•
Monorystalline silionThe produtionofthemonorystalline silionisthemostexpensive
and time onsuming proess. This is due to the fat that it takes
moretime togrowamonorystalompared toapolyrystal. The
long prodution time and proedure leed to a high level of energy
onsumption.
Today the eieny of theommerial monorystalline silion ells
is about12-16%.
The exibility is rather limited, beause the ellannot resist even
mediumanglesofbending. Iftheellisbenttoomuhitwillsimply
break and beomedysfuntional. Furthermore,itis notpossibleto
repairabrokenell.
•
PolyrystallinesilionThe prodution of the polyrystallinesilion ellsis faster and less
time-onsuming than the monorystalline silion. This results in
lowereonomialexpenses omparedtothemonorystalline.
Theeienyappearsintheareaof9-12%.
Polyrystallinehasthesamelimitedexibilityasthemonorystalline
silion.
•
AmorphoussilionOftenreferredtoasthinlm ell.
The expenses in relation to the prodution of amorphoussilion is
in the same area as polyrystalline. It is hoped that produtions
anbearriedoutatfarlowerexpenses.Furthermore,theamountof
materialneededislessthan1
µm
inthikness. Inomparisontothetwo other tehnis the thikness of amorphous silion is about 200
timesless.
One of the drawbaks of amorphous silionis that the eieny is
onlyin between3-8%.
Amorphoussilionanbesputteredonurvedsurfaesandalsoover
largeareas.
Thefatsabovearefoundin[Laukampet al.1998℄and[Andresen2002℄.
Tosumupthebulletsabovethedeisionproessisaostbenetanalysiswhere
theosts,needsandfuntionsareweightedagainsteahother. Forthemoment
the polyrystallinesilion PV modules are desirabledue to an aeptable
e-ieny andlowerexpensesin relationtoprodutionandinvestment.
In short, the blok is ut into thin slied ells, of 200-300
µm
. The ells arethen doped andanti-reetionoated in orderto inreasethe eieny ofthe
ells. Finallytheellshaveto besreenprinted. Afterthetreatmentthemost
ommonproedure istoonnettheellsinseriesto onstrutamodule. The
series of ellsare plaedbetween materials that anresist all kindof weather
onditions. Thearetwodominatingmaterials: glassand tedler. InFigure 6.1
thestrutureofthemoduleanalyzedin thisreportisillustrated. ThePV ells
are polyrystallinesilion. Inthe phaseof prodution it is importantthat all
airgatheredbetweenthe sheets ofglass isremoved,otherwise thiswould lead
to lowereieny of themodule. Anotherveryimportantissueis that, in
a-ordanebasitheory of eletriity, theweakest ellin aseries will determine
theeienyofthemodule. Due tothisallellsaretestedandlassied.
00000000000000000000 00000000000000000000 11111111111111111111 11111111111111111111 00000000000000000000 00000000000000000000 11111111111111111111 11111111111111111111
Glass
PV cells and interconnects
Glass
EVA (Ethyl Vinyl Acetate)
EVA (Ethyl Vinyl Acetate) Fibre glass
Figure6.1: IllustrationofthestrutureofthePVmodule
6.4 Standards for PV modules
A surveyamong theEuropeanMembers States reveals that standards of
al-ulation donot overthearea ofrenewableenergy [Bloem n.d.a℄. Indierent
parts oftheworlddierentgenerelstandardsareappliable,but inanover-all
perspetivethe standards are rather idential. The standardsover both the
module set-up, the testing, and the measuring methods. Thedata applied in
thisreportaremeasuredinaordanewiththeEuropeanStandard,IEC61215.
Thereasonwhyitmaybeprotabletoinvestigatethestandardsisforinstane
that guidelines are set outfor whih observations are neessary in relation to
modelling or analyzing theperformane of amodule. It is important to keep
inmindthattheeienyofthemoduleanditstemperatureareloselylinked
together. Thehigherthetemperatureofthemodule beomes,thelesseient
the module. Thestandardsalso haveregulations of how to arryout testing.
