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Extrapolating Accelerated UV Weathering Data:
 

Perspective From PVQAT Task Group 5 

David C. Miller1, Eleonora Annigoni2, Amal Ballion3, Jayesh G. Bokria4, Laura S. Bruckman5, David M. Burns6,
 

Lamont Elliott7, Roger H. French5, Sean Fowler8, Xiaohong Gu9, Christian C. Honeker10, Michael D. Kempe1,
 

Hussam Khonkar11, Michael Köhl3, Peter J. Krommenhoek9, Laure-Emmanuelle Perret-Aebi12, Nancy H. Phillips6,
 

Kurt P. Scott7, Fanny Sculati-Meillaud2, Tsuyoshi Shioda13, Shigeo Suga14, Shin Watanabe14, and John H. Wohlgemuth1
 

1National Renewable Energy Laboratory (NREL), 15013 Denver West Parkway, Golden, CO 80401, USA
 2École Polytechnique Fédérale de Lausanne (EPFL), Rue de la Maladière 71B, Ch 2002 Neuchâtel, Switzerland
 3Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstrasse 2, 79110 Freiburg, Germany
 4Specialized Technology Resources, Inc. (STR), 10 Water Street, Enfield, CT, USA 06082
 5Case Western Reserve University (CWRU), White 538, 10900 Euclid Avenue, Cleveland, OH 44106, USA
 6The 3M Company, 3M Center, Building 235 67 15, St. Paul, MN, 55144, USA
 7Atlas Material Testing Technology LLC, 1500 Bishop Court, Mount Prospect, IL 60056, USA,
 8Q Lab Corporation, 800 Canterbury Road, Cleveland, OH 44145 USA
 9National Institute of Standards and Technology (NIST), 100 Bureau Dr., Gaithersburg, MD 20899 8615, USA
 10Fraunhofer Center for Sustainable Energy Systems (CSE), 5 Channel Center, Boston, MA 02210, USA
 11King Abdulaziz City for Science and Technology (KACST), 17 King Abdullah Road, Riyadh, 11442, Saudi Arabia
 12Centre Suisse d'Electronique et Microtechnique SA. (CSEM), Rue Jaquet Droz 1, Ch 2002 Neuchâtel, Switzerland
 13Mitsui Chemicals, Inc., 580 32 Nagaura cho, Sodegaura shi, Chiba, 299 0265, Japan
 14Suga Test Instruments Co., Ltd., 5 4 14 Shinjuku, Shinjuku ku, 160 0022, Tokyo Japan
 

*Presenter & TG5 US: David.Miller@nrel.gov; 

TG5 China: fjt79@163.com (Leo Feng, CEI); TG5 Europe: michael.koehl@ise.fraunhofer.de; TG5 Japan: Tsuyoshi.Shioda@mitsui-chem.co.jp 

NREL PV Module Reliability Workshop
 

Golden Ballroom Salons A-D, Denver Marriott West, Golden, CO
 

13:45-14:15 Tues, 2015/2/24
 - This presentation contains no proprietary information - NREL/PR-5J00-64340 

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. 
 

 

 

 

 

 

Overview
 •Motivation and goals of TG5. 

•Ea interlaboratory experiment for encapsulation (present US-led effort). 

Encapsulation discoloration experiment: 

•Test description 

•Transmittance results (appearance, spectral τ, solar-weighted τ) 

•Effect of specimen temperature (accelerated aging) 

•Effect of light sources (Xe vs. UVA-340 fluorescent) 

Encapsulation attachment strength (CST): 

•Test description 

•Early stress and resilience results 

•Application and timeline of TG5 activities. 

Not covered today: 

•Edge seal attachment strength (part of Ea experiment) 

•SoPhia round-robin for backsheet (present Europe effort) 

PVMRW 2015 2

•Other TG5 efforts (China and Japan) 
 

 

 

 

 

 

 

 

 

 

 

 

Goal and Activities for QA TG5 (UV, T, RH)
 •	 IEC qualification tests (61215, 61646, 61730-2) presently prescribe up to 137 days field
 

equivalent (IEC 60904-3 AM 1.5) UV-B dose. This is << 25 years!
 

•	 Goal: develop UV- and temperature-facilitated test protocol(s) that may be used to
 

compare PV materials, components, and modules relative to a field deployment.
 

Core Activities: 

1: Consider weathering literature and climate meteorology (location-dependent information). 

e.g., known benchmark locations...Miami, FL; Phoenix, AZ 

2: Leverage existing standards, including other industries.
 

- summary exists from Kurt Scott et. al.
 

3: Improve understanding of existing PV UV tests. 

4: Improve understanding of module durability.
 

4-1 Collect information about field failure modes.
 

e.g., the literature, site inspections
 

4-2 Confirm appropriate models for UV aging.
 

5: Consider suitable UV sources. 

- summary of module capable equipