EP1382079A4 - Integrated solid oxide fuel cell system - Google Patents

Integrated solid oxide fuel cell system

Info

Publication number
EP1382079A4
EP1382079A4 EP02728838A EP02728838A EP1382079A4 EP 1382079 A4 EP1382079 A4 EP 1382079A4 EP 02728838 A EP02728838 A EP 02728838A EP 02728838 A EP02728838 A EP 02728838A EP 1382079 A4 EP1382079 A4 EP 1382079A4
Authority
EP
European Patent Office
Prior art keywords
fuel cell
supply
subassembly
reformer
air
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02728838A
Other languages
German (de)
French (fr)
Other versions
EP1382079A2 (en
Inventor
Karl Jacob Haltiner Jr
Michael Thomas Faville
Malcolm James Grieve
John Noetzel
Chris M Deminco
Kevin Richard Keegan
John F O'brien
Subhasish Mukerjee
David Robert Schumann
Steven R Shaffer
Juergen T Kammerer
Catherine C Vavonese
James Michael Haller
Donald Jack Armstrong
Harry Laurie Husted
Haskell Simpkins
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Delphi Technologies Inc
Original Assignee
Delphi Technologies Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US09/838,661 external-priority patent/US6627339B2/en
Priority claimed from US09/845,531 external-priority patent/US6562496B2/en
Application filed by Delphi Technologies Inc filed Critical Delphi Technologies Inc
Publication of EP1382079A2 publication Critical patent/EP1382079A2/en
Publication of EP1382079A4 publication Critical patent/EP1382079A4/en
Withdrawn legal-status Critical Current

Links

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
    • H01M8/04—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
    • H01M8/02—Details
    • H01M8/0297—Arrangements for joining electrodes, reservoir layers, heat exchange units or bipolar separators to each other
    • 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
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H01M8/04225—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells during start-up
    • 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
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04302—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during start-up
    • 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
    • H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
    • H01M8/2425—High-temperature cells with solid electrolytes
    • H01M8/2432—Grouping of unit cells of planar configuration
    • 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
    • H01M8/10—Fuel cells with solid electrolytes
    • H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
    • H01M2008/1293—Fuel cells with solid oxide electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2250/00—Fuel cells for particular applications; Specific features of fuel cell system
    • H01M2250/40—Combination of fuel cells with other energy production systems
    • H01M2250/405—Cogeneration of heat or hot water
    • 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
    • H01M8/04014—Heat exchange using gaseous fluids; Heat exchange by combustion of reactants
    • H01M8/04022—Heating by combustion
    • 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
    • H01M8/06—Combination of fuel cells with means for production of reactants or for treatment of residues
    • H01M8/0606—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants
    • H01M8/0612—Combination of fuel cells with means for production of reactants or for treatment of residues with means for production of gaseous reactants from carbon-containing material
    • 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
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02B90/10—Applications of fuel cells in buildings
    • 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

  • the present invention relates to solid oxide fuel cells.
  • Automobile emissions are said to be a significant contributor to pollution. Automobiles emit hydrocarbons, nitrogen oxides, carbon monoxide and carbon dioxide as a result of the combustion process. In the United State, the Clean Air Act of 1970 and the 1990 Clean Air Act set national goals of clean and healthy air for all and established responsibilities for industry to reduce emissions from vehicles and other pollution sources. Standards set by the 1990 law limit automobile emissions to 0.25 grams per mile (gpm) non-methane hydrocarbons and 0.4 gpm nitrogen oxides. The standards are predicted to be further reduced by half in the year 2004, and similar air quality standards have been or are predicted to be adopted worldwide. It is expected that automobiles will continue to be powered by internal combustion engines for decades to come.
  • gpm grams per mile
  • SOFC solid oxide fuel cells
  • a fuel cell is a device that converts chemical energy into electrical energy. More particularly, a SOFC generates electricity and heat by electrochemically combining across an ion-conducting electrolyte a gaseous fuel, such as hydrogen, carbon monoxide, or a hydrocarbon, and an oxidant, such as air or oxygen.
  • a conventional SOFC system typically includes a SOFC, a reformer and a waste energy recovery unit.
  • the SOFC is a solid-state device, and includes two electrodes disposed on opposite sides of the ion-conducting electrolyte.
  • a SOFC system In operation, a SOFC system generates electricity and heat by directing a flow of oxidant over the oxygen electrode or cathode while the fuel is passed over the fuel electrode or anode, thereby generating electricity, water and heat.
  • the fuel (or reformate) provided to the SOFC is produced in the reformer.
  • the reformer converts a hydrocarbon or oxygenated fuel into reformats thereof, e.g., hydrogen and carbon monoxide, and byproducts thereof, such as carbon dioxide and water.
  • Byproducts from the SOFC, a supply of oxidant, and a supply of reformate are typically directed through the discrete waste energy recovery unit.
  • the waste energy recovery unit converts chemical and thermal energy into input thermal energy for the SOFC via one or more heat exchangers.
  • the waste energy recovery unit unlike the solid-state SOFC itself, is relatively large and bulky, is constructed of relatively durable and heat transferable materials, and includes many tubes and connections for directing the chemical and thermal energy through the unit.
  • SOFC systems were used primarily for stationary power generation in the power generating industry.
  • Conventional SOFC systems were not readily adaptable or suitable for use in a motor vehicle.
  • Other types of fuel cell systems such as, for example, proton exchange membrane (PEM) systems, have been adapted for use in motor vehicles.
  • PEM systems require costly and relatively complex systems for the on-board storage and/or generation of hydrogen and water management systems for on-board fuel reforming and system hydration.
  • PEM proton exchange membrane
  • the present invention provides an integrated solid oxide fuel cell system.
  • the present invention comprises, in one form thereof, a solid oxide fuel cell subassembly having a fuel cell stack fluidly interconnected with a distribution manifold.
  • a waste energy recovery subassembly includes a heat exchanger and combustion zone. The waste energy recovery subassembly is fluidly interconnected with the distribution manifold.
  • a reformer subassembly is fluidly connected to the waste energy recovery subassembly.
  • An advantage of the present invention is that it is suitable for use in a motor vehicle.
  • Another advantage of the present invention is that the fuel cell, waste recovery unit and reformer are combined into one unit or system suitable for installation within a vehicle.
  • a further advantage of the present invention is that any two or more of the fuel cell system subassemblies can be integrated into one subassembly.
  • FIG. 1 is a schematic diagram of one embodiment of an integrated SOFC fuel cell system of the present invention
  • FIG. 2 is a schematic diagram of a single electrochemical cell of the SOFC fuel cell stack of Fig. 1 , and illustrates the operation thereof;
  • FIG. 3 is a perspective view of the electrochemical cell of Fig. 2;
  • FIG. 4 is a perspective view an exemplary integration of the SOFC subassembly and waste energy recovery subassembly of Fig. 1, and illustrates the flow of gasses therethrough;
  • FIG. 5 is a perspective view of the integrated SOFC subassembly and waste energy recovery subassembly of Fig. 4.
  • SOFC fuel cell system 10 includes reformer subassembly 12, waste energy recovery subassembly 14 and SOFC subassembly 16. Reformer subassembly 12, waste energy recovery subassembly 14 and SOFC subassembly 16 are all disposed within a single system enclosure 20. More particularly, system enclosure 20 includes a first chamber 22, second chamber 24 and third chamber 26. Each of reformer subassembly 12, waste energy recovery subassembly 14 and SOFC subassembly 16 are disposed in first chamber 22. Insulation layer 28 surrounds first chamber 22, and bulkhead 30, such as, for example, a metal or composite plate member, separates second chamber 24 and third chamber 26.
  • Reformer subassembly 12 includes main reformer 32 and micro-reformer 34.
  • reformer subassembly 12 converts a supply of fuel F and a supply of air A into a flow of reformate, i.e., fuel, to SOFC subassembly 16 via waste energy recovery subassembly 14.
  • each of main reformer 32 and micro-reformer 34 receive from fuel supply F a flow of fuel 36a, 36b, respectively, via respective fuel control valves 38a, 38b, such as, for example, fuel injectors, and receive from air supply A respective flows of air 40a, 40b via respective air control valves 42a, 42b.
  • Main reformer 32 is fluidly connected to reformate control valve 44, and supplies thereto a flow of fuel/reformate 46.
  • Micro-reformer 34 is fluidly connected to main reformer 32 and, as will be more particularly described hereinafter, supplies a flow of pre-reformate 48 to main reformer 32.
