Cell control system

Abstract

To provide a cell control system capable of suppressing the deterioration of an electrochemical cell by efficiently decreasing the internal resistance of the electrochemical cell.SOLUTION: A cell control system 1 controls the internal resistance of an electrochemical cell 2. The cell control system 1 comprises a deteriorated area identification unit 31 and an operation determination unit 32. The deteriorated area identification unit 31 performs deterioration diagnosis to identify a deteriorated area of the electrochemical cell 2. The operation determination unit 32 determines a reduction operation based on the result of the deterioration diagnosis by the deteriorated area identification unit 31. The reduction operation is an operation of the electrochemical cell 2 for reducing the internal resistance of the electrochemical cell 2, having increased due to the deterioration in the deteriorated area. By carrying out the reduction operation, the cell control system 1 performs control such that the internal resistance of the electrochemical cell 2, the voltage applied to the electrochemical cell 2 and the like, each become a predetermined target value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cell control system. [Background technology]

[0002] For example, as described in Patent Document 1, a hydrogen production system equipped with an electrolysis cell stack for extracting hydrogen by electrolyzing a raw material is known. When the internal resistance of the electrolysis cell stack increases due to deterioration, this hydrogen production system attempts to reduce the internal resistance of the electrolysis cell stack by increasing the temperature of the electrolysis cell stack. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6704998 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the hydrogen production system described in Patent Document 1 attempts to reduce the internal resistance by controlling the temperature of the cells, without identifying the deteriorated parts of the cells that make up the electrolysis cell stack. Therefore, there is a risk that the internal resistance of the cells may not be reduced sufficiently. In other words, the causes of increased internal resistance may differ depending on the parts that make up the cell. Therefore, the cell operation details for efficiently reducing the internal resistance may differ for each deteriorated part of the cell, and there is a risk that the internal resistance may not be reduced sufficiently by simply controlling the cell temperature. Therefore, it can be said that the hydrogen production system described in Patent Document 1 has room for improvement in terms of efficiently reducing the internal resistance of the cells and suppressing cell deterioration.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a cell control system that can suppress deterioration of an electrochemical cell by efficiently reducing the internal resistance of the electrochemical cell. [Means for solving the problem]

[0006] A first aspect of the present invention is a cell control system (1) for controlling the internal resistance of an electrochemical cell (2) including a cathode flow path (21), an anode flow path (22), and an electrolyte (23) disposed between the anode flow path and the cathode flow path, the cell control system comprising: the electrochemical cell is configured to electrolyze a raw material (11) using supplied power to produce hydrogen; a deterioration portion identifying unit (31) that performs a deterioration diagnosis to identify a deterioration portion of the electrochemical cell; an operation determination unit (32) that determines, based on a result of the deterioration diagnosis by the deterioration portion identification unit, a reduction operation that is an operation of the electrochemical cell for reducing the internal resistance of the electrochemical cell that has increased due to the deterioration of the deterioration portion identified by the deterioration portion identification unit, The cell control system controls at least one of the internal resistance of the electrochemical cell, the voltage applied to the electrochemical cell, and the current flowing through the electrochemical cell to reach a predetermined target value by implementing the reduction operation determined by the operation determination unit.

[0007] A second aspect of the present invention is a cell control system (1) for controlling the internal resistance of an electrochemical cell (2) including a cathode flow path (21), an anode flow path (22), and an electrolyte (23) disposed between the anode flow path and the cathode flow path, the cell control system comprising: the electrochemical cell is configured to generate electricity by supplying a gas containing an oxidant (12) to the cathode flow path and a gas containing a fuel (13) to the anode flow path; a deterioration portion identifying unit (31) that performs a deterioration diagnosis to identify a deterioration portion of the electrochemical cell; an operation determination unit (32) that determines, based on a result of the deterioration diagnosis by the deterioration portion identification unit, a reduction operation that is an operation of the electrochemical cell for reducing the internal resistance of the electrochemical cell that has increased due to the deterioration of the deterioration portion identified by the deterioration portion identification unit, The cell control system controls at least one of the internal resistance of the electrochemical cell, the output voltage of the electrochemical cell, and the output current of the electrochemical cell to reach a predetermined target value by implementing the reduction operation determined by the operation determination unit. [Effects of the Invention]

[0008] The cell control system includes a degradation portion identification unit and an operation determination unit. Therefore, it is possible to perform a reduction operation according to the degradation portion of the electrochemical cell. Therefore, it is possible to efficiently reduce the internal resistance of the electrochemical cell. As a result, it is possible to operate the electrochemical cell with low internal resistance, thereby suppressing degradation of the electrochemical cell.

[0009] As described above, according to the above aspect, it is possible to provide a cell control system that can efficiently reduce the internal resistance of the electrochemical cell, thereby suppressing deterioration of the electrochemical cell. In addition, the symbols in parentheses in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described below, and do not limit the technical scope of the present invention. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a configuration diagram of a hydrogen production device including a cell control system according to a first embodiment. [Figure 2] FIG. 1 is a diagram showing a cell control system according to a first embodiment. [Figure 3] FIG. 3 is a flowchart showing the flow of degradation diagnosis and reduction operations in the first embodiment. [Figure 4] FIG. 4 is a diagram showing the timing of performing a deterioration diagnosis in the first embodiment. [Figure 5] FIG. 4 is a diagram showing the relationship between oxygen partial pressure and electrolysis voltage during deterioration diagnosis in the first embodiment. [Figure 6] FIG. 4 is a diagram showing the relationship between oxygen partial pressure and electrolysis voltage during reduction operation in the first embodiment. [Figure 7] 4A and 4B are diagrams showing specific examples of diagnostic items and reduction operations for each part in the first embodiment. [Figure 8] FIG. 4 is a diagram showing the relationship between cell temperature and electrolysis voltage during deterioration diagnosis in the first embodiment. [Figure 9] FIG. 4 is a graph showing the relationship between cell temperature and electrolysis voltage during a reduction operation in the first embodiment. [Figure 10] FIG. 10 is a flowchart showing the flow of degradation diagnosis and reduction operations in the second embodiment. [Figure 11] FIG. 10 is a configuration diagram of a hydrogen production device including a cell control system according to a third embodiment. [Figure 12] FIG. 10 is a configuration diagram of a hydrogen production device including a cell control system according to a fourth embodiment. [Figure 13] FIG. 10 is a configuration diagram of a hydrogen production device including a cell control system according to a fifth embodiment. [Figure 14] FIG. 13 is a configuration diagram of a hydrogen production device including a cell control system according to a sixth embodiment. [Figure 15] FIG. 13 is a configuration diagram of a hydrogen production device including a cell control system according to a seventh embodiment. [Figure 16] FIG. 13 is a configuration diagram of a hydrogen production device including a cell control system according to an eighth embodiment. [Figure 17] FIG. 20 is a diagram showing a cell control system in a ninth embodiment. [Figure 18] FIG. 20 is a configuration diagram of a fuel cell device including a cell control system according to a ninth embodiment. [Figure 19] FIG. 20 is a flowchart showing the flow of degradation diagnosis and reduction operations in the ninth embodiment. [Figure 20] FIG. 20 is a diagram showing the relationship between oxygen partial pressure and output voltage during deterioration diagnosis in the ninth embodiment. [Figure 21] FIG. 20 is a graph showing the relationship between oxygen partial pressure and output voltage during reduction operation in the ninth embodiment. [Figure 22] FIG. 20 is a configuration diagram of a fuel cell device including a cell control system according to a tenth embodiment. [Figure 23] FIG. 10 is a configuration diagram of a hydrogen production device including a cell control system when a temperature adjustment unit is provided in a cathode supply flow path or the like. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Embodiment 1) An embodiment of a cell control system will be described with reference to FIGS. The cell control system 1 of this embodiment controls the internal resistance of the electrochemical cell 2. As shown in Fig. 2, the electrochemical cell 2 includes a cathode flow path 21, an anode flow path 22, and an electrolyte 23 disposed between the anode flow path 22 and the cathode flow path 21. In this embodiment, the electrochemical cell 2 is configured to electrolyze a raw material 11 using supplied power to produce hydrogen.

[0012] As shown in FIG. 1 , the cell control system 1 has a degradation portion identifying unit 31 and an operation determining unit 32. The degradation portion identifying unit 31 performs a degradation diagnosis to identify a degradation portion of the electrochemical cell 2. The operation determining unit 32 determines a reduction operation based on the result of the degradation diagnosis by the degradation portion identifying unit 31. The reduction operation is an operation of the electrochemical cell 2 to reduce the internal resistance of the electrochemical cell 2 that has increased due to degradation of the degradation portion identified by the degradation portion identifying unit 31. By implementing the reduction operation determined by the operation determining unit 32, the cell control system 1 controls at least one of the internal resistance of the electrochemical cell 2, the voltage applied to the electrochemical cell 2, and the current flowing through the electrochemical cell 2 to reach a predetermined target value.

[0013] The cell control system 1 of this embodiment can be used, for example, as a means for controlling a hydrogen production device that produces hydrogen by electrolyzing a raw material 11 using supplied power. In this embodiment, a gas containing water vapor is supplied to the cathode flow path 21 of the electrochemical cell 2 shown in FIG. 2, and air is supplied to the anode flow path 22. The electrochemical cell 2 is configured to decompose the water vapor using power supplied from a power source 51 to produce hydrogen gas. That is, in this embodiment, the raw material 11 is water. Furthermore, the water as the raw material 11 is supplied to the cathode flow path 21 in the form of water vapor.

[0014] 1, the cell control system 1 has a control unit 3 that controls the operating conditions of the electrochemical cell 2. The control unit 3 has a deterioration part identifying unit 31 and an operation determining unit 32. The control unit 3 has a processor and a memory. Data processed by the processor and the like are stored in the memory.

[0015] The cell control system 1 of this embodiment also includes a cell stack 20 in which a plurality of electrochemical cells 2 are stacked. In the cell stack 20, the plurality of electrochemical cells 2 are electrically connected in series. In the cell stack 20, the plurality of electrochemical cells 2 are stacked in the arrangement direction Z (see FIG. 2 ) of the cathode flow path 21, the electrolyte 23, and the anode flow path 22 in the electrochemical cell 2. The plurality of electrochemical cells 2 are sandwiched between a pair of end plates (not shown) arranged at both ends of the cell stack 20 in the arrangement direction Z.

[0016] The cell stack 20 is accommodated in a housing 15 covered with a heat insulating material. The housing 15 maintains the electrochemical cell 2 at a temperature suitable for electrolysis of the raw material 11. A temperature adjustment unit 151 for adjusting the temperature of the cell stack 20 is accommodated in the housing 15. The temperature adjustment unit 151 may be, for example, an electric heater or a heat exchanger. The control unit 3 controls the temperature adjustment unit 151 to maintain the temperature of the electrochemical cell 2 at, for example, 600 to 800°C.

[0017] The cell control system 1 has a power supply 51 that supplies power to the cell stack 20. The power supply 51 supplies the electrochemical cell 2 with the power required for electrolysis of the raw material 11. In this embodiment, the control unit 3 controls the current supplied from the power supply 51 to the electrochemical cell 2 so that the magnitude of the current is kept constant.

[0018] The cell control system 1 includes a cathode supply flow path 53 that supplies gas to the cathode flow path 21 of the electrochemical cell 2, and an anode supply flow path 54 that supplies gas to the anode flow path 22 of the electrochemical cell 2. In this embodiment, the cathode supply flow path 53 supplies gas containing water vapor of the raw material 11 to the cathode flow path 21, and the anode supply flow path 54 supplies air to the anode flow path 22. The cathode supply flow path 53 is provided with a flow rate adjuster 531 that adjusts the flow rate of the gas supplied to the cathode flow path 21. The flow rate adjuster 531 may be, for example, an electromagnetic valve. The anode supply flow path 54 is provided with an air pump 541 that supplies pressurized air to the anode flow path 22. The control unit 3 controls the flow rate adjuster 531 and the air pump 541 to adjust the flow rates of the gas supplied to the cathode flow path 21 and the anode flow path 22, and the pressures in the cathode flow path 21 and the anode flow path 22.

