JP2008269879A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress reduction of degree of freedom of designing while improving power generation efficiency of a hydrogen separation membrane fuel cell. <P>SOLUTION: This fuel cell is equipped with a power generator having a hydrogen separation membrane, an electrolyte layer, and a cathode electrode layer, a first separator which is arranged and installed neighboring the face of the hydrogen separation membrane side of the power generator and in which a fuel gas flow passage to supply the fuel gas to the hydrogen separation membrane is formed, and a second separator which is arranged and installed neighboring the face of the cathode electrode layer side of the power generator and in which an oxidation gas flow passage to supply an oxidation gas to the cathode electrode layer is formed. Furthermore, this is equipped with a heat transfer suppressing structure in which heat formed by a chemical reaction in the power generator is suppressed to be transferred from the power generator to other parts to constitute the fuel cell. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for improving the power generation efficiency of a fuel cell.

  In recent years, fuel cells that generate electricity by electrochemical reactions have attracted attention as clean and highly efficient power generation means, and various systems have been developed. One of them is a solid oxide fuel cell. A solid oxide fuel cell generally operates in a high temperature range of about 700 to 1000 degrees Celsius using zirconia, which is a ceramic, as an electrolyte. In addition, in this solid oxide fuel cell, a dense membrane of hydrogen permeable metal is used as a base material, and an electrolyte layer is formed thereon to sufficiently reduce the thickness of the electrolyte layer to 200 to 600 degrees Celsius. A hydrogen separation membrane type fuel cell has also been developed in which the operating temperature is reduced to a certain extent. As such a hydrogen separation membrane type fuel cell (hereinafter referred to as “hydrogen separation membrane cell”), for example, the one described in Patent Document 1 below is known. Since the hydrogen separation membrane battery can form an electrolyte membrane very thinly, it has a feature of low membrane resistance and high output per area.

JP 2006-79888 A

  Most of the cell resistance of the hydrogen separation membrane battery is an electrolyte resistance and a cathode polarization resistance. Since both resistances have a negative correlation with temperature, the power generation efficiency of the hydrogen separation membrane battery increases as the temperature increases. On the other hand, the energy required for starting the hydrogen separation membrane battery is the product of the heat capacity and the operating temperature, so that the required energy increases as the operating temperature increases. Further, when the operating temperature is increased, the selection range of the sealing material and the structural material constituting the fuel cell is narrowed, and the degree of freedom in design is reduced. That is, it can be said that there is a trade-off relationship between the operating temperature of the hydrogen separation membrane battery and its merits and demerits.

  In view of such problems, the problem to be solved by the present invention is to suppress a reduction in the degree of freedom in design while improving the power generation efficiency of the hydrogen separation membrane battery.

  Based on the above problems, a fuel cell which is one embodiment of the present invention is configured as follows. That is, a hydrogen separation membrane that selectively permeates hydrogen from the fuel gas supplied to one surface to the other surface is used as a base material, and an electrolyte layer is formed on the other surface of the base material. A power generation body having a cathode electrode layer formed adjacent to the layer, and a fuel gas flow path disposed adjacent to the surface of the power generation body on the hydrogen separation membrane side and supplying the fuel gas to the hydrogen separation membrane And a second separator having an oxidant gas flow path for supplying an oxidant gas to the cathode electrode layer. The first separator is formed adjacent to a surface of the power generator on the cathode electrode layer side. The gist is to include a separator and a heat transfer suppressing structure that suppresses heat generated by an electrochemical reaction in the power generation body from the power generation body to other parts constituting the fuel cell.

  According to the fuel cell having the above-described configuration, the heat generated by the power generation body can be prevented from being transferred to other parts constituting the fuel cell by the heat transfer suppression structure. Therefore, although a power generation body becomes high temperature, a temperature rise can be suppressed about parts other than a power generation body. As a result, it is possible to improve the power generation efficiency of the fuel cell and to suppress a decrease in the degree of freedom in design.

  In the fuel cell having the above-described configuration, at least a part of the heat transfer suppression structure may be a heat insulating layer formed in the hydrogen separation membrane. With such a configuration, heat conduction from the electrolyte layer, which is a main heat generation source, toward the first separator can be suppressed.

