Solid oxide cell system

Abstract

A solid oxide cell system (1) having a solid oxide cell module (100) to which a plurality of solid oxide cell stacks (10) are connected and capable of switching between an SOFC mode and an SOEC mode, wherein, in any period during an operation period, at least one solid oxide cell stack (10) is controlled to operate in the SOFC mode or the SOEC mode, and input / output is stopped with respect to at least one other solid oxide cell stack (10) and thus the at least one other solid oxide cell stack is controlled to enter a sleep state and not to operate in either the SOFC mode or the SOEC mode.

Description

Solid Oxide Cell System

[0001] The present disclosure relates to solid oxide cell systems.

[0002] A solid oxide fuel cell (SOFC) can output electricity and heat using hydrogen, hydrocarbon, or carbon monoxide as a raw material. It can also function as a solid oxide electrolysis cell (SOEC), which performs the reverse reaction of electrolysis, electrolyzing water vapor or carbon dioxide into hydrogen, carbon monoxide, or oxygen. A power storage and supply system using a reversible SOEC (solid oxide cell) capable of both power generation and electrolysis has been proposed (see, for example, Patent Document 1).

[0003] Patent No. 6881007

[0004] Typically, power storage and supply systems have a stack structure in which multiple SOCs are stacked. In conventional systems using reversible SOCs, because the operating temperatures differ for each operating mode, a downtime is required to adjust the operating temperature of the SOC stack when switching between operating modes. If the temperature were to change suddenly during this downtime, there was a risk of physical damage to the SOC due to heat, reducing its durability. Meanwhile, the downtime poses a problem of delayed response to requested input and output.

[0005] The present disclosure discloses a technology for solving the above-mentioned problems, and aims to provide a solid oxide cell system that can suppress a decrease in SOC durability without delaying output when switching operating modes.

[0006] The solid oxide cell system of the present disclosure comprises: a solid oxide cell module having a solid oxide cell stack switchable between an SOFC mode in which a first gas is used to generate and output electric power, and an SOEC mode in which electric power is input and a second gas is electrolyzed, the solid oxide cell module being formed by connecting a plurality of the solid oxide cell stacks; and a control device for controlling the operation of the plurality of solid oxide cell stacks, wherein the control device is configured to control at least one of the plurality of solid oxide cell stacks to operate in the SOFC mode or the SOEC mode during any period within an operating period in which the control device controls the operation of the solid oxide cell stacks while switching between the SOFC mode and the SOEC mode, and to stop the input and output of electric power to at least one other solid oxide cell stack, controlling it to a hibernation state in which it does not operate in either the SOFC mode or the SOEC mode.

[0007] According to the present disclosure, it is possible to improve responsiveness when switching between operation modes and suppress a decrease in durability of the SOC stack.

[0008] 5A is a diagram showing the configuration of a solid oxide cell system according to embodiment 1. FIG. 5B is a diagram showing the temperature control pattern of the SOC stack when switching the operation mode of the solid oxide cell system according to embodiment 1. FIG. 5C is a diagram showing the input / output control pattern of each SOC stack when switching the operation mode of the solid oxide cell system according to embodiment 1. FIG. 5D is a diagram showing the temperature control pattern of each SOC stack when switching the operation mode of the solid oxide cell system according to embodiment 1. FIG. 5D is a flowchart showing the control state of the SOC stack when switching the operation mode of the solid oxide cell system according to embodiment 1. 7A and 7B are diagrams showing input / output control and temperature control patterns of the SOC stack provided in the solid oxide cell system according to the second embodiment in comparison with those of a comparative example. Fig. 7A is a diagram showing the input / output control pattern of the SOC stack when switching the operation mode of the solid oxide cell system in the comparative example, Fig. 7B is a diagram showing the temperature control pattern of the SOC stack when switching the operation mode of the solid oxide cell system in the comparative example, Fig. 7C is a diagram showing the input / output control pattern of each SOC stack when switching the operation mode of the solid oxide cell system according to the second embodiment, and Fig. 7D is a diagram showing the temperature control pattern of each SOC stack when switching the operation mode of the solid oxide cell system according to the second embodiment. Fig. 7B is a diagram showing the input / output control pattern of each SOC stack when switching the operation mode of the solid oxide cell system according to the second embodiment. Fig. 7C is a diagram showing the input / output control pattern of each SOC stack when switching the operation mode of the solid oxide cell system according to the second embodiment. Fig. 7D is a diagram showing the temperature control pattern of each SOC stack when switching the operation mode of the solid oxide cell system according to the second embodiment. Fig. 7D is a flowchart for explaining the control state of the SOC stack when switching the operation mode of the solid oxide cell system according to the second embodiment. Fig. 7D is a flowchart for explaining a method of temperature control of the SOC stack provided in the solid oxide cell system according to the third embodiment.10 is a flowchart for explaining a method of controlling the temperature of the SOC stack provided in the solid oxide cell system according to embodiment 3. FIG. 11 is a diagram showing an example of the hardware configuration of a control device for the solid oxide cell system according to embodiments 1 to 3.

[0009] An embodiment of a solid oxide cell system according to the present disclosure will be described below with reference to the drawings. This disclosure focuses on a solid oxide cell system using a reversible SOC that has both SOFC and SOEC functions. Note that the same reference numerals in each drawing indicate the same or corresponding parts. Therefore, detailed descriptions thereof may be omitted to avoid duplication. In the following, a solid oxide cell will be referred to as an SOC, a solid oxide cell stack will be referred to as an SOC stack, and a solid oxide cell module will be referred to as an SOC module. The operating mode in which the SOC stack operates as an SOFC will be referred to as the SOFC mode, and the operating mode in which it operates as an SOEC will be referred to as the SOEC mode.

