WO2000002281A2 - Systeme de refroidissement interne destine a une pile a combustible a ensemble d'electrodes membranes ondulees - Google Patents

Systeme de refroidissement interne destine a une pile a combustible a ensemble d'electrodes membranes ondulees Download PDF

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Publication number
WO2000002281A2
WO2000002281A2 PCT/GB1999/002072 GB9902072W WO0002281A2 WO 2000002281 A2 WO2000002281 A2 WO 2000002281A2 GB 9902072 W GB9902072 W GB 9902072W WO 0002281 A2 WO0002281 A2 WO 0002281A2
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Prior art keywords
fuel cell
layer
mea
hydrogen
separator
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PCT/GB1999/002072
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English (en)
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WO2000002281A3 (fr
Inventor
Gerard Francis Mclean
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Ballard Power Systems Inc.
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Application filed by Ballard Power Systems Inc. filed Critical Ballard Power Systems Inc.
Priority to AU45262/99A priority Critical patent/AU4526299A/en
Publication of WO2000002281A2 publication Critical patent/WO2000002281A2/fr
Publication of WO2000002281A3 publication Critical patent/WO2000002281A3/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0204—Non-porous and characterised by the material
    • H01M8/0221—Organic resins; Organic polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0204—Non-porous and characterised by the material
    • H01M8/0223—Composites
    • H01M8/0228—Composites in the form of layered or coated products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0247—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the form
    • H01M8/0254—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the form corrugated or undulated
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
    • H01M8/0263—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant having meandering or serpentine paths
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0267—Collectors; Separators, e.g. bipolar separators; Interconnectors having heating or cooling means, e.g. heaters or coolant flow channels
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • H01M8/04067—Heat exchange or temperature measuring elements, thermal insulation, e.g. heat pipes, heat pumps, fins
    • H01M8/04074—Heat exchange unit structures specially adapted for fuel cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/2457—Grouping of fuel cells, e.g. stacking of fuel cells with both reactants being gaseous or vaporised
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/2465—Details of groupings of fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/2465—Details of groupings of fuel cells
    • H01M8/2483—Details of groupings of fuel cells characterised by internal manifolds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0082—Organic polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • This invention relates to the cooling of fuel cell stacks, particularly proton exchange membrane (PEM)-type fuel cell stacks employing an undulate membrane electrode assembly (MEA) .
  • PEM proton exchange membrane
  • MEA undulate membrane electrode assembly
  • heat-conductive cooling plates are interspersed with fuel cell strata in order to conduct heat from the stack to a coolant, such as water, flowing therethrough.
  • the coolant plates have a coolant flow field extending over at least one of their surfaces; the flow field entrance and exit ports are connected to supply and sink plena for the coolant.
  • the fuel cell strata in the stack are provided with aligned apertures that, in the stack dimension, constitute plena for the supply of coolant fluid to the stack and exhaust of heated effluent coolant from the stack. Heat is removed from the fuel cells to the cooling plates and thence to the coolant as it flows past the cooling plates, thereby cooling the stack. Ballard U.S.
  • Patent No. 5,230,966 (Voss) issued 27 July 1993 illustrates a typical cooling arrangement for a PEM-type fuel cell stack.
  • the cooling plates are interspersed in the stack in the ratio of approximately one cooling plate for every three to five fuel cells in the stack. This inclusion of a cooling plate in the stack of course contributes appreciably to the stack dimensions, increasing the overall stack volume and weight by an amount depending upon the size and mass of the cooling plate.
  • fuel cell stacks of this type are intended for use in vehicles and other mobile applications, it is desirable to keep bulk and weight of fuel cell stacks to a minimum. Since the use of such coolant plates contributes to both bulk and weight of the fuel cell stack in an undesirable manner, it would be desirable to eliminate the coolant plates.
  • the coolant is manifolded in a manner similar to the manner of manifolding reactant gases to the stack.
  • the requirement for coolant flow in plena extending in the stack dimension through the stack necessitates that the fuel cell membrane electrode assembly (MEA) layers in the stack be punctured to provide the necessary aperture for the flow of coolant therethrough. Puncturing of the MEA of the stack is inherently undesirable; for example, it complicates the manufacturing process and risks damage to the MEA layers.
  • Breault U.S. Patent 4,233,369, issued 11 November 1980, describes a cooler assembly for use between consecutive cells in a fuel cell stack that comprises a fibrous gas porous holder layer sandwiched between and bonded to a pair of gas impervious graphite plates.
