CREATING TOMORROW’S SOLUTIONS
RENEWABLE ENERGY I SOLAR INDUSTRY
SILICONES FOR
SOLAR APPLICATIONS
The Material of Choice for the Solar Age
“ I’D PUT MY MONEY ON THE
SUN AND SOLAR ENERGY.
WHAT A SOURCE OF POWER!
I HOPE WE DON’T HAVE TO WAIT
UNTIL OIL AND COAL RUN OUT
BEFORE WE TACKLE THAT.”
Thomas Edison, 1931
2
Contents
Standard Solar Modules 4
Additional Possibilities for Customized
Solar Modules 6
Concentrator Photovoltaics 8
Concentrated Solar Power 12
Expertise on Five Continents 15
In the 21st century, our society faces the Putting Silicones in the Right Light
global challenges of climate protection and • Standard solar modules
resource conservation while requiring more – Frame sealing
and more electrical power to drive industrial – Bonding junction boxes and other
and consumer applications. Photovoltaics components
therefore plays an increasingly important – Potting of junction box components
role. To support the shift from conventional • Additional possibilities for customized
energy sources to renewable energy, WACKER solar modules
offers high-quality silicone rubber grades. – Encapsulation of solar cells
– Lamination of flexible modules
ELASTOSIL® Silicones Are True Outdoor • Concentrator photovoltaics
Standard solar modules Specialists – Molding of Fresnel lenses for highly
Whether for encapsulating, sealing, adhesive concentrating PV (HCPV) modules
bonding, molding or laminating, ELASTOSIL® – Optical coupling of secondary
Solar silicone grades from WACKER present optical elements of HCPV modules
the ideal long-lasting properties for outdoor – Thermal management of solar cells
applications: – Mirror bonding for solar concentrators
• Long-term weathering resistance against: • Concentrated solar power
– High or low temperatures – Bonding mirrors to the support
– UV radiation structure
– Environmental impacts – Silicone fluids as heat transfer
• Water-repellency media
• Low ion content for excellent
electric insulation Frame Sealing
Concentrator photovoltaics
• No embrittlement under outdoor Silicones can also be used for the assembly
conditions of solar collectors, e.g. for bonding the front
• Good environmental compatibility glass to the frame structure.
Concentrated solar power
ELASTOSIL®, WACKER® and HELISOL® are registered
trademarks of Wacker Chemie AG.
3
STANDARD SOLAR MODULES
Frame Sealing and Bonding of Junction Boxes
or Other Module Components
WACKER silicone rubber grades are ideal for
bonding the PV laminate, usually comprising a 1
front glass, encapsulation films in front of and
behind the solar cells, and a back-sheet, to the
aluminum frame. Silicones are also a reliable 2
solution to fix system components, such as 1
Bonding of the PV
junction boxes. laminate (composed of
front glass, encapsulation
films, solar cells and
Relevant benefits of ELASTOSIL® Solar back-sheet) to the metal
silicones: framing
• Easy processing 2
Bonding of the junction
• No release of corrosive volatiles box to the back-sheet
• Adhesion to typical PV substrates
• Long-term resistance to weathering and sunlight
WACKER’s dedicated silicone portfolio comprises
one-part moisture curing silicones and two-part
materials.
3
Potting of Junction Box Components
4
The potting of electronic and electrical compo-
nents in the junction box requires reliable materi-
als. Silicone gels offer the perfect protection.
