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CREATING TOMORROW'S SOLUTIONS
Dr. Stefan Ritter, WACKER CHEMIE AG, Engineering Silicones
European Coatings Conference, 22./23.11.2011
SILICONE ADHESIVES FOR SOLAR AND WIND POWER GENERATION
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OUTLINE
• Properties of Silicones
• Silicones in Solar Power Generation
• Standard Modules
• CPV Modules
• Special Applications
• Silicones in Wind Power Generation
• Applications in general
• Silica additivated glues
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WHAT ARE SILICONE RUBBERS ?
R = H, methyl-, ethyl-, vinyl,
fluorpropyl or phenyl
• class of synthetic polymers, based on Si-O bonds
• 3-dimensional crosslinked polysiloxanes with network structure
• elastic material with unique properties
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UNIQUE PROPERTIES OF SILICONES
• easy processing
• very good heat stability (standard grades: 180 °C; special grades: 250-300 °C)
• flexible at low temperatures (standard grades: -40 °C; special grades: -120 °C)
• good mechanical properties, almost constant from -40 to +180°C
• low Young‘s modulus and very good compression set
• outstanding weathering & UV stability
• water repellent surface, low absorption of humidity
• biocompatible & chemical/physiological almost inert
• good & reliable adhesion to glass, many metals and plastics
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CREATING TOMORROW'S SOLUTIONS
SILICONE ADHESIVES FOR SOLAR POWER GENERATION
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GENERAL ADVANTAGES OF SILICONES IN PV APPLICATIONS
• Long term UV and weathering resistance (no embrittlement).
• Usage in outdoor applications (construction, automotive, high voltage insulation) for more than 20 years.
• Transparent grades show no absorption of light down to 250 nm (no yellowing, higher efficiency).
• Primerless adhesion to glass, aluminum and plastic components.
• Low Young’s modulus allows compensation of different thermal expansion coefficients.
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USAGE OF SILICONES IN STANDARD PV APPLICATIONS
• Frame gluing with condensation curing RTV2 grades.
• Encapsulation of solar cells with high transparent addition curing RTV2 grades.
• Lamination with high transparent silicone copolymers.
• Gluing of the junction box to the back sheet with RTV1 grades.
• Potting of the junction box with RTV2 grades (elastomers or gels).
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SILICONE RUBBERS FOR FRAME GLUING
• Mainly RTV2 silicones.
• Easy to process, rel. fast curing.
• Neutral curing systems.
• Primerless adhesion to glass, aluminum and plastic components.
• Compatible with other compounds (e.g. butyl rubber), no inhibition.
• Reliable sealing of the modules (TÜV-, UV-, weathering tests).
• UL94 & ETAG approved.
• Low Young’s modulus allows compensation of different thermal expansion coefficients.
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SILICONE RUBBERS FOR FRAME GLUING
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ENCAPSULATION OF SOLAR CELLS
• Crystal clear transparent grades.
• Processing: silk screen or jet printing (bubble free).
• Rapid curing at RT.
• Adhesion to typical substrates.
• No Yellowing.
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ENCAPSULATION OF SOLAR CELLS
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No yellowing of the silicone, no delamination after 24 years
ENCAPSULATION OF SOLAR CELLS
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Module with EVA Module with Silicone
ENCAPSULATION OF SOLAR CELLS
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POTTING OF THE JUNCTION BOX
• Protection of bypass diodes against moisture & environmental influences.
• Low viscosity, easy processing.
• Fast curing, adhesion at RT.
• Low modulus for reducing thermomechanical stress.
• UL94 approved.
• Optional: increased thermal conductivity (up to 2.5 W/mK).
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SILICONE GELS PROVIDE GOOD THERMO STRESS COMPENSATION
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DIELECTRICAL PROPERTIES OF SILICONES
• Silicones provide an effective electrical insulation in medium and high voltage insulators since >15 years.
• Very good dielectric properties which are almost unaffected by even harsh environmental influences.
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• Dielectric strength: 23 kV/mm (IEC 243).
• Volume resistivity: 1015 Ωcm (IEC 93) unaffected after 100h in boiling water.
• Breakdown voltage after 100 h in boiling water: >12 kV (Ref.: Bärsch et al., IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 6 No.5, 1999).
DIELECTRICAL PROPERTIES OF SILICONES
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glass
Fresnel-lens (silicone)
silicon solar cell
secondary optical unit
SILLICONE ON GLASS FRESNEL LENSES FOR CPV APPLICATIONS
• High transparent grades for the manufacturing of Fresnel lens structures.
• Easy processing, fast curing, adhesion at room temperature.
• Excellent fidelity of reproduction.
• No yellowing and low loss of light due to scattering at the glass surface.
• The glass front sheet allows a safe and stable operating over many years even under demanding conditions (deserts, seaside).
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SILLICONE ON GLASS FRESNEL LENSES FOR CPV APPLICATIONS
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SILLICONE ON GLASS FRESNEL LENSES FOR CPV APPLICATIONS
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SILLICONE ON GLASS FRESNEL LENSES FOR CPV APPLICATIONS
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LAMINATION OF FLEXIBLE THIN FILM SOLAR CELLS
• Transparent addition curing RTV2 silicone for the lamination of flexible thin film solar cells.
• Low viscosity, easy processing (e.g. roll to roll lamination).
• Excellent primerless adhesion at RT to relevant materials (e.g. PET; PEN, activated ETFE).
• No yellowing and low loss of light due to scattering.
• Reliable long term encapsulation and protection of solar cells against environmental influences.
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SILICONE ADHESIVES IN SPACE APPLICATIONS
• Bonding of cover glass to solar cells with transparent silicones.
• Bonding/potting of other components.
• Low temp flexible (-115°C).
• High radiation resistance.
• Extremely low content of volatiles (meeting NASA/ESA specifications).
• Prevention of electrostatic charging via ablative bonding.
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cover glass
cover glass adhesive
solar cells
adhesive for solar cells
composite backsheet
carbon fibre / aluminium (honeycomb structure) /carbon fibre / polyesterimide film
SILICONE ADHESIVES IN SPACE APPLICATIONS
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CREATING TOMORROW'S SOLUTIONS
SILICONE ADHESIVES FOR WIND POWER GENERATION
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SILICONE ADHESIVES & SEALANTS FOR WIND POWER GENERATION
• Sealing & glueing of rotor blade connections.
• Sealing of housings and generator components.
• Impregnation of coils in the generator with silicone resin (class C insulation; T>180°C).
• Silicone fluids as lubricants and insulation material in transformers.
• Protection against water/moisture, salt and further environmental influences
• Improved thermal management, electrical insulation and fire safety.
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PYROGENIC SILICA INCREASES PERFORMANCE OF BONDING PASTES
• Pyrogenic silica is used as an additive (<10 weight%) in epoxy glues for wind turbines.
• Improved rheological properties: Increase of viscosity and thixotropy non-sag, but still easy to process
• Increased storage stability.
• Low amount required less embrittlement of the adhesive.