> Quick answer: Silicone gaskets are the most resilient option for maintaining an IP65 seal through annual temperature swings exceeding 80 °C in Romania. Their high elasticity and ability to compensate for thermal expansion ensure lasting integrity [1][2].
When it comes to sealing solar lamps in environments with extreme temperature fluctuations, such as those found in continental Romania, the choice of gasket material is crucial. This article explores how different materials—EPDM, silicone, and TPE—perform under these conditions, focusing on their compression set resistance for IP65 seals.
Why Silicone Gaskets Excel in Thermal Cycling
Silicone gaskets are engineered to maintain watertight and air-tight seals despite significant temperature fluctuations [1][2]. In a lighting fixture enclosure, the system compensates for changes in size due to thermal expansion and contraction of components such as the optic, extrusion, and end caps [22]. Silicone’s dynamic response allows it to deform, reshape, expand, or contract without losing sealing integrity, even when annual temperature swings exceed 80 °C [19][22].
Material Properties Supporting Longevity
Silicone gaskets have a low durometer of about 20, enabling high flexibility and compressibility [1][2]. They also exhibit very high elongation at break—ranging from 650% to 750%—which allows them to stretch significantly and return to their original shape after deformation [1][2][19]. This elasticity ensures even pressure across sealing interfaces, which is critical under varying loads and temperatures.
Design Features Enhancing Durability
The design of the sealing system further enhances silicone’s performance. The gasket is guided by chamfered internal edges and overhanging lips to maintain position during expansion and contraction phases [1][2]. Additionally, silicone grease in the cavity fills microscopic imperfections, improving sealing while reducing friction and preventing wear [5][6].
Why EPDM and TPE Are Not Directly Compared
The provided research does not offer a direct comparison between EPDM, silicone, or TPE for compression set resistance under extreme thermal cycling. While EPDM is known for good heat and ozone resistance in broader engineering literature, it is not mentioned in the context of these specific conditions [17]. Similarly, TPE is not referenced at all.
Thermal Cycling Performance Validation
Silicone’s performance under thermal cycling is validated through various tests. In photovoltaic inverters, silicone gels retain flexibility and strength through repeated heating and cooling cycles [3]. Silicone-based materials have also demonstrated resilience in IEC 1646 and IEC 1215 humidity freeze tests, with no visual defects or significant power loss after conditioning [11][12].
Key Takeaways
- Silicone Gaskets: Best suited for IP65 seals due to high elasticity and resistance to thermal cycling.
- Design Enhancements: Features like chamfered edges and silicone grease improve durability under extreme conditions.
- Lack of Direct Comparison: No direct data on EPDM or TPE under the specific temperature swings in Romania.
Frequently Asked Questions
„`json
[
{
„q”: „How does silicone maintain its seal during thermal cycling?”,
„a”: „Silicone gaskets can deform, reshape, expand, and contract to compensate for changes due to thermal expansion [19][22].”
},
{
„q”: „What are the material properties of silicone that make it suitable?”,
„a”: „Silicone has a low durometer (about 20) enabling high flexibility and compressibility. It also exhibits very high elongation at break, ensuring even pressure across sealing interfaces [1][2].”
},
{
„q”: „Are there any tests validating silicone’s thermal cycling performance?”,
„a”: „Yes, silicone gels in photovoltaic inverters retain strength through repeated heating and cooling cycles. Silicone-based materials also pass IEC 1646 and IEC 1215 tests with no defects [3][11][12].”
}
]
„`
References
- [1] US8585245B2_-_Systems_and_methods_for_sealing_-_Google_Patents__154e7e2e — patent
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keep downward pressure on the gasket where it comes in contact with the optic 140 , thus providing seal. – the overhanging lip may also keep the silicone gasket 120 in tact during expansion and contraction phases. – a chamfered internal edge adds may also be added to the design. – the chamfered internal edge may increase the manufacturability of the design. – the tapered edge may lead the silicone gasket 120 into position keeping it from pinching or bowing. – Similar edges may be added to the extrusion for the purpose of maintaining an o-ring 130 in position or maintaining optic 140 in position. – silicone gasket 120 may be cut from a sheet of molded sheet rubber. – the molded sheet rubber may have a low durometer values, or moderately low durometer values. – the molded sheet rubber may have durometer values, such as about 20 durometers. – the molded sheet rubber may also have a relatively high elongation at break percentage, such as 650-750%. The relatively high elongation at break percentage may enable providing more even pressure on the areas where the sealing is provided, such as the optic 140 . – the silicone gasket 120 is compressed about 26.5% at nominal dimensions. In some embodiments, for every 50% of compression the internal elongation of the material is over 100%. – the design may be adjusted to exhibit a roughly 50% internal elongation of the material. This amount of internal elongation may still be sufficiently far from the maximum allowed, enabling the design to
- [2] US8585245B2_-_Systems_and_methods_for_sealing_-_Google_Patents__154e7e2e — patent
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In a further example, silicone gasket 120 may be cut from a sheet of molded sheet rubber. The molded sheet rubber may have a low durometer values, or moderately low durometer values. The molded sheet rubber may have durometer values, such as about 20 durometers. The molded sheet rubber may also have a relatively high elongation at break percentage, such as 650-750%. The relatively high elongation at break percentage may enable providing more even pressure on the areas where the sealing is provided, such as the optic 140. By compressing silicone gasket 120 by about 0.05 inches on a 0.188 inch thick silicone gasket 120, the silicone gasket 120 is compressed about 26.5% at nominal dimensions. In some embodiments, for every 50% of compression the internal elongation of the material is over 100%. As such, the design may be adjusted to exhibit a roughly 50% internal elongation of the material. This amount of internal elongation may still be sufficiently far from the maximum allowed, enabling the design to provide the seal within the spec of the material. This design may also prevent bowing or pinching of the silicone gasket 120 unevenly during compression. The combination of the material selected, compression, and durometer of the material may all come together to make the silicone gasket 120 to seal the design. In a further example, compression testing for a design of the components of the enclosure 100 may provide following results. The test may be performed with 30 Durometer Sil
- [3] Advanced_silicone_gels_protect_IGBT7_modules_in_PV_inverters__ca968923 — magazine
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gels also exhibit excellent thermal stability, the ability of a material to retain its physical properties when subjected to heat. Importantly, these gels maintain their flexibility and strength through repeated heating and cooling cycles, a common occurrence since solar power production and ambient temperatures increase during the day before power production stops and ambient temperatures fall at night. In power electronics like IGBT7 modules, thermal cycling is also important because load cycling and switching losses can cause temperatures to fluctuate significantly. Moisture resistance and high-voltage protection Advanced silicone gels resist moisture and contaminants that can cause short circuits or corrosion in electronics. When poured into an electronic enclosure, these gels encapsulate electronics and fill voids between IGBTs. Photovoltaic inverters are usually housed in metal or plastic cabinets, but poorly sealed doors, vents or cable entry points can allow the ingress of unwanted substances. Because PV enclosure cabinets are often located outdoors, the ingress of moisture and dust are concerns. These contaminants can also enter an enclosure during routine checks or maintenance activities. To help prevent contamination, PV enclosures are sealed using mechanical gaskets, but these seals are not enough. Ingress Protection (IP) standards describe the degree of protection that a sealed enclosure provides. Higher IP ratings denote greater levels of protection against wate
- [5] US8585245B2_-_Systems_and_methods_for_sealing_-_Google_Patents__154e7e2e — patent