3
5 Potting material
Relevant benefits of WACKER’s silicone gels:
4
• Easy processing Soldering tags for
electrical components
• Productivity increase via UV curing (optional)
5
• No release of corrosive volatiles Plastic housing
• Perfect void-free potting of cavities and
undercuts due to low viscosity
• Low thermomechanical stress due to high
damping properties
• Intrinsic tackiness and thus excellent
adhesion to surfaces
• Protection against water penetration,
hence against corrosion
4
Product Portfolio for Standard Solar Modules
Application Frame Sealing, Bonding of Junction Boxes Junction Box Potting
ELASTOSIL® ELASTOSIL® ELASTOSIL® ELASTOSIL® ELASTOSIL® ELASTOSIL®
Solar 1101 Solar 1109 Solar 1200 Solar 2202 Solar 2203 Solar 2205
Product type / 1-part / moisture 1-part / moisture 2-part / room-tem- 2-part / platinum 2-part / platinum 2-part / platinum
curing system curing curing perature curing cure cure cure
(base + catalyst*: (A/B 1:1) (base + catalyst**: (base + catalyst**:
10:1) 10:1) 10:1)
By-product Alcohol Alcohol Alcohol None None None
during cure
Consistency Paste-like Paste-like Paste-like Low viscous Very low viscous Very low viscous
(1,000 mPa·s) (200 mPa·s) (200 mPa·s)
Skin-forming 10 – 15 min. 20 – 35 min. w/ curing agent 150 min. Depending on Depending on
time / potlife T77: 15 – 20 min. curing catalyst curing catalyst
(at room w/ curing agent used** used**
temperature) T77 PLUS:
5-10 min.
Curing time Several days Several days Several hours Several hours Several hours Several hours
(at room (curing speed: (curing speed: (tack-free time:
temperature) 1.5 mm/day) 1.0 mm/day) 30 – 60 min.,
depending on
curing agent*)
Color / aspect Translucent Black, white Black Transparent Transparent Transparent
Hardness Sh A 30 Sh A 35 Sh A 36 N. a. N. a. N. a.
(soft silicone gel) (soft silicone gel) (hard silicone gel)
Additional Curing speed High intrinsic tack Curing mode Curing mode
features tunable via mixing (room tempera- (room tempera-
ratio and choice of ture, UV) and ture, UV) and
curing catalyst* curing speed curing speed
tunable via choice tunable via choice
of curing catalyst** of curing catalyst**
* Suitable curing catalysts: WACKER® Catalyst T 77 or WACKER® Catalyst T 77 PLUS
** Suitable curing catalysts: ELASTOSIL® CAT PT, ELASTOSIL® CAT PT-F or ELASTOSIL® CAT UV
5
ADDITIONAL POSSIBILITIES
FOR CUSTOMIZED SOLAR MODULES
Whereas, in standard photovoltaic modules, Lamination of Flexible Modules
silicones are limited to bonding and potting ap- Flexible modules are a special type of customized
plications, their properties make them suitable solar modules which are particularly common for
for a wider range of applications in customized organic photovoltaics (OPV). Silicones are the ideal
solar panels (e.g. building integrated photovol- laminating adhesives for the c
ontinuous roll-to-roll
taics), where they play an essential role in the manufacture of such multilayer composite modules
generation of energy. - typically comprising a cover-film, the organic
solar cell layer embedded in a film laminate and a
Encapsulation of Solar Cells back-film.
In order to improve a solar module’s degree of
efficiency, a transparent liquid silicone can be used Benefits of silicones:
to encapsulate the solar cells. This is particularly • High process efficiency due to rapid curing
important for tailored solar panels that cannot • Fast and void-free lamination
be made by standard lamination processes, for • No delamination thanks to long-term adhesion
instance. to typical substrates
• High module efficiency through
Benefits of silicones: – High transparency
• Fast and void-free encapsulation – No yellowing
• No delamination thanks to long-term adhesion – Long-term resistance to sunlight
to typical substrates
• High module efficiency due to:
– High transparency
– No yellowing
– Long-term resistance to sunlight
The ELASTOSIL® Solar range comprises low-viscous and fast-curing silicones that are ideal for encapsulating rigid and
flexible solar modules.
