JP5435393B2 - Solid oxide fuel cell system - Google Patents

Description

The present invention relates to a solid oxide fuel cell (hereinafter referred to as SOFC) system, and more particularly to an electrical connection between fuel cell stacks.

  Since the output of one solid oxide fuel cell is limited, in actual SOFC, a plurality of SOFC cells are assembled and used. Usually, a module has been proposed in which a stack composed of a plurality of SOFC cells is used as a basic unit, and a plurality of stacks are electrically connected by a current collector plate. (For example, see Patent Document 1 below)

  By the way, an enormous number of cells are required as the solid oxide fuel cell system becomes larger. In the polymer electrolyte fuel cell, when the characteristics of one cell deteriorate, an electrolysis reaction opposite to the electromotive force reaction is forced on the cell in question due to the electromotive force of another cell. This phenomenon is called “polarization”, and it has been pointed out that once a problem occurs, the deterioration progresses at an accelerated rate (for example, see Non-Patent Document 1 below and Non-Patent Document 2 below). ing. (For example, see Patent Document 3 below and Patent Document 4 below)

However, this problem that occurs in polymer electrolyte fuel cells is unlikely to occur in SOFC. This is because the operating temperature of SOFC is a high temperature of 800 ° C. or higher, and the material of the SOFC cell is composed of a chemically stable material at a temperature of 800 ° C. or higher. Compared to polymer fuel cells that are driven at low temperatures, the chemical stability of the materials is high, and it has not been expected that SOFCs will deteriorate due to “polarization” in SOFC systems with large capacities.
JP 2007-157424 A JP 2008-21606 A JP 2007-250271 A Fuel Cell Design Technology Science Forum Issued September 30, 1987 Electron and ion functional chemistry series vol.1 NTS June 25, 2001

In recent years, the development of SOFC has been rapid, and in particular, the capacity of SOFC systems has been increasing, but there are still some drawbacks. One of the problems of the current large-capacity SOFC system is that one of a large number of cells deteriorates when a sudden potential change occurs, for example, a short circuit occurs between external electrodes for current extraction. Revealed by experiments. For example, when starting up, as the temperature rises, the structural members thermally expand, causing displacement, and there is a possibility of causing an electrical short circuit due to generation of incombustible material in the supply gas or flaws generated from the constituent materials. Although the probability is further increased by the conversion, the current SOFC system cannot avoid the cell deterioration due to the short circuit. When a cell deteriorates and becomes damaged, the surrounding healthy cells are damaged and the damage is expanded.

The present invention relates to an SOFC system with an increased capacity, and it is an object of the present invention to provide an electrical connection means, in particular, between SOFC stacks that does not damage the SOFC cell even when a sudden potential change occurs due to a short circuit or the like.

In order to solve the above problems, a fuel cell system of the present invention includes a fuel cell stack including a solid oxide fuel cell, a conductive member that electrically connects the plurality of fuel cell stacks, and a plurality of An electric circuit including the fuel cell stack and the conductive member, a circuit opening / closing unit that electrically connects or disconnects the plurality of fuel cell stacks , and whether or not the fuel cell stack is at a temperature capable of generating power. A temperature measuring means for judging; and a voltage measuring means for judging whether or not the fuel cell stack is at a potential capable of generating electric power, wherein the circuit opening / closing part is a stand-up of the fuel cell system. during the raising, the temperature exceeds a predetermined threshold in any of the measuring means of the measuring means and the voltage measuring means, have been possible power determined that power generation is possible A state in which the plurality of fuel cell stacks are electrically disconnected until a predetermined state is reached, and when the power generation is possible, the plurality of fuel cell stacks are electrically connected. To do.

  According to the present invention, an SOFC system with an increased capacity does not damage the SOFC cell even when a sudden potential change occurs due to a short circuit or the like.

  Prior to describing the best mode for carrying out the present invention, the function and effect of the present invention will be described.

The fuel cell system of the present invention includes a fuel cell stack including a solid oxide fuel cell, a conductive member that electrically connects the plurality of fuel cell stacks, a plurality of the fuel cell stack, and the conductive member. An electric circuit comprising: a circuit opening / closing unit that electrically connects or disconnects the plurality of fuel cell stacks; temperature measuring means that determines whether the fuel cell stack is at a temperature capable of generating power; and the fuel A voltage measuring unit that determines whether or not the battery stack is at a potential capable of generating power , wherein the circuit opening and closing unit, when starting up the fuel cell system, the temperature measuring unit and the more than a predetermined threshold value also predetermined in any of the measuring means of the voltage measuring means, until the power generation capable predetermined state is determined to the power generation is possible in The inter fuel cell stack continues electrically disconnected state, and characterized by electrically connecting a plurality of the fuel cell stack becomes electricity can be generated a predetermined state.