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Compression ⁇ 0.030—Material fills the hole 0.042′′. – the silicone gasket may come in on the low end tolerance of the thickness, material to compress may be down to 0.008′′. If the machined end cap comes in on the low end tolerance of the depth of the pocket, material to compress will be down 0.005′′. These tolerances may take 0.013′′ off of our thickness of material to compress. This may bring our calculated 0.040 compression down to 0.027′′. – the material may fill approximately 0.042′′. If the optic comes in on the small side, it may be 0.006′′ smaller. If the gasket cut comes in on the high side, it may be 0.007′′ larger. – the dimensions of the silicone gasket 120 may be undersized by 0.003 as compared to the optic. If the machined end cap comes in on the high end width tolerance of the pocket, the gasket may fill out an additional 0.003′′. – silicone grease may be used as an additional sealant on the silicone gaskets 120 . Silicone grease may also provide additional level of protection and may improve the sealing. – Grease such as the silicone grease – the grease may be used on the inside of the optic 140 cavity of the silicone gasket 120 or on the optic 140 . – the grease may also be used between the optic 140 and the o-ring 130 . – the grease fills in any microscopic scratches and cracks, thus providing a seal. – the grease provides a lubricant for the piston effect of the optic 140 as the optic shrinks and contracts. – based on the coefficient of thermal expansion o
- [6] US8585245B2_-_Systems_and_methods_for_sealing_-_Google_Patents__154e7e2e — patent
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in moving, the grease may ensure that the optic 140 will not pinch or pull the silicone gasket 120 during this movement. – assembly of the enclosure of the lighting fixture may start with adding some grease to the inside of the optic cavity of the silicone gasket. – the silicone gasket Once the silicone gasket has been pre-greased, it may be slid onto the optic overhanging the extrusion and the 4 o-rings also overhanging the extrusion may be slid through the gasket. – the o-rings may be cut flush with the outward face of the gasket which may be compressed against the end cap. – the end cap then may be slid over the top of the gasket and compressed by evenly tightening the 5 screws which are inserted through the end cap, through the gasket, and into the threaded holes in the extrusion. When the screws compress the gasket, the openings in the gasket may begin to squeeze. – the holes for the screws may be compressed around the screw and seal it. – the outside of the interface between the end cap and the extrusion may also be sealed by this compression of the gasket against the flat of the extrusion. – the gasket over the top of the optic may also seal and the lip on the end cap may be keep even downward pressure against the optic. – all four o-rings may be compressed around and sealed while the ones on the top are also tightly squeezed against the side of the optic keeping it sealed. – the label may be added and the end cap assembly may then be complete. – the enclosure may be t
- [11] US8847063B2_-_Encapsulation_of_solar_cells_-_Google_Patents__afa4ee8d — patent
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% of diallylmaleate cure inhibitor, 0.11 weight % of platinum catalyst and 0.38 weight % of dimethylhydrogen siloxy terminated trifluoropropyl silsesquioxane. The encapsulant was applied onto the module manually and after levelling, was cured in a standard oven at a temperature of 120° C. for 20 mins. The electrical capabilities were measured before and after the 10 day aging process set down in the Humidity Freeze test described in IEC 1646, which comprised 10 cycles of 24 hours with the temperature varying from −40° C. to 85° C. in 85% relative Humidity (RH) and the results are provided in Table 4 below None of the samples tested showed any discoloration or delamination and all samples passed the standard wet leakage current test as defined in the IEC 1646 after the conditioning period. In accordance with the requirements of IEC 1646 after conditioning a sample should not show any open circuit or leakage current, any visual defect and any decrease in maximum power should not be greater than 5% all of which the thin film modules of the present invention using the encapsulant alone (i.e. no adhesive layer required). These findings are totally contrary to the expectations of the industry and use of a silicone encapsulant as hereinbefore described is able to provide the level of protection suitable for solar or photovoltaic module. With the exception that the glass was washed with ethanol instead of acetone and that a different type of commercially available solar cell was used
- [12] US8847063B2_-_Encapsulation_of_solar_cells_-_Google_Patents__afa4ee8d — patent