  • Main and micro-reformers 32, 34 are integrally disposed within reformer subassembly housing 50.
  • Main and micro- reformers 32, 34 are configured as exothermic partial oxidation (POx) reformers, and therefore the need for a separate supply of water and/or to re-circulate anode exhaust gases to obtain water vapor are avoided.
  • POx exothermic partial oxidation
  • Main reformer 32 includes a heating device and/or igniter 32a that heats the catalyst (not shown) contained in main reformer 32 thereby expediting the attainment of a desired operating temperature by main reformer 32.
  • Micro-reformer 34 is sized to provide sufficient heat when in a full or substantially full combustion mode and sufficient reformate when in the reforming or normal operation mode to preheat and start-up the downstream device, i.e., main reformer 32, in a predetermined or desired period of time. Operation of main and micro-reformers 32, 34, respectively, is monitored with appropriate sensors (not shown), such as, for example, pressure, temperature, and gas pressure and composition sensors. Main and micro-reformers 32, 34, respectively, are connected in series.
  • Waste energy recovery subassembly 14 integrates a catalytic combustion zone 52 and one or more heat exchangers 54. Generally, waste energy recovery subassembly 14 receives a flow of reformate from main reformer 32 via reformate control valve 44. Depending on the mode of operation of SOFC system 10, waste energy recovery subassembly 14 either combusts the reformate, or heats the reformate and a flow of air. The flows of heated reformate and air are supplied to SOFC subassembly 16. Thus, waste energy recovery subassembly 14 converts unused chemical energy (such as unused reformate) and thermal energy (such as the exothermic reaction heat from the SOFC subassembly 16) to input thermal energy for SOFC fuel cell system 10.
  • unused chemical energy such as unused reformate
  • thermal energy such as the exothermic reaction heat from the SOFC subassembly 16
  • waste energy recovery subassembly 14 receives a plurality of working fluids and/or gases.
  • Combustion zone 52 and heat exchanger 54 are each fluidly connected to reformate control valve 44.
  • reformate control valve 44 Under predefined operating conditions, such as, for example, during a start-up mode of operation of SOFC fuel cell system 10, at least a portion of reformate flow 46 is directed by reformate control valve 44 to combustion zone 52 as start-up or low-grade reformate flow 62.
  • at least a portion of reformate flow 46 is directed by reformate control valve 44 to heat exchanger 54 as operating reformate flow 64.
  • Combustion zone 52 is further fluidly connected to and receives from SOFC subassembly 16 a flow of cathode exhaust 74 and anode exhaust 76. Under certain operating conditions, such as, for example, shut down, a flow of purge air from first chamber 22 is fluidly coupled to combustion zone 52 via inlet 78.
  • Waste energy recovery subassembly 14 also exhausts and/or transfers a plurality of fluids and/or gases during the operation of SOFC fuel system 10. More particularly, the flows of operating reformate 64 and cathode air 66 are passed through heat exchanger 54 and to SOFC subassembly 16, as will be more particularly described hereinafter. Further, waste energy recovery subassembly 14 emits exhaust flow 80, e.g., a flow of reaction byproducts such as water, carbon dioxide and air, to the exterior of system enclosure 20.
  • exhaust flow 80 e.g., a flow of reaction byproducts such as water, carbon dioxide and air
  • Waste energy recovery subassembly 14 is embodied as a series of connected generally flat plate structures (not shown) having one or more openings or manifold passages along or bordering the edge of the plate for guiding the flow of oxidant, reformate or exhaust gases.
  • the plates also include features (not shown), such as, for example, etchings, chevrons or channels, that are disposed, for example, in or near the center portion of the plates for guiding the movement of the oxidant, reformate or exhaust.
  • the oxidant, reformate and exhaust enter the waste energy recovery subassembly 14 via respective inputs, as described above, and are guided through respective features/channels and across the plates to corresponding outlet passages.
  • the flows of oxidant, reformate and/or exhaust are separated from each other by the features/channels to prevent mixing of the gases.
  • SOFC subassembly 16 includes SOFC fuel cell stack 90 and distribution manifold 92. Generally, SOFC subassembly 16 distributes the flow of operating reformate 64 and cathode air 66, and converts those flows to electricity.
  • SOFC fuel cell stack 90 is a multi-layer ceramic / metal composite fuel cell having the capacity to produce a predetermined amount of electricity, such as, for example, a level of current sufficient to drive the electrical load presented by the various electrical devices found on a typical automobile.
  • SOFC fuel cell stack 90 produces electricity at an operating temperature of from approximately 600°C to approximately 1000°C, and
  • SOFC fuel cell stack 90 includes one or more electrically and fluidly interconnected multi-cell modules (not shown), and includes an electrode 94 that extends from system enclosure 20 for connecting SOFC fuel cell stack 90 to an electrical load, such as, for example, a power bus (not shown) of a motor vehicle.
  • a schematic representation of a single cell 100 of mutli- layer, multi-cell fuel cell stack 90 is shown to illustrate the operation of fuel cell stack 90.
  • Anode 102 and cathode 104 are disposed on opposite sides of and spaced apart by oxygen ion conducting electrolyte 106.
  • Reformate flow 64 is directed over anode 102, and cathode air flow 66 is passed over cathode 104 of cell 100. Cathode flow 66 is reduced in the presence of electrolyte 106. Oxygen ions (O "2 ) are thereby generated and move through electrolyte 106 to anode 102, as summarized by the following reaction: O 2 + 4e " -> 2(O "2 ).
  • reformate flow 64 is oxidized in the presence of electrolyte 106 and the migrating oxygen ions.
  • the reaction of reformate flow 64 with the oxygen ions produces electrons (e " ), which flow to external circuit 110 and back to cathode 104.
  • Unreacted fuel byproducts such as, for example, carbon monoxide, water, and carbon dioxide, exit cell 100 in anode exhaust flow 76, which is in turn directed by distribution manifold 92 to combustion zone 52 of waste energy recovery subassembly 14.
  • cell 100 includes anode plate 102 which is spaced apart and separated from cathode plate 104 by electrolyte 106.
  • Collector 112 is disposed adjacent the side (not referenced) of anode 102 that is opposite electrolyte 106, and collector 114 is disposed adjacent the side (not referenced) of cathode 104 that is opposite electrolyte 106.
  • An anode plate 116 of a second cell (not shown) is disposed below, i.e., on the opposite side of, collector 114, thereby illustrating the placement of and ability to stack several cells in electrical communication with cell 100.
  • the anode 102 and cathode 104 which with electrolyte 106 form phase boundaries between gas/electrolyte/catalyst commonly known as triple points, are disposed adjacent to and/or integral with electrolyte 106.
  • Anode 102 and cathode 104 are generally formed of porous material capable of functioning as an electrical conductor and capable of facilitating the reactions described herein. More particularly, the porosity of the material that comprises anode 102 and cathode 104 should be sufficient to enable dual directional flow of gases, i.e., the admission of fuel or oxidant gases and the exit of byproducts. Even more particularly, the porosity of the material that comprises anode 102 and cathode 104 should be up to approximately 40 percent and ideally from approximately 20 to approximately 40 percent.
  • Anode 102 and cathode 104 are constructed of material that include elements such as zirconium, yttrium, nickel, manganese, strontium, lanthanum and oxides, alloys and combinations including at least one of the foregoing elements.
  • Anode 102 is preferably formed upon a ceramic skeleton, such as, for example, a yttria-stabilized zirconia, for thermal compatibility.
  • Both anode 102 and cathode 104 are formed on electrolyte 106 by a variety of techniques, such as, for example, sputtering, chemical vapor deposition, screen printing, spraying, dipping, stenciling and painting.
  • the anode 102 and cathode 104 electrodes are typically up to approximately 1 ,000 microns in thickness, with a thickness of from approximately 10 to approximately 50 microns typically being preferred.
  • cell 100 can be configured as an anode supported cell by forming electrolyte 106 and cathode 104 on anode 102 using any of the above deposition/application techniques.
  • cathode 104 or an inert layer (not shown) can be substituted as the support for cell 100.
  • Electrolyte 106 is an ion conductor capable of transporting oxygen ions from the cathode 104 to the anode 102, and which is compatible with the environment in which SOFC fuel cell system 10 is to be used, such as, for example, in temperatures of up to approximately 1000°C.
  • suitable materials for electrolyte 106 include ceramics, such as, for example, perovskite and/or fluorite, metals, such as, for example, alloys, oxides, and/or gallates.
