KR20060059461A - Fuel cell system and stack of the same - Google Patents

Abstract

A fuel cell system according to the present invention includes a stack having an aggregate structure by a plurality of electricity generating units, a fuel supply source for supplying hydrogen to the electricity generation unit, an oxygen supply source for supplying oxygen to the electricity generation unit, and the electricity generation A heat carrier source for providing a heat carrier to the portion,

The stack forms a cooling passage for passing the heat carrier between neighboring electricity generating units, in which case the cooling passage is gradually heated from the injection side of the hydrogen and oxygen to the discharge side with respect to the electricity generation unit. It is a structure in which the flow area of a carrier becomes small gradually.

Fuel cell, stack, electricity generation, heat, cooling, fuel supply, oxygen supply, heat carrier, heat carrier supply, cooling passage

Description

FUEL CELL SYSTEM AND STACK OF THE SAME

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 showing a first embodiment of the stack shown in FIG.

3 is a cross-sectional view of the coupling cross-sectional view of FIG.

4 is a plan view showing the cooling passage of the separator shown in FIG.

5 is an exploded perspective view illustrating a second embodiment of the stack illustrated in FIG. 1.

FIG. 6 is a plan view illustrating the cooling passage of the cooling plate illustrated in FIG. 5.

The present invention relates to a fuel cell system and a stack thereof, and more particularly, to a fuel cell system and a stack thereof in which the cooling structure of the stack is improved.

As is known, a fuel cell is a power generation system that generates electrical energy through an electrochemical reaction of hydrogen and oxygen contained in a hydrocarbon-based material such as methanol, ethanol and natural gas.

Such a fuel cell system has a stack for substantially generating electricity. The stack consists of several to tens of cells in a continuous arrangement of units consisting of a membrane-electrode assembly (MEA) and a separator called a bipolar plate in the art. At this time, the separator forms a hydrogen passage and an oxygen passage for supplying hydrogen and oxygen required for the reaction of the fuel cell to the MEA.

In such a fuel cell system, heat of a predetermined temperature is generated by a reduction reaction of hydrogen and oxygen, so that the stack must be maintained at an appropriate driving temperature to ensure stability of the electrolyte membrane and prevent performance degradation. To this end, the stack has a cooling passage therein and cools heat generated in the stack by flowing a low temperature heat carrier such as air or cooling water through the cooling passage.

However, according to the conventional fuel cell system, when the stack is driven, hydrogen and oxygen are actively reacted in the MEA at the injection side rather than at the discharge side of the hydrogen passage and the oxygen passage. Temperature deviation occurs on the discharge side. In the cooling structure of the conventional fuel cell system, the cooling passage is formed such that the contact area per unit area of the heat carrier with respect to the heat generating portion of the stack is the same. As a result, the temperature variation of the entire stack as described above cannot be reduced, resulting in a decrease in cooling efficiency and performance of the stack.

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 and a stack having improved structure of a cooling passage for passing a heat carrier into the stack to improve the cooling efficiency and performance of the stack. There is.

The stack for a fuel cell system according to the present invention for achieving the above object is composed of a plurality of electricity generating unit for generating electrical energy through an electrochemical reaction of hydrogen and oxygen, between the neighboring electricity generating unit A cooling passage for passing the heat carrier is formed, and in this case, the cooling passage has a structure in which the flow area of the heat carrier gradually decreases from the injection portion side of the hydrogen and oxygen to the discharge portion side with respect to the electricity generating portion.

In the stack for a fuel cell system according to the present invention, the electricity generating unit is composed of a separator (Separator) in close contact with both sides of the membrane-electrode assembly (MEA) in the center, the upper side of the separator The injection part may be formed, and the discharge part may be formed at a lower side.

In addition, in the stack for a fuel cell system according to the present invention, the cooling passage may be formed in the separator. In this case, the cooling passage is formed in the form of a channel on one surface of the separator and the adjacent surface of the neighboring separator that is in close contact with the separator so that the two channels are combined to form one hole, and the separator is formed on the opposite side of the MEA.                     

In addition, the stack for a fuel cell system according to the present invention may include a cooling plate interposed between separators of the electricity generation unit adjacent to each other, and may form the cooling passage in the cooling plate.

