the critical role of pv material durability to ensure...
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The Critical Role of PV Material Durability to Ensure System Longevity
Solar Energy UK October, 2014
Birmingham
Stephan Padlewski Marketing Manager, EMEA
DuPont Photovoltaic Solutions
© DuPont 2014
Tedlar® PVF Films for Backsheet
Protecting PV modules
DuPont Ionomer Encapsulants
Delivering long-term protection of cells
Solamet® Metallization Pastes
Driving higher energy conversion efficiency
DuPont Photovoltaic Materials
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• DuPont has been ranked among the top 10 companies for solar energy patent grants
• 40 Year track record in photovoltaic materials, service and support
14 Solar Plants on DuPont Sites 11 Million kWh/year
78 © DuPont 2014
Shenzhen, China Taoyuan, Taiwan Hyderabad, India
Rooftop Thin Film & c-Si Rooftop Thin Film Rooftop c-Si
Rooftop Thin Film
Parlin, NJ, USA
Ground Mount Thin Film
Tlalnepantla, Mexico
Ground Mount c-Si & Thin Film
Waimea, HI, USA
Ground Mount c-Si
Ground Mount c-Si
Wilmington, DE, USA Cernay, France
Ground Mount c-Si
© DuPont 2014
© DuPont 2014
3 Areas Driving Next Wave of Growth in Solar
Efficiency Lifetime
Continuous cell performance
improvement from innovative materials
Safe, in-spec power generation for 25 or
more years
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Cost
Continuous improvement in material content cost, laydown and system designs
Effic
ienc
y (%
)
Year
Conventional Cells Solamet® PV14x
High Efficiency Cells Solamet® PV15x, 16x
High Efficiency LDE Cells
Solamet® PV17x, 18x
New LBSF (LDE) Architectures
Solamet® PV36x
N-type Cells Bi-facial: Solamet® PV3Nx
IBC:One paste solution
Back Contact MWT : Solamet® PV70x, PV71x
LCOE Reduction through Efficiency Improvement Roadmap
DuPont™ Solamet® metallization technology is on target to help achieve 22% cell efficiency in 2015
80 © DuPont 2014
© DuPont 2014
Impressive Track Record of Solamet® Paste Technology
Source: DuPont
Approx. 70% reduction in metal laydown
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© DuPont 2014
3 Areas Driving Next Wave of Growth in Solar
Efficiency Lifetime Cost
Continuous cell performance
improvement from innovative materials
Safe, in-spec power generation for 25 or
more years
Continuous improvement in material content cost, laydown and system designs
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System Lifetime Impacts Investment Returns
8
Three factors significantly impact system lifetime – bill of materials, component design and manufacturing practices
© DuPont 2014
DuPont Ionomer Na+ “Shield” to Prevent PID Degradation
• 50-100um Ionomer film between EVA and glass prevents PID
• Ionomers pass 500 hrs of simulated PID test (Strd test is 96 hrs)
• EVA-based encapsulants show severe degradation, even ‘PID-resistant’ EVAs
• PID-free performance has been validated at several potential customers
85C / 85% / -1000V
Ionomers ~0%
EVAs >>5%
Source: DuPont-Yingli EU PVSEC 2014 9 © DuPont 2014
© DuPont 2014
Qualification Tests 25 Years In-Field
* Artur Skoczek, Tony Sample and Ewan D. Dunlop, The Results of Performance Measurements of Field-aged Crystalline Silicon Photovoltaic Modules, Wiley InterScience, 2008
• Multiple environmental and mechanical stresses
• 171 kWh per m2 rear side of UV radiation (temperate) *
• 1000s of thermal cycles
• Higher operating temperature
• Stresses endured with solar load (in operation)
• 1 to 2 stresses in series
• 15 kWh per m2 of UV radiation (front) – no irradiation on the back
• 200 thermal cycles
• No solar load (not in operation) in testing chambers
Industry Standards not Reflecting Long-term Performance
“Long-term outdoor exposure is the ultimate test for all module components, material quality and manufacturing quality.”*
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IEC testing protocols do not adequately simulate the rooftop stress environment
© DuPont 2014
Stress Intensity: Operating Temperature