  For example, in the fuel cell having the above-described configuration, a non-hydrogen permeable heat insulating material or a space is embedded in the hydrogen separation membrane at predetermined intervals in the hydrogen separation membrane as the heat insulator. Also good. In the hydrogen separation membrane, a hydrogen permeable substance having higher heat insulation than the hydrogen separation membrane may be embedded as the heat insulator. Further, in the configuration described above, the heat insulator may be embedded in the vicinity of the electrolyte layer in the hydrogen separation membrane. According to these configurations, heat conduction from the electrolyte layer to the first separator can be effectively suppressed.

  In the fuel cell configured as described above, at least a part of the heat transfer suppression structure is formed on at least one of a contact surface between the first separator and the power generator, and a contact surface between the second separator and the power generator. It is good also as what is done. For example, in the fuel cell having the above-described configuration, the heat transfer suppression structure includes a heat insulating material on at least one of a contact surface between the first separator and the power generator, and a contact surface between the second separator and the power generator. It is good also as what is formed by arrange | positioning. With such a configuration, conduction of heat from the power generator to the first or second separator can be suppressed with a simple structure.

  In the fuel cell having the above-described configuration, the heat transfer suppression structure is formed by reducing a contact area of the first separator or the second separator and a central portion of the power generator to be smaller than a contact area of a peripheral portion. It is good as it is. If it is such a structure, it can suppress that a heat | fever conducts to a separator directly from the center part of the electric power generation body where an electrochemical reaction mainly advances. Moreover, if it is such a structure, heat conduction can be suppressed at low cost, without providing separate members, such as a heat insulating material.

  In the fuel cell having the above-described configuration, the first separator or the second separator has a plurality of convex portions formed on a contact surface with the power generation body, and the heat transfer suppression structure includes the first separator. It is good also as what is formed by making the number of the convex parts formed in the center part of a separator or the said 2nd separator smaller than the number of the convex parts of a peripheral part. With such a configuration, it is possible to easily suppress heat conduction only by adjusting the number of convex portions.

  The fuel cell having the above configuration further includes a support plate for fixing the power generation body in the fuel cell, and at least a part of the heat transfer suppression structure is a heat insulating portion at a contact portion between the power generation body and the support plate. It is good also as what is formed by providing. With such a configuration, it is possible to suppress heat from being conducted to the support plate having a relatively large heat capacity.

In the fuel cell having the above-described configuration, a porous current collector is further provided between at least one of the power generator and the first separator and between the power generator and the second separator,
The heat transfer suppression structure may be formed by providing a heat insulator between the porous current collector and the power generator. Even with such a configuration, it is possible to suppress heat conduction from the power generation body to the porous current collector or the separator with a simple configuration.

  It should be noted that the various configurations of the present invention described above can be combined as appropriate, or a part of the configurations can be omitted. The present invention can also be configured as a fuel cell system or a vehicle including the fuel cell described above.

Hereinafter, in order to further clarify the operations and effects of the present invention described above, embodiments of the present invention will be described based on examples in the following order.
A. 1st Example (insulation material on convex part of separator):
B. Second Embodiment (Part of the separator convex part is omitted):
C. Third Example (Insulating material on support plate):
D. Example 4 (Insulating layer on porous current collector):
E. Example 5 (Heat separation layer on hydrogen separation membrane):

A. 1st Example (insulation material on convex part of separator):
FIG. 1 is a schematic cross-sectional view of a fuel cell 10a as a first embodiment of the present invention. In the fuel cell 10a, a porous current collector 15, a hydrogen separation membrane 18, an electrolyte layer 17, a cathode electrode layer 16, and a porous current collector 14 are stacked in this order inside two support plates 20, and these layer structures are formed. The separators 13 and 19 are formed by sandwiching them from both sides. Hereinafter, a portion including the porous current collector 15, the hydrogen separation membrane 18, the electrolyte layer 17, the cathode electrode layer 16, and the porous current collector 14 is referred to as “power generation body 30”. The support plate 20 is made of, for example, SUS, and a portion that comes into contact with the power generation body 30 is subjected to insulation treatment to prevent a short circuit.

