储能技术入门总结

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EnErgYSToragETEcHnoLogYPrIMEr:

aSuMMarY

Background

Energycanbestoredinelectrical,mechanical,electro-chemical,chemicalandthermalmeans,whiledeliveringthefinalenergyinelectricalform.(SeeFigure1.)

Type

Sub-group

Examples(notexhaustive)

TypicalApplications

Electrical

Capacitors

Capacitorsandultracapacitors

Powerquality

Superconductors

SuperconductingMagneticEnergyStorage(SMES)

Powerquality,reliability

Mechanical

Potentialenergyinstoragemedium

Pumpedhydro,

Energymanagement,reserve

Compressedairenergystorage(CAES)

Energymanagement,reserve

Kineticenergyinstoragemedium

Low-speedflywheels

Uninterruptiblepowersupply

Advancedflywheels

Powerquality

Electro-chemical

Low-temperaturebatteries

Lead-acid

Powerquality,standbypower

Nickel-cadmium

Powerquality

Lithiumcells

Powerquality

High-temperaturebatteries

Sodium-sulphur

Multi-functional

Sodium-nickelchloride

Standbypower,remoteareaapplications

Flowbatteries

Zinc-bromine

Multi-functional

Vanadium

Remoteareaapplications

Polysulphide-bromine

Multi-functional

Cerium-zinc

-

Chemical

Hydrogencycle

Electrolyser/fuelcellcombination

-

Otherstoragemedia

e.g.chemicalhydrides

-

Thermal

Hotwater

-

Peakshaving

Ceramics

-

Peakshaving

Moltensalt/steam

-

Integrationofrenewable

Ice

-

Peakshaving

Figure1:StorageTypegroupedbyTechnology1

1Source:anthonyPrice,“ElectricalEnergyStorage-areviewofTechnologyoptions”(nov2005),ProceedingsofIcE,civilEngineering158,pgs52-58.

EnergyStorageTechnologyPrimer:aSummary

STagESoFcoMMErcIaLMaTurITY

VRB

Lead-AcidBatteries

Ni-CdBatteries

PumpedHydro

Zn-Br

currently,energystorage(ES)systemspresentedinFigure2areinvariousstagesofcommercialmaturity.Forstationaryutilityapplication2,pumpedhydroelectricityisthedominantcommerciallyavailablesolution(~123gW)globally,withotheradvancedenergysolutionssuchassodium-sulfur,lead-acidandzinc-brominebatteries3,compressedairenergystorage(caES)4,thermalenergystorage5,batteries,flywheels6andotherstrailingbehindandunderdevelopment.Fortransportapplication(i.e.electromobility,ore-mobility),extensivedevelopmentalworkhasbeenfocusedonbatterytechnologies.Lead-acidbatteryisamatureenergystoragetechnology7buthasnotbeencommerciallyviablefore-mobilityapplication.Themainenergystoragetechnologiesaredescribedatappendixa.Figure3presentsestimatedworldwideinstalledenergystoragecapacity.

ThermalEnergyStorage

LithiumBatteries

Metal-Air

LargeSMES

NASBatteries

LowEnergySupercapacitors

CAES

FlowBatteries

HighEnergySupercapacitors

LowSpeedFlywheels

FuelCell

Micro-SMES

Design Developmentand

Prototype

MatureProducts

HighSpeedFlywheels

Figure2:commercialmaturityofdifferentenergystoragesystems

2canbeeithercentralizedordistributedandcanbeutility-owned,customer-ownedorthird-partyowned.

3Mainlydemonstrationorprototypeunitsandoftenalongsiderenewableand/ordistributedenergysources.

4IncaES,off-peakpowerisusedtopumpairintoasealedundergroundcaverntoahighpressure.Whenneeded,thishighpressureaircandriveturbinestogeneratepowerduringpeakhours.

5Thermalenergystorage(TES)isaconceptwherebyenergyisstoredasthermalenergyinenergystoragereservoirstobalanceenergydemandbetweendaytimeandnighttime.Thethermalreservoirmaybemaintainedatatemperatureabove(hotter)orbelow(colder)thatoftheambientenvironment.Themainusesareproductionoficeorchilledwatertocoolenvironmentsduringtheday,andthegenerationofelectricalenergy(throughtheuseofsteam)byhightemperaturestoragesaltswhenthedemandishighintheday.

6Flywheelsworkbyacceleratingrotorswithasignificantmomentofinertia,andmaintainingtheenergyinthesystemasrotationalenergy.Thisenergycanbeconvertedtoelectricalenergywhenneeded.

7notasamainsourceofenergy,replacinggasoline,butmainlyasanauxiliarypowersource.

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Flywheelsandothers:95MW

Batteries:451MW

Thermal:1002MW

compressedair:440MW

MoltenSalt:142MW

Figure3:Estimatedworldwideinstalledenergystoragecapacity(2128MW)in20108

aPPLIcaTIonoFEnErgYSToragEInSIngaPorE

TheuseofenergystorageinSingaporeismostapplicableinthefollowingareas:

Electricvehicleswhichrequiremediumscaleenergystorage(100kWto500kW);

Smartgridsupportinginfrastructurewhichrequiremediumtolargescaleenergystorage(atleast0.1MW);

Buildingmanagement/renewableenergysmoothingwithsmalltomediumscaleenergystorage(1kWto100kW).SeeFigure4.

ElectricVehicle(EnergyStorage)

(TransportscaleES)

Fuel/Energy

Generation

Transmission

Distribution

ElectricityCustomers

EnergyStorage

EnergyStorage

SmartGrid

(LargetomediumscaleES)

HousingandBuilding

(MediumtosmallscaleES)

1GW 100MW 10MW 100kW 10kW

Power

Figure4:ElectricityValuechain

8Source:StrategenandcESaresearch.Excludespumpedhydrocapacity,estimatedat~123gW.

Energystoragetechnologiesthatareapplicabletotheseapplicationsconsistofmainlybattery-basedtechnologies,aswellasFlywheels,HydrogenStorage,Supercapacitor,PumpedHydroelectricity,compressedairEnergyStorage(caES),SuperconductingMagneticEnergyStorage(SMES)andThermalEnergyStorage.asummaryoftherelevantenergystoragetechnologiesareshowninFigure5.

Applications

EnergyStorageTechnologies

E-Mobility

Lead-AcidBatteries •FuelCell*

Li-ionBatteries •Supercapacitor

MetalAirBatteries

NiCdBatteries

SmartGrid

NaSBatteries •HighPower •Pumped- •Super- •FlowZnBr

Lead-Acid Flywheels hydroelectricity capacitor •FlowVRB

Batteries •MicroSMES •CAES •FuelCell*

Li-ionBatteries •LargeSMES •Thermal

MetalAir

Batteries

NiCdBatteries

Housing&Building

Lead-AcidBatteries •Thermal

Li-ionBatteries •FuelCell*

MetalAirBatteries

Figure5:Energystoragetechnologiesandtheirapplications

*utiliseschemicalenergyfromHydrogenstorage.

EnErgYSToragEForTranSPorTaPPLIcaTIonInSIngaPorE

ElectricVehicles(EVs)areseenasthefuturesustainablemodeoftransportworldwideastheyofferthefollowingadvantagesoverinternalcombustionenginecars:

EnergyEfficient.Theelectricmotorsconvert75%ofthechemicalenergyfromthebatteriestopowerthewheels.Thisisunlikeinternalcombustionenginesthatonlyconvert20%oftheenergystoredinthegasoline.

Environmentalfriendliness.currentwell-to-wheelemissionestimatesfromoriginalEquipmentmanufacturers(oEMs)showabout66%reductionincarbonemissionswhenswitchingfromagasolinecartoanequivalent-sizeEV.9Thisreducespollutionintraffics,althoughthesametailpipepollutantswillbepresentatfossil-fuelbasedpowerplantthatproducestheneededelectricity.Therewillbenoairpollutantforelectricityproducedfromrenewableenergysources(e.g.wind,solar,hydroetc.)

9“renault-nissanalliancePartnerswithSingaporegovernmentforZero-EmissionMobility”(accessed29april2011).

