JP2013229342A - Flat plate fuel cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vary effective electrode areas of unit cells so as to improve temperature distribution characteristics and enhance durability of a flat plate fuel cell stack.SOLUTION: A flat plate fuel cell stack 1 includes power generation units 2 that are laminated in multiple tiers and connected electrically in series to each other. Each power generation unit 2 has: a flat plate unit cell 6 that has a fuel electrode 4 and an air electrode 5 formed on two respective sides of a solid oxide electrolyte 3; housing members 7 and 8 that house the unit cell 6 and also supply fuel gas to the fuel electrode 4 and oxidant gas G2 to the air electrode 5; and a collector member 11 that is disposed between the unit cell 6 and the housing members 7 and 8. The power generation units 2 are divided into at least two kinds of power generation units 2 where the respective unit cells 6 have different effective electrode areas. The effective electrode area of each unit cell 6 is determined by an area of the collector member 10 or 11 on a side of the less conductive one of the air electrode 5 and the fuel electrode 4.

Description

  The present invention relates to a flat plate type fuel cell stack provided with a flat plate type single cell and a housing member for housing the single cell.

  A flat solid oxide fuel cell (SOFC: Solid Oxide Fuel Cell, hereinafter also referred to as a flat fuel cell) is a single cell in which an air electrode and a fuel electrode are respectively formed on the front and back surfaces of a flat electrolyte layer. A plurality of interconnectors having passages for supplying and exhausting fuel gas and oxidant gas are alternately stacked and electrically connected in series to form a flat plate fuel cell stack. In this fuel cell, power is generated by supplying fuel gas to the fuel electrode of a single cell and supplying oxidant gas to the air electrode (see, for example, Patent Document 1).

  9 and 10 are diagrams showing a conventional example of such a flat fuel cell stack. FIG. 9 is a schematic cross-sectional view of the flat fuel cell stack, and FIG. 10 is a cross-sectional view of the power generation unit. In these drawings, a flat plate fuel cell stack 1 is configured by stacking a plurality of power generation units 2 having the same structure and electrically connecting them in series, and is housed in a heat insulating container A surrounded by heat insulating walls. Has been.

  The power generation unit 2 includes a flat electrode 3, a fuel electrode-supporting single cell 6 including a fuel electrode 4 and an air electrode 5 formed on both surfaces of the electrolyte 3, and a recess 7 a that accommodates the single cell 6. A fuel electrode interconnector (fuel electrode separator) 7, an air electrode interconnector (air electrode separator) 8 that forms a container for the power generation unit 2 in cooperation with the fuel electrode interconnector 7, and a fuel electrode interconnector. An insulating member 9 disposed between the fuel electrode 7 and the air electrode interconnector 8, a fuel electrode side current collecting member 10 disposed between the fuel electrode 4 and the fuel electrode interconnector 7, and an air electrode 5. An air electrode side current collecting member 11 and the like disposed between the air electrode interconnector 8 and the like.

  The fuel electrode 4 is electrically connected to the fuel electrode interconnector 7 via the fuel electrode side current collecting member 10, and the air electrode 5 is electrically connected to the air electrode interconnector 8 via the air electrode side current collecting member 11. It is connected to the. The fuel electrode interconnector 7 and the air electrode interconnector 8 are electrically connected to the adjacent fuel electrode interconnector 7 or air electrode interconnector 8, respectively. Then, a flat fuel cell stack 1 is constructed by configuring a load circuit using the uppermost air electrode interconnector 8 and the lowermost fuel electrode interconnector 7 as terminals.

Further, the fuel electrode interconnector 7, the fuel flow path 7b, having a fuel supply passage 7c and the fuel discharge passage 7d, the fuel supply line 7c is connected to the fuel supply manifold 12 for supplying the fuel gas G _1, the fuel discharge route A fuel discharge manifold 13 for discharging unreacted fuel gas G ₁ that has not reacted in the single cell 6 is connected to 7d. Air electrode interconnector 8 has an air path 8a and an air supply path 8b, air supply path 8b is connected to an air supply manifold 14 for supplying oxidant gas G _2.

