Water electrolysis system and method of controlling water electrolysis

Abstract

To provide a water electrolysis system capable of preventing the deterioration of a water electrolysis stack resulting from a high temperature by grasping the temperature distribution in the electrolysis stack.SOLUTION: A water electrolysis system 1 comprises a temperature distribution estimation unit 52 that estimates a temperature distribution in a water electrolysis stack 10 using characteristics measurement data, i.e., data for measuring a characteristic value relating to the temperature distribution in the water electrolysis stack 10, corresponding to each of a plurality of water flows, when the plurality of different water flows are supplied to the water electrolysis stack 10 composed of a plurality of water electrolysis cells, and an operating condition establishing unit 53 of establishing the operating conditions of the water electrolysis stack according to the temperature distribution in the water electrolysis stack estimated by the temperature distribution estimation unit 52.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, hydrogen has been attracting attention as a next-generation energy source, and it is expected to be used as a clean energy source when combined with carbon dioxide (CO2)-free electricity from renewable energies. For this reason, there is a growing demand for large-scale water electrolysis hydrogen production systems in order to quickly realize a hydrogen society. Water electrolysis hydrogen production systems use renewable electricity to produce green hydrogen without emitting CO2 when splitting water into oxygen and hydrogen to produce hydrogen.

[0003] In addition, with the advancement of development of hydrogen production technology by water electrolysis, there is also a demand for reducing hydrogen production costs. In order to reduce hydrogen production costs, it is necessary to suppress the deterioration of the water electrolysis stack of the water electrolysis system and operate it for a long life. As a deterioration phenomenon of the water electrolysis stack, for example, a phenomenon in which the resistance components of the multiple water electrolysis cells constituting the water electrolysis stack increase over time is known. As a cause of deterioration of the water electrolysis stack, for example, in a solid polymer water electrolysis stack, there is deterioration of components such as an electrolyte membrane and a catalyst due to high temperature, and in an alkaline water electrolysis stack, there is deterioration of components such as a diaphragm and a catalyst. In order to suppress deterioration of the water electrolysis stack, it is necessary to manage the internal temperature of the water electrolysis stack and perform operation control while preventing deterioration of components due to high temperature. Therefore, as a technology for suppressing deterioration of the water electrolysis stack due to high temperature, for example, the technology described in Patent Document 1 and Patent Document 2 is disclosed.

[0004] Patent document 1 states that "the device comprises a pressure adjustment unit that adjusts the pressure within the first storage unit, a temperature detection unit that detects the temperature within the first storage unit, and a control unit that controls the pressure adjustment unit based on a detection signal from the temperature detection unit."

[0005] Furthermore, Patent Document 2 states that "The first temperature measurement unit is provided inside the first anode mouth, and the second temperature measurement unit is provided inside the second anode mouth. The temperature measurement results by the first temperature measurement unit and the second temperature measurement unit are input to a control unit. The control unit switches the conditions using the measurement results input from the first temperature measurement unit and the second temperature measurement unit." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2023-25292 A [Patent Document 2] Patent Publication No. 2022-139785 Summary of the Invention [Problem to be solved by the invention]

[0007] As the size of the water electrolysis system increases, the number of water electrolysis cells included in the water electrolysis stack tends to increase, and the electrode area of ​​each water electrolysis cell tends to increase. As the number of water electrolysis cells increases, the technology described in Patent Document 1 for detecting the temperature of each water electrolysis cell and controlling pressure adjustment has a problem of increased cost and control processing load. In addition, the temperature of the high-temperature part inside the water electrolysis stack has a distribution in the stacking direction of the water electrolysis cells and in the plane of the electrolyte membrane, and is higher than the measurement value of the water thermometer. Therefore, the technology described in Patent Document 2 for controlling the operating conditions using the measured water temperature of the supply water at the inlet and outlet of the water electrolysis stack has a problem of low effectiveness in suppressing deterioration of parts in the high-temperature part because it cannot grasp the temperature distribution of the high-temperature part inside the water electrolysis stack. Similarly, the technology described in Patent Document 1 also has a problem of not being able to grasp the temperature distribution of the high-temperature part inside the water electrolysis stack.

[0008] As a result, there is a concern that the deterioration of the water electrolysis stack will be accelerated if the water electrolysis system continues to operate without noticing the presence of high-temperature parts inside the water electrolysis stack, which deteriorate quickly. There is also a concern that the operating costs of the water electrolysis system will increase if an excessive amount of cooling water is supplied to the water electrolysis stack in an attempt to avoid the occurrence of high-temperature parts inside the water electrolysis stack.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a water electrolysis system that can grasp the temperature distribution inside the water electrolysis stack and suppress deterioration of the water electrolysis stack due to high temperatures. [Means for solving the problem]

[0010] The water electrolysis system of the present invention includes a temperature distribution estimation unit that estimates a temperature distribution inside the water electrolysis stack using characteristic measurement data, which is data for measuring characteristic values ​​related to a temperature distribution inside the water electrolysis stack corresponding to each of the different water flow rates when different water flow rates are supplied to a water electrolysis stack composed of a plurality of water electrolysis cells, and an operating condition formulation unit that formulates operating conditions for the water electrolysis stack based on the temperature distribution inside the water electrolysis stack estimated by the temperature distribution estimation unit. Effect of the Invention

[0011] According to the present invention having the above configuration, it is possible to provide a water electrolysis system that is capable of grasping the temperature distribution inside the water electrolysis stack and suppressing deterioration of the water electrolysis stack due to high temperatures. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram showing an example of the configuration of a water electrolysis system according to a first embodiment of the present invention. FIG. [Diagram 2] FIG. 3 is a graph showing an example of current-voltage characteristics of the water electrolysis stack of the water electrolysis system according to the first embodiment of the present invention. [Diagram 3]1 is a diagram showing an equivalent circuit of a water electrolysis cell of the water electrolysis stack according to the first embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing Example 1 of a time constant distribution and a voltage transient response of a water electrolysis stack. [Diagram 5] FIG. 11 is a diagram showing Example 2 of the time constant distribution and voltage transient response of a water electrolysis stack. [Figure 6] FIG. 11 is a diagram showing Example 3 of the time constant distribution and voltage transient response of a water electrolysis stack. [Figure 7] FIG. 11 is a diagram showing Example 4 of the time constant distribution and voltage transient response of a water electrolysis stack. [Figure 8] FIG. 4 is a graph showing the relationship between the standard deviation of the time constant distribution of the water electrolysis stack and the exponent of the fitting function of the voltage transient response in the water electrolysis system according to the first embodiment of the present invention. [Figure 9] FIG. 3 is a diagram showing Example 1 of the correspondence relationship between the characteristic values ​​of the water electrolysis stack and the water flow rate in the water electrolysis system according to the first embodiment of the present invention. [Figure 10] FIG. 4 is a diagram showing the correspondence relationship between pre-measured characteristic values ​​and temperature distribution of the water electrolysis stack in the water electrolysis system according to the first embodiment of the present invention. [Figure 11] FIG. 4 is a diagram showing a second example of the correspondence relationship between the characteristic values ​​of the water electrolysis stack and the flow rate of supplied water in the water electrolysis system according to the first embodiment of the present invention. [Figure 12] FIG. 4 is a diagram showing a procedure of a temperature distribution estimation process in the water electrolysis system according to the first embodiment of the present invention. [Figure 13] FIG. 3 is a diagram showing the procedure of Example 1 of a process for formulating operating conditions in the water electrolysis system according to the first embodiment of the present invention. [Figure 14] FIG. 4 is a diagram showing the procedure of Example 2 of the process for formulating operating conditions in the water electrolysis system according to the first embodiment of the present invention. [Figure 15] FIG. 4 is a diagram showing a procedure of a first example of an operation for measuring characteristics of a water electrolysis stack under a plurality of flow rate conditions in the water electrolysis system according to the first embodiment of the present invention. [Figure 16]FIG. 4 is a diagram showing Example 1 of changes over time in water flow rate and current when characteristics of the water electrolysis stack are measured in the water electrolysis system according to the first embodiment of the present invention. [Figure 17] FIG. 6 is a diagram showing a procedure of Example 2 of the operation for measuring characteristics of the water electrolysis stack under a plurality of flow rate conditions in the water electrolysis system according to the first embodiment of the present invention. [Figure 18] FIG. 6 is a diagram showing a second example of changes over time in water flow rate and current when characteristics of the water electrolysis stack are measured in the water electrolysis system according to the first embodiment of the present invention. [Figure 19] 1 is a diagram illustrating an example of a hardware configuration of a water electrolysis control device according to a first embodiment of the present invention. [Figure 20] FIG. 4 is a block diagram showing an example of the configuration of a water electrolysis system according to a second embodiment of the present invention. [Figure 21] FIG. 11 is a diagram showing a procedure of an operation control process based on future deterioration of the water electrolysis stack in a water electrolysis system according to a second embodiment of the present invention. [Figure 22] FIG. 11 is a block diagram showing an example of the configuration of a water electrolysis system according to a third embodiment of the present invention. [Figure 23] FIG. 11 is a block diagram showing an example of the configuration of a water electrolysis system according to a fourth embodiment of the present invention. [Figure 24] FIG. 13 is a block diagram showing an example of a configuration in which a water electrolysis system according to a fifth embodiment of the present invention is linked to a power transmission and distribution system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functions or configurations are designated by the same reference numerals, and redundant description will be omitted.