/En/nEWS/2009/_STorY/090507-05-e.html

TheauthorsassessthatinSingapore,batteryisthemajormeanofenergystoragetoprovideelectricitytothevehicleandoneofthekeytechnologiesforvehicleelectrification.However,EVsfacesignificantbattery-relatedchallenges.Amongthecurrentbatteryoptions,theauthorsrecommendthatlithium-ionbatteriesarethemostpromising,astheyholdmorethan5timesthespecificenergyand10timesofspecificpowercomparedtotheconventionalleadacidbatteries-promisingaviableformofenergystorage.However,thetechnologystillfacesthefollowingkeyhurdlesforeffectivedeployment:

Longchargingtime.Lithium-ionbatteriesarenotsuitedforfastcharging.unlikecurrentre-fuelingwhichtakesaround5-10minsatpetrolstation,afullrechargeoflithium-ionbatteriescantake2to8hours10.Even“quickcharging”technologiesto80%capacitycantake30minutesandcanbedetrimentaltothebatterylifecycle.

Lowerenergystoragecapacitycomparedtogasoline.Thecommutingrangeofafullychargedbatterypackdependsverymuchonthecapacityofthebatteries,thetypeofroutestraveled,whetherair-conditioning(usesalotofelectricpower)isturnedonandalsodriverhabits.currentbatterytechnologyonafullchargewouldallowarangeofbetween90kmto160km5.Thisismuchlowerthanthetypicalrangeofgasolinethatgoesabove400kmonafulltank.Thiscallsformorefrequentrecharge.

BatteryCost.currentbatterypacksforEVsareexpensive.ThecurrentexpectedcostisarounduSd400-uSd800/kWh.ThisisexpectedtoreducetouSd300-uSd500/kWhby202011.IEaestimatedbatterycostsforPlug-inHybridEVs(PHEVs)andEVsmustdroptowardsuSd300/kWhtobringEVscosttocompetitivelevels.

Lowersafetylevel.underhighstressoperationconditions,largelithium-ionbatterypacksmayundergoathermalrunaway,whicheventuallyresultsinthebatterycatchingfireandexploding.Thisriskishigherasbatteriesbecome“older”butcanbealleviatedbyusingadvancedbatterymanagementsystems(BMS).

E-MoBILITYProjEcTSInSIngaPorE

anEVtaskforce,chairedbytheEnergyMarketingauthority(EMa)andtheLandTransportauthority(LTa)hasbeensetupwithrepresentativesfromgovernmentagenciestoleadtestsandresearchintotheintroductionofEVsinSingaporefrom2010.9,12S$20millionoffundingwassetasidetosupportinfrastructuredevelopmentandtoanalysetherobustness,cost-effectivenessandenvironmentalimpactofelectric-poweredvehiclesinatropicalclimateandautomakers,suchasrenaultandnissan13,havebeeninvolvedinthesestudies.

TheEVtest-bedwaslaunchedinjune2011andwilllasttillend2013.Thetest-bedwillfocusongatheringdataandinsightstoguidetheplanningforthefuturedeploymentofEVs,includingtheoptimalratioofchargingstationsto

10“FactsheetonElectricVehicles(EVs)”,EMa.

11“ElectricPlug-InHybridVehicleroadmap”,IEa(2010).

12“EMaleadsstudytoputelectricvehiclesonSingaporeroads”(accessed17april2011).

/stories/

singaporelocalnews/view/427272/1/.html

vehicles.Fortheconvenienceofthetest-bedparticipants,chargingstationshavebeendesignedtoautomaticallycollectdataontheEVusers’chargingpatterns.Participantsofthistest-bedschemecanapplyforthetaxincentivescheme,EnhancedTechnologyInnovationanddevelopmentScheme(TIdES-PLuS)whichwaivesallvehicletaxessuchasadditionalregistrationFees(arF),certificateofofEntitlement(coE),roadtaxandexciseduty,forthepurposesofr&dandtest-beddingoftransporttechnologies14.

Injan2011,theTechnischeuniversitatMunchen(TuM)teamedupwiththenanyangTechnologicaluniversity(nTu)tosetuptheTuM-crEaTEcentreofElectromobilitytostudyhowe-mobilitywouldworkinmegacitiesinasia,andthetechnologyinfrastructureneededtosupportthiseffort.ThecentreisaprojectunderthenationalresearchFoundation’s(nrF)crEaTE15programme,forresearchonsustainabilityofelectricvehicle16.

