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SOLAR ENERGY PROMOTION & URBAN CONTEXT PROTECTION : LESO‐QSV (QUALITY‐SITE‐VISIBILITY) METHOD

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Research summary Increased use of solar collectors in buildings is necessary but poses major challenges in existing built environments, especially where architectural coherence is an issue. The large size of solar systems at the building scale requires careful planning, as they may end up compromising the aesthetics of buildings, threatening the identity of entire contexts. A new method named Leso‐QSV has been developed to help authorities preserve the quality of pre‐existing urban areas while promoting solar energy use. The method is based on the concept of architectural " criticity " of building surfaces. The level of "criticity" of a surface is defined by the Sensitivity of the urban context and by the Visibility of this surface from the public domain: the more sensitive the urban area, the more visible the surface, the higher its " criticity " (Fig.1), and consequently, the need for Quality in integration. The method is composed of two complementary tools, "Leso‐QSV Acceptability" and "Leso‐QSV Crossmapping". The first is meant for city protection and is addressed to authorities, to support assessing solar systems acceptability: a simple integration quality evaluation method is proposed, and software is provided to help adapt acceptability requirements to city specificities. The second is addressed to planners. It maps the architectural criticity of city surfaces and superimposes it with the GIS solar irradiation map, so as to weight the solar potential of each surface with the expected architectural integration effort. The result shows the interest/difficulty to use the various city surfaces for solar energy production, and helps tailor energy policies to city specificities. The vision underlining the approach is that solar integration is possible also in delicate contexts, if appropriate design efforts and adequate cost investments are made. If these investments cannot be afforded it may be better to postpone the operation, as poor integrations usually end up just discouraging new users. By contrast, if well designed, such examples can be among the strongest driving forces for solar change, repaying by far their extra cost.
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SOLARENERGYPROMOTION&URBANCONTEXTPROTECTION:
LESOQSV(QUALITYSITEVISIBILITY)METHOD
MariaCristinaMunariProbstEPFL/Laboratoired'EnergieSolairemariacristina.munariprobst@epfl.ch
ChristianRoeckerEPFL/Laboratoired'EnergieSolairechristian.roecker@epfl.ch

Fig1:architecturalcriticityofcitysurfaces
Researchsummary
Increaseduseofsolarcollectorsinbuildingsisnecessarybutposesmajorchallengesinexistingbuilt
environments,especiallywherearchitecturalcoherenceisanissue.Thelargesizeofsolarsystemsat
thebuildingscalerequirescarefulplanning,astheymayendupcompromisingtheaestheticsof
buildings,threateningtheidentityofentirecontexts.AnewmethodnamedLesoQSVhasbeen
developedtohelpauthoritiespreservethequalityofpreexistingurbanareaswhilepromotingsolar
energyuse.Themethodisbasedontheconceptofarchitecturalcriticityofbuildingsurfaces.The
levelof"criticity"ofasurfaceisdefinedbytheSensitivityoftheurbancontextandbytheVisibility
ofthissurfacefromthepublicdomain:themoresensitivetheurbanarea,themorevisiblethe
surface,thehigheritscriticity(Fig.1),andconsequently,theneedforQualityinintegration.The
methodiscomposedoftwocomplementarytools,"LesoQSVAcceptability"and"LesoQSV
Crossmapping".Thefirstismeantforcityprotectionandisaddressedtoauthorities,tosupport
assessingsolarsystemsacceptability:asimpleintegrationqualityevaluationmethodisproposed,
andsoftwareisprovidedtohelpadaptacceptabilityrequirementstocityspecificities.Thesecondis
addressedtoplanners.Itmapsthearchitecturalcriticityofcitysurfacesandsuperimposesitwith
theGISsolarirradiationmap,soastoweightthesolarpotentialofeachsurfacewiththeexpected
architecturalintegrationeffort.Theresultshowstheinterest/difficultytousethevariouscity
surfacesforsolarenergyproduction,andhelpstailorenergypoliciestocityspecificities.