For example, when starting up, even if the constituent members thermally expand as the temperature rises and the position shifts, or even if the external electrodes 312 are short-circuited due to generation of non-combustible material in the supply gas or flaws generated from the constituent materials, This cuts off the electrical connection between the SOFC stacks . Thereafter, when a predetermined state in which power generation is possible is established, the SOFC stacks are electrically connected to each other by the circuit opening / closing unit. By doing so, even if the external electrodes 312 are short-circuited before a predetermined state in which power generation is possible , no potential change occurs in the fuel cell module, and cell deterioration and damage can be avoided. . In solid polymer fuel cells, deterioration due to “inversion” proceeds even under normal operation, but in SOFC, “inversion” does not occur unless there is a sudden potential change due to a short circuit or the like, and it has been stable over the long term. Power generation performance can be obtained.

The fuel cell system of the present invention further includes a fuel cell stack including solid oxide fuel cells, a conductive member that electrically connects the plurality of fuel cell stacks, and an electrical connection between the plurality of fuel cell stacks. A circuit opening / closing part to be connected or disconnected, temperature measuring means for determining whether or not the fuel cell stack is at a temperature capable of generating power, and determining whether or not the fuel cell stack is at a potential capable of generating power An operation method at the time of start-up of the fuel cell system comprising voltage measuring means, and after the start of start-up of the fuel cell system, power generation is possible in a state where the electrical connection between the plurality of fuel cell stacks is interrupted It performs a process of determining whether such or predetermined state, the step of determining whether the or electricity can be generated a predetermined state at hotel to any of the measuring means of said temperature measuring means and said voltage measuring means However, it is a step that is determined by whether or not it is determined that power generation is possible, exceeding a predetermined threshold value, and when it is determined that power generation is possible in any of the measurement means Is a process that determines that the power generation is possible and if it is determined that any one of the measuring means is not capable of power generation, it is determined that the power generation is not possible. After determining that the fuel cell stack is in a predetermined state, a step of electrically connecting the plurality of fuel cell stacks may be performed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Although not particularly limited, the following examples are SOFC systems suitable as cylindrical solid oxide fuel cells.

  FIG. 1 is a schematic view of a fuel cell 1 constituting a fuel cell system 4 according to the present invention. However, these are only examples and are not limited. In the fuel cell 1, an air electrode 11 is formed on an inner surface of a cylindrical electrolyte 12, and a fuel electrode 13 is formed on an outer surface, and an interconnector 14 electrically connected to the air electrode 11 is electrically connected to the fuel electrode 13. It is formed with a structure that is electrically connected. At this time, the air electrode 11 is formed of a porous perovskite oxide such as LaCoO 3, LaMnO 3, LaFeO 3, etc., doped with Sr, Ca, etc. at the La site, undoped, or a composite material thereof. The electrolyte 12 is formed of stabilized zirconia doped with Y, Sc, Ca or the like. The interconnector 14 is made of LaCrO3 doped with Sr, Ca or the like.

FIG. 2 is a schematic view of the basic structure of the fuel cell stack 2 constituting the fuel cell system 4 according to the present invention. In this embodiment, the fuel cell stack 2 has a configuration in which twelve fuel cells 1 are electrically arranged in 2 parallels × 6 series. For example, 1 parallel × 5 series, 3 parallels × 3 series, etc. These are only examples and are not limited. 1 is a holding member 28a that also serves as a conductive member around 12 fuel cells in which a plurality of interconnectors are stacked in two parallel 6 series with the interconnector facing upward. , 28b and the holding member 28c. These fuel cells 1 are electrically connected in series and / or in parallel by the conductive member 29 and the conductive member 210. That is, although not shown, the fuel electrode 13 and the interconnector 14 are connected, and / or the fuel electrode 13 and the fuel electrode 13 are connected, and / or the interconnector 14 and the interconnector 14 are connected. The fuel cell is pressed by the upper and lower holding members 28a and 28b. The upper and lower holding members 28a and 28b are connected to the side surface holding member 28c by the connecting portion 212 and are fixed in a pressed state. The holding member 28b is electrically connected to the air electrode side of the plurality of fuel cells 1, and is insulated from the side surface holding member 28c by the connection portion 212. On the other hand, the holding member 28 c is electrically connected to the fuel electrode side of the fuel cell 1 and is insulated from the side surface holding member 28 c by the connection portion 212. For the connection portion 212, alumina, mullite, magnesia, zirconia, or the like can be used. Conductive members 213a and 213b are integrated with the holding members 28a and 28b for electrical connection between the fuel cell bundles. The generated electric power is output between the conductive members 213a and 213b.

