ATE551742T1 - Wasserverwaltung in brennstoffzellen - Google Patents

Wasserverwaltung in brennstoffzellen

Info

Publication number
ATE551742T1
ATE551742T1 AT04806257T AT04806257T ATE551742T1 AT E551742 T1 ATE551742 T1 AT E551742T1 AT 04806257 T AT04806257 T AT 04806257T AT 04806257 T AT04806257 T AT 04806257T AT E551742 T1 ATE551742 T1 AT E551742T1
Authority
AT
Austria
Prior art keywords
fuel cells
water management
management
water
fuel
Prior art date
Application number
AT04806257T
Other languages
English (en)
Inventor
Jeremy Stephen Matcham
Nathan Grange
Paul Alan Benson
Scott Baird
Ashley Kells
Jonathan Cole
Paul Adcock
Peter David Hood
Simon Edward Foster
Original Assignee
Intelligent Energy Ltd
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
Application filed by Intelligent Energy Ltd filed Critical Intelligent Energy Ltd
Application granted granted Critical
Publication of ATE551742T1 publication Critical patent/ATE551742T1/de

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
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0432—Temperature; Ambient temperature
    • H01M8/0435—Temperature; Ambient temperature of cathode exhausts
    • 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
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
    • H01M8/0263—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant having meandering or serpentine paths
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/0267—Collectors; Separators, e.g. bipolar separators; Interconnectors having heating or cooling means, e.g. heaters or coolant flow channels
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • 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
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H01M8/04119—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
    • H01M8/04126—Humidifying
    • 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
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04544—Voltage
    • H01M8/04559—Voltage of fuel cell stacks
    • 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
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H01M8/04574—Current
    • H01M8/04589—Current of fuel cell stacks
    • 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
    • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
    • H01M8/04746—Pressure; Flow
    • H01M8/04753—Pressure; Flow of fuel cell reactants
    • 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
    • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
    • H01M8/04828—Humidity; Water content
    • H01M8/04835—Humidity; Water content of fuel cell reactants
    • 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
    • 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
    • H01M8/2465—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
    • H01M8/04—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
    • H01M8/04029—Heat exchange using liquids
    • 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
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H01M8/04119—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
    • H01M8/04126—Humidifying
    • H01M8/04134—Humidifying by coolants
    • 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

Landscapes

  • 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)
AT04806257T 2003-12-31 2004-12-31 Wasserverwaltung in brennstoffzellen ATE551742T1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0330272A GB2409763B (en) 2003-12-31 2003-12-31 Water management in fuel cells
PCT/GB2004/005463 WO2005064727A2 (en) 2003-12-31 2004-12-31 Water management in fuel cells

Publications (1)

Publication Number Publication Date
ATE551742T1 true ATE551742T1 (de) 2012-04-15

Family

ID=31503355

Family Applications (1)

Application Number Title Priority Date Filing Date
AT04806257T ATE551742T1 (de) 2003-12-31 2004-12-31 Wasserverwaltung in brennstoffzellen

Country Status (16)

Country Link
US (2) US8277998B2 (de)
EP (1) EP1719199B1 (de)
JP (1) JP5193467B2 (de)
KR (1) KR101166251B1 (de)
CN (1) CN100502118C (de)
AR (1) AR047358A1 (de)
AT (1) ATE551742T1 (de)
BR (1) BRPI0418263B1 (de)
CA (1) CA2551674C (de)
ES (1) ES2394955T3 (de)
GB (1) GB2409763B (de)
MX (1) MXPA06007516A (de)
NO (1) NO336638B1 (de)
RU (1) RU2356133C2 (de)
WO (1) WO2005064727A2 (de)
ZA (1) ZA200605295B (de)