Source: Creep in Photovoltaic Modules: Examining the Stability of Polymeric Materials and Components (2010) 35th IEEE Photovoltaic Specialists Conference (PVSC ’10) Honolulu David C. Miller, Michael Krempe, Stephen Glick and Sarah Kurtz Viridian Solar – January 2014
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BIPV BAPV Flat
+15ºC +15ºC
Ground Air
+10ºC
Type of module installation impacts thermal stress level
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Daily & Seasonal Temperature Fluctuations Stress PV Modules
Daily Cycling ∆ = 20-30 °C
Seasonal Variation ∆ = ~30 °C
Partial Shading Can Cause Locally Elevated Temperatures (Hot Spots)
Source: http://www.calsolarworks.com/demo/shading-on-solar/ Source: http://www.project2061.org/publications/EducatorsGuide/online/Examples/Seasons/seasons.html
Stress Intensity: Thermal Cycling
• PV modules experience thousands of thermal cycles over their expected 20+ year lifetime
• Risk of partial shading is typically higher on rooftop projects,
increasing the risk of diffused hot spot formation
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Backsheets account for more than 40% of all the visual changes observed
Defect Types and Occurrence
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Example of Defects Observed in the Field
4 Years of operation in Valencia, Spain. 2.3 MW field - estimated that
approximately 5,000 modules in the park affected
Some modules failed wet insulation test No loss of power to date 2 Year warranty on materials and
workmanship had elapsed with no replacement of panels
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PET-based backsheet 4 years of operation in Valencia, Spain Module taken out of operation
Very deep crack all the way through the depth of the backsheet. Solder ribbon and metallization visible.
Example of Defects Observed in the Field
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Frontside yellowing 4 Different countries (Belgium, Spain,
USA and Germany) – 50% of occurrence
Modules less than 5 years in the field
5 Different manufacturers
Example of Defects Observed in the Field
© DuPont 2014
3-Year old system (Spain) Module removed from service Cracking & Yellowing Hot spot caused backsheet to burn Areas around high temperature
regions or hot spots may predict how materials will age
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Yellowing, Cracking and Burned
Example of Defects Observed in the Field
© DuPont 2014
10-Year old module DuPont™ Tedlar® film-based backsheet
10-Year old module PET-based backsheet
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Example of Defects Observed in the Field
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Backsheets can Impact Long-Term Power Performance
Source: Joint Research Centre (Italy); AIST (Japan)
PET-based Tedlar®-based
9% 0%
Pow
er lo
ss p
er y
ear
5-14 years 11-19 years
BoM can significantly impact the long-term power output of the PV module, affecting both the LCOE and the IRR
Backsheet Impact First US utility scale – 1984 Sacramento, CA DuPont™ Tedlar® - based backsheet DuPont™ Solamet® metallization <0.9%/Yr Power Loss for 30 years
© DuPont 2014
First grid-connected system in Europe (Switzerland) 10 kW rooftop system DuPont™ Tedlar® film-based backsheet Low 0.4% annualized power loss after 31 years of service
University of Applied Sciences and Arts of Southern Switzerland (SUPSI) Powering Reliably Since 1982
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Tedlar® Protecting Rooftops for More Than 30 Years
Source: DuPont Photo courtesy of Sharp Corporation
Installed in 1983 Nara, Japan
97 © DuPont 2014
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Summary
Think in terms of £/kWh instead of £/Wp
High efficiency modules can reduce system costs – especially on rooftops
Rooftops induce high thermal stress
Ground mounts induce UV / thermal stress
Know what’s in your module
Select backsheets with demonstrated track record in the field
Work with well-established industry leaders up and down the value chain.
(Picture of rooftop)
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