KR20110007341A - Fuel cell stack assembly - Google Patents

Abstract

PURPOSE: A fuel cell stack assembly is provided to generate fixed current from an adjacent unit cell, to improve performance and durability of whole unit cells, and to replace the corresponding unit stack through a storage method. CONSTITUTION: A fuel cell stack assembly(100) includes: a plurality of unit stacks(10) in which many unit cells(11) are pressurized and coupled through end plates(21); and an accommodation package member(40) which forms a plurality of accommodation spaces and accommodates the unit stack. The package member stores the unit stacks and includes a storage case.

Description

Fuel Cell Stack Assembly {FUEL CELL STACK ASSEMBLY}

An exemplary embodiment of the present invention relates to a fuel cell stack, and more particularly, to an assembly fastening structure of a fuel cell stack.

As is known, a fuel cell is a power generation system that converts hydrogen contained in a hydrocarbon-based fuel and chemical reaction energy of an oxidant directly into electrical energy.

Such fuel cells are divided into various types according to the components of the system and the type of fuel. The fuel cells may be classified into polymer electrolyte fuel cells and direct oxidation fuel cells.

The polymer electrolyte fuel cell is provided with a reforming gas of a hydrogen component generated from fuel in an reformer and an oxidant such as air to generate electrical energy as an electrochemical reaction between the reforming gas and the oxidant.

Here, the fuel may include an alcohol liquid fuel such as methanol, ethanol, and the like, and may include a hydrocarbon-based liquefied gas mainly composed of methane, ethane, propane, butane.

The reformer generates thermal energy as an oxidation method of fuel by a catalyst, and steam reforming (SR), partial oxidation (POX: partial oxidation) or autothermal reforming (ATR: Auto) of the fuel using the thermal energy. -Thermal Reforming is a reaction that generates a reformed gas rich in hydrogen.

On the other hand, unlike a polymer electrolyte fuel cell, a direct oxidation fuel cell generates electric energy as an electrochemical reaction between hydrogen contained in the fuel and a oxidant provided separately by directly receiving fuel without using a reforming gas. Let's do it.

Such a fuel cell comprises a stack in which a series of unit cells consisting of a membrane electrode assembly (MEA) and a separator (commonly referred to in the art as a "bipolar plate") are continuously arranged. Configure.

Such a stack is stacked with several to hundreds of unit cells, and produces a power of several W to several MW.

Here, the membrane-electrode assembly has a structure in which a catalyst layer as an anode electrode and a cathode electrode is formed on both surfaces of the electrolyte membrane.

The separator is disposed on both sides thereof with the membrane electrode assembly interposed therebetween, and serves as a passage for supplying a reforming gas or fuel (hereinafter referred to as “fuel” for convenience) and an oxidant to the membrane electrode assembly, and a membrane electrode. It simultaneously functions as a conductor connecting the anode and cathode electrodes of the assembly in series.

Thus, when fuel and oxidant are supplied to the unit cells of the stack, fuel is supplied to the anode electrode of the membrane-electrode assembly, and oxidant is supplied to the cathode electrode by the separator.

In this process, the stack undergoes electrochemical oxidation of the hydrogen component contained in the fuel at the anode electrode, and electrochemical reduction of the oxidant at the cathode electrode, thereby generating electrical energy as a movement of electrons generated.

In the stack as described above, the pressure plates (hereinafter referred to as "end plates" commonly known in the art) disposed at the outermost sides of the unit cells are fastened to each other by a fastening means, and the unit cells are pressed at a constant pressure. Keep it.

That is, in the state in which the unit cells are continuously aligned when assembling the stack, the end plate is in close contact with the outermost unit cell with the unit cells interposed therebetween, and receives the fastening pressure through the fastening means to press the unit cells to a constant pressure. do.

Such a stack is composed of tens to hundreds of unit cells as one assembly through the end plate according to the amount of power required. The end plate must be press-fitted.

However, in the prior art, it is not easy to control the clamping pressure of the end plate corresponding to the pressure displacement by the operator's skill difference or the mechanical error of the torque device.

Therefore, conventionally, the clamping pressure of the end plate is excessively applied or too weakly applied to the unit cells, which requires additional work, such as checking and adjusting the tightening degree of the fastening means, and manufacturing the entire stack. The problem is that it takes longer.

