Classifications

• • 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
• • 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
  • H01M8/14—Fuel cells with fused electrolytes
  • H01M8/144—Fuel cells with fused electrolytes characterised by the electrolyte material
  • H01M8/145—Fuel cells with fused electrolytes characterised by the electrolyte material comprising carbonates
• • 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
  • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
  • H01M8/0273—Sealing or supporting means around electrodes, matrices or membranes with sealing or supporting means in the form of a frame
• • 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
  • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
  • H01M8/0276—Sealing means characterised by their form
• • 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
• • 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
  • H01M8/242—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes comprising framed electrodes or intermediary frame-like gaskets
• • 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
  • 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
  • H01M8/2484—Details of groupings of fuel cells characterised by external manifolds
  • H01M8/2485—Arrangements for sealing external manifolds; Arrangements for mounting external manifolds around a stack
• • 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
  • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
  • H01M8/028—Sealing means characterised by their material
  • H01M8/0282—Inorganic material
• • 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
  • H01M8/0289—Means for holding the electrolyte
  • H01M8/0295—Matrices for immobilising electrolyte melts
• • 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 fuel cells and, in particular, to an externally manifolded fuel cell system adapted to impede the flow of electrolyte from the fuel cell stack of the system to the manifold used with the stack.
• a fuel cell is a device which directly converts chemical energy stored in hydrocarbon fuel into electrical energy by means of an electrochemical reaction.
• a fuel cell comprises an anode and a cathode separated by an electrolyte, which serves to conduct electrically charged ions.
• Fuel cells operate by passing a reactant fuel gas through the anode, while passing oxidizing gas through the cathode.
• a number of individual fuel cells are stacked in series with an electrically conductive separator plate between each cell.
• a fuel cell stack may be an internally manifolded stack or an externally manifolded stack.
• An internally manifolded stack typically includes gas passages for delivery of fuel and oxidant gases built into the fuel cell plates.
• fuel cell plates are left open on their ends and gas is delivered to the cells by way of manifolds sealed to the respective faces of the fuel cell stack.
• the manifolds in each type of fuel cell stack provide sealed passages for delivery of fuel and oxidant gases to the fuel cells and prevent those gases from leaking to the environment and to the other manifolds. These functions of the manifolds must be performed under the operating conditions of the fuel cell stack and for the duration of the stack life.
• the fuel cell stack is electrically conductive and has an electrical potential gradient along its length such that one end of the stack is at a positive-most electrical potential (the positive potential end of the stack) and the other end is at a negative- most electrical potential (the negative potential end of the stack).
• External manifolds which are typically made from metallic materials, must therefore be electrically isolated from the fuel cell stack so as not to short circuit the stack.
• Electrical isolating assemblies which include dielectric insulators and one or more gaskets, have been used between the metallic manifold and the fuel cell stack to produce the desired electrical isolation.
• a typical external manifold system includes three to four manifolds each employing similar electrical isolation assemblies to provide similar seals and dielectric isolation for each of the manifolds.
• FIG. 1 A schematic exploded view of one manifold and an electrical isolating assembly in a typical arrangement for a conventional externally manifolded fuel cell system 100 is shown in FIG. 1.
• the system 100 includes a fuel cell stack 1, a manifold comprising a metallic manifold 6 which covers a face Ia of the stack 1 and an electrical isolating assembly 101 disposed between the stack 1 and the manifold 6.
• the assembly 101 includes a dielectric member 5, a wet gasket 2 abutting the stack face Ia, a ceramic block or member 3 abutting the wet gasket 2 and a dry gasket 4 disposed between the ceramic block 3 and the dielectric member 5 in an abutting relationship.
• the other manifolds of the fuel cell system use a similar design.
• electrical isolation provided by the electrical isolating assembly 101 may be severely compromised when liquid electrolyte in the fuel cells migrates from the stack to a point where it wets the components of the isolating assembly abutting the manifold 6.
• the stack face Ia becomes wet with liquid electrolyte, which is absorbed by the wet gasket 2.
