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The deployment of solar photovoltaics (PV) and electric vehicles (EVs) is continuously increasing during urban energy transition. With the increasing deployment of energy storage, the development of the energy sharing concept and the associated advanced controls, the conventional solar mobility model (i.e., solar-to-vehicles (S2V), using solar energy in a different location) and context are becoming less compatible and limited for future scenarios. For instance, energy sharing within a building cluster enables buildings to share surplus PV power generation with other buildings of insufficient PV power generation, thereby improving the overall PV power utilization and reducing the grid power dependence. However, such energy sharing techniques are not considered in the conventional solar mobility models, which limits the potential for performance improvements. Therefore, this study conducts a systematic review of solar mobility-related studies as well as the newly developed energy concepts and techniques. Based on the review, this study extends the conventional solar mobility scope from S2V to solar-to-buildings, vehicles and storage (S2BVS). A detailed modeling of each subsystem in the S2BVS model and related advanced controls are presented, and the research gaps that need future investigation for promoting solar mobility are identified. The aim is to provide an up-to-date review of the existing studies related to solar mobility to decision makers, so as to help enhance solar power utilization, reduce buildings' and EVs' dependence and impacts on the power grid, as well as carbon emissions.
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Sustainability2020,12,7035;doi:10.3390/su12177035www.mdpi.com/journal/sustainability
Review
ATechnicalReviewofModelingTechniquesfor
UrbanSolarMobility:SolartoBuildings,Vehicles,
andStorage(S2BVS)
PeiHuang
1
,XingxingZhang
1,
*,BenedettaCopertaro
1
,PuneetKumarSaini
1
,DaYan
2
,YiWu
2
andXiangjieChen
3
1
EnergyTechnology,DalarnaUniversity,79188Falun,Sweden;phn@du.se(P.H.);bcp@du.se(B.C.);
pks@du.se(P.K.S.)
2
SchoolofArchitecture,TsinghuaUniversity,Beijing100084,China;yanda@tsinghua.edu.cn(D.Y.);
ywu17@mails.tsinghua.edu.cn(Y.W.)
3
SchoolofArchitecture,CentreforRenewableEnergySystemsTechnology,LoughboroughUniversity,
LeicestershireLE113TU,UK;X.J.Chen@lboro.ac.uk
*Correspondence:xza@du.se;Tel.:+46(0)23778789
Received:24July2020;Accepted:26August2020;Published:28August2020
Abstract:Thedeploymentofsolarphotovoltaics(PV)andelectricvehicles(EVs)iscontinuously
increasingduringurbanenergytransition.Withtheincreasingdeploymentofenergystorage,the
developmentoftheenergysharingconceptandtheassociatedadvancedcontrols,theconventional
solarmobilitymodel(i.e.,solartovehicles(S2V),usingsolarenergyinadifferentlocation)and
contextarebecominglesscompatibleandlimitedforfuturescenarios.Forinstance,energysharing
withinabuildingclusterenablesbuildingstosharesurplusPVpowergenerationwithother
buildingsofinsufficientPVpowergeneration,therebyimprovingtheoverallPVpowerutilization
andreducingthegridpowerdependence.However,suchenergysharingtechniquesarenot
consideredintheconventionalsolarmobilitymodels,whichlimitsthepotentialforperformance
improvements.Therefore,thisstudyconductsasystematicreviewofsolarmobilityrelatedstudies
aswellasthenewlydevelopedenergyconceptsandtechniques.Basedonthereview,thisstudy
extendstheconventionalsolarmobilityscopefromS2Vtosolartobuildings,vehiclesandstorage
(S2BVS).AdetailedmodelingofeachsubsystemintheS2BVSmodelandrelatedadvancedcontrols
arepresented,andtheresearchgapsthatneedfutureinvestigationforpromotingsolarmobilityare
identified.Theaimistoprovideanuptodatereviewoftheexistingstudiesrelatedtosolarmobility
todecisionmakers,soastohelpenhancesolarpowerutilization,reducebuildings’andEVs’
dependenceandimpactsonthepowergrid,aswellascarbonemissions.
Keywords:solarmobility;electricvehicles;buildingcluster;energystorage;energysharing;
advancedcontrol
1.Introduction
1.1.Background
Buildingenergyusecurrentlyaccountsforover40%oftotalprimaryenergyconsumptioninthe
U.S.andE.U.[1].Thetransportationsectoralsorepresentsalargeenergyenduserandconsumes
approximately25%oftheprimaryenergyworldwide[2].Tomeetthelargeenergyneedsinboththe
buildingsectorandtransportationsector,renewableenergy,whichhasmuchlowercarbonemissions
andrelativelylowercostscomparedwiththeconventionalfossilfuelbasedenergy,offersa
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promisingsolution[3].Inthisregard,manycountriesandassociationshaveestablishedregulations
ortargetstopromotethedeploymentofrenewableenergy.Forinstance,theEuropean‘202020
targets’aimtoachievea20%reductioninCO2emissions(comparedto1990levels),20%ofenergy
comingfromrenewables,anda20%increaseintheenergyefficiencyby2020.TheE.U.alsosetsa
targetof32%ofenergygenerationfromrenewablesby2030,andaminimumshareofatleast14%of
fuelfortransportpurposesmustcomefromrenewablesourcesby2030[1,4].Indifferentstatesofthe
U.S.,differentrenewableenergytargetshavealsobeendefined.Forinstance,Connecticutsetsatarget
of48%renewablegenerationshareofelectricitysalesby2030,andNewJerseysetsatargettoincrease
itsrenewableportfoliostandardstargetto50%.Amongallthestates,Californiaisthemostambitious
andsetsagoaltoachieve100%carbonfreepowerby2045[5].China,astheworld’sbiggestenergy
consumer,alsoaimsfora35%ofrenewablebasedelectricitygenerationby2030[6].Inorderto
achievetheserenewableenergytargets,twoimportantaspects,thewayrenewableenergyisused
andrenewableenergyselfutilization,shouldbecarefullydetermined.
1.1.1.MarketTrendsofPVs
Theglobalsolarphotovoltaics(PV)marketisincreasingwithanapproximateexponentialtrend
[7].In2018,atotalof102.4GWPVpanelswereinstalledglobally,representinga4%yearonyear
growthoverthe98.5GWinstalledin2017.Thisledtoatotalglobalsolarpowercapacityofover500
GW.TheAsiaPacificregion(includingChina)wasleadingtheglobalPVmarket,anditownedmore
thanhalf(55%)oftheglobalsolarpowergenerationcapacity.Inthisregion,Chinaaloneoperated
nearly1/3rdoftheworld’ssolarpowergenerationcapacities.TheEuropeansolarpioneersranked
second,buttheirshareslippedto25%basedonacumulativePVcapacityof125.8GW.TheAmericas
weretheworld’sthirdlargestsolarregionin2018—withacumulativeinstalledcapacityof78.2GW
anda15%stake.