[0010] First Embodiment A solid oxide cell system according to a first embodiment will be described below with reference to the drawings. <Configuration of the solid oxide cell system> Fig. 1 is a diagram showing the configuration of a solid oxide cell system according to a first embodiment, and Fig. 2 is a diagram showing the configuration of an SOC stack. In Fig. 1, the solid oxide cell system 1 includes a gas supply unit 21 that supplies the raw material gas required in the SOFC mode, and a gas supply unit 22 that supplies water vapor (H ２ The solid oxide cell system 1 includes a water vapor supply unit 22 that supplies a gas (water vapor) containing oxygen (O), a temperature adjustment device 20 that adjusts the temperature of the supplied gas and water vapor, an SOC module 100 to which gas adjusted to a preset temperature by the temperature adjustment device 20 is supplied, and a control device 200 that switches the operation modes of the temperature adjustment device 20 and the SOC module 100 and controls the opening and closing of valves V1-V6 provided in the gas piping. These constitute the main components 1A of the solid oxide cell system 1 shown by the dotted line area in Fig. 1. An external device 300 is connected to the SOC module 100. The external device 300 is a load to which power generated by the SOC module 100 in the SOFC mode is supplied, or a current source that supplies power to the SOC module 100 in the SOEC mode.

[0011] The SOC module 100 is an assembly of multiple SOC stacks 10_1-10_n (n is a natural number equal to or greater than 2) connected together. Each SOC stack 10 is provided with an SOC stack temperature regulator 18. The temperature regulator 18 is, for example, a heater or other heating device. Note that the SOC stacks are collectively referred to as the SOC stack 10.

[0012] <Configuration of SOC Stack> Here, the structure of the multiple SOC stacks 10 that make up the SOC module 100 will be described with reference to Fig. 2. The SOC module 100 is an assembly of multiple SOC stacks 10_1-10_n (n is a natural number of 2 or more) connected together. Each SOC stack 10 is configured by stacking multiple SOCs 11_1-11_m (m is a natural number of 2 or more).

[0013] Taking the kth (1<k≦m; k is a natural number) SOC11_k as an example, each SOC11 has a structure in which an electrolyte 13 is sandwiched between an air electrode 12 and an anode 14, and is connected to adjacent SOC11s by an interconnector 15. A diffusion prevention layer to suppress material degradation may be inserted between the air electrode 12 and the electrolyte 13. Note that SOCs are collectively referred to as SOC11.

[0014] The control device 200 includes a system control unit 201 and a temperature control unit 202. The system control unit 201 switches the operation mode of the SOC module 100 and controls the opening and closing of valves V1 to V6 provided in the gas piping. The temperature control unit 202 controls the temperature adjustment device 20 so that the supplied gas and steam reach a preset temperature, and also controls the SOC stack temperature regulator 18 so that each SOC stack 10 reaches a preset temperature.

[0015] As described above, the external device 300 is a load or a current source. The load to which the energy generated by the SOC module 100 in the SOFC mode is supplied is, for example, a power converter or a motor connected via a power converter. The current source to which the SOC module 100 is supplied in the SOEC mode is, for example, a power converter or a current source such as a grid.

[0016] The gas supply unit 21 supplies hydrogen (H ２ ), etc., and in SOEC mode, hydrogen, carbon dioxide (CO ２ ) or the like. A gas cylinder may be provided externally and supplied to the gas supply unit 21. In addition, the gas supplied to the air electrode in the SOFC mode may be, for example, oxygen (O ２ ), air, etc. These are also used in the SOEC mode, and since the gas species are theoretically the same during supply (upstream) and after reaction (downstream), the gas may be circulated.

[0017] The temperature adjustment device 20 adjusts the temperature of the (upstream) gas and steam pipes supplied to the SOC module 100, and is, for example, a heater or a heating device provided around the pipes. In addition, the downstream gas generated from the SOC module 100 may be used as a heat source to heat the upstream gas.

[0018] Optional components of the solid oxide cell system 1 may include a reformer 30, a steam generator 31, a water storage unit 32, a condenser 33, a gas storage unit 34, and a storage gas adjustment unit 35. The reformer 30 is used when using city gas (gas mainly composed of methane) in the SOFC mode. Downstream gas generated from the SOC module 100 may be supplied as fuel to a burner, which is a heat source during reforming.

[0019] The water vapor generator 31 heats water supplied from the water storage unit 32 to generate water vapor, and supplies the water vapor to the SOC module 100 via the water vapor supply unit 22. Water vapor may be supplied directly from the outside without using the water vapor generator 31.

[0020] The water reservoir 32 stores water to be supplied to the steam generator 31. Steam in the downstream gas on the fuel electrode side discharged from the SOC module 100 may be recovered and reused as supply gas or fuel for the reformer 30.

[0021] The condenser 33 dehydrates the downstream gas on the fuel electrode side discharged from the SOC module 100. For example, in the SOFC mode, the condenser 33 separates the water vapor generated in the SOC module 100 from unreacted hydrogen and the like by dehydration, and in the SOEC mode, the condenser 33 separates the hydrogen and the like generated in the SOC module 100 from unreacted water vapor by dehydration.

[0022] The gas storage unit 34 recovers the downstream gas (hydrogen, etc.) on the fuel electrode side discharged from the SOC module 100 in the SOEC mode and stores it as the upstream gas on the fuel electrode side required in the SOFC mode. The gas discharged from the SOC module 100 may be directly supplied to the outside of the system.

[0023] The storage gas adjusting unit 35 adjusts the gas by appropriately processing it in order to store it in the gas storage unit 34. For example, the form of the gas is adjusted by compressing the gas using a compressor, separating a mixed gas of, for example, hydrogen and carbon monoxide (CO), which is the gas downstream on the fuel electrode side discharged from the SOC module 100 in the SOEC mode, using a separator, or synthesizing methane using hydrogen and carbon monoxide (CO) in a methanation reactor. The gas adjusted by the storage gas adjusting unit 35 is stored in the gas storage unit 34.

[0024] In Figure 1 and the following figures showing the configuration of a solid oxide cell system, each line indicates the following: Solid line: Pre-reaction gas flow path (upstream) Dash-dotted line: Post-reaction gas flow path (downstream) Dashed line: Flow path for gases used other than fuel cells and steam electrolysis reactions Black arrow: Gases supplied to or discharged from the fuel electrode (hydrogen, nitrogen, carbon monoxide, hydrocarbons, water vapor, carbon dioxide, etc.) Open arrow: Gases supplied to or discharged from the air electrode (oxygen, air, etc.)

[0025] <Operation in SOFC Mode> Next, the operation of the solid oxide cell system 1 in the SOFC mode will be described. Figure 3 shows the gas flow in the SOFC mode in Figure 1, indicated by the bold line. In the SOFC mode, gases described below are supplied to the anode 14 and the cathode 12, respectively, and the generated electric power is output.

[0026] (1) Gas Supply to SOC Module 100 (Upstream) A gas containing hydrogen as its main component is supplied to the fuel electrode 14 side. The gas containing hydrogen as its main component is supplied from the gas supply unit 21 to the SOC module 100 via the temperature adjustment device 20. A gas containing hydrogen as its main component may be supplied from the gas storage unit 34. A gas containing methane as its main component may be supplied to the fuel electrode 14 side. The gas containing methane as its main component may be supplied from the gas storage unit 34 to the SOC module 100 via the temperature adjustment device 20. Alternatively, the gas may be supplied from the outside via the reformer 30. Alternatively, the gas may be supplied from the gas storage unit 34 via the reformer 30. In the reformer 30, steam reforming is carried out using steam supplied from the water storage unit 32 through the following reaction, and the reformed gas is supplied to the fuel electrode 14 side. CH ４ +H ２ O → CO + 3H ２ As will be explained below, when the SOC module 100 is not operating in SOFC mode and is undergoing temperature adjustment or is at rest, a purge gas or reducing gas containing hydrogen and nitrogen as its main components is supplied from the gas supply unit 21 or the gas storage unit 34 to the fuel electrode 14 side of the SOC stack 10.

[0027] Oxygen or air is supplied to the air electrode 12 side from a gas supply unit 21. Oxygen or air is also supplied to the air electrode 12 side of the SOC stack 10 of the SOC module 100 that is not operating in SOFC mode and is undergoing temperature adjustment or is at rest. In gas supply to the SOC module 100, the gas supply source to the anode 14 side is determined by the opening and closing direction of valve V1. When the gas supplied to the anode 14 side is a gas mainly composed of methane, the opening and closing direction of valve V2 is controlled to supply the gas mainly composed of methane from a gas storage unit 34 to the reformer 30. The opening and closing direction of valve V3 is determined by whether or not gas is supplied from the reformer 30. These valves V1 to V3 are three-way valves, and their opening and closing directions are controlled by a system control unit 201.

[0028] (2) Gas Discharge from the SOC Module 100 (Downstream) When a gas containing hydrogen as a main component is supplied from the fuel electrode 14 side, water vapor and unreacted hydrogen, etc. are discharged, and when a gas containing methane as a main component is supplied, water vapor and carbon dioxide, etc. are discharged. The discharged gas may be discharged directly to the outside, or, as shown in FIG. 3 , the water vapor and other gases may be separated in a condenser 33, and then the hydrogen and carbon dioxide, etc. may be separated in a storage gas adjustment unit 35. The water vapor may be stored in a water reservoir 32. Unreacted oxygen or air is discharged from the air electrode 12 side. The discharged gas may be returned to the gas supply unit 21 to circulate through the system.

[0029] When gas is exhausted from the SOC module 100, water can be supplied from the water reservoir 32 when the reformer 30 is operating by opening and closing the valve V5. Also, part of the exhaust gas can be supplied as fuel for the heat supply burner of the reformer 30 by opening and closing the valve V4. The valve V4 is a three-way valve, and the valve V5 is an on-off valve, and the opening and closing directions and opening and closing operations are controlled by the system control unit 201.

[0030] The temperature adjustment device 20 may be provided with a heat exchange function so that the supply gas is heated by heat exchange with the exhaust gas. During operation, the temperatures of the temperature adjustment device 20, the SOC stack temperature regulator 18, and the reformer 30 are controlled to the respective set temperatures by a temperature control unit 202.

[0031] <Operation in SOEC Mode> Next, the operation of the solid oxide cell system 1 in the SOEC mode will be described. Figure 4 shows the gas flow in the SOEC mode in Figure 1, indicated by the bold line. In the SOEC mode, gases described below are supplied to the anode 14 and cathode 12, respectively, and an electrolysis reaction occurs due to the input power.

[0032] (1) Gas Supply to SOC Module 100 (Upstream) A gas containing water vapor as a main component is supplied to the anode 14 side from a water vapor supply unit 22. Water vapor may be introduced directly from the outside, or water supplied from a water reservoir 32 may be heated by a water vapor generator 31 to generate water vapor, as shown in FIG. 4 . Alternatively, hydrogen may be supplied from a gas storage unit 34 or a gas supply unit 21, mixed with water vapor by a temperature adjustment device 20, and supplied to the anode 14 side. Alternatively, a gas containing carbon dioxide as a main component may be supplied to the anode 14 side from the gas supply unit 21. At this time, a mixed gas of water vapor and carbon dioxide may be supplied to the anode 14 side. As will be described below, a purge gas or reducing gas containing hydrogen and nitrogen as main components is supplied from the gas supply unit 21 or a gas storage unit 34 to the anode 14 side of the SOC stack 10 of the SOC module 100 that is not operating in the SOEC mode and is undergoing temperature adjustment or is at rest.

[0033] Oxygen or air is supplied to the air electrode 12 side from a gas supply unit 21. Oxygen or air is also supplied to the air electrode 12 side of the SOC stack 10 of the SOC module 100 that is not operating in the SOEC mode and is undergoing temperature adjustment or is at rest. In supplying gas to the SOC module 100, the gas supply source to the fuel electrode 14 side is determined by the opening and closing direction of valve V1 and the opening and closing of valve V6. Valve V1 is a three-way valve, and valve V6 is an on-off valve, and the opening and closing direction and opening and closing operation are controlled by a system control unit 201.

