European Solar ThermalElectricity Association
december
2012
SOLAr THermAL eLecTrIcITY
STrATegIc reSeArcH AgendA 2020-2025
European Solar ThermalElectricity Association
European Solar Thermal Electricity Association
Rue d’Arlon, 63-67B - 1040 - Brussels
Tel. : +32 (0)2 400 10 90 Fax : +32 (0)2 400 10 91
www.estelasolar.eu
Printed on Satimat green, silk coated paper, FSC® certified, produced from 60% FSC® certified
recycled fibre and 40% FSC® certified virgin fibre, ensuring a reduced impact on the environment. De
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Copyright © 2012 by Association Européenne pour la promotion de l’Electricité Solaire Thermique, a.s.b.l.
ESTELARue d’Arlon, 63-651040 – Bruxelles, Belgique
All rights reserved. This book or any portion thereofmay not be reproduced or used in any manner whatsoeverwithout the express written permission of the publisherexcept for the use of brief quotations in a book review.
Printed in Belgium
First Printing, December 2012
december 2012
European Solar ThermalElectricity Association
SOLAr THermAL eLecTrIcITY
STrATegIc reSeArcH AgendA 2020-2025
4 STrATegIc reSeArcH AgendA 2020-2025
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Acknowledgments 6
Preface 7
Glossary 8 IntroductiontoESTELA 10TheScientificandTechnicalCommittee 11 ExecutiveSummary 131 History 19
2 TheBrilliantFutureofSolarThermalElectricityPlants 23
2.1 Dispatchabilityandothertechnicalfeatures. . . . . . . . . . . . . . . . . . . . . . . . .24 2.2 Macroeconomicimpactonlocaleconomies. . . . . . . . . . . . . . . . . . . . . . . .24 2.3 Competitiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
3 IndustryOverviewandRelatedEconomicAspects 27
3.1 Nationalandregionalmarkets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 3.2 Employment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 3.3 Economics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 3.4 Standardisation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
4 PolicyOverview 39
4.1 ContributiontoEU’srenewableenergypolicy. . . . . . . . . . . . . . . . . . . . . . .40 4.2 Energytransmissioninfrastructure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 4.3 Europeancontextandframeworks2014-2020. . . . . . . . . . . . . . . . . . . . . .41 4.4 Researchoverview:participationoftheSTEsectorintheEUinstruments. . . . . .42
5 State-of-the-ArtofSTETechnologies 45
6 STEMainChallengesonInnovation 53
6.1 STEEuropeanIndustrialInitiative 54 6.2 Upcomingchallenges 56
7 StrategicResearchAgenda 59
7.1Objective1:Increaseefficiencyandreducegeneration,operationandmaintenancecosts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60
7.1.1 Cross-cuttingIssues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61 7.1.1.1 Mirrors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61 7.1.1.2 Receivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62 7.1.1.3 Heattransferfluids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63 7.1.1.4 Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64 7.1.1.5 Controlandoperationtools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
7.1.2 ParabolicTroughCollectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66 7.1.2.1 Receivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66 7.1.2.2 Heattransferfluids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67 7.1.2.3 Systemcomponentswithenhancedproperties. . . . . . . . . . . . . . . . . . . . . . .68 7.1.2.4 Systemsize,componentmanufacturingandotherimprovements. . . . . . . . . . .69 7.1.2.5 Controlandoperationstrategy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
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7.1.3 CentralReceivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71 7.1.3.1 Heliostatfield. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72 7.1.3.2 Receiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72 7.1.3.3 Heattransferfluids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73 7.1.3.4 Newconversioncyclesandsystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73 7.1.4 LinearFresnelReflectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76 7.1.4.1 Mirrors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76 7.1.4.2 Receivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77 7.1.4.3 Heattransferfluids. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77 7.1.4.4 Controlandoperationstrategy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78 7.1.4.5 Fielddesignandconfiguration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78 7.1.5 ParabolicDishes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80 7.1.5.1 Stirlingengine. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80 7.1.5.2 Gasturbines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82 7.1.5.3 Receivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82 7.1.5.4 Dispatchability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82 7.1.5.5 Systemcomponentswithenhancedmaterialproperties. . . . . . . . . . . . . . . . .83 7.1.5.6 Controlsandoperationissues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83
7.2Objective2:Improvedispatchability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84 7.2.1 Hybridisationandintegrationsystems. . . . . . . . . . . . . . . . . . . . . . . . . . . .86 7.2.1.1 Integrationwithlargesteamplants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86 7.2.1.2 Integrationwithgasturbineandcombinedcycleplants. . . . . . . . . . . . . . . . .87 7.2.1.3 Integrationwithbiomassplants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87 7.2.1.4 Hybridisationforthedirectsystemsusingthesamemoltensaltmixture
asHTFandHSM(heatstoragemedium) . . . . . . . . . . . . . . . . . . . . . . . . . .88 7.2.2 Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90 7.2.2.1 Storagedesign. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90 7.2.2.2 Storageoptimisation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91 7.2.2.3 Newstorageconcepts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92 7.2.2.4 Storageasenergyintegrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92 7.2.3 Forecastingtools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94 7.2.3.1 Operationstrategy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94 7.2.3.2 Solarresourceassessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94
7.3Objective3:Improveenvironmentalprofile. . . . . . . . . . . . . . . . . . . . . . . . . . . .97 7.3.1 Heattransferfluids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97 7.3.1.1 Heattransferfluidsvsenvironmentimpact. . . . . . . . . . . . . . . . . . . . . . . . . .97 7.3.1.2 Heattransferfluidcharacteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98 7.3.1.3 Leakageconsequences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 7.3.2 Reductionofwaterconsumption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100 7.3.2.1 Improvedcoolingsystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100 7.3.2.2 Desalination. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100 7.3.2.3 Solutionsfordesertlocations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
Conclusion 104
Bibliography 105
IndexFiguresandTables 106
ANNEXI:KeyPerformanceIndicators 108
ANNEXII:PastandpresentEU-fundedprojects 110
ANNEXIII:Heattransferfluidsvs.environmentalcomponents 111
Notes 112
hePresidentandtheSecretaryGeneraloftheEuropeanSolarThermalElectricityAssociationwouldliketotakethisopportunitytoexpressourdeepappreciationtotheauthorsandothercollaboratorsfortheirexcellentworkanddedicationprovidedbyallofthem.Withouttheirsupportthishugeprojectwouldnothavebeenaccomplished.
Weexpressourdeepestgratitude to the followingpeople for theirdevoted time,valuablecontributionandanalyticalandtechnicalsupporttothispublication:ManuelBlanco,ManuelCollaresPereira,FabrizioFabrizi,GillesFlamant,GuglielmoLiberati,HansMueller-Steinhagen,RobertPitz-Paal,WernerPlatzer,ManuelSilvaandEduardoZarza.AllofthemarethemembersofESTELA’sScientificandTechnicalCommitteethathavetakenonboardthetasksofelaboratingthefirstresearchagendaforsolarthermalelectricity.
WewouldliketothankourstaffandinternofESTELA,FernandoAdán,ElenaDufour,StefanEckhoff,MicaelaFernández,JanisLeung,JoséMartínez-Fresneda,for theirexcellentcollaborationtoboththeauthorsandtheAssociationinmakingthisprojectasuccessfulone.
Inaddition,aspecialthanktoJoséMartinwhohasbeenour“PierredeRosette”forhisengagementinmakingacomprehensivedocument.
FinallywewouldliketothankthesuccessivemembersoftheExecutiveCommitteeofthelasttwoyears-NikolausBenz,EduardoGarcía,MichaelGeyer,HennerGladen,CayetanoHernández,LeonardoMerlo,JoséAlfonsoNebrera,JoséManuelNieto,MarcoSimiano,ShmuelFledel-andtheMembersofESTELAforsupportingtheinitiativethatweproposedaboutoneyearandahalfago.WehopewewillhavetheirsupportforthenexteditionoftheStrategicResearchAgenda.
Dr.LuisCrepo MariàngelsPérezLatorrePresidentofESTELA Secretary-General
AcknOwLedgmenTS
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december 2012 7
enewableenergy isakeycomponentof thefutureenergysupplyasacknowledgedintheEU2050EnergyRoadmap.TheEUhaspursuedasustainedsupportfortheintroductionofrenewable
energiesintheenergymixbecauseoftheirimportancefor reducing thecarbon footprintof theeconomy, forimproving thesecurityof theenergysupplyand forpromoting theregionaleconomicandsocialdevelop-ment.Moreandbetterresearchanddevelopmentcanhelpovercometwomajorobstaclestothewideruptakeofsomepromisingrenewables,whicharetheirhighercostsandintermittency.
ConcentratingSolarPower(CSP)hasthepotentialtosupplysubstantialquantitiesofrenewableenergyinEuropeandabroad.Europe'sleadingpositionworldwideonmanykeytechnologicalcomponentsofCSPandthereadinessoftheEuropeanstakeholderstoworktogetherinviewofspeedingupthecommercialisationofthistechnologyledtothelaunchoftheSolarEuropeIndustrialInitiativeundertheStrategicEnergyTechnologyPlan.
DGResearchand Innovationwelcomes thisStrategicResearchAgenda,whichprovidesavisionforthedevel-opmentofthesectorintheyearstocomeandhighlightsprioritiesandareasforcooperation.ThisdocumentwillbeofusetothesectortocontributetothediscussionontheforthcomingFrameworkProgrammeforResearchandInnovation -Horizon2020.Mywish is for thesectortocontinueconsolidatingitspositionthroughindustrialandresearchcollaborations,notablyatEuropeanlevel.
Robert-JanSmitsDirector-GeneralforResearch&InnovationEuropeanCommission
Pre
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PreFAce
8 STrATegIc reSeArcH AgendA 2020-2025
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AENOR SpanishAssociationforNormalisationandCertification
AEN/CTN SpanishAssociationforNormalisation/TechnicalCommitteeforNormalisation
AHS AuxiliaryHeatingSystem
ARENA AustralianRenewableEnergyAgency
ASME AmericanSocietyofMechanicalEngineers
CAES CompressedAirEnergyStorage
CAPEX CapitalExpenditure
CENER NationalRenewableEnergyCentreofSpain
CIEMAT CentrodeInvestigacionesEnergéticasMedioambientalesyTecnológicas
CLFR CompactLinearFresnelReflector
CNRS FrenchNationalCentreforScientificResearch
CR CentralReceiver
CSP ConcentratedSolarPower
DNI DirectNormalIrradiation
DKE GermanCommissionforElectrical,Electronic&InformationTechnologies
DSG DirectSteamGeneration
EC EuropeanCommission
ECMWF EuropeanCentreforMedium-RangeWeatherForecasts
EERA EuropeanEnergyResearchAlliance
EIB EuropeanInvestmentBank
EII EuropeanIndustrialInitiative
ENEA ItalianNationalAgencyforNewTechnologies,EnergyandSustainableEconomicDevelopment
EPC EngineeringProcurementConstruction
ERANET EuropeanResearchAreaNetwork
ESFRI EuropeanStrategyForumonResearchInfrastructure
ESTELA EuropeanSolarThermalElectricityAssociation
EU-Solaris EuropeanSolarResearchInfrastructureforCSP
EU EuropeanUnion
FiT Feed-in-Tariff
FP7 SeventhFrameworkProgramme
GDP GrossDomesticProduct
GUISMO GuidelinesCSPPerformanceModelling
GWh Gigawatthour
HCE HeatCollectionElement
HDH Humidification-Dehumidification
HSM HeatStorageMedium
HTF HeatTransferFluid
HVDC HighVoltageDirectCurrent
ISCC IntegratedSolarCombined-Cycle
IEC/TC InternationalElectro-technicalCommission/TechnicalCommittee
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9december 2012
KPI KeyPerformanceIndicator
kWp Kilowattpeak
LCOE LevelisedCostofElectricity
LF LinearFresnelReflector
LWC LevelisedWaterCost
MBE MeanBiasError
MD MembraneDistillation
MED Multi-EffectDistillation
MENA MiddleEastandNorthAfrica
MoU MemorandumofUnderstanding
MSH MoltenSaltHeater
MS MoltenSalt
MSP MediterraneanSolarPlan
MTBF MeanTimeBetweenFailure
MWe Megawattofelectricity
MWth MegawattofThermalEnergy
NER300 NewEntrantReserve300
NREAP NationalRenewableEnergyActionPlan
NWP NumericalWeatherPrediction
OHL OverHeadLines
O&M OperationandMaintenance
OPEX OperatingExpenditure
OPTS OptimisationofaThermalEnergyStorageSystemwithIntegratedSteamGenerator
ORC OrganicRankineCycle
PCM PhaseChangeMaterial
PD ParabolicDish
PPA PowerPurchaseAgreement
PT ParabolicTrough
PV Photovoltaic
R&D ResearchandDevelopment
REFIT RenewableEnergyFeed-In-Tariff
RES RenewableEnergySources
RMSE RootMeanSquareError
RO ReverseOsmosis
SEGS SolarEnergyGeneratingSystems
SETIS InformationSystemfortheEuropeanStrategicEnergyTechnologyPlan
SET-Plan StrategicEnergyTechnologyPlan
SEII SolarEuropeanIndustrialInitiative
SFERA SolarFacilitiesfortheEuropeanResearchArea
SolarPACES SolarPowerAndChemicalEnergySystems
STE SolarThermalElectricity
TES ThermalEnergyStorage
wt% PercentinWeight
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STrATegIc reSeArcH AgendA 2020-2025
STELAisanassociationcreatedbytheEuropeanindustrytosupporttheemergingEuropeansolarthermalelectricityindustryforthegenerationofgreenpowerinEuropeandotherregions,particularlytheMediter-raneanandNorthAfricanregion.
ESTELAinvolvesandisopentoallmainactorsinEurope:promoters,developers,manufacturers,utilities,engi-neeringcompaniesandresearchinstitutions.
OneofthemainactivitiesofESTELAanditsmembersistocollaboratewithinstitutionsintheEuropeanUnion(EU)todevelopsolarthermalelectricitygenerationanditssupportingindustryacrossEurope.
Anothercoreactivityinclosecollaborationwithacademiaistoproduceandcoordinatestudiesonscientific,technical,economic,legalorpolicyissuestofurtherdevelopsolarthermalelectricitytechnologies.
Finally,ESTELAconsidersofparamountimportancetoraiseawarenessbydisseminatinginformationaboutsolarthermalelectricityandtheEuropeanAssociationbyorganisingmeetings,workshops,conferencesandothereventstopromotesolarthermalelectricity.
TheemergingindustryofsolarthermalelectricityhasstrongEuropeanroots.Itisgrowingtoagreatextentduetothetechnicalandeconomicsuccessofthefirstprojectsandtothestablegreenpricingorsupportmechanismstobridgetheinitialgapintheelectricitycosts–mechanismssuchasfeed-intariffs(FiT).FuturegrowthwilldependonasuccessfulcostsreductionandastrongeffortinR&Dtorealisethegreatexistingpotentialfortechnicalimprovement.Inthelong-term,itisenvisionedthatnewmarketsandmarketopportunitieswillappear:aparticularlyexcitingpossibilityisthegenerationofsolarthermalpowerintheMediterraneanregionanditstransmissiontootherpartsofEurope.
ESTELAmemberswillensurethesolarthermalelectricityindustrycontributiontotheachievementofrenewableenergyobjectivesby2020,providedthatthenecessarymeasuresaretakenbothinthemarketandinresearchtosupporttheeffortsoftheindustry.
ESTELAmembersbelievethattheEU,intheshortandmedium-term,shouldinstalldemand-pullinstrumentsandpromotesupportmechanismssuchasfeed-in-lawsasthemostpowerfulinstrumentstofurthersolarthermalelectricitygenerationgoals.Inthelongterm,theEuropeantransmissiongridshouldbeopenedtobringsolarelectricityfromNorthAfricaandregionalagreementsshouldbeimplementedtosecurethisreliablepowerimport.
Theworld’s“SunBelt”,thatextendsfromaboutlatitudes35Northto35Southandborderareas,receivesseveralthousandtimestheenergyneededtomeettheworld’senergydemand.Thisresourceisnotbeingcurrentlyexploited.Atthesametime,dramaticchangesaretobeimplementedinthecurrentenergysystemstomitigatetheirnegativeimpactontheenvironmentandontheworld’sclimate.AlargepartoftheenormousenergyresourceavailableintheSunBeltcouldbeharnessedthroughsolarthermaltechnologies,conveyedandusedinasustainableway.
THe eurOPeAn SOLAr THermAL eLecTrIcITY ASSOcIATIOn (eSTeLA)
The objectives of ESTELA are:
n To promote high and mid temperature solar tech-nologies for the production of thermal electricity to move towards sustainable energy systems;
n To promote thermal electricity in Europe at policy and administrative levels (local, regional, national and European);
n To support EU’s action in favour of European industry development and to contribute to reach the Union’s energy objectives and its main renewable energy targets;
n To support research and innovation, including vocational training, and favouring equal op-portunities for all;
n To promote excellence in the planning, design, construction and operation of thermal electric-ity plants;
n To promote thermal electricity internationally, mainly in the Mediterranean area and in de-veloping countries;
n To cooperate at the international level to combat climate change;
n To represent the solar thermal electricity sector in Europe and the world.
11
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inceitscreationin2007,ESTELAhasdevelopeditsscientificandtechnicalactivitiesinsupportofresearchandinnovation.Ithasestablishedguidingprioritiesfortheshortandlong-termeffortstofosterthemarketpenetra-tionofsolarthermalpowerplantsandtoconsolidatethegloballeadershippositionoftheEuropeanindustry.
Tocreateaninnovationstrategy,ESTELAhastakenadvantageofhavingamongitsmembersthemainresearchinstitutionsactiveinthisfieldinEurope.
InSeptember2011,ESTELAsteppedupitseffortsbycreatingtheScientificandTechnicalCommitteetohelptheAssociationbuildaStrategicResearchAgendafor2020andbeyond.Thisistherightmomenttostrengthentheseeffortsfortwomainreasons.First,theeconomicandfinancialcrisiscallsformoreinnovationandforamid-andlong-termvision.Second,ESTELA’smissionistocontributetotheEU’sdebateontheprogrammestosupportresearch,demonstrationandinnovationintheframeworkofthefinancialperspectivesfortheperiod2014-2020.
TheScientificandTechnicalCommitteehastenmembers,eightofthemfrominstitutionswhicharemembersofESTELA,andtwofromuniversities:
n Dr.GuglielmoLiberati(Coordinator):ESTELA,Italyn Dr.ManuelBlanco:CENER,Spainn Prof.ManuelCollaresPereira:ÉvoraUniversity,Portugaln Dr.FabrizioFabrizi:ENEA,Italyn Dr.GillesFlamant:CNRS,Francen Prof.HansMüller-Steinhagen:DresdenUniversity,Germanyn Prof.RobertPitz-Paal:DLRSolarResearchInstitute,Germanyn Dr.WernerPlatzer:FraunhoferISE,Germanyn Dr.ManuelSilvaPérez:SevilleUniversity,Spainn Dr.EduardoZarzaMoya:PlataformaSolardeAlmería,Spain
ThesemembersconstitutewhatcanjustifiablybeconsideredaTeamofExcellence,becausetheyrepresentsomeofthebestscientificknowledgeinthesectorinEuropeandbeyond.
THe ScIenTIFIc And TecHnIcAL cOmmITTee
12 STrATegIc reSeArcH AgendA 2020-2025
he totalamountofelectricitygeneratedbySolarThermalElectricity (STE)plantsaround theworld isgrowingsteadily.Morethan1GWhavebeenconnectedtothegridinSouthernEuropeinthepastfewyears,andthisfigureisexpectedtogrowtomorethan2GWbytheendof2012.Operatingexperiencehasledtoreductionsincostsandrisk,andplantsgeneratinganother1GWarenowunder
constructioninNorthAmerica,Africa,AsiaandAustralia.TheEuropeanindustryhasastrongpresenceinmanyofthoseprojects,andtheRenewableEnergySources(RES)DirectiveopensthewayforevenmoreopportunitiesinSouthernEuropeandintheMiddleEastandNorthAfrica(MENA)region.
Generatingtheelectricitythattheworldneedswithoutreleasingadditionalgasesisnowtechnicallypossible,andthecharacteristicsofSTEplantsmakethemanessentialpartofaneffectiverenewableportfolio.Dispatchabilityisamajoradvantageoftheseplants,andthischaracteristicmaymakeitpossibleforautilitytoaccommodateanevenlargeramountofotherintermittenttechnologies.
STEtechnologieshaveahugepotentialandresearchanddevelopment(R&D)isessentialtoimprovethecompe-tivenessofthecurrentdesigns.Animportantpushmustbegiventospecifictechnologydevelopmentactivitiesandtosupportinnovativedemonstrationplantsofcommercialsizeinordertocontributetolowergenerationcostsandtoenhancethebankabilityoftheprojects.
Theregulatoryconditionsfor implementingSTEplants, includingtheRESDirectiveandtheFeed-in-Tariff (FiT)systemsinsomeEuropeancountries,particularlySpain,havebeenthedrivingforceforthedeploymentofthefirstgenerationofSTEplants.Duetotheexpectedcostreductionsthroughtechnologicaladvancementandmassproduction,thetechnologywillprobablynolongerdependonsuchsupportinafewyears,whenitwillbecomecompetitivewithelectricitygenerationusingfossilfuels.
ThisStrategicResearchAgendahasbeenelaboratedbytheEuropeanSolarThermalElectricityIndustryAssocia-tioninordertoalignR&Deffortswiththesupportofthepublicadministrations,includingtheEuropeanUnion.
WehavedecidedtobeinclusiveandtheStrategicResearchAgendacoversthefourbroadcategoriesthatuptonowhavebeenproposedforthethermalconversionofsolarenergybythescientists.Tovaryingdegrees,theyhavebeenthesubjectofconsiderableinterestanddevelopmentandarealreadymakingsmallbutmeaningfulcontributionstosatisfyingelectricityneedsinmanyregionsoftheworld.Itispossiblethatadvancesinotherfields(materialsandcontrols,tonametwo)maycreatetheconditionswhereotherthermalconversiontechnolo-gieswillbeconceived.Thereisnowaytoknowwhat,ifany,approachmaysomedayrevolutionisethefield,but,thekindofresearchanddevelopmentsuggestedinthisreportisthebestwaytofosterinnovationandopenpossibilitiesastheclockticksfortheinhabitantsofourplanettofindasustainablepath.
WehopethisStrategicResearchAgendawillcontributetoacoherentdevelopmentofthesectorandtoamoreefficientallocationofR&Dresourceswiththefinalgoalofreachingcompetitivenessassoonaspossible.
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heStrategicResearchAgendaisthefirst-of-its-kindfortheSolarThermalElectricity(STE)technology.DraftedbyhighlyqualifiedexpertresearchersinEuropecomposingESTELA’sScientificandTechnicalCommittee,itsetsasolidbasisforpresentandfutureresearchuntil2025.
Uncertaintydetersmarketpenetrationforanytechnology.ThediversityofviabletechnicalapproachesforsolarthermalenergyconversionisoneofthegreatadvantagesofSTE,becausedifferentoptionshavethepotentialtoaddressdifferentneedsandmarketnichesmosteffectively.Diversityalsoposeschallenges,becausethereissomeuncertaintyassociatedwitheachoption.Uncertaintyderivesfrommanysources,fromweathertothechangingpoliticalandeconomicenvironment.Anothersourcearisesfromtechnologyitself,andfromtheexpectationoffuturetechnologicaladvances.Fortunately,supportforresearchanddevelopmentisaneffectivetooltolowerthisuncertainty,andgovernmentsandconsortiacanwieldthistoolmosteffectively.
Itisthegoalofthisdocumenttoassistdecisionmakersbyprovidingareviewofthecurrenteconomic,financialandtechnologicaltrendsoftheSTEsectoraswellastheexistingpolicyandlegalframeworkindifferentcountrieswithintheEU.Thesearedescribedinchapters1to6.Thedetailedresearchtopicsandrelatedtargetsforeachtechnologyconstitutechapter7.ThetopicsarebasedonthreemainobjectivesdefinedbytheSTEindustry.
eXecuTIVe SummArY
1- General overview 2- Technical aspects STE-SEII SET-Plan
n Historyn Industryoverviewandrelated
economicaspectsn Policyoverviewn State-of-the-artofSTEtechnologiesn STEmainchallengesoninnovation
n Cross-cuttingissuesn ParabolicTroughcollectorsn CentralReceivern LinearFresnelreflectorsn ParabolicDishes
Objective 1: Increase efficiency and reduce costs
n Hybridisationandintegrationsystems
n Storagen Optimisedispatchability
Objective 2: Improve dispatchability
n Environmentprofile Objective 3: Improve environmental profile
Economic and political trendsGlobalwarmingandeconomicgrowtharemajorcurrent issuesworldwide.STE technologiescancontributesignificantlytomitigatetheimpactofelectricityproductionontheglobaltemperatureincreaseandtoreachamuchmorebalancedsituationregardingavailabilityofaffordablepowerinindustrialisedanddevelopingcountriesthanitisthecasetoday.
Acarbon-freegenerationsystemcanonlybeachievedwith renewableanddispatchable technologies,andSTEplantsarethealternativewiththelargestpotentialamongstallrenewableenergysystems.Atthesametime,STEplantsaddthelargestadditionallocalvalue,evenforthefirstplantinarow.ThisfactwillbeakeydriverforpolicydecisionsinfavourofSTEplantsinmanycountries.
ThatiswhySTEisanadvantageoustechnologywhichhelpstopavethewayoutoftheeconomiccrisisintheSouthernEuropeancountries.BecauseoftheleadingpositionoftheEuropeanindustry,thisrepresentsahistoricopportunitytocreatepartnershipsandcreatebusinessthroughouttheworld,andparticularlyintheneighbouringMENAregion.
Bymid-2012,thetotalelectricpowergeneratedbySTEplantsintheworldhasreached2GW;plantsgenerating3GWarecurrentlyunderconstruction.ThemajorityoftheseplantsaresitedinSpainandintheUnitedStates.Interestgrowsintherestoftheworld,asnewprojectsarebeinglaunchedinNorthAfrica,India,ChinaandSouthAfrica.Plantsgenerating10GWcanbeexpectedtobeinplaceworldwideby2015.
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InEurope,thecompulsorytargetsestablishedonJune30,2010throughtheNationalRenewableEnergyActionPlans(NREAP)for2020includetheuseofsolarthermalelectricityforthesunniestEuropeancountries.
Country Cyprus France Greece Italy Portugal Spain TotalNREAPtargetsfor2020 75MW 540MW 250MW 600MW 500MW 5,079MW 7,044MW
Regardingnationalsubsidies,thesituationinEuropeiscurrentlyuncertainduetotheeconomiccrisis,andnewmeasuresarebeingtakenatthenationalleveltoleverageinvestmentinitiativesforrenewableprojects.Atthemoment,forsolarthermalelectricity,theFeed-in-Tariffisaround0.30c€/kWh,dependingonthecountryandtheplantparameters.
TheSTEindustrycreatesmanyjobs.InSpain,inparticular,thenumberofjobsrelatedtoSTEhasmorethandoubledbetween2008and2010.ThissuggestsaverypromisingfutureforjobscreationfromtheplannedSTEprojects.
Thelevelisedcostofelectricity(LCOE)isthemaineconomicparametertocomparedifferentrenewabletechnologies.Thisfiguredependsontheratiobetweenallcostsandelectricitygeneration,anditreliesonthedirectnormalirradiation(DNI)foragivenarea(InSpain,theDNIreachesupto2,100kWh/m2).AlowerLCOEisexpectedinthenextfewyearsbecauseofforthcomingtechnologicalimprovements.
TheEuropeanresearchpolicycontextissetbytheCommonFrameworkProgrammeforResearchandInnovationfortheperiod2014-2020,knownas‘Horizon2020’.TheProgrammeplacesagreatemphasisonrenewableenergiesandfirst-of-a-kinddemonstrationplants.ItalsoincludestheStrategicEnergyTechnologyPlan(SET-Plan)anditsindustrialinitiatives,aninstrumentespeciallyfocusedonthedevelopmentoflowcarbontechnologies.Inparallel,theexpansionofthegridandtheimplementationoftheinter-continental‘electricityhighways’areunderway.
Standardisation:StandardsforSTEtechnologyarecrucialforacceleratingcostreduction.Manyeffortshavebeenmadetowardsstandardisation,butmuchimprovementisstillneeded.TheEN12975standardforsolarconcentratorsisnowapartoftheISO9806standard,currentlyunderrevision.Workinggroupshavebeencreatedinthelastyears,particularlyintheframeofSolarPACES,andfurtherguidelinesareexpectedtobereleasedin2012and2013.
Standardsmustevolvetowardsacommonframeworkandeffortsneedtobeintensifiedinthefollowingfields:qualification,certification,testingprocedures,componentsandsystemsdurabilitytesting,commissioningproce-dures,model-basedresultsandsolarfieldmodeling.
Objective 1: Increase efficiency and reduce generation, operation and maintenance costsThedifferenttargetstoreachthefirstobjective(‘Improveefficiencyandreducecosts’)arelistedforeachtechnologyintheschemesonnextpage.However,cross-cuttingissuesexistbetweenthedifferenttechnologiesandneedtobetakenintoconsideration.Thetransversalresearchtopicstobeinvestigatedare:
MirrorsLight reflectives surfaces
Antisoiling coatingsHigh reflective
HEAT TrAnsfEr fluidsLow melting temperature mixtures
Pressurised gasesDirect steam generation with high
pressure absorber tubesHigh working temperatures
OTHERSSelective coating receivers
with better optical propertiesNew storage concept
Improve control, prediction and operation tools
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Schemes listing the different investigation topics for each typical technology plant
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PARABOLIC TROUGH COLLECTORSResearch topics to be investigated to reach objective 1 for parabolic trough collectors
COLLECTORS-Scale-upeffect-Bettercollectordesignandmanufacture-Bettersolarfieldcontrol-Autonomousdriveunitsandlocalcontrols(wireless)
RECEIVERTUBES-Betteroptimalstabilityoftheselectivecoatings-Designswithvacuum,withoutweldsorwithoutlowerH2permeation
-Cheaperinterconnectingelements
HEATTRANSFERFLUID-Useofcompressedgases(CO2,N2,air…)
-Directsteamgeneration-Moltensalt+auxiliaryheating
CENTRAL RECEIVERSResearch topics to be investigated to reach objective 1 for central receivers
NEWCONVERSIONCYCLESANDSYSTEMS-Braytoncycles-Combinedcyclesandsupercriticalsteamcycles
-Hybridisationwithbiomass-Secondaryconcentrators
HEATTRANSFERFLUID-Moltensaltforsupercriticalsteamcycles
-AirandCO2asprimaryfluids-Directsuperheatedsteam-Particlereceiversystems
HELIOSTATFIELD-Multiplesmalltowersconfiguration-Reliablewirelessheliostatcontrolsystems
-Optimisedheliostatfield-Improvedrivemechanisms-Autonomousdriveunitsandlocalcontrols(wireless)
RECEIVER-Advancedhightemperaturereceiver(directabsorption)-Newengineeredmaterials(ceramictubes)
LINEAR FRESNEL REFLECTORSResearch topics to be investigated to reach objective 1 for linear Fresnel reflectors
HEATTRANSFERFLUID-Super-heateddirectsteamgeneration-Moltensaltsonly-PressurisedCO2orairinnon-evacuatedreceivers
RECEIVERS-Evacuatedtubularreceivers-Newgenerationofnon-evacuatedtubularreceivers
MIRRORS-Secondstageconcentration-Thinfilmsoncurvedsupportsurfaces
CONTROLANDDESIGN-Bettertrackingoptions-HybridisationoftowerandFresneltechnologies
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Objective 2: Improve dispatchabilityDispatchabilityisoneofthecharacteristicsthatmakesSTEafavoredoptionamongotherrenewableresources,and“Improvingdispatchability”isevenmoreisamostobjectiveforSTEdevelopment.Indeed,systemswiththeflexibilitytofeedthegridondemandarethekeyforsolarthermalelectricitytoreachitspotential.Althoughmanyplantsarealreadybuiltwithastoragesystem,moreeffortsneedtobedone.
Integration systems:The integration of solar heat in large steam plantscanbeachievedthroughthewaterpreheatinglineorthroughtheboilersteam/watercircuit.Inthefirstcase,anappropriateboilerdesignisrequiredtodealwithtemperaturedifferences.Iftheintegrationisdonewiththeboiler,animprovementofitsdesignandcontrolsystemisneeded.
The integration of solar heat with gas turbine or combined cycle plants isalsoanoption.Withagasturbine,the temperatureof theaircanbeincreasedinhigh temperaturesolarcollectors, leadingtohighconversionefficiencies.Theabilitytohandletransientphasesrequiresanimprovementofthedesignofthecontrolsystem.
The integration of solar heat with biomass, moreappropriateforsmallsizedfacilities,isagoodcombinationforanall-renewablefuelledplant.Althoughthecombustionofbiomassisnoteasy,itispossibletouseorganicfluidthermodynamiccycles(ORC),whichsimplifyoperationwhileincreasingtheoverallefficiency.
Storage:DependingontheHTF(HeatTransferFluid),differentdesignscanbesetup:
If the HTF is thermal oil,asinglestoragetankwithgoodtemperaturestratificationinsteadofatwotankconfigu-rationcangreatlysimplifystorage.Asingletankcanalsobeoptimisedbyasolidseparationbetweentheheatexchangerandthestoragematerial.
If the HTF is molten salts, noexchangerisneededbetweenthesolarfieldandthestoragecircuit.Newsaltmixtureswithlowerfreezingpointandwhichavoidcorrosionproblemsaretheresearchanddevelopmentgoalsforthistopic.
If the HTF is steam,noexchangerisneededbeforethepowerblock.Solid/liquidphasechangematerialsappliedforsaturatedsteamaretobeinvestigated.
If the HTF is gas,veryhightemperatureapplicationsarefeasible.Thechallengesarehowtodesigneffectiveheattransfersystemsandtofindsuitablestoragematerials.
Ingeneral,improvedstrategiesforcharginganddischargingthermalheatarenecessarytomaximisestoragecapacity.Conceptsforthermo-chemicalenergystoragesystemsarealsotobeinvestigated.
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PARABOLIC DISHESResearch topics to be investigated to reach objective 1 for parabolic dishes
GASTURBINES-Hybridisationwithnaturalgasorbiogas
-CombinationofdishturbinewithCAESsystems
RECEIVERS-Refluxreceiversagainstthelowerthermalinertia
SYSTEMCOMPONENTS-Synergieswithcarmanufacturingindustry-Improvedtrackingsystem
DISPATCHABILITY-Electromechanicalandthermalstorage-Alternativeenergysource(biomass)inthereceiver
STIRLINGENGINE-KinematicengineoLesscomponentfailuresoLessH2leakageoMassproduction-FreepistonengineoBettercontrolanddesignoflinear
generator
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HTF VERSUS TECHNICAL, ENVIRONMENTAL AND ECONOMIC CHARACTERISTICS
Improve forecasting:Goodforecastsareessentialforreliableestimatesofthecostsofaplantinagivensite.Manysolutionscanbeenvisioned,suchaselaboratingaveryshorttermforecastforvariableskyconditions,developinganelectricityforecastingsystemsoftwaretoregulateandmanageelectricityproduction,improvinggroundbasedDNImeasure-ments,usingmeteorologicalsatelliteresults,andimprovingnumericalweatherpredictionmodelsforDNIforecasting,analysingitsinter-annualvariabilityandthetimeandspacecorrelationbetweensolarandwindenergysources.
Objective 3: Improve environmental profileHeat transfer fluidsareofconcernbecauseoftheirpotentialimpactontheenvironment:thepollutionfromsyntheticoilisoneofthemostworrying.Theenvironmentalandeconomicparametersofdifferentfluidshavebeenstudied.
