大西洋理事會-氫燃料能減少航空對氣候的影響嗎？（英）-2023.3

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MARCH2023

AtlanticCouncil

GLOBALENERGYCENTER

CanHydrogenFuelReduceAviation’sClimateImpact?

BYJOSEPHWEBSTER

INTRODUCTION

A

stheUnitedStateslookstoreduceitsgreenhousegasemissions,loweringitscarbonfootprintwillrequireanall-of-the-abovestrategyacrossmultiplesectors.Decreasingaviation-sectoremissionswillbecriticaltoensuringtheUnitedStatesreachesitsemissionsgoals.Indeed,theaviationsectoraccountsforabout720milliontonsofenergy-relatedcarbonemissions,andworlddemandforjettravelhasincreasednearlycontinuouslyfordecades,withtheimportantexceptionofduringtheCOVID-19pandemic.1Withtheworstofthepandemicseeminglyintherearviewmirror,however,pas-sengerthroughputisrebounding.

Reducingtheaviationsector’sgreenhousegasemissionswillrequireatran-sitiontonewenergyresources.Liquidhydrogenfuel(H2)hasemergedasapromisingalternativetoconventionaljetfuel.Alternativecleanenergyoptionsforaviation,suchasbatteriesandsustainableaviationfuel(SAF),existbuthavelimitations.Severalanalystshaveidentifiedcleanammonia,whichisproducedfromhydrogenandnitrogenviacleanelectricity,asapotentialalternativetoliquidhydrogen.However,thisstudyassumesthatthelatterwillprevailinthefuelcompetition,astheoverwhelmingmajorityoftechnicalaviationexpertsinterviewedbytheauthorbelievethatliquidH2willultimatelybeadoptedbytheindustry.Withfewalternativetechnologiesavailableforsystematicdecar-bonizationoftheaviationsector,itisimperativethatpolicymakerscloselyexaminehydrogen’sroleinaviationdecarbonization.

TheGlobalEnergyCenter

promotesenergysecuritybyworkingalongsidegovernment,industry,civilsociety,andpublicstakeholderstodeviseprag-maticsolutionstothegeopoliti-cal,sustainability,andeconomicchallengesofthechangingglobalenergylandscape.

Severalchallengeswillneedaddressingoverthenexttenyearsormorebeforetheindustrycanbegintoconvertto,orpartiallyswitchto,hydrogen.Engineersmustdesignplanestoaccommodatehydrogen;hydrogen-fuelinfrastructure,althoughgrowingintheUnitedStates,mustexpandfurthertosupporthydrogenjetfuelneedsatscale;andadditionalhydrogenuses,suchaslong-haultrucking,wouldimprovetheeconomiccase.Thisissuebriefwillexaminethesechallenges,andthepolicysolutionsneededforincludingavia-tioninthenascenthydrogeneconomyandenergytransition.

1“Aviation,”InternationalEnergyAgency,September2022,/reports/aviation.

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THENEEDFORALTERNATIVEJETFUELS

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ntheUnitedStates,datafromtheEnvironmentalProtec-tionAgency(EPA)showthatthenumberoftotaltravel-ersin2021rose76percentfrom2020levels,reachingnearly66percentof2019throughputlevels.2

MorerecentTransportationSecurityAdministration(TSA)passengerthroughputdataindicatethat2022passengerthroughputwilltrackatabove90percentof2019levels.3Aspassengersreturntotheskies,aviation-relatedemis-sionswillalsorise.Indeed,aviation-relatedemissionsrosecontinuouslyfrom2013untilthepandemictemporarilygroundedairtraffic.

Figure1:NumberofUSJetPassengers

Millions

1200

DomesticInternational

Source:“Passengers:AllCarriers—AllAirports,”BureauofTransportationStatistics,lastvisitedNovember21,2022,

/Data_Elements.aspx?Data=5

.

2“Passengers:AllCarriers—AllAirports,”BureauofTransportationStatistics,lastvisitedNovember21,2022,

/Data_Elements.aspx?Data=5

.

3“TSACheckpointTravelNumbers(CurrentYearversusPriorYear(s)/SameWeekday),”USTransportationSecurityAdministration,lastupdated

November21,2022,

/coronavirus/passenger-throughput

.

