solar water heating -wiki
DESCRIPTION
Solar water heatingTRANSCRIPT
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Roofmountedclosecoupledthermosiphonsolarwaterheater.
SolarwaterheatingFromWikipedia,thefreeencyclopedia
Solarwaterheating(SWH)istheconversionofsunlightintorenewableenergyforwaterheatingusingasolarthermalcollector.Solarwaterheatingsystemscomprisevarioustechnologiesthatareusedworldwideincreasingly.
Ina"closecoupled"SWHsystemthestoragetankishorizontallymountedimmediatelyabovethesolarcollectorsontheroof.Nopumpingisrequiredasthehotwaternaturallyrisesintothetankthroughthermosiphonflow.Ina"pumpcirculated"systemthestoragetankisgroundorfloormountedandisbelowthelevelofthecollectorsacirculatingpumpmoveswaterorheattransferfluidbetweenthetankandthecollectors.
SWHsystemsaredesignedtodeliverhotwaterformostoftheyear.However,inwintertheresometimesmaynotbesufficientsolarheatgaintodeliversufficienthotwater.Inthiscaseagasorelectricboosterisusedtoheatthewater.
Contents
1Overview2History
2.1Mediterranean2.2AsiaPacific
3Systemdesignrequirements3.1Freezeprotection3.2Overheatprotection
4Typesofsolarwaterheatingsystems4.1Directandindirectsystems4.2Passiveandactivesystems4.3Passivedirectsystems4.4Activeindirectsystems:drainbackandantifreeze4.5PoweringaheatpumphotwaterheaterviaSolarPVpanels4.6Aroughcomparisonofsolarhotwatersystems
5CollectorsusedinmoderndomesticSWHsystems6Heatingofswimmingpools7Economics,energy,environment,andsystemcosts
7.1Energyproduction7.2Systemcost7.3Operationalcarbon/energyfootprintandlifecycleassessment
7.3.1Terminology7.3.2Carbon/energyfootprint7.3.3Lifecyclecarbon/energyassessment
8Doityourself(DIY)systems9Systemspecificationandinstallation10Standards
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AsolarwaterheaterinstalledonahouseinBelgium
10Standards10.1Europe10.2UnitedStates10.3Australia
11APPENDIX1.Worldwideuse11.1Topcountriesworldwide11.2SolarheatinginEuropeanUnion+Switzerland
12Seealso13References14Externallinks
Overview
Waterheatedbythesunisusedinvariousways.Whileperhapsbestknowninaresidentialsettingtoprovidedomestichotwater,solarhotwateralsohasindustrialapplications,e.g.togenerateelectricity.[1]Designssuitableforhotclimatescanbemuchsimplerandcheaper,andcanbeconsideredanappropriatetechnologyfortheseplaces.TheglobalsolarthermalmarketisdominatedbyChina,Europe,JapanandIndia.
Inordertoheatwaterusingsolarenergy,acollector,oftenfastenedtoarooforawallfacingthesun,heatsaworkingfluidthatiseitherpumped(activesystem)ordrivenbynaturalconvection(passivesystem)throughit.[2]Thecollectorcouldbemadeofasimpleglasstoppedinsulatedboxwithaflatsolarabsorbermadeofsheetmetal,attachedtocopperheatexchangerpipesanddarkcolored,orasetofmetaltubessurroundedbyanevacuated(nearvacuum)glasscylinder.Inindustrialcasesaparabolicmirrorcanconcentratesunlightonthetube.Heatisstoredinahotwaterstoragetank.Thevolumeofthistankneedstobelargerwithsolarheatingsystemsinordertoallowforbadweather,andbecausetheoptimumfinal
temperatureforthesolarcollectorislowerthanatypicalimmersionorcombustionheater.Theheattransferfluid(HTF)fortheabsorbermaybethehotwaterfromthetank,butmorecommonly(atleastinactivesystems)isaseparateloopoffluidcontainingantifreezeandacorrosioninhibitorwhichdeliversheattothetankthroughaheatexchanger(commonlyacoilofcopperheatexchangertubingwithinthetank).Copperisanimportantcomponentinsolarthermalheatingandcoolingsystemsbecauseofitshighheatconductivity,resistancetoatmosphericandwatercorrosion,sealingandjoiningbysoldering,andmechanicalstrength.Copperisusedbothinreceiversandprimarycircuits(pipesandheatexchangersforwatertanks).[3]
Anotherlowermaintenanceconceptisthe'drainback':noantifreezeisrequiredinstead,allthepipingisslopedtocausewatertodrainbacktothetank.Thetankisnotpressurizedandisopentoatmosphericpressure.Assoonasthepumpshutsoff,flowreversesandthepipesareemptybeforefreezingcouldoccur.
Residentialsolarthermalinstallationsfallintotwogroups:passive(sometimescalled"compact")andactive(sometimescalled"pumped")systems.Bothtypicallyincludeanauxiliaryenergysource(electricheatingelementorconnectiontoagasorfueloilcentralheatingsystem)whichisactivatedwhenthewaterinthetankfallsbelowaminimumtemperaturesettingsuchas55C.Hence,hotwaterisalwaysavailable.The
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HowaSolarHotWatersystemworks
AnadvertisementforaSolarWaterHeaterdatingto1902
combinationofsolarwaterheatingandusingthebackupheatfromawoodstovechimneytoheatwater[4]canenableahotwatersystemtoworkallyearroundincoolerclimates,withoutthesupplementalheatrequirementofasolarwaterheatingsystembeingmetwithfossilfuelsorelectricity.
Whenasolarwaterheatingandhotwatercentralheatingsystemareusedinconjunction,solarheatwilleitherbeconcentratedinapreheatingtankthatfeedsintothetankheatedbythecentralheating,orthesolarheatexchangerwillreplacethelowerheatingelementandtheupperelementwillremaininplacetoprovideforanyheatingthatsolarcannotprovide.However,theprimaryneedforcentralheatingisatnightandinwinterwhensolargainislower.Therefore,solarwaterheatingforwashingandbathingisoftenabetterapplicationthancentralheatingbecausesupplyanddemandarebettermatched.Inmanyclimates,asolarhotwatersystemcanprovideupto85%ofdomestichotwaterenergy.Thiscanincludedomesticnonelectricconcentratingsolarthermalsystems.InmanynorthernEuropeancountries,combinedhotwaterandspaceheatingsystems(solarcombisystems)areusedtoprovide15to25%ofhomeheatingenergy.
History
TherearerecordsofsolarcollectorsintheUnitedStatesdatingbacktobefore1900,[5]comprisingablackpaintedtankmountedonaroof.In1896ClarenceKempofBaltimore,USAenclosedatankinawoodenbox,thuscreatingthefirst'batchwaterheater'astheyareknowntoday.AlthoughflatplatecollectorsforsolarwaterheatingwereusedinFloridaandSouthernCaliforniainthe1920stherewasasurgeofinterestinsolarheatinginNorthAmericaafter1960,butespeciallyafterthe1973oilcrisis.
SeeAppendix1atthebottomofthisarticleforanumberofcountryspecificstatisticsonthe"Useofsolarwaterheatingworldwide".Wikipediaalsohascountryspecificarticlesaboutsolarenergyuse(thermalaswellasphotovoltaic)inAustralia,Canada,China,Germany,India,Israel,Japan,Portugal,Romania,Spain,theUnitedKingdomandtheUnitedStates.
Mediterranean
Israel,CyprusandGreecearethepercapitaleadersintheuseofsolarwaterheatingsystemswithover30%40%ofhomesusingthem.[6]
FlatplatesolarsystemswereperfectedandusedonaverylargescaleinIsrael.Inthe1950stherewasafuelshortageinthenewIsraelistate,andthegovernmentforbadeheatingwaterbetween10pmand6am.LeviYissarbuiltthefirstprototypeIsraelisolarwaterheaterandin1953helaunchedtheNerYahCompany,Israel'sfirstcommercialmanufacturerofsolarwaterheating.[7]DespitetheabundanceofsunlightinIsrael,solarwaterheaterswereusedbyonly20%ofthepopulationby1967.Followingtheenergycrisisinthe1970s,in1980theIsraeliKnessetpassedalawrequiringtheinstallationofsolarwaterheatersinallnewhomes(excepthightowerswithinsufficientroofarea).[8]Asaresult,Israelisnowtheworldleaderinthe
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Passive(thermosiphon)solarwaterheatersonarooftopinJerusalem
Newsolarhotwaterinstallationsduring2007,worldwide.
useofsolarenergypercapitawith85%ofthehouseholdstodayusingsolarthermalsystems(3%oftheprimarynationalenergyconsumption),[9]estimatedtosavethecountry2millionbarrels(320,000m3)ofoilayear,thehighestpercapitauseofsolarenergyintheworld.[10]
In2005,Spainbecamethefirstcountryintheworldtorequiretheinstallationofphotovoltaicelectricitygenerationinnewbuildings,andthesecond(afterIsrael)torequiretheinstallationofsolarwaterheatingsystemsin2006.[11]
AsiaPacific
Theworldsawarapidgrowthoftheuseofsolarwarmwaterafter1960,withsystemsbeingmarketedinJapanandAustralia.[5]Technicalinnovationhasimprovedperformance,lifeexpectancyandeaseofuseofthesesystems.Installationofsolarwaterheatinghasbecomethenormincountrieswithanabundanceofsolarradiation,liketheMediterranean,[12]Japan,andAustralia.
