Process Heat Generation Potential from Solar Concentration Technologies in Latin America

22 Pages·2017·11.77 MB·English

energies
Article
Process Heat Generation Potential from Solar
Concentration Technologies in Latin America:
The Case of Argentina
IsidoroLillo1,ElenaPérez2,*,SaraMoreno1andManuelSilva1
1 DepartmentofEnergyEngineering,UniversityofSeville,CaminodelosDescubrimientos,s/n41092Seville,
Spain;[email protected](I.L.);[email protected](S.M.);[email protected](M.S.)
2 AndalusianAssociationforResearchandIndustrialCooperation,CaminodelosDescubrimientos,
s/n41092Seville,Spain
* Correspondence:[email protected];Tel.:[phone]
AcademicEditor:AdolfAcquaye
Received:7February2017;Accepted:10March2017;Published:17March2017
Abstract:Thispaperevaluatesthepotentialofsolarconcentrationtechnologies—compoundparabolic
collector(CPC),linearFresnelcollector(LFC)andparabolictroughcollector(PTC)—asanalternative
toconventionalsourcesofenergyforindustrialprocessesinLatinAmerica,wherehighlevelsof
solarradiationandisolatedareaswithoutenergysupplyexist. Theanalysisisaddressedfromenergy,
economicandenvironmentalperspective. AspecificapplicationforArgentinainwhichfourteen
locations are analyzed is considered. Results show that solar concentration technologies can be
aneconomicallyandenvironmentallyviablealternative. Levelizedcostofenergy(LCOE)ranges
between 2.5 and 16.9 c€/kWh/m2 and greenhouse gas (GHG) emissions avoided range between
33and348kgCO /(m2·year). CPCtechnologystandsoutasthemostrecommendabletechnology
2
whentheworkingfluidtemperaturerangesfrom373Kto423K.Astheworkingfluidtemperature
increasesthedifferencesbetweentheLCOEvaluesoftheCPCandLFCtechnologiesdecrease. When
523KisreachedLFCtechnologyistheonewhichpresentsthelowestLCOEvaluesforallanalyzed
sites,whiletheLCOEvaluesofPTCtechnologyareclosetoCPCtechnologyvalues. Resultsshow
thatsolarconcentrationtechnologieshavereachedeconomicandenvironmentalcompetitiveness
levelsundercertainscenarios,mainlylinkedtosolarresourceavailable,thermallevelrequirements
andsolartechnologycost.
Keywords: feasibility;solarthermalenergy;heatprocess;greenhousegasemissions
1. Introduction
Thereviewofthecurrentsituationoftheenergysectorshowsthatprimaryenergyconsumption
iscontinuouslyincreasing[1]. Theanalysisoftheglobalenergysourcesmatrixshowsthatthisprimary
energydemandcontinuestopreferoil,withashareof35.7%ofthetotalenergyconsumption. Natural
gashasreplacedcoalasthesecondenergyresource,meeting25.6%ofthedemand,mainlyasaresult
ofconsumptionintheUnitedStatesandtheMiddleEast. Coalhasbeenrelegatedtothethirdenergy
source,representing19.3%oftheconsumption[2]. Fromthesedataitisextractedthatfossilfuelsstill
accountformorethan80%oftheglobalenergymatrix.
InthecaseofLatinAmerica,withabout9%oftheworldpopulation,theenergyconsumption
representsabout6%ofthetotalenergyconsumption. Inthisregionabout45%oftheenergydemandis
suppliedwithoil,25%withnaturalgasandtherestbyrenewableenergy,mainlyhydroandbiomass.
In the case of Latin America approximately one third of the total energy consumption is for the
transportsector,anotherthirdfortheindustrialsectorandtheremainingthirdfordomesticandother
uses[3].
Energies2017,10,383;doi:10.3390/en10030383 www.mdpi.com/journal/energies
Energies2017,10,383 2of22
Energies 2017, 10, 383 2 of 21
Energies 2017, 10, 383 2 of 21
FoFsossilsiel neenregrygye xeixsitsstsi ninL LaatitninA Ammeerriiccaa,, bbuutt rreenneewwaabbllee eenneerrggyy rreessoouurcrcees saarer ealaslos oavaavialailbalbe.l eW. Wateart er
Fossil energy exists in Latin America, but renewable energy resources are also available. Water
anadndbi boimomasassas raereth teheo nonlylyo onneesst hthaattp prreesseenntt aa ssiiggnniifificcaanntt uussee.. TThhee uusseess oof fooththeersr ssusuchch asa ssosloalra orro wrwinidn d
and biomass are the only ones that present a significant use. The uses of others such as solar or wind
arearnee gnleiggliibgliebdlee sdpeistpeihtea vhianvginagh iag hhsigohla rsorelasro urercseouinrcvei ritnu avlilrytuaallllcyo uanllt rcioeusn[4tr,5ie]s. O[4n,5e]a. sOpnecet atospceocnts itdo er
are negligible despite having a high solar resource in virtually all countries [4,5]. One aspect to
iscthonesfiadcetrt hisa tthien fsaocmt tehLata itnin sAommee rLiacatinn cAomunetrricieasn, scuouchntariseEs,c suuacdho arso ErcPuearduo,rn aotru Praerlug,a nsaitsusrualb sgiadsi zise d.
consider is the fact that in some Latin American countries, such as Ecuador or Peru, natural gas is
Thssiuusbbhssaiiddsiiazzeendde..g TTahhtiiivss ehhaaimss aap annceetggoaanttiivvteeh eiimmdppeavaccettl ooopnnm tthheeen ddteeavvneedlloouppsmmeeeonnfttr eaannneddw uuassbee looeff e rrneeennreegwwieaasbb.llee eenneerrggiieess..
AvAAevvreearrgaaeggeed addiaalyiillyyg gglolloobbbaaalllh hhooorrriziizzooonnntttaaalll rrraaadddiiiaaatttiiiooonnn vvvaaallluuueeesss ooofff LLLaaattiitnnin AAAmmmeerreiircciaac arraarnnaggneeg fferroofrmmo m 33..553 .kk5WWkhhW//mmh/22 mttoo 277 t o
7kkkWWWhhh///mmm22 2pppeerre rdddaayya yaallatthhltoohuuogguhhg hmmmoossott sootff otthhfeeth sseuurrsffuaarccfeea csshheooswwhoss wvvaaslluvuaeesslu bbeeesttwwbeeeteewnn e44e kknWW4hhk//Wmm2h2 aa/nnmdd2 66a kknWWdhh6//kmmW22.. hTT/hhmee 2.
ThAAennAddneeaadnne aaanrreeaaa riiess a tthhisee otohnneee otthhnaaett tpphrraeetsseepnnrttesss hheiinggthhseehrr ivvgaahlleuureessv,, aaalssu FFeiisgg,uuarrsee F11i gsshhuoorwwess1 [[s66h]]..o IIwnn stthh[ee6 ]cc.aaIssnee oothff eddiicrraeesccett nnooofrrdmmiraaell ct
radiation there are regions in which the annual values are higher, for example some parts of Chile
norramdiaaltiroand itahteiroen atrhee rreegaiorensr eigni ownhsicinh wthhe iachnntuhael avnanluueasl varael uheisghaerre, hfoigr heexra,mfoprlee xsaommpe lpeasrotms oef pCahritlse of
and Mexico (Figure 2) [6]. As both figures show, the countries of Latin America generally receive
Chainled aMndexMiceox (iFcoig(uFrieg u2r)e [62]). [A6]s. Abosthbo ftihgufirgeus rsehsoswho, wth,et hceouconutrnietrsi eosf oLfaLtiant iAnmAemriecrai cgaegneenraelrlayl lryecreeciveeiv e
high levels of radiation that could be exploited.
highhighle vleevleslos forfa rdaidaitaitoionnt hthaattc coouuldldb beee exxppllooiitteedd..