  • the fibrous gas porous holder layer has coolant tubes passing therethrough within channels in the layer.
  • the channels have substantially the same depth as the holder layer thickness and as the outer diameter of the tubes.
  • Breault ' s design does not appreciably reduce the volume required by the cooling components of the stack, and thus does not appreciably contribute to the efficient use of space within the fuel cell stack.
  • Grevstad U.S. Patent 3,969,145, issued 13 July 1976, describes a cooler comprising a number of cooler tubes located in the separator plates between fuel cells in a stack. In the Grevstad configuration, a separate sealed piping structure is inserted into grooves cut into separator plates.
  • the Grevstad design is similar to that of Voss, mentioned previously, except that instead of forming coolant flow channels directly within separator plates as Voss discloses, Grevstad instead inserts a separately formed coolant conduit into the separator plate grooves. As best seen in Figure 2 of the Grevstad patent, this prior design does not alter the manner in which the reactant gas flow channel walls contact the electrode layers relative to conventional structures. Indeed, Grevstad pays little or no attention to the resulting coolant flow field deriving from his cooling arrangement.
  • McElroy U.S. Patent 4,678,724, issued 7 July 1987, discloses internally cooled bipolar separator plates within a fuel cell stack.
  • the cooling structure proposed by McElroy is in addition to the reactant gas flow path arrangements and does not attempt, in conjunction with the flow paths, to minimize the overall volume required.
  • Reiser U.S. Patent 3,964,930, issued 22 June 1976, discloses tubes for carrying coolant through a fuel cell stack.
  • the tubes are located in tubes or passageways formed in the separator plates.
  • Reiser's coolant conduit structure does not occupy its own plane within the fuel cell stack, but is coplanar with one of the reactant gas flow fields. As illustrated in Figure 3 of the Reiser patent, the cooling conduits lie in direct contact with the adjacent electrode layer.
  • Reiser's coolant tubes are electrically insulated from the rest of the fuel cell structure, and thus are not useful to carry electric current between adjacent fuel cells.
  • Chan, U.S. Patent 5,804,326 discloses a structure in which coolant and reactant gases flow in the same plane within a separator plate.
  • the coolant flow is segmented into a different region than the reactant gas flow, however, and is isolated to the perimeter of the cell. This is done to provide cooling of the seals used in the stack.
  • the cooling facility is integrated into the bipolar separator, it consumes space that is not used (and is not disclosed by the patentee to be available to be used) for any fuel cell function other than cooling.
  • Katsunori Japanese published patent specification 3- 89467 filed 31 August 1989 discloses a design for a molten carbonate fuel cell in which a connected set of coolant- carrying jackets is inserted between an eletrode layer and a current collecting layer, interspersed with the reactant gas flowfield.
  • the coolant jackets consume the full height of the flow region and thus displace the functions of either current collection or gas distribution.
  • the insertion of the cooling jackets next to the electrode layers renders certain portions of the electrode surface ineffective. Overall, the design does not offer significant volume reduction.
  • Horioka Japanese published patent specification 6- 260190 filed 1 March, 1993 presents a design for concurrent cooling and humidification of a PEM fuel cell by inserting porous coolant carrying conduits within the reactant gas distribution channels. No means of manufacturing the proposed cell are disclosed, nor is there any discussion of the effect of the coolant/humidification channel on the overall performance of the cell. Improving the volumetric power density of the stack through the improved utilization of space within the stack does not appear to be an objective of the invention.
  • a fuel cell stack to which the present invention relates comprises a series of fuel cells in which reactant flowfields are provided between an undulate membrane electrode assembly (MEA) layer and separator layers of each fuel cell.
  • the flowfield comprises, for each reactant gas, a number of parallel flow channels formed implicitly by the association of the undulate MEA layer with a separator layer, which flow channels are interconnected via an internal or external manifolding arrangement to form a flowpath for each reactant gas that involves more than one pass along the length of the cell.
  • the flowpath is serpentine, comprising an array of longitudinally extending parallel flow channels suitably interconnected to form a serpentine path.
  • the MEA layers are formed in opposed pairs between which separator plates are located, generating a stacked series of symmetrical arrays of separator plates and MEA layers.
  • Explicitly formed internal coolant conduits are provided that lie in the plane of or nearly in the plane of at least some of the separator layers (enough conduits are provided for cooling of the stack) .
  • the coolant conduits extend adjacent and parallel to the reactant gas flow channels and preferably are well spaced away from the MEA layers, so that flow of reactant gas to MEA layers is not impeded. Cooling of the stack is obtained by flow of coolant through the internal coolant conduits thus provided, and without the need of any special cooling plates.
