SOLID OXIDE CELL STATE ESTIMATION DEVICE, SOLID OXIDE CELL SYSTEM, SOLID OXIDE CELL STATE ESTIMATION METHOD, AND COMPUTER PROGRAM

Abstract

To estimate a state of a solid oxide type cell at a low cost and in a simple manner.SOLUTION: An apparatus for estimating a state of a solid oxide type cell includes: an acquisition unit for acquiring an impedance of a specific frequency in the solid oxide type cell; and an estimation unit for estimating a degradation state of the solid oxide type cell using any of the components constituting the acquired impedance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for estimating the state of a solid oxide cell. [Background technology]

[0002] Solid oxide electrolyzer cells (SOECs) and solid oxide fuel cells (SOFCs) using solid oxide cells are known (see, for example, Patent Documents 1 and 2). The technology described in Patent Document 1 evaluates the integrity of SOFCs using an impedance spectrum obtained by measuring impedance over a wide frequency range. The technology described in Patent Document 2 measures impedance over a wide frequency range and derives the ohmic resistance, anode reaction resistance, and cathode reaction resistance of the SOFC from a Cole-Cole plot using the measured impedance spectrum. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4488284 [Patent Document 2] Patent No. 6163933 Summary of the Invention [Problem to be solved by the invention]

[0004] The techniques described in Patent Documents 1 and 2 require impedance measurement over a wide frequency range to measure the integrity and ohmic resistance of SOFCs. Measuring impedance over a wide frequency range for a large SOFC system made up of multiple cell stacks requires many measuring devices. Because SOFC impedance measuring devices are expensive, it is extremely costly to measure the integrity and ohmic resistance of an SOFC system made up of multiple cell stacks.

[0005] The present invention has been made to solve at least part of the above-mentioned problems, and has an object to easily estimate the state of a solid oxide cell at low cost. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms. A state estimating device for a solid oxide cell, comprising: an acquisition unit that acquires impedance of the solid oxide cell at a frequency of 100 Hz or more and 10 kHz or less, the impedance including a component representing an absolute value of resistance, a component representing a phase difference, a component representing a real part of resistance, and a component representing an imaginary part of resistance, and an estimation unit that estimates a degradation state of the solid oxide cell using a rate of change obtained by dividing the imaginary part of resistance in the acquired impedance by the imaginary part of resistance at the start of steam electrolysis.The present invention can also be realized in the following forms.

[0007] (1) According to one aspect of the present invention, there is provided a state estimation device for a solid oxide cell, comprising: an acquisition unit that acquires impedance at a specific frequency in the solid oxide cell; and an estimation unit that estimates a degradation state of the solid oxide cell using any component of the acquired impedance.

[0008] According to this configuration, the impedance corresponding to a specific frequency of the solid oxide cell is acquired. The degradation state of the solid oxide cell is estimated using any of the components of the acquired impedance. In this configuration, instead of measuring impedance over a wide frequency range, the frequency measurement is limited to one or a few points. This simplifies the state estimation device and reduces the cost of estimating the degradation state of the solid oxide cell. Furthermore, by feeding back the estimated degradation state of the solid oxide cell to the operating condition control of large-scale SOEC or SOFC systems, which require complex solid oxide cell replacement and maintenance, the system's lifespan can be extended.

[0009] (2) In the state estimating device of the above aspect, the estimating unit may estimate the degradation state using a rate of change in any one of components that make up the impedance obtained from the solid oxide cell. According to this configuration, the degradation state of the solid oxide cell is estimated by using the rate of change of any of the components that make up the acquired impedance. By using the rate of change instead of the component's actual value, the degradation state of the solid oxide cell can be more appropriately estimated.

[0010] (3) In the state estimation device of the above aspect, the acquisition unit may use a frequency of 100 Hz or more and 10 kHz or less as the specific frequency. According to this configuration, the specific frequency applied to the solid oxide cell to measure the impedance is between 100 Hz and 10 kHz. Therefore, the rate of change of the impedance component with respect to the frequency in this range is more sensitive to the degradation state of the solid oxide cell than in other frequency ranges. In other words, by setting the specific frequency between 100 Hz and 10 kHz, the degradation state can be more appropriately estimated.