ColombiadevelopedalocalsolarwaterheatingindustrythankstothedesignsofLasGaviotas,directedbyPaoloLugari.Drivenbyadesiretoreducecostsinsocialhousing,theteamofGaviotasstudiedthebestsystemsfromIsraelandmadeadaptationsastomeetthespecificationssetbytheBancoCentralHipotecario(BCH)whichprescribedthatthesystemmustbeoperationalincitieslikeBogotwheretherearemorethan200daysovercast.TheultimatedesignsweresosuccessfulthatLasGaviotasoffereda25yearwarrantyonanyofitsinstallationsin1984.Over40,000wereinstalledandstillfunctionaquarterofacenturylater.
Australiahasavarietyofincentives(nationalandstate)andregulations(state)forsolarthermalintroducedstartingwithMRETin1997.[13][14][15]
SolarwaterheatingsystemshavebecomepopularinChina,wherebasicmodelsstartataround1,500yuan(US$235),muchcheaperthaninWesterncountries(around80%cheaperforagivensizeofcollector).Itissaidthatatleast30millionChinesehouseholdsnowhaveoneandthatthepopularityisduetotheefficientevacuatedtubeswhichallowtheheaterstofunctionevenundergrayskiesandattemperatureswellbelowfreezing.[16]
Systemdesignrequirements
Thetype,complexity,andsizeofasolarwaterheatingsystemismostlydeterminedby:
Changesinambienttemperatureandsolarradiationbetweensummerandwinter.Thechangesinambienttemperatureduringthedaynightcycle.Thepossibilityofthepotablewaterorcollectorfluidoverheating.
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Thepossibilityofthepotablewaterorcollectorfluidfreezing.
Theminimumrequirementsofthesystemaretypicallydeterminedbytheamountortemperatureofhotwaterrequiredduringwinter,whenasystem'soutputandincomingwatertemperaturearetypicallyattheirlowest.Themaximumoutputofthesystemisdeterminedbytheneedtopreventthewaterinthesystemfrombecomingtoohot.
Freezeprotection
Freezeprotectionmeasurespreventdamagetothesystemduetotheexpansionoffreezingtransferfluid.Drainbacksystemsdrainthetransferfluidfromthesystemwhenthepumpstops.Manyindirectsystemsuseantifreeze(e.g.Propyleneglycol)intheheattransferfluid.
Insomedirectsystems,thecollectorscanbemanuallydrainedwhenfreezingisexpected.Thisapproachiscommoninclimateswherefreezingtemperaturesdonotoccuroften,butissomewhatunreliablesincetheoperatorcanforgettodrainthesystem.Otherdirectsystemsusefreezetolerantcollectorsmadewithflexiblepolymerssuchassiliconerubber.
Athirdtypeoffreezeprotectionisfreezetolerance,wherelowpressurepolymerwaterchannelsmadeofsiliconerubbersimplyexpandsonfreezing.OnesuchcollectornowhasEuropeanSolarKeymarkaccreditation,followingextradurabilitytesting.
Overheatprotection
Whennohotwaterhasbeenusedforadayortwo,thefluidinthecollectorsandstoragecanreachveryhightemperaturesinallsystemsexceptforthoseofthedrainbackvariety.Whenthestoragetankinadrainbacksystemreachesitsdesiredtemperature,thepumpsareshutoff,puttinganendtotheheatingprocessandthuspreventingthestoragetankfromoverheating.
Onemethodofprovidingoverheatprotectionistodumptheheatintoahottub.
Someactivesystemsdeliberatelycoolthewaterinthestoragetankbycirculatinghotwaterthroughthecollectorattimeswhenthereislittlesunlightoratnight,causingincreasedheatloss.Thisismosteffectiveindirectorthermalstoreplumbingandisvirtuallyineffectiveinsystemsthatuseevacuatedtubecollectors,duetotheirsuperiorinsulation.Nomatterthecollectortype,however,theymaystilloverheat.Highpressuredsealedsolarthermalsystemsversionsultimatelyrelyontheoperationoftemperatureandpressurereliefvalves.Lowpressure,openventedoneshavesimpler,morereliablesafetycontrols,typicallyanopenvent.
Typesofsolarwaterheatingsystems
Directandindirectsystems
Directoropenloopsystemscirculatepotablewaterthroughthecollectors.Theyarerelativelycheapbutcanhavethefollowingdrawbacks:
Theyofferlittleornooverheatprotectionunlesstheyhaveaheatexportpump.
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Directsystems:(A)PassiveCHSsystemwithtankabovecollector.(B)Activesystemwithpumpandcontrollerdrivenbyaphotovoltaicpanel
Theyofferlittleornofreezeprotection,unlessthecollectorsarefreezetolerant.Collectorsaccumulatescaleinhardwaterareas,unlessanionexchangesoftenerisused.
Untiltheadventoffreezetolerantsolarcollectors,theywerenotconsideredsuitableforcoldclimatessince,intheeventofthecollectorbeingdamagedbyafreeze,pressurizedwaterlineswillforcewatertogushfromthefreezedamagedcollectoruntiltheproblemisnoticedandrectified.
Indirectorclosedloopsystemsuseaheatexchangerthatseparatesthepotablewaterfromthefluid,knownasthe"heattransferfluid"(HTF),thatcirculatesthroughthecollector.ThetwomostcommonHTFsarewaterandanantifreeze/watermixthattypicallyusesnontoxicpropyleneglycol.Afterbeingheatedinthepanels,theHTFtravelstotheheatexchanger,whereitsheatistransferredtothepotablewater.Thoughslightlymoreexpensive,indirectsystemsofferfreezeprotectionandtypicallyofferoverheatprotectionaswell.
Passiveandactivesystems
Passivesystemsrelyonheatdrivenconvectionorheatpipestocirculatewaterorheatingfluidinthesystem.Passivesolarwaterheatingsystemscostlessandhaveextremelylowornomaintenance,buttheefficiencyofapassivesystemissignificantlylowerthanthatofanactivesystem.Overheatingandfreezingaremajorconcerns.
Activesystemsuseoneormorepumpstocirculatewaterand/orheatingfluidinthesystem.
Thoughslightlymoreexpensive,activesystemsofferseveraladvantages:
Thestoragetankcanbesituatedlowerthanthecollectors,allowingincreasedfreedominsystemdesignandallowingpreexistingstoragetankstobeused.Thestoragetankcanbehiddenfromview.Thestoragetankcanbeplacedinconditionedorsemiconditionedspace,reducingheatloss.Drainbacktankscanbeused.Superiorefficiency.Increasedcontroloverthesystem.
Modernactivesolarwatersystemshaveelectroniccontrollersthatofferawiderangeoffunctionality,suchasthemodificationofsettingsthatcontrolthesystem,interactionwithabackupelectricorgasdrivenwaterheater,calculationandloggingoftheenergysavedbyaSWHsystem,safetyfunctions,remoteaccess,and
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Thebubbleseparatorofabubblepumpsystem
informativedisplays,suchastemperaturereadings.
Themostpopularpumpcontrollerisadifferentialcontrollerthatsensestemperaturedifferencesbetweenwaterleavingthesolarcollectorandthewaterinthestoragetankneartheheatexchanger.Inatypicalactivesystem,thecontrollerturnsthepumponwhenthewaterinthecollectorisabout810Cwarmerthanthewaterinthetank,anditturnsthepumpoffwhenthetemperaturedifferenceapproaches35C.Thisensuresthewateralwaysgainsheatfromthecollectorwhenthepumpoperatesandpreventsthepumpfromcyclingonandofftoooften.(Indirectsystemsthis"ondifferential"canbereducedtoaround4Cbecausethereisnoheatexchangerimpediment.)
SomeactiveSWHsystemsuseenergyobtainedbyasmallphotovoltaic(PV)paneltopoweroneormorevariablespeedDCpump(s).Toensureproperperformanceandlongevityofthepump(s),theDCpumpandPVpanelmustbesuitablymatched.SomePVpumpedsolarthermalsystemsareoftheantifreezevarietyandsomeusefreezetolerantsolarcollectors.Thesolarcollectorswillalmostalwaysbehotwhenthepump(s)areoperating(i.e.,whenthesunisbright),andsomedonotusesolarcontrollers.Sometimes,however,adifferentialcontroller(thatcanalsobepoweredbytheDCoutputofaPVpanel)isusedtopreventtheoperationofthepumpswhenthereissunlighttopowerthepumpbutthecollectorsarestillcoolerthanthewaterinstorage.OneadvantageofaPVdrivensystemisthatsolarhotwatercanstillbecollectedduringapoweroutageifthesunisshining.Anotheradvantageisthattheoperationalcarbonclawbackofusingmainspumpedsolarthermal(whichtypicallynegatesupto23%ofitscarbonsavings)iscompletelyavoided.
Anactivesolarwaterheatingsystemcanbeequippedwithabubblepump(alsoknownasgeyserpump)insteadofanelectricpump.Abubblepumpcirculatestheheattransferfluid(HTF)betweencollectorandstoragetankusingsolarpower,withoutanyexternalenergysource,andissuitableforflatpanelaswellasvacuumtubesystems.Inabubblepumpsystem,theclosedHTFcircuitisunderreducedpressure,whichcausestheliquidtoboilatlowtemperatureasitisheatedbythesun.Thesteambubblesformageyserpump,causinganupwardflow.Thesystemisdesignedsuchthatthebubblesareseparatedfromthehotfluidandcondensedatthehighestpointinthecircuit,afterwhichthefluidflowsdownwardtowardtheheatexchangercausedbythedifferenceinfluidlevels.[17][18][19]TheHTFtypicallyarrivesattheheatexchangerat
70Candreturnstothecirculatingpumpat50C.InfrostproneclimatestheHTFiswaterwithpropyleneglycolantifreezeadded,usuallyintheratioof60to40.Pumpingtypicallystartsatabout50Candincreasesasthesunrisesuntilequilibriumisreached,whichdependsontheefficiencyoftheheatexchanger,thetemperatureofthewaterbeingheated,andthetotalsolarenergyavailable.
