Solid oxide cell system

Abstract

In a solid oxide cell system (1) having a solid oxide cell module (100) with at least one solid oxide cell stack (10) and capable of switching between an SOFC mode and an SOEC mode, the solid oxide cell stack (10) that switches from one of the SOEC mode and the SOFC mode to the other mode is continuously operated in one of the modes, and the temperature of the solid oxide cell stack (10) is controlled so as to approach a preset operating temperature of the other mode through a thermal reaction of the solid oxide cell stack (10) due to operation in one mode.

Description

[Technical field]

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

[0002] A solid oxide fuel cell (SOFC) can output electricity and heat using hydrogen, hydrocarbon, or carbon monoxide as raw materials. It can also operate as a solid oxide electrolysis cell (SOEC) that electrolyzes water vapor or carbon dioxide into hydrogen, carbon monoxide, or oxygen, which is the reverse reaction. A power storage and supply system using a reversible SOC (Solid Oxide Cell) that has the functions of power generation and electrolysis has been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6881007 Summary of the Invention [Problem to be solved by the invention]

[0004] Typically, power storage and supply systems have a stack structure in which multiple SOCs are layered. In systems using conventional reversible SOCs, the operating temperatures differ for each operating mode, so switching between operating modes is accompanied by a temperature change. However, when the temperature of the SOC changes suddenly, it can be physically damaged by heat, which can reduce its durability.

[0005] The present disclosure discloses technology for solving the problems described above, and aims to provide a solid oxide cell system that can suppress a decrease in the durability of the SOC by controlling the temperature change of the SOC stack to prevent a sudden change when switching operation modes. [Means for solving the problem]

[0006] The solid oxide cell system of the present disclosure comprises: a solid oxide cell module having at least one solid oxide cell stack capable of switching between a SOFC mode in which a first gas is used to generate electricity and output the electricity, and a SOEC mode in which electricity is input and a second gas is electrolyzed; a control device for controlling an operation of the solid oxide cell stack; The control device includes: The solid oxide cell stack is switched from one of the SOEC mode and the SOFC mode to the other mode, and is continuously operated in the one mode, and a temperature of the solid oxide cell stack is increased to a preset operating temperature of the other mode by a thermal reaction of the solid oxide cell stack due to the operation in the one mode. and then switching the solid oxide cell stack from the one mode to the other mode. It is structured as follows. Effect of the Invention

[0007] The solid oxide cell system of the present disclosure makes it possible to prevent abrupt changes in temperature of the SOC stack when switching between operation modes, and to slow down the change in durability of the SOC stack. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration of a solid oxide cell system according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing a configuration of a SOC stack according to the first embodiment. [Diagram 3]FIG. 2 is a diagram for explaining the operation in a SOFC mode in the solid oxide cell system according to the first embodiment. [Figure 4] FIG. 2 is a diagram for explaining operation in an SOEC mode in the solid oxide cell system according to the first embodiment. [Diagram 5] FIG. 4 is a diagram showing the relationship between the difference between the amount of heat generated and the amount of heat absorbed by the SOC stack corresponding to the operation mode and the applied voltage. [Figure 6] FIG. 4 is a diagram showing input / output control and temperature control patterns of the SOC stack provided in the solid oxide cell system according to the first embodiment. [Figure 7A] 4 is a flowchart for explaining a control method at the time of switching the operation mode of the SOC stack provided in the solid oxide cell system according to the first embodiment. [Figure 7B] 4 is a flowchart for explaining a control method at the time of switching the operation mode of the SOC stack provided in the solid oxide cell system according to the first embodiment. [Figure 8] FIG. 4 is a diagram showing input / output control and temperature control patterns of the SOC stack provided in the solid oxide cell system according to the first embodiment. [Figure 9A] 4 is a flowchart for explaining a control method at the time of switching the operation mode of the SOC stack provided in the solid oxide cell system according to the first embodiment. [Figure 9B] 4 is a flowchart for explaining a control method at the time of switching the operation mode of the SOC stack provided in the solid oxide cell system according to the first embodiment. [Figure 10] FIG. 2 is a diagram showing an example of a hardware configuration of a control device of the solid oxide cell system according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of a solid oxide cell system according to the present disclosure will be described with reference to the drawings. This disclosure is directed to a solid oxide cell system using a reversible SOC having both SOFC and SOEC functions. In addition, 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, the solid oxide cell will be referred to as SOC, the solid oxide cell stack as SOC stack, and the solid oxide cell module as SOC module, and the operating mode in which the SOC stack operates as a SOFC will be referred to as SOFC mode, and the operating mode in which it operates as a SOEC will be referred to as SOEC mode.