In addition, the stack does not generate a predetermined power according to the stacking number of the unit cells by the fastening pressure, the fuel / oxidant supply, and the combination of the separators described above. This breakage causes problems in cell performance and durability of the entire stack.

Therefore, in the prior art, the unit cell in question is replaced or repaired by disassembling and disassembling the stack. The assembly of the stack is not easy, and the entire stack is replaced or newly manufactured. It causes problems.

Exemplary embodiments of the present invention have been created to improve the above-described problems, and include a fuel cell stack configured to construct a unit stack each consisting of several unit cells in a module form, and to package the unit stack as an assembly form. Provide the assembly.

To this end, a fuel cell stack assembly according to an exemplary embodiment of the present invention includes: i) a plurality of unit stacks formed by pressing a plurality of unit cells through an end plate, and ii) a plurality of unit stacks for accommodating each unit stack. Comprising a receiving space of the compartment and comprises a package member for receiving the unit stack in each of the receiving space individually.

In the fuel cell stack assembly, the package member stores the unit stacks in the receiving spaces along the arrangement direction of the unit cells, and forms at least one open surface along the arrangement direction of the unit stacks. It can be made as a case.

In the fuel cell stack assembly, the package member may be provided with a plurality of partition walls spaced apart at regular intervals to form the respective accommodation spaces inside the storage case.

In the fuel cell stack assembly, the package member is a base on which the unit stacks can be continuously seated along the arrangement direction of the unit cells, and at least one connected in a vertical direction to an edge portion in the longitudinal direction of the base. It may include a vertical plate and a plurality of partitions are installed upright in the vertical direction spaced apart at regular intervals along the longitudinal direction on the plane of the base to form the respective receiving space.

In the fuel cell stack assembly, the partitions are disposed between the unit stacks and in the outermost unit stacks, and may be formed as cooling plates for cooling the heat generated in the unit stacks.

In the fuel cell stack assembly, each of the barrier ribs may be formed of any one of aluminum, copper, and iron having thermal conductivity.

The fuel cell stack assembly includes: (i) a fuel supply line connected to each unit stack and supplying fuel to the unit stack, and iii) an oxidant supply line connected to each unit stack and supplying an oxidant to the unit stack. A fuel discharge line connected to each of the unit stacks and discharging unreacted fuel discharged from the unit stacks, and iv) discharging unreacted oxidants and water connected to the unit stacks and discharged from the unit stacks. It may include an oxidant discharge line.

In the fuel cell stack assembly, the fuel supply line may be selectively detachably connected to a fuel supply manifold formed on an end plate of each unit stack.

In the fuel cell stack assembly, the oxidant supply line may be detachably connected to an oxidant supply manifold formed in the end plate of each unit stack.

In the fuel cell stack assembly, the fuel discharge line may be connected to a fuel discharge manifold formed on an end plate of each unit stack.

In the fuel cell stack assembly, the oxidant discharge line may be connected to an oxidant discharge manifold formed in the end plate of each unit stack.

In the fuel cell stack assembly, each unit stack may be formed by fastening the end plate through a fastening means.

In the fuel cell stack assembly, each of the partition walls may have upper and lower guide grooves for guiding the fastening means, respectively, when the unit stack is accommodated in the accommodation space.

In the fuel cell stack assembly, the package member may include at least one cover covering an open surface of the storage case.

According to the exemplary embodiment of the present invention as described above, unlike the prior art that press-fasten dozens to hundreds of unit cells through the end plate to output the required amount of power to form a single stack, divided into several Since the unit stack can be packaged as an assembly in the package member, the entire assembly can be easily assembled and manufactured.

In addition, in the present embodiment, since the unit stacks are formed by pressing and fastening several unit cells through the end plate, unit cells of the entire assembly may be fastened at a predetermined pressure in accordance with a predetermined pressure displacement, and thus, in unit cells adjacent to each other. It is possible to generate a constant current, thereby improving the cell performance and durability of the entire unit cells.

In this embodiment, since the corresponding unit stack of the unit cell in question, such as a decrease in current amount, may be replaced by a storage method, the entire unit stack is separated as in the prior art, and the unit cell in which cell performance is degraded is replaced and reassembled. Or build a new stack.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

1 is a perspective view illustrating a fuel cell stack assembly according to an exemplary embodiment of the present invention, FIG. 2 is an exploded perspective view of FIG. 1, and FIG. 3 is a front configuration diagram of FIG. 1.