Passivedirectsystems
Anintegratedcollectorstorage(ICSorBatchHeater)systemusesatankthatactsasbothstorageandsolarcollector.Batchheatersarebasicallythinrectilineartankswithaglasssidefacingthepositionofthesunatnoon.Theyaresimpleandlesscostlythanplateandtubecollectors,buttheysometimesrequireextra
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Anintegratedcollectorstorage(ICS)system
bracingifinstalledonaroof(sincetheyareheavywhenfilledwithwater[400700lbs],)sufferfromsignificantheatlossatnightsincethesidefacingthesunislargelyuninsulated,andareonlysuitableinmoderateclimates.
Aconvectionheatstorageunit(CHS)systemissimilartoanICSsystem,exceptthestoragetankandcollectorarephysicallyseparatedandtransferbetweenthetwoisdrivenbyconvection.CHSsystemstypicallyusestandardflatplatetypeorevacuatedtubecollectors,andthestoragetankmustbelocatedabovethecollectorsforconvectiontoworkproperly.ThemainbenefitofaCHSsystemsoveranICSsystemisthatheatlossislargelyavoidedsince(1)thestoragetankcanbebetterinsulated,and(2)sincethepanelsarelocatedbelowthestoragetank,heatlossinthepanelswillnotcauseconvection,asthecoldwaterwillprefertostayatthelowestpartofthesystem.
Activeindirectsystems:drainbackandantifreeze
Pressurizedantifreezeorpressurizedglycolsystemsuseamixofantifreeze(almostalwaysnontoxicpropyleneglycol)andwatermixforHTFinordertopreventfreezedamage.
Thougheffectiveatpreventingfreezedamage,antifreezesystemshavemanydrawbacks:
IftheHTFgetstoohot(forexample,whenthehomeownerisonvacation,)theglycoldegradesintoacid.Afterdegradation,theglycolnotonlyfailstoprovidefreezeprotection,butalsobeginstoeatawayatthesolarloop'scomponents:thecollectors,thepipes,thepump,etc.Duetotheacidandexcessiveheat,thelongevityofpartswithinthesolarloopisgreatlyreduced.Mostdonotfeaturedrainbacktanks,sothesystemmustcirculatetheHTFregardlessofthetemperatureofthestoragetankinordertopreventtheHTFfromdegrading.Excessivetemperaturesinthetankcauseincreasedscaleandsedimentbuildup,possiblesevereburnsifatemperingvalveisnotinstalled,and,ifawaterheaterisbeingusedforstorage,possiblefailureofthewaterheater'sthermostat.Theglycol/waterHTFmustbereplacedevery38years,dependingonthetemperaturesithasexperienced.Somejurisdictionsrequiredoublewalledheatexchangerseventhoughpropyleneglycolisnontoxic.EventhoughtheHTFcontainsglycoltopreventfreezing,itwillstillcirculatehotwaterfromthestoragetankintothecollectorsatlowtemperatures(e.g.below40F(4C)),causingsubstantialheatloss.
AdrainbacksystemisanindirectactivesystemwheretheHTF(almostalwayspurewater)circulatesthroughthecollector,beingdrivenbyapump.Thecollectorpipingisnotpressurizedandincludesanopendrainbackreservoirthatiscontainedinconditionedorsemiconditionedspace.Ifthepumpisswitchedoff,theHTFdrainsintothedrainbackreservoirandnoneremainsinthecollector.Sincethesystemreliesuponbeingabletodrainproperly,allpipingabovethedrainbacktank,includingthecollectors,mustslope
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downwardinthedirectionofthedrainbacktank.Installedproperly,thecollectorcannotbedamagedbyfreezingoroverheating.[20]Drainbacksystemsrequirenomaintenanceotherthanthereplacementoffailedsystemcomponents.
PoweringaheatpumphotwaterheaterviaSolarPVpanels
WiththedrasticdropinthepricesofPhotovoltaicscirca2010itbecameincreasinglypopularinresidentialsettingswithlowhotwaterdemandstoconsiderheatingwaterviaanelectricheatpumphotwaterheaterpoweredbyasolarPVarray.Thishasthefollowingadvantages:1)simpler/cheaperinstallationandmaintenance,2)excessenergycollectedcanbeusedforhouseholdelectricityuseorputbackintothegrid,and3)theheatpumpdehumidifiesthelivingspace.Seeforexample:GettingintoHotWaterPart1MarcRosenbaum(http://www.greenbuildingadvisor.com/blogs/dept/guestblogs/gettinghotwaterpart1)
Aroughcomparisonofsolarhotwatersystems
ComparisonofSWHsystems[21]
Characteristic ICS(Batch) ThermosiphonActivedirect
Activeindirect Drainback
BubblePump
LowprofileunobtrusiveLightweightcollector
SurvivesfreezingweatherLowmaintenance
Simple:noancillarycontrolRetrofitpotentialtoexisting
storeSpacesaving:noextra
storagetank
CollectorsusedinmoderndomesticSWHsystems
Solarthermalcollectorscaptureandretainheatfromthesunanduseittoheataliquid.[22]Twoimportantphysicalprinciplesgovernthetechnologyofsolarthermalcollectors:
Anyhotobjectultimatelyreturnstothermalequilibriumwithitsenvironment,duetoheatlossfromthehotobject.Theprocessesthatresultinthisheatlossareconduction,convectionandradiation.[23]Theefficiencyofasolarthermalcollectorisdirectlyrelatedtoheatlossesfromthecollectorsurface(efficiencybeingdefinedastheproportionofheatenergythatcanberetainedforapredefinedperiodoftime).Withinthecontextofasolarcollector,convectionandradiationarethemostimportantsourcesofheatloss.Thermalinsulationisusedtoslowdownheatlossfromahotobjecttoitsenvironment.ThisisactuallyadirectmanifestationoftheSecondlawofthermodynamicsbutwemaytermthisthe'equilibriumeffect'.Heatislostmorerapidlyifthetemperaturedifferencebetweenahotobjectanditsenvironmentislarger.Heatlossispredominantlygovernedbythethermalgradientbetweenthetemperatureofthecollectorsurfaceandtheambienttemperature.Conduction,convection,andradiationalloccurmorerapidlyoverlargethermalgradients.[23]Wemaytermthisthe'deltateffect'.
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Flatplatesolarthermalcollector,viewedfromrooflevel
Themostsimpleapproachtosolarheatingofwateristosimplymountametaltankfilledwithwaterinasunnyplace.Theheatfromthesunwouldthenheatthemetaltankandthewaterinside.Indeed,thiswashowtheveryfirstSWHsystemsworkedmorethanacenturyago.[5]However,thissetupwouldbeinefficientduetoanoversightoftheequilibriumeffect,above:assoonasheatingofthetankandwaterbegins,theheatgainedstartstobelostbackintotheenvironment,andthiscontinuesuntilthewaterinthetankreachestheambienttemperature.Thechallengeisthereforetolimittheheatlossfromthetank,thusdelayingthetimewhenthermalequilibriumisregained.
ICSorbatchcollectorsreduceheatlossbyplacingthewatertankinathermallyinsulatedbox.[1][24]Thisisachievedbyencasingthewatertankinaglasstoppedboxthatallowsheatfromthesuntoreachthewatertank.[25]However,theotherwallsoftheboxarethermallyinsulated,reducingconvectionaswellasradiationtotheenvironment.[26]Inaddition,theboxcanalsohaveareflectivesurfaceontheinside.Thisreflectsheatlostfromthetankbacktowardsthetank.InasimplewayonecouldconsideranICSsolarwaterheaterasawatertankthathasbeenenclosedinatypeof'oven'thatretainsheatfromthesunaswellasheatofthewaterinthetank.Usingaboxdoesnoteliminateheatlossfromthetanktotheenvironment,butitlargelyreducesthisloss.
StandardICScollectorshaveacharacteristicthatstronglylimitstheefficiencyofthecollector:asmallsurfacetovolumeratio.[27]Sincetheamountofheatthatatankcanabsorbfromthesunislargelydependentonthesurfaceofthetankdirectlyexposedtothesun,itfollowsthatasmallsurfacewouldlimitthedegreetowhichthewatercanbeheatedbythesun.CylindricalobjectssuchasthetankinanICScollectorinherentlyhaveasmallsurfacetovolumeratioandmostmoderncollectorsattempttoincreasethisratioforefficientwarmingofthewaterinthetank.Therearemanyvariationsonthisbasicdesign,withsomeICScollectorscomprisingseveralsmallerwatercontainersandevenincludingevacuatedglasstubetechnology,atypeofICSsystemknownasanEvacuatedTubeBatch(ETB)collector.[1]
Flatplatecollectorsareanextensionofthebasicideatoplaceacollectorinan'oven'likeboxwithglassinthedirectionoftheSun.[1]Mostflatplatecollectorshavetwohorizontalpipesatthetopandbottom,calledheaders,andmanysmallerverticalpipesconnectingthem,calledrisers.Therisersarewelded(orsimilarlyconnected)tothinabsorberfins.Heattransferfluid(waterorwater/antifreezemix)ispumpedfromthehotwaterstoragetank(directsystem)orheatexchanger(indirectsystem)intothecollectors'bottomheader,andittravelsuptherisers,collectingheatfromtheabsorberfins,andthenexitsthecollectoroutofthetopheader.Serpentineflatplatecollectorsdifferslightlyfromthis"harp"design,andinsteaduseasinglepipethattravelsupanddownthecollector.However,sincetheycannotbeproperlydrainedofwater,serpentineflatplatecollectorscannotbeusedindrainbacksystems.
