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Imp 154 D - INESE.Gerritsen – workshop BIFI PV, May 2014, Chambéry

VERTICAL POTENTIAL OF BIFACIAL MODULES

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2nd workshop on BIFACIAL-PV 26/27 May 2014, Chambéry, France

Ya Brigitte ASSOA - Building energy lab (LCEB)Bruno SORIA - PV-modules lab (LMPV)Masakazu ITO - PV-systems lab (LSPV)Eric GERRITSEN - PV-modules lab (LMPV)


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Vertical potential of bifacial modules

3 case studies :

Double-skin facade integrationBI2PV: bifacial building integrated-PV

Vertical facade demonstratormethodology to evaluate the annual potential of innovativebifacial module architectures optical / electrical characterization & simulation

Vertical ground-mounted bifacial systemsglobal simulation of annual yield using direct and diffuse radiation plus land reflected albedo


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3 case studies :

Double-skin facade integration - Brigitte Assoa

Vertical facade demonstrator

Vertical ground-mounted bifacial systems


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ventilation IAQ/IEQair tightness

glazed surfaces Coupling of PV, thermal & visual comfort. Passive heat gain

structuresthermal inertia

BIPV systemsfacades & roofs

insulation layersThermal exchangeWater transferLife cycle analysis (LCA )

INES - Building Energy Lab

rolling shutterscontrol strategy

solar thermal systemsHot water systems (CESI/ CESCAI) Solar combined systems (SSC) Interseasonal thermal storageSolar cooling


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integration of bifacial PV-modulesinto a double-skin facade

Objectives : • impact of configuration parameters on thermal and electrical performance.

• impact of solar heated air in the double-skin on building heating demand

Parameters :• distance between front- and backside of double-skin facade (10 to 80 cm)

• reflectivity (color/roughness) of the inner surfaces

south-oriented double-skin facade of a PASSYS unit with

two bifacial PV modules

reflective surfaces insidedouble-skin facade

test unit / reference unit (reflective coating / plywood)


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Effect of coating reflectivity on relative electrical ga in (in Wh, relative to plywood reference) :

white 1: R = 85-90% � gain = 8%white 2: R = 70-80% � gain = 6%white 3: R = 50-80% � gain = 3%reference (plywood): R = 20-80% � gain = 0black: R = 5% � loss = -9%

� gain (bifacial – monofacial ) = 17%

Effect of distance between inner and outer wallon relative electrical gain (compared to plywood reference)

� gain increases with distance …..

spectral reflectivity

white 1

white 2

white 3

white 1

white 2

white 3

The choice of reflector material and double-skin thickness dependson customer requirements for either electrical (� white coating / large gap)

or thermal (� dark coating / narrow gap) energy mix optimisation


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3 case studies :

Double-skin facade integration

Vertical facade demonstrator – Bruno Soria

Vertical ground-mounted bifacial systems


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INDOOR CARACTERIZATION

OUTDOOR VALIDATION

RAY-TRACING SIMULATION: TracePro®

double mirror setup in PASAN solar simulator

vertical façade test bench& additional configurations

‘ the sky is the limit ’diffuse/direct

reduced scale vertical façade application with 2x2 cell modules

BIF vertical east-west

monofaciallatitudeangle


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1st step: INDOOR CARACTERIZATION � IV parameters for various architectures

resistive losses withincreasing irradiance

upto 2 suns� use half-cells

standard half-cells

gain of half-cells vs. standard : linear gain with irradiation due to lower resistive losses

textured glass

Isc gain with texturedglass vs. flat glass: angular response for 2 orientations


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2nd step: RAY-TRACING SIMULATION

15-22 % bifacial gainfor optimized distance

standard architecture

linear power gain fromindoor characterization

(‘quantity’)+

irradiance non-uniformityon front and backside

(‘quality’)

half-cell architecture

non-uniform distribution on back � beneficial impact of half-cellarchitecture ?

angular response fromindoor characterization

+angular distribution

on front and backside

textured glass architecture

example : 20/02/13 at 12h

FRONT BACK

angular distribution of diffuseirradiance � beneficial

impact of textured glass ?

BACKFRONT


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3rd step: OUTDOOR VALIDATION � on several configurations and different seasons

model validated by outdoor measurements

standard architecture

gain (half/std) with increasingirradiance. Additional gain for

non-uniform irradiance

half-cells

large gain for direct flux in morning & evening.

Low gain for diffuse flux throughout the day

� overall gain: 4-6%

textured glass


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3 case studies :

Double-skin facade integration - Brigitte Assoa

Vertical facade demonstrator

Vertical ground mounted bifacial systems - Masakazu Itovisiting scientist Tokyo Institute of Technology

now at Waseda University (Japan)


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Irradiation data: NASA/SSE

Albedo data: ISLSCP II MODIS (collection 4)Example on next slide

GREEN: vertical bifacial oriented East/West performs at least 5% better (in annual kWh) thanmonofacial oriented South at latitude tilt angle. YELLOW : at least 5% worse. -5%< GREY <+5%

starting points :• Bifacial double-glass modules resistant to harsh desert conditions (like N-Africa)• Vertical installation may reduce the effects of soiling � ~ 20% performance gain

But ….is vertical installation compatible with the lower geographical lattitudes of these regions ?

vertical ground mounted bifacial systems

Yes ! when oriented East/West and by exploiting the high local albedo


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example : worldmap albedo in May


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close-up of ‘BIFACIAL BELT’ green on map below

• gain upto 30% in the bifacial belt for vertical bifacial E/W orientation

• this adds up with the ~20% expected gain from reduced soiling on vertical modules


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gain bifacial @ vertical compared to monofacial @ lattitude angleGREEN > +5% gain -5% < GREY < +5% gain YELLOW > 5% loss

bifacial back-to-front ratio (BTFR) critical for vertical bifacial performance

BTFR=100% BTFR=90%

BTFR=80% BTFR=55%


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conclusions & perspectives :

Integrated in double-skin facades bifacial modules can offer a 15-20% performance gain over monofacial ones

A half-cell module architecture can offer a gain from 3 to 6% in bifacial modules and allows to reduce sensitivity to non-unform backside irradiance

Linearly textured glass on vertical modules can offer a performance gain of 4 to 6%

Vertical installation in desert areas can take a double-benefit from ground albedo and reduced soiling losses.

Bifacial building integrated PV (‘BI2PV’) remains to be explored and exploited for itscombination of thermal and electrical energy, daylighting and sunshading

Opto-geometrical modelling by Ray-Tracing useful to optimise the optical environment of modules for bifacial and BIPV applications.


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vertical..…WHY ?

30°northsouth


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EVOLUTION !

north

east

west

south

Commissariat à l’énergie atomique et aux énergies alternatives

INES RDI | Savoie Technolac – BP332 – 50 avenue du Lac Léman

73377 Le Bourget-du-Lac

T. +33 (0)4 7979 2804

Email : [email protected]

public establishment with industriel et commercial caracter | RCS Paris B 775 685 019

thank you for your attention !

Division of Technological ResearchSolar Technologies DepartmentLaboarorory for PhotoVoltaic Modules

acknowledgements :

• Paul Lefillastre & the INES module team• Yannick Veschetti• Yves Delesse †

• Luc Bernhard (AGC Glass Europe)

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Presentations & Public Speaking

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