[0019] The cell control system 1 also includes a cathode exhaust flow path 57 through which gas discharged from the cathode flow path 21 flows, and an anode exhaust flow path 58 through which gas discharged from the anode flow path 22 flows.

[0020] The cell control system 1 of this embodiment has an inert gas supply channel 55 that supplies an inert gas to the electrochemical cell 2. The inert gas supply channel 55 is connected to the cathode supply channel 53 and the anode supply channel 54, and is configured to supply the inert gas to the cathode channel 21 and the anode channel 22, respectively. The inert gas supply channel 55 is provided with flow rate adjusters 551 and 552 that adjust the flow rate of the inert gas supplied to the cathode channel 21 or the anode channel 22. The flow rate adjusters 551 and 552 may be, for example, solenoid valves. The control unit 3 adjusts the flow rate of the inert gas supplied to the cathode channel 21 or the anode channel 22 by controlling the flow rate adjusters 551 and 552.

[0021] The cell control system 1 of this embodiment includes a hydrogen supply flow path 56 for supplying hydrogen gas to the cathode flow path 21. The hydrogen supply flow path 56 is connected to the cathode supply flow path 53. The hydrogen supply flow path 56 is also provided with a flow rate adjuster 561 that adjusts the flow rate of hydrogen gas supplied to the cathode flow path 21. The flow rate adjuster 561 may be, for example, an electromagnetic valve. The hydrogen supply flow path 56 supplies hydrogen gas to the cathode flow path 21 as needed to suppress oxidation of the cathode diffusion layer 242 and the cathode reaction layer 241, which will be described later, and prevent deterioration. The control unit 3 controls the flow rate adjuster 561 to adjust the flow rate of hydrogen gas supplied to the cathode flow path 21.

[0022] The cell control system 1 includes a return flow path 571 that branches off from the cathode discharge flow path 57 and connects the cathode discharge flow path 57 to the cathode supply flow path 53. The return flow path 571 is a flow path for supplying water vapor and hydrogen that have not been decomposed by the electrochemical cell 2 and have been discharged to the cathode discharge flow path 57 back to the cathode flow path 21. The return flow path 571 is provided with a pump 572 for supplying gas from the cathode discharge flow path 57 to the cathode flow path 21 via the cathode supply flow path 53. The control unit 3 controls the pump 572 to adjust the flow rate of gas from the cathode discharge flow path 57 that is supplied to the cathode flow path 21.

[0023] The cell control system 1 includes a temperature measurement unit (not shown) that measures the temperature of the electrochemical cell 2. Information on the temperature measured by the temperature measurement unit is transmitted to the control unit 3. The temperature measurement unit can be, for example, a thermocouple or a resistance temperature detector. When the temperature measurement unit is a sheathed thermocouple, the temperature of the electrochemical cell 2 can be measured by inserting the sheathed thermocouple inside end plates (not shown) provided at both ends of the cell stack 20 in the arrangement direction Z.

[0024] The cell control system 1 includes a pressure measurement unit (not shown) that measures the pressure in the cathode flow channel 21 and the anode flow channel 22. The pressure measurement unit can be installed in, for example, the electrochemical cell 2, thereby directly measuring the pressure in the cathode flow channel 21 and the anode flow channel 22. Information on the pressure measured by the pressure measurement unit is transmitted to the control unit 3. The pressure measurement units can also be installed in, for example, the cathode supply flow channel 53, the cathode discharge flow channel 57, the anode supply flow channel 54, and the anode discharge flow channel 58. In this case, for example, the magnitude of the pressure in the cathode supply flow channel 53, the cathode discharge flow channel 57, the anode supply flow channel 54, and the anode discharge flow channel 58 can be regarded as the magnitude of the pressure in the cathode flow channel 21 and the anode flow channel 22, and control such as deterioration diagnosis can be performed. The control unit 3 can also calculate the magnitude of the pressure in the cathode flow channel 21 and the anode flow channel 22 based on the magnitude of the pressure in the cathode supply flow channel 53, the anode supply flow channel 54, etc.

[0025] The cell control system 1 has a flow rate measuring unit (not shown) that measures the flow rate of the gas flowing through the cathode flow path 21 and the anode flow path 22. Information on the gas flow rate measured by the flow rate measuring unit is transmitted to the control unit 3. The flow rate measuring unit may be provided, for example, in the cathode supply flow path 53 and the anode supply flow path 54. In this case, the flow rates in the cathode supply flow path 53 and the anode supply flow path 54 can also be considered as the flow rates in the cathode flow path 21 and the anode flow path 22. The control unit 3 can also calculate the flow rates in the cathode flow path 21 and the anode flow path 22 based on the flow rates in the cathode supply flow path 53 and the anode supply flow path 54. The flow rate measuring unit may be, for example, a mass flow meter, a volumetric flow meter, or the like. Furthermore, the volumetric flow rate of the gas containing water vapor 11 flowing through the cathode flow path 21 changes easily depending on the temperature and pressure. Therefore, when a volumetric flow meter is used as the flow rate measuring unit, it is preferable to convert it into a mass flow rate and use it to control the electrochemical cell 2. That is, it is preferable to convert the volume flow rate, which is the measurement data of the volumetric flowmeter, into a mass flow rate based on the measurement data of the temperature measurement unit and the pressure measurement unit, and use the mass flow rate to control the electrochemical cell 2.

[0026] As shown in FIGS. 1 and 2, the cell control system 1 has a voltage measurement unit 52 that measures the magnitude of the voltage applied to the electrochemical cell 2. Information on the voltage measured by the voltage measurement unit 52 is transmitted to the control unit 3. The cell control system 1 also has a current measurement unit (not shown) that measures the magnitude of the current flowing through the electrochemical cell 2. Information on the current measured by the current measurement unit is transmitted to the control unit 3.

[0027] Next, the electrochemical cell 2 will be described with reference to FIG. In this embodiment, the electrochemical cell 2 is a solid oxide cell. That is, in this embodiment, the electrochemical cell 2 is an SOEC (Solid Oxide Electrolysis Cell). The electrolyte 23 is made of a solid oxide ceramic and contains oxide ions (O 2-The electrolyte 23 can be made of, for example, yttria-stabilized zirconia, perovskite-type oxide, yttria-partially stabilized zirconia, or the like.

[0028] The electrochemical cell 2 includes a porous cathode reaction layer 241 provided on one side of the electrolyte 23 in the arrangement direction Z, and a porous cathode diffusion layer 242 provided between the cathode reaction layer 241 and the cathode flow channel 21. In this embodiment, the cathode reaction layer 241 contains a catalyst such as nickel for promoting the decomposition reaction of the water vapor 11. The cathode diffusion layer 242 has the function of diffusing the water vapor 11 from the cathode flow channel 21 to the cathode reaction layer 241, and also has the function of diffusing the hydrogen gas generated by electrolysis from the cathode reaction layer 241 to the cathode flow channel 21. The cathode reaction layer 241 and the cathode diffusion layer 242 can be made of a material such as a metal or a metal compound, for example.

[0029] The electrochemical cell 2 also includes a porous anode reaction layer 251 provided on the other side of the electrolyte 23 in the arrangement direction Z, and a porous anode diffusion layer 252 provided between the anode reaction layer 251 and the anode flow channel 22. In this embodiment, the anode reaction layer 251 contains a catalyst for promoting the generation of oxygen gas. The anode diffusion layer 252 has the function of diffusing the oxygen gas generated in the anode reaction layer 251 from the anode reaction layer 251 to the anode flow channel 22. The anode reaction layer 251 and the anode diffusion layer 252 can be made of materials such as metals and metal compounds. The anode reaction layer 251 can also contain, for example, perovskite-type oxides as a catalyst.

[0030] Next, the electrolysis of water vapor 11 in the electrochemical cell 2 will be described. In this embodiment, the water vapor 11 supplied to the cathode flow path 21 passes through the cathode diffusion layer 242 and reaches the cathode reaction layer 241, where it is converted into "H2O+2e - →H2+O 2-In the anode reaction layer 251, the electrolytic reaction of "O 2- →1 / 2O2+2e - That is, in the cathode reaction layer 241, the water vapor 11 is electrolyzed to produce hydrogen gas and oxide ions (O 2- ) is generated. The hydrogen gas diffuses into the cathode flow channel 21. The oxide ions pass through the electrolyte 23 and move toward the anode flow channel 22, where they are oxidized in the anode reaction layer 251 to form oxygen gas, which diffuses into the anode flow channel 22. The hydrogen gas produced by this electrolysis reaction is discharged from the cathode flow channel 21 to the cathode exhaust flow channel 57, and the oxygen gas produced is discharged from the anode flow channel 22 to the anode exhaust flow channel 58.

[0031] Next, the control of the electrochemical cell 2 by the control unit 3 will be described with reference to the flowchart of FIG. First, in step S1, the control unit 3 determines whether the electrochemical cell 2 is in a state where it can be operated at a predetermined rated output. That is, the control unit 3 determines whether the temperature, etc. of the electrochemical cell 2 has reached a predetermined temperature, etc. where it can be operated at the rated output. If, in step S1, the electrochemical cell 2 is in a state where it can be operated at the rated output, the control unit 3 proceeds to step S2. On the other hand, if, in step S1, the electrochemical cell 2 is not in a state where it can be operated at the rated output, the control unit 3 returns to step S1 and determines again whether the electrochemical cell 2 is in a state where it can be operated at the rated output.

[0032] Next, in step S2, the voltage measurement unit 52 (see FIGS. 1 and 2) measures the voltage applied to the electrochemical cell 2. Then, in step S3, it is determined whether the voltage value of the electrochemical cell 2 is equal to or greater than a predetermined threshold. That is, in this embodiment, it is determined whether the electrochemical cell 2 has deteriorated based on the magnitude of the voltage applied to the electrochemical cell 2 when a constant current is controlled to flow through the electrochemical cell 2. Then, as shown in FIG. 4, if the value of the electrolysis voltage applied to the electrochemical cell 2 exceeds the target value and becomes equal to or greater than the threshold, the process proceeds to step S4, where degradation diagnosis and mitigation operation are performed under predetermined conditions. On the other hand, if the electrolysis voltage value of the electrochemical cell 2 is less than the threshold in step S3, the process proceeds to step S5. That is, as shown in FIG. 4, as the operating time of the electrochemical cell 2 elapses, the electrochemical cell 2 gradually deteriorates, and the electrolysis voltage gradually increases from the initial target value. Then, when the value of the electrolysis voltage becomes equal to or greater than the threshold, degradation diagnosis and mitigation operation are performed under predetermined conditions, as will be described later. This reduces the electrolysis voltage, which is the voltage applied to the electrochemical cell 2, to a predetermined target value. The threshold value can be, for example, a voltage value that is 5% higher than the target voltage. The target value can be, for example, the electrolysis voltage of an undegraded electrochemical cell 2 during rated operation.

[0033] 3, step S5 determines whether a predetermined period of time has passed since the previous identification of a deteriorated portion by the deteriorated portion identifying unit 31. If step S5 determines that a certain period of time has passed since the previous identification of a deteriorated portion, the process proceeds to step S4 even if the electrolysis voltage value is below the threshold. On the other hand, if a certain period of time has not passed since the previous identification of a deteriorated portion, the process returns to step S1, and the determination of each step is performed again. That is, as shown in FIG. 4, if, for example, one week has passed since the previous identification of a deteriorated portion, deterioration diagnosis is performed even if the electrolysis voltage value is below the threshold.

