DuPont Photovoltaic Solutions Risk mitigation strategies for solar assets by climate type
and application sensitivity
Introducing innovation for bifacial c-Si panels
21 June 2018
Dr. Stephan Padlewski, Marketing Leader, EMEA
DuPont Photovoltaic Solutions
Photovoltaic Solutions
DuPont™ Tedlar®
PVF Films for Backsheet
Protecting PV
modules
DuPont™ Solamet® Metallization Pastes
Driving higher energy
conversion efficiency
DuPont Photovoltaic Materials Portfolio
© DuPont 2018 2
Over 50% of panels installed in the field since 1975 contain DuPont materials
PV LCOE
• System Lifetime • Reliability
• Durability
• System Efficiency • Shading / Dusting
• Low-light Performance
• Design,…
÷
System
Revenue
Return
Lifetime Power
Output (kWh)
System
Cost ($)
Levelized Cost of Energy (LCOE)
• Modules
• BoS
• Installation
• Financing
Initial Cost
Operating
Cost • O&M
• Interest
© DuPont 2018 3
The Backsheet is Critical for Protecting the PV Panel
Ultra Violet (UV)
• Transmitted
• Reflected
Physical Protection
• Abrasion
• Impact
Corrosive Environment
• Atmospheric chemicals
• Ammonia
• Marine environment
Stress Environment
• Peak
• Cycling
Temperature
• Humidity
• Precipitation
• Condensation
Moisture
Inner Layer
Middle Layer
Outer Layer
Backsheet structure
© DuPont 2018 4
Backsheet must provide reliable electrical protection of module
over the expected lifetime (and beyond)
Global DuPont Field Surveys (2017)
Source: DuPont Field Module Program 2017 analysis
Note: All percentage numbers are based on MW
• Surveyed: 286 Installations in North America, Europe & Asia Pacific
• Figures reported below: 45 module manufacturers, 1,047 MW > 4.2 MM modules
• Range of exposure: from newly commissioned modules to 30 years in service
• From multiple climates
5
22.5% of panels affected
© DuPont 2018
Backsheet is one of the main components affected
Climatic Sensitivity vs. Polymer Degradation
Source: DuPont Field Module Program 2017
Note: All percentage numbers are based on MW
Temperature
6
-
5,0
10,0
15,0
20,0
25,0
Hot Tropical Temperate
Def
ects
in %
Backsheet
Encapsulant
© DuPont 2018
Higher temperature seems to accelerate degradation rates of the
encapsulant and backsheet
Application Sensitivity
Source: DuPont Field Survey 2017
Ground Mounted Rooftop Mounted
Temperature
7
77,2%
11,9%
9,2% 1,3%
0,4%
67,5%
9,7%
22,3%
0,3% 0,1%
No defects % Cell % Backsheet % EVA % Other defects %
© DuPont 2018
Higher defect rates for rooftop vs ground installations.
Differences are likely due to higher temperatures for rooftop
systems
Types of Degradation Affecting the Backsheet
Source: DuPont Field Survey 2016
© DuPont 2018 8
Cracking and delamination represent serious threats to the
electrical protection of the panel (59% of defects).
Yellowing is an indicator that the polymer has started to degrade
5%
54%
3%
38%
Delamination Cracking
Air side yellowing Front side Yellowing
Material Sensitivity vs. Backsheet Defect Rates
Defect rate as a function of backsheet used
PA = Polyamide
PVDF = Polyvinylidene Difluoride
PET = Polyethylene Terephthalate
FEVE – Fluoroethylene Vinylether
* No field data available © DuPont 2018 8
DuPont Sequential Stress Test (MAST) vs. Field
IEC 6125 MAST (DuPont)
10 © DuPont 2018
Sequential tests correlate better with degradation seen in the field • Combine most important stress factors
• Use stress levels / dosages that match field exposures
• Accelerate with highest temperature but • Do NOT produce degradation not found in the field
Stress PET PVDF PA Tedlar® Comment
Field Yellowing
Mech Prop Loss
Cracking
Cracking
Front Side
Yellowing
Yellowing
Mech Prop Loss
Cracking
Low
defects
Effects of simultaneous
and sequential stresses
Damp Heat (1000 hrs) Slight Yellowing No Change Mech Prop Loss No Change Misses UV degradation
UV (4000 hrs) Yellowing
Mech Prop Loss No Change Mech Prop Loss No Change
Misses hydrolysis and
moisture
DH/UV/TC (MAST
Sequential Test)
Yellowing
Mech Prop Loss Cracking
Cracking
Front Side Yellowing
Yellowing
Mech Prop Loss Cracking
No Change Combines key stresses Gives best correlation
Bifacial: An Opportunity to Lower LCOE
Benefits
• Can boost power output by 8-30% • System design, e.g. tracker, pitched
• Ground characteristics, e.g. albedo
• Cell technology
• Can use existing cell PV manufacturing
infrastructure
Concerns
• Glass-glass: weight, risk of cracking
• Frameless (usually), mounting
• Higher cost non-EVA encapsulant
required • To prevent acetic acid entrapment
• Higher NOCT (by >3oC)
• Cost premium vs standard
• Lack of long track record in the field,
bankability
Source: LONGi Solar
For ground installations operating in high albedo environments
© DuPont 2018 11
Glass-Glass Panels in the Field
2008: Cracking glass 2016: Bending
2016: Edge cracking, bending 2016: Delamination
© DuPont 2018 12
Durable Clear Tedlar® for Transparent Backsheets
Transparent Tedlar®
based backsheet
© DuPont 2018 13
Field-proven
First year of
service: 2003
Location:
Italy
Key Properties
• Field-proven, 20+ years
• High transparency
• Compatible with incumbent production assembly
• Blocks UV durably
• Compatible with EVA (breathable)
• Lighter weight
• Easier mounting, framed panels
-25%
-20%
-15%
-10%
-5%
0%
5%
10%
15%
20%
25%
30%
20% 22% +10% +20% 20 y
30 y
Efficiency (18%)
Power Output (1800kWh/kWp)
Lifetime (25 years)
LCOE Sensitivity
• Irradiation
• Bifacial
• Tracking
• PERC
• HTJ
• Panel Packaging
• BoS Components
• BoM/Panels
2.3 USD cents/kWh
LCOE
Variation
© DuPont 2018 14
Summary
Think in terms of USD/kWh rather than USD/Wp - reliability & durability are key
IEC certification is not designed to predict the long-term performance of the panels,
consider sequential testing approach, as more representative of field observations
Consider field-proven BoM, select the most UV and thermally resistant backsheet
materials, if panels are expected to operate in harsh environments
Bifacial system designs have the potential to significantly improve power output. But the
use of glass-glass may impact panel durability
PV cell innovation can significantly lower LCOE; preserving/extending panel lifetime is
also critical
Mitigate risks through panel and BoM selection, and EPC and O&M best practices.
© DuPont 2018 15
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or its affiliates.
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