1.1.2.MarketTrendsofElectricVehicles(EV)
EVs,whicharepoweredbyelectricity,areconsideredasapromisingsolutiontoroadsideair
pollutionandassociatedhealthdamage,sincetheydirectlycutoffpollutionfromthesource.When
EVsarechargedbyrenewableenergy,suchasPVandwindturbines,theiroperationsaretotally
carbonfreeandthusEVscanmakesubstantialcontributionstogreenhousegasemissions.Todate,
alotofgovernmentshaveestablishedpoliciesorgoalstopromotethedeploymentofEVs.For
instance,theSwedishgovernmenthassetagoalthat100%ofthenationalenergyusedinvehicle
fleetsshouldbeindependentoffossilfuelby2030[8].TheU.S.Federalgovernmenthasenacted
policiesandlegislationtopromotetheU.S.marketforEVs,suchasimprovementsintaxcreditsunder
currentlaw,andcompetitiveprogramstoencouragecommunitiestoinvestininfrastructure
supportingthesevehicles[9].TheHongKonggovernmenthasmadeeffortsinpromotingitspractical
applications,e.g.,taxreductions,aoneforonereplacementscheme,subsidiesforEVpurchaseand
EVlicenses[10,11].TheSingaporegovernmenthasshowngreatinterestinadoptingEVs[12].The
EnergyMarketAuthority(EMA)andtheLandTransportAuthority(LTA)ofSingaporelaunchedthe
EVtestbedin2011todecideonthemassadoptionofEV.Followingpositiveresults,theyapproved
BlueSGPteLtd.[13],asubsidiaryofBolloréGroup,tolaunchanEVcarsharingprogramby2017[4].
TheFrenchgovernmentsetatargetoftwomillionEVsin2020[14].ThestockofEVs(i.e.,thenumber
ofEVsontheroad)isprojectedtoreach18.7millionin2030[15].Theauthorsin[16]stipulatedthe
introductionofaBuildingPlanstatingthat,witheffectfrom2020,thedeploymentofrechargeable
electricandhybridvehicles(HV)shouldrepresent30%ofallvehiclesalesby2020.Hence,thepublic
acceptanceofEVsandtheirswiftglobalmarketpenetrationsbecauseofthisareimposingincreased
impactsonthedeploymentofPVandsmartgrids.
1.1.3.MarketTrendsofStorage
AsreportedbytheKPMG(i.e.,KPMGInternationalCooperative),in2016,theUnitedStateshad
thelargestmarketforenergystorage,bothbynumberofprojectsandinstalledcapacity.Insome
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states,innovativeenergystorageincentiveprogramshavebeenimplemented.Atotalcapacityof62
MWofenergystoragehadbeeninstalledby2014,andthecountryhassetthetargetofa1325MW
energystoragecapacityby2020.Japanhassetanambitioustargettoproducehalfoftheworld’s
batteriesby2020.Thecountryhasasubsidyprogramfor66%ofthecostforhomesandbusinessthat
installlithiumionbatteries.Japanalsohasatargetof30%renewablesimplementationby2030.India
hasatargetof40GWofrenewableenergycapacityby2030.Amongthedifferentenergystorage
types,electricitystorageisaneconomicsolutionoffthegridinsolarhomesystemsandinminigrids
whereitcanalsoincreasethefractionofrenewableenergyinthesystemtoashighas100%[17].The
InternationalRenewableEnergyAgencyreportedatotalbatterycapacityinstationaryapplications
of11GWhin2017.Thetotalcapacityisexpectedtoreach100~167GWhby2030inthiscase.The
largebatterystoragemarketiscontributedbypairingabatterystoragesystemwiththeinstallation
ofnewsmallscalesolarPVsystems.Forexample,motivatedbythefinancialsupportforbattery
storage,nearly40%ofsmallscalesolarPVsystemsinGermanyhavebeeninstalledwithbattery
systemsinthepastfewyears.InAustralia,althoughthereisnoanyfinancialsupport,nearly7000
smallscalebatterysystemswerestillinstalledin2016.Theeconomicsofbatterystorageinsuch
applicationsarealsoprojectedtoincreasesignificantlyinthefuture.Thegrowingcapacityofenergy
storageprovidesgreatopportunitiesforrenewableenergyutilizationandpromotessolarmobility.
1.1.4.BuildingProsumersRole
Buildingsconsumeabout40%ofenergyworldwide[18],andthispercentageisevenlargerin
highdensitycities(e.g.,over90%inHongKong)[19].Toreducetheenergyusageinthebuilding
sector,renewableenergysystems,suchasPVpanelsandwindturbines,arewidelyinstalledin
buildings[20].Bysuchrenewableenergysystemsintegration,buildingsaretransferringtheirroles
fromconventionalelectricityconsumerstoelectricityprosumers.Asdefinedin[21,22],electricity
prosumersareelectricityconsumerswhoproduceelectricityfortheirownconsumptionusing
distributedenergytechnologies.Fromtheperspectiveofbuildings,thistransformationcanhelpcut
downgridpowerusage,therebyreducingtheelectricitycostsaswellasreducingcarbonemissions
ifgridpowerisproducedfromfossilfuels[23].Fromtheperspectiveofthepowergrid,thereduced
demandsonthebuildingsidecanhelpalleviatethegridstressandtherebypromotethepowergrid’s
stableandreliableoperation[24].Commontypesofelectricityprosumersarezeroenergybuildings
(ZEBs),whichproducethesameamountofenergytheyconsume.
