat radiation from the circulating water piping.

[0041] Furthermore, as shown in the prediction model, the temperature prediction unit 521 may predict the temperature change of the circulating water based on the amount of temperature decrease of the circulating water due to the supply water supplied to the oxygen-gas-liquid separator 3. This makes it possible to predict the temperature change of the circulating water taking into account the temperature decrease of the circulating water due to the supply water, thereby improving the accuracy of the temperature change prediction.

[0042] In this way, the temperature prediction unit 521 acquires detection signals from various sensors in the water electrolysis system 100, and can predict the circulating water temperature change ΔPe based on input values ​​including, for example, the electrolytic cell heat generation amount ΔPe, the circulating water temperature Tw, and the ambient temperature Te.

[0043] (Pre-trained model) The temperature prediction unit 521 may predict the temperature change of the circulating water using a trained model (learning model) that has been machine-learned using training data that associates various input values ​​from various sensors with the temperature change of the circulating water.

[0044] In this case, the trained model may be constructed by machine learning using training data indicating the relationship between the explanatory variables and the target variable. The training data may be a set of input values ​​including at least one of the electrolytic cell heat generation amount ΔPe, the circulating water volume Qw, the circulating water specific heat Cw, the circulating water temperature Tw, the ambient temperature (outside air temperature) Te, and the feedwater volume ΔQs, all of which are acquired in the water electrolysis system 100 (the target facility), associated with the circulating water temperature change ΔTw. In this manner, the data collected in the water electrolysis system 100 can be used as training data to predict the temperature change of the circulating water in the water electrolysis system 100. By using the trained model, the temperature prediction unit 521 can predict the circulating water temperature change ΔTw without performing the calculation described above. This trained model is stored, for example, in the storage unit 53.

[0045] The learning algorithm of the trained model is not particularly limited as long as it can derive a target variable from the explanatory variables described above. For example, a learning algorithm such as a neural network or a support vector machine may be applied. Also, for example, a forward propagation neural network such as an extreme learning machine (ELM) may be applied. By applying ELM as the trained model, the circulating water temperature change amount ΔTw can be predicted with sufficient accuracy for practical use using a relatively small amount of training data.

[0046] The control device 5 may generate a trained model or generate the above-mentioned teacher data used in the machine learning. In this case, a teacher data acquisition unit that generates or acquires teacher data and a learning unit that generates a trained model using the teacher data may be added to the control device 5.

[0047] Furthermore, the control device 5 may predict the amount of change in circulating water temperature ΔTw using an initial trained model during operation of the water electrolysis system 100, and then perform relearning based on the prediction results to repeatedly update the trained model.

[0048] [Control of water electrolysis system 100] Next, a description will be given of an example of control (control method) of the water electrolysis system 100 by the control device 5. Fig. 3 is a flowchart showing an example of control of the water electrolysis system 100. After the water electrolysis system 100 starts operating, the control device 5 repeatedly executes the control flow shown in Fig. 3.

[0049] After the water electrolysis system 100 starts operating, as shown in FIG. 3, the temperature prediction unit 521 acquires detection signals from various sensors in the water electrolysis system 100 (step S1).

[0050] Next, the temperature prediction unit 521 predicts the circulating water temperature (step S2: temperature prediction step). For example, the temperature prediction unit 521 reads the above-mentioned trained model from the memory unit 53 and predicts the circulating water temperature change amount ΔTw using the trained model. In this case, the electrolytic cell heat generation amount ΔPe based on the detection signal, the circulating water volume Qw, the circulating water specific heat Cw, the circulating water temperature Tw, the ambient temperature Te, and the feedwater volume ΔQs are input to the trained model, and the circulating water temperature change amount ΔTw is output from the trained model. The temperature prediction unit 521 calculates the circulating water temperature prediction value T1 from, for example, the circulating water temperature Tw and the circulating water temperature change amount ΔTw, and outputs the temperature prediction result including the temperature prediction value T1 to the equipment control unit 522.