[0014] First Embodiment [Example of water electrolysis system configuration] First, the configuration of a water electrolysis system 1 according to a first embodiment of the present invention will be described. Fig. 1 is a block diagram showing an example of the configuration of the water electrolysis system 1 according to this embodiment. As shown in Fig. 1, the water electrolysis system 1 includes a water electrolysis stack 10, a measuring device 20, an auxiliary device 30, a power supply 40, and a water electrolysis control device 50. The measuring device 20, the auxiliary device 30, and the power supply 40 are each connected to the water electrolysis stack 10. The measuring device 20, the auxiliary device 30, and the power supply 40 are also each connected to the water electrolysis control device 50.

[0015] The water electrolysis stack 10 is composed of a plurality of cell stacks for water electrolysis (hereinafter referred to as "water electrolysis cells"), and generates hydrogen by decomposing water into hydrogen and oxygen using supplied water and electricity. Here, it is assumed that the water electrolysis stack 10 is a solid polymer water electrolysis stack, but the water electrolysis stack 10 may be an alkaline water electrolysis stack. When the water electrolysis stack 10 is an alkaline water electrolysis stack, in the following description, the electrolyte membrane may be replaced with a diaphragm, and water may be replaced with an electrolytic solution.

[0016] The measuring instrument 20 is an instrument that measures the voltage and current applied to the water electrolysis stack 10, current-voltage characteristics (also referred to as "IV characteristics"), EIS (Electro-chemical Impedance Spectroscopy) characteristics, etc. The measurement data of the measuring instrument 20 is data for measuring characteristic values ​​of the water electrolysis stack 10, and is hereinafter referred to as "characteristic measurement data". Examples of the characteristic values ​​include an index for evaluating the non-uniformity of the time constant distribution of the voltage transient response to a current change in the water electrolysis stack 10, and a deviation width from an exponential function in the low current range of the Tafel plot. An index for evaluating the non-uniformity of the time constant distribution of the voltage transient response to a current change in the water electrolysis stack 10 is, for example, an exponent β of a fitting function of the voltage (current) transient response to a current (voltage) change in the water electrolysis stack 10 described below.

[0017] The auxiliary machine 30 is an example of a controller that controls the operating conditions of the water electrolysis stack 10 (such as the water flow rate, the water temperature, and the pressure of the water electrolysis stack 10), and controls the operating conditions in accordance with operation commands (commands for temperature, water flow rate, etc.) from the water electrolysis control device 50. The power supply 40 supplies power (current and voltage) to the water electrolysis stack 10 in accordance with a current command from the water electrolysis control device 50. The power supply 40 includes, for example, a DC stabilized power supply, a DC / DC converter, etc. capable of generating a time waveform.

[0018] 1, the water electrolysis controlling device 50 includes a measurement data receiving unit 51, a temperature distribution estimating unit 52, and an operating condition formulating unit 53. The measurement data receiving unit 51 receives characteristic measurement data from the measuring instruments 20 and outputs the data to the temperature distribution estimating unit 52.

[0019] The temperature distribution estimation unit 52 estimates the temperature distribution inside the water electrolysis stack 10 using characteristic measurement data corresponding to each of the water flow rates when different water flow rates are supplied to the water electrolysis stack 10. Specifically, the temperature distribution estimation unit 52 calculates an average time constant of the transient response and an index for evaluating the non-uniformity of the time constant distribution of the transient response by analyzing a fitting function of the transient response of the voltage. In addition, the temperature distribution estimation unit 52 identifies a characteristic value when an infinite water flow rate is supplied to the water electrolysis stack. The temperature distribution estimation unit 52 estimates the temperature distribution based on the characteristic values ​​corresponding to each of the water flow rates when different water flow rates are supplied, the characteristic value when the identified infinite water flow rate is supplied, and the correspondence relationship between the characteristic value and the temperature distribution measured in advance.

[0020] The operating condition formulation unit 53 formulates operating conditions for the water electrolysis stack 10 based on the temperature distribution inside the water electrolysis stack 10 estimated by the temperature distribution estimation unit 52.

[0021] Next, estimation of the internal temperature distribution based on the characteristic values ​​of the water electrolysis stack 10 will be described. Here, an example will be described in which the exponent β of a fitting function (stretched exponential) of the transient response of the voltage to a step change in the current of the water electrolysis stack 10 is used as the characteristic value. Hereinafter, estimation of the internal temperature distribution of the water electrolysis stack 10 using measurement data of the characteristic value (exponent β) will be described with reference to Figs. 2 to 10.

[0022] FIG. 2 is a diagram showing an example of the current-voltage characteristics of the water electrolysis stack 10 of the water electrolysis system 1 according to this embodiment. The solid curve in the diagram shows the current-voltage characteristics of a normal (non-degraded) water electrolysis stack. The dashed curve in the diagram shows the current-voltage characteristics of a degraded water electrolysis stack. As shown in the diagram, the voltage of the degraded product is higher than the voltage of the normal product at the same operating current. This is because the resistance component (hereinafter abbreviated as "resistance component") involved in the catalytic reaction of each electrode of the water electrolysis stack increases with aging. The resistance component of the water electrolysis stack will be described with reference to FIG. 3.

[0023] 3 is a diagram showing an equivalent circuit of the water electrolysis cell of the water electrolysis stack 10 according to the present embodiment. As shown in FIG. 3, the equivalent circuit of the water electrolysis cell of the water electrolysis stack 10 has a cell resistance (electrolyte membrane resistance) R s , charge transfer resistance (resistance component) R ct , and the electric double layer capacitance C dl It is composed of cell resistance R s is the charge transfer resistance R ct and electric double layer capacitance C dl The resistance component of the water electrolysis stack changes not only with age but also with temperature, so the temperature distribution inside the water electrolysis stack can be estimated by evaluating the magnitude of the distribution of the resistance component.

[0024] One method for evaluating the resistance component of a water electrolysis stack is to analyze the transient response of the voltage (or current) when the current (or voltage) is changed stepwise for a small water electrolysis stack. The charge transfer resistance Rct Therefore, C dl R ct The transient response can be analyzed by analyzing the time-dependent change in Rs. Note that the response due to the cell resistance Rs occurs in an extremely short time and requires measurements with high time resolution, so it is expected that evaluation in an actual system will be difficult.

[0025] Here, the transient response of a small water electrolysis stack having a simple time constant distribution will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a diagram showing Example 1 of the time constant distribution and voltage transient response of a water electrolysis stack. Fig. 4A is a diagram showing the time constant distribution of a water electrolysis stack. Fig. 4B is a diagram showing the voltage transient response corresponding to the time constant distribution shown in Fig. 4A.