In such a power generation unit 2, the fuel electrode side current collecting member 10, the single cell 6, and the air electrode side current collecting member 11 are sequentially stacked on the fuel flow path 7 b formed on the bottom surface of the recess 7 a of the fuel electrode interconnector 7. After that, the air cell interconnector 8 is joined to the fuel electrode interconnector 7 through the insulating member 9, and the air electrode side current collecting member 11 is pressed against the air electrode 5, whereby the single cell 6 and the current collecting members 10, 11 are connected. It is held between the fuel electrode interconnector 7 and the air electrode interconnector 8.

The flat plate fuel cell stack 1 thus formed operates as follows. First, the flat fuel cell stack 1 is heated and maintained at a predetermined power generation temperature (for example, 700 to 1000 ° C.), and the fuel gas G ₁ and the oxidant gas G ₂ are supplied to the single cell 6 of each power generation unit 2. . The fuel gas G ₁ is made of hydrogen or the like, and is supplied from the fuel supply manifold 12 to the fuel electrode 4 of each power generation unit 2 from the fuel flow path 7 b through the fuel supply path 7 c of the fuel electrode separator 7. On the other hand, the oxidant gas G ₂ is made of air or the like, and is supplied from the air supply manifold 14 to the air electrode 5 through the air supply path 8 b of the air electrode interconnector 8 of each power generation unit 2. Thus, by supplying the fuel gas G ₁ and the oxidant gas G ₂ to the single cell 6 of each power generation unit 2, an electromotive force having a predetermined voltage level is generated between the fuel electrode 4 and the air electrode 5. be able to.

JP 2008-117737 A

Since the conventional flat plate fuel cell stack 1 described above forms all the power generation units 2 equally, the effective electrode areas of the single cells 6 in each power generation unit 2 are equal. Equal and nearly the same amount of heat was dissipated. As a result, heat is concentrated in the middle portion of the flat fuel cell stack 1 where the single cells 6 are concentrated, and heat is radiated at the upper and lower ends. As a result, a temperature distribution is generated in the stack 1 and the durability of the single cells 6 is improved. There was a problem that variations occurred. The flat plate is also affected by the influence of other heat absorption and heat generation parts accommodated in the heat insulating container A adjacent to the stack 1, for example, heat absorption parts such as reformers and heat exchangers and heat generation parts such as exhaust gas combustors. Due to the temperature distribution in the fuel cell stack 1, the durability of the single cell 6 may vary. Specifically, as the single cell 6 in the high temperature part increases in resistance component due to deterioration, Joule heat due to internal resistance further increases, and the other part is in a normal state, but it is devastatingly deteriorated. As a result, the entire flat fuel cell stack 1 may become unusable.

  Therefore, as a result of intensive studies, the present inventors have changed the effective electrode area of the single cell in each stacked power generation unit in accordance with the temperature distribution in the stack, and particularly close to the upper and lower stages of the stack and an apparatus that generates an endothermic reaction. About the unit cell of the power generation unit in the part where heat is easily taken away such as the part, the effective electrode area is reduced, and the unit cell of the power generation unit in the part where heat is not easily taken away such as the center part of the stack or the part near the device that generates exothermic reaction Has found that by increasing the effective electrode area, the temperature distribution in the stack can be suppressed or averaged, and the durability of the stack can be improved.

  The present invention has been made on the basis of the above-mentioned conventional problems and examination results. The object of the present invention is to improve temperature distribution characteristics by changing the effective electrode area of a single cell, and to have a highly durable flat plate type. An object is to provide a fuel cell stack.

In order to achieve the above object, a flat plate fuel cell stack according to the present invention accommodates a flat plate single cell in which a fuel electrode and an air electrode are formed on the front and back surfaces of an electrolyte made of a solid oxide, and the single cell. And a power generation member including a housing member that supplies fuel gas to the fuel electrode and that supplies an oxidant gas to the air electrode, and a current collecting member disposed between the single cell and the housing member. In a flat plate fuel cell stack in which a plurality of units are stacked and electrically connected in series, the power generation unit is composed of at least two types of power generation units having different effective electrode areas of the single cell, and the effective electrode of the single cell An area is prescribed | regulated by the area of the current collection member in the electrode side with low electroconductivity among the said air electrode or the said fuel electrode.

  Further, according to the present invention, in the above-described invention, the effective electrode area of the single cell in the power generation unit arranged at the lowermost stage and the uppermost stage of the stack is more than the effective electrode area of the single cell in the electric power generation unit arranged in the center of the stack. Is also made smaller.