Thetypeofglassusedinflatplatecollectorsisalmostalwayslowiron,temperedglass.Beingtempered,theglasscanwithstandsignificanthailwithoutbreaking,whichisoneofthereasonsthatflatplatecollectorsareconsideredthemostdurablecollectortype.
Unglazedorformedcollectorsaresimilartoflatplatecollectors,excepttheyarenotthermallyinsulatednorphysicallyprotectedbyaglasspanel.Consequentlythesetypesofcollectorsaremuchlessefficientfordomesticwaterheating.Forpoolheatingapplications,however,thewaterbeingheatedisoftencolderthan
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theambientrooftemperature,atwhichpointthelackofthermalinsulationallowsadditionalheattobedrawnfromthesurroundingenvironment.[28]
Evacuatedtubecollectors(ETC)areawayinwhichheatlosstotheenvironment,[1]inherentinflatplates,hasbeenreduced.Sinceheatlossduetoconvectioncannotcrossavacuum,itformsanefficientisolationmechanismtokeepheatinsidethecollectorpipes.[29]Sincetwoflatsheetsofglassarenormallynotstrongenoughtowithstandavacuum,thevacuumisrathercreatedbetweentwoconcentrictubes.Typically,thewaterpipinginanETCisthereforesurroundedbytwoconcentrictubesofglasswithavacuuminbetweenthatadmitsheatfromthesun(toheatthepipe)butwhichlimitsheatlossbacktotheenvironment.Theinnertubeiscoatedwithathermalabsorbent.[30]Lifeofthevacuumvariesfromcollectortocollector,anywherefrom5yearsto15years.
FlatplatecollectorsaregenerallymoreefficientthanETCinfullsunshineconditions.However,theenergyoutputofflatplatecollectorsisreducedslightlymorethanevacuatedtubecollectorsincloudyorextremelycoldconditions.[1]MostETCsaremadeoutofannealedglass,whichissusceptibletohail,breakinginroughlygolfballsizedhail.ETCsmadefrom"cokeglass,"whichhasagreentint,arestrongerandlesslikelytolosetheirvacuum,butefficiencyisslightlyreducedduetoreducedtransparency.
Heatingofswimmingpools
Bothpoolcoveringsystemsfloatingatopthewaterandseparatesolarthermalcollectorsmaybeusedforpoolheating.
Poolcoveringsystems,whethersolidsheetsorfloatingdisks,actasinsulationandreduceheatloss.Muchofapool'sheatlossoccursthroughevaporation,andusingacoverprovidesabarrieragainstevaporation.Usingapoolcoverwillsupplementthesolarthermalcollectorsdiscussedbelow.SeeSwimmingPoolCoversforadetaileddiscussion.
Solarthermalcollectorsfornonpotablepoolwateruseareoftenmadeofplastic.Poolwater,mildlycorrosiveduetochlorine,iscirculatedthroughthepanelsusingtheexistingpoolfilterorsupplementalpump.Inmildenvironments,unglazedplasticcollectorsaremoreefficientasadirectsystem.Incoldorwindyenvironmentsevacuatedtubesorflatplatesinanindirectconfigurationdonothavepoolwaterpumpedthroughthem,theyareusedinconjunctionwithaheatexchangerthattransferstheheattopoolwater.Thiscauseslesscorrosion.Afairlysimpledifferentialtemperaturecontrollerisusedtodirectthewatertothepanelsorheatexchangereitherbyturningavalveoroperatingthepump.[31]Oncethepoolwaterhasreachedtherequiredtemperature,adivertervalveisusedtoreturnpoolwaterdirectlytothepoolwithoutheating.[32]Manysystemsareconfiguredasdrainbacksystemswherethewaterdrainsintothepoolwhenthewaterpumpisswitchedoff.
Thecollectorpanelsareusuallymountedonanearbyroof,orgroundmountedonatiltedrack.Duetothelowtemperaturedifferencebetweentheairandthewater,thepanelsareoftenformedcollectorsorunglazedflatplatecollectors.Asimpleruleofthumbfortherequiredpanelareaneededis50%ofthepool'ssurfacearea.[32]Thisisforareaswherepoolsareusedinthesummerseasononly,notyear'round.Addingsolarcollectorstoaconventionaloutdoorpool,inacoldclimate,cantypicallyextendthepool'scomfortableusagebysomemonthsormoreifaninsulatingpoolcoverisalsoused.[28]Anactivesolarenergysystemanalysisprogrammaybeusedtooptimizethesolarpoolheatingsystembeforeitisbuilt.
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AlaundromatinCaliforniawithpanelsontheroofprovidinghotwashingwater.
Economics,energy,environment,andsystemcosts
Energyproduction
Theamountofheatdeliveredbyasolarwaterheatingsystemdependsprimarilyontheamountofheatdeliveredbythesunataparticularplace(theinsolation).Intropicalplacestheinsolationcanberelativelyhigh,e.g.7kW.h/m2perday,whereastheinsolationcanbemuchlowerintemperateareaswherethedaysareshorterinwinter,e.g.3.2kW.h/m2perday.Evenatthesamelatitudetheaverageinsolationcanvaryagreatdealfromlocationtolocationduetodifferencesinlocalweatherpatternsandtheamountofovercast.UsefulcalculatorsforestimatinginsolationatasitecanbefoundwiththeJointResearchLaboratoryoftheEuropeanCommission[33]andtheAmericanNationalRenewableEnergyLaboratory.[34][35]
Belowisatablethatgivesaroughindicationofthespecificationsandenergythatcouldbeexpectedfromasolarwaterheatingsysteminvolvingsome2m2ofabsorberareaofthecollector,demonstratingtwoevacuatedtubeandthreeflatplatesolarwaterheatingsystems.Certificationinformationorfigurescalculatedfromthosedataareused.Thebottomtworowsgiveestimatesfordailyenergyproduction(kW.h/day)foratropicalandatemperatescenario.Theseestimatesareforheatingwaterto50Caboveambienttemperature.
Withmostsolarwaterheatingsystems,theenergyoutputscaleslinearlywiththesurfaceareaoftheabsorbers.Therefore,whencomparingfigures,takeintoaccounttheabsorberareaofthecollectorbecausecollectorswithlessabsorberareayieldlessheat,evenwithinthe2m2range.SpecificationsformanycompletesolarwaterheatingsystemsandseparatesolarcollectorscanbefoundatInternetsiteoftheSRCC.[36]
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Dailyenergyproduction(kWth.h)offivesolarthermalsystems.Theevactubesystemsusedbelowbothhave20tubesTechnology Flatplate Flatplate Flatplate Evactube Evactube
Configuration Directactive ThermosiphonIndirectactive
Indirectactive
Directactive
Overallsize(m2) 2.49 1.98 1.87 2.85 2.97
Absorbersize(m2) 2.21 1.98 1.72 2.85 2.96
Maximumefficiency 0.68 0.74 0.61 0.57 0.46Energyproduction(kW.h/day):Insolation3.2kW.h/m2/day(temperate)e.g.Zurich,Switzerland
5.3 3.9 3.3 4.8 4.0
Insolation6.5kW.h/m2/day(tropical)e.g.Phoenix,USA
11.2 8.8 7.1 9.9 8.4
Thefiguresarefairlysimilarbetweentheabovecollectors,yieldingsome4kW.h/dayinatemperateclimateandsome8kW.h/dayinamoretropicalclimatewhenusingacollectorwithanabsorberareaofabout2m2insize.Inthetemperatescenariothisissufficienttoheat200litresofwaterbysome17C.Inthetropicalscenariotheequivalentheatingwouldbebysome33C.Manythermosiphonsystemsarequiteefficientandhavecomparableenergyoutputtoequivalentactivesystems.Theefficiencyofevacuatedtubecollectorsissomewhatlowerthanforflatplatecollectorsbecausetheabsorbersarenarrowerthanthetubesandthetubeshavespacebetweenthem,resultinginasignificantlylargerpercentageofinactiveoverallcollectorarea.Somemethodsofcomparison[37]calculatetheefficiencyofevacuatedtubecollectorsbasedontheactualabsorberareaandnotonthe'roofarea'ofthesystemashasbeendoneintheabovetable.Theefficiencyofthecollectorsbecomeslowerifonedemandswaterwithaveryhightemperature.