  FIG. 3 is a schematic cross-sectional view of the fuel cell module 3 constituting the fuel cell system 4 according to the present invention, showing a state where electrical connection is cut off. In the present embodiment, the fuel cell stack 2 has a configuration in which 15 sets of 3 × 5, which are electrically arranged in series, are, for example, 2 × 10, 5 × 5, and the like, and are limited. Is not to be done. A partition member 330 is disposed between the fuel cell stacks 2 to prevent the fuel cell stacks from being electrically short-circuited. In the fuel cell module 3, 15 fuel cell stacks 2 are connected in series via conductive members 311, and power is supplied to the outside via external electrodes 312. In the fuel cell module 3, the gas-tight container 321 prevents the gas inside the fuel cell module 3 from leaking to the outside. In addition, heat radiation from the fuel cell module 3 to the outside is suppressed by the ceramic members 322 and 317 serving both as heat insulation and electric insulation, and the fuel cell stack 2 or the conductive member 311 or the external electrode 312 is electrically connected to the gas-tight container 321. To prevent short circuit. Further, the circuit opening / closing part 315 is movable, and when the electrical connection is interrupted, an insulating space 316 is formed between the circuit opening / closing part 315 and the fuel cell stack 2. The fuel cell stack 2 is connected to the external electrode 312, the fuel cell stack 2 and another fuel cell stack 2 are electrically connected by the conductive member 311, and the same configuration is repeated, so that the fuel cell stack 2 is connected to the external electrode 312. It is connected to the.

  FIG. 4 is a schematic view of a fuel cell system according to the present invention. However, these are only examples and are not limited. The SOFC module 4 is connected to a voltage measuring device 45 and a voltage converter (load control unit) 44, for example, a DC-DC converter. When supplying AC current, the voltage converter 44 is replaced with a DC-AC converter. The SOFC module is grounded for safety. A temperature measuring instrument 47 and a voltage measuring instrument 46 inside the SOFC module 3 are connected. The fuel cell system 4 is connected to the power network 42 via the interconnection circuit breaker 41. As shown in FIGS. 2, 3, and 4, an electric circuit is formed.

  The operation of this system will be described. However, these are only examples and are not limited. The temperature measuring device 47 determines the temperature at which power generation is possible. The temperature at which power can be generated is less likely to cause a short circuit between the external electrodes 312 due to thermal expansion of the components of the SOFC module, resulting in misalignment, or due to generation of non-combustible material in the supply gas or flaws generated from the component materials. The temperature within the SOFC module becomes uniform and the internal resistance variation of the SOFC cell decreases, and the fuel atmosphere in the SOFC module becomes uniform and the electromotive force variation of the SOFC cell decreases. Usually, it is desirable to set the temperature at 600 ° C. or higher. Preferably it is set to 750 ° C. or higher.

  The voltage measuring device 45 determines the potential that can be generated. The potential at which power can be generated is a potential that can guarantee that the constituent members of the SOFC module and the ground are insulated, and it is usually desirable to set the open circuit voltage of a single cell to 0.5 V or more.

  When the fuel cell system 4 is started up, the electrical connection between the SOFC stacks is interrupted by the circuit opening / closing unit 315. When it is determined that the temperature can be generated by the temperature measuring device 47 and the potential can be generated by the voltage measuring device 45, the circuit opening / closing unit 315 that is blocking the electrical connection moves, and the SOFC Connect the stacks electrically. Even if it is determined that the temperature can be generated by the temperature measuring device 47, the electrical disconnection by the circuit opening / closing unit 315 is continued when it is determined by the voltage measuring device 45 that the potential cannot be generated. Even if it is determined that the potential can be generated by the voltage measuring device 45, the electrical disconnection by the circuit opening / closing unit 315 is continued when it is determined by the temperature measuring device 47 that the temperature cannot be generated.