[0034] (2) Gas Discharge (Downstream) from the SOC Module 100 When a gas primarily composed of water vapor is supplied, hydrogen and unreacted water vapor are discharged from the fuel electrode 14 side. When a gas primarily composed of carbon dioxide is supplied, carbon monoxide and unreacted carbon dioxide are discharged. The discharged gas may be discharged directly to the outside of the system. However, as shown in FIG. 4 , the water vapor and other gases may be separated in a condenser 33, and then the hydrogen and carbon monoxide may be separated in a storage gas adjustment unit 35. Alternatively, the mixed gas containing hydrogen and carbon monoxide may be introduced as is into the methanation reactor to produce methane. Gases such as hydrogen, carbon monoxide, and methane processed in the storage gas adjustment unit 35 are stored in a gas storage unit 34. Unreacted water vapor may be stored in a water reservoir 32 and then supplied to the fuel electrode 14 again. Generated oxygen or air with a high oxygen concentration is discharged from the air electrode 12 side. The discharged gas may be returned to the gas supply unit 21 to circulate through the system.

[0035] The temperature adjustment device 20 may be provided with a heat exchange function so that the supply gas is heated by heat exchange with the exhaust gas. Also, the steam generator 31 may be provided with a heat exchange function so that steam is generated by heat exchange with the exhaust gas. As in the SOFC mode, the temperature of the temperature adjustment device 20 during operation and the temperature of the SOC stack temperature regulator 18 are controlled to respective set temperatures by the temperature control unit 202.

[0036] The operation of the SOC module 100 according to the first embodiment will be described below. The SOC module 100 includes a plurality of SOC stacks 10, each of which is provided with piping and valves (not shown) so that gas can be supplied and discharged independently. Power input and output are controlled so that each operation mode can be controlled independently, and temperature control is possible independently for each of the SOC stacks 10.

[0037] <Example of Operation of SOC Module 100> Next, the operation of the SOC module 100 according to the first embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 shows the operational control pattern and temperature control pattern of the SOC stack when switching between operation modes of the solid oxide cell system according to the first embodiment, compared with a comparative example. FIGS. 5A and 5B show the comparative example, and FIGS. 5C and 5D show the solid oxide cell system according to the first embodiment. In FIGS. 5A-5D, the horizontal axis represents time, and for convenience of explanation, time blocks t1-t9, each having a time span, will be used for explanation. In FIGS. 5A and 5C, the vertical axis represents power input / output in arbitrary units from -3 to +3. The positive direction represents the SOFC mode, which generates power and outputs it to the outside, and the negative direction represents the SOEC mode, which performs electrolysis using an external input. Input / output requests to the system are indicated by hatching dots, and the SOC stack is controlled to achieve input / output according to those requests. 5B and 5D, the vertical axis indicates the operating temperature of the SOC stack, and temperature control patterns corresponding to the operations of the SOC stacks in FIGS. 5A and 5C are shown, respectively.

[0038] The SOC module 100 according to the first embodiment described below includes three SOC stacks 10, each designated as stack A, B, and C. Stacks A, B, and C are assumed to have equivalent functions. The SOC module of the comparative example also includes three equivalent stacks, i.e., it is equivalent to having three stacks A. In the comparative example, the three SOC stacks operate uniformly, while the SOC stacks A, B, and C according to the first embodiment operate independently. Each stack is capable of controlling power input and output by ±3. Furthermore, each SOC stack requires a rest period of at least one hour block when switching between operation modes. During the rest period, the input and output of the stack is zero. Each SOC stack is also maintained at an SOEC operating temperature T ＥＣ and operate in SOEC mode, and the SOFC operating temperature T ＦＣ The temperature is lowered to operate in the SOFC mode.

[0039] In Figures 5A and 5C, an input request for "3" is made at time blocks t1 and t2, an output request for "3" is made at time blocks t3 and t4, an input request for "3" is made at time blocks t5 and t6, an output request for "3" is made at time blocks t7 and t8, and an input request for "3" is made at time block t9.

[0040] 5A and 5B for the comparative example, in time blocks t1 and t2, each SOC stack is controlled in response to an input of "1" and operates in the SOEC mode. That is, three SOC stacks corresponding to the input of "1" correspond to a total of "3" inputs. At this time, each SOC stack is in the SOEC mode, and therefore each SOC stack operates at the SOEC operating temperature T ＥＣ is controlled by.

[0041] Even if an output request of "3" is received in time block t3, all SOC stacks cannot respond because they require a rest period, and the output becomes 0. At this time, the operating temperature is set to the SOEC operating temperature T ＥＣ to the SOFC operating temperature T ＦＣ At time block t4 after one time block has elapsed, each SOC stack enters the SOFC mode and is controlled at an output of "1", making it possible to respond to a total output request of "3". At this time, since the SOC stack is in the SOFC mode, each SOC stack is at the SOFC operating temperature T ＦＣ is controlled by.

[0042] In addition, even if an input request of "3" is received in time block t5, all SOC stacks cannot respond because they require a rest period, and the operating temperature is set to the SOFC operating temperature T ＦＣ to the SOEC operating temperature T ＥＣ At time block t6 after one time block has elapsed, each SOC stack enters the SOEC mode and is able to respond to the input request of "3". At this time, since the OC stack is in the SOEC mode, each SOC stack is heated to the SOEC operating temperature T ＥＣ Thereafter, the input / output control and the operating temperature control of the SOC stack are repeated in the same manner.

[0043] In the input / output control patterns and the operating temperature control patterns of the stacks A, B, and C of the first embodiment shown in Figures 5C and 5D, in time block t1, the stack C of the SOC stack 10 responds to the input request "3" and operates in the SOEC mode. At this time, the other stacks A and B are in a rest period, but the stack A operates at the SOFC operating temperature T ＦＣ and stack B is maintained at an SOEC operating temperature T ＥＣ In time block t2, stack A is maintained in the idle period and is heated to the SOFC operating temperature T ＦＣ Stack B operates in the SOEC mode in response to the input request of "3", and stack C enters a rest period, and the SOFC operating temperature T ＦＣ The temperature is lowered to

[0044] In the time block t3, the output request is switched to "3", and the SOFC operating temperature T ＦＣ Stack A, which has been maintained at the SOFC operating temperature T ＥＣ The stack C is maintained at the SOFC operating temperature T ＦＣ The temperature continues to fall to .