  The hydrogen separation membrane 18 is a dense layer formed of a metal having hydrogen permeability, and functions as an anode. For this hydrogen separation membrane 18, for example, palladium (Pd) or a Pd alloy having an activity of dissociating hydrogen molecules can be used. In addition, the hydrogen separation membrane 18 is made of a group 5 metal such as vanadium (V), niobium (Nb), tantalum (Ta), or an alloy of group 5 metal as a base material, and at least the surface on the separator 19 side has Pd or Pd. A multilayer film in which an alloy layer is formed can be used. It is also possible to use other metals having an activity of dissociating hydrogen molecules, such as amorphous alloys. In this embodiment, palladium (Pd) is used as the hydrogen separation membrane 18.

  Since the hydrogen separation membrane 18 becomes a base material for forming the electrolyte layer 17, a certain strength is required. In addition, a certain thickness is required from the problem of handling the laminate in the manufacturing process of the fuel cell 10. Therefore, the thickness of the hydrogen separation membrane 18 is preferably about 10 to 100 μm, for example. In this example, the thickness of the hydrogen separation membrane 18 was 80 μm. Of course, it can be set as appropriate in consideration of required strength and handling properties.

The electrolyte layer 17 is a layer formed on the hydrogen separation membrane 18 and is made of a solid oxide having proton conductivity. For the electrolyte layer 17, for example, a SrZrInO ₃ -based, SrCeO ₃ -based, BaCeO ₃ -based ceramic proton conductor, or the like can be used. In this example, SrZr _0.8 In _0.2 O ₃ was used. The electrolyte layer 17 can be formed, for example, by depositing SrZr _0.8 In _0.2 O ₃ on the hydrogen separation film 18 using a PLD (Pulsed Laser Deposition) apparatus.

  Since the electrolyte layer 17 is formed on the hydrogen separation membrane 18 having a dense and sufficient thickness, the electrolyte layer 17 can be thinned. Therefore, the thickness of the electrolyte layer 17 can be about 0.1-5 micrometers, for example. In this embodiment, the thickness is 2 μm. Of course, it is possible to set appropriately considering the film resistance and strength. By reducing the thickness of the electrolyte layer 17 in this way, the membrane resistance of the electrolyte layer 17 can be reduced, and the temperature is lower than the operating temperature of the conventional solid oxide fuel cell at about 200 to 600 ° C. The fuel cell can be operated.

The cathode electrode layer 16 is a layer formed on the electrolyte layer 17 and has electronic conductivity, catalytic activity for promoting an electrochemical reaction, and oxide ion conductivity. The cathode electrode layer 16 can be used LaSrCoO ₃ type, or a conductive ceramics ₃ system or the like LaSrMnO, platinum (Pt), Pd, rhodium (Rh), silver (Ag) or the like of a metal or alloy. In this example, La _0.6 Sr _0.4 CoO ₃ was used. The thickness was 25 nm. The cathode electrode layer 16 can be formed, for example, by depositing La _0.6 Sr _0.4 CoO ₃ on the electrolyte layer 17 using a PLD apparatus.

  The porous current collectors 14 and 15 are members having gas permeability and conductivity. The porous current collector 14 becomes a part of the oxidizing gas passage 21 for supplying air as the oxidizing gas to the power generation body 30 and collects electricity by interposing it with the separator 13. Further, the porous current collector 15 becomes a part of the fuel gas flow path 22 for supplying the fuel gas to the power generator 30 and is interposed between the separator 19 and collects current. The porous current collectors 14 and 15 can be formed of, for example, a carbon member such as carbon cloth, carbon felt, or carbon paper, a metal member such as foam metal or metal mesh, conductive ceramics, or the like. In this example, a SUS mesh having a thickness of 2 mm was used. If sufficient current collection is possible in the fuel cell 10, at least one of the porous current collector 14 and the porous current collector 15 may be omitted.

  The separators 13 and 19 are gas-impermeable members formed of a conductive material such as carbon or metal. The separators 13 and 19 are formed with a concavo-convex shape on the surface in contact with the power generation body 30. As a result, an oxidizing gas passage 21 and a fuel gas passage 22 are formed in the fuel cell 10. At least one of a contact portion between the separator 13 and the support plate 20 and a contact portion between the separator 19 and the support plate 20 is insulated. When a plurality of fuel cells 10 are stacked to form one fuel cell unit, the separator 13 and the separator 19 can be configured integrally.

In this embodiment, a heat insulating material 40 is joined to the tips of the convex portions of the separators 13 and 19. As the heat insulating material 40, (1) a conductive heat insulating material or (2) a heat insulating material obtained by physically mixing a conductive heat insulating material and a non-conductive heat insulating material can be used. As the former heat insulating material, for example, La _0.6 Sr _0.4 MnO ₃ , La _0.6 Sr _0.4 CoO ₃ , La _0.8 Sr _0.2 Cr _0.9 Co _0.1 O ₃ can be used. On the other hand, stainless steel fiber and nickel fiber can be used as the conductive heat insulating material constituting the latter heat insulating material, and silica, alumina, silica alumina, and zirconia fiber can be used as the non-conductive heat insulating material.

  According to the fuel cell 10 of the present embodiment, since the heat insulating material 40 is disposed on the contact surface between the separators 13 and 19 and the power generator 30, the heat generated in the electrolyte layer 17 due to power generation is generated by the separators 13 and 19. It is possible to suppress conduction to the surface. As a result, the temperature of the power generation body 30 rises, and the power generation efficiency can be improved. Further, since conduction of heat from the power generation body 30 to other parts is suppressed, the range of selection of the sealing material and other members constituting the fuel cell 10 is increased. As a result, it is possible to improve the power generation efficiency of the fuel cell 10 and suppress a reduction in design freedom.

  In addition, although the example which provides the heat insulating material 40 in all the convex parts of the separators 13 and 19 was shown in FIG. 1, you may abbreviate | omit either the heat insulating material 40 of the separator 13 or the separator 19. FIG. In this case, since the heat generated in the electrolyte layer 17 tends to be transmitted to the hydrogen separation membrane 18 more easily than the cathode electrode layer 16, the heat insulating material 40 of the cathode side separator 13 is omitted from the anode side separator 19. Is preferred.

  Moreover, it is good also as what provides the heat insulating material 40 only in a one part convex part instead of providing the heat insulating material 40 in all the convex parts of the separator 13 or the separator 19. FIG. In the electrolyte layer 17, more electrochemical reaction proceeds in the central portion than in the peripheral portion, so that the temperature of the central portion of the power generator 30 is higher than that of the peripheral portion. Therefore, when providing the heat insulating material 40 only in some convex parts, it is set as the structure which leaves the heat insulating material 40 in the convex part of the center part of the separators 13 and 19, and abbreviate | omits the heat insulating material 40 of a peripheral convex part. It is preferable.

B. Second Embodiment (Part of the separator convex part is omitted):
FIG. 2 is a schematic sectional view of a fuel cell 10b as a second embodiment of the present invention. The fuel cell 10b of the present embodiment is different from the fuel cell 10a of the first embodiment in the structure of the separator. In 1st Example, although the heat insulating material 40 shall be provided in the convex part of the separators 13 and 19, separators 13b and 19b of a present Example are the structure which abbreviate | omits the convex part located in the center part of the electric power generation body 30. did.

  FIG. 3 is an explanatory diagram showing the effect of this embodiment. FIG. 3A shows the temperature profile of the fuel cell 10b when the separator protrusion is not omitted. On the other hand, FIG. 3B shows a temperature profile of the fuel cell 10b when the convex portion is omitted as shown in FIG. In these drawings, the horizontal axis indicates the position in the longitudinal direction of the power generation body 30 in FIG. 2 (x0 to x1 in FIG. 2), and the vertical axis indicates the temperature of the power generation body 30 at that position.

  As shown in FIG. 3 (a), when the convex portion of the separator is not omitted, the heat generated in the power generation body 30 is conducted to the outside through the entire convex portion. Lower. On the other hand, when the convex part located in the center part of the electric power generation body 30 is abbreviate | omitted, as shown in FIG.3 (b), the center part of the electric power generation body 30 becomes high temperature. As a result, the power generation efficiency of the fuel cell 10b can be improved. In the electrolyte layer 17, since the electrochemical reaction proceeds more in the central portion than in the peripheral portion, as in this embodiment, by reducing the number of convex portions in the central portion instead of the peripheral portion, more effectively, Heat conduction to the separator can be suppressed. In the present embodiment, the number of convex portions located in the peripheral portion of the power generation body 30 is not reduced. Therefore, unnecessary heat is released through this portion. Therefore, it can suppress that the electric power generation body 30 becomes high temperature more than necessary.