Figure 1. Map of global horizontal radiation of Latin America.
FFigiguurere1 1..M Maapp ooff gglloobbaall hhoorriizzoonnttaall rraaddiiaattiioonn ooff LLaatitnin AAmmeerirciac.a .

FFigiguurere2 2..M Maapp ooff ddiirreecctt nnoorrmmaall rraaddiiaattiioonn ooff LLaattinin AAmmeerirciaca. .
Figure 2. Map of direct normal radiation of Latin America.
Energies2017,10,383 3of22
Highlevelsofsolarradiationhavepotentialforharnessingsolarenergy.Therolethatsolarenergy
could acquire as a thermal energy source for industrial processes in which high levels of thermal
energyarerequiredisespeciallyinteresting. TherearemanyisolatedplacesinLatinAmericainwhich
theaccesstoconventionalsourcesofenergyaselectricityornaturalgasisunfeasibleandthatwill
befavoredbytheimplementationofthistypeofsolarsystems. Thelackofenergysupplyinthese
areashasledtothedevelopmentoftheeconomybelowitspotential. Forexample,thedevelopment
andcommercializationofproductsbasedonrawmaterialshasnotbeenpossible. Theavailabilityof
thissourceofenergywouldprovideisolatedareaswiththeopportunityofdevelopingthisbusiness,
whichwouldundoubtedlybeassociatedwiththeeconomicdevelopmentoftheregion,withanimpact
onthelivelihoodsofpeople.
Most of the energy needs of industrial processes are below 523 K, a temperature level which
couldbereadilybesuppliedbysolarthermalenergy(STE)[7]. Table1summarizesthetemperature
rangeofpotentialindustrialprocesses. IntheparticularcaseofisolatedareasofLatinAmericathere
aretwooftheseapplicationsthatareespeciallyinteresting,namelytherefrigerationanddryingof
agriculturalproducts.
Table1.Temperaturerangeofpotentialindustrialprocesses.
Industry Process TemperatureRange(K)
Sterilization 373–393
Dairy
Drying 393–453
Cannedfood Sterilization 383–393
Agriculturalproducts Drying 353–473
Drying 373–403
Textile
Degreasing 433–453
Paper Bleach 403–423
Soaps 473–533
Syntheticrubber 423–473
Chemistry
Processheat 393–453
Petroleum 373–423
Woodproducts Pulppreparation 393–443
Desalinization Heattransferfluid 373–523
Drying
Concentratesmelting
Mining 373–673
Heatingsolutions
Washing
Preparation 393–413
Distillation 413–423
Separation 473–493
Plastics
Extension 413–433
Drying 453–473
Mixing 393–413
Thermaltreatment Mediumtempering 623–723
Refrigeration Doubleeffectsolarchiller 393–463
The field of application of solar technologies is large, as it allows heat transfer fluid delivery
temperatureshigherthan1200K,between318Kand673Kincaseoflinearfocussolarconcentration
technologies. Theselectionofoneoranothertechnologydependsonthermalrequirementsmainly
associatedwitheachindustrialprocess.
Recentlyseveralstudiesthatfocusonanalyzingthepossibilitiesofcouplingasolarinstallation
toanindustrialprocesshavebeendeveloped. Thesestudiesidentifyneededimprovementsinthe
Energies2017,10,383 4of22
collectorsusedinsolarinstallationsresponsibleforgeneratingprocessheat,analyzethecurrentmarket
andcompileaseriesofrecommendationsbasedonknowledgeacquiredthroughexperimentalfacilities.
Barriersthatstillhinderthedevelopmentofsolarinstallationssuchashighinvestmentcost,lackof
publicfundingandlowcostsofconventionalenergyareidentified[8–12]. Thefirstsolarinstallations
coupledtoanindustrialprocesswerebasedonconventionalsolartechnologies,usedforobtaining
electricity,butcurrentlyindustrialprocessesapplicationshavedevelopedspecificdesigns. Asnew
developmentsbecomeavailable,moresolarheatforindustrialprocessesapplicationswillbecome
viable[13,14].
Thebroadrangeofpossibilitiesofferedbysolarenergyhasraisedtheinterestofdifferentcountries