[0051] Next, when the temperature prediction result is obtained from the temperature prediction unit 521, the equipment control unit 522 determines whether the predicted temperature value T1 of the circulating water indicated in the temperature prediction result is higher than a predetermined specified temperature T2 of the circulating water (e.g., 80°C) (step S3).

[0052] If the predicted temperature value T1 is higher than the specified temperature T2 (YES in step S3), the equipment control unit 522 sets the water supply threshold to HI (high) so as to increase the amount of water supplied from the pure water tank 4 to the oxygen-gas-liquid separator 3 (step S4). On the other hand, if the predicted temperature value T1 is equal to or lower than the specified temperature T2 (NO in step S3), the equipment control unit 522 sets the water supply threshold to LOW (low) so as to decrease the amount of water supplied from the pure water tank 4 to the oxygen-gas-liquid separator 3 (step S5).

[0053] Fig. 4 is a cross-sectional view of the oxygen gas-liquid separator 3, illustrating an example of the water supply control shown in Fig. 3. As shown in Fig. 4, the oxygen gas-liquid separator 3 has two water supply thresholds, LOW (low) and HI (high), set to control the amount of water supplied from the pure water tank 4. The water supply threshold HI (second water supply threshold) is set to maintain a liquid level FL that is higher than the water supply threshold LOW (first water supply threshold). When the water electrolysis system 100 starts operating, the water supply threshold may be set to LOW, for example.

[0054] If the predicted temperature value T1 is higher than the specified temperature T2 in step S3 (YES in step S3), that is, if a rise in the circulating water temperature exceeding the specified temperature T2 is predicted, the device control unit 522 sets the water supply threshold to HI (step S4). As a result, for example, if the liquid level FL in the oxygen-gas-liquid separator 3 is lower than the water supply start threshold H1 (in the case of the liquid level FL1 in the figure), water is supplied from the pure water tank 4 to the oxygen-gas-liquid separator 3 until the liquid level FL reaches the water supply stop threshold H2. In this way, by controlling the supply pump 91 to increase the amount of water supplied to the oxygen-gas-liquid separator 3 when it is predicted that the circulating water temperature will exceed the specified temperature T2, the rise in the circulating water temperature can be suppressed. Note that if the water supply threshold has already been set to HI at the time of step S4, the device control unit 522 maintains the water supply threshold as HI.

[0055] On the other hand, if the predicted temperature value T1 is equal to or lower than the specified temperature T2 (NO in step S3), that is, if the circulating water temperature is predicted to fall below the specified temperature T2, the device control unit 522 sets the water supply threshold to LOW (step S5). As a result, for example, if the liquid level FL in the oxygen-gas-liquid separator 3 is higher than the water supply start threshold L1 (in the case of the liquid level FL2 in the figure), water is not supplied from the pure water tank 4 to the oxygen-gas-liquid separator 3 until the liquid level FL falls to the water supply start threshold L1 due to consumption of circulating water. Thus, if the circulating water temperature is predicted to fall below the specified temperature T2, the device control unit 522 controls the supply pump 91 to reduce the amount of water supplied to the oxygen-gas-liquid separator 3. This prevents further reduction in the circulating water temperature due to water supply and prevents the circulating water from being overcooled. If the water supply threshold was already set to LOW at the time of step S5, the device control unit 522 maintains the water supply threshold at LOW.

[0056] Next, after the water supply control described above, the equipment control unit 522 controls the heat exchanger 82 to perform temperature control to adjust the circulating water temperature. For example, if the water supply threshold is set to HI in step S4, the equipment control unit 522 calculates the difference between the predicted temperature value T1 and the specified temperature T2 (step S6). Then, the equipment control unit 522 adjusts the cooling water valve opening of the heat exchanger 82 in accordance with the difference (step S7: equipment control step). This adjusts the amount of cooling water flowing through the heat exchanger 82 in accordance with the predicted temperature value T1, and the circulating water can be appropriately cooled so that the circulating water temperature approaches the specified temperature T2.