C. Third Example (Insulating material on support plate):
FIG. 4 is a schematic cross-sectional view of a fuel cell 10c as a third embodiment. In FIG. 4, the detailed structure of the power generator 30 is not shown, but the overall structure is substantially the same as that of the first embodiment. However, in this embodiment, the heat insulating material 42 is provided not in the convex portion of the separator but in the contact portion between the power generation body 30 and the support plate 20. As the heat insulating material 42, for example, a non-conductive heat insulating material such as glass or ceramic can be used.

  According to the fuel cell 10c of the present embodiment, it is possible to suppress the heat of the power generator 30 from being conducted to the support plate 20 having a relatively large heat capacity. Therefore, the temperature of the power generation body 30 can be kept high, and the power generation efficiency can be improved.

  FIG. 5 is an explanatory view showing a modification of the third embodiment. In the fuel cell 10d shown in FIG. 5, a heat insulating material 42 is not provided at the contact portion between the support plate 20 and the power generation body 30, but a recess 44 is formed by pressing the vicinity of the support plate of the power generation body 30. The thickness of the part was reduced. Even in such an aspect, it is possible to suppress heat conduction from the power generation body 30 to the support plate 20.

D. Example 4 (Insulating layer on porous current collector):
FIG. 6 is a schematic cross-sectional view of a fuel cell 10e as a fourth embodiment of the present invention. The fuel cell 10e of this embodiment is different from the fuel cell 10a of the first embodiment in the place where the heat insulating material is disposed. That is, in the first embodiment, the heat insulating material 40 is disposed between the separators 13 and 19 and the power generation body 30, but in this embodiment, the space between the porous current collector 14 and the cathode electrode layer 16 is used. In addition, a heat insulating material 46 is disposed between the porous current collector 15 and the hydrogen separation membrane 18. As a material of the heat insulating material 46, a porous heat insulating material having conductivity can be used.

  Even with this configuration of the present embodiment, heat generated in the power generation body 30 can be suppressed from being conducted to the outside. Therefore, similarly to the other embodiments, it is possible to suppress a decrease in the degree of freedom in design while improving the power generation efficiency. In this embodiment, as shown in FIG. 6, the heat insulating material 46 is provided between the porous current collector 14 and the cathode electrode layer 16, and between the porous current collector 15 and the hydrogen separation membrane 18. However, any one of them may be omitted.

E. 5th Example (heat insulation layer in a hydrogen separation membrane):
FIG. 7 is a schematic sectional view of a fuel cell 10f as a fifth embodiment of the present invention. In this embodiment, the heat insulating material 48 is embedded in the vicinity of the electrolyte layer 17 in the hydrogen separation membrane 18 with a predetermined interval.

Examples of the heat insulating material 48 embedded in the hydrogen separation membrane 18 include various heat insulating materials described in the first embodiment, and a ceramic hydrogen permeable membrane having a higher heat insulating property and a lower hydrogen permeability than the hydrogen separating membrane 18. Any hydrogen permeable material can be used. As such a hydrogen permeable substance, for example, SrZr _0.8 Y _0.1 Ru _0.1 O ₃ or BaCe _0.8 Y _0.1 Ru _0.1 O ₃ can be used. When the heat insulating material 48 has hydrogen permeability, the above-described interval can be omitted.

  The hydrogen separation membrane 18 having the heat insulating material 48 inside may be formed, for example, by preparing two layers of hydrogen separation membranes, placing the heat insulating material 48 between them, and then diffusion bonding the whole. it can. In this embodiment, the heat insulating material 48 is embedded in the hydrogen separation membrane 18. However, the heat insulating effect can be obtained even if the space is used instead of the heat insulating material 48. Of course, the heat insulating material 48 and the space may be mixed in the hydrogen separation membrane 18.

  In the foregoing, various embodiments of the present invention have been described. According to the various embodiments described above, local heat generated in the electrolyte portion in the fuel cell can be prevented from being conducted to other portions. Therefore, the temperature of the power generation body 30 rises and the power generation efficiency can be improved. Further, since conduction of heat from the power generation body 30 to other parts is suppressed, the range of selection of the sealing material and other members constituting the fuel cell 10 is increased. As a result, it is possible to suppress a reduction in the degree of freedom in design while improving the power generation efficiency of the fuel cell 10.