  FIG. 5 is a schematic view of the circuit opening / closing part 315 constituting the fuel cell system 1 according to the present invention. However, these are only examples and are not limited. The upper diagram of FIG. 5 is a circuit opening / closing portion 315 in a state of current interruption, and a metal member is attached to the SOFC stack 2 having a conductive member 213a such as Ni for improving electrical connection to the holding member 28a. 51 (second metal member) is disposed facing each other. In FIG. 5, in order to improve the electrical connection between the metal member 51 and the conductive member 213a, the metal member 51 may be a conductive member such as Ni. Further, although not shown, the metal member 51 has an area enough to satisfactorily electrically connect the conductive members 213a of two adjacent SOFC stacks. The metal member 51 is integrated with the holding member 52 and the insulating holding member 53. The moving jig 54 moves the insulating holding member 53 left and right in FIG. Dedicated 55 and the gas-tight container 321 meet with a screw 57 to maintain airtightness. The rod 55 can be moved by a motor 56. FIG. 5 shows a state in which the conductive member 213a and the metal member 51 are separated and electrically disconnected. The state of the electric switching part before a load control part controls so that an electric current may be sent from a solid oxide fuel cell is represented. FIG. 6 shows a state in which the conductive member 213a and the metal member 51 are connected and current is supplied. The state of the electric switching part when the load control part is controlling so that an electric current may be sent from a solid oxide fuel cell is represented.

  By interposing the insulating holding member 53 between the electrically connected metal member 51 and the drive unit, the gas-tight container and the metal member can be electrically insulated. The metal member 51 can be made of a material having high electrical conductivity such as nickel and having high heat resistance. Furthermore, the reliability of electrical connection may be increased using a conductive member. The drive unit can be made of a strong metal material such as heat resistant steel. The insulating member may be ceramic such as alumina or mullite.

  The driving of the motor 56 for moving the rod 55 may be automatically performed upon receiving the determination. In the case of automatic, it can be driven by a hydraulic cylinder, a pneumatic cylinder, a motor or the like.

  It should be noted that the dedicated 55 and the gas-tight container 321 are preferably associated with each other by the screw 57, but may be kept airtight by using a magnetic seal, heat-resistant packing, mating using a ceramic sliding material, metal flexure, or the like.

  The present inventor has devised the present invention by clarifying the mechanism of cell damage due to a short circuit through numerous reliability tests and experimental verifications. Hereinafter, an example of a verification test using a cylindrical vertical stripe SOFC cell using an air electrode as a support will be described.

The SOFC cell 1 used in this verification experiment has an effective length of 600 mm, the composition of the air electrode support 11 is La _0.75 Sr _0.25 MnO ₃ and a thickness of 2 mm, and the composition of the solid electrolyte 12 is 90 mol% ZrO ₂ -10 mol% Sc ₂ O _3. The composition of the fuel electrode 13 is 100 μm thick with a mixed material of Ni and 90 mol% ZrO ₂ -10 mol% Y ₂ O _3, and the composition of the interconnector 14 is La _0.8 Ca _0.2 CrO ₃ with a thickness of 30 μm. .

A set of 12 SOFC cells electrically connected in series is formed by a set of two SOFC cells electrically connected in parallel, and a stack is formed by electrically connecting the 8 stacks in series. . A 10 KW class power generation system can be obtained by electrically connecting two of the two modules in series.

  In the power generation test, air was supplied to the inside of the SOFC cell, and fuel gas (H2 + N2 mixed gas) was supplied to the outside. After passing through the conditions shown in Table 1, the temperature was raised to 900 ° C. to generate power.

After confirming that the power generation system operates normally without problems, start-up, operation, and termination, while the power generation system is being started up again, short-circuit both ends of the external electrode to extract 10 kW power generation from the power generation system. When the potential was suddenly lowered to 0 V, one of 180 SOFC cells constituting two modules deteriorated.

FIG. 7 shows the result of observing the vicinity of the interface between the air electrode and the electrolyte of the SOFC cell deteriorated by this test with an electron microscope. In FIG. 7, a range 71 is an air electrode, and a range 72 is an air electrode catalyst layer. It can be seen from FIG. 7 that minute irregularities are generated in the structure near the interface between the air electrode and the air electrode catalyst layer. Detailed analysis using an energy dispersive X-ray analyzer (EDX), an X-ray diffractometer (XRD), and the like revealed that the minute irregularities are the result of reductive decomposition of the air electrode material. Further, when the operation was continued in a short-circuited state, the SOFC cell was destroyed and the surrounding normal SOFC cell was damaged.

