KR20060020020A - Fuel cell system and stack - Google Patents

Abstract

Fuel cell system according to the present invention, at least one electricity generating unit for generating electrical energy through the electrochemical reaction of hydrogen and oxygen; A fuel supply source for supplying a fuel containing hydrogen to the electricity generating section; And an oxygen supply source for supplying oxygen to the electricity generating unit, wherein the electricity generating unit has a close contact structure by a membrane-electrode assembly (MEA) and separators disposed on both sides of the membrane-electrode assembly, respectively. The electrode assembly and separator are shaped such that each vertex of the reference rectangle is inscribed for any reference rectangle.

Fuel Cell, Stack, Separator, MEA, Active Area, Circular, Oval

Description

FUEL CELL SYSTEM AND STACK

1 is a block diagram schematically showing the overall configuration of a fuel cell system according to an embodiment of the present invention.

2 is an exploded perspective view illustrating a structure of a stack for a fuel cell system according to an exemplary embodiment of the present invention.

FIG. 3 is a schematic diagram for explaining the structures of the separator and the membrane-electrode assembly shown in FIG. 2.

4 is a schematic view for explaining a modification of the separator and the membrane-electrode assembly according to the embodiment of the present invention.

The present invention relates to a fuel cell system, and more particularly, to a fuel cell system having an improved stack structure for a fuel cell.

In general, a fuel cell is a power generation system that directly converts chemical energy into electrical energy by an electrochemical reaction generated by using hydrogen and oxygen contained in a hydrocarbon-based material such as methanol, ethanol or natural gas as a fuel. . In particular, the fuel cell is characterized in that it can simultaneously use the electricity generated by the electrochemical reaction of the fuel gas and the oxidant gas and heat by-products thereof without a combustion process.

Polymer electrolyte fuel cells (PEMFCs, hereinafter referred to as PEMFCs), which are being developed in recent years, have excellent output characteristics, low operating temperatures, and fast start-up and response characteristics compared to other fuel cells.

In order for the above PEMFC to basically have a system configuration, a fuel cell body (hereinafter referred to as a stack for convenience) called a stack, a fuel tank, and a fuel pump for supplying fuel from the fuel tank to the stack, etc. This is necessary. In the process of supplying the fuel stored in the fuel tank to the stack, a reformer for reforming the fuel to generate hydrogen gas and supplying the hydrogen gas to the stack is further needed.

In such a fuel cell system, a stack that substantially generates electricity is a membrane-electrode assembly (MEA) and a separator (also referred to in the art as a bipolar plate). Cells of units consisting of several to several dozens have a stacked structure. Here, the separator has a substantially rectangular shape and is disposed on both sides with the MEA interposed therebetween to supply hydrogen gas and oxygen required for the reaction of the fuel cell to the MEA, and to connect the anode and cathode electrodes of each MEA in series. Simultaneously plays the role of connecting conductor.

On the other hand, in the fuel cell described above, the stack is required to have a structural design so as to increase the contact area of hydrogen fuel and oxygen passing through the separator with respect to the MEA in order to improve the efficiency of the fuel cell. One of the matters is the shape of the separator and the MEA. In other words, the shape of the separator and the MEA is an important factor that determines the performance of hydrogen fuel and oxygen diffusion into the MEA and the amount of power generated from the MEA in the active region of the MEA.

Therefore, in order to improve the efficiency of the fuel cell system, it is important to optimize the contact area of hydrogen fuel and oxygen passing through the separator with respect to the MEA by improving the shape of the separator and the MEA as in the prior art. There is nothing that does not help to improve the efficiency of the fuel cell.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a fuel cell system which improves the shape of the separator and the MEA to increase the contact area per unit area of hydrogen and oxygen to the active region of the MEA.

In order to achieve the above object, a stack for a fuel cell system according to the present invention includes at least one electricity generating unit for generating electrical energy through an electrochemical reaction between hydrogen and oxygen,

The electricity generating unit is made of a close contact structure by a membrane-electrode assembly (MEA) and a separator disposed on both sides of the membrane-electrode assembly,

The membrane-electrode assembly and separator are shaped such that each vertex of the reference rectangle is inscribed with respect to any reference rectangle.