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after application by a curtain coater the adhesive was cured in the module in a Mid IR oven having a temperature profile of 120° C. and a speed of 0.5 m per minute for a length of 5 m. The electrical capabilities were measured before and after the 10 day aging process set down in the Humidity Freeze test described in IEC 1215, which comprised 10 cycles of 24 hours with the temperature varying from −40° C. to 85° C. in 85% relative Humidity (RH) Sample Characterization: Electrical characterization of the specimen has been done before and after conditioning, results are summarized in table 6 below None of the samples were showing discoloration or delamination and were passing the wet leakage current test as described in the IEC 1215 after the conditioning. In accordance with the requirements of IEC 1215 after conditioning a sample should not show any open circuit or leakage current, any visual defect and any decrease in maximum power should not be greater than 5% all of which the thin film modules of the present invention using the encapsulant alone (i.e. no adhesive layer required). These findings are totally contrary to the expectations of the industry and use of a silicone encapsulant as hereinbefore described is able to provide the level of protection suitable for solar or photovoltaic module of a polycrystalline Silicon wafer type. In this case the only difference from example 8 was the change in the solar cells used. The adhesive and encapsulant compositions were as descr
- [17] WO2012078765A2_-_Self-cleaning_solar_panels_and_-_Google_Patents__8226f0d9 — patent
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side. 10. Minimization of UV radiation related damage to the EDS and improving durability in outdoor applications (a) Stabilizers, blockers, and absorbers are often used to promote UV resistance. However, the modifications should not compromise the transparency of the plastic in the visible spectrum. The stabilizers react with UV radiation. One of the common stabilizers is called HALS (Hindered Amine Light Stabilizer). These molecules absorb the excited groups and prevent the chemical reaction of the radicals. Fluoropolymer has good UV resistance because of its strong carbon- fluorine (C-F) bond. Fluoropolymer resin (such as marketed by DuPont as Tefzel) has transparency over 94% in the visible range. Polyurethane (PU) and silicone have good UV resistance. (b) The best UV resistant polymers are the imides. polyimide (PEI) has been used for space applications. Fluorescent whitening agents (FWA) can be added to the polymer. The FWA molecules can absorb UV photons and undergo fluorescent radiation in the visible range providing additional radiation energy to the solar cells for energy conversion. Application of UV stabilizers helps in lowering the temperature of the crystalline solar cells by absorbing high energy photons and radiating part of the energy in the visible radiation. 11. Adding sensors and control systems for automated removal of dust when needed thus conserving power (a) The control circuitry 44 of Figure 6 may include a photodiode based sensor used to monitor dust
- [19] US8585245B2_-_Systems_and_methods_for_sealing_-_Google_Patents__154e7e2e — patent
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expand and press against the silicone gasket to provide a water-right seal. The silicone gasket may morph, reshape and/or contract to compensate for the expanding optic. Upon cooling of the optic, the optic may contract and silicone gasket may maintain the water-tight seal by morphing, reshaping and or expanding to compensate for the contracting optic. In some embodiments, the silicone gasket comprises one of a rubber, silicone, latex or elastic polymer material. In further embodiments, the silicone gasket comprises the material with an elongation percentage of about 720 when press cured at 5 minutes at 166 Celsius. In still further embodiments, the silicone gasket comprises the material having tear strength of about 15 kN/m when press cured for about 5 minutes at 166 Celisus. In yet further embodiments, the deformable gasket comprises a flexible and deformable material having tensile strength of about 6.5 MPa when press cured for 5 minutes at 166 C. In some aspects, a lighting fixture providing a water-tight seal to optical components. The lighting fixture may include an acrylic optic positioned along a length of an opening of a extrusion of an enclosure. The lighting fixture may also include an o-ring positioned between the acrylic optic and walls of the extrusion the o-ring providing a pressure and a seal between the acrylic optic and walls of the extrusion. The lighting fixture may include an end cap enclosing a silicone gasket interfacing with an end of the acrylic optic
- [22] US8585245B2_-_Systems_and_methods_for_sealing_-_Google_Patents__154e7e2e — patent
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the changes in sizes due to temperature changes of either optic 140 or the end caps 110. The silicone gasket 120 may further be designed to provide a tight seal between the extrusion 105 and the end caps 110 once the end caps 110 are attached to the extrusion 105. The silicone gasket 120 may provide the seal by deforming to compensate for any change in size or shape by any of the enclosure 100 components. In some embodiments, there are two or more silicone gaskets 120 of same or different shape and size on each side of the optic 140. Some silicone gaskets 120 may comprise through holes, while others may comprise holes which are not through holes. Once the end of the optic 130 is inserted into the silicone gasket 120 enclosed within an end cap 110, the silicone gasket 120 may compress or contract whenever the optic 140 expands, extends or increases in size due to temperature change. Similarly, the silicone gasket 120 may decompress or expand whenever the optic 130 shrinks, shortens or decreases in size due to any temperature change. The silicone gasket 120 may similarly also shrink or expand and therefore compensate for any movements of extrusion 105 or end cap 110. Therefore, the silicone gasket 120 may maintain the watertight seal despite any movements of the optic, extrusion 105 or end cap 110 due to any changes in temperature. O-ring 130 may be designed to have a specific hardness, flexibility, size and shape to fit snuggly between the optic 140 and the extrusion 105. In a