Families Citing this family (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2382455B (en) * 2001-11-07 2004-10-13 Intelligent Energy Ltd Fuel cell fluid flow field plates
GB2412784B (en) * 2002-01-18 2006-08-23 Intelligent Energy Ltd Fuel cell oxygen removal and pre-conditioning system
GB2390738B (en) * 2002-07-09 2005-05-11 Intelligent Energy Ltd Fuel cell direct water injection
GB2401986B (en) * 2003-05-17 2005-11-09 Intelligent Energy Ltd Improvements in fuel utilisation in electrochemical fuel cells
GB2409763B (en) 2003-12-31 2007-01-17 Intelligent Energy Ltd Water management in fuel cells
GB2413002B (en) * 2004-04-08 2006-12-06 Intelligent Energy Ltd Fuel cell gas distribution
GB2422716B (en) * 2005-01-26 2007-08-22 Intelligent Energy Ltd Multi-layer fuel cell diffuser
GB2434845B (en) * 2006-02-01 2010-10-13 Intelligent Energy Ltd Variable compressibility gaskets
US7943259B1 (en) 2006-12-18 2011-05-17 University Of South Florida Method of controlled delivery for use of electrochemical power source
GB2453126B (en) 2007-09-26 2013-02-06 Intelligent Energy Ltd Fuel cell system
GB2453127A (en) 2007-09-26 2009-04-01 Intelligent Energy Ltd Fuel Cell System
GB2464946B (en) * 2008-10-30 2012-05-16 Intelligent Energy Ltd Fuel cell cooling
FR2940196B1 (fr) 2008-12-22 2010-12-10 Renault Sas Dispositif et procede de refroidissement d'un organe thermique de vehicule automobile
WO2012047184A1 (en) * 2010-10-06 2012-04-12 Utc Power Corporation Evaporatively cooled fuel cells with water passageways enhanced by wicks
WO2012117525A1 (ja) * 2011-03-01 2012-09-07 トヨタ自動車株式会社 燃料電池システム
GB2533265B (en) * 2014-12-01 2021-09-15 Intelligent Energy Ltd Fuel cell system
JP6696696B2 (ja) * 2017-03-21 2020-05-20 株式会社東芝 電気化学反応装置
CN109256573B (zh) * 2018-10-24 2023-05-26 天津中德应用技术大学 用于质子交换膜氢燃料电池堆的空气流量调节方法及装置
EP3918655A2 (de) 2019-01-29 2021-12-08 Bloom Energy Corporation Brennstoffzellensystem mit wasserinjektor und betriebsverfahren dafür
EP4225603A1 (de) * 2020-10-05 2023-08-16 Alakai Technologies Corporation Gesundheitsbewertungs- und überwachungssystem und verfahren für elektrofahrzeuge mit sauberem kraftstoff
CN114335623A (zh) * 2021-12-29 2022-04-12 潍柴动力股份有限公司 燃料电池堆阴阳极液态水耐受性测试方法及装置