In the stack for a fuel cell system according to the present invention, the cooling passage forms an inlet at one end and an outlet at the other end, the inlet is located on the inlet side of the separator and the outlet is the It is a structure located on the discharge part side of a separator. In this case, the cooling passage is preferably configured such that the flow path of the heat carrier gradually narrows from the inlet to the outlet.

In addition, the fuel cell system according to the present invention for achieving the above object, the stack consisting of the aggregate structure of a plurality of electricity generating unit, a fuel supply source for supplying hydrogen to the electricity generating unit, and oxygen to the electricity generating unit An oxygen source for supplying and a heat carrier source for providing a heat carrier to the electricity generating unit,

The stack forms a cooling passage for passing the heat carrier between neighboring electricity generating units, in which case the cooling passage is gradually heated from the injection side of the hydrogen and oxygen to the discharge side with respect to the electricity generation unit. It is a structure in which the flow area of a carrier becomes small gradually.

In the fuel cell system according to the present invention, it is preferable to use air as the heat carrier.                     

In addition, in the fuel cell system according to the present invention, the electricity generating unit is composed of a separator (Separator) arranged in close contact with both sides of the membrane-electrode assembly (MEA), the upper side of the separator An injection part may be formed, and the discharge part may be formed at a lower side.

In the fuel cell system according to the present invention, the cooling passage is formed in a channel shape on one surface of the separator and a contact surface of a neighboring separator that is in close contact with the separator so that the two channels are combined to form one hole. .

In addition, the fuel cell system according to the present invention may include a cooling plate interposed between the electricity generating units adjacent to each other, and may form the cooling passage in the cooling plate.

The fuel cell system according to the present invention has a structure in which the fuel supply source supplies hydrogen gas or the liquid fuel to the electricity generating unit.

Moreover, the fuel cell system which concerns on this invention is a structure which the said oxygen supply source supplies air to the said electricity generating part.

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 this drawing, the fuel cell system 100 according to the present invention is described. The fuel cell system 100 reforms a fuel containing hydrogen to generate hydrogen gas, and generates the hydrogen gas and the oxidant gas. A polymer electrolyte fuel cell (PEMFC) method that chemically reacts to generate electrical energy is employed.

In such a fuel cell system 100, a fuel for generating electricity generally refers to a fuel made of a liquid or gaseous state containing hydrogen such as methanol, ethanol or natural gas. However, the fuel described in this embodiment is defined as a fuel made of a liquid phase for convenience.

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

The fuel cell system 100 according to the embodiment of the present invention basically generates a fuel cell stack 16 for generating electrical energy through an electrochemical reaction between hydrogen and oxygen, and generates hydrogen gas from the above-described fuel. And a fuel supply source 10 for supplying this hydrogen gas to the stack 16, and an oxygen supply source 12 for supplying air to the stack 16.

The stack 16 is connected to a fuel supply source 10 and an oxygen supply source 12 to receive the hydrogen gas from the fuel supply source 10 and to receive air from the oxygen supply source 12 to supply hydrogen in the hydrogen gas. And a fuel cell that generates electrical energy by electrochemically reacting oxygen in the air.

The fuel supply source 10 includes a fuel tank 22 for storing fuel as described above, a fuel pump 24 for discharging fuel stored in the fuel tank 22 with a predetermined pumping force, and a fuel tank 22. And a reformer 18 receiving fuel from the fuel cell to generate hydrogen gas from the fuel and supplying the hydrogen gas to the stack 16.

The oxygen source 12 includes an air pump 26 of a conventional structure which sucks air with a predetermined pumping force and supplies this air to the stack 16.

Reformer 18 in the fuel source 10 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 other words, the reformer 18 generates hydrogen gas from the fuel through catalytic reaction such as steam reforming, partial oxidation, or autothermal reaction. The reformer 18 reduces the concentration of carbon monoxide contained in the hydrogen gas by a catalytic reaction such as a water gas conversion method, a selective oxidation method, or purification of hydrogen using a separator. The reformer 18 as described above may be made of a conventional reformer, so detailed description thereof will be omitted herein.

Alternatively, the fuel cell system 100 according to the present invention may employ a direct methanol fuel cell (DMFC) method capable of supplying the fuel directly to the stack 16 to produce electricity. have. Unlike the polymer electrolyte fuel cell as described above, the direct methanol type fuel cell includes a fuel tank 22 and a fuel pump 24 in the fuel supply source 10, and requires a reformer 18. I never do that. Hereinafter, the fuel cell system 100 employing the polymer electrolyte fuel cell method will be described as an example. However, the present invention is not necessarily limited thereto.