Desalination isavery interestingapplicationofsolar thermalenergy.Despite thedrawbacks related to therequirementsforsiting,desalinationpresentssignificanttechnicalandeconomicadvantages.Thereareseveraltechnicalsolutions,suchasmulti-effectdistillation,reverseosmosis,humidification-dehumidificationprocessandmembranedistillation.Thedesalinationsystemcanalsobe thecoolerpartof theconventionalpowerblock.Thus,theoptimisationoftheintegratedorcombinedcoolingprocessneedstobeconsideredasaresearchtopic.
Conclusion:Thenumerousinvestigationsunderwayafterthecreationofresearchprojectsconsortiaatdifferentlevels(local,national, international)haveopenedthewayfor theSTEsector toachievegreat technological improvementsandlowergenerationcosts.Despitethepresentcircumstancesaffectingnationallegislativeframeworksandthechangingsupportschemes,manyeffortsarebeingmadeattheEuropeanleveltostabiliseandharmonisethemarketandtoachievecompetitiveness.
ThesetofKeyPerformanceIndicators(KPI)elaboratedbyESTELA’sScientificandTechnicalCommittee(ANNEXI)liststhemostimportantparameterstobetakenintoconsiderationfortheassessmentofthetechnologyimprove-mentsanddeterminestheprogresstobeachievedby2015andforthetimeframebetween2020and2025.Thelevelisedcostofelectricity(LCOE)isthemaincompetitivenessindicatorandtheestimatedimpactonthiscostfromdifferentexpectedimprovementsisreportedseveraltimesinthedocument,andinparticularinthetableswithineachchapter.
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Soil pollution
Water pollution
Air pollution
Toxicity to human presence
Cost
Freezing temperature
Cost of handlingequipment and system
Upper thermal limit8
10
2
0
4
6
n Thermaloiln Na,K(MS)n Li,Na,K(MS)n Ca,Na,K(MS)n HitechMSwithnitriten CO2
n H2On Na,KMS+nanopn CO2+nanopn H2O+nanop
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HISTOrY
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Hist
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oncentratedsolarpowerplantsthatusedirectsolarradiationtofeedathermodynamicconversioncyclefortheproductionofelectricitywereintroducedintheearly1980’s.
Thefirstdemonstrationplantsusedmainlyacentralreceiverconfiguration(SolarONE,SSPS-CRS1,CESA1Themis,Eurelios,Nio,Crimea)withahighnumberofheliostatsdirectingthesolarradiation
tothetopofatower.Ataboutthesametime,SSPS-DCS2provedthefeasibilityofproducingelectricitywithaparabolictroughconcept.IssuesonthereceiverdesignandthehighcostoftheheliostatsatthattimeresultedinthechoiceofparabolictroughsystemsforthefirstcommercialscaleplantsinCaliforniain1984.Thistechnologyusedanovelvacuumtypeabsorbertubethatallowedreasonableperformancebutwithaconsiderablylowerconcentrationratiothanthetowerconcept.
From1986until1991,nineplantsofthistypewerebuiltveryclosetooneanotherrapidlyreachingalmost400MWeofinstalledpower.ThoseSEGSplants,locatedinCalifornia,arestilloperatingandgeneratingrevenues,beingthebasisoftheconfidenceofbankswhenfinancingtherecentdeploymentofmorethan2GWinSpain.
Foralongperiodnoothersolarpowerplanthasbeenbuilt.Thiswasmainlyduetotheavailabilityofcheapfossilfuelsandtheconcurrentdevelopmentofthecombinedcycletechnology,whichallowedlowinvestmentcostsandveryhighconversionefficiencies.
AnincreasedinterestonenvironmentalissuesbeganwiththeKyotoprotocolwhichraisedagaintheattentionontheproductionofelectricitywithnoCO2emissions.ThisinternationalcommitmenttriggeredanewriseofR&D,bothinthePVandtheSTEsector.ASpanishlaw,issuedin2004andimprovedin2007,providedareason-ableFiTlevelwhichallowedthefinancingandquickdeploymentofSTEplantsandsuddenlyahighnumberofprojectstookoffwithapipelinesummingupto2,500MWe.Thankstothehighconfidenceforinvestingjustifiedbyitsaccumulatedoperatinglifetime,theparabolictroughtechnologywasthemostsuitableoptionforthissetofplants.Thisledtothedevelopmentoftwo“standard”50MWeparabolictroughsolarplantdesigns,withandwithoutthermalstorage(50MWeisthemaximumplantsizeallowedbytheSpanishlaw).
However,thecentralreceivertechnologyalsoreceivedsomeattention,achievinghigherplantefficienciesathighertemperatures.ThefirstcommercialplantoftheSTSdawnintheworldwasthePS10-towerconceptwithsaturatedsteam-inFebruary2007.Afterwards,thefirstcommercialmoltensaltcentralreceiverplantwasconstructedinSpainin2011with20MWenominalpowerand15hoursofstoragecapacity,whichallowedtheplanttooperate24hoursroundtheclockduringthesummermonths.FollowingSpain,othercountriessetupincentivesforSTE.IntheUnitedStates,thefirstnewplantofthisperiodwascompletedby2007(64MWparabolictroughtypeinNevada).ThenewAmericanlarge(>100MW)projectsunderconstructionarebalancedbetweencentralreceiverandparabolictroughtechnologies.Theprojects‘Ivanpah’and‘Tonopah’arebasedonthetowerconceptandusesuperheatedsteamormoltensaltrespectivelyasprimaryfluidwhile‘Solana’and‘Genesis’usetheparabolictroughconcept.FurtherinitiativesaregoingonincountrieslikeMorocco,ArabEmirates,India,AustraliaandSouthAfrica.PlansfordeployingSTEarealsobeingconsideredinmanyothercountriesintheSun-Belt.
MeanwhileotherpromisingSTEtechnologieswithdistinctfeatures,suchaslinearFresnelreflectorsandparabolicdishes,havebeenstudiedanddemonstratedbymeansofseveralpilotanddemonstrationplants.
1-SmallSolarPowerSystems-CentralReceiverSystem2-SmallSolarPowerSystems-DistributedCollectorSystem
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FourtechnologiesarerelevantintheSTEsector,andeachoneofthemhasreachedadifferentstateofdevelop-ment,duemostlytothehistoricalpathwayoutlinedabove:
n ParabolicTrough(PT)n CentralReceiver(CR)n LinearFresnelreflector(LF)n ParabolicDish(PD)
Thedegreeofmaturityanddevelopmentcanbeexpressedintermsof“generations”.
STEcommercialplants,currentlyinoperationorunderadvancedconstructionare“firstgenerationplants”.
The“secondgeneration”ofSTEplantsshouldachievehigherefficiencieswithhigherfluidtemperatures(500°Candabove)andincorporatedesignimprovementstoimprovedispatchabilitybymeansofadvancedstorageandhybridisationtechniques.
The“thirdgeneration”ofplantsisexpectedtobefullycompetitivebydrawingonlessonslearnedandapplyingthebestdesignconceptsandtheuseofveryhightemperaturesandhigherefficiencyconversioncycles.
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3-Until20154-Until20205-Until2025andbeyond
Thetimewhensuchacostparityisreached,thatis,thepointatwhichelectricityproductioncostsfromsolar-thermalpowerplantsareequaltothecostsforgeneratingpowerfromconventionalplants,dependsonboththespeedofcostreductionandthetrendoffossilfuelprices.Differentscenariosassumethatcostparityforsolar-thermalpowergenerationcanrealisticallybereachedbetween2017and2020.However,insomeregionsoftheplanet,thepeakloadsupplycanalreadybeprovidedbysolar-thermalpowerplantsinacompetitiveway,asindividualcontractsareconcludedwithutilitiesforregionsandtimesofthedaydependingontheneed.
ForthepurposeoftheStrategicResearchAgendaallSTEtechnologiesaretakenintoaccountas,atthisearlystage,thefourtechnologiesshowhighpotentialforcostreductionandefficiencyincrease.
StatusTechnology Generation Present Short term 3 Mid term 4 Long term 5
PT123
CR123
LF123
PD123
nUnderdevelopmentnMature
TABLE1:Technologies maturity for short, mid and long term period
1
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lobalwarmingandeconomicgrowtharethemajorcurrentissuesintheworldbesidesotheronesofpoliticalnature.Fortunately,STEtechnologiescancontributesignificantlytoaddressthesetwoissues,helping tomitigate the impactofelectricitygenerationongreenhouseemissionswhileprovidingapathwayforthesustainableandbalancedgrowthofthesupplyofaffordableelectricityinboth
industrialisedanddevelopingcountries.
Acarbon-freegenerationsystemcanonlybeachievedwithrenewabledispatchabletechnologies,andresourceandtechnologyconsiderationspointtoSTEplantsasthealternativewiththegreatestpotentialtomeettheworld’sgrowingenergyneeds.Theyarealsothealternativewiththelargestfractionofvalueprovidedbylocalsources,evenfortheveryfirstplantbuilt.“Localvalueadded”considerationsmaywellbeakeyfactorinpolicydecisionsinmanycountries.
ThethreemainargumentsforalargedeploymentofSTEplantsare6:
2.1DispatchabilityandothertechnicalfeaturesSolarthermalelectricityplantshaveproventheirreliabilitysincethe80s.Morerecently–since2008–STEplantswithlargethermalstoragesystemshavebeenincommercialoperation,charginganddischargingthosesystemseveryday.
STEplantscanbedesignedandoperatedtobefullydispatchable.Becauseofstorageandthepossibilityofhybridisation,theycaneffectivelyfollowthedemandcurvewithhighcapacityfactorsdeliveringelectricityreliablyandaccordingtoplan.
Duetothelargemechanicalinertiaofitsgenerationequipment–turbine+alternator–STEplantswillhelpinmaintainingthenominalfrequencyofthegridincaseofunexpectedincidences.STEplantswithstoragecanparticipateinancillaryservices.Forexample,ifthereisapotentialforexcessgeneration,thegenerationequip-mentmaybedisconnectedandthecollectedthermalenergystored.
Firmnessanddispatchabilityarethemainadvantagesoverotherintermittentformsofrenewableenergy,suchasPVorwind.Thesetechnologiesrequireadditionalinvestmentsinconventionalpowerplantstobackupgenerationtofollowdemand:inadditiontotheextrainvestmentrequiredandtheimplicationsforresourcesecurity,theywillnotprovideaCO2freegenerationsystem.
2.2MacroeconomicimpactonlocaleconomiesDecisionsconcerningtheelectricalgenerationmixhaveasubstantialinfluenceonacountry’seconomy.FossilfuelimportshaveanegativeimpactondomesticGDP.Asanexample,around80%ofthecostoftheelectricityfromacombinedcycleplantwillgooutofacountrywhichdoesnothavenaturalgasandwhichimportsmostpartoftheplantcomponents.
Amongallrenewableenergies,solarthermalelectricity(STE)standsoutforitshighmacroeconomicimpactontheeconomyofacountryaddingtoitsGDPthroughhighinvestments,fiscalcontributions,fuelimportsreductionandjobcreation,duringboththeconstructionandtheoperationoftheplant.
IntermsoftheFeed-inTariffs(FiTs)thatSTEplantsstillneednow,thepoolpriceinthepowermarketsisreducedaslesssupplyisrequiredfromthemoreexpensiveconventionalplantsthatdeterminethepriceforthewholesystem.Additionally, renewableenergiesprovidestableandknowncosts thatmakeplanning for the futurepossible:uncertaintiesregardingthepriceevolutionoffossilfuelshamperinvestmentdecisions.
6-ESTELAhaspublishedapositionpaperthatpresentsthemainreasonsthatwillboostthedeploymentofSTEplantsallaroundtheworld’sSunBelt.
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AnotherpositiveaspectofSTEplantsistheireconomicimpactinjobcreationandinthedevelopmentoflocalmarketsduringplantconstructionandafterwards.Itisestimatedthat,iftheconstructionofSTEplantsisplannedatarhythmofafewhundredMWperyear,theattractedinvestmentsforthelocalfabricationofequipmentwillraisethelocalcontentcertainlyuptoa70%inafewyears.InSpain,approximately400MWhavebeeninstalledperyearsince2008,andin2011alocalcontentof80%hadbeenreached7.The50MWplantswiththermalstorageinstalledinSpainneed2,250“oneyearequivalentjobs”fromtheirdesigntofinalconstruction.Oncerunning,theplantsrequire50personsfortheiroperationandmaintenance.
Taxesfromcompanyprofitsandfromtheaddedin-countryvalue,aswellasthepersonaltaxesfromworkers,willcompensateforthesupporttothedeploymentofSTEplants,andeliminateunemploymentsubsidies.
Inthistimeofeconomiccrisis,incentivesforrenewableenergiesmustnotbeviewedasaloadtotheelectricitysystembutratherasacatalystforeconomicgrowth,industrialdevelopmentandjobcreation;thatsupportalsoopensthewaytosustainability.SupporttothedeploymentofrenewableenergygenerationtechnologiesintheformofadequateandprogressivelydecreasingFiTwillmobiliseprivateinvestmentsinproductiveassets.
7-ForfurtherinformationonSpain’sSTEdataandfigures,pleaserefertotheMacroeconomicStudyoftheSTEsectorin2010elaboratedbyDeloitte:http://www.protermosolar.com/prensa/2011_10_25/Protermo_Solar_21x21_INGLESC.pdf
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2.3CompetitivenessLastbutnotleast,thecostofSTEplantswillsoondecreasesignificantly:theywillbecomefullycompetitivewithotherconventionalplantsinthenearfuture.
Thesupportthatisnowrequiredwillbelessandlessnecessaryanditwillbenolongerrequiredinafewyears.
Since2007,attractivecostreductionresultshavebeenachievedwithalearningcurveofonly2GWofinstalledcapacity.Asreference,wemaynotethatthecurrentcostofPVprofitedfromalearningcurveof70GW;forWind,fromtheexperienceofaround250GW.
ThecostoftheelectricityproducedbySTEhascomedownfrom28c€/kWhfortheprojectsapprovedinSpainin2009to14c€/kWhforthelatestprojectawardedinMoroccoin2012.
Newplantconcepts,largersizes,improvedcomponentperformanceandscalefactorswillsignificantlycontributetolowerthecosts.Therefore,itisreasonabletosaythatifby2020the30GWthresholdisachieved,STEpowerplantscouldbefeedingdispatchableandpredictableelectricitytothegridat10-12c€/kWh,dependingontheavailableirradiation.Inotherwords,thistechnologywillbecometotallycompetitivewithconventionalpowergenerationinthenearfuture.
Againsttheprospectsofrisingandunpredictablepricesforfossilfuelsandwiththeawarenessoftheweaknessesofnon-dispatchablerenewabletechnologies,thepredictableanddecreasingcostsofSTEwillopenthewaytoasafetransitiontowardsasustainablemodelofelectricitygeneration.
Europehasenoughrenewableenergyresourcestobecomeenergyindependentandtodrasticallycutitsgreen-housegasemissionsinthenearfuture.AEuropeanenergysystemmainlybasedinSolarandWindwithacertaincontributionofHydroandBiomassalongwiththeSupergridisbothfeasibleanddesirable.
Inthenearfuture,dispatchability,jobcreation,theneedtolimitgreenhouseemissionsandthepotentialforcostreductionwillensurethatSTEwillaccountforanimportantshareoftheelectricitygenerationworldwide.ThisiswhySTErepresentssuchagreatopportunitytohelppavethewayoutoftheeconomiccrisisintheSouthernEuropeancountries.ThisisahistoricopportunitytostrengthentheEuropeanbusinesspresenceinthewholeworld;giventhepresentleadingpositionoftheEuropeanindustry,itisalsoanunprecedentedopportunitytocollaboratewithpartnersintheneighboringMENAregionforthebenefitofall.
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InduSTrY OVerVIew And reLATed ecOnOmIc ASPecTS
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n Operationn Construction/Awardedn Promotionn Estimatedby2020
NorthAmerica
SouthEurope
MENA
SouthAfricaSouthAmerica
India
Australia
China
510
MW
2.5
MW
2.5
MW
1,73
1 M
W
175
MW
9.3
MW
1,31
2 M
W
10 M
W
200
MW
694
MW
290
MW
500
MW
5,00
0 M
W
2,00
0 M
W
3,00
0 M
W 1,00
0 M
W
600
MW
290
MW
150
MW
2,00
0 M
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2,00
0 M
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1,00
0 M
W 2,00
0 M
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160
MW
40 M
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Source:ESTELAandProtermosolar,October2012
7,00
0 M
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4,00
0 M
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10,0
00 M
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5,00
0 M
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3,00
0 M
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uropeanindustryandtechnologicalcentrescoverthewholevaluechainofSTEplants.Advancedresearchisperformedinhighlyqualifiedlaboratoriesandresearchinstitutions.Europeanpromotersaredevelopingprojectsallaroundtheworld.Europeanmanufacturingcompaniesprovidesolarspecificcomponents,powerblocksandallthenecessarybalanceofplantequipment.PrivateEuropeanfinancinginstitutionsandfunds,along
withtheEuropeanInvestmentBank,havesupportedthefastSTEplantdeploymentinSpain.Technicalandlegalconsultants,O&MserviceprovidersandEuropeanelectricalutilitiescompletetherestofaddedvalueinthissector.
Fromthebasisofthetotaloutputfromplantswhicharealreadyinoperation,significantincreasescanbeexpectedinmajorregionsandcountriesinthenextfewyears.Cumulatively,itisexpectedthatSTEplantswillbegeneratingapproximately10GWofelectricityby2015.For2020,thiscanbecomplementedwithinformationonthecapacityfromnewplantswhichareeitherpartofpresentofficialplansorwhoseimplementationcanbederivedfromreasonableexpectationsbasedoncurrentdevelopment(Figure1).Moreinformationonnationalandregionalmarketsisoutlinedbelow.
FIGURE1:STE estimate installed capacity8(PlannedSTEplantsrefertoeitherofficialplansorreasonableexpectationsaccordingtocurrentdevelopment)
8-Source:Protermosolar
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3.1Nationalandregionalmarkets
Spain
TheSpecialRegimeforelectricitygenerationfromrenewablesourceswasestablishedinSpainin1998.Never-theless,STEplantsneededtowaituntil2004withtheroyaldecreelawR.D.L436tohavetheappropriateFiTtoallowthepromotionofprojects.TheFiTwassubstantiallyimprovedin2007.WiththeR.D.L661whichreallyboostedthepromotionofnewplants,thebanksfoundmorefavourableconditionstofinancetheprojects.
ThefirstSTEcommercialplantintheworld–afterthelongperiodsincethelastonewascommissionedin1991inCalifornia–wasthePS10inSeville.This11MWplantusedatowerconceptwithsaturatedsteamandsmallpressurisedsteambufferstorage.
Sincethen,thetotalcommissionedpowerreached61MWin2008(includingthefirstEuropeanPTpowerplant,Andasol1),331MWin2009,532MWin2010,999MWin2011and1,925MWin2012.
AccordingtotheroyaldecreelawR.D.L6/2009,60plants–includingtheplantsalreadyinoperation–wereregisteredunderthecurrentFiTframework.Alltheseplants,totalling2,475MWmustbecommissionedbeforetheendof2013inordertoreceivetheformerFiT.Thecurrenttarifffortheseprojects(for2012),whichvarieswiththeannualconsumerpriceratio,is29.89c€/kWh.
Asaresultoftheeasierfinancingconditions,whichtendedtorewardmaturetechnologiesandplantsofacertainscale,94%ofthepowerisgeneratedinplantsbasedonPT,whiletheotherthreeSTEtechnologiesshareonlyaminorpart.
Inadditiontoallregisteredplants,siteandprojectdevelopmentwascarriedoutformorethan10,000MW,insiteswherelandsuitability,accesstothegrid,environmentalconditions,wateravailability,etc.aresuitabletodevelopSTEplants.
TheRenewableEnergyNationalActionPlan(RENAP),submittedbytheSpanishGovernmenttotheEUCommis-sionin2010,foresawatotalinstalledcapacityof5,079MWby2020.InthenewRenewableEnergyPlan,thisfigurewasreducedto4,800MW.
Inaddition,another50MWmoltensalttowerplant,tobeplacedonlineafter2013,hasbeenincludedundertheSTEInnovativeProjectprogramme.Another50MWhybridtowerplant,basedonahybridtowerconcept,hasbeenawardedforfundingundertheNER300scheme.
Earlyin2012,theSpanishGovernmentissuedalaw(R.D.L1/2012)stoppingtheapprovalofanewsetofprojectsuntilacompletereviewofthesituationregardinginstalledpowerontheSpanishelectricalsystemisdone,andanewpathtoreachthe2020targetsisdefined.
PowerplantsResearchfacilities
InteractiveWorldMapofSTEplantsandresearchfacilitiesonESTELA’shomepage:www.estelasolar.eu
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Italy
AccordingtotheRENAPestablishedinMarch2011,STEplantsareexpectedtoreach600MWby2020,generatingsome1,700GWh,or0.5%oftheelectricityconsumption.
AnewDecree for the renewableenergymixhasbeenreleased in July2012by theMinisterofEconomicDevelopmentincoordinationwiththeMinisterofEnvironment.TheFiTwillbeinforcestartingfromJanuary2013.
TheDecreeregulatesanewincentiveschemeforlargescaleSTEplantsaccordingtotheFiTschedulegivenbelow:
System in which the solar fraction is higher than 85 % 0.32e/kWh-EnergySaleSystem in which the solar fraction is between 50 % and 85 % 0.30e/kWh-EnergySaleSystem in which the solar fraction is below 50 % 0.27e/kWh-EnergySale
ItispossibletoholdtheFiTwithadditionalpublicfinancialcontribution.Inordertobenefitfromtheincentive,twoconditionsmustbemet:anon-pollutingheattransfersystemmustbeused(unlessthesystemissitedinindustrialareas)andinstallationsmustshowtheminimumaccumulationcapacityestablishedbytheDecree.
Incentivesareavailableforuptoamaximumof2.5millionm2ofmirrorsurfaceandagraceperiodof36monthsisgrantedafterthatmaximumoftotalinstalledmirrorsurfaceisreached,toallowconnectingSTEplanttothegridaccessingtotheFiT(thisgraceperiodisstillunderdiscussion).
For small scale STE plants,thenewdecreeregulatesthefollowingupdatedincentivescheme:
System in which the solar fraction is higher than 85 % 0.36e/kWh-EnergySaleSystem in which the solar fraction is between 50 % and 85 % 0.32e/kWh-EnergySaleSystem in which the solar fraction is below 50 % 0.30e/kWh-EnergySale
TheseincentivesapplytoSTEplantswithlessthan2,500m2ofinstalledsolarcollectors.
For all type of STE plants(bothlargeandsmallscale),theincentives,calculatedattheratesgivenabove,areinadditiontotherevenuesfromthesaleofelectricitygeneratedandfedintothenationalgrid.TheFiTwillbereducedby5%forthepowerplantsconnectedtothegridin2016andby10%forthoseconnectedin2017.Theincentiveswillbepaidfor25years.
ThefirstSTEplantusingmoltensaltasHTFisalreadyinoperationinItaly.Itisa5MWplant.Itfeaturesthermalstorageandisbasedonacombinedcycle.ApotentialmarketofhundredsofMWsisexpectedinItalyby2017.
France
AccordingtotheFrenchNREAPapprovedinJune2010,STEplantsareestimatedtoreach540MWofcapacityby2020,generatingsome972GWhperyear),or0.2%oftheelectricityconsumptioninFrance.
A12MWplant,AlbaNova1,wasapprovedbytheFrenchgovernmentinJuly2012.TheplantwillbebuiltinCorsicaandwillcombinelinearFresnelreflectors,directsteamgenerationandthermalstorage.The‘CaissedesDépôtsetConsignations’,theFrenchsovereignwealthfund,isfinanciallysupportingtheproject.Another9MWFresnelconceptinthePyreneesregionhasbeenapprovedaswell.
TheFiTsareingeneralfairlysatisfactoryforthedifferentrenewabletechnologies,exceptforSTE,becauseofthelowDNIlevelsinthecountry.
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Portugal
Portugalhasaveryhighpotentialfortheimplementationofsolarenergytechnologies,giventhehighsolaravail-abilityinthecountry(oneofthehighestinEurope)andtheirverygoodpublicacceptance.
Since2000,thePortuguesegovernmentkeptregulatedtariffsforendconsumersbelowtherealcostofthegener-atedelectricity.A‘tariffdebt’wasthenaccumulatedandfinancedannuallywithaguaranteebythegovernment.However,theshareofthattariffdebtattributabletorenewableenergy(mainlyforwindenergy)hasbeenshown9tobesmall(lessthan15%).FollowingmajorupdatesinFiTschemes,theIberianElectricityMarketMIBELenteredinoperationin2007.Tendersforsolartechnologyplantsbeganin2009,eventhoughsomeconsortiaattemptedatapplyingforSTElicensesasearlyas2007.
The2008crisisledtoariseofinterestrates,aggravatingtheburdenthattheaccumulatedtariffdebtrepresentedtothenationaleconomy.Afterpeakingin2009,theoveralltariffdebtbecameprogressivelysmallerstartingin2010.ThefallofthegovernmentinMay2011wasfollowedbythefinancialbailoutofthecountry.AnMoUwasagreedwiththeEU,andthisalsorequiredareviewofsupportschemesforRES.
In2010theGovernmentissuedlicensesto10STEdemonstrationprojects(twoprojectsof4MWeeachforPT,CRandLFtechnologiesandfourprojectsofupto1.5MWeforPDtechnologies).In2012,becauseoftheuncertaintiessurrounding theenergypolicy for renewableenergies,and inparticular forSTE,noneof theseprojectshadbeenstarted.Infact,someofthelicenseswerelost,afteradeadlinewasestablishedbyDGGE11forconfirmationoftheintentiontoproceed.InMay2012,thegovernmentannouncedregulatorychangesintherulesaffectingtheRES,takingadvantageoftheuncertaintiesinlegislationtochangetheFiTconditions.
InanycasethePortuguesetargetestablishedbytheNREAPforSTEfor2020hasbeenloweredfrom500MWto50MW12.
TheFiTassignmentofnewgridconnectionlicensesforREShasbeensuspendeduntil2014/2015.Inthemean-time,thegovernmentstillsupportsthedevelopmentofongoing,licensedandalreadyassignedprojectsforRES.Mostoftheseprojectsarewindprojects.
Greece
AccordingtotheGreekNREAPapprovedinJune2010,STEplantsareexpectedtoreach250MWby2020,generatingsome714GWh,or1%oftherenewableelectricityconsumption.
GreeceprovidesaFiTof26.5c€/kWh,whichrisesto28.5c€/kWhifatleast2hoursstorageisincorporated.ThisFiTispayablefor20years.
TheNREAPwillbethebasisforaMinisterialDecreethatwillallocate2020installedcapacitytargetstothedifferentRESsectors.Achangeinthesupportmechanismisnotforeseen:itisexpectedthatitwillremainafixedFiT.
Thelawonthe“AccelerationofRESDevelopment”streamlinesadministrativeproceduresandaddresseeslocalbarrierstoRESdeployment.Furthermore,thenewgovernmenthasmergedseveraladministrationsintotheMEECC(MinistryofEnvironmentEnergyandClimateChange)thatnowfunctionsasaone-stop-shopforRESlicensing.WiththePhysicalPlanninglaw(2008),theMEECCgivesprioritytoRESprojectsoverotherlandusesanddeterminesrestrictedaswellaspriorityareasfordevelopment.
OnelargescaledishStirlingpowerplant(75.3MW)anda50MW-centralreceiverpowerplantwithsuperheatedsteamhavebeenawardedinGreecewithinthefirstcalloftheNER300scheme.
9-Source:APREN(PortugueseRenewableEnergyAssociation).StudyfromRolandBerger,201110-Source:ERSE(PortugueseRegulatoryEntityofEnergeticServices)11-Source:DGEG(PortugueseGeneralDirectionofEnergyandGeology)12-Source:DGEG(PortugueseGeneralDirectionofEnergyandGeology)
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Cyprus
AccordingtotheCyprusNREAP,approvedinJune2010,STEplantsareexpectedtoreach75MWby2020,generatingsome224GWh,or3%oftheelectricityconsumptioninthecountry.
Thereisanindicationthatfutureamendmentstotherenewableenergylaw(thelawaffectingtheFiT)mayre-establishinvestmentsecurityforthemajorpartoftherenewableenergyindustry.
CyprushasbeenawardedbythefirstcalloftheNER300withalargescaledishStirlingpowerplant(50.76MW).
SEAPEK(CyprusAssociationofRenewableEnergyEnterprises)believesthatCypruscanachievemuchmorethanthebindingtargetof13%ofgeneratedenergyfromrenewablesourcesby2020,asforeseenintheRESDirec-tive.However,thiswouldrequiresomegovernmental,financialandadministrativeeffort.
NorthAfrica
ThelaunchofinitiativessuchastheMSP(MediterraneanSolarPlan),whichwasstronglysupportedbyESTELA,hasalreadyplacedSTEontopofutilities’,governments’anddecisionmakers’agendas.
TheMSPaimsatincreasingtheuseofsolarenergyandotherrenewableenergysourcesforpowergeneration.Thekeyelementof theproposalissettingupacommonlegal,regulatoryandinvestmentframeworktodevelop20GWofnewrenewablegenerationcapacityinthecountriesaroundtheMediterraneanSeaby2020.Tothisend,theMSPwillbuildontheenormouspotentialforrenewableelectricitygenerationavailableinthesecountries,mostlythroughthedevelopmentofSTEbutalsothroughotheravailableandmaturetechnologiessuchasPVandwindenergy.
TheMSPneedstoovercometheimportanttransmissionissueaswellasadministrativeandlegalbarriers.Thefigureofasolventoff-takerasrecommendedbyESTELAcouldbeanessentialpiecetolaunchthisambitiousplan.Asoftoday,therearethreeintegratedsolarcombined-cycle(ISCC)plantsinMorocco,AlgeriaandEgyptwithanequivalentelectricpowerofabout25MWeach.Thesolarcontributiontotheseplantsrepresentsconsiderablegassavings.
InMoroccothetenderprocessforthefirstSTEplantintheregion,a150MWPTtypewithstorage,underapurePPAcommercialschemehasbeencompletedinOctober2012andthecontracthasbeenawarded.
IndependentlyofthenationalplansincorporatedintheMSP,STEdeploymenthasbeenannouncedinmostofthenorthernAfricancountries.Theseplansrangefromsomehundredsto2,000MWpercountry.
MiddleEast
ThefirstplantinAbuDhabiofabout100MW,Shams1,isnearlycompletedanditisexpectedtobefollowedbyShams2and3.OtherArabEmiratesandSaudiArabiahavealsoincludedSTEintheirrespectiveplans,foratotalpowerof900MWby2013andafinalamountof25GWinthefuture.
Israelhasitsfirstplantsunderconstructionandplanstohave1,000MWofinstalledcapacityintheshortterm.Othercountriesintheregion(Jordan,Iran,Syria,etc.)arealsoconsideringtheconstructionofSTEplants.
UnitedStatesofAmerica
Therearealreadyover500MWofinstalledSTEcapacity,includingthe354MWSEGSplantswhichhavebeenincontinuousoperationfor25years.ThelargestISCCintheworldwith75MWhasbeenrecentlycompleted.
Therearehugeprojectsunderconstruction.Fourprojectswithatotalpowerof500MWaretowerplantsusingeithersuperheatedsteamormoltensaltasthereceiverfluid.ThreelargePTtypeprojectswilladdanother810MW.
TheseprojectsarebasedonsignedPPAswiththeutilitiesandtheytakeadvantageoftaxcreditsandwarranteedloans.
Newsupportmechanismsneedtobeestablishedinthenearfuturetorealisethelargecurrentpipelineofprojects.
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SouthAfrica
TheREFITprogram(underFiTschemes)foresees1,200MWforSTEin2030.Nevertheless,theprogramwillbereviewedperiodicallyandtheshareamongdifferenttechnologiescanbeinterchangedaccordingtotechnologydevelopmentsandpolicyconsiderations.
Thefirstthreeprojectshavebeenrecentlyawarded:thesearea100MWPT,a50MWPTanda50MWCRplantwithsuperheatedsteam.Inaddition,thepublicutilityispreparingfeasibilitystudiestolaunchatenderprocessforatotalof150MWintheshortterm.
Australia
Alongtermgoalof25%ofsolarpowerhasbeensetfor2050.
TheCleanEnergyInitiativewithintheSolarFlagshipsProgrammehasbeenlaunchedwithsolarprojectstotalling1,000MW.Thefirstcallfor400MW(PVandCSP)isclosed.ThenewagencyARENAhasmadeclearthatsolarthermalelectricitydevelopmentisverymuchinitsthinking,andhasstructureditsinitialstrategicprioritiesinawaythatshouldbefavorableforSTEprojects.Arecentstudyestimatesatleast2000MWSTEplantsby2020.
India
Thereisatremendousneedforadditionalelectricitygenerationinthiscountry.Anambitioussolaragendaisbeingplanned,aimedatgenerating20GWfrombothSTEandPVplantsby2022.
Awardsforthefirst500MWofSTEplantshavebeengiventolocalpromotersunderacombinedbidding/FiTscheme,andmostofthemhavealreadystartedconstruction.
China
Atthemoment,thereare250MWSTEplantsabouttostartconstruction.Thereisapipelineofprojectsunderdevelopmentwhichexceeds4,000MWalthoughthesupportconditionsarestillnotclearlydefined.Internationalsuccessreferencesmightacceleratetheseplans.
LatinAmerica
Thereisonlyoneprojectunderconstruction:anISCC15MWequivalentinMexico.
SeveralprojectsarebeingpromotedinChileunderdirectPPAschemeswithminingcompanies.
NosupportschemesarebeingconsidereduntilnowbythegovernmentsbuttherearespecificplaceswhereSTEisveryclosetocompetitiveness.MacroeconomicimpactsandenergydependencymaycontributetotheestablishmentofsupportmechanismsforSTEplants. 3
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3.2Employment
ThegrowthoftheSTEindustryinSpainhashadamajorimpactintermsofthenumberofjobsithascreatedinrecentyears.Manyofthesejobsareduringconstruction;therestarefromoperationandmaintenanceactivities.Theyallhaveamultiplicativeeffectontherestoftheeconomy.Thenumberofequivalentjobsgeneratedduring2008-2010hasbeenquantifiedintermsofequivalentjobsperyear.Theinformationfortheestimateshavebeendrawnfromthefollowingsources:
n Forspecificplantconstruction,assemblyandcommissioningactivities,inquiriesweremadeoftheconstructioncompaniesandverifiedwithplantrecords.Coefficientsofemploymentperunitofaddedvaluespecifictoeachindustrywereusedtoquantifyemploymentgeneratedinthoseindustriesandintherestoftheeconomy.
n Forplantoperationandmaintenanceactivities,thecompanieswereaskednotonlyforinformationontheworkforcedirectlyemployedbythembutalsobythesubcontractorsinchargeofoperationandmaintenance.Theimpactonothereconomicindustries(powersupply,water,gas,insurance,etc.)wasaddedtothis,basedongenerallyacceptedemploymentmultipliers.Accordingtotheinformationcollected,theSTEindustryemployedatotalof23,844peoplein2010:23,398peopleduringconstructionand446peopleduringoperation.