[0034] Furthermore, the cell control system 1 of this embodiment is configured to prohibit the execution of at least one of the degradation diagnosis and the reduction operation under a predetermined prohibition condition. Therefore, in step S4, it is determined whether or not the diagnosis prohibition condition does not apply. The diagnosis prohibition condition is a condition for determining that the execution of at least one of the degradation diagnosis and the reduction operation from step S6 onward, which will be described later, should be prohibited. If the diagnosis prohibition condition does not apply in step S4, the system proceeds to step S6. If the diagnosis prohibition condition applies, the system proceeds to step S7. In this embodiment, the diagnosis prohibition condition can be, for example, when the remaining amount of hydrogen gas in a hydrogen storage tank (not shown) for storing hydrogen gas produced by the electrochemical cell 2 is equal to or less than a predetermined value. In other words, performing a degradation diagnosis may result in a decrease in the amount of hydrogen gas produced by the electrochemical cell 2 or a temporary stoppage of hydrogen gas production. Therefore, a condition in which hydrogen gas production should be prioritized over degradation diagnosis is set as a diagnosis prohibition condition, and degradation diagnosis is not performed as necessary.

[0035] In step S7, it is determined whether the period during which degradation diagnosis or mitigation operation has been prohibited due to the diagnosis prohibition condition being met is equal to or longer than a predetermined period. If the period during which degradation diagnosis, etc. has been prohibited is equal to or longer than the predetermined period, the process proceeds to step S6 even if the diagnosis prohibition condition is met. On the other hand, if in step S7 the period during which degradation diagnosis, etc. has been prohibited is shorter than the predetermined period, the process returns to step S1. In other words, in this embodiment, if the prohibition of at least one of degradation diagnosis and mitigation operation continues for a predetermined period, the cell control system 1 controls the degradation diagnosis and mitigation operation to be performed even if the prohibition condition is met. In step S7, the predetermined period can be, for example, one week.

[0036] Next, in steps S6, S8, S9, and S10, the degradation diagnosis is performed by the degradation part identifying unit 31. Specifically, the following are set as diagnostic items for the degradation part identifying unit 31: the temperature of the electrochemical cell 2, the pressure in the cathode flow path 21, the pressure in the anode flow path 22, the partial pressure of water vapor 11 in the gas supplied to the cathode flow path 21, the partial pressure of oxygen in the gas supplied to the anode flow path 22, the gas flow rate in the cathode flow path 21, and the gas flow rate in the anode flow path 22. At this time, the degradation part identifying unit 31 identifies the degradation part of the electrochemical cell 2 by changing the value of at least one diagnostic item among the multiple diagnostic items.

[0037] Furthermore, the degradation part identifying unit 31 measures a measurement change amount, which is the amount of change in the state of the electrochemical cell 2 when the value of the diagnostic item is changed. Then, the degradation part identifying unit 31 identifies a degradation part of the electrochemical cell 2 by comparing the measurement change amount with a predetermined reference value for the amount of change in the state of the electrochemical cell 2. Furthermore, in this embodiment, the amount of change in the state is the amount of change in the magnitude of the voltage applied to the electrochemical cell 2 when the output current to the electrochemical cell 2 is controlled to a constant current. In this embodiment, the degradation part of the electrochemical cell 2 is identified by changing the value of at least one or more diagnostic items other than the temperature of the electrochemical cell 2 in addition to the temperature of the electrochemical cell 2.

[0038] In this embodiment, the values ​​of the multiple diagnostic items are changed one by one, without changing them simultaneously. Furthermore, in this embodiment, degradation diagnosis is performed by changing the values ​​of all of the multiple diagnostic items. In step S6, the value of one of the multiple diagnostic items is changed, and the process proceeds to step S8. Next, in step S8, the electrolysis voltage applied to the electrochemical cell 2 before changing the value of the diagnostic item and the change in the electrolysis voltage after changing the value of the diagnostic item in step S6 are measured as the measured change amount. After step S8, the process proceeds to step S9, where it is determined whether all of the diagnostic items have been changed. If the values ​​of all of the diagnostic items have been changed, the process proceeds to step S10, where the deteriorated part is identified based on the measured change amount. On the other hand, if the values ​​of all of the diagnostic items have not been changed in step S9, the process returns to step S6, and the value of the next diagnostic item is changed. Then, steps S6 to S9 are repeated for all of the diagnostic items until their values ​​have been changed.

[0039] As a specific example, the diagnosis content when the diagnosis item is "oxygen partial pressure of gas supplied to the anode flow path 22" will be described with reference to the graph in FIG. 5. In the graph in FIG. 5, the horizontal axis represents the oxygen partial pressure in the anode flow path 22, and the vertical axis represents the electrolysis voltage applied to the electrochemical cell 2. In the graph in FIG. 5, "initial operation" refers to normal rated operation of the electrochemical cell 2 immediately before degradation diagnosis was performed. In addition, in the graph in FIG. 5, the black circles represent data from a previous test, which shows the relationship between oxygen partial pressure and electrolysis voltage when a non-degraded electrochemical cell 2 was used. In addition, the white circles represent the relationship between oxygen partial pressure and electrolysis voltage for a deteriorated electrochemical cell 2 for which degradation diagnosis up to step S10 was actually performed. In the graph in FIG. 5, when the data for the deteriorated electrochemical cell 2 and the data for the non-degraded electrochemical cell 2 during initial operation are compared, it can be seen that the electrolysis voltage of the deteriorated electrochemical cell 2 increases, indicating that the electrolysis voltage increases due to degradation. Furthermore, characteristic line L1 is an approximate straight line of the plot of past test result data, and is a straight line that indicates the characteristics of an electrochemical cell 2 that has not deteriorated.

[0040] Furthermore, when performing degradation diagnosis, first, the value of the oxygen partial pressure in the anode flow channel 22 is changed from the value C0 during initial operation. In this embodiment, the value of the oxygen partial pressure is decreased from the value C0 during initial operation to a value C1. Then, the degradation part identifying unit 31 measures the electrolysis voltage V1b when the oxygen partial pressure is the value C1 using the voltage measuring unit 52. Furthermore, the degradation part identifying unit 31 measures the voltage difference ΔV1, which is the difference between the electrolysis voltage V1a at the oxygen partial pressure C0 during initial operation and the electrolysis voltage V1b when the oxygen partial pressure is the value C1. In other words, the voltage difference ΔV1 is the amount of change measured.

[0041] In this embodiment, the predetermined reference value for the amount of change in the state of the electrochemical cell 2 is a voltage difference ΔV0, which is the difference in the magnitude of the electrolysis voltage applied to the electrochemical cell 2 when the oxygen partial pressure is changed under the same conditions using a non-degraded electrochemical cell 2. That is, as shown in FIG. 5 , the voltage difference ΔV0 is the difference between the electrolysis voltage V0a at the oxygen partial pressure C0 during initial operation and the electrolysis voltage V0b at the oxygen partial pressure C1 when a non-degraded electrochemical cell 2 is used. The degradation portion identifying unit 31 compares the voltage difference ΔV1 with the voltage difference ΔV0. If the voltage difference ΔV1 is greater than a predetermined value relative to the voltage difference ΔV0, the unit determines that the anode reaction layer 251 is degraded and identifies the degraded portion. Here, degradation of the anode reaction layer 251 refers to, for example, adhesion of foreign matter contained in the gas supplied to the anode flow path 22 to the anode reaction layer 251, or a reduction in the reaction area of ​​the anode reaction layer 251 due to structural changes caused by high temperatures, which makes it difficult for oxide ions to oxidize. Deterioration of the anode reaction layer 251 increases the overvoltage of the anode reaction layer 251 during operation of the electrochemical cell 2. As shown in Fig. 5, by lowering the oxygen partial pressure in the anode flow channel 22 through deterioration diagnosis, the oxidation ability of oxide ions in the anode reaction layer 251 is restored, and the electrolysis voltage decreases. In other words, the reaction in the anode reaction layer 251 is more sensitive to changes in the oxygen partial pressure in the anode flow channel 22 than reactions in the electrolyte 23, the cathode reaction layer 241, etc. Therefore, the result of this deterioration diagnosis based on oxygen partial pressure makes it possible to identify that, among the various parts of the electrochemical cell 2, the anode reaction layer 251 has deteriorated.

[0042] Next, as described above, after identifying the deteriorated portion in step S10, the process proceeds to step S11 in the flowchart of Fig. 3, where a reduction operation is performed so that the electrolytic voltage applied to the electrochemical cell 2 reaches a predetermined target value. After that, the process returns to step S1 again, and the same control is performed.

[0043] In this embodiment, the reduction operation is an operation that changes at least one of the temperature of the electrochemical cell 2, the pressure of the cathode flow path 21, the pressure of the anode flow path 22, the partial pressure of water vapor 11 in the gas supplied to the cathode flow path 21, the partial pressure of oxygen in the gas supplied to the anode flow path 22, the flow rate of the gas in the cathode flow path 21, and the flow rate of the gas in the anode flow path 22.

[0044] Specifically, the operation determination unit 32 determines the reduction operation shown in Fig. 6 based on the deterioration diagnosis result shown in Fig. 5. In the graph of Fig. 6, the characteristic line L2 is an approximate straight line of the plot of data when the deterioration diagnosis is performed on the deteriorated electrochemical cell 2, and is a straight line that indicates the characteristics of the electrochemical cell 2 when deteriorated.

[0045] In this embodiment, the operation determination unit 32 determines the oxygen partial pressure at which the target voltage V0, which is the target value, is reached based on the characteristic line L2. Then, as the reduction operation, the oxygen partial pressure of the gas supplied to the anode flow channel 22 is reduced to a value C2. Here, in this embodiment, the anode flow channel 22 is configured to allow air to flow. The cell control system 1 changes the oxygen partial pressure of the anode flow channel 22 by flowing a gas other than air through the anode flow channel 22. Specifically, the cell control system 1 reduces the oxygen partial pressure of the anode flow channel 22 by flowing, for example, nitrogen gas or helium gas other than air through the anode flow channel 22. That is, an inert gas is fed from the inert gas supply channel 55 (see FIG. 1) to the anode flow channel 22 via the anode supply channel 54. As a result, the oxygen concentration of the gas supplied to the anode flow channel 22 becomes lower than 21%, which is the oxygen concentration of air. This makes it easier for the oxygen gas generated in the anode reaction layer 251 to be dispersed to the anode flow channel 22 and to be released to the outside through the anode flow channel 22, thereby reducing the overvoltage of the electrochemical cell 2. This allows the electrolysis voltage of the electrochemical cell 2 to reach a predetermined target value.

[0046] In this embodiment, the content of the reduction operation is the same as the content of the diagnostic items. That is, for example, the operation for identifying the deterioration of the anode reaction layer 251 and the reduction operation for reducing the overvoltage of the anode reaction layer 251 are changes in the oxygen partial pressure in the anode flow path 22.