Referring to the drawings, the fuel cell stack assembly 100 according to an exemplary embodiment of the present invention is configured as a power generation system that generates electrical energy by reaction of fuel and oxidant.

Here, the fuel may include an alcoholic liquid fuel such as methanol, ethanol, and the like, and may include a hydrocarbon-based liquefied gas fuel mainly composed of methane, ethane, propane, butane.

The fuel may also include reformed gas of a hydrogen component produced from the liquid fuel or liquefied gas fuel described above via a reformer referred to in the art as a "reformer."

In addition, the oxidant may be oxygen gas stored in a separate storage tank, or may be natural air.

The fuel cell stack assembly 100 according to the present exemplary embodiment is configured as a plurality of module types that can be defined as stacks, packages the modules in an assembly form, and has a structure that can be replaced as a storage method.

To this end, the fuel cell stack assembly 100 according to the exemplary embodiment of the present invention basically includes a plurality of unit stacks 10 and a package member 40 for receiving the unit stacks 10. If this is described for each configuration as follows.

In the present exemplary embodiment, each unit stack 10 is a module as mentioned above, and is formed of an electricity generating assembly of units, and has a structure in which several unit cells 11 are continuously arranged.

The unit cells 11 are fuel cells of a unit for generating electrical energy by an electrochemical reaction of a fuel and an oxidizing agent. The unit cells 11 may be made of a polymer electrolyte fuel cell according to the above-described fuel, or may be made of a direct oxidation fuel cell. have.

As shown in FIG. 4, the unit cells 11 include a membrane-electrode assembly (MEA) 13 and a separator 15 disposed in close contact with each other with the membrane-electrode assembly 13 at the center thereof. .

At this time, the unit cells 11 have a gasket GK interposed between both side edges of the membrane-electrode assembly 13 and the separator 15, and maintain the airtightness of the membrane-electrode assembly 13 and the separator 15. do.

The separator 15 has a conductive plate shape, and forms channels CH for flowing fuel and oxidant on a surface closely contacting the membrane-electrode assembly 13.

Here, the membrane-electrode assembly 13 has a structure in which an anode electrode is formed on one surface, a cathode electrode is formed on the other surface, and an electrolyte membrane is formed between these two electrodes.

The anode electrode oxidizes the fuel supplied through the channel CH of the separator 15 to separate electrons and hydrogen ions, the electrolyte membrane moves hydrogen ions to the cathode electrode, and the cathode electrode receives electrons received from the anode electrode side. , Hydrogen ions, and the oxidizing agent provided through the channel (CH) of the separator 15 to reduce the reaction to generate a function of water and heat.

Since the membrane-electrode assembly 13 and the separator 15 are made of a membrane-electrode assembly and a separator (also referred to as a "bipolar plate") well known in the art, a detailed description thereof will be made herein. Will be omitted.

In each unit stack 10 as described above, the unit cells 11 are pressed against each other through the end plates 21 on both sides, which end plates 21 comprise a plurality of fastening rods 23. It is fastened to each other through the fastening means.

That is, the end plates 21 are in close contact with the outermost separators 15 of the unit cells 11, and the fastening members 25 are fastened to the end portions of the respective fastening rods 23 passing therethrough, so as to face each other. The unit cells 11 are pressed.

In the above, at least each corner portion of the end plate 21 is formed with a through hole 22 into which the fastening rod 23 is fitted.

In addition, the fastening rod 23 is for connecting a pair of end plates 21, and is fitted into each through hole 22 of one end plate 21 while each through hole of the other end plate 21 ( 22).

The fastening rod 23 is disposed along the arrangement direction of these unit cells 11 outside the unit cells 11, and has a bolt head at one end and a bolt having a screw at the other end.

The fastening member 25 is for fastening the pair of end plates 21 and providing a predetermined pressing force to each end plate 21. The fastening member 25 is provided with a nut screwed to the threaded portion of each fastening rod (23).

In assembling the unit stack 10 configured as described above, the unit cells 11 are continuously aligned between the pair of end plates 21. The fastening rod 23 is fitted into each through hole 22 of the end plates 21.