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Figure2:USAviationEmissions

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2011201220132014201520162017201820192020

CommercialAviationMilitaryAircraftGeneralAviationTotalU.S.Emissions(RHS)

Source:EnvironmentalProtectionAgency4

StrongconsumerdemandforairtravelisnotjustaUSstory.TheInternationalAirTransportAssociation(IATA)notesthattotalworldoperatedflightsin2022areexpectedtoreach33.8million,ornearly87percentof2019levels.5TheIATAalsoexpectsthatpassengerrevenueswillincreasefrom$239billionin2021to$498billionin2022,anincreaseofmorethan108percent.6Astheglobalmiddleclassexpands,demandforairtravel—and,therefore,forjetfuel—willalsoincrease.AlthoughbusinesstravelremainslowerduetoCOVID,demandforcommercialflightswilllikelycontinuetorisefortheforeseeablefuture.Aviationdemandandaviation-sectorgreenhousegasemissions(GHG)are,therefore,settorisefrompandemiclevels,necessitatingsustainableapproachesthatcaneconomi-callyreduceemissionsatscale.

CLEANEROPTIONSFOR

POWERINGAIRTRAFFIC

R

esearchersinindustry,government,andacademiaareexploringoptionstoreduceaviation’sclimateimpactthroughalternativetypesoffuelorpowersources.Alternativestoconventionaljetfuelincludebatter-ies,whichproducenoemissionsduringflight;sustainableaviationfuels(SAF),whichhavelowercarbonemissions;andhydrogen,whichemitswaterwhenusedasafuel.

WhilebatteriesandSAFcanbeimplementedrelativelyquickly,theydonotrepresentlong-termsolutions,duetosignificant—potentiallyinsurmountable—hurdlestoscalingupforlong-distancetravelandultimatelymeetingthe

4“InventoryofU.S.GreenhouseGasEmissionsandSinks:1990-2020.”USEnvironmentalProtectionAgency,2022,TableES-2,37,https://www.

/system/files/documents/2022-04/us-ghg-inventory-2022-main-text.pdf.;“FastFactsonTransportationGreenhouseGasEmissions.”USEnvironmentalProtectionAgency,July14,2022,/greenvehicles/fast-facts-transportation-greenhouse-gas-emissions.;“FastFacts:U.S.TransportationSectorGreenhouseGasEmissions,1990-2020”USEnvironmentalProtectionAgency,May2022,/Exe/ZyPDF.cgi?Dockey=P10153PC.pdf.

5“TravelRecoveryRebuildingAirlineProfitability—ResilientIndustryCutsLossesto$9.7Billion,”InternationalAirTransportAssociation,pressrelease,

June20,2022,

/en/pressroom/2022-releases/2022-06-20-02/#:

~:text=Flights%20operated%20in%202022%20are,%24239%20

billion%20generated%20in%202021.

6Ibid.

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requirementsoftheglobalaviationsector.Batteriesaregenerallyconsideredunsuitableforlong-distanceflightsduetotheirweightrequirements.Indeed,jetfuel’senergydensitystandsat43megajoulesperkilogram(MJ/kg)—versusonly0.72MJ/kgfoundintoday’slithium-ionbatter-ies.7Electrifiedairplaneswould,therefore,needtocarrymassivebatterypacks,especiallyforlong-haulflights,whichwouldlimitthenumberofavailableseatsandharmtheeconomicsofbattery-poweredplanes.Ontheotherhand,SAF,whichreliesonwasteoilsandfatsaswellaswoodybiomass,willlikelyfacesupplyconstraints.Addition-ally,thoughSAFcostsaredeclining,theyareneverthelessaboutthreetofourtimesmoreexpensivethankerosene.8Finally,SAFisnotemissionsfree,asitstillreleasesaboutone-fifthofthecarbonreleasedbykerosenejetfuel.9WhileSAFwillplayaroleinaviationdecarbonization,particularlyintheshortandmediumterms,duetoitsversatilityandeaseofuseasadrop-infuel,policymakerswilllikelyneedtoprioritizeH2jet-fueldevelopmenttoachievemidcenturynet-zerogoals.