When the fuel cell system 100 according to the present invention configured as described above is supplied with hydrogen gas generated through the reformer 18 and air sucked by the air pump 26 to the stack 16, Stack 16 generates electrical energy through an electrochemical reaction of hydrogen in hydrogen gas and oxygen contained in air.

Embodiments constituting the stack 16 in the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is an exploded perspective view illustrating a first embodiment of the stack illustrated in FIG. 1, and FIG. 3 is a cross-sectional configuration diagram of FIG. 2.

Referring to the stack 16 with reference to this figure, the stack 16 applied to the present system 100 is a membrane-electrode assembly (MEA) (hereinafter referred to as 'MEA') 32 ) And a separator (also referred to in the art as a 'bipolar plate') 34 on both sides thereof to include a minimum generation of electricity generation unit 30 for generating electricity. Therefore, the stack 16, which is an aggregate structure of the electricity generating unit 30 according to the present embodiment, may be formed by providing a plurality of the above-described electricity generating units 30 and closely arranging them.                     

The MEA 32 has a structure in which an anode electrode is positioned on one surface and a cathode electrode (not shown) is positioned on the other surface, and an electrolyte membrane (not shown) is provided between the two electrodes. The anode electrode functions to oxidize hydrogen gas to convert hydrogen into hydrogen ions (protons) and electrons. The cathode electrode has a function of reducing and reacting oxygen in air and hydrogen ions transferred 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 34 are arranged in close contact with each other with the MEA 32 interposed therebetween, so that the hydrogen gas supplied from the reformer 18 (FIG. 1) and the air supplied by the air pump 26 (FIG. 1) are supplied to the MEA 32. In addition to the function of supplying the anode electrode and the cathode electrode of the to serve as a conductor that connects the anode electrode and the cathode electrode in series. In this case, the separator 34 may be disposed such that the surface opposite to the surface in close contact with the MEA 32 is in close contact with the surface opposite to the MEA 32 in the separator 34 of the neighboring electricity generating unit 30. In addition, each separator 34 includes a hydrogen passage 36 for supplying hydrogen gas to the anode electrode of the MEA 32 and an air passage 38 for supplying air to the cathode electrode of the MEA 32. Forming. Each separator 34 includes an injection section 39a for injecting hydrogen gas and air into the hydrogen passage 36 and the air passage 38, and the MEA 32 while passing through the passages 36 and 38. ), A discharge portion 39b for discharging the remaining hydrogen gas and air is formed. In this case, considering that the hydrogen gas and air flow in the gravity direction through the hydrogen passage 36 and the air passage 38, the injection portion 39a is formed above the separator 34, and the discharge is performed. It is preferable that the part 39b is formed below the separator 34.

During the operation of the fuel cell system 100 configured as described above, heat is generated in the electricity generating unit 30 of the entire stack 16 by the reduction reaction of hydrogen and oxygen as described above. This heat acts as a factor to deteriorate the performance of the stack 16 by drying the MEA 32.

Accordingly, the fuel cell system 100 according to the exemplary embodiment of the present invention has a structure in which the heat carrier is circulated into the stack 16 to cool the heat generated by the electricity generator 30.

To this end, the system 100 flows the heat carrier source 14 for supplying the heat carrier into the stack 16 and the heat carrier supplied from the heat carrier source 14 to the electricity generator 30. It is provided with a cooling passage 41 formed between the electricity generating unit 30 adjacent to each other to give.

The heat carrier supply source 14 has a structure which sucks a heat carrier and supplies this heat carrier to the electricity generation part 30. In the present invention, the heat carrier may be a coolant in a liquid state, but more preferably in a gaseous state. Thus, air which is easily taken in its natural state and lower than the temperature inside the stack 16 during operation can be used as the heat carrier. Accordingly, the heat carrier supply source 14 includes a fan 28 that sucks air at a predetermined rotational force and supplies the air to the electricity generator 30. At this time, the fan 28 is preferably installed in the housing 17 surrounding the entire stack 16, as shown in phantom line in Figure 3 to eject air to the entire stack (16).