TofacilitatetheapplicationofZEBs,manygovernmentshaveestablishedpoliciesandgoals.For
instance,Directive2010/31/EU,theEnergyPerformanceofBuildingsDirective(EPBD),setsthegoal
thatallnewbuildingsbuiltfromthebeginningof2021mustbenearlyzeroenergyandcostoptimal
[25].Thenearlyzeroenergybuildingstrategy2020(ZEBRA2020)waslaunchedby17countriesin
2014,forthepurposeofcreatinganobservatoryfornetzeroenergybuildings(NZEBs)basedon
marketstudiesandvariousdatatoolsandthereforegeneratesdataandevidenceforoptimization
andpolicyevaluation[26].TheU.S.governmentsetsatargetthat50%ofcommercialbuildingswill
achievezeroenergyby2040,andallcommercialbuildingswillachievezeroenergyby2050[20].The
CaliforniaPublicUtilitiesCommissionoftheUSAhassetanetzeroenergytargetforallnew
residentialbuildingsby2020andforallnewcommercialbuildingsby2030[27].Similarpromotion
policiesandtargetscanalsobeobservedinChina,Korea,JapanandAustralia[28].Asreportedby
Tronchinetal.,thebuiltenvironmentrepresentsasuitableintermediatescaleofanalysisinMulti
LevelPerspectiveplanning,collocatedamonginfrastructureandusers[29].Temporalandspatial
decouplingofsupplyanddemandisanimportantelementthatshouldbeconsideredforthe
evolutionofbuiltenvironment,especiallywhencreatingsectoriallevelplanningstrategiesand
policies.Theyalsodeterminedtheneedforresearchintodevelopinginnovationpathwaysfortheco
evolutionofthebuiltenvironmentandinfrastructure.Insuchacontext,theanalysisof
complementaritiesisparticularlypowerfulandshouldreceivemoreattention.Solarmobility
development,whichseekscomplementaritiesinmultiplesystems(i.e.,buildings,EVs,PVsand
energystorage),isinlinewiththiscontext.
Sustainability2020,12,70354of37
1.2.DefiningtheConceptofSolarMobility
AsproposedbyCEAINES(namelytheFrenchNationalInstituteforSolarEnergy)[30],the
conceptofsolarmobilityseeksasynergybetweenthefollowingthreesystems:EVs,PVsystemsand
theelectricitynetwork.ThebasicideaistocombineastandardgridconnectedPVsystemwith
standardEVs,alsoconnectedtothegrid[31].Inordertoensurethesolarchargingofthevehiclesand
minimizethegridimpact,alocalEnergyManagementSystemdecidesontheenergyflows.This
processiscalledsolartovehicles(S2V)insomestudies[32],representingchargingEVsdirectlyusing
electricityfromPVs.Vehiclescanbechargedathomeusingresidentialchargingstationsoratpublic
chargingstationsinprivatebusinessorpubliccarparks.Theyconsidersuchaprocessreasonable
sincetheaveragecarisparked95%ofthetimeandchargingcantakealongtimebasedoncurrent
usagemodels.Intheirproposedconcept,theelectricityproducedbytheresidentialPVpanelsis
firstlyusedtosupplythehomeelectricalequipment(e.g.,householdappliances,multimediadevices,
etc.),andthentochargetheEVbattery,asshowninFigure1.Ifthereisanysurplusgeneration,such
anamountisfedintothepowergrid.Thesmartgridwillcollectdataonthegridloadsandpower
needsandredistributethesurplusgenerationtomeettheseloads/needs.Insuchacontext,buildings,
equippedwithPVsystemsandenergystoragesystems,arebecomingenergyproductionsiteswhere
EVscanbecharged.ThisconvergencebetweenbuildingsandtransportwillenableEVbatteriestobe
usedasameansofstorageandsupplyoflowcarbonelectricitytomeetfluctuationsinproduction
andconsumption.NotethattheEVbatteryisalsoallowedtodischargeelectricitybacktothe
building/powergridinsuchamodel.Thisisadvantageousforgridmanagementandespeciallyfor
peaksmoothing.Thisconcepthasbeenextensivelystudiedfromatechnologicalviewpointin[33–
38].
Figure1.Conceptofsolarmobilitywithselfconsumption[31].
1.3.Values,ProblemsandChallengestotheSolarMobility
Values:WiththeincreasingdeploymentofPVs,EVsandenergystoragesystems,itisimportant
tosmartlyintegratethemtomaximizetheenergyefficiencyandcostbenefitsand,meanwhile,
minimizetheimpactonthepowergrid.Undersuchacontext,solarmobilitycanhelpimprovethree
values:autonomy,sustainability,andaffordability.Specifically,autonomyindicatesreducingthe
dependenceandimpactsonthepublicpowergrid.Ideally,withinabuildingcommunity/microgrid,
byactingasanelectricityprosumerandconsideringtheEVdemand,buildingscanbelargelycovered
bytheirownPVsystem.Sustainabilityindicatesincreasingtheselfconsumptionoflocallyproduced
PVpower,andthustheneedforpowerfromthepublicgrid,whichlargelydependsonfossilenergy
inmanycountries.Affordabilityindicatesincreasingtheeconomicbenefitsofthewholesystem.
Problems:AlthoughtheimportanceofPVs,EVs,andenergystoragehasbeenwellrecognized
globally,howtointegrateandmanagetheminaholisticway,simultaneouslytakinginto
considerationbuildingloadsandoccupants’livingrequirements,needstobeaddressed.Problems
suchaslargepowerpenetrationinthepowergrid,lowenergyefficiencyandloweconomic
performanceurgentlyneedtobesolved.Moreover,withthedevelopmentoftheenergysharing
conceptandassociatedadvancedcontrols,theconventionalsolarmobilityconceptandcontextare
Sustainability2020,12,70355of37
becominglesscompatibleandlimited.Forinstance,energysharingwithinabuildingclusterenables
buildingstosharetheirsurplusgenerationwithotherbuildings(includingtheirEVdemands)with
insufficientsupply,therebyhelpingimprovetheoverallrenewableenergyutilizationandreducing
gridpowerdependence.However,suchenergysharingnetworks,includingthesystemarchitecture
andassociatedadvancedcontrols,arenotconsideredintheconventionalsolarmobilitymodels.This
willlimitthepotentialforperformanceimprovementsthatcanbeotherwisebearticulatedand
demonstratedbythenewlydevelopedconceptsandmethods.Anotherexampleisthelackofenergy
storageintegrationintheexistingsolarmobilitymodel(notethat,inthisstudy,EVsareconsidered
tohaveaseparaterolefromenergystorage).
Challenges:Intermittencyisoneofthemajorshortfallsofsolarpower,whichhasadirect
influenceonthevoltagestabilityandtheoverallpowersystemsecurity,while,forEVs,theircharging
loadsaredifficulttopredictastheyarehighlyaffectedbydrivingpatternsanddrivingdistances.