[0010] Embodiment 1 The solid oxide cell system according to the first embodiment will be described below with reference to the drawings. <Solid oxide cell system configuration> FIG. 1 is a diagram showing the configuration of a solid oxide cell system according to the 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 a raw material gas required in the SOFC mode, a steam supply unit 22 that supplies steam (H2O) in the SOEC mode, a temperature adjustment device 20 that adjusts the temperature of the supplied gas and steam, 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 mode 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 are the main components 1A of the solid oxide cell system 1 shown in 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 the power generated by the SOC module 100 in the SOFC mode is supplied, or a current source to which the SOC module 100 supplies power in the SOEC mode.

[0011] The SOC module 100 is an assembly formed by connecting a plurality of SOC stacks 10_1 - 10_n (n is a natural number greater than or equal to 2). Each SOC stack 10 is provided with a temperature regulator 18 for the SOC stack. The temperature regulator 18 is, for example, a heater such as a heater. When collectively referring to the SOC stacks, they are referred to as SOC stack 10.

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

[0013] Taking the k-th (1 < k ≤ m; k is a natural number) SOC 11_k as an example, each SOC 11 has a structure in which an air electrode 12 and a fuel electrode 14 sandwich an electrolyte 13, and is connected to an adjacent SOC 11 by an interconnector 15. In some cases, a diffusion prevention layer for suppressing material deterioration is inserted between the air electrode 12 and the electrolyte 13. When collectively referring to the SOCs, they are referred to as SOC 11.

[0014] The control device 200 includes a system control unit 201 and a temperature control unit 202. The system control unit 201 performs operations such as switching the operation mode of the SOC module 100 and controlling the opening and closing of valves V1 - V6 provided in the gas pipeline. The temperature control unit 202 controls the temperature adjustment device 20 so that the supplied gas and water vapor reach a preset temperature, and controls the temperature regulator 18 for the SOC stack so that each SOC stack 10 reaches a preset temperature.

[0015] The external device 300 is a load or a current source as described above. A load to which the power 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. A 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 system. The control device 200 controls the external device 300 to control the voltage of each SOC stack.

[0016] The gas supply unit 21 supplies hydrogen (H2) and the like as the raw material gas for the fuel electrode side required in the SOFC mode, and supplies hydrogen, carbon dioxide (CO2), and the like in the SOEC mode. The gas supply unit 21 may have external gas cylinders and supply the gas to the gas supply unit 21. The gas supplied to the air electrode in the SOFC mode is, for example, oxygen (O2), air, and the like. 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 piping temperature of the (upstream) gas and water vapor supplied to the SOC module 100, and is, for example, a heater or a heating device provided around the piping. In addition, the downstream gas generated from the SOC module 100 may be used as a heat source to heat the upstream gas.

[0018] The solid oxide cell system 1 may include optional components such as a reformer 30, a steam generator 31, a water storage section 32, a condenser 33, a gas storage section 34, and a storage gas adjustment section 35. The reformer 30 is used in the SOFC mode when city gas (gas mainly composed of methane) is used. The 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 storage unit 32 stores water to be supplied to the steam generator 31. The steam in the downstream gas on the fuel electrode side discharged from the SOC module 100 may be collected and reused as the supply gas or fuel for the reformer 30.

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

[0022] The gas storage unit 34 collects 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 adjustment unit 35 adjusts the gas by appropriately processing it in order to store each gas in the gas storage unit 34. For example, the form of the gas is adjusted by compressing the gas with a compressor, separating a mixed gas of, for example, hydrogen and carbon monoxide (CO), which is the gas downstream of the fuel electrode side discharged from the SOC module 100 in the SOEC mode, with a separator, or synthesizing methane using, for example, hydrogen and carbon monoxide (CO) in a methanation reactor. The gas adjusted by the storage gas adjustment unit 35 is stored in the gas storage unit 34.

[0024] In FIG. 1 and the following figures showing the configuration of the solid oxide cell system, each line indicates the following: Solid line: Pre-reaction gas flow path (upstream) Dot-dash line: Post-reaction gas flow path (downstream) Dashed lines: Gas flow paths used for purposes other than fuel cells and steam electrolysis reactions Black arrow: Gas (such as hydrogen, nitrogen, carbon monoxide, hydrocarbon, water vapor, carbon dioxide, etc.) supplied to or discharged from the fuel electrode White arrow: Gas (such as oxygen, air, etc.) supplied to or discharged from the air electrode

[0025] <Operation in SOFC mode> Next, the operation of the solid oxide type cell system 1 in the SOFC mode will be described. FIG. 3 shows the gas flow in FIG. 1 in thick lines during the SOFC mode. In the SOFC mode, gases described below are supplied to the fuel electrode 14 and the air electrode 12 respectively, and the generated electric power is output.

[0026] (1) Gas supply to the SOC module 100 (upstream) A gas mainly composed of hydrogen is supplied to the fuel electrode 14 side. The gas mainly composed of hydrogen is supplied from the gas supply unit 21 to the SOC module 100 via the temperature adjustment device 20. A gas mainly composed of hydrogen may be supplied from the gas storage unit 34. A gas mainly composed of methane may be supplied to the fuel electrode 14 side. The gas mainly composed of methane is supplied from the gas storage unit 34 to the SOC module 100 via the temperature adjustment device 20. Alternatively, it may be supplied from the outside via the reformer 30. Also, it may be supplied from the gas storage unit 34 via the reformer 30. In the reformer 30, steam reforming is performed by the following reaction using the steam supplied from the water storage unit 32, and the reformed gas is supplied to the fuel electrode 14 side. CH4 + H2O → CO + 3H2 As will be described below, during temperature adjustment or during a pause in the SOC stack 10 of the SOC module 100 that is not operating in the SOFC mode, a purge gas or a reducing gas mainly composed of hydrogen and nitrogen is supplied to the fuel electrode 14 side from the gas supply unit 21 or the gas storage unit 34.

[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 in the SOC module 100 that is not operating in the SOFC mode and is undergoing temperature adjustment or is at rest. In gas supply to the SOC module 100, the opening and closing direction of valve V1 determines the supply source of gas to the fuel electrode 14 side. When the gas supplied to the fuel electrode 14 side is gas mainly composed of methane, the opening and closing direction operation of valve V2 supplies the gas mainly composed of methane from the 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-V3 are three-way valves, and their opening and closing direction operations are controlled by the system control unit 201.

[0028] (2) Gas discharge from SOC module 100 (downstream) When a gas mainly composed of hydrogen is supplied from the fuel electrode 14 side, water vapor and unreacted hydrogen are discharged, and when a gas mainly composed of methane is supplied, water vapor and carbon dioxide are discharged. The discharged gas may be discharged directly to the outside, but in FIG. 3, the water vapor and other gases may be separated in a condenser 33, and then the hydrogen and carbon dioxide may be separated in a storage gas adjustment unit 35. The water vapor may be stored in a water storage unit 32. Unreacted oxygen or air is discharged from the air electrode 12. 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 storage unit 32 when the reformer 30 is operating by opening and closing the valve V5. Also, depending on the opening and closing direction of the valve V4, a part of the exhaust gas can be supplied as fuel for the heat supply burner of the reformer 30. 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 as to heat the supply gas by heat exchange with the exhaust gas. In addition, the temperature of the temperature adjuster 20 during operation, the temperature of the temperature adjuster 18 for the SOC stack, and the temperature of the reformer 30 are controlled by the temperature control unit 202 to the temperatures set respectively.

[0031] <Operation in SOEC mode> Next, the operation of the solid oxide cell system 1 in the SOEC mode will be described. FIG. 4 shows the gas flow in the SOEC mode in FIG. 1 with thick lines. In the SOEC mode, gases described below are supplied to the fuel electrode 14 and the air electrode 12 respectively, and an electrolysis reaction occurs due to the input power.

[0032] (1) Gas supply to the SOC module 100 (upstream) To the fuel electrode 14 side, a gas mainly composed of water vapor is supplied from the water vapor supply unit 22. Although water vapor may be directly introduced from the outside, as shown in FIG. 4, the water supplied from the water storage unit 32 may be heated by the water vapor generator 31 to generate water vapor. Also, hydrogen may be supplied from the gas storage unit 34 or the gas supply unit 21, mixed with water vapor by the temperature adjuster 20, and supplied to the fuel electrode 14 side. Also, a gas mainly composed of carbon dioxide may be supplied from the gas supply unit 21 to the fuel electrode 14 side. At this time, a mixed gas of water vapor and carbon dioxide may be supplied to the fuel electrode 14 side. Note that, as will be described below, to the fuel electrode 14 side of the SOC stack 10 that is not operating in the SOEC mode in the SOC module 100 and is under temperature adjustment or in a standby state, a purge gas or a reducing gas mainly composed of hydrogen and nitrogen is supplied from the gas supply unit 21 or the gas storage unit 34.

[0033] To the air electrode 12 side, oxygen or air is supplied from the gas supply unit 21. Similarly, oxygen or air is supplied to the air electrode 12 side of the SOC stack 10 that is not operating in the SOEC mode in the SOC module 100 and is under temperature adjustment or in a standby state. In supplying gas to the SOC module 100, the opening / closing direction of the valve V1 and the opening / closing of the valve V6 determine the gas supply source to the fuel electrode 14. The valve V1 is a three-way valve, and the valve V6 is an on-off valve, and the opening / closing direction and opening / closing operation are controlled by the system control unit 201.