[0047] Furthermore, as shown in FIG. 7 , the cell control system 1 of this embodiment can change, for example, the fluid flow rate of the gas flowing through the anode flow path 22, the temperature of the cell stack 20, and the like, in addition to the oxygen partial pressure described above, during degradation diagnosis and mitigation operations. This makes it possible to identify the anode reaction layer 251 and the anode diffusion layer 252 as degraded parts, and by improving oxygen discharge properties and the like, it is possible to reduce the overvoltage of the anode reaction layer 251 and the anode diffusion layer 252. Similarly, in the case of the cathode reaction layer 241, for example, it is possible to identify the cathode reaction layer 241 as a degraded part by changing the partial pressure of water vapor 11 in the cathode flow path 21, the temperature of the cell stack 20, and the like. Furthermore, by changing the partial pressure of water vapor 11 and the like, it is possible to improve reactivity to water vapor 11 and reduce the overvoltage of the cathode reaction layer 241. In the case of the cathode diffusion layer 242, for example, the fluid flow rate of the gas flowing through the cathode flow path 21 and the temperature of the cell stack 20 can be changed to identify the cathode diffusion layer 242 as a deteriorated portion and reduce the overvoltage of the cathode diffusion layer 242. That is, if the diffusion efficiency of the water vapor 11 or hydrogen gas decreases due to deterioration of the cathode diffusion layer 242, the diffusion efficiency can be increased by, for example, increasing the fluid flow rate of the gas through the cathode flow path 21, thereby reducing the electrolysis voltage, etc. In the case of the electrolyte 23, for example, the temperature of the electrochemical cell 2, or the temperature of the cell stack 20, can be changed to identify the deteriorated portion and reduce the internal resistance or electrolysis voltage of the electrolyte 23 to a target value. Identification of the electrolyte 23 as a deteriorated portion and the reduction operation for the electrolyte 23 will be described below.

[0048] The graph in FIG. 8 shows the results of a deterioration diagnosis when the diagnosis item is the "temperature of the electrochemical cell 2." In the graph in FIG. 8, the horizontal axis represents the temperature of the electrochemical cell 2 (hereinafter referred to as the cell temperature), and the vertical axis represents the electrolysis voltage. To perform the deterioration diagnosis, the cell temperature is first changed from the temperature C0 during initial operation. In this embodiment, the cell temperature is increased from the temperature C0 during initial operation to a value C3. The deterioration part identifying unit 31 then measures the electrolysis voltage when the cell temperature is at the value C3 using the voltage measuring unit 52. Furthermore, the deterioration part identifying unit 31 measures the voltage difference ΔV1 between the electrolysis voltage V1c of the deteriorated electrochemical cell 2 at the cell temperature C0 during initial operation and the electrolysis voltage V1d when the cell temperature is at the value C3. Note that in the graph in FIG. 8, the characteristic line L3 is an approximation line of the plot of past test result data and represents the characteristics of an undegraded electrochemical cell 2.

[0049] In this embodiment, the reference value for the amount of state change is the voltage difference ΔV0 between the electrolysis voltages when the cell temperature is changed under the same conditions using an undegraded electrochemical cell 2. That is, the voltage difference ΔV0 is the difference between the electrolysis voltage V0c at the cell temperature C0 during initial operation when an undegraded electrochemical cell 2 is used, and the electrolysis voltage V0d when the cell temperature is C3. The degradation portion identifying unit 31 then compares the voltage difference ΔV1 with the voltage difference ΔV0. If the voltage difference ΔV1 is greater than a predetermined value relative to the voltage difference ΔV0, the unit determines that the electrolyte 23 has deteriorated and identifies the deteriorated portion. Here, deterioration of the electrolyte 23 refers to, for example, a state in which oxide ions have difficulty passing through the electrolyte 23 due to a structural change caused by high temperature. The deterioration of the electrolyte 23 increases the overvoltage of the electrolyte 23.

[0050] Next, the operation determination unit 32 determines the reduction operation based on the degradation diagnosis result, as shown in Fig. 9. In the graph of Fig. 9, characteristic line L4 is an approximate straight line of the plot of data when the degradation diagnosis is performed on the deteriorated electrochemical cell 2, and is a straight line that indicates the characteristics of the deteriorated electrochemical cell 2.

[0051] Specifically, the operation determination unit 32 determines the cell temperature at which the target voltage V0, which is the target value, is reached based on the characteristic line L4. Then, as a reduction operation, the value of the cell temperature is increased to the determined value C4. Specifically, the control unit 3 controls the temperature adjustment unit 151 to increase the cell temperature. This allows oxide ions generated in the cathode reaction layer 241 to easily pass through the electrolyte 23, reducing the overvoltage of the electrolyte 23. This sets the electrolysis voltage of the electrochemical cell 2 to a predetermined target value.

[0052] Next, the effects of this embodiment will be described. The cell control system 1 includes a degradation portion identifying unit 31 and an operation determining unit 32. Therefore, it is possible to perform a reduction operation according to the degradation portion of the electrochemical cell 2. This makes it possible to efficiently reduce the internal resistance of the electrochemical cell 2. As a result, it is possible to operate the electrochemical cell 2 with a low internal resistance, and it is possible to suppress degradation of the electrochemical cell 2.

[0053] Water electrolysis occurs through reactions at various locations in the electrochemical cell 2. For the reaction process in the electrochemical cell 2 to proceed, overvoltage is required in addition to the theoretical voltage. The overvoltage of the electrochemical cell 2 increases due to the deterioration of various locations in the electrochemical cell. Operating the electrochemical cell under high overvoltage conditions may accelerate the deterioration of the electrochemical cell. Furthermore, if an attempt is made to reduce the internal resistance or overvoltage solely by controlling the cell temperature without identifying the deteriorated locations in the electrochemical cell, the internal resistance or overvoltage may not be sufficiently reduced if the operation required to reduce the internal resistance, etc. is other than changing the cell temperature. Furthermore, if the temperature of the electrochemical cell is raised excessively, catalyst aggregation may occur, which may accelerate the deterioration of the electrochemical cell. Therefore, in this embodiment, deterioration diagnosis and reduction operations are performed. This allows the deteriorated locations to be identified and reduction operations appropriate for each deteriorated location to be performed. Therefore, the internal resistance of the electrochemical cell 2 can be efficiently reduced, and the overvoltage can also be efficiently reduced. Therefore, the electrochemical cell 2 can be operated in a state where the overvoltage is low, and it is possible to suppress deterioration of the electrochemical cell 2. As a result, the life of the electrochemical cell 2 can be extended.

[0054] In this embodiment, the reduction operation is an operation of changing at least one of the temperature of the electrochemical cell 2, the pressure of the cathode flow channel 21, the pressure of the anode flow channel 22, the partial pressure of water vapor in the gas supplied to the cathode flow channel 21, the partial pressure of oxygen in the gas supplied to the anode flow channel 22, the flow rate of the gas in the cathode flow channel 21, and the flow rate of the gas in the anode flow channel 22. This makes it easy to sufficiently reduce the internal resistance and overvoltage of the electrochemical cell 2. Furthermore, the reduction operation can be performed using a device used for water electrolysis, without the need to provide a new device or the like for performing the reduction operation. As a result, it is easy to simplify the structure and reduce the size.

[0055] The degradation part identifying unit 31 identifies the degradation part of the electrochemical cell 2 by changing the value of at least one of the above-mentioned multiple diagnostic items. Furthermore, the degradation part identifying unit 31 identifies the degradation part of the electrochemical cell 2 by comparing the measured change amount with a reference value. This makes it easy to accurately identify the degradation part. As a result, it is easy to sufficiently reduce the internal resistance and overvoltage of the electrochemical cell 2. Furthermore, because the degradation part can be identified by measuring the measured change amount of the above-mentioned diagnostic items, degradation diagnosis can be performed using equipment used for water electrolysis, etc., without the need to install a new device or the like for performing degradation diagnosis. As a result, it is easy to simplify and miniaturize the structure.

[0056] In this embodiment, the values ​​of multiple diagnostic items are changed to identify the deteriorated portion of the electrochemical cell 2. This makes it easier to identify the deteriorated portion more accurately. As a result, the overvoltage can be sufficiently reduced, and the deterioration of the electrochemical cell 2 can be further suppressed.

[0057] In this embodiment, the anode flow path 22 is configured to allow air to flow through it. The cell control system 1 changes the oxygen partial pressure in the anode flow path 22 by also flowing a gas other than air through the anode flow path 22. This allows the oxygen partial pressure in the anode flow path 22 to be changed sufficiently and easily. As a result, reduction operations and deterioration diagnosis can be performed accurately and easily.

[0058] In this embodiment, the amount of state change is the amount of change in the magnitude of the voltage applied to the electrochemical cell 2 when the output current to the electrochemical cell 2 is controlled to a constant current. This makes it easy to accurately identify the deteriorated portion and to easily perform deterioration diagnosis. Furthermore, deterioration diagnosis can be performed without providing a new device or the like for performing deterioration diagnosis, which makes it easy to simplify and miniaturize the structure.

[0059] The electrochemical cell 2 is a solid oxide cell, which makes it easy to improve the power generation efficiency.

[0060] The cell control system 1 of this embodiment is configured to prohibit at least one of the degradation diagnosis and the reduction operation under predetermined prohibition conditions. Therefore, for example, when the remaining amount of hydrogen gas in the hydrogen storage tank for storing the hydrogen gas produced by the electrochemical cell 2 is equal to or less than a predetermined value, it is possible to suppress a decrease in the amount of hydrogen gas produced. As a result, it is easy to ensure a sufficient amount of hydrogen gas is produced.

[0061] In the cell control system 1 of this embodiment, when the prohibition of at least one of the degradation diagnosis and the mitigation operation continues for a predetermined period, the cell control system 1 controls the degradation diagnosis and the mitigation operation to be performed even if the prohibition conditions are met. Therefore, the overvoltage of the electrochemical cell 2 can be sufficiently reduced. As a result, the life of the electrochemical cell 2 can be sufficiently extended. Furthermore, it is easy to maintain sufficient productivity of hydrogen gas for a long period of time.

[0062] In this embodiment, the content of the reduction operation is the same as the diagnosis items, so that the overvoltage of the electrochemical cell 2 can be more easily reduced sufficiently based on the results of the deterioration diagnosis.

[0063] As described above, according to this embodiment, it is possible to provide a cell control system 1 that can efficiently reduce the internal resistance of the electrochemical cell 2, thereby suppressing deterioration of the electrochemical cell 2.

[0064] In the first embodiment, the temperature measurement unit measures the temperature of the cell stack 20. However, the temperature measurement unit can also measure, for example, the temperature of the gas in the cathode exhaust flow path or the anode exhaust flow path, and use that temperature as the representative temperature of the electrochemical cell. Alternatively, the temperature measurement unit can measure, for example, the temperature at the end of the cell stack in the stacking direction, the temperature at the center of the cell stack, or the temperature at the end of the gas supply side or exhaust side of the cathode flow path or the anode flow path of the electrochemical cell, and use that temperature as the representative temperature of the electrochemical cell.

[0065] In the first embodiment, the voltage measurement unit 52 measures the voltage applied to the cell stack 20. However, the voltage measurement unit can also measure, for example, the voltage of a specific electrochemical cell. That is, the voltage measurement unit can measure, for example, the voltage of an electrochemical cell that is relatively hotter than the other electrochemical cells that make up the cell stack, and therefore more reactive and prone to degradation. The voltage measurement unit can also measure, for example, the voltage of an electrochemical cell that is more likely to have a relatively lower flow rate of gas flowing through the cathode flow path or the anode flow path than the other electrochemical cells that make up the cell stack. The voltage measurement unit can also be configured to measure the power supply terminal voltage.

[0066] Furthermore, by simultaneously performing a plurality of reduction operations, the internal resistance or electrolysis voltage of the electrochemical cell 2 can be reduced to a target value.

[0067] (Embodiment 2) This embodiment is configured to control the voltage applied to the electrochemical cell 2 to a constant value.

[0068] In this embodiment, the amount of change in state is the amount of change in the magnitude of the current flowing through the electrochemical cell when the output voltage to the electrochemical cell 2 is controlled to a constant voltage. In other words, the power supply applies a constant voltage to the cell stack.

