This application claims the benefit of Korean Patent Application No. 10-2008-0066352, filed with the Korean Intellectual Property Office on Jul. 9, 2008, the disclosure of which is incorporated herein by reference in its entirety.
1. Technical Field
The present invention relates to a stack and a fuel cell power generation system having the same.
2. Description of the Related Art
The fuel cell power generation system is a system for generating electricity by electrochemically reacting a hydrogen-containing fuel, such as methanol, etc., with an oxidizing gas, such as air, etc. The fuel cell power generation system is regarded as a clean energy source for satisfying the increasing demand for power consumption while providing a solution to environmental problems resulting from the use of fossil energy.
The fuel cell power generation system generally includes a fuel cell stack, in which a multiple number of unit cells for generating electricity are stacked over one another. The basic structure of the stack includes multiple unit cells stacked between end plates and fastened together with bolts and nuts. A unit cell may be composed of a membrane electrode assembly (MEA) having a fuel electrode and an air electrode attached to either side of an electrolyte membrane and separators, i.e., bipolar plates, which are positioned on either side of the membrane electrode assembly and in which fluid channels are formed.
The bipolar plate operates to supply the hydrogen-containing fuel and oxygen to the fuel electrode and air electrode, respectively, and discharge the carbon dioxide and water generated at the fuel electrode and air electrode, respectively, to the outside.
Here, current collectors are provided, for collecting the electricity generated by the membrane electrode assembly, between the bipolar plates positioned at the outermost ends of the group of unit cells (hereinafter referred to as “outermost bipolar plates”) and the end plates. A current collector not only collects the electricity but also provides reinforcement against the brittleness of the outermost bipolar plates when fastening the bolts and nuts.
Recently, a flexible type of the current collector has been used. In this case, the flexible type may be more easily deformed than a rigid type, causing a problem of reliability in the attachment of the stacking structure of the stack.
The present invention provides a reliable stack and a fuel cell power generation system equipped with the stack by forming a firmly stacking structure using a current collector having an adhesive layer.
An aspect of the present invention provides a stack. In accordance with an embodiment of the present invention, the stack, which generates electrical energy by reacting hydrogen with oxygen and in which the hydrogen is supplied as a fuel and the oxygen is in the air, includes: a membrane electrode assembly (MEA), which includes an electrolyte membrane and a pair of electrodes coupled to either surface of the electrolyte membrane; and a pair of current collectors, which is formed on either surface of the membrane electrode assembly, in which the current collector includes: an insulating polymer film; and a conductive adhesive layer, which is interposed between the insulating polymer film and the membrane electrode assembly.
The conductive adhesive layer can include an adhesive epoxy and at least one of metal powder and metal wire. The polymer film can be made of a flexible material.
The current collector can further include a metal pad, which is interposed between the polymer film and the conductive adhesive layer, and the metal pad can be made of a material comprising gold (Au).
The electrode can be constituted by a plurality of unit electrodes, and the metal pad can be constituted by a plurality of unit pads in accordance with a shape of the unit electrode. Each of the unit pads can have a terminal formed thereon, in which the terminal is protruded outward from the current collector.
The current collector can include a plurality of apertures formed thereon, and a pair of end plates can be formed on the outside of the current collector.
The end plate of a side from which the fuel is supplied has a slit formed thereon in a shape of serpentine, and an aperture of the current collector of a side to which the fuel is supplied can be shaped to correspond to the slit.
The end plate of a side to which the air is supplied can have a hole for air flow formed thereon, and an aperture of the current collector of a side to which the air is supplied can be shaped to correspond to the hole. The hole can be rectangular and occupy 65% of the total area of the electrode.
The stack can further include a gasket, which is interposed between the current collector and the membrane electrode assembly and seals a gap between the current collector and the membrane electrode assembly.
Another aspect of the present invention provides a fuel cell power generation system. The fuel cell power generation system in accordance with an embodiment of the present invention includes: a fuel cell stack, which generates electrical energy by reacting hydrogen with oxygen and in which the hydrogen is supplied as fuel and the oxygen is in the air; a fuel supplying unit, which supplies a fuel to the fuel cell stack and in which the fuel contains hydrogen; and an air supplying unit, which supplies air to the fuel cell stack, in which the fuel cell stack includes: a membrane electrode assembly (MEA), which includes an electrolyte membrane and a pair of electrodes coupled to either surface of the electrolyte membrane; and a pair of current collectors, formed on either surface of the membrane electrode assembly, and in which the current collector includes: an insulating polymer film; and a conductive adhesive layer, which is interposed between the polymer film and the membrane electrode assembly.
The conductive adhesive layer can include an adhesive epoxy and at least one of metal powder and metal wire. The polymer film can be made of a flexible material.
The current collector can further include a metal pad, which is interposed between the polymer film and the conductive adhesive layer, and the metal pad can be made of a material comprising gold (Au).
The electrode can be constituted by a plurality of unit electrodes, and the metal pad can be constituted by a plurality of unit pads in accordance with a shape of the unit electrode. Each of the unit pads can have a terminal formed thereon, in which the terminal is protruded outward from the current collector.
The current collector can include a plurality of apertures formed thereon, and a pair of end plates can be formed on the outside of the current collector.
The end plate of a side from which the fuel is supplied has a slit formed thereon in a shape of serpentine, and an aperture of the current collector of a side to which the fuel is supplied can be shaped to correspond to the slit.
The end plate of a side to which the air is supplied can have a hole for air flow formed thereon, and an aperture of the current collector of a side to which the air is supplied can be shaped to correspond to the hole. The hole can be rectangular and occupy 65% of the total area of the electrode.
The fuel cell power generation system can further include a gasket, which is interposed between the current collector and the membrane electrode assembly and seals a gap between the current collector and the membrane electrode assembly.