[0026] In FIG. 4A, the horizontal axis indicates the time constant in seconds (s), and the vertical axis indicates the number of water electrolysis cells constituting the water electrolysis stack. Here, the number of water electrolysis cells in the small water electrolysis stack is 100, and R ct =37.26Ω, C dl =0.318F, τ(time constant)=1 / R ct C dl = 12 s (seconds), and it is assumed that τ (time constant) becomes 20 s due to temperature changes, etc. It is also assumed that all water electrolysis cells in the small water electrolysis stack have the same time constant (20 s). For this reason, the time constant distribution shown in Fig. 4A is the distribution indicated by the bar at 100 cells and a time constant of 20 s. Fig. 4B shows the voltage change (V i →V f ), i.e., the voltage transient response corresponding to the time constant distribution shown in FIG. 4A is shown. In FIG. 4B, the horizontal axis indicates time in seconds (s) and the vertical axis indicates the voltage of the water electrolysis stack in volts (V). The voltage transient response shown in FIG. 4B can be fitted with a single exponential function (exp(-t / τ)).

[0027] FIG. 5 is a diagram showing Example 2 of the time constant distribution and voltage transient response of a water electrolysis stack. FIG. 5A is a diagram showing the time constant distribution of a water electrolysis stack. FIG. 5B is a diagram showing the voltage transient response corresponding to the time constant distribution shown in FIG. 5A. In the example shown in FIG. 5, it is assumed that all water electrolysis cells of a small water electrolysis stack do not have the same time constant, but that the time constants are distributed around 20 s (τ_1) and 70 s (τ_2). Note that the assumed conditions other than the above are the same as the assumed conditions described in FIG. 4, and therefore repeated explanations will be omitted.

[0028] As shown in the bar graph of FIG. 5A, the time constants are distributed around 20 s (τ_1) and 70 s (τ_2). The voltage transient response corresponding to the time constant distribution shown in FIG. 5A is shown in FIG. 5B. The voltage transient response shown in FIG. 5B can be fitted by the sum of two exponential functions at a predetermined ratio (Aexp(-t / τ_1)+Bexp(-t / τ_2)). Here, "A" and "B" are the ratios in the sum of the two exponential functions, respectively.

[0029] Analysis of the transient response of a small-scale water electrolysis system having a simple time constant distribution, i.e., a simple resistance component distribution, as described in Figures 4 and 5 can be achieved by changing the current in a stepwise manner. When this analysis method is applied to a large-scale water electrolysis stack, a response characteristic with a mixture of multiple time constants is obtained due to the influence of the temperature distribution inside the large-scale water electrolysis stack.

[0030] Next, the transient response of a large-scale water electrolysis stack having a continuous time constant distribution will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a diagram showing Example 3 of the time constant distribution and voltage transient response of a water electrolysis stack. Fig. 6A is a diagram showing the time constant distribution of a water electrolysis stack. Fig. 6B is a diagram showing the voltage transient response corresponding to the time constant distribution shown in Fig. 6A.

[0031] In the example shown in Figure 6A, an example of the time constant distribution of a water electrolysis stack having a continuous distribution with an average time constant of 20 s and a standard deviation of 2 s is shown. The voltage transient response corresponding to the time constant distribution shown in Figure 6A is shown in Figure 6B. The voltage transient response shown in Figure 6B can be fitted with a function of the following formula (1).

[0032]

number

[0033] In the above formula (1), τ a is the average time constant and β is the exponent. β is also a number in the (0,1) space. The smaller β is, the larger the standard deviation (the more non-uniform the distribution). The transient response shown in Figure 6B has an average time constant τ a = 20s, β = 0.98. The function shown in equation (1) is obtained by simulating the transient response of the measured voltage.

[0034] FIG. 7 shows Example 4 of the distribution of time constants and voltage transient response of a water electrolysis stack. FIG. 7A shows the time constant distribution of a water electrolysis stack. FIG. 7B shows the voltage transient response corresponding to the time constant distribution shown in FIG. 7A. In the example shown in FIG. 7A, an example of the time constant distribution of a water electrolysis stack having a continuous distribution with an average time constant of 20 s and a standard deviation of 6 s is shown. The voltage transient response shown in FIG. 7B shows the time constant distribution of a water electrolysis stack having a continuous distribution with an average time constant τ a It can be fitted using equation (1) for =20s and β=0.95.

[0035] Next, the relationship between the standard deviation of the time constant distribution and the exponent β will be described with reference to FIG. 8. FIG. 8 is a diagram showing the relationship between the standard deviation of the time constant distribution of the water electrolysis stack and the exponent of the fitting function of the transient response of the voltage in the water electrolysis system 1 according to this embodiment. In FIG. 8, the horizontal axis indicates the standard deviation of the time constant distribution in seconds, and the vertical axis indicates the exponent β. As shown in FIG. 8, the larger the exponent β, the smaller the standard deviation. By utilizing this correlation, the measured transient response of the voltage of the water electrolysis stack 10 can be analyzed to calculate the average time constant τ of the fitting function of the transient response. a and the index β, it is possible to estimate the time constant distribution (average time constant and standard deviation) of the resistance component of the water electrolysis stack 10. In other words, it is possible to estimate the distribution of the time constant of the resistance component of the water electrolysis stack 10 due to aging by analyzing the transient response of the water electrolysis stack 10. Note that, although an example in which the temperature distribution estimation unit 52 analyzes the voltage transient response has been described above, the present invention is not limited to this, and the temperature distribution estimation unit 52 may analyze the current transient response.

[0036] Next, a method for estimating the temperature distribution inside the water electrolysis stack 10 using the characteristic value (index β) estimated by the analysis of the transient response described in FIG. 4 to FIG. 8 will be described with reference to FIG. 9 to FIG. 11. The temperature of the water supplied to the water electrolysis stack 10 is higher at the outlet than at the inlet as a result of heat exchange with members such as an electrolyte membrane. It is considered that when the water flow rate is infinite, the water temperature difference in the flow path direction between the inlet and the outlet and the water temperature difference in the cell stacking direction disappears, and the water temperature becomes equal to the temperature of the members adjacent to the flow path. Even at an infinite water flow rate, the temperature distribution associated with thermal diffusion (balance between heat generation and cooling) in the cell surface remains. Therefore, if the characteristic value at an infinite water flow rate can be estimated in advance by experiment or numerical calculation, the effect of the temperature distribution at an infinite water flow rate can be grasped. Therefore, the effect of the temperature distribution caused by the water flow rate at the normal operation can be estimated by analyzing the difference in the characteristic value from the water flow rate at the normal operation using the characteristic value at the infinite water flow rate as a reference.

[0037] FIG. 9 is a diagram showing an example 1 of the correspondence relationship between the characteristic value of the water electrolysis stack 10 and the water flow rate in the water electrolysis system 1 according to the present embodiment. In FIG. 9, the horizontal axis indicates the inverse of the water flow rate (1 / flow rate), and the vertical axis indicates the characteristic value η (for example, the above-mentioned index β). The black dots in FIG. 9 represent specific values ​​measured under each of a plurality of (three in the figure) normal flow rate conditions (water flow rates). The white dots in FIG. 9 represent characteristic values ​​at infinite water flow rates (hereinafter referred to as "extrapolation points") determined based on the measured characteristic values. In the example shown in FIG. 9, since the correlation between the characteristic value and the inverse of the water flow rate is linear, the specific value when the inverse of the water flow rate is "0" is determined as the characteristic value at infinite water flow rate, that is, the extrapolation point η0. The temperature distribution inside the water electrolysis stack 10 can be estimated based on the extrapolation point η0 and the correlation between the specific value of the water electrolysis stack measured in advance and the temperature distribution.

[0038] Fig. 10 is a diagram showing a correspondence relationship between a characteristic value measured in advance and temperature distribution of the water electrolysis stack in the water electrolysis system 1 according to the present embodiment. In Fig. 10, the horizontal axis represents the characteristic value η, and the vertical axis represents the magnitude ΔT of the temperature distribution inside the water electrolysis stack. In the example shown in Fig. 10, the correspondence relationship between the characteristic value measured in advance and the temperature distribution of the water electrolysis stack is linear, but the present invention is not limited to this, and the correspondence relationship differs depending on the type of characteristic value.

[0039] The correspondence relationship between the characteristic values ​​and the temperature distribution of the water electrolysis stack is measured in advance using another water electrolysis stack having the same configuration as the water electrolysis stack 10. That is, the temperature distribution estimation unit 52 estimates the temperature distribution based on the characteristic values ​​and the correspondence relationship between the characteristic meter values ​​and the temperature distribution, which are previously acquired in the other water electrolysis stack having the same configuration as the water electrolysis stack 10. The temperature distribution estimation unit 52 can also analyze the correspondence relationship between the characteristic values ​​and the temperature distribution of the other water electrolysis stack using a distribution function of the temperature distribution over a predetermined period inside the other water electrolysis stack, which is previously acquired in the other water electrolysis stack, to estimate the temperature distribution.

[0040] In addition, by measuring the correspondence between the characteristic values ​​and the temperature distribution using a separate water electrolysis stack, it is not necessary to connect various devices required for measurement to the water electrolysis stack 10 (the water electrolysis stack in actual operation), which is the measurement target. This reduces the effort required to switch between measurement and actual operation.

[0041] Based on the correspondence relationship between the characteristic values ​​and temperature distribution of the water electrolysis stack shown in Fig. 10, the magnitude ΔT0 of the temperature distribution corresponding to the extrapolation point η0 can be determined using the extrapolation point η0 determined by the method described in Fig. 9. Based on the determined η0 and ΔT0 and the correlation between the characteristic values ​​and the temperature distribution, the measured characteristic value η N The magnitude of the temperature distribution ΔT N can be estimated.

[0042] The correspondence relationship between the characteristic value of the water electrolysis stack 10 and the water flow rate is not limited to the example shown in FIG. 9, and may be, for example, the correspondence relationship shown in FIG. 11. FIG. 11 is a diagram showing Example 2 of the correspondence relationship between the characteristic value of the water electrolysis stack and the water flow rate in the water electrolysis system 1 according to the present embodiment. Example 2 shown in FIG. 11 shows the correspondence relationship between the characteristic value and the water flow rate when the characteristic value of the water electrolysis stack is the exchange current density i0. The horizontal axis of FIG. 11 indicates the inverse of the water flow rate (1 / flow rate), and the vertical axis indicates the exchange current density i0 (characteristic value η). Conditions A to C in the diagram correspond to three different materials of the water electrolysis cells of the water electrolysis stack. Although the value of i0 differs for each of Conditions A to C, they have in common a tendency that i0 approaches a constant value as the water flow rate approaches infinity. In order to identify the extrapolation point of the characteristic value, it is necessary to obtain in advance the function form of the correspondence relationship between the characteristic value and the water flow rate for each of a plurality of flow rate conditions. For example, under condition A, the exchange current density i0 at the water flow rate (1 / (flow rate)) corresponding to multiple white circle marks can be measured to obtain the functional form of the correspondence between the characteristic value (exchange current density i0) and the water flow rate.

[0043] In the above description, an example has been described in which the temperature distribution is estimated based on the correspondence between the characteristic values ​​of the water electrolysis stack 10 and the temperature distribution. However, the present invention is not limited to this, and the temperature may be estimated based on the correspondence between the characteristic values ​​of the water electrolysis stack 10 and the temperature. Here, the temperature of the water electrolysis stack 10 is the temperature of the components of the water electrolysis cell, such as the electrolyte membrane and the catalyst, and is defined as a representative temperature (T A ) means the representative temperature T A If it is possible to evaluate the temperature distribution inside the water electrolysis stack 10, in combination with the above-mentioned temperature distribution ΔT, it is possible to express the magnitude of the temperature distribution inside the water electrolysis stack 10 as a range of absolute temperatures, and to estimate the maximum temperature inside the water electrolysis stack 10. This makes it possible to more accurately predict the rate at which degradation progresses.

[0044] Representative temperature T A To evaluate the characteristic of the water electrolysis stack, the representative temperature T is calculated based on the characteristic measurement data of the water electrolysis stack under multiple water temperature conditions and the function form of the dependence of the characteristic value on temperature. A (generally higher than the water temperature) can be evaluated. A The characteristic values ​​related to the temperature include the voltage, current, resistance, and Tafel coefficient obtained from the IV characteristics. A The characteristic values ​​related to the resistance include high frequency resistance obtained from EIS (Electro-chemical Impedance Spectroscopy) characteristics, low frequency resistance obtained from EIS characteristics, and a response time constant to a step change in current or voltage.

[0045] For example, the response time constant to a step change in current or voltage is used to calculate the representative temperature T A When evaluating the representative temperature, the transient response of the voltage or current to a step change in the current or voltage can be analyzed to evaluate the representative temperature. act =(RT / zαF)log(i / i0) is differentiated with respect to the current density i to obtain R ct (R ct =RT / (zαFi) can be calculated. ctis proportional to the temperature T, so by evaluating the time constant, the representative temperature T A Therefore, the temperature distribution estimation unit 52 estimates a representative temperature, which is the temperature of the components of the water electrolysis cell, based on the average time constant of the transient response of the water electrolysis stack 10, and can estimate the maximum temperature inside the water electrolysis stack from the estimated representative temperature and the temperature distribution. Here, R is the gas constant, T is the absolute temperature, z is the number of charges involved in the electrolysis reaction (z=2 in the case of water electrolysis), α is the charge transfer coefficient, F is the Faraday constant, and i0 is the exchange current density.

[0046] [Temperature distribution estimation process procedure] Next, the procedure of the temperature distribution estimation process in the water electrolysis system 1 according to the present embodiment will be described. Fig. 12 is a diagram showing the procedure of the temperature distribution estimation process in the water electrolysis system 1 according to the present embodiment. The process described below is executed at predetermined intervals (for example, several months) or is started manually when it is desired to execute the process outside the predetermined intervals.

[0047] First, the measuring instrument 20 measures characteristic measurement data of the water electrolysis stack 10 under a plurality of flow rate conditions (step S10). In this process, the measuring instrument 20 performs a measurement process shown in Fig. 15 to be described later, and outputs the characteristic measurement data to the water electrolysis control device 50.

[0048] Next, the measurement data receiving unit 51 of the water electrolysis control device 50 receives characteristic measurement data under a plurality of flow rate conditions from the measuring instrument 20, and outputs the data to the temperature distribution estimating unit 52 (Step S11).

[0049] Next, the temperature distribution estimation unit 52 of the water electrolysis control device 50 analyzes the transient response by using the characteristic measurement data (step S12). In this process, the temperature distribution estimation unit 52 performs fitting on the measured transient response and derives an average time constant τ a and calculate the exponent β.

[0050] Next, the temperature distribution estimation unit 52 estimates the time constant distribution and the temperature distribution inside the water electrolysis stack 10 (step S13). In this process, the temperature distribution estimation unit 52 estimates the time constant distribution and the temperature distribution inside the water electrolysis stack 10 based on the calculated average time constant τ a and the exponent β, and a correlation function between the previously determined exponent β and the standard deviation value of the time constant distribution, to estimate the time constant distribution and evaluate the distribution of the resistance component. In this process, the temperature distribution estimation unit 52 estimates the temperature distribution inside the water electrolysis stack 10 based on the measured exponent β and the previously obtained correspondence relationship between the exponent β and the temperature distribution. When estimating the temperature distribution, the temperature distribution estimation unit 52 identifies an extrapolation point (η0) for an infinite water flow rate using measured values ​​of the characteristic values ​​of the water electrolysis stack 10 at multiple water flow rates (see FIG. 9 ). Note that the measurement of the characteristic values ​​of the water electrolysis stack 10 at multiple water flow rates may be performed in a periodic evaluation. In addition, the temperature distribution estimation unit 52 estimates the measured specific value (η N ) corresponding to the magnitude of the temperature distribution (ΔT N ) is estimated (see FIG. 10). The previously obtained correspondence relationship (correlation function) between the exponent β and the standard deviation value of the time constant distribution and the correspondence relationship (correlation function) between the exponent β and the temperature distribution are calculated based on measurement data of another water electrolysis stack having the same configuration as the water electrolysis stack 10. After the process of step S13, the temperature distribution estimation process ends.