In the stack for a fuel cell system according to the present invention, each separator may be in close contact with one surface of the membrane-electrode assembly to form a hydrogen passage, and may be in close contact with another surface to form an air passage.

In the stack for a fuel cell system according to the present invention, when the reference rectangle is square, the membrane-electrode assembly and the separator are preferably circular.

In the stack for a fuel cell system according to the present invention, when the reference rectangle is rectangular, the membrane-electrode assembly and the separator are preferably oval.

In addition, in the stack for a fuel cell system according to the present invention, the passage may be formed spirally on one surface of the separator.

In the stack for a fuel cell system according to the present invention, the separator may be formed to penetrate an inflow portion communicating with the start end of the passage, and an outlet portion communicating with the end of the passage.

In addition, the fuel cell system according to the present invention to achieve the above object, at least one electricity generating unit for generating electrical energy through the electrochemical reaction of hydrogen and oxygen; A fuel supply source for supplying a fuel containing hydrogen to the electricity generating section; And an oxygen supply source for supplying oxygen to the electricity generator,

The electricity generating unit is made of a close contact structure by a membrane-electrode assembly (MEA) and a separator disposed on both sides of the membrane-electrode assembly,

The membrane-electrode assembly and separator are shaped such that each vertex of the reference rectangle is inscribed with respect to any reference rectangle.

A fuel cell system according to the present invention, wherein the fuel supply source comprises: a fuel tank for storing the fuel; And it may include a fuel pump connected to the fuel tank.

Further, in the fuel cell system according to the present invention, the fuel supply source is disposed between the fuel tank and the electricity generating unit to receive fuel from the fuel tank to generate hydrogen gas, and supply the hydrogen gas to the electricity generating unit. It may also include a reformer.

In the fuel cell system according to the present invention, the oxygen supply source may include at least one air pump that sucks air and supplies the air to the electricity generator.

In addition, in the fuel cell system according to the present invention, a plurality of the electric generators may be provided to form a stack having a stacked structure of the electric generators.

In the fuel cell system according to the present invention, the separators are in close contact with one surface of the membrane-electrode assembly to form a hydrogen passage, and are in close contact with the other surface to form an air passage.                     

In the fuel cell system according to the present invention, when the reference rectangle is square, the membrane-electrode assembly and the separator are preferably circular.

In the fuel cell system according to the present invention, when the reference rectangle is rectangular, the membrane-electrode assembly and the separator are preferably oval.

In addition, in the fuel cell system according to the present invention, the passage may be formed spirally on one surface of the separator.

In the fuel cell system according to the present invention, the separator may pass through an inflow portion communicating with the start end of the passage and through the outflow portion communicating with the end of the passage.

The fuel cell system according to the present invention configured as described above employs a polymer electrolyte fuel cell (PEMFC) method.

As an alternative, the fuel cell system according to the present invention may employ a direct methanol fuel cell (DMFC) method.

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. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

1 is a block diagram schematically showing the overall configuration of a fuel cell system according to an embodiment of the present invention.

Referring to the fuel cell system 100 according to the present invention with reference to the drawings, the fuel cell system 100 reforms a fuel containing hydrogen to generate hydrogen gas, electrochemically the hydrogen gas and oxygen A polymer electrolyte fuel cell (PEMFC) method that generates electrical energy by reacting with a battery is adopted.

In the fuel cell system 100, the fuel for generating electricity includes methanol, ethanol, natural gas, and the like.

The system 100 may use pure oxygen gas stored in a separate storage means as oxygen reacting with hydrogen, and may use air containing oxygen as it is. However, the latter example is explained below.

The fuel cell system 100 basically includes a stack 10 that generates electrical energy through an electrochemical reaction between hydrogen and oxygen, and generates hydrogen gas from the fuel and transfers the hydrogen gas to the stack 10. A fuel supply source 30 for supplying and an oxygen supply source 40 for supplying air to the stack 10.

The stack 10 is connected to a fuel supply source 30 and an oxygen supply source 40 to receive the hydrogen gas from the fuel supply source 30 and to receive air from the oxygen supply source 40. It consists of a fuel cell that electrochemically reacts with oxygen to generate electrical energy.