BothPVpowerproductionandEVpowerdemandarehighlyuncertain.Forinstance,anEVcanbe
usedforcommutingpurposesduringthedaywhereaccesstochargingfacilitiesisnotavailable.This
meansthatchargingcouldonlyhappeninanEVowner’spremisesduringthenighttimewhenno
electricitycanbegeneratedbyPV.Suchtimemismatcheswilllimitthedeploymentofsolarenergy
inthemobilitysector.Thus,itischallengingtobridgethetemporalandspatialsupply–demand
mismatchtofacilitatesolarmobility.Whenbuildingsandenergystorageareintegratedintothesolar
mobilitycontext,anotherchallengeisthepropermanagementofdifferenttypesofsystemswith
variousresponsecharacteristicsandoperatingconstraints.Thisreviewpaperwillaimtopropose
someusefulsolutionsfromexistingstudiestoaddressthesechallenges.
1.4.AimandContributionsofThisReview
Thisstudyconductsatechnicalreviewofsolarmobilityrelatedstudiesaswellasnewly
developedenergyconceptsandtechniques.Byreviewingtheexistingstudies[39–41],thisstudy
extendstheconventionalsolarmobilitymodelfromS2Vtosolartobuildings,vehiclesandstorage
(S2BVS).Intheextendedcontext,solarmobilityinvolvessolarenergyflowandexchangethrough
buildings,vehiclesandstorageandtherenewableenergysharingnetwork.Theelectricitygenerated
byPVpanelsisappliedtoprovideelectricitytobuildingsandchargebatteries/thermalenergy
storage(e.g.,byheatpump(HP)),whileEVscanbechargedatresidentialchargingstationsorat
publicchargingstationsinprivatebusinessorpubliccarparks.TheassociatedS2BVSsystem
architectureandmodelsareproposed,andtheassociatedadvancedcontrolsintheexistingliterature
arereviewed.TheaimistohelpimprovethesolarmobilityconceptbyintroducinguptodateS2BVS
models,toenhancerenewableenergyutilization,reducethedependenceandimpactsofbuildings
andEVsonthepowergrid,andreducethecarbonemissionsinresponsetoafuturescenariowith
increasedPVcapacity,EVnumbersandstoragecapacity.Themajorcontributionsofthisrevieware
summarizedasfollows:
Assessvalues,problemsandchallengesofsolarpowerdeploymenttopromotesolarmobility.
Extendtheexistingsolartovehicles(S2V)concepttosolartobuildings,vehiclesandstorage
(S2BVS)withtheintegrationofrenewableenergysystems,buildings,energystoragesystems,
EVsand,moreimportantly,therenewableenergysharingnetwork.
Identifytheresearchgapsthatneedfutureinvestigationtopromotesolarpowerutilizationand
solarmobility.
2.OverviewoftheExistingStudiesonSolarMobility
Extensiveeffortshavebeendevotedtopromotingsolarmobility,andmanypapershavebeen
publishedregardingthistopic.Figure2definestheextendedscopeofsolarmobility(comparedwith
Figure1)andhighlightsthelocationofreviewsforeachsubsystem.Table1summarizesthemain
existingstudieswithsuchascope.
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Table1.Summaryoftheexistingstudiesonsolarmobility.
AuthorsRegion
System
ModelingToolsMainWorkDoneSpecialPoints
BuildingPVStorageEVsOther
Techniques
Bertholdetal.,
(2011)[42]FranceYYNYWind
energy
Developedageneralcontrolstrategywhichaimsat
minimizingthebuilding’stotalenergycostsby
optimizingthecharging/dischargingofPHEVs’
batteries.Theconsideredsystemsincludethepower
grid,localproductionfromrenewables,andvehicles.
UsingtheEVbatterytopowerhomeappliancesis
allowed.
Unlikeconventionalhometo
vehicle(H2V),thisstudyalso
enablesvehicletohome
(V2H)fordemandresponse
control.
Querinietal.,
(2012)[43]
Germany,
Denmark,
Sweden,
Spain,France,
UK,Italy.
NYNYWind
energyGabi4
1.Studiedthelifecycleofgreenhousegas(GHG)
emissionslinkedwithEVsusingPVandwind
electricityindifferentregionsofEuropeancountries.
2.AnalyzedthelifecycleofGHGemissionsusing
windenergy,solarenergy,andconventionalfossil
fuel.
WhenusingPVelectricity,
GHGemissionsarealways
lowerthanconventional
thermalvehicles
Zhangetal.,
(2012)[35]Kansai,JapanNYNYHeatpump
(HP)
VisualStudio
C#.net2008
1.Developedanhourbyhoursimulationmodelto
derivearealtimesupply–demandbalance.2.
EvaluatedtheimpactsofintegratingPVpowerinto
futureelectricitysystemswithEVsandHPsunder
smartcontrolstrategiesinKansai.3.Analyzedasetof
scenarioswithdifferentpenetrationsofPV,EVand
HP.
TheEVsareconsideredas
virtualbatteries,similarto
electricitystoragesystems,
whichcannotonlybe
chargedbygridpower(G2V),
butcanalsodischarge
electricitytothepowergrid
(V2G).
Dallingeretal.,
(2013)[44]
Germanyand
U.S.
(California)
NYNYNPowerACE
1.Developedamethodtocharacterizethefluctuating
electricitygenerationofrenewableenergysourcesand
comparethedifferencebetweenCaliforniaand
Germany.2.Analyzedthepotentialcontributionof
gridconnectedvehiclestobalancethegenerationfrom
renewableenergysourcesfora2030scenarioin
CaliforniaandGermanybasedonthedeveloped
method.
1.Correlationbetween
renewableenergysystem
generationandtheloadcurve
affectingtheintegrationof
RES.2.EVsplayanimportant
roleinreducingresidualload
fluctuationifsmartcharging
isused.
Suetal.,(2014)
[45]Illinois,U.S.NYYYWind
energy
CPLEX+Matlab+
OpenDSS
1.Formulatedastochasticproblemformicrogrid
energyscheduling,whichaimsatminimizingthe
expectedoperationalcostofthemicrogridandpower
lossesbyoptimallydispatchingtheEVchargingload
andschedulingdistributedgeneratorsanddistributed
energystoragedevices.2.Investigatedtheimpactof
EVsonmicrogridenergyschedulingundervarious
chargingschemes.
CombinedschedulingofEV
chargingloadsandenergy
storagesystems.
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Chaouachietal.,
(2016)[46]ItalyNYNYNMatpoweropen
sourcepackage
1.Proposedaconceptualsmartgridframeworkand
assessmentmethodology,toenabledecentralized
operationalsynergybetweenintermittentPV
generationandEVs,basedoncoordinatedEV
charging.2.Testedtheproposedmethodologywitha
realdistributionsystem,wheredifferentPVandEV
penetrationscenariosareassessedagainstcharging
behaviorvariants.
Impactsofcoordinated
chargingonPVpenetration
andcarbonemission
reduction.
Islamand
Mithulananthan
(2017)[47]
AustraliaNYNYNMatlab
1.DevelopedanoniterativePVoutputmodelthat
doesnotrequireadditionalmeasurementsor
meteorologicaldata,whichsavesmoneyandtime.2.
Developedacombined,StageofCharge(SOC)based,
fairchargingstrategywhichsimultaneouslyreduces
theruntimebyloweringthenumberofvariables
involvedandincreasesthechargingfairness.The
reducedruntimemakesitsuitableformorefrequent
controlofchargingofalargeEVpopulation.
Considergridside
parameters,suchasvoltage
topology,structure,etc.
ThePVoutputmodeland
chargingstrategytogether
lessentheprobabilityof
voltagelimitviolationsand
enhancethePVharvest.
Sunetal.,(2018)
[48]Glasgow,UKYYYYNMatlab(GA
optimizationtool)
1.Developedamodelforminimizingtheenergycost
ofaresidentialhouseholdwithanEV,asharedenergy
storagesystem(ESS),andotherresidentialloads,
wheretheEV’susagepatternsaredescribedby
probabilitylevels.2.Conductedapracticalsurveyof
EVdailyusageincludingdrivingpurposesandusage
atdifferenttimeperiods.3.Investigatethetotalcost
savingthroughcasestudiesforvariousscenarios
underfixedandtimeofuse(TOU)tariffs.
Theoptimizationresults
basedonthismodelcanbe
usedtodeterminewhether
V2GisbeneficialforEV
ownersundertheoptimal
charginganddischarging
strategy.
Taşcıkaraoğlu
(2018)[39]
Austin,TX,
USAYYYN
Energy
sharing
network
GeneralAlgebraic
ModelingSystem
(GAMS)with
solverCPLEX
1.Developedtheconceptofenergysharingenabled
neighborhoodareanetworks,whicharecomposedof
asharedenergystoragesystemandmultiple
consumerpremises.2.Developedanovelenergy
managementstrategybasedontheimplementation
andschedulingtheuseofthissharedenergystorage
system(ESS)withtheobjectiveofexploitingtheESS
unitinthecontextofanenergycreditbaseddemand
responseprogram.
Energysharingenabled
neighborhoodareanetworks
(NANs)forclusterlevel
performanceimprovements.
Suchenergysharingcan
reducetheenergycostsand
peakdemandsignificantly.
Sustainability2020,12,70358of37
Huangetal.,
(2019)[49]Yuxi,ChinaYYNY N
HOMER(for
demand/supply
calculation)
Matlab(forcontrol)
1.ProposedaretiredEVbattery(REVB)modelbased
onthemathematicalmodelofcapacityfadeofLiion
batterycellstosimulateREVB’scapacityloss.2.
Developedapowermanagementsystemtomitigate
thedegradationofREVBandprotectothersystem
components.3.Constructedatriobjective
optimizationmodelconsideringreliability,energy
wasteandcost.
UseretiredEVbatteriesfor
energystorageinbuildings.
Baroneetal.,
(2019)[50]Naples,ItalyYYNYNMatlab
Proposedanovelenergymanagementsystemfor
buildingsconnectedinamicrogrid,byconsidering
EVsasactivestoragecomponentsofsuchanenergy
scheme.
SuchB2V2B(i.e.,Buildingto
vehicletobuilding)
integrationenablesrenewable
sharingamongdifferent
buildings.
Sustainability2020,12,70359of37
Intheextendedsolarmobilityscope,theenergyprosumersareequippedwiththeirown
renewableenergysystems,electricalstorage,EVsandotherelectricalappliances.Thebuildingsare
connectedinarenewableenergysharingmicrogrid,inwhichthesurplusrenewableproductioncan
bedeliveredfromonebuildingtoanother.Suchanenergysharingnetworkprovidesaplatformfor
thebuildingsinamicrogridtosharetheirsurplusrenewableenergygenerationwithotherbuildings,
thushelpingenhancetheoverallclusterlevelperformances.Theenergysharingmicrogridisalso
connectedtothepowergrid,incasethereissurplus/insufficientclusterlevelrenewablegenerations
andelectricityexchangeswiththepowergridareneeded.Thepowerexchangeofthebuildingcluster
withthepowergridismeteredbyadvancedmeteringfacilities.
Figure2.Scopeofsolarmobilityandthemajorsubsystems.
2.1.PVandEVInteractionviathePublicGrid
Makinguseofthecharging/dischargingcapabilityofEVbattery,theEVscanbeusedasflexible
electricitystorageinthepowergridandinteractdirectlywiththepowergrid.Forinstance,Zhanget
al.,investigatedtheenergyandenvironmentalimpactsofintegratingPVpowerintoelectricity
systemsinKansai,Japan,undervariousscenarioswithdifferentEVpenetrationsandheatpump
capacities[35].ItwasfoundthatEVsandheatpumpswerehelpfulforkeepingmorePVpowerin
thesmartelectricitysystems.Intheirstudy,theEVswereconsideredasvirtualbatteries,similarto
electricitystoragesystems,whichcannotonlybechargedbygridpower(G2V),butcanalso
dischargeelectricitytothepowergrid(V2G).Sunetal.,investigatedtheeconomyviabilityof
dischargingEVpowerbacktothegrid,whichiscalledvehicletogrid(V2G)[48].Theydevelopeda
modelfortheminimizationoftheenergycostofaresidentialhouseholdwithresidentialloads,an
ESS,andanEVwithitsusagepatternsdescribedbyprobabilitylevels.Usingthedevelopedmodel,
theystudiedthetotalcostsavingforvariousscenariosunderfixedandtimeofuse(TOU)tariffs.
Theirstudyresultsrevealthatcertainthresholdlevelsoffeedintariffsareexpectedtoallowusers
benefitfromV2Gtechnology.NoussanandNeirotticomparedthreearchetypalchargingprofiles(i.e.,
home,publicandwork)evaluatedon10Europeancountriesoverfouryears,toinvestigatetheeffects
ofnationalelectricitymixesandofthetypeofcharginglocationontheaverageemissionfactorofthe
electricitysuppliedtoelectricvehicles[51].Theirstudyresultsshowthatthevariabilityrelatedto
chargingprofilesisgenerallylimited(withanaveragevariationrangeof6%)inalltheselected
countries,whileinseveralcountriesthevariabilityindifferentyearsismuchlarger(withanaverage
rangeof18%).