[0051] [Procedure for Example 1 of Operation Condition Formulation Processing] Next, the procedure of Example 1 of the operation condition formulation process in the water electrolysis system according to the present embodiment will be described. Fig. 13 is a diagram showing the procedure of Example 1 of the operation condition formulation process in the water electrolysis system 1 according to the present embodiment. The process described below starts when the process described in Fig. 12 ends.

[0052] First, the operating condition formulating unit 53 of the water electrolysis control device 50 calculates the magnitude of the temperature distribution estimated by the temperature distribution estimating unit 52 (ΔT N ) is obtained (step S20).

[0053] Next, the operating condition formulation unit 53 calculates the magnitude of the estimated temperature distribution (ΔTN ) exceeds a predetermined threshold value ΔT0 of the magnitude of the temperature distribution registered in advance (step S21).

[0054] In the process of step S21, the operating condition formulating unit 53 calculates the magnitude of the estimated temperature distribution (ΔT N ) exceeds the threshold value ΔT0 of the magnitude of the predetermined temperature distribution (YES in step S21), the flow rate of the supply water is increased (step S22).

[0055] On the other hand, in the process of step S21, the operating condition formulation unit 53 determines the magnitude of the estimated temperature distribution (ΔT N If it is determined that the difference ΔT0 does not exceed the threshold value ΔT0 of the magnitude of the predetermined temperature distribution (NO in step S21), the process proceeds to step S23, which will be described later.

[0056] If the determination in step S21 is NO, or after the process of step S22, the operating condition formulation unit 53 continues the operation of the water electrolysis stack 10 under the set operating conditions (step S23). After the process of step S23, the operating condition formulation process ends.

[0057] [Procedure for Example 2 of Operation Condition Formulation Processing] Next, a procedure of Example 2 of the process for formulating operating conditions in the water electrolysis system according to this embodiment will be described. In Example 2 of the process for formulating operating conditions, the temperature distribution estimation unit 52 calculates the temperature distribution ΔT and the representative temperature T A and . Fig. 14 is a diagram showing the steps of Example 2 of the process for formulating operating conditions in the water electrolysis system 1 according to the present embodiment. The process described below starts when the process described in Fig. 12 ends, similar to Example 1 described in Fig. 13.

[0058] First, the operating condition formulating unit 53 of the water electrolysis control device 50 calculates the magnitude of the temperature distribution estimated by the temperature distribution estimating unit 52 (ΔT N ) and typical temperature T A is obtained (step S30).

[0059] Next, the operating condition formulation unit 53 calculates the representative temperature T A is the threshold value T A0 It is determined whether or not the difference exceeds the threshold (step S31).

[0060] In the process of step S31, the operating condition formulation unit 53 calculates the estimated representative temperature T A is the threshold value of the given representative temperature T A0 If it is determined that the temperature exceeds the threshold value (YES in step S31), the water temperature of the supply water is lowered (step S32).

[0061] On the other hand, in the process of step S31, the operating condition formulation unit 53 calculates the estimated representative temperature T A is the threshold value of the given representative temperature T A0 If it is determined that the number of times ...

[0062] If the determination in step S31 is NO, or after the process in step S32, the operating condition formulation unit 53 determines the maximum temperature T M (T A +ΔT N ) is calculated (step S33).

[0063] Next, the operating condition formulation unit 53 determines the maximum temperature T M is the pre-registered maximum temperature threshold T M0 It is determined whether or not the difference exceeds the threshold (step S34).

[0064] In the process of step S34, the operating condition formulation unit 53 determines the maximum temperature T M is the predetermined maximum temperature threshold T M0 If it is determined that the flow rate of the supply water exceeds the predetermined value (YES in step S34), the flow rate of the supply water is increased (step S35).

[0065] On the other hand, in the process of step S34, the operating condition formulation unit 53 determines the maximum temperature T M is the predetermined maximum temperature threshold T M0If it is determined that the number of times ...

[0066] If the determination in step S34 is NO, or after the process of step S35, the operating condition formulation unit 53 continues the operation of the water electrolysis stack 10 under the set operating conditions (step S36). After the process of step S36, the operating condition formulation process ends.

[0067] [Water electrolysis stack characteristic measurement operation] Next, the characteristic measurement operation of the water electrolysis stack 10 under a plurality of flow rate conditions will be described. Fig. 15 is a diagram showing the procedure of Example 1 of the characteristic measurement operation of the water electrolysis stack 10 under a plurality of flow rate conditions in the water electrolysis system 1 according to this embodiment. The process described below is called as a subroutine in step S10 shown in Fig. 12, and is repeatedly executed the number of times (e.g., N) for the flow rate conditions registered in advance.

[0068] First, the operating condition generator 53 of the water electrolysis control device 50 sets the flow rates in accordance with pre-registered flow rate conditions (step S101).

[0069] Next, the operating condition formulating unit 53 causes the water electrolysis stack 10 to wait until the water flow rate inside the water electrolysis stack 10 becomes stable (step S102).

[0070] Next, the operating condition formulating unit 53 changes the current or voltage supplied to the water electrolysis stack 10 in a stepwise manner (step S103). In this process, the operating condition formulating unit 53 changes the current or voltage in a step form, for example, as shown in Fig. 16 described below. Note that the size and number of steps may be changed depending on the accuracy of the characteristic measurement.

[0071] Next, the operating condition formulating unit 53 measures the voltage or current of the water electrolysis stack 10 (step S104). After the process of step S104, the current loop ends.

[0072] FIG. 16 is a diagram showing example 1 of changes over time in water flow rate and current when measuring the characteristics of the water electrolysis stack 10 in the water electrolysis system 1 according to the present embodiment. In FIG. 16, the curve drawn with a dashed line indicates the change over time in water flow rate. Moreover, the curve drawn with a solid line indicates the change over time in current. As shown in FIG. 16, during the period of each flow rate condition, the current changes in a step shape, and the time change characteristic of the current has the same step shape. Although an example in which the current is changed in a step shape has been described in FIGS. 15 and 16, the present invention is not limited thereto, and when measuring the current of the water electrolysis stack 10, the voltage may be changed in a step shape.

[0073] Fig. 17 is a diagram showing a procedure of Example 2 of the operation for measuring the characteristics of the water electrolysis stack 10 under a plurality of flow rate conditions in the water electrolysis system 1 according to the present embodiment. The steps other than step S103a of the process shown in Fig. 17 are the same as the steps shown in Fig. 15, and therefore repeated description will be omitted.

[0074] In the process of step S103a, the operation condition formulating unit 53 sweeps the current or voltage supplied to the water electrolysis stack 10 (step S103a). In this process, the operation condition formulating unit 53 changes the current or voltage, for example, like a sweep current shown in Fig. 18 described later.

[0075] Fig. 18 is a diagram showing a second example of time changes in water flow rate and current when measuring the characteristics of the water electrolysis stack 10 in the water electrolysis system 1 according to the present embodiment. The time change characteristic of the water flow rate shown in Fig. 18 is the same as the time change of the water flow rate shown in Fig. 16, so a duplicated description will be omitted. The time change of current shown in Fig. 18 is the same sweep current for the period of each flow rate condition. Note that, although Figs. 17 and 18 have described examples in which the current is swept to change, the present invention is not limited thereto, and when measuring the current of the water electrolysis stack 10, the voltage may be swept to change it.