[0057] On the other hand, if the water supply threshold is set to LOW in step S5, the equipment control unit 522 closes the cooling water valve of the heat exchanger 82 (step S8: equipment control step). This stops the cooling water from flowing through the heat exchanger 82, making it possible to prevent a further decrease in the circulating water temperature due to the cooling water.

[0058] 3 (steps S4 and S5) is not essential and can be omitted. In this case, after determining whether the predicted temperature value T1 is higher than the specified temperature T2 in the temperature prediction step (step S3) described above, temperature control (steps S6 to S8) for controlling 82 may be performed according to the determination result.

[0059] Fig. 5 is a graph showing an example of the transition of the measured temperature value when heat exchanger 82 is controlled based on the measured value (actual value) of the circulating water temperature. Fig. 6 is a graph showing an example of the transition of the measured temperature value when heat exchanger 82 is controlled based on the predicted temperature value of the circulating water temperature. In Figs. 5 and 6, the horizontal axis represents time [S] and the vertical axis represents the measured temperature value [°C].

[0060] The graph shown in Fig. 5 shows the transition of the measured temperature value when the heat exchanger 82 is controlled based on the measured value (actual measured value) of the circulating water temperature as in the conventional case, without performing the above-mentioned water supply control and temperature control. On the other hand, Fig. 6 shows the transition of the measured temperature value when the water supply control and temperature control are performed based on the temperature prediction value as in the present disclosure.

[0061] When the heat exchanger 82 is controlled based on the measured value of the circulating water temperature, it is susceptible to various factors that cause temperature changes in the circulating water, such as a drop in the supply water or the current in the electrolytic cell 1. In particular, in a large-scale water electrolysis system 100, the responsiveness and tracking of the circulating water temperature control are poor, which can lead to a decrease in electrolysis efficiency. For this reason, as shown in Fig. 5, the circulating water temperature is prone to oscillation (symbol R1 in the figure), and the circulating water may be excessively cooled if a sudden drop in the current in the electrolytic cell 1 occurs (symbol R2 in the figure).

[0062] On the other hand, when heat exchanger 82 is controlled based on the predicted temperature value of the circulating water temperature, it becomes possible to control the circulating water temperature while taking into account the various factors that cause temperature changes in the circulating water, as described above, and the influence of a deterioration in responsiveness that accompanies an increase in the size of the water electrolysis system 100, by predicting the circulating water temperature. Therefore, as shown in Fig. 6, the responsiveness of the control of the circulating water temperature is improved, making the circulating water temperature less likely to oscillate, and preventing the circulating water from being excessively cooled even when a sudden drop in current occurs in the electrolytic cell 1.

[0063] Fig. 7 is a graph showing the relationship between the voltage and circulating water temperature of the electrolytic cell 1. In Fig. 7, the horizontal axis represents the circulating water temperature (oxygen side temperature of the electrolytic cell) [°C], and the vertical axis represents the cell voltage [V] of the electrolytic cell 1.

[0064] 7, in the electrolytic cell 1, the higher the circulating water temperature, the lower the voltage value required for electrolysis. Therefore, by suppressing excessive cooling of the circulating water and maintaining the circulating water temperature near a specified temperature, as in the present disclosure, the voltage value of the electrolytic cell 1 can be reduced, thereby improving the electrolysis efficiency.

[0065] [Actions and Effects of the Control Device 5] As described above, the control device 5 according to this embodiment includes a temperature prediction unit 521 that predicts the temperature change of the circulating water circulating between the electrolytic cell 1 that electrolyzes water and the oxygen-liquid separator 3 that separates the oxygen generated in the electrolytic cell 1 from the water, and an equipment control unit 522 that controls the heat exchanger 82 that cools the circulating water based on the temperature prediction result of the temperature prediction unit 521.