[0045] In time block t4, stack A enters a rest period, and the SOEC operating temperature T ＥＣ The stack B is maintained in the idle state and is heated to the SOEC operating temperature T ＥＣ , and stack C operates in SOFC mode and outputs "3".

[0046] In time block t5, the input request is switched to "3", the stack A is maintained in the idle period, and the SOEC operating temperature T ＥＣ The temperature continues to rise to the SOEC operating temperature T ＥＣ Stack B, which had been maintained at 3, operates in the SOEC mode in response to the input request of "3", and stack C enters a rest period, and the SOFC operating temperature T ＦＣ is maintained.

[0047] In time block t6, stack A operates in the SOEC mode in response to the input request of “3”, stack B is in a quiescent period, and the SOFC operating temperature TＦＣ The stack C is cooled to the SOFC operating temperature T ＦＣ is maintained.

[0048] <Control Pattern of SOC Stack> Fig. 6 is a diagram showing a control pattern of the SOC stack according to the first embodiment. Hereinafter, an example of the stack C shown in Figs. 5C and 5D will be described. First, the stack C is controlled to operate in the SOEC mode in time block t1 (step S101), and the SOFC operating temperature T ＦＣ The temperature is controlled to decrease to (step S102).

[0049] In time block t4, the SOFC is controlled to operate in the SOFC mode (step S103), and in time block t5-t6, the SOFC operating temperature T ＦＣ (Step S104). In the time block t7, the SOFC is controlled to operate in the SOFC mode (Step S105). In the time block t8-t9, the SOEC operating temperature T ＥＣ The control in time block t9 corresponds to the control of stack B in time block t1. Therefore, the control of stack C after time block t10 is not shown, but will be described with reference to the control of stack B after time block t2.

[0050] The stack C is controlled to operate in the SOEC mode in time block t10 (step S107), and the SOEC operating temperature T ＥＣ The time block t13 returns to the time block t1 again, and the operation is controlled to operate in the SOEC mode (step S101).

[0051] Stack A shown in FIGS. 5C and 5D is an example in which stacks start from step S104 in FIG. 6, and stack B starts from step S106 in FIG. 6 and circulates.

[0052] As described above, in the first embodiment, the SOC module 100 includes a plurality of SOC stacks 10, and the input / output control and temperature control of each of the plurality of SOC stacks 10 are performed independently. Furthermore, during the operation period of the SOC module 100, all of the SOC stacks 10 are controlled so as not to operate in the same operation mode. Therefore, it is possible to suppress deterioration of the SOC stacks 10 compared to the comparative example in which all of the SOC stacks 10 operate in the same operation mode. Furthermore, if each SOC stack 10 continues to operate in the same mode, deterioration is likely to progress. In the first embodiment, the operation modes of each SOC stack 10 are switched within a certain period of time, thereby suppressing deterioration of each SOC stack 10.

[0053] Furthermore, since all of the SOC stacks 10 are controlled so as not to operate in the same operation mode, the idle periods of all of the SOC stacks 10 do not overlap, and all of the SOC stacks 10 are not idle. In other words, at least one SOC stack 10 is operating in any operation mode, and at least one other SOC stack 10 is idle. This eliminates a period during which input / output requests cannot be responded to, eliminates delays in response to input / output requests, and improves response capability. Note that there may be a period during which none of the SOC stacks 10 is stopped.

[0054] Furthermore, because control is performed so that all SOC stacks 10 do not operate in the same operating mode, one SOC stack 10 will have a larger input / output than in the comparative example. However, while one SOC stack 10 is operating in one operating mode, it is possible to adjust the temperature of another SOC stack 10 during a pause period. This allows control that can suppress deterioration of the SOC stack 10 in response to input / output requirements. For example, by operating one SOC stack 10 in the same operating mode multiple times, it is possible to reduce the number of temperature changes. By setting a longer temperature adjustment period than in the comparative example, it is possible to slow down the temperature adjustment speed and reduce the load on the SOC stack 10.

[0055] As described above, according to the first embodiment, there is provided a solid oxide cell system including a solid oxide cell module having a plurality of connected solid oxide cell stacks, each of which has a solid oxide cell stack that can switch between an SOFC mode in which a first gas is used to generate and output electric power, and an SOEC mode in which electric power is input and a second gas is electrolyzed, and the solid oxide cell system includes a control device that controls the operation of the plurality of solid oxide cell stacks, and the control device controls at least one of the plurality of solid oxide cell stacks to operate in the SOFC mode or the SOEC mode rather than in a dormant state during any period within an operating period in which the control device controls the operation of the solid oxide cell stack while switching between the SOFC mode and the SOEC mode, and controls at least one other solid oxide cell stack to operate in a dormant state in which power input / output to / from the other solid oxide cell stack is stopped and the other solid oxide cell stack does not operate in either the SOFC mode or the SOEC mode. This eliminates a period in which all of the solid oxide cell stacks are stopped, i.e., there is no period in which the control device cannot respond to input / output requests, resulting in no delays in input / output requests and improved responsiveness. The first gas is, for example, a gas whose main component is hydrogen or a gas whose main component is methane supplied to the fuel electrode side, or oxygen or air supplied to the air electrode side, and the second gas is, for example, a gas whose main component is water vapor or a gas whose main component is carbon dioxide supplied to the fuel electrode side, or oxygen or air supplied to the air electrode side.

[0056] Furthermore, by reducing the number of temperature changes and extending the temperature adjustment period, the temperature adjustment speed can be reduced, thereby reducing the load on the SOC stack 10 and preventing a decrease in the durability of the SOC stack.

[0057] Second Embodiment A solid oxide cell system according to a second embodiment will be described below with reference to the drawings. In the second embodiment, the operation of the SOC module 100 in response to input / output requests different from those in the first embodiment will be described. The configuration of the solid oxide cell system 1 according to the second embodiment is the same as that of the first embodiment, and the operation in the SOEC mode and the SOFC mode is also the same, so a description thereof will be omitted.