  • suitable electrolyte materials include, for example, zirconium, yttrium, calcium, cerium, magnesium, aluminum, rare earth metals, oxides, gallates, aluminates, and combinations and/or composites of at least one of the foregoing materials.
  • a rare earth oxide such as, for example, yttria, gadolinia, neodymia, and the like doped with aliovalient oxides, such as, for example, magnesia, calcia, strontia, and other +2 valence metal oxides, are used for the material of electrolyte 106.
  • a yttria-stabilized zirconia material is used for electrolyte 106.
  • Collectors 112, 114 include passages (not referenced) for guiding the flow of fuel and oxidant, respectively.
  • Collectors 112 and 114 are generally formed of electrically conductive material that is capable of withstanding the temperatures and pressures under which SOFC fuel cell system 10 is operated.
  • collectors 112 and 114 are constructed of materials, such as, for example, silver, copper, ferrous materials, strontium, lanthanum, chromium, chrome, gold, platinum, palladium, nickel, titanium, conducting ceramics, or composites and combinations of at least one of the foregoing, that are capable of withstanding the operating conditions of a motor vehicle, i.e., ambient temperatures from approximately - 40°C to operating temperatures of approximately 1000°C.
  • Each individual cell 100 generates approximately from 0.5 volts to approximately 1.2 volts direct current.
  • the desired output voltage of SOFC fuel cell system 10 is obtained by connecting in series a plurality of cells 100 together, as described herein.
  • Gas distribution manifold 92 fluidly interconnects SOFC fuel cell stack 90 with waste energy recovery subassembly 14. More particularly, gas distribution manifold 92 receives heated reformate flow 64 and heated cathode air flow 66 from waste energy recovery subassembly 14 via inlet/outlet manifold 120 (Figs. 4 and 5), and distributes those flows to the SOFC fuel cell stack 90. Gas distribution manifold 92 further directs anode and cathode exhaust flows 74 and 76, respectively, from SOFC fuel cell stack 90 to combustion zone 52 of waste energy recovery subassembly 14. After combustion thereof, any remaining byproducts are exhausted via exhaust flow 80. It should be particularly noted that, as best shown in Figs.
  • gas distribution manifold 92 integrates into a unitary subassembly (not referenced) the waste energy recovery subassembly 14 and SOFC subassembly 16. More particularly, as shown in Fig. 5, fuel cell stack 90, distribution manifold 92, waste energy recovery subassembly 14 and inlet/outlet manifold 120, are integrated into a single unitary subassembly (not referenced) by fasteners 121 , such as, for example, bolts.
  • anode exhaust 76 and cathode exhaust 74 are routed back to combustion zone 52 of waste energy recovery subassembly 14, where they are mixed with air flow 70 and burned.
  • the burning of the anode and cathode exhausts 76, 74, respectively, in combustion zone 52 heats heat exchanger 54 of waste energy recovery subassembly 14.
  • cooling air control valve 122 is actuated and connects a flow of cooling air 124 to cathode air flow 66, thereby blending cooler air with cathode air flow 66 and controlling the temperature of SOFC subassembly 16.
  • the thermal management (not referenced) of SOFC fuel cell system 10 should be particularly noted.
  • the thermal management system of SOFC fuel cell system includes first, second and third chambers 22, 24 and 26, respectively, and is designed to insulate the internal hardware of SOFC fuel cell system 10 and maintain the exterior temperature of system enclosure 20 at approximately 90°C or less.
  • System enclosure 20 supports the components of SOFC fuel cell system 10, and can optionally be actively temperature controlled in a known manner.
  • System enclosure 20 surrounds and defines at least in part second and third chambers 24 and 26, respectively.
  • First chamber 22 is housed internally to second chamber 24, and contains reformer subassembly 12, waste energy recovery subassembly 14, SOFC subassembly 16 and other high-temperature components (not shown), such as, for example, sensors and controllers.
  • reformer subassembly 12, waste energy recovery subassembly 14 and SOFC subassembly 16 are integrated within first chamber 22.
  • the thermal management system includes two means that actively control the temperature of system enclosure 20.
  • cooling air lid passage 128 is defined by lid 126 of system enclosure 20.
  • Lid 126 incorporates a thin heat exchanger (not shown) across the entire surface thereof.
  • the surface of lid 126 provides a contact point to vehicle 130 and therefore operates at a lower temperature than the other surfaces of system enclosure 20.
  • Main blower 132 is disposed within system enclosure 20 and together with air control valve 134 selectively draws cooling air A through cooling air lid passage 128, thereby cooling the surface of system enclosure 20 that is in contact with vehicle 130 and pressurizing third chamber 26 to a pressure P1.
  • main blower 132 and valve 134 are controlled and adjusted dependent at least in part upon the temperature of the incoming cooling air, and preferably cools the surface of system enclosure 20 to approximately 90°C or less, and more preferably to approximately 45°C or less.
  • Air control valve 136 controls the flow of air into second chamber 24 and thereby regulates pressure P2 and ensures the appropriate degree of cooling is attained.
  • Insulation layer or wall 28 is disposed between first chamber 22 and second chamber 24, and also forms part of the thermal management system of SOFC fuel cell system 10.
  • a flow of air 137 from second chamber 24 through insulation layer 28 and into first chamber 22 cools first chamber 22.
  • the flow of air 137 pressurizes first chamber 22 to a pressure P3, which is maintained at a level that is a predetermined amount less than P2. Once the flow of air has reached first chamber 22, the air is referred to as purge air.
  • the purge air is drawn (or pushed by the pressure P2 and P3 differentials) into inlet 78 of waste energy recovery system 14, and is exhausted from SOFC fuel cell system 10.
  • the above described thermal management system controls the exterior temperature of first chamber 22 to a temperature of approximately 200°C or less, and
  • a process air system (not referenced) provides cooling air to the thermal management system and to the other components of SOFC fuel cell system 10 that utilize/require air.
  • the process air system draws air from air supply A, such as, for example, an external air supply.
  • Air supply A is processed through air filter 142 and directed through cooling air passage 128 in lid 122 and to main blower 132, as described above.
  • Main blower 132 is disposed within third chamber 26, and delivers air through process air control valve 134 to third chamber 26 and, thus, to the thermal management system of SOFC fuel cell system 10.
  • Main blower 132 pressurizes the chambers 22, 24 and 26, thereby providing for the cooling and purging thereof.
  • main blower 132 pressurizes the chambers appropriately and as described above.
  • Fuel supply F enters and thus pressurizes the fuel system and operation of micro-reformer 34 is commenced, such as, for example, by energizing an electrically heated element (not shown) in the fuel vaporization zone thereof.
  • Micro-reformer 34 receives fuel flow 36a from fuel injector 38a and receives air flow 40a from air control valve 42a, and produces pre-reformate 48.
  • Pre-reformate flow 48 is routed through and heats main reformer 34.
  • pre-reformate flow 48 is also routed through and heats waste energy recovery subassembly 14 and SOFC subassembly 16.
  • Appropriate sensors monitor the properties of reformate flows 62 and 64.
  • a predetermined minimum start-up temperature such as, for example, approximately 600°C
  • fuel valve 38b and air control valve 42b are actuated to thereby supply fuel flow 36b and air flow 40b to main reformer 32.
  • Main reformer 32 thus begins producing operating reformate flow 46.
  • At least a portion of reformate flow 46 is directed by reformate control valve 44 through combustion zone 52 as refromate flow 62 during the start up operating mode of SOFC fuel cell system 10.
  • the combustion of reformats within combustion zone 52 heats heat exchangers 54.
  • fuel cell stack 90 reaches a predetermined lower or minimum operational temperature limit, such as, for example, approximately 650°C or greater and preferably
  • SOFC subassembly 16 transitions from the start-up mode of operation to the normal mode of operation. At least a portion of reformate flow 46 is re-directed by reformate control valve 44 to flow as reformate flow 64 through heat exchanger 54 and to SOFC subassembly 16, rather than through combustion zone 52 as reformate flow 62.
  • the output, i.e., cathode and anode exhaust flows 74, 76, respectively, are routed through combustion zone 52 where they are mixed with air flow 70 and catalyzed.
  • Shutdown from normal operating mode includes cooling SOFC system 10 to near ambient conditions, the electrical load placed upon SOFC system 10 is removed and anode supply 64 is reduced to a predetermined minimum flow necessary to avoid/prevent anode oxidation.
  • Cathode air supply 66 and pressures P1, P2 and P3 are maintained at least in part to promote air cooling of SOFC fuel system 10 and exhaust purge air therefrom via inlet 78.
