WHAT IS IMPORTANT FOR BIPV? Dirk Herfurth, zkan Yildiz Mounting
Systems GmbH Mittenwalder Strae 9a D 15834 Rangsdorf Tel. 0049
33708 529 0, Fax. 0049 33708 529 199
[email protected]
ABSTRACT:Inthecourseoftheongoingglobalisationofthemarketforrenewableenergy,ever-newerfieldsof
application for photovoltaic (PV) and solar thermal plants are
being developed. Architects and planners are thus making
increasingly frequent use of modules and collectors in visually
attractive variants, such as for building integration and faade
systems. With these systems, the focus is put on aesthetics and the
often somewhat greater yield as compared to standard systems.
However, the effort required in order to ensure these systems are
designed in a secure manner that complies with applicable standards
is much greater than for regular roof top and outdoor systems. For
example, specific standards must be observed, and corrosion
protection and seal tightness become fundamentally important. This
lecture provides an overview of the possibilities for integrating
PV and thermal systems into buildings (roof and faade). It is
intended to illustrate the challenges faced during the planning and
installation of such systems. This includes observing and applying
the corresponding standards, regulations and codes. The goal is to
clarify what must be taken into account by the planner of the
structure from a structural stability standpoint and where the
challenges in a design lie. 1FUNDAMENTALS OF BUILDING INTEGRATION
In Germany, a good basis for the development of all kinds of solar
plants has existed since the entry into force of the EEG (Renewable
Energies Act) in April 2000. The
mostwidespreadandfamiliarareundoubtedly roof top
applicationsandground-mountedsystemsforopen spaces. But to secure
the greatest possible interaction of the functional aspect of the
photovoltaic (PV) module or
thermalcollectorandtheaestheticaspectasbuilding element,
building-integrated PV (BIPV) makes the most sense.Three basic
types can be distinguished. In the case of integration in the roof
area, the existing roof cladding is replaced by solar modules or
collectors and the wind and
weatherrepellentlayerformedbythesystemitself.In
thecaseoffaadesystems,theintegrationoccurs
vertically.Itservesasaprotectivesheathagainstthe elements or
assumes the function of a partition between the external and
internal climate. Shading elements form the third largest type of
use of building integrated solar systems. Duetothetechnical
propertiesofmodulesand collectors,theangleof
arrivalofthesunlightand associatedintensityofthe insolation play a
major role in the attainable efficiency ofthesystem.InGerman
latitudestheideal orientationis30 inclinationtothesouth.
Figure1showstheyield onvarioussurfacesofa
buildinginpercent.Thedegreeofshadowhasavery much greater influence
on the efficiency of a system. In the case of roof integration,
this influence is naturally not as relevant as in the case of
mounting on the faade surfacesofabuilding.Figure2showsvariousshadow
forms(trees,otherbuildings,ownshadow)whichcan scarcely be avoided,
especially in urban areas.Asaresultofthese,thesystemissubjectto
performancelosses,sincelessenergyisconvertedinto electricity. It
has been shown that 70% of the optimum can still be achieved on a
vertical faade with southward
orientation.Inaddition,buildingintegrationis remunerated with the
highest ct / kWh by the EEG. The
goalistoensurethatnewbuildingsarealready constructed with
solar-active surfaces and in the case of
restorationthatexistingbuildingsareretrofitted.Roof top
applications hold first place in Germany, with about two-thirds of
total output installed, followed by outdoor systems. Consequently,
the marginal share of BIPV can still be greatly increased.
Figure1:Yieldonvarious building surfaces in percent Figure 2:
Shadow forms on buildings 25th European Photovoltaic Solar Energy
Conference and Exhibition /5th World Conference on Photovoltaic
Energy Conversion, 6-10 September 2010, Valencia,
Spain51172BUILDING INTEGRATION OPTIONS
Diverseaestheticdesignoptionscanbeobtainedby
buildingintegrationwhilesimultaneouslygenerating
emission-freeenergyandcoolingandovershadowing rooms. Various
examples are explained
below.Inthecaseofroof-integratedmounting,thePV
modulesorsolarcollectorsreplacetheactualroof cladding. If early
planning occurs, the integration can be
adesigntoolfornewbuildings.Butretrospective installation in
existing roofs using systems available on
themarketisrelativelyunproblematic(cp.illustrations below).