FIGURE2:Total number of jobs created by the STE industry (2008-2010) in Spain 13
0
5,000
10,000
15,000
20,000
25,000
30,000
2008
2009
2010
11,724 jobs
18,600 jobs
23,844 jobs
TABLE2:Breakdown by industry activity of jobs created by the STE industry (2008-2010) in Spain 14
Jobs 2008 2009 2010Construction 11,713 18,492 23,398- Plan contracting construction and assembly 4,399 6,447 8,049- Components and equipment 4,515 7,442 9,542- Jobs in the rest of the economy 2,799 4,603 5,807Power production - O&M 13 123 446- Plant operation and maintenance 11 108 344- Jobs in the rest of the economy 2 15 102TOTALJOBS 11,724 18,600 23,844
13-Sources:Deloitte/Protermosolar.MacroeconomicimpactoftheSolarThermalElectricityIndustryinSpain,October201114-Sources:Deloitte/Protermosolar.MacroeconomicimpactoftheSolarThermalElectricityIndustryinSpain,October2011
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50 %
60 %
70 %
80 %
90 %
100 %
2012 2015 2020 2025
Economies of scale
Economies of scale
Implementation of major technological improvements
Validated provenimprovement measures
Conservative outlook
Cost and efficiency improvements
70-95 %
50-65 %
45-60 %
5-30 %
35-50 %40-55 %
Cost & efficiency improvements
100 %
1st large scale plants
18-22%points
Cost
28-37% points
10-15%points
Efficiency
21-33%points
Economies of scale
45-60%
LCOE 2025
-40-55%points
EstimatedtariffreductionsMaindriversfortariffreduction
FIGURE3:Expected LCOE reductions from 2012 to 2025 15
FIGURE4:STE project lifetime 16
Procurement Construction Operation and maintenanceEngineering
2-3 years
Heavy investment period
Projectisbuiltwithtechnologyavailable
2to3yearsbeforeproductionsstarts
Debt repayment period
Cashflow
Project start
Start of electricity production
Break-even
40 years
3.3Economics
GiventhedevelopmentforSTEtechnologiesdescribedinthisStrategicResearchAgenda,andconsideringspecifi-callypredictedchangesincostandscalethathaveanimpactonplants’CAPEXandefficiency,itispossibletoestimatetheirrelativeimpactontheLCOEforSTEprojectsinthefollowingyears(Figure3).
15-Source:A.T.Kearney/ESTELA.SolarThermalElectricity2025-Cleanelectricityondemand:attractiveSTEcoststabiliseenergyproduction,June2010
16-Source:A.T.Kearney/ESTELA.SolarThermalElectricity2025-Cleanelectricityondemand:attractiveSTEcoststabiliseenergyproduction,June2010
From2013onwards,significantcostreductionscanbeexpectedforSTEplants,drivenbythedeploymentoftechnologicalimprovementsandbytheeconomiesofscalerelatedtotheincreaseoftheplantsize.By2015,areductionrangingfrom5to30%canbeexpected,dependingonSTEtechnologyandthedispatchabilityoftheplant.
Between2015and2020,with the implementationof theremaining technical improvementsalreadyin thepipelineandwithfurtherplantsizeincreases,tariffsforSTEcanbereducedbyupto50%.Withtheexpectedcostdevelopmentandfurtherbreakthroughinnovationandscalegainby2025,tariffsareexpectedtobelessthan50%comparedwithcurrentones.SuchcostdevelopmentwouldenableSTEtechnologiestobecomeself-sustainedwithouttheneedforsupportschemesfornewlyinstalledplants.
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AnotherfactorthatcanfurtherdrivedowntherequiredtariffforSTEprojectsisthesolarirradiationlevelofthedeploymentlocation.Thelargertheavailablesolarresourceis,thehighertheannualoutputwillbe,andthelowertherequiredtariffforthesameplant’sCAPEX.Figure3showshowtheDNIlevelofaspecificlocationcaninfluencetheminimumrequiredtariff.
FIGURE5:Impact of direct normal insolation (DNI) on levelised cost of electricity 17
6065707580859095
100105
% 110
2,00
02,
100
2,20
02,
300
2,40
02,
500
2,60
02,
700
2,80
02,
900
3,00
0
-18 -19 %
-24 -25 %
-33 -35 %
- 4,5 % per 100 kWh/m2a
- Italy- Greece- Southern Turkey
- Portugal- United Arab Emirates
1-ReferenceplantlocationhasaDNIof2,084kWh/m2aat100percent
- Arizona (U.S.)- Saudi Arabia
- California (U.S.)- Algeria- South Africa
- Tunisia - Morocco- Nevada (U.S.)- Australia
- Chile- Spain
%comparedtoreferenceplantinSpain1
DNIinkWh/m2a
17-Source:A.T.Kearney/ESTELA.SolarThermalElectricity2025-Cleanelectricityondemand:attractiveSTEcoststabiliseenergyproduction,June2010
18-Source:A.T.Kearney/ESTELA.SolarThermalElectricity2025-Cleanelectricityondemand:attractiveSTEcoststabiliseenergyproduction,June2010
Onaverage,tariffscandecreaseupto4.5%pereachadditional100kWh/m2aofDNI.ThismeansthatforhighDNIlocationssuchastheMENAregionorCalifornia(US)aSTEprojectrequiresless25%ofminimumtarifftobreakevenwhencomparedwiththesameprojectinSpain.(Fortheseestimates,onlythevariationofDNIwasconsidered.Countryspecificrisk,financingandlabourcostsvariationsalsoplayasignificantpartindefiningtheminimumrequiredtariff.)
ThesefactsdemonstratethatSTEtechnologyhasthepotentialtoimproveitscompetitivenessinthenearfutureandthattheindustryiscommittedtomaterialisethiswiththedevelopmentoftechnologicalimprovements,constructionoflargerplantsandwiththeSTEdeploymentinhighDNIregionssuchMENA.Alloftheseinitiativescontributetotheachievementoftheindustryvisionlaidoutearlier.
Also,accordingtothedefinedtechnologicalandcostroadmap18,STEtechnologycanachieveitspositioningwithintheenergysourcesportfoliomixwhichshallbediscussednext.ThereisawiderangeofSTEconceptsfrompurepeakpowertobase-loadincludingdesignswithaverynarrowdispatchprofilewithlargestorageandturbinestoprovideelectricitywhenthepriceishighest.Inaddition,significanteconomiescanbeachievedthroughhybridisationofpowerplantsoracombinationofsolarfieldswithexistingornewplants.ISCCplants,orschemestoboosttheperformanceofcoal-firedthermalpowerplantscanbeeffectiveoptions.
3.4StandardisationStandardsareveryimportantinanytechnologyfield,butespeciallyinyoungtechnologieslikeSTE.Infact,theimplementationofstandardsiscrucialforthecommercialsuccessofthetechnology.Aquickdeploymentofnewmarketsrequirescustomers’confidenceintheperformanceanddurabilityoftheproducts.Standardsplayalsoanimportantroleinacceleratingcostreduction,sincetheyallowforabettertransparencyofproductqualityandforthecomparabilityofdifferentproducts.Thisleadstomorecompetitionbasedonknowledgeaboutqualityandcost.
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AlthoughstandardsusedinothersectorscouldbepartiallyusedforSTEtechnologies,theuniquenessofthesetechnologiesdemandspecificstandardsthathavenotbeendevelopedyet.Developmentofthesespecificstandardsisthe“leitmotif”ofthestandardisationworkinitiatedduringthelastyears,onbothnationalandinternationallevels.Whilepresentsolarcollectorstandards,suchasEN12975,mightsetabackgroundforsolarconcentratortestingmethodologiesandsimulationmodels,theirearlydevelopmentwasforstationarycollectors,mostlyfactory-made.Theyreallyfallshortwhendealingwithmorecomplex(and/oraccuracydemanding)opticaleffectspresentinSTEtechnologies.TheimportanceofestablishingacommonframeworkforthetestingandcharacterisationofsolarconcentratorshasbeenalreadyrecognisedinthelatestrevisionsofEN12975,anditisalsothedriverforthenewISO9806,whichispresentlyundergoingtheinquirystage.
Existingstandardsrelatedtosolarcollectorsaremainlyintendedforfactory-madecollectorswhicharesmall(uptoafewm2insize),andthatareeitherflatorhaverelativelylowconcentrations.Ontheotherhand,STEtech-nologiesrequirelargesizeconcentrators,on-sitefieldassembled,withhighconcentrations,andwithavarietyof2Dor3Dgeometries,thuscreatinganewsetofproblemsanddemands.STEtechnologiesthereforedemandspecificstandardsthatarenotyetavailable.
SeveralworkinggroupshavebeensetuptodevelopspecificstandardsforSTEtechnologies,andafewnewstandardsarealreadyinanadvancedstageofdevelopment.ThemembersofSolarPACESestablishedworkinggroupsin2008withthechargetodevelopstandardsforPTcomponents,andafirstdraftguidelineformirrorreflect-ancemeasurementwaspublishedinMay2011.Anotherdraftguidelineformirrormoduleshapemeasurementisexpectedtobereleasedin2012,followedbyaguidelineforPTreceiverperformancemeasurementsin2013.
Otherworkinggroupsforstandardsdevelopmenthavebeensetupwithintheframeworkofdifferentstandardsorganizations:
n IEC/TC117“SolarThermalElectricplants”(threeworkinggroupsestablishedin2012).Mirrorcommitteesinseveralcountrieswillbeestablished;
n AENOR(Spain)sub-committeeAEN/CTN206/SC“Solarthermalpowersystems”,launchedin2010forstandardsonsystems,storageandkeycomponents;
n ASMEPTC52PerformanceTestCodeforConcentratingSolarPowerPlants(fourworkinggroupsestablishedin2011forPT,LF,powertower,storage);
n DKE(Germany):fundingofdevelopmentofguidelinesforstandardsforreflectors.
Therefore,thefirststepstodeveloptherequiredstandardsforSTEtechnologieshavebeenalreadytaken,butthisefforthastobesupportedandfurtherpromotedbecauseverylimitedfundingisstillavailableforstandardisationactivities.Thismustbeconsideredahigh-prioritytopicbecausetheavailabilityofproperstandardswillsignificantlyenhancethecommercialdevelopmentofSTEtechnologies.Standardisationactivitiesshouldcoverseveralfields,whicharesummarisedinthefollowingparagraphs.
a)Qualification/certificationandtestingprocedures:Adequateproceduresapplicabletodifferenttechnologiesarerequired.Theymustspecifymanufacturer-independentstandardsdefiningtheprocedurestotestandqualifynotonlycomponents(e.g.reflectors,receivertubes,solartrackingsystems,etc.),butalsocompletesolarconcentratingsystems(e.g.heliostats,PTcollectors,linearFresnelmodules,etc.)andcompletesystems(e.g.,solarfield,thermalstoragesystem,etc.)Thesearerequiredtomakeafairandneutralcomparisonoftechnicalfeaturespossible.Thesestandardsmustcovernotonlytheprocedurestomeasurethermal,opticalandgeometricalparameters,butalsoacleardefinitionofthoseparametersinordertoavoidpossiblemisunderstandingsconcerningtheirmeaning(e.g.,cleardefinitionsofabsorptivity,specularreflectance,hemisphericalreflectance,etc.).Thesestandardsshoulddefinetherequirementstobefulfilledbyadequatetestinginfrastructuresandtheyalsomustsettleanumberofcurrentopenquestions,suchas:
n Thedefinitionandimportanceof“nearnormalincidence”conditionsthroughoutthetestingperiod.Thesearedifficulttomatchwhentestingprimaries(theprimarysetofmirrorsresponsibleinthefirststageofradiationconcentration)oflinearconcentratorsystemssuchasLForevenfield-installedPTs;
n Thevalidityofabiaxialapproachtoreproducethetrueincidenceanglemodifierasthesimpleproductofthelongitudinalandthetransversalincidenceanglemodifiers;
n Theimportanceofcircumsolarradiationconditionsintheexperimentalresultsobtainedthroughoutthetestingperiod.
Anotherimportantitemwithinthescopeofthesestandardsisthedefinitionofmethodologiesandequipmentforopticalcharacterisationofsolarconcentrators,namelyinthedetectionandquantificationofmanufacturingerrors,reflectorsurfacedeviationsorconcentratormisalignments,etc.
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Concerningcertification,productcertificationschemesmustbedefinedalso,becausethisisawell-provenstrategytoraiseconsumerawarenessandbuildmarkettrust.Thiswillenablethegenerationofindependentproductassess-mentresultsandguaranteeproductreliabilitywithinawell-definedproductoperationframework.Asinthecaseofthedevelopmentoflowtemperaturesolarcollectors,theincreaseofavailabletechnologiesandproductsreachingthemarketwillbenefitfromthedevelopmentofacertificationscheme,relyingnotonlyonstandardisedtestingresults,butalsoonthecertificationofthemanufacturingprocessesusedinthefabricationofagivenproduct.Producingclear,reliableandcomparableresults,suchcertificationschemeis likely tocontributedecisively tothecreationofmorefavorablebankabilityconditions,reducingtheimportanceofthosebasedinoperationtimerecordswhicharenotavailableforsomeverypromisingtechnologies.
b)Components/systemdurabilitytesting:Systemlifetimeis,ofcourse,afundamentalparameterwhenassessingtheoverallenergyproductionandprofitabilityattainablewithagivenSTEsystem.Standardsmustconsidertheageingprocessstartingaftermanufacturingbycomponentassessment,andperformancedegradationoftheoverallsystemfromoneyeartothenext.Fromthistypeofinformationderivedfromacceptablestandards,itispossibletoextrapolatetheestimatesofsystemlifetime.Therefore,specifictestingofthestandardpropertiesofmaterialsand/orcomponentsusedinthemanufacturingofsolarconcentratorsmustbedefined,enablinganinference/estimateofsystemlifetime.Aspecialattentionshouldbedevotedtothedevelopmentofreflectorandabsorberdurabilitytestingprocedures,includingacceleratedagingproceduresfortheanalysisofthedecayofopticalproperties,theimpactofsandinreflectivitydecay(thisisveryimportantforaridzones),theeffectofprolongedexposuresathightemperature(especiallyimportantforCRsystems),etc.Resultsobtainedusingthesestandardswillpromotemarketconfidence,enhancingSTEtechnologiesbankability.
c)Commissioningprocedures:Thelackofstandardsdefiningtheprocedureforthecommissioningofsystems(e.g.,solarfield,thermalstoragesystem,etc.)andcompleteSTEplantshasbecomeevidentduringthestart-upprocessoftheSTEplantsputintooperationduringthelastyears.ThislackofstandardshasledtheEPCcompaniestodefinetheirownprocedures,whichareusuallydifferentfromtheproceduresdefinedbyothercompanies.ThissituationisasignificantbarriertotheeffortstoraiseawarenessandsignificantbarriertoSTEplantsbankability.DevelopmentofthistypeofstandardsinEuropeisalreadyunderwaywithintheframeworkoftheSpanishAEN/CTN206standardisationgroups,withoutanypublicfinancialsupport.DuetothecurrentsituationoftheSTEmarket,thisstandardisationactivityshouldbeincludedinthelistofhigh-prioritytopicstobesupported.
d)Model-basedresults:Duetothedifficultiestofulfillsometestconditionsexperimentally(e.g.,normalincidenceangleontolinearFresnelconcentrators)model-basedresultsmightbeusedinstead(e.g.,resultsobtainedwithraytracingmodels).Theuseofmodel-basedresultsintheprocessoftesting,qualificationand/orcertificationshouldberegulatedbyproperstandardstoassurecompatibilityofresultsobtainedbydifferententities.
e)Solarfieldmodeling:theestablishmentofacommonframeworkforsolarfieldandSTEplantsmodelingisveryimportanttoavoidthedifferencesfoundatpresentwhencomparingtheresultsdeliveredbytheavailablesimula-tionmodels.ThesedifferencesaresometimesverylargeandtheydonothelptoenhancethebankabilityofSTEtechnologies.Differentlevelsofqualitymustbedefinedtoclassifythesimulationmodelsaccordingtothewaytheyconsiderallrelevantparametersandoperatingconditionsaffectingthesolarfieldand/orSTEplantyield.Thisclassificationofsimulationmodelswouldavoidcomparisonofresultsdeliveredbymodelsofverydifferentquality.
DuetothecomplexityofaSTEplant,thenumberofparameters(receiverthermallosses,mirrorreflectivity,pipingthermalinertia,etc.)andoperatingconditions(ambienttemperature,effectofwindspeedanddirectionontheopticalandthermalefficiencyofsolarconcentrators,atmospheretransmissivity,etc.)affectingitsyearlyyieldishigh.Theycanbesimulatedwithdifferentaccuracylevels,leadingtothepossibilityofhavingsimulationmodelsofverydifferentquality.ThedevelopmentofacommonframeworkforsolarfieldandSTEmodelingis,thus,ofparamountimportanceforobtainingreliableandcomparablesolarfieldyieldresultswhicharesuitableforbothplantdesignandprojectfinance.Thisstandardisationactivitywaslaunchedin2010anditiscurrentlyunderwaywithintheSolarPACESprojectGUISMO.
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4.1ContributiontoEU’srenewableenergypolicyDramaticchangesmustbemadetothepresentenergysystemstomitigatethenegativeimpactofgreenhouseemissionsonclimate.Europehassofaradoptedbindingtargetsforrenewableenergyconsumptionandcreatedacarbonemissionmarket,theEmissionTradingScheme.Ithasalsotakenseveralothermeasurestofosterandpromotesustainabledevelopment.
STEiscrucial inEurope’senergyfuture. It is themainrenewableenergygenerationtechnologythatdoesnotrequireadditionalbackupfromconventionalpowerplantstomeetdemand.Ithastheuniquecharacteristicofbeingpredictableandtotallydispatchable: itcancontribute tomeetingdemandatall times,dayandnight.Italsocontributes to thestability to thetransmissiongrid.Barringunforeseeableandunlikelybreakthroughsintechnologieswhichbytheirownnaturedonotsharethesecharacteristics,STEpresentsimportantadvantagesincomparisonwithotherrenewablesources.
SixcountrieshavereflectedSTEintheirNationalRenewableActionPlans(NREAPs):Cyprus,France,Greece,Italy,PortugalandSpain.Intotal,theseplanswouldhaveaddedatotalof7GWtothegeneratingcapacityby2020.However,changesinthefinancialcircumstancesintheContinentareforcingarevisionofthisprediction,loweringthetargetto2GW.TheseplansaretobeimplementedbyMemberStatesonthebasisoftheRenew-ableEnergyDirectiveof2009,whichsettheregulatoryframeworktoachievetheUnion’sbindingtargetof20%offinalenergysupplyfromrenewableenergiesby2020.
Overall,STEcontributesenormouslytomeetingcarbonemissiontargetswhilealleviatingthepricepressureonfinitefossilfuelsandensuringthesecurityoftheelectricitysupply.Thecontributiontosecurityandreliabilityhasthepotentialtobeespeciallysignificantformidloadswhicharemetcurrentlyonlybyconventionalenergysources.Finally,asSTEreliesonanunlimited‘fuel’supplywhich,unlikegasandoil,isindependentofmarketfluctuations,itensuresthepredictabilityofthecostofelectricityandenablesbetterlong-termpoliticaldecision-makingregardingtheenergysupply.
4.2EnergytransmissioninfrastructureTheenergyinfrastructureneedsaredrawingfocussedattentionfromEuropeanpolicymakers,becauseonlyanupdatedenergytransmissionsystemwillmakethefreecirculationofelectricitypossible.Presently,theEuropeanCommissionisworkingonanewregulatoryframeworkforinfrastructure.Inthelong-term,the‘ElectricityHighway’systemshallmakeitpossibletodeliverthroughoutthecontinenttheincreasingshareofelectricitygeneratedbyrenewableanddistributedplants.
ThenewInfrastructureregulationproposalfromtheEuropeanCommissionsetsdowntherulesfortheidentificationandtimelydevelopmentofprojectsofcommoninterest.Theseareunderstoodtomakeuptheenergytransmis-sioninfrastructurethatisessentialtoensuresecurityofsupplytotheEuropeanUnionandtheeffectivefunctionoftheinternalmarket.Alongwiththe‘ConnectingEuropeFacility’,thisnewregulatoryframeworkisembodiedinthenextMultiannualFinancialFramework2014-2020,whichidentifies12keyenergytransmissioncorridorsandsetsoutprovisionsonnewwaysforthefinancingoftheprojects.OneofthesecorridorsistheNorth-SouthCorridorinWesternEurope,whichwillhelptoeliminateenergybottlenecksbetweentheIberianPeninsulaandtherestofEurope.TheNorth-SouthCorridorwillalsomakeitpossibletoimportrenewableenergyfromNorthAfrica:thelargestpotentialforSTEliesinwhatisknownastheMediterraneanSolarRing,whichcomprisesnotonlytheSouthernEuropeancountriesbutalsotheMiddleEastandNorthAfricaRegion.
The transition towardsa100%decarbonisedenergymarket in theEUrequires thedevelopmentofa largertransmissioncapacitybetweenremotegenerationandexistingloadcentres.Thisnewtrans-European‘ElectricityHighways’shallnotbeanextensionofexistinginterconnectorsbetweenstatesbutanewnetworkofhighvoltagedirectcurrent(HVDC)transmissionlines.‘ElectricityHighways’willbethemosteconomicandefficientwaytoconnectEuropeanditsneighbouringcountries,facilitatingtheintegrationoflarge-scalerenewableenergyandthebalancingandtransportationofelectricitytocreateawell-functioninginternalelectricitymarket.
Inthiscontext,theEuropeanNetworkofTransmissionSystemOperatorsofelectricity(ENTSOe),incoordinationwiththeEuropeanCommission,haselaboratedthe“StudyRoadmaptowardsaModularDevelopmentPlanonpan-EuropeanElectricityHighwaysSystem”(MoDPEHS)toestablishguidelinesforthestrategicplanningtoreacha2050pan-Europeanelectricitysystem.
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4.3Europeancontextandframeworks2014-2020TheFrameworkProgrammeforResearchandInnovationHorizon202019
Horizon2020istheEuropeanFrameworkProgrammeforResearchandInnovationfortheperiod2014-2020.Itstreamlinesandidentifiesthedirectionsforfutureresearchandcoversabroadrangeofsectors.TheProgrammeisformulatedalongthreesections:‘ExcellenceScience’,‘IndustrialLeadership’and‘SocietalChallenges’.ThefundingdedicatedtoHorizon2020(about80b€)ispartoftheMulti-annualFinancialFramework(MFF)fortheperiod2014-2020.
Following theSeventhFrameworkProgrammeforResearchand Innovation (FP7),Horizon2020gets ridofadministrativebarriersandseamlesslyintegratesresearchandinnovationactivitiesbyallowingmoreflexibilityandinnovativeinitiativesthaninthepreviousFrameworkProgrammeFP7.
Inthecontextoftheknowledgetriangleofresearch,educationandinnovation,theKnowledgeandInnovationCommunities(KIC),undertheEuropeanInstituteofInnovationandTechnology(EIT),willhelpaddresstheobjec-tivesofHorizon2020,includingthesocietalchallenges,byintegratingresearch,educationandinnovation.
Horizon2020andtheSTE:
Theemphasisgiven toRenewableEnergyandEnergyEfficiency inHorizon2020issignificant: It isexpectedtoaccountforalmosttwothirdsofthetotalcommitments,andthisisproportionaltotheenvi-ronmentalchallenges thatmustbeaddressedin thenear future.Theframework includes theSET-Plan,whichisexpectedtofacilitategreatlythedevelopmentoffirst-of-its-kindprojectsandtobringresearchtomarketintherenewableenergyfield.
Withastrongfocusontechnologicaldemonstrationprojects,this framework is of great importance for the STE sectorandamaindrivertoreachtheobjectivesdescribedintheSTESolarIndustrialInitiative:toreducecost,increaseefficiencyandimprovedispatchabilityandenvironmentprofile.
19-COM(2011)809:ProposalforaregulationoftheEuropeanParliamentandoftheCouncilestablishingHorizon2020TheFrameworkProgrammeforResearchandInnovation(2014-2020)
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FIGURE6:Overview of the European schemes for STE funding
EUROPEAN COMMISSION - FP6 (2000-2006) - FP7 (2007-2013) - Horizon 2020 (2014-2020)
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4.4Researchoverview:participationoftheSTEsectorintheEUinstrumentsThesolarthermalindustrydependsfullyonthestrongsupportfromboththepublicandprivatesectorstoreachquicklytheintegrationleveloftheotherrenewablesourcesalreadyinthemarket.Inthepast,MemberStateshaveawardedsignificantincentivesandEuropeanentitieshavefundedimportantprojects.PastandpresentprojectsfinancedbytheEuropeanCommissionarelistedinANNEXII:PastandpresentEU-fundedprojects.
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Toachievethetargetsleadingtoadecarbonisedenvironmentinthecomingdecades,theEuropeanCommis-sionhasimplementedasetoftoolstargetedtoresearchinstitutionsandindustry.Thosetoolsareelaboratedtoenhanceknowledgeexchangeandcooperationamongalltheplayersintherenewableenergyfield.Monitoring,coordinationandsupportfortheimplementationofenergyresearchprojectsconstitutefurtheraddedvaluefromthoseinstruments.
TheSTEtechnologybenefitsfromthefollowinginstruments:
EERA:TheEuropeanEnergyResearchAlliance(EERA)isoneoftheinitiativesoftheSET-Plan(StrategicEnergyTechnologyPlan).ItisaninstrumentoftheEuropeanCommissionaimedatacceleratingthedevelopmentanddeploymentofcost-effectivelowcarbontechnologiesfortheachievementofEurope’s2020targetsandvisionongreenhousegasemissions,renewableenergyandenergyefficiency.
TheassociatedJointProgrammeonConcentratedSolarPoweriscoordinatedbyCIEMAT:itaimstointegrateandcoordinatescientificcollaborationamongtheleadingEuropeanSTEresearchinstitutionstocontributetotheachievementofthe'SolarThermalElectricity-EuropeanIndustrialInitiative'(STE-EII).Elevenpartnersareinvolved.Withinthisscheme,theOPTS(OptimisationofaThermalEnergyStorageSystemwithIntegratedSteamGenerator’)programmehasbeenlaunchedinearly2012:thisiscoordinatedbyENEA.
SETIS: TheStrategicEnergyPlanInformationSystem(SETIS),elaboratedbytheEuropeanCommissionandledbytheJointResearchCentre,providesacompletesetofinformationrelatedtotheimplementationoftheSET-PlaningeneralandtotheSTEtechnologyinparticular.KeyPerformanceIndicators(KPI)havebeendefinedandapprovedbytheSETISteaminordertodefinewithprecisionthetargetstobereachedandtheimprovementstobemadeinthecomingdecades.AtechnologymapandamaterialroadmapelaboratedbyasetofSTEexpertswerereleasedattheendof2011.
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ESFRI:TheEuropeanStrategyForumonResearchInfrastructure(ESFRI)waslaunchedinApril2002tocoordinatetheworkonnewresearchinfrastructuretoaddressindustryneedsandtoensureabetterexploitationofexistingfacilities.TheForumbringstogetherrepresentativesfromEUMembersandassociatedStatestoworkonregulatoryissuesofresearchinfrastructuresledbyacommonadvancingstrategy.
Apan-Europeansolarthermalelectricityresearchinfrastructure“EU-Solaris”,promotedandcoordinatedbyCTAER(CentroTecnológicoAndaluzdeEnergíasRenovables)andsupportedbyESTELA,hasbeenincludedintheESFRIRoadmapbytheEuropeanCommissionanditwillbefinanciallysupportedbytheFP7foritspreparatoryphase.ThisprojectaimstoestablishaneffectivenetworkamongthemostrelevantSTEresearchcentresinEuropeandassociatedcountries.Itwillprovideaneffectiveinterfacebetweenthetechnologycentresandtheindustry.ThisSTEcoordinatedanddistributedresearchinfrastructurewillalsoplayanimportantroleinreachingthegoalsoftheEuropeanStrategicEnergyTechnologyPlan(SET-Plan).
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ERANET:TheEuropeanResearchAreaNet(ERANET)fitsintheFP7andisintendedtosupportMemberStates’jointactionsintheformofpublic-privatepartnerships.
Thespecificprogramme‘SolarERANET’isdedicatedtosolarenergyandwilllast4years,startinginthebegin-ningof2013.TheSTEtechnologybenefitsfromthisprogrammethroughtheimplementationofconcreteresearchactionsselectedbypriorityorder.2M€areprovidedforcoordinationactionstomitigatecostsandefforts.
SFERA:The‘SolarFacilitiesfortheEuropeanResearchArea’(SFERA)isaprojectoftheEuropeanCommissionwithintheframeoftheFP7.ItaimstoboostscientificcollaborationamongtheleadingEuropeanresearchinstitutionsinsolarconcentratingsystems,financingnetworkingactivitiesthroughyearlyrounds.
Education and training initiative:At thebeginningof2012, theEuropeanCommission launchedanexercise todefine theEuropeanEnergyEducationandTrainingInitiative,buildingonthetechnologyandresearchinitiativesoftheSET-PlantoensureacoordinatedapproachtoassessthecurrentandfuturesituationregardingenergyskillsinEuropeandtoengageinactionsaimedatbuildingupandattractingenergyexpertise.
Thescopeofthisinitiativeistoestablishastrategicdocumentaddressingthewholeinnovationchain,frombasicresearchthroughappliedresearchanddevelopment,tofirst-of-its-kinddemonstration.
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Parabolictroughcollectors
Theparabolictrough(PT)iscurrentlythemostwidelyusedtechnologyaroundtheworld,particularlyinSpainandintheUnitedStateswhereplantsinoperationgenerateover1,000MWand500MW,respectively.
PTtechnologyconsistsofinstallingrowsorloopsofparabolictrough-shapedmirrorsthatcollectthesolarradiationandconcentrateitontoareceivertubewhereafluidisheateduptoabout400°C.Thisfluidislaterusedtoeithergeneratesteamtodriveaturbineconnectedtoageneratorortoheatastoragesystemconsistingoftwotanksofmoltensalt.
Thecollectorrowsareusuallyorientednorth-southtomaximisetheamountofenergycollectedduringtheyear.Atrackingsystemmovesthecollectorsfromeasttowestduringtheday,followingthesuntoensuretheproperangleofincidenceofthedirectsolarirradiationonthemirrors.
Theheattransferfluid(HTF)usedintheseplantsisasyntheticdiathermicoil.AlthoughthespecificformulationoftheHTFhasvariedslightlyduringtheyears,theHTFsetslimitsintheuppertemperatureandconsequentlyintheconversionefficiencyofthewholesystem.Someconcernshavebeenexpressedabouttheenvironmentalcompat-ibilityoftheHTF.Fluidsallowinghighertemperaturesandhavingalesserenvironmentalimpactarebeingtested.
Theseplantscanbedesignedtoallowrathersimplehybridisationwithothertechnologies,sotheycanbeusedwithatraditionalfossilorbiomassfueltogenerateelectricityduringthenightoroncloudydays,boostingsolaroperation.Theadvantagesofhybridisationarethatitmakesitpossibletomaximisetheuseoftheturbinegeneratorandthatitallowsthedesignofmorerobustdispatchablesystems.This,inturn,makesitpossibletotakeadvantageofeconomiesofscaleinmanysubsystemsoftheprojectduringbothoperationandconstruction:powerlinesareanobviousexample.
CurrentpowerplantsinSpainarelimitedto50MWperplantbytheSpecialRegime.About60%oftheplantswhichhavebeenregisteredfortheFiTincludeamoltensalttwo-tanksystemproviding7.5hoursofstorage.IntheUnitedStates,powerplantsarebeingbuiltwithmuchlargerturbines(>100MW),takingadvantageofthefactthat,inthistechnology,whileenergycollectionperformanceispracticallyunaffectedbysize,costsofgenerationareloweredconsiderably.
Intermsofthematurityofthetechnology,PTcanbeconsidered“mature”,sinceanumberofmanufacturersareavailable forerectingentireplantsorsubsystems.There isgoodexperience inengineeringprocurementandconstruction(EPC)and20-yearoperatingexperienceallowsforgoodconfidenceontheoperation.Therefore,thesecanbeconsideredlow-riskprojects.AlltheexistingcommercialPTplantscanbeplacedinthe“firstgenera-tion”categoryasdefinedinChapter1.
Anew“secondgeneration”ofPTplantswillaimtoreachahigherHTFtemperature,allowingthefullintegrationofthesolarfieldandthestoragesystem.This“secondgeneration”shouldprovidesignificantimprovementsintheaverageconversionefficiencyandfurtherreductionofcosts.Althoughademonstrationplanthasalreadybeenbuilt,adequateoperatingexperienceisstillneededandcomponentswithenhancedperformanceanddurabilityarebeingstudiedanddeveloped.
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Centralreceivers
Solartowerswithcentralreceiver(CR)concentratesolarradiationbymeansofafieldofheliostats,eachconsistingofareflectingsurfacemountedonapedestalwhichcantrackthesunontwoaxes.Theheliostatsreflectthesolarradiationontoareceiverlocatedatthetopofatower.AHTF,whichincurrentpowerplantsiseithersteamormoltensalt,isheatedinthereceiverandusedtogenerateelectricityinaconventionalsteamturbine.
TheefficiencyoftheseplantsisusuallybetterthanPTplants,becausefluidtemperaturesarehigher–around550°C.Thisleadstobetterthermodynamicperformanceanditalsofacilitatesstorage:smallervolumesarepossiblebecauseofthehighertemperaturedifferencebetweenthecoldandthehottanks.Atpresent,thereareonlythreecommercialsizepowerplantsofthistypeinSpain;intheUnitedStates,severallargerprojectsarecurrentlyunderconstruction.
AlthoughcommercialexperiencewithCRplantsislimited,itisestimatedthatthecost(LCOE)oftheelectricityfromsuchplantscouldbelowerthanthatgeneratedinPTplants,eventhoughlanduseisslightlylessefficient.Therequirementsfor“flatland”arelessdemandingthanforPT.Growingconfidenceforthistypeofplantisexpectedasmoreofthemgointooperation.Theseplantscouldhavearatedpowerofover100MWealthoughtheirefficiencydecreasesslightlywiththesize.
ThefirsttwocommercialCRplantsusingsaturatedsteambelow300°Ccanbeconsideredas“firstgeneration”technology,whereaslatersystemsarealreadyinthe“secondgeneration”category.ThisisespeciallytruewhentheHTFisamoltensaltorwhentheplantincludesan“integratedstoragesystem”.CRplantsarestillontheirwaytowardsmaturity.Muchofthedevelopmentworkoutlinedlaterwillbefocusedontheoptimisationofcomponents,systemsandoperatingstrategies,basedonthefindingsfromtheoperationoftheseplants.
InafuturegenerationofCRplants,thefullcapacityofthehighconcentrationallowedbyCRwillbeexploitedtoreachtemperatureswhicharehighenoughtodrivetheadvancedpowercycles,suchascombinedcyclesandsupercriticalsteam/gasturbines,whichareassociatedwithmuchhigherconversionefficiency.
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Thistechnologyisalsobasedonsolarcollectorrowsorloops.However,inthiscase,theparabolicshapeisachievedbyalmostflatlinearfacets.Theradiationisreflectedandconcentratedontofixedlinearreceiversmountedoverthemirrors,combinedornotwithsecondaryconcentrators.Oneoftheadvantagesofthistechnology(“linearFresnelreflectors”,orLF)isitssimplicityandthepossibilitytouselowcostcomponents.Directsaturatedsteamsystemswithfixedabsorbertubeshavebeenoperatedwithoutproblems.ThistechnologyeliminatestheneedforHTFandheatexchangers.Increasingtheefficiencydependsonsuperheatingthesteam;however,thisisstillachallenge.Overcomingthischallengehasstilltobedemonstrated.
Thistechnologyiscurrentlylessdeployedthantheothertwo(PTandCR)alreadydescribed.Concentrationandtemperatureofthefluidinthesolarfield–todatemostlysaturatedsteam–arelowerthanintheothertwotech-nologies.Becausesteamistheworkingfluid,itismoredifficulttoincorporatestoragesystems.However,otherfluidsand/orsolutionscanbeconsideredtoallowforstorage.