6
Product Portfolio for Customized or Flexible Solar Modules
Application Encapsulation of Solar Cells Lamination of Flexible Modules
ELASTOSIL® ELASTOSIL® ELASTOSIL® ELASTOSIL®
Solar 2202 Solar 2203 Solar 2205 Solar 2200
Product type / 2-part / platinum cure 2-part / platinum cure 2-part / platinum cure 2-part / platinum cure
curing system (A/B 1:1) (base + catalyst**: 10:1) (base + catalyst**: 10:1) (A/B 1:1)
By-product None None None None
during cure
Consistency Low viscous Very low viscous Very low viscous Self-leveling
(1,000 mPa·s) (200 mPa·s) (200 mPa·s) (30,000 mPa·s)
Potlife 150 min. (23 °C) Depending on curing Depending on curing 2 days (23 °C)
catalyst used** catalyst used**
Curing time Several hours (23 °C) Several hours (23 °C) Several hours (23 °C) 4 – 5 min. (120 °C)
Color / aspect Transparent Transparent Transparent Slightly translucent
Hardness N. a. (soft silicone gel) N. a. (soft silicone gel) N. a. (hard silicone gel) Sh A 35
Additional features High intrinsic tack Curing mode (room Curing mode (room Self-bonding to a wide range
temperature, UV) and temperature, UV) and of substrates
curing speed tunable via curing speed tunable via
choice of curing catalyst choice of curing catalyst
** Suitable curing catalysts: ELASTOSIL® CAT PT, ELASTOSIL® CAT PT-F or ELASTOSIL® CAT UV
7
CONCENTRATOR PHOTOVOLTAICS
In regard to the construction of solar power
plants, concentrator photovoltaics (CPV) rep-
resent an alternative to the classical standard
module technology. Concentrator photovolta-
ics use optical elements (such as lenses or
mirrors) to concentrate the sunlight and hence
increase the power output per covered area.
The CPV technology is thus more efficient than
conventional PV arrays in terms of land con-
sumption per kWh generated.
One way to concentrate sunlight is to use m irror
systems like those found in parabolic trough power
plants, where the concentrated sunlight is used
to heat a heat-transfer fluid. Another o ption is
Fresnel lens systems, which concentrate s unlight
onto small but highly efficient solar cells (e.g.
multiple-junction cells based on III-V semicon
ductors having an efficiency >40%).
Silicones are equally suitable for both technologies,
and provide several advantages, for example:
• Excellent adhesion
• Long-term resistance to weathering and sunlight
• High transparency and no yellowing
• Easy processing
• No release of corrosive volatiles
8
Molding of Fresnel Lenses The SOG Fresnel lenses offer the best
By concentrating the sunlight, the solar cell area combination of:
can be reduced to a fraction of the cell area that • Design flexibility
is required for a conventional solar module having • Easy, cost-efficient processing
a similar electricity output. The sunlight concen- • Weight reduction
tration factor is typical for each CPV system and • High transparency and high light transmission
usually ranges from hundreds to over 1000. Most • Long-term resistance to abrasion, sunlight
compact module designs can be realized with and weathering
highly concentrating Fresnel lenses placed in front
of the solar cells. In collaboration with leading CPV companies,
WACKER has developed specific silicones to meet
Fresnel lenses can be made of glass, transparent all relevant requirements of this industry, namely:
thermoplastics (such as polycarbonate and poly- • Low viscosity for quick filling of large molds
methyl methacrylate) or silicone, which is molded • Highly precise reproduction of lens details
onto a glass substrate in a process called silicone- • Very high light transmission from 250 nm to
on-glass (SOG) technology. Usually, several single >1100 nm
lenses are combined side-by-side to form a par- • No change in light transmission on long term
quet of Fresnel lenses, which is placed in front of light-exposure
the solar cell array.
The precisely formed Fresnel
lenses are manufactured
from a highly transparent
silicone specifically d
esigned
for optical applications.
9
Optical Coupling of Secondary Optical Frame Sealing and Bonding Note
Elements As with standard PV modules, the WACKER WACKER’s dedicat-
Normally and in most cases, Fresnel lenses are silicone rubber grades are ideal for bonding ed silicone portfolio
already quite sufficient to concentrate the sunlight. system components of CPV modules, such comprises one-part
In some specific cases however, the Fresnel lens as the backplate, the Fresnel lens parquet, the moisture curing sili-
parquet – considered as the primary optical ele- metal frame structure, junction boxes, etc. cones and two-part
ment – is combined with glass prisms as second- materials.
ary optical elements, which are placed between Benefits of silicones:
the SOG structure and the solar cells, guiding the • Easy processing
concentrated sunlight to the cells. • No release of corrosive volatiles
• Adhesion to typical PV substrates
The main requirements for the optical bonding • Long-term resistance to weathering and sunlight
silicone that connects the glass prism with the
solar cell, are:
• Transparency
• Resistance to sunlight
• Non-yellowing
• Fast curing to allow short process time
• Ideally thixotropic and easy to apply
1
Thermal Management of Solar Cells
As the complete sunlight spectrum, including
the infrared part, is focused on the solar cells,
effective heat dissipation is a key factor to prevent
overheating of the solar cells and, hence, to guar-
antee an optimum conversion of light into electric-
ity. For an effective thermal management WACKER
has developed thermally conductive grades that
keep their properties even at permanently high
temperature and over a lifetime of the CPV panel.
These highly filled materials present the following
properties: 2
• Thermal conductivity up to 1 W/m·K
1 3
• Shear thinning and optimized rheology
for easy processing
• Reliable surface contact under permanent
thermal stress
1
Frame sealing and bonding
2
Optical coupling of secondary optical elements
3
Thermal management of solar cells
10
Product Portfolio for Concentrator Photovoltaics
Application Molding of Fresnel Lenses Optical Coupling of
Secondary Optical
Elements
ELASTOSIL® ELASTOSIL® ELASTOSIL® SEMICOSIL®
Solar 3210 Solar 3211 Solar 3201 988 1K
Product type / 2-part / platinum cure 2-part / platinum cure 2-part / platinum cure 1-part / heat curing
curing system (A/B 9:1) (base + catalyst*: 10:1) (base + catalyst**: 10:1)
By-product None None None None
during cure
Consistency Low viscous Low viscous Low viscous Paste-like
(3,500 mPa·s) (2,300 mPa·s) (1,600 mPa·s)
Potlife Approx. 100 min. Depending on curing 30 – 40 min. 9 months
(23 °C) catalyst used* (23 °C) (23 °C)
Curing time Approx. 20 min. Approx. 20 min. Approx. 100 min. 60 min.
(70 °C) (50 °C) (50 °C) (130 °C)
Color / aspect Crystal clear Crystal clear Crystal clear Translucent
Hardness Sh A 45 Sh A 52 Sh A 42 Sh A 35
Additional Very high light Very high light Very high light Self-bonding on many
features transmission in transmission in the range transmission in the range substrates (no surface
the range of 250 nm of 250 nm to 1100 nm. of 250 nm to 1100 nm. pretreatment necessary)
to 1100 nm Curing mode (room Self-bonding on low-iron
temperature, UV) and glass.
curing speed tunable via
choice of curing catalyst*
Application Frame Sealing Bonding of Heat Sink /
Bonding of Junction Boxes Thermal Management
ELASTOSIL® ELASTOSIL® ELASTOSIL® ELASTOSIL® WACKER®
Solar 1101 Solar 1109 Solar 1200 TC 9800 Silicone Paste P12
Product type / 1-part / 1-part / 2-part / 1-part / 1-part (non-curable
curing system moisture curing moisture curing room temperature moisture curing silicone paste)
curing
(base + catalyst***: 10:1)
By-product Alcohol Alcohol Alcohol Alcohol N. a. (non-curable
during cure silicone paste)
Consistency Paste-like Paste-like Paste-like Slightly self-leveling Paste
paste
Skin forming 10 – 15 min 20 – 35 min. w/ curing agent T77: 5 – 15 min. N. a. (non-curable
time / potlife 15 – 20 min. silicone paste)
(at room w/ curing agent T77
temperature) PLUS: 5 – 10 min.