  In addition, the present invention provides a single cell in a power generation unit according to the above-mentioned invention, comprising a device for generating an endothermic reaction and a device for generating an exothermic reaction arranged around the stack, the power generating unit being disposed in a portion close to the device for generating the endothermic reaction. The effective electrode area is made smaller than the effective electrode area of the single cell in the power generation unit arranged in a portion close to the device that generates the exothermic reaction.

  Further, the present invention is the above invention, further comprising an apparatus for generating an exothermic reaction arranged around the stack, and the effective electrode area of a single cell in a power generation unit arranged in a portion close to the apparatus is far from the apparatus. This is larger than the effective electrode area of the single cell in the power generation unit arranged in the part.

  Furthermore, the present invention is the above-described invention, comprising a device for generating an endothermic reaction arranged around the stack, and the effective electrode area of the single cell in a portion near the device is arranged in a portion far from the device. This is smaller than the effective electrode area of a single cell in the unit.

  In the flat plate fuel cell stack in which the power generation units are electrically connected in series and stacked, the currents flowing in the single cells of each power generation unit are all the same. However, in a power generation unit with a small effective electrode area of a single cell, the density of current flowing in the single cell is high, and the amount of heat dissipated by the internal resistance is larger than in a power generation unit with a large effective electrode area of a single cell. Become. Thereby, the temperature distribution in the stack can be adjusted or suppressed. In particular, the effective electrode area of a single cell in a power generation unit placed in a part where heat is easily lost, such as the upper and lower stages of the stack and the part close to the device that generates endothermic reaction, is reduced, and it is close to the center part of the stack and the device that generates an exothermic reaction. By increasing the effective electrode area of the single cell in the power generation unit arranged in a portion where heat is not easily removed, the temperature distribution in the stack is averaged, so that the durability of the stack can be improved.

1 is a cross-sectional view showing a first embodiment of a flat plate fuel cell stack according to the present invention. It is sectional drawing which shows one electric power generation unit contained in the flat fuel cell stack of this invention. It is sectional drawing which shows the other electric power generation unit contained in the flat fuel cell stack of this invention. It is sectional drawing which shows 2nd Embodiment of the flat fuel cell stack which concerns on this invention. It is sectional drawing which shows 3rd Embodiment of the flat fuel cell stack which concerns on this invention. It is sectional drawing which shows 4th Embodiment of the flat fuel cell stack which concerns on this invention. It is sectional drawing which shows 5th Embodiment of the flat fuel cell stack which concerns on this invention. It is sectional drawing which shows 6th Embodiment of the flat fuel cell stack which concerns on this invention. It is sectional drawing which shows the conventional flat type fuel cell stack. It is sectional drawing which shows the electric power generation unit contained in the conventional flat type fuel cell stack.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The first embodiment of the present invention shown in FIGS. 1 to 3 shows an example applied to a fuel electrode support type flat fuel cell stack 20. A flat plate fuel cell stack (hereinafter also simply referred to as a stack) 20 is configured by stacking a plurality of stages of two types of power generation units 2 and 2A having different effective electrode areas of the single cells 6 and 6A and electrically connecting them in series. In that respect, it is different from the conventional flat fuel cell stack 1 shown in FIGS.

  In FIG. 2, one power generation unit 2 has the same structure as the power generation unit 2 shown in FIG. 9, and includes a flat electrolyte 3 and a flat fuel electrode 4 formed on one surface of the electrolyte 3. And a fuel cell supporting type single cell 6 composed of a flat air electrode 5 formed on the other surface of the electrolyte 3, a fuel electrode interconnector 7 having a recess 7 a for accommodating the single cell 6, and An air electrode interconnector 8 that forms a container for the power generation unit 2 in cooperation with the fuel electrode interconnector 7, and an insulating member 9 disposed between the fuel electrode interconnector 7 and the air electrode interconnector 8. The fuel electrode side current collecting member 10 disposed between the fuel electrode 4 and the fuel electrode interconnector 7 and the air electrode side current collecting member disposed between the air electrode 5 and the air electrode interconnector 8. 11.