[0069] Next, the control by the control unit will be described with reference to the flowchart of FIG. In step S11A of this embodiment, the same control as step S1 of embodiment 1 is performed. In this embodiment, the magnitude of the current flowing through the electrochemical cell 2 is measured in step S12. After measuring the magnitude of the current in step S12, in step S13, it is determined whether the value of the current flowing through the electrochemical cell 2 is equal to or less than a predetermined threshold. That is, in this embodiment, whether the electrochemical cell has deteriorated is determined based on the magnitude of the current flowing through the electrochemical cell when the output voltage to the electrochemical cell 2 is controlled to a constant voltage. If the current value of the electrochemical cell is equal to or less than the threshold, the process proceeds to step S14. On the other hand, if the current value of the electrochemical cell is greater than the threshold in step S13, the process proceeds to step S15. That is, as the operating time of the electrochemical cell elapses, the electrochemical cell gradually deteriorates and the overvoltage increases. As a result, the current value of the electrochemical cell gradually decreases from the initial target value. Then, when the current value becomes equal to or less than the threshold, degradation diagnosis and reduction operation are performed under predetermined conditions. As a result, the value of the current flowing through the electrochemical cell 2 is increased to a predetermined target value. Steps S14, S15, and S17 in this embodiment are controlled in the same manner as steps S4, S5, and S7 in the first embodiment, and therefore their explanation will be omitted.

[0070] Next, in step S16, the value of one of the multiple diagnostic items is changed, and the process proceeds to step S18. Next, in step S18, the amount of change in the current flowing through the electrochemical cell before the value of the diagnostic item is changed and the amount of change in the current flowing through the electrochemical cell after the value of the diagnostic item is changed in step S16 are measured as the amount of measurement change. In other words, the degradation part identifying unit measures the amount of change in the magnitude of the current flowing through the electrochemical cell when the value of the diagnostic item is changed, as the amount of measurement change.

[0071] After step S18, the process proceeds to step S19, where it is determined whether or not all of the diagnostic items have been changed. If the values ​​of all of the diagnostic items have been changed, the process proceeds to step S110, where the deteriorated part is identified based on the amount of change in the measurement. On the other hand, if it is determined in step S19 that the values ​​of all of the diagnostic items have not been changed, the process returns to step S16, where the value of the next diagnostic item is changed. Then, steps S16 to S19 are repeated until all of the diagnostic items have been changed.

[0072] Next, after identifying the deteriorated portion in step S110, the process proceeds to step S111, where a reduction operation is performed so that the value of the current flowing through the electrochemical cell 2 reaches a predetermined target value. Thereafter, the process returns to step S11A, and the same control is performed. Other aspects are the same as those of embodiment 1. Note that, among the symbols used in embodiment 2 and onwards, the same symbols as those used in the previous embodiments represent the same components, etc. as those in the previous embodiments, unless otherwise specified.

[0073] In this embodiment, the amount of change in state is the amount of change in the magnitude of the current flowing through the electrochemical cell 2 when the output voltage to the electrochemical cell 2 is controlled to a constant voltage. This makes it easy to accurately identify the deteriorated portion and to perform deterioration diagnosis. Furthermore, deterioration diagnosis can be performed using equipment used for water electrolysis, without the need to install a new device or the like for performing deterioration diagnosis. In addition, the same effects as those of the first embodiment are achieved.

[0074] (Embodiment 3) As shown in FIG. 11, this embodiment is configured so that carbon dioxide is supplied to the cathode flow channel 21.

[0075] 11 , the cell control system 1 has a carbon dioxide supply channel 59 that supplies a gas containing carbon dioxide to the cathode flow channel 21 via the cathode supply flow channel 53. The carbon dioxide supply channel 59 is connected to the cathode supply flow channel 53. A flow rate adjuster 591 is provided in the carbon dioxide supply channel 59. The control unit 3 adjusts the flow rate adjuster 591 to adjust the amount of gas containing carbon dioxide that flows into the cathode flow channel 21.

[0076] That is, carbon dioxide gas is supplied to the cathode flow path 21 in addition to water vapor. The electrochemical cell 2 generates hydrogen and carbon monoxide from the water vapor and carbon dioxide through co-electrolysis. The gas containing hydrogen and carbon monoxide is then discharged to the cathode discharge flow path 57. Here, co-electrolysis is an electrolysis reaction in which water and carbon dioxide are electrolyzed simultaneously, and the reaction "3H2O + CO2 → CO + 3H2 + 2O2" occurs in the electrochemical cell 2. The rest is the same as in the first embodiment.

[0077] In this embodiment, the electrochemical cell 2 produces hydrogen and carbon monoxide from water vapor and carbon dioxide by co-electrolysis. Therefore, the produced gas containing hydrogen and carbon monoxide can be used, for example, to produce methane. In addition, the same effects as those of the first embodiment are achieved.

[0078] (Embodiment 4)

[0079] As shown in FIG. 12, the cell control system 1 of this embodiment is provided with a return flow path 581 that branches off from the anode discharge flow path 58 and connects the anode discharge flow path 58 and the anode supply flow path 54.

[0080] By driving a pump 582 provided in the reflux channel 581, the reflux channel 581 supplies the gas flowing through the anode discharge channel 58 back to the anode channel 22 via the anode supply channel 54. In addition, the controller 3 controls the pump 582 to adjust the amount of gas in the anode discharge channel 58 that is refluxed to the anode channel 22. The rest is the same as in the first embodiment.

[0081] The cell control system 1 of this embodiment includes a return flow path 581. Therefore, the gas at a relatively high temperature flowing through the anode exhaust flow path 58 can be supplied again to the anode flow path 22. Therefore, the exhaust heat of the gas flowing through the anode exhaust flow path 58 can be recovered. As a result, energy efficiency can be improved. In addition, the same effects as those of the first embodiment are achieved.

[0082] (Embodiment 5) As shown in FIG. 13, this embodiment is configured to supply air to the anode flow channel 22 using high-pressure gas.

[0083] In this embodiment, high-pressure gas from a factory or a cylinder is supplied to the inert gas supply channel 55. The internal pressure of the inert gas supply channel 55 is higher than the internal pressure of the anode supply channel 54. In this embodiment, the internal pressure of the anode supply channel 54 is equivalent to atmospheric pressure. The pressure of the gas supplied to the inert gas supply channel 55 can be, for example, several hundred kPaG or less.

[0084] 13, an ejector 62 is provided in the inert gas supply channel 55. The ejector 62 is also connected to the anode supply channel 54. The ejector 62 uses the high-pressure inert gas in the inert gas supply channel 55 as a driving flow to suck in air flowing through the anode supply channel 54 and supplies it together with the inert gas to the electrochemical cell 2. In this embodiment, an air pump is not provided in the anode supply channel 54.

[0085] A flow rate adjusting unit 551 is provided in a portion of the inert gas supply path 55 upstream of the ejector 62. The control unit 3 adjusts the flow rate adjusting unit 551 to adjust the amount of inert gas flowing into the ejector 62. The rest is the same as in the first embodiment.

[0086] In this embodiment, an ejector 62 is used to supply gas from the anode supply flow path 54 to the anode flow path 22. Therefore, air can be introduced into the electrochemical cell 2 without providing an air pump in the anode supply flow path 54. As a result, it is possible to simplify the equipment and reduce costs. In other words, when introducing an inert gas into the anode flow path 22 during normal operation or for the purpose of reduction operation, the air can be supplied to the anode flow path 22 using the pressure of the inert gas without using an air pump. In addition, the same effects as those of the first embodiment are achieved.

[0087] (Embodiment 6) This embodiment is configured to adjust the pressure in the cathode flow channel 21 and the anode flow channel 22 by adjusting the back pressure of the electrochemical cell 2.

[0088] 14 , in this embodiment, the cathode exhaust flow path 57 and the anode exhaust flow path 58 are provided with pressure adjustment units 573 and 583, respectively. The pressure adjustment units 573 and 583 are configured to adjust the flow path resistance of the cathode exhaust flow path 57 or the anode exhaust flow path 58, thereby adjusting the pressure in the cathode flow path 21 or the anode flow path 22. The pressure adjustment units 573 and 583 may be, for example, solenoid valves. The control unit 3 controls the pressure adjustment units 573 and 583 to adjust the pressure in the cathode flow path 21 or the anode flow path 22. The rest is the same as in the first embodiment.

[0089] In this embodiment, the pressure adjusting units 573, 583 are configured to adjust the pressure in the cathode flow path 21 or the anode flow path 22. This makes it easy to adjust the pressure in the cathode flow path 21 or the anode flow path 22. This makes it easy to perform deterioration diagnosis and reduction operations using the pressure in the cathode flow path 21 and the anode flow path 22. As a result, the overvoltage of the electrochemical cell 2 can be reduced more efficiently. In addition, the same effects as those of the first embodiment are achieved.

[0090] (Embodiment 7) This embodiment is provided with a plurality of cell stacks 20 as shown in FIG.

[0091] As shown in Fig. 15, the cell control system 1 of this embodiment includes a plurality of cell stacks 20, a plurality of temperature adjustment units 151, and a plurality of housings 15. In this embodiment, two housings 15 are provided, and two cell stacks 20 are housed in each housing 15. The temperature of each cell stack 20 is adjusted by a separate temperature adjustment unit 151. A cathode exhaust flow path 57 and an anode exhaust flow path 58 are connected to each of the two housings 15. Pressure adjustment units 573 and 583 are provided in the two cathode exhaust flow paths 57 and the two anode exhaust flow paths 58, respectively, so that the pressure of the cathode flow path and the anode flow path can be adjusted for each housing 15.

[0092] A cathode supply flow path 53, an anode supply flow path 54, and the like are connected to each of the two housings 15. Although not shown, an inert gas is introduced from an inert gas supply path into each anode supply flow path 54. A flow rate adjusting unit (not shown) is provided in each of the cathode supply flow path 53, the anode supply flow path 54, and the inert gas supply path, so that the flow rate, oxygen partial pressure, and the like of the cathode flow path and anode flow path of the electrochemical cell can be adjusted for each housing 15. The rest is the same as in the sixth embodiment.

[0093] In this embodiment, a plurality of cell stacks 20 are provided, which makes it possible to further improve the hydrogen production capacity.

[0094] Furthermore, in this embodiment, multiple housings 15 are provided, each housing 15 containing a cell stack 20. Therefore, it is possible to adjust the temperature of the cell stack 20, the flow rate, pressure, oxygen partial pressure, etc. of the cathode flow path and anode flow path for each housing 15. Therefore, it is possible to perform degradation diagnosis and mitigation operations at different times and with different contents for each housing 15. In addition, the same effects as those of the sixth embodiment are obtained. (Embodiment 8) In this embodiment, as shown in FIG. 16, heat shields 16 are provided between a plurality of cell stacks 20. In the embodiment shown in FIG.

[0095] In this embodiment, as shown in Fig. 16, a plurality of cell stacks 20 are accommodated in the housing 15. In this embodiment, two cell stacks 20 are accommodated in the housing 15. Furthermore, in order to adjust the temperature of each cell stack 20 separately, a temperature adjustment unit 151 is provided for each of the two cell stacks 20. In this embodiment, the controlled temperatures of each cell stack 20 are different from each other.

[0096] Furthermore, the cell stack 20 reaches a high temperature of approximately 700°C during operation, and this heat is released to the outside as radiant heat. Therefore, in this embodiment, a heat shield 16 is provided between the two cell stacks 20 to block the radiant heat emitted from the cell stacks 20. The heat shield 16 can be, for example, a heat shield plate. The rest is the same as in the first embodiment.

[0097] In this embodiment, a heat shield 16 is provided between the two cell stacks 20. This makes it possible to suppress heat transfer from a cell stack 20 with a relatively high temperature to a cell stack 20 with a relatively low temperature. Therefore, even if two or more cell stacks 20 are housed in the housing 15, it is easy to adjust the temperature of each cell stack 20 to a desired temperature. This makes it easy to manage the temperature of each cell stack 20. In addition, the same effects as those of the first embodiment are achieved.