Problems can arise here as a result of inadequate
sealingandstructuralstresses.Damagemayarise
becauseofchangesinexternalinfluences.Itisthus
advisabletousethesamestandardsandrecognised
technologicalrulesaswhenerectingaglassroof.The different materials
employed (glass, metal) have different thermal expansion
coefficients. To avoid the damage this causes, back ventilation of
the system is suggested. The
wasteheatproducedcanbeutilisedtosupportthe buildingsheating. Figure
1: Examples for roof integrations
Faadeintegrationscatchtheviewerseyemore
thanrooftopversions.Itisthusessentialtoattach particular importance
to the aesthetics and attractiveness
ofintegratedsolarsystems.Mountingofmodulesand collectors in the
faade is unproblematic. Examples for
thisaresuspendedfacades,glazedstairwellsand parapets. The following
illustrations present the options.
Systemsintegratedinthefaadecanbedistinguished
accordingtotheiradditionalfunctions.Suspended
ventilatedfacadesaresolelyintendedfortheweather
protectionoftheactualexternalenvelope.Thanksto integrated PV
modules or thermal collectors, CO2-neutral energy can in this way
be generated. A thermal insulating
faadecanlikewisecontainPVandthermalelements.
However,itisassignedevenfurtherfunctions,suchas weather and noise
protection and the thermal insulation of the
building.AnotherapplicationoptionisusingPVmodulesas
partly-transparentsurfaces.Forexample,theadmission of light into
the building can be individually influenced
bydesigningthemodulestobetransparent.Asaside effect, an interesting
interplay between light and shadow in the room interiors is
obtained. Hence,directinsolationbehindglazedfacadescan lead to heat
accumulation behind glazed surfaces and the
heatingupofrooms.Thisisaproblemformodern
skyscrapersinparticular,whichareusually extensively
glazed.Anotherversionoftheintegrationofsolar systems can be used
here. Integration of sun protection installations makes sense
especially in office buildings
withhighthermalloadingfromcomputerworkplaces, where room cooling
enjoys priority. Figure 3: Examples for sun protection integrations
For installation on the outside of buildings, rigid and
moveablesystemscanbedistinguished.Inthecaseof both options, PV
modules or solar thermal components, such as vacuum tube
collectors, can be fitted. In this way
eitherelectricityforaconventionalcoolingsystemor energy for a solar
thermal version can be obtained. The simplest type of rigid
mounting is as awning, projecting roof or parapet element.
However,givenweakdaylight,theseinstallations can have a negative
effect, since the then in any case low
lightintensityintheroomisfurtherreduced.Rotating systems provide a
remedy. These can be guided by the
horizontaland/orverticalaxis.Acomputer-controlled motor makes the
solar system track the sun, which can
enhancetheefficiencyoftheyieldbyupto30%.To
keeptheadditionalstressonthefaadeaslowas
possible,thestructuresforattachingthesolarsystems usually consist
of light metals such as aluminium. At the
sametime,thesystemshouldbedesignedsuchthat moving parts do not lead
to it casting shadows on itself as far as possible. When the sky is
overcast, such systems can be set at a neutral position, increasing
the admission oflightintoabuilding'sroomscomparedtorigid
installations. 3RULESANDREGULATIONSFORBUILDING INTEGRATION It is
the case that solar systems of all kinds are building
structuresinthemeaningofbuildinglaw.Thismeans
theymustcomplywithallbuildinglawregulations. Figure 2: Examples for
facade integrations 25th European Photovoltaic Solar Energy
Conference and Exhibition /5th World Conference on Photovoltaic
Energy Conversion, 6-10 September 2010, Valencia,
Spain5118Beforebuildingbeginsacheckmustbemadeoneach occasion
whether the building project complies with the regulations of the
Building Code (BauGB). In order to be
abletoexerciseforesightincontrollingurban development, the cities
and municipalities are in control
ofplanning.Adecisionismadeastowhetherthe
structuralinstallationformsaconnectionwiththe
surroundingdevelopment,i.e.fitsintotheimmediate
environment.Solarsystems,whethersubjecttoapprovalornot, have to
comply with public law regulations. In the case of faade and roof
top integrations in which load-bearing
glassstructuresareused,eitherageneralbuilding
standardspermit,approvalintheindividualcaseora building standards
test certificate is required. The glass building types which have
to meet the above-mentioned
requirementscanbesubdividedasfollows:Overhead