The fuel supply source 30 includes a fuel tank 31 for storing the fuel of the above-described negotiation, a fuel pump 33 connected to the fuel tank 31 and discharging the fuel with a predetermined pumping force; And a reformer 35 receiving fuel from the fuel tank 31 to generate hydrogen gas from the fuel and supplying the hydrogen gas to the stack 10.

The oxygen source 40 includes an air pump 41 that sucks air with a predetermined pumping force and supplies this air to the stack 10.

Reformer 35 in the fuel source 30 has a conventional reformer structure that generates hydrogen gas from the fuel through a chemical catalytic reaction by thermal energy and reduces the concentration of carbon monoxide contained in the hydrogen gas. In detail, the reformer 35 generates hydrogen gas from the fuel through catalytic reaction such as steam reforming, partial oxidation, or autothermal reaction. As an example, the reformer 35 reduces the concentration of carbon monoxide contained in the hydrogen gas by a method such as a catalytic reaction such as a water gas conversion method, a selective oxidation method, or purification of hydrogen using a separator.

As an alternative, the fuel cell system 100 according to the present invention is a direct methanol fuel cell (DMFC) system capable of producing electricity by directly supplying the fuel of the above-described arrangement to the stack 10. May be employed. This direct methanol fuel cell does not require a reformer 35, unlike the polymer electrolyte fuel cell described above. Hereinafter, the fuel cell system 100 using the polymer electrolyte fuel cell method will be described as an example. However, the present invention is not necessarily limited thereto.                     

Stack 10 of the hydrogen gas generated through the reformer 35 of the fuel supply source 30 and the air sucked by the air pump 41 during the operation of the fuel cell system 100 according to the present invention configured as described above When supplied to, the stack 10 generates electrical energy through the electrochemical reaction of the hydrogen gas and oxygen contained in the air.

With reference to the accompanying drawings, an embodiment constituting the stack 10 in the present invention will be described in detail.

2 is an exploded perspective view illustrating a structure of a stack for a fuel cell system according to an exemplary embodiment of the present invention.

Referring to the drawings, the stack 10 applied to the present system 100 has a membrane-electrode assembly (MEA) (hereinafter referred to as 'MEA') 12 on both sides thereof. A separator (also referred to as 'bipolar plate' in the art) 13 is disposed to include an electricity generating unit 11 of a minimum unit for generating electricity. Therefore, the stack 10 of the laminated structure according to the present exemplary embodiment may be formed by sequentially stacking the plurality of electricity generating units 11 as described above.

The MEA 12 interposed between the separators 13 has an anode electrode and a cathode electrode (not shown) disposed on both surfaces thereof, and an electrolyte membrane (not shown) is provided between the two electrodes. . The anode electrode functions to oxidize hydrogen gas supplied through the separator 13 to convert hydrogen into hydrogen ions (protons) and electrons. The cathode electrode reduces and reacts oxygen in the air supplied through the separator 13 with hydrogen ions and electrons moved from the anode electrode to generate heat and moisture at a predetermined temperature. The electrolyte membrane is formed of a solid polymer electrolyte having a thickness of 50 to 200 µm, and functions as an ion exchange to move hydrogen ions generated at the anode electrode to the cathode electrode.

The separators 13 are arranged in close contact with each other with the MEA 12 interposed therebetween to form hydrogen passages 15 and air passages 17 on both sides of the MEA 12, respectively. Here, the hydrogen passage 15 is formed on one side separator 13 positioned on the anode electrode side of the MEA 12 to supply hydrogen gas supplied from the reformer 35 to the anode electrode. In addition, the air passage 17 is formed on the other side separator 13 positioned on the cathode electrode side of the MEA 12 to supply oxygen in the air supplied from the air pump 41 to the cathode electrode. In addition, the separator 13 also functions as a conductor that connects the anode electrode and the cathode electrode in series.

 FIG. 3 is a schematic view for explaining the structure of the separator shown in FIG. 2, wherein each of the separators 13 according to an embodiment of the present invention is based on a square reference rectangle A shown as a virtual line in the drawing. , Each vertex of the reference quadrangle A has a shape in which the vertices are in contact with the inside of the concentric circle, that is, a circular shape. At this time, the reference rectangle (A) means a square-shaped separator as in the prior art.