In addition, the cooling passage 41 may be formed by channels 41a respectively formed on the contact surfaces of the separators 34, which are in close contact with each other with respect to neighboring electricity generating units 30. At this time, the channel 41a is opposite to the surface of the separator 34 that is in close contact with the MEA 32 of the separator 34 and the neighboring electricity generator that is in close contact with the separator 34. 30 may be formed on the contact surface of the separator 34. Therefore, in the process in which the separator 34 of one electricity generation unit 30 and the separator 34 of the other electricity generation unit 30 adjacent to the electricity generation unit 30 are in close contact with each other. By combining the channels 41a, the cooling passage 41 according to the present exemplary embodiment may be formed. The cooling passage 41 formed in this way is formed on the opposite side of the MEA 32 of the separator 34 and has excellent cooling performance since it cools over the entire area of the MEA 32, that is, the active area and the inactive area.

4 is a plan view showing the cooling passage of the separator shown in FIG.

2 and 4, the cooling passage 41 according to the present embodiment is based on the injection portion 39a and the discharge portion 39b of the separator 34 with respect to the entire stack 16. A plurality of portions are formed in the direction toward the discharge portion 39b in the portion 39a, and the flow cross-sectional area of the heat carrier gradually decreases in the direction described above.

The cooling passage 41 is configured to inject the heat carrier through one end and to discharge the heat carrier through the other end. That is, the cooling passage 41 forms a plurality of inlets 41b for injecting the heat carrier into one edge side of the separator 34 in close contact with each other, and the other edge side corresponding to the edge side. A plurality of outlets 41c for discharging the heat carrier are formed in the chamber. At this time, the inlet (41b) is preferably located on the injection portion (39a) side of the separator 34, the outlet (41c) is preferably located on the discharge portion (39b) side of the separator 34. Therefore, in the cooling passage 41 according to the present embodiment, the cross-sectional area of the inlet 41b is larger than the cross-sectional area of the outlet 41c, and the flow path of the heat carrier gradually narrows from the inlet 41b to the outlet 41c. In the form of

The reason why the cooling passage 41 is formed in the above structure is that the oxidation / reduction reaction of hydrogen and oxygen is actively performed at the injection portion 39a side of the separator 34 when the stack 16 is driven. As a result, a temperature deviation occurs at the injection portion 39a side and the discharge portion 39b side of the separator 34 with respect to the entire stack 16, and thus the injection portion 39a side and the discharge portion 39b of the separator 34. This is to change the contact area per unit area of the heat carrier with respect to the side) to maintain the temperature distribution of the entire stack 16 uniformly.

Looking at the operation of the fuel cell system 100 according to the present invention configured as described above, during the generation of electricity through the stack 16, the heat generated in the electricity generating unit 30 by the reduction reaction of hydrogen and oxygen. Will occur. At this time, since the stack 16 is active in the oxidation / reduction reaction of hydrogen and oxygen at the injection portion 39a side of the separator 34, the injection portion of the separator 34 with respect to the entire stack 16 ( The temperature deviation occurs at the 39a) side and the discharge part 39b side.

In this state, when the heat carrier flows through the heat carrier source 14 to the cooling passage 41 according to the present embodiment, the heat carrier cools the heat while passing through the cooling passage 41.

At this time, the cooling passage 41 according to the present embodiment has a form in which the flow path of the heat carrier gradually narrows from the inlet 41b to the outlet 41c, so that the separator ( The substantial contact area between the heat carrier and the separator 34 passing through the injection portion 39a side of the 34 increases, and passes through the discharge portion 39b side of the separator 34 through the cooling passage 41. Substantial contact area for the heat carrier and separator 34 discharged through the outlet 41c is reduced.

Therefore, according to the fuel cell system 100 according to the present invention, the heat exchange amount per unit time for the heat carrier and the heat energy generated at the injection portion 39a side of the separator 34 with respect to the entire stack 16 is maximized. In addition, by reducing the amount of heat exchanged per unit time for the heat carrier and the heat energy generated at the injection portion 39b side of the separator 34, the temperature distribution of the entire stack 16 can be maintained uniform.

FIG. 5 is an exploded perspective view illustrating a second embodiment of the stack illustrated in FIG. 1, and FIG. 6 is a plan view illustrating a cooling passage of the cooling plate illustrated in FIG. 5.