Afterafirstpilotscaleapplication inAustralia,a fewnewpilotplantshavebeen tested inSpainandin theUnitedStates,andafirstcommercial30MWeLFplantisalreadyinoperationinSpain.FrancehasalreadyimplementedaLFpilotplantandiscurrentlybuildingtwonewcommercialplantswiththistechnology,of9and12MWrespectively.
Comparedtoothertechnologies,theinvestmentcostspersquaremeterofcollectorfieldusingLFtechnologytendtobelowerbecauseofthesimplersolarfieldconstruction,andtheuseofdirectsteamgenerationpromisesrelativelyhighconversionefficiencyandasimplerthermalcycledesign.Manyimprovementsintheabsorbertubesandthegeometryareunderdevelopment.Someofthoseongoingimprovementeffortsrelatetotheshapeandthedispositionofmirrorstoaccommodatesomeofthepeculiaritiesofthistechnologyandtoachieveaperformancewhichisclosertothatofothertechnologies,inparticularPT.
TheLFtechnologyisalsoquiteusefulfordirectthermalapplications,suchascoolingorgeneratingprocesssteam.
ThefuturedeploymentoftheLFtechnologywilldependonwhetherinvestmentandgenerationcostscanbeloweredenoughtocompensatefortheslightlylowerperformanceandfulfilitspromiseofbeingcompetitive.
Duetothesmallnumberofdemonstrationinstallations,wecannotrefertoamature“firstgeneration”plant,butitisexpectedthatthiswillchangeverysoon.Thegaininoperatingexperiencewithpresentandfutureinstalla-tionswilldefinethisbasiclevel.Futureimprovementsmatchedwithimportantcostreductionswhicharepossiblebecauseofthesimplifieddesigncanrenderthistechnologyverycompetitive,especiallywhencombinedwithotherenergysystems.
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Parabolicdishes
Powerplantsusingparabolicdishes(PD)withStirlingenginesconsistoftwobasiccomponents,aconcentratororsolardishandapowergenerator.Eachcompleteunitproduceselectricitybyitself.Thepowerofthecurrentdevicesvariesfrom3kWto25kWperunit.
Theparaboloidalconcentratorscollectthesolarradiationdirectlyandreflectitontoareceiverlocatedoverthedishclosetothefocalpoint.Thestructurerotates,trackingthesunandthusconcentratingtheraysontothefocuswherethereceiver–connectedtotheengine–islocated.Themostcommonthermo-mechanicalconverterusedisaStirlingengineconnectedtoanalternator.TheStirlingengineusesaheatedgas,usuallyheliumorhydrogen,togeneratemechanicalenergyinitsshaft.Theefficiencyoftheseplantsismuchhigherthanthoseoftheotherthreetechnologiesalreadydescribed.
Thisdesigneliminatestheneedforwater,becausecoolingoftheengineisachievedbymeansofaradiatorsimilartothoseusedinsomecars.Thisisanadvantagecomparedtotheusualdesignsemployedbyothertechnologies–althoughsomeofthemcouldalsoutilisedrycoolingsystems.Ontheotherhand,asthePD’saresingleunits,ThermalEnergyStorage(TES)andhybridisationsolutionsarenoteasytoimplementandthisconstitutesamajorbottlenecktothelargescaledevelopmentofthistechnology.Dispatchabilityandstabilityareotherimportantissues,asthePDsystemshavenothermalinertia.However,thistechnologycanbedisplayedmodularlyandPD’sareeasiertositeonunevenlandthanothercollectingsystems.Therefore,PDscouldbeasolutionfordistributedgeneration.
Storage
Oneofthemainchallengesforrenewableenergytechnologiesisfindingsolutionstoproblemsderivedfromthevaryingorintermittentnatureofmanyrenewableresources.Amongtheseresources,solarenergyhassomemajoradvantages,notonlybecauseitismuchmoreabundantthananyothersourcebutalsobecausethehoursofsolarradiationaremorepredictable.However,thekeyadvantagesforthethermaloptionarethatthermalenergystorage(TES)isefficientandrelativelycheapandthattherearealreadymanyavailablecommercialsolutions.Inaddition,becauseSTEplantsareeminentlysuitableforhybridisation,aplantwhichtakesadvantageofthesolarradiationwhenitisavailablecandeliverenergyuponrequestandcanfollowthedemandcurveevenwhenneithersunnorstoredenergyisavailable.
Theenergycollectedcanbestoredforlateruseduringthenightoroncloudydaysbyincreasingtheinternalenergyofasubstance.Storagemakesitpossibletoseparateenergycollectionfromelectricitygeneration,andthereforethestoragesystemfortheSTEplantcanhaveahighcapacityfactor.
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Inmanyregions,dailypeakdemandcoincideswiththehoursofhighestsolarradiationavailability.Dependingontheseason,forafewhoursaftersundownthereisasecondpeakdemand.InSpain,inparticular,plantswithstorageusuallyhaveupto7.5additionalhoursofcapacity;thisallowstheoperationofthesolarthermalplantstobeextendedandmakesthemmorecompetitive.
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FIGURE7:Electricity demand and STE production on 11th July 2012 and in the full month of July 2012 20
Figure7showsthecurveofelectricitydemandinSpain(scaleontheleft)andtheaggregatedproductionofalltheSTEplants(scaleontheright)on11thJuly2012andinthefullmonthofJuly.Thereisagoodmatchbetweenthecurves.
Practicallyallsolar thermalplantshaveeitherstoragesystemsorallowhybridisationwithother technologies.Thishelpstoregulateproductionandguaranteethatpowerisavailable,especiallyduringpeakdemandhours.
Hybridisation
ForSTEplants,hybridisationisthecombinationoftheuseofsolarenergywithheatcomingfromothersourcessuchasbiomassorconventionalfossilfuels.Theadvantagesofhybridisationare:
n Makingitpossibletoconvertthecollectedsolarpowerwithhigherefficiency;n Ensuringdispatchabilitytocoverpeakdemandanddeliverenergyondemand;n Overcomingthevariabilityofthesolarradiation;n Reducingstart-uptime;andn Minimisingthegenerationcost(LCOE).
Steamproducedwithsolarenergycanbeusedtoboostthecapacityofaconventionalfossil-fuelpowerplant,savingfuel,reducingCO2emissionsandachievinghighersolarenergyconversionefficiencies.
AllSTEplants(PTs,CRandLF),withorwithoutstorage,canbeequippedwithfuel-poweredbackupsystemsthathelptopreparetheworkingfluidforstart-up,regulateproductionandguaranteecapacity(Figure8).Thefuelburners(whichcanusefossilfuel,biomass,biogasor,possibly,solarfuels)canprovideenergytotheHTForthestoragemediumordirectlytothepowerblock.InareaswhereDNIislessthanideal,fuel-poweredbackupmakesitpossibletoalmostcompletelyguaranteetheproductioncapacityoftheplantatalowercostthaniftheplantdependedonlyonthesolarfieldandthermalstorage.Providing100%firmcapacitywithonlythermalstoragewouldrequiresignificantlymoreinvestmentinalargersolarfieldandstoragecapacity,whichwouldproducerelativelylittleenergyovertheyear.
20-Source:ESTELAPositionPaper'TheEssentialRoleofSolarThermalElectricity:ArealopportunityforEurope'October2012.
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Fuelburnersalsoboosttheconversionefficiencyofsolarheattoelectricitybyraisingtheworkingtemperaturelevel;insomeplants,theymaybeusedcontinuouslyinhybridmode.STEcanalsobeusedinhybridmodebyaddingasmallsolarfieldtofossilfuelplantssuchascoalplantsorcombined-cyclenaturalgasplantsinso-calledintegratedsolarcombined-cycleplants(ISCC)ThereareoperatingexamplesinseveralnorthernAfricancountrieswithsolarfieldsof25MWeequivalentand,intheUnitedStates,thereareexampleswithalargersolarfield(75MWe.)Apositiveaspectofsolarfuelsaversistheirrelativelylowcost:withthesteamcycleandturbinealreadyinplace,onlycomponentsspecifictoSTErequireadditionalinvestment.
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Otherapplications(desalination,processheat,solarfuels)
Thethermalenergygeneratedinsolarthermalpowerplantscanalsobeusedforindustrialpurposesotherthantheproductionofelectricityandthusenhancetheapplicabilityoftheplants.Oneconceivableoptionwouldbethecombinationofelectricityproductionwiththedesalinationofseawater.Particularlyinaridcoastalareas,itwouldbeaninterestingperspectivenotonlytogenerateelectricitybuttomakedrinkingwaterthatisoftenscarceintheseareasavailableaswell.
Furthermore,theplantscanalsoprovidesteam,heatorcoolingforindustrialpurposes.Oneexampleistheuseofconcentratingsolarthermalsystemsforthegenerationofsteamtoenhanceoilrecovery,asprovedinacommis-sionedfeasibilitystudyforaplantinthesultanateofOman.Here,hotsteamisinjectedintothemostlyexploiteddepositsunderhighpressureinordertominetheremainingresources.Previously,fossilfuelsweremainlyusedforthegenerationofsteam.However,ifthesteamisprovidedusingsolarthermalmethods,emissionsthatareharmfultotheclimatecouldbereducedsignificantly.
Regardingproductionoffuelsfromconcentratedsolarpowertherearebasicallytworoutes.ThefirstoneistheelectrochemicalroutewhichusesthesolarelectricitygeneratedbySTEplantstopoweranelectrolyticprocess.Anotherapproachisthethermochemicalroutewhichusessolarheatathightemperaturesfollowedbyanendo-thermicthermochemicalprocess.Solarfuelscouldbethemeanstostoresolarenergytoenhancetheperformanceofasolarthermalplantandtheycouldalsobethemeanstotransportthecollected(andtransformed)solarenergytositesthatmaybefarfromthecollectorfields.
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6.1TheSTEEuropeanIndustrialInitiativeTheStrategicEnergyTechnologyPlan(SET-Plan)isthemajorinstrumentelaboratedbytheEuropeanCommissiontostrengthenandgivecoherencetotheoverallEuropeanefforttoaccelerateinnovationincuttingedgeEuropeanlowcarbontechnologies.Indoingso,theSET-Planwillfacilitatetheachievementofthe2020targetsandthe2050visionoftheEnergyPolicyforEurope.InitsCommunicationentitled‘AEuropeanStrategicTechnologyPlan’21, theEuropeanCommissionproposesto launchtheEuropeanIndustrial Initiatives(EII) toacceleratethedevelopmentanddeploymentofcost-effectiveLowCarbonTechnologies.EIIshavelaunchedinsixsectors:Solar,Wind,Bioenergy,Grid,CarbonCaptureandSequestration(CCS)andNuclear.The“SolarEuropeInitiative”encompasseslarge-scaledemonstrationprojectsforbothPVandSTE.
InJuly2009,ESTELAreleasedits“EuropeanSolarThermo-ElectricIndustryInitiative”(STEII)contributingtotheSET-PlanoftheEuropeanCommission.AfinalversionincludestheKeyPerformanceIndicators(KPIs),developedbyESTELAincollaborationwiththeSETISteam.
TheproposedSTEIIhasbeendevelopedforthepurposeofachievingtwomaingoalsfortheEU:
n TocontributetoachievetheEUtargetsfor2020andbeyondbyimplementinglarge-scaledemonstrationprojectstobecarriedoutbyindustryandaimedatincreasingthecompetivenessofthesolarthermalelectricitysector.
n ToenhancemarketpenetrationandtoconsolidatetheEuropeanindustrygloballeadershipthroughoutmedium-termresearchactivitiesaimedatreducinggenerationandoperationcostsinsolarthermalelectricitygenerationplants.
Inparticular,theSTEindustryinitsSTE-EII(EuropeanIndustrialInitiative)22hasidentifiedthreetechnologyobjectivestobeconsideredforfunding:
n Increaseefficiencyandreducecostsn Improvedispatchabilityn Reduceenvironmentalimpact
Increaseefficiencyandreducecosts
ThisobjectiveisofutmostimportanceforthedevelopmentofSTEtechnologiesandtofurthertheirmarketpenetra-tion.Manyimprovementsneedtobeachievedthroughtechnologicaladvancementsoncomponentsandcycleefficiency,creatinganewgenerationofefficientsolarthermalpowerplants.ThisaspectcannotbedissociatedfromasubstantialreductionofinvestmentandO&Mcosts,anoptimisationoftheinformationandcommunicationtechnologies,abetteruseoftheinstallations(betteruseofland,largerplants)andmoreadequatetermsofcredit(lowerinterestrates,lesstechnicalrisks).
21-COM(2007)723:CommunicationfromtheCommissiontotheCouncil,theEuropeanParliament,theEuropeanEconomicandSocialCommitteeandtheCommitteeoftheRegions–AEuropeanStrategicEnergyTechnologyPlan(SET-Plan)
22-Source:ESTELA.‘SolarPowerfromEurope’sSunbelt’,AEuropeanSolarThermo-ElectricIndustryInitiativeContributingtotheEuropeanCommission‘StrategicEnergyTechnologyPlan’,June2009
23-Source:A.T.Kearney/ESTELA.SolarThermalElectricity2025-Cleanelectricityondemand:attractiveSTEcoststabiliseenergyproduction,June2010
FIGURE9:LCOE comparison of solar thermal energy versus conventional sources 23
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Studiesperformedtoanalysehowthesolarfieldsizeinfluencesthespecificinvestmentcostin€/m2haveshownthatthecurrentcapof50MWeimposedinSpainforSTEplantsisaratherartificiallimitanditisbynomeansatechnicallimit.AsPTtechnologyisverysensibletotheeffectofscaling-up,thedesignofbiggersolarfieldscouldleadtoasignificantcostreduction.
Themaximumpoweroutputofasingleplantistheoreticallynotlimitedbyanyphysicalconstraint.Inpractice,thepressuredropoftheHTFdoesimplythatthereisanoptimumscaleandthiseffectivelylimitsthesizeofthesolarfield.However,STEplantsofmorethanonehundredMWwithasinglepowerunitarebeingdesigned.
Improvedispatchability
Dispatchabilityisastrongadvantageoverotherrenewablesources.Itallowsflexibility,financialsavings,andcompetitionwithfossilfuels.Theimprovementofthethermalenergystoragesystems(throughimprovementsinfillermaterials,transferfluids,phase-changesystems,“ultra”capacitors)andthehybridisationwithotherpowerplantswillleadtoanincreaseinthehoursofproductionandhaveadirectimpactontheoverallplantperform-anceandeconomics.
ThedispatchabilityofSTEplantscanbefurtherincreased,whenthinkingintermsofsystemcollectionsratherthanindividualplants,byconnectingtheplantsinaninter-continentalgrid,increasingtheflexibilityandavailabilityofthepowersupplyondemand.
Reduceenvironmentalimpact
Examplesofmeasurestoreduceenvironmentalimpactarethedevelopmentofnewcoolingsystemswithlowerwaterneeds(steamcycles)andthedeploymentofenhanceddrycoolingsystems.Abetteruseoflandandmate-rialsandthedesalinationandpurificationofwaterwillalsocontributetofulfillthisobjective.
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TABLE3:Solar power cost reduction factors
Components Systems ConfigurationsSolarreceivers:linearandcentral Receptorsystems:hotairtogasturbine HybridisationMirrors HTFsystems:directsteamgeneration Dualelectricitywater-plantsNewHTFs StorageSystemsStoragemedia Coolingsystems:hybridcoolingsystemsSupportingstructuresTrackersAuxiliarysystems:pumps,valves
6.2UpcomingchallengesThefirstobjectivedescribed in thepreviouschapter iscrucial toallelectricitygeneratingrenewableenergysystemsiftheyaretobecompetitivewithconventionalpowerplants,eveniffundingisreducedorphasedoutinthefuture.Thesecondobjectiveisrelatedtothe“quality”oftheelectricitysupply,i.e.toprovidegridstabilityandavailabilityondemand.ThesearetwoofthemajoradvantagesofSTEplantsthankstotheirthermalinertia,storabilityandtheirabilitytooperateinhybridmode.ThethirdobjectiveislargelyimposedbytheSTEindustryonitself,becausetheindustryanditsmarketacceptancearedrivenbythegoaltoachievesustainability,andtoeliminateorreducethecostofexternalitiesiskeytoachievingsustainability.
Themeasurestakentomeettheseobjectivesaffectcomponents,systemsandconfigurations.Table3illustrateswheremeasuresarebeingtakentoachievetheobjectivetoreducecosts.AdetaileddescriptionincludingKPIsisgiveninANNEXI:KeyPerformanceIndicators.
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FIGURE10:From innovation to commercial operation
ThedifferentSTEtechnologiespresentedinchapter5representdifferentstagesofmaturity,sincePTsandCRsaswellasLFsinanearlystagealreadyexistascommerciallyoperatingpowerplants.Barringsomeunforeseenbreakthrough,therefore,thechallengesforthesetechnologiescanbeaddressedthroughincrementalinnovation,althoughthe“increments”maybequiteimportant.Thesituationisdifferentforparabolicdishes,however,sincesofarthesehaveonlybeentestedasdemonstrationplants.ForPD,therefore,thefirstchallengeistoprovethatplantsbasedonthistechnologycanalsobeoperatedcommercially.
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The reflector concentrates the sunlight to a receiver tube, through which the HTF is circulated.
✔ 30 years✔ Utility scale power
Heliostats follow the sun to reflect the sunlight to the top of a tower where the HTF is heated.
✔ 5 years✔ Utility scale power
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✔ Demonstration✔ Heat applications
A group of mirrors with a parabolic shape reflect the sun to an engine located in the focus point
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Description
Track recordApplication
Next challenges Incrementalinnovationandpossiblebreakthroughs
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Incrementalchanges(suchasnewcollectordesignsinanexistingcollectorfieldorinnovativemirrorcleaningmechanisms)canhelp improve theperformanceofanSTEplantandmeet theobjectivesalreadydescribed.However,veryoften,thiskindofshorttermdemonstrationisnotpossibleincommercialpowerplants,sincesomeinnovativecomponentsandsystemscannoteasilybeincorporatedintoanexistingpowerplant.Togivejustoneexample,itwouldbealmostimpossibletotestadirectsteamgenerationsysteminaplantwhichusesanoilheat transferfluidsystem.Therefore,besidesshort termdemonstrationof innovativecomponentsandsystems,akeyneedintermsofR&DfundingtoachievecommerciallyviableSTEplantsisthefinancingoffirst-of-its-kindcommercialpowerplantswithinnovativetechnologies.Thesepowerplantsaretypicallylargerthan“pure”R&Ddemonstrationplantsand,thus,requiresignificantlymoreinvestments,buttheyaretoosmalltooperateasefficientlyascommercialpowerplants(cf.diagrambelow).
FIGURE11:Financing first commercial plants for breakthrough technologies
Demo Plant First Commercial Commercial PlantSize 1-5MW 5-20MW >20MWCost 5,25Me 25-100Me >100Me
Financing Instrument
BalanceSheetR&DFunding
ProjectFinancingFeed-in-Tariffs/PPAs
n Essential to achieve bankability, especially for breakthrough technologies
n Risk too high for individual CSP players
n Suboptimal scale to operate efficiently
n R&D funding and FiT exclude each other
Asaconsequence,financialinstrumentsareneededtohelprolloutbothincrementalandbreakthroughinnovation.Inaddition,risksharingmechanismsforfirst-of-its-kindandcommercialpowerplantsarerequired.
ToclarifytheprioritiesforR&DeffortsinSTEplants,itisusefultodividetheobjectivesforinnovationintoshort-mid-andlong-term.Theindividualtargetstoaddresseachobjectivearedescribedindetailinthefollowingchapters.
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nthistimeofgrowingconcernforfutureinvestment,theStrategicResearchAgendaappearslikeanecessaryandinevitablestepforsettingupthebaselinesfortheshorttolongtermresearchforSTEtechnology.Itstargetistoidentifyclearlythebottlenecks,milestonesandchallengesofthisemergingtechnologythroughtheaccomplishmentofthethreeobjectivesoutlinedabove:toincreaseefficiencyandreducecosts,toimprovedispatchabilityandtoimprovetheenvironmentalprofile.
STEresearchprioritytopicsaredefinedinthefollowingchapters,orderedbyobjectiveandtechnology,withdedicatedchaptersforcross-cuttingissues.Theyincludestorage,hybridisationandenvironmentalprofile.Atableattheendofeachchapterbringstolighttheobjectivestobeachievedintheshort(2015),mid(2020)orlongterm(2025andbeyond).Thetablealsoshowstheassociatedtargets.
Thesetechnicaltopicsmustbeaddressedwithdueconsiderationtothestandardisationaspectsthathavebeendescribedinchapter3.4.Anefficientandconcretereductionofcostsisnotpossiblewithouttheestablishmentofclearinternationalstandards.
7.1Objective1:Increaseefficiencyandreducegeneration,operationandmaintenancecostsReductionofcostisthekeypointforthefuturelargescaledeploymentofSTEplants.Itcanbeachievedbyincreasingtheefficiencyofthesystems,reducingthecostsoftheequipmentandloweringO&Mcosts.Certainlytheircombinationwillprovideafurtherreductiononthecostsofthegeneratedelectricity.
Largersizeofplantsalongwithscalefactorsincomponentmanufacturingandthelessonslearnedinassemblyofcomponentsandconstructionofplantswillcertainlycontributetoachievethecostreductionobjective.
InourpreviousapproachontheSEII,increasingefficiencyandreducingcostswereconsideredindependently.However,theyaresointerconnectedthatwehavepreferredtopresentthemjointlyinthisStrategicResearchAgenda.
TheSTEindustryiscommittedtopushtechnologicalimprovementinitiativesalongtheselinesinclosecollabora-tionwiththetechnologicalresearchcentres.
By2015,whenmostoftheplannedimprovementsaretobeimplementedinnewplants,energyproductionboostsgreaterthan10%andcostdecreasesupto20%areexpectedtobeachieved.Furthermore,economiesofscaleresultingfromtheincreaseoftheplantsizewillalsocontributetoreducetheCAPEXperproducedunitofenergyupto30%.STEdeploymentinlocationswithhighsolarradiationwillfurthercontributetoachievingcostcompetitivenessbyreducingLCOEbyupto25%.
Allthesefactorscanleadtoelectricitycostsavingsofupto30%by2015andupto50%by2025,thusreachingcompetitivelevelswithconventionalsources(e.g.coal/gaswithLCOE<10c€/kWh).
FIGURE12:Sensitivity analysis of several parameters on the LCOE of a 50 MWe PT plant with 7.5 hours of thermal storage (Reference case: plant located in Southern Spain, 2011)
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Reductionoffixedchargerate Incrementofoverallplantefficiency Lifetimeincrease Reductionofsolarfieldcost ReductionofO&Mcosts
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Figure12showstheimpactofchangesinseveralcharacteristicsontheLCOE.Theitemsrepresentedinthegraphandtheirreferencevaluesare:
n Plantlifetime(referencevalue:20years)n Solarfieldspecificcosts(referencevalue:225€/m2)n Plantoperationandmaintenancecosts,excludingthepowerblock(referencevalue:40€/MWh)n FixedChargeRate(referencevalue:0.0682)n Overallplantyearlyefficiency(referencevalue:15.2%)
AlthoughvaluesrepresentedinFigure12arefora50MWePTplantwith7.5hoursofthermalstoragesystemwithmoltensalt,sensitivitiesshowninthisgraphareverysimilartothevaluesfora50MWeplantwithoutstorage.
ThetwoparametersshowingagreaterinfluenceontheLCOEarethefixedchargerate(financialcosts)andtheoverallplantefficiency.TheimpactofareductionoftheO&Mcosts(€/MWhe)andofthespecificsolarfieldcosts(€/m2)haveasmallerinfluence.
Thelifetimeoftheplanthasanintermediateimpact,andanincreasefrom20to30yearswouldreducetheLCOEbyabout17%.Thisnumbershowsthegreatimportanceofimprovementsonthedurabilityofcomponentstoextendlifetime.
Today,aquickevolutionthroughthelearningcurvecanbeobservedintheSTEtechnology.Mostofthenewplantswhichhavebeenrecentlyconnectedto thegridwereconstructedinSpainrequiringFiTswhichweresettledin2009atalevelofaround27c€/kWh.OngoingprojectswhichhavebeenawardedoncompetitivebasesinIndiaorMoroccoorwhichresultedonbilateralPPAnegotiationsbetweenutilitiesandpromotersintheUnitedStatesshowpromisingresults,inaccordancewiththeA.T.Kearney/ESTELAcostreductionforecast.
Thedevelopmentof the topics included in thisStrategicResearchAgendaof theSTE industrywillcertainlycontributetoreachingthesegoals.
7.1.1Cross-cuttingIssues
7.1.1.1 MirrorsSincemirrorsarekeyelementsinanySTEplant,improvementsreducingthemanufactureormaintenancecostsassociatedwithmirrorswillbeimportanttoachievethepursuedLCOEreduction.
Thestate-of-the-artforthereflectivesurfaceofsolarreflectorsisrepresentedbyeitherfacetsofthick(4-5mm)glassmirrorswithstructural functionsor thin (0.8-1.1mm)glassmirrorsattached toastructuralsurface(fibreglass,composite,metallic…)thatprovidesshapeandstiffness.Whilethefirstsolutioniscurrentlyusedinallfourtechnologiesconsideredinthisdocument(PTcollectors,heliostats,LFandPD),thinglassmirrorshavebeenusedmainlyinPD.Theuseofotherreflectivesurfaces,suchassilverpolymerfilms,ispossiblebutitwillrequireprovendurability.
Light reflective surfacesTheuseoflightweightreflectivesurfaceswillresultincheapermirrors.However,alternativesolutions to thickglassmirrorsmustbeat leastcomparableintermsofdurabilityandreflectance.
Glass reflector with anti-soiling coatingMirrorwashingisoneofthemostfrequentmaintenanceactivitiesatthesolarfieldofsolarthermalpowerplants.Anyimprovementthatreducesthenumberofwashingswouldalsoreducenotonlythemaintenancecostsbutalsotheplantwaterconsumption,whichisacriticalfactorforthecommercialdeploymentofSTEplantsindesertareas.
Mirrorsamplesexposedtooutdoorconditionstoevaluateanti-soilingcoatings
(CIEMAT-PSA,PlataformaSolardeAlmería)
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Mirror glass with higher solar transmissivityThesolartransmissivityoftheglasscurrentlyusedforsolarreflectorscanbeimproved.Improvementoftransmis-sivitywillimprovethemirrorreflectivityandloweropticallossesforthefourSTEtechnologies;inaddition,forPTandlinearFresnelsystems,itwillalsoimprovetheoverallefficiencyofthereceivertubesbyimprovingthesolartransmittanceoftheirglasscover.
7.1.1.2 ReceiversThereceiveristhekeycomponentofaSTEplant,becauseitisinthereceiverthattheconcentratedsolarradiationisconvertedintothermalenergy.ThereceiverefficiencyiskeyfortheoverallSTEplantperformance.Therefore,anyimprovementthatincreasestheefficiencyofthereceiverwillhaveasignificantimpactonthefinalLCOE,providedthattheadditionalcostsassociatedwithsuchimprovementareaffordable.
Selective coatings with better optical propertiesThesolar-to-thermalconversionefficiencydependsgreatlyon theopticalpropertiesof the receiverselectivecoating.Theopticalpropertiesofselectivecoatingscurrentlyavailableforevacuatedtubes(usedinPTandinLFcollectors)areexcellent,buttheiremittanceandabsorptancepropertiescouldstillbeimproved.However,fornon-evacuatedtubes,therearenocommerciallyavailablecoatingsforoperatingtemperaturesabove400°C.ThislimitationisparticularlysevereforlinearFresneltechnologies.Also,fortowerapplications,selectivecoatingswhicharestableatatmosphericconditionsattemperatureshigherthan600°Carenotavailableyet.
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7.1.1.3 Heat transfer fluidsThethermaloilusednowadaysasworkingfluidinmostPTcollectorslimitsthemaximumworkingtemperature(398°C).Italsoposessomeenvironmentalhazardsduetopossibleleaksandfires.Thesefactorsincreasetheoperationandmaintenancecostsandtheylimitthemaximumpowerblockefficiency.
Synthetic oil with new chemical formulation
Theperformanceofexistingsolarplantsusingoilasheat transferfluidcanbeenhancedifanewchemicalformulationisdevelopedthatreducesthechemicaldegradationwithtime.Newfluidswithlowerviscosityatlowtemperaturecanbestudied,avoidingtheneedtopreheatthefluidandtomaintainitaboveaminimumtemperature.TheadditionofPCM,nanoparticles(nanocrystals)orfullerenesaresomeofthepossiblesolutions.Binarysystemssuchasionicliquid-carbonnanotubescanalsobeconsidered.
Low melting-temperature salt mixtures
Moltensalt,mostcommonly,aNa/K60/40wt%24nitratesmixtureusedasathermalstoragemediuminSTEplants,wouldbeanalternativetothermaloilasthesaltremainsstableattemperatureshigherthan400°C.Onedrawback,however,isthemeltingtemperatureofthesaltmixturenormallyusedintheTES,whichliesbetween220and240°C.Thismeansthatthetemperatureinthesolarfieldmustalwaysbekeptabovethisrangetopreventthesaltfromsolidifyingintheabsorbertubes,orthatsomealternativesolutionmustbefound.
Therefore,thedevelopmentofnovelmoltensaltmixtureswithalowermeltingtemperature(i.e.<100°C)andwhicharethermallystableupto450°C(suchas.Na/K/Canitratesmixture)orhigher(suchasNa/K/Linitratesmixture),andwhichhaveanacceptablecostwouldbeasignificantimprovementforPTandcompactlinearFresnelsystems.Suchmixtureswouldallowmoreefficientthermalstoragesystemsbasedonatwo-tankmoltensaltdirectsystem,becausethecurrentoil/moltensaltheatexchangerswouldnolongerbeneeded.Howeverifthecostofthenovelmixtureishigh,itwouldbenecessarytomaintaintheintermediateheatexchanger(indirectsystem)usingthemixtureonlyinthesolarfield–exactlyaswiththeoil.
ForCRplants, the reductionof themelting temperaturemustbeaccomplishedwithout reducing the thermalstabilityat600°Cormore.Thismeansthatameltingtemperaturelowerthan100°Cmustbecomplementedwithagoodthermalstabilityuptoatleast600°C.Otherwisethelowerovernightthermallossesduetolowersalttemperatureswouldnotcompensateforthelowerplantefficiencyduringsunlighthoursandthenetimpactontheyearlyplantefficiencywouldbenegative.Therefore,differenttargetsmustbedefineddependingontheSTEtechnologybeingconsidered.
Pressurised gas
Theuseofpressurisedgas(air,CO2,etc.)forbothPTandCRplantsshouldbefurtherinvestigated.Inspiteoftheirpoorerheattransferpropertiespressurisedgaseshavenotemperaturelimitsandnoimportantconstraintsregardingthereceivertubematerials.Althoughpressurelossesarehigherwithpressurisedgasthanwithliquids,thisproblemcanbesignificantlyovercomewithanoptimiseddesignofthepiping.FurthermoreusingpressurisedairastheworkingfluidforCRplantswouldmakethesolarcombinedcycleconceptpossiblewithsomesupportofgasfiringbeforetheairentersthegasturbine,andthishasthepotentialtoresultinaconsiderableincreaseintheconversionefficiencyfromsolarenergyintoelectricity.
Direct steam generation
Theuseofwater/steamasworkingfluidinPT,CRorcompactlinearFresnelSTEplantshasbeenwidelystudiedduringthelasttwodecades.ItsadvantagesanddisadvantageshavebeenevaluatedandcomparedtootheroptionsforcommercialSTEplants(moltensaltorairinCR,thermaloilinPTorinlinearFresnelsystems).ForPTplants,inparticular,costassessmentsperformedrecentlyhaveshownthata6-7%LCOEreductioncanbeachievedbydirectsteamgeneration(DSG)incomparisonwithoptionsbasedonheatingupthermaloilinplantswithoutthermalstorage.
Peculiaritiesduetotheexistenceofatwo-phaseflowinthereceivertubesintroducesometechnicaluncertain-ties,relatedtocontrolsinparticular,thatmustbefullyclarified.AlthoughthetechnicalfeasibilityofDSGinPT,CRandlinearFresnelplantshasbeenalreadyproven,therearemanyaspectsforoptimisationthatmustbefullyinvestigatedtoassessthecommercialpotentialofDSG.
24-Na/K60/40wt%:Percentageinweightof1stcomponent/2ndcomponentofthemixture
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Development of high pressure/temperature absorber tubes for direct steam generation DSGtechnologyallowsavoidingtheuseofanintermediateHTFbetweenthesolarfieldandtheconversioncycle,withapotentiallybeneficialeffectonplantcosts.Highefficiencysteamcyclesarecharacterisedbyhighsteamtemperatureandpressure.Theycanbeusedprimarilyinlineartypeconcentrators(PTandlinearFresnel),althoughtheremayalsobesomepotentialforCRapplications.DSGtechnologyusesthewater/steamfluiddirectlyintheabsorbertubes.Inordertohaveagoodconversionefficiency,steamcycleconditionsarerequiredwithpressureshigherthan100barat500°Cormore.Absorbertubesaretobebuiltaccordinglyandspecialcoatingscouldberequired.
7.1.1.4 StorageThepotentialtostorethermalenergytofollowthedemandisoneofthemostimportantadvantageofSTEcomparedtoPV.EnhancingthisfeatureatthelowestpossiblecostisessentialtoincreasetheshareofSTEinthefuture.
Advanced high temperature thermal storage systemsThetwo-tankmoltensaltconceptisprovenandreliable.However,duetosaltstability,themaximumoperatingtemperatureislimitedtoaround550°C.Therefore,newmaterialsandconceptsneedtobedevelopedtoprovideefficientandeconomicstoragesystemwhenworkingat600°Corbeyond.
7.1.1.5 Control and operation toolsUser-friendlyequipmentandproceduresforon-sitecheckingofopticalandgeometricalqualityofsolarconcentra-torsconstituteanimportanttool.Veryefficientqualitycontrolproceduresareimplementedduringtheassemblyofthesolarcollectorsattheconstructionsite,butthereisalackofequipmentandproceduresallowinganeasyandquickevaluationoftheiropticalandgeometricalqualityaftertheirinstallationinthesolarfield.