[0011] (4) In the state estimation device of the above aspect, the impedance acquired from the solid oxide cell includes a component representing an absolute value of resistance, a component representing a phase difference, a component representing a real part of resistance, and a component representing an imaginary part of resistance, and the estimation unit may estimate the degradation state using a rate of change of the component representing the imaginary part of resistance. According to this configuration, the component representing the imaginary part of the resistance in the measured impedance is used to estimate the degradation state of the solid oxide cell. The rate of change in the imaginary part of the resistance in the impedance has a higher sensitivity to the degradation state of the solid oxide cell than other components. In other words, by using the imaginary part of the resistance in the impedance, the degradation state can be more appropriately estimated.

[0012] (5) In the state estimation device of the above aspect, the estimation unit may change the specific frequency used to newly estimate the degradation state, depending on the degradation state estimated in the past. According to this configuration, a specific frequency for newly estimating the state of degradation is determined based on a specific frequency used in a previous estimation of the state of degradation. Therefore, the specific frequency with the highest sensitivity to the rate of change when previously estimating the state of degradation can be used to newly estimate the state of degradation. As a result, the state of degradation of the solid oxide cell can be newly estimated more appropriately.

[0013] (6) The state estimation device of the above aspect may further include a memory unit that stores estimation reference data that associates the previously estimated degradation state with the change rate, and the estimation unit may determine the degradation state of the solid oxide cell from which the impedance has been acquired by comparing the change rate from the acquired impedance with the change rate included in the stored estimation reference data. According to this configuration, the state of degradation of a solid oxide cell whose impedance has been newly measured is estimated using the rate of change calculated from the impedance based on a previously estimated state of degradation. Therefore, by referring to the state of degradation associated with the rate of change of the component calculated from the impedance among the data on the previously estimated state of degradation, the state of degradation of the solid oxide cell whose impedance has been measured can be easily estimated.

[0014] (7) In the state estimating device of the above aspect, the solid oxide cell may be a solid oxide electrolysis cell used in a steam electrolysis device. According to this configuration, since the solid oxide cell is the cell used in the SOEC, it is possible to operate the SOEC system with an extended life.

[0015] (8) According to another aspect of the present invention, there is provided a solid oxide cell system comprising the solid oxide cell, the state estimation device of the above aspect, and an operation control unit that controls the amount of hydrogen generated by the solid oxide cell using supplied steam, and the operation control unit may control the amount of hydrogen generated by the solid oxide cell in accordance with the degradation state estimated by the estimation unit. According to this configuration, the amount of hydrogen produced by the solid oxide cells is controlled according to the state of degradation of the solid oxide cells. That is, the estimated state of degradation is fed back to control the amount of hydrogen produced by the solid oxide cells, thereby suppressing the rate at which the solid oxide cells deteriorate, and enabling operation of the solid oxide cell system of this configuration with an extended lifespan.

[0016] The present invention can be realized in various forms, such as a solid oxide cell state estimation device, an SOEC system, an SOFC system, a solid oxide cell state estimation method and a system including these devices, a computer program for executing these devices, a server device for distributing this computer program, and a non-transitory storage medium storing the computer program. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic block diagram of a state estimation device provided in an SOEC system according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram illustrating the change over time of the imaginary part of the resistance for each frequency. [Figure 3] FIG. 10 is an explanatory diagram of the change over time in each component of impedance when the frequency is 1 kHz. [Figure 4] FIG. 1 is an explanatory diagram of an accelerated durability test of an SOEC. [Figure 5] 1 is a flowchart of a state estimation method for an SOEC according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] <Embodiment> 1. State estimator configuration: FIG. 1 is a schematic block diagram of a state estimation device 10 included in an SOEC system 100 according to one embodiment of the present invention. As shown in FIG. 1, the SOEC system (solid oxide cell system) 100 includes a solid oxide electrolyzer cell (SOEC) 40 that generates hydrogen from supplied water vapor, a power source PS that supplies the power required for the SOEC 40 to generate hydrogen, and a state estimation device 10 that estimates the degradation state of the SOEC 40. In this embodiment, the state estimation device 10 measures the impedance of the SOEC 40 while the SOEC 40 is generating hydrogen from water vapor using the power supplied from the power source PS. The state estimation device 10 estimates the degradation state of the SOEC 40 using the rate of change in the imaginary part of the resistance, which is one of the components included in the measured impedance.