InthenationaluniversityofSingapore(nuS),severalresearchershaveconductedr&donenergystorageforEVapplications.detailsofsuchr&dprojectsaredescribedinappendixB.

EnErgYSToragEForSMarTgrIdaPPLIcaTIonSInSIngaPorE

Smartgridsaredigitally-enhancedversionsoftheconventionalelectricitygrid,andakeyenablerforenergysecurityandreliabilityandintegrationofrenewableenergyresources.ThekeydifferencesinthecharacteristicsofsmartgridsandconventionalgridsaresummarisedinFigure6.Inparticular,unlikesmartgrids,conventionalgridsoperatewithlittleornoenergystorage17.Energystoragetechnologiesplayanimportantroleinfacilitatingtheintegrationandstorageofelectricityfromrenewableenergyresourcesintosmartgrids.Energystorageapplicationsinsmartgridsincludetherampingupandsmoothingofpowersupply,anddistributedenergystorage.

Characteristic

Consumerparticipation

Integratinggenerationandstorage

Marketevolution

Resiliency

ConventionalGrid

Consumersareunder-informedandnon-participativewithpowersystem

Dominatedbycentralgeneration.Manyobstaclesexistforintegratingdistributedenergyresources

Limitedwholesalemarkets,notwellintegrated.Limitedopportunitiesforconsumers

Vulnerabletonaturaldisastersandmaliciousactsofterror

SmartGrid

Informed,involvedandactiveconsumers-demandresponseanddistributedenergyresources

Manydistributedenergyresourceswithplug-and-playconvenience,focusonrenewables

Mature,well-integratedwholesalemarkets,growthofnewelectricitymarketsforconsumers

Resilienttoattacksandnaturaldisasterswithrapidrestorationcapabilities

Figure6:Smartgridversus.conventionalgridcharacteristics

14Pressrelease“LaunchofSingapore’sElectricVehicleTest-bed”,(25jun2011).

15crEaTE-campusforresearchExcellenceandTechnologicalEnterprise.

16“oneelectriccar,twouniversities,100researchers”,TheStraitsTimes,(22jan2011).

17drdennisgross,cleantechMagazine(july/august2010.

TheelectricitygridinSingaporeisconsideredreliableandrobust.networklossesarereportedtobeonlyaround3%.Theauthorsforthe“SmartgridPrimer:aSummary”haverecommendedthatapossibleareaofr&dforSingaporeistheintegrationofdistributedgenerationandrenewablesintothegrid,whichrequiresthesupportofenergystoragetechnologies.See“SmartGridPrimer:ASummary”formoreinformation.

Forlarge-scaleenergystoragepurposes,pumpedhydroelectricityandcaESaretechnologieswhicharetypicallyadopted.However,Singaporeisgeologicallydisadvantagedtoimplementthesetechnologiesduetoourlandconstraint.Thereisnosuitableabovegroundsiteforconventionalpumpedhydroelectricity.Similarly,thedeploymentofcaESfaceschallengeinSingaporeduetoalackofsuitablesites.Tothebestknowledgeoftheauthors,SingaporehasnosealedundergroundairpocketsorabandonedmineswhicharerequiredfortheimplementationofcaES.

Theauthorsrecommendthatmid-scaledistributedenergystoragemaybemoresuitableinSingapore

forthefollowingapplications:

Integrationofdistributedrenewableenergygenerationsuchassolarphotovoltaics;

ancillaryservicessuchasfrequencyregulation,i.e.regulationoftheinstantaneousfrequencyofthealternatecurrentsupplyinSingaporetobestabilizedat50Hz,topreventload-sheddingandblackouts.

applicationofrenewableenergyforoff-gridislandapplication.

Singaporehasplanstoincluderenewableenergyinitsurbanlandscape.18Moreover,thereispotentialformid-scaleenergystoragetoplayaroleinoff-gridislandapplicationinSingapore(e.g.SemakauLandfill,Pulauubin,Lighthouses,etc).

