各种介绍Concentrating-solar-power

ConcentratingsolarpowerThelimitedsupplyoffossilhydrocarbonresourcesandthenegativeimpactofCO2emissionsontheglobalenvironmentdictatetheincreasingusageofrenewableenergysources.Concentratedsolarpower(CSP)isthemostlikelycandidateforprovidingthemajorityofthisrenewableenergy,becauseitisamongstthemostcost-effectiverenewableelectricitytechnologiesandbecauseitssupplyisnotrestrictediftheenergygeneratedistransportedfromtheworld'ssolarbelttothepopulationcentres.Threemaintechnologieshavebeenidentifiedduringthepastdecadesforgeneratingelectricityinthe10kWtoseveral1000MWrange:●dish/enginetechnology,whichcandirectlygenerateelectricityinisolatedlocations●parabolicandFresneltroughtechnology,whichproduceshighpressuresuperheatedsteam●solartowertechnology,whichproducesairabove1000°Corsynthesisgasforgasturbineoperation.Whilethesetechnologieshavereachedacertainmaturity,ashasbeendemonstratedinpilotprojectsinIsrael,SpainandtheUSA,significantimprovementsinthethermo-hydraulicperformancearestillrequiredifsuchinstallationsaretoachievethereliabilityandeffectivenessofconventionalpowerplants.ThisfirstarticlefocusesonpresentCSPtechnologies,theirhistoryandthestateoftheart.Thesecondarticle,inthenextissueofIngenia,looksatthetechnical,environmental,socialandeconomicissuesrelatingtoCSPinthefuture.ingenia43HANSMÜLLER-STEINHAGENFREngANDFRANZTRIEBINSTITUTEOFTECHNICALTHERMODYNAMICS,GERMANAEROSPACECENTRE(DLR),STUTTGART,GERMANYENERGYConcentratingsolarpowerAreviewofthetechnologyIssolarpowertheanswertotheever-growingproblemsofglobalwarminganddepletingfossilfuelsupplies?InthefirstoftwoarticlesHansMüller-SteinhagenandFranzTriebexplaintheprinciplesanddevelopmentofconcentratedsolar-thermalpowerandoutlineitsconsiderablepotentialforalleviatingtheconstantpressureonourexistingresources.InQuarterlyoftheRoyalAcademyofEngineeringIngenia18,February/March2004CapacityConcen-PeaksolarAnnualsolarThermalcycleCapacityfactorLanduseunitMWtrationefficiencyefficiencyefficiency(solar)m2MWh–1y–1Trough10–20070–8021%(d)10–15%(d)30–40%ST24%(d)6–817–18%(p)25–70%(p)Fresnel10–20025–10020%(p)9–11%(p)30–40%ST25–70%(p)4–6Powertower10–150300–100020%(d)8–10%(d)30–40%ST25–70%(p)8–1235%(p)15–25%(p)45–55%CCDish-Stirling0.01–0.41000–300029%(d)16–18%(d)30–40%Stirl.25%(p)8–1218–23%(p)20–30%GTTechnicalprinciplesIngeneral,solarthermaltechnologiesarebasedontheconceptofconcentratingsolarradiationtoproducesteamorhotair,whichcanthenbeusedforelectricitygenerationusingconventionalpowercycles.Collectingthesolarenergy,whichhasrelativelylowdensity,isoneofthemainengineeringtasksinsolarthermalpowerplantdevelopment.Forconcentration,mostsystemsuseglassmirrorsbecauseoftheirveryhighreflectivity.Othermaterialsareunderdevelopmenttomeettheneedsofsolarthermalpowersystems.Pointfocusingandlinefocusingsystemsareused,asdepictedinFigure1.Thesesystemscanuseonlydirectradiation,andnotthediffusepartofsunlightbecausethiscannotbeconcentrated.Linefocusingsystemsareeasiertohandle,buthavealowerconcentrationfactorandhenceachievelowertemperaturesthanpointfocusingsystems.Table1givesanoverviewofsomeofthetechnicalparametersofthedifferentconcentratingsolarpowerconcepts.Parabolictroughs,linearFresnelsystemsandpowertowerscanbecoupledtosteamcyclesof10to200MWofelectriccapacity,withthermalcycleefficienciesof30–40%.Thevaluesforparabolictroughs,byfarthemostmaturetechnology,havebeendemonstratedinthefield.Today,thesesystemsachieveannualsolar-to-electricityefficienciesofabout10–15%,withtheaimthattheyshouldreachingenia44about18%inthemediumterm.Thevaluesforothersystemsare,ingeneral,projectionsbasedoncomponentandprototypesystemtestdata,andtheassumptionofmaturedevelopmentofcurrenttechnology.Overallsolar-electricefficienciesarelowerthantheconversionefficienciesofconventionalsteamorcombinedcycles,astheyincludetheconversionofsolarradiativeenergytoheatwithinthecollectorandtheconversionoftheheattoelectricityinthepowerblock.Theconversionefficiencyofthepowerblockremainsessentiallythesameasinfuelfiredpowerplants.Becauseoftheirthermalnature,eachofthesetechnologiescanbe‘hybridised’,oroperatedwithfossilfuelaswellassolarenergy.HybridisationhasthepotentialtoimprovedramaticallythevalueofCSPtechnologybyincreasingitspoweravailabilityanddispatchability,decreasingitscost(bymakingmoreeffectiveuseofthepowerblockequipment),andreducingthetechnologicalriskbyallowingconventionalfueluseif,forexample,thecollectorhastoberepaired.Solarheatcollectedduringthedaytimecanbestoredinconcrete,moltensalt,ceramicsTable1Performancedataforvariousconcentratingsolarpower(CSP)technologiesFigure1Technologiesforconcentratingsolarradiation:leftsideparabolicandlinearFresneltroughs,rightsidecentralsolartowerreceiverandparabolicdish(Source:DLR)(d)=demonstrated;(p)=projected;STsteamturbine;GTgasturbine;CCcombinedcycle.Solarefficiency=Capacityfactor=solaroperatinghoursperyear8760hoursperyearnetpowergenerationincidentbeamradiationENERGYorphase-changemedia.Atnight,itcanbeextractedfromstoragetorunthepowerblock.Fossilandrenewablefuelssuchasoil,gas,coalandbiomasscanbeusedforco-firingtheplant,thusprovidi