Sustainability2020,12,703510of37
2.2.PVandEVInteractionviatheBuildings
Besidesbeingusedforelectricitystorageinthepowergrid,theEVscanalsobeusedasflexible
electricitystoragesystemsinbuildings.Forinstance,Bertholdetal.,developedacontrolstrategy,
whichaimsatminimizingthebuilding’stotalenergycostsbyoptimizingthecharging/discharging
ofthebatteriesofpluginhybridelectricvehicles(PHEVs)[42].Theconsideredsystemsincludethe
powergrid,localproductionfromrenewableenergysystems,andvehicles.Unliketheconventional
controlswhichonlyenablehometoEV(H2E)powertransmission,thisstudyalsoenablesEVtohome
(V2H)powertransmission,whichextendstheutilizationofEVsintermsofthebuildingdemand
response.InordertomaximizethevalueofEVbatteries,Huangetal.,proposedaretiredEVbattery
(REVB)modelbasedonthemodelofcapacityfadingoflithiumbatterycells[49].Usingthedeveloped
REVBmodel,apowermanagementstrategy(PMS),whichconsidersmultipleobjectivesincluding
minimizingthelossofpowersupply,systemcostandpotentialenergywaste,wasdevelopedto
regulatetheenergyflowtoprotecttheREVBandothersystemcomponents.Amultiobjective
evolutionaryalgorithm,NSGAII,wasusedtogeneratetheParetosetoftheoptimalsolution.The
applicationofthedevelopedmethodinaresidentialbuildingindicatesthataPV–hydrogen–REVB
hybridenergysystemisapromisingwaytoexploitREVBs’residualcapacities.Similarly,Baroneet
al.,proposedtheconcept‘BuildingtoVehicletoBuilding’(B2V2B),whichenablesthebidirectional
electricityexchangeofEVbatterieswithbuildings[50].Theyalsodevelopedanovelenergy
managementsystemforbuildingsconnectedinamicrogrid,byconsideringEVsasactive
componentsofsuchanenergyscheme.Renewableenergysources(i.e.,PV),energystoragesystems
andbidirectionalelectricityexchangewiththebuildingsandthegridweretakenintoaccount.A
highlightoftheirproposedsystemisthatPVpowersharingisenabledamongdifferentbuildingsby
applyingbidirectionalEVcharging/discharging,asshowninFigure3.Suchenergysharingcan
significantlyimprovePVpowerutilization,andthusbringeconomicandenvironmentalbenefits.
InFigure3,Case1representstheconventionalunidirectionalBuildingtoVehicle(B2V)system
operation.Here,thepluginEVislinkedwiththepowergridbyactingasapowerload.TheEVis
chargedthroughahomechargerandnorenewableenergysystemsandbatteriesareinstalledonsite.
Case2representsanovelconceptofbidirectionalBuildingtoVehicletoBuilding(B2V2B)system
operation.ThepluginEVislinkedwiththepowergridactingasapowerloadaswellasasource
forthehousebuilding,andasasourcefortheofficespace.Arenewableenergysystem,consistingof
PVpanels,isinstalledonsiteonthetiltedroofofthehousebuilding.Thehouseisalsoequippedwith
astationarybattery(HSB),whichcanalsofeedtheEVbattery(incaseofavailablestoredenergy,
otherwisetheEVbatteryisconventionallysuppliedbythegrid).Anadditionalnoveltyisrepresented
herebythetransfertotheoffice,throughanEVbattery,oftheelectricitypotentiallyproducedbythe
houseʹsPVpanels.TheEVbatterycanalsobechargedattheoffice,ifnecessary.Case3alsorepresents
anovelconceptofbidirectionalBuildingtoVehicletoBuilding(B2V2B)systemoperation,basedon
swappablebatteries.ThesystemoperationfollowsthatofCase2.ThedifferencewithCase2liesin
thebatteries;specifically,inCase3thehouseisequippedwithabatteryidenticaltotheEVoneand
aquickswapofbatteriesisallowedbetweentheEVandthehouse.Theswappingoptionprevents
theneedforenergytransferfromtheHSBtotheEVbattery(whenEVbatterychargeisrequired),
andthusrelatedlosses.Case4representsadifferentnovelconceptofbidirectionalV2Bsystem
operation.ThemaindifferencewiththepreviousCases1and2isrelatedtothesiteofthePVpanels,
whichareinstalledonthefaçadeoftheofficespace,wherenodedicatedbattery(i.e.,HSB)is
considered(solarenergyisstoreddirectlyintotheEVbattery).ThepluginEVcommunicateswith
thepowergrid,acting,inthiscase,asapowerloadaswellasasourcefortheofficespace,andasa
sourceonlyforthehousebuilding.InCase4,thenoveltyisrepresentedbythepossibletransferto
thehouse,throughanEVbattery,ofelectricityproducedbytheoffice’sPVpanels.TheEVcanbe
chargedbothatthehouseandofficebuildings.
Sustainability2020,12,703511of37
Figure3.Fourdifferentmethodsofbuilding–electricvehicle(EV)–solarphotovoltaics(PV)–grid
integration[50].
2.3.PVandEVInteractionviatheEnergySharingNetworkConsideringBuildingsandEnergyStorage
Inadditiontomakinguseoftheflexibilitycharging/dischargingcapabilityofEVstoenable
energysharing,amoredirectway(i.e.,micropowergrid)canalsobeusedforalargeamountof
energysharing.Forinstance,Taşcıkaraoğludevelopedasystemstructureforasharedenergystorage
system(ESS)inaneighborhoodcommunity,asshowninFigure4[39].Intheirstudy,eachbuilding
isequippedwithatopPVbaseddistributedgenerationsystemandisconnectedtoasharedESS.The
sharedESS,thetransformerandallthehouseholdsareconnectedtoacommonpoint,whichisnamed
thepointofcommoncoupling(PCC).BidirectionalpowerflowisenabledbetweenPCCandthe
powergridviaaneighborhoodtransfer,betweenPCCandthesharedESS,andalsobetween
buildingsandPCC.Suchsystemconfigurationmakesthreetypesofpowerexchangeavailable,i.e.,
internallocalpowerexchangesamongtheneighborhoodbuildings,powerexchangesbetweenthe
neighborhoodbuildingsandthegrid,andpowerexchangesbetweenthesharedESSand
grid/neighborhoodbuildings.Inotherwords,thepowerconsumedbyabuildingcanbeproduced
byitsPVsystem,beproducedlocallybythePVsystemofotherbuildingsand/orbedrawnfromthe
powergrid/sharedESS.TheEVs’chargingloadisconsideredasanormalelectricityloadinthisstudy.
BysharingtheESS,thebuildingscandelivertheirsurplusrenewableenergytootherbuildingswith
insufficientsupply,thusincreasingtheoverallrenewableselfutilizationratesand,meanwhile,
reducingtheinteractionswiththepowergrid.Theirstudyresultsshowthatsharedstoragecanhelp
decreasethepeakelectricitydemandofabuildingclusterbyasmuchas30%and,meanwhile,reduce
theelectricitycostsofthebuildingclusterbyover10%.However,theinvestmentinasharedESS
withalargecapacitywillbemuchhigherthandistributedESSwithsmallcapacities.Inaddition,the
energylossesmaybelargeduetothelongtransmissiondistancefromthebuildingstotheshared
ESS.
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Figure4.Schemesofthesharedenergystoragesystem(ESS)unitservinganeighborhoodwith
multiplehouseholds[39].
Zhangetal.,alsodevelopedanovelstructureforpromotingsolarmobilityinresidential
buildings,asshowninFigure5[40].Intheirstudy,eachresidentialbuildinghasamicrogrid,which
connectstheelectricityproductionfacilities(e.g.,PVpanels)andelectricityconsumptiondevices(e.g.,
lighting,washingmachine,EVs,etc.).TheEVsareusedforflexibleelectricitystoragewhichcanbe
chargedbythePVsystem/gridelectricityinperiodswithsufficientsupplyordischargepowerto
buildings/thepowergridinperiodswithinsufficientsupply.Anaggregatorisutilizedtoconnect
multiplemicrogrids,whichcoordinatestheenergysharingamongdifferentmicrogridsaswellas
theirinteractionswiththepowergrid.Basedonthedevelopedsystemstructure,theydevelopeda
twostagecontrolmethodtocontroltheEVcharging/dischargingratesaswellastheenergytrades
withinthemultiplemicrogridsandwiththepowergrid.Comparedwiththeconceptproposedby
Baroneetal.[50],whichusesEVbatterieswithlimitedcapacityasthemediumforenergysharing
amongdifferentbuildings,Zhangetal.’sdevelopedstructureismuchmoreflexibleandenables
largeramountofenergysharing.However,thestochasticchargingbehaviorofEVs,theintegration
ofthermalenergystoragesystemsanddynamicelectricitypricesarenotconsideredintheirstudy.
Moreover,theinitialcostsforconstructingsuchmicrogridwouldbehigh,whichmaycreateahurdle
forthismethod’slargescaleapplication.
Figure5.Thestructureofmultipleresidentialmicrogrids[40].
Sustainability2020,12,703513of37
Similarly,Huangetal.,appliedadvancedenergyconceptsforretrofittingaresidentialbuilding
clusterinSweden[41].ThestudiedsystemincludesPVpanels(installedinindividualbuildings),
centralizedthermalenergystorage,aheatpump,andEVs.Adirectcurrent(DC)microgridbased
energysharingnetwork,whichisdevelopedbyFerroamp,isconstructedinthebuildingcluster.The
excessivePVproductioncanbestoredintheformofheatenergyinthethermalstoragebypowering
theheatpumptowork.Theirstudyresultsshowthatbyenablingrenewableenergysharingand
integratingenergystorageandEVs,thePVpowerselfutilizationcanbeashighas77%inthebaseline
case.
Tosummarize,existingstudieshavedevelopedthreeapproachesfordeployingPVpowerinthe
EVs,i.e.,viapublicpowergrid,viabuildings,andviaenergysharingnetworksconsideringbuildings
andenergystorage.Amongthesethreeapproaches,thethirdapproachissuperiortotheothertwo
approaches,astheenergysharingnetworkmakestheEVchargingmoreflexible(i.e.,fromdifferent
PVpowersources)andefficient(i.e.,withenhancedPVpowerlocalusage),andallowsthe
integrationoftwootherimportantplayers(i.e.,buildingsandenergystorage)intheenergysystems.
Suchanextendedscopeofsolarmobility,withPVs,EVs,energystorage,buildings(i.e.,S2BVS),and
energysharingnetworks,isafuturedevelopmenttrend.
3.ModelingofSubSystems
Thissectionreviewsthemodelingtechniquesintheessentialcomponentsrelatedtosolar
mobility,includingbuildingsidemodeling,EVsidemodeling,gridmodelingandadvancedcontrol.
Designandcontroloptimizationaretwomainmeanstohelpimprovethedeploymentandutilization
ofsolarenergy.Thissectionwillreviewthesetwoaspects.
3.1.BuildingSideModeling
3.1.1.SolarResourceMapping
Thereareseveralcommercialdatabasesavailableforsolarresourcemappingsuchas
Meteonorm[52]andglobalsolarAtlas[53].Thesetoolsmakeuseofdatainputsfromgeostationary
satellitesandmeteorologicalmodelssuchasairtemperaturemodelsandclearskymodelstopredict
theincidentenergyonearthsurfaceatadefinedspatial–temporalresolution.Zhangetal.,carried
outacriticalreviewandcomparedvariousmodelswhichareusedtoestimatesolarirradiationon
basisoftimescaleandestimationmethods[54].Basharatetal.,compared78differentmodelsused
forglobalsolarirradiationestimation[55].Theyproposedasystematicclassificationofthesemodels
basedontheinputparameterswhichcanbeusedtodoasimilaranalysis.Thesolarresourcedata
obtainedfromvarioustoolsareoftendetachedfromsurfacetopographyandthespatialdistribution
ofthebuildingstocks.However,whileestimatingthesolarresourcepotentialinanurbancontext,it
isimportanttoconsidertheeffectofvariousobjectssuchasneighboringbuildingsontotalincident
surfaceirradiation.
Mostofthecommerciallyavailabledatabasesdonotconsidertheeffectofurbanclimateonthe
solarresources.Theatmosphericthermodynamicsinanurbanclimateareaffectedbyseveralfactors
suchastopography,shadingobjects,vegetation,urbaninfrastructureandtheheatislandeffect[56].
Thesimulationofanenergysystembasedonaweatherdatabase,whichdoesnotconsiderthese
factors,canresultinmismatchesbetweenthesimulatedandrealenergysystemperformances.To
addresssuchissues,researchershaveproposedtocouplethegeographicinformationsystem(GIS)
toolandmeteorologicaldatabasestoassessthesolarpotentialinanexistingurbancontext.For
instance,Quanetal.,proposedaGISbasedenergymodelingsystemfortheurbanenergycontext
whichintegratesbuildingenergymodelingandsolarresourcemodelingusingathreedimensional
urbanenvironmentalengine[57].Bergamascoetal.,proposedandappliedahierarchicalprocedure
whichmakesuseofGISdata,availablesolarradiationmapsandstatisticaldataonenergy
consumption,todeterminethePVenergypotentialforanItalianclimaticlocation[58].Withthe
developmentintheavailabilityofhighqualitylightdetectionandranging(LIDAR)data,thereis
significantinterestfromvariousstakeholderstointegrateurbanscale3DmodelsandLIDARdatafor
Sustainability2020,12,703514of37
highaccuracyenergypotentialestimationsontheurbanscale[59].Jochemetal.[60]proposeda
methodologyforsolarpotentialestimationinurbanclimatesusingairborneLIDARdataand3D
informationfromthepointcloud.
3.1.2.PVDesignOptimization
TheinstallationofPVarrays(e.g.,theirpositiononbuildingfacadesandtheirtiltangles)has
significantimpactsonPVpowerproduction.Existingstudieshaveinvestigatedtheimpactsofthese
factorsanddevelopedpropermethodstooptimizethem.Forinstance,AbdulWahabetal.,employed
aHybridOptimizationModelforElectricRenewables(HOMER)tofindthebestPVsystemamong
15availablealternativesandthebestlocationforinstallingPVarraysforOman’sconditionsby
analyzingandcomparingtheircostsandthecarbonemissionreductions[61].Ningetal.,developed
ageneticalgorithmbasedoptimizationmethodtodesigntheposition,tiltanglesandazimuthofPV
panels,withfactorssuchasshapesandorientationsofbuildingexteriorsandthesurrounding
obstaclesconsidered[62].
TheirmethodcaneffectivelyimprovethePVsystempoweroutputby36.1%
andreducethecapitalinvestmentperunitpoweroutputby4.5%,meanwhilesignificantlyreducing
thehumanlabor.Similarly,MagnorandSaueralsodevelopedageneticalgorithmbased
optimizationmethodtooptimizePVsysteminstallation,includingthetiltangleandazimuthangle
ofthePVgeneratorundervariousboundaryconditions.Ullahetal.,developedamethodtooptimize
thePVtiltangleunderdifferentscenarios(fixed,seasonal,monthly,daily)forLahoreandsomeof
theothermajorcitiesinPakistan[63].Theyalsoproposedamodeltoestimatetheupper/lower
boundsofsoilinglossesandexploredthetiltangleeffectonthesoilinglossesbydoingsoiling
experiments.Shirazietal.,proposedanintegratedtechnoeconomicevaluationtooltoidentifythe
mostappropriatePVinstallationfaçadesinurbanareasinTehran,Iran[64].Theyfoundthatthe
properselectionoftheanglesandbuildingfaçadesforinstallingPVpanelscouldsignificantly
increasethesolarpowerproductionandtheinternalrateofreturn.Huangetal.,developedan
iterativemethodbasedonageneticalgorithmtooptimizethecapacityandpositionsofPVmodules
attheclusterlevel,withthepurposeofmaximizingtheselfconsumedelectricityunderanon
negativenetpresentvalueduringtheeconomiclifetime[41].BoecklandKienbergerdevelopeda
FourierseriesapproximationbasedmethodforsizingagridconnectedPVstoragesystemto
maximizesolarenergyselfutilization[65].
3.1.3.ElectricandThermalEnergyDemand
Theenergydemandmodelingapproachesforbuildingscanberoughlydividedintophysical
modeling[66]andstatisticalmodeling[67].Physicalmodelsaremathematicalrepresentationsofheat
andmasstransferphenomenabetweenbuildings,people,andtheenvironment.Forinstance,
PalaciosGarciaetal.[68]developedahighresolutionmodelforcalculatingtheelectricitydemand
ofheatingandcoolingappliances,consideringvariablessuchasthenumberofresidents,location,
typeofday(weekdayorweekend)anddate.In[69],amodelforsimulatinglightingpower
consumptionprofilesinSpainwasdeveloped,consideringthenumberofhouseholdresidentsand
differentiatingbetweenweekdaysandweekends.In[70],Widéndevelopedamodelforcomputing
theoccupancyandelectricityloadinSweden.Physicsbasedmodelsusuallyreporthighaccuracyat
theexpenseofhighdegreesofcomplexityanddatarequirements.Statisticalmodelsaremathematical
representationsoftherelationshipbetweenanobservedsetofhistoricalvariables.In[71],a
systematicreviewoftheregressionanalysisbasedstatisticalmodelingapproachwasconducted.A
simpleandmultiplelinearregressionanalysisalongwithaquadraticregressionanalysiswere
analyzedandcompared.In[72],asystematicreviewofthedatadrivenstatisticalmodelingapproach
wasconducted.Thedatadrivenstatisticalmodelingapproachwasfurtherclassifiedintoartificial
neuralnetworkbasedapproaches,clusteringbasedapproaches,statisticalandmachinelearning
basedapproaches,andsupportvectormachinebasedapproaches.Statisticalmodelsofferamore
parsimoniousmodelingalternativeattheexpenseofdetailedphysicalexplanatorypower.
Sustainability2020,12,703515of37
3.1.4.ElectricandThermalEnergyStorage
Generally,therearetwomainpotentialstoragetechnologies:electricalandthermalenergy
storage.Specifically,electricalenergystorageisabletoprovideoperationalflexibilityamonga
buildingcluster,regulatingthepowertofitabuilding’sdemandsandenhancingtheenergyself
sufficiency.Thermalenergystoragestorestheenergyintheformofthermalenergy(e.g.,heat).
Similarly,thermalenergystoragecanovercome,intheshortterm,hourly,dailyorweekly
mismatches,while,inthelongterm,itcanovercomeseasonalvariationsbetweenrenewableenergy
supplyanddemand,maximizingthesynergiesamongthebuildingsinacluster.
Someofthestudieshavebeenfocusedonthermalenergystorage.Asanexample,Hsiehetal.,
evaluatedtheperformanceofdifferent