Hydrogenisincreasinglyregardedasanenviron-ment-friendlyandcost-effectivefuelsourceforhard-to-de-carbonizesectors,includingaviation.Unlikeburningcoalorotherhydrocarbons,hydrogencombustionoruseinfuelcellsproduceswaterasabyproduct—notcarbonorotherGHG.Althoughmostexistinghydrogenfuelispro-ducedfromhydrocarbons,itcanalsobeproducedviaprocessespoweredbyrenewablesorverylow-emissionsenergysources,includingsolar,wind,naturalgaswithcarbonstorage,andnuclear.HydrogeniswidelyexpectedtobecomeacleanerfuelsourceasrenewablesadoptionincreasesduetotheInflationReductionAct’sclimatepro-visions.

Hydrogendevelopmenthasbeenconstrained,todate,bymultiplefactors,including:economicdisadvantagesrel-ativetootherfuelsources;challengesadaptingequip-mentforH2fuelinnontraditionalapplications,suchassteel,cement,andtrucking;limitedH2infrastructurealong

thesupplychain,beginningingenerationandcontinuingthroughtransmission,enduse,andstorage;thedifficultyofcreatingandhandlingliquidH2,whichmustbefrozento-253degreesCelsius;and,finally,differentstandardsandrules,particularlyacrossinternationallines.

ThereisalsouncertaintyaroundtheGHGimpactofcon-trailsfromwatervapor.OneIATAstudyestimatedthatH2combustionemitsabout2.6timesmorewatervaporthankerosenefuel.10Accordingtoa2021studypublishedinNature,contrailcirrusisthelargestsinglecontributiontoaviationneteffectiveradiativeforcing,greaterthanaircraftcarbon-dioxide(CO2)andnitrogenoxide(NOx)emissions.11Neteffectiveradiativeforcing,ortheconditionthatoccurswhentheamountofenergythatenterstheEarth’satmo-sphereisdifferentfromtheamountofenergythatleavesit,canforcechangestotheEarth’sclimate.12Accordingly,somestudiesbeingundertakenwouldenableairlinestoavoidthecool,humidairthatcanleadtocontrailforma-tion.13Airbushaslaunchedatestprogramtostudythecon-trailsproducedbyahydrogen-combustionengine.14Whilethescientificdebateoncontrailformationremainsunre-solved,itisanimportantareaofresearch,givenitspoten-tialGHGimpact.

Someoftheproblemsaroundhydrogen’seconomiccom-petitivenessarebeingaddressed.AsH2technologycon-tinuestoimprove,marketforceswillcontinuetodrivehydrogenpriceslower,whilegovernmentsaremobilizingresourcestoimproveH2economics(includingthroughtheUSDepartmentofEnergy’sHydrogenShotinitiative,whichseekstoreducethecostofcleanhydrogenby80percent,to$1peronekilograminonedecade—orthe“111”goal).15

UScleanhydrogenalsoreceivedamajorboostfromtheInflationReductionAct(IRA),aUSlawthatwasenactedinAugust2022.Thelegislationprovidessupportfortheentirehydrogenvaluechain,withincentivesextendedtomanufacturingandmining,cleanenergygeneration,andanH2taxcreditofupto$3perkilogram.16Numerousstudies

7JohnathanHolladay,ZiaAbdullah,andJoshuaHeyne,“SustainableAviationFuel:ReviewofTechnicalPathways,”USDepartmentofEnergy,September2020,

/sites/prod/files/2020/09/f78/beto-sust-aviation-fuel-sep-2020.pdf

.

8SiddharthVikramPhilipandBenElgin,“AirlinesRushTowardSustainableFuelButSuppliesAreLimited,”Bloomberg,November10,2021,

/news/articles/2021-11-10/airlines-rush-toward-sustainable-fuel-but-supplies-are-limited?sref=lDgLmqjg

.

9PeterWilson,“AirlinersPoweredbySustainableFuelRemainaDistantGoal,”NewYorkTimes,June29,2022,

/2022/06/29/climate/planes-sustainable-fuel-flight.html

.

10“LiquidHydrogenasaPotentialLowcarbonFuelforAviation,”InternationalAirTransportAssociation,August2019,

/contentassets/d13875e9ed784f75bac90f000760e998/fact_sheet7-hydrogen-fact-sheet_072020.pdf

.

11ChristianeVoigt,etal.,“CleanerBurningAviationFuelsCanReduceContrailCloudiness,”CommunicationsEarth&Environment2,1(2021),

/10.1038/s43247-021-00174-y

.

12DavidChandlerandKerryEmanuel,“RadiativeForcing,”MITClimatePortal,September25,2020,/explainers/radiative-forcing#:~:text=Radiative%20forcing%20is%20what%20happens,infrared%20radiation%20exiting%20as%20heat.

13JenniferChu,“NewMapsShowAirplaneContrailsovertheU.S.DroppedSteeplyin2020,”MITNews,March7,2022,

/2022/airplane-contrails-map-0307

.

14“AirbustoTakeuptheHydrogenContrailCharacterisationChallenge,”Airbus,pressrelease,July20,2022,

/en/newsroom/press-releases/2022-07-airbus-to-take-up-the-hydrogen-contrail-characterisation-challenge

.

15“HydrogenShot,”USDepartmentofEnergy,HydrogenandFuelCellTechnologiesOffice,lastvisitedNovember21,2022,

/eere/fuelcells/hydrogen-shot

.

16AndrewC.Hanson,etal.,“TheInflationReductionActandtheRiseofCleanHydrogen,”PerkinsCoie,August26,2022,

/en/news-insights/client-update-the-inflation-reduction-act-and-the-rise-of-clean-hydrogen.html

.

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suggestthatthelegislationwillsignificantlyimprovehydro-geneconomics,particularlygreenhydrogenproducedfromrenewablesfeedstocks.17

Despitechallengestoshort-andmedium-termadoption,hydrogenoffersuniqueopportunitiesforaviationdecar-bonizationoverthelongterm.Cleanhydrogenproducesfewemissions,whileitsrefuelingcapabilitiesaresimilartoexistingjetfuel:H2iscapableofrapidrefuelingandworkswellincoldclimates.Moreover,thereisalreadyaproofofconcept,asaSovietTupolevTu-155conducteddozensofflightsin1988whileusingliquidH2.18WhileH2-fueledjet-flighttechnologyhasexistedfordecades,theeco-nomicintegrationofliquidH2(LH2)aboardflightsisstillinitsinfancy,andavarietyofcompaniesareexperimentingwithdifferentdesignmodels,includingturbofans,turbo-props,andblended-wingbodies.19Airbusaloneistestingthreedifferenthydrogen-fueledmodels,whilestartupZeroAviacompletedtheworld’sfirsthydrogen-fueledcom-mercial-gradeaircraftflightin2020.20PolicymakersattheFederalAviationAdministration,andperhapstheDepart-mentofEnergy’sLoansProgramOffice,couldhelpacceler-ateH2adoptionbydirectlysupportingtheinitialprototypingandresearch-and-development(R&D)phasesofH2jet-fueldevelopment.

WhiletherearemanyopportunitiesforH2-poweredplanes,thetechnologyalsofacesmanyhurdles.Themostimport-antobstacleisthecostofoverhaulingthefleetandrelatedinfrastructure.Estimatesvarywildlyduetouncertaintyaroundadoption,butthecostsofdesigningnewairframes,buildingtheinfrastructuretogenerateH2,investinginanewfuelecosystem,andmaintaininghydrogen-fueledplaneswillbeimmense.A2020McKinseystudyfortheEuropeanCommissionfoundthataircraftinitialcapitalexpendituresforH2aircraftareexpectedtobehigherthanforconventionalaircraft,duetoLH2tank-structureintegra-tion,increasedaircraftsize,andotherfactors.21ThestudyalsoassessedthatH2planes’largerairframesandonboardstoragetankscouldresultinmoresafetychecksandmain-tenancecosts,particularlyintheshortterm,althoughitalsonotedthatmaintenancecostsforthepropulsionsystemcouldfallovertime.22

Inadditiontofinancialobstacles,thereareseveraltechni-calchallengesthatwillneedtobeovercomethroughR&D.AstudyfromtheInternationalCouncilonCleanTransporta-tionfoundthat,“Comparedtofossil-fuelaircraft,LH2-pow-eredaircraftwillbeheavier,withanincreasedmaximumtakeoffmass(MTOM),andlessefficient,withahigherenergyrequirementperrevenue-passenger-kilometer(MJ/RPK).Theywillalsohaveashorterrangethanfossil-fuelaircraft.”23Similarly,refuelingtimesforH2aircraft,whileshorterthanchargingtimesforbattery-poweredplanes,mayneverthelessbelongerthanforkerosene-fueledair-craft.