[0076] In the present embodiment, the characteristic measurement operation under a plurality of flow rate conditions has been described, but the present invention is not limited thereto. In the water electrolysis system 1, in addition to a plurality of flow rate conditions, the characteristic measurement operation under a plurality of temperature conditions (temperature of the water electrolysis stack 10 or temperature of the supply water) may also be performed. In the present embodiment, the characteristic measurement target is the water electrolysis stack 10, but the present invention is not limited thereto. For example, the water electrolysis stack 10 may be composed of 60 water electrolysis cells, and characteristic measurement may be performed for every 10 water electrolysis cells. In this case, six measurements are performed on the water electrolysis stack 10. When the unit of measurement per time is smaller (when the number of water electrolysis cells is smaller), the time and cost required for measurement increase, but the estimation accuracy of the temperature distribution improves.

[0077] [Example of hardware configuration for water electrolysis control device] Next, an example of a hardware configuration of the water electrolysis control device 50 will be described. Fig. 19 is a diagram showing an example of a hardware configuration of the water electrolysis control device 50 according to the present embodiment. As shown in Fig. 19, the water electrolysis control device 50 includes a central processing unit (CPU) 50a, a read only memory (ROM) 50b, and a random access memory (RAM) 50c, each of which is connected to a bus 50d. The water electrolysis control device 50 further includes a non-volatile storage 50e and a network interface 50f.

[0078] The CPU 50a reads out the program code of the software for realizing each function according to the present embodiment from the ROM 50b, loads it into the RAM 50c, and executes it. Variables and parameters generated during the arithmetic processing of the CPU 50a are temporarily written into the RAM 50c, and these variables and parameters are read out by the CPU 50a as appropriate. However, an MPU (Micro Processing Unit) may be used instead of the CPU 50a.

[0079] The nonvolatile storage 50e may be, for example, a hard disk drive (HDD), a solid state drive (SSD), a flexible disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, or a nonvolatile memory. The nonvolatile storage 50e stores an operating system (OS) and various parameters, as well as programs for operating the water electrolysis control device 50. The ROM 50b and the nonvolatile storage 50e store programs, data, and the like necessary for the CPU 50a to operate, and are used as an example of a computer-readable non-transitory storage medium storing programs executed by the water electrolysis control device 50.

[0080] The network interface 50f may be, for example, a network interface card (NIC), and various data can be transmitted and received between devices via a local area network (LAN) or dedicated line connected to a terminal of the NIC.

[0081] [effect] As described above, the water electrolysis control device 50 of the water electrolysis system 1 according to the present embodiment measures the voltage (current) of the water electrolysis stack 10 and analyzes the transient response of the voltage (current). The water electrolysis control device 50 estimates the distribution of the resistance components of the water electrolysis stack 10 based on the analysis result of the transient response of the voltage (current) (average time constant and exponent) and the correspondence between the previously acquired characteristic values ​​and the standard deviation of the time constant distribution of the water electrolysis stack 10. The water electrolysis control device 50 estimates the temperature distribution (representative temperature) inside the water electrolysis stack 10 based on the measured characteristic values ​​and the correspondence between the previously acquired characteristic values ​​and the temperature distribution (representative temperature). The water electrolysis system 1 controls the operation by adjusting the flow rate (water temperature) of water supplied to the water electrolysis stack 10 according to the estimated temperature distribution (representative temperature) so that the temperature does not become too high, which may cause deterioration of the water electrolysis stack 10. Therefore, the water electrolysis system 1 according to the present embodiment is able to grasp the temperature distribution inside the water electrolysis stack and suppress deterioration of the water electrolysis stack due to high temperatures.

[0082] <Second embodiment> Next, a water electrolysis system 2 according to a second embodiment of the present invention will be described. Fig. 20 is a block diagram showing a configuration example of the water electrolysis system 2 according to the second embodiment of the present invention. As can be seen by comparing Fig. 20 with Fig. 1, the water electrolysis system 2 further includes a deterioration prediction unit 54 in addition to the components shown in Fig. 1. Note that the components shown in Fig. 20 other than the deterioration prediction unit 54 are the same as the components of the water electrolysis system 1 shown in Fig. 1, and therefore repeated description will be omitted.

[0083] The deterioration prediction unit 54 predicts future deterioration of the water electrolysis cells based on deterioration characteristics, which are the relationship between the deterioration rate and operating conditions of the water electrolysis cells of the water electrolysis stack 10, and the estimated temperature distribution. Even under the same operating conditions, deterioration of water electrolysis cells with high temperatures is more likely to progress. When the operating temperature of the water electrolysis cells increases by 5°C, the membrane deterioration rate tends to increase by about 1.3 times. For this reason, in this embodiment, the operating condition formulation unit 53 formulates operating conditions for the water electrolysis stack 10 so as to suppress the future deterioration of the water electrolysis cells predicted by the deterioration prediction unit 54.

[0084] The deterioration prediction unit 54 selects a plurality of representative points from the temperature distribution inside the water electrolysis stack 10 estimated by the temperature distribution estimation unit 52. The representative points include, for example, points where the temperature is particularly high, particularly low, or intermediate. The deterioration prediction unit 54 also estimates the relationship between the deterioration rate of the water electrolysis cell and the operating conditions for each of the selected representative points, and predicts future deterioration of the water electrolysis cell at each of the representative points. The deterioration prediction unit 54 estimates future deterioration of the water electrolysis cell based on the operating conditions corresponding to each of the representative points and the initial state (undegraded state) of the water electrolysis stack 10. Therefore, the operating condition formulation unit 53 formulates operating conditions for the water electrolysis stack so as to suppress the future deterioration of the water electrolysis cell predicted at each of the representative points. Here, the operating conditions corresponding to the representative points of the temperature distribution include the temperature of the supply water, the flow rate of the supply water, the operating power (current or voltage), and the operating pressure at the time of estimating the temperature distribution at the representative points.

[0085] 21 is a diagram showing a procedure of the operation control process based on future deterioration of the water electrolysis stack 10 in the water electrolysis system 2 according to this embodiment. The process described below starts when the temperature distribution estimation process ends.

[0086] First, the deterioration predicting unit 54 acquires information (estimated result) of the temperature distribution estimated by the temperature distribution estimating unit 52 (step S40).

[0087] Next, the deterioration predicting unit 54 selects a representative point from the temperature distribution (step S41).

[0088] Next, the deterioration prediction unit 54 estimates future deterioration of the water electrolysis stack 10 based on the operating conditions corresponding to each of the selected representative points and the initial state of the water electrolysis stack 10 (step S42).

[0089] Next, the operation condition formulating unit 53 formulates operation conditions capable of suppressing future deterioration based on the information on the temperature distribution and future deterioration of the water electrolysis stack 10, and performs operation control (step S43). After the process of step S43, the operation control process based on the future deterioration is terminated.

[0090] [effect] As described above, the water electrolysis system 2 according to the present embodiment determines operating conditions capable of suppressing future deterioration based on information on predicted future deterioration of the water electrolysis stack, as well as the estimated temperature distribution of the water electrolysis stack 10. Therefore, the water electrolysis system 2 according to the present embodiment has the same effects as the water electrolysis system 1 according to the first embodiment, and can also improve the effect of suppressing deterioration of the water electrolysis stack.

[0091] <Third embodiment> Next, a water electrolysis system 3 according to a third embodiment of the present invention will be described. FIG. 22 is a block diagram showing a configuration example of the water electrolysis system 3 according to the third embodiment of the present invention. As can be seen by comparing FIG. 22 with FIG. 1, the water electrolysis system 3 includes a plurality of water electrolysis stacks (for example, water electrolysis stacks 10a to 10d shown in the figure) connected in series, and auxiliary units (auxiliary units 30a to 30d) connected to the plurality of water electrolysis stacks, respectively. The plurality of water electrolysis stacks are divided into a plurality of blocks (for example, blocks 61 and 62 shown in the figure). The block 61 includes the water electrolysis stacks 10a and 10b. The block 62 includes the water electrolysis stacks 10c and 10d. In the water electrolysis system 3, one measuring instrument (measuring instrument 20a to measuring instrument 20b) is connected to each block. Specifically, the measuring instrument 20a is connected to the block 61, and the measuring instrument 20b is connected to the block 62. 22. The same components as those in the water electrolysis system 3 shown in FIG. 22 and the water electrolysis system 1 shown in FIG. 1 will not be described repeatedly.