• the ceramic block 3 comes into contact with liquid electrolyte through its surface abutting the surface of the wet gasket 2.
• the dielectric capacity of the ceramic block 3 is substantially reduced.
• electrical isolation between the manifold 6 and the stack 1 becomes difficult to maintain with the dry gasket being responsible for most of the voltage drop between the stack 1 and the manifold 6. This voltage drop may be as high as 500 Volts.
• the electrolyte migration from the stack face Ia across the electrical isolating assembly 101 is facilitated by the difference in electrical potential between the fuel cell stack and the manifold.
• the manifold has a constant electrical potential floating between the positive-most and the negative-most electrical potentials of the stack. This causes the manifold to be at a lower potential than the positive potential end of the stack.
• a fuel cell system comprising a fuel cell stack having a positive potential end and a negative potential, a manifold for use in coupling gases to and from a face of the fuel cell stack, an electrical isolating assembly for electrically isolating the manifold from the stack, and a unit for adjusting an electrical potential of the manifold such as to impede the flow of electrolyte from the stack across the isolating assembly. More particularly, the unit is adapted to adjust the electrical potential of the manifold so that it at least approaches the electrical potential of the positive potential end of the stack and, preferably, becomes equal to or greater than this potential.
• the unit takes the form, in one case, of a power supply such as, for example, a battery, and in another case, of an electrical wire.
• a method for retarding electrolyte migration from a fuel cell stack through an electrical isolating assembly is also disclosed.
• a dielectric member of an electrical isolating assembly is adapted to prevent debris build up from compromising the electrical isolation provided between a fuel cell stack and its manifold.
• FIG. 1 shows a schematic exploded view of a typical arrangement of a conventional externally manifolded fuel cell system
• FIG. 2 shows an exploded view of an externally manifolded fuel cell system in accordance with the principles of the present invention
• FIG. 3 shows an alternative embodiment of the fuel cell system of FIG. 2
• FIG. 4A shows an exploded side view of a modified arrangement of the fuel cell systems 200 of FIGS. 2 and 3 in accord with the present invention
• FIG. 4B shows a front view of a dielectric member of FIG. 4A.
• FIG. 2 shows an exploded view of an externally manifolded fuel cell system 200 in accordance with the principles of the present invention.
• the fuel cell system 200 has a fuel cell stack 1 and a manifold 6 covering a face Ia of the stack 1.
• An electrical isolating assembly 201 is disposed between the fuel cell stack 1 and the manifold 6 for electrically isolating the manifold 6 from the stack.
• the assembly 201 has a similar construction as the electrical isolating assembly 101 of FIG. 1 and comprises a dielectric member 5, a wet gasket 2, which abuts the stack face Ia, followed by a ceramic block 3 and a dry gasket 4 disposed in an abutting relationship with one another.
• the members 2-5 are all fo ⁇ ned to have picture-frame configurations.
• the dielectric member 5 has high dielectric resistivity, i.e. greater than 10 8 ohm-cm at 600 0 C. Mica sheet materials such as 503P phlogopite mica manufactured by Cogebi, Inc. may be used to form the dielectric member 5.
• the fuel cell stack 1 has a large electrical potential gradient along its length. As shown, the negative potential end Ib of the stack 1 having the negative terminal IbI is at a negative-most electrical potential, while the positive potential end Ic of the stack having the positive terminal IcI is at a positive- most potential.
• the manifold 6 is at a constant electrical potential which is between the positive-most and the negative-most electrical potentials of the stack 1. In particular, the manifold 6 is at a lower electrical potential than the electrical potential at the positive potential end Ic of the stack. As discussed above, this causes electrolyte to flow from the end Ic of the stack to the manifold through the electrical isolation assembly 101.
• the fuel cell system 200 is provided with a unit 7 for adjusting the electrical potential of the manifold 6 so as to impede electrolyte flow from the stack to the manifold.
• the unit 7 adjusts the electrical potential of the manifold 6 so that it approaches the electrical potential of the positive end Ic of the stack. Preferably, this adjustment is such that the electrical potential at the manifold 6 becomes equal to or greater than the electrical potential at the stack end Ic.
• the unit 7 is in the form of a power supply 7a connected between the stack end Ic and the manifold 6.
• the power supply can be a battery having its positive terminal 7al connected to the manifold 6 and its negative terminal 7a2 connected to the positive end I c of the stack 1. Batteries, such as 12 volt car battery, are suitable for use as the power supply 7a.
• the power supply 7a applies a positive electrical potential to the manifold 6 to increase the manifolds' electrical potential so that it approaches that at the positive end Ic of the stack.