refereneenvironment(SRE),whenidentifying thenominaloperatingell
tem-perature(NOCT):
•
Tilt angle: At normal inidene to the diret solar beam at loal solarnoon
•
800m W 2
irradiane•
20o C
ambienttemperature•
Windspeed: 1m s
•
Open-rakmountedmoduleTheproblemonerningthestandardisthatoperationalPVmodules,espeially
theBIPVmodules,andtheenvironmentrarelysatisfytheonditionsstipulated
in thestandard. Forthemoment, internationalstandardorganisationsare
de-velopingstandardssuitableforthegrowingmarketofBIPVandonthedemand
from building designers. In relationto BIPV most ofthe onditionsstated in
the present standard is not fullled. The irradiane of 800
W
m 2
is theirradi-ane at noon for a PV module in the optimal position. BIPV modules will
nearlyalwaysbeplaedvertially in thefaade. Furthermore there is no free
airowattherearsideasforanopen-rakedmodule. Themainproblemabout
the BIPV modules not fullling the standard, is that the fators listed above
haveonsiderableinueneonthemoduletemperature. InaDuthalulation
norm for the Energy Performane of dwellings and residential buildings it is
estimated that the eieny of the modules is redued by 0.7 for roof
instal-lations [Bloem n.d.a℄. This is mainly due to the raise in temperature. The
temperaturehasimpaton theeletrial eienyof themoduleof about0.5
%/
o C
referring to theonditions at 25o C
. In Figure 6.2 twourves show therelationshipbetweenthe irradianeand theeieny at dierenttemperature
levels. 45
o C
is not an unusual module temperature. The highest tempera-ture in thetop ofthe module analyzed in this thesisis about 50o C
. Withouttheforedventilationthemoduletemperatureangetevenhigher[Christ2001℄.
In extension to these obvious deviations a test ontaining four dierent
se-narios has been arriedout onaspei day at JRC in Ispra. Thetest maps
outthediereneineienybyexaminingthetemperaturedierenebetween
themoduleandtheambienttemperature. Inshort,theonstrutionsofthefour
Figure6.2: Thisplotshowstheinueneofthemoduletemperatureontheeieny
referringtotheonditions at25
o C
and1000W/m 2
irradiane[Christ 2001℄.In Figure 6.3 both the theoretial notion and the result of the test are
illus-trated. Thetest isdesribed in severalartiles, e.g. [Jiménezet al.2006℄ and
[Bloem n.d.b℄. It an beseenthat the line of thefree-raked hasthe smallest
slope. Thisimpliesthatthemoduletemperatureofthefree-rakisthelowestof
thefourfromthetestonstrution. Theplotsalsorevealthatthelinereferring
to the façade integrated module is plaedjust belowthe line of the insulated
module. ThisgivesaguidanethattheBIPVmoduleshavehighermodule
tem-peratureswhihleadstoalowereieny. Thefatthatthelinesdonotfollow
thesamelineforthandbakisduetotheheatingofthemoduleduringtheday
hours.
Apartformrelatingto thetestenvironment,thestandardalsoontains
guide-lines for how to arry out testing and guiding as to whih variable must be
measured and olleted. Further, it is stated in the standard what kind of
equipment that hasto beused in thetesting. Thestandardrulesthat the
in-tervalofthemeasurementofthevariablesmustbeofmaximum60seonds. As
aminimumirradiane,ambienttemperature,elltemperature,windspeedand
Figure6.3: Therelationbetweenthedierenebetweenthemoduleandtheambient
temperatureversusthe irradiane[Jiménez etal. 2006℄. ICT denotesthe insulation
elltemperature. The upperplotshowthetheoretialrelationships, whilethe other
plotarisefrommeasurements.
6.4.1 Prior researh in the eld of modelling of PV
mod-ules
InthesearhforpreviousmathematialmodellingofBIPVoranalysisofsimilar
testsofBIPV,ithasbeomelearthatnotmuhresearhhasbeendone. More
researhhasbeenarriedoutonstandardPVfree-rakmountedmodules. This
researhanalso beofinterest,sinethemostfundamentaldierenebetween
thePVandtheBIPVistheventilatedair-gapbehindthemoduleandthe
devi-ationsfromthestandard. Theprimarymodelofinterestisthethermalmodels
explainingtheeienyofthemodules.
The mathematial method, utilizing stohasti dierential equations, applied
inthisreportisonlyreognizedin [Jiménezet al.2006℄,from whihthisthesis
arises. InbothasestheestimationofthemodelsisarriedoutinCTSM.One
of the big advantages of CTSM is that it is possible to estimate models
on-tainingnon-linearterms. ThisartilepresentsmodelsforBIPVmodulesandis
basedonthesamedataasappliedin Setion8. Inoneartileneuralnetworks
andlinearregressionareappliedtoestimateamodel[TamizhManiet al.2003℄.
Previousresearh may give someguidelines asto determining whih variables
havetobeonsideredinthemodels. In[Luque&Hegedus2003℄,itismentioned
that the humidity may inuene the performane of the PV module. Besides
that,the ambient temperature, theirradiane andthe wind speed the
humid-ityand thediretion are inluded in theintrodutorymodels in [TamizhMani
etal.2003℄. Afterreduingthemodel,itisfoundthatneitherthehumiditynor
the winddiretion are signiant. The data are measuredat the present test
site,butthese variablesarenotinludedinthedatasets. Inafurther analysis
itould beinterestingto investigate ifthendingsaboveanbeprovento be
orret.
The Applied Variables and
the Measuring Methods
This hapter givesan introdutionof the test site and the data olletedand
applied.
AlldataanalyzedinthepresentreporthavebeenolletedattheTestReferene
Enviroment,TRE,attheJointResearhCenter,JRC,inIspra,Italyin2002