  • Such coolant conduits may be provided in association with one or both of the reactant gas flow fields for each fuel cell, depending upon the configuration and the cooling needs of the stack. It is contemplated that at least one set of such coolant conduits will be provided for each fuel cell within a stack, although depending upon stack geometry, some stacks may be adequately cooled with fewer sets of coolant conduits .
  • the reactant gas flow channels formed in fuel cell strata within a fuel cell stack are not optimally utilized throughout the cross-section of the flow channels for their primary purpose, viz to supply reactant gas to the adjacent porous electrode layers of the MEA strata in the stack.
  • Those portions of the flow-channel cross-section that are nearest to the porous electrode layer are most effective in enabling reactant gas to reach and penetrate the porous electrode layer.
  • those portions of the flow channel more remote from the MEA layer are relatively inefficient for transferring reactant gas to the porous electrode layer. From this insight, the inventor has recognized that such inefficient portion of the flow channel could instead be utilized for the provision of a coolant conduit that would follow at least a portion of such flow channel, and would provide individual cooling for the fuel cell in which it is located.
  • coolant conduits may be more favourably located within a fuel cell stack than are conventional coolant conduits, and may be conveniently and economically located within or between other layers in a fuel cell stack so as to eliminate the need for separate cooling plates.
  • This invention achieves the function of providing cooling without the disadvantage of thereby increasing the volume of the stack. An increase in stack volume is avoided by using space within the stack for cooling that was previously under-utilized for its intended function of delivering reactant gases.
  • coolant conduits may be formed within a composite separator stratum or adjoining successive portions of a composite separator stratum in the fuel cell stack, thereby providing continuity of the separator stratum.
  • the inventor has recognized that given the possibility of altering flow-channel cross-section (given flow channels of conventional size) without unduly impeding reactant transfer to the porous one of the electrode layer adjacent, it is possible to reconfigure the internal structure of fuel cells so as to provide suitable coolant conduits in convenient spaces within or between fuel cell strata. Further, because the fuel cells may each provide (or share in the provision of) integrated internal cooling arrangements according to the invention, the provision in the stack of separate special-purpose cooling plates can be completely eliminated, and fuel cell stack dimensions and weight can be correspondingly reduced, thereby improving the overall power density of the fuel cell stack.
  • the separator strata in the fuel cell stack may advantageously be designed to perform not only their primary conventional separation function but also, in combination with the coolant conduits, an auxiliary cooling function.
  • the auxiliary cooling function may be implemented within or between the separator strata while maintaining the overall thin dimensions of the separator for stacking efficiency.
  • undulate MEA fuel cell stack configurations comprise extended parallel reactant gas conduits that are space-efficient and economical to manufacture.
  • Such configurations lend themselves to end connection or coupling to supply and exhaust plena for the reactant gases.
  • Coolant conduits according to the present invention could be coupled to inlet and outlet coolant plena respectively located at the ends of the coolant conduits. With such configurations, the risk of puncturing MEA layers is low, thus lowering the risk of damage or contamination and also obviating the special sealing problems associated with conventional PEM-type fuel cell stacks .
  • cooling conduits of the present invention are easily isolated from the electrochemical activity of the fuel cell stack, and consequently may carry readily ionizable cooling fluids such as antifreeze, technically and economically superior cooling is possible without undue risk of contamination of, or electrochemical interaction with, the vital active components of the fuel cell stack.
  • present conventional designs frequently require the use of such fluids as de-ionized water for use as the coolant in order to avoid creating unwanted conductive paths within the stack, and so as to avoid damage to membranes and catalysts.
  • Each fuel cell has an MEA layer and two discrete associated reactant-gas impermeable separator layers.
  • the MEA layer has a porous anode electrode, a porous cathode electrode, an electrolytic membrane layer disposed between the two electrodes, an anode electro-catalyst layer disposed between the electrolytic membrane layer and the anode electrode, and a cathode electro-catalyst layer disposed between the electrolytic membrane layer and the cathode electrode.
  • One side of one separator layer in conjunction with the MEA layer provides at least one flowpath of a flow field for hydrogen and one side of the other separator layer in conjunction with the MEA layer provides at least one flowpath of a flow field for a selected oxidant.
