A Startup Wants to Power Data Centers With ‘Supercritical’ Carbon Dioxide
6 min read
Summary
A new company has a plan to make the dirty gas turbines powering data centers more efficient: liquid carbon dioxide.
American Supercritical came out of stealth Wednesday, announcing 8millioninfunding.Itwantstoretrofit[inefficientgasturbines](https://www.wired.com/story/us−data−centers−drive−gas−power−expansion/)thatmanydatacentersrelyonforpowerwithunitsthatcangeneratemorepower,withoutaddingmoreemissions(thoughthegas−firedturbineswillcontinueto[emitcarbonpollution](https://www.wired.com/story/data−centers−taking−over−texas−pollution−could−be−catastrophic/)).Thetechnologycanalsotheoreticallybeusedonawidevarietyofenergysourcesatatimewhenpowerdemandisskyrocketing.“Wewanttostartwithgasturbinesbuteventuallyexpandbeyondthat,”sayscofounderSimonShuham.Mostlargegas−firedpowerplantsintheUnitedStatesuseanarrayofheatenginesinwhat’sknownasacombined−cycleprocess:First,turbinesgenerateelectricityfromburningcompressedairandnaturalgas,thenaseparateengineusesthehotexhausttomakesteamandcreateadditionalenergy.Butforavarietyofreasons,datacentersacrosstheUShave[optedtopowertheiroperations](https://www.wired.com/story/elon−musk−spacex−spending−gas−turbines−grok/)withwhatareknownassimple−cycleturbines,andexcludethesteamcomponent.Theseturbinesaremuchlessefficientthancombined−cycleplants.Usually,onlyabout35percentoftheenergyfromsimple−cycleturbinesisconvertedtoelectricity,whiletherestescapesasexhaust.(Incombined−cycleplants,thatfigurehoverscloserto60to65percent.)Thatexhaustincludesgreenhousegases,makingplantsthatrunonsimple−cycleturbinesamuchworsechoicefortheenvironmentthancombined−cycleplants.Thesizeofsomeoftheseplantscombinedwiththeirinefficiencyisarecipeforclimatedisaster.Amassivedata−centerpowerplantinTexasthatAmazonisbuildingwithjustsimple−cycleturbines,forinstance,ispermittedtoemitmorethan33milliontonsofgreenhousegasesperyear—morethanthe[annualtotalofsomesmallcountries](https://www.wired.com/story/new−gas−powered−data−centers−could−emit−more−greenhouse−gases−than−entire−nations/).Butallthesesmall,inefficientturbinescouldbeagreatmatchforsupercriticalCO2technology,AmericanSupercritical’sfounderssay.Carbondioxidebecomessupercriticalwhenit’spressurizedandheldatacertaintemperature.Inthisstate,itgetsthedensityofliquidbutstillbehaveslikeagas,meaningitcanmoveenergymoreefficientlythroughmuchsmalleramountsofequipment.AmericanSupercriticalwantstoattachitsunitstosmallgasturbinesandhelpgeneratemoreenergy.Whiletheturbinesthemselveswouldstillusegas,thesupercriticalCO2unitcanusethehotexhaustgeneratedfromthoseturbinestocreateadditionalelectricity.Insteadofusingthatheattoboilwaterandcreatesteam,theheatistransferreddirectlybythepressurizedCO2togenerateadditionalenergywithnoadditionalemissions.“We’reessentiallybuildingminiaturecombined−cycleplants,”saysShuham.UsingsupercriticalCO2alsocaneliminateorgreatlyreducewateruseinthepowergenerationprocess—somethingthat’sdrawnintensescrutinywhenitcomestodatacenters.Importantly,theCO2involvedoperatesinaclosed−loopsystem,meaningthatitdoesn’thavetoberefilled.CofounderMatthewCarlson,whoresearchedsupercriticalCO2formorethanadecade,likensittorefrigerationsystemsthatcirculateCO2tofacilitatecooling.Thecompanyplanstoinitiallysella10−megawattunit—relativelysmallbygasplantstandards.ByAmericanSupercritical’smath,addingsupercriticalCO2unitscouldincreaseturbines’efficiencybyupto50percentwithoutaddinganymoregreenhousegasemissionsorwateruse.Butretrofittingallofthecountry’sinefficientgasturbinespoweringdatacenterswithsupercriticalCO2unitswon’treduceemissionstozero.Naturalgasproductionanduse,evenwithefficientturbines,warmstheplanet.Datacentersalsorepresentamassivenewsourceofpollution—rightatatimewhentheworldneedstobescalingbackonitsuse.UsingsupercriticalCO2forpowerhasbeenstudiedformorethan50yearsinUSnationallabs.Overthepasttwodecades,researchhasmovedawayfromtheorytowardtryingoutpracticalapplications,assistedbytechnologicalbreakthroughsthathelpwiththepressurizationprocess.DougHofer,anadvisertoAmericanSupercriticalwhospenttwodecadesatGEasaturbineengineer,saysthatoneimportantinnovationhasbeenthedevelopmentofmorecompactandmoreaffordableheatexchangers—devicesthathelpbothheatandcooltheCO2.AmericanSupercriticalisn’ttheonlycompanytryingtobringthistechnologytomarket,saysSubithVasu,aprofessorofengineeringattheUniversityofCentralFlorida,whorunsalabattheschool’sCenterforAdvancedTurbomachineryandEnergyResearch.Thecompaniesstillhavehurdlestoovercometoachievecommercialsuccess.“Wheneveryouareventuringintonewtechnologies,youneedtohavealltheassociatedcomponents,thesupplychain,”inplace,hesays.Technicalchallengesalsoabound,headds,“andcosthasbeenahugeissue.”Hofersaysthatpartofthedelayhasalsosimplybeenbecauselargercompaniesaresatisfiedwiththeperformanceoftraditionalpowerplantsandunwillingtoinvestindifferenttechnologies—andturbinemakersarenotinterestedinfundingpotentialcompetitors.“It’stheinnovator’sdilemma,right?”hesays.“Gettingthis[technology]outthereneedstohaveanoutsideinfluence.”The7 trillion set to be invested in data centers globally by 2030 has helped open up a whole new potential market, especially for an industry racing to get as much power on the grid as it possibly can to come out ahead in the AI race.
“There’s this incredible willingness to pay [for power], but they’re bottlenecked,” says Shuham. “The goal is to come in here, retrofit their existing systems, and give them the ability to build additional data centers—or get rid of some of the gas turbines.”
Earlier this year, China announced that operations started at the world’s first geothermal plant using supercritical CO2. Carlson says that in his career, he’s worked on supercritical CO2 applications in nuclear, geothermal, and solar energy. He and Shuham say that their units could be converted to work with small modular reactors, a technology that’s enjoyed strong support from the Trump administration. (The company says it has already signed an initial agreement with one company, though it didn’t name it). It can work with other sources of heat as well.
“We just need to get something hot, and then we can convert that into electricity,” says Carlson.
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