[0019] The SOEC 40 is a cell stack consisting of multiple solid oxide cells. Each solid oxide cell is composed of an electrolyte layer (not shown) capable of conducting oxide ions within a solid, an air electrode disposed on one side of the electrolyte layer, and an anode disposed on the other side of the electrolyte layer. In this embodiment, the solid oxide cell is heated to 700 degrees Celsius (°C), air is introduced into the air electrode, and a gas containing water vapor is introduced into the anode. Power is applied between the air electrode and the anode from a power source PS. As a result, water vapor is electrolyzed at the anode to produce hydrogen gas and oxide ions, and the hydrogen gas is obtained as the anode output gas. Meanwhile, the oxide ions generated at the anode are conducted through the electrolyte layer from the anode side to the air electrode side. The oxide ions conducted to the air electrode are oxidized to produce oxygen gas, which is discharged as the cathode output gas.

[0020] The state estimation device 10 controls steam electrolysis using the SOEC 40 and performs impedance measurements using a specific frequency during steam electrolysis. As shown in FIG. 1 , the state estimation device 10 includes a detection device 30 that applies a voltage amplitude of a specific frequency to the SOEC 40 and detects a current response, and a control device 20 that estimates the degradation state of the SOEC 40. In this embodiment, the detection device 30 applies a voltage amplitude of a frequency not less than 100 Hz and not more than 10 kHz to the SOEC 40 as the specific frequency. The voltage amplitude of the specific frequency applied to the SOEC 40 is determined by the control device 20. Note that in other embodiments, a current amplitude of the specific frequency may be applied to the SOEC 40 and the voltage response may be detected.

[0021] The control device 20 is a personal computer that performs various processes in accordance with user operations received by a user interface consisting of a keyboard and mouse (not shown) and detection values ​​of the detection device 30. As shown in Fig. 1, the control device 20 includes a CPU (Central Processing Unit) 25 and a storage unit 26 that stores various data.

[0022] The storage unit 26 is configured with a hard disk drive (HDD) etc. The storage unit 26 includes a detection database (detection DB) 27 that stores time-series data of the detection values ​​of the detection device 30, and an estimation database (estimation DB) 28 that is used to estimate the degradation state of the SOEC 40.

[0023] The detection DB 27 stores time-series data correlating the voltage amplitude applied to the SOEC 40 by the detection device 30 with the current response, which is the value detected by the detection device 30, to the voltage amplitude. The estimation DB 28 stores estimation reference data correlating the deterioration state, which indicates the life of the SOEC and was measured in advance using an SOEC different from the SOEC 40, with the rate of change in the impedance component. The correlation between the deterioration state and the rate of change in the impedance component will be described later.

[0024] The CPU 25 controls the SOEC 40 and the power supply PS by expanding and executing a computer program stored in a ROM (Read Only Memory) not shown in the figure into a RAM (Random Access Memory), and also functions as a component calculation unit 21, a ratio calculation unit 22, a deterioration estimation unit 23, and an operation control unit 24.

[0025] Using the voltage amplitude applied to the SOEC 40 and the current response, which is the detection value of the detection device 30, the component calculation unit 21 calculates the absolute value |Z| of the resistance, which is a component included in the impedance, and the phase difference θ of the frequency responsive to a specific frequency (e.g., 1 kHz) applied to the SOEC 40. Using the calculated absolute value |Z| of the resistance and the phase difference θ, the component calculation unit 21 further calculates the components included in the impedance, namely, the real part Z1 and the imaginary part Z2 of the resistance, which are shown in the following equations (1) and (2). In other words, the component calculation unit 21 obtains the impedance of the SOEC 40 at a specific frequency. Z1=|Z|cosθ (1) Z2=|Z|sinθ (2)

[0026] The ratio calculation unit 22 calculates the ratio of change in the absolute value |Z| of the resistance, the phase difference θ, the real part Z1 of the resistance, and the imaginary part Z2 of the resistance of each component of the impedance calculated by the component calculation unit 21. The calculated ratio of change in each component is the value obtained by dividing the calculated value of each component by the value of the SOEC 40 at the start of steam electrolysis.