suchasAustralia,Germany,MexicoorTunisia. IntheAustraliancasetheresearch,developmentand
demonstrationprograminsolarindustrialprocessheatingwasledprincipallybytheCommonwealth
ScienceandIndustrialResearchOrganisation,CSIRO[15]. AstudydevelopedinAustraliatriedto
identifypotentialsitesforutilizationofSTE.Thereviewidentified2498individualsitesbylocation,
industrytype,energyuseandcharacteristicprocesstemperature. Thisdataispresentedonmapsin
termsofbothindustrytype,andcharacteristicprocesstemperature,indiscreterangesforcomparison
withtheapproximateirradiationpatternsandtoidentifysitesthatshouldbeconsideredformore
detailedanalysis. Relativelyfewindustrialsiteswerepresentinareasofhighirradiation. Inareaswith
moderateirradiation,outsidemajorcities,therearenumeroussitesinthefoodprocessing,building
products,textilesandwoodproductsindustriesthatcouldutilizelowtomoderatetemperaturesolar
heat[16]. Germanstudiesalsohaveattemptedtoselectthesectorswiththegreatestpotentialamong
themchemicals,paperorrubberindustries. Thesesectorsareanalyzedtoidentifysuitableprocesses
fortheintegrationofsolarheat. TheresultsofthesestudiesfacilitatetheprioritizedapplicationofSTE
inindustrialsectorsandprocesses[17]. MeanwhileTunisiahasanalyzedthefeasibilityofintegrating
thermalcollectorsasasourceofenergysupplyofindustrialprocesses. Resultsshowthatin2012solar
thermalsystemswerenoteconomicallyinterestingforenduserswithcurrentsubsidyschemes,but
they could lead to significant economic benefits for the government [18]. Finally, Mexico has also
analyzedthepotentialofsolarenergyasasourceofenergysupplyforthetextileandfoodsectors[19].
Asshownsolarheatforindustrialprocesseshasbeenidentifiedrepeatedlyasanimportantmarketfor
solarthermalapplicationsastheindustrialheatdemand,proofofthatarethenumerousemergent
applications [20]. Several reports have thoroughly analyzed the contributions of solar energy in
meetingtheenergyrequirementsofseveralkindofindustries,fromtheoilindustrytothepaper,textile
orpharmaceuticalindustry[21–27].
LatinAmericaalreadyhassomeexamplesofsolarsystemsthatprovidetotallyorpartiallythe
thermalenergyrequiredbysomeindustrialprocess. OneexampleistheKraftFoodprojectinBrazil,
inthiscasecorrespondingtothefoodindustry. Thisprojectconsistsofathermalenergysystemthat
deliversheattocook,clean,dryandpasteurizefoods. Thesolarfieldusesparabolictroughcollector
(PTC)technologytoheatpressurizedwateratatemperatureof383K.Especiallystrikingisthecouple
formedbysolarsystemsandminingcompaniesinChile. Oneofthemostprominentexamplesis
ElTesoro,asubsidiaryofAntofagastaMineralsthatdisposesof1280PTCPT-1modulestoprovide
processheatforcopperminingproduction. LevelsofsolarradiationintheAtacamaDesert,whereEl
Tesoroislocated,areveryhigh[28,29].Thereisawiderangeofpossibilitiesforcouplingasolarsystem
toanindustrialprocess[30]. Theselectionofoneorotherisdoneaccordingtotheindustrialprocess
requirementsineachcase. Figures3and4showsomeofthem. Thefirstdiagramshowsaninstallation
inwhichresidualuseofthermalenergyexists. Theindustrialprocesspresentedinthisfigurerequires
twolevelsofthermalenergy. Figure4showsanotherconfigurationinwhichanauxiliaryboileranda
heatrecoverysystemareincluded.
Energies2017,10,383 5of22
EEnneerrggiieess 22001177,, 1100, , 338833 55 ooff 2211

FFFiiiggguuurrreee 333.. . PPPrrroooccceeessssss hhheeeaaatt t sssccchhheeemmmeee iininnccclluluudddiininnggg uuussseee aaannnddd tttwwwooo llleeevvveeelllsss ooofff ttthhheeerrrmmmaaalll eeennneeerrrgggyyy...