Theauthorsassessthatsuitableenergystoragetechnologiesforrenewableenergygenerationintegrationandoff-gridislandapplicationincludelithium-ionbatteries,flowbatteries,sodiumsulfurbatteriesandadvancedlead-acidbatteries.Forpowerapplicationssuchasfrequencyregulation,ontheotherhand,lithium-ionbatteries,advancedlead-acidbatteriesandflywheelsmaybeapplicable.

EnErgYSToragEForHouSIngandBuILdIngaPPLIcaTIonSInSIngaPorE

Energystoragetechnologiescanbepartoffutureplanstoincorporatehigheramountsofenergyfromrenewableenergysources,suchassolarphotovoltaics.Examplesincludethermalenergystoragewhichcanpotentiallybeappliedformajorenergyusage(e.g.thermalenergystoragesystemforcoolingapplicationinrepublicPolytechnicandresortWorldSentosa)inSingapore,fuelcellinprimaryorbackuppowersystem,andbatterysystemsforstorageofenergyfromrenewablesourcessuchassolarandwindenergy.anexampleofenergystorageapplicationforhousingapplicationcanbeseeninthe“SmartHouses”conceptexploredinjapan.19

18reportoftheEconomicStrategiescommittee(February2010),EconomicStrategiescommittee.availablefrom:

.sg/data/cmsresource/ESc%20Full%20report.pdf

19andyBae,“SmartHouseinjapan”,availablefrom:

/blog/articles/smart-house-in-japan.

(accessed1May2011).

Threeformsofenergystoragearesuitableforhousingandbuildingapplications–(i)batteries;(ii)thermalenergystorage;and(iii)fuelcell.(SeeFigure5.)Theenergystorageforhousingandbuildingindiscussionismainlythermalenergystorage(TES),whichisamaturetechnology.This,however,takesupvaluablelandarea,whichisscarceinSingapore.assuch,applicationsattheconsumersideusuallytargetelectricbillreduction,viaeitherdemandchargesorTime-of-usePricing.

Typically,thesinglebiggestcomponentofutilitycostsistheelectricbillforair-conditioning,whichcanbeashighas50%.20ThedeploymentofaTESsystemisthusanattractiveoptionasitcanhelptostorecoolingenergyduringoff-peakhours(whenutilitycostischeaper)anduseitduringthepeakloadatdaytime.Thishelpsthebuildingownertosaveupto40%ofelectricitybill(e.g.$380,000perannumforrepublicPolytechnic)andprovidesenergysavingsof10-20%dependingonthetypeofTESsystem(e.g.air/Water/PhasechangeMaterials).

PoSSIBLEr&darEaSForSIngaPorE

ThereareseveralfundamentalandappliedresearchprojectsintheareaofenergystoragebeingcarriedoutatinstitutessuchasnuSandnTu.Someoftheresearchprojectsandprogrammescurrentlyunderwayattheseinstitutesaredescribedinappendixc.

IntheSingaporecontext,takingintoaccounttheavailableresearchandr&dinstitutionsandcompetencies,theauthorshaveidentifiedbatteriesasthemaintechnologicalopportunityforenergystorageforthenexttwodecades.Torealisethepotentialofbatterytechnologies,Singapore’sr&deffortsshouldbefocusedonsolutionstothecurrentdrawbacksasfollows:

LeadAcid,Nickel-basedandRedoxFlowbatteries:toxicmaterials;

NickelMetal-hydride(NiMH)batteries:Self-dischargeissues;Performanceisalsosensitivetotemperatureconditions;

Lithium-ionbatteries:chargestoragecapacityneedsleadtohighcostforEVs;Safetyissues;

Sodium-basedbatteries:corrosionduetomoltensulfur;and

Flywheels:LimitedtoStationaryutilityEnergyStorage(SuES)applications;highcosts.

r&dforsomeofthesetypesofbatterieswillrequiremorein-depthresearchtosolvetheproblemsofcharging/discharging/depthofcharge/self-dischargelosses.

20Singapore’sSecondnationalcommunication:undertheunitednationsFrameworkconventiononclimatechange,(november2010)nEa.