[0066] The control device 5 controls the heat exchanger 82 based on the temperature prediction result that predicts future temperature changes in the circulating water. Therefore, by predicting temperature changes in the circulating water while taking into account, for example, various factors that cause temperature changes in the circulating water and the influence of deterioration in responsiveness due to an increase in the size of the water electrolysis system 100, it becomes possible to control the heat exchanger 82 while taking into account these influences.

[0067] Therefore, according to this embodiment, it is possible to appropriately cool the circulating water, and the electrolysis efficiency of the water electrolysis system 100 can be improved.

[0068] Furthermore, such effects will also contribute to the achievement of Goal 7 of the United Nations' Sustainable Development Goals (SDGs), such as "Ensure access to affordable, reliable, sustainable and modern energy for all."

[0069] [Software implementation example] The functions of the control device 5 (hereinafter referred to as the "device") are realized by a control program that causes a computer to function as the device, and by a control program that causes a computer to function as each control block of the device (particularly each part included in the control device 5).

[0070] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program to realize each function described in the embodiment.

[0071] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0072] In addition, some or all of the functions of each control block can be realized by a logic circuit. For example, an integrated circuit in which a logic circuit that functions as each control block is formed is also included in the scope of the present disclosure. In addition, the functions of each control block can be realized by, for example, a quantum computer.

[0073] 〔summary〕 The control device according to aspect 1 of the present disclosure is a control device for a water electrolysis system that electrolyzes water to generate oxygen and hydrogen, and includes a temperature prediction unit that predicts a temperature change in circulating water that circulates between an electrolytic cell that electrolyzes water and an oxygen-liquid separator that separates the oxygen generated in the electrolytic cell from the water, and an equipment control unit that controls a cooling device (heat exchanger 82) that cools the circulating water based on the temperature prediction result of the temperature prediction unit.

[0074] In the control device according to aspect 2 of the present disclosure, in aspect 1, the temperature prediction unit may predict the temperature change of the circulating water based on the amount of temperature increase of the circulating water due to self-heating of the electrolytic cell and the amount of temperature decrease of the circulating water due to heat radiation from the circulating water piping through which the circulating water flows.

[0075] In the control device according to aspect 3 of the present disclosure, in aspect 1 or 2, the temperature prediction unit may further predict a change in temperature of the circulating water based on an amount of temperature drop of the circulating water caused by supply water supplied to the oxygen gas-liquid separator.

[0076] In the control device according to aspect 4 of the present disclosure, in any one of aspects 1 to 3, the temperature prediction unit may predict the temperature change of the circulating water based on input values ​​including the heat generation amount of the electrolytic cell, the temperature of the circulating water, and the ambient temperature.

[0077] In the control device according to aspect 5 of the present disclosure, in any of aspects 1 to 4, the temperature prediction unit may predict the temperature change of the circulating water using a learning model trained by machine learning using training data that associates input values ​​including the heat generation amount of the electrolytic cell, the temperature of the circulating water, and the ambient temperature with the temperature change of the circulating water.

[0078] In the control device according to aspect 6 of the present disclosure, in any of aspects 1 to 5, the equipment control unit may control a supply device (supply pump 91) that supplies supply water to the oxygen gas-liquid separator based on the temperature prediction result.

[0079] In the control device according to aspect 7 of the present disclosure, in aspect 6, the equipment control unit may control the supply device to reduce the amount of supply water when the predicted temperature value of the circulating water indicated in the temperature prediction result is below a specified temperature.