The fastening member 25 is screwed to the threaded portion of each fastening rod 23 to fasten the end plates 21 and at the same time provide a predetermined pressing force to the end plates 21. Then, the end plates 21 press the unit cells 11 in directions facing each other.

Meanwhile, the end plate 21 of each unit stack 10 includes a fuel supply manifold 31 for supplying fuel to the unit cells 11, and an oxidant supply manifold for supplying an oxidant to the unit cells 11. The fold 32, the fuel discharge manifold 33 for discharging the unreacted fuel remaining in the unit cells 11, and the oxidant remaining in the unit cells 11 and generated in the unit cells 11. An oxidant discharge manifold 34 for discharging moisture to be formed is formed.

Here, the fuel supply manifold 31 and the fuel discharge manifold 33 are connected to the channel CH of the separator 15 in close contact with the anode electrode of the membrane-electrode assembly 13, and the oxidant supply manifold 32. ) And the oxidant discharge manifold 34 are connected to the channel CH of the separator 15 in close contact with the anode electrode of the membrane-electrode assembly 13.

Reference numeral 29, which is not described in the drawing, denotes a current collector plate for collecting electricity generated in the unit cells 11 of the unit stack 10.

In this embodiment, the package member 40 is for packaging the unit stacks 10.

As shown in FIG. 5, the package member 40 partitions a plurality of accommodating spaces 41 for accommodating each unit stack 10, and individually unit stacks 10 in each accommodating space 41. It is made as a storage case 42 which can be accommodated.

In addition, the package member 40 includes a plurality of partition walls 55 for partitioning each accommodating space 41 into the storage case 42.

In the above, the storage case 42 is for accommodating the unit stacks 10 in the respective accommodating spaces 41 along the arrangement direction of the unit cells 11. Therefore, at least one open surface is formed.

Preferably, the open surface is formed on the top and front of the storage case 42, based on the drawings.

Specifically, the package member 40 according to the present embodiment includes a base 51, a vertical plate 53, and a plurality of partition walls 55 mentioned above.

The base 51 is a bottom plate of the storage case 42 and has a predetermined width and is formed to be long as a predetermined length so that the unit stacks 10 can be seated.

The vertical plate 53 is a rear plate of the storage case 42 and is installed to be connected in the vertical direction to the edge portion of the base 51 along the length direction.

In addition, each partition wall 55 is for forming a plurality of accommodation spaces 41 in the storage case 42 and is installed upright in a vertical direction to be spaced apart at regular intervals on a plane along the longitudinal direction of the base 51. do.

Here, each of the partition walls 55 positioned on the outermost side of the partition walls 55 is formed as both side walls of the storage case 42.

Thus, the unit stack 10 is packaged while being accommodated in the receiving space 41 between the partition walls 55, in which case each partition wall 55 is located between the unit stacks 10 and the outermost. It is in close contact with the unit stack 10 located.

In the present embodiment, the partitions 55 are formed of a cooling plate 57 for cooling the heat generated in the unit stack 10 while being in close contact with the end plate 21 of each unit stack 10.

That is, during operation of the unit stacks 10, heat generated in the unit cells 11 of each unit stack 10 is transferred to the partition walls 55 through the separator 15 and the end plate 21 and is cooled in water. Or air cooled.

To this end, the partitions 55 are preferably made of aluminum, copper, or iron material having thermal conductivity and heat dissipation.

In addition, the partition walls 55 as described above, when the unit stack 10 is accommodated in the accommodation space 41 through the open surface of the storage case 42, the head of the fastening rod 23 and the fastening member Guide grooves 59 in the form of rails for guiding (25: nuts) are formed in the upper and lower portions, respectively.

The guide grooves 59 are formed on both side surfaces of the partition walls 55, and are formed along the width direction of the base 51 at upper and lower ends.

The guide grooves 59 support the respective unit stacks 10 in the accommodation spaces 41 between the partition walls 55, and fasten rods when the unit stacks 10 are accommodated in the accommodation spaces 41. The head portion and the fastening member 25 of the 23 is to prevent the hooking to the partitions (55).

On the other hand, in the present embodiment, the package member 40 is in a state in which the unit stacks 10 are accommodated in the accommodation space 41 through the open surface of the storage case 42, covering the open surface to accommodate the storage space 41. ) Further includes a cover 48 for sealing.

