AlternativestoHydrogen:LiquidRegenerableFuels
WilliamAhlgrenElectricalEngineeringDepartment
CaliforniaPolytechnicStateUniversitySanLuisObispo,CA93407-0355
IEEEmergingTechnologiesReviewSantaBarbara,May10,2018
Fueldominatesenergytrade
Fueliscrucialintheglobalenergysystem.Replacementbyelectricpoweralone
isunlikely.
Regenerablefuelsareneeded
Energyin
Energyout
Reduction Oxidation
Fuel+oxygen
Air+water
Regenerable?
Regenerablefueloptions
• Hydrogen
• Ammonia
• Methanol
Reduction⇄
Oxidation
Thetroublewithhydrogen• Hydrogenisdifficulttoliquefy• Incompatiblewithlegacyinfrastructure• Seriouscompetitivedisadvantagevis-à-visfossilfuels!
Liquid regenerablefuelsareneededtodisplacefossilfuelsinacompetitivemarket.
PowerdensityVaclavSmil,2015
FuelpowerdensityWilliamAhlgren,2012
FiguresofmeritforfuelsName– Formula - State
𝒑 𝝆 𝒉𝑯 𝒉𝑳 𝝆𝒉𝑳 𝒉𝑳� 𝑭
bar kg/m3 MJ/kg MJ/kg GJ/m3 km/s TW/m2
Hydrogen H2 g 50 4.06 141.80 120.97 0.49 11.00 5.41
Methane CH4 g 50 35.85 55.50 50.01 1.79 7.07 12.68
Ammonia NH3 l 10 681.90 22.50 18.65 12.71 4.32 54.90
Propane C3H8 l 10 507.70 50.35 46.36 23.54 6.81 160.24
Methanol CH3OH l 1 791.80 22.66 19.92 15.77 4.46 70.40
Octane C8H18 l 1 688.00 47.89 44.43 30.57 6.67 203.73
Ammoniaandmethanolarenotasgoodaspropaneandoctane,butbetterthanhydrogenandmethane.
Ammoniaisaconvenient“liquidformofhydrogen”
• Liquidhydridestoragematerial
• Chemicalvs.cryogenicliquefaction
• Energysupplychainadvantage:‒ Front-endconversioncost‒ Downstreamsavingsintransport,storage,distribution,anduse
Thetroublewithammonia
Inhalationhazardmakesammoniaunsuitableforsomeapplications
Methanoliswell-known
Thetroublewithcarbon-basedfuels
CO2 feedstockmustbeextractedfromambientair
Sherwoodplot:costtoextractisinversetoconcentration
ExpectN-fuel tobemuch less costly
thanC-fuel
Figure 1. Relation Between the Valueof Pure Substances and TheirConcentrations in the Mixtures fromWhich They are Obtained.• NITROGEN
• CARBONDIOXIDE
Ammonia-methanoldual-fuelpair• Ammoniaiscarbon-free…
…buthighrelativetoxicity• Methanolislowrelativetoxicity…
…butcontainscarbon• Complementary:eachhasstrengthtocompensatetheother’sweakness
Together,ammoniaandmethanolareasuperioralternativetohydrogen
Carbon-basedregenerablefuels
𝑛CHWOH → 𝑛CHY + 𝑛HYO
• Methanol(MeOH)– primarycarbon-basedrenewablefuel– simplestandlowestcost—servesmostuses
• Dimethylether(DME)– “equivalent”toMeOH—inter-convertibleathighefficiencyandlowcost
– betterforsomeuses—cookingandheating,diesel• Methyl-derivedfuel(MDF)
– complexmixtureofhigherhydrocarbonsproducedfromMeOHorDME:
– Highenergydensity—likegasolineandjetfuel
Costhierarchyofregenerablefuels
NH3 lowestcost‒buthardtohandle
MeOH/DME morecostly‒buteasiertohandle
MDF highestcost‒highenergydensity
Ammoniafuelmeetsmostneeds
80%N-fuel 20%C-fuel
20%C-fuelincludes:• 15%MeOH/DMEformosthighwaytransport• 5%MDFforhigh-energydensity(aviation,military)
• Professionalfuelhandlers• Moderateenergydensity
Ammoniaissues
• Inhalationhazard—butextensivesafehandlingexperience• Fire/explosionadvantage• Environmentalrisks—lessthanoil• NOxemission—anotheradvantage!
Ammoniasaferthanhydrogen?
Healthhazard
Flammable
Unstable
Special
Mandatorytrainingevery twoyears
AmmoniausedtosuppressNOx
Notperfect– goodenough?
Fuelproduction• Petrochemical(chemical-to-chemical)
• Thermochemical(heat-to-chemical)
• Photochemical(light-to-chemical)
• Electrochemical(electric-to-chemical)
• Hybrid(photo-electrochemical,thermo-electrochemical,e.g.SOEC;etc.)
Petrochemicalproduction?• De-carbonizenaturalgas• CO2 capturepriortocombustionratherthanafter
• Requirescarbonsequestration• Near-term“bridge”solution• Strategy:growmarketforammoniaasfuel
Feedbackpreventschange
Statusquoisstabilizedinavicious cycle:economicinertia.
Noreasontoproduceengine
Enginenotavailable
Fuelnotavailable
Noreasontoproducefuel
Feedbackwillenablechange
Changeisdrivenbyavirtuous cycleafterathresholdstimulusisapplied
Increasedfueldemand
Moreengines
Lowerfuelcost
EngineR&Dtousefuel
Trigger
Half-cost,stablesupply
Newfuels:two-stepstrategy
Ammoniaasenergycarrierenablesnear-termde-carbonizationofelectricpowergeneration
Baseload(GW)electricpower
Replacenaturalgaswithammonia• Onlyboilerburnersneedmodification• Relativelylowcosttoimplement• Ammoniaalreadyfamiliar(thermalde-nox)• Zerocarbondioxideemissionsatpowerplant
5gasfields390gaspowerplants
CaptureCO2 atgasfields
CO2 easilycapturedinNH3 process1/3oftotal 2/3oftotal
Source:R.StraitandM.Nagvekar,“Carbondioxidecaptureandstorageinthenitrogenandsyngasindustries.”Nitrogen+Syngas 303(Jan-Feb):1-3(2010).
GeologicsequestrationofCO2• InjectCO2 fromproducinggasfieldsintonear-bydepletedgasfields
• Neteffect:replaceCH4 withCO2• Carbonpricingmechanismsrequired
Scenario2035
Supposeallglobalelectricityproductionprojectedtobesuppliedbynaturalgas
andcoalin2035wereinsteadsuppliedbyammonia.
Howmuchammoniawouldbeneeded?
FeasiblepathtoGHGmitigation• 2035globalammoniaproductionwouldhavetobeabout21Gt/y
• 84-foldincreaseover0.25Gt/y,thecurrentprojectionforfertilizerdemandin2035.
• Largebutfeasible.• Outcomeiscompletede-carbonizationofthe electricpowersector.
Apathworthexploring!