  As a result of the study by the present inventors, the deterioration of the SOFC cell occurs only when there is a sudden voltage change such as a short circuit in a large power generation system in which the cells are arranged in series and the potential between the external electrodes is 100 V or more. I found it.

  The present inventor has repeatedly studied and elucidated the mechanism by which a specific SOFC cell deteriorates due to a short circuit between external electrodes, and predicted that a short circuit at startup deteriorates a specific cell. Details are described below.

The potential En of the cell n is described by Equation 1 using the electromotive force Vn, the current i, and the internal resistance Rn.
Formula 1 En = Vn−iRn
Further, the potential E 1 at both ends when n cells are connected in series is described by Equation 2.
Formula 2 E = ΣEn
= ΣVn-iΣRn
Since E = 0 when short-circuited, Expressions 3 to 3 are obtained.
Formula 3 ΣVn = iΣRn
That is, the current i flowing through the cell n is expressed by Equation 4.
Formula 4 i = ΣVn / ΣRn
From Formula 4 and Formula 1, the potential (= electromotive force) of the cell n is obtained.
Formula 5 En = Vn−Rn · ΣVn / ΣRn
If the average value of the electromotive force of each cell is Vave and the internal resistance Rave, and the difference from the average value of the cell n is ΔV and ΔR, Expression 5 is converted into Expression 6.
Formula 6 En = (Vave + ΔV) − (Rave + ΔR) · Vave / Rave
= ΔV−ΔR · i

  In the SOFC fuel cell system, when both ends of the output terminal are short-circuited, Equation 6 means that a negative potential, that is, “inversion” occurs in a cell whose electromotive force is lower than average and whose internal resistance is higher than average. ing. Possible cases where the electromotive force is low include oxygen potential, that is, a small difference in oxygen concentration between electrolytes, poor cell quality, and the like. Possible cases where the internal resistance is high include low cell temperature and poor cell quality. The oxygen concentration difference is closely related to the non-uniformity of the oxygen atmosphere in the SOFC module, and the cell temperature difference is closely related to the temperature distribution in the SOFC module.

By the way, the cell used for SOFC has a solid electrolyte thin film (ZrO2, CeO2, etc.) having oxygen ion (O2-) permeability and no gas permeability, and an air electrode (LaMnO3, etc.) sandwiching the solid electrolyte thin film. On one side, a fuel electrode (Ni-based cermet or the like) is formed. Of these, the air electrode is a reaction field of oxygen and electrons in the air, and also serves as a conductive path for supplying electrons from an external load to the reaction field. As a material satisfying these functions, a perovskite oxide having high conductivity is used. By the way, when the oxygen partial pressure in the vicinity of the oxide decreases, reductive decomposition of the air electrode occurs. Although the oxygen concentration dependency differs depending on the material, the ambient temperature of the air electrode material (for example, (La _0.75 Sr _0.25 ) _y MnO ₃ ) and the oxygen concentration threshold value that causes reductive decomposition when both conductivity and oxygen stability are achieved. Table 2 shows the results obtained experimentally. Below the threshold value, the air electrode material is decomposed, internal stress is generated due to decomposition and expansion, and cell deterioration is accelerated.

The theoretical value (open circuit voltage: OCV) of the electromotive force Vn of the cell n is given by Equation 7. μ (O 2, a) is the oxygen potential of the anode, μ (O 2, c) is the oxygen potential of the cathode, and F is the Faraday constant. That is, the electromotive force Vn is determined by the difference in oxygen potential between both sides of the electrolyte.

Formula 7 Vn = − (μ (O2, a) −μ (O2, c)) / 4F

  Under normal operating conditions, the cathode oxygen concentration never falls below the threshold. Even if a negative potential is generated by “polarization”, a small-scale SOFC system does not generate a potential in the cell that is lower than the oxygen concentration threshold value. Will not deteriorate.

  However, when the SOFC system becomes large-scale and the variation in atmosphere and temperature in the SOFC module increases, the oxygen concentration falls below the threshold value.