[0058] <Operation of SOC module 100> The operation of the SOC module 100 according to the second embodiment will be described with reference to Figs. 7 and 8. Fig. 7 is a diagram showing the operational control pattern and temperature control pattern of the SOC stack when switching the operation mode of the solid oxide cell system according to the second embodiment in comparison with a comparative example. Figs. 7A and 7B are those of the comparative example, and Figs. 7C and 7D are those of the solid oxide cell system according to the second embodiment. The horizontal axis, vertical axis, and legend in the diagrams are the same as those in Figs. 5A to 5D.

[0059] 7A and 7C, an input request of "3" is made in time block t1, an output request of "3" is made in time blocks t2 and t3, an input request of "3" is made in time block t4, an output request of "3" is made in time blocks t5 and t6, an input request of "3" is made in time block t7, and an output request of "3" is made in time blocks t8 and t9. In other words, this is an example in which an input request for one hour block and an output request for two hour blocks are repeated.

[0060] 7A and 7B of the comparative example, in time block t1, each SOC stack is controlled in response to an input of "1" and operates in the SOEC mode. That is, three SOC stacks corresponding to the input of "1" correspond to a total of "3" inputs. At this time, each SOC stack is in the SOEC mode, and therefore each SOC stack operates at the SOEC operating temperature T ＥＣ is controlled by.

[0061] Even if an output request of "3" is received in time block t2, all SOC stacks cannot respond because they require a rest period, and the output becomes 0. At this time, the operating temperature is set to the SOEC operating temperature T ＥＣ to the SOFC operating temperature T ＦＣ At time block t3 after one time block has elapsed, each SOC stack enters the SOFC mode and is controlled at an output of "1", making it possible to respond to a total output request of "3". At this time, since the SOC stack is in the SOFC mode, each SOC stack is at the SOFC operating temperature T ＦＣ is controlled by.

[0062] Even if an input request of "3" is received in the next time block t4, all SOC stacks cannot respond because they require a rest period. Furthermore, since an output request of "3" is received in the time block t5, the operating temperature of each SOC stack in the time block t4 is the SOFC operating temperature T ＦＣ In time block t5, in response to the output request of "3", each SOC stack is maintained at the SOFC operating temperature T ＦＣ are maintained, they are controlled in the SOFC mode so as to output "1".

[0063] In the time block t6, the output request of "3" is maintained, but in the next time block t7, an input request of "3" is received, so in the time block t6, each SOC stack enters a rest period, and the operating temperature is reduced to the SOFC operating temperature T ＦＣ to the SOEC operating temperature T ＥＣ In other words, the output request of time block t6 cannot be met. When an input request of "3" is received in time block t7, each SOC stack is controlled in the SOEC mode and each responds to the input request of "1", making it possible to meet a total of "3" input requests.

[0064] On the other hand, unlike FIG. 7A, if each SOC stack is controlled in SOFC mode while remaining in time block t5 in response to an output request of "3" in time block t6, a rest period is required in time block t7, and therefore the input request of "3" cannot be accommodated.

[0065] In this way, a period of time during which temperature adjustment is paused is required when switching the operation mode, and therefore, in the comparative example, a dead time occurs during which input / output requests cannot be responded to.

[0066] In the input / output control patterns and the operating temperature control patterns of the stacks A, B, and C of the second embodiment shown in Figures 7C and 7D, in time block t1, the stack C of the SOC stack 10 responds to the input request "3" and operates in the SOEC mode. At this time, the other stacks A and B are in a rest period, but both stacks A and B are in the SOFC operating temperature T ＦＣ is maintained at

[0067] In time block t2, when the output request is switched to "3", both stacks A and B are controlled in the SOFC mode, stack A outputs "2", stack B outputs "1", and the total is controlled to output "3". Stack C enters a rest period, and the SOFC operating temperature T ＦＣ The temperature is lowered to

[0068] In time block t3, the output request of "3" continues, the output of stack A is controlled from "2" to "1", the output of stack C is controlled to be "2", stack B is in a rest period, and the SOEC operating temperature T ＥＣ The temperature is raised to

[0069] In the next time block t4, stack B responds to the input request "3" and operates in the SOFC mode. The other stacks A and C are in the idle period, but both stacks A and C are operating at the SOFC operating temperature T ＦＣ is maintained at

[0070] In the next time block t5, when the output request is switched to "3", both stacks A and C are controlled in the SOFC mode, stack A outputs "1", stack C outputs "2", and stack B outputs "3". ＦＣ The temperature is lowered to

[0071] In time block t6, the output request of "3" continues, the output of stack C is controlled from "2" to "1", the output of stack B is controlled to be "2", stack A is in a rest period, and the SOEC operating temperature T ＥＣ Thereafter, each SOC stack is controlled with a similar input / output control pattern and operating temperature control pattern to correspond to input / output requirements. In each of time blocks t2, t3, t5, t6, t8, and t9, of the two SOC stacks controlled in the SOFC mode, one stack is an example of a first SOC stack, and the other SOC stack is an example of a second SOC stack.

[0072] <Control Pattern of SOC Stack> Fig. 8 is a diagram showing the control pattern of the SOC stack according to the first embodiment. Hereinafter, an example of stack C shown in each of the control patterns of Figs. 7C and 7D will be described. First, stack C is operated in the SOEC mode in time block t1 and controlled to correspond to the input of "3" (step S201). Time block t2 is a quiescent period, and the SOFC operating temperature T ＦＣ The temperature is controlled to decrease to (step S202).

[0073] In the time block t3, the SOFC mode is set and the output is controlled to be "2" (step S203). In the time block t4, the SOFC operating temperature T ＦＣ In time block t5, the control is performed to output "2" in the SOFC mode (step S205), and in time block t6, the control is performed to output "1" in the SOFC mode (step S206).

[0074] The time block t7 is a rest period, but the SOFC operating temperature T ＦＣ (Step S207). In time block t8, the control is performed so that the SOFC mode is set and "1" is output (Step S208).

[0075] Time block t9 is a rest period, and the SOEC operating temperature T ＥＣ 7C and 7D are examples in which stack A starts from step S204 in Fig. 8, and stack B starts from step S207 in Fig. 8, and the cycle is repeated.