Maincontributors:

nationaluniversityofSingapore(nuS)

assistantProfessorPalaniBaLaYa(Leadauthor)ProfessorjimYangLEE

ProfessorLiLu

ProfessorB.V.r.cHoWdarIassociateProfessorStefanadaMSassistantProfessorQingWangProfessorHaogong

associateProfessorHansongcHEngassociateProfessorWenFengLuassistantProfessorPohSengLEE

nanyangTechnologicaluniversity(nTu)

VisitingProfessorrachidYaZaMI(Leadauthor)

EnergyresearchInstitute@nTu(ErI@n)EngkiongkoH(TechnicalWriter)MsEvakPILLaI(TechnicalWriter)

InstituteofMaterialsresearchandEngineering(IMrE)drchaoBinHE

drZhaolinLIudrjianweiXudrkuiYao

drMarkYewchoonTan

Disclaimer,LimitationofLiability

Thisreportrepresentsthepersonalopinionsofthecontributors.Thecontributors,ErI@n,thenationaluniversityofSingapore(nuS),nanyangTechnologicaluniversity(nTu)andInstituteofMaterialsresearchandEngineering(IMrE)excludeanylegalliabilityforanystatementmadeinthereport.Innoeventshallthecontributors,ErI@n,nuS,nTuandIMrEofanytierbeliableincontract,tort,strictliability,warrantyorotherwise,foranyspecial,incidentalorconsequentialdamages,suchas,butnotlimitedto,delay,disruption,lossofproduct,lossofanticipatedprofitsorrevenue,lossofuseofequipmentorsystem,non-operationorincreasedexpenseofoperationofotherequipmentorsystems,costofcapital,orcostofpurchaseorreplacementequipmentsystemsorpower.

Acknowledgement

TheauthorshavebenefitedfromcommentsfromseveralcolleaguesfromnuS,nTuandIMrEaswellasfromthefollowinggovernmentalagencies:a*STar,EdB,EMa,LTa,nccSandnrF.FinallywethankkoHEngkiong(ErI@n)forhistirelesseffortinupdatingandconsolidatingthemanyversionsofthisTechnologyPrimer.

Thisreportwasfirstpublishedinaugust2011.Thecontentsoftheprimerreflecttheviewsoftheauthorsandnottheofficialviewsofthegovernmentagencies.ThepublicationoftheprimershasbeenmadepossiblebynccSandnrF,andreproductionofthecontentissubjecttothewrittenconsentoftheauthors,nccSandnrF

APPENDIXA

MAINENERGySTORAGETECHNOLOGIES

Lead-acidbattery

Lead-acidbatterytechnologyisoneoftheoldestandmostdevelopedbatterytechnologies(SeeFigurea1).Theycomeintwobasicforms:floodedleadacidbatteries,whichareconsideredawellprovenandrobustdesign,andvalveregulatedleadacid(VrLa,or“maintenancefreebatteries”)batteries.Thesebatteriesarealsousedintractionforlifts,golfcarts,uninterruptiblePowerSupply(uPS),minesetc.Lead-acidbatterieshavesomeknowndrawbacksandlimitations.Theyareheavy,givingrisetoverypoorenergy-to-weightandpower-to-weightratiosthatlimittheirapplications.Theleadcontentandthesulfuricacidelectrolytemakethebatteryenvironmentallyunfriendly(althoughapproximately98%21oflead-acidbatteriesarerecycled).Theyhaveshortcycle-lifeandlongrechargetimes.Theycanonlyaccommodateasmallnumberoffull(“deep”)dischargesandcannotbestoredinadischargedconditionwithoutservicelifefailure.

relativelylowself-dischargerateoflead-acidbatteriesmakesthemacommonchoiceforstandbystationaryenergystoragesuchasuninterruptiblepowersupplies(uPS).Lead-acidbatterieshavebeenusedforutilityapplicationssuchaspeakshaving.However,theeconomicsandlife-cyclerequirementsdonotworkoutwellforlead-acidbatteries.TheyarethereforenotthedominantproviderofStationeryutilityEnergyStorage(SuES)applications.TheirpopularityisexpectedtodeclineasadvancesinothertechnologiesoccurwiththeexceptionofStarting,LightingandIgnition(SLI)applications.