FFFiiiggguuurrreee 444.. . PPPrrroooccceeessssss hhheeeaaattt sssccchhheeemmmeee iiinnncccllluuudddiiinnnggg aaannn aaauuuxxxiiillliiiaaarrryyy bbboooiiillleeerrr aaannnddd aaa hhheeeaaattt rrreeecccooovvveeerrryyy sssyyysssttteeemmm...
222... SSSooolllaaarrr TTThhheeerrrmmmaaalll EEEnnneeerrrgggyyy
SSSTTTEEE iiisss aaa ssseeettt ooofff ttteeeccchhhnnnooolllooogggiiieeesss fffooorrr hhhaaarrrnnneeessssssiiinnnggg sssooolllaaarrr eeennneeerrrgggyyy fffooorrr uuussseee iiinnn iiinnnddduuussstttrrryyy,,, rrreeesssiiidddeeennntttiiiaaalll ooorrr
cccooommmmmmeeerrrccciiiaaalll ssseeeccctttooorrrsss.. . TTThhheee gggeeennneeerrraaatttiiiooonnn ooofff ttthhheeerrrmmmaaalll eeennneeerrrgggyyy fffrrrooommm sssooolllaaarrr rrraaadddiiiaaatttiiiooonnn iiisss hhhiiiggghhhlllyyy rrreeecccooommmmmmeeennndddeeeddd
bbbeeecccaaauuussseee ooofff ttthhhiiisss oooppptttiiiooonnn mmmiiitttiiigggaaattteeesss cccllliiimmmaaattteee ccchhhaaannngggeee aaannnddd rrreeeppplllaaaccceee eeexxxhhhaaauuussstttiiibbbllleee sssooouuurrrccceeesss... IIInnn aaaddddddiiitttiiiooonnn tttooo ttthhheee
eeennnvvviiirrrooonnnmmmeeennntttaaalll bbbeeennneeeffifiittstss aaallrlrereeaaadddyyy mmmeenennttiitooinonneededd,, s,sooslolaalrra trteetccehhcnnhoonllooolggoiigeesise asarreae r rereelrlaeatlteaedtde tdtoo t oootthhoeetrhr ebbreenbneeefnfiitetssfi lltiisnnklkieneddk ettodo
iitnnoccrirneeacasrseeedads eeednneeerrnggeyyr gssyeellfsf-e-sslufu-ffsffuiiccfifiieencnicceyyn cooyff oeefaacechah c chcoocuuonnuttrnryyt,r, y p,prproorvvoiivddiede eaacacccceecssesss sttoot o eeennneerergrggyyy rrreeeqqquuuiirirreeeddd iiinnn iiisssooolllaaattteeeddd
dddeeeppprrreeesssssseeeddd aaarrreeeaaasss aaannnddd eeemmmpppllloooyyymmmeeennnttt c ccrrereeaaattitioioonnn e eefffffefecectct.t..R RReeleallataettededdt ottoot h ttheheel a llasatsstit s isissussueueae n aadnnddin iintnh tethhpee a ppratairrcttuiiccluaurllaacrra cscaeassoeef
ooSfpf SaSpipnaaitinhn e tthheece o eenccooomnnooicmmiimicc p iimmacpptaahccatts hhbaaesse bnbeeeeevnna eleuvvaaatleluudaa.tteTedhd.e. TTrhehseeu rrletesssufuolltrtss a ffotoyrr p aai c ttayylpp5iic0caaMll 55W00 MpMaWWra b ppoaalriracabbtrooolliuiccg thtrroopuulaggnhht
pwpllaiatnnhtt 7 ww.5iitthhh s 77t.o.55r hah g ssettoocrraaapggaeec cictaayp,patahccieittymy,, otthshete w mmiodosestts wpwriieddaeedsspptyrrepeaaeddi n ttyySpppeea iiinnn , SSappraeaiin[n3,, 1 aa]r:ree [[3311]]::
•• AA ttoottaall ooff 22221144 eeqquuiivvaalleenntt jjoobbss ppeerr yyeeaarr dduurriinngg ccoonnttrraaccttiinngg aanndd ccoonnssttrruuccttiioonn,, iinncclluuddiinngg
ccoonnttrraaccttiinngg,, ccoonnssttrruuccttiioonn aanndd aasssseemmbbllyy,, aass wweellll aass mmaannuuffaaccttuurree ooff ccoommppoonneennttss aanndd eeqquuiippmmeenntt,,
ssuuppppllyy ooff sseerrvviicceess aanndd iinnddiirreecctt eemmppllooyymmeenntt..
•• AA ttoottaall ooff 4477 eeqquuiivvaalleenntt jjoobbss ppeerr yyeeaarr dduurriinngg ooppeerraattiioonn..
Energies2017,10,383 6of22
• Atotalof2214equivalentjobsperyearduringcontractingandconstruction,includingcontracting,
construction and assembly, as well as manufacture of components and equipment, supply of
servicesandindirectemployment.
Energies 2017, 10, 383 6 of 21
• Atotalof47equivalentjobsperyearduringoperation.
Solar thermal energy collectors mainly used are flat plate (FP), compound parabolic collector
(CPSCo)l,a lrintehaerr mFraelsenneel rcgoylleccotlolerc (tLoFrsCm) aanindl yPTuCse. dTahree lflasatt tphlraetee o(FnPes), acroem thpeo umnodstp aursaebdo cliocllceocltloercst ofror
(CinPdCu)s,tlriinael aprrFocreessnseesl. collector (LFC) and PTC. The last three ones are the most used collectors for
industrialprocesses.
2.1. Compound Parabolic Collector
2.1. CompoundParabolicCollector
A CPC vacuum tube collector ,see Figure 5, is a system composed of a few rows of transparent
ACPCvacuumtubecollector,seeFigure5,isasystemcomposedofafewrowsoftransparent
glass tubes connected to a head pipe. Each tube contains therein an absorption tube coated with
glass tubes connected to a head pipe. Each tube contains therein an absorption tube coated with
selective paint. The heat transfer fluid runs inside this pipe. Vacuum is applied to minimize
selectivepaint.Theheattransferfluidrunsinsidethispipe.Vacuumisappliedtominimizeconduction
conduction and convection heat losses. In this type of collectors solar radiation passes through the
andconvectionheatlosses. Inthistypeofcollectorssolarradiationpassesthroughtheglassoutertube,
glass outer tube, strikes the absorber tube and is finally transformed into heat. The overall
strikestheabsorbertubeandisfinallytransformedintoheat. Theoverallperformanceofvacuum
performance of vacuum tube collectors is higher than that of conventional collectors and maintains a
tubecollectorsishigherthanthatofconventionalcollectorsandmaintainsamoreconstantbehavior.
more constant behavior. CPC collectors include annular reflectors that allow a greater concentration
CPCcollectorsincludeannularreflectorsthatallowagreaterconcentrationofsolarradiationontothe
of solar radiation onto the absorber tube.
absorbertube.

