ESTELA Strategic Research Agenda 2020-2025

European Solar ThermalElectricity Association

december

2012

SOLAr THermAL eLecTrIcITY

STrATegIc reSeArcH AgendA 2020-2025


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

[email protected]

www.estelasolar.eu

Printed on Satimat green, silk coated paper, FSC® certified, produced from 60% FSC® certified

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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




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

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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

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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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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

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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.

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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


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


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

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0

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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


Hist

ory

1

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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Hist

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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.


Hist

ory

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

THe brILLIAnT FuTure OF SOLAr THermAL eLecTrIcITY PLAnTS

23december 2012

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.

2

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InduSTrY OVerVIew And reLATed ecOnOmIc ASPecTS


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

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10 M

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200

MW

694

MW

290

MW

500

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5,00

0 M

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2,00

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3,00

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290

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150

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2,00

0 M

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2,00

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1,00

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40 M

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00 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


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



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.


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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STATe-OF-THe-ArT OF STe TecHnOLOgIeS


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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.

Infinia–YumaPowerDishII

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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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FIGURE8:Combination of storage and hybridisation in a solar plant

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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


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

Rows of mirrors concentrate the sunrays onto a receiver tube where the HTF is pumped.

✔ Demonstration✔ Heat applications

A group of mirrors with a parabolic shape reflect the sun to an engine located in the focus point

✔ Demonstration✔ Distributed power

Description

Track recordApplication

Next challenges Incrementalinnovationandpossiblebreakthroughs

PT CR LF PD

Commercialoperation

Commerciallyprovenforutility

scalepower

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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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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)

62STrATegIc reSeArcH AgendA 2020-2025

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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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LaboratoryatFraunhoferISEfortestingthedynamicaloperationofhightempera-turestoragesystemsandsmallsteamheatenginesforcombinedheatandpower.Thesteamoutputofasolarfieldusingconcentratingcollectorsissimulatedinrealtimebyagasheaterwithevaporator

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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

X X

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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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


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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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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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


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

7


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


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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

1

Sola

r Out

put

2

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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Hybridisation with large steam plants

HTF/Steamcycleheatexchangers

•Increasesolarheat-to-electricityconversionefficiency

Parameter:ηth-elec(includingheatexchangers)

Target1:ηth-elec>40% X


Boilerdesign •Newboilerdesignbestsuitedtothecouplingwithexternalheat

Parameter:ηth-elec(includingheatexchangers)



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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Storage design

StoragesystemforthermaloilasHTF

Singletanksolutions

•Reducethecostsofstorageandincreasethestorageefficiencyanddispatchability

Parameter:SpecificcostsTarget:25€/kWhth

X

Solidmediastoragesolutions



X

StoragesystemformoltensaltasHTF

Newsaltmixtures •Reducethecostsofstorageandincreasethedispatchability

•Workingathighertemperaturestoincreasethecycleefficiencyoftheplant

•Increasesolartothermalefficiencyusingsaltwithlowerfreezingtemperatureduetolowerovernightheatlosses.


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



X

•Decreasethethermallossesbyintegrationofthesteamgeneratorintothetank

Parameter:ηth-elec

Target:ηth-elec=+1%X

StoragesystemforsteamasHTF •Minimiseenergylossesinheattransferandreducethecostofstorage


(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


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



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

7


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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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

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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

Ind

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december 2012 107december 2012


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


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


note

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