Referring to the drawings, in the stack 16A according to the present embodiment, a cooling plate 43 is provided between the separators 34A of neighboring electricity generating units 30A, and a heat carrier is attached to the cooling plate 43. It is structured to form a cooling passage 45 for circulating. The cooling plate 43 functions as a heat sink for dissipating heat transferred to the separator 34A when electricity is generated by the electricity generating unit 30A. The cooling plate 43 may be formed of aluminum, copper, iron, or the like having thermal conductivity. In addition, the cooling passage 45 may be formed to penetrate from one edge side to the other edge side of the cooling plate 43 corresponding to each other for smooth distribution of the heat carrier to the entire stack 16A.

Specifically, the cooling passage 45 forms a plurality of inlets 45a for injecting heat carriers into the upper edges of the cooling plate 43 and discharges the heat carriers to the lower edges corresponding thereto. A plurality of outlets 45b are formed to make them easy. As in the previous embodiment, the inlet 45a of the cooling passage 45 is located on the inlet 39a side of the separator 34A relative to the entire stack 16A, and the outlet 45b is the outlet of the separator 34A. It is located in the part 39b side. The cooling passage 45 has a cross-sectional area of the inlet 45a that is larger than the cross-sectional area of the outlet 45b, and the flow path of the heat carrier gradually narrows from the inlet 45a to the outlet 45b, as in the electric embodiment. Taking shape.

Since the rest of the configuration and operation of the stack 16A according to the present embodiment are the same as in the above embodiment, detailed description thereof will be omitted.

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.

According to the fuel cell system according to the present invention, by forming a cooling passage configured to change the contact area of the heat carrier with respect to the separator, it is possible to further improve the cooling efficiency and performance of the stack by reducing the temperature variation of the entire stack.

Claims (16)

A stack for a fuel cell system comprising a plurality of electricity generating units for generating electrical energy through an electrochemical reaction between hydrogen and oxygen, Forming a cooling passage for passing the heat carrier between the neighboring electricity generating units, The cooling passage is a stack for a fuel cell system in which the flow area of the heat carrier gradually decreases from the injection side of hydrogen and oxygen to the discharge side with respect to the electricity generating portion. The method of claim 1, The electricity generating unit is composed of a separator (Separator) in close contact with both sides of the membrane-electrode assembly (MEA) in the center, And an injection portion formed above the separator and the discharge portion formed below the separator. The method of claim 2, And a stack for forming the cooling passage in the separator. The method of claim 3, wherein The cooling passage is a stack for a fuel cell system formed in the form of a channel on the contact surface of the separator and the neighboring separator that is in close contact with the separator, the two channels are combined to form one hole. The method of claim 4, wherein And the cooling passage is formed on the side opposite to the MEA of the separator. The method of claim 2, And a cooling plate interposed between the separators adjacent to each other, wherein the cooling passage is formed on the cooling plate. The method according to claim 4 or 6, The cooling passage forms an inlet at one end and an outlet at the other end, And the inlet is located at the inlet side of the separator and the outlet is at the outlet side of the separator. The method of claim 7, wherein And the cooling passage is configured such that a flow path of the heat carrier gradually narrows from the inlet to the outlet. A stack having an aggregate structure by a plurality of electricity generating units; A fuel supply source for supplying hydrogen to the electricity generator; An oxygen supply source for supplying oxygen to the electricity generator; And A heat carrier source for providing a heat carrier to the electricity generator Including; The stack forms a cooling passage for passing the heat carrier between neighboring electricity generating units, And the cooling passage is configured such that the flow area of the heat carrier gradually decreases from the injection side of hydrogen and oxygen to the discharge side with respect to the electricity generation unit. The method of claim 9, And the heat carrier is air. The method of claim 9, The electricity generating unit is composed of a separator (Separator) in close contact with both sides of the membrane-electrode assembly (MEA) in the center, And an injection portion formed above the separator, and a discharge portion formed below the separator. The method of claim 11, And the cooling passage is formed in a channel shape on one surface of the separator and a contact surface of a neighboring separator that is in close contact with the separator, and the two channels are combined to form one hole. The method of claim 9, And a cooling plate interposed between the electricity generating units adjacent to each other, and forming the cooling passage in the cooling plate. The method of claim 9, And a fuel supply system supplying hydrogen gas to the electricity generating unit. The method of claim 9, And the fuel supply source supplies liquid fuel to the electricity generator. The method of claim 9, And a fuel supply system configured to supply air to the electricity generator.

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