Thevisionunderliningtheapproachisthatsolarintegrationispossiblealsoindelicatecontexts,if
appropriatedesigneffortsandadequatecostinvestmentsaremade.Iftheseinvestmentscannotbe
affordeditmaybebettertopostponetheoperation,aspoorintegrationsusuallyendupjust
discouragingnewusers.Bycontrast,ifwelldesigned,suchexamplescanbeamongthestrongest
drivingforcesforsolarchange,repayingbyfartheirextracost.
Kwords:solarintegration,criticity,solarenergy,architecturalquality,urbancontextprotection,solarmap.
1.Introduction
Thereductionofbuildingenergyconsumption
andthereplacementoffossilenergyby
renewableshavebecomeprioritiesfor
authoritiesandplanners.Newenergy
regulations,togetherwithmandatorysolar
fractionsforelectricityandDHWare
introducingnewmaterialitiesandgeometries
inbuildings,resultinginnewformsof
architecturalexpressionwhichareslowly
modifyingouroldcitylandscapes(Fig.2).
Theincreaseduseofactivesolarcollectorsin
buildingsisnecessary,butclearlyposesmajor
challengesintheexistingenvironments.The
largesizeofsolarsystemsatthebuildingscale
asksforthoughtfulplanning,asthesesystems
mayendupcompromisingtheaestheticsof
thebuildings,andmayaffecttheidentityand
thequalityofentirecontexts(Fig.3).
Fig.2:NewSolarBuildings(left:3Mofficebuilding,Milan,M.Cucinella;Endesapavilion,IAAC,Barcelona)
Fig.3:Solarrenovations(left:FranciscanMonastery,Graz,Austria;right:SchlossWalbeckCastel,Germany).
Sacrificingarchitecturalqualitytopromote
solarspreadcanbecounterproductive,
leadingstraighttotheoppositeeffectinthe
longterm.Hotdiscussionsarealready
ongoinginmostcitiesbetweenthedifferent
involvedparties.Ononeside“solarpros”,
concernedbytheurgencyofmaximizing
renewableenergyuseaskforatotal
installationfreedom;ontheotherside,
architectsandbuildingheritageinstitutions
expresstheirworriesabouttheurbanimpact
ofsuchsystemsandasktorestricttheiruse
tocertainurbancontextsonly.Defacto,both
concernsofmaximizingsolarenergyspread
andprotectingthearchitecturalqualityofthe
builtenvironmentarejustified,andboth
shouldpossiblybesatisfiedatthesametime.
Furthermore,goodarchitecturalintegrations
canbepossiblealsointhemostcritical
situations,buttheyclearlyneedappropriate
designandcostinvestments(Fig.4).Ifwell
conceived,theseexamplescanactuallybe
veryconvincingandbecomestrongdriving
forcesfortheenergetictransition,repaying
byfartheirextradesignandcost.
2.LESOQSVapproachobjectives
Thequestionisnolongertobeinfavouror
againsttheuseofsolarsystemsincities,but
becomesrathertodefineminimallocallevels
ofintegrationquality,andtoidentifythe
factorsneededtosetsmartsolarenergy
policies,abletopreservethequalityofpre
existingurbancontextswhileallowingsolar
energyuse.TheLESOQSVapproachgives
clearandobjectiveanswersinthisdebate.
a‐ Firstitclarifiesthenotionofarchitectural
integrationqualityandproposesasimple
qualityevaluationmethod(seeSection3);
b‐ Thenithelpsauthoritiessetand
implementlocalacceptabilityrequirements
basedonthenotionofarchitectural"criticity"
ofcitysurfaces(LESOQSVacceptability)(see
Section4andSection5);
c‐ Finallyitproposesawaytotailorsolar
energypoliciestolocalurbanspecificitiesby
mappingthearchitectural"criticity"ofcity
surfaces,andcrossingthismapwiththecity
solarirradiationmap(LESOQSV
crossmapping)(seeSection6).
