current trends in backsheet evolution
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Current Trends in Backsheet Evolution
Prepared and presented by:
Marina TemchenkoR&D ManagerMadico, Inc.March 2012
Presentation Outline
1. Backsheet history
2. Current trends in Backsheet design
3. Backsheet contribution to module performance
4. New Technologies
5. Conclusions
Backsheet History
Required performance properties:
1. Mechanical protection2. Electrical insulation3. Water/Moisture vapor resistance4. Solvent resistance5. UV stability6. Adherence to encapsulant7. Adherence to sealants, labels, etc8. Thermal stability9. Dimensional stability10. Flame retardancy11. Compatibility with module
components
The backsheet is an outer layer of the module; Often a highly engineered, multi-layered structure.
Backsheets HistoryFrom Tedlar to New Materials
Tedlar®/Polyester/Tedlar®designs
TechnicalPerformanceEvolution
Time
Tedlar®/Polyester/EVAdesigns
Madico Patentcirca 2005
All Polyesterdesigns
Protekt® Coating/Polyester/EVAdesigns
Alternative Coatings(fluorinated or non)/
PE/Other?designs
Alternative Process Methodsdesigns
Current Trend: Superior Cost Performance
The Holistic Design ProcessCreativity/Innovation/Action
Sequential Logic is the key to Innovative Backsheet Design!
1. It begins with the outer Weather-able Layer:
Composition Choice: A) Inherently weather-able polymers, or
B) Additive-compounded polymers
Thickness Choice: A) Commercially available films
B) Precision Coating
2. Next in the chain is the Inner Layer:
3. The third building block: the interior Outer Layer:
Composition Choice: A) Degree of Reflectivity B) Thermal Conductivity
C) Compliment to Module Design
1. For Bi-facial Modules
2. For back-contact cells
1. Polyethylene terephtalate: A) Hydrolytically unstable B) Cost
Current design
2. Polyamides
3. Polyolefins
4. Others
Weather-able Layer: Composition Choice
1. Inherently weather-able polymersa. Fluoropolymers
2. Additive-compounded polymersa. Wide range of base resins – all rely on the
presence, performance, and durability of additives
*International Union of Pure and Applied Chemistry (1994). "Bond dissociation energy"Compendium of Chemical Terminology (Internet edition)
Bond strength488 kJ/mol
Bond strength348 kJ/mol
TheSmart Choice!
Weather-able Layer:Precise Thickness
Weather-able Layer: Durability and material selection
Product 1Product 2
Interior Outer Layer (Adjacent to the encapsulant)
Performance Requirements:
1. Excellent adhesion to the encapsulant2. Low moisture vapor transmission3. Good dielectric properties4. Increased reflectivity5. Enhanced thermal conductivity
Interior Outer Layer (Adjacent to the encapsulant)
Differential Performance Measures:1. Reflectivity!
Increased reflectivity results in higher PV module power output
Pmax vs. Reflectance
y = 0.0189x + 76.523
R2 = 0.9863
77.6
77.8
78
78.2
78.4
78.6
78.8
79
79.2
60 65 70 75 80 85 90 95Reflectance (%)
Pm
ax (
W)
Interior Outer Layer (Adjacent to the encapsulant)
Differential Performance Measures:1. Reflectivity 2. Sustained Reflectivity over module
performance life
Product 1Product 2
Current TrendAdhesive-less construction
Possibilities:• Coating/PET/Coating• Coating/PET/extruded layer
Possible Benefits:• “Greener” manufacturing process – less VOC• Elimination of weak link – an adhesive
Adhesive-less construction
Product 1 Product 2
Compliment PV Module Designs Bifacial Solar Cells
• Converts the sunlight incident on both sides of the modules
• Increase module efficiency by 3-4%
• Requires transparent backsheet
Transparent Backsheets
Transparent Backsheets
Conclusion
1. High performance Low cost backsheets
2. Specifically designed films or coatings for PV applications, replacing off the shelf pre-engineered films
3. Adhesiveless construction
4. Compliment Module Design
Amy Schweighardt Andrea JonesBrad Forest Dave Avison Katrina SampsonRobert ComeauSam Lim Shreyans ShingiTony LimVenkatesh Natarajan
Special thanks to the contributors of this presentation
Questions?
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