Curing time Several days Several days Several hours (tack-free Several days N. a. (non-curable
(at room (curing speed: (curing speed: time: 30 – 60 min., (curing speed: silicone paste)
temperature) 1.5 mm/day) 1.0 mm/day) depending on curing 1.0 mm/day)
agent***)
Color / aspect Translucent Black, white Black White White
Hardness Sh A 30 Sh A 35 Sh A 36 Sh A 70 N.a. (silicone paste)
Additional Curing speed tunable via Thermal conductivity: Thermal conductivity:
features mixing ratio and choice 0.85 W/(m·K) 0.8 W/(m·K)
of curing catalyst***
* Suitable curing catalysts: ELASTOSIL® CAT PT, ELASTOSIL® CAT PT-F or ELASTOSIL® CAT UV
** Suitable curing catalysts: ELASTOSIL® CAT CPV or ELASTOSIL® PT-F
*** Suitable curing catalysts: WACKER® Catalyst T 77 or WACKER® Catalyst T 77 PLUS
11
CONCENTRATED SOLAR POWER
Bonding Mirrors to the Support Structure Silicone Fluid as Heat Transfer Medium
WACKER silicone adhesives are ideal for bond- Durable heat transfer fluids are key components
ing the mirror panes of solar concentrators used of concentrated solar power (CSP) systems.
at concentrated solar power plants. The fast cur- Long-term resistance to extreme thermal stress,
ing, non-slumping silicone grades allow the pre- excellent heat transfer properties and a stable
cise fixing of mirrors on the support structure and level of viscosity over the fluid’s lifetime are key
a fast installation process. The silicone rubbers’ factors for the highly economical and reiiable
resilience to thermal cycling and their resistance to running of a CSP plant.
permanent thermal stress, makes them a reliable
bonding solution for concentrated solar power To meet the specific requirements of parabolic
plants. trough power plants, WACKER has developed
a range of specialized silicone fluids which provide
Benefits of silicones: significant advantages over conventional heat
• Easy processing transfer media. HELISOL® fluids are purely
• Fast curing silicone-based and offer valuable benefits that
• No release of corrosive volatiles are prerequisites for highly efficient and cost-
• Adhesion to glass, metal and painted effective energy conversion:
surfaces • High thermal stability, up to 425 °C, and even
• Long-term resistance to heat, weathering in the long term, resulting in a high level of
and sunlight operational reliability
• A very low viscosity level for an optimized
WACKER’s dedicated silicone portfolio material flow in the CSP plant’s pipelines,
comprises one-part moisture curing silicones minimizing the build-up of pressure
and two-part materials. • A very low pour point keeping the fluid liquid
down to even -40 °C, making anti-freeze
Operating Temperature of HELISOL® Heat Transfer measures obsolete
Fluids • Good heat transfer for a high power-block
efficiency
min. use max. working max. film
temperature temperature temperature • Non-corrosive and no critical degradation
products, such as hydrogen, allowing a long
lifetime of both the heat fluid receivers and
the heat exchangers
• No risk of fouling
• Non-toxic, very low environmental impact,
thus easy disposal of used or spilled fluid in
an environmentally friendly way
Furthermore HELISOL® heat transfer fluids can
– 40 °C 425 °C 450 °C be filled in the piping system irrespective of
limitations due to ambient temperature. This
Recommended working temperature:
allows system maintenance regardless of weather
−40 °C to 425 °C
conditions at virtually any time.
12
Schematic of a Parabolic Trough Plant – Advantages of HELISOL®
Operating tempera-
1
tures up to 425 °C
and thus much higher
3 2
efficiency levels and
energy yields
Longer lifetime of
2
receivers due to less
hydrogen generation
3 Excellent low-
temperature behavior
6 (can be used down
4 to -40 °C); no need
5 for freeze protection
4 Higher working
temperature allows
reduced storage
volume
5
Cold weather
independent mainte-
nance increases the
degree of utilization
Improved economics,
6
reliability and profit-
ability of CSP plants
7 Potential 5% LCOE
7
reduction
13
Product Portfolio for Concentrated Solar Power
Application Bonding of Mirrors to the Support Structure
ELASTOSIL® ELASTOSIL® ELASTOSIL®
Solar 1101 Solar 1109 Solar 1200
Product type / 1-part / moisture curing 1-part / moisture curing 2-part / room-temperature curing
curing system (base + catalyst*: 10:1)
By-product Alcohol Alcohol Alcohol
during cure
Consistency Paste-like Paste-like Paste-like
Skin forming time / potlife 10 – 15 min 20 – 35 min. w/ curing agent T77: 15 – 20 min.