Preferably, the cover 48 is provided as a pair to cover the open surface of the front surface and the upper surface of the storage space 41 of the storage case 42, the base 51, through a fastening means such as bolts, It is fixed to the vertical plate 53 and the partition walls 55.

On the other hand, the fuel cell stack assembly 100 according to the present embodiment and the fuel supply line 60 for supplying fuel to each unit stack 10 accommodated in the receiving space 41 of the package member 40 and And an oxidant supply line 70 for supplying an oxidant.

The fuel supply line 60 is connected to a fuel supply source (not shown) and is connected to the fuel supply manifold 31 of the end plate 21 in each unit stack 10. It is made in the form of branching from one main line 61 to each fuel supply manifold 31.

At this time, each of the first branch lines 63 branching from the first main line 61 of the fuel supply line 60 is detachably coupled to each of the fuel supply manifolds 31.

In other words, the first branch line 63 can be male and female fit to each fuel supply manifold 31 through a rubber ring (not shown).

The oxidant supply line 70 is connected to an oxidant supply source (not shown), and is connected to the oxidant supply manifold 32 of the end plate 21 in each unit stack 10. Branch from the second main line 71 to each oxidant supply manifold 32.

At this time, the second branch line 73 branching from the second main line 71 of the oxidant supply line 70 is detachably coupled to each oxidant supply manifold 32 as a male and female.

In other words, the second branch line 73 can be hermetically fitted to each oxidant supply manifold 32 through a rubber ring (not shown).

In this embodiment, the fuel discharge line 80 for discharging the unreacted fuel remaining after reacting in each unit stack 10, the oxidant remaining after reacting in each unit stack 10, and the unit stack 10. It further includes an oxidant discharge line 90 for discharging the water generated in the.

The fuel discharge line 80 is connected as a line to the fuel discharge manifold 33 of the end plate 21 in each unit stack 10. An oxidant discharge line 90 is connected as a line to the oxidant discharge manifold 34 of the end plate 21 in each unit stack 10.

Reference numeral 49, which is not described in the drawing, is formed in each partition wall 55 of the package member 40 to form a through hole through which the fuel discharge line 80 and the oxidant discharge line 90 pass by the vertical plate 53. Indicates a mounting groove.

Accordingly, according to the fuel cell stack assembly 100 according to the exemplary embodiment of the present invention configured as described above, the unit stack 10 in which several unit cells 11 are assembled as an aggregate by the end plate 21. Is coupled as a storage form to each accommodation space 41 through the open face of the storage case 42.

That is, each unit stack 10 is packaged while being accommodated in the accommodation space 41 between the partition walls 55, in which case the head of the fastening rod 23 and the fastening member 25 is partitioned ( Guided along the guide groove 59 of the 55 is received in the accommodation space (41).

As described above, in a state in which the unit stack 10 is accommodated in each accommodation space 41 of the package member 40, in this embodiment, the fuel supply line 60 is connected to the fuel supply manifold 31 of each unit stack 10. ) And the oxidant supply line 70 to the oxidant supply manifold 32 of each unit stack 10.

In this embodiment, the fuel discharge line 80 is connected to the fuel discharge manifold 33 of each unit stack 10, and the oxidant discharge line 90 is connected to the oxidant discharge manifold of each unit stack 10. 34).

After the above process, and finally covering the cover 48 to the open surface of the storage case 42, the assembly of the fuel cell stack assembly 100 according to the present embodiment is completed.

As described above, the fuel cell stack assembly 100 according to the exemplary embodiment of the present invention configures the unit stack 10 including the several unit cells 11 in the form of modules, and the unit stack 10. ) Can be stably fixed to the package member 40 and packaged as an assembly form.

Therefore, in the present embodiment, unlike the prior art in which a single stack is formed by press-fitting tens to hundreds of unit cells through an end plate in order to output a required amount of power, the unit stack 10 divided into several pieces is packaged. Since the package 40 can be packaged in an assembly form, the entire stack assembly 100 can be easily assembled / manufactured.

