prospects for grid storage 9-2012 v2

7/30/2019 Prospects for Grid Storage 9-2012 v2

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ZAIWhitepaper:TheProspectsforGridScaleEnergyStorage Page1

TheProspectsforGridScaleEnergyStorage

Dr.RonBrost,P.Eng.,CTO,ZincAirInc.

ExecutiveSummary

TheeconomicengineoftheUnitedStatesusesover40quadrillionBTUsofenergyperyear,withonlya

smallpartof thisbeingsuppliedbyrenewableenergysources(RES).ThelowrateofadoptionofRESsislargely due tounder-utilization of theseenergy sources caused by thehighly variablepowercapability

(sunlightforPVandwindcurrentsforturbines)andamisalignmentofthatpowercapabilitywithdemand.

A solution to this problem is large-scale energy storage, which will allow RESs to store energy locally

duringpeakgeneratingperiodsandthenreliablydeliverstoredenergyondemand.Theseenergystorage

solutionsmustbesafe,environmentallybenign,efficient,usematerialsthatareavailabletomeetthetotal

demand for the technologies, and provide the lowest cost alternative. ZAIs Zinc Iron Flow Battery

uniquelymeets these requirementsand offers safe, efficient, reliable and affordable grid-scale energy

storagesolutions.

EnergyStorageandNationalPolicy

Energyisthelifebloodofourcivilization;whenaccesstoclean,safe,andabundantenergyislimited,

growthandsustainabilityofanynationiscrushed.Energyisthenewcurrencymanufacturing,food

production, transportation, and even the information superhighway are all dependent on reliable

sourcesofenergy,andtheabilitytoharnessandtransportthatenergyisapersistentchallengetoour

civilization.

Ourenergyneedsareofanenormousscale:theworld

requiresover200quadrillionBTUs(1quadrillionBTUs

=1Quad)ofenergyperyeartomeetitsserviceneeds,

andtheUSusesabout20%ofthis,orabout40Quads.

At0.05$perkilowatt-hour,theUSenergybillisabout

600billionUSDperyear;thisisabout$1700foreachUS citizen, equivalent to what we spend on food.

Furthermore, over thenext 25years theUS need will

grow to about 50 Quads per year while the need in

Chinawillincreasetoabout80Quadsperyear.

Todayourenergysupplyisservicedfromnon-renewableenergysources(NRES)suchascoal,petroleum,

natural gas, and nuclear fission, plus renewable energy sources (RES) such as hydro, wind, solar,

biomass, and geothermal generation. In 2009, the United States spent about 95 Quads of primary

energytoproduce40Quadsofservice(useful)energy.Thirtypercent(30%)ofthisenergywasin the

formofelectricalpower.

Nationalenergypolicy is drivenbyboth theeffectof carbonemissions on theenvironment andtheeffectofenergydependenceonnationalsecurity. Thecarbonoffsetcostasaconsequenceofenergy

storagecanbequantified throughan assumption of 1 terawatt-hour being equivalent to0.6 million

tonnes ofcarbondioxide per day,or 216milliontonnesperyear. Ifweassume acostof 100B$per

terawatt-hourinstallationanda 20yearlife,thecostofcarbondioxideabatementusingthismethod

wouldbe$23pertonne.Whiletheincomederivedfromsaleofcarbonoffsetsmaynotcoverthiscost,

theresultingcarboncreditwouldstillprovideavaluestreamthatwouldaugmentrevenuesfromenergy

arbitrageorregulation.


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Withregardtoenergysecurity,1Quadofenergyisequivalentto

172 million barrels of oil; by this metric, 1 terawatt-hour of

storagecosting100B$wouldreduceimportsby4.4billionbarrels

over 20 years, worth about 375B$ at current oil prices. The

normalized cost of a barrel of oil equivalent for this service

(excludingtheopportunitycostoftheenergyproduction)is$22,

whilereducingournationaldependenceonoilbyupto6%per

terawatthourofenergystorage.

Theconcurrentneedsofcarbonreduction,energysecurity,andastrongeconomyareoftendescribed

ascountervailing;asoneispromoted,atleastoneoftheothersisreduced.Thewidespreaddeployment

ofRESshasbeenencouragedtohelpclosethisgap,butwithoutanenablingenergystoragedevice,the

valueoftheenergyproducedandtheabilityoftheREStodeliverondemandareseverelylimited.The

energystoragedevice,however,mustmeetkeyrequirementsofsafety,naturalabundanceofcritical

components,andcost.

TheRoleofEnergyStorage

Therearemanywaystogenerateelectricalpower,bothinanon-renewableandrenewablesense.With

thecurrentimperativesofenvironmentalprotectioncoupledwithenergysecurity,however,theidealenergy source should be safe and sustainable; that is, derived from a source that is essentially

inexhaustiblewhilenotcontributingtonetgreenhousegasesemissions.Inthisrespect,hydro,biomass,

wind,geothermal,andsolarhavebecometheenergysourcesmostpreferred.Distributionofsomeof

theseislimitedbygeography,whilethedemandcapabilityofothersispoorandwouldleadtogapsin

griddeliveryiftheywerethesoleprimarysourceofenergy.Inaddition,thegridisnotparticularlystable

orevenpredictablethegridiscontinuallyperturbedbyvariationinsupplyanddemandduetonatural

diurnalandseasonalcycles.

Currentmethods to balance theelectrical grid arebased on over- capacitation, eitherby increasing

nameplatecapacityoftheplantorbyopeningpeakerplantsthatcomeonlinetomeetpeakdemands.

BothofthesesolutionsentailsignificantinvestmentandofferpoorROIsincetheadditionalcapacityis

usedforonlybriefperiods.Someimprovementtothesupplyanddemandbalanceispossibleifthere

are favorable geographic features that allow both wind and solar installations; however, even such

mixes are subject to regular gaps in supply and demand. Although peaker plants could be used to

supportthegridduringthesegaps,theseplantsaretypicallyfossil-fueledandthereforereduceoreven

eliminatethebenefitsoftheRES.

AnalternativemeanstosupportthegridandfacilitatetheuseofRESsistoprovidelargescaleelectrical

energystoragesolutions.Withsufficientstorage,singlepointRESs suchaswindfarmsorsolararrays

could provide a ready and predictable response to power demand without the need for additional

generationfacilities.

Thescaleofthesefacilitieswouldofcoursebelarge;ononeextreme,wherewepresumeelectrification

oftheUnitedStatestomeetallenergyneedsusingwindorsolar,thestorageneedcouldbehalfofthe

totalenergyneedtoload-shift.Presuminga24hcycle,theenergystorageneedfortheUSwouldbeon

theorderof25terawatt-hours;globallythiswouldexceed100terawatt-hours.

Althoughphysicalmeansofload-shiftingelectricalenergystoragehavebeenproposed,theyoftenare

limitedbygeography(pumpedhydrostorageorcompressedair),orbycapacityorcost(super-capacitor

or flywheel). In order to meet the needs of a large scale solution, it is necessary to consider

electrochemicalmeansofstoragesincechemicalenergyoffersthebestopportunityforacontrollable

andeffectivemeansofenergystorage.


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ElectrochemicalBasis

Batteries are electrochemical devices that allow oxidation of a substance at one location (anode),

reductionofsubstanceatanotherlocation(cathode),ameanstocollecttheresultingelectricalcharge

anddeliverittoanexternaldevice(thecircuit),andameanstodepolarizethechargetransferthough

theexchangeofions(theelectrolyte).

Therearemanypossiblecombinationsofsubstancestoprovidethebasisofabattery,butasonemight

expect, not all combinations make a good battery, let alone a commercially viable battery. A

commerciallysuccessfulstoragebatterymust:

1. besafeandfreefromtoxicmaterials

2. beconstructedofgloballyavailableandinquantitiessufficienttomeetlongtermneeds

3. beefficient,rechargeable,andmakeeconomicsense.

Thefirstcriterion,safety,hasmanyimplicationswhenselectinganelectrochemicalcouple.Inparticular,

flammabilityisachronicconcerninbatterychemistry.Moreover,asthecellstringsbecomelongerto

meettheefficiencyneedsofthetransformers,convertersandinverters,theriskofacellreversalor

severeovercharge(acommonsourceofignition),becomesmuchgreater.Withtheseconcernsinmind,

a non-flammableelectrolyte such as water is a prudent and tactical design decision. The use of anaqueouselectrolytecarrieswithitanumberofchemically-relatedrestrictions,however:

Anythingwithanoxidationpotentialhigherthantheoxidation potentialofwater willreduce

watertohydrogenspontaneously

Anythingwith a reduction potential higherthanthe reduction potential ofwater willoxidize

watertooxygen.

both of which should be avoided. If we consider all commonly available materials, those with high

oxidation potentials (such as lithium, sodium,andaluminum)andhigh reduction potentials (such as

chlorine)areexcludedduetothechemistrywithwater.Thisleavesamuchsmallersubsetof suitable

materials.

