DuPont Photovoltaic Solutions The Crucial Role of Materials in Protecting the Longevity of Solar Investments Riyadh, Saudi Arabia October 3 rd, 2017

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1 DuPont Photovoltaic Solutions The Crucial Role of Materials in Protecting the Longevity of Solar Investments Riyadh, Saudi Arabia October 3 rd, 2017 Dr. Stephan Padlewski, Marketing Leader, EMEA DuPont Photovoltaic Solutions stephan.padlewski@dupont.com For over 40 years our material innovations have led the photovoltaics industry forward, and helped our clients transform the power of the Sun into power for us all. Today we offer a portfolio of solutions that deliver proven power and lasting value over the long term. Whatever your material needs, you can count on quality DuPont Photovoltaic Solutions to deliver the performance, efficiency and value you require, day after day after day

2 DuPont Photovoltaic Materials Portfolio DuPont Solamet Metallization Pastes DuPont Tedlar PVF Films for Backsheet Driving higher energy conversion efficiency Protecting PV modules DuPont

3 Climatic Environment and Stress Factors IEC standards do not take into account the specific stresses endured by the panels IEC Average Temperature Multiple environmental and mechanical stresses 275 kwh per m 2 rear side of UV radiation (desert, 12% albedo) 1000s of thermal cycles Higher operating temperature Stresses endured with solar load (in operation) Source: University of Wisconsin Source: Köppen Segmentation 25 Years In-Field DuPont

4 Levelized Cost of Energy (LCOE) Returns System Revenue System Cost ($) Initial Cost Operating Cost Modules BoS Installation Financing O&M Interest PV LCOE Lifetime Power Output (kwh) System Efficiency System Life Insolation Annual Degradation Shading / Dusting Low-light Performance Component Failures Reducing system lifetime by 5 years can increase the LCOE by 30% This is equivalent to an increase in system costs by >$0.25/Wp DuPont

5 Global DuPont Field Surveys (2016) Surveyed: >190 Installations in North America, Europe & Asia Pacific Figures reported below: 45 module manufacturers, >450 MW, > 1.9 MM modules (2016) Range of exposure: from newly commissioned modules to 30 years in service From multiple climates 22% of panels affected Backsheet is one of the main components affected Source: DuPont Field Module Program 2016 analysis Note: All percentage numbers are based on MW DuPont

6 Climatic Environment Sensitivity Hot & Arid Temperate 41.6% of panels affected Backsheet 25.9% 28.4% of panels affected Backsheet 8.7% Temperature Higher temperature seems to accelerate degradation rates of the encapsulant and backsheet (Arrhenius Kinetic Rate) Source: DuPont Field Module Program 2016 Note: All percentage numbers are based on MW DuPont

7 Application Sensitivity 11,3% Rooftop Mounted 0,2% 0,1% No defects 25,3% 63,0% 37% of panels affected Backsheet 25.3% Cell Backsheet EVA Other defects 11,3% Ground Mounted 7,0% 2,8% 0,5% 78,4% 21.6% of panels affected Backsheet 7% Temperature Higher defect rates for rooftop vs ground installations Differences are likely due to higher temperatures for rooftop systems Source: DuPont Field Survey 2016 DuPont

8 Types of Degradation Affecting the Backsheet Cracking and delamination represent serious threats to the electrical insulation of the panel Yellowing is an indicator that the polymer has started to degrade Source: DuPont Field Survey 2016 DuPont

9 Backsheet Yellowing UV transmitted UV reflected Operating temperature Thermal cycling Front side yellowing 2yr Solar farm PVDF-based backsheet Rear side yellowing Yellowing correlates with loss of elongation 4yr Solar farm PET-based backsheet DuPont

10 Hot Spots Material selection can help mitigate the effect of hot spots Partial shading ~ 50 C Soiling ~100 C Blistering Cracking Delamination DuPont

11 Years in Service Sensitivity vs Materials Tedlar Based PVDF Based PET Based <0.1% 7% 8.6% Rate of defects Defect Rate by Type of Backsheet and Climatic Zone 80% 60% 40% 20% 0% Hot & Arid Temperate Tedlar Based PVDF Based PET Based Defects rate by type of backsheet Source: DuPont Field Survey 2016 DuPont

12 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 UV irradiation combined with thermal stress can affect the integrity of the solar panels Beware of panel soiling the possible resulting hot spot stress factor can further accelerate panel degradation The Bill of Materials (e.g. backsheet) needs to be carefully considered especially in harsh climatic environments In high thermal/uv stress environments, we recommend the use of a tri-layer backsheet made of Tedlar /polyester/tedlar - the only backsheet with over 30 years proven performance in all types of climatic conditions. DuPont

13 photovoltaics.dupont.com Copyright 2017 DuPont. All rights reserved. The DuPont Oval Logo, DuPont, The miracles of science, Materials Matter, and all products denoted with or are registered trademarks or trademarks of E.I. du Pont de Nemours and Company or its affiliates.

14 The backsheet is critical for protecting the PV panel Stress Environment Ultra Violet (UV) Transmitted Reflected Temperature Peak Cycling Moisture Humidity Precipitation Condensation Corrosive Environment Atmospheric chemicals Ammonia Marine environment Inner Layer Middle Layer Outer Layer Backsheet structure Physical Protection Abrasion Impact Backsheet must provide reliable electrical protection of module over the expected lifetime (and beyond) DuPont

15 Cracking: Backsheet Loses Insulation and Places Modules at High Risk for Failure and Safety 9yrs roof array Arizona: 55kW PET-based backsheet PET based backsheet ~15% of modules cracked, 100% airside yellowing. 4yrs solar farm NA: 40kW PVDF-based backsheet PVDF-based Backsheet cracking & delamination 57% of modules cracked 4yrs solar farm China: 20MW PA-based backsheet PA-based Backsheet large amount of cracking with ~40% of modules cracked. DuPont

16 Backsheet Degradation Under UV & Thermal Stress- Yellowing and Mechanical Loss PET Tedlar PVF UV + Elevated Temperature => Yellowing across broad test panel Tedlar PVF demonstrated strongest stability at elevated temperature and high UV level PET and other backsheets show higher degradation and sensitivity to heat and UV Yellowing and mechanical loss are correlated and due to polymer degradation Fraunhofer Institute Study and DuPont data Source: EU-Project SOPHIA - Fraunhofer Institute for Solar Energy Systems: Round Robin on UV-Testing with different radiation sources (started 2012). 10 backsheets tested; DuPont loss of mechanical strength study. 16

17 DuPont Tedlar Film-Based Backsheets: Available in Two Configurations Double-sided Tedlar Single-sided Tedlar Tedlar Tedlar TPT The only backsheet construction with over 30 years of field proven experience Best protection from UV, thermal, moisture, mechanical and chemical stresses Inner Tedlar layer more stable under heat and UV exposure than single sided tie layers DuPont 2016 Tedlar TPX Critical outer layer features Tedlar that has protected solar panels for more than 30 years Offers the best balance of properties in single-sided backsheets for generalpurpose applications 17

18 Key Stress Conditions in the Field PID and corrosion 18

19 Module Accelerated Sequential Testing (MAST) Thermal Cycling Thermal Cycling Thermal Cycling 1000 hours 1000 hours 200X 200X 200X 1000 hours 1000 hours 1000 hours Damp Heat UVA UVA UVA UVA 1000 Hours in a Humidity Chamber Amounts to > 25+ years worth of stress 600 Thermal Stress Cycles Mimics thermal stresses seen in the field 4000 Hours in a UVA Chamber Amounts to 24 years worth of UV stress Repeated sequential stresses mimic field exposures Resulting degradation better matches field degradation that is not detected by single tests and current industry standards. 19

20 Comparison of MAST and Field Results Double Sided Fluoro Film Single Sided Fluoro Film Non-Fluoro SEQUENTIAL TEST Measurement Yellowing Mechanical Loss-Cracking Tedlar PVF PVDF Tedlar PVF PVDF PA (polyamide) HPET (Hydrostabilized PET Yellowing FIELD Mechanical Loss- Cracking Excellent Fair / Yellowing Poor / Cracking 1s PVDF Cracking 1000h DH 1000h UVA 3x(200 cycles TC 1000h UVA) DH 85C/85%RH UVA 65W/sqm (300nm-400nm) 70C BPT TC 85C ó -40C AAA Cracking Yellowing and mechanical loss after MAST exposure 20

21 Risk Mitigation at Material Level Select materials providing the highest thermal stability Temperature Length Rate of Change * (µm/ C m) JIS K7196 Heat Deformation Test- weighted stylus impinges on sample being heated, thermal transitions noted High softening point temperatures and lower coefficients of thermal expansion (CTE) decrease the risk of adhesion loss that can result in backsheet cracking, blistering and delamination under high thermal stress environments DuPont