Additional aspects and advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the present invention are encompassed in the present invention. In the description of the present invention, certain detailed explanations of related art are omitted when it is deemed that they may unnecessarily obscure the essence of the invention.
The terms used in the present specification are merely used to describe particular embodiments, and are not intended to limit the present invention. An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. In the present specification, it is to be understood that the terms such as “including” or “having,” etc., are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, numbers, steps, actions, components, parts, or combinations thereof may exist or may be added.
A stack and a fuel cell power generation system equipped with the stack according to certain embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. Those components that are the same or are in correspondence are rendered the same reference numeral regardless of the figure number, and redundant explanations are omitted.
The gasket 20, the current collectors 30 and 40 and the end plates 50 and 60 are successively placed on both sides of the membrane electrode assembly 10 from the center to the outside. The membrane electrode assembly 10 is practically for generating electricity by using fuel, and the gasket 20 is for preventing the leakage of fuel and air. The current collectors 30 and 40 are for accumulating the electricity generated from the membrane electrode assembly 10. The end plates 50 and 60, which are positioned on either side of the stack 100, complete the stacking structure of the stack 100 by compressing the stack 100 from the outermost edge of the stacking structure. Detailed descriptions about each component will be described with reference to
Hereinafter, the reactions at each electrode will be described with an example of a polymer electrolyte membrane fuel cell (PEMFC) using hydrogen as fuel.
[Reaction Scheme 1] Fuel electrode: H2→2H++2e−
[Reaction Scheme 2] Air electrode: (½)O2+2H++2e−→H2O
[Reaction Scheme 3] Overall Reaction: H2+(½)O2→H2O
Through these reactions, electricity is generated, and water is generated at the air electrode. As described above, the above reactions occur only if the polymer electrolyte membrane fuel cell (PEMFC) using hydrogen as fuel is used, and it shall be obvious that the reactions at each electrode can be varied, depending on the type of a fuel cell.
The electrode can be constituted by a fuel electrode and an air electrode, which are separated by the electrolyte membrane 12, but, as illustrated in
Next,
The current collectors 30 and 40 are devices that accumulate electrical energy generated from the membrane electrode assembly (10 in
As illustrated in
The polymer film 32 can be made of a flexible material, which is polymer resin, for example, polyimide, and has a good chemical resistance and relatively high heat resistance.
The conductive adhesive layer 36 can be formed by coating a conductive adhesive, in which an adhesive epoxy is mixed with metal powder or metal wire. The metal powder and the metal wire can be made of a material including nickel (Ni) and silver (Ag) and mixed with the epoxy in various ratios, depending on the adhesion and electrical conductivity.
Although the conductive adhesive layer 36 itself conducts electricity and functions as the current collectors 30 and 40, as illustrated in
The metal pad 34 can be formed by coating a highly electrical conductive material, for example, gold (Au). The metal pad 34 can be constituted by a plurality of unit pads 31 and 41, as illustrated in the drawings. Each of the unit pads 31 and 41 is divided by the insulating polymer film 32.
The terminals 35 and 45, which are for connecting the unit pads 31 and 41, can be protruded outward from the current collectors 30 and 40. By stacking the current collector 30 adjacent to the air electrode and the current collector 40 adjacent to the fuel electrode on the membrane electrode assembly (10 in
The current collector 30 adjacent to the air electrode can have the aperture 38 formed thereon such that air can be supplied to the membrane electrode assembly (10 in
The current collector 40 adjacent to the fuel electrode can have the aperture 48 form thereon such that hydrogen as fuel can be supplied to the membrane electrode assembly (10 in
Next, referring to
The role of the end plates 50 and 60 is to compress the stacking structure of the stack with appropriate pressure from the outermost edge of the stacking structure. Accordingly, a rigid end plate is required, and an insulation treatment is needed for the end plates to prevent electrical short circuits. As a result, the end plates 50 and 60 can be made of a light material such as aluminum (Al), and an oxide film or a Teflon coating can be formed on the end plates in order to prevent short circuits.
Illustrated in
In the case of the flat type stacking structure, however, oxygen in the air can be supplied through the hole 58 by forming the hole 58 on the stacking structure. Since the hole 58 is for supplying oxygen in the air to the air electrode, the hole has to be properly shaped with an appropriate opening ratio. The opening ratio means the relationship between the size of the hole 58 and the size of the air electrode (16 in
Referring to
The aperture (38 in
Referring to
Since fuel travels along the slit 68, the aperture (48 in
Next,
Each stacking structure of the stack in accordance with an embodiment of the present invention has been described with reference to
By using the stack described above, a fuel cell power generation system equipped with the stack can be presented.
The fuel supplying unit 200 is for supplying hydrogen as fuel of the fuel cell. Here, hydrogen can be supplied directly by using a hydrogen tank, or the fuel supplying unit 200 itself can be a hydrogen generator to generate and supply hydrogen. The hydrogen generator includes an electrode and an electrolyte aqueous solution, which have different ionization tendency, and generates hydrogen from water by using electrons generated through the oxidization reaction of metal.
The air supplying unit 300 is for supplying oxygen to the fuel cell, and thus an air pump can be used to inject air into the stack. Nevertheless, since oxygen can be supplied without an additional air supply device, i.e., the air pump, in the present embodiment, the air pump can be omitted. The structure of the stack 100 being used in the fuel cell power generation system are substantially the same as that of the stack described above, and thus redundant descriptions will be omitted.
While the spirit of the invention has been described in detail with reference to certain embodiments, the embodiments are for illustrative purposes only and shall not limit the invention. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the invention. As such, many embodiments other than those set forth above can be found in the appended claims.
Number | Date | Country | Kind |
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10-2008-0066352 | Jul 2008 | KR | national |