  The fuel electrode 4 has the same area as the electrolyte 3 and is sufficiently thick. The air electrode 5 is formed to be smaller than the electrolyte 3 and the fuel electrode 4 and has a size having the same area as the air electrode side current collecting member 11. The fuel electrode side current collecting member 10 is formed to have a larger area than the area of the fuel electrode 4.

  One power generation unit 2 including a single cell 6 composed of the electrolyte 3, the fuel electrode 4, and the air electrode 5 is stacked in a plurality of stages, and the other power generation unit 2A is provided at the uppermost and lowermost stages, respectively. It is arranged.

  In FIG. 3, the other power generation unit 2A differs from the power generation unit 2 in that the effective electrode area of the air electrode 5A constituting the single cell 6A is smaller than the effective electrode area of the air electrode 5 of the single cell 6; Everything except is the same. For this reason, the same components are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  Such a power generation unit 2 </ b> A is formed in the same manner as the power generation unit 2. That is, first, after sequentially laminating the fuel electrode side current collecting member 10, the single cell 6A and the air electrode side current collecting member 11 on the fuel flow path 7b formed on the bottom surface of the recess 7a of the fuel electrode interconnector 7, The air electrode interconnector 8 is joined to the fuel electrode interconnector 7 via the insulating member 9, and the air electrode side current collecting member 11 is pressed against the air electrode 5. As a result, the single cell 6A has the fuel electrode 4 side via the fuel electrode side current collecting member 10 via the fuel electrode interconnector 7 and the air electrode 5 side via the air electrode side current collecting member 11 via the air electrode separator 6 respectively. By being pressed to the electrolyte 3 side, it is held between the fuel electrode interconnector 7 and the air electrode interconnector 8, and the power generation unit 2A is formed.

Next, as shown in FIG. 1, the required number of power generation units 2 shown in FIG. 2 are stacked, and the power generation unit 2A shown in FIG. To construct. According to such a flat plate fuel cell stack 20, the temperature distribution characteristics in the stack 20 can be improved even when all the currents flowing through the single cells 6 and 6A in the power generation units 2 and 2A are the same during power generation. Can do. That is, the power generation unit 2A shown in FIG. 3 includes a single cell 6A in which the effective electrode area of the air electrode 5A is smaller than the effective electrode area of the air electrode 5 of the power generation unit 2 shown in FIG. Therefore, the heat generated by the internal resistance is larger than that of the power generation unit 2. For this reason, the temperature of the uppermost power generation unit 2A and the lowermost power generation unit 2A can be increased and kept at the same temperature as the intermediate power generation unit 2. In other words, the temperature distribution in the stack 20 can be averaged, and as a result, the durability of the stack 20 can be increased. In addition, although this Embodiment showed the example using two types of electric power generation units 2 and 2A which varied the effective electrode area of the air electrodes 5 and 5A, not only this but the effective electrode area of the fuel electrode 4 was shown. Two different power generation units may be used. That is, the effective electrode area of the single cells 6 and 6A is defined by the smaller one of the air electrode and the fuel electrode, or the fuel electrode side current collecting member 10 or the air electrode side current collecting member 11 as described later. What is necessary is just to prescribe | regulate by the area of the smaller one of these.

FIG. 4 is a cross-sectional view of a flat plate fuel cell stack showing a second embodiment of the present invention.
The flat plate fuel cell stack 21 according to the present embodiment includes three types of power generation units 2 including single cells 6, 6A, 6B having different effective electrode areas of the air electrodes 5, 5A, 5B formed on the electrolyte 3.
2A and 2B are stacked in multiple stages, and an apparatus 22 with an endothermic reaction is installed thereon. As the apparatus 22 that involves an endothermic reaction, for example, a reformer that generates a reformed gas by reacting the fuel gas G ₁ with a catalyst is used.

  When the apparatus 22 with an endothermic reaction is installed at the uppermost stage of the stack 21, the power generation unit near the uppermost stage is cooled more than the flat plate fuel cell stack 1 shown in the first embodiment. For the upper power generation unit 2B, the effective electrode area of the air electrode 5B of the single cell 6B is minimized, and for the power generation units 2A arranged at the second and lowermost stages from the top, the air electrode of the single cell 6A. The effective electrode area of 5A is then increased, and for the power generation unit 2 arranged in the middle, the effective electrode area of the air electrode 5 of the single cell 6 is maximized. Here, the power generation units 2 and 2A are the same as the power generation units 2 and 2A of the first embodiment shown in FIG. On the other hand, the remaining power generation unit 2B is completely the same as the power generation units 2 and 2A except that the effective electrode area of the air electrode 5B is the smallest.

  Also in the flat plate fuel cell stack 21 having such a structure, by changing the effective electrode areas of the air electrodes 5, 5A, 5B, the internal resistances of the power generation units 2, 2A, 2B are changed as in the above-described embodiment. The heat dissipated by is larger than that of the power generation unit 2 and the temperature distribution in the stack 21 can be averaged, so that the durability of the stack 21 can be improved.

  Note that the device 22 with an endothermic reaction does not need to be arranged at the uppermost stage of the stack 21. For example, even when the device 22 is arranged at the center of the stack, the effective electrode area of the single cell included in the power generation unit close to the device 22 is reduced. By making it smaller, the same effect can be obtained. Further, although the reformer is used as the device 22 with endothermic reaction, the present invention is not limited to this, and when other devices with endothermic reaction such as a heat exchanger are arranged, the same configuration is adopted, so that the durability of the stack 21 is improved. Can be improved.

FIG. 5 is a cross-sectional view of a flat plate fuel cell stack showing a third embodiment of the present invention.
The flat fuel cell stack 23 according to the present embodiment is composed of two types of power generation units 31 and 31A composed of electrolyte-supported single cells 30 and 30B, as shown in FIGS. Unlike the flat plate fuel cell stacks 20 and 21 shown in the first and second embodiments, the other components are the same, so the same components are denoted by the same reference numerals and the description thereof is omitted.

One power generation unit 31 includes a single cell 30 that includes an electrolyte 3A, and a fuel electrode 4B and an air electrode 5 that are formed on the front and back surfaces of the electrolyte 3A and have a small plate thickness. The electrolyte 3A is formed thicker than the electrolytes 3 of the single cells 6, 6A, 6B shown in the first and second embodiments.

  The fuel electrode 4B has the same area as the fuel electrode 4 of the single cells 6, 6A, 6B shown in the first and second embodiments, but is formed thinner.

  The air electrode 5 has the same area and thickness as the air electrode 5 of the single cell 6 shown in the first and second embodiments.

The other power generation unit 31A includes a single cell 30A that is composed of an electrolyte 3A, and a fuel electrode 4B and an air electrode 5A that are formed on the front and back surfaces of the electrolyte 3A and have a small plate thickness.
The air electrode 5 </ b> A has a smaller effective electrode area than the fuel electrode 4 </ b> B and the air electrode 5 of one power generation unit 31.

  Also in the flat plate fuel cell stack 23 having such a configuration, the single cells 30 and 30A are electrolyte support types, and the fuel electrode support type flat plate fuel cell stack 20 of the first and second embodiments described above, Since the rest of the configuration is the same as that of the flat plate fuel cell stack 20 of the first embodiment, the same effect is obtained.

FIG. 6 is a cross-sectional view of a flat plate fuel cell stack showing a fourth embodiment of the present invention.
The flat plate fuel cell stack 24 according to the present embodiment includes three types of power generation units 2, 2A, and 2B composed of fuel cell-supported single cells 6, 6A, and 6B, as in the second embodiment. The apparatus 26 is configured by stacking in multiple stages, and an apparatus 26 with an exothermic reaction is arranged at the lowest stage. For example, an exhaust gas combustor is used as the device 26 that involves an exothermic reaction.

  When the device 26 with an exothermic reaction is installed at the lowermost stage of the stack 24, the lowermost power generation unit 2 of the flat plate fuel cell stack 24 is heated most, so that the single cell 6 included in the lowermost power generation unit 2. The effective electrode area of the air electrode 5 is maximized. Between the second stage from the bottom and the second stage from the top, the power generation units 2A in which the effective electrode area of the air electrode 5A of the single cell 6A is smaller than the air electrode 5 are stacked in multiple stages. In the uppermost stage, the power generation unit 2B having the smallest effective electrode area of the air electrode 5B of the single cell 6B is arranged. Other configurations are exactly the same.

  Also in the flat plate fuel cell stack 24 having such a structure, the effective electrode area of the single cell 6 of the power generation unit 2 close to the device 26 with an exothermic reaction is maximized, and the power generation units 2A and 2B far from the device 26 are arranged. Since the effective electrode areas of the single cells 6A and 6B are relatively small, the temperatures of the power generation units 2, 2A and 2B can be maintained at substantially the same level in the stack 24 as in the above-described embodiment. Thus, the durability of the stack 24 can be improved.

FIG. 7 is a cross-sectional view of a flat plate fuel cell stack showing a fifth embodiment of the present invention.
The flat plate type fuel cell stack 27 according to the present embodiment is configured by stacking four types of power generation units 2, 2A, 2B, and 2C composed of fuel cell support type single cells 6, 6A, 6B, and 6C in multiple stages. The apparatus 22 with an endothermic reaction is arranged at the uppermost stage, and the apparatus 26 with an exothermic reaction is arranged at the lowermost stage.

  In this case, since the lowermost power generation unit 2 of the flat fuel cell stack 27 is heated most, the effective electrode area of the air electrode 5 of the single cell 6 included in the lowermost power generation unit 2 is maximized. For the power generation unit 2A arranged between the second stage from the bottom and the third stage from the top, the effective electrode area of the air electrode 5A of the single cell 6A is made smaller than the air electrode 5. About the electric power generation unit 2B arrange | positioned in the 2nd step | paragraph from the top, the effective electrode area of the air electrode 5B of the single cell 6B is made smaller than the said air electrode 5A. And about the electric power generation unit 2C arrange | positioned at the uppermost stage, the effective electrode area of the air electrode 5C of the single cell 6C is made the smallest. Other configurations are exactly the same.

  Even in the flat plate fuel cell stack 27 having such a structure, the effective electrode areas of the single cells 6B and 6C are reduced for the power generation units 2B and 2C close to the device 22 that generates an endothermic reaction, so that the device 26 with an exothermic reaction is used. Since the effective electrode area of the single cell 6 of the near power generation unit 2 is maximized, the temperatures of the power generation units 2, 2A, 2B, and 2C can be kept substantially the same as in the above-described embodiment, The temperature distribution in the stack 27 is suppressed, and the durability of the stack 27 can be enhanced. Note that it is not always necessary to arrange the apparatus 22 with an endothermic reaction at the uppermost stage and the apparatus 26 with an exothermic reaction at the lowermost stage. For example, the apparatus 22 that generates an endothermic reaction even when arranged at the center of the stack 27 or the like. In the vicinity of, the effective electrode area of the single cell included in the power generation unit is reduced, and for the power generation unit arranged in the vicinity of the device 26 that generates an exothermic reaction, the effective electrode area of the single cell is increased. The effect of can be obtained.

  Here, in each of the above-described embodiments, the example in which the effective electrode area of the single cell is defined by the area of the air electrode has been described. However, the present invention is not limited to this, and the current collection in the fuel electrode 4 or the air electrode 5 is performed. You may prescribe | regulate by the area of the members 10 and 11. FIG. An example is shown in FIG.

FIG. 8 is a cross-sectional view of a flat plate fuel cell stack showing a sixth embodiment of the present invention.
In the present embodiment, a flat plate fuel cell stack 28 is configured by two types of power generation units 31 and 31C using electrolyte-supported single cells 30 and 30C, as in the third embodiment. In this embodiment, the effective electrode area of the single cells 30 and 30C is defined by the area of the air electrode side current collecting members 11 and 11A instead of the air electrode 5. That is, in the case of the flat plate fuel cell stack 28 in which the conductivity of the air electrode 5 is lower than the conductivity of the fuel electrode 4, as shown in FIG. 8, the fuel electrode 4 and the air electrode 5 of each power generation unit 31, 31 C Power generation is performed in such a manner that the areas of the air electrode side current collecting members 11A disposed between the air electrode 5 and the air electrode interconnector 8 of the uppermost power generation unit 31C are kept in the middle. The effective electrode area of the single cell 30C of the uppermost and lowermost power generation units 31C is made smaller than the air electrode side current collecting member 11 disposed between the air electrode 5 and the air electrode interconnector 8 of the unit 31. Is to change. This is because an electrode having a low conductivity cannot be expected to have an effect that current flows laterally in the electrode and the effective electrode area is widened compared to an electrode having a high conductivity.

  One power generation unit 31 is the same as the power generation unit 31 of the third embodiment shown in FIG. 5, and the other power generation unit 31 </ b> C is disposed at the uppermost and lowermost stages.

  The other power generation unit 31C is different in that the air electrode side current collecting member 11A is formed to have a smaller area than the air electrode side current collecting member 11 of the one power generation unit 31, and the other configuration is the other power generation unit 31. Is the same.

Also in the flat plate fuel cell stack 28 having such a configuration, the effective electrode area of the single cells 30, 30C can be reduced by the air electrode side current collecting members 111, 1A. Can be made larger than the calorific value of one power generation unit 31, and the same effects as those of the flat plate fuel cell stacks 20, 21, 23, 24, 27 of the first to fifth embodiments described above can be obtained. Is. The flat fuel cell stack 28 shown in FIG. 8 shows an example in which the electrolyte-supporting single cells 30 and 30C are used. However, the flat-type fuel cell stack 28 can also be applied to a fuel electrode-supporting single cell. Further, although the case where the conductivity of the air electrode 5 is lower than the conductivity of the fuel electrode 4 has been shown, the fuel electrode 4 and the fuel are similarly treated when the conductivity of the fuel electrode 4 is lower than the conductivity of the air electrode 5. By reducing the area of the fuel electrode side current collecting member 10 disposed between the electrode interconnector 7 and the electrode interconnector 7, the effective electrode area of the single cell can be reduced.

DESCRIPTION OF SYMBOLS 1 ... Flat type fuel cell stack 2, 2, 2A, 2B, 2C ... Power generation unit 3, 3A ... Electrolyte 4 ... Fuel electrode 5, 5A, 5B, ... Air electrode, 6, 6A, 6B, 6C ... Single cell 7 ... Fuel electrode interconnector, 7a ... Recess, 7b ... Fuel flow path, 7c ... Fuel supply path, 7d ... Fuel discharge path, 8 ... Air electrode interconnector, 8a ... Air path, 8b ... Air supply path, 9 ... Insulating member, 10 ... Fuel electrode side current collecting member, 11, 11A ... Air electrode side current collecting member, 20, 21, 23, 24, 27, 28 ... Flat plate fuel cell stack, 22 ... Device with endothermic reaction, 26 ... devices with exothermic reaction, 30, 30A, 30B, 30C ... single cell, 31, 31A, 31C ... power generation unit.

Claims (5)

A flat unit cell in which a fuel electrode and an air electrode are formed on the front and back surfaces of an electrolyte made of a solid oxide;
A housing member that houses the single cell, supplies a fuel gas to the fuel electrode, and supplies an oxidant gas to the air electrode; and a current collector disposed between the single cell and the housing member In a flat plate fuel cell stack in which a plurality of power generation units provided with members are stacked and electrically connected in series,
The power generation unit comprises at least two types of power generation units having different effective electrode areas of the single cell,
An effective electrode area of the single cell is defined by an area of a current collecting member on an electrode side with low conductivity of the air electrode or the fuel electrode. A flat plate fuel cell stack, wherein: The flat plate fuel cell stack according to claim 1,
A flat plate fuel characterized in that the effective electrode area of the single cell in the power generation unit arranged at the bottom and top of the stack is smaller than the effective electrode area of the single cell in the power generation unit arranged at the center of the stack Battery stack. The flat plate fuel cell stack according to claim 1,
An effective electrode area of a single cell in a power generation unit that is provided in a portion close to the device that generates an endothermic reaction and a device that generates an endothermic reaction and a device that generates an exothermic reaction arranged around the stack A flat plate fuel cell stack characterized in that it is smaller than the effective electrode area of a single cell in a power generation unit arranged in a portion close to the resulting device. The flat plate fuel cell stack according to claim 1,
A device for generating an exothermic reaction is provided around the stack, and the effective electrode area of the single cell in the power generation unit disposed in a portion near the device is the same as that in the power generation unit disposed in a portion far from the device. A flat plate fuel cell stack characterized by being larger than the effective electrode area of the cell. The flat plate fuel cell stack according to claim 1,
A device having an endothermic reaction arranged around the stack is provided, and an effective electrode area of the single cell in a portion near the device is smaller than an effective electrode area of the single cell in a power generation unit arranged in a portion far from the device. A flat plate fuel cell stack characterized by that.

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