PEM Fuel Cells: Theory and Practice

528 Pages·2012·18.787 MB·English

by  Frano Barbir

PEM F C
UEL ELLS
THEORY AND PRACTICE
FRANO BARBIR
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LibraryofCongressCataloging-in-PublicationData
Barbir,Frano,1954-
PEMfuelcells:theoryandpractice/FranoBarbir.–2nded.
p.cm.
Includesbibliographicalreferencesandindex.
ISBN978-0-12-387710-9(alk.paper)
1.Protonexchangemembranefuelcells.2.Ion-permeablemembranes.3.Fuelcells.
I.Title.II.Title:Protonexchangemembranefuelcells.
TK2931.B372013
621.31'2429–dc23
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AcataloguerecordforthisbookisavailablefromtheBritishLibrary.
ForinformationonallAcademicPresspublications
visitourwebsiteathttp://store.elsevier.com
PrintedintheUnitedStatesofAmerica
09101112 987654321
CONTENTS
Foreword ix
Prefaceandacknowledgments xi
PrefacetotheSecondEdition xv
1 Introduction 1
1.1. WhatIsaFuelCell? 1
1.2. AVeryBriefHistoryofFuelCells 4
1.3. TypesofFuelCells 8
1.4. HowDoesaPEMFuelCellWork? 10
1.5. WhyDoWeNeedFuelCells? 12
1.6. FuelCellApplications 13
References 16
2 Fuel Cell Basic Chemistryand Thermodynamics 17
2.1. BasicReactions 17
2.2. HeatofReaction 17
2.3. HigherandLowerHeatingValueofHydrogen 18
2.4. TheoreticalElectricalWork 19
2.5. TheoreticalFuelCellPotential 20
2.6. EffectofTemperature 21
2.7. TheoreticalFuelCellEfficiency 24
2.8. CarnotEfficiencyMyth 26
2.9. EffectofPressure 28
2.10. Summary 29
Problems 30
Quiz 31
References 32
3 Fuel Cell Electrochemistry 33
3.1. ElectrodeKinetics 33
3.2. VoltageLosses 39
3.3. CellPotential:PolarizationCurve 48
3.4. DistributionofPotentialAcrossaFuelCell 50
3.5. SensitivityofParametersinPolarizationCurve 52
3.6. FuelCellEfficiency 59
3.7. ImplicationsandUseofFuelCellPolarizationCurve 61
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vi Contents
Solution 65
Solution 66
Solution 67
Problems 69
Quiz 70
References 72
4 Main Cell Components, MaterialProperties, andProcesses 73
4.1. CellDescription 73
4.2. Membrane 75
Solution 90
4.3. Electrodes 92
4.4. GasDiffusionLayer 97
4.5. BipolarPlates 104
Problems 112
Quiz 113
References 115
5 Fuel Cell Operating Conditions 119
5.1. OperatingPressure 119
5.2. OperatingTemperature 121
5.3. ReactantFlowRates 124
5.4. ReactantHumidity 130
5.5. FuelCellMassBalance 144
5.6. FuelCellEnergyBalance 149
Problems 154
Quiz 155
References 157
6 Stack Design 159
6.1. SizingaFuelCellStack 159
6.2. StackConfiguration 163
6.3. UniformDistributionofReactantstoEachCell 167
6.4. UniformDistributionofReactantsInsideEachCell 172
Solution 187
6.5. HeatRemovalfromaFuelCellStack 189
Solution 194
Solution 199
6.6. StackClamping 208
Contents vii
Problems 211
Quiz 212
References 213
7 Fuel Cell Modeling 217
7.1. TheoryandGoverningEquations 218
7.2. ModelingDomains 228
7.3. ModelingExamples 231
7.4. Conclusions 259
Problems 259
Quiz 260
References 261
8 Fuel Cell Diagnostics 265
8.1. ElectrochemicalTechniques 266
8.2. PhysicalandChemicalMethods 282
8.3. Conclusions 295
Problems 297
Quiz 297
References 299
9 Fuel Cell SystemDesign 305
9.1. Hydrogen/OxygenSystems 305
9.2. Hydrogen/AirSystems 314
Solution 317
Solution 318
9.3. FuelCellSystemswithFuelProcessors 333
9.4. ElectricalSubsystem 358
9.5. SystemEfficiency 364
Problems 368
Quiz 369
References 371
10 FuelCell Applications 373
10.1. TransportationApplications 373
10.2. StationaryPower 392
10.3. BackupPower 414
10.4. FuelCellsforSmallPortablePower 419
10.5. RegenerativeFuelCellsandTheirApplications 422
viii Contents
Problems 429
Quiz 431
References 432
11 Durability of Polymer Electrolyte FuelCells 435
11.1. Introduction 435
11.2. ScopeandOrganizationofThisChapter 436
11.3. TypesofPerformanceLosses 438
11.4. PEFCComponentsAssociatedwithDifferentTypesofLosses 441
11.5. OperatingConditions 447
11.6. AcceleratedTestProtocols 460
11.7. ConclusionsandFutureOutlook 464
Acknowledgments 466
References 466
12 Future of Fuel Cellsand Hydrogen 469
12.1. Introduction 469
12.2. ABriefHistoryofHydrogenasaFuel 470
12.3. HydrogenEnergyTechnologies 472
12.4. IsthePresentGlobalEnergySystemSustainable? 487
12.5. PredictingtheFuture 491
12.6. SustainableEnergySystemoftheFuture 495
12.7. TransitiontoHydrogenora“HydricityEconomy” 500
12.8. TheComingEnergyRevolution? 503
12.9. Conclusions 505
References 505
Index 509
FOREWORD
Thereare twokeyproblems with continueduseof fossilfuels, which meet
about80%oftheworldenergydemandtoday.Thefirstproblemisthatthey
are limited in amount and sooner or later will be depleted. According to
petroleum company estimates, the production of the most conveniently
utilizablefossilfuels,petroleumandnaturalgas,willpeaksometimebetween
2015 and 2020 and then begin to decrease. This means that there will be
a gap between demand and production of fluid fuels beginning around
2015.
Thesecondproblemisthatfossilfuelsarecausingseriousenvironmental
problems, such as global warming, climate changes, melting of ice caps,
rising sea levels, acid rain, pollution, ozone layer depletion, oil spills, forest
andagriculturallanddamagecausedbysurfaceminingofcoal,andsoon.It
isestimatedthatthisworldwideenvironmentaldamageaddsuptosome$5
trillion per year.
Earlyinthe1970sahydrogenenergysystemwasproposedasasolution
for these two interconnected global problems. Since then, during the last
quarter of the last century, through research and development work in
universities and research laboratories around the world, foundations of the
hydrogenenergysystemwereestablished.Earlierinthiscentury,conversion
to the hydrogen economy began.
Hydrogenisanexcellentenergycarrierwithmanyuniqueproperties.It
is the lightest, most efficient, and cleanest fuel. One of hydrogen’s unique
properties is that through electrochemical processes, it can be converted to
electricityinfuelcellswithhigherefficienciesthanconversionoffossilfuels
tomechanicalenergyininternalcombustionenginesortoelectricalenergy
in thermal power plants. This unique property of hydrogen has made
hydrogenfuelcellstheautomotivepowerplantofchoiceforcarcompanies.
It has also made fuel cells the power plant of choice for companies
manufacturingpowerplantsforthefuture.Thereasonforhigherefficiency
of hydrogen fuel cells is that they are electrochemical engines, not heat
engines, and as such they are not subject to Carnot cycle limitations.
Consequently, it is expected that during the 21st century fuel cells will
replace heat engines (internal combustion engines, steam turbines, and gas
turbines) as hydrogen replaces fossil fuels.
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x Foreword
Researchhasbeenandiscurrentlybeingconductedintoseveraltypesof
fuelcells,suchasalkalinefuelcells,protonexchangemembrane(PEM)fuel
cells,phosphoricacidfuelcells,moltencarbonatefuelcells,solidoxidefuel
cells, and so forth. Some of these technologies are already commercialized,
whereas others are close to commercialization. They are expected to find
applications in almost every energy-utilizing plant and/or device, from
power plants to cars and homes, from laptop computers to mobile phones.
PEM fuel cells in particular have desirable properties. They operate at
relativelylowtemperatures,whichmakesthemeasiertocontainandreduces
thermal losses. They are also smaller in volume and lighter in weight,
makingthemperfectforautomotiveandportableapplications.Thatiswhy
all the hydrogen-fueled buses and cars on the market today from major
companies are powered by PEM fuel cells and why about 90% of fuel cell
research and development work involves PEM fuel cells. Consequently,
today’sandtomorrow’sengineersengagedinenergyengineeringshouldbe
thoroughly knowledgeable about PEM fuel cells, just as the energy engi-
neers of yesterday had to have a thorough knowledge of heat engines.
The author of this book, PEM Fuel Cells: Theory and Practice, Dr. Frano
Barbir, is a well-established hydrogen energy scientist. After receiving his
Ph.D. degree in hydrogen energy, he became and has continued to be
closelyinvolvedinPEMfuelcellresearchanddevelopmentworkinfuelcell
companies. He has also seen the need for educating engineers in fuel cell
technologies.Asaresult,hehasdevelopedandtaughtsenior-andgraduate-
level courses on fuel cells in two universities. Consequently, he is well
qualified to write an authoritative textbook on PEM fuel cells. The book
starts with the fundamentals of PEM fuel cells, then covers materials,
operations, modeling, design, and applications. It is a well-written,
comprehensive, and well-organized look into PEM fuel cells.
Consequently,IstronglyrecommendthistextbookonPEMfuelcellsto
all senior- and graduate-level engineering students, whether they are
mechanical, electrical, chemical, industrial, environmental, or energy
engineers,whoarestudyingenergyconversionandenergyapplications.The
libraryofanyengineerandresearcherinvolvedinpowergeneration,vehicle
automotive power plants, and power units for portable systems would also
be well served by this textbook.
Dr. T. Nejat Vezirog(cid:1)lu
Director,UNIDO-InternationalCentreforHydrogenEnergyTechnologies,
Istanbul,Turkey,February2005
PREFACE AND ACKNOWLEDGMENTS
The idea for this book came about many years ago. Over the years of
workingasanengineer,researcher,scientist,andcompanyexecutive,Igave
numerouspresentationsonfuelcelltechnology,progress,andperspectives.I
immenselyenjoyedpreparingthepresentations,organizingmythoughtsand
views,andsupportingthemwithfactsandgraphics.IndoingsoIalwayshad
an audience in mind. I tailored my presentations to suit that audience and
designedthemtobesimpleandeasytofollow.Thisbookisadirectresultof
those numerous presentations. I take pleasure in sharing my enthusiasm
aboutthisnewandexcitingtechnology,andIparticularlytreasureteaching
this new technology to the next generationdyoung engineers I have
worked with and the students I have had the opportunity to advise and
teach. After all, they will be the ones implementing this technology and
benefiting from it.
For nine years I worked for Energy Partners, a small, privately owned
company in West Palm Beach, Florida. It was an amazing educational
experience:asandboxforengineers.Insteadoflearningfrombooks(atthat
timetherewerenobooksonfuelcells),welearnedfromthefuelcellitself.
Westartedwithaworkingfuelcell,acubic-foot“magicbox”thatsometimes
hadamindofitsown.Myjobwastomakethisboxdowhatwewanteditto
do. To do that, I had to learn everything about fuel cells: their theory,
materials,components,design,operation,diagnostics,supportingsystem,and
soondeverythingIdidnotgetachancetolearnwhileIwasinschool.Of
course,Icouldnothavedoneitalone.IenjoyedsharingwhatIhadlearned
withmyyoungcolleaguesasmuchasIenjoyedlearningtogetherwiththem.
Soon wemade theworld’sfirst PEMfuel cell-poweredpassenger automo-
bile,followedbyanextendedgolf-cart/peopletransporterandseveralutility
vehicles(JohnDeereGators).Everynewvehiclewasleapsandboundsbetter
thanthepreviousone,andthroughthisprocessIaccumulatedknowledge.It
is unfortunate that at one time we were expected to start making profit,
which the fuel cell technology was not yet capable of. Not at that time.
Nevertheless, I am grateful to Mr. John H. Perry, Jr., the owner of Energy
Partners,forallowingmetohavesuchfunandtolearnsomuch.
In my career I had a chance to work with and learn from many
outstanding engineers and scientists, and I would like to take this oppor-
tunity to thank them:
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