Family Cites Families (29)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2533215C3 (de) * 1975-07-25 1980-08-14 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Verfahren zur Konstanthaltung der Betriebstemperatur und Elektrolytkonzentration einer für Rohgas/Luft-Betrieb ausgebildeten Brennstoffzellenbatterie mit festgelegtem sauren Elektrolyten
DE3738370C1 (de) 1987-11-12 1989-04-13 Dornier System Gmbh Elektrochemische Zelle mit immobilem Elektrolyten
US5935726A (en) 1997-12-01 1999-08-10 Ballard Power Systems Inc. Method and apparatus for distributing water to an ion-exchange membrane in a fuel cell
US6174616B1 (en) * 1998-10-07 2001-01-16 Plug Power Inc. Fuel cell assembly unit for promoting fluid service and design flexibility
JP4200576B2 (ja) * 1999-02-23 2008-12-24 トヨタ自動車株式会社 燃料電池システム
IT1312198B1 (it) 1999-04-21 2002-04-09 De Nora Spa Cella a combustibile raffreddata mediante iniezione diretta di acqualiquida
US6316135B1 (en) * 1999-07-22 2001-11-13 International Fuel Cells Llc Direct antifreeze cooled fuel cell
US6376111B1 (en) 2000-01-25 2002-04-23 General Motors Corporation System and method for controlling the humidity level of a fuel cell
JP2001351655A (ja) * 2000-06-05 2001-12-21 Honda Motor Co Ltd 燃料電池用ガス供給装置
DE10036916B4 (de) * 2000-07-28 2006-12-21 Truma Gerätetechnik GmbH & Co. KG Brennstoffzellenstapel und Verfahren zur Befeuchtung eines Reaktionsmittels bei einem Brennstoffzellenstapel
US6485857B2 (en) * 2000-12-29 2002-11-26 Utc Fuel Cells, Llc Fuel cell hybrid flow field humidification zone
CA2379363A1 (en) * 2001-03-28 2002-09-28 Ballard Power Systems Inc. Methods and apparatus for improving the cold starting capability of a fuel cell
JP4950386B2 (ja) 2001-04-06 2012-06-13 本田技研工業株式会社 燃料電池暖機装置
JP4708623B2 (ja) * 2001-08-22 2011-06-22 株式会社西部技研 燃料電池
JP2003068337A (ja) * 2001-08-24 2003-03-07 Toyota Motor Corp 燃料電池システム
GB2382455B (en) 2001-11-07 2004-10-13 Intelligent Energy Ltd Fuel cell fluid flow field plates
US6794077B2 (en) * 2001-12-28 2004-09-21 Utc Fuel Cells, Llc Passive water management fuel cell
GB2412784B (en) 2002-01-18 2006-08-23 Intelligent Energy Ltd Fuel cell oxygen removal and pre-conditioning system
GB2387959B (en) 2002-03-28 2005-02-09 Intelligent Energy Ltd Fuel cell compression assembly
JP4281382B2 (ja) 2002-04-19 2009-06-17 ソニー株式会社 生成水処理システム及び発電装置
ITMI20021338A1 (it) * 2002-06-17 2003-12-17 Nuvera Fuel Cells Europ Srl Generatore elettrochimico a membrana con iniezione diretta di acqua liquida nei agenti gassosi
JP3760895B2 (ja) 2002-07-03 2006-03-29 日本電気株式会社 液体燃料供給型燃料電池、燃料電池用電極、およびそれらの製造方法
GB2390738B (en) 2002-07-09 2005-05-11 Intelligent Energy Ltd Fuel cell direct water injection
GB2396688B (en) 2002-11-22 2006-06-28 Intelligent Energy Ltd Thermal energy management in electrochemical fuel cells
GB2401986B (en) 2003-05-17 2005-11-09 Intelligent Energy Ltd Improvements in fuel utilisation in electrochemical fuel cells
GB2409763B (en) 2003-12-31 2007-01-17 Intelligent Energy Ltd Water management in fuel cells
GB2413002B (en) 2004-04-08 2006-12-06 Intelligent Energy Ltd Fuel cell gas distribution
GB2422717B (en) 2005-02-01 2007-11-14 Intelligent Energy Ltd Detachable fuel cell power unit for vehicle applications
GB2434845B (en) 2006-02-01 2010-10-13 Intelligent Energy Ltd Variable compressibility gaskets

Also Published As

Publication number Publication date
GB0330272D0 (en) 2004-02-04
BRPI0418263A (pt) 2007-08-21
US8277998B2 (en) 2012-10-02
KR101166251B1 (ko) 2012-07-17
GB2409763A (en) 2005-07-06
CA2551674C (en) 2012-05-22
NO336638B1 (no) 2015-10-12
RU2356133C2 (ru) 2009-05-20
ES2394955T3 (es) 2013-02-07
EP1719199A2 (de) 2006-11-08
EP1719199B1 (de) 2012-03-28
MXPA06007516A (es) 2006-08-31
US8609288B2 (en) 2013-12-17
ZA200605295B (en) 2012-12-27
BRPI0418263B1 (pt) 2015-09-22
CN1922749A (zh) 2007-02-28
US20080248336A1 (en) 2008-10-09
GB2409763B (en) 2007-01-17
KR20060128989A (ko) 2006-12-14
WO2005064727A3 (en) 2006-05-18
CA2551674A1 (en) 2005-07-14
JP2007517365A (ja) 2007-06-28
CN100502118C (zh) 2009-06-17
NO20062957L (no) 2006-07-31
AR047358A1 (es) 2006-01-18
US20120321972A1 (en) 2012-12-20
WO2005064727A2 (en) 2005-07-14
RU2006127407A (ru) 2008-02-10
JP5193467B2 (ja) 2013-05-08

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