Specifically, the separator 13 according to the present exemplary embodiment has a circular shape having a diameter equal to the diagonal length of the reference rectangle A. The separator 13 has an outer periphery having the same length as that of the conventional separator and is better than the conventional separator. It has a larger area than the hatched area.                     

In the separator 13, the hydrogen passage 15 and the air passage 17 through which hydrogen gas and air pass through are formed in a spiral from the edge portion of the separator 13 toward the center portion, as shown in FIG. 2. have. At this time, the separator 13 is connected to the start of the hydrogen passage 15 and the air passage 17, the inlet portion (15a, 17a) for injecting hydrogen gas and air, and the hydrogen passage 15 and Outlets 15b and 17b connected to the ends of the air passage 17 to pass through the hydrogen passage 15 and the air passage 17 to react with the MEA 12 and discharge the remaining hydrogen gas and air are provided. Forming.

The MEA 12 interposed between the separators 13 having the above-described structure is formed in the same circular shape as the separator 13. Like the separator 13, the MEA 12 has a circular shape in which each vertex of the reference rectangle A, which means a conventional MEA made of a square, is in contact with the inner side of the concentric circle. That is, the MEA 12 has a circular shape having the same diameter as the diagonal length of the reference rectangle A, and has a larger area than the conventional MEA while having the outer periphery of the same length as the conventional MEA (FIG. 3). Reference). In other words, the MEA 12 forms a larger active area 12a than the conventional MEA. In the edge portion of the MEA 12, a sealing material for sealing the edge portion of the contact surface 13 of the separator 13 corresponding to the active region 12a of the MEA 12 is preferably formed with a gasket 12b.

Therefore, the separator 13 is disposed on both sides of the MEA 12 as described above, and the electricity generating unit 11 is formed, and the electricity generating unit 11 is provided in plural and according to the present embodiment. Form the stack 10. At this time, the outermost of the stack 10 may be a pressing plate 29 for pressing and contacting the plurality of electricity generating units 11 described above. However, the stack 10 according to the present invention excludes the pressure plate 29 and may be configured such that the separator 13 positioned at the outermost portion of the plurality of electricity generating units 11 takes the role of the pressure plate. Can be. In addition to the function of bringing the pressure plates 29 into close contact with the plurality of electricity generating units 11, the pressure plate 29 may be configured to have a unique function of the separator 13. At this time, the pressing plate 29 is formed in a rectangular shape, as shown by a virtual line in the figure, but is not necessarily limited to this may be formed in various forms such as a circle.

As an alternative, the shapes of the separator 13 and the MEA 12 according to the present embodiment are exemplified as a circle capable of optimizing the area while having the same outer perimeter as the conventional square separator and MEA as described above. However, the present invention is not limited to the shape thereof, and may be formed in the shape of a polygon except a quadrangle.

In the operation of the present system 100 having the stack 10 as described above, hydrogen gas is supplied to the anode electrode of the MEA 12 through the hydrogen passage 15 of the separator 13, while the air of the separator 13 is supplied. Oxygen-containing air is supplied to the cathode electrode through the passage 17. Therefore, the anode decomposes the hydrogen gas into electrons and hydrogen ions (protons) through an oxidation reaction of the hydrogen gas. At this time, the hydrogen ions are moved to the cathode electrode through the electrolyte membrane, and the electrons are not moved through the electrolyte membrane, but are moved to the cathode electrode of the neighboring MEA 12 through the separator 13, at which time the current flows through the electrons. And concomitantly generates heat and moisture.                     

Accordingly, the fuel cell system 100 according to the present invention includes a circular MEA 12 and a separator 13 having a relatively large area while having the same outer circumference as the outer circumference of the conventional MEA and the separator. Alternatively, the area of contact of hydrogen gas and air with respect to the active region 12a of the MEA 12 can be maximized, thereby increasing the power production per unit area of the active region 12a, and consequently further improving the performance of the fuel cell. You can.

4 is a schematic view for explaining a modification of the separator and the membrane-electrode assembly according to the embodiment of the present invention.