  • the flowpaths are constituted over their greater length by parallel transversely spaced and longitudinally extending flow channels interconnected in the vicinity of their ends to form the flowpaths.
  • the MEA layer is installed in the stack between the associated separator layers so that the side of the separator layer that in conjunction with the MEA layer provides flow channels of a flow field for hydrogen faces and is in contact with the anode side of the MEA layer, whilst the side of the separator layer providing flow channels of a flow field for oxidant faces and is in contact with the cathode side of the MEA layer, so that the hydrogen flow channels are closed to form a conduit for supplying hydrogen to the MEA layer and the oxidant flow channels are closed to form a conduit for supplying oxidant to the MEA layer.
  • the fuel cells are stacked in sequence, the anode electrode of the fuel cell at one extremity of the stack being electrically connected to the anode terminal, the cathode electrode of the fuel cell at the other extremity of the stack being electrically connected to the cathode terminal, and the anode electrode of each of the other fuel cells in the stack being electrically connected to the cathode electrode of the next adjacent fuel cell.
  • Figure 1 is a schematic isometric view of a portion of a fuel cell stack of conventional design illustrating coolant plates interspersed with fuel cells in the stack.
  • Figure 2 (prior art) is a schematic fragmentary section view of a portion of a conventional fuel cell arrangement showing a membrane electrode assembly (MEA) layer sandwiched between fuel and oxidant distribution/separator plates.
  • Figure 3 is a fragmentary section view of an undulate MEA layer sandwiched between consecutive separator plates in a stackable fuel cell arrangement and including explicit cooling conduits within the troughs of the undulate MEA layer, constructed in accordance with the principles of the invention.
  • MEA membrane electrode assembly
  • Figure 4 is a schematic fragmentary section view of an undulate MEA layer positioned in contact with an adjacent separator layer, and showing the relatively effectively utilized portion of the reactant flow channel and the relatively poorly utilized portion of the reactant flow channel .
  • Figure 5 is a schematic fragmentary section view of a portion of an alternative undulate MEA layer/separator layer configuration including cooling conduits constructed in accordance with an embodiment of the invention.
  • Figure 6 is a schematic exploded section view of the structure of Figure 5.
  • the stack dimension is the dimension in which fuel cell layers and other layers are stacked; it is generally perpendicular to the broad surfaces of the layers within the stack.
  • the flow dimension is the dimension parallel to the major flow channels comprising the reactant gas flow fields. (In a stack, depending upon configuration, it is conceivable that the fuel gas flow channels might be designed to lie perpendicular to the oxidant gas flow channels. However, relative to any one flow field, the flow dimension is free from ambiguity. )
  • the transverse dimension is that dimension that, for any given flow field, is perpendicular to both the flow and stack dimensions. Note that the flow dimension presupposes a generally parallel arrangement of straight flow channels suitably interconnected at their ends to form the complete flowfield.
  • cooling plates 14 made of a suitable material that functions as an effective heat conductor while avoiding contamination of the fuel cells or reactant gases therein.
  • the fuel cell stack 10 illustrated in Figure 1 is partial only; one might expect as many as 100 or more fuel cells to be mounted in a stack.
  • the lowermost portion of the stack 10 is illustrated, resting upon terminal base plate 15.
  • Cooling plates 14 are illustrated in Figure 1 as constituting every fourth layer of the fuel cell stack, three fuel cells 12 being interposed between each consecutive pair of cooling plates 14. It follows that fuel cell 12b, relatively remote from the nearest cooling plate 14, will operate at a higher temperature than fuel cells 12a and 12c that are in contact with an adjacent cooling plate 14.
  • the cooling plates 14 and the fuel cells 12 are provided with apertures 16 so as to provide, in the stack dimension of stack 10, plenum chambers for incoming and effluent fuel and oxidant gases.
  • Coolant plenum apertures 18 are provided for inlet and effluent coolant flow within the stack. Heat flow is predominantly from the coolant plates 14 (which receive heat from the fuel cells in the stack) into the conductive coolant that flows therethrough from and into respective supply and exhaust plenum chambers formed by the sequence of aligned apertures 18 throughout the stack 10.
  • FIG. 2 illustrates a fragment of an individual fuel cell layer within the stack 10.
  • a membrane electrode assembly (MEA) layer 22 is shown sandwiched between a fuel gas distribution and separator plate 24 and an oxidant gas distribution and separator plate 26.
  • Each of the plates 24, 26 is provided with a serpentine flowpath (not apparent from Figure 2, but conventional) which, in cross-section, appears as a series of spaced flow channels 28. Electrical conductivity through the stack is maintained by physical and electrical contact between the solid abutting portions 27 of the distribution plates 24, 26, and the sandwiched MEA layer 22 kept under compression between the abutting solid portions 27 of the distribution plates 24, 26.