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Topics Objectives Parameter/Target/Action Short Mid Long
Mirrors Lightreflectivesurfaces
•Identifyanddeveloplight-weightanddurablereflectivesurfaceswithhighreflectance
Parameter:DurabilityDemonstratethedurabilityofaluminum,thinglassmirrorsandpolymerfilms
X
Glassreflectorswithanti-soilingcoating
•Reducemaintenancecostandplantwatercon-sumption=>enhancecom-mercialdeploymentofSTEplantsindesertareaswithhighsolarradiationlevels
Parameter:Waterrequirementformirrorwashing[m3/m2/y]Target:<0.015(waterconsumption=-50%insouthernSpain)LCOE=-0.1%
X
Mirrorglasswithhighersolartransmissivity
•Increasethereflectanceofglasssolarreflectorsandtheefficiencyofthereceivertubes
Parameter:Glasssolartransmittance(ρ)Target:ρ =0.93forglassthickness=3.5mmLCOE=-1%forCRLCOE=-2%PT&LF
X
Receivers Selectivecoatingswithbetteropticalproperties
•Increasesolar-to-thermalefficiency-ofthereceivertubesusedinPTandCLFRsystems-ofthetubularreceiversinCRsystems
Parameter1:Solaremittance(ε)Parameter2:Solarabsorbance(α)PTandLF:Target1:ε<0.1(450°C)Target2:α ≥0.96(vacuumconditions)LCOE=-1.5%CR:Target1:ε<0.25(600°C)Target2:α ≥0.94(stableatmosphericconditions)LCOE=-2%
X
Heat transfer fluids
Syntheticoilwithnewchemicalformulation
•Lowerthevalueofviscosityatlowtemperature
•AddPCM•Considerbinarysystems
Parameter:O&MsolarfieldcostTarget:5to10%reduction
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Lowmelting-temperaturesaltmixtures
•ReducethethermallossesovernightandtheriskforcrystallisationinthepipingofSTEplantsusingmoltensalt
=>reducemaintenancecosts
Parameter1:Meltingtemperature(T)andthermalstabilitylimitofthenovelsaltmixtureParameter2:OverallefficiencyηParameter3:Cost(C)
Target1:T≤100°C(goodthermalstabilityupto450°C)Target2:η =+4%(15.2%>15.8%)Target3:C<40%ofthecostofoilLCOE=-4%
X
Target1:T≤100°C(goodthermalstabilityT>=600°C)Target2:η =+6%(15.2%>16.1%)Target3:C<120%ofthecostoftheNa/K60/40wt%nitratesmixtureLCOE=-5.5%
X
Action:Implementationofasmallplant(<5MWe)toinvestigateO&Mrelatedissuesusingnewworkingfluidunderrealsolarworkingconditions
Pressurisedgas
•Increasesolar-to-electricefficiency
Parameter:overallconversionefficiency
DevelopmentofhighpressureabsorbertubesforDSG
•Developnoveldesignabsorbertubes,withsuitablemetalsandthicknesstowithstandpressureandtemperaturelimits
Parameter:Workingpressure(p)andtemperature(T)oftheabsorbertubesTarget1:p=125baratT=575°CforPTandLFTarget2:p=150baratT=700°CforCR
X
Storage Advancedhightemperaturethermalstoragesystems
•Developnewsystemsbasedonnewmaterialsornewconceptsinordertoobtaintechnicalandeconomicallyfeasiblesolutionsattemperaturesabove600°C
Parameter:Storageworkingtemperature(T)
Target1:T=600°CStorageconceptsforairreceiverswithT=800°Cby2015
X
Target2:StorageconceptsforairreceiverswithT>1,000°Cby2020
X
Control and operation tool •Developfaster&cheapertools&procedures
=>maximisesolarradiation=>improveefficiency
andLCOE
Parameter:Costandtimerequiredtoassesstheopticalqualityofalife-sizesolarconcentratorTarget:<2kW,<6h,totaluncertainty<1.5%(11.2x5.7mPTmodule,a120m2heliostat,oranyconcentratorwithanaperturearea≥30m2)Action:Implementationandevaluationofaprototypefortheintendedon-siteevaluationequipment
X
TABLEI:RESEARCHPRIORITIESFORCROSS-CUTTINGISSUES
Thecross-cuttingissuesthathavebeenidentifiedabovearesummarisedinthefollowingTable.Bythespecificparameters,itidentifiestargetsandactionitemswhereapplicable.
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7.1.2ParabolicTroughCollectors
Parabolictrough(PT)isbyfarthesolarthermalelectricity(STE)technologywiththewidestcommercialimplementationtoday,withahighnumberofcommercialplantsinoperation.However,thepotentialfortechnicalandeconomicimprovementsisstillhighandasignificantcostreductionoftheelectricitygeneratedbythistypeofSTEplantsispossible.
AsignificantR&Deffortisstillneededtoincreaseefficiencyandreduceoperationandmaintenancecosts.Togetherwithbetterdurabilityandreliability,thiseffortshouldleadtoaveryimportantcostreductionoftheelectricityproducedbythistypeofSTEplants.
Researchprioritiesdescribedbelowfocusonefficiencyanddurability improvementsandon thereductionofoperationandmaintenancecostsforPTs.AssumingabaselineLCOEof0.21€/kWhin2011fora50MWeSTEPTplantwithoutthermalstorage,and0.19€/kWhforaplantwith7.5hoursofthermalstorage,successfuldevelopmentandimplementationoftheseimprovementswouldleadtoachievingtheLCOE-relatedKPIestimatedbyESTELAfor2013(15%LCOEreduction)and2020(45%LCOEreduction).
7.1.2.1 ReceiversReceivertubesarethekeycomponentofsolarfieldswithPTcollectors,becausetheoverallsolarfieldefficiencyverymuchdependsontheirperformance.Improvementsrelatedtoreceivertubesmayincreasetheoverallplantefficiencyifhigherworkingtemperaturesareachieved;andmayalsoreducetheO&Mcostassociatedtothereplacementofthetubesthemselves,ifahigherdurabilityisachieved.
Evacuated receiver tubes suitable for higher temperaturesEvacuatedreceivertubesusingcurrentdesign(i.e.,metallicbellows,glass/metalweldsandgetters)andsuitableforhighertemperatures(550°Catthesteelpipe,atleast)needthedevelopmentofnewselectivecoatingswithbetterthermalstabilitythanthecurrentchoices.Achievinganimprovementofthereliabilityanddurabilityoftheglasstometalweldsathighertemperatureswithoutincreasingthecostisalsoanimportantgoalwithinthisresearchpriority.
Innovative receiver tube designsThisR&Ditemincludesnotonly innovativereceiverdesignswithvacuumandwithoutglass-to-metalwelds (theweldsarethemostcriticalpartincurrentcommercialreceivertubes)butalsostandarddesignswithimprovementstoreduceH2-permeationthroughthesteelpipe.
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7.1.2.2 Heat transfer fluidsThermaloilistheHTF(heattransferfluid)usedatpresentinPTSTEplants.Thermaloilhastwomajordisadvantages:
n Lowthermallimitof398°C,becausetheoilsuffersahighdegradationrateifthistemperaturelimitisexceeded.Itimposesatemperaturelimittothesuperheatedsteamproducedforthepowerblockandlimitsitsefficiency;
n HighO&Mcostsduetotheneedforsafetyequipment(becauseoffirehazards)andofapurificationplant(theso-calledullagesystem).
ThesetwodisadvantagesofthermaloilmaketheconsiderationofdifferentHTFsadvisableinordertoreduceO&Mcostswhileincreasingthepowerblockefficiency.
Pressurised gasPressurisedgas(e.g.CO2,N2,air,etc.),isusuallysuitablefortemperaturesofatleast500°C,whichcanleadtohigherefficienciesthanthecurrentthermaloilusedinparabolictroughplants.Althoughpressurelossesarehigherwithpressurisedgasthanwithliquids(duetohigherspeedsinthegas),thisproblemcanbesignificantlyovercomewithanoptimiseddesignofthepiping.
The direct steam generation once-through option
InaDSG(directsteamgeneration)solarfieldoperatedinonce-throughmode,thepreheating,evaporationandsteamsuper-heatingsectionsofeachrowinthesolarfieldaredirectlyconnected:theendofeachprecedingsectionisdirectlyconnectedtothebeginningofthenextsectionwithoutanydeviceinbetween.
Sincetheonce-throughoperationmodedoesnotneedwater/steamseparatorsorwaterrecirculationsysteminthesolarfield,theinvestmentcostforaDSGsolarfieldtooperateinonce-throughmodeislowerthanifoperatingininjectionorrecirculationmodes.
Ontheotherhand,withtheonce-throughmode,technicalrequirementstoensureastablesteamtemperatureandpressureatthesolarfieldoutletintroducesomeuncertaintiesontechnicalandcommercialfeasibility.ExperimentalR&Disneededtoassessandaddresstheseuncertainties.
Direct steam generation: assessment of saturated steam vs. superheated steam
ADSGsystemcanproducesaturatedorsuperheatedsteam,andbothoptionshaveadvantagesanddisadvantages.Anin-depthstudyofbothoptionsunderrealsolarconditionsisimportant.
ThePSAHTFtestfacility,whichisusedforevaluationofnewcomponentsandparabolictroughdesigns(CIEMAT-PSA,PlataformaSolardeAlmería)
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Molten saltTheuseofmoltensaltasHTFwouldhaveclearadvantageswhencomparedtothethermaloilcurrentlyusedinPTSTEplants.Fromanenvironmentalpointofview,sodiumandpotassiumnitrateshavebeenusedinagricultureasfertilizersforalongtime,andthemaximumworkingtemperaturewithanaffordablecorrosionrateinmetalliccomponentsishigherthan525°C.
Atpresent,thereareonlydemonstrationorexperimentalfacilitiesthatusethesamesaltmixture(Na/Kbinarynitratesmixture)asheatstoragemediumorasHTF.Themixturemakesitpossibletoreachupto550°Cinthesolarfieldinadirectsystem–moltensaltdirectlyheatedinthereceivertubesofthePTcollectors,withoutusinganyotherHTFbetweenthesolarfieldandthemoltensaltsystem.Duringoperation,thefluidcirculation(nightandday)avoidsanykindofproblems.However,duringmaintenanceoperations(whilecharginganddischargingtheloops,orwhencoolingorwarmingoftheloopsbyanauxiliaryheatingsystem)thelowerthefreezingtemperaturetheloweraretherisksofoccurrenceofsolidifiedsaltplugsinsidethepipingduringcoldperiods.
7.1.2.3 System components with enhanced propertiesTheoperationalexperiencegainedbycurrentSTEplantswithPTcollectorsshowsthatsomeimprovementsconcerningsystemcomponentsarenotonlypossiblebutalsoadvisablebecauseoftheirpotentialtoreduceO&Mcosts.Severalresearchprioritiesarerecommendedhere:
Interconnecting elements for receiver tubeInterconnectingtheelementsmaylowerthecostsassociatedwiththeball-jointsandflexiblehosesnowusedtoconnectthereceivertubesofadjacentPTcollectors,aswellastheinletandoutletofeveryrowwiththeheaderpiping.
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FIGURE13:Different interconnecting elements used nowadays
Ball-jointconnection Flex-hoseconnection
Autonomous drive units and local controlsThehydraulicdriveandlocalcontrolunitsbeingusednowinPTplantsrequireapowersupplyfromcentralswitch-boardcabinetslocatedclosetotheplantcentralcontrolroom.Thousandsofmetersofelectricalwiresarerunalloverthesolarfieldtosupplyelectricitytoeachdriveunitandlocalcontrol.Thousandsofmetersofcommunica-tionwiresarealsousedtosendandreceivecommandstoandfromthelocalcontrolstothemaincontrolroom.Uninterruptedpowersupplyisalsorequiredtoassuresafetyconditionsincaseofafailureintheconventionalpowersupply.DevelopmentofautonomousdriveunitsandwirelesscontrolsystemspoweredbysmallPVcellsandbatteries,similartothealreadydevelopedandpatentedforthe“AutonomousHeliostatConcept”,couldlowertheinvestmentcostwithoutpenalisingthereliabilityanddurabilityofthesystem.
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7.1.2.4 System size, component manufacturing and other improvementsThescale-upeffectisveryimportantinthetechnologyofPTcollectors,becausetheinfrastructureneededfortheon-siteassemblyofcomponentscanbeoptimised.SincetherearemanyelementscomposingaPTcollector,theoptimisation(e.g.automation)ofthemanufacturingprocesscanalsoplayasignificantroleinthefinalinvestmentcost,andthereforeontheLCOEofacommercialSTEplant.
Improved collector designsNewPTcollectordesignscouldleadtoasignificantreductionintheplantinvestmentcosts.Thiscostreductioncanbeachievedindifferentways,suchasincreasingthecollectorsizeandoptimisingthemanufactureandassemblyprocessestoreducemanpowerrequirements.
7.1.2.5 Control and operation strategyTheamountofthermalenergydeliveredbythesolarfieldcanbeincreasedwithoptimisedcontrolsystemsandastrategythatwouldmaximisetheamountofsolarradiationcapturedbythesolarcollectorsduringthesunlighthours.TheoperationalexperiencegainedbySTEplantsalreadyinoperationhasshownthatthesolarfieldoutputcanbesignificantlyincreasedduringdayswithsoftcloudtransientsifpropercontrolandoperationstrategiesareimplemented.
Solar field controlInexistingplants,thesolarfieldoutlettemperatureisusuallycontrolledbypartiallydefocusingsolarcollectorstochangetheamountofsolarenergycollectedandtransmittedtotheworkingfluid.Sincethispartialdefocusingreducesthesolarfieldactivecollectingarea,newcontrolapproachesbasedonthesolarfieldmassflowinsteadofthesolarfieldcollectingareawouldincreasetheamountofsolarenergycollectedatthesolarfieldincreasetheoverallplantefficiency.Developmentofnewadvancedcontrolandoperationstrategiesshouldthereforebebasedonthemaximisationoftheamountofsolarradiationcollectedduringbothcleardaysanddayswithcloudtransients.
Early detection of HTF leakageLeakagesareaconcerninPTplantsusingthermaloilastheworkingfluid.Theearlydetectionoftheseleakagesisthekeytoavoidspillsandtopreventpossiblefires.Oilspillsalsocausesoilcontamination:savingsinoperatingcostsandanimportantreductionofenvironmentalhazardscanbetargetedwithdedicatedinstrumentsandmethodstoalertaboutaleakage.
Auxiliary heating system for molten salt plantsTheuseofmoltensaltasworkingfluidinPTsolarfieldsrequirestheinstallationofanAuxiliaryHeatingSystem(AHS)forthereceivertubes,pipingandothercomponentsthroughoutthemolten-saltcircuit.AlthoughtheAHSshouldoperateonlyforshortperiodsduringtheyeartomeetthemaintenanceneedsofthesolarplantorinthecaseofaccidentsthatrequiretheAHSsupport,thecurrentinvestmentcostsofthisAHSarehigh,andsoistheassociatedelectricityconsumption.Thesecostsshouldbecompensatedbythelowercostsofthemoltensalt,i.e.,lowerpurchasingcostandlowerdegradationrate(longerlifetime),incomparisontooil.
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Topics Objectives Parameter/Target/Action Short Mid Long
Receivers Evacuatedreceivertubessuitableforhighertemperatures
•Increasesolar-to-electricplantefficiency
Parameter:Maximummetaltemperature(T)withspecificoperatinglifewarranty
Target1:T=575°Cin2013LCOE:-5%
X
Target2:T=600°Cin2020LCOE:-6%
X
Action:Qualificationofprototypesatexistingsolartestfacilities
X
Innovativereceivertubedesigns
•ReduceO&Mcostsandincreasereceivertubeslifetime
Parameter:CommercialevacuatedreceiverswithlowerO&Mcosts
Target1:Evacuatedreceivertubeswithoutglass/metalwelds,lifetime25y
X
Target2:Commercialevacuatedreceiverswithglass/metalweldsandaH2permeation50%lowerthanin2011LCOE:areductionof1%intheyearlyrepositionrateofreceivertubeswouldreduceLCOEbyabout1%.(from200to198€/MWh)
X
Heat transfer fluids
Compressedgasses
•Increaseoverallplantefficiency
Parameter:MaximumworkingfluidoperatingtemperatureTarget:T≥500°C
X X
•Decreasethermalstoragesystemsize
•Reduceoilenvironmentalimpact
Action:achieveforsmallSTEplants(<15MWe)thesameLCOEasthatofbiggerplantswithRankinecycle
X
TheDSGonce-throughoption
•ReduceLCOE(Feasibilitytobeassessedunderrealsolarconditions)
Parameter:LCOE[€/kWh]Target:LCOE:-9%(ifsolarfieldconnectedtoaPCMstoragesystemof50€/kWhth)
X
DSG:assessmentofsaturatedsteamversussuper-heatedsteam
•Increaseworkingtempera-tureandreduceinvestmentcostduetoasimplificationoftheplantconfiguration
•=>LCOEreduction
Parameter:LCOE[€/kWh]Target:LCOE:-6%(w/oTES)-9%(wTES50€/kWhth)Action:implementationofasmallplant(between3and5MWe)abletooperatewiththetwosolarfieldoptions
X
Moltensalt •Increaseworkingtemperatureforahigherpowerblockefficiency
•Reducemoltensaltquanti-ties=>reducestoragecost
•Reducefirehazard•Reducethefreezing
temperature
Parameter:ηsol-elec/y&LCOE[€/kWh]Target:ηsol-elec/y:+5%(15.2%to16%)LCOE:-5%
X
System com-ponents with enhanced properties
Interconnectingelementsforreceivertube
•ReduceinvestmentcostsandO&Mcosts=>reducecostsofelectricity
Parameter:Investmentcosts(purchasingandinstallation)ofthenewinterconnectingelementsandguaranteedlifetimeTarget:2,500€percompleteinterconnectionbetweenadjacentcollectorsLCOE:-1%(25%costsreduction)
X
Autonomousdriveunitsandlocalcontrols
•ReduceinvestmentandO&Mcosts
Parameter:Totalcost(purchasing+installation)ofthedriveandlocalcontrolunitsTarget:4,000€LCOE:-1%
X
System size, component manufactur-ing and other improvements
Improvedcollectordesigns
•Developnewcollectorde-signswithlowercostsandmanpowerrequirements
Parameter:Solarfieldinvestmentcost[€/m2]Target:-25%comparedto2011LCOE:-6%
X
Control and operation strategy
Solarfieldcontrol
•Moreefficientcontrolandoperationstrategies=>increasesolartoelectricefficiency
Parameter:yearlyaverageηsol-th
Target:ηsol-th:+5%(consideringabaselinesolarfieldefficiencyof46%forPTplantsin2010)LCOE:-9%Action:ImplementationinacommercialPTplantbyreplac-ingtheoldcontrolsystembasedoncollectorsdefocusing
X
EarlydetectionofHTFleakage Target:Availabilityofaninnovativeearlyleakagedetectionsystem
X
Auxiliaryheatingsystemformoltensaltplants
•Developmorecost-effectiveauxiliaryheatingsystemsformoltensaltplants
Parameter:AHSspecificinvestmentcost(Ci)in€/m2andyearlyelectricenergyconsumptioncost(Cec)in€/m2ofsolarfieldforalifetimeofthesolarplantassumedtobe25years,comparedwiththecost(Coil)ofasinglechargeofoilinthesolarfieldforthenumberofsubstitutionsforeseeninthelifeofthesolarplant,assumedtobe4Target:Ci+Cec*25<Coil*4LCOE:-1%
X
TABLEII:RESEARCHPRIORITIESFORPARABOLICTROUGHCOLLECTORS
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7.1.3CentralReceivers
Thecentralreceiver(CR)orsolartowertechnologyhasagreatpotential.BecauseofthehighconcentrationratiosthatcanbeachievedinCRsystems,thesecanoperateathightemperatures.Thehighoperatingtemperaturesmakeitpossibletoachievehighersolar-to-electricityconversionefficienciesthanthosepossiblewithothertechnologies.
TotransformtheCRpromiseintoreality,asignificantR&Deffortisstillneeded.Thiseffortshouldbetargetedtoimproveefficiencies,increasedurabilityandreliabilityandreduceinvestmentandO&Mcosts.Theresearchpriori-tiesdescribedbelowareintendedtoachievesubstantialprogressineachofthetechnologytargetssummedupinthetableattheendofthechapter.
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7.1.3.1 Heliostat fieldGeneralissuesregardingmirrorshavebeenalreadydescribedinpoint7.1.1.
Asageneralcomment,itmaybestatedthatmechanicalrequirementsaremuchhigherinparaboliccurvedmirrorswheretemperedtechniquesareapplied.Inthecaseofheliostatfields,floatglass,acheapersolution,ispreferred.
However,reflectivityimprovementsareessential,andreflectivitymaybeimprovedbyreducingthethicknessofthefrontlayerofthemirrors.Incomparisonwithconventionalflatmirrormanufacturingtechniques,costandperform-anceconsiderationsmayjustifynewmanufacturingtechniquestoreducethethickness.
Optimisation of the heliostat field layouts YearlyaverageopticalperformancesofheliostatfieldsincurrentlargecommercialCRplantsareoftheorderof55%to60%.Inthoseplants,thesolarcollectionandconcentratingsystemsarecomposedofoneheliostatfieldandasingletower.Thereareotheroptionsthatshouldbeexplored,suchastheuseofmultiplesmallertowersdeliveringtheHTFtoacentralpowerblockwithstorage.
Wireless heliostat control systemsInordertotrackthesunproperlyandtohaveanautonomousheliostatfield,atwo-waycommunicationsystembetweenthecentralcomputer,thegroupcontrolboxesandtheindividualheliostatcontrolboxesmustbecontinu-ouslyinoperation.Somedevelopmentsareunderwaytoassessthefeasibilityofwirelessconnectionsbetweentheheliostatindividualcontrolboxes,thegroupcontrollersandthecentralcomputerforthiskindofautonomouspowersupplyandasafeandeffectivecontrolofthefield.
Theaimistodevelopsecureandreliablewirelessheliostatcontrolsystemswithalowoverallcost.
Optimisation of heliostat technologyState-of-the-artinheliostattechnologyisrepresentedbytheso-calledT-typeheliostatconfigurations.Thepotentialofdifferentdrivetechnologiesaswellasotherorientationsoftherotationaxesthatallowforimprovedperformanceand/ordenserheliostatpositioningshouldbeexplored.
7.1.3.2 ReceiverThereceiveristheheartofCRplantsanditsdesignisstrictlydependentonthechosenworkingfluid.Efficiencyanddurabilityaretheessentialconcernsofeachapproach.
Advanced high temperature receiversTheCRtechnologycanachievehighconcentrationratiosontothereceiver,usuallyoneorderofmagnitudehigherthanPTcollectors.Thehighertemperaturesintheworkingfluidmakehigherconversionefficienciesandbetteroverallperformancepossible.Handlinghighradiationfluxesathightemperaturesisaverychallengingissue,however,andfurtherdevelopmentisneededinnewreceiverconceptsandmaterials.Amongthosenewconcepts,directabsorptionreceiversofferthepotentialtoaddressthematerialchallengeswhilemakinghighefficienciesachievable.
New engineered materials for high temperature solar receiversResearchanddevelopmenttoimprovetheopticalandmechanicalperformanceanddurabilityofmaterialsisneeded.RecentdevelopmentsondesignsshowimprovedperformanceonmetallictubereceiversthroughimprovementsintheopticalandmechanicalfeaturesofthecoatingsandoftheInconelbasedalloys.
Reachingoutlettemperaturesof1,000°Cormorecanonlybeachievedbyusingceramicmaterialseitherinstuddedtubedesignsorpressurisedvolumetricreceivers.Headersandjoiningpartsoftheceramictubesareimportantchallengesthatneedtobeaddressed.
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7.1.3.3 Heat transfer fluidsWorkingfluidssuitableforhighertemperaturesandradiationfluxesaretobeselected.
Molten salt, othersNewmoltensalt,liquidmetals,airorCO2aswellsteamathighertemperaturesandpressureshavetobeinvestigated.
Moltensaltappears tobe theshort-termnextstepwithworking temperaturesup to620°C; thesewillmakesupercriticalsteamcyclespossible.Ternaryfluidsratherthanthecurrentbinarymixturescouldprovideahighertemperaturerangeandlowercosts.
AirandCO2allowforworkingtemperaturesabove1,000°Candtheycanbetheprimaryfluidsforsolarcombinedcycles.
Directsuperheatedsteamatsupercriticalconditionscanbealsoconsideredforfuturepowerplants.Thecurrenttubepanelmustbecorrespondentlyadaptedtoovercomeimportantmechanicalandthermalissues.
Anotherpromisingoptionisparticlereceiversystems.Thesesystemsofferthepotentialforefficientoperationatevenhighertemperatures.Inthisoption,theheatedparticlesalsoserveasthestoragematerial.
7.1.3.4 New conversion cycles and systemsCurrentreceiveroperatingconditionsonlyallowforconventionalRankinecycles.Reachingmorethan600°Cinasupercriticalsteamturbinesataworkingpressureof25MPacouldprovideasignificantincreaseintheconversionefficiencyand,therefore,ontheplantperformanceandcost.
Usingairasprimarycoolantfluidinthereceivermakesitpossibletoconceiveasolarcombinedcycleandtoincreaseconsiderably theconversionefficiencyfromthermalenergy toelectricity.Nevertheless,acombustionchamberbetweentheairreceiverandtheturbinehastobedesignedinordertoreachandmaintainstabletheoptimalinletconditionsintothegasturbine.
Inaddition,newpossibilitiesmayappearintermsofhybridisationwithbiomass.Withgasifiedbiomass,forexample,onecanconceivearenewablecombinedcyclewherebiomassisusedfortheBraytoncycle(opencyclebasedonairorgasturbinesreachingveryhightemperatures)whilesolarenergyisusedfortheRankineone(aclosedcyclebasedonwater/steamturbines,operatingatlowertemperaturesthantheBraytoncycle).Gasifiedbiomasscouldalsobeusedinasolarcombinedcyclewithairreceiversinsteadofnaturalgas,recoveringthehightemperaturesfromtheBraytoncycleandenhancingtheoverallefficiency.
Advanced power cycles and thermal storage system integration schemesAdvancedpowercyclesandthermalstorageintegrationschemes,suchascombinedcyclesorsupercriticalsteamcycles,offergreatpotentialforperformanceimprovements,andtheymustbeexplored.
Advanced hybridisation schemes with other renewable energy sourcesAdvancedhybridisationschemeswithotherrenewableenergysourcessuchas integratedsolar-biomassplantsshouldtobeexplored.
BiomassboilersorHTFheaterscanbeeasilyintegratedintotheSTEdesigns.BiomasscanthenfunctioneitherasabackupofthesolarenergywhenheatingtheHTFindifferentoperationalmodesorasanalternativetothesolarradiationproducingorsupplementingthesuitablesteamconditionsfortheturbine.Althoughthistechnologycanbeconsideredstate-of-the-art,thereisnoSTEplantusingityet.Therefore,appliedresearchisalsoneededtooptimisetheintegratedoperation.
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Secondary concentratorsSecondstageconcentratorsforheliostatfieldsaremeanttoproducehighersolarenergyfluxlevelsincomparisontothoseachievedatconventionalsolarfurnaces.Higherconcentrationfactorswillpermithigheroperatingtempera-tures;leadingtohigherthermodynamicconversionefficienciesorcreatingbetterconditionsforotherapplicationsofconcentratedsolarenergy(applicationssuchassolarfuelsproduction,thermo-chemistryathightemperatures,etc.).
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Secondstageconcentrationcanbeachievedat the topof thetower,butcanalsobecombinedwithotheropticalsolutionssuchasthebeam-downreflectorsthatredirecttheimpingingraysfromtheheliostatfieldontoareceiverplacedatgroundlevel.
Forlargeheliostatfields,effectiveopticalsolutionsarelikelytorequiretheuseofacombinationofsecondstageconcentrators(multiplesecondstageconfigurations)facingdifferentportionsofthefield.
For largeflux levels,coolingof thesecondaryand/or tertiarymirrors isstillan issuewhich requires furtherattention,inparticulariftheenergyabsorbedbythemirrorsproducestemperaturesthatmayleadtotheirquickdegradationordestruction.
Solarfurnacesorcavitiesatgroundlevelcombinedwithbeam-downsolutions,arealsodifferentintheirgeometryandconfigurationfromconventionalfurnacesattowerlevel,and,therefore,willconstituteanimportantR&Dtopicbythemselves.
FIGURE14:Typical secondary concentrator redirecting the impinging sun rays from the heliostat field to a receiver placed at ground level
ThenewVariableGeometryCentralReceiverTestFacilityattheCTAERpremisesinTabernas,Almería.Inthefirstphase,recentlycommissioned,thefacilityonsistsofafieldof13heliostatsmountedonmobilesupportsandatowerwitharotatingplatformontop,equippedtohostdifferenttypesofreceivers.ThefacilityhasbeencommissionedinOctober2012
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Topics Objectives Parameter/Target/Action Short Mid Long
Heliostat Field
Optimisationoftheheliostatfieldlayouts
•Exploreadvancedopticaldesigns(bio-inspired,multicavitiesorpoli-towers)
Parameter:ηSol-thTarget:ηSol-th=5%
X
Wirelessheliostatcontrolsystems
•Developmentofalowoverallcost,secureandreliablewirelessheliostatcontrolsystem
•Wideuseofwirelesssystembefore2020
Parameter:€/m2
Target:-5%X
Optimisationofheliostattechnology
•Developmentofadvancedstructureanddrivemechanisms
Parameter:€/m2
Target:-15%X
Receiver Advancedhightemperaturereceiver
•Improvetheperformanceanddurabilityofconventionalpressurisedtubereceiversworkingwithdifferentfluids
•ExploreadvancedCRdesigns(highefficiencyandhightemperatureheatpipe,particles,andcompressedgasreceivers)
•Exploresolarreceiverdesignsbasedontheuseofnewmaterialsandofmeta-materialswithimprovedthermalandopticalproperties
Parameter:Outletreceivertemperature(T)inairpressurisedmodulesTarget:T=1,000°C(Fortubes<8mandvolumetricmodules<50m2)
X
Newengineeredmaterialsforhightemperaturesolarreceiver
•Increasetubecoatingabsorptivity
•Reducetimedegradationeffect
•Increasemechanicalcharacteristicsandpanelarraydesignstowithstandhigherfluxesathighertemperatures
Parameter:Maxpressureradiationflux(p)Target:p=1.5MW/m2
X
Heat Transfer Fluids
Moltensalt,others
•Increaseofreceiveroutlettemperaturewithsafeandstableconditions=>increaseplantperformance
Parameter:ExtendeduseofnewfluidsTarget:Moltensaltusewithworkingtemperatureupto620°CAction:Directsuperheatedsteamatsupercriticalconditionsinfuturepowerplants
X
New conver-sion cycles and systems
Advancedpowercyclesandthermalstoragesystemintegrationschemes
•TakeadvantageofthehightemperaturesthatcanbereachedwithtowersystemsbyimplementingthemostappropriatecyclesdependingontheHTFusedinthereceiver
Parameter:ηSol-thConversionefficiencywithsolarcombinedcycleTarget:ηSol-th=+25%
X
Advancedhybridisationschemeswithotherrenewableenergysources
•Usebiomassinorderto:-IncreasedispatchabilityandfirmnessofSTEplants-ReduceLCOE
Parameter:PlantrobustnessandreliabilityAction:Implementhybridsolar/biomassplantsinawiderangeofcoverage
X
2013:Simpleintegrationconcept X
2015:HybridplantsusinggasifiedbiomassclassicalRankinecycles
X
2020:CombinedcyclesusingbiomassfortheairandsolarenergyforthesteamLCOE=-10%
X
Secondaryconcentrators Parameter:Breakthroughapplications2020:Implementlargerinstallations(higherthan10MWth)forspecificapplicationsdifferentthanelectricitygeneration
X
TABLEIII:RESEARCHPRIORITIESFORCENTRALRECEIVERS
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7.1.4LinearFresnelReflectors
Itisimportanttoplaceastrongemphasisonearlydevelopment,demonstrationandup-scalingprojectsdesignedtocreatetherightopportunitiesfortheFresneltechnologytofollowitslearningcurveandreachastatusofmaturitywhereitcanexhibitandproveitscompetitiveness.Referencedemonstrationsprojectsaremajorrequirementsforthebankabilityofatechnology.
Thestate-of-the-artlinearFresneltechnologyonthemarketisasingleormultipletubereceiverwithadirectlyattrib-utedmirrorfield(primaryconcentrators),wheresaturatedsteamisgenerateddirectlyinthesingleormultiple-tubereceiveratabout270°C.OtherHTFsuchasthermaloilsarealsoused.Insomedesignswithsingletubereceiversthereisasecondstageconcentrator,concentratingradiationfromtheprimaryconcentratorsontothereceiver.Thesedifferentconfigurationsstillexhibitalowsolartoelectricityconversionefficiency(intheorderof8to9%)becauseofthelowoperationtemperatureandthesimpleturbinedesigns.Itisimportanttomodifythecollectorstoproduce(directlyorindirectlythroughanotherHTF)superheateddirectsteamat450°Candabout120bar.Then,withmoresophisticatedthermodynamiccyclesusingturbinesforsuperheatedsteam,averyimportantandpromisingalternativeforlow-costelectricityproductionathigherefficienciescanbedeployed.
InordertomakethelinearFresneltechnologybankable,itisnecessaryto:
n Demonstrateandvalidatenewconceptsandcomponents,includingcontrolandoperationstrategies;n Achieve linearFresnel reflectorsystemswithadaptedstorageconcepts, includingoptimisedchargingand
dischargingoperationandpressure-steammanagement;n Ensurethestabilityofoperationunderfluctuatingconditions;n Designpredictivecontrolstrategiesformaximisedusefulsolargains,profitandminimisedstressonplantcomponents.
Efficiencyimprovementandcostreductioncancomethroughanumberofdifferentdevelopmentsattheleveloftheopticalpropertiesofmaterials,newmaterialsandmanufacturesolutions,etc.
7.1.4.1 MirrorsAnimportantresearchtargetistheincreaseinopticalefficiencyforbothdesign(atmidday)andoff-designcondi-tions.Theopticalperformancedependsontheopticalconfiguration.InthecaseofFresnelopticstherearedesignsthatconsiderjustaprimarysetofmirrorsandthereareotherswherebothprimaryandsecondstageconcentrationarepresent.Optimisedperformancewillresultfromchangesinthesize,shapeandplacementofthemirrors,andfromtheopticalpropertiesofallthematerialsused.
Second stage concentration and optical performance optimisationIncreasingconcentrationleadstohighertemperaturesandhigherefficiencies.However,thisshouldnotbeachievedbysacrificingthedesirablehighopticalefficiencyofthewholesystem.Thisimpliesthatnewdesignsrequirethejointoptimisationofprimaryandsecondaryconcentrationstagesthattakeintoaccounttheconservationofradiantpowerperareaandsolidangle(i.e.“etendue”conservation)atallstagesofopticalcollectionandtransmission.
Solutionswillbedifferentforevacuatedandnon-evacuatedtubularreceivers,requiringspecificdesignsandresultingindifferentfinalsolutions.
Secondstageconcentratorscanbedesignedforevacuatedandfornon-evacuated tubular receivers,andthedesignshouldminimiseopticalgaplosses.
Primary mirrors performance and manufactureMirrorperformanceiscrucialandlinearFresnelmirrorsarecurrentlyfabricatedfromflat(thin)glassmirrors,forcedtobeslightlycurvedtoaccommodatetheproperprimaryperformancerequirements.Alternatively,thinfilmscanbegluedorappliedoveralreadyslightlycurvedsupportingsurfaces.Thesetechniquesarenotyetmassivelydevel-opedandtherearemanypossiblepracticalwaysstilltobeexplored.Shapeaccuracyisthekeyformirrorswithlargedistancetothefocalline.Propertiessuchasstiffness,torsionresistanceandopticalpropertiesofthereflectingsurfacesareveryrelevanttotheopticalperformance.
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7.1.4.2 ReceiversReceiversareanintegralpartofareceivercavity.Theperformanceof the linearFresnelconcentrator isverydependentonthethermalbehaviourofthecavity,withorwithoutsecondstageconcentration.Receiverswiththeproperemissivityandabsorptivityarerequiredforoperationat500°C.Thetypeofreceiver,evacuatedornon-evacuated,isdeterminantofthekindofR&Dneeded.
Evacuated tubular receiversThebestevacuatedtubesforlinearFresneltechnologiesarenotnecessarilythesameastheonesstandardisedforPTcollectors.Animportantdesignissueisthecost-effectivechoiceoftheprimarymirrorwidth,thenumberofmirrors,thesecondaryconcentratordesignandthetubediameter.Acost-optimisedconfigurationwillprobablyneeddifferenttubediameters.Secondstageconcentrationisalsoparticularlysensitivebecauseoftheradiationlossinthegapbetweenthetubes.ThesizeadvantageofLFcollectors–i.e.thefactthatverylargeprimarymirrorscanbeconsidered–islostwhenusingevacuatedtubeswhichwereoriginallydesignedforsmallerPTaperturewidths.