  Needless to say, the present invention is not limited to the above-described embodiments, and various configurations can be adopted without departing from the spirit of the present invention. The various embodiments described above can be combined as appropriate. For example, if the first embodiment and the third embodiment are combined, heat conduction not only to the separator but also to the support plate can be suppressed, so that heat insulation can be performed more effectively.

It is a cross-sectional schematic diagram of the fuel cell 10a as the first embodiment. It is a cross-sectional schematic diagram of the fuel cell 10b as 2nd Example. It is explanatory drawing which shows the effect of 2nd Example. It is a cross-sectional schematic diagram of the fuel cell 10c as 3rd Example. It is explanatory drawing which shows the modification of 3rd Example. It is a cross-sectional schematic diagram of the fuel cell 10e as a 4th Example. It is a cross-sectional schematic diagram of the fuel cell 10f as 5th Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10a-10f ... Fuel cell 13, 19 ... Separator 14,15 ... Porous collector 16 ... Cathode electrode layer 17 ... Electrolyte layer 18 ... Hydrogen separation membrane 20 ... Support plate 21 ... Oxidation gas channel 22 ... Fuel gas channel 30 ... Power generator 40, 42, 46, 48 ... Insulating material

Claims (11)

A fuel cell,
A hydrogen separation membrane that selectively permeates hydrogen from the fuel gas supplied to one surface to the other surface is used as a base material, and an electrolyte layer is formed on the other surface of the base material. A power generator having a cathode electrode layer formed adjacent thereto;
A first separator disposed adjacent to a surface of the power generation body on the hydrogen separation membrane side and having a fuel gas flow path for supplying the fuel gas to the hydrogen separation membrane;
A second separator disposed adjacent to the cathode electrode layer side surface of the power generation body and having an oxidizing gas flow path for supplying an oxidizing gas to the cathode electrode layer;
A fuel cell comprising: a heat transfer suppression structure that suppresses heat generated by an electrochemical reaction in the power generation body from being transferred from the power generation body to another part of the fuel cell. The fuel cell according to claim 1,
At least a part of the heat transfer suppression structure is a heat insulator formed in the hydrogen separation membrane. The fuel cell according to claim 2, wherein
In the hydrogen separation membrane, a non-hydrogen-permeable heat insulating material or a space is embedded as the heat insulator at a predetermined interval. Fuel cell. The fuel cell according to claim 2, wherein
In the hydrogen separation membrane, a hydrogen permeable substance having higher heat insulation than the hydrogen separation membrane is embedded as the heat insulator. A fuel cell according to any one of claims 2 to 4, wherein
The heat insulator is embedded in the vicinity of the electrolyte layer in the hydrogen separation membrane. A fuel cell according to any one of claims 1 to 5,
At least a part of the heat transfer suppression structure is formed on at least one of a contact surface between the first separator and the power generation body, and a contact surface between the second separator and the power generation body. The fuel cell according to claim 6, wherein
The heat transfer suppression structure is formed by disposing a heat insulating material on at least one of the contact surface between the first separator and the power generator and the contact surface between the second separator and the power generator. Fuel cell. The fuel cell according to claim 6, wherein
The heat transfer suppression structure is formed by reducing a contact area of the first separator or the second separator and a central portion of the power generator to be smaller than a contact area of a peripheral portion. The fuel cell according to claim 8, wherein
In the first separator or the second separator, a plurality of convex portions are formed on the contact surface with the power generator,
The said heat-transfer suppression structure is formed by making the number of the convex parts formed in the center part of the said 1st separator or the said 2nd separator smaller than the number of the convex parts of a peripheral part. Fuel cell. A fuel cell according to any one of claims 1 to 9,
And a support plate for fixing the power generator in the fuel cell.
At least a part of the heat transfer suppressing structure is formed by providing a heat insulating portion at a contact portion between the power generation body and the support plate. A fuel cell according to any one of claims 1 to 10,
Furthermore, a porous current collector is provided between at least one of the power generator and the first separator and between the power generator and the second separator,
At least a part of the heat transfer suppression structure is formed by providing a heat insulator between the porous current collector and the power generator.

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