Figure 5. Compound parabolic collector. Source: SOLFEX Energy Systems.
Figure5.Compoundparaboliccollector.Source:SOLFEXEnergySystems.
2.2. Linear Fresnel Collector
2.2. LinearFresnelCollector
The concept of LFC, see Figure 6, is based on the idea of simulating a continuous concentrator,
TheconceptofLFC,seeFigure6,isbasedontheideaofsimulatingacontinuousconcentrator,in
in this case a parabolic trough collector as a set of elements, rows of mirrors properly arranged on a
thiscaseaparabolictroughcollectorasasetofelements,rowsofmirrorsproperlyarrangedonaplane.
plane. Problems related to the construction of large concentrators are avoided, allowing taking lower
Problemsrelatedtotheconstructionoflargeconcentratorsareavoided,allowingtakinglowercost
cost solutions. LFC are therefore a low cost alternative to parabolic trough collectors. This kind of
solutions. LFCarethereforealowcostalternativetoparabolictroughcollectors. Thiskindofsystems
systems is composed of long parallel rows of mirrors of relatively small width which can rotate
iscomposedoflongparallelrowsofmirrorsofrelativelysmallwidthwhichcanrotateabouttheir
about their longitudinal axis. These mirrors concentrate solar radiation on a fixed central receiver
longitudinalaxis. Thesemirrorsconcentratesolarradiationonafixedcentralreceiversuspendedata
suspended at a certain height. This geometry allows two or more receivers in parallel, relatively
certainheight. Thisgeometryallowstwoormorereceiversinparallel,relativelyclosetoeachother,
close to each other, thus enabling the ranks of mirrors to be shared by two of the receptors. This
thusenablingtheranksofmirrorstobesharedbytwoofthereceptors. Thisconfigurationoptimizes
configuration optimizes the use of land and minimizes blockages among rows of mirrors. The main
theuseoflandandminimizesblockagesamongrowsofmirrors. Themainelementofthistechnology
element of this technology is the absorber tube, which is essentially similar to one used in parabolic
istheabsorbertube,whichisessentiallysimilartooneusedinparabolictroughcollectorsystems.
trough collector systems.

Figure 6. Linear Fresnel collector (LFC).Source: AREVA solar.
Energies 2017, 10, 383 6 of 21
Solar thermal energy collectors mainly used are flat plate (FP), compound parabolic collector
(CPC), linear Fresnel collector (LFC) and PTC. The last three ones are the most used collectors for
industrial processes.
2.1. Compound Parabolic Collector
A CPC vacuum tube collector ,see Figure 5, is a system composed of a few rows of transparent
glass tubes connected to a head pipe. Each tube contains therein an absorption tube coated with
selective paint. The heat transfer fluid runs inside this pipe. Vacuum is applied to minimize
conduction and convection heat losses. In this type of collectors solar radiation passes through the
glass outer tube, strikes the absorber tube and is finally transformed into heat. The overall
performance of vacuum tube collectors is higher than that of conventional collectors and maintains a
more constant behavior. CPC collectors include annular reflectors that allow a greater concentration
of solar radiation onto the absorber tube.

Figure 5. Compound parabolic collector. Source: SOLFEX Energy Systems.
2.2. Linear Fresnel Collector
The concept of LFC, see Figure 6, is based on the idea of simulating a continuous concentrator,
in this case a parabolic trough collector as a set of elements, rows of mirrors properly arranged on a
plane. Problems related to the construction of large concentrators are avoided, allowing taking lower
cost solutions. LFC are therefore a low cost alternative to parabolic trough collectors. This kind of
systems is composed of long parallel rows of mirrors of relatively small width which can rotate
about their longitudinal axis. These mirrors concentrate solar radiation on a fixed central receiver
suspended at a certain height. This geometry allows two or more receivers in parallel, relatively
close to each other, thus enabling the ranks of mirrors to be shared by two of the receptors. This
configuration optimizes the use of land and minimizes blockages among rows of mirrors. The main
Eenleermgieesn2t0 1o7f, 1th0,i3s8 t3echnology is the absorber tube, which is essentially similar to one used in para7boofl2ic2
trough collector systems.
Energies 2017, 10, 383 7 of 21
2.3. Parabolic Trough Collector
PTC is one of the most mature CSP technologies, accounting for more than 90% of the currently
installed CSP capacity. As illustrated in Figure 7, PTC consists of a series o f parabolic reflectors that
concentrate solar radiFaitgiuorne 6o.n L irneecaer iFvriensgn epl cipolelse ctcoorn (tLaFiCni)n.Sgo utrhcee: AheRaEtV tAr asnoslafre.r fluid that is heated
Figure6.LinearFresnelcollector(LFC).Source:AREVAsolar.
throughout the process. These collectors are placed in parallel rows that make up the solar field
aligned in a north-south or east-west axis. The receivers have a special coating to maximize energy
2.3. ParabolicTroughCollector
absorption, minimize infrared re-irradiation and work in an evacuated glass envelope to avoid
convPecTtCionis hoenaet olfotshseesm. Nosotwmaadtuayres CmSoPstt escyhsnteomlosg iaerse, aecmcopulnoytiendg ftoor ombotarient healenct9r0ic% poofwtheer.c Iunr rtehnetslye
icnassteasl lseodlaCr ShPeacta ipsa mciotyv.edA sbyil lau shteraatt etdraninsfFeirg fulureid7 f,loPwTCingco inns tihstes roefceaivseerr iteusboef apnadr atbraonliscferrerfleedc ttoor as
tshteaatmco gnecneenrtartaotre tsoo plarrodraudciea tthioen suonperre-cheeiavtiendg spteipames tchoant trauinnisn tgheth tuerhbeinate.t rManirsrfoerrs flaunidd rtehcaetiviserhs etaratecdk
tthhreo usugnh’osu pttahthe parloocnegs sa. Tshinegselec oalxleisc.t oArsna arerrpalya coefd miniprraorrasl leclarno wbes tuhpat tmo a1k0e0u mpt hloensgo lawrifithe lda acluigrvneedd
ianpaerntuorreth o-sf o5u–t6h mor. east-westaxis. Thereceivershaveaspecialcoatingtomaximizeenergyabsorption,
minimMiozset iPnTfrCa rpeldanrets-i crruardreianttiloyn ina nodpewraotrikonin haanvee vcaacpuaactiteidesg olaf sbseetwnveeelno p1e4 taonadv 8o0i dMcWonev, eefcftiicoinenhceieast
loofs saerso.uNndo w1a4d%a–y1s6m% oastndsy smteamxismaureme moppelroayteindgt oteombtpaeirnaetulercetsr icofp o66w3e rK.,I nwthhiecshe cisa sleismsioteladr bhye atthies
mdeogvreaddabtyioan hoef astyntrtahnestfice roflilu uisdedfl ofwori nhgeaitn trtahnesrfeecre. iTvheer utusbe eofa nmdotltreann ssfaelrtr aetd 8t2o3 aKs ftoera mhegate ntrearnastfoerr tios
purnoddeurc deetmheosnusptreart-ihoena.t Hedigshte-atemmtpheartartuunres tmheolttuernb sinaelt. mMairyr oinrscraenadser ebcoetihv eprlsatnrta cekffitchieensucyn ’asnpda tthhearlmonagl
astsoirnagglee caaxpisa.cAityn [a3r2r]a.y ofmirrorscanbeupto100mlongwithacurvedapertureof5–6m.