Non-evacuated tubular receivers and receiver cavitiesNonevacuatedreceivercavitiesarepresentlybeingusedinlinearFresneltechnologies.However,goingfrom270°C,whichisthecurrentdaypractice,tomorethan450°Coreven550°Crequiresanewgenerationofmaterialsandmaterialscombinationsforthecavitytubesandcoatingswhichwillhavetobestudied,developedanddemonstrated.
7.1.4.3 Heat transfer fluidsTheresearchinHTFshouldaddresstheissuesarisingfromraisingthetemperaturefrom270°C,wherewetsteamcanbeproduced,toabout500°C,forhigh-pressuresuperheatedsteamorabout560°C,formoltensalt.Usingsteam,thethermodynamicefficiencyofthepowerblockcanbevastlyenhancedfromaround25%tocloseto40%.
Superheated direct steam productionTheuseofenvironmentally friendlywater/steamas theworkingfluid isstandardin linearFresnelsolarfields.However,superheatingandcontrolstrategieshavetobeinvestigatedmorethoroughly.
Peculiaritiesduetotheexistenceofatwo-phaseflowinthereceivertubesofthesolarfieldevaporatingsectionintroducessometechnicaluncertaintiesthatmustbefullyclarified.AlthoughthetechnicalfeasibilityofDSG(directsteamgeneration)inlinearFresnelcollectorshasalreadybeenproven,therearemanyaspectsforoptimisationthatmustbefullyinvestigatedtoassessthecommercialpotentialofDSG.
Molten saltTheuseofmoltensaltastheworkingfluidinthesolarfieldcouldreplacethecurrentoil/moltensaltheatexchangers,reducingcostsandincreasingefficiency.Ifalowermeltingpointiscomplementedwithgoodthermalstabilityattemperaturesabove450°C,theimprovementwouldbeevenmoreimportantbecauseitwouldallowbothhigherpowerblockefficienciesandasmallersizeofthethermalstoragesystem.
Pressurised CO2 or air in non-evacuated receiversTheuseofcompressedairasHTFisanentirelynewpossibilityandmustbestudiedanddemonstratedfor thekindofextendedtubularreceiverswhichareappliedinPTandlinearFresneltechnologies.
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7.1.4.4 Control and operation strategyAgeneralaimshouldbetominimiseenergyandhydraulicpressure lossinparallel loopsandtoincreasetheoverallplantefficiency.
Particularfocusshouldbelaidonthetrackingsystem.
Tracking optionsLFandcompactlinearFresnelreflectors(amultiplereceiverconfiguration)withsecondstageconcentrationandnewsolutionsthatconservethe“etendue”,canbenefitfrommoresophisticatedaimingstrategies.Astrategymaybebasedontrackinglongrowsindividually;alternatively,itmaybebasedonmovingcompletegroupswithonemotor.Inaddition,thecommunicationbetweenthetrackingmotorsandthecontrolcentrecanbeachievedindifferentways.
7.1.4.5 Field design and configuration
Hybridisation of collector fields with different performance parametersTowerandLFcanbecombinedinordertoboostoperationtemperatures.OnepossibilityistouseLFforthephasechangepartoftheheatingcycleandthetowerforsuperheating,withthegoalsofreducingcostandlanduse.AnotherpossibilityisthecombinationofacheapersaturatedsteamlinearFresnelconfigurationwithsuperheatinglinearFresnelcollectors.
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Topics Objectives Parameter/Target/Action Short Mid Long
Mirrors Secondstageconcentrationandopticalperformanceoptimisation
•Increaseconcentrationbyuseofsecondstageoptics•Optimisesimultaneouslyprimaryandsecondarymirrors•Designoflow-weight,modularand
heatresistantcavityconcepts
Parameter:ImprovemaintenancerequirementsandreliabilityTarget:Lifetime=20years
X X
Primarymirrorperformanceandmanufacture
•Newmaterialsandsupportconstructionsforprimarymirrors
•Increaseopticalefficiency(mirrorwidth,accurateshapeandhighrigidityparameters)
•Lowerweightandreducecomponentcosts
Parameter:€/m2
Target1:-5%X
Target2:-10% X
Receivers Evacuatedtubularreceivers
•Newmaterialsandcoatingsfornon-evacuatedandevacuatedreceivers(forT~500°C)
•Newproductiontechniquesandconfigurations(relationbetweentheinnerandtheoutertubediameter)
Parameter:Temperature(T)Target:T=500°C
X
Non-evacuatedtubularreceiversandreceivercavities
•Multipletubularreceiversarrangedindifferentgeometriesandadaptedtothesecondstageconcentrators
Parameter:€/mTarget1:-5%
X
•Newmaterialsandnewselectivecoatingsforhightemperatures
•Gasfilledcavitiesandotherconvectionsuppression/reductiontechniques
•Insulationmaterials,connectors,bearings,cover,betteradaptedtothehighoperatingtemperatures
•Newmaterialsforsecondstagemirrorscapableofwithstandinghightemperaturesresultingfromenergyabsorption
•Coverswithlowemissivity/anti-reflectivecoatings
Target2:-10% X
Heat transfer fluids
Superheateddirectsteamproduction
•Raiseoperatingtemperatureforincreasedthermodynamiccycleefficiencyconversion=>LCOEreduction
Parameter:LCOE[€/kWh]Target:LCOE:-10%
X
Moltensalt •Newmoltensalt:-Freezeprevention/riskreduction-Othermaterialsorsystemconcepts-Cheapsaltcompositions•Raiseoperatingtemperatureforincreased
thermodynamiccycleefficiencyconversion•Reducethecostandincreasetheefficiency
ofthethermalstoragesystem•Reducesizeofthethermalstoragesystem•Proofconceptinnon-evacuated
tubularreceiverconfigurations•Proofconceptinevacuatedtubular
receiverconfigurations•Prooffreezingpreventionmeasures
Parameter:verificationoffeasibilityAction:Twolevelsofinvestigation:1.experimentalinasmall
solartestfacilitytoprovethetechnicalfeasibility
2.O&Mrelatedissuesusingthenewworkingfluidinasmallplant(i.e.<5MWe)underrealsolarworkingconditions
X
PressurisedCO2orairinnon-evacuatedreceivers
•Optimisethewholecollectorfieldforpossiblenewconcentrationfactorandreceiverconfiguration
•Newheatextractionloop(pressureandtemperatureoptimisationinviewofbetteroverallenergyperformance)
Parameter:Temperature(T)Target:≥550°C
X X
Control and operation strategy
Trackingoptions
•Mosteffectiveaimingstrategies•Reducecostswithparasiticlosses•Controlcommunicationstrategies•Reductionofmaintenance
Parameter:LCOETarget:LCOE:-3%
X
Field design and configuration
Hybridisationofcollectorfieldswithdifferentperformanceparameters
•Checkthecostreductionpotentialusingdifferentmaterialsintemperature-specificcollectorfieldsegments
Parameter:cost/m2
Target:-5%X
TABLEIV:RESEARCHPRIORITIESFORLINEARFRESNELREFLECTORS
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7.1.5ParabolicDishes
Themostattractivefeaturesoftheparabolicdishtechnologyare:
n Highefficiencyin theconversionofsolar radiation toelectricity,derivedfromtheability tooperateathightemperaturesthankstothehighconcentrationratiosachievable;
n Modularityandnegligiblerequirementofwaterforenginecooling,whenthepowerconversionsystemisbasedonStirlingenginesorgasturbines.
ThedevelopmentofthistechnologyhasbeenverycloselyconnectedtoStirlingengines.Infact,thehighestrecordintheconversionofsolarradiationtoelectricityhasbeenachievedwithacombinationofaparabolicdish(PD)concentratorandaStirlingengine,aconfigurationcommonlyknownasdish-Stirlingsystem.
Dish-Stirlingsystemshaveattractedmuchattentionduetotheirhighefficiency,modularity,negligiblewaterconsump-tionandpotentialformass-productionoftheirmajorcomponents.Playingagainstthesepositivefeatures,thereistheissueofdispatchability.Thedispatchabilityofdish-Stirlingsystemsiscompromisedbythefactthatthereisnoproventhermalenergystoragesystemwhichcanbeefficientlycoupledtodish-Stirlingsystems:noneofthemostdevelopedsystemshasbeenhybridisedinanefficientwaysofar. In thiscontext,dish-StirlingsystemshavetocompetedirectlywithPVintermsofinvestmentandelectricitygeneratingcosts,whiletheirO&Missignificantlymorecomplex.Therefore, the futureviabilityof this technologyrelieson the improvementofdispatchabilitybyaddingstorageorhybridisationcapabilitiesand/orsignificantcostreductions,reachinglevelsatleastcomparabletothoseofPVgeneration.
Itdoesnotseemrealistictoexpectgreatimprovementsinthepeakefficiencyofdish-Stirlingsystemsinthenearfuture.Thedevelopmentofthedish-StirlingtechnologyduringthelastyearshasbeenmainlyorientedtowardsthereductionofcostsforbothPDconcentratorandStirlingengineandtheimprovementofthesystemreliabilityandavailability.However,thereisnolargecommercialplantinoperationatthismomentandthereareseriousconcernsaboutthefutureofthemostsignificantprojectsinSpainandtheUnitedStates.
Theeffortstoreducethecostsofthedifferentsystemcomponents–mainlytheparabolicconcentratorandtheStirlingengine–havebeenfocusedonthepotentialformassproductionoftheseelements.Inbothcases,synergieswiththecarmanufacturingindustrieshavebeenidentifiedandexploredtodifferentlevels.Despitethefactthattherehasbeensignificantprogress,thishasbeeninsufficienttobringthistechnologytothemarketsofar.
AnotherpotentialpathofdevelopmentofthePDtechnologyisthecombinationofthePDconcentratorwithotherpowerconversionsystems,suchasgasturbines25,26,27orsteamengines28.
AccordingtotheSETISKPIdocumentdefinedin2010,thebaselineyearlysolar-to-electricefficiencyfordish-Stirlingsystemsis17%.Thisfigurereflectstherelativelyhighdowntime(unavailability)ofthesesystemsduetopreventiveorcorrectivemaintenance.Therefore,theR&Deffortsshouldbedirectedtotheimprovementoftheavailabilityofthesystemmorethantotheincreaseinefficiencyitself.However,formass-productioncomponents,therearesomechallengesrelatedtothesystemefficiency.
Thecurrenttotalcapitalinvestmentforalargedish-Stirlingsolarplantislikelyintherangeof4€/W.
7.1.5.1 Stirling engineAlthoughtherehasbeensomeexperiencewithgasturbinesorsteamenginesincombinationwithPDconcentrators,theStirlingengineisbyfarthemostcommonlyusedthermalenginewiththistypeofconcentrators.ThecharacteristicsoftheStirlingenginemakeitextremelyattractiveforsolarelectricitygeneration.Someofthesecharacteristicsarethedependenceonanexternalheatsupply,highefficiency,silentperformanceandrelativelywell-knownmechanics.
TwotypesofStirlingenginesarebeingconsideredforSTE:kinematicenginesandfree-pistonengines. In thekinematicengines,thepistonsareconnectedbyacrankmechanism,whereasinthefree-pistonenginesthereisnomechanicallinkagebetweenthemovingcomponentsandthedisplaceroscillatesbyresonance.
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25-Source:Buck,R.;Heller,P.;Koch,H.ReceiverdevelopmentforaDish-Braytonsystem.ProceedingsoftheASME1996InternationalSolarEnergyConference,1996;p91-96,1996
26-Source:Bammert,K.;Seifert,P.Designandpart-loadbehaviorofareceiverforasolar-heatedgasturbinewithaparabolicdishcollector.AmericanSocietyofMechanicalEngineers(Paper),1984
27-Source:www.swsolartech.com/pages/SolarTurbineEngine28-Source:www.greencarcongress.com/2009/05/cyclone-renovalia-20090507.html
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FIGURE15:Free-piston Stirling generator 29
29-Source:Infinia
Kinematicenginesrequirecompleteisolationbetweentheworkinggas(usuallyhydrogen,helium)andthelubri-cantofthedrivemechanism.DuetothehighoperatingpressureofStirlingengines,thesealshavetobereplacedregularly.Finally,enginesoperatingwithhydrogenaresubject to leaks thatmakeitnecessarytorechargethehydrogendepositsafteracertainnumberofoperationhours,dependingontheengine.Asaresult,maintenancerequirementsofkinematicStirlingenginesarerelativelyhighandexpensive,andtheoperationalavailabilityoftheseenginesisrelativelylow.
Freepistonengines(Figure15)usedinsolarapplicationshaveonlytwomovingpartsinasinglecylinderandgenerateelectricitybymeansofalineargenerator.Theyareconceptuallysimplerandeliminatemostoftheprob-lemsassociatedtokinematicengines,includingleaksofworkingfluidandreplacementofringsandseals.Theyalsoexhibitexcellentpart-loadperformanceandeasystart-up.However,thecomplexcontrolandthedesignofthelineargeneratorneedtobeimprovedtoachievetheexpectedperformance.
Increase availability (increase MTBF: Mean Time between Failures)AreductionofcomponentfailuresandmaintenancerequirementsforkinematicStirlingenginesisessentialforthistechnology.Theuseofnewmaterialsforringsandsealsandtheredesignoftheenginestothispurposeseemtobethebestalternatives.
Reduce needs for H2 refilling in kinematic enginesHydrogenhasabetterthermodynamicperformanceasworkingfluidoftheStirlingengineincomparisontohelium.However,kinematicStirlingenginesusinghydrogenhavesufferedleakageproblemstodifferentdegrees,makingitnecessarytorefillthehydrogenreservoirsperiodicallyinordertomakesurethattherequiredhighoperatingpressurescanbeachieved.Thisrequirestheinstallationofrefillingstationsinmostunitsasashorttomediumtermsolution.
Regenerator
Flexure Bearings
Cooling
Power Piston
HEATIN
ELECTRICITYOUT
Flexure Bearings
Linear Alternator
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Optimise manufacturing Stirlingengines,especiallythekinematicones,havemanysimilaritieswiththeinternalcombustionenginesusedintransportation.SignificantcostreductioncanbeachievedbyredesigningtheStirlingunitstotakeadvantageofmassproductionandthequalitycontrolandassurancetechniquesdevelopedinthecarmanufacturingindustry.
7.1.5.2 Gas turbinesThecombinationofgasturbinesandPDconcentratorsisnotnew,butitbecamemoreattractivewiththedevelopmentofsmallandefficientgasturbinesandtheneedtoprovidedispatchablepower.Inthisrespect,theintegrationofthegasturbinefacilitatesthehybridisationwithnaturalgasorbiogasorthecombinationofthedish-turbinesystemwithcompressedairenergystorage(CAES)system.
7.1.5.3 ReceiversThelowthermalinertiaofthereceiversofsolarStirlingenginesresultsinhighrampratesofthepoweroutput,especiallyduringcloudpassages.Thislowinertiamakesitmoredifficulttocontrolthesystem.Thischallengecanbeaddressedbyreplacingthecurrentlyusedtubularreceiversbyrefluxreceiversofeitherthepoolboilerorheatpipetypes.
Increase thermal inertia (improve part-load operation)Existingdish-Stirlingenginesexhibitaveryfastreactiontosolarradiationchanges,dueagaintotheverylowthermalinertiaofthereceiver.Thisisadisadvantagefromthepointofviewofintegrationinpowergrids.
7.1.5.4 DispatchabilityDispatchability,basedeitheronenergystorageorhybridisationwithotherenergysourcesisakeyfactorforthesuccessofthedish-Stirlingtechnology.However,developingenergystorageandhybridisationsystemsforPDisstillataveryearlystageandonlyafewpilotexperiments30havebeenconductedsofar.
Developing storage concept Duetothegeometricalandstructuralconstraintsofdish-Stirlingsystems,onlysmallthermalenergystoragecanbeintegratedintopresentdesigns.Alternativesforlargerenergystoragesystemsarebeingexplored.AccordingtotheATKearneyreportforESTELA31,“therearecurrentlytwoalternativesbeingpursuedtodevelopstoragesolutionsforthedish-Stirlingtechnology:thesearetheelectro-mechanicalandthethermalstorage.Basedonthestageofdevelopmentofthesealternatives,largecommercialdeploymentofstorageforthedish-Stirlingtechnologycanbeexpectedbetween2013and2016”.AtleastoneAmericancompanyisconsideringtheuseofCompressedAirEnergyStorage(CAES)asanalternative.
Developing hybrid receiver/heater unitsDispatchabilitycanbeachievedby integratinganalternativeorsecondaryenergysourcesuchasnaturalgasorbiomass.Ideally,thisintegrationshouldbeachievedinthereceiver,toavoidduplicityofelements.HybridisationwouldalsoeasetheuseofPDinstand-aloneapplicationssuchaspowergenerationforremoteareas.
30-Source:Ramos,H.;Ordóñez,I.;Silva,M.Anoverviewofhybridreceiversforsolarapplications.In:ProceedingsOfSolarPACES2010.TheCSPConference:Electricity,FuelsandCleanWaterfromConcentratedSolarEnergy(Cd-Rom).Perpignan,France.2010
31-Source:A.T.Kearney/ESTELA.SolarThermalElectricity2025-Cleanelectricityondemand:attractiveSTEcoststabiliseenergyproduction,June2010
Infinia-SuperQuark
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Topics Objectives Parameter/Target/Action Short Mid Long
Stirling engine
Increaseavailability(increaseMTBF,reducescheduledmaintenance)
•IncreaseMTBFofessentialenginecomponents Parameter:Kinematicengineoperatinghours[h]Target:4,000h
X
ReduceneedsforH2refilling(kinematicengines)
•Reduceoreliminatehydrogenleakagesbyusingtheappropriatematerialsandcomponents(valves,seals)
Parameter:GasrepositionrateTarget:0ornegligible
X
Optimisemanufacturing
•Achieveasignificantcostreductionviaefficientmassproduction(know-howfromcarmanufacturingindustry)
Parameter:StirlingenginecostTarget:50%costreduction
X
Gas Turbines •Easehybridisationandenergystorage Parameter:YearoffirstcommercialunitsTarget:2013-2014
X X
Receivers Increasethermalinertia
•Increaseoperationalstabilityandcontrollabilitybyimprovingthethermalinertiaofthereceiver
Improvepart-loadoperation X X
Dispatch-ability
Developingstorageconcept
•Developmentofeconomicandefficientenergystoragesystems
Atpresent,thereisnothermalstoragesystemcommerciallyavailableforparabolicdishes
X X
Developinghybridreceiver/heaterunits
•Develophybridreceiversabletooperatebothfromtheconcentratedsolarradiationandanalternativeenergysource(naturalgas,biogas)
Parameter:YearoffirstoperationalprototypeTarget:2015
X X
System compo-nents with enhanced material properties
Structureandtrackingsystem
•Developlighterandmoreefficientstructures•Optimisemanufacturingbyexploitingsynergies
withthecarmanufacturingindustry•Easeon-fieldinstallation•Developon-factoryadjustmentproceduresthatreduce
oreliminatetheneedforon-fieldadjustment•Reducethecostoftrackingsystems
Parameter:ConcentratorcostTarget:30%costreduction
X
Controls and operating issues •Developthepowerelectronicsandcontrolsrequiredtoeasetheintegrationofalargenumberofunits;
•Developefficientpowerelectronicsforfree-pistonengines
Parameter:Efficiencyofpowerelectronicsforfree-pistonenginesystemTarget:+2%
X X
TABLEV:RESEARCHPRIORITIESFORPARABOLICDISHES
7.1.5.5 System components with enhanced material propertiesThePDconcentratorneedstobeefficient(thatis,itmusthaveahighinterceptfactorandhavethefluxdistribu-tionmatchedtothereceiverdesign)andeconomic,bothfromthepointsofviewofmanufactureandinstallation.Economyofscalecanbeachievedbyexploringandexploitingthesynergieswiththecarmanufacturingindustry,assomemanufacturershaverecentlydonebothintheUnitedStatesandinEurope.Efficiencyreliesonmirrorreflect-ance,stiffnessofthestructureandtrackingaccuracy.Theuseofnewreflectivesurfacesandnewmaterialsforthestructure–includingstructuralsupportforthereflectivesurfaceifnecessary–mayhelptoachievetheseobjectives.
Structure and tracking systemThePDconcentratorisbasicallyaparaboloidalreflectivesurfacemountedonastructurethatincludesatwo-axistrackingsystem.Thereflectivesurfacecanbeconstructedindifferentwaysandwithdifferentmaterials.Asforthestructureandtrackingsystem,therearetwobasicmountingtypes:pedestalandcarrousel.Thepresentcostsoftheconcentrator,includingtracking,installationandadjustment,areabove2.5€/W.Theinterceptfactorvarieswidelybetweendifferentdesigns,withvaluesrangingbetween85%and95%.Concentratorcostshouldbereducedbyatleast50%tomakethistechnologycompetitivewithPV.
7.1.5.6 Controls and operation issuesTheoperationoflargePDfarmsrequirespowerelectronicsandoperatingstrategiestoeasegridintegration.Thechallengesaresimilartothoseofwindfarms,althoughtheyarelessdemandingandhaveparticularcharacteristics.Inthecaseoffree-pistonengines,thecontrolofthelineargeneratorisamajorissue.
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7.2 Objective2:Improvedispatchability
ASTEplantcomprisesfourmainsub-systems(Figure16):concentratingsystem,heattransfersystem,storageand/orsupplementaryfiring(labelled‘thermalstorage’inFigure16)andpowerblock.Theyarelinkedtogetherbyradiationtransferorfluidtransport.Theheattransfersystemabsorbstheconcentratedsolarenergyandtransferstheenergytothepowerblockand/orintoahotstoragetank.
OPTICAL CONCENTRATOR
RECEIVER
POWER BLOCK
THERMAL STORAGE
Beamsolarradiation
ConcentratedSolarRadiation
Heat
Electricity
Wasteheat
FIGURE16:Main components and sub-systems of a STE plant including storage
ToillustratethekeydriversforthecostreductionforSTEtechnology,asimplifiedcostmodelofaSTEpowerplantcanbeused,evaluatingthespecificinvestmentandannualenergyoutput.ThereferenceplantissupposedtobethepresenttechnologyPT50MWplantwithoutstorage.Theratiooftotalinvestmenttotheannualoutput,whichrepresentsanimportantpartofLCOEandcanbenamed“costindex”,isusedasasimplefigureofmerit.Plantswithstoragearesupposedtoprovideasubstantialincreaseinenergyoutputincomparisontoasimilarplantwithoutstorage.Thesolarfieldsizeisincreasedaccordinglyandadditionalstoragelossesareoffsetbyaddingsuitablecoststoover-sizethesolarfieldandHTFsystems.
Estimatesforthefollowingplantshavebeenmade(Figure17):
n OilThroughwithoutstoragen OilTroughwithstoragen 2015SaltHTFat550°Cn 2015Hybrid32
n AdvancedHTF33
n AdvancedHybrid34
32-Hybridsystem:Injectionofheatfromothersources(suchasbiomass,etc.)tothethermodynamicconversioncycleortotheHTF.33-AdvancedHTFsystem:UseofhightemperatureHTF,increasingoverallefficiency.34-Advancedhybridsystem:CombinationofahybridsystemwithahightemperatureHTFwithincreasedperformancesduetotechnicalimprovements.
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Animportantlessontobedrawnfromtheillustratedresultsistherolethatthermalenergystorageplaysontheexpectedelectricitycostinthecaseofstate-of-the-artPTtechnologyusingthermaloilandtwo-tankmoltensaltthermalenergystorage.Systemswithstorageandoversizedsolarfieldsproducetwicetheenergyofthereferenceplant,butdonotrequiretwicetheinvestmentsbecauseotherpartsoftheplant,e.g.thepowerblock,donotneedtobescaled.Electricityfromasystemwithstorageisthereforelessexpensivethanelectricityfromonewithoutstorage.
Conceptswithstoragearethereforeparticularlycompetitiveformarketswhichassignextravaluetosolar-onlydispatch-ability.Therearekeydriversthatcanfurtherhelptoreducetheelectricitycostswhileprovidingdispatchableelectricity.
IftheHTFisusedalsoasstoragemediumandelevatedtemperaturesarereached(whichisnotthecaseforstate-of-the-artconfigurations),thespecificcostofthestoragecanbesignificantlyreducedbecause:
n onlyonefluidcircuitisneeded,insteadofseparatecircuitsforHTFandstorage;n heatexchangersarenotrequired;n moreenergycanbestoredinthesamevolumebecauseofthehighertemperatureachievablewiththemoltensalt.
Furthermore,asthehighermoltensalttemperaturealsoleadstohigherpowerblockefficiency,lesssolarcollectorfield(andHTFcircuit)isneededperkWeandthespecificcostofthesecomponentscouldalsobereduced.Botheffectsleadtoasignificantlyimprovedoutput-to-investmentratioandalowercostindex,0.73.
FurtherimprovementscanbeachievedifadvancedHTFscanbedevelopedthatallowforawidertemperaturerange.Highersubsystemefficienciesandadvanceddesignswithlowermanufacturingcostswillgreatlycontributetothecostreduction.Theexpectedachievablecostindexis0.55.
Itisveryreasonabletoconsiderthatsomemarkets,andinparticularthosewherethedemandisgrowingcontinu-ously,willtargetnotonlyfordispatchableenergybutalsoforfirmcapacity.
ThehybridisationofSTEpowerplantswithfossilorbiofuelisanattractiveoptionforthesemarkets.Hybridplantconceptshavesomebenefitsthatcouldhelptoreducetheoverallsystemcostsofthesolarelectricitythatdiffersinpartfromthoseconceptsthatemploystorage:
n Lowerspecificpowerplantcostsduetomoreconventionalplantdesign;n Lowerspecificfieldcostsduetohigherplantefficiencywhenoperatedathighertemperature;n LowerHTFsystemcostduetosimplerandlessexpensive(HTFsuchassteamorgas).
Duetothesefactors,hybridplantsystemsin2015couldhaveacostindexaslowas0.7.Furtherimprovementsareexpected,forexample,throughthechangetoadvancedpowercyclesusinggasturbinetechnology.Highersubsystemefficiencyandadvanceddesignswithlowermanufacturingcostswillcontributetoanadditionalcostreductionwithanexpectedcostindexreaching0.52,i.e.aboutonehalfofthepresentdayreferenceplant.
FIGURE17:Comparison of today’s state-of-the-art PT power plants with and without storage and targets for solar-only and hybrid concepts in 2015
ADVHTF
2015 Molten
Salt
OilTrough
2015Hybrid
ADVHybrid
Storage
No storage
Future development
Specific Investment
Hybrids
0.52 0.7 1
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1 2
1
Cost index = Specific Investment Solar output
Technologies
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7.2.1Hybridisationandintegrationsystems
7.2.1.1 Integration with large steam plantsHybridisationcanbeperformedbyinjectingsolarheatatdifferenttemperaturelevelsinthewaterpreheatinglineorintheboilerwater/steamcircuits.Althoughintegrationwiththeboilerismoredifficultbecauseoftheheavyinteractionwiththedelicateequilibriumofheattransferparametersinsidetheboiler,itshouldbepreferred,asahigherconversionefficiencycanbeobtainedthroughintegration.However,evenalower-temperatureapplicationinthepreheatingline,whichgenerallyrequiresalowercostsolarcollectingfieldsuchasoneofLF,couldresultinasimplerandcheaperdesignofthecyclemodificationsandpossiblyalowerLCOE.
Thereareseveraldesignconceptsforhybridisingasolarpowerplantwithfossilfuels(gasorcoal)orbiomass(solidorgasified).
Theoptimaldesignandtheeconomicconvenienceoftheapplicationmustbeevaluatedonthebasisofglobalplantcost.
Independentlyofthedesignapproachandsolutionadopted,animportantaspecttobedevelopedandstudiedindepthisthemodificationofthepowerplantcontrolsystemstoaccommodatetheissuesderivingfromthevariabilityofthesolarsource.Foreachapplication,theoptimaloperationofthehybridisationisthekeyforachievingthebestcosteffectivenessoftheplant.
Largesteamcycleplantsarecommonlyusedforbaseloadoperationorheavyintermediateload.
Positiveeffectsondispatchingareexpectedfromthesesystemsbecausetheymakeitpossibletosavefuelintheearlymorninghours,andthisfuelcanthenbefreelyusedintheeveningpeakhourstoproducecheapenergyathighmarketprices.
HTF/steam cycle heat exchangers
ThedifferenttemperaturesandpressurelevelsofthesteamcycleboilerrequireacleverlydesignedsetofheatexchangersbetweentheHTF(heattransferfluid)andthewater(orsteam)ofthethermalcycle,becausetheheatexchangemustbebalancedbetweendifferentsectionsoftheboilertooptimisetemperaturedifferencesandheattransfer.Theresultingsolarheat-to-electricityconversionefficiencystronglydependsonthedesignchoices.
Boiler design
Thecouplingofsolarheatexchangerstothesteamcycleboilercanbebuiltindifferentways,providingvariousflowsolutions(e.g.seriesorparallel),valvepositioning,pumpmodificationsandotheroptions.Thedesignanddimensioningdependonthespecificsteamcycleconfigurationchosen.Thepossiblevariationsinshort-termperiodsofsolarcollectioncanbehandledbythecontrolsystemonlywithinthelimitationsarisingfromthepracticalboilerdesignandsetup.
However,anoptimisedcouplingbetweentheHTFandthethermalcycleisrequired,andthisistobeachievedthroughspecificdesignsandexperimentalanddemonstrationinstallationsthatleadtofullsizeapplications.
Boiler control system
Thecombinedoperationofthesolarsteamgeneratorandthesteamcycleboilerrequiresacarefulmodificationofthecurrentboilercontrolsystemdesignstoenablethemtomaintainthestabilityofthepowerplantoperationwithvaryingsolarradiationinthecourseofthedayandyear.
Therefore,modificationstotheboilercontrolsystemmustbemadeinordertohandlethevariations.
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7.2.1.2 Integration with gas turbine and combined cycle plantsThemostconvenientwayto improvestability is to interactwith thesteambottomingcycle. In thiscaseall theconsiderationsmadeforthehybridisationwithsteamplantsareapplicable.
Highertemperaturesolarcollectors,eitherPTorCR,canbeeffectivelyusedtopreheatairinthegasturbineatthecompressoroutput,beforetheinjectionofthefuel.Thiswillraisethetemperatureoftheair,loweringtheamountoffuelneededforthesameoutputpower.Theresultisaveryhighefficiencyoftheconversionofsolarenergyintoelectricity.
Thisapplicationrequires thedevelopmentofcompact,high temperature-to-airheatexchangers thatare tobecloselycoupledtothegasturbinebodyorapressurisedairreceivertechnology.Anadaptationofthegasturbinecombustionsystemsduetotheincreasedinlettemperatureisnecessary.
Anintermediateandnecessarystepinresearchanddevelopmentisthehybridisationwiththegasturbinealone,intendedtodevelopandoptimisetheheatexchangerandtotest theoperationofthiscriticalcomponentatalowpowerlevel.Theresultisasolargasturbinehybridplantwithasolarheat–to-electricityconversionefficiencyintherangeof35-39%.Thefinalstepwillleadtoafullcombinedcyclesolarhybridwithsolarheat-to-electricityconversionefficiencyofabove50%.
Acleverre-designofthecontrolsystemisnecessarytohandlesolartransientsandtobalancetheoperationofthegasturbineandthesteamturbineundereverypossibleworkingconditionsofsolaravailabilityandloaddemand.
Design of HTF/steam cycle heat exchangersTheheatrecoverysteamgeneratorofacombinedcycleisatypeofboilerwhichdiffersfromwhatisnormallyusedinsteamonlypowerplants.Dependingonthedesign,twoorthreedifferentwater/steamcircuitsatdifferentpressurelevelsareused.Consequently,thecouplingwithasolarheatgeneratormustbeoptimisedinordertogetthemaximumefficiencyofsolarheat-to-electricityconversion.
Materials for high temperature heat exchangers (such as ceramic or metal)Integrationofheatintothegasturbinesectionofacombinedcyclerequiresexchangingheatathightemperature.Typically,thetemperatureoftheoutputairfromthecompressorisaround350°C,whiletheturbineinputtempera-turerangesfrom1,100°Cto1,400°C.Compactheatexchangersrequirespecialmaterialsandspecialcompactdesigntoallowforhighefficiencyandlowthermalandfluiddynamiclosses.
Overall system design optimisationToachieveefficientcouplingbetweenthesolarfieldandthecombinedcyclerequiresanefforttooptimisethedesign,properlyplacingtheheatexchangersandthevarioussystemcomponents(pumps,valvesetc.).Combinedcycleswithaheatrecoverysteamgeneratorareoftendesignedusingtwoorthreedifferentpressurelevels,andmanyfeaturesarestudiedandoptimisedtomaximisetheoverallcombinedcycleefficiency.Theadditionofexternalheathastobedesignedinsuchawaythatitdoesnotproducenegativeeffects.Sizingofcombinedcyclecomponentsisalsoaffectedanddifferentdesigns(1-on-1or1-on-2)canbeeffectivelyusedtoachievethebestsolarhybridsystemperformance.Thegoal,ofcourse,istomaximisethesolarheat-to-electricityconversionefficiency.
7.2.1.3 Integration with biomass plants
Theintegrationofsolarenergywithabiomassfuelledplantallowsthebuildingofanall-renewableresourcewhichcanoperateallyearlong,takingadvantageofthebenefitsderivingfromthetwodifferentsources.
Forestsandenergycropsmustbebroughttothebiomassplantfromanextensiveareaofland,andthismakesthefuellingandsittingofaverylargesizepowerplantdifficult.ThesizeisthereforenormallylimitedtotherangeofafewMWeorevenless.Theconversionefficiencyofsuchcyclesisnotveryhighbecauseofthesmallsizeoftheplantandthehigherrelativeimportanceofcyclelosses.
Combustionmaybenoteasybecauseofthecompositionoftheavailablebiomass,andspeciallydesignedfirebedsandboilersareneededwhichmayhavealowerboilerefficiencyandaloweroutputsteamtemperature.Alternatively,biomassgasifierscanproducehotgastobeusedintheboilerswithreducedfoulingproblems.
Bio-gasorbio-oilobtainedfromappropriateprocessingplants(fomenters,digesters,pyrolysers,etc.)canalsobeusedasfuels.
Somerecentapplicationsuseorganicfluidthermodynamiccycles(ORC),heatedbyburningthebiomass,forenergyconversionwithlowtemperatureworkingfluids(about300°C).
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Theheat fromdifferentsourcescanalsobeintegratedintoTES(thermalenergystorage)andthismayhaveabeneficialeffectondispatchability.
Relatedresearchprioritiesare:
Integration of low cost solar fields with biomass steam boiler or ORCThesmallsizeofavailablebiomassplantsandtherelativelylowtemperaturesoftheconversioncyclesmakethemwellsuitedtohostalow-costsolarhybridisationbymeansoflowcostsolarfield,suchasoneusingLF.TheuseofORC,whichisalreadyappliedinbiomassfuelledapplicationsaswellasinsolarplants,willsimplifytheoperationwhileincreasingtheefficiency.
Theresearchanddevelopmentgoalhereistodesignsmallsizesolar/biomasshybridconfigurationstoobtainanall-renewablepowerplant.
Molten salt PD developmentThePDpresentlyusedindish-StirlingsystemscanbeeffectivelyusedtoheatmoltensaltHTFtohightemperatures,andthesesystemscanbecoupledwithabiomassplantbymeansofheatexchangers.