Thenextselectioncriterionisavailabilityoftheenergystoragematerial.Ifweconsiderthecommercial

abundanceandthedistributionofmetalsintheUSandtherestoftheworld,thepossibilitiesarelimited

shouldwewanttocommitanationalinitiativetoaparticularenergystoragemethod.Forexample,

althoughlithiumisalreadyexcludeddueits

highoxidationpotential,evenifweallowit

to be considered it falls far short of the

needs in the United States and is in fact

barely capable of supplying the ultimate

needsoftheworld.Exacerbatingtheissue

is the localization of lithium deposits, of

which75%arelocatedinChile.Inthisview,

even elements such as lead or nickel aredeficient as they are not capable of

meeting theneeds for batteryproduction

sufficient topromotesustainability.Of the

elements that are stable in water,

manganese, chromium, zinc, and copper

aresufficientonthebasisofworldwideavailability,butthedistributionofalloftheseelementsdonot

necessarilymatchthegeopoliticalboundaries;wherethereisadeficiencyoftheseelementswithinthe


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geographicboundariesofanymajorpoliticalpower,relianceonthoseelementsformattersofnational

securitymaynotbeasensibleoption.

Ifweconsider the political boundaries of the highest energy consumers, the US, China, and Europe

(including Russia), neither lithium, nickel, nor lead are sufficient in quantity and appropriately

distributedtomeettheneedsofthepopulation.Ofthedown-selectedelectro-activemetals,onlyzinc

andcoppermeettheneedsofsafetyandavailability.

Withzincandcopperascontenderbatterychemistries,weshouldnowconsiderthechemicalpotentials

ofeach.Basedonthevoltageofthehalfcellsofeach,itisapparentthattheenergyavailablefromzinc

(at1.28Voxidationpotentialforthesolubleformofzincoxideinalkali)issubstantiallygreaterthanthat

ofcopper(-0.34V),andsotheloweroxidationpotentialofcopperreducesthedesirabilityofcopperas

ananode.Whencoupledwiththemetalprices,thecostofcopperisovertentimesthatofzinconan

energybasis.Thecostofzinconanenergystoragebasisisinfactonethirdthatofleadorlithium,and

whilethedesignofthebatteryissuchthatthecostofthemetalmaybeamodestfractionoftheoverall

costofthecell,it isstilla significantconsideration inlightofthescaleofournationalenergystorage

needs.

BatteryDesign

Batteriesforgridenergystoragemaybedesignedforeitherhighrate/lowercapacity(forshorttime

scale frequency response), for lower rate / high capacity (for longer timescale load shifting), or for

balancedperformancein between.However,RESsaremostdependentontheavailabilityoflowcost

energystorageatlongerdischargeratesthatapproacheighthoursormore. Thedependencyoncost

drives thebatterydesign to smaller and thickerelectrode area (which is expensive toproduce) and

largerbutless expensive storageof theelectro activematerials. Forthis reason,flow batterieshave

dominatedgridstoragesincethecapacityofthecellislargelydependentontheamountofstorage,

whichcanbelowcostwithappropriateelectrolytes--aqueouselectrolyteshaveaparticularadvantage

inthatmanyofthematerialsofconstructioncanbeinexpensivepolymers,sostockRoto-moldedtanks

andpolypropylenetankscanbeusedforprocessequipment.Ofcourse,thepumpenergycanbecome

significantand lead tosubstantialefficiencylosses, sothesystemaswhole (theelectrodedesign,the

storage,theflowrate,andthemobilephaseelectrolytes)istypicallyoptimizedsimultaneously.

FlowBatteriesandtheZinc-IronSystem

Thereareseveralcompetitorsintheflow-batteryfield,butmanyofthemhavefailedtoachievesuccess

dueto cost andthe toxic/corrosivenatureof theirchemistry.Zincbromine,zincchlorine,polysulfide

bromide,vanadiumredoxandzincceriumarecurrentlybeingcommercialized,butconcernsforpublic

safety and developmental setbacks have limited their success and appeal to date. Flow battery

technologiesusingvanadiumoxideshavealsoseenlimitedcommercialsuccessduetonotonlytechnical

issues,butalsothecostofvanadium,whichisusedinsteelmanufacturingandhasbecomealimited

andstrategicmaterialthatislargelycontrolledbyforeigninterests.

Iron-chromiumionflowbatteriesareinanearlydevelopmentalstagebutoffermostofthepositiveattributesthatflowbatteriespromise.However,thenatureoftheiron-chromiumionchemistryleadsto

lowelectrochemicalefficiencythatcompromisestheabilitytomeetcommercialrequirements.

ZAIszinc - iron flow battery consistsof a zinc / zincate anode, a cathodiciron anioncomplexin an

aqueous alkaline supporting electrolyte, and proprietary high efficiency electrodes in a stack

configuration that allows parallel electrolyte feeds without significant shunt losses. The selection of

chemistry permits the use of common and low cost materials such as zinc oxide, iron salts,

polypropylene, steels, and nickel coatings. The electrochemistry has round-trip energy efficiency


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comparabletolithiumion,yetasawater-basedelectrolyte,providesunsurpassedsafety.Thelowcost,

safety,andefficiencyinherenttothissystemtherebyprovidesanaturalscalabilitytothemegawatt-

hourrangeandabove.

ThecommercializationoftheZAIZincIronbatteryhasfocusedonthreecriticalareas:

Electrodes:ZAIhasdevelopedhighefficiency(lowpolarizingatlowflowratesandlowgassing)

electrodedesignsandalloysthat improvethecostofoperationof thebattery.Consequently,theseelectrodesallowhighpowerchargeanddischargethatmakesthedesignssuitable fora

varietyofrevenuestreams.

Electrolytes: Low-cost aqueous electrolyte blends have been developed that improve the

depositionqualityofzincandthuscapacityandallowsextendedreliableservice.Inaddition,

these electrolyte blends allow higher concentrations of metal salts without the associated

problemsofprecipitation.

Manifolds:A manifolding systemhasbeen developed that minimizes parasitic shunt currents

withoutimpedingflowsignificantly.

Usingtheseinnovations,ZAIhasdevelopedtheZ20-60(60kW/120kWh)energystoragesystem,which

isscheduledforproductionin2013.TheZ20isacontainerizedmodule,designedtobeintegratedinto

megawatt-sizedsystems.TheZ20 isamongthemostcosteffectivesolutions,is locationindependent,

andyetstillcoversalargeapplicationrangeforflexiblerevenueoptions.

Conclusion

It is proposed in this presentation that the energy needs for the world can be reconciled with a

combinationofRESsandlargescalestoragesolutions.Zincisalogicalcost-effectivemeanstoachieve

thisandwillallowregionalintereststogeneratetheirowngridinfrastructurewiththenaturalresources

athand.Inparticular,ZAIsZ-20familyofproductscanmeettheseneedswithbothhighpowerandhigh

capacitycellssuitableforlarge-scaledeploymentontheelectricalgrid,andprovidesthelowest-riskpath

to stable carbon emissions, energy security, and the establishment of a safe means todevelop our

nation.

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ContactInformation

ForinformationregardingZAIslineofenergystorageproductcontactMr.DaveWilkins,CEO-ZAI,at

406-755-9462([email protected])

AbouttheAuthor

Dr.RonBrostisChiefTechnologyOfficerforZAIwherehe leadstechnicaldevelopment.Dr.Brosthasbeenactiveinbatteryandfuelcelldevelopmentfortwentyyearsandhasheldexpertandsupervisory

roleswithGeneralMotorsandFordMotorCompanythatincludeddevelopmentoflithiumbatteries,

VRLA(AGM)batteries,nickelmetalhydridecells,andhydrogenfuel cells.Dr.Brostis aDesignforSix

SigmaBlackbeltandisanexpertin advancedmodelingandcomputeraideddesignofelectrochemical

systems.Hehasauthoredoverthirtypatents,publications,andconferencepapers.Dr.Brostholdsa

PhDinChemistryfromtheUniversityofVictoriaandaB.AppliedScience(ChemicalEngineering)from

theUniversityofBritishColumbia,andhasbeenaprofessionalengineerforover20years.

prospects for grid storage 9-2012 v2

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