[0076] In this way, even for requests different from the input / output requests shown in the first embodiment, the SOC module 100 is provided with a plurality of SOC stacks 10, and the plurality of SOC stacks 10 are independently controlled for input / output and temperature, and are controlled so that all of the SOC stacks 10 do not operate in the same operation mode during the operation period of the SOC module 100. Therefore, as in the first embodiment, there is no period during which an input / output request cannot be responded to, and therefore there is no delay in the input / output request, and response capability is improved.

[0077] As described above, according to the second embodiment, the same effects as those of the first embodiment are achieved. Furthermore, in the second embodiment, the control device controls the first SOC stack and the second SOC stack to operate in the SOFC mode during any period of the operation period, and the output power of the first SOC stack and the output power of the second SOC stack to be different from each other, thereby improving the degree of freedom in adjusting the output power of the solid oxide cell system.

[0078] Third Embodiment A solid oxide cell system according to a third embodiment will be described below with reference to the drawings. In the first and second embodiments, it has been described that the SOC module 100 includes a plurality of SOC stacks 10, and that the input / output and temperature of each of the plurality of SOC stacks 10 are independently controlled. In the third embodiment, a specific method of temperature control during the rest period of each SOC stack 10 will be described.

[0079] During the rest period of the SOC stack 10, (1) when switching from the SOEC mode to the SOFC mode, the SOC stack 10 is heated to the SOEC operating temperature T ＥＣ to the SOFC operating temperature T ＦＣ (2) When switching from the SOFC mode to the SOEC mode, the SOC stack 10 is cooled to the SOFC operating temperature T ＦＣ to the SOEC operating temperature T ＥＣ (3) raising the temperature of the SOC stack 10 to the SOEC operating temperature T ＥＣ or SOFC operating temperature T ＦＣThe temperature control methods for the above cases (1) and (2) will be described below.

[0080] 9A and 9B are flowcharts showing the temperature control procedure, which will be explained with reference to the gas flow shown in FIG. 4 of the first embodiment as appropriate.

[0081] (1) Cooling of SOC Stack When the temperature of the SOC stack 10 is to be lowered (No in step S301), the power input / output and heat supply to the target SOC stack 10 are interrupted (step S302). The heat supply is interrupted by turning off the heater of the SOC stack temperature regulator 18. When gas is not to be supplied to the target SOC stack 10 (No in step S303), the valve (not shown) of the gas pipe to the target stack 10 of the SOC module 100 is closed. This allows heat to be dissipated naturally.

[0082] When gas is supplied to the target SOC stack 10 (Yes in step S303), the temperature control method differs depending on the type of gas supplied (step S305). When hydrogen is supplied from the gas storage unit 34 to the fuel electrode 14 side of the target SOC stack 10, and hydrogen, nitrogen, or a mixture thereof, or a reducing gas is supplied from the gas supply unit 21 to the fuel electrode 14 side, and oxygen or air is supplied from the gas supply unit 21 to the air electrode 12 side, high-temperature gas remaining in the target SOC stack 10 is scavenged to cool the target SOC stack 10 (step S307). Here, adjusting the temperature of the gas supplied to the target SOC stack 10 in the temperature adjustment device 20 enables efficient cooling of the target SOC stack 10. That is, the rate of temperature decrease of the target SOC stack 10 can be adjusted. The temperature adjustment device 20 may be set to a lower temperature than when operating in the SOEC mode or the SOFC mode, for example. The purge gas and reducing gas supplied to the fuel electrode 14 side may also be supplied from outside the system.

[0083] When methane is supplied from the gas storage unit 34 to the fuel electrode 14 side of the target SOC stack 10 and steam is supplied from the steam supply unit 22, steam reforming and CH ４ +H ２ O → CO + 3H２ This reaction is called internal reforming, and because it is an endothermic reaction, it is possible to cool the target stack while discharging hydrogen (step S306). As described above, the discharged hydrogen is separated in the storage gas adjustment unit 35 and stored in the gas storage unit 34 or discharged to the outside. At this time, oxygen or air is supplied to the air electrode 12 side from the gas supply unit 21. The methane and water vapor supplied to the fuel electrode 14 side may be supplied from outside the system, or the water vapor may be generated in the water vapor generator 31 from water supplied from the water storage unit 32. When internal reforming is used, the temperature drop rate can be adjusted by adjusting the gas flow rate.

[0084] SOEC operating temperature T ＥＣ to the SOFC operating temperature T ＦＣ When the temperature is decreased to the SOFC operating temperature T ＦＣ If the target temperature is reached, the process ends (Yes in step S303). If the target temperature is not reached, one of the above methods may be repeated, or a different method may be used. The temperature drop rate may be adjusted using these methods so that the target temperature is reached within a preset time. At this time, the temperature of the SOC stack 10 may be dropped by selecting or combining appropriate methods depending on the situation.

[0085] (2) Heating the SOC Stack When the temperature of the SOC stack 10 is to be increased (Yes in step S301), power input / output to the target SOC stack 10 is interrupted (step S311). When heat is not supplied to the target SOC stack 10 (No in step S312), the target SOC stack 10 is heated by radiant heat (step S313). The temperature is increased by radiant heat from another SOC stack operating in SOFC mode or from an SOC stack with a higher temperature than the target SOC stack 10. At this time, a valve (not shown) in the gas pipe of the target SOC stack 10 is closed to prevent gas from being supplied. Alternatively, purge gas or reducing gas is supplied to the anode 14 side from the gas supply unit 21 or from outside the system, and oxygen or air is supplied to the cathode 12 side from the gas supply unit 21. Here, by adjusting the temperature of the gas supplied to the target SOC stack 10 by the temperature adjustment device 20, the target SOC stack 10 can be efficiently heated. That is, it is possible to adjust the temperature rise rate of the target SOC stack 10 .

[0086] When heat is supplied to the target SOC stack 10 (Yes in step S312), the temperature may be controlled using a heater or the like of the SOC stack temperature regulator 18 (step S314). In this case, too, a purge gas or a reducing gas may be supplied to the fuel electrode 14 side from the gas supply unit 21 or from outside the system, and oxygen or air may be supplied to the air electrode 12 side from the gas supply unit 21. By adjusting the temperature of the gas supplied to the target SOC stack 10 in the temperature regulator 20 together with the SOC stack temperature regulator 18, it becomes possible to efficiently increase the temperature of the target SOC stack 10. In other words, it becomes possible to adjust the rate of temperature increase of the target SOC stack 10.