7.2.1.4 Hybridisation for the direct systems using the same molten salt mixture as HTF and HSM (heat storage medium)IntheSTEdirectsystems,wherethesamemoltensaltsmixtureisusedasHTFandHSM,anotheroptionalreadyexplored(i.e.demonstrativeFP7projectsMATS,OPTSandHYSOL)istohybridisethesystemusingagas-firedmoltensaltheaterplacedinparallelwiththesolarfield.Thegas-firedheaterentersinoperationifthesolarenergyinputdecreasesbelowacertainvalue.Whenitdoes,themoltensaltcirculatinginthesolarfieldisswitchedtothemoltensaltheaterloopwhereitisheatedtotheoperatingtemperatureandflowsintotheTES(and/ortheSteamGenerator).Thissuppliesalltheback-upthermalenergynecessaryforacontinuousoperation.
Inthisway,theoperationoftheTESandthepowerblockneversuffersfromvariationsofsolarradiationandthedispatchabilitycanbegreatlyimproved.ThisoptionlowerstheLCOElargelybecausetheinvestmentcostonthepowerblockissharedoveralargenumberofoperationhours.
Onanannualbasis,thepercentageofhybridisationofthedispatchedelectricenergydependsonthesizeofTESandofthesolarfieldrelativetotheratedpoweroftheplant.Eachcomponentisselectedbycomparingyearlytheir impacton theLCOEfromthedifferentsolarcomponents,whichdependon theinvestmentcostsandthesolarradiationonthesite.Fortheback-upcomponent,theimpactontheLCOEdependsontheexpensesfortheintegrativegaseousfuel.Therelatedresearchprioritiesare:
Gas-fired molten salt heater for the system back-up Themoltensaltheaterhastobedesignedcarefullybysuitablethermo-fluiddynamicandthermo-mechanicalcodesinordertouseatbestthecharacteristicsofthemoltensalt,upto550°C,andtoavoidhotspotsinthetubebundlethatcouldcausethedecompositionofmoltensaltwithdevelopmentofgas.Thecombustionchambershallbeseparatedfromthetubebundle,whichwillbefloodedbyexhaustgasesatcontrolledtemperature,withoutdirectexpositiontotheflame.Thedischargeoffluegasattheoutletofagas-turbineshallbealsoconsidered.
Thesensibleheatofthefluegasescanbeusedforheatingthemoltensaltdowntotheminimumtemperatureofoperationofthesolarfield(e.g.290°C),andmoreorlessdownto120°C,forproducingauxiliarysteamforthepowerblockorotherheatingservices.Amongthepossiblegaseousfuel,gasifiedbiomassshouldbeconsideredasmainoption.
Demonstrationsatrelevantscaleclosetocommercialonearenecessary.
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Topics Objectives Parameter/Target/Action Short Mid Long
Hybridisation with large steam plants
HTF/Steamcycleheatexchangers
•Increasesolarheat-to-electricityconversionefficiency
Parameter:ηth-elec(includingheatexchangers)
Target1:ηth-elec>40% X
Target2:ηth-elec>45% X
Boilerdesign •Newboilerdesignbestsuitedtothecouplingwithexternalheat
Parameter:ηth-elec(includingheatexchangers)
Target1:ηth-elec>40% X
Target2:ηth-elec>45% X
Action:Specificdesignsandexperimental/demoinstallationleadingtofullsizeapplications
Boilercontrolsystem
•Obtainasetofcontrolsystemalgorithmsandprocedurestobeinsertedintheboilercontrolsystemtomaintaintheboilerfullyoperationalwiththehighestperformanceandstability
Parameter:Availabilityofavalidatedsetofcontrolalgorithmsimplementedintoahybridplantboilercontrolsystem
X X
Integration with gas turbine and combined cycle plants
DesignofHTF/steamcycleheatexchangers Parameter:ηth-elec(includingheatexchangers)Target:ηth-elec>40%
X
Materialsforhightemperatureheatexchang-ers(suchasceramic,metal)
•Selectanddevelopmaterialsanddesignssuitableforhighperformanceforgasturbineheatexchangersthatcanbeappliedinhightemperaturesolarhybridcombinedcycle
Parameter:ηth-elec(includingheatexchangers)Target:ηth-elec>45%
X
Overallsystemdesignoptimisation
•ObtainasetofschematicsystemlayoutsrelatedtohybridsolarplantstoincreaseplantdispatchabilityandlowertheLCOE
Parameter:ηth-elec(includingheatexchangers)Target:ηth-elec>55%
X
Action1:Constructionofsignificantsizedemoplants30to50MWe(solarequivalent)withsteambottominghybridisation
X
Action2:1to5MWe(solarequivalent)withsimplegasturbinehybridisation
X
Action3:30to50MWe(solarequivalent)completecombinedcyclehybridisation(gasturbineandinsteamcycle)
X
Integration with biomass plants
IntegrationoflowcostsolarfieldswithbiomasssteamboilerorORC
•Designofsmallsizesolar/biomasshybridplantstoobtainanall-renewablepowerplant
Target:AvailabilityofoneormorereferencedesignforthistypeofplantAction:Constructionofsmallsizedemo
X
Moltensaltparabolicdishesdevelopment
•Designandtestverysmallsizesolar/biomasshybridplants
Target:AvailabilityofoneormorereferencedesignforthistypeofplantAction:Constructionofsmallsizedemo
X
Hybridisation for the direct systems using the same molten salt mixture as HTF and HSM
Gasfiredmoltensaltheaterforthesystemback-up
•NewMSheaterdesignsuitedtocouplewithaback-upenergysourcesuppliedasgaseousfuel
Parameter:numberofhoursofoperationinayear:NTarget1:N>5,500h/y
X
Target2:N>7,000h/y X
OverallsystemdesignOptimisation
•DesignofthesystemaimedtocontroleasilyandtomanageatthebesttheplantfortheintegrationofthetwoenergywithgreatbenefitontheLCOE
Target:LCOE<20%thanonlysolar X
TABLEVI:RESEARCHPRIORITIESFORHYBRIDISATIONANDINTEGRATIONSYSTEMS
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Overall system design optimisationThedesignoftheoverallsystemshouldoptimisetheenergeticcontributionofthesolarradiationandtheback-upfuel.ThesolarfieldandtheTESshallbesizedaccordingtotheratedpowerandthesolarradiationatthesite.TheMSH(moltensaltheater)shallbesizedsothatitcanprovidethepowernecessarytointegratethesystemintheabsenceofsolarradiation.
TheMSHloopisplacedinparallelwiththesolarfieldupstreamoftheTESsothatitcancompensateforanykindoffluctuationsandavoidanyinfluenceontheoperationofthepowerblock.Thisfacilitateseasycontrolandmakesitpossibletomanagetheplanteffectively.Theintegrationofthetwoenergysourcesmakesitpossibletoextendthehoursofplantoperationgreatly,withgreatbenefitontheLCOE.
Demonstrationsatascalelargeenoughtoapproximateactualcommercialplantsarenecessary.
7.2.2Storage
Thermalenergystorage(TES)systemsareanintegralpartofaSTEpowerplant.DuetothevarietyofSTEconceptsreflectedbydifferentHTFandoperatingtemperatures,thereisnosinglestorageconceptwhichcouldbeappliedtoallSTEplants.
Thecostandperformanceofstoragedependsnotonlyonthestoragedesign,butisalsoaffectedbytheintegrationofthestoragesystemintotheoverallSTEsystem.ThevalueaddedbystoragedependsontheinvestmentsinthestorageanditsintegrationintoaSTEpowerplantbutitalsodependscriticallyontheconditionsfromthegrid,i.e.onhowmuchthegridvaluesdispatchability.
Today’sreferenceforstorageisanindirecttwotankmoltensaltstorageintegratedintoaPTpowerplantusingthermaloilasHTF.Theresearchtargetsaretoreducetheinvestmentcostsofstorage(SeeANNEXI:KeyPerform-anceIndicators,2010:35,000€/MWhth;202015,000€/MWhth),andtoincreasetheefficiencyofstorage(ANNEXI:KeyPerformanceIndicators:2010:94%;2020:96%).Astoday,itisnotclearwhichofthedifferentSTEtechnologies(characterisedbythedifferentHTF)willfinallybefoundtobethemosteffective,anditisneces-sarytofollowuponseveralconceptsinparallel.
ThefiguresgivenaboverefertotheconventionalPTdesignwherethetemperaturedifferencebetweenthecoldandhottanksis100°C.CRswherethetemperaturedifferenceisaround300°Ccouldhavelowervalues.
7.2.2.1 Storage designTo lower thestoragecostandincreasestorageefficiency, the followingprioritieshavebeenidentifiedfor thedifferentsystems:
Storage system for thermal oil as HTFPTsystemsusingthermaloilasHTFstillconstitutethemajorityofall installedSTEsystems.Two-tankmoltensaltstoragesystemscoupledthroughaheatexchangerwiththeHTFcircuitarestate-of-the-arttechnology.Inordertoreducethestoragecosts,twoapproachesarediscussedbelow.Thefirstideaistolimitthestoragecontainertoasingletankandtheotheristousealow-costsolidmaterialasanalternativestoragemedium.
-SingletanksolutionsAsingletanksolutionrequiresanoptimisedthermalstoragedesigninordernottopenalisethestorageefficiencybymixinghotandcoldstoragefluid.Forthispurposeanexcellenttemperaturestratificationorseparationbetweenthehotandcoldsectionsinthetankneedstobeachieved.
-SolidmediastoragesolutionsAthermalstoragedesignthatallowsaseparationoftheheatexchangermaterial(whichrelatestopower)andthestoragematerial(whichrelatestocapacity)mustbedevelopedtotakeadvantageoflowmaterialcosts.
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Storage system for molten salt as HTFSignificantcostreductioncanbeachievedifmoltensaltisnotonlyusedasstoragemediumbutalsoasHTF,becausethisavoidstheuseoftwoindependentHTFcircuitsandoftheheatexchangersystem.Ifthetemperatureofthesaltmixturecanbefurtherincreased,highercycleefficienciesareexpected.LowercostsfortheHTFsystemareachievablebychoosinganHTFwithalowerfreezingpoint.Threedifferentapproachesarediscussedbelow.
-NewsaltmixturesAsstoragematerials,newsaltmixtureswithlowerfreezingpointandhighertemperaturestabilityaretargeted.Screeningofsaltmixturesandevaluationofthephysicalandchemicalpropertiesofthemostpromisingmixturesisrequired.Inaddition,longertermstabilityandcorrosiontestsneedtobedone.
-Storagecontainermaterials,innerliners,gasblanketsNewsaltmixturesoperatedathighertemperaturesmayresultincorrosionproblems.Newmaterials,innerlinersandgasblanketscanpotentiallylowertheoverallmaterialcost.
-SingletanksolutionsAsingletanksolutionrequiresanoptimisedthermalstoragedesigninordernottopenalisethestorageefficiencybymixinghotandcoldstoragefluid.Forthispurpose,optionsthatleadtoanexcellenttemperaturestratificationorseparationbetweenthehotandcoldsectionsinthetankneedtobedeveloped.Theintegrationofthesteamgeneratorintothetankispossible,thusenhancingthecapabilityofstratificationandfurtheringthereductionofcosts.
Storage system for steam as HTFSteamasHTFisattractiveasitcanbedirectlyusedinthepowerblock.However,steamstorageconceptsmusttake intoaccount thatwaterundergoesaphasechange(atconstant temperature)duringevaporation. In thiscontext,phasechangematerials(PCM),typicallybasedonsaltmixtures,canbeusedasstoragemediabecausetheyundergoaphasechangeintherequiredtemperaturerange.Thewatermaybepreheateduntilitreachestheevaporationpointandtheresultingsteammaybesuperheatedwiththeheatfromsensibleheatstoragewhichmaybesolidorliquid.
Thereareresearchactivitiesinapplicationsusingsaturatedandsuperheatedsteam.Conceptsbasedonsolid/liquidPCMtoheatsaturatedsteamwouldmakeitpossibletousesteamasasingleHTFintheSTEsystem.ThiscouldprovidecertainadvantagestoPTandlinearFresnelsystems.
Storage system for gas as HTFGasesusedasHTFhavenopracticallimitforupperandlowertemperatureoperationandarethereforeconsideredofinterestforveryhightemperatureapplications.Duetothelowdensityandheatcapacityofthegas,however,storagesystemsarebasedonsolidorliquidstoragemedia.Adesignforaneffectiveheattransferandtheidenti-ficationofsuitablehightemperaturestoragematerialsaremajorchallenges.
-HeattransferoptimisationinstorageconceptsTheheattransferinstorageconceptsbasedongastosolidorgastoliquidhastobeoptimised.
-Lowcostmaterials/particlesasstoragesmediaLowcostmaterials/particlesasstoragemediasuitableforpackedbedorfluidisedbedconfigurationshavetobeinvestigated.
7.2.2.2 Storage optimisation
Optimised charging and discharging strategiesOptimisedcharginganddischargingstrategiestomaximisethestoragecapacityofexistingstoragedesignsshouldbebasedonadetaileddynamicmodellingofexistingstorageconfigurationsinordertooptimisethefuturedesignstakingintoaccountthecompletesystemoftheplant.
Thesestrategiesshouldbebasedonadetaileddynamicmodellingofexistingstorageconfigurations.
Optimised multi-storage conceptsAcombinationofmultiplestoragetanksofdifferenttypesandcapacitiesmaybeusedtoachievecost-effectiveoptimisation,notonlywhenusingdirectsteamasHTFbutalsoforothersystems.Multiplestoragecanalsobecombinedtoachieveabettermatchofstoragecapacitytotheoperatingtemperaturerange.
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7.2.2.3 New storage conceptsTheadvantageofstoringsolarenergyinchemicalformisthatthestoragetimecanbeextendedwithoutfurtherlosses.Thehigherenergydensityachievableinchemicals,incomparisonwithstorageintheformofsensibleheatallowsmovingthestoredenergytootherlocations.ThisoffersavarietyofbenefitsthatclearlygoesbeyondtheTEStechnology.Howeverthedevelopmentofthetechnologyisstillinanearlyphaseandfundamentalproblemsneedtoberesolved.
Thermo-chemical energy storage systemsReversiblechemicalreactionsbasedonnon-toxiclow-costmaterialscanbedrivenbyhightemperatureSTE.Insystemsbasedonsuchchemicalstorage,theheatisreleasedwhenthereversereactiontakesplace.
It isnecessarytoevaluateconceptsthatusechemicalreactionsasheatstoragesystemsinengineeringstudiesandtocharacterisethethermo-physical,kinetics,andstabilityofthosematerialsinlaboratoryscaleresearchthatisalreadyunderway.
7.2.2.4 Storage as energy integratorInordertoidentifythemostreasonablemarketsforSTEsystemswithstorage,itisimportanttoidentifyandquantifythevalueofenergy,capacityandgridservicesinfutureenergyscenarios.
Comprehensive electric grid modelsThereisaneedtodevelopandupdatecomprehensiveelectricgridmodelsthatallowestimatesofthevalueofSTEsystemswithstoragefordifferentscenariosofEurope’senergysystemuntil2050.TheyareneededtopredictthevalueofdispatchableelectricityinafutureenergysystemandtoidentifysuitablemarketsforSTEtechnology.
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Topics Objectives Parameter/Target/Action Short Mid Long
Storage design
StoragesystemforthermaloilasHTF
Singletanksolutions
•Reducethecostsofstorageandincreasethestorageefficiencyanddispatchability
Parameter:SpecificcostsTarget:25€/kWhth
X
Solidmediastoragesolutions
•Reducethecostsofstorageandincreasethestorageefficiencyanddispatchability
Parameter:SpecificcostsTarget:25€/kWhth
X
StoragesystemformoltensaltasHTF
Newsaltmixtures •Reducethecostsofstorageandincreasethedispatchability
•Workingathighertemperaturestoincreasethecycleefficiencyoftheplant
•Increasesolartothermalefficiencyusingsaltwithlowerfreezingtemperatureduetolowerovernightheatlosses.
Parameter:SpecificcostsTarget:20€/kWhth
X
Parameter:ηth-elec
Target:ηth-elec=42%X
Parameter:ηth-elec
Target:ηth-elec=+1%X
Storagecontainermaterials/innerliners/gasblankets
•Reducethecostsofstorageandincreasethedispatchability
Parameter:Specificcosts[€/kWhth]Target:-10%comparedtohightemperaturealloydesign
X
Singletanksolutions
•Reducethecostsofstorageandincreasethestorageefficiencyanddispatchability
Parameter:SpecificcostsTarget:20€/kWhth
X
•Decreasethethermallossesbyintegrationofthesteamgeneratorintothetank
Parameter:ηth-elec
Target:ηth-elec=+1%X
StoragesystemforsteamasHTF •Minimiseenergylossesinheattransferandreducethecostofstorage
Parameter:SpecificcostsTarget:25€/kWhth
(sensibleheatsystems)Target:50€/kWhth
(latentheat,PCM)Parameter:ηStorageTarget:ηStorage=95%
X
StoragesystemforgasasHTF
Heattransferoptimisationinstorageconcepts
•Increasetheenergyefficiency Parameter:ηStorage
Target:ηStorage=95%X
Lowcostmaterials/particlesasstoragesmedia
•Reducethecostofstorageandminimiseenergylosses
Parameter:storageandenergylossTarget1:20€/kWhth
Target2:95%
X
Storage optimisation
Optimisedcharginganddischargingstrategies
•Maximisestoragecapacityofexistingstoragedesignsthusreducingspecificstoragecost(€/kWh)
Parameter:Specificcosts[€/kWhth]Target:-10%comparedtononoptimisedstrategy
X
Optimisedmulti-storageconcepts
•Minimisestoragecostbyeffectivecombinationofseveralindividualstoragesdependingontemperaturelevelandcapacity
Parameter:Specificcosts[€/kWhth]Target:-10%comparedtonon-optimisedcombinationforDSG
X
New storage concepts
Thermo-chemicalenergystoragesystems
•Increasetheroundtripstorageefficiency(heat-to-heat)
Parameter:ηStorage[%]Target:90€/kWhth
X
Storage as energy integrator
Comprehensiveelectricgridmodels
•Predictthevalueofdispatchableelectricityinafutureenergysystem
(NotechnicalKPIofSTEapplicablehere)
X
TABLEVII:RESEARCHPRIORITIESFORSTORAGE
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7.2.3Forecastingtools
7.2.3.1 Operation strategy
Studies on the use of solar irradiance for very short term forecast Amajorconcerninthemanagementofsolarthermalpowerplantisthepotentialinstabilitiesduetosteepchangesinthesolarradiationalongsolarfieldareaassociatedwiththepresenceofscatteredcloudsand/ortransientsoriginatedbycloudmovements.Thiskindofskyconditionsrequiresspecialplantoperationstrategiestoaccom-modatethelocalsolarradiationspatialvariabilityandtoreducethethermalstressintothesolarfield.
Anaccurateveryshort-termforecastcanincreaseplantprofitsbydispatchingenergyintothetimeperiodsofgreatestvalue.
Electricity production forecasting systemApreciseelectricityforecastreducestheamountofbackuppowerneededinnetworkmanagement.
Systemswithstoragefacilitycanbeoperatedmoreefficientlyifthesolarforecastisknown,avoidinginefficiencies(forexample,byfirstfeedingthestorageandrunningthepowersystematfullloadoutofthestorage).
Thegoal is todevelopprototypesoftware that integratesall forecasting,modellingandoutputgenerationforconcentratingsolartechnologies.
7.2.3.2 Solar resource assessmentBeforeaSTEprojectisundertaken,itiscriticallyimportanttohavethebestpossibleinformationregardingthequalityandreliabilityoftheenergysource.Thatis,projectdevelopersneedtohavereliabledataonthesolarresourceavailableatspecificlocations,includinghistorictrendswithseasonal,daily,hourly,and(preferably)sub-hourlyvariability,inordertopredictthedailyandannualelectricityoutput.
Improving DNI measurement ground base data networkBecausesiteselectionisalwaysbasedonhistoricsolardataandweatherpatternchangesfromyear-to-year,amaximumnumberofyearsofdataarebetterfordeterminingarepresentativeannualdataset.
Therefore,theradiationdatabasebasedonanetworkofgroundsolarradiationsensorswithextendedgeographicalcoverageofSouthernEuropeandotherMediterraneanandNorthAfricanregionshastobeimproved.
Deriving the global and beam irradiance components from meteorological satellite imagesModelsconvertingsatelliteimagesintothedifferentradiationcomponentsarebecomingincreasinglyaccurateandtheyallowtheaccesstoagoodnumberofstatisticsandphysicalmodels.Moreaccuracyinthedatacouldbeobtainedbycomparingandvalidatingthedifferentmodels.ThiscouldbedonebyderivingtheglobalandbeamirradiancecomponentsfrommeteorologicalsatelliteimagesfordifferentlatitudesandaltitudesinEurope,toobtainingreliableandaccurateknowledgeoftheaerosolopticaldepthandofthebeamirradianceforspecificareas.
Bothstatisticsandphysicsmodelsaretobedevelopedfurther.
DNI forecasting systemSolarpowerforecastingistheprimaryrequirementforefficientintegrationofSTEintopowersystemsandforthereductionofgridintegrationcosts.Theelectricityproductionforecastisdrivenmainlybythedirectnormalirradiance(DNI)forecast.
TwoapproachesmustbefollowedtoobtainreliableDNIdata: thefirstonebasedonsatelliteimages,whichprovidesvaluableforecastsforatimehorizonofupto6hoursandthesecondonebasedonnumericalweatherpredictionmodelswhichprovidevaluableforecastforatimehorizonofupto72hours.
Thisincludestheanalysisofthedependenceontheforecastsreliabilityonthetimehorizon,seasonoftheyearandskyconditions.
Improved Numerical Weather Prediction (NWP) models for DNI forecastingDNIforecastsaretheprimaryrequirementforefficientintegrationofSTEplantsintopowersystems.NumericalWeatherPrediction(NWP)modelsaretheonlytoolsthatprovideDNIforecastwithupto72hourtimehorizon.
Therefore,increasingthereliabilityoftheDNIforecastsbasedonNWPmodelshasadirectimpactonthereduc-tionofgridintegrationcosts.
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Analysis of the inter-annual variability of the DNIAccurateresourceevaluationisakeyissueinthefirststagesofanyrenewableenergyproject.Particularly,asthelifespanofsolarpowerplantsisabout20years,theeconomicfeasibilitystudyofsuchprojectsmusttaketheinter-annualvariabilityoftheresourceintoaccount.
Therefore,analysisofthecausesoftheinterannual/decadalvariabilityoftheDNIinregionsofinterestiscrucialforabetterpredictabilityoftheexpectedperformance.
Analysis of the space-time correlation between solar energy (DNI) and wind energy resourcesAmajorchallengeforthefutureregardingrenewableenergywillbetheintegrationofmajorwindandsolaryieldsintotheexistingenergysupplyinfrastructure,consideringthefluctuationoftheseresourcesandtheirsensitivitytoweatherpatterns.
Oneofthemostpromisingwaystoreducethepowerfluctuationfromsolarandwindenergyistotakeadvantageofthespatialvariabilityoftheseresources.Sincethespatialcorrelationofwindand(toalesserextent)solarenergyresourcesdiminisheswithdistance,interconnectionofwindandsolarpowerinaregionwillreducefluctuationsintotalproduction.Thisbalancingeffectbecomessignificant,providedthatweatherconditionsacrosstheintercon-nectingregionaresufficientlyvariableand/ortheterraincomplexityislarge.
Therefore,theanalysisofthebalancingbetweensolarresources(DNI)andwindenergyresourcesinkeyregionsisanimportantissueforexamination.
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TABLEVIII:RESEARCHPRIORITIESFORDISPATCHABILITY
Topics Objectives Parameter/Target/Action Short Mid Long
Optimised operation strategy
Studiesontheuseofsolarirradianceforveryshorttermforecast
•Reduceinstabilitiesintheplants•Maximiserevenuesattheelectricity
stockexchangebysellingtheelectricitypreferablyathighpricetimesratherthanatlowpricetimes
Parameter:MBETarget:<5%Parameter:RMSETarget:<10%
X
Electricityproductionforecastingsystem
•Developaprototypesoftwarethatintegratesallforecasting,modellingandoutputgenerationforconcentratingsolartechnologies
Parameter:DeviationfromplannedtoproductionTarget:-5%
X
Improved solar resource assessment
ImprovingDNImeasurement-groundbasedatanetwork
•ImprovesolarradiationdatabasebasedongroundsolarradiationsensorsnetworkwithextendedgeographicalcoverageofSouthernEuropeandotherMediterraneanandNorthAfricanregions
Parameter:SolarresourcedataAction:Extendthecurrentsolarradiationnetworktoareasofhighinterestwithlackofdata(NorthernAfrica)Action:Extendthelengthofthemeasureddataperiodtoabout10years
X
Derivingtheglobalandbeamirradiancecomponentsfrommeteorologicalsatelliteimages
•ValidateandcomparedifferentproductsderivingtheglobalandbeamirradiancecomponentsfrommeteorologicalsatelliteimagesfordifferentlatitudesandaltitudesinEurope.
•Obtainreliableandaccurateknowledgeoftheaerosolopticaldepthandthebeamirradiance.
Parameter:AccuracyofthebeamirradianceTarget:<10%,standarddeviation=20%
X
DNIforecastingsystem
•Maximisetheeconomicpotentialoftheparticipationatpremiumtariffs
•Reducethesolarenergyyieldintegrationcostsbyaccurateinformationonexpectedsolarirradiance
Parameter:MBETarget:<10%Parameter:RMSETarget:<15%
X
ImprovedNumericalWeatherPrediction(NWP)ModelsforDNIforecasting
•IncreasingthereliabilityoftheDNIforecastsbasedonNWP
Parameter:ForecastreliabilityAction:HighspatialandtemporalresolutionDNIforecastsprovidedbyreferenceNWPmodelsasthoseoftheECMWF
X
AnalysisoftheinterannualvariabilityoftheDNI
•Increasethecurrentunderstandingonthecausesoftheinterannual/decadalvariabilityoftheDNIinregionofinterest
•Analysetherelativerolesofcloudsandaerosolsinthisvariability
•Obtainbetterestimatesoftheexpectedinterannual/decadalvari-abilityintheoutputofsolarpowerplantsintheregionsofinterest
Parameter:DNIvariabilityAction:EvaluationoftherelativeinfluenceofaerosolandcloudsoninterannualvariabilityoftheDNIinkeyregion
X
Analysisofthespatial-temporalbalancingbetweensolarenergy(DNI)andwindenergyresources
•Evaluatethespatialbalancingbetweensolarandwindenergyresourcesinkeyregions
•Determineifbyinterconnectingadvantageously-distributedwindfarmsandSTEplants,itmaybepossibletoachievereducedminimumoutput,eventuallytransformingthesumofthethermalenergyandwindfarmenergyintoareliablesupply
Parameter:CorrelationbetweenDNIandwindAction:Studiesoncombinationofweatherforecastanddemandatalargeregionalscale
X
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7.3Objective3:ImproveEnvironmentalProfile
7.3.1Heattransferfluids
7.3.1.1 Heat transfer fluids vs. environment impactTheenvironmentalcomponentsthatcouldbeaffectedbyleaksoremissionsofHTF(heattransferfluid)arethesoil,groundwaterandsurfacewater,airandhumanpresence.Asareferencesituation,thecaseofsyntheticoilasHTFistakenandcomparedtootherpossibleHTFswhichareexpectedtobefriendliertotheenvironment.
PT,linearFresnelandPDtechnologiesdependonawidespreaddistributionofthereceivers,thatis,awidedistribu-tionoftubesormotorsinthesolarfieldsandthereforeapotentialinvolvementoflargetractsoflandbypossibleHTFleakages.UnderstandingthisservesasacautionarywarningthattheuseofHTFsmaybehazardoustotheenvironment.ThisaspectislessproblematicforthelimitedareadevotedtotheTESandtotheprocessequipment.Inthiscase,aproofingsurfacemayprovideasolution.
AccidentalleakagescouldoccurduringthecirculationoftheHTFinsomepartsnotshieldedbyinsulation,suchasaCR.Inthiscasethepressurisedfluidissprayedoutsideand,duetotheheightofthetowertheareaofdispersioncouldbelarge.
Synthetic oilNowadaysPTplantsinCaliforniaandSpainexhibitsomeleakagesofthesyntheticoilusedasHTF.ThereisalsoaprevailingHTFsmellintheinstallations.Leakageshavebeenmorecontrolledbynewinterconnectionelements(balljoints),whilesoilpollutioncanberecoveredbybacteriologicaldecontaminationorbyremovingandsubstitutinglargeamountsofground.Wheretherearesuperficialpondsorshallowgroundwater,thesyntheticoilpollutesthesoilandcouldpassveryfasttothewater,whereitmaybehighlytoxic.Thisfactsuggeststhatoilshouldbeavoidedinthecaseofveryvulnerableaquifers.
Theresearchanddevelopmentofthepastyearshaveledtovariousnewsystemsthatdonotneedanymorethesyntheticoil,butusewater/steamdirectlyasHTF,asinDSG(directsteamgeneration),gasesormoltensaltmixturesindirect/indirectsystems.ThechoiceoftheHTFhasvariousconstraintsbesidestheenvironmentsafeguardcosts,suchastheirimpactontheperformanceandefficiencyoftheplants.Thisimpliesacompromiseinordertocomplywithsafesolutions.
Advanced HTF solutionsOtheroptionsinvolveadvancedHTFs,including:
n Pressurisedgas,currentlyundertesting,e.g.atthePlataformaSolardeAlmería,Spain.Additionalworkisneededtoimproveheattransfersinthereceivertubesandtoensurecontrolofthesolarfield,whichismorecomplexthanthereferenceoildesign;
n MoltensaltdirectlyusedinthesolarcollectorsfieldthussimplifyingtheTES,becausetheHTFalsoservesasstoragemedium,e.g.intheArchimededemoplant,Italy.Theusedmoltensaltmixture,i.e.thelessexpensive“solarsalt”nowadaysusedforTES,solidifiesbelow235°C;thereforeauxiliaryheatingequipmentandexpensesareneededtoprotectthefieldagainstfreezing.Othermoltensaltmixturesareunderinvestigationtoreducethefreezingpointtoaslowas100°C;
n Densegas-particlesuspensions:itisproposedtousedensegas-particlesuspensions(approximately50%ofsolid)intubesasHTF.Thesetubes,setinabundle,constitutethesolarabsorber(orreceiver),placedatthetopofaCRsystem.ThisnewHTFbehaveslikealiquidwithanextendedworkingtemperaturerange:itstaysalmostliquidatanytemperature(thereisnofreezingtemperature)anditpermitstoincreasetheworkingtemperatureupto700°Candhigher.Moreover,itmaybeusedasanenergystoragemediumbecauseofitsgoodthermalcapacity.Itiscomposedofanyparticulatemineralthatwithstandshightemperatures,thusreducingtheenvironmentalimpactandaddressingthesafetyconcernincomparisonwithstandardHTF;
n Addingnanoparticles to theabovementionedfluids, thusobtaining theso-callednanofluids,wouldgreatlyenhancephysicalandtransportproperties,implyingapositiveimpactontheenvironment;
n Otherattemptstoreducethemeltingpointformoltensaltmixturesthroughtheuseofspecialadditiveshavetobeconsideredtoreducethepotentialenvironmentimpact.
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7.3.1.2 Heat transfer fluid characteristicsIntheANNEXIII:Heattransferfluidsvs.environmentalcomponents,differentHTFsarelistedtogetherwiththeimpactoftheircharacteristicsonthepossibleenvironmentalhazards.InTable4,thevariousfluidsareevaluatedonthebasisofavaluescalerangingfrom1to10onthebasisoftheirimpacttotheenvironmentcomponentsandtheirtechnicalandeconomiccharacteristics.
AmongallthepossibleHTFs,onlythemostcommonlyemployedand/orstudiedoneshavebeenselected,togetherwithsomelessinvestigatedbutverypromisingnanofluids,i.e.fluidscontainingnanoparticles:
n Thermaloil:Gilotherm,Therminol,etc;n Na,K(MS):NitratebinarymixtureNaNO3/KNO360:40wt%(generallydefinedas“solarsalt”);n Li,Na,K(MS):Nitrateternarymixturecontaininglithium,atthe“eutectic”composition:
NaNO3/KNO3/LiNO318:53:30wt%;n Ca,Na,K(MS):Nitrateternarymixturecontainingcalcium,atthe“eutectic”composition:
NaNO3/KNO3/Ca(NO3)215:42:42wt%;n HitechMSwithnitrite:TernarymixturecontainingNitrite(CoastalHitech©salt):
NaNO3/KNO3/NaNO27:53:40wt%;n CO2andH2O:CO2,air,steam;n Na,K(MS+nanoparticle):Solarsaltaddedwithnanoparticles(carbonnanotubes,Al2O3,TiO2);n CO2+nanoparticle:CO2,steamaddedwithnanoparticles(Al2O3,TiO2,CuO);n H2O+nanoparticle:Densegas-particlesuspensionsofoxidesorcarbides,typicalparticlediameter,50µm.
HTFs Thermal oil
Na, K (MS)
Li, Na, K (MS)
Ca, Na, K (MS)
Hitech MS with
nitrite
CO2 H2O Na, K MS+
nanop
CO2 + nanop
H2O + nanop
Parameters
Soilpollution 10 2 5 2 2 1 1 3 2 2Waterpollution 10 3 5 3 6 1 1 4 4 4Airpollution 10 1 1 1 1 2 1 2 3 3Toxicitytohumanpresence
10 1 1 1 3 2 1 2 2 2
Cost 10 1 5 3 2 1 1 4 4 4Freezingtemperature 1 10 2 5 2 1 1 10 1 1Costofhandlingequipmentandsystem
8 5 8 8 8 5 8 8 8 10
Upperthermallimit 10 2 2 6 6 1 1 3 2 2
TABLE4:HTF and environmental parameters
Theratingevaluationsareassignedconsideringavalueof10forthematerialpresentingtheworstlevelforthecharacteristicconcerned,andassigningtotheotherHTFsarelativevaluerespecttothemaximumone(from1to9),inparticular:
n Soil,water,airpollution;toxicityforhumans:thermaloilsarethemostpotentiallyharmfulmaterial,andtheyarealsoflammable;
n Freezingtemperature:thebinaryNaNO3/KNO360:40wt%exhibitsthehigherfreezingpoint;n HTFcost:thermaloilsarethemostexpensivematerialsatthemoment,however,thecostsfornanomaterials
particles,consideringtheirpreparationprocedures,havetobemorecarefullyestablished;n Costforhandlingequipmentandsystems:asystemconsistingofsteamandnanoparticlesispotentiallythemost
expensive.
ThechoicetousenormalisedvaluesallowsaqualitativecomparisonoffirstapproximationamongthevariousHTFs,inordertodefinethemostsuitableoneforaspecificapplication.Foramorepreciseandcarefulcomparisonitisnecessarytohavemoredatafromlaboratoryexperimentsanddemonstrationprojects.
Besidestheaspectsalreadyconsidered,thecomplexityandthepossibilityofrecoveryfromlikelyaccidents,e.g.asuddenleakofHTFfromaruptureofaflexibleorrotatingconnection,havetobeevaluated.
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7.3.1.3 Leakage consequencesInabsolute,theleaksofpuregasesandsteamaretheleastcomplex,presentingamomentaryhazardaroundthepointofdispersionoffluidathighpressureandhightemperature.Oncethedischargeends,noappreciablepollutionshouldremain.However, ifnanoparticleshavebeenaddedto the liquid, thepollutionmaybeveryimportant,dependingontheirnoxiousness.Ifthematerialisdispersedoveralargearea,norealisticpossibilityofremediationisachievable.