[0034] (2) Gas discharge from SOC module 100 (downstream) When a gas mainly composed of water vapor is supplied from the fuel electrode 14 side, hydrogen and unreacted water vapor are discharged, and when a gas mainly 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, but in FIG. 4, the water vapor and other gases are separated in a condenser 33, and then the hydrogen and carbon monoxide are separated in a gas adjustment unit for storage 35, or the mixed gas containing hydrogen and carbon monoxide may be introduced as it is into a methanation reactor to generate methane. The gases such as hydrogen, carbon monoxide, and methane processed in the gas adjustment unit for storage 35 are stored in a gas storage unit 34. The unreacted water vapor may be stored in a water storage unit 32 and supplied again to the fuel electrode 14. The generated oxygen or air with a high oxygen concentration is discharged from the air electrode 12. The discharged gas may be returned to the gas supply unit 21 to circulate the system.

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

[0036] <Relationship between operation mode and amount of heat generated and absorbed by SOC stack> FIG. 5 is a diagram showing an example of the relationship between the SOC stack voltage and the difference between the heat generation amount and the heat absorption amount generated in the SOC stack with respect to the input / output current density of the SOC stack at a certain temperature. In the figure, the solid line represents the SOC stack voltage, and the dashed-dotted line represents the difference between the heat generation amount and the heat absorption amount generated in the SOC stack. Note that the voltage OCV (Open Circuit Voltage) in the figure is the open circuit voltage.

[0037] When the current density is on the positive side, the SOC stack generates power in the SOFC mode, that is, it is the output side of the current. The combustion reaction (oxidation reaction) of hydrogen during power generation is an exothermic reaction, and the heat generation amount increases as the output current density of the SOC stack increases. Therefore, if there is no heat dissipation from the SOC stack to the outside, the temperature of the SOC stack will rise.

[0038] When the current density is on the negative side, it is the input side where current is input to the SOC stack and electrolysis is performed in the SOEC mode. Although it is an endothermic reaction during electrolysis, Joule heat (RI 2 ) is also generated due to the electrical resistance of the SOC peripheral members such as the SOC and the interconnect. When the input current density to the SOC stack increases, until the SOC stack voltage reaches the thermal neutral voltage V th , the heat absorption amount exceeds the heat generation amount. Therefore, if there is no heat supply from outside the SOC stack, the temperature of the SOC stack will decrease. Hereinafter, the exothermic reaction and the endothermic reaction in the SOC stack are collectively referred to as the heat reaction.

[0039] When the input current density to the SOC stack further increases and the SOC stack voltage exceeds the thermal neutral voltage V th , the heat generation amount exceeds the heat absorption amount, and if there is no heat dissipation from the SOC stack to the outside, the temperature of the SOC stack will rise.

[0040] <Control Method during Operation Mode Switching from SOEC Mode to SOFC Mode> Next, a control method for switching the operation mode from the SOEC mode to the SOFC mode in the solid oxide cell system 1 according to the first embodiment will be described with reference to Figs. 6, 7A, and 7B. Fig. 6 shows the magnitude of input and output of the SOC stack 10 and the operating temperature of the SOC stack 10 over time when the operation mode is switched from the SOEC mode to the SOFC mode. The input and output current density of the SOC stack 10 is shown in arbitrary units of -3 to +3, with the positive direction representing the SOFC mode in which power is generated and output to the outside, and the negative direction representing the SOEC mode in which electrolysis is performed by input from the outside. Generally, the SOEC operating temperature T EC is the SOFC operating temperature T FC Since the temperature is set higher, the SOC stack 10 is at the SOEC operating temperature T EC From the SOEC mode operating at the SOFC operating temperature T FC The temperature is then lowered to operate in SOFC mode.

[0041] 6, first, it is assumed that the SOC stack 10 operates in the SOEC mode and is compatible with an input of “2 or more.” At this time, gas is supplied in the same manner as described with reference to FIG. When the SOC stack 10 switches its operation mode from the SOEC mode to the SOFC mode, the system control unit 201 first detects whether the voltage of the SOC stack 10 is equal to the thermal neutral voltage V th The input is controlled so that it is less than the thermal neutral voltage V th The magnitude of the input corresponding to is "2". The stack voltage is the thermal neutral voltage V th If the input is controlled so that it is less than the thermal neutral voltage V th Until the temperature of the SOC stack 10 reaches the SOEC operating temperature T EC The stack voltage is maintained at the thermal neutral voltage V th When the time t SW The temperature of the SOC stack 10 is the SOFC operating temperature T FCWhen it reaches, the system control unit 201 switches the output control of the SOC stack 10, switches the gas supply to the gas supply for power generation described with reference to FIG. 3, and operates in the SOFC mode.