keep downward pressure on the gasket where it comes in contact with the optic 140 , thus providing seal. – the overhanging lip may also keep the silicone gasket 120 in tact during expansion and contraction phases. – a chamfered internal edge adds may also be added to the design. – the chamfered internal edge may increase the manufacturability of the design. – the tapered edge may lead the silicone gasket 120 into position keeping it from pinching or bowing. – Similar edges may be added to the extrusion for the purpose of maintaining an o-ring 130 in position or maintaining optic 140 in position. – silicone gasket 120 may be cut from a sheet of molded sheet rubber. – the molded sheet rubber may have a low durometer values, or moderately low durometer values. – the molded sheet rubber may have durometer values, such as about 20 durometers. – the molded sheet rubber may also have a relatively high elongation at break percentage, such as 650-750%. The relatively high elongation at break percentage may enable providing more even pressure on the areas where the sealing is provided, such as the optic 140 . – the silicone gasket 120 is compressed about 26.5% at nominal dimensions. In some embodiments, for every 50% of compression the internal elongation of the material is over 100%. – the design may be adjusted to exhibit a roughly 50% internal elongation of the material. This amount of internal elongation may still be sufficiently far from the maximum allowed, enabling the design to
In a further example, silicone gasket 120 may be cut from a sheet of molded sheet rubber. The molded sheet rubber may have a low durometer values, or moderately low durometer values. The molded sheet rubber may have durometer values, such as about 20 durometers. The molded sheet rubber may also have a relatively high elongation at break percentage, such as 650-750%. The relatively high elongation at break percentage may enable providing more even pressure on the areas where the sealing is provided, such as the optic 140. By compressing silicone gasket 120 by about 0.05 inches on a 0.188 inch thick silicone gasket 120, the silicone gasket 120 is compressed about 26.5% at nominal dimensions. In some embodiments, for every 50% of compression the internal elongation of the material is over 100%. As such, the design may be adjusted to exhibit a roughly 50% internal elongation of the material. This amount of internal elongation may still be sufficiently far from the maximum allowed, enabling the design to provide the seal within the spec of the material. This design may also prevent bowing or pinching of the silicone gasket 120 unevenly during compression. The combination of the material selected, compression, and durometer of the material may all come together to make the silicone gasket 120 to seal the design. In a further example, compression testing for a design of the components of the enclosure 100 may provide following results. The test may be performed with 30 Durometer Sil
gels also exhibit excellent thermal stability, the ability of a material to retain its physical properties when subjected to heat. Importantly, these gels maintain their flexibility and strength through repeated heating and cooling cycles, a common occurrence since solar power production and ambient temperatures increase during the day before power production stops and ambient temperatures fall at night. In power electronics like IGBT7 modules, thermal cycling is also important because load cycling and switching losses can cause temperatures to fluctuate significantly. Moisture resistance and high-voltage protection Advanced silicone gels resist moisture and contaminants that can cause short circuits or corrosion in electronics. When poured into an electronic enclosure, these gels encapsulate electronics and fill voids between IGBTs. Photovoltaic inverters are usually housed in metal or plastic cabinets, but poorly sealed doors, vents or cable entry points can allow the ingress of unwanted substances. Because PV enclosure cabinets are often located outdoors, the ingress of moisture and dust are concerns. These contaminants can also enter an enclosure during routine checks or maintenance activities. To help prevent contamination, PV enclosures are sealed using mechanical gaskets, but these seals are not enough. Ingress Protection (IP) standards describe the degree of protection that a sealed enclosure provides. Higher IP ratings denote greater levels of protection against wate