Referring to the drawings, in this case, the MEA 52 and the separator 53 are formed in an elliptical shape in which each vertex of the reference rectangle B is in contact with the inside of the concentric circle with respect to the reference rectangle B made of a rectangle. Can be configured.

In detail, the MEA 52 and the separator 53 have an outer circumference of the same length as that of the conventional separator corresponding to the reference rectangle B, and have a larger area than that of the conventional separator.

Therefore, according to the present modification, the MEA 52 and the separator 53 of elliptical shape having a relatively large area and having the same outer circumference as the outer circumference of the conventional MEA and the separator are provided. Since it is possible to maximize the contact area of the hydrogen gas and air to the active area of the, it is possible to improve the power production per unit area of the active area, as a result can further improve the performance of the fuel cell.

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.

As described above, according to the fuel cell system according to the present invention, unlike the prior art, as the shape of the MEA and the separator is improved, the diffusion performance of hydrogen gas and air with respect to the active area of the MEA and the contact area per unit area of the hydrogen gas and air By increasing the power consumption of the fuel cell (performance of the fuel cell) can be further improved.

Claims (18)

At least one electricity generating unit for generating electrical energy through the electrochemical reaction of hydrogen and oxygen, The electricity generating unit, It consists of a close contact structure by the membrane-electrode assembly (MEA) and the separator which is arrange | positioned on both surfaces of this membrane-electrode assembly, And the membrane-electrode assembly and the separator are configured such that each vertex of the reference rectangle is inscribed with respect to an arbitrary reference rectangle. The method of claim 1, Wherein each separator is in close contact with one surface of the membrane-electrode assembly to form a hydrogen passage, and is in close contact with the other surface to form an air passage. The method of claim 2, And the membrane-electrode assembly and the separator are circular when the reference rectangle is square. The method of claim 2, And the membrane-electrode assembly and the separator are elliptical when the reference rectangle is rectangular. The method according to claim 3 or 4, And a passage formed spirally on one surface of the separator. The method of claim 5, wherein And the separator penetrates through an inflow portion communicating with the start end of the passage and through an outlet portion communicating with the end of the passage. At least one electricity generating unit generating electrical energy through an electrochemical reaction between hydrogen and oxygen; A fuel supply source for supplying a fuel containing hydrogen to the electricity generating section; And An oxygen supply source for supplying oxygen to the electricity generator Including, The electricity generating unit, It consists of a close contact structure by the membrane-electrode assembly (MEA) and the separator which is arrange | positioned on both surfaces of this membrane-electrode assembly, And the membrane-electrode assembly and the separator are configured such that each vertex of the reference rectangle is inscribed with respect to an arbitrary reference rectangle. The method of claim 7, wherein The fuel supply source, A fuel tank for storing the fuel; And A fuel cell system comprising a fuel pump connected to the fuel tank and installed. The method of claim 8, The fuel supply source, And a reformer disposed between the fuel tank and the electricity generation unit to receive fuel from the fuel tank to generate hydrogen gas, and to supply the hydrogen gas to the electricity generation unit. The method of claim 7, wherein And the oxygen source includes at least one air pump that sucks air and supplies the air to the electricity generator. The method of claim 7, wherein And a plurality of electricity generating portions to form a stack having a stacked structure of the electricity generating portions. The method of claim 7, wherein Wherein each separator is in close contact with one surface of the membrane-electrode assembly to form a hydrogen passage, and is in close contact with the other surface to form an air passage. The method of claim 12, And the membrane-electrode assembly and the separator are circular when the reference rectangle is square. The method of claim 12, And the membrane-electrode assembly and the separator are elliptical when the reference rectangle is rectangular. The method according to claim 13 or 14, And the passage is spirally formed on one surface of the separator. The method of claim 15, And the separator penetrates through an inflow portion communicating with a start end of the passage and through an outlet portion communicating with an end of the passage. The method according to claim 7 or 9, The fuel cell system is a fuel cell system comprising a polymer electrolyte fuel cell (PEMFC) method. The method of claim 7, wherein The fuel cell system is a fuel cell system comprising a direct methanol fuel cell (DMFC) system.

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