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

stephan.padlewski@dupont.com

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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