Figurea1:Lead-acidcarBattery

accordingtotheEnergyadvisorycouncil(Eac),themarketforLead-acidbatteriesisestimatedtobeapproximately

$3billionandgrowinginexcessof8%peryear.

21ExcludingBrazil,russia,Indiaandchina.

NickelBasedBatteries

Therearetwotypesofnickelbatteries,theolder,nickel-cadmium(NiCd)batteries,andthenewer,nickelmetal-hydride(NiMH)batteries,botharerechargeable.

Nickel-Cadmium(NiCd)Batteriesusenickeloxy-hydroxideandmetalliccadmiumastheelectrodes.Theycomeintwodesigns:sealedandvented.nicdarerelativelyinexpensive,abletosustaindeepdischarge,rechargequickly,andhavealongcyclelife.nicdcanalsoendureveryhighdischargerateswithnodamageorlossofcapacity.Hencetheyarecommonamongpowertools.

However,nicdareextremelyenvironmentallyunfriendlybecauseoftheuseoftoxiccadmium.Theyhaverelativelylowenergydensityandrelativelyhighself-dischargerates,whichrequirerechargeafterrelativelyshortstorageperiods.Thechargingratesareverysensitivetohotandcoldtemperatureconditions.Therearealsoknownmemoryeffectsthatshortenthebatteryshelflife.TheycompareunfavorablyintermsofavailabilityandenergydensitywiththenickelMetalHydride(niMH)andLi-ionbatteries.

Therehavebeenafewdemonstrationsoflarge-scaleSuESapplications,suchasthesysteminstalledbythegoldenValleyElectricassociationInc.(gVEa)inFairbanks,alaska.Thesystemconsistsof13,760cellsandcanprovide40MWofpowerforuptosevenminutes.(SeeFigurea2)However,theinherentdisadvantagesofnicdrelativetootheremergingbatterytechnologiesandenvironmentalconsiderationshavelargelyrelegatedni-cdtothebackburner.Thereislittle,ifany,anticipatedgrowthfornicdinSuESapplications.

Figurea2:goldenValleyElectricassociation(gVEa)locatedinFairbanks,ala,13760SaftSBH920highperformancerechargeablenickel-cadmiumcells22

22

/images/PdFs_articles_whitepaper_appros/appProBESS.pdf

Nickelmetal-hydride(NiMH)batteriesareanotheralkalinenickel-basedbatterytechnologythathasreplacednicdinmanyapplications.niMHbatteriesprovide30to40%moreenergycapacityandpowercapabilitiescomparedtothesamesizenicdcell.niMHisabletomeetthehighpowerrequirementsinhybridelectricvehicles(HEV);andassuchhasbeenthedominantbatterytechnologypoweringtoday’sHEVssuchastheToyotaPrius.niMHbatteriesareconsiderablymoreenvironmentallyfriendlycomparedwithleadacidandnicdbatteries.Theycanbechargedinabout3hours,although,likenicd,chargingratesaresensitivetobothhotandcoldtemperatureconditions.WhileniMHbatteriesarecapableofhighpowerdischarge,consistentuseinhigh-currentconditionscanlimitthebattery’slife.

TheniMH’sself-discharge23rateisquitehigh,upto400%greaterthanthatofalead-airbattery.ThemostsignificantoperationalchallengewithniMHrelatestorechargesafety.ThetemperatureandinternalpressureofaniMHbatterycellrisessignificantlyasitreaches100%stateofcharge.Topreventthermalrunaway,complexcell-monitoringelectronicsandsophisticatedchargingalgorithmsmustbedesignedintothebatterysystem.WithniMHtechnologygainingprominenceintheelectricandhybridelectricvehiclemarketsindustryparticipantsbelievethereareloomingpressuresonnickelsupplies,whichisonesignificantfactorthatmaylimitthetechnologies’abilitytoscale.

Thegeneralsenseamongtheindustryisthatothertechnologiesofferamorefavorableenergydensityandcostprofileforutility-scaleenergystorageapplications.

RedoxFlowBatteries

Zinc-bromineflowbatteryisatypeofhybri