[0042] As the temperature of the SOC stack 10 decreases, due to the increase in resistance, the calorific value generated due to electrical resistance and the like for the same input increases. Therefore, the system control unit 201 adjusts the stack input power according to the temperature decrease. For example, as shown in FIG. 6, until the thermal neutral voltage V th is reached, the input is gradually and gently decreased to suppress the increase in the calorific value so that the difference between the calorific value and the heat absorption amount becomes maximum, and the control is performed so that the temperature decrease progresses. After that, the input is set to "0".

[0043] Note that, as shown by the broken line, at the time t SW before reaching, at the time t rest of the SOC stack 10, the temperature is controlled to reach the SOFC operating temperature T FC , and a temperature stabilization time for stabilizing the temperature between the time t rest and the time t SW may be provided, and an input / output pause period for interrupting the input / output may be set.

[0044] <Cooling of the SOC stack> Next, the specific system control and temperature control procedures when switching the operation mode of the SOC stack 10 from the SOEC mode to the SOFC mode will be described with reference to FIGS. 7A and 7B. When switching the operation mode from the SOEC mode to the SOFC mode, first, when heat is supplied to the SOC stack 10 so as to maintain the SOEC operating temperature T EC , the temperature control unit 202 stops the heat supply. The heat supply is, for example, a heater or the like of the temperature regulator 18 for the SOC stack provided in the SOC stack 10, and if there are other heat supply sources, they are also included (step S101).

[0045] Next, when the temperature of the SOC stack 10 reaches the SOFC operating temperature T FCThe system control unit 201 controls the stack voltage to reach the thermal neutral voltage V th The control is performed within a range less than this (step S102). Next, it is determined whether or not to provide a temperature stabilization time for stabilizing the temperature when the operation mode is switched (step S103).

[0046] When setting the temperature stabilization time (Yes in step S103), the stack voltage is set to the thermal neutral voltage V th When the temperature of the SOC stack 10 is controlled within the range of less than the SOFC operating temperature T FC This is because it is determined whether the SOFC operating temperature T FC This is to determine whether the

[0047] SOFC operating temperature T FC If it is determined that the temperature does not reach the temperature limit (No in step S104), a means for cooling the temperature of the SOC stack 10 is added to accelerate the temperature reduction and the reduction speed (step S105). In this state, the gas described with reference to Fig. 4 is supplied to the SOC stack 10, so that, for example, the temperature of the gas supplied by the temperature adjustment device 20 may be reduced, or the flow rate of the gas supplied may be increased to reduce the gas utilization rate of the SOC stack 10 and promote the endothermic reaction, or the temperature may be reduced by circulating the gas. These methods may be performed alone or in combination.

[0048] SOFC operating temperature T FC If it is determined that the temperature of the SOC stack 10 reaches the SOFC operating temperature T FC The control of the stack voltage continues until the stack voltage reaches the threshold voltage (step S106).

[0049] The temperature of the SOC stack 10 is the SOFC operating temperature T FC If the temperature reaches the predetermined value (Yes in step S107), the input to the SOC stack 10 is set to 0, the gas supply is stopped, and a temperature stabilization time is started (step S108). After the temperature stabilization time has elapsed and time t SW is reached, the system control unit 201 and the temperature control unit 202 perform output control corresponding to the output request, gas supply, and temperature control of the SOC stack 10 described with reference to FIG. 3 on the SOC stack 10, and control it to operate in the SOFC mode (step S109).

[0050] If the temperature stabilization time is not set (No in step S103), it is determined whether the temperature of the SOC stack 10 reaches the SOFC operating temperature T th only by the endotherm when controlling within the range where the stack voltage is less than the thermal neutral voltage V FC (step S110). Steps S110 to S113 are the same as steps S104 to S107 described above, so the description is omitted.

[0051] If the temperature of the SOC stack 10 reaches the SOFC operating temperature T FC at step S113 (Yes at step S113), the operation mode is switched. Then, the system control unit 201 and the temperature control unit 202 perform output control corresponding to the output request, gas supply, and temperature control of the SOC stack 10 so that the SOC stack 10 operates in the SOFC mode (step S114).

[0052] <Control Method at the Time of Switching the Operation Mode from the SOFC Mode to the SOEC Mode> Next, a specific system control and temperature control method when switching the operation mode of the SOC stack 10 from the SOFC mode to the SOEC mode will be described with reference to FIGS. 8, 9A, and 9B. FIG. 8 shows the time transition of the input / output magnitude of the SOC stack 10 and the operating temperature of the SOC stack 10 when switching the operation mode from the SOFC mode to the SOEC mode. The input / output current density of the SOC stack 10 is shown from -3 to +3 in arbitrary units. The positive direction is the SOFC mode in which power is generated and output to the outside, and the negative direction is the SOEC mode in which electrolysis is performed by an external input. Also, generally, the SOEC operating temperature T EC is the SOFC operating temperature TFC Since the SOFC operating temperature T FC From the SOFC operating mode at the SOEC operating temperature T EC The temperature is then raised to 400° C. and the device is operated in the SOEC mode.