  • FIG. 3 a waved, or undulate, MEA layer 70 is sandwiched between separator layers 72 that make electrical connection with the apices 74 of the MEA layer 70.
  • the separator layers 72 together with the sandwiched undulate MEA layer 70 form flow channels 76, 78 for the reactant gases.
  • Such an arrangement is described in British patent application 9814123.7 (McLean) filed on 1 July 1998 and in derivative and divisional applications thereof.
  • the uppermost "troughs" of the undulate MEA layer 70 constitute fuel flow channels 76 and the lower complementary channels 78 serve to carry the oxidant gas, or vice versa - the selection is arbitrary, as is the orientation shown in the illustration.
  • coolant flow conduits 79 may be provided immediately adjacent the separator layers 72 and spaced away from the MEA layer 70 so as to leave ample flow within channels 76, 78 sufficient to feed the exposed surfaces of MEA layer 70.
  • coolant conduits 79 are shown both in the oxidant flow channels 78 and in the fuel flow channels 76.
  • Each of the coolant conduits 79 can be connected between inlet and outlet coolant plenum chambers (not shown) to complete the coolant cycling system.
  • each coolant conduit 79 is located so as to lie in a region that is relatively remote from the active surfaces of the nearby MEA layer 70.
  • Figure 4 shows the layout of a single undulation in an undulate MEA layer 70, a planar separator layer 72 and an interior space relatively remote from the MEA layer 70 that can be used to locate cooling conduit 79. It is logical to excise from flow channel 78, shown bounded by separator layer 72 and MEA layer 70 in that illustration, the inefficient portion of the flow channel and to make the inefficient portion available to accommodate the coolant conduit 79.
  • the cooling conduit 79 is placed adjacent and preferably fixed to the separator plate 72 so that it remains well out of contact with the MEA layer 70.
  • Figure 4 has taken, by way of example, an undulate MEA layer and planar separator arrangement such as that illustrated in Figure 3, the principles derived from a review of Figure 4 can be applied to most, if not all, other reactant channel configurations, such as reactant channels formed between an undulate MEA and undulate separators .
  • the coolant conduits 79 are bonded to the adjacent portions of separator layers 72. If the separator layers 72 and the coolant conduits 79 are made of metal, then such bonding may be by welding or soldering. If they are not made of metal or are provided with non-metallic surfaces, the use of a cement such as an high-temperature- resistant epoxy resin may be suitable. Materials other than metals can be used for constructing the conduits 79; suitable materials that have adequate heat transfer capability and yet are sufficiently inert that they can be used in direct contact with the reactant gases include solid and woven graphite materials. An alternative inert material with satisfactory heat conductivity that is expected to be useful is polytetrafluoroethylene (PTFE) such as that sold under the trademark TEFLON.
  • PTFE polytetrafluoroethylene
  • Boundary walls 80 of cooling conduits 79 may be made of either conductive material or non-conductive material in the designer's preference. Non-conducting walls for the cooling conduits would have the advantage of allowing conductive coolant fluids to be used without disturbing the internal electrical balance within the fuel cell, since the conductive coolant fluids would be electrically isolated from the electrochemically active portions of the fuel cell by the non-conductive walls of the cooling conduit. On the other hand, if the walls 80 are made of conductive material, then the conduit walls themselves may, depending upon the configuration chosen, serve a useful function in current collection and transmission.
  • Figure 3 does not lend itself to such electrically conductive function of the conduit walls 80, but other configurations can easily be imagined in which the coolant conduit is shaped, dimensioned and located in such a position that electrical conductivity of the walls might be advantageous for collection and transmission of fuel cell current.
  • the walls 80 or other coolant conduit walls to be described below are selected to be conductive or non-conductive, it is of course important that the coolant within the coolant conduits 79 be isolated physically from the reactant gases and MEA layers; it is important to prevent migration of the coolant materials into the electrolytic membrane layer.
  • the separator plates are configured to provide coolant channels that serve two adjacent reactant gas areas.
  • the MEA layers are advantageously formed as sequential opposed undulate layers as illustrated in Figure 5, a schematic exploded view of which appears in Figure 6.
  • a composite separator layer 72 is built up from flat sheet portions 87 alternating with tubular cooling members 89.
  • successive MEA layers 70 are shown as being opposed, i.e. completely out of phase with one another, so that the length of the electrically conductive path through the separator layer 72 joining adjacent MEA layers 70 is minimum. This means that the requirement for conductivity of the separator 72 is localized in the vicinity of the apices of the undulate MEA layers 70.
  • the flat plate portions 87 of the composite separator 72 are made from conductive material such as graphite or metal or otherwise provide a conductive path from one surface to the other .