[0087] SOFC operating temperature T ＦＣ to the SOEC operating temperature T ＥＣ When the temperature is increased to , the target temperature is the SOEC operating temperature T ＥＣIf the target temperature is reached, the process ends (Yes in step S315). If the target temperature is not reached, one of the above methods may be repeated, or a different method may be used. The heating rate may be adjusted using these methods so that the target temperature is reached within a preset time. At this time, the SOC stack 10 may be heated by selecting or combining appropriate methods depending on the situation.

[0088] As described above, according to the third embodiment, the temperature of the SOC stack during the idle period is controlled so that it reaches the target temperature within a preset time, so that the temperature of the SOC stack during the idle period can be controlled to the target temperature without inducing a sudden change in temperature, and deterioration of the SOC stack due to heat can be suppressed. Furthermore, because the temperature is controlled to reach the target temperature during the idle period, there is no delay in responding to input / output requests, which contributes to improved responsiveness.

[0089] 10 is a diagram showing an example of the hardware configuration of the control device 200 included in the solid oxide cell systems according to embodiments 1 to 3. The control device 200 includes a processor 1000 and a storage device 2000. The processor 1000 includes, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or the like.

[0090] The main memory of the storage device 2000 is composed of a volatile memory device such as a random access memory, and the auxiliary memory device is a nonvolatile memory device such as a flash memory or a hard disk. The auxiliary memory device stores a predetermined program to be executed by the processor 1000, which reads and executes the program as appropriate to perform various arithmetic processing. At this time, the predetermined program is temporarily stored in the volatile memory device from the auxiliary memory device, and the processor 1000 reads the program from the volatile memory device. The processor 1000 may also output data such as arithmetic results to the volatile memory device of the storage device 2000, or may store the data in the auxiliary memory device via the volatile memory device.

[0091] In order to enable remote control, a transmitter and a receiver (neither of which are shown) may be provided as a communication module for communicating with the outside.

[0092] <Other Embodiments> In the first and second embodiments, the SOC module 100 has been described as having three independently controllable stacks A, B, and C, but the number of stacks is not limited to three. Alternatively, an assembly of multiple stacks controlled in the same manner as stacks A, B, and C may be provided, and each group may be controlled independently as stack groups A, B, and C. Controlling the groups so that they are not all in the same operating mode or in a suspended period simultaneously during the operation of the solid oxide cell system 1 will provide the same effects as those of the first and second embodiments.

[0093] Although various exemplary embodiments and examples are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are anticipated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0094] 1: Solid oxide cell system, 10: SOC stack, 11: SOC, 12: Air electrode, 13: Electrolyte, 14: Anode, 15: Interconnector, 18: Temperature regulator for SOC stack, 20: Temperature regulator, 21: Gas supply unit, 22: Steam supply unit, 30: Reformer, 31: Steam generator, 32: Water storage unit, 33: Condenser, 34: Gas storage unit, 35: Storage gas adjustment unit, 100: SOC module, 200: Control device, 201: System control unit, 202: Temperature control unit, 1000: Processor, 2000: Storage device.

Claims

1. A solid oxide cell system comprising: a solid oxide cell module having a plurality of connected solid oxide cell stacks having solid oxide cell stacks switchable between an SOFC mode in which a first gas is used to generate electricity and output electric power, and an SOEC mode in which electric power is input and a second gas is electrolyzed, and a control device for controlling the operation of the plurality of solid oxide cell stacks, wherein the control device controls at least one of the plurality of solid oxide cell stacks to operate in the SOFC mode or the SOEC mode during any period within an operating period in which the operation of the solid oxide cell stacks is controlled while switching between the SOFC mode and the SOEC mode, and controls at least one other solid oxide cell stack to a dormant state in which it does not operate in either the SOFC mode or the SOEC mode by stopping the input / output of electric power to or from at least one other solid oxide cell stack.

2. The solid oxide cell system according to claim 1, wherein the control device controls at least one of the plurality of solid oxide cell stacks to operate in the SOFC mode or the SOEC mode during any period of the operating period, and stops input / output of power to at least one other solid oxide cell stack, thereby controlling it to a hibernation state in which it does not operate in either the SOFC mode or the SOEC mode.

3. A solid oxide cell system as described in claim 1 or 2, wherein the plurality of solid oxide cell stacks include a first solid oxide cell stack and a second solid oxide cell stack, and the control device controls the first solid oxide cell stack and the second solid oxide cell stack to operate in the SOFC mode during any period of the operating period, and the output power of the first solid oxide cell stack and the output power of the second solid oxide cell stack are different from each other.

4. A solid oxide cell system according to any one of claims 1 to 3, wherein the control device controls the input / output power and temperature for each of the plurality of solid oxide cell stacks.

5. A solid oxide cell system as described in claim 4, further comprising a stack temperature regulator for adjusting the temperature of each of the solid oxide cell stacks, wherein when the control device is to lower the temperature of the solid oxide cell stack in a dormant state within a preset time, the control device controls the temperature using at least one of the following methods: natural heat dissipation from the solid oxide cell stack, stopping the heat supply by the stack temperature regulator, scavenging gas remaining in the solid oxide cell stack to the outside, or causing an endothermic reaction in the solid oxide cell stack.

6. A solid oxide cell system as described in claim 4, comprising: a stack temperature regulator that adjusts the temperature of each of the solid oxide cell stacks; and a temperature regulator that adjusts the temperatures of the first gas and the second gas, wherein when the solid oxide cell stack in a dormant state is to be heated within a preset time, the controller controls the temperature using at least one of the following methods: heat supply by the stack temperature regulator; and gas supply heated by the temperature regulator.

7. The solid oxide cell system according to claim 4, wherein the control device, when raising the temperature of the solid oxide cell stack in a dormant state within a preset time, performs temperature control using radiant heat from another solid oxide cell stack operating in the SOFC mode or the SOEC mode.

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