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

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

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

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

CREATING TOMORROW'S SOLUTIONS

SILICONE ADHESIVES FOR SOLAR POWER GENERATION

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.

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).

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.

SILICONE RUBBERS FOR FRAME GLUING

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.

ENCAPSULATION OF SOLAR CELLS

No yellowing of the silicone, no delamination after 24 years

ENCAPSULATION OF SOLAR CELLS

Module with EVA Module with Silicone

ENCAPSULATION OF SOLAR CELLS

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).

SILICONE GELS PROVIDE GOOD THERMO STRESS COMPENSATION

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.

• 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

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).

SILLICONE ON GLASS FRESNEL LENSES FOR CPV APPLICATIONS

SILLICONE ON GLASS FRESNEL LENSES FOR CPV APPLICATIONS

SILLICONE ON GLASS FRESNEL LENSES FOR CPV APPLICATIONS

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.

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.

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

CREATING TOMORROW'S SOLUTIONS

SILICONE ADHESIVES FOR WIND POWER GENERATION

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.

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.