Systemcost
Insunny,warmlocations,wherefreezeprotectionisnotnecessary,anICS(batchtype)solarwaterheatercanbeextremelycosteffective.[26]Inhigherlatitudes,thereareoftenadditionaldesignrequirementsforcoldweather,whichaddtosystemcomplexity.Thishastheeffectofincreasingtheinitialcost(butnotthelifecyclecost)ofasolarwaterheatingsystem,toalevelmuchhigherthanacomparablewaterheateroftheconventionaltype.Thebiggestsingleconsiderationisthereforethelargeinitialfinancialoutlayofsolarwaterheatingsystems.[38]Offsettingthisexpensecantakeseveralyears[39]andthepaybackperiodislongerintemperateenvironmentswheretheinsolationislessintense.[40]Whencalculatingthetotalcosttoownandoperate,aproperanalysiswillconsiderthatsolarenergyisfree,thusgreatlyreducingtheoperatingcosts,whereasotherenergysources,suchasgasandelectricity,canbequiteexpensiveovertime.Thus,whentheinitialcostsofasolarsystemareproperlyfinancedandcomparedwithenergycosts,theninmanycasesthetotalmonthlycostofsolarheatcanbelessthanothermoreconventionaltypesofwaterheaters(alsoinconjunctionwithanexistingwaterheater).Athigherlatitudes,solarheatersmaybelesseffectiveduetolowersolarenergy,possiblyrequiringlargerand/ordualheatingsystems.[40]Inaddition,governmentincentivescanbesignificant.
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CostsandpaybackperiodsforresidentialSWHsystemswithsavingsof200kW.h/month(using2010data)
Country Currency Systemcost Subsidy(%)Effective
costElectricitycost/kW.h
Electricitysavings/month
Paybackperiod(y)
Brazil BRL 2500[42] 0 2500 0.25 50 4.2
SouthAfrica ZAR 14000 15
[43] 11900 0.9 180 5.5
Australia AUD 5000[44] 40[45] 3000 0.18[46] 36 6.9
Belgium EUR 4000[47] 50[48] 2000 0.1[49] 20 8.3
UnitedStates USD 5000
[50] 30[51] 3500 0.1158[52] 23.16 12.6
UnitedKingdom GBP 4800
[53] 0 4800 0.11[54] 22 18.2
ThecalculationoflongtermcostandpaybackperiodforahouseholdSWHsystemdependsonanumberoffactors.Someoftheseare:
Priceofpurchasingsolarwaterheater(morecomplexsystemsaremoreexpensive)EfficiencyofSWHsystempurchasedInstallationcostPriceofelectricityuseformainspumping(ifthisisused)Priceofwaterheatingfuel(e.g.gasorelectricity)savedperkW.hAmountofwaterheatingfuelusedpermonthbyahouseholdUpfrontstateorgovernmentsubsidyforinstallationofasolarwaterheaterRecurrentorannualtaxrebatesorsubsidyforoperatingrenewableenergyAnnualmaintenancecostofSWHsystem(e.g.antifreezeorpumpreplacements)Savingsinannualmaintenanceofconventional(electric/gas/oil)waterheatingsystem
Thefollowingtablegivessomeideaofthecostandpaybackperiodtorecoverthecosts.Itdoesnottakeintoaccountannualmaintenancecosts,annualtaxrebatesandinstallationcosts.However,thetabledoesgiveanindicationofthetotalcostandtheorderofmagnitudeofthepaybackperiod.Thetableassumesanenergysavingsof200kW.hpermonth(about6.57kW.h/day)duetoSWH.Unfortunatelypaybacktimescanvarygreatlyduetoregionalsun,extracostduetofrostprotectionneedsofcollectors,householdhotwateruseetc.somoreinformationmaybeneededtogetaccurateestimatesforindividualhouseholdsandregions.ForinstanceincentralandsouthernFloridathepaybackperiodcouldeasilybe7yearsorlessratherthanthe12.6yearsindicatedonthechartfortheUS.[41]
Twopointsareclearfromtheabovetable.Firstly,thepaybackperiodisshorterincountrieswithalargeamountofinsolationandeveninpartsofthesamecountrywithmoreinsolation.Thisisevidentfromthepaybackperiodlessthan10yearsinmostsouthernhemispherecountries,listedabove.Thisispartlybecauseofgoodsunshine,allowingusersinthosecountriestoneedsmallersystemsthanintemperateareas.Secondly,eveninthenorthernhemispherecountrieswherepaybackperiodsareoftenlongerthan10years,solarwaterheatingisfinanciallyextremelyefficient.ThisispartlybecausetheSWHtechnologyisefficientincapturingirradiation.Thepaybackperiodforphotovoltaicsystemsismuchlonger.[40]Inmany
-
casesthepaybackperiodforaSWHsystemisshortenedifitsuppliesallornearlyallofthewarmwaterrequirementsusedbyahousehold.ManySWHsystemssupplyonlyafractionofwarmwaterneedsandareaugmentedbygasorelectricheatingonadailybasis,[39]thusextendingthepaybackperiodofsuchasystem.
SolarleasingisnowavailableinSpainforsolarwaterheatingsystemsfromPretasol[55]withatypicalsystemcostingaround59eurosandrisingto99eurospermonthforasystemthatwouldprovidesufficienthotwaterforatypicalfamilyhomeofsixpersons.Thepaybackperiodwouldbefiveyears.
AustraliahasinstitutedasystemofRenewableEnergyCredits,basedonnationalrenewableenergytargets.Thisexpandsanoldersystembasedonlyonrebates.[45]
Operationalcarbon/energyfootprintandlifecycleassessment
Terminology
Operationalenergyfootprint(OEF)isalsocalledenergyparasiticsratio(EPR)orcoefficientofperformance(CoP).Operationalcarbonfootprint(OCF)isalsocalledcarbonclawbackratio(CCR).LifecycleassessmentisusuallyreferredtoasLCA.
Carbon/energyfootprint
ThesourceofelectricityinanactiveSWHsystemdeterminestheextenttowhichasystemcontributestoatmosphericcarbonduringoperation.Activesolarthermalsystemsthatusemainselectricitytopumpthefluidthroughthepanelsarecalled'lowcarbonsolar'.Inmostsystemsthepumpingcancelstheenergysavingsbyabout8%andthecarbonsavingsofthesolarbyabout20%.[56]However,somenewlowpowerpumpswillstartoperationwith1Wanduseamaximumof20W.[57][58]Assumingasolarcollectorpaneldelivering4kW.h/dayandapumprunningintermittentlyfrommainselectricityforatotalof6hoursduringa12hoursunnyday,thepotentiallynegativeeffectofsuchapumpcanbereducedtoabout3%ofthetotalpowerproduced.
Thecarbonfootprintofsuchhouseholdsystemsvariessubstantially,dependingonwhetherelectricityorotherfuelssuchasnaturalgasarebeingdisplacedbytheuseofsolar.Exceptwhereahighproportionofelectricityisalreadygeneratedbynonfossilfuelmeans,naturalgas,acommonwaterheatingfuel,inmanycountries,hastypicallyonlyabout40%ofthecarbonintensityofmainselectricityperunitofenergydelivered.Thereforethe3%or8%energyclawbackinagashomereferredtoabovecouldthereforebeconsidered8%to20%carbonclawback,averylowfigurecomparedtotechnologiessuchasheatpumps.
However,PVpoweredactivesolarthermalsystemstypicallyusea530WPVpanelwhichfacesinthesamedirectionasthemainsolarheatingpanelandasmall,lowpowerdiaphragmpumporcentrifugalpumptocirculatethewater.Thisreducestheoperationalcarbonandenergyfootprint:agrowingdesigngoalforsolarthermalsystems.
Workisalsotakingplaceinanumberofpartsoftheworldondevelopingalternativenonelectricalpumpingsystems.Thesearegenerallybasedonthermalexpansionandphasechangesofliquidsandgases,avarietyofwhichareunderdevelopment.
-
Lifecyclecarbon/energyassessment
Nowlookingatawiderpicturethanjusttheoperationalenvironmentalimpacts,recognisedstandardscanbeusedtodeliverrobustandquantitativelifecycleassessment(LCA).LCAtakesintoaccountthetotalenvironmentalcostofacquisitionofrawmaterials,manufacturing,transport,using,servicinganddisposingoftheequipment.Thereareseveralaspectstosuchanassessment,including:
Thefinancialcostsandgainsincurredduringthelifeoftheequipment.Theenergyusedduringeachoftheabovestages.TheCO2emissionsduetoeachoftheabovestages.
EachoftheseaspectsmaypresentdifferenttrendswithrespecttoaspecificSWHdevice.
Financialassessment.Thetableintheprevioussectionaswellasseveralotherstudiessuggestthatthecostofproductionisgainedduringthefirst512yearsofuseoftheequipment,dependingontheinsolation,withcostefficiencyincreasingastheinsolationdoes.[39]
Intermsofenergy,some60%ofthematerialsofaSWHsystemgoesintothetank,withsome30%towardsthecollector[59](thermosiphonflatplateinthiscase)(Tsiligiridisetal.).InItaly,[60]some11GJofelectricityareusedinproducingtheequipment,withabout35%oftheenergygoingtowardsthemanufacturingthetank,withanother35%towardsthecollectorandthemainenergyrelatedimpactbeingemissions.TheenergyusedinmanufacturingisrecoveredwithinthefirsttwotothreeyearsofuseoftheSWHsystemthroughheatcapturedbytheequipmentaccordingtothissouthernEuropeanstudy.
Movingfurthernorthintocolder,lesssunnyclimates,theenergypaybacktimeofasolarwaterheatingsysteminaUKclimateisreportedasonly2years.[61]Thisfigurewasderivedfromthestudiedsolarwaterheatingsystembeing:direct,retrofittedtoanexistingwaterstore,PVpumped,freezetolerantandof2.8sqmaperture.Forcomparison,asolarelectric(PV)installationtookaround5yearstoreachenergypayback,accordingtothesamecomparativestudy.