BUILDINGHYDROGENAVIATION

INFRASTRUCTURE

T

hereislittletonoexistinghydrogenaviationinfra-structuretospeakof,outsideofhighlyspecializedandnichemarkets,suchastheNationalAeronau-ticsandSpaceAdministration(NASA),oronsiteforkliftsatairports.Hydrogen-capableairportswillrequireaccesstounprecedentedamountsofliquidhydrogen,andwillthere-foreneedtobesitednearhydrogenproductionordedi-catedH2pipelines,justasexistingairportsaccessjetfuelthroughrefined-productpipelines.Forinstance,theHarts-field-JacksonAtlantaInternationalAirportishundredsofmilesfromrefiningcapacity,butliesastridetheColonialcrude-productpipeline.TheUnitedStateshasanexist-ingstockof1,600milesofhydrogen-dedicatedpipelines,mostlyconcentratedintheGulfCoast.24Consequently,hydrogen-capableairportsoutsideoftheGulfCoastwillbeconfrontedwithadilemma:barringapossible(butunlikely)buildoutoflong-haulhydrogen-dedicatedpipelines,air-portsmayneedtorelyontheblendingofhydrogenintoexistingnaturalgaspipelinesthatservicetheairportwith,potentially,somehydrogenseparationperformedattheairportitself.Althoughthereissomedebateoverthecostandpracticalityofthisapproach,moststudiesonthetopicindicatethatatleastafractionofnaturalgaspipelinecapacitycanberepurposedforH2use,atleastonatech-nicalbasis.Alternatively,orasacomplementtoH2frompipelines,airportscanturntolocal,orevenonsite,H2pro-duction.TruckingLH2toairportscouldserveasaninterme-

17JohnLarsen,“ATurningPointforUSClimateProgress:AssessingtheClimateandCleanEnergyProvisionsintheInflationReductionAct,”RhodiumGroup,August18,2022,

/research/climate-clean-energy-inflation-reduction-act/

.

18MarkPiesing,“TheEpicAttemptstoPowerPlaneswithHydrogen,”BBC,March21,2022,/future/article/20220316-the-epic-attempts-to-power-planes-with-hydrogen.

19“Zeroe:TowardstheWorld’sFirstZero-EmissionCommercialAircraft,”Airbus,June24,2021,/en/innovation/zero-emission/

hydrogen/zeroe.

20Ibid.;KelseyReichmann,“ZeroAviaCompletesFirstHydrogen-PoweredFlight,”AviationToday,September29,2020,

/2020/09/29/zeroavia-completes-first-hydrogen-electric-turboprop-flight/

.

21“Hydrogen-PoweredAviation:AFact-BasedStudyofHydrogenTechnology,Economics,andClimateImpactby2050,”McKinsey&Companyand

EuropeanCommission,May2020,https://www.fch.europa.eu/sites/default/files/FCH%20Docs/20200507_Hydrogen%20Powered%20Aviation%20report_FINAL%20web%20%28ID%208706035%29.pdf.

22Ibid.

23JayantMukhopadhayaandDanRutherford,“PerformanceAnalysisofEvolutionaryHydrogen-PoweredAircraft,”InternationalCouncilonCleanTransportation,January2022,

/wp-content/uploads/2022/01/LH2-aircraft-white-paper-A4-v4.pdf

.

24“HydrogenPipelines,”USDepartmentofEnergy,HydrogenandFuelCellTechnologiesOffice,lastvisitedNovember21,2022,

/eere/fuelcells/hydrogen-pipelines

.

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diatesolution,butthescaleofH2wouldalmostcertainlyrequirealternativesupplies.Astheyweighthecostsandbenefitsofeachsourcingapproach,airportsandairlineswilllikelyseektoensuresupplybyseekinglocal(butnotnecessarilyonsite)H2production.

Inadditiontonearbyproduction,airportsmayalsobenefitfromproximitytootherendusers.Oneobviouscomple-mentaryenduseristhelong-haultruckingindustry.Whilemostindustryexpertsbelievethatelectricvehicleswillbeutilizedforshort-haul,intra-citycommutes,hydrogenmayprovetobethesuperioralternativeforlong-haul,inter-citytrips,duetohydrogen’ssuperiorchargingspeedsandcargocapacity.25Airportsthataresitednearlong-haultruckingnodescould,therefore,benefitfromeconomiesofscale,sharedinfrastructure,anda“hydrogenecosystem”ofknow-howandskilledlabor.LAX,forinstance,issitu-atedclosetotheLosAngelesandLongBeachportsandtheirassociatedlong-haultruckingcomplexes.Airportscanalsohelpcreateotherlocalend-userdemand,suchasbyrequiringground-transportationvehiclesatairportstoswitchtohydrogen.