glazing,verticalglazing,fallprotectionglazing,
structuralglazingfacadesandwalkableglazing.It makes no difference
in this regard whether these contain solar cells or solar thermal
components. The modules or collectors can be subjected to a test
regarding the already mentionedapprovalinindividualcasesonaproject
basis.Forthispurposeseveraltestspecimensundergo
controlleddestruction.Itmustbeguaranteedovera certain period that
no fragments separate from them and as a result lead to damage to
persons and material. In the area of German standards and rules,
building standardimplementationregulationshavebeen
introducedforvariouskindsofglazing,namelythe Technical regulations
for measuring and implementing punctual supported glazing (TPRV) in
its final version of August 2006, the Technical regulations for the
use of linearsupportedglazing(TRLV)ofSeptember2005
andtheTechnicalregulationsfortheuseoffall protection glazing (TRAV)
of March 2001. It is the case
underalloftheseregulationsthatiftheplannerhas adhered to them, no
approval is required for the structure
inindividualcases.Thebasictenorofthetechnical
regulationsisthatsystemswithoverheadandvertical
glazingareonlypermissibleif,afterfailureofthe
structure,noglassfragmentsfalldownforacertain period and no harm to
people can occur. The glass used in such structures must correspond
to a laminated safety glass(LSG)product.Thankstoafilmincludedinthe
laminatewhichbindsfragments,thisglassguarantees safety in the event
of glass breakage.Ingeneral,mostphotovoltaicmodulesandsolar
collectorsdonothaveanyoverheadpermit.However, the module structure,
consisting of a glass-film laminate,
permitsuseintheoverheadandfaadearea.The respective manufacturers
can provide information in this regard. Allstatic analysis and
flexing proofs required must
beprovidedbytheplannerofasolarfaadeorroof
application.ThelistinDIN1055Influencesonload-bearingstructuresmustbetakenintoconsiderationas
influences on the load-bearing structure and solar-active
elements.Itisaboveallthesnowandwindloadsthat
occurwhichplayamajorrole.Thetechnicalcodesin
turnassisttheplannerfortheproof.Theycontainthe
tensionsandflexingpermissibleforvarioustypesof
glass.Structuralimplementationdetailsprovidethe
plannerwithadditionalinstructionduringthedesign
phasewithregardtosealtightnessandcorrosion protection of the
fastenings used. 4CONCLUSION
ThereisstillalargemarketforBIPVinGermany and Europe. The share in
the installed overall output in Germany and Europe is marginal and
still susceptible to
verygreatexpansion.Attractiveandaestheticsolutions can be found for
all types of facades and roof areas with
photovoltaicmodulesandsolarcollectors.Whenit comes to new
buildings, integration can be an interesting
planningaspect,forwhichthesystemoperatoris remunerated with the
highest EEG rate by legislation.
However,planningandexecutioninvolvesmore effort than in the case of
the other installation types, such as roof top applications or
ground mounted systems on open spaces. The planner bears a higher
responsibility for life and limb, as damaged parts of a faade or
overhead installation can injure people far more
easily.Consequently,ahighdegreeofcareisrequired during planning and
construction. The planning engineer is provided with regulations to
gauge building integration safely in the form of the technical
regulations for glazing and on glass. Structural details provide
tips for a wind- andweather-tightandcorrosion-freedesign.Forthe
customer, a complete and statically correct calculation of his
system is important in order to have it insured. 5REFERENCES
[1]Technical regulations for the use of linear supported glazing
(TRLV), August 2000
[2]Technicalregulationsfortheuseoffallprotection glazing (TRAV),
March 2001 [3]Technicalregulationsformeasuringand
implementingpunctualsupportedglazing(TPRV), September 2005 [4]DIN
EN 14449, Glas im Bauwesen, Verbundglas und Verbundsicherheitsglas
[5]G. Sedlacek, K. Blank, W. Laufs, J . Gsgen, Glas im
KonstruktivenIngenieurbau,Bauingenieurpraxis,Ernst & Sohn, 1.
Auflage, Berlin 1999 [6]E.-J .Lee,Untersuchungder
AnwendungsmglichkeitenvonPhotovoltaikan
GebudeninSdkorea,Promotionsarbeit,Universitt Dortmund, 1999
[7]S.Rexroth,GestaltungspotentialvonSolarpaneelen
alsneueBauelementeSonderaufgabeDenkmal, Promotionsarbeit,
Universitt der Knste, Berlin, 2005 25th European Photovoltaic Solar
Energy Conference and Exhibition /5th World Conference on
Photovoltaic Energy Conversion, 6-10 September 2010, Valencia,
Spain5119