Figure 7. Parabolic trough collector. Source: Enerstar.
Figure7.Parabolictroughcollector.Source:Enerstar.
3. Configuration of the Plant
MostPTCplantscurrentlyinoperationhavecapacitiesofbetween14and80MW ,efficienciesof
e
arounTdhe1 4p%la–n1t6 %thaatn ids manaaxliymzuedm ionp tehriast ipnagpteerm cpoenrsaitduerress tohfa6t6 t3hKe ,swolharic ehniesrlgimy istyedstebmy tihse cdoeugprlaedda ttioo na
opfresvyinotuhselyti cexoiisltiunsge dinfdourshtreiaalt ptrraoncesfsesr. .TTheh esoulaser soyfsmtemol tseunpspallitesa tth8e2 3thKermfoarl heenaetrgtrya nnsefeedreids tuon rduenr
dtheem polnansttr.a Ttihoen c.oHnivgehn-tteiomnpael rsaotuurrceem oof letnenersgaylt omf athyei npclarenats weboorkths apsla annt aefufixciileianrcyy paonwdetrh esrymstaelms tionr athgee
cnaepwa cciotynf[i3g2u]r.ation. Its function is to replace the new system when solar radiation transients do not
allow meeting the needs of the industrial process. The characterization of this industrial process is
3n.oCt tohnefi sguubrjaetcito onfo tfhtish epaPplaenr tbut its needs; especially the working temperature determines the most
appropriate solar technology. The plant that is analyzed in this paper is mainly composed of a solar
Theplantthatisanalyzedinthispaperconsidersthatthesolarenergysystemiscoupledtoa
field, a heat exchanger and a thermal energy storage system (Figure 8). Thermal energy storage
previouslyexistingindustrialprocess. Thesolarsystemsuppliesthethermalenergyneededtorun
system is considered infinite, in other words, all energy generated is used. Solar part also relies on a
theplant. Theconventionalsourceofenergyoftheplantworksasanauxiliarypowersysteminthe
control system that manages the operation of the installation depending on weather conditions. The
newconfiguration. Itsfunctionistoreplacethenewsystemwhensolarradiationtransientsdonot
solar field is in charge of capturing solar radiation and raising the temperature of the heat transfer
allowmeetingtheneedsoftheindustrialprocess. Thecharacterizationofthisindustrialprocessis
fluid. To cover the entire temperature range this paper analyzes CPC, LFC and PTC technologies.
notthesubjectofthispaperbutitsneeds;especiallytheworkingtemperaturedeterminesthemost
To evaluate the thermal energy available at the output of the solar field the efficiency curves of
each technology are required. The efficiency curves associated with the best available technology
have been selected. The general expression of efficiency curves is as follows:
η =η −(c +c ⋅ΔT)⋅(ΔT/G ) (1)
sf 0 1 2 T
where ηsf: instantaneous solar field efficiency; η0: optical efficiency; c1: first order heat loss coefficient
(W/K·m2); c2: second order heat loss coefficient (W/K2·m2); ΔT: difference between the mean fluid
temperature and the ambient temperature (K); and GT: incident solar radiation (W/m2).
Energies2017,10,383 8of22
appropriatesolartechnology. Theplantthatisanalyzedinthispaperismainlycomposedofasolar
field,aheatexchangerandathermalenergystoragesystem(Figure8). Thermalenergystoragesystem
isconsideredinfinite,inotherwords,allenergygeneratedisused. Solarpartalsoreliesonacontrol
systemthatmanagestheoperationoftheinstallationdependingonweatherconditions. Thesolarfield
isinchargeofcapturingsolarradiationandraisingthetemperatureoftheheattransferfluid. Tocover
tEhneergeinest i2r0e17t,e 1m0, p38e3r aturerangethispaperanalyzesCPC,LFCandPTCtechnologies. 8 of 21