  • the tubular cooling members 89 are shown finned to facilitate heat transfer. These tubes 89 need not be made of conductive material, and are designed in such a way as to provide convenient means of manufacturing. For example, the coolant tubes 89 may be extruded and then cut to length. Flat plates 87 and coolant tubes 89 are attached to form the overall composite separator 72.
  • the small tangs 91 shown on the transverse edges of coolant tubes 89 provide a convenient means for the coolant tubes 89 to be bonded or otherwise mechanically attached to the adjacent flat plates 87.
  • the means of attaching the two components 87, 89 to form the overall composite separator 72 is at the discretion of the designer.
  • the components 87, 89 could be designed to mechanically interlock with each other, or an epoxy or other adhesive bond could be created, or mechanical fasteners could be used.
  • the bond or fastening must provide mechanical strength as required, and must also provide a seal between the reactant gas conduits on either side of the separator 72. There is no requirement for the bond or fastener to be conductive.
  • coolant conduits within the separator layer does not limit the options available to the designer for manifolding the cell in order to create the desired flowpaths.
  • Such options may include internal manifolding arrangements. Since the present invention is based on the interaction of interconnected but separate component layers, it remains possible to employ an internal manifolding technique by forming interconnecting reactant flowpaths within the component layers.
  • Manufacturing cost may be expected to play a significant role; that parameter, together with the power density parameter previously discussed, may influence a number of design choices.
  • individual designers will have their own respective preferences and priorities, and will be able to choose appropriate designs while relying upon the general principles apparent from the foregoing description.
  • the accompanying drawings are schematic; engineering details of any given design implementation of the invention may vary according to designers' preferences that meet objectives that may or may not directly relate to cooling.
  • the designer may wish to increase reactant gas turbulence to improve transfer of reactant gas to the electrochemically active portions of the fuel cell.
  • the designer may choose rough or irregular surfaces for the walls enclosing reactant gas flowpaths. It may be convenient for the designer to select rough or irregular coolant conduit external walls (that will be in contact with reactant gases) to help achieve such objective.
  • the cross- sectional shape and dimensions of the coolant conduits can be selected not only with cooling in mind but also for optimization of the reactant gas flowpath cross-section.
  • An integrated design approach should facilitate the achievement of such technical objectives while permitting the designer to aim for manufacturing simplicity and relatively low cost of manufacture.
  • Hydrogen may be used as a fuel gas in a fuel cell stack incorporating the separators described above.
  • Each fuel cell stack is connectable via a cathode terminal (not shown) and an anode terminal (not shown) to an external load (not shown) .
  • Each fuel cell has a discrete MEA layer 70 and is associated with two of the reactant-gas impermeable composite separator layers 72.
  • Each MEA layer 70 has a porous anode electrode (not shown) , a porous cathode electrode (not shown) , an electrolytic membrane layer (not shown) disposed between the two electrodes, an anode electro-catalyst layer (not shown) disposed between the electrolytic membrane layer and the anode electrode, and a cathode electro-catalyst layer (not shown) disposed between the electrolytic membrane layer and the cathode electrode.
  • One side of one associated separator layer in conjunction with the MEA layer 70 provides at least one flowpath of a flow field for hydrogen and one side of the other associated separator layer in conjunction with the MEA layer 70 provides at least one flowpath of a flow field for a selected oxidant.
  • the flowpaths are constituted over their greater length by parallel transversely spaced and longitudinally extending flow channels interconnected in the vicinity of their ends to form the flowpaths.
  • Each MEA layer 70 is installed in the stack between the associated composite separator layers 72 so that the side of the composite separator layer 72 that in conjunction with the MEA layer provides flow channels of a flow field for hydrogen faces and is in contact with the anode side of the MEA layer, whilst the side of the separator layer providing flow channels of a flow field for oxidant faces and is in contact with the cathode side of the MEA layer 70, so that the hydrogen flow channels are closed to form a conduit for supplying hydrogen to the MEA layer 70 and the oxidant flow channels are interconnected in the manner described above to form a conduit for supplying oxidant to the MEA layer 70.
  • the reactant gas flow channels are indicated by reference numerals 76 and 78.
  • the fuel cells are stacked in sequence and the anode electrode of the fuel cell, say, at one extremity of the stack electrically connected to the anode terminal, the cathode electrode of the fuel cell at the other extremity of the stack electrically connected to the cathode terminal, and the anode electrode of each of the other fuel cells in the stack electrically connected to the cathode electrode of the next adjacent fuel cell.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Fuel Cell (AREA)