[0098] (Embodiment 9) 17 to 21, the cell control system 1 of this embodiment controls an electrochemical cell 2 that functions as a fuel cell. In this embodiment, the electrochemical cell 2 is an SOFC (Solid Oxide Fuel Cell) and is electrically connected to an external load 18.

[0099] 17, the electrochemical cell 2 is configured to generate power by supplying a gas containing an oxidant 12 to the cathode flow path 21 and a gas containing a fuel 13 to the anode flow path 22. In this embodiment, the reduction operation determined by the operation determination unit 32 is performed, thereby controlling at least one of the internal resistance of the electrochemical cell 2, the output voltage of the electrochemical cell 2, and the output current of the electrochemical cell 2 to be a predetermined target value.

[0100] In this embodiment, the cathode supply flow path 53 supplies air to the cathode flow path 21, and the anode supply flow path 54 supplies gas containing fuel 13 to the anode flow path 22. In this embodiment, the oxidant 12 is oxygen, and the fuel 13 is hydrogen gas. Also, in this embodiment, gas with a low oxygen partial pressure from the electrochemical cell 2 flows through the cathode discharge flow path 57, and gas containing a large amount of water vapor generated by the electrochemical cell 2 flows through the anode discharge flow path 58. In other words, air after oxygen 12 has been consumed by the electrochemical cell 2 flows through the cathode discharge flow path 57.

[0101] 18 , the cathode supply flow path 53 is provided with an air pump 532 for supplying air to the cathode flow path 21. The anode supply flow path 54 is provided with a flow rate adjuster 542 for adjusting the flow rate of gas containing fuel 13 to be supplied to the anode flow path 22. The flow rate adjuster 542 may be, for example, an electromagnetic valve. The control unit 3 controls the air pump 532 and the flow rate adjuster 542 to adjust the amount of air supplied to the cathode flow path 21, the amount of fuel 13 supplied to the anode flow path 22, the partial pressure of the fuel 13 in the anode flow path 22, etc.

[0102] As shown in FIG. 17, in the cathode reaction layer 241, oxygen 12 is reduced to generate oxide ions. In the anode reaction layer 251, a reaction occurs in which protons and electrons are generated from hydrogen gas in the fuel 13. The generated electrons then flow to the external load 18, and the protons react with oxide ions that have migrated to the anode reaction layer 251 through the electrolyte 23, generating water vapor. The generated water vapor diffuses in the anode diffusion layer 252, migrates to the anode flow path 22, and is discharged to the anode exhaust flow path 58. The cathode reaction layer 241 and the anode reaction layer 251 each contain a catalyst to promote the reaction in their respective reaction layers.

[0103] Next, the control by the control unit 3 will be described with reference to the flowchart of FIG. In step S21 of this embodiment, the same control as in step S1 of embodiment 1 is performed. In this embodiment, in step S22, the output voltage from the electrochemical cell 2 to the external load 18 is measured. After measuring the magnitude of the output voltage in step S22, in step S23, it is determined whether the value of the output voltage of the electrochemical cell 2 is equal to or less than a predetermined threshold. That is, in this embodiment, deterioration of the electrochemical cell 2 is determined based on the output voltage of the electrochemical cell 2 to the external load 18. If the output voltage value of the electrochemical cell 2 is equal to or less than the threshold, the process proceeds to step S24. On the other hand, if the output voltage value exceeds the threshold in step S23, the process proceeds to step S25. That is, as the operating time of the electrochemical cell 2 elapses, the electrochemical cell 2 gradually deteriorates, and the output voltage value of the electrochemical cell 2 gradually decreases from the initial target value due to an increase in overvoltage. Then, when the output voltage becomes equal to or less than the threshold, deterioration diagnosis and reduction operation are performed under predetermined conditions. As a result, the output voltage of the electrochemical cell 2 is increased to the predetermined target value. Steps S25 and S27 in this embodiment are controlled in the same manner as steps S5 and S7 in the first embodiment, and therefore their explanation will be omitted.

[0104] In step S24, it is determined whether or not the diagnosis prohibition condition is met. In this embodiment, the diagnosis prohibition condition may be, for example, when the amount of power generation required of the electrochemical cell 2 is equal to or greater than a predetermined value.

[0105] Next, in step S26, the value of one of the multiple diagnostic items is changed, and the process proceeds to step S28. Next, in step S28, the amount of change in the output voltage before the value of the diagnostic item is changed and the amount of change in the output voltage after the value of the diagnostic item is changed in step S26 are measured as the amount of measurement change. In other words, the degradation part identifying unit 31 measures the amount of change in the magnitude of the output voltage when the value of the diagnostic item is changed, as the amount of measurement change.

[0106] In this embodiment, the temperature of the electrochemical cell 2, the pressure of the cathode flow path 21, the pressure of the anode flow path 22, the partial pressure of oxygen 12 in the gas supplied to the cathode flow path 21, the partial pressure of fuel 13 in the gas supplied to the anode flow path 22, the gas flow rate in the cathode flow path 21, and the gas flow rate in the anode flow path 22 are each set as diagnostic items for the deterioration part identification unit 31.

[0107] After step S28, the process proceeds to step S29, where it is determined whether or not all of the diagnostic items have been changed. If the values ​​of all of the diagnostic items have been changed, the process proceeds to step S210, where the deteriorated part is identified based on the amount of change in the measurement. On the other hand, if it is determined in step S29 that the values ​​of all of the diagnostic items have not been changed, the process returns to step S26, where the value of the next diagnostic item is changed. Then, steps S26 to S29 are repeated until all of the diagnostic items have been changed.

[0108] Next, after identifying the deteriorated portion in step S210, the process proceeds to step S211, where a reduction operation is performed so that the output voltage value of the electrochemical cell 2 reaches a predetermined target value. Thereafter, the process returns to step S21 again, and the same control is performed.

[0109] In addition, in this embodiment, the reduction operation is an operation that changes at least one of the temperature of the electrochemical cell 2, the pressure of the cathode flow path 21, the pressure of the anode flow path 22, the partial pressure of the fuel 13 in the gas supplied to the anode flow path 22, the partial pressure of the oxygen 12 in the gas supplied to the cathode flow path 21, the flow rate of the gas in the cathode flow path 21, and the flow rate of the gas in the anode flow path 22.

[0110] Next, as a specific example, the diagnosis content when the diagnosis item is "oxygen partial pressure of gas supplied to the cathode flow path 21" will be described with reference to the graph in FIG. 20. In the graph in FIG. 20, the horizontal axis represents the oxygen partial pressure in the cathode flow path 21, and the vertical axis represents the output voltage of the electrochemical cell 2. In the graph in FIG. 20, the black circles represent data from a previous test, showing the relationship between the oxygen partial pressure and the output voltage when a non-degraded electrochemical cell 2 was used. Furthermore, the white circles represent the relationship between the oxygen partial pressure and the output voltage when a degradation diagnosis was performed on a degraded electrochemical cell 2. In the graph in FIG. 20, when the data for the degraded electrochemical cell 2 and the data for the non-degraded electrochemical cell 2 are compared during initial operation, the output voltage of the degraded electrochemical cell 2 is lower, indicating that the output voltage of the electrochemical cell 2 decreases due to degradation. Furthermore, the characteristic line L5 is an approximation line of the plot of the past test result data, showing the characteristics of the non-degraded electrochemical cell 2.

[0111] Furthermore, when performing degradation diagnosis, first, the value of the oxygen partial pressure in the cathode flow path 21 is changed from the value C0 during initial operation. In this embodiment, the value of the oxygen partial pressure is increased from the value C0 during initial operation to a value C5. Then, the degradation part identifying unit 31 measures the output voltage when the oxygen partial pressure is the value C5 using the voltage measuring unit. Furthermore, the degradation part identifying unit 31 measures the voltage difference ΔV1, which is the measured change amount, and is the difference between the output voltage V1g at the oxygen partial pressure C0 during initial operation and the output voltage V1h when the oxygen partial pressure is the value C5.

[0112] In this embodiment, the reference value for the amount of state change is the voltage difference ΔV0 between the output voltages when the oxygen partial pressure is changed under the same conditions using a non-degraded electrochemical cell 2. That is, the voltage difference ΔV0 is the difference between the output voltage V0e at an oxygen partial pressure of C0 during initial operation using a non-degraded electrochemical cell 2 and the output voltage V0f when the oxygen partial pressure is C5. The degradation portion identifying unit 31 then compares the voltage difference ΔV1 with the voltage difference ΔV0. If the voltage difference ΔV1 is greater than a predetermined value relative to the voltage difference ΔV0, the degradation portion identifying unit 31 determines that the cathode reaction layer 241 is degraded and identifies the degraded portion. Here, degradation of the cathode reaction layer 241 refers to, for example, adhesion of foreign matter contained in the gas supplied to the cathode flow path 21 to the cathode reaction layer 241, or a reduction in the reaction area of ​​the cathode reaction layer 241 due to structural changes caused by high temperatures, which makes it difficult to reduce oxygen 12. As the cathode reaction layer 241 deteriorates, the overvoltage of the cathode reaction layer 241 increases.

[0113] Next, after identifying the deteriorated portion, the operation determination unit 32 determines the reduction operation based on the result of the deterioration diagnosis, as shown in Fig. 21. In the graph of Fig. 21, the characteristic line L6 is an approximate straight line of the plot of data when the deterioration diagnosis is performed on the deteriorated electrochemical cell 2, and is a straight line that indicates the characteristics of the deteriorated electrochemical cell 2.

[0114] Specifically, the operation determination unit 32 determines the oxygen partial pressure at which the target voltage V0, which is the target value, is reached, based on the characteristic line L6. Then, as a reduction operation, the oxygen partial pressure of the gas supplied to the cathode flow channel 21 is increased to a value C6. Specifically, the oxygen partial pressure is increased by flowing a gas with a high oxygen partial pressure into the cathode flow channel 21, and the oxygen concentration in the cathode flow channel 21 is increased to above 21%. This makes it easier for oxygen 12 to be reduced in the cathode reaction layer 241, and the overvoltage of the cathode reaction layer 241 is reduced. This sets the output voltage of the electrochemical cell 2 to a predetermined target value.

[0115] That is, in this embodiment, the cathode flow channel 21 is configured to allow air to flow through it. The cell control system 1 changes the oxygen partial pressure in the cathode flow channel 21 by flowing a gas other than air through the cathode flow channel 21. In this embodiment, as shown in FIG. 18 , an oxygen-enriched gas supply channel 61 is provided that supplies an oxygen-rich gas containing a large amount of oxygen to the cathode flow channel 21. The oxygen-enriched gas has a higher oxygen partial pressure than air. The oxygen-enriched gas supply channel 61 is connected to the cathode supply flow channel 53 and supplies the oxygen-enriched gas to the cathode flow channel 21 via the cathode supply flow channel 53. This increases the oxygen partial pressure in the cathode flow channel 21. In addition, the oxygen-enriched gas supply channel 61 is provided with a flow rate regulator 611 that regulates the flow rate of the oxygen-enriched gas supplied to the cathode flow channel 21. The control unit 3 controls the flow rate regulator 611 to control the oxygen partial pressure in the cathode flow channel 21. The flow rate adjusting unit 611 may be, for example, an electromagnetic valve. The rest is the same as in the first embodiment.

[0116] In this embodiment, the cell control system 1 also has a deteriorated portion identifying unit 31 and an operation determining unit 32. Therefore, it is possible to perform a reduction operation according to the deteriorated portion of the electrochemical cell 2. As a result, it is possible to suppress the deterioration of the electrochemical cell 2.