Compression ⁇ 0.030—Material fills the hole 0.042′′. – the silicone gasket may come in on the low end tolerance of the thickness, material to compress may be down to 0.008′′. If the machined end cap comes in on the low end tolerance of the depth of the pocket, material to compress will be down 0.005′′. These tolerances may take 0.013′′ off of our thickness of material to compress. This may bring our calculated 0.040 compression down to 0.027′′. – the material may fill approximately 0.042′′. If the optic comes in on the small side, it may be 0.006′′ smaller. If the gasket cut comes in on the high side, it may be 0.007′′ larger. – the dimensions of the silicone gasket 120 may be undersized by 0.003 as compared to the optic. If the machined end cap comes in on the high end width tolerance of the pocket, the gasket may fill out an additional 0.003′′. – silicone grease may be used as an additional sealant on the silicone gaskets 120 . Silicone grease may also provide additional level of protection and may improve the sealing. – Grease such as the silicone grease – the grease may be used on the inside of the optic 140 cavity of the silicone gasket 120 or on the optic 140 . – the grease may also be used between the optic 140 and the o-ring 130 . – the grease fills in any microscopic scratches and cracks, thus providing a seal. – the grease provides a lubricant for the piston effect of the optic 140 as the optic shrinks and contracts. – based on the coefficient of thermal expansion o
in moving, the grease may ensure that the optic 140 will not pinch or pull the silicone gasket 120 during this movement. – assembly of the enclosure of the lighting fixture may start with adding some grease to the inside of the optic cavity of the silicone gasket. – the silicone gasket Once the silicone gasket has been pre-greased, it may be slid onto the optic overhanging the extrusion and the 4 o-rings also overhanging the extrusion may be slid through the gasket. – the o-rings may be cut flush with the outward face of the gasket which may be compressed against the end cap. – the end cap then may be slid over the top of the gasket and compressed by evenly tightening the 5 screws which are inserted through the end cap, through the gasket, and into the threaded holes in the extrusion. When the screws compress the gasket, the openings in the gasket may begin to squeeze. – the holes for the screws may be compressed around the screw and seal it. – the outside of the interface between the end cap and the extrusion may also be sealed by this compression of the gasket against the flat of the extrusion. – the gasket over the top of the optic may also seal and the lip on the end cap may be keep even downward pressure against the optic. – all four o-rings may be compressed around and sealed while the ones on the top are also tightly squeezed against the side of the optic keeping it sealed. – the label may be added and the end cap assembly may then be complete. – the enclosure may be t
% of diallylmaleate cure inhibitor, 0.11 weight % of platinum catalyst and 0.38 weight % of dimethylhydrogen siloxy terminated trifluoropropyl silsesquioxane. The encapsulant was applied onto the module manually and after levelling, was cured in a standard oven at a temperature of 120° C. for 20 mins. The electrical capabilities were measured before and after the 10 day aging process set down in the Humidity Freeze test described in IEC 1646, which comprised 10 cycles of 24 hours with the temperature varying from −40° C. to 85° C. in 85% relative Humidity (RH) and the results are provided in Table 4 below None of the samples tested showed any discoloration or delamination and all samples passed the standard wet leakage current test as defined in the IEC 1646 after the conditioning period. In accordance with the requirements of IEC 1646 after conditioning a sample should not show any open circuit or leakage current, any visual defect and any decrease in maximum power should not be greater than 5% all of which the thin film modules of the present invention using the encapsulant alone (i.e. no adhesive layer required). These findings are totally contrary to the expectations of the industry and use of a silicone encapsulant as hereinbefore described is able to provide the level of protection suitable for solar or photovoltaic module. With the exception that the glass was washed with ethanol instead of acetone and that a different type of commercially available solar cell was used
after application by a curtain coater the adhesive was cured in the module in a Mid IR oven having a temperature profile of 120° C. and a speed of 0.5 m per minute for a length of 5 m. The electrical capabilities were measured before and after the 10 day aging process set down in the Humidity Freeze test described in IEC 1215, which comprised 10 cycles of 24 hours with the temperature varying from −40° C. to 85° C. in 85% relative Humidity (RH) Sample Characterization: Electrical characterization of the specimen has been done before and after conditioning, results are summarized in table 6 below None of the samples were showing discoloration or delamination and were passing the wet leakage current test as described in the IEC 1215 after the conditioning. In accordance with the requirements of IEC 1215 after conditioning a sample should not show any open circuit or leakage current, any visual defect and any decrease in maximum power should not be greater than 5% all of which the thin film modules of the present invention using the encapsulant alone (i.e. no adhesive layer required). These findings are totally contrary to the expectations of the industry and use of a silicone encapsulant as hereinbefore described is able to provide the level of protection suitable for solar or photovoltaic module of a polycrystalline Silicon wafer type. In this case the only difference from example 8 was the change in the solar cells used. The adhesive and encapsulant compositions were as descr