[0027] The degradation estimation unit 23 estimates the degradation state of the SOEC 40 using the rate of change of any one of the components calculated by the rate calculation unit 22. Specifically, the degradation estimation unit 23 estimates the degradation state of the SOEC 40 performing steam electrolysis by comparing the rate of change of the imaginary part Z2 of the resistance, among the components calculated by the rate calculation unit 22, with previously estimated estimation reference data stored in the estimation DB 28. For example, once the rate of change of the imaginary part Z2 of the resistance is identified, the degradation estimation unit 23 can estimate the degradation state of the SOEC 40 by comparing the identified rate of change with the rate of change of the imaginary part Z2 of the resistance included in the estimation reference data. Note that in this embodiment, the detection device 30 and the component calculation unit 21 correspond to an acquisition unit, and the rate calculation unit 22 and the degradation estimation unit 23 correspond to an estimation unit.

[0028] Furthermore, the degradation estimation unit 23 of this embodiment changes the frequency of the voltage amplitude used for estimation of the SOEC 40 for which a new degradation state is to be estimated, depending on the degradation state of the SOEC estimated in the past. As will be described in detail later, the frequency used as an index for estimating the degradation state changes depending on the degradation state of the SOEC 40. In other words, the degradation estimation unit 23 changes the specific frequency to be used for estimating the degradation state depending on the degradation state of the SOEC 40.

[0029] The operation control unit 24 controls steam electrolysis by controlling the voltage applied to the SOEC 40 by the power supply PS in accordance with the requested amount of hydrogen generation transmitted from another device. The operation control unit 24 also controls the voltage applied to the SOEC 40 in accordance with the degradation state estimated by the degradation estimation unit 23. For example, when the change in the rate of change in the imaginary part Z2 of the resistance from time t1 to time t2 (>t1) is equal to or greater than a preset threshold, the operation control unit 24 performs hydrogen generation at a voltage lower than the voltage determined by the requested amount of hydrogen generation. In this way, the operation control unit 24 controls the amount of hydrogen generated by the SOEC 40 in accordance with the estimated degradation state of the SOEC 40.

[0030] 2.Evaluation of each component of impedance: Specific frequencies suitable for estimating the degradation state of the SOEC 40 and the impedance components used as the estimation criteria were evaluated. Figure 2 illustrates the time variation of the imaginary part of the resistance Z2 at each frequency. Figure 2 shows the rate of change of the imaginary part of the resistance Z2 at frequencies of 1 Hz, 10 Hz, 100 Hz, 1 kHz, and 10 kHz as a function of the operating time of the SOEC 40. Specifically, the rate of change at 1 Hz is indicated by black circles and a solid line, the rate of change at 10 Hz by white circles and a dashed line, the rate of change at 100 Hz by black squares and a dot-dash line, the rate of change at 1 kHz by white squares and a thin line, and the rate of change at 10 kHz by white triangles and a two-dot-dash line. As shown in Figure 2, at the five frequencies, the rate of change at 1 kHz of the SOEC 40 is significant and increases as the operating time of the SOEC 40 increases. That is, it is preferable to use the rate of change at 1 kHz rather than 1 Hz, 10 Hz, 100 Hz, and 10 kHz to estimate the degradation state of the SOEC 40.

[0031] FIG. 3 is an explanatory diagram of the time change of each impedance component at a frequency of 1 kHz. FIG. 3 shows the absolute value of resistance |Z|, the phase difference θ, the real part of resistance Z1, and the imaginary part of resistance Z2, as well as the rate of change of each component depending on the operating time at a frequency of 1 kHz. Specifically, the rate of change of the absolute value of resistance |Z| is indicated by white circles and dashed lines, the rate of change of the phase difference θ is indicated by black circles and solid lines, the rate of change of the real part of resistance Z1 is indicated by white squares and dashed lines, and the rate of change of the imaginary part of resistance Z2 is indicated by black squares and dashed lines. As shown in FIG. 3, for each impedance component, the rate of change of the imaginary part of resistance Z2 is large and increases with increasing operating time of the SOEC 40. In other words, to estimate the degradation state of the SOEC 40, it is preferable to use the imaginary part of resistance Z2, which has a large rate of change.