Still,localgeographyinCaliforniawouldlikelyrequirenewinfrastructure—andpotentiallyevenhydrogen-dedicatedpipelinesthattraveloffshoretoskirtpopulationcenters.Theneedfornew,short-range,hydrogen-dedicatedpipe-lineswillnotbeuniquetoLAX.Duetotheurbancharacter-isticsofalmosteverymajorairport,thelimitationsofexistinghydrogenconnectivity,andsubstantialLH2demandsfromflights,H2-capableairportswilllikelyrequirenewshort-haulpipelinesthatconnecttolocalproduction,otherendusers,orboth.

Inadditiontonewpipelineconnections,airportswilllikelyrequiremassivenewstoragefacilitiestohouseliquidhydrogenonsite.Storagerequirementsatairportscouldbequitesubstantialifhydrogenadoptionaccelerates.Car-negieMellonresearchersfoundthatasingleAirbusZeroEJFK-to-Heathrowflightofabout3,440mileswouldrequiremorethan47,000gallonsofliquidhydrogen(versusabout10,800gallonsofA-1jetfuel).26WhileH2maynotbesuit-ableforverylong-distanceflights(suchasaJFK-to-Heath-rowflight)duetoliquidH2’smassiveonboardvolumerequirements,thefuelmaybeidealformedium-rangeflights.Therefore,ifH2technologyreachesmaturity,majorairportswouldalmostcertainlyexpecttooperateseveral

dozenorevenhundredshort-andmedium-rangeH2flightseveryday.Overtime,H2-capableairportsmay,therefore,requirethecapabilitytosafelystoreandprocesshundredsofthousandsofgallons,orevenmillionsofgallons,ofLH2throughput.Indeed,astudybytheAerospaceTechnol-ogyInstitutefoundthatalargeairportcouldrequireaboutonemilliongallonsofLH2storageby2035and13.2milliongallonsofstorageby2050.27

Thereisnoprecedentforthislevelofliquid-hydrogenstorage,ortheamountofdailythroughputastoragespherewouldneedtoprocess.Toputthesestoragerequire-mentsinperspective,NASAisbuildingtheworld’slargest,1.25-million-gallonliquid-storagespheretosupportspaceoperationsattheKennedySpaceCenter.Thenewstoragespherewillmarkthefirstconstructionofaliquid-hydrogenstoragefacilityinNorthAmericainnearlytwodecades;itwillalsobenearly50percentlargerthanacomparable1966facility.28Finally,NASA’sstoragespheresareusedfordiscretelaunches,whereasairportoperationswouldrequirenear-continuousdischarges.Futurerequirementsforstoringliquidhydrogenforjetfuelwilllikelybeordersofmagnitudelargerandmorecomplexthanthoseseentodate.

Fortunately,theprivatesectorisalreadymakinginitialstridesincreatinglarger,moreefficienthydrogenstoragespheres.McDermott’sCB&I,thecompanythatisconstruct-ingtheNASAstoragesphere,isalsocompletingdesignsforstoragetanksthatareeighttimeslargerthanexistingfacil-ities.29CB&IStorageSolutions—alongwithShellInterna-tionalExplorationandProduction,NASA’sKennedySpaceCenter,GenH2,andtheUniversityofHouston—havebeenawarded$6millionbytheDepartmentofEnergy(DOE)HydrogenandFuelCellTechnologiesOfficetoexplorethefeasibilityofliquid-hydrogenstorageatmassivescale.30BecauseevenlimitedH2flightoperationswillrequiremassivereservesofliquidH2instorage,thetechnicalfea-sibilityandeconomicreliabilityofthesefacilitieswillbeofmajorimportance.

WhiletheDOE’sfundingofafeasibilitystudyforimportandexportLH2terminalswilladvancethebodyofknowledge,therearemajoroperationaldifferencesbetweenamaritimeexport/importH2facilityandanairportru