• the battery potential is such that it is equal to or exceeds the potential at the stack end Ic.
• the electrical potential gradient between the stack 1 and the manifold 6 is at least decreased and in the preferred form of the battery 7, is zeroed or is reversed.
• the carbonate ions at the stack face Ia are less attracted to the manifold 6 and, therefore, the driving of the electrolyte across the isolating assembly 201 is at least reduced, if not stopped or reversed.
• FIG. 3 shows an alternative embodiment of the fuel cell system 200 of FIG. 2 in accord with the present invention.
• the unit 7 is in the form of an electrical conductor 7b which connects the positive end Ic of the fuel cell stack
• the conductor 7b typically might be an electrical wire sized according to the National Electrical Code.
• a typical wire might be a 1/16 inch SS316 welding rod.
• the electrical conductor might also contain a resistor and a fuse sized according to the National Electric Code based on a power rating of the fuel cell. The presence of the electrical conductor 7b acts similarly to the battery in FIG.
• the system 200 usually will have like manifolds 6 and associated isolating assemblies 201 adjacent one or more of the other faces of the stack.
• these manifolds will be connected electrically so as to be at the same potential.
• a common stack manifold clamping system or a wire or wires 202 such as a 1/16 inch SS316 welding rod, may be used so as to provide the electrical connection.
• the unit 7 between one of the manifolds and its associated stack face will be sufficient to provide all manifolds with a potential closer to that of the positive end I c of the stack.
• a unit 7 can be provided between each face of the stack at the positive potential end of the stack and the facing manifold.
• the fuel cell system 200 shown in FIGS. 2 and 3 may be further modified to provide a barrier to prevent debris from compromising the electrical or dielectric isolation between the manifold 6 and the stack 1.
• debris comprising conductive materials is typically formed in the system 200 due to the presence of corrosive materials at high temperatures. This debris accumulates on the upper outer surface 201a of the electrical isolation assembly 201 and the upper surface at the upper end 6a of the manifold 6 and also on the upper inner surface 201b of the assembly 201 and the upper surface at the lower end 6b of the manifold 6.
• FIG. 4A shows an exploded side view of a modified arrangement of the fuel cell system 200 of FIGS. 2 and 3 adapted to inhibit the bridging of this debris.
• dielectric member 5 whose upper end 5a has an outer surface 5al which extends beyond the upper outer surfaces 3al , 4al and 6al of the upper outer ends 3a, 4a and 6a of the ceramic block 3, dry gasket 4 and manifold 6, respectively. Additionally, the upper inner surface 5b 1 of the lower end 5b of the dielectric member 5 extends above the upper inner surfaces 3bl, 4bl, 6bl of the lower ends 3b, 4b and 6b of the gasket 3, ceramic block 4 and manifold 6. As a result, dielectric member 5, forms a physical barrier separating the surfaces 3aland 4al from the surface 6al and the surfaces 3bl and 4bl from the surface 6b 1. The debris on the ceramic block 3 and dry gasket 4 is thus prevented from bridging with the debris on the manifold 6. The electrical coupling or connection of these elements and, thus, the manifold and stack by the debris 9 is thus avoided.
• FIG. 4B shows a front view of the dielectric member 5 of FIG. 4A viewed from the face of the dielectric member 5 abutting the dry gasket 4.
• the upper surface 5al of the upper outer end 5a of the dielectric member 5 extends beyond the upper surface 6a 1 of the upper outer end 6a of the manifold 6 so as to form a barrier, as discussed above. As also discussed above, this barrier prevents debris on the surfaces 3al and 4al from bridging with the debris on the surface 6a 1.
• the upper surface 5bl of the lower end 5b of the dielectric member 5 extends beyond upper surface 6bl of the lower end 6b of the manifold 6 so as to form another barrier.
• This barrier similarly prevents debris on the surfaces 3bl, 4bl from bridging with the debris on the surface 6b 1.
• These barriers therefore prevent debris accumulating on the ceramic member 3 and dry gasket 4 from connecting with debris on the manifold 6. In this way, electrical isolation between the manifold 6 and the stack 1 is improved, thus extending the life and performance of the system.

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

Priority Applications (3)

Applications Claiming Priority (2)

Publications (3)

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ID=36611997

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• 2004
  • 2004-12-23 US US11/020,593 patent/US7276304B2/en not_active Expired - Lifetime
• 2005
  • 2005-12-22 KR KR1020077016881A patent/KR101310483B1/ko not_active Expired - Lifetime
  • 2005-12-22 EP EP05855543A patent/EP1839355B1/en not_active Expired - Lifetime
  • 2005-12-22 JP JP2007548574A patent/JP2008525970A/ja active Pending
  • 2005-12-22 CN CNA2005800445381A patent/CN101088186A/zh active Pending
  • 2005-12-22 WO PCT/US2005/047002 patent/WO2006071841A2/en not_active Ceased

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