[0032] Figure 4 is an explanatory diagram of an accelerated durability test of an SOEC. Figure 4 shows the change in the imaginary part of the resistance Z2 as a function of frequency for each endurance time when an accelerated durability test was conducted using an SOEC smaller than SOEC40. In the accelerated durability test, the frequency of the voltage amplitude applied to the SOEC was not fixed, and the impedance spectrum was measured in the range of 0.1 Hz to 100 kHz.

[0033] In Figure 4, the change in the imaginary part Z2 of the resistance after 20 hours of endurance is shown by the dashed curve C20. Similarly, the imaginary part Z2 after 30 hours of endurance is shown by the solid curve C30, the imaginary part Z2 after 40 hours of endurance is shown by the thin double-dashed curve C40, and the imaginary part Z2 after 50 hours of endurance is shown by the thin dashed curve C50. The imaginary part Z2 after 60 hours of endurance is shown by the thin dashed curve C60, the imaginary part Z2 after 70 hours of endurance is shown by the thin solid curve C70, and the imaginary part Z2 after 80 hours of endurance is shown by the double-dashed curve C80. The imaginary part Z2 after 90 hours of endurance time has elapsed is shown by the dashed curve C90, the imaginary part Z2 after 100 hours of endurance time has elapsed is shown by the dashed curve C100, and the imaginary part Z2 after 110 hours of endurance time has elapsed is shown by the solid curve C110.

[0034] In FIG. 4, black dots are added to the maximum values ​​of the imaginary part Z2 for each of the curves C40 to C110. As shown by the black dots in FIG. 4, the frequency at which the imaginary part Z2 is at its maximum differs for each endurance time. Specifically, as the endurance time increases from 40 hours, the frequency at which the rate of change of the imaginary part Z2 is at its maximum decreases from 1 kHz. As the endurance time approaches 110 hours, the frequency at which the rate of change of the imaginary part Z2 is at its maximum decreases from 1 kHz. 2 ) Hz. That is, the specific frequency used to estimate the degradation state may be changed depending on the degradation state of the SOEC 40. For example, when the endurance time is 30 hours, the frequency approaches 1 kHz (=10 3 In the case where the endurance time is 110 hours, the deterioration state may be estimated using the imaginary part Z2 of a frequency of 100 Hz.

[0035] 3. SOEC state estimation method: 5 is a flowchart of a state estimation method for the SOEC 40 in this embodiment. In the state estimation flow shown in FIG. 5, first, the detection device 30 applies a voltage amplitude of a specific frequency to the SOEC 40 (step S1). The detection device 30 detects a current response, which is a response signal of the voltage amplitude (step S2). The component calculation unit 21 uses the voltage amplitude applied to the SOEC 40 and the current response, which is a response signal, to calculate the absolute value |Z| of the resistance of each component of the impedance, the phase difference θ, the real part Z1 of the resistance, and the imaginary part Z2 of the resistance (step S3). The processing from steps S1 to S3 corresponds to an acquisition step.

[0036] The ratio calculation unit 22 calculates the ratio of change of each component of the calculated impedance of the SOEC 40 (step S4). The degradation estimation unit 23 estimates the degradation state of the SOEC 40 by comparing the ratio of change of the imaginary part Z2 of the resistance of the four calculated components with the estimation reference data stored in the estimation DB 28 (step S5), and determines whether to end the state estimation flow (step S6). For example, if hydrogen generation by the SOEC 40 is to be continued, the state estimation flow does not end (step S6: NO), and the processing from step S1 onwards is repeated. If hydrogen generation by the SOEC 40 is to be ended (step S6: YES), the state estimation flow ends.