Fig.4:PhotovoltaicsystemintegratedontheroofofAulaPierluigiNervi,Vatican
3.Assessingarchitecturalintegrationquality
Requiringacertainlevelofintegrationquality
impliestobeabletoassessthatquality.
Oftenthisisconsideredamatterofpersonal
taste,butrecentstudieshaveconfirmedthe
existenceofimplicitcriteriasharedbythe
architectscommunityandleadingdefacto
thearchitecturalintegrationquality
perception[Krippneretal.2000];[Munari
Probstetal2007];[MunariProbstetal2012].
Tobeperceivedasintegrated,thesystemhas
tobedesignedasanintegralpartofthe
buildingarchitecture,i.e.alltheformal
characteristicsofthesolarsystem(field
size/position;visiblematerials;surface
textures;colours;moduleshape/size;joints)
havetobecoherentwiththeglobalbuilding
designlogic.
BasedonthesefindingstheLESOQSV
approachproposesaqualitativeassessment
methodarticulatedinto3simplesteps,
groupingtheintegrationcriteriatokeepthe
procedurelightandmakingtheevaluationas
objectiveaspossible(Fig.6).
ThecoherencyofSystemgeometry,System
materiality,andSystemdetails,isevaluated
usingathreelevelscale(fully‐partly‐not
coherent).Thisbeingaqualitativeevaluation,
thepartialresultscannotbeexpressedby
numbersandcannotbesynthesizedina
singlemeanvalue.Hencethechoiceto
representeachpartialevaluationasa
colouredarcofacircle(green,yelloworred
accordingtothelevelofcoherency)tobe
combinedwiththeotherstoformacomplete
circlemadeof3sectors.Theglobalsystem
qualityisgivenbythenumberofsectorsof
eachcolour(Fig.5).
4.Architectural"criticity"ofcitysurfaces
Integrationqualityisalwaysdesirable,butnot
alwaysthatcrucial.Inaconcerntospreadthe
useofsolarenergy,expectationstoward
integrationqualitymaybereduced,for
instanceinindustrialorcommercialareas
and/oronnotvisiblecitysurfaceslikeflat
roofs.Thelevelofvisibilityofthesurfacefrom
thepublicdomainandthelevelofsensitivityof
theurbancontextdeterminedefactothe
architecturalcriticityofacitysurface,andthe
relatedneedforintegrationquality.To
structuretheissue,acriticitygridisestablished
bycrossingthethreeidentifiedlevelsof
Fig.5:Threestepsqualityevaluationmethod
visibility(lowmediumhigh,Fig6)withthe
threeidentifiedlevelsofsensitivity(low
mediumhigh,Fig.7),definingninecriticity
situationsforwhichqualityexpectationshave
tobeset(seecriticitygridinthefirstpage,
Fig.1).
Fig.6:differentlevelsofvisibilityofcitysurfacesfromthepublicdomain
Fig.7:differentdegreesofsensitivityofexistingurbancontexts
5“LESOQSVAcceptability”tool
Thelevelofqualitytoberequiredforeach
criticitysituationisnotabsoluteandconstant,
butdependsonmanytemporalandlocal
factors,suchastheenergycontext,the
availabilityofotherrenewableenergysources,
thegeneralintegrabilityofmarketproducts
andtheconsequentdifficultyindesigninggood
integrationsolutions,thecityidentityand
image,itspoliticalorientationandeconomic
structure,etc..Forthisreasonthemethod
doesnotprovideanabsolutegridofquality
requirements,andisratherconceivedto
supportauthoritiesinestablishinglocalquality
expectationgrids,moreorlesssevere
dependingonthelocalreality.
5.1‐LESOQSVGRIDsoftware
Tohelpauthoritiesapplythismethod,amulti
purposesoftwaretoolhasbeendeveloped,
calledLESOQSVGRID(Fig9,nextpage).
Qualityexpectationsarerepresentedbythe
samethreesectorscirclesusedforthe
Fig.a8a:aacceptabilitygridsetting.
evaluationoftheintegrationqualitydescribed
inSection4.Three“standard”setsofquality
requirementsofgradualseverity(demanding‐
standard‐permissive)aremadeavailableto
authorities(“choixdegrille”),togetherwiththe
additionaloptionofsettingafullycustomized
grid(Fig.8).
Tohelpauthoritieschoosethemost
appropriate“acceptabilitygrid”,alarge
paletteofintegrationcasesisdisplayedthat
showsinrealtimewhichintegrationswould
beacceptableandwhichoneswouldhaveto
berejectedwiththeselectedsettings.This
examplesdatabasecanbescrolledthrough,
showingtheeffectofthegridoveravery
extensivesetofintegrationapproachesand
criticitysituations.
Thesamesoftwareisintendedtobeused
withminoradaptationsalsoasaneducation
toolforarchitects,installersandbuilding
owners.Thewidepaletteofexamplescan
provideinspirationfromgoodexamples,
showerrorstobeavoidedorgiveideason
howtoimprovethequalityofaprojectwhich
wouldberejectedinitspresentstate.Itcan
alsohelpmunicipalitiesexplaininan
interactiveandvisuallyconvincingwayhow
themethodworksandjustifytousers
eventualprojectsrejections.
Selectionbuttonsareavailableinthebottom
partofthescreen,todisplayachosensubset
ofintegrationexamples,inselectedsituations
(visibility/contextsensibility/typeandsize
ofsolarsystems,…)(Fig9).
6‐"LESOQSVCrossmapping"tool
Iftheabovedescribedacceptabilitytoolis
reactiveandmeantmainlyforprotection,the
secondtoolderivedfromthecriticity
concept,called"LESOQSVCrossmapping",is
proactiveandmeantforenergypolicy
planning.
Fig.9:LESOQSVgridsoftwaretool‐screenshot
Presently,theonlyinformationavailableto
plannersandauthoritiestomakedecisionson
solarpromotion,regulationsorfinancial
incentivesistheamountofsolarenergy
receivedbythevariouscitysurfaces,
displayedonsolarmaps(GIS).Thesemaps
varyinaccuracyanddetaillevels(rough
surfacesonly,roofstiltornot,facades…)but
theironlygoalisalwaystoassessthesolar
potentialofcitysurfaces,withnoconcernfor
theirurbanspecificities.Asalreadyexplained,
thesespecificitieshaveinrealityamajor
impactonsolarapplicationstrategiesand
shouldthereforealsobemadeavailableto
planners.Toanswerthisneedthe"LesoQSV
Crossmapping"toolproposestomapthe
architecturalcriticityofcitysurfaces,as
definedinSection4,andtosuperimposethis
informationovertheGISsolarirradiation
map.Thisallowstoweightthesolar
potentialofeachsurfacewiththeexpected
architecturalintegrationeffort.
Differentiatedpoliciesandeducated
decisionscanthenbebasedonthismore
comprehensiveinformation,keepinginmind
thatsolarintegrationsarepossiblealsoin
delicatesituations(Fig4).Inthesecases
though,designeffortsandcostinvestments
willprobablybehigher.Iftheseextraefforts
cannotbeaffordeditmightbepreferableto
postponetheoperation,aspoorintegrations
usuallyendupjustdiscouragingnewusers.
Bycontrastifwelldesigned,suchexamples
canbeamongthestrongestdrivingforcesfor
thesolarchange,repayingbyfartheirextra
cost.
6.1Nextsteps
Thecriticitymapmentionedaboveindicates
foreachcitysurfaceitsvisibilityfromthe
publicdomain,anditssensitivityinrelationto
theurbancontext.Aprocesstoautomatically
establishthevisibilityofthesurfacesinthe
3Dmodelsofcitiesiscurrentlybeing
developedatourlaboratory,aspartofaPhD
thesiswork.Theinformationrelatedto
surfacevisibilitywillnotonlyconsiderthe
purelyphysicalvisibilityfromthepublic
domain,butwillalsohierarchizethedifferent
pointsofviewinrelationtotheirimportance
(theviewfromamajorcitysquarebeing
usuallymorecrucialthantheonefroma
secondaryparkinglot).
7‐Conclusion
Asmoreandmorepressureisbuildingupto
increasetheuseofsolarasareplacementfor
fossilenergies,thereisanurgentneedfor
newresponsiblewaystoimplementthesolar
collectingelementsintheurbancontexts.
Westronglybelievethattheconceptof
“architecturalcriticity”atthebasisofthe
LESOQSVmethodoffersvaluablepossibilities
toimplementsuchresponsiblepolicies.
Wedohopethatthetwoinferredtoolswill
contributetofindingvaluablesolutionstothe
problematicSolarEnergypromotionAND
UrbanContextProtectionequation.
8‐Acknowledgments
AuthorsaregratefultoSwissFederalOffice
ofEnergyforfinancialsupportofthiswork.
9‐References
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energysystemsinarchitecture‐integration
criteriaandguidelines,IEASHCTask41,2012.
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Building-integrated photovoltaics (BIPV) is seen as a promising architectural application of PV technology on building envelopes for generating on-site renewable energy. In contrast to the traditional negative notion to-wards the visual impact of BIPV, “aesthetic BIPV” may even enhance the integration quality and produce a positive visual impact. Therefore, this research aims to objectively quantify the visual impact of BIPV in the built environment and clarifies its quality at the same time. The objective VIA approach is developed based on saliency mapping, a computer vision technique predicting human visual attention. As a case study, the proposed meth-odology is implemented to evaluate the perceived visual impact of a retrofitted coloured BIPV on four selected building frontages along Orchard Road in Singapore. Subjective surveys are implemented to validate the objective results, in which ratings of the visual impact of BIPV are collected based on the comparative street views with and without BIPV applications. Through validation, the proposed objective VIA methodology was determined as “qualified” for predicting the visual impact of BIPV. The proposed method can be applied as a planning or building design tool for urban planners and architects to objectively predict the visual impact of BIPV at the preliminary design stage.
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Deployment of building integrated photovoltaics (BIPV) requires smart planning to optimise the production of renewable energies, while preserving the aesthetic quality of the urban landscape, especially in densely built-up urban environments. A comprehensive mapping tool is proposed here to investigate the feasibility of BIPV applications, by introducing a quantitative visual impact assessment in addition to the traditional energy yield projections. The concept is tested in a case study of buildings along Orchard Road, the main commercial and tourist boulevard in the South-East Asian city state of Singapore. First, a visibility analysis of each building surface is conducted from the perspective of simulated pedestrians at street-level, based on line-of-sight. This is followed by an assessment of the solar energy harvesting potential based on simulated annual solar irradiation values on the various building surfaces. Lastly, the visibility assessment is overlaid on the 3D solar irradiation map to identify and visualise the most suitable building surfaces for BIPV applications. In addition, the influence of road-side trees on the feasibility of BIPV has been studied. Depending on the degree of visual impact, different strategies are proposed for the optimum deployment of BIPV, ranging from high-efficiency technologies to aesthetic BIPV and media walls. The proposed methodology could evolve as a standard tool for the decision-making process in high-density urban environments and thus further assist in promoting the large-scale adoption of BIPV.
Towards an improved architectural quality of building integrated solar thermal systems (BIST), Solar Energy
  • R Krippner
  • T Herzog
  • M C Munari Probst
  • C Roecker
Krippner, R., Herzog, T., Architectural aspects of solar techniques-Studies on the integration of solar energy systems, in Proceedings Eurosun 2000, Copenhagen, Denmark, 2000. Munari Probst, MC., Roecker, C., Towards an improved architectural quality of building integrated solar thermal systems (BIST), Solar Energy,2007,doi:10.1016/j.solener.2007.02.009
Solar energy systems in architecture-integration criteria and guidelines, IEA SHC Task 41
  • Munari Probst
  • M C Roecker
Munari Probst, MC., Roecker, C., editors, Solar energy systems in architecture-integration criteria and guidelines, IEA SHC Task 41, 2012.