  • Reformer subassembly 12 is shut down when the air cooling has lowered the temperature of SOFC subassembly has decreased to a point below that at which anode oxidation occurs, i.e., approximately 200°C.
  • each of main and micro-reformers 32, 34 are configured as partial oxidation reduction reformers.
  • each of main and micro- reformers 32, 34 respectively, receive from fuel supply F a flow of fuel 36a, 36b, respectively, via respective fuel control valves 38a, 38b, such as, for example, fuel injectors, and receive from air supply A respective flows of air 40a, 40b via respective air control valves 42a, 42b.
  • the present invention can be alternately configured, such as, for example, with one or more micro and/or main steam reformer(s), thereby requiring a source of steam or water be fluidly connected to the reformer(s) rather than a supply of air.
  • the integrated SOFC fuel system of the present invention is configured to include the fuel cell stack, fuel reformer, and waste energy recovery subassembly (including one or more heat exchangers and a combustor) into a single unit or housing.
  • the present invention can be alternately configured as a system that integrates any combination of the above, such as, for example, a combustor, reformer and heat exchanger, or a fuel cell, reformer and one or more heat exchangers into a single unit or housing.
  • the integrated SOFC fuel system of the present invention integrates into a single chamber, within a single system enclosure, a reformer, waste energy recovery subassembly, and SOFC subassembly.
  • a reformer waste energy recovery subassembly
  • SOFC subassembly SOFC subassembly.
  • the present invention can be alternately configured with chambers and an enclosure having a different geometric configuration, such as, for example, generally concentric spherical chambers generally concentrically contained within a generally spherical system enclosure.
  • the micro-reformer is configured as an exothermic POx reduction reformer.
  • the micro-refromer can be alternately configured, such as, for example, as a reformer, a catalytic or gas phase combustor. While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the present invention using the general principles disclosed herein. Further, this application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

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Abstract

An integrated solid oxide fuel cell (SOFC) system (10) includes a solid oxide fuel cell subassembly (16) having a fuel cell stack (90) fluidly interconnected with a distribution manifold (92). A waste energy recovery subassembly (14) includes a heat exchanger (54) and combustion zone (52). The waste energy recovery subassembly (14) is fluidly interconnected with the distribution manifold (92). A reformer subassembly (12) is fluidly connected to the waste energy recovery subassembly (14).

Description

INTEGRATED SOLID OXIDE FUEL CELL SYSTEM
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Patent Application Nos. 09/838,661 and 09/845,531, filed April 19, 2001 and April 30, 2001, respectively, each of which are incorporated herein by reference.
TECHNICAL FIELD
The present invention relates to solid oxide fuel cells.
BACKGROUND OF THE INVENTION
Automobile emissions are said to be a significant contributor to pollution. Automobiles emit hydrocarbons, nitrogen oxides, carbon monoxide and carbon dioxide as a result of the combustion process. In the United State, the Clean Air Act of 1970 and the 1990 Clean Air Act set national goals of clean and healthy air for all and established responsibilities for industry to reduce emissions from vehicles and other pollution sources. Standards set by the 1990 law limit automobile emissions to 0.25 grams per mile (gpm) non-methane hydrocarbons and 0.4 gpm nitrogen oxides. The standards are predicted to be further reduced by half in the year 2004, and similar air quality standards have been or are predicted to be adopted worldwide. It is expected that automobiles will continue to be powered by internal combustion engines for decades to come. As the world population continues to grow, and standards of living continue to rise, there will be an even greater demand for automobiles. This demand is predicted to be especially great in developing countries. To prevent the increasing number of automobiles from causing a proportionate increase in pollution, automobile manufacturers must reduce the level of undesirable emissions from each vehicle.
Some automobile manufacturers have attempted to utilize alternative transportation fuels and/or alternative sources of power, such as, for example, solid oxide fuel cells (SOFC). Generally, a fuel cell is a device that converts chemical energy into electrical energy. More particularly, a SOFC generates electricity and heat by electrochemically combining across an ion-conducting electrolyte a gaseous fuel, such as hydrogen, carbon monoxide, or a hydrocarbon, and an oxidant, such as air or oxygen. A conventional SOFC system typically includes a SOFC, a reformer and a waste energy recovery unit. The SOFC is a solid-state device, and includes two electrodes disposed on opposite sides of the ion-conducting electrolyte. In operation, a SOFC system generates electricity and heat by directing a flow of oxidant over the oxygen electrode or cathode while the fuel is passed over the fuel electrode or anode, thereby generating electricity, water and heat. The fuel (or reformate) provided to the SOFC is produced in the reformer. The reformer converts a hydrocarbon or oxygenated fuel into reformats thereof, e.g., hydrogen and carbon monoxide, and byproducts thereof, such as carbon dioxide and water. Byproducts from the SOFC, a supply of oxidant, and a supply of reformate, are typically directed through the discrete waste energy recovery unit. The waste energy recovery unit converts chemical and thermal energy into input thermal energy for the SOFC via one or more heat exchangers. The waste energy recovery unit, unlike the solid-state SOFC itself, is relatively large and bulky, is constructed of relatively durable and heat transferable materials, and includes many tubes and connections for directing the chemical and thermal energy through the unit.
Due to their size and bulk, such SOFC systems were used primarily for stationary power generation in the power generating industry. Conventional SOFC systems were not readily adaptable or suitable for use in a motor vehicle. Other types of fuel cell systems, such as, for example, proton exchange membrane (PEM) systems, have been adapted for use in motor vehicles. However, these PEM systems require costly and relatively complex systems for the on-board storage and/or generation of hydrogen and water management systems for on-board fuel reforming and system hydration. Such systems for storing and handling hydrogen and/or water are not typically found on conventional motor vehicles.
Therefore, what is needed in the art is a SOFC fuel cell system that is suitable for use in a motor vehicle.
Furthermore, what is needed in the art is a SOFC fuel cell system that integrates the fuel cell, waste recovery unit and reformer into one unit or system that is suitable for installation within a vehicle. SUMMARY OF THE INVENTION
The present invention provides an integrated solid oxide fuel cell system. The present invention comprises, in one form thereof, a solid oxide fuel cell subassembly having a fuel cell stack fluidly interconnected with a distribution manifold. A waste energy recovery subassembly includes a heat exchanger and combustion zone. The waste energy recovery subassembly is fluidly interconnected with the distribution manifold. A reformer subassembly is fluidly connected to the waste energy recovery subassembly.
An advantage of the present invention is that it is suitable for use in a motor vehicle.
Another advantage of the present invention is that the fuel cell, waste recovery unit and reformer are combined into one unit or system suitable for installation within a vehicle.
A further advantage of the present invention is that any two or more of the fuel cell system subassemblies can be integrated into one subassembly.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and be more completely understood by reference to the following description of one embodiment of the invention when read in conjunction with the accompanying drawings, wherein: FIG. 1 is a schematic diagram of one embodiment of an integrated SOFC fuel cell system of the present invention;
FIG. 2 is a schematic diagram of a single electrochemical cell of the SOFC fuel cell stack of Fig. 1 , and illustrates the operation thereof; FIG. 3 is a perspective view of the electrochemical cell of Fig. 2;
FIG. 4 is a perspective view an exemplary integration of the SOFC subassembly and waste energy recovery subassembly of Fig. 1, and illustrates the flow of gasses therethrough; and
FIG. 5 is a perspective view of the integrated SOFC subassembly and waste energy recovery subassembly of Fig. 4.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, and particularly to Fig. 1 , there is shown one embodiment of an integrated SOFC fuel cell system of the present invention. SOFC fuel cell system 10 includes reformer subassembly 12, waste energy recovery subassembly 14 and SOFC subassembly 16. Reformer subassembly 12, waste energy recovery subassembly 14 and SOFC subassembly 16 are all disposed within a single system enclosure 20. More particularly, system enclosure 20 includes a first chamber 22, second chamber 24 and third chamber 26. Each of reformer subassembly 12, waste energy recovery subassembly 14 and SOFC subassembly 16 are disposed in first chamber 22. Insulation layer 28 surrounds first chamber 22, and bulkhead 30, such as, for example, a metal or composite plate member, separates second chamber 24 and third chamber 26.