[0037] As described above, the component calculation unit 21 of the state estimation device 10 of this embodiment acquires the impedance of a specific frequency in the SOEC 40. The degradation estimation unit 23 estimates the degradation state of the SOEC 40 using the rate of change of any of the components calculated by the rate calculation unit 22. In this embodiment, instead of measuring the impedance over a wide frequency range, the frequencies measured in the SOEC 40 are limited to one or several specific frequencies. This simplifies the state estimation device 10 and reduces the cost of estimating the degradation state of the SOEC 40. Furthermore, by feeding back the estimated degradation state of the SOEC 40 to the operating condition control of a large-scale SOEC system 100, which requires complex replacement and maintenance of solid oxide cells in the SOEC 40, the lifespan of the SOEC system 100 can be extended. Furthermore, by using the rate of change of any of the components constituting the impedance instead of the actual numerical value of each component to estimate the degradation state of the SOEC 40, the degradation state of the SOEC 40 can be more appropriately estimated.

[0038] In addition, the detection device 30 of this embodiment applies a voltage amplitude of 1 kHz as the specific frequency to the SOEC 40. As shown in Fig. 2, the rate of change of the impedance component at 1 kHz is more sensitive to the deterioration state of the SOEC 40 than in other frequency ranges. In other words, by using the 1 kHz frequency for impedance measurement, the deterioration state of the SOEC 40 can be more appropriately estimated.

[0039] Furthermore, the degradation estimation unit 23 of this embodiment estimates the degradation state of the SOEC 40 using the rate of change in the imaginary part Z2 of the resistance, which is one of the components representing the absolute value |Z| of the resistance, the phase difference θ, the real part Z1 of the resistance, and the imaginary part Z2 of the resistance included in the impedance calculated by the rate calculation unit 22. As shown in FIG. 3 , the rate of change in the component representing the imaginary part Z2 of the resistance in the impedance has a higher sensitivity to the degradation state of the SOEC 40 than the other components (the absolute value |Z| of the resistance, the phase difference θ, and the real part Z1 of the resistance). In other words, by using the component representing the imaginary part Z2 of the resistance of the impedance, the degradation state of the SOEC 40 can be more appropriately estimated.

[0040] Furthermore, the degradation estimation unit 23 of this embodiment may change the frequency of the voltage amplitude used for estimation of the newly estimated degradation state of the SOEC 40, depending on the previously estimated degradation state of the SOEC. In this embodiment, the frequency used to newly estimate the degradation state of the SOEC 40 is determined based on the frequency used to previously estimate the degradation state. Therefore, the new degradation state of the SOEC 40 can be estimated using the specific frequency with the highest sensitivity to the rate of change when previously estimating the degradation state of the SOEC. As a result, the newly estimated degradation state of the SOEC 40 can be more appropriately estimated.

[0041] Furthermore, the degradation estimation unit 23 of this embodiment estimates the degradation state of the SOEC 40 performing steam electrolysis by comparing the rate of change in the imaginary part Z2 of the resistance, among the components calculated by the rate calculation unit 22, with previously estimated estimation reference data stored in the estimation DB 28. That is, the degradation determination unit 23 newly estimates the degradation state of the SOEC 40 using the rate of change calculated from the impedance, with the previously estimated degradation state as a reference. Therefore, by referencing the degradation state associated with the rate of change of the component included in the impedance, among the previously estimated degradation state data, the degradation state of the SOEC 40, whose impedance has been measured, can be simply estimated.

[0042] Furthermore, the deterioration estimation unit 23 of this embodiment estimates the deterioration state of the SOEC 40. That is, since the SOEC 40 is used as a solid oxide cell, the SOEC system 100 can be operated with an extended lifespan.

[0043] Furthermore, in the SOEC system 100 of this embodiment, the operation control unit 24 of the control device 20 controls the amount of hydrogen generated by the SOEC 40 in accordance with the estimated deterioration state of the SOEC 40. That is, the estimated deterioration state of the SOEC 40 is fed back to control the amount of hydrogen generated by the SOEC 40, thereby suppressing the rate at which the SOEC 40 deteriorates, and enabling operation of the SOEC system 100 with an extended lifespan.

