School of Photovoltaics and Renewable Energy Engineering

Xinyi ZhangDr Jose BilbaoRenewable Energy Systems & Policy Group – UNSW Sydney

Assessment of different chemical

compounds for EVA delamination

Background - The Growing PV Capacity

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International Energyy Agency (IEA) (2018) Snapshot of Global Photovoltaic Markets

Total Installed Capacity

Background – PV recycling technology generation

Generation 1

• Down-cycling: recycling PV module using mechanical process (similar to WEEE recycling

process).

Generation 2

• Hybrid down-cycling & up-cycling: delamination of PV modules for recover whole piece of glass,

other contents goes to mechanical process (e.g. WEEE recycling process)

Generation 3

• Up-cycling: recover all the valuable components of a PV module for their direct reuse or

recycling

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General Generation 3 Recycling Process

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Delamination – Removal of EVA (ethylene vinyl acetate)

Chemical treatment – chemical solvents

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Chemical structure of EVA

Atomic structure of EVA before and after lamination

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Experiment – Organic/inorganic solvents

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WeightofEVA

(g)

Solvent

Concentration

Volumeofsolvent

(ml)

Period

(hours)

g X1 1,2-Dichlorobenzene 0.0385 99% 10 3

ml T Toluene 0.0985 99% 10 3

hours C CholineChloride 0.1015 70% 10 3

X2 NaOH 0.1131 70% 10 3

X3 KOH 0.0881 70% 10 3

Solvents

Hydrophilic-Polar Hydrophobic-Non-polar

Acetone Lacquerthinner

Ethanol Toluene

Isopropanol Petroleumbenzine

MethylethylKetone 1,2-Dichlorobenzene

MethylisobutylKetone Tetrahydrofuran

Ethyleneglycol Trichloroethylene

Doi, T. et al. (2001) ‘Experimental study on PV module recycling with organic solvent method’

Results

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1,2-Dichlorobenzene:

Swelling +

degradation

Toluene:

Swelling

Non-organic solvents:

No reaction

NaOH KOH

air sensitivity

Toluene

• Accelerate reaction rate with:

- Hot Plate (3 hours at 60 dec C)

- Ultrasonic Bath (3 hours at 60 deg C)

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SolventSampleweightbeforetreatment

(g)

Sampleweightaftertreatment

(g)

Massdifference

(g)%difference

Toluene-ultrasonicbath 0.0523 0.8375 0.7852 1501%

Toluene-hotplate 0.0985 0.9242 0.8257 838%

FT-IR: EVA treated with Toluene

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11

0

20

40

60

80

100

120

5001000150020002500300035004000

%Transm

ittance

Wavenumber/cm^-1

%T- beforetreatment %T- aftertreatment

FT-IR: EVA treated with Toluene

Mechanism of Swelling

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University of Southern Mississippi (2000) How a polymer gets dissolved.

Toluene + PV module (5x5cm)

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Toluene + PV module (5x5cm)

Toluene – One-cell PV module

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Toluene – One-cell PV module

After 24 hours After 72 hours

Toluene – One-cell module

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After 1 weekAfter 96 hours

Swelling of EVA – Cell breakage

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Toluene – One-cell PV module

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Glass is clean

Backsheet is

clean

This is the only method that backsheet can be

recovered

What can we do to eliminate the breakage?

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1.Looking for chemicals – dissolve EVA

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• EVA behave like emulsifier

between H2O and toluene

– Solution stays as turbid

– Suspension even after

several days/weeks

– Precipitate appear powdery

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EVA in toluene + NaOH in TBA (Tertiary butyl alcohol ) +

H2O

Advantages of Emulsions

• Untangle long chain polymers into small aggregated particles

• Speed up removal process by forcing precipitation

• Prevent over swelling that can break cells

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Cell breakage (7 days soak)

2. Looking for new encapsulant – easy to

dissolve

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Thank you

Any questions?

Xinyi Zhang – jerri_xinyizhang@outlook.com

Renewable Energy Systems & Policy Group – UNSW Sydney

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