Abstract

Selon cette invention, des conduites de refroidissement explicitement aménagées dans une pile à combustible du type à membrane échangeuse de protons suivent les voies d'écoulement des gaz réactifs de l'un des côtés des couches de l'ensemble d'électrodes membranes ondulées et sont intercalées avec les parties planes des couches séparatrices, de manière à assurer l'écoulement du liquide de refroidissement pour évacuer la chaleur de la pile à combustible. Ces conduites de refroidissement rendent superflues les couches séparées pour conduites de refroidissement qui traversent les couches de l'ensemble d'électrodes membranes dans le sens d'empilement.
PCT/GB1999/002072 1998-07-01 1999-07-01 Systeme de refroidissement interne destine a une pile a combustible a ensemble d'electrodes membranes ondulees WO2000002281A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU45262/99A AU4526299A (en) 1998-07-01 1999-07-01 Internal cooling arrangement for undulate mea fuel cell stack

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9814120.3 1998-07-01
GBGB9814120.3A GB9814120D0 (en) 1998-07-01 1998-07-01 Cooling of fuel cell stacks

Publications (2)

Publication Number Publication Date
WO2000002281A2 true WO2000002281A2 (fr) 2000-01-13
WO2000002281A3 WO2000002281A3 (fr) 2000-04-13

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Family Applications (3)

Application Number Title Priority Date Filing Date
PCT/GB1999/002056 WO2000002267A2 (fr) 1998-07-01 1999-07-01 Mecanisme de refroidissement interne pour empilage de piles a combustible a electrodes a membrane ondulee
PCT/GB1999/002074 WO2000002271A2 (fr) 1998-07-01 1999-07-01 Systeme de refroidissement interne pour pile a combustible
PCT/GB1999/002072 WO2000002281A2 (fr) 1998-07-01 1999-07-01 Systeme de refroidissement interne destine a une pile a combustible a ensemble d'electrodes membranes ondulees

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PCT/GB1999/002056 WO2000002267A2 (fr) 1998-07-01 1999-07-01 Mecanisme de refroidissement interne pour empilage de piles a combustible a electrodes a membrane ondulee
PCT/GB1999/002074 WO2000002271A2 (fr) 1998-07-01 1999-07-01 Systeme de refroidissement interne pour pile a combustible

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AU (3) AU4526299A (fr)
CA (1) CA2336314A1 (fr)
GB (4) GB9814120D0 (fr)
WO (3) WO2000002267A2 (fr)

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US6566004B1 (en) 2000-08-31 2003-05-20 General Motors Corporation Fuel cell with variable porosity gas distribution layers
US7592089B2 (en) 2000-08-31 2009-09-22 Gm Global Technology Operations, Inc. Fuel cell with variable porosity gas distribution layers

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JP4345205B2 (ja) * 2000-07-14 2009-10-14 トヨタ自動車株式会社 絶縁性を考慮した燃料電池の冷却
DE10040792C2 (de) * 2000-08-21 2003-04-10 Proton Motor Fuel Cell Gmbh Polymerelektrolytmembran-Brennstoffzellensystem mit Kühlmedium-Verteilungsraum und-Sammelraum und mit Kühlung durch fluide Medien
US6663994B1 (en) 2000-10-23 2003-12-16 General Motors Corporation Fuel cell with convoluted MEA
DE10045098A1 (de) * 2000-09-12 2002-04-04 Siemens Ag Brennstoffzellenanlage mit verbesserter Reaktionsgasausnutzung
JP3700642B2 (ja) 2001-12-11 2005-09-28 日産自動車株式会社 燃料電池
US6838202B2 (en) 2002-08-19 2005-01-04 General Motors Corporation Fuel cell bipolar plate having a conductive foam as a coolant layer
FR2870388B1 (fr) * 2004-05-12 2006-08-25 Peugeot Citroen Automobiles Sa Cellule de pile a combustible a electrolyte solide
KR100637490B1 (ko) * 2004-09-17 2006-10-20 삼성에스디아이 주식회사 연료 전지용 스택과 이를 갖는 연료 전지 시스템
ATE517446T1 (de) * 2005-02-03 2011-08-15 Siemens Ag Brennstoffzelle
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Publication number Priority date Publication date Assignee Title
US6566004B1 (en) 2000-08-31 2003-05-20 General Motors Corporation Fuel cell with variable porosity gas distribution layers
US7592089B2 (en) 2000-08-31 2009-09-22 Gm Global Technology Operations, Inc. Fuel cell with variable porosity gas distribution layers

Also Published As

Publication number Publication date
GB2339068A (en) 2000-01-12
AU4525399A (en) 2000-01-24
AU4526299A (en) 2000-01-24
GB9915294D0 (en) 1999-09-01
GB2339067A (en) 2000-01-12
WO2000002271A3 (fr) 2000-04-13
WO2000002281A3 (fr) 2000-04-13
GB9915295D0 (en) 1999-09-01
GB9915293D0 (en) 1999-09-01
CA2336314A1 (fr) 2000-01-13
GB2339066A (en) 2000-01-12
GB9814120D0 (en) 1998-08-26
WO2000002271A2 (fr) 2000-01-13
WO2000002267A2 (fr) 2000-01-13
AU4526499A (en) 2000-01-24
WO2000002267A3 (fr) 2000-09-14

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