IntermsofCO2emissions,alargedegreeoftheemissionssavingtraitsofaSWHsystemisdependentonthedegreetowhichwaterheatingbygasorelectricityisusedtosupplementsolarheatingofwater.UsingtheEcoindicator99pointssystemasayardstick(i.e.theyearlyenvironmentalloadofanaverageEuropeaninhabitant)inGreece,[59]apurelygasdrivensystemmaybecheaperintermsofemissionsthanasolarsystem.Thiscalculationassumesthatthesolarsystemproducesabouthalfofthehotwaterrequirementsofahousehold.TheproductionofatestSWHsysteminItaly[60]producedabout700kgofCO2,withallthecomponentsofmanufacture,useanddisposalcontributingsmallpartstowardsthis.Maintenancewasidentifiedasanemissionscostlyactivitywhentheheattransferfluid(glycolbased)wasperiodicallyreplaced.However,theemissionscostwasrecoveredwithinabouttwoyearsofuseoftheequipmentthroughtheemissionssavedbysolarwaterheating.InAustralia,[39]thelifecycleemissionsofaSWHsystemarealsorecoveredfairlyrapidly,whereaSWHsystemhasabout20%oftheimpactofanelectricalwaterheaterandhalfoftheemissionsimpactofagaswaterheater.
Analysingtheirlowerimpactretrofitfreezetolerantsolarwaterheatingsystem,Allenetal.(qv)reportaproductionCO2impactof337kg,whichisaroundhalftheenvironmentalimpactreportedintheArdenteetal.(qv)study.
-
Whereinformationbasedonestablishedstandardsareavailable,theenvironmentaltransparencyaffordedbylifecycleanalysisallowsconsumers(ofallproducts)tomakeincreasinglywellinformedproductselectiondecisions.Asforidentifyingsectorswherethisinformationislikelytoappearfirst,environmentaltechnologysuppliersinthemicrogenerationandrenewableenergytechnologyarenaareincreasinglybeingpressedbyconsumerstoreporttypicalCoPandLCAfiguresfortheirproducts.
Insummary,theenergyandemissionscostofaSWHsystemformsasmallpartofthelifecyclecostandcanberecoveredfairlyrapidlyduringuseoftheequipment.Theirenvironmentalimpactscanbereducedfurtherbysustainablematerialssourcing,usingnonmainscirculation,byreusingexistinghotwaterstoresand,incoldclimates,byeliminatingantifreezereplacementvisits.
Doityourself(DIY)systems
Peoplehavebegunbuildingtheirown(smallscale)solarwaterheatingsystemsfromscratchorbuyingkits.PlansforsolarwaterheatingsystemsareavailableontheInternet.[62]andpeoplehavesetaboutbuildingthemfortheirowndomesticrequirements.DIYSWHsystemsareusuallycheaperthancommercialones,andtheyareusedbothinthedevelopedanddevelopingworld.[63]
Systemspecificationandinstallation
ExceptinrareinstancesitwillbeinsufficienttoinstallaSWHsystemwithnoelectricalorgasorotherfuelbackup.ManySWHsystemshaveabackupelectricheatingelementintheintegratedtank,theoperationofwhichmaybenecessaryoncloudydaystoensureareliablesupplyofhotwater.Thetemperaturestabilityofasystemisdependentontheratioofthevolumeofwarmwaterusedperdayasafractionofthesizeofthewaterreservoir/tankthatstoresthehotwater.Ifalargeproportionofhotwaterinthereservoirisusedeachday,alargefractionofthewaterinthereservoirneedstobeheated.Thisbringsaboutsignificantfluctuationsinwatertemperatureeveryday,withpossiblerisksofoverheatingorunderheating,dependingonthedesignofthesystem.Sincetheamountofheatingthatneedstotakeplaceeverydayisproportionaltohotwaterusageandnottothesizeofthereservoir,itisdesirabletohaveafairlylargereservoir(i.e.equaltoorgreaterthandailyusage,)whichwillhelppreventfluctuationsinwatertemperature.Ifamplestorageispreexistingorcanotherwisebereasonablyacquired,alargeSWHsystemismoreefficienteconomicallythanasmallsystem.[59]Thisisbecausethepriceofasystemisnotlinearlyproportionaltothesizeofthecollectorarray,sothepricepersquaremeterofcollectorischeaperinalargersystem.Ifthisisthecase,itpaystouseasystemthatcoversnearlyallofthedomestichotwaterneeds,andnotonlyasmallfractionoftheneeds.Thisfacilitatesmorerapidcostrecovery.Notallinstallationsrequirenewreplacementsolarhotwaterstores.Existingstoresmaybelargeenoughandinsuitablecondition.Directsystemscanberetrofittedtoexistingstoreswhileindirectsystemscanbealsosometimesberetrofittedusinginternalandexternalheatexchangers.TheinstallationofaSWHsystemneedstobecomplementedwithefficientinsulationofallthewaterpipesconnectingthecollectorandthewaterstoragetank,aswellasthestoragetank(or"geyser")andthemostimportantwarmwateroutlets.Theinstallationofefficientlaggingsignificantlyreducestheheatlossfromthehotwatersystem.Theinstallationoflaggingonatleasttwometersofpipeonthecoldwaterinletofthestoragetankreducesheatloss,asdoestheinstallationofa"geyserblanket"aroundthestoragetank(ifinsidearoof).IncoldclimatestheinstallationoflaggingandinsulationisoftenperformedevenintheabsenceofaSWHsystem.ThemostefficientPVpumpsaredesignedtostartveryslowlyinverylowlightlevels,soifconnecteduncontrolled,theymaycauseasmallamountofunwantedcirculationearlyinthemorning
-
forexamplewhenthereisenoughlighttodrivethepumpbutwhilethecollectorisstillcold.Toeliminatetheriskofhotwaterinthestoragetankfrombeingcooledthatwaythisisveryimportant.solarcontrollermayberequired.Themodularityofanevacuatedtubecollectorarrayallowstheadjustmentofthecollectorsizebyremovingsometubesortheirheatpipes.Budgetingforalargerthanrequiredarrayoftubesthereforeallowsforthecustomisationofcollectorsizetotheneedsofaparticularapplication,especiallyinwarmerclimates.Particularlyinlocationsfurthertowardsthepolesthan45degreesfromtheequator,roofmountedsunfacingcollectorstendtooutperformwallmountedcollectorsintermsoftotalenergyoutput.However,itistotalusefulenergyoutputwhichusuallymattersmosttoconsumers.Soarraysofsunnywallmountedsteepcollectorscansometimesproducemoreusefulenergybecausetherecanbeasmallincreaseinwintergainattheexpenseofalargeunusedsummersurplus.
Standards
Europe
EN806:Specificationsforinstallationsinsidebuildingsconveyingwaterforhumanconsumption.General.EN1717:Protectionagainstpollutionofpotablewaterinwaterinstallationsandgeneralrequerementsofdevicestopreventpollutionbybackflow.EN60335:Specificationforsafetyofhouseholdandsimilarelectricalappliances.(221)UNE94002:2005Thermalsolarsystemsfordomestichotwaterproduction.Calculationmethodforheatdemand.
UnitedStates
OG300:OG300CertificationofSolarWaterHeatingSystems.[64]
Australia
RenewableEnergy(Electricity)Act2000RenewableEnergy(Electricity)(LargescaleGenerationShortfallCharge)Act2000RenewableEnergy(Electricity)(SmallscaleTechnologyShortfallCharge)Act2010RenewableEnergy(Electricity)Regulations2001RenewableEnergy(Electricity)Regulations2001STCCalculationMethodologyforSolarWaterHeatersandAirSourceHeatPumpWaterHeatersRenewableEnergy(Electricity)Amendment(TransitionalProvision)Regulations2010RenewableEnergy(Electricity)Amendment(TransitionalProvisions)Regulations2009
AllrelevantparticipantsoftheLargescaleRenewableEnergyTargetandSmallscaleRenewableEnergySchememustcomplywiththeaboveActs.[65]
APPENDIX1.Worldwideuse
Topcountriesworldwide
-
SolarhotwatersysteminstalledonlowcosthousingintheKougaLocalMunicipality,SouthAfrica
Topcountriesusingsolarthermalpower,worldwide:GWth[11][66][67][68][69][70][71]
# Country 2005 2006 2007 2008 2009 2010 2011 2012 20131 China 55.5 67.9 84.0 105.0 101.5 117.6 EU 11.2 13.5 15.5 20.0 22.8 23.5 25.6 29.7 31.42 UnitedStates 1.6 1.8 1.7 2.0 14.4 15.3 3 Germany 7.8 8.9 9.8 10.5 11.4 12.14 Turkey 5.7 6.6 7.1 7.5 8.4 9.3 5 Australia 1.2 1.3 1.2 1.3 5.0 5.8 6 Brazil 1.6 2.2 2.5 2.4 3.7 4.3 7 Japan 5.0 4.7 4.9 4.1 4.3 4.0 8 Austria 2.5 3.0 3.2 2.8 3.4 3.59 Greece 2.7 2.9 2.9 2.9 2.9 2.9
10 Israel 3.3 3.8 3.5 2.6 2.8 2.9 World(GWth) 88 105 126 149 172 196
SolarheatinginEuropeanUnion+Switzerland
-
SolarthermalheatinginEuropeanUnion(MWth)[72][73][74]
# Country 2008 2009 2010[68] 2011 2012 2013
1 Germany 7,766 9,036 9,831 10,496 11,416 12,0552 Austria 2,268 3,031 3,227 2,792 3,448 3,5383 Greece 2,708 2,853 2,855 2,861 2,885 2,9154 Italy 1,124 1,410 1,753 2,152 2,380 2,5905 Spain 988 1,306 1,543 1,659 2,075 2,2386 France 1,137 1,287 1,470 1,277 1,691 1,8027 Poland 254 357 459 637 848 1,0408 Portugal 223 395 526 547 677 7179 CzechRepublic 116 148 216 265 625 681
10 Switzerland 416 538 627 11 Netherlands 254 285 313 332 605 61612 Denmark 293 339 379 409 499 55013 Cyprus 485 490 491 499 486 47614 UK 270 333 374 460 455 47515 Belgium 188 204 230 226 334 37416 Sweden 202 217 227 236 337 34217 Ireland 52 85 106 111 177 19618 Slovenia 96 111 116 123 142 14819 Hungary 18 59 105 120 125 13720 Slovakia 67 73 84 100 108 11321 Romania* 66 80 73 74 93 11022 Bulgaria* 22 56 74 81 58 5923 Malta* 25 29 32 36 34 3524 Finland* 18 20 23 23 30 3325 Luxembourg* 16 19 22 25 23 2726 Estonia* 1 1 1 3 10 1227 Latvia* 1 1 1 3 10 1228 Lithuania* 1 2 2 3 6 8
Total EU27+Sw(MWth) 19,08 21,60 23.49 25.55 29.66 31.39
*=estimation,F=Franceasawhole
Seealso
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WikimediaCommonshasmediarelatedtoSolarwaterheating.