In addition, in the present embodiment, since the unit stack 10 is configured by pressure-fastening several unit cells 11 through the end plate 21, the unit cells 11 of the entire assembly may be fixed to a predetermined pressure displacement. Since it can be fastened by pressure, it is possible to generate a constant current in the unit cells 11 adjacent to each other, and as a result, it is possible to improve the cell performance and durability of the entire unit cells (11).

In the present embodiment, the unit stack 10 may be packaged in the package member 40 to replace the unit stack 10 as a storage method.

Therefore, in the present embodiment, since the corresponding unit stack 10 of the unit cell 11 which is a problem such as a decrease in the amount of current can be replaced by a storage method, the unit in which the cell performance is degraded by separating the entire stack as in the prior art. There is no need to replace and reassemble the cell or build a new stack.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

Since these drawings are for reference in describing exemplary embodiments of the present invention, the technical idea of the present invention should not be construed as being limited to the accompanying drawings.

1 is a perspective view illustrating a fuel cell stack assembly according to an exemplary embodiment of the present invention.

2 is an exploded perspective view of FIG. 1.

3 is a front configuration diagram of FIG. 1.

4 is an exploded perspective view illustrating the unit stack illustrated in FIG. 2.

5 is a perspective view showing the package member shown in FIG.

<Description of reference numerals for the main parts of the drawings>

10 ... Unit Stack 11 ... Unit Cell

13 ... membrane-electrode assembly 15 ... separator

21 ... End plate 23 ... Tightening rod

25 ... fasteners 31 ... fuel supply manifold

32 ... oxidant supply manifold 33 ... fuel exhaust manifold

34 ... oxidant exhaust manifold 40 ... package member

41 ... Accommodation space 42 ... Storage case

48 ... cover 51 ... base

53 ... vertical plate 55 ... bulk

57 ... cooling plate 59 ... guide groove

60 ... fuel supply line 70 ... oxidant supply line

80 ... fuel discharge line 90 ... oxidant discharge line

Claims (11)

A plurality of unit stacks formed by pressing a plurality of unit cells through an end plate; And A package member configured to define a plurality of accommodating spaces for accommodating each unit stack, and individually accommodating the unit stack in each accommodating space Fuel cell stack assembly comprising a. According to claim 1, The package member, And a storage case accommodating the unit stacks in the accommodating spaces along the arrangement direction of the unit cells, and forming at least one open surface along the arrangement direction of the unit stacks. The method of claim 2, The package member, And a plurality of partition walls spaced apart from each other by a plurality of partitions for partitioning the accommodation spaces in the storage case. According to claim 1, The package member, A base on which the unit stacks are continuously seated along an arrangement direction of the unit cells; At least one vertical plate connected in a vertical direction to an edge portion in the longitudinal direction of the base; A plurality of partition walls installed upright in a vertical direction at regular intervals along a longitudinal direction on the plane of the base to form the respective accommodation spaces; Fuel cell stack assembly comprising a. The method according to claim 3 or 4, Each of the partitions, A fuel cell stack assembly disposed between the unit stacks and in an outermost unit stack, the cooling cell stack being a cooling plate for cooling heat generated in the unit stack. 6. The method of claim 5, Wherein each of the barrier ribs is made of any one of thermally conductive aluminum, copper, and iron. According to claim 1, A fuel supply line connected to each unit stack and supplying fuel to the unit stack; An oxidant supply line connected to each unit stack and supplying an oxidant to the unit stack; A fuel discharge line connected to each unit stack and discharging unreacted fuel discharged from the unit stack; An oxidant discharge line connected to each unit stack and discharging unreacted oxidant and water discharged from the unit stack. Fuel cell stack assembly comprising a. 8. The method of claim 7, The fuel supply line is selectively detachably connected to a fuel supply manifold formed on an end plate of each unit stack, And the oxidant supply line is detachably connected to an oxidant supply manifold formed on an end plate of each unit stack. 8. The method of claim 7, The fuel discharge line is connected to a fuel discharge manifold formed in the end plate of each unit stack, The oxidant discharge line is connected to an oxidant discharge manifold formed in the end plate of each unit stack. The method according to claim 3 or 4, The unit stack is made by fastening the end plate through a fastening means, Each of the partition walls includes a guide groove for guiding the fastening means, respectively, when the unit stack is accommodated in the accommodation space. The method of claim 2, The package member, And at least one cover covering an open surface of the storage case.

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