[0053] 8, first, it is assumed that the SOC stack 10 operates in the SOFC mode and meets the output requirement of "2." At this time, the gas supply is as described with reference to FIG. When the SOC stack 10 switches its operation mode from the SOFC mode to the SOEC mode, the system control unit 201 detects whether the temperature of the SOC stack 10 reaches the SOEC operating temperature T EC Adjust the output so that the temperature rises to .

[0054] The system control unit 201 adjusts the output of the SOC stack 10 according to the temperature rise. Specifically, if the SOC stack 10 is operated in the SOFC mode so as not to reduce the output, the temperature of the SOC stack 10 rises. If the temperature rise is insufficient or the rate of rise is slow, the output is increased to "3" or heat is supplied to the SOC stack 10 to raise the temperature of the SOC stack 10. Possible causes of insufficient temperature rise include, for example, heat loss to the outside of the SOC stack 10. In addition, the temperature of the SOC stack 10 is the SOEC operating temperature T EC If it is predicted that the output will exceed this limit, the output will be reduced and controlled.

[0055] Pre-set time t SW By the time the temperature of the SOC stack 10 reaches the SOEC operating temperature T EC The system control unit 201 performs output control so that the As shown by the dashed line in FIG. SW Before reaching time t rest When the temperature of the SOC stack 10 reaches the SOEC operating temperature T EC At time t rest and time t SW A temperature stabilization time for stabilizing the temperature may be provided between the input and output terminals, and an input / output pause period during which input / output is suspended may be set.

[0056] <Heating of the SOC stack> Next, with reference to FIGS. 9A and 9B, the specific system control and temperature control procedures when switching the operating mode of the SOC stack 10 from the SOFC mode to the SOEC mode will be described. When switching the operating mode from the SOFC mode to the SOEC mode, first, the system control unit 201 controls the output of the SOC stack 10 so that the temperature of the SOC stack 10 reaches the SOEC operating temperature T EC (step S201).

[0057] Next, it is determined whether to provide a temperature stabilization time for stabilizing the temperature during the operation mode switch (step S202). When setting the temperature stabilization time (Yes in step S202), it is determined whether the temperature of the SOC stack 10 reaches the SOEC operating temperature T EC only by the heat generation due to the output of the SOC stack 10 (step S203). This is to determine whether the SOEC operating temperature T SW is reached by the preset operation mode switch time t EC .

[0058] If it is determined that the SOEC operating temperature T EC is not reached (No in step S203), heat is supplied to the SOC stack 10 to promote the temperature rise and the rate of rise (step S204). Specifically, the output is increased, or heat is supplied to the SOC stack 10 to raise the temperature of the SOC stack 10. The heat supply may be performed by heating with the temperature regulator 18 for the SOC stack. Either the method of increasing the output or the heat supply to the SOC stack 10 may be selected, or both may be combined.

[0059] If it is determined that the SOEC operating temperature T EC is reached only by the heat generation due to the output of the SOC stack 10 (Yes in step S203), the system control unit 201 continues to control the output of the SOC stack 10 (step S205).

[0060] The temperature of the SOC stack 10 is the SOEC operating temperature T EC If it has reached this value (Yes in step S206), the output is set to 0, the gas supply is stopped, and a temperature stabilization time is started (step S207). After the temperature stabilization time, at time t SW When this is reached, the system control unit 201 and the temperature control unit 202 perform input control in response to the input request, gas supply and temperature control of the SOC stack 10 as described with reference to FIG. 4, etc. so that the SOC stack 10 operates in the SOEC mode (step S208).

[0061] If the temperature stabilization time is not set (No in step S202), the temperature of the SOC stack 10 will not exceed the SOEC operating temperature T EC It is determined whether or not the number of the first and second vertices reaches the threshold (step S210). Steps S210 to S213 are similar to steps S203 to S206 described above, and therefore the description thereof will be omitted.

[0062] In step S213, the temperature of the SOC stack 10 is increased to the SOEC operating temperature T EC If the output voltage Vcc reaches the SOEC voltage Vcc (Yes in step S213), the operation mode is switched. Then, the system control unit 201 and the temperature control unit 202 perform input control corresponding to the output request, gas supply described with reference to FIG. 4, and temperature control of the SOC stack 10 (step S214).

[0063] 10 is a diagram showing an example of a hardware configuration of a control device 200 included in the solid oxide cell system according to embodiment 1. The control device 200 includes a processor 1000 and a storage device 2000. The processor 1000 includes, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), etc.