side. 10. Minimization of UV radiation related damage to the EDS and improving durability in outdoor applications (a) Stabilizers, blockers, and absorbers are often used to promote UV resistance. However, the modifications should not compromise the transparency of the plastic in the visible spectrum. The stabilizers react with UV radiation. One of the common stabilizers is called HALS (Hindered Amine Light Stabilizer). These molecules absorb the excited groups and prevent the chemical reaction of the radicals. Fluoropolymer has good UV resistance because of its strong carbon- fluorine (C-F) bond. Fluoropolymer resin (such as marketed by DuPont as Tefzel) has transparency over 94% in the visible range. Polyurethane (PU) and silicone have good UV resistance. (b) The best UV resistant polymers are the imides. polyimide (PEI) has been used for space applications. Fluorescent whitening agents (FWA) can be added to the polymer. The FWA molecules can absorb UV photons and undergo fluorescent radiation in the visible range providing additional radiation energy to the solar cells for energy conversion. Application of UV stabilizers helps in lowering the temperature of the crystalline solar cells by absorbing high energy photons and radiating part of the energy in the visible radiation. 11. Adding sensors and control systems for automated removal of dust when needed thus conserving power (a) The control circuitry 44 of Figure 6 may include a photodiode based sensor used to monitor dust
expand and press against the silicone gasket to provide a water-right seal. The silicone gasket may morph, reshape and/or contract to compensate for the expanding optic. Upon cooling of the optic, the optic may contract and silicone gasket may maintain the water-tight seal by morphing, reshaping and or expanding to compensate for the contracting optic. In some embodiments, the silicone gasket comprises one of a rubber, silicone, latex or elastic polymer material. In further embodiments, the silicone gasket comprises the material with an elongation percentage of about 720 when press cured at 5 minutes at 166 Celsius. In still further embodiments, the silicone gasket comprises the material having tear strength of about 15 kN/m when press cured for about 5 minutes at 166 Celisus. In yet further embodiments, the deformable gasket comprises a flexible and deformable material having tensile strength of about 6.5 MPa when press cured for 5 minutes at 166 C. In some aspects, a lighting fixture providing a water-tight seal to optical components. The lighting fixture may include an acrylic optic positioned along a length of an opening of a extrusion of an enclosure. The lighting fixture may also include an o-ring positioned between the acrylic optic and walls of the extrusion the o-ring providing a pressure and a seal between the acrylic optic and walls of the extrusion. The lighting fixture may include an end cap enclosing a silicone gasket interfacing with an end of the acrylic optic
the changes in sizes due to temperature changes of either optic 140 or the end caps 110. The silicone gasket 120 may further be designed to provide a tight seal between the extrusion 105 and the end caps 110 once the end caps 110 are attached to the extrusion 105. The silicone gasket 120 may provide the seal by deforming to compensate for any change in size or shape by any of the enclosure 100 components. In some embodiments, there are two or more silicone gaskets 120 of same or different shape and size on each side of the optic 140. Some silicone gaskets 120 may comprise through holes, while others may comprise holes which are not through holes. Once the end of the optic 130 is inserted into the silicone gasket 120 enclosed within an end cap 110, the silicone gasket 120 may compress or contract whenever the optic 140 expands, extends or increases in size due to temperature change. Similarly, the silicone gasket 120 may decompress or expand whenever the optic 130 shrinks, shortens or decreases in size due to any temperature change. The silicone gasket 120 may similarly also shrink or expand and therefore compensate for any movements of extrusion 105 or end cap 110. Therefore, the silicone gasket 120 may maintain the watertight seal despite any movements of the optic, extrusion 105 or end cap 110 due to any changes in temperature. O-ring 130 may be designed to have a specific hardness, flexibility, size and shape to fit snuggly between the optic 140 and the extrusion 105. In a