Australia:SolarhotwaterinAustralia
SolarthermalcollectorSolarairheatingSolarairconditioningConcentratingsolarpowerPassivesolarRenewableheatSolarcombisystemSolarenergySolarthermalenergyRenewableenergycommercializationSustainabledesign
References1. C.Marken(2009)."Solarcollectors:Behindtheglass"(http://www.homepower.com/articles/solarcollectors
behindglass).HomePower133:7076.2. BrianNorton(2011)SolarWaterHeaters:AReviewofSystemsResearchandDesignInnovation,Green.1,189
207,ISSN(Online)186987783. 2011globalstatusreportbyRenewableEnergyPolicyNetworkforthe21stCentury(REN21)4. Gulland,John."Heatingwaterwithawoodstove"(http://www.woodheat.org/heatingwaterwithawood
stove.html).woodheat.org.WoodHeatOrganizationInc.Retrieved29March2012.5. SolarEvolutionTheHistoryofSolarEnergy(http://www.californiasolarcenter.org/history_solarthermal.html),
JohnPerlin,CaliforniaSolarCenter6. DelChiaro,BernadetteandTelleenLawton,Timothy(April2007)."SolarWaterHeating(HowCaliforniaCan
ReduceItsDependenceonNaturalGas)"(http://web.archive.org/web/20071021142503/https://www.environmentcalifornia.org/uploads/at/56/at563bKwmfrtJI6fKl9U_w/SolarWaterHeating.pdf)(PDF).EnvironmentCaliforniaResearchandPolicyCenter.Retrieved29September2007.
7. JohnChristopherBacher(2000).Petrotyranny(http://books.google.com/books?id=P7LPZk8NuBgC&pg=PA70).Dundurn.p.70.ISBN9780888669568.
8. "Israel'sSolarIndustry:ReclaimingaLegacyofSuccess"(http://www.climate.org/topics/internationalaction/israelsolar.html#i).Climate.org.Retrieved10February2012.
9. MinicyCatomSoftwareEngineeringLtd.www.catom.com."TheSamuelNeamanInstituteforAdvancedStudiesinScienceandTechnologyPublicationsSolarenergyfortheproductionofheatSummaryandrecommendationsofthe4thassemblyoftheenergyforumatSNI"(http://web.archive.org/web/20080803082041/http://www.neaman.org.il/neaman/publications/publication_item.asp?fid=590&parent_fid=490&iid=3639).Neaman.org.il.Retrieved20120623.
10. IsraeliSectionoftheInternationalSolarEnergySociety(http://www.ises.org.il/assets/files/ISES%20Info/IsraelSectionISESfinal.pdf),editedbyGershonGrossman,FacultyofMechanicalEnergy,Technion,HaifaFinaldraft.
11. "RenewablesGlobalStatusReport:EnergyTransformationContinuesDespiteEconomicSlowdown"(http://web.archive.org/web/20100209005403/http://www.ren21.net/globalstatusreport/g2009.asp).ren21.net.13May2009.Retrieved20May2010.
12. "ChromagensSolarWaterHeatingSystems"(http://web.archive.org/web/20081006111652/http://www.heatingcentral.com/Chromagen_Solar_Water_Heating_Systems).heatingcentral.com.
13. "5StarHousingPerformanceBasedBuildingRegulationDelivers"(http://www.docstoc.com/docs/26723075/5StarHousing%E2%80%93PerformanceBasedBuildingRegulationDelivers).Docstoc.com.Retrieved10February2012.
14. "BuildingsThinkChange"(http://www.environment.gov.au/sustainability/energyefficiency/buildings/homes/index.html).
-
(http://www.environment.gov.au/sustainability/energyefficiency/buildings/homes/index.html).Environment.gov.au.1November2010.Retrieved10February2012.
15. IsraeldelMundoandIanWills(2005)TheEconomicsoftheMandatoryRenewableEnergyTarget(MRET)(http://web.archive.org/web/20080722132746/http://www.aares.info/files/2005_delmundo.pdf),DepartmentofEconomicsMonashUniversity,Australia.
16. EnergyHungryChinaWarmstoSolarWaterHeaters(http://www.planetark.org/dailynewsstory.cfm?newsid=36636)discussesChinaHiminSolarEnergyGroupinDezhou.Reutersarticle,postedonPlanetArksite
17. AvanHouten(Sunnovations),HowaGeyserPumpworks(http://www.sunnovations.com/content/howsunnovationssystemworks)
18. WilfriedC.Sorensen(1985)Autogeneoussolarwaterheater(http://www.google.com/patents?id=pjkyAAAAEBAJ),USPatent4607688.
19. Bubblepumpdescription(http://www.bubbleactionpumps.com/overview/pumpovr1.htm)atbubbleactionpumps.com
20. Lane,T.andOlson,K.(2002)."Solarhotwaterforcoldclimates:PartIIDrainbacksystems".HomepowerMagazine86:6270.
21. SolarWaterHeatingBasics(http://homepower.com/basics/hotwater/).homepower.com22. Norton,Brian(2013).HarnessingSolarHeat.Springer.ISBN9789400772755.23. W.M.Rohsenow,J.P.Harnett,Y.I.Cho(1998).Handbookofheattransfer3rdEd..McGrawHill,Chicago,
USA.24. C.Schmidt,A.GoetzbergerA.(1990)."Singletubeintegratedcollectorstoragesystemswithtransparent
insulationandinvolutereflector".SolarEnergy45(2):93.doi:10.1016/0038092X(90)900339(https://dx.doi.org/10.1016%2F0038092X%2890%29900339).
25. M.Smyth,P.C.Eames,B.Norton(2006)."Integratedcollectorstoragesolarwaterheaters".RenewableandSustainableEnergyReviews10(6):503.doi:10.1016/j.rser.2004.11.001(https://dx.doi.org/10.1016%2Fj.rser.2004.11.001).
26. M.Souliotis,S.Kalogirou,Y.Tripanagnostopoulos(2009)."ModellingofanICSsolarwaterheaterusingartificialneuralnetworksandTRNSYS".RenewableEnergy34(5):1333.doi:10.1016/j.renene.2008.09.007(https://dx.doi.org/10.1016%2Fj.renene.2008.09.007).
27. Y.Tripanagnostopoulos,M.Souliotis,T.Nousia(1999)."SolarICSsystemswithtwocylindricalstoragetanks".RenewableEnergy16:665.doi:10.1016/S09601481(98)002481(https://dx.doi.org/10.1016%2FS09601481%2898%29002481).
28. D.Lane(2003)."Solarpoolheatingbasics,Part1".HomePower94:7077.29. YongKim,TaebeomSeo(2007)."Thermalperformancescomparisonsoftheglassevacuatedtubesolar
collectorswithshapesofabsorbertube".RenewableEnergy32(5):772.doi:10.1016/j.renene.2006.03.016(https://dx.doi.org/10.1016%2Fj.renene.2006.03.016).
30. ShiYueyan,YangXiaoji(1999)."Selectiveabsorbingsurfaceforevacuatedsolarcollectortubes".RenewableEnergy16:632.doi:10.1016/S09601481(98)002407(https://dx.doi.org/10.1016%2FS09601481%2898%29002407).
31. "SolarPoolHeatingControlandAutomation"(http://rimstar.org/renewnrg/solar_pool_heating_control_automation.htm#AUTOMATIC_CONTROL).rimstar.org.Retrieved16August2010.
32. D.Lane(2003)."Solarpoolheatingbasics,Part2".HomePower95:6067.33. "interactivemaps"(http://sunbird.jrc.it/pvgis/imaps).Sunbird.jrc.it.30October2008.Retrieved10February
2012.34. "APerformanceCalculatorforGridConnectedPVSystems"
(http://web.archive.org/web/20060110075524/http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/).Rredc.nrel.gov.Retrieved10February2012.
35. "NationalRenewableEnergyLaboratory(NREL)HomePage"(http://www.nrel.gov).Nrel.gov.6February2012.Retrieved10February2012.