[0080] A water electrolysis system according to an eighth aspect of the present disclosure includes the control device of any one of the first to seventh aspects; an electrolytic cell that electrolyzes water; an oxygen-gas-liquid separator that separates oxygen generated in the electrolytic cell from water; and a cooler that cools circulating water circulating between the electrolytic cell and the oxygen-gas-liquid separator. Includes:

[0081] A control method according to a ninth aspect of the present disclosure is a control method for a water electrolysis system that electrolyzes water to generate oxygen and hydrogen, and includes a temperature prediction step of predicting a temperature change of circulating water circulating between an electrolytic cell that electrolyzes water and an oxygen-liquid separator that separates the oxygen generated in the electrolytic cell from the water, and an equipment control step of controlling a cooling device that cools the circulating water based on a temperature prediction result of the temperature prediction step.

[0082] A control program according to a tenth aspect of the present disclosure is a control program for causing a computer to function as the control device according to the first aspect, and causes the computer to function as the temperature prediction unit and the device control unit.

[0083] The present disclosure 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 disclosure. [Explanation of symbols]

[0084] 1: Electrolytic cell 3: Oxygen gas-liquid separator 8: Water circulation line (circulating water piping) 82: Heat exchanger (cooling device) 91: Supply pump (supply device) 521: Temperature prediction unit 522: Equipment control unit S2: Temperature prediction step S7: Device control step S8: Equipment control step T1: Temperature prediction value T2: Specified temperature

Claims

1. A control device for a water electrolysis system that electrolyzes water to generate oxygen and hydrogen, a temperature prediction unit that predicts a temperature change of circulating water that circulates between an electrolytic cell that electrolyzes water and an oxygen gas-liquid separator that separates oxygen generated in the electrolytic cell from water; an equipment control unit that controls a cooling device that cools the circulating water based on a temperature prediction result of the temperature prediction unit; A control device comprising:

2. The temperature prediction unit an amount of temperature rise of the circulating water due to self-heating of the electrolytic cell; and the amount of temperature decrease of the circulating water due to heat radiation from the circulating water piping through which the circulating water flows; The control device according to claim 1 , wherein the temperature change of the circulating water is predicted based on the above.

3. The temperature prediction unit 3. The control device according to claim 2, further comprising: a controller for predicting a change in temperature of the circulating water based on an amount of temperature decrease of the circulating water caused by supply water supplied to the oxygen gas-liquid separator.

4. The control device according to claim 1 , wherein the temperature prediction unit predicts a change in the temperature of the circulating water based on input values ​​including a heat generation amount of the electrolytic cell, a temperature of the circulating water, and an ambient temperature.

5. 4. The control device according to claim 1, wherein the temperature prediction unit predicts the temperature change of the circulating water using a learning model that has been machine-learned using training data that associates input values ​​including the heat generation amount of the electrolytic cell, the temperature of the circulating water, and the ambient temperature with the temperature change of the circulating water.

6. The control device according to claim 1 , wherein the equipment control unit controls a supply device that supplies feed water to the oxygen gas-liquid separator based on the temperature prediction result.

7. The device control unit The control device according to claim 6 , wherein when the predicted temperature value of the circulating water indicated in the temperature prediction result is equal to or lower than a specified temperature, the control device controls the supply device so as to reduce the supply amount of the supply water.

8. The control device according to any one of claims 1 to 3; an electrolytic cell for electrolyzing water; an oxygen gas-liquid separator that separates the oxygen and water generated in the electrolytic cell; a cooler that cools the circulating water circulating between the electrolytic cell and the oxygen gas-liquid separator; A water electrolysis system comprising:

9. A method for controlling a water electrolysis system that electrolyzes water to generate oxygen and hydrogen, comprising: a temperature prediction step of predicting a temperature change of circulating water circulating between an electrolytic cell that electrolyzes water and an oxygen gas-liquid separator that separates oxygen generated in the electrolytic cell from water; an equipment control step of controlling a cooling device that cools the circulating water based on a temperature prediction result of the temperature prediction step; A control method comprising:

10. 2. A control program for causing a computer to function as the control device according to claim 1, the control program causing the computer to function as the temperature prediction unit and the device control unit.

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