[0117] In this embodiment, the reduction operation is an operation that changes at least one of the temperature of the electrochemical cell 2, the pressure in the cathode flow channel 21, the pressure in the anode flow channel 22, the partial pressure of the fuel 13 in the gas supplied to the anode flow channel 22, the partial pressure of the oxygen 12 in the gas supplied to the cathode flow channel 21, the gas flow rate in the cathode flow channel 21, and the gas flow rate in the anode flow channel 22. This makes it easy to sufficiently reduce the internal resistance and overvoltage of the electrochemical cell 2. As a result, it is easy to ensure sufficient output voltage and output current of the electrochemical cell 2. Furthermore, the reduction operation can be performed using equipment used for power generation, without the need to provide a new device or the like for performing the reduction operation. As a result, it is easy to simplify the structure and reduce the size.

[0118] In this embodiment, the degradation part identifying unit 31 also identifies the degradation part of the electrochemical cell 2 by changing the value of at least one of the above-mentioned multiple diagnostic items. This makes it easy to accurately identify the degradation part. Furthermore, since the degradation part can be identified by measuring the amount of change in the measurement of the above-mentioned diagnostic items, degradation diagnosis can be performed using equipment used for power generation, without the need to install a new device or the like for performing degradation diagnosis. As a result, it is easy to simplify the structure and reduce the size.

[0119] The cell control system 1 changes the oxygen partial pressure in the cathode flow path 21 by flowing a gas other than air through the cathode flow path 21. Therefore, the oxygen partial pressure in the cathode flow path 21 can be changed sufficiently and easily. As a result, reduction operations and deterioration diagnosis can be performed accurately and easily.

[0120] In this embodiment, the oxygen-enriched gas supply channel 61 is provided. This makes it easy to adjust the oxygen partial pressure of the gas flowing through the cathode flow channel 21. This makes it easy to perform deterioration diagnosis and reduction operations based on the oxygen partial pressure in the cathode flow channel 21. As a result, the overvoltage of the electrochemical cell 2 can be efficiently reduced, and deterioration of the electrochemical cell 2 can be efficiently suppressed. In addition, the same effects as those of the first embodiment are achieved.

[0121] In the case of a cell control system for controlling an electrochemical cell functioning as a fuel cell, as in the above-described embodiment 9, the amount of change in state can be, for example, the amount of change in the magnitude of the output voltage of the electrochemical cell when the output current of the electrochemical cell is controlled to a constant current. Furthermore, in the case of a cell control system for controlling an electrochemical cell functioning as a fuel cell, the amount of change in state can be, for example, the amount of change in the magnitude of the output current of the electrochemical cell when the output voltage of the electrochemical cell is controlled to a constant voltage. In these cases, it is easy to accurately identify the deteriorated portion and to easily perform deterioration diagnosis. Furthermore, deterioration diagnosis can be performed without the need to newly install a device for performing deterioration diagnosis, which facilitates simplification and miniaturization of the structure.

[0122] (Embodiment 10) In this embodiment, the fuel 13 that is not utilized by the electrochemical cell 2 and is discharged is used to adjust the temperature of the electrochemical cell 2.

[0123] In the cell control system 1 of this embodiment, as shown in FIG. 22 , a cathode exhaust flow path 57 and an anode exhaust flow path 58 merge to form a merged flow path 17. An off-gas burner 152, which will be described later, is provided in the merged flow path 17. The cathode supply flow path 53 is provided with a branch flow path 533 that branches off from a flow path that supplies air to the cathode flow path 21 and is connected to the cathode exhaust flow path 57. The branch flow path 533 is provided with a flow rate adjuster 534 that adjusts the flow rate of air supplied to the cathode exhaust flow path 57. The control unit 3 controls the flow rate adjuster 534 to adjust the flow rate of air supplied to the cathode exhaust flow path 57. The flow rate adjuster 534 can be, for example, an electromagnetic valve.

[0124] The anode exhaust flow path 58 also contains hydrogen that has not been used in the power generation by the electrochemical cell 2. The off-gas burner 152 combusts oxygen contained in the gas that flows from the branch flow paths 533 and the cathode exhaust flow path 57 into the combined flow path 17, and hydrogen that remains in the gas that flows from the anode exhaust flow path 58 into the combined flow path 17. The high-temperature gas combusted by the off-gas burner 152 flows through the combined flow path 17 into the temperature adjustment unit 151. In this embodiment, the temperature adjustment unit 151 is configured to be heated by the high-temperature gas combusted by the off-gas burner 152, and to adjust the temperature of the cell stack 20 using the heat. The rest is the same as in the ninth embodiment.

[0125] In this embodiment, a temperature adjustment unit 151 is provided that adjusts the temperature of the electrochemical cell 2 using high-temperature gas generated by combustion in an off-gas burner 152. Therefore, the energy of the fuel 13 contained in the gas discharged from the electrochemical cell 2 can be used to adjust the temperature of the electrochemical cell 2. As a result, energy efficiency can be further improved. In addition, the same effects as those of the ninth embodiment are obtained.

[0126] In the tenth embodiment, the electrochemical cell 2 is heated using high-temperature gas generated by combustion in the off-gas burner 152. However, the heat generated by the off-gas burner can also be used to regulate the temperature of other equipment besides the electrochemical cell.

[0127] Furthermore, as in the above-described Embodiments 9 and 10, it is also possible to combine a cell control system 1 in which the electrochemical cell 2 is used as a fuel cell with a cell control system 1 in which the electrochemical cell 2 is used as a hydrogen production device, as in Embodiments 1 to 8. That is, hydrogen can be produced by introducing gas containing a large amount of water vapor and gas with a low oxygen partial pressure discharged from an electrochemical cell that is a fuel cell into the cathode flow path or the anode flow path of an electrochemical cell that is a hydrogen production device. Furthermore, it is also possible to configure the gas with a low oxygen partial pressure discharged from an electrochemical cell that is a fuel cell to be temporarily stored in a storage facility and used in the hydrogen production device at a predetermined timing.

[0128] Alternatively, a configuration may be adopted in which gas with a high oxygen partial pressure and gas containing a large amount of hydrogen discharged from the electrochemical cells constituting the hydrogen production device are supplied to the electrochemical cells constituting the fuel cell. In this case, the gas with a high oxygen partial pressure may also be temporarily stored in a storage facility. That is, the gas stored in the storage facility may be used directly, or the ratio of the gas stored in the storage facility to air may be adjusted and used for degradation diagnosis or reduction operations. In this case, the electrochemical cell may also be used as a fuel cell after being used as a hydrogen production device. That is, the cell control system may be used to control an electrochemical cell that can switch between power generation and hydrogen production. In this case, it is easy to flexibly respond to fluctuations in demand for hydrogen gas and power generation.

[0129] Furthermore, when the electrochemical cell is used as a fuel cell, carbon monoxide can be used in addition to hydrogen as a fuel. In this case, the cell control system 1 can be equipped with, for example, a reformer (not shown). The reformer reforms methane gas or city gas containing methane as a main component through a catalytic reaction to produce a fuel gas containing hydrogen and carbon monoxide. The fuel gas produced by the reformer is then supplied to the anode flow path via the anode supply flow path. In this case, in the electrochemical cell, hydrogen gas reacts with oxide ions to produce water, and carbon monoxide reacts with oxide ions to produce carbon dioxide, thereby outputting electrical energy. Furthermore, by using the carbon dioxide produced at this time in the cell control system 1 of embodiment 3, for example, hydrogen and carbon monoxide can be produced by co-electrolysis, thereby generating methane.

[0130] In the above-described first embodiment and the like, the temperature of the electrochemical cell 2 is adjusted by the temperature adjustment unit 151. However, for example, a configuration may be adopted in which, without using a temperature adjustment unit, the temperature of the electrochemical cell is adjusted by using Joule heat generated by the voltage or power applied to the cell stack or heat generated by the reaction between the oxidizer and fuel during power generation. In other words, although the electrolysis reaction of water vapor is an endothermic reaction, Joule heat is generated by the internal resistance of the electrochemical cell when electricity is applied to the electrochemical cell. Then, the amount of Joule heat generated can be adjusted by controlling the power supply using a control unit, thereby adjusting the temperature of the electrochemical cell.

[0131] In the above-described first embodiment and the like, the temperature of the cell stack 20 is adjusted by a temperature adjustment unit 151 provided in the housing 15. However, for example, as shown in FIG. 23 , it is also possible to provide a temperature adjustment unit 151 that heats the cathode supply flow path 53 and the anode supply flow path 54 without providing a temperature adjustment unit in the housing 15. In this case, the temperature of the electrochemical cell 2 can be adjusted by supplying gas heated to a desired temperature to the anode flow path 22 and the cathode flow path 21.

[0132] In addition, in the case of the ninth embodiment, for example, the oxygen partial pressure in the cathode flow channel can be changed by flowing into the electrochemical cell a dry gas having low humidity, i.e., a low water vapor partial pressure, and a high oxygen partial pressure.

[0133] The degradation portion identifying unit can also identify the degradation portion using, for example, AC impedance measurement, current interruption, or current sweeping. Specifically, when AC impedance measurement is used, multiple AC currents with different frequencies are passed through the electrochemical cell and the voltage response at that time is compared with a predetermined reference value, thereby identifying the degradation portion. That is, the degradation portion can be identified based on, for example, the speed of the voltage response when AC currents of each frequency are passed. When the current interruption method is used, the degradation portion can be identified by comparing the voltage response when the current passed through the electrochemical cell is turned off in a stepwise manner with a predetermined reference value. That is, the degradation portion can be identified based on, for example, the way the voltage drops when the current is turned off, the voltage waveform, or the speed of the response. When the current sweeping method is used, the degradation portion can be identified based on the voltage characteristics measured when the current density passed through the electrochemical cell is swept. Furthermore, it is also possible to identify deteriorated parts by combining AC impedance measurement, current interruption method, and current sweep method, or by combining AC impedance measurement, current interruption method, and current sweep method with the above-mentioned diagnostic items.

[0134] Furthermore, if the temperature of the electrochemical cell is too low, it is prone to degradation due to high voltage, and if the temperature is too high, it is prone to degradation due to high temperature. Therefore, the temperature measurement unit can measure the temperature of the end of the cell stack, where the temperature is likely to be low, or the temperature of the center of the cell stack, where the temperature is likely to be high, and use this temperature as the temperature of the electrochemical cell that serves as the reference for performing degradation diagnosis and mitigation operations.

[0135] The electrochemical cells of the cell control system may be solid polymer type cells, for example, in addition to solid oxide type cells.

[0136] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments within the scope of the present invention.