[0092] In this embodiment, when each water electrolysis stack is operated under the same operating conditions, the temperature distribution estimation unit 52 of the water electrolysis system 3 estimates the temperature distribution for each block using the characteristic measurement data for each block. This is because, when the operating conditions are the same, it is difficult to distinguish between the measurement data for each water electrolysis stack and the measurement data between the water electrolysis stacks. In this embodiment, the operating condition formulation unit 53 formulates the operating conditions for each block based on the temperature distribution for each block.

[0093] Furthermore, when each water electrolysis stack included in a block is operated under different operating conditions by each auxiliary machine (controller), the temperature distribution estimation unit 52 estimates the internal temperature distribution of each water electrolysis stack using the characteristic measurement data of each water electrolysis stack included in the block. Therefore, the operating condition formulation unit 53 formulates operating conditions for each water electrolysis stack based on the respective temperature distributions of each water electrolysis stack.

[0094] In the above description, the water electrolysis system 3 includes two water electrolysis stacks each as one block, but the present invention is not limited to this. The number of water electrolysis stacks included in each block may be changed depending on the total number of water electrolysis stacks.

[0095] [effect] As described above, the water electrolysis control device 50 of the water electrolysis system 3 according to the present embodiment includes a plurality of water electrolysis stacks connected in series, and controls the plurality of water electrolysis stacks by dividing them into a plurality of blocks. The water electrolysis control device 50 of the water electrolysis system 3 estimates the temperature distribution for each block to control the operating conditions. Furthermore, when the water electrolysis stacks included in a block are operated under different operating conditions, the water electrolysis system 3 can also estimate the temperature distribution for each water electrolysis stack to control the operating conditions. Therefore, the water electrolysis system 3 according to the present embodiment has the same effects as the water electrolysis system 1 according to the first embodiment, and when the water electrolysis system 3 includes a plurality of water electrolysis stacks, the water electrolysis system 3 can reduce the load of the control process by estimating the temperature distribution for each block to control the operating conditions.

[0096] <Fourth embodiment> Next, a water electrolysis system 4 according to a fourth embodiment of the present invention will be described. FIG. 23 is a block diagram showing a configuration example of the water electrolysis system 4 according to the fourth embodiment of the present invention. As can be seen by comparing FIG. 23 with FIG. 20, the water electrolysis system 4 includes a plurality of water electrolysis stacks (for example, the water electrolysis stacks 10a and 10b shown in the figure) connected in parallel. Furthermore, a power converter (a power converter 70a and a power converter 70b) is connected to each of the water electrolysis stacks (the water electrolysis stacks 10a and 10b). Each power converter is also connected to a power source 40 and a water electrolysis control device 50, and adjusts the amount of power supplied to the connected water electrolysis stack according to a current command from the water electrolysis control device 50. Note that a duplicated description of the components that are the same as those of the water electrolysis system 4 shown in FIG. 23 and the water electrolysis system 2 shown in FIG. 20 will be omitted.

[0097] In this embodiment, the operating condition formulating unit 53 formulates a distribution of power amounts and power waveforms among the multiple water electrolysis stacks so as to level out the progression of deterioration of the multiple water electrolysis stacks, based on information on future deterioration of each water electrolysis stack predicted by the deterioration prediction unit 54. Specifically, the operating condition formulating unit 53 formulates a distribution of power amounts and power waveforms among the parallel water electrolysis stacks so as to level out the progression of deterioration of the multiple water electrolysis stacks, based on the predicted power waveforms after distribution and the relationship between the power amounts and the deterioration rates. Furthermore, the operating condition formulating unit 53 generates and outputs power commands for each power converter, based on the formulated distribution of power amounts and power waveforms.

[0098] [effect] As described above, the water electrolysis system 4 according to the present embodiment controls the supply of power by determining the distribution of power amounts and power waveforms so as to level out the progression of deterioration of each water electrolysis stack connected in parallel. Therefore, the water electrolysis system 4 according to the present embodiment has the same effects as the water electrolysis system 1 according to the first embodiment, and can also level out the progression of deterioration of multiple water electrolysis stacks.

[0099] <Fifth embodiment> Next, a water electrolysis system 2a according to a fifth embodiment of the present invention will be described. In the fifth embodiment of the present invention, the water electrolysis system 2a is linked to a power transmission and distribution system 80 to predict future deterioration according to the state of power supply and demand, and also predicts the demand for hydrogen production by the water electrolysis stack based on the estimated temperature distribution. The water electrolysis system 2a also formulates operating conditions that can simultaneously suppress deterioration of the water electrolysis stack 10 and adjust supply and demand based on the predicted future deterioration and the demand for power. FIG. 24 is a block diagram showing an example of a configuration of cooperation between the water electrolysis system 2a according to the fifth embodiment of the present invention and the power transmission and distribution system 80. The components of the water electrolysis system 2a other than the deterioration prediction unit 54a and the operating condition formulation unit 53a have been described in FIG. 20, and therefore will not be described again. As shown in FIG. 24, the power transmission and distribution system 80 includes a power system 81, a distributor 82, a hydrogen distribution and heat generation unit 83, and a consumer 84. A management system 90 is connected to the water electrolysis system 2a and the power transmission and distribution system 80.

[0100] The power transmission and distribution system 80 supplies power to the water electrolysis stack 10, and also supplies power to consumers 84 to which hydrogen is supplied from the water electrolysis stack 10. The power system 81, the distributor 82, and the consumers 84 are connected in this order. The distributor 82 is connected to the water electrolysis stack 10 of the water electrolysis system 2, and the water electrolysis stack 10 is further connected to a hydrogen distribution and heat generation unit 83.

[0101] The power grid 81 supplies electric power to the water electrolysis stack 10 in the water electrolysis system 2 and consumers 84 via a distributor 82 in accordance with a power instruction from a management system 90.

[0102] The distributor 82 supplies the power provided by the power grid 81 to the water electrolysis stack 10 in the water electrolysis system 2 and to consumers 84 in accordance with the distribution power ratio input from the management system 90.

[0103] The management system 90 outputs a hydrogen supply instruction to the water electrolysis system 2 in response to the hydrogen requested by the consumer 84 (supply target). The management system 90 also outputs a hydrogen distribution instruction or a heat generation instruction to the hydrogen distribution and heat generation unit 83 in response to a hydrogen or heat request from the consumer 84 (supply target). The management system 90 also generates and outputs to the distributor 82 a power distribution ratio between the water electrolysis stack 10 and the consumer 84 in response to the power demand for hydrogen production predicted by the deterioration prediction unit 54 of the water electrolysis control device 50 and the power requested by the consumer 84 (supply target).

[0104] The management system 90 is composed of a calculation unit, a storage unit, a communication unit, an operation unit, and a display screen for realizing the above functions. Specifically, the management system 90 includes, for example, a CPU, a ROM, a RAM, a non-volatile storage, an input / output interface, and a network interface.

[0105] The hydrogen distribution and heat generation unit 83 issues hydrogen distribution instructions or generates heat in accordance with hydrogen distribution instructions or heat generation instructions from the management system 90. Hydrogen distribution methods include a method of filling a container with hydrogen in the form of high-pressure hydrogen gas, liquefied hydrogen, organic hydride, etc. and transporting it, and a method of transporting it through a gas pipeline. Specific examples of hydrogen distribution instructions include instructions to change container filling and transportation, instructions to start, stop, and change the quantity and speed of pipeline transportation, etc. Methods of heat generation include a method of using combustion equipment that uses hydrogen as fuel, and a method of recovering exhaust heat from power generation equipment that uses hydrogen as fuel, etc. Specific examples of heat generation instructions include instructions to start, stop, and change the output of combustion equipment and power generation equipment, etc.

[0106] The hydrogen distribution and heat generation unit 83 is composed of a calculation unit, a storage unit, and a communication unit for realizing the above functions. Specifically, the hydrogen distribution and heat generation unit 83 includes, for example, a CPU, a RAM, a ROM, and a network interface.