FFiigguurree 88.. CCoonnffiigguurraattiioonn ooff tthhee aannaallyyzzeedd ppllaanntt..
Table 2 specifies the coefficients of the equation above. ThePTC efficiency coefficients shown in
Toevaluatethethermalenergyavailableattheoutputofthesolarfieldtheefficiencycurvesof
Table 2 correspond to an evolved version of collectors used in solar thermal power plants. Although
eachtechnologyarerequired. Theefficiencycurvesassociatedwiththebestavailabletechnologyhave
traditionally PTC can also be allocated to process heat, cooling or heating, new collectors have been
beenselected. Thegeneralexpressionofefficiencycurvesisasfollows:
recently developed specially designed for producing thermal energy in building environments. New
collectors are usually simpler anηd m=orηe c−om(cpa+ct cth·a∆t tTh)e· o(t∆hTer/ oGne)s used for electricity productio(1n).
sf 0 1 2 T
Their new configuration allows them to be integrated easily in urban or industrial environments.
wSohmeree oηf :thinesirta cnhtaanraecotuesrissotilcasr afireel dae lfofiwcieern coyp;eηni:nogp, tihceailgehftfi cainednc wy;ecig:hfitr, swtohridcher gheenaetrlaolslys croeesfufilctsie nint
sf 0 1
(fWaci/liKti·ems 2in); tcra:nssepcoorntd anordd aesrshemeabtllyo.s scoefficient(W/K2·m2);∆T:differencebetweenthemeanfluid
2
temperatureandtheambienttemperature(K);andG : incidentsolarradiation(W/m2).
T
TTaabbllee 22.s Cpeoceiffificeisenthtse ocfo eeffffiicciieennctys coufrtvhees. eCqPuCa:t icoonmapboouvned. pTahreaPboTlCic ecfofillceicetnorc;y LcFoCe:f filicnieeanr tsfresshnoewl nin
Tableco2llceocrtorer sapnodn PdTtCo: panareabvoollivc etrdouvgehrs cioolnleoctfocro. llectorsusedinsolarthermalpowerplants. Although
traditionallyPTCcanalsobeallocatedtoprocessheat,coolingorheating,newcollectorshavebeen
Technology η0 c1 c2 References
recentlydevelopedsCpPeCci allyde0s.i6g9n3 edfor0.p9r2o1d5 ucingth0.e0r0m38a lenergyin[3b0,u3i3l–d3i5n]g environments. New
collectorsareusuallLyFsCim plera0n.6d67m orec0o.1m02p0a ctthat0t.h00e0o2t heronesus[e3d0,3fo6]r electricityproduction.
TheirnewconfiguratPioTnC allows0th.7e1m8 tobe0i.5n0t0e0g ratedea0s.0il0y05in urbanor[in30d,3u6s,t3r7ia] lenvironments. Some
oftheircharacteristicsarealoweropening,heightandweight,whichgenerallyresultsinfacilitiesin
transFpiogrutraen d9a sssheomwbsly .the efficiency evolution of medium temperature solar concentration
technologies in a temperature range from 293 K to 633 K. It is noted that the CPC efficiency curve
showTsa bglreea2t.eCr oveafrfiicaibeinlittsyo, fwehffiicleie tnhcey sctueravdeise.sCt bPeCh:acvoimopuor uisn daspsaorcaibaotelidc wcoiltlehc ttohre; LLFFCC: tleincheanroflroegsnye. l
collectorandPTC:parabolictroughcollector.
Technology η c c References
0 1 2
CPC 0.693 0.9215 0.0038 [30,33–35]
LFC 0.667 0.1020 0.0002 [30,36]
PTC 0.718 0.5000 0.0005 [30,36,37]
Figure9showstheefficiencyevolutionofmediumtemperaturesolarconcentrationtechnologies
inatemperaturerangefrom293Kto633K.ItisnotedthattheCPCefficiencycurveshowsgreater
variability,whilethesteadiestbehaviourisassociatedwiththeLFCtechnology.

Figure 9. Efficiency curves.
Thermal energy generated in the solar field is transferred to the industrial process through the
heat exchanger and the solar storage system. The estimated efficiencies of the
equipment—exchanger ηhe and energy storage system ηSAT—are 90% [38].
4. Economic Parameters
Table 3 summarizes the investment costs (CI), operation and maintenance costs (COM) and
replacement costs (CR) related to each one of the analyzed technologies. CI is calculated on the basis
of the area used while the other two costs are calculated as a percentage of the CI.
Energies 2017, 10, 383 8 of 21

Figure 8. Configuration of the analyzed plant.
Table 2 specifies the coefficients of the equation above. ThePTC efficiency coefficients shown in
Table 2 correspond to an evolved version of collectors used in solar thermal power plants. Although
traditionally PTC can also be allocated to process heat, cooling or heating, new collectors have been
recently developed specially designed for producing thermal energy in building environments. New
collectors are usually simpler and more compact that the other ones used for electricity production.
Their new configuration allows them to be integrated easily in urban or industrial environments.
Some of their characteristics are a lower opening, height and weight, which generally results in
facilities in transport and assembly.
Table 2. Coefficients of efficiency curves. CPC: compound parabolic collector; LFC: linear fresnel
collector and PTC: parabolic trough collector.
Technology η0 c1 c2 References
CPC 0.693 0.9215 0.0038 [30,33–35]
LFC 0.667 0.1020 0.0002 [30,36]
PTC 0.718 0.5000 0.0005 [30,36,37]
Figure 9 shows the efficiency evolution of medium temperature solar concentration
technologies in a temperature range from 293 K to 633 K. It is noted that the CPC efficiency curve
Energies2017,10,383 9of22
shows greater variability, while the steadiest behaviour is associated with the LFC technology.

Figure 9. Efficiency curves.
Figure9.Efficiencycurves.
Thermal energy generated in the solar field is transferred to the industrial process through the
Thermalenergygeneratedinthesolarfieldistransferredtotheindustrialprocessthroughthe
heat exchanger and the solar storage system. The estimated efficiencies of the
heatexchangerandthesolarstoragesystem. Theestimatedefficienciesoftheequipment—exchanger
equipment—exchanger ηhe and energy storage system ηSAT—are 90% [38].
η andenergystoragesystemη —are90%[38].
he SAT
4. Economic Parameters
4. EconomicParameters
TTaabbllee 33 ssuummmmaarriizzeess tthhee iinnvveessttmmeenntt ccoossttss ((CCI)),, ooppeerraattiioonn aanndd mmaaiinntteennaannccee ccoossttss ((CCOM)) aanndd
I OM
rreeppllaacceemmeenntt ccoossttss ((CCR)) rreellaatteedd ttooe eaacchho onneeo offt htheea naanlaylzyezdedte tcehcnhonloolgoigesie.sC. CiIs icsa clcaulcluatleadteodn otnh ethbea sbiassoisf
R I
othf ethaere aareuas eudsewdh wilheitlhee thoeth oetrhtewr otwcoo sctossatrse acrael ccaullcauteladteads aasp ae rpceerncteangteaogfe tohfe thCe. CI.
I

Table3.Solartechnologycosts.
Costs
Technology CI COM CR References
€/m2 %CI %CI
CPC 325 2.5 10.0 [8,30,39]
LFC 425 5.0 10.0 [8,30,36,40,41]
PTC 560 5.5 10.0 [30,36,37,39,41]
C iscalculatedannuallywhileC isrelatedtoaninstallationoverhaulthatiscarriedoutinthe
OM R
fifteenthyearofoperation. Toaddresstheeconomicanalysisisnecessarytodefinetheusefullifeof
theanalyzedinstallation,30yearsinthisstudy[42]. Theresidualvalueofsolarsystemafterthese30
yearsisconsideredvoid.
5. Methodology
Themethodologydevelopedinthisreportconsistsofthreephasesinwhichareincludedthe
evaluationofthermalenergygeneratedbythesolarfield,theestimationoflevelizedcostofenergy
(LCOE)andtheanalysisofenvironmentaladvantages.
5.1. EvaluationofThermalEnergyGeneratedbytheSolarField
This first phase attempts to evaluate the thermal energy generated by the solar field for the
selectedsite,technologyandthermallevel.Themainobjectiveinthisphaseistoquantifytherelevance
thatsolarenergycanachieveasthermalenergysourcebyitsincorporationintotheindustrialsector.
The thermal energy generated by the solar field (E ) is evaluated according to the following
sf
expression in which the variable I represents the hourly incident solar radiation on the collector,
t
Energies2017,10,383 10of22
dependingonthetechnologyunderconsideration. GlobalradiationwhenCPCtechnologyisused
anddirectradiationwhenLFCorPTCareconsidered. Thesolarfieldefficiency(η )ofthisexpression
sf
isspecifiedforeachtechnologyinTable2. Toevaluatethethermalenergygeneratedperunitareaover
afullyearisconsideredthesumoftheproductofhourlyradiationandsolarfieldefficiencyfromfirst
(i)tolast(i)record:
i f
if
∑
E = I ·η (2)
sf t sft
t=ii
Theavailableenergyattheoutputofthesolarfielddiffersfromtheusefulenergyfortheindustrial
process(EIP)duetothermallossesassociatedtotheheatexchangerandthethermalenergystorage
system. To evaluate the useful energy at the output of the energy storage system the estimated
efficienciesofbothequipmentsη andη areused,respectively. Accordingtotheconfigurationof
he SAT
theplantshowedinFigure8,thefollowingexpressionisapplied:
if
∑
E = E ·η ·η (3)
IP sft he SAT
t=ii
5.2. EstimationofLevelizedCostofEnergy
ThesecondstageofthemethodologyestimatestheLCOEparameter. Thisisusedtocomparethe
costassociatedwiththegenerationofthermalenergywhendifferentsolartechnologiesorthermal
levels are analyzed. The LCOE is evaluated according to the following expression in which the
numeratorconsiderstheexpensesthattakeplacethroughoutalltheusefullifeandthedenominator
considerstheenergygeneratedoverthesameperiod[43]. Thevariablesrandsofthisexpression
representtheaveragerateofconsumerpriceindexandtheaverageenergyprice,bothofthemhighly
dependentonthecountryexamined:
(cid:34) (cid:35)
if
C + ∑ COMt + CR
LCOE = I t=(cid:34)ii (1+r)t (cid:35)(1+r)15 (4)
if
∑ EIPt
t=ii (1+s)t
5.3. AnalysisofEnvironmentalAdvantages
Thelastphaseofthismethodologyevaluatestheenvironmentaladvantagesassociatedwiththe
replacement of conventional sources of energy by solar systems. These advantages are evaluated
intermsofgreenhousegas(GHG)avoided. Thispaperconsiderstwoscenarios,thesubstitutionof
electricityandnaturalgas. Inbothcasesitisnecessarytocalculatethequantityofelectricityornatural
gasthatallowtoobtainanequivalentamountofthermalenergytotheonegeneratedbythesolar
system(E ).
IP
To evaluate the equivalent amount of electricity (E ) it is considered Joule effect. The GHG
e
emissionsavoidedbytheuseofasolarsysteminsteadofelectricity(GHG )arecalculatedusingthe
e
electricityconversionfactor(FP )characteristicofeachsiteanalyzed:
e
GHG = E ·FP (5)
e e e
In the case of natural gas it is considered that the fuel is used in a boiler. Thermal energy is
generatedbyacombustionprocess. Thenaturalgaslowerheatingvalue(LHV)andtheefficiency