(at room temperature) w/ curing agent T77 PLUS:
5 – 10 min.
Curing time Several days Several days Several hours
(at room temperature) (curing speed: 1.5 mm/day) (curing speed: 1.0 mm/day) (tack-free time: 30 – 60 minutes,
depending on curing agent*)
Color / aspect Translucent Black, white Black
Hardness Sh A 30 Sh A 35 Sh A 36
Additional features Curing speed tunable via
mixing ratio and choice of
curing catalyst*
Application Heat Transfer Fluids
HELISOL® 5A HELISOL® 10A HELISOL® XA HELISOL® XLP
Pour point (in use) ** < -55 °C < -55 °C -36 °C -45 °C
Density at 25 °C 0.92 g / cm³ 0.93 g / cm³ 0.94 g / cm³ 0.95 g / cm³
Vapor pressure at 425 °C 20 bar 16.3 bar 15.9 bar 12.6 bar
(in use)**
Viscosity at 25 °C ~5 mPa∙s ~10 mPa∙s ~20 mPa∙s ~35 mPa∙s
Flash point (ISO 2719) 120 °C 175 °C 225 °C 222 °C
* Suitable curing catalysts: WACKER Catalyst T 77 or WACKER Catalyst T 77 PLUS
® ®
** In use = 720 hours at 425 °C
14
EXPERTISE AND SERVICE NETWORK
ON FIVE CONTINENTS
Vertriebs-
Sales undproduction
offices, Produktionsstandorte sowie competence
sites and technical
technische
centers Kompetenzzentren
around the world. weltweit
WACKER is one of the world’s leading Spanning the globe with 4 business customers worldwide in the develop-
and most research-intensive chemical divisions, we offer our customers highly- ment of products tailored to regional
companies, with total sales of €6.21bn. specialized products and comprehensive demands, supporting them during every
Products range from silicones, binders service via 26 production sites, 23 techni- stage of their complex production pro-
and polymer additives for diverse industrial cal competence centers, 14 WACKER cesses, if required.
sectors to bioengineered pharmaceutical ACADEMY training centers and 52 sales WACKER e-solutions are online services
actives and hyperpure silicon for semi- offices in Europe, North and South America, provided via our customer portal and as
conductor and solar applications. As a and Asia – including a presence in China. integrated process solutions. Our custom-
technology leader focusing on sustainability, With a workforce of some 14,400, we see ers and business partners thus benefit
WACKER promotes products and ideas ourselves as a reliable innovation partner from reliable service and comprehensive
that offer a high value-added potential to that develops trailblazing solutions for, information to enable projects and
ensure that current and future generations and in collaboration with, our customers. orders to be handled fast, reliably and
enjoy a better quality of life, based on We also help them boost their own suc- highly efficiently.
energy efficiency and protection of the cess. Our technical competence centers Visit us anywhere, anytime around the
climate and environment. employ local specialists, who assist world at: www.wacker.com
All figures are based on fiscal 2021.
Wacker Chemie AG
7938e/07.22
Hanns-Seidel-Platz 4
81737 Munich, Germany
www.wacker.com/contact
www.wacker.com
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The data presented in this medium are in accordance with the present state of our knowledge but do not absolve the user from carefully checking all supplies immediately on receipt.
We reserve the right to alter product constants within the scope of technical progress or new developments. The recommendations made in this medium should be checked by preliminary
trials because of conditions during processing over which we have no control, especially where other companies’ raw materials are also being used. The information provided by us
does not absolve the user from the obligation of investigating the possibility of infringement of third parties’ rights and, if necessary, clarifying the position. Recommendations for use
do not constitute a warranty, either express or implied, of the fitness or suitability of the product for a particular purpose.