The inventor conducted an experiment in which one SOFC cell 1 was used, a DC stabilized power source 82 was connected to the SOFC cell 81, and a negative potential was applied between the cell electrodes by an electrometer 83 between the cell electrodes. FIG. 7 shows a circuit diagram. The SOFC cell 1 used in this systematic experiment has an effective length of 600 mm, the composition of the air electrode support 11 is La _0.75 Sr _0.25 MnO ₃ and a thickness of 2 mm, and the composition of the solid electrolyte 12 is 90 mol% ZrO ₂ -10 mol% Sc ₂ O. ₃ is 30 μm thick, and the composition of the fuel electrode 13 is 100 μm thick with a mixed material of Ni and 90 mol% ZrO ₂ -10 mol% Y ₂ O ₃ , and the interconnector 14 is La _0.8 Ca _0.2 CrO ₃ with a thickness of 30 μm. is there.

In this experiment, cell deterioration was not observed at a cell potential of -0.5V, but a slight increase in internal resistance was observed when the cell voltage was -1.0V, and the cell potential was -2.0V. Has deteriorated.

That is, the cell deteriorates when a potential exceeding the threshold value of oxygen partial pressure is applied. Such an event is a phenomenon that is limited when a malfunction such as a short circuit occurs in a large-capacity SOFC device. In addition, when the module temperature is 600 ° C. or lower, the potential exceeding the oxygen partial pressure threshold is particularly dangerous because the cell internal resistance variation is large due to the temperature variation in the module, and the cell electromotive force variation is large due to the atmosphere variation of the module. . Once a short circuit occurs, the current SOFC device does not recognize that the cell will be seriously damaged, leading to cell failure and damaging the entire SOFC module. Such damage can be prevented by the present invention.

It is a figure which shows the SOFC cell of this embodiment. It is a figure which shows the SOFC stack of this embodiment. It is a figure which shows the SOFC module of this embodiment. It is the schematic of the fuel cell system of this embodiment. It is a figure which shows the circuit opening / closing part of this embodiment. (Current interruption state) It is a figure which shows the circuit opening / closing part of this embodiment. (Current conduction state) It is an electron microscopic image of the vicinity of the interface between the air electrode and the electrolyte of the SOFC cell deteriorated by this test. It is the circuit diagram used for the experiment which makes a negative electric potential act between cell electrodes.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... SOFC cell, 2 ... SOFC bundle, 3 ... SOFC module, 4 ... SOFC power generation device, 213a ... Conductive member, 315 ... Circuit switching part

Claims (2)

A fuel cell stack comprising solid oxide fuel cells,
A conductive member for electrically connecting the plurality of fuel cell stacks;
An electrical circuit comprising a plurality of the fuel cell stack and the conductive member;
A circuit opening / closing part for electrically connecting or disconnecting a plurality of the fuel cell stacks;
Temperature measuring means for determining whether or not the fuel cell stack is at a temperature capable of generating electricity;
Voltage measuring means for determining whether or not the fuel cell stack is at a potential capable of generating power, and a fuel cell system comprising:
When the fuel cell system is started up, the circuit opening / closing unit exceeds a predetermined threshold value in any of the temperature measurement unit and the voltage measurement unit, and is determined to be capable of power generation. The plurality of fuel cell stacks are kept in an electrically disconnected state until a predetermined state in which power generation is possible, and the plurality of fuel cell stacks are electrically connected in a predetermined state in which power generation is possible. A fuel cell system. A fuel cell stack comprising solid oxide fuel cells,
A conductive member for electrically connecting the plurality of fuel cell stacks;
A circuit opening / closing part for electrically connecting or disconnecting a plurality of the fuel cell stacks;
Temperature measuring means for determining whether or not the fuel cell stack is at a temperature capable of generating electricity;
Voltage measuring means for determining whether or not the fuel cell stack is at a potential capable of generating power, and an operation method at the time of start-up of the fuel cell system,
After the start-up of the fuel cell system,
Performing a step of determining whether or not a predetermined state in which power generation is possible in a state where electrical connection between the plurality of fuel cell stacks is interrupted;
Whether the step of determining whether or not the power generation is in a predetermined state exceeds a predetermined threshold value in any of the temperature measurement means and the voltage measurement means, and has been determined that power generation is possible If it is determined that power generation is possible in any of the measurement means, it is determined that the power generation is in a predetermined state, and power generation is also performed in either of the measurement means. When it is determined that it is not possible, it is a step that determines that it is not in a predetermined state where power generation is possible,
A method of operating the fuel cell system at the time of start-up, comprising performing a step of electrically connecting the plurality of fuel cell stacks after it is determined that the power generation is in a predetermined state.

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