Reformer subassembly 12 includes main reformer 32 and micro-reformer 34. Generally, reformer subassembly 12 converts a supply of fuel F and a supply of air A into a flow of reformate, i.e., fuel, to SOFC subassembly 16 via waste energy recovery subassembly 14. More particularly, each of main reformer 32 and micro-reformer 34 receive from fuel supply F a flow of fuel 36a, 36b, respectively, via respective fuel control valves 38a, 38b, such as, for example, fuel injectors, and receive from air supply A respective flows of air 40a, 40b via respective air control valves 42a, 42b.
Main reformer 32 is fluidly connected to reformate control valve 44, and supplies thereto a flow of fuel/reformate 46. Micro-reformer 34 is fluidly connected to main reformer 32 and, as will be more particularly described hereinafter, supplies a flow of pre-reformate 48 to main reformer 32. Main and micro-reformers 32, 34, respectively, are integrally disposed within reformer subassembly housing 50. Main and micro- reformers 32, 34 are configured as exothermic partial oxidation (POx) reformers, and therefore the need for a separate supply of water and/or to re-circulate anode exhaust gases to obtain water vapor are avoided. Main reformer 32 includes a heating device and/or igniter 32a that heats the catalyst (not shown) contained in main reformer 32 thereby expediting the attainment of a desired operating temperature by main reformer 32. Micro-reformer 34 is sized to provide sufficient heat when in a full or substantially full combustion mode and sufficient reformate when in the reforming or normal operation mode to preheat and start-up the downstream device, i.e., main reformer 32, in a predetermined or desired period of time. Operation of main and micro-reformers 32, 34, respectively, is monitored with appropriate sensors (not shown), such as, for example, pressure, temperature, and gas pressure and composition sensors. Main and micro-reformers 32, 34, respectively, are connected in series.
Waste energy recovery subassembly 14 integrates a catalytic combustion zone 52 and one or more heat exchangers 54. Generally, waste energy recovery subassembly 14 receives a flow of reformate from main reformer 32 via reformate control valve 44. Depending on the mode of operation of SOFC system 10, waste energy recovery subassembly 14 either combusts the reformate, or heats the reformate and a flow of air. The flows of heated reformate and air are supplied to SOFC subassembly 16. Thus, waste energy recovery subassembly 14 converts unused chemical energy (such as unused reformate) and thermal energy (such as the exothermic reaction heat from the SOFC subassembly 16) to input thermal energy for SOFC fuel cell system 10.
More particularly, waste energy recovery subassembly 14 receives a plurality of working fluids and/or gases. Combustion zone 52 and heat exchanger 54 are each fluidly connected to reformate control valve 44. Under predefined operating conditions, such as, for example, during a start-up mode of operation of SOFC fuel cell system 10, at least a portion of reformate flow 46 is directed by reformate control valve 44 to combustion zone 52 as start-up or low-grade reformate flow 62. Under other predefined operating conditions, such as, for example, steady state or normal mode operation, at least a portion of reformate flow 46 is directed by reformate control valve 44 to heat exchanger 54 as operating reformate flow 64. A flow of cathode air 66, controlled and/or regulated by cathode air control valve 68, is passed through heat exchanger 54. A flow of process control air 70, fluidly connected to and regulated by process air control valve 72, is passed through heat exchanger 54. Combustion zone 52 is further fluidly connected to and receives from SOFC subassembly 16 a flow of cathode exhaust 74 and anode exhaust 76. Under certain operating conditions, such as, for example, shut down, a flow of purge air from first chamber 22 is fluidly coupled to combustion zone 52 via inlet 78.
Waste energy recovery subassembly 14 also exhausts and/or transfers a plurality of fluids and/or gases during the operation of SOFC fuel system 10. More particularly, the flows of operating reformate 64 and cathode air 66 are passed through heat exchanger 54 and to SOFC subassembly 16, as will be more particularly described hereinafter. Further, waste energy recovery subassembly 14 emits exhaust flow 80, e.g., a flow of reaction byproducts such as water, carbon dioxide and air, to the exterior of system enclosure 20.
Waste energy recovery subassembly 14 is embodied as a series of connected generally flat plate structures (not shown) having one or more openings or manifold passages along or bordering the edge of the plate for guiding the flow of oxidant, reformate or exhaust gases. The plates also include features (not shown), such as, for example, etchings, chevrons or channels, that are disposed, for example, in or near the center portion of the plates for guiding the movement of the oxidant, reformate or exhaust. The oxidant, reformate and exhaust enter the waste energy recovery subassembly 14 via respective inputs, as described above, and are guided through respective features/channels and across the plates to corresponding outlet passages. The flows of oxidant, reformate and/or exhaust are separated from each other by the features/channels to prevent mixing of the gases.
SOFC subassembly 16 includes SOFC fuel cell stack 90 and distribution manifold 92. Generally, SOFC subassembly 16 distributes the flow of operating reformate 64 and cathode air 66, and converts those flows to electricity.
SOFC fuel cell stack 90 is a multi-layer ceramic / metal composite fuel cell having the capacity to produce a predetermined amount of electricity, such as, for example, a level of current sufficient to drive the electrical load presented by the various electrical devices found on a typical automobile. SOFC fuel cell stack 90 produces electricity at an operating temperature of from approximately 600°C to approximately 1000°C, and
preferably from approximately 600°C to approximately 800°C. SOFC fuel cell stack 90 includes one or more electrically and fluidly interconnected multi-cell modules (not shown), and includes an electrode 94 that extends from system enclosure 20 for connecting SOFC fuel cell stack 90 to an electrical load, such as, for example, a power bus (not shown) of a motor vehicle. Referring now to Fig. 2, a schematic representation of a single cell 100 of mutli- layer, multi-cell fuel cell stack 90 is shown to illustrate the operation of fuel cell stack 90. Anode 102 and cathode 104 are disposed on opposite sides of and spaced apart by oxygen ion conducting electrolyte 106. Reformate flow 64 is directed over anode 102, and cathode air flow 66 is passed over cathode 104 of cell 100. Cathode flow 66 is reduced in the presence of electrolyte 106. Oxygen ions (O"2) are thereby generated and move through electrolyte 106 to anode 102, as summarized by the following reaction: O2 + 4e" -> 2(O"2).
At anode 102, reformate flow 64 is oxidized in the presence of electrolyte 106 and the migrating oxygen ions. The reaction of reformate flow 64 with the oxygen ions produces electrons (e"), which flow to external circuit 110 and back to cathode 104. Unreacted fuel byproducts, such as, for example, carbon monoxide, water, and carbon dioxide, exit cell 100 in anode exhaust flow 76, which is in turn directed by distribution manifold 92 to combustion zone 52 of waste energy recovery subassembly 14. At cathode 104, excess cathode oxidant flow 66 exits cell 100 in cathode exhaust flow 74, which is also directed by distribution manifold 92 to combustion zone 52 of waste energy recovery subassembly 14. As best shown in Fig. 3, cell 100 includes anode plate 102 which is spaced apart and separated from cathode plate 104 by electrolyte 106. Collector 112 is disposed adjacent the side (not referenced) of anode 102 that is opposite electrolyte 106, and collector 114 is disposed adjacent the side (not referenced) of cathode 104 that is opposite electrolyte 106. An anode plate 116 of a second cell (not shown) is disposed below, i.e., on the opposite side of, collector 114, thereby illustrating the placement of and ability to stack several cells in electrical communication with cell 100.
The anode 102 and cathode 104, which with electrolyte 106 form phase boundaries between gas/electrolyte/catalyst commonly known as triple points, are disposed adjacent to and/or integral with electrolyte 106. Anode 102 and cathode 104 are generally formed of porous material capable of functioning as an electrical conductor and capable of facilitating the reactions described herein. More particularly, the porosity of the material that comprises anode 102 and cathode 104 should be sufficient to enable dual directional flow of gases, i.e., the admission of fuel or oxidant gases and the exit of byproducts. Even more particularly, the porosity of the material that comprises anode 102 and cathode 104 should be up to approximately 40 percent and ideally from approximately 20 to approximately 40 percent.
Anode 102 and cathode 104 are constructed of material that include elements such as zirconium, yttrium, nickel, manganese, strontium, lanthanum and oxides, alloys and combinations including at least one of the foregoing elements. Anode 102 is preferably formed upon a ceramic skeleton, such as, for example, a yttria-stabilized zirconia, for thermal compatibility.
Both anode 102 and cathode 104 are formed on electrolyte 106 by a variety of techniques, such as, for example, sputtering, chemical vapor deposition, screen printing, spraying, dipping, stenciling and painting. The anode 102 and cathode 104 electrodes are typically up to approximately 1 ,000 microns in thickness, with a thickness of from approximately 10 to approximately 50 microns typically being preferred. Alternatively, cell 100 can be configured as an anode supported cell by forming electrolyte 106 and cathode 104 on anode 102 using any of the above deposition/application techniques. Further alternatively, cathode 104 or an inert layer (not shown) can be substituted as the support for cell 100.