[0137] <Other> The features of the present invention are as follows. [Section 1] A cell control system (1) for controlling the internal resistance of an electrochemical cell (2) including a cathode flow path (21), an anode flow path (22), and an electrolyte (23) disposed between the anode flow path and the cathode flow path, comprising: the electrochemical cell is configured to electrolyze a raw material (11) using supplied power to produce hydrogen; a deterioration portion identifying unit (31) that performs a deterioration diagnosis to identify a deterioration portion of the electrochemical cell; an operation determination unit (32) that determines, based on a result of the deterioration diagnosis by the deterioration portion identification unit, a reduction operation that is an operation of the electrochemical cell for reducing the internal resistance of the electrochemical cell that has increased due to the deterioration of the deterioration portion identified by the deterioration portion identification unit, A cell control system that controls at least one of the internal resistance of the electrochemical cell, the voltage applied to the electrochemical cell, and the current flowing through the electrochemical cell to reach a predetermined target value by implementing the reduction operation determined by the operation determination unit. [Section 2] the raw material is water, Item 1. The cell control system according to item 1, wherein the reduction operation is an operation of changing at least one of the temperature of the electrochemical cell, the pressure of the cathode flow channel, the pressure of the anode flow channel, the partial pressure of water vapor in the gas supplied to the cathode flow channel, the partial pressure of oxygen in the gas supplied to the anode flow channel, the flow rate of the gas in the cathode flow channel, and the flow rate of the gas in the anode flow channel. [Section 3] the raw material is water, when the temperature of the electrochemical cell, the pressure of the cathode flow path, the pressure of the anode flow path, the partial pressure of water vapor in the gas supplied to the cathode flow path, the partial pressure of oxygen in the gas supplied to the anode flow path, the flow rate of the gas in the cathode flow path, and the flow rate of the gas in the anode flow path are set as diagnostic items of the deterioration part identifying unit, the deterioration part identifying unit identifies a deterioration part of the electrochemical cell by changing a value of at least one of the diagnostic items; 3. The cell control system according to claim 1, wherein the deterioration portion identifying unit measures a measurement change amount, which is a change amount in the state of the electrochemical cell when the value of the diagnostic item is changed, and identifies a deterioration portion of the electrochemical cell by comparing the measurement change amount with a predetermined reference value for the change amount in the state of the electrochemical cell. [Section 4] Item 2 or 3. The cell control system according to item 2 or 3, wherein the anode flow path is configured to allow air to flow therethrough, and the oxygen partial pressure in the anode flow path is changed by flowing a gas other than air through the anode flow path. [Section 5] Item 4. The cell control system according to item 3, wherein the amount of change in state is the amount of change in the magnitude of the voltage applied to the electrochemical cell when the output current to the electrochemical cell is controlled to a constant current. [Section 6] Item 4. The cell control system according to item 3, wherein the amount of change in state is the amount of change in the magnitude of the current flowing through the electrochemical cell when the output voltage to the electrochemical cell is controlled to a constant voltage. [Section 7] A cell control system (1) for controlling the internal resistance of an electrochemical cell (2) including a cathode flow path (21), an anode flow path (22), and an electrolyte (23) disposed between the anode flow path and the cathode flow path, comprising: the electrochemical cell is configured to generate electricity by supplying a gas containing an oxidant (12) to the cathode flow path and a gas containing a fuel (13) to the anode flow path; a deterioration portion identifying unit (31) that performs a deterioration diagnosis to identify a deterioration portion of the electrochemical cell; an operation determination unit (32) that determines, based on a result of the deterioration diagnosis by the deterioration portion identification unit, a reduction operation that is an operation of the electrochemical cell for reducing the internal resistance of the electrochemical cell that has increased due to the deterioration of the deterioration portion identified by the deterioration portion identification unit, A cell control system that controls at least one of the internal resistance of the electrochemical cell, the output voltage of the electrochemical cell, and the output current of the electrochemical cell to reach a predetermined target value by implementing the reduction operation determined by the operation determination unit. [Section 8] the oxidizing agent is oxygen; Item 8. The cell control system according to Item 7, wherein the reduction operation is an operation of changing at least one of the temperature of the electrochemical cell, the pressure of the cathode flow channel, the pressure of the anode flow channel, the partial pressure of the fuel in the gas supplied to the anode flow channel, the partial pressure of the oxygen in the gas supplied to the cathode flow channel, the flow rate of the gas in the cathode flow channel, and the flow rate of the gas in the anode flow channel. [Section 9] the oxidizing agent is oxygen; when the temperature of the electrochemical cell, the pressure of the cathode flow path, the pressure of the anode flow path, the partial pressure of the oxygen in the gas supplied to the cathode flow path, the partial pressure of the fuel in the gas supplied to the anode flow path, the flow rate of the gas in the cathode flow path, and the flow rate of the gas in the anode flow path are set as diagnostic items of the deterioration part identifying unit, the deterioration part identifying unit identifies a deterioration part of the electrochemical cell by changing a value of at least one of the diagnostic items; Item 9. The cell control system according to item 7 or 8, wherein the degradation part identifying unit measures a measurement change amount, which is a change amount of the state of the electrochemical cell when the value of the diagnostic item is changed, and identifies a degradation part of the electrochemical cell by comparing the measurement change amount with a predetermined reference value for the change amount of the state of the electrochemical cell. [Section 10] Item 8 or 9, wherein the cathode flow path is configured to allow air to flow through it, and the oxygen partial pressure in the cathode flow path is changed by flowing a gas other than air through the cathode flow path. [Section 11] Item 10. The cell control system according to item 9, wherein the amount of change in state is the amount of change in the magnitude of the output voltage of the electrochemical cell when the output current of the electrochemical cell is controlled to a constant current. [Section 12] 10. The cell control system according to item 9, wherein the amount of change in state is an amount of change in magnitude of the output current of the electrochemical cell when the output voltage of the electrochemical cell is controlled to a constant voltage. [Section 13] Item 13. The cell control system according to any one of items 1 to 12, wherein the electrochemical cell is a solid oxide cell. [Section 14] 14. The cell control system according to any one of items 1 to 13, wherein the cell control system is configured to prohibit the execution of at least one of the degradation diagnosis and the reduction operation under a predetermined prohibition condition. [Section 15] Item 15. A cell control system as described in item 14, wherein if the prohibition of the implementation of at least one of the degradation diagnosis and the reduction operation continues for a predetermined period, the cell control system controls the implementation of the degradation diagnosis and the reduction operation even if the prohibition condition is met. [Explanation of symbols]

[0138] 1... cell control system, 2... electrochemical cell, 11... raw material, 21... cathode flow path, 22... anode flow path, 23... electrolyte, 31... deterioration portion identifying unit, 32... operation determining unit

Claims

1. A cell control system (1) for controlling the internal resistance of an electrochemical cell (2) including a cathode flow path (21), an anode flow path (22), and an electrolyte (23) disposed between the anode flow path and the cathode flow path, the electrochemical cell is configured to electrolyze a raw material (11) using supplied power to produce hydrogen; a deterioration portion identifying unit (31) that performs a deterioration diagnosis to identify a deterioration portion of the electrochemical cell; an operation determination unit (32) that determines, based on a result of the degradation diagnosis by the degradation portion identification unit, a reduction operation that is an operation of the electrochemical cell for reducing the internal resistance of the electrochemical cell that has increased due to the degradation of the degradation portion identified by the degradation portion identification unit, A cell control system that controls at least one of the internal resistance of the electrochemical cell, the voltage applied to the electrochemical cell, and the current flowing through the electrochemical cell to reach a predetermined target value by implementing the reduction operation determined by the operation determination unit.

2. The raw material is water, 2. The cell control system according to claim 1, wherein the reduction operation is an operation of changing at least one of the temperature of the electrochemical cell, the pressure of the cathode flow channel, the pressure of the anode flow channel, the partial pressure of water vapor in the gas supplied to the cathode flow channel, the partial pressure of oxygen in the gas supplied to the anode flow channel, the flow rate of the gas in the cathode flow channel, and the flow rate of the gas in the anode flow channel.

3. The raw material is water, when the temperature of the electrochemical cell, the pressure of the cathode flow path, the pressure of the anode flow path, the partial pressure of water vapor in the gas supplied to the cathode flow path, the partial pressure of oxygen in the gas supplied to the anode flow path, the flow rate of the gas in the cathode flow path, and the flow rate of the gas in the anode flow path are set as diagnostic items of the deterioration part identifying unit, the deterioration part identifying unit identifies a deterioration part of the electrochemical cell by changing a value of at least one of the diagnostic items; 2. The cell control system according to claim 1, wherein the deterioration portion identifying unit measures a measured change amount, which is a change amount in the state of the electrochemical cell when the value of the diagnostic item is changed, and identifies the deterioration portion of the electrochemical cell by comparing the measured change amount with a predetermined reference value for the change amount in the state of the electrochemical cell.

4. 4. The cell control system according to claim 2, wherein the anode flow path is configured to allow air to flow therethrough, and the oxygen partial pressure in the anode flow path is changed by flowing a gas other than air through the anode flow path.

5. 4. The cell control system according to claim 3, wherein the amount of change in state is an amount of change in the magnitude of the voltage applied to the electrochemical cell when an output current to the electrochemical cell is controlled to a constant current.

6. 4. The cell control system according to claim 3, wherein the amount of change in state is an amount of change in the magnitude of the current flowing through the electrochemical cell when the output voltage to the electrochemical cell is controlled to a constant voltage.

7. A cell control system (1) for controlling the internal resistance of an electrochemical cell (2) including a cathode flow path (21), an anode flow path (22), and an electrolyte (23) disposed between the anode flow path and the cathode flow path, the electrochemical cell is configured to generate electricity by supplying a gas containing an oxidant (12) to the cathode flow path and a gas containing a fuel (13) to the anode flow path; a deterioration portion identifying unit (31) that performs a deterioration diagnosis to identify a deterioration portion of the electrochemical cell; an operation determination unit (32) that determines, based on a result of the degradation diagnosis by the degradation portion identification unit, a reduction operation that is an operation of the electrochemical cell for reducing the internal resistance of the electrochemical cell that has increased due to the degradation of the degradation portion identified by the degradation portion identification unit, A cell control system that controls at least one of the internal resistance of the electrochemical cell, the output voltage of the electrochemical cell, and the output current of the electrochemical cell to reach a predetermined target value by implementing the reduction operation determined by the operation determination unit.

8. the oxidizing agent is oxygen; 8. The cell control system according to claim 7, wherein the reduction operation is an operation of changing at least one of the temperature of the electrochemical cell, the pressure of the cathode flow channel, the pressure of the anode flow channel, the partial pressure of the fuel in the gas supplied to the anode flow channel, the partial pressure of the oxygen in the gas supplied to the cathode flow channel, the flow rate of the gas in the cathode flow channel, and the flow rate of the gas in the anode flow channel.

9. the oxidizing agent is oxygen; when the temperature of the electrochemical cell, the pressure of the cathode flow path, the pressure of the anode flow path, the partial pressure of the oxygen in the gas supplied to the cathode flow path, the partial pressure of the fuel in the gas supplied to the anode flow path, the flow rate of the gas in the cathode flow path, and the flow rate of the gas in the anode flow path are set as diagnostic items of the deterioration part identifying unit, the deterioration part identifying unit identifies a deterioration part of the electrochemical cell by changing a value of at least one of the diagnostic items; 8. The cell control system according to claim 7, wherein the deterioration portion identifying unit measures a measured change amount, which is a change amount in the state of the electrochemical cell when the value of the diagnostic item is changed, and identifies a deterioration portion of the electrochemical cell by comparing the measured change amount with a predetermined reference value for the change amount in the state of the electrochemical cell.

10. 10. The cell control system according to claim 8, wherein the cathode flow path is configured to allow air to flow therethrough, and the oxygen partial pressure in the cathode flow path is changed by flowing a gas other than air through the cathode flow path.

11. 10. The cell control system according to claim 9, wherein the amount of change in state is an amount of change in magnitude of the output voltage of the electrochemical cell when the output current of the electrochemical cell is controlled to a constant current.

12. 10. The cell control system according to claim 9, wherein the amount of change in state is an amount of change in magnitude of the output current of the electrochemical cell when the output voltage of the electrochemical cell is controlled to a constant voltage.

13. The cell control system according to claim 1 or 7, wherein the electrochemical cell is a solid oxide cell.

14. The cell control system according to claim 1 or 7, wherein the cell control system is configured to prohibit the execution of at least one of the deterioration diagnosis and the reduction operation under a predetermined prohibition condition.

15. The cell control system of claim 14, wherein if the prohibition of the performance of at least one of the degradation diagnosis and the reduction operation continues for a predetermined period, the cell control system controls the performance of the degradation diagnosis and the reduction operation even if the prohibition condition is satisfied.

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