[0107] The deterioration prediction unit 54a of the water electrolysis control device 50 in the water electrolysis system 2a predicts future deterioration of the water electrolysis stack 10, and also predicts the power demand required for hydrogen production by the water electrolysis stack 10, based on the estimated temperature distribution of the water electrolysis stack 10. In addition, the deterioration prediction unit 54a outputs the predicted power demand to the management system 90.

[0108] The operating condition formulation unit 53a of the water electrolysis control device 50 of the water electrolysis system 2a formulates operating conditions that can simultaneously suppress deterioration of the water electrolysis stack 10 and adjust supply and demand, based on the future deterioration and electric power demand predicted by the deterioration prediction unit 54a.

[0109] [effect] As described above, the water electrolysis control device 50 of the water electrolysis system 2 according to this embodiment is connected to the power transmission and distribution system 80, and predicts future deterioration based on the amount of power and temperature distribution required to supply hydrogen demanded by consumers 84 (supply targets). Furthermore, based on the predicted future deterioration and the demand for power for hydrogen production, the water electrolysis control device 50 determines operating conditions that can both suppress deterioration of the water electrolysis stack 10 and adjust supply and demand, and controls the operation of the water electrolysis stack 10. Therefore, the water electrolysis system 2 according to this embodiment can both suppress deterioration of the water electrolysis stack 10 and adjust supply and demand (system stabilization).

[0110] It should be noted that the present invention is not limited to the above-described embodiments, and various other applications and modifications are possible without departing from the gist of the present invention as set forth in the claims. For example, each of the above-described embodiments describes the configuration of a water electrolysis system in detail and specifically in order to clearly explain the present invention, and is not necessarily limited to having all of the described configurations. In addition, it is possible to replace part of the configuration of the embodiments described here with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is also possible to add, delete, or replace part of the configuration of each embodiment with another configuration. In addition, the control lines and information lines shown are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are connected to each other. [Explanation of symbols]

[0111] 1, 2, 2a, 3, 4... Water electrolysis system, 10, 10a, 10b, 10c, 10d... Water electrolysis stack, 20, 20a, 20b... Measuring instrument, 30, 30a, 30d... Auxiliary equipment, 40... Power source, 50... Water electrolysis control device, 51... Measurement data receiving unit, 52... Temperature distribution estimating unit, 53, 53a... Operating condition formulating unit, 54, 54a... Deterioration predicting unit, 61, 62... Block, 70a, 70b... Power converter, 80... Power transmission and distribution system, 81... Power system, 82... Distributor, 83... Hydrogen distribution and heat generation unit, 90... Management system

Claims

1. a temperature distribution estimation unit that, when a plurality of different water flow rates are supplied to a water electrolysis stack including a plurality of water electrolysis cells, estimates a temperature distribution inside the water electrolysis stack using characteristic measurement data that is data for measuring characteristic values ​​related to a temperature distribution inside the water electrolysis stack corresponding to each of the plurality of water flow rates; an operating condition formulation unit that formulates operating conditions for the water electrolysis stack based on the temperature distribution inside the water electrolysis stack estimated by the temperature distribution estimation unit. Water electrolysis system.

2. The characteristic value is an index for evaluating the nonuniformity of the time constant distribution of the transient response of the voltage to the current change of the water electrolysis stack. The water electrolysis system according to claim 1 .

3. The temperature distribution estimation unit calculates an average time constant and the exponent of the transient response by analyzing a fitting function of the transient response of the voltage, identifies the characteristic value when an infinite water flow rate is supplied to the water electrolysis stack, and estimates the temperature distribution based on the characteristic values ​​corresponding to each of the water flow rates when a plurality of different water flow rates are supplied, the characteristic value when the identified infinite water flow rate is supplied, and a correspondence relationship between the characteristic value and the temperature distribution measured in advance. The water electrolysis system according to claim 2 .

4. The temperature distribution estimation unit estimates the temperature distribution based on the characteristic values ​​and the correspondence relationships between the characteristic values ​​and the temperature distributions, which are previously acquired in another water electrolysis stack having the same configuration as the water electrolysis stack. The water electrolysis system according to claim 3.

5. The temperature distribution estimation unit analyzes a correspondence relationship between the characteristic value and the temperature distribution of the other water electrolysis stack using a distribution function of a temperature distribution over a predetermined period inside the other water electrolysis stack, the distribution function having been previously acquired for the other water electrolysis stack, and estimates the temperature distribution. The water electrolysis system according to claim 4.

6. The temperature distribution estimation unit estimates a representative temperature, which is a temperature of a component of the water electrolysis cell, based on the average time constant, and estimates a maximum temperature inside the water electrolysis stack from the estimated representative temperature and the temperature distribution. The water electrolysis system according to claim 3.

7. The current change in the water electrolysis stack is a step-like current change. The water electrolysis system according to claim 2 .

8. a deterioration prediction unit that predicts future deterioration of the water electrolysis cell based on a deterioration characteristic, which is a relationship between a deterioration rate of the water electrolysis cell and the operating conditions, and on the temperature distribution, The operating condition formulation unit formulates the operating conditions of the water electrolysis stack so as to suppress future deterioration of the water electrolysis cells predicted by the deterioration prediction unit. The water electrolysis system according to claim 1 .

9. the deterioration prediction unit selects a plurality of representative points from the temperature distribution, estimates a relationship between a deterioration rate of the water electrolysis cell and the operating conditions for each of the plurality of representative points, and predicts future deterioration of the water electrolysis cell at each of the plurality of representative points; The operating condition formulation unit formulates the operating conditions of the water electrolysis stack so as to suppress future deterioration of the water electrolysis cells predicted at each of the representative points. The water electrolysis system according to claim 8.

10. The water electrolysis stack is a plurality of water electrolysis stacks connected in series, the plurality of water electrolysis stacks are divided into a plurality of blocks, and each block includes a predetermined number of the water electrolysis stacks; the temperature distribution estimation unit estimates the temperature distribution for each of the blocks; The operating condition formulation unit formulates operating conditions for each of the blocks based on the temperature distribution for each of the blocks. The water electrolysis system according to claim 1 .

11. a controller for controlling the operating conditions of each of the plurality of water electrolysis stacks; When the controller causes each water electrolysis stack included in the block to operate under different operating conditions, the temperature distribution estimation unit estimates an internal temperature distribution of each water electrolysis stack using characteristic measurement data of each water electrolysis stack included in the block; The operating condition formulation unit formulates operating conditions for each water electrolysis stack based on a temperature distribution of each water electrolysis stack. The water electrolysis system according to claim 10.

12. the water electrolysis stack is a plurality of water electrolysis stacks connected in parallel, The operating condition formulation unit formulates a distribution of power amounts and power waveforms among the plurality of water electrolysis stacks so as to level out the progress of deterioration of the plurality of water electrolysis stacks based on information on future deterioration of each water electrolysis stack predicted by the deterioration prediction unit. The water electrolysis system according to claim 8.

13. a power transmission and distribution system that supplies power to the water electrolysis stack also supplies power to a hydrogen supply target of the water electrolysis stack; the degradation prediction unit predicts future degradation of the water electrolysis stack and predicts an amount of power demand required for hydrogen production by the water electrolysis stack based on the estimated temperature distribution of the water electrolysis stack, and outputs the predicted amount of power demand to a management system that controls a power supply operation of the power transmission and distribution system; the operating condition formulation unit formulates operating conditions for the water electrolysis stack based on the future deterioration and the demanded power amount predicted by the deterioration prediction unit; The management system generates and outputs a power supply distribution ratio between the water electrolysis stack and the supply target in accordance with the power demand of the water electrolysis stack and the power request of the supply target. The water electrolysis system according to claim 8.

14. when a plurality of different water flow rates are supplied to a water electrolysis stack including a plurality of water electrolysis cells, estimating a temperature distribution inside the water electrolysis stack using characteristic measurement data, which is data for measuring characteristic values ​​related to a temperature distribution inside the water electrolysis stack corresponding to each of the plurality of water flow rates; determining operating conditions for the water electrolysis stack based on the estimated temperature distribution inside the water electrolysis stack. Water electrolysis control method.

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