Electrolyte 106 is an ion conductor capable of transporting oxygen ions from the cathode 104 to the anode 102, and which is compatible with the environment in which SOFC fuel cell system 10 is to be used, such as, for example, in temperatures of up to approximately 1000°C. Generally, suitable materials for electrolyte 106 include ceramics, such as, for example, perovskite and/or fluorite, metals, such as, for example, alloys, oxides, and/or gallates. Further, suitable electrolyte materials include, for example, zirconium, yttrium, calcium, cerium, magnesium, aluminum, rare earth metals, oxides, gallates, aluminates, and combinations and/or composites of at least one of the foregoing materials. Preferably, a rare earth oxide, such as, for example, yttria, gadolinia, neodymia, and the like doped with aliovalient oxides, such as, for example, magnesia, calcia, strontia, and other +2 valence metal oxides, are used for the material of electrolyte 106. Most preferably, a yttria-stabilized zirconia material is used for electrolyte 106.
Cell 100 is electrically connected with other cells (not shown) through interconnects / collectors 112 and 114. Collectors 112, 114 include passages (not referenced) for guiding the flow of fuel and oxidant, respectively. Collectors 112 and 114 are generally formed of electrically conductive material that is capable of withstanding the temperatures and pressures under which SOFC fuel cell system 10 is operated. More particularly, collectors 112 and 114 are constructed of materials, such as, for example, silver, copper, ferrous materials, strontium, lanthanum, chromium, chrome, gold, platinum, palladium, nickel, titanium, conducting ceramics, or composites and combinations of at least one of the foregoing, that are capable of withstanding the operating conditions of a motor vehicle, i.e., ambient temperatures from approximately - 40°C to operating temperatures of approximately 1000°C. Each individual cell 100 generates approximately from 0.5 volts to approximately 1.2 volts direct current. The desired output voltage of SOFC fuel cell system 10 is obtained by connecting in series a plurality of cells 100 together, as described herein.
Gas distribution manifold 92, as shown in Figs. 1 and 4, fluidly interconnects SOFC fuel cell stack 90 with waste energy recovery subassembly 14. More particularly, gas distribution manifold 92 receives heated reformate flow 64 and heated cathode air flow 66 from waste energy recovery subassembly 14 via inlet/outlet manifold 120 (Figs. 4 and 5), and distributes those flows to the SOFC fuel cell stack 90. Gas distribution manifold 92 further directs anode and cathode exhaust flows 74 and 76, respectively, from SOFC fuel cell stack 90 to combustion zone 52 of waste energy recovery subassembly 14. After combustion thereof, any remaining byproducts are exhausted via exhaust flow 80. It should be particularly noted that, as best shown in Figs. 1 and 4, gas distribution manifold 92 integrates into a unitary subassembly (not referenced) the waste energy recovery subassembly 14 and SOFC subassembly 16. More particularly, as shown in Fig. 5, fuel cell stack 90, distribution manifold 92, waste energy recovery subassembly 14 and inlet/outlet manifold 120, are integrated into a single unitary subassembly (not referenced) by fasteners 121 , such as, for example, bolts.
Referring back to Figs. 1 and 4, anode exhaust 76 and cathode exhaust 74 are routed back to combustion zone 52 of waste energy recovery subassembly 14, where they are mixed with air flow 70 and burned. The burning of the anode and cathode exhausts 76, 74, respectively, in combustion zone 52 heats heat exchanger 54 of waste energy recovery subassembly 14. During periods of high temperature operation of waste energy recovery subassembly 14 cooling air control valve 122 is actuated and connects a flow of cooling air 124 to cathode air flow 66, thereby blending cooler air with cathode air flow 66 and controlling the temperature of SOFC subassembly 16.
The thermal management (not referenced) of SOFC fuel cell system 10 should be particularly noted. The thermal management system of SOFC fuel cell system includes first, second and third chambers 22, 24 and 26, respectively, and is designed to insulate the internal hardware of SOFC fuel cell system 10 and maintain the exterior temperature of system enclosure 20 at approximately 90°C or less. System enclosure 20 supports the components of SOFC fuel cell system 10, and can optionally be actively temperature controlled in a known manner. System enclosure 20 surrounds and defines at least in part second and third chambers 24 and 26, respectively. First chamber 22 is housed internally to second chamber 24, and contains reformer subassembly 12, waste energy recovery subassembly 14, SOFC subassembly 16 and other high-temperature components (not shown), such as, for example, sensors and controllers. Thus, reformer subassembly 12, waste energy recovery subassembly 14 and SOFC subassembly 16 are integrated within first chamber 22.
The thermal management system includes two means that actively control the temperature of system enclosure 20. Referring again to Fig. 1, cooling air lid passage 128 is defined by lid 126 of system enclosure 20. Lid 126 incorporates a thin heat exchanger (not shown) across the entire surface thereof. The surface of lid 126 provides a contact point to vehicle 130 and therefore operates at a lower temperature than the other surfaces of system enclosure 20. Main blower 132 is disposed within system enclosure 20 and together with air control valve 134 selectively draws cooling air A through cooling air lid passage 128, thereby cooling the surface of system enclosure 20 that is in contact with vehicle 130 and pressurizing third chamber 26 to a pressure P1. The operation of main blower 132 and valve 134, and thus pressure P1 , are controlled and adjusted dependent at least in part upon the temperature of the incoming cooling air, and preferably cools the surface of system enclosure 20 to approximately 90°C or less, and more preferably to approximately 45°C or less.
Bulkhead plate 30 separates third chamber 26 and second chamber 24. Air control valve 136 controls the flow of air into second chamber 24 and thereby regulates pressure P2 and ensures the appropriate degree of cooling is attained. Insulation layer or wall 28 is disposed between first chamber 22 and second chamber 24, and also forms part of the thermal management system of SOFC fuel cell system 10. A flow of air 137 from second chamber 24 through insulation layer 28 and into first chamber 22 cools first chamber 22. The flow of air 137 pressurizes first chamber 22 to a pressure P3, which is maintained at a level that is a predetermined amount less than P2. Once the flow of air has reached first chamber 22, the air is referred to as purge air. The purge air is drawn (or pushed by the pressure P2 and P3 differentials) into inlet 78 of waste energy recovery system 14, and is exhausted from SOFC fuel cell system 10. Thus, the above described thermal management system controls the exterior temperature of first chamber 22 to a temperature of approximately 200°C or less, and
preferably from approximately 100°C to approximately 80°C or less.
A process air system (not referenced) provides cooling air to the thermal management system and to the other components of SOFC fuel cell system 10 that utilize/require air. The process air system draws air from air supply A, such as, for example, an external air supply. Air supply A is processed through air filter 142 and directed through cooling air passage 128 in lid 122 and to main blower 132, as described above. Main blower 132 is disposed within third chamber 26, and delivers air through process air control valve 134 to third chamber 26 and, thus, to the thermal management system of SOFC fuel cell system 10. Main blower 132 pressurizes the chambers 22, 24 and 26, thereby providing for the cooling and purging thereof. Other components of the process air system, such as air control valves 42a, 42b, 68, 72, and 122, along with fuel injectors 38a and 38b, and other lower-temperature components of SOFC fuel cell system 10 are disposed within third chamber 26 to ensure operation within their lower operation temperature range.
In use, during start-up of SOFC fuel system 10, main blower 132 pressurizes the chambers appropriately and as described above. Fuel supply F enters and thus pressurizes the fuel system and operation of micro-reformer 34 is commenced, such as, for example, by energizing an electrically heated element (not shown) in the fuel vaporization zone thereof. Micro-reformer 34 receives fuel flow 36a from fuel injector 38a and receives air flow 40a from air control valve 42a, and produces pre-reformate 48. Pre-reformate flow 48 is routed through and heats main reformer 34. Although not shown, pre-reformate flow 48 is also routed through and heats waste energy recovery subassembly 14 and SOFC subassembly 16. Appropriate sensors (not shown), such as, for example, temperature and/or sampling sensors, monitor the properties of reformate flows 62 and 64. Once main reformer 32 has reached a predetermined minimum start-up temperature, such as, for example, approximately 600°C, fuel valve 38b and air control valve 42b are actuated to thereby supply fuel flow 36b and air flow 40b to main reformer 32. Main reformer 32 thus begins producing operating reformate flow 46. At least a portion of reformate flow 46 is directed by reformate control valve 44 through combustion zone 52 as refromate flow 62 during the start up operating mode of SOFC fuel cell system 10. The combustion of reformats within combustion zone 52 heats heat exchangers 54.
Once fuel cell stack 90 reaches a predetermined lower or minimum operational temperature limit, such as, for example, approximately 650°C or greater and preferably
from approximately 650°C to approximately 800°C or greater, SOFC subassembly 16 transitions from the start-up mode of operation to the normal mode of operation. At least a portion of reformate flow 46 is re-directed by reformate control valve 44 to flow as reformate flow 64 through heat exchanger 54 and to SOFC subassembly 16, rather than through combustion zone 52 as reformate flow 62. The output, i.e., cathode and anode exhaust flows 74, 76, respectively, are routed through combustion zone 52 where they are mixed with air flow 70 and catalyzed.
Shutdown from normal operating mode includes cooling SOFC system 10 to near ambient conditions, the electrical load placed upon SOFC system 10 is removed and anode supply 64 is reduced to a predetermined minimum flow necessary to avoid/prevent anode oxidation. Cathode air supply 66 and pressures P1, P2 and P3 are maintained at least in part to promote air cooling of SOFC fuel system 10 and exhaust purge air therefrom via inlet 78. Reformer subassembly 12 is shut down when the air cooling has lowered the temperature of SOFC subassembly has decreased to a point below that at which anode oxidation occurs, i.e., approximately 200°C.
In the embodiment shown, each of main and micro-reformers 32, 34, are configured as partial oxidation reduction reformers. Thus, each of main and micro- reformers 32, 34, respectively, receive from fuel supply F a flow of fuel 36a, 36b, respectively, via respective fuel control valves 38a, 38b, such as, for example, fuel injectors, and receive from air supply A respective flows of air 40a, 40b via respective air control valves 42a, 42b. However, it is to be understood that the present invention can be alternately configured, such as, for example, with one or more micro and/or main steam reformer(s), thereby requiring a source of steam or water be fluidly connected to the reformer(s) rather than a supply of air.
In the embodiment shown, the integrated SOFC fuel system of the present invention is configured to include the fuel cell stack, fuel reformer, and waste energy recovery subassembly (including one or more heat exchangers and a combustor) into a single unit or housing. However, it is to be understood that the present invention can be alternately configured as a system that integrates any combination of the above, such as, for example, a combustor, reformer and heat exchanger, or a fuel cell, reformer and one or more heat exchangers into a single unit or housing.
In the embodiment shown, the integrated SOFC fuel system of the present invention integrates into a single chamber, within a single system enclosure, a reformer, waste energy recovery subassembly, and SOFC subassembly. Although configured and shown in the figures as having generally rectangular and/or square chambers and a correspondingly shaped enclosure, it is to be understood that the present invention can be alternately configured with chambers and an enclosure having a different geometric configuration, such as, for example, generally concentric spherical chambers generally concentrically contained within a generally spherical system enclosure.
In the embodiment shown, the micro-reformer is configured as an exothermic POx reduction reformer. However, it is to be understood that the micro-refromer can be alternately configured, such as, for example, as a reformer, a catalytic or gas phase combustor. While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the present invention using the general principles disclosed herein. Further, this application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims

WHAT IS CLAIMED
1. An integrated solid oxide fuel cell (SOFC) system (10), comprising: a solid oxide fuel cell (16) including a fuel cell stack (90); a waste energy recovery subassembly (14) including at least one of a heat exchanger (54) and a combustion zone (52); a distribution manifold (92) fluidly interconnecting said fuel cell stack (90) and said waste energy recovery subassembly (14); and a reformer subassembly (12) fluidly connected to said waste energy recovery subassembly (14).
2. The fuel cell system (10) of claim 1 , wherein: said fuel cell stack (90) includes stack supply (64, 66) and stack exhaust passages (74, 76) therethrough; said waste energy recovery subassembly (14) includes combustion supply (70, 74, 76, 78) and combustion exhaust passages (80) through said combustion zone (52), and exchange supply (64, 66) and exchange exhaust (64, 66) passages through said heat exchanger (54); and said distribution manifold (92) integrally and fluidly connecting said fuel cell stack (90) and said waste energy recovery subassembly (14), said distribution manifold (90) including manifold supply (64, 66) and manifold exhaust passages (74, 76), said manifold supply passage (64, 66) fluidly interconnecting said stack supply passage (64, 66) with said exchange exhaust passage (64, 66), said manifold exhaust passage (74, 76) fluidly interconnecting said stack exhaust passage (74, 76) with corresponding ones of said combustion supply passage (74, 76).
3. The fuel cell system (10) of claim 2, further comprising an inlet/outlet (IO) manifold (120) having IO supply (64, 66) and IO exhaust (74, 76) passages therethrough, said IO supply passage (64, 66) fluidly interconnecting said exchange exhaust passage (64, 66) with said manifold supply passage (64, 66), said IO exhaust passage (74, 76) fluidly interconnecting said manifold exhaust passage (74, 76) with said corresponding combustion supply passages (74, 76).
4. The fuel cell system (10) of claim 2, wherein said distribution manifold (92) further comprises a temperature control air flow passage (124) fluidly interconnected with said manifold exhaust passage (74, 76).
5. The fuel cell system (10) of claim 4, further comprising: a temperature control valve (122) in fluid communication with said temperature control air flow passage (124), a temperature control air flow regulated and controlled by said temperature control valve (122), said temperature control air flow flowing through said temperature control air flow passage (124).
6. The fuel cell system (10) of claim 2, wherein: said stack supply passage (64, 66) includes an anode stack supply passage (64) and a cathode stack supply passage (66); said combustion supply passage (74, 76) includes an anode combustion supply (76) and a cathode combustion supply (76) passage; and said manifold supply passages (64, 66) including an anode manifold supply (64) and a cathode manifold supply (64) passage, said anode manifold supply passage (64) fluidly connecting said anode stack supply passage (64) with said anode waste supply passage (76), said cathode manifold supply passage (66) fluidly interconnecting said cathode stack supply passage (66) with said cathode waste supply passage (74).
7. The fuel cell system (10) of claim 2, further comprising: at least one fastener (121) coupling together into an integrated subassembly at least two of said fuel cell stack (90), said waste energy recovery subassembly (14), said distribution manifold (92) and said reformer subassembly (12).
8. The fuel cell system (10) of claim 7, further comprising: an inlet/outlet manifold (IO) (120) having IO supply (64, 66) and IO exhaust passages (74, 76) therethrough, said IO supply passage (64, 66) fluidly interconnecting said exchange exhaust passage (74, 76) with said manifold supply passage(64, 66), said IO exhaust passage (74, 76) fluidly interconnecting said manifold exhaust passage (74, 76) with said combustion supply passage (74, 76); and at least one fastener (121) coupling together into an integrated subassembly at least two of said fuel cell stack (90), said waste energy recovery subassembly (14), said distribution manifold (92), said reformer subassembly (12) and said inlet/outlet manifold (120).
9. The fuel cell system (10) of claim 1 , further comprising a system housing (20), said fuel cell stack (90), said waste energy recovery subassembly (14), said distribution manifold (92) and said reformer subassembly (12) disposed within said system housing.
10. The fuel cell system (10) of claim 9, further comprising first (22), second (24), and third (26) chambers disposed within said system housing (20), said fuel cell stack (90), said waste energy recovery subassembly (14), said distribution manifold (92) and said reformer subassembly (16) disposed within said first chamber (22); and an insulation material (28) defining at least in part a boundary between said first (22) and said second (24) chambers, said insulation material (28) having a predetermined porosity to thereby permit the flow of air therethrough.
11. The fuel cell system (10) of claim 10, further comprising: a bulkhead plate (30) defining at least in part a boundary between said third (26) and second (24) chambers.
12. The fuel cell system (10) of claim 10, further comprising: a main blower (132) pressurizing said third chamber (26) to a pressure P1 ; and an air control valve (136) controlling the flow of air from said third chamber (26) to said second chamber (24), said air control valve (136) regulating a pressure within said second chamber (24) to a pressure P2.
13. The fuel cell system (10) of claim 9, further comprising a purge air inlet (78) passage fluidly connecting said first chamber (22) with said combustion zone (52) of said waste energy recovery subassembly (14).
14. The fuel cell system (10) of claim 1, further comprising a reformate control valve (44) fluidly connecting said reformer subassembly (12) with at least one of said heat exchanger (54) and said combustion zone (52) of said waste energy recovery subassembly (14).
15. The fuel cell system (10) of claim 1 , wherein said reformer subassembly (12) includes a micro-reformer (34) fluidly connected to a main reformer (32), each of said micro-reformer (34) and said main reformer (32) being fluidly connected to a respective flow of air (40a, 40b) and a respective flow of fuel (36a, 36b).
16. The fuel cell system (10) of claim 15, wherein at least one of said micro- reformer (34) and said main reformer (32) comprise exothermic partial oxide reduction reformers.
17. A method of operating a solid oxide fuel cell (10), comprising: pressurizing a third chamber (26) to a predetermined pressure, said third chamber (26) housing a plurality of fuel and air control valves (38a, 38b, 42a, 42b, 68, 72, 122, 134, 136) and at least one blower (132); directing a first supply of fuel (36a) and a first supply of air (40a) to a micro- reformer (34); creating a heated pre-reformate (48) in said micro-reformer (34); preheating a main reformer (32) with said heated pre-reformate (48); directing a second supply of fuel (36b) and a second supply of air (40b) to said main reformer (32); creating a heated main reformate (46) in said main reformer (32); heating a cathode supply (66) with the heated main reformate; and further heating the solid oxide fuel cell (90) with the heated cathode supply (66).
18. The method of claim 17, wherein said further heating step comprises heating the solid oxide fuel cell (90) to a temperature of approximately 120°C.
19. The method of claim 17, further comprising: selectively directing at least a portion of the heated pre-reformate (48) and at least a portion of the heated main reformate (46) to at least one of a heat exchanger (54) and combustion zone (52); and providing the heated pre-reformate (48) and heated main reformate (46) exiting the heat exchanger (54) to the solid oxide fuel cell.
20. The method of claim 17, further comprising pre-heating the micro-reformer (34).
21. The method of claim 17, further comprising monitoring at least one of a pressure, temperature and rate of flow of the heated main reformate (46).
22. A method of transitioning a solid oxide fuel cell system (10) from a start-up operating condition to a normal operating condition, comprising operating a main reformer (32), the main reformer (32) producing a reformate (46); catalytically combusting a first stream (62) of the reformate; heating a second stream (64) of the reformate and a flow of air (66) with heat generated by said catalytically combusting step, thereby creating a heated stream of reformate (64) and a heated flow of air (66); and directing the heated stream of reformate (64) and the heated flow of air (66) to the solid oxide fuel cell (90), thereby heating the solid oxide fuel cell (90).
23. The method of claim 22, wherein said directing step is regulated to place and maintain the solid oxide fuel cell (90) at a temperature of from approximately 600°C to
approximately 1000°C.
24. The method of claim 22, wherein said directing step is regulated to place and maintain the solid oxide fuel cell (90) at a temperature of from approximately 650°C to
approximately 800°C.
25. A method of operating a solid oxide fuel cell system (10), said solid oxide fuel cell system (10) having a fuel cell stack (90), said method comprising: directing a supply of reformate (64) from a waste energy recovery subassembly (14) to the solid oxide fuel cell stack (90); providing a supply of air (66) to the solid oxide fuel cell stack (90); generating electrical energy in the solid oxide fuel cell stack (90) from the reformate (64) and supply of air (66); harnessing said electrical energy; sensing a condition of the reformate (64); and adjusting at least one of the supply of reformate (64) and the supply of air (66) dependent at least in part upon said sensing step to supply a requested amount of electrical energy.
26. The method of claim 25, wherein said sensing step comprises sensing at least one of a temperature, pressure, gas content and rate of flow of the reformate (64).
27. A method of shutting down a solid oxide fuel cell system (10) having a fuel cell stack (90), comprising: maintaining a supply of air (66) to the fuel cell stack (90) and a supply of air to at least one thermal enclosure (20, 22, 24, 26); decreasing a supply of reformate (64) to the fuel cell stack (90); stopping the supply of reformate (64) after an anode oxidation period has passed; and stopping the supply of air (66) to the fuel cell stack.
28. The method of claim 27, further comprising maintaining the supply of reformate (64) at a flow sufficient to prevent anode oxidation during the anode oxidation period.
29. The method of claim 27, further comprising exhausting stored thermal energy through a waste energy recovery subassembly (14) with said supply of air to said at least one thermal enclosure (20, 22, 24, 26).
30. A method of operating a solid oxide fuel cell system (10) having a fuel cell stack (90), comprising: directing a supply of reformate (64) and a supply of air (66) to the fuel cell stack (90); operating the fuel cell stack (90); reducing the supply of reformate (64) and the supply of air (66) to the fuel cell stack (90); and maintaining the fuel cell stack (90) at a standby temperature of approximately 400°C to approximately 600°C.
31. The method of claim 30, further comprising transitioning the fuel cell system (10) from the standby temperature to an operating temperature, the operating temperature from approximately 600°C or less.
32. A solid oxide fuel cell system (10) for a vehicle (130), comprising: a solid oxide fuel cell subassembly (16); a reformer subassembly (12) in fluid communication with said fuel cell subassembly (16); a waste energy recovery subassembly (14)in fluid communication with the solid oxide fuel cell subassembly (16) and said reformer subassembly (12); a system enclosure (20) within which is disposed said solid oxide fuel cell subassembly (16), said waste energy recovery subassembly (14), and said reformer subassembly (12); and a thermal management system disposed within said system enclosure (20).
33. The solid oxide fuel cell system (10) of claim 32, wherein said thermal management system comprises: first, second, and third chambers (22, 24, 26) disposed within said system enclosure (20), said fuel cell subassembly (16), said waste energy recovery subassembly (14), and said reformer subassembly (12) disposed within said first chamber; and an insulation material (28) defining at least in part a boundary between said first (22) and said second (24) chambers, said insulation material (28) having a predetermined porosity to thereby permit the flow of air therethrough.
34. The solid oxide fuel cell system (10) of claim 33, further comprising: a bulkhead plate (30) defining at least in part a boundary between said third (26) and second (24) chambers.
35. The solid oxide fuel cell system (10) of claim 33, further comprising: a main blower (132) pressurizing said third chamber (26) to a pressure P1 ; an air control valve (136) controlling the flow of air from said third chamber (26) to said second chamber (24), said air control valve (136) regulating a pressure within said second chamber (24) to a pressure P2; wherein said porosity of said insulation layer (28) regulates a pressure of said third chamber (26) to a pressure of P3, P3 being a predetermined amount less than P2.
36. The solid oxide fuel cell system (10) of claim 33, further comprising a purge air inlet passage (78) fluidly connecting said first chamber (22) with said combustion zone (52) of said waste energy recovery subassembly (14).
37. The solid oxide fuel cell system (10) of claim 32, further comprising a reformate control valve (44) fluidly connecting said reformer subassembly (12) with said waste energy recovery subassembly (14).
38. An integrated solid oxide fuel cell (SOFC) system (10), comprising: a solid oxide fuel cell (16) including a fuel cell stack (90); a waste energy recovery subassembly (14) including at least one of a heat exchanger (54) and a combustion zone (52); a distribution manifold (92) fluidly interconnecting said fuel cell stack (90) and said waste energy recovery subassembly (14); and a reformer subassembly (12) fluidly connected to said waste energy recovery subassembly (14).
39. The integrated solid oxide fuel cell (SOFC) system (10) of claim 38, wherein at least two of said fuel cell stack (90), said heat exchanger (54), said combustion zone (52), said distribution manifold (92) and said reformer subassembly (12) are integrated together in a composite unit.
40. The integrated solid oxide fuel cell (SOFC) system (10) of claim 38, wherein at least two of said heat exchanger (54), said combustion zone (52), said distribution manifold (92) and said reformer subassembly (12) are integrated together in a composite unit.
EP02728838A 2001-04-19 2002-04-19 Integrated solid oxide fuel cell system Withdrawn EP1382079A4 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US09/838,661 US6627339B2 (en) 2000-04-19 2001-04-19 Fuel cell stack integrated with a waste energy recovery system
US838661 2001-04-19
US845531 2001-04-30
US09/845,531 US6562496B2 (en) 2000-05-01 2001-04-30 Integrated solid oxide fuel cell mechanization and method of using for transportation industry applications
PCT/US2002/012315 WO2002087052A2 (en) 2001-04-19 2002-04-19 Integrated solid oxide fuel cell system

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