[0044] <Modifications of the above embodiment> The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the present invention, including, for example, the following modifications: In the above-described embodiment, part of the configuration realized by hardware may be replaced by software, and conversely, part of the configuration realized by software may be replaced by hardware.

[0045] The state estimation device 10 of the above embodiment is merely an example, and can be modified within the scope of estimating the degradation state of the solid oxide cell using the rate of change of any component of the measured impedance of the solid oxide cell. For example, an SOFC may be used as the solid oxide cell instead of the SOEC 40. The frequency of the voltage amplitude or current amplitude applied to the SOEC 40 may be other than 1 kHz. The applied frequency is preferably 100 Hz or higher and 10 kHz or lower, but the frequency can be appropriately changed by improving the sensitivity of the rate of change depending on the level of noise cancellation. The impedance component used to estimate the degradation state of the SOEC 40 may be any of the absolute value of the resistance |Z|, the phase difference θ, and the real part of the resistance Z1, other than the imaginary part of the resistance Z2, or a combination of multiple components. The component calculation unit 21 may calculate only the component used to estimate the degradation state of the SOEC 40, without calculating all of the impedance components.

[0046] Furthermore, the impedance component used to estimate the degradation state of the SOEC 40 may be the numerical value of the imaginary part of resistance Z2 or the like, rather than the rate of change of the component such as the imaginary part of resistance Z2. For example, when replacing a deteriorated SOEC 40 with a new SOEC 40 of the same standard, the degradation state of the newly replaced SOEC 40 may be estimated by comparing the numerical value of the imaginary part of resistance Z2 measured on the deteriorated SOEC 40 with that of the new SOEC 40.

[0047] In the above embodiment, the degradation estimation unit 23 changes the frequency of the voltage amplitude applied to the SOEC 40 to measure the impedance according to the degradation state of the SOEC 40. However, the frequency of the voltage amplitude may be constant. Well-known materials may be used for the cathode, anode, and electrolyte layer that constitute the SOEC 40. The detection device 30 and control device 20 included in the state estimation device 10 may be well-known devices that can measure the impedance of the SOEC 40 and calculate the rate of change of each component of the impedance.

[0048] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0049] The present invention can also be realized in the following forms. [Application example 1] A state estimation device for a solid oxide cell, comprising: an acquisition unit that acquires the impedance of a specific frequency in the solid oxide cell; an estimation unit that estimates a degradation state of the solid oxide cell using any of the components that make up the acquired impedance; A state estimation device comprising: [Application example 2] The state estimation device according to Application Example 1, The state estimation device, wherein the estimation unit estimates the degradation state using a rate of change in any component that constitutes the impedance obtained from the solid oxide cell. [Application example 3] The state estimation device according to Application Example 1 or Application Example 2, A state estimation device, wherein the acquisition unit uses a frequency of 100 Hz or more and 10 kHz or less as the specific frequency. [Application example 4] The state estimation device according to any one of Application Examples 1 to 3, the impedance obtained from the solid oxide cell includes a component representing an absolute value of resistance, a component representing a phase difference, a component representing a real part of resistance, and a component representing an imaginary part of resistance; The state estimation device, wherein the estimation unit estimates the degradation state using a rate of change in a component representing an imaginary part of the resistance. [Application example 5] The state estimation device according to any one of Application Examples 1 to 4, The state estimation device, wherein the estimation unit changes the specific frequency used to newly estimate the degradation state in accordance with the degradation state estimated in the past. [Application Example 6] The state estimation device according to any one of Application Examples 1 to 5, further comprising: a storage unit that stores estimation reference data that associates the previously estimated deterioration state with the change rate; The state estimation device, wherein the estimation unit determines a state of degradation of the solid oxide cell from which the impedance has been acquired by comparing the rate of change from the acquired impedance with the rate of change included in the stored estimation reference data. [Application Example 7] The state estimation device according to any one of Application Examples 1 to 6, The state estimation device, wherein the solid oxide cell is a solid oxide electrolysis cell used in a steam electrolysis device. [Application Example 8] 1. A solid oxide cell system comprising: the solid oxide cell; The state estimation device according to any one of Application Examples 1 to 7, an operation control unit that controls the amount of hydrogen generated using the supplied water vapor from the solid oxide cell; Equipped with The operation control unit controls the amount of hydrogen generated by the solid oxide cell in accordance with the degradation state estimated by the estimation unit. [Application Example 9] A method for estimating a state of a solid oxide cell, comprising: acquiring an impedance of a specific frequency in the solid oxide cell; an estimation step of estimating a degradation state of the solid oxide cell using any of the components constituting the acquired impedance; A state estimation method that performs [Application Example 10] A computer program comprising: an acquisition function for acquiring the impedance of a specific frequency in the solid oxide cell; an estimation function for estimating a degradation state of the solid oxide cell using any of the components constituting the acquired impedance; A computer program that enables a computer to realize the above. [Explanation of symbols]