36. SRCCCertificationPrograms(http://web.archive.org/web/20070220142041/http://www.solarrating.org/certification/certification.htm).solarrating.org
37. ISO98062:1995.TestmethodsforsolarcollectorsPart2:Qualificationtestprocedures.InternationalOrganizationforStandardization,Geneva,Switzerland
38. H.M.Healey(2007)."EconomicsofSolar".Cogeneration&DistributedGenerationJournal22(3):3549.doi:10.1080/15453660709509122(https://dx.doi.org/10.1080%2F15453660709509122).
-
doi:10.1080/15453660709509122(https://dx.doi.org/10.1080%2F15453660709509122).39. R.H.CrawfordG.J.TreloarB.D.IlozorP.E.D.Love(2003)."Comparativegreenhouseemissionsanalysis
ofdomesticsolarhotwatersystems".BuildingResearch&Information31:34.doi:10.1080/09613210210160800(https://dx.doi.org/10.1080%2F09613210210160800).
40. C.Marken,J.Sanchez(2008)."PVvs.SolarWaterHeating:SimpleSolarPayback"(http://www.homepower.com/articles/pvvssolarwaterheating).HomePower127:4045.
41. SimplifiedResidentialSolarHotWaterSystemCalculator(http://www.fsec.ucf.edu/en/consumer/solar_hot_water/homes/calculator/index.htm),FloridaSolarEnergyCenter(2007).
42. MiltonS.&KaufmanS.(2005).SolarWaterHeatingasaClimateProtectionStrategy:TheRoleforCarbonFinance(http://www.greenmarkets.org/Downloads/SWH_carbon.pdf).GreenMarketsInternational.ArlingtonMA,USA
43. "Eskom"(http://www.eskom.co.za).Eskom.Retrieved10February2012.44. "HillsSolarEvacuatedTubeSolarHotWaterSystems"(http://www.envirofriendly.com/evacuatedtubesolar
hotwater.shtml).Envirofriendly.com.Retrieved10February2012.45. EnergyEfficientHomesPackage
(http://web.archive.org/web/20090206120159/http://environment.gov.au/energyefficiency/index.html).environment.gov.au
46. "AERissuesreportonhighelectricitypricesinSouthAustralia"(http://web.archive.org/web/20080720013337/http://www.aer.gov.au/content/index.phtml/itemId/717887).Aer.gov.au.4March2008.Retrieved10February2012.
47. WATkosteenzonneboiler?(http://www2.vlaanderen.be/economie/energiesparen/doc/folder_zonneboiler.pdf)vlaanderen.be,30April2008.
48. "Premiesvoorenergiebesparendemaatregelen|Vlaanderen.be:uwlinkmetdeoverheid"(http://www.vlaanderen.be/servlet/Satellite?pagename=Infolijn/View&cid=1090509343446&c=Solution_C&p=1186804409590&context=).Vlaanderen.be.Retrieved10February2012.
49. "Noaspx|Electrabel"(http://www.electrabel.be/residential/energy_saving/duplicate/build_renovate/build_renew_hot_water_nl.aspx).Electrabel.be.Retrieved10February2012.
50. "SRPEarthWiseSolarEnergyforyourhome"(http://www.srpnet.com/environment/earthwise/solar/default.aspx).Srpnet.com.Retrieved10February2012.
51. "FederalTaxCreditsforEnergyEfficiency:ENERGYSTAR"(http://www.energystar.gov/index.cfm?c=tax_credits.tx_index).Energystar.gov.20120103.Retrieved20120623.
52. "AverageRetailPriceofElectricitytoUltimateCustomersbyEndUseSector,byState"(http://www.eia.doe.gov/cneaf/electricity/epm/table5_6_b.html).
53. "Solarwaterheatingsystemsexplainedbenefits,costs,savings,earnings,suitability"(http://www.energysavingtrust.org.uk/Generateyourownenergy/Solarwaterheating).Energysavingtrust.org.uk.Retrieved20120623.
54. "ElectricityRunningCostCalculator|ElectricityPrices|ElectricityCosts"(http://www.ukpower.co.uk/tools/running_costs_electricity/).Ukpower.co.uk.Retrieved20120623.
55. April17,2009(20090417)."SolarLeasingPretasol"(http://www.pretasol.com).Pretasol.com.Retrieved20120623.
56. C.MartinandM.Watson(2001).Sidebysidetestingofeightsolarwaterheatingsystems(http://sahotwater.com.au/solarwiki.html).DTIpublicationURN01/1292.London,UK
57. "DCSolarPumps"(http://web.archive.org/web/20100119014925/http://lainginc.itt.com/LGpumpDCSolarPumps.asp).lainginc.itt.com.Retrieved5November2010.
58. "NominatiesVSKAwards"[LaingITTEcocircpumpnominatedforprestigiousVSKawardinheatingcategory](http://www.bouwwereld.nl/web/Actueel/Nieuws/Nieuws/08820/NominatiesVSKAwards.htm).bouwwereld.nl(inDutch).Retrieved5November2010.
59. G.Tsilingiridis,G.MartinopoulosandN.Kyriakis(2004)."Lifecycleenvironmentalimpactofathermosyphonicdomesticsolarhotwatersystemincomparisonwithelectricalandgaswaterheating".RenewableEnergy29(8):1277.doi:10.1016/j.renene.2003.12.007(https://dx.doi.org/10.1016%2Fj.renene.2003.12.007).
60. F.Ardente,G.Beccali,M.Cellura(2005)."Lifecycleassessmentofasolarthermalcollector:Sensitivityanalysis,energyandenvironmentalbalances".RenewableEnergy30(2):109.doi:10.1016/j.renene.2004.05.006
-
Externallinks
Partsofasolarheatingsystem(http://www.nrel.gov/docs/fy04osti/34279.pdf)
Retrievedfrom"https://en.wikipedia.org/w/index.php?title=Solar_water_heating&oldid=672968230"
Categories: Residentialheatingappliances Heating,ventilating,andairconditioningSolarthermalenergy Alternativeenergy Sustainablebuilding Renewableenergy
analysis,energyandenvironmentalbalances".RenewableEnergy30(2):109.doi:10.1016/j.renene.2004.05.006(https://dx.doi.org/10.1016%2Fj.renene.2004.05.006).
61. S.R.Allen,G.P.Hammond,H.Harajli1,C.I.Jones,M.C.McManusandA.B.Winnett(2008)."Integratedappraisalofmicrogenerators:Methodsandapplications".ProceedingsoftheICEEnergy161(2):5,Fig.1.doi:10.1680/ener.2008.161.2.73(https://dx.doi.org/10.1680%2Fener.2008.161.2.73).
62. "DMOZDIYSolarwaterheatingcollector"(http://www.dmoz.org/Science/Technology/Energy/Renewable/Solar/Solar_Thermal/).Dmoz.org.20100503.Retrieved20120623.
63. TechnicalInformationOnline."DIYsolarwaterheatinginthedevelopingworld"(http://practicalaction.org/practicalanswers/product_info.php?cPath=21_59&products_id=174).Practicalaction.org.Retrieved20120623.
64. "SolarRating&CertificationCorporationSystemRatings"(http://www.solarrating.org/facts/system_ratings.html).solarrating.org.2012.RetrievedSeptember19,2012.
65. "RETCompliance"(http://ret.cleanenergyregulator.gov.au/ForIndustry/retcompliance).AustralianGovernment,CleanEnergyRegulator.2Jan2013.Retrieved20140925.
66. RENEWABLESGLOBALSTATUSREPORT2009Update(http://web.archive.org/web/20100307001055/http://ren21.net/pdf/RE_GSR_2009_Update.pdf).DeutscheGesellschaftfrTechnischeZusammenarbeit.ren21.net
67. "RenewablesGlobalStatusReport2010"(http://web.archive.org/web/20100820221548/http://www.ren21.net/globalstatusreport/REN21_GSR_2010_full.pdf)(PDF).REN21.Retrieved20120623.
68. Solarthermalenergybarometer2010(http://www.eurobserver.org/pdf/baro197.pdf)EurObservERSystmessolairesLejournaldesnergiesrenouvelablesn197,5/2010
69. WernerWeissandFranzMauthner(May2011)."SolarHeatWorldwide"(http://web.archive.org/web/20110812220754/http://www.ieashc.org/publications/downloads/Solar_Heat_Worldwide2011.pdf)(PDF).Retrieved20120623.
70. WernerWeissandFranzMauthnerSolarHeatWorldwideMarketsandContributiontotheEnergySupply2010(http://web.archive.org/web/20120614195029/http://www.ieashc.org/publications/downloads/Solar_Heat_Worldwide2012.pdf).ieashc.org
71. Solarthermalandconcentratedsolarpowerbarometer(http://www.eurobserver.org/pdf/baro209ST_H.pdf).EurObservERn209(May2012).
72. SolarthermalmarketinEurope2010(http://www.estif.org/fileadmin/estif/content/market_data/downloads/2010%20European%20Solar%20Thermal%20Markets.pdf)TrendsandMarketStatistics,ESTIF6/2011
73. SolarthermalmarketgrowsstronglyinEurope2009(http://www.estif.org/fileadmin/estif/content/market_data/downloads/2009%20solar_thermal_markets.pdf)ESTIF2010
74. SolarthermalmarketgrowsstronglyinEurope2008(http://www.estif.org/fileadmin/estif/content/market_data/downloads/2008%20Solar_Thermal_Markets_in_Europe_2008.pdf)ESTIF5/2009
-
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