Similarleaksofmoltensalt,otherthanthemomentaryhazardduringdischarge,resultinaspillofliquidthatsolidifiesveryfastontheground,avoidingpenetrationofthesoil.Oncecooled,thesolidifiedmoltensaltcanberemovedalmostcompletelywithmechanicaltools,minimisingsoilimpact.Onlyinthecaseofconcurrentraincouldthesoilbepolluted,aswellasthegroundwater,iftherainisabundant.Thiswouldbemoresevereforamoreaggressivemixturesuchasmoltensaltwithlithium.WhileNaandKnitratesareusedinagricultureasfertiliserswithadefinitequantitysquaremeteroftreatedsoil,largerdispersedquantityofmoltensaltmixtureswithhigherimpactcouldpollutevulnerableaquiferssuchasshallowgroundwaterorponds.
Besidestheaspectsalreadyconsidered,thecomplexityandthepossibilityofrecoveryfromlikelyaccidents,e.g.asuddenleakofHTFfromaruptureofaflexibleorrotatingconnection,hastobeevaluated.
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7.3.2Reductionofwaterconsumption
7.3.2.1 Improved cooling systemsWaterconsumptionoftraditionalwet-coolingsystemsisveryhighanditisasignificantbarrierforthecommercialdeploymentofthistechnologyinaridareaswithalackofwaterresourcesandhighsolarradiationlevels.Develop-mentofnewapproacheswithwaterconsumptionlowerthancurrentwet-coolingsystemsandwithsimilarcostandefficiencyisaveryimportantR&Dtopic.
Althoughdry-coolingsystemsarealreadyavailable,theirhighercostandlowerefficiencyoftenmakethemnon-competitive.TwoexamplesofpossibleapproachestolowerthewaterneedsofSTEplantswithPTcollectorsaretheuseoftheso-callednegativegradientindesertareas,wheretheairtemperatureatnightismuchlowerthanthetemperatureduringsun-lighthours,andtheimplementationofhybridcoolingsystemsthatdependonwet-coolingforthesummeranddry-coolingforthewinter.
7.3.2.2 DesalinationDesalinationisavitalnecessitytomanycountries.Thisiswhyithasbeenhighlydevelopedduringthelastdecade,witheveryindicationthatthisactivitywillcontinuetogrowinthenearfuture.
Advantages:Desalinationneedsalargeamountofenergyandrequirestheassociationoflargeplantswithconventionalpowerfacilities.Therefore,thecombinationorintegrationofdesalinationintosolarthermalpowerplantsisaveryinterestingissuethatcanprovideasignificanttechnicalandeconomicadvantageforthefollowingreasons:
n Thetypicalgeographiccoincidenceofwatershortageandlimitationproblemswiththeexistenceofhighlevelsofsolarradiation,whichnormallymakewaterissuesatoppriorityformanysunnylocationsandforcestheuseofdrycoolinginsteadofwatercoolingsystemsforsolarthermalpowerplantswhennowaterisavailableorsevererestrictionsprevail;
n Thepossibilitytoreduceortheoreticallyeliminatetheconventionalcoolingrequirementsforsolarpowerplants;n Thereductionoffinancialschemesbasedonthesynergyeffectbetweenthetwotechnologies,solarpowerand
desalination,duetoreducedoverallinvestmentsbycombiningtwonormallyseparatedplantsintooneandbyobtaininghigherrevenuesthankstotheproductionoftwodifferentgoods:electricityandwater.
Drawbacks:However,thiscombinedconcepthasalsosomedrawbacks.Onedrawbackisthattheplantsneedlargeamountsoflandclosetothesea,whiletheDNIisnormallylowerincoastalareas.
ItshouldbenotedthattheLCOEandthelevelisedwatercosts(LWC)normallyincreaseasaconsequenceoftheenergylossesandtheefficiencyreductionatlocallevelbutthecombinedefficiencyandtheintegratedeconomicscouldimprovesignificantly.Thismayhaveapositivefinancialimpact.Therefore,inthesecases,indicatorssuchasreturnofinvestmentorpresentnetvaluemaybebetterparametersthantheLCOEandtheLWC,consideredseparately.
Asaconsequence,themainobjectiveofresearchactivitiesinthetopicistoincreasethecombinedefficiencyandlowerthecombinedcosts.
Integration
Strategicgoalsandobjectivespursuedarethefollowing:
n OptimisingheatextractionindifferentSTEtechnologiestobeabletodrivedesalinationprocesses;n Reducingcoolingrequirementsofsolarpowercycleswithoutpenalisingthethermodynamiccycleandexergy
efficiency;n Optimisingtheenergyandexergyofcombinedpowerandseawaterdesalinationprocesses;n Optimisingdesalinationtechnologiesforbettermatchingsolarpowercycleconditions.
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Multi-effect distillation (MED)
-InlettemperatureMulti-effectdistillation(MED)is,todate,themostthermodynamicallyefficientthermaldesalinationtechnology,withenergyconsumptionsbetween65and75kWhth/m3ofdesaltedwater(i.e.aconsumptionof65-75kWhofthermalenergypercubicmeterofdistilledwaterproducedbytheMEDunit).TypicalelectricityconsumptionofMEDplantsisaround1.5kWhe/m3.
ThemaininterestinusingthistechniqueisthattypicalenthalpyvaluesoftheexhauststeamofthepowerturbineareclosetotheonesrequiredbytheconventionalMEDtechnologywiththeadvantagethatthelatentheatofthissteamisveryhigh.Therefore,thetotalamountofenergynormallyrejectedishuge,thusmakingthedesalinationprocessveryattractive.AstheMEDplantwouldalsobethecoolerelementofthepowerblock,thetypicalcoolingissuescouldbereducedoreveneliminated.
-Thermo-compressionTypicalMEDplantsassociatedwithpowerfacilitiesincludethermo-compressiondevicestoincreasetheefficiencyofthewaterproduction.Thus,theyheavilypenalisethepowerproduction.Asaconsequence,thechallengeistodevelopimprovedMEDconceptsandspecifictechnologiesdealingwithsomekeycomponentssoastooptimise,fromthethermodynamicpointofview,theoverallcombinedefficiencywhencombinedwithsolarthermoelectricplants.
-TubebundlesUsingnanotechnologyforthetubebundlecoatingscanbeaninterestingoptiontoachieveaneffectiveheattransfer.Itcouldalsohaveapositiveimpactoncosts.
Reverse osmosis (RO)-EnergyrecoveryReverseosmosis(RO)istheleadingworldwidedesalinationtechnologytoday,duetoitslowenergyconsumption(from3.0to4.5kWhe/m3dependingonseawaterconditions;evenlowerconsumptionispossiblewithbrackishwater).Thishasresultedfromsignificantadvancementswithmembranesandenergyrecoverydevices.AsROonlyuseselectricity,thecouplingwithsolarthermoelectricplantsdoesnotprovideanyparticularsynergyeffects,asthedesalinationplantcanbeatadifferentlocationandthereforebeconsideredlikeanyotherpowerconsumptionsource.
-MechanicalenergyInaddition,therearesomeinterestingconceptsthatdeservetobeexplored.ROneedsmechanicalenergytoreachtherequiredpressure(around70bar),whichcanbeprovidedbythesolarsteamcycleatahigherefficiencythanconventionalelectricallydrivenpumps.Intheory,thiscouldavoidtheinefficiencies(implyingeconomicsavings)duetotheelectricityconversion.Thesavedelectricitycanthenbeusedtoproducetheadditionalmechanicalenergynecessaryforthereverseosmosisprocess.Thisapproachcouldalsopermittheexplorationofotherpromisingideasrelatedtotheimprovementofcurrentenergyrecoverydevices,thusincreasingtheoverallefficiency.
Other desalination technologies-Humidification-dehumidification(HDH)TheHDHisadesalinationprocesswheredistillationisachievedunderatmosphericconditionsbyanair loopsaturatedwithsteam.HDHisbasedontheprincipleofmassdiffusionusingdryairtoevaporatesalinewater,thushumidifyingtheair.Thehumidificationcycleisacombinationofevaporatorandcondenser:theairflowishumidi-fiedintheformeranddehumidifiedinthelatter.Aircirculatesbynaturalorforcedconvection.Airflowextractsthesteamfromsaltwater.Sensibleheatandfreshwaterisproducedbycondensingoutthesteam,whichresultsinthedehumidificationoftheair.Thecondensationoccursinanotherexchangerinwhichsaltwaterispreheatedbylatentheatrecovery.Solarenergyisexternallyprovidedtocompensateforthesensibleheatloss.
-Membranedistillation(MD)MembraneDistillation(MD)isanevaporativeprocessinwhichthesteam,drivenbyadifferenceinsteampres-sure,permeatesthroughahydrophobicmembrane,thusseparatingthewaterphasefromthesalt.Oncethesteamhaspassedthroughthemembrane(porediameterintherangeofMFbetween100nmand1µm,withtypicalvaluesaround0.3µm)itcanbeextractedordirectlycondensedinthechannelontheothersideofthemembrane.Theseparationeffectofthesemembranesisbasedonthehydrophobicityofthepolymermaterialconstitutingthemembrane,asmolecularwaterintheformofsteamcanpassthroughthemembranebutnottheliquid.However,thisistrueuptoacertainlimitingpressure,theliquidentrypressure,which,ifexceeded,wetsthemembrane,thuslosingitsproperties.
Theresearchanddevelopmenteffortsinthesetechnologiesareofspecialinterestwithviewtotheadaptationofspecificturbineexhauststeamconditionswhichlimitoravoidanypowerproductionpenaltyatthepowerblock.
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35-TheGOR(GainOutputRatio)istheratiobetweentheamountof(latent)heatneededfortheevaporationofthewaterproducedandtheinputenergysuppliedtothesystem.TheGORisameasureoftheamountofthermalenergyconsumedinadesalinationprocessandthereforetranslatestheefficiencyoftheprocess.
Cooling implications-Thermo-electricplantcoolingAnotherresearchtopicofinteresttothecouplingofsolarthermalelectricityanddesalinationisrelatedtotheimpli-cationthatallthesepossiblecombinationsandtechnologiescouldhaveoverthecoolingofthepowerblock.Thetopicisofspecialinterestaswaterisoneofthemajorissueswhensolarplantsarelocatedinwaterscarcityareas,whicharethemostcommonlocationsindesertorsemi-desertenvironments.
Consideringthatthedesalinationunitcanbethe“cooler”oftheconventionalpowerblockandthatmostdesalina-tiontechnologiesalsoneedscooling,anotherimportantareaofresearchistheoptimisationoftheintegratedorcombinedcoolingprocess,whichissummarisedinthefollowingfigure.
Once-through
Hybrid Cooling
CSP POWER PLANT
Wet Cooling
DESALINATION PLANT
Once-through
FIGURE18:Interactions and possible cooling options between solar thermal and desalination plants
7.3.2.3 Solutions for desert locationsPlantsisolatedindesert locationssufferfromtechnicaldifficulties: theanti-soilingcoatingshouldnotjeopardisethereflectivityofmirrorsandshouldpossiblyenhancethetransmissivityofcoverglasses.Thechallengescanbealleviatedbythereductionofsoilingbysurfacecoatings,theanalysisofsitespecificdusting,themanagementofcleaningcycleandthedevelopmentofcleaningtechnologieswithlowwateruseandwithahighautomation.
Thistopichasaspectsthataresharedwithothertechnologies,butgiventheparticulargeometryoflinearFresnelprimarymirrors;thereisroomforresearchanddemonstrationofsolutionsadaptedtolongalmost-flatmirrors.PrimarylinearFresnelmirrorscanalsobeturnedfacedownatnight,reducingcondensationproblemsassociatedwithradiativecoolingofthemirrorsurfaceatnight.
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TABLEIX:RESEARCHPRIORITIESFORENVIRONMENTALPROFILE
Topics Objectives Parameter/Target/Action Short Mid Long
Heat transfer fluids
Heattransferfluidsvs.environmentimpact
•ReducetheimpactontheenvironmentfromemissionsandaccidentalleaksofHTFs,maintainingareasonableequilibriumwithcostsandefficiency
Parameter:Levelofrisktowardswaterandland(R)Target:R=MediumAssumingtheregulationECN°1272/2008,and91/155/CEE),thesubstancetobeconsideredshouldbenotclassifiedasverytoxic,toxicandharmful(Xn)
X
Heattransferfluidchar-acteristics
•ReducethecostoftheHTFandofequipmentandsystemnecessaryforitshandlingwithrespectofoil
Parameter:CostofequipmentandsystemforHTFhandlingTarget1:50%Target2:30%
X
Leakageconse-quences
•ForthefeasiblenewHTFsshallbeissuedproceduresanddevicesforremediationofpollutantaccidents
Parameter:costofremediation(C)intherespectofactualonefortheaccidentwithoilleakage(e.g.fullbreakofametallichose)Target:C<40%Action:Anyprocedureofremediationwillensurethefullrestorationoftheprevioussituation
X
Improved cooling systems •Lowerthewaterconsumptioninordertoachieveabettersustainability
Parameter:PowerblockwaterconsumptionperkWhofelectricityproducedkg/kWheTarget1:<2.5kg/kWhe
X
Target2:<2kg/kWhe X
Desa
linat
ion Integration Mechanical
energy•OptimisetheintegrationofMED
desalinationintothermoelectricsolarpowerplants
Parameter:PowerblockinvestmentTarget:-10%inthewholeinvestmentagainsttheindependentinstallationofequivalentsolarpoweranddesalinationplants
X
Intermittentdesalina-tionsystemoperation
•Optimisetheintermittenceofdesalinationplantoperationstoavoidanynegativeinteractionwithpowercycle
Parameter:TimeforstartupofthermallydrivendesalinationunitTarget:<1hour
X
Multi-EffectDistillation(MED)
Inlettemperature
•DesigninnovativeMEDsystemsreducinginlettemperaturetobettermatchingwithexhaustturbinesteam
Parameter:CombinedpowerandwaterproductionthermodynamicefficiencyTarget:+5%
X
Thermo-compression
•Optimisethethermo-compressiontotheeffectiveuseofexhaustturbinesteamtoMEDenergyfeeding
Parameter:ConventionalcoolingrequirementsofsteampowercycleTarget:atleast-50%
X
Tubebundles
•Increasetheeffectiveheattransfersurfacebynanotechnologycoating
Parameter1:CostsoftubebundlesmaterialsandothermetallicsurfacesTarget1:-30%Parameter2:MEDinvestmentcostsTarget2:-10%
X
ReverseOsmosis(RO)
Energyrecovery
•Integrateenergyrecoveryintodirecthighpressuremechanicalsystem=>reductionofnetme-chanicalenergysupplyneeded
Parameter:AchievementofmechanicalenergyrecoveryTarget:>98%
X
Mechanicalenergy
•UsesteamfromturbineextractiontoproducethemechanicalenergyneededbythehighpressureROpumps
Parameter:Directpressureproduction(p)andexergyefficiencies(η)Target:p=70barandη >90%
X
Otherdesalinationtechnologies
Humidifica-tion-Dehu-midification(HDH)
•DevelopadequateHDHtechnologiestotheeffectiveuseofexhaustturbinesteam
Parameter1:Achievementofeffectiveseawaterdesalination(GOR32)andassociatedinlettemperature(T)Target1:GOR>4andT<60°CParameter2:PowerblocknormalcoolingrequirementsTarget2:-25%
X
MembraneDistillation(MD)
•DevelopadequateMDtechnologiestotheeffectiveuseofexhaustturbinesteam
Parameter1:Achievementofeffectiveseawaterdesalination(GOR)andassociatedinlettemperature(T)Target1:GOR>4andT<60°CParameter2:PowerblocknormalcoolingrequirementsTarget2:-25%
X
Coolingimplications
Thermo-electricplantcooling
•Deductionofexternalactivecoolingneeds
Parameter:OverallthermalenergyremovalfromtheintegratedpoweranddesalinationplantTarget:-50%
X
Solutions for desert locations •Reductionofoperationandmaintenancecost
Parameter:WaterrequirementsforwashingTarget:Reductionoftypically1,500m3/(MW*a)byafactorof10(90%reduction)
X X
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arringanunthinkablecatastrophe,theexpansionoftheworldpopulationwillnotabateinthenearormediumterm,andneitherwillthelegitimatedemandsofthatpopulationformoreenergytomeetbasicphysicalneeds.Tomeetthoseneedsatall,immediatechallengesmustbeaddressed,andfewareascriticalasthechallengetogenerateelectricityreliablywithoutaddingtogreenhousegasemissions.
Fortunately,thesolarsourceincidentonEarthismorethanenoughtomeetthoseneedsinthenearandmediumterm,ifitcanbeconvertedwithareasonableefficiencyandatareasonablecost.Severaloptionsholdthepromisetomeetthisneed:thermalconversion(STE)anddirectconversion(notablyPV)aretwoofthemostpromising.Itislikelythatbothoftheseoptionswillhaveanimportantroleashumanslearntoaddressthechallengestheyface,butsomecharacteristicsofSTEmakethisoptionofparticularinterest.
Oneofthesecharacteristicsis“dispatchability”–aproperlydesignedSTEplantcanprovideenergyintheformofelectricitywhenandifneeded.Theotherveryimportantcharacteristicistheefficiencyofconversionofthesolarresource.Thermodynamiclimitscanbeverygenerouswhenthethermalsourceisoneatveryhightemperature.
GreatprogresshasbeenachievedinSTEinaveryshorttimeframewithrelativelymodestgovernmentsupport,butpastresultsgiveonlyahintofwhatispossiblewithalongerlearningcurveandwithafirmcommitmentfromgovernmentanddecisionmakers.SomeofthiscommitmentmusttaketheformofsupportforR&D.
ESTELAhasgeneratedthisdocumenttoidentify,withineachoftheSETtechnologiesthoseareaswhereR&Dholdsthemostpromisetofurtherthesharedgoalstoimproveperformanceandlowercosts.Someofthepromisedimprove-mentsmayleadtoincrementalimprovementsbythemselves.Together,theymayleadtomajorbreakthroughsandeventodisruptivetechnologies.
AmajoradvantageofSTEisthattherearemanyoptionsthathavebeenidentifiedandthattheseoptionsmayservedifferentnichesofenergygeneration.Twomajortechnologiesdiscussedinthisreporthavebeenparabolictroughsandcentralreceivers:bothoftheseoptionsledthemselvestointegrationwithinageneratingsystemwithstorage.Theother twooptionsdiscussedhavebeenparabolicdishesandFresnel lenses,whichcanmeet theneedsofhighefficiencyofconversionandverylowcost,respectively.ImprovementsandareasofR&Dhavebeenidentifiedforalloptions.
Theyhavealsobeencomparedintermsofthepotentialforthealleviationofenvironmentalimpact,thedevelopmentoflocalindustryandthecreationofjobs.
ThevarietyofSTEoptionsalsoposesachallenge,becauseresourcesarefiniteanddecisionsonR&Dresourceallocationmayunwittinglypenalisedisruptiveoptionswithagreatpotential.Evenwhenconsideringfinancialincentivesinsupportoftherenewableindustry,decisionsmaypenalisesomeoptions.InadditiontoidentifyingthepathsopenforR&Dforcomponents,subsystemsandsystems,andareaswhereexternalsupportmaybeneeded,thisdocumenthassuggestedpossibletoolstoassistdecisionmakers.
Importantrecommendationsfromthisreportarethatsupportmustbegiventosustaindemonstrationprojectsforlessmaturetechnologies,aswellasforR&Dincomponentsandsystemstodrawonanundeniablealbeitshorthistoryofsuccesstobridgethegaptoafullysustainablefuture.AnotherimportantrecommendationisthatsomesupportmustalsobegiventoR&DinscientificallysoundinnovativeSTEoptionswiththepotentialtosuccessfullycombateclimatechange,savetheEarthandmeethumanenergyneedsfortheforeseeablefuture.
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bIbLIOgrAPHY
n ANEST.CSPinItaly:2012-2014theageofaccomplishments.Presentation.Brussels,June2012
n A.T.Kearney/ESTELA.SolarThermalElectricity2025-Cleanelectricityondemand:attractiveSTEcoststabiliseenergyproduction,June2010
n Deloitte/Protermosolar.MacroeconomicimpactoftheSolarThermalElectricityIndustryinSpain,October2011
n EREC.MappingRenewableEnergyPathwaystowards2020.EURoadmap.Brussels,March2011
n ESFRI.StrategyReportonResearchInfrastructures.Roadmap.2010
n ESTELA.SolarThermalElectricityEuropeanIndustrialInitiative(STE-EII)-ImplementingPlan2010-2012.Brussels,May2010
n ESTELA.‘SolarPowerfromEurope’sSunbelt’,AEuropeanSolarThermo-ElectricIndustryInitiativeContributingtotheEuropeanCommission-‘StrategicEnergyTechnologyPlan’.Brussels,June2009
n ESTELA.TheEssentialRoleofSolarThermalElectricity-ArealOpportunityforEurope.PositionPaper-Brussels,October2012
n ESTELA.TheFirst5YearsofESTELA.Brussels,February2012
n ESTELA.WorkshoponFinancingtheSET-Plan.Presentation.Brussels,June2011
n EuropeanAcademiesScienceAdvisoryCouncil.Concentratingsolarpower:itspotentialcontributiontoasustainableenergyfuture.EASACpolicyreport16,November2011
n GDFSUEZEnergyIberia.PortugalasalivinglabforRESpilotproject.PresentationfortheEUsustainableEnergyWeek.Brussels,June2012
n IEA.TechnologyRoadmap.ConcentratedSolarPower.Paris,2010
n SETIS–EPIA–ESTELA.KeyPerformanceIndicatorsfortheSolarEuropeIndustrialInitiative.Version1,Brussels,October2011
bibl
iogr
aphy
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IndeX FIgureS And TAbLeS
n Figure 1 STEestimateinstalledcapacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28n Figure 2 TotalnumberofjobscreatedbytheSTEindustry(2008-2010)inSpain13. . . . . . . . . . . .34n Figure 3 ExpectedLCOEreductionsfrom2012to2025. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35n Figure 4 STEprojectlifetime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35n Figure 5 Impactofdirectnormalinsolation(DNI)onlevelisedcostofelectricity. . . . . . . . . . . . . . . .36n Figure 6 OverviewoftheEuropeanschemesforSTEfunding. . . . . . . . . . . . . . . . . . . . . . . . . . . .42n Figure 7 ElectricitydemandandSTEproductiononJuly11th2012 . . . . . . . . . . . . . . . . . . . . . . .50n Figure 8 Combinationofstorageandhybridisationinasolarplant. . . . . . . . . . . . . . . . . . . . . . . .51n Figure 9 LCOEcomparisonofsolarthermalenergyversusconventionalsources . . . . . . . . . . . . . . .54n Figure 10 Frominnovationtocommercialoperation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57n Figure 11 Financingfirstcommercialplantsforbreakthroughtechnologies . . . . . . . . . . . . . . . . . . . .58n Figure 12 SensitivityanalysisofseveralparametersontheLCOEofa50MWePTplantwith7.5hours
ofthermalstorage(Referencecase:plantlocatedinSouthernSpain,2011). . . . . . . . . . . .60n Figure 13 Differentinterconnectingelementsusednowadays. . . . . . . . . . . . . . . . . . . . . . . . . . . . .68n Figure 14 Typicalsecondaryconcentratorredirectingtheimpingingsunrays
fromtheheliostatfieldtoareceiverplacedatgroundlevel. . . . . . . . . . . . . . . . . . . . . . .74n Figure 15 Free-pistonStirlinggenerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .81n Figure 16 Maincomponentsandsub-systemsofaSTEplantincludingstorage. . . . . . . . . . . . . . . . .84n Figure 17 Comparisonoftoday’sstateoftheartPTpowerplantswithandwithoutstorageand
targetsforsolar-onlyandhybridconceptsin2015 . . . . . . . . . . . . . . . . . . . . . . . . . . . .85n Figure 18 Interactionsandpossiblecoolingoptionsbetweensolarthermalanddesalinationplants. . .102
n Table 1 Technologiesmaturityforshort,midandlongtermperiod. . . . . . . . . . . . . . . . . . . . . . . .22n Table 2 BreakdownbyindustryactivityofjobscreatedbytheSTEindustry(2008-2010)inSpain . .34n Table 3 Solarpowercostreductionfactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56n Table 4 HTFandenvironmentalparameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
n Table I ResearchPrioritiesforCross-cuttingIssues. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65n Table II ResearchPrioritiesforParabolicTroughCollectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70n Table III ResearchPrioritiesforCentralReceiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75n Table IV ResearchPrioritiesforLinearFresnelReflectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79n Table V ResearchPrioritiesforParabolicDishes.....................................83n Table VI ResearchPrioritiesforHybridisationandIntegrationSystems . . . . . . . . . . . . . . . . . . . . . .89n Table VII ResearchPrioritiesforStorage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93n TableVIII ResearchPrioritiesforDispatchability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96n Table IX ResearchPrioritiesforEnvironmentalProfile. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103
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108 STrATegIc reSeArcH AgendA 2020-2025
Atafirststage,asetofKPIhasbeenelaboratedfortheSTESolarEuropeanIndustrialInitiative(SEII)inordertoensurethemonitoringoftheSET-PlanInformationSystem(SETIS).TheKPIhavebeenreviewedfortheStrategicResearchAgendaandsomeparametershavebeenincluded.
Thelevelisedcostofelectricity(LCOE)couldbeconsideredasthemainindicatortomonitortheoverallprogressoftheSEIItowardsincreasedcostcompetitiveness.
TheLCOEcanbeexpressedbythefollowingstandardformula:
Anne
x I
AnneX I: keY PerFOrmAnce IndIcATOrS
ESTELAdevelopedasetofKPIinordertofollowtheprogressininnovationoftheSTEindustry.
OVER-ARCHINGKPIDescription Metric Values
BASELINE TARGETS
2010 2015 2020/2025
Competitiveness KPI-1 Levelisedcostofelectricity(c€/kWh)fora50MWplantlocatedinsouthernEuropewithalocalDNIof2,050kWh/m².
22c€/kWh -15% -45%
ACTIVITYKPIsDescription Metric BASELINE TARGETS
2010 2015 2020/2025
1.Increaseefficiencyandreducecosts
KPI-2 Increasedsolar-to-electricityconversionefficiency 15%Trough
8.5%Fresnel17%Dish12.5%Tower
(relativetobaseline)+5%Trough+15%Fresnel+15%Dish+50%Tower36
(relativetobaseline)+20%Trough+30%Fresnel+30%Dish+65%Tower
KPI-3 IncreaseHTFTemperature 400°CTrough280°CFresnel650°CDish250°CTower
560°CTower420°CFresnel
>500°CTrough500°CFresnel
>900°CDish>900°CTower
KPI-4 ReducecostofinstalledproductsandO&Mforstate-of-the-artcommercialplants
2%ofCAPEX -10% -20%
KPI-5 Reducepowerblockcosts 1,300€/kWpTroughwiththermaloil
1,300€/kWpMoltenSaltasHTF1,000€/kWpHybridplant
1,200€/kWpAdvancedHTF800€/kWpAdvancedhybridplant
KPI-6 Reducecollectorcosts 250€/m2Troughwiththermaloil
250€/m2
MoltenSaltorhybridplant
200€/m2
Advancedhybridplant
KPI-7 ReducethespecificcostoftheHTFsystem
330€/kWth
Troughwiththermaloil295€/kWthMoltenSaltasHTF165€/kWth
Hybridplant
120€/kWthAdvancedHTF100€/kWth
Advancedhybridplant
2.Improvedispatchability[Figuresconcerningstoragearebasedonlyonmoltensalttechnology]
KPI-8 Investmentcostofstorage 35,000€/MWhth 20,000€/MWhth 15,000€/MWhth
KPI-9 Increaseefficiencyofstorage
94% 96%
3.Improvetheenvironmentalprofile
KPI-10 Substantialreductionofwaterconsumptionwithonlyminorlossofperformancerelativetocurrentwatercoolingsystem
3.5liters/kWh <1liter/kWh
36-AfterGemasolarbreakthrough
It+Mt+Ft
(1+rt)t
Et
(1+rt)t
LCOE=
∑t=1
∑t=1n
n
109december 2012
Anne
x I
WhereIt,MtandFtaretheexpendituresoninvestments,maintenanceandinterestsinyeart,Etistheelectricitygeneratedinyeart,rtisthecostofcapitalinyeartandnisthelifespanoftheplantinyears.
Itisessentiallytheresultofdividingthepresentvalueofthecostsbythepresentvalueoftheenergyproduced.Eachcostisconvertedintoitspresentvalue,dependingontheyearinwhichthiscostisincurredandthesamehappenstotheelectricityproduced.Therefore,thewayinwhichthecapitalisinvestedplaysaveryimportantroleindeterminingtheLCOEalongwiththeO&Mandfinancialcosts.
Thesimplifiedcostbreakdownstructureofa50MWSTEplantwith7.5hoursofstorageisconsideredasfollows:
nSolarfield 50%nPowerblockandrelatedinfrastructure 25%nStoragesystem 20%nOthers 5%
ThisbreakdownisusedinordertocalculatetheimpactofthecostreductiontargetsatsubsystemlevelintheLCOE.
Forthepurposeofmonitoring,atafirststage,referenceSTEplantsandtheirrespectiveLCOEswillbeconsideredas50MWPTplantlocatedintheSouthofEurope–DNIaround2,050kWh/m².Thereferenceplantassump-tionsforcalculationoftheLCOEKPIareindicatedinthistablefor2010:
CSP reference systemDNI 2,050kWh/m²
Totalplantcapacity 50MW
Capitalinvestmentcost 300M€
O&Mcosts(inpercentageofinvestmentcosts) 2%
Capacityfactor 42%
Costofcapital 9%
Projectlifetime 40years
BaselineLCOEfor2010 22c€/kWh
110 STrATegIc reSeArcH AgendA 2020-2025
Anne
x II
AnneX II: PAST And PreSenT eu-Funded PrOjecTS
FP Topic description Projects EC contribution (€)
DemonstrationPlants
FP 5 PS10Firstsolarthermaltowerplant PS10 5.000.000
FP 5 MainCSPcomponentsforhigh-temperatureoperation AndaSol 5.000.000
FP 5 SolarTressolarthermalpowerplantwithstorage SOLARTRES/GEMASOLAR 5.000.000
FP 7 Demonstrationofinnovativemulti-purposesolarpowerplant MATS 11.755.552
Systems,ComponentsandStorage
FP 5 DirectSolarSteamgeneration DISS 2.000.000
FP 5 Solarvolumetricairreceiverforcommercialsolarplants SOLAIR 1.497.092
FP 6 CostreductionfordishStirlingsystems EURODISH 750.000
FP 6 EnergystorageforDirectSteamSolarpowerplants DISTOR 2.228.917
FP 6 EuropeanCSProad-mapping ECOSTAR 223.129
FP 7 UsingCSPforwaterdesalination MED-CSD 999.960
FP 7 ImprovetheenvironmentalprofileoftheCSPinstallations SOLUGAS 5.997.752
FP 7 UsingCSPforwaterdesalination DIGESPO 3.280.000
FP 7 Energyproductionbyacombinedsolarthermionic-thermoelectricsystem E2PHEST2US 1.980.000
FP 7 Dry-coolingmethodsformulti-MWsizedconcentratedsolarpowerplants MACCSOL 4.088.546
FP 7 MainCSPcomponentsforhigh-temperatureoperation HITECO 3.440.194
FP 7 ThermochemicalEnergyStorageforConcentratedSolarPowerPlants TCSPOWER 2.850.000
FP 7 AdvancedheattransferfluidsforCSPtechnology CSP2 2.260.000
FP7 Newsystemforthermalenergystorageusingmoltensalt OPTS 8.650.000
SolarHybridPlants
FP 5 Solarhybridgasturbineelectricpowersystem SOLGATE 1.498.772
FP 5 DishStirlinghybridsystem HYPHIRE 971.894
FP 5 Desalinationandprocessheatcollector EUROTHROUGH 1.199.899
FP 6 Solar-HybridPowerandCogenerationplants SOLHYCO 1.599.988
FP 7 Novelsolar-assistedfuel-drivenpowersystem SOLASYS 1.568.320
FP7 PThybridisedwithbiomassproducingelectricityandfreshwater ARCHETYPESW550 14.385.217
FP7 InnovativeconfigurationforafullyrenewablehybridCSPplant HYSOL 6.168.484
SolarChemistry
FP 5 Solarcarbothermicproductionofzinc SOLZINC 1.284.282
FP 5 / 6 Solarhydrogenviawatersplitting HYDROSOLIandII 3.499.849
FP 6 Solarsteamre-formingofmethane-richgas SOLREF 2.100.000
FP 6 Hydrogenfromsolarthermalenergy SOLHYCARB 1.997.300
ResearchInfrastructure
FP 6 HighfluxsolarfacilitiesforEurope SOLFACE 345.000
TOTAL 103.620.147
111december 2012
Anne
x II
I
AnneX III: HeAT TrAnSFer FLuIdS VS. enVIrOnmenTAL cOmPOnenTS
HTF Melting (liquid) point
Risk for environment (according to regulation (EC) No 1272/2008, and 91/155/CEE)
Toxicity (according to regulation (EC) No 1272/2008, and 91/155/CEE)
Compatibility with air
Upper thermal point (°C)
Approximate cost, taking as unity the value for thermal oils
Nitratescontainingmixtures
≈90°C-235°C •Waterandlandenvironment:lowrisk(mediumiflithiumisemployed)
•Oxidisingagent•Verytoxicforfishes•Lithiumisextremely
toxicforplants
•Relativelylowacuteoraltoxicity
•Causesseriouseyeirritation
Stable ≈600°C,≈430°Cifcalciumisemployed
From1/7(Na/K60/40wt%mixture)to1/2(iflithiumisemployed)
Nitratesandnitritescontainingmixtures
≥142°C •Waterandlandenvironment:mediumrisk
•Oxidisingagent•Verytoxictoaquaticlife,
especiallyforalgae
•Medium-highoraltoxicity
•Causesseriouseyeirritation
Possibleoxidation
450(underair)538(undernitrogen)
1/3
Thermaloils(biphenyl-diphenyloxidemixtures,alsoterphenylandphenantrene)
-18°C-12°C •Waterandlandenvironment:highrisk
•Verytoxictoaquaticlifewithlonglastingeffects
•Marinepollutant•Verytoxicforalgae,
fishes,crustaceans
•Harmfulifinhaled•Causeseyeburns,
irritationtorespira-torytractandskin
•Containsmaterialwhichcancauseliverandnervedamage
Firepoint:127°C-143°CAutoignitionTemperature(ASTMD-2155)585°C-621°C
≤440(undernitrogenpressure)
1
Gases/steam Gas 1/10
Nanoparticlesmaterials(nanoparticlesadditivetogasesorliquids)
Ceramicnanoparticles:Al2O3, TiO2
Practicallyinsolubleinwater,canbeconsideredecologicallysafe.
Fewdataavailable,butprobablylowtoxiceffects.
Dependsonnanoparticlesandcarrierfluidchemicalnature.Ninanoparticlesisaflammablesubstance.
Riskofparticlessizegrowingathightemperatures
DependsonnanoparticlesandcarrierfluidchemicalnatureMetaloxides
nanoparticlesCuO:Verytoxictoaquaticorganisms,maycauselong-termadverseeffectsintheaquaticenvironment.SnO2:Noparticulareco-logicalproblemsexpected.
CuO:Harmfulforingestion.SnO2:Ifparenteraladministeredtincompoundsarehighlytoxic.
Metallicnanoparticles:Ni
Harmfultoaquaticorganisms,maycauselong-termadverseeffectsintheaquaticenvironment.
Dangerofseriousdamagetohealthbyprolongedexposurethroughinhalation.Maycausesensitisationbyskincontact
Carbonnanotubes
Noparticularecologicalproblemsexpected.
Causesseriouseyeirritationandrespira-torytractirritation
112 STrATegIc reSeArcH AgendA 2020-2025
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