[0050] 10...State estimation device 20...Control device 21...Component calculation unit (acquisition unit) 22...Ratio calculation unit (estimation unit) 23...Deterioration estimation section (estimation section) 24...Operation control unit 25...CPU 26...Storage section 27…Detection DB 28…Estimated DB 30...Detection device (acquisition unit) 40...SOEC (Solid Oxide Cell) 100...SOEC system (Solid Oxide Cell System) PS…Power supply C20, C30, C40, C50, C60, C70, C80, C90, C100, C110... Curve of the imaginary part of the resistor |Z|…Absolute value of resistance Z1: Real part of resistance Z2: Imaginary part of the resistance t1,t2…time θ…Phase difference

Claims

1. A state estimation device for a solid oxide cell, comprising: an acquisition unit that acquires impedance at a frequency of 100 Hz or more and 10 kHz or less in the solid oxide cell, the impedance including a component representing an absolute value of resistance, a component representing a phase difference, a component representing a real part of resistance, and a component representing an imaginary part of resistance; an estimation unit that estimates a degradation state of the solid oxide cell using a rate of change obtained by dividing the imaginary part of the resistance in the acquired impedance by the imaginary part of the resistance at the start of steam electrolysis; A state estimation device comprising:

2. 2. The state estimation device according to claim 1, The state estimation device, wherein the estimation unit changes a frequency used to newly estimate the degradation state in accordance with the degradation state estimated in the past.

3. The state estimation device according to claim 2, further comprising: a storage unit that stores estimation reference data that associates the previously estimated deterioration state with the change rate; The state estimation device, wherein the estimation unit determines a state of degradation of the solid oxide cell from which the impedance has been acquired by comparing the rate of change from the acquired impedance with the rate of change included in the stored estimation reference data.

4. The state estimation device according to any one of claims 1 to 3, The state estimation device, wherein the solid oxide cell is a solid oxide electrolysis cell used in a steam electrolysis device.

5. 1. A solid oxide cell system comprising: the solid oxide cell; The state estimation device according to any one of claims 1 to 3; an operation control unit that controls the amount of hydrogen generated using the supplied water vapor from the solid oxide cell; Equipped with The operation control unit controls the amount of hydrogen generated by the solid oxide cell in accordance with the degradation state estimated by the estimation unit.

6. A method for estimating a state of a solid oxide cell, comprising: an acquiring step of acquiring impedance at a frequency of 100 Hz or more and 10 kHz or less in the solid oxide cell, the impedance including a component representing an absolute value of resistance, a component representing a phase difference, a component representing a real part of resistance, and a component representing an imaginary part of resistance; an estimation step of estimating a degradation state of the solid oxide cell using a rate of change obtained by dividing the imaginary part of the resistance in the acquired impedance by the imaginary part of the resistance at the start of steam electrolysis; A state estimation method that performs

7. A computer program comprising: an acquisition function for acquiring impedance in a solid oxide cell at a frequency of 100 Hz or more and 10 kHz or less, the impedance including a component representing an absolute value of resistance, a component representing a phase difference, a component representing a real part of resistance, and a component representing an imaginary part of resistance; an estimation function of estimating a degradation state of the solid oxide cell using a rate of change obtained by dividing the imaginary part of the resistance in the acquired impedance by the imaginary part of the resistance at the start of steam electrolysis; A computer program that enables a computer to realize the above.

Images