[0064] The main storage device of the storage device 2000 is composed of a volatile storage device such as a random access memory, and the auxiliary storage device is a non-volatile storage device such as a flash memory or a hard disk. A specific program executed by the processor 1000 is stored in the auxiliary storage device, and the processor 1000 reads and executes this program as appropriate to perform various arithmetic processing. At this time, the specific program is temporarily saved from the auxiliary storage device to the volatile storage device, and the processor 1000 reads the program from the volatile storage device. The processor 1000 may output data such as the results of the arithmetic processing to the volatile storage device of the storage device 2000, or may save the data in the auxiliary storage device via the volatile storage device.

[0065] In order to enable remote control, a transmitting device and a receiving device (neither shown) may be provided as a communication module for communicating with the outside.

[0066] As described above, according to the first embodiment, the solid oxide cell system includes a solid oxide cell module having at least one solid oxide cell stack that can be switched between an SOFC mode in which a first gas is used to generate electricity and output the electricity, and an SOEC mode in which electricity is input and a second gas is electrolyzed, and a control device that controls the operation of the solid oxide cell stack, and the control device operates the solid oxide cell stack, which switches from one of the SOEC mode and the SOFC mode to the other mode, continuously in one mode, and brings the temperature of the solid oxide cell stack close to a preset operating temperature of the other mode by a thermal reaction of the solid oxide cell stack due to the operation of the one mode. With this configuration, it is possible to make the temperature change of the SOC stack when the operation mode is switched gradually rather than suddenly, and it is possible to suppress a decrease in the durability of the SOC stack. 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, and 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, and oxygen or air supplied to the air electrode side.

[0067] The control device controls the SOC stack to continue operating in the SOEC mode when the SOC stack is switched from the SOEC mode to the SOFC mode, sets the voltage of the solid oxide cell stack to be lower than the thermal neutral voltage at which the amount of heat absorption and the amount of heat generation are balanced, and lowers the temperature of the SOC stack. When the preset operating temperature in the SOFC mode is reached, the control device stops the input of power to the SOC stack and stops the supply of the second gas to switch to the SOFC mode. The control device controls the SOC stack to continue operating in the SOFC mode when the SOC stack is switched from the SOFC mode to the SOEC mode, determines whether the preset operating temperature in the SOEC mode is reached by the operation in the SOFC mode, and if the preset operating temperature in the SOEC mode is not reached, heats the SOC stack to increase the temperature of the SOC stack. When the preset operating temperature in the SOEC mode is reached, the control device stops the output of power from the solid oxide cell stack and stops the supply of the first gas to switch to the SOEC mode. This configuration enables fine temperature control when switching between operation modes.

[0068] That is, the temperature change is controlled within the current operation mode according to the endothermic reaction in SOEC mode, the exothermic reaction in SOFC mode, and the heat generation factors of the SOC stack, and taking into consideration the relationship between the input / output power (current density) of the SOC stack and the stack voltage, etc., so it is possible to make the temperature change of the SOC stack gentle rather than sudden. Also, this effect can be obtained by a simple means that does not require a configuration to circulate a heat medium for temperature control.

[0069] The multiple SOC stacks 10 included in the SOC module 100 described above are provided with pipes and valves (not shown) so that gas can be supplied and discharged independently, and the control device controls the input and output of power so that each operation mode can be controlled independently, and the temperature can be controlled independently. In addition to the effects of the first embodiment, the present embodiment is expected to improve the operation efficiency of the SOC module 100, such as by expanding the tolerance of the operation pattern and improving the ability to follow input / output requests.

[0070] Furthermore, the plurality of SOC stacks 10 included in the above-described SOC module 100 may be configured to perform power input / output and temperature control so that the operation mode is uniformly controlled for each SOC module 100 by a control device. In addition to the effects of the first embodiment, it becomes possible to control the SOC module 100 with a simple operation pattern.

[0071] Furthermore, although the above-mentioned SOC module 100 is an example having a plurality of SOC stacks 10, the same effect can be achieved even if there is only one SOC stack 10.

[0072] Although exemplary embodiments are described in this disclosure, the various features, aspects, and functions described in the embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are expected within the scope of the technology disclosed in this specification, including, for example, modifying, adding, or omitting at least one component. [Explanation of symbols]

[0073] 1: solid oxide cell system, 10: SOC stack, 11: SOC, 12: air electrode, 13: electrolyte, 14: fuel electrode, 15: interconnector, 18: temperature regulator for SOC stack, 20: temperature regulator, 21: gas supply section, 22: steam supply section, 30: reformer, 31: steam generator, 32: water storage section, 33: condenser, 34: gas storage section, 35: storage gas regulator, 100: SOC module, 200: control device, 201: system control section, 202: temperature control section, 1000: processor, 2000: storage device.

Claims

1. a solid oxide cell module having at least one solid oxide cell stack capable of switching between an SOFC mode in which a first gas is used to generate electricity and output the electricity, and an SOEC mode in which electricity is input and a second gas is electrolyzed; a control device for controlling an operation of the solid oxide cell stack; The control device includes: a solid oxide cell system in which the solid oxide cell stack is switched from one of the SOEC mode and the SOFC mode to the other mode, and the solid oxide cell stack is continuously operated in the one mode, and a temperature of the solid oxide cell stack is controlled to reach a preset operating temperature of the other mode through a thermal reaction of the solid oxide cell stack due to operation in the one mode, and then the solid oxide cell stack is switched from the one mode to the other mode.

2. The control device includes:

2. The solid oxide cell system according to claim 1, wherein the solid oxide cell stack that is switched from the SOEC mode as the one mode to the SOFC mode as the other mode is continuously operated in the SOEC mode, and a voltage of the solid oxide cell stack is set to be lower than a voltage at a thermal neutral state where an amount of heat absorbed by electrolysis and an amount of heat generated by the solid oxide cell stack are balanced, thereby controlling a temperature of the solid oxide cell stack to reach an operating temperature in the SOFC mode, and then the solid oxide cell system is switched from the SOEC mode to the SOFC mode.

3. The control device includes:

3. The solid oxide cell system according to claim 2, wherein when the temperature of the solid oxide cell stack reaches an operating temperature in the SOFC mode, the input of electric power to the solid oxide cell stack is stopped, and the supply of the second gas is stopped, thereby switching to the SOFC mode.

4. The control device includes:

2. The solid oxide cell system according to claim 1, wherein the solid oxide cell stack that switches from the SOFC mode as the one mode to the SOEC mode as the other mode is continuously operated in the SOFC mode, and a determination is made as to whether the operation in the SOFC mode reaches a preset operating temperature in the SOEC mode, and if the preset operating temperature in the SOEC mode is not reached, the solid oxide cell stack is heated to increase the temperature of the solid oxide cell stack.

5. The control device includes:

5. The solid oxide cell system according to claim 4, wherein when the temperature of the solid oxide cell stack reaches a preset operating temperature in the SOEC mode, the output of power from the solid oxide cell stack is stopped and the supply of the first gas is stopped, thereby switching to the SOEC mode.

6. a temperature regulator that adjusts a temperature of the solid oxide cell stack and a temperature regulator that adjusts temperatures of the first gas and the second gas, The control device includes:

4. The solid oxide cell system according to claim 1, wherein the temperature of the solid oxide cell stack is controlled by at least one of the following methods: stopping heat supply from the temperature regulator to the solid oxide cell stack that switches from the SOEC mode to the SOFC mode, and continuing to operate the solid oxide cell stack in the SOEC mode, and increasing a flow rate of the second gas so that a preset operating temperature in the SOFC mode is reached within a preset time; and lowering a temperature of the second gas by the temperature regulator.

7. a temperature regulator that adjusts a temperature of the solid oxide cell stack and a temperature regulator that adjusts temperatures of the first gas and the second gas, The control device includes:

6. The solid oxide cell system according to claim 1, 4, or 5, wherein the temperature of the solid oxide cell stack is controlled by at least one of the following methods: the solid oxide cell stack that switches from the SOFC mode to the SOEC mode is continuously operated in the SOFC mode, and an output power in the SOFC mode is controlled so that a preset operating temperature in the SOFC mode is reached within a preset time; and heat is supplied to the solid oxide cell stack by the temperature regulator.

8. The control device includes:

4. The solid oxide cell system according to claim 1, wherein when a preset operating temperature in the SOFC mode is reached, the input of power to the solid oxide cell stack is stopped and the supply of the second gas is stopped for the solid oxide cell stack to be switched from the SOEC mode to the SOFC mode, and then the solid oxide cell stack is switched to the SOFC mode after a preset temperature stabilization time has elapsed.

9. The control device includes:

6. The solid oxide cell system according to claim 1, wherein when a preset operating temperature in the SOEC mode is reached for the solid oxide cell stack that switches from the SOFC mode to the SOEC mode, output of power to the solid oxide cell stack is stopped, supply of the first gas is stopped, and a preset temperature stabilization time has elapsed before switching to the SOEC mode.

10. The control device includes:

6. The solid oxide cell system according to claim 1, wherein the solid oxide cell module comprises a plurality of the solid oxide cell stacks, and the input / output power and temperature are controlled for each of the solid oxide cell stacks.

11. The control device includes:

6. The solid oxide cell system according to claim 1, wherein the solid oxide cell module comprises a plurality of the solid oxide cell stacks, and the power and temperature input / output to the plurality of solid oxide cell stacks comprised by the solid oxide cell module are uniformly controlled.

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