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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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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 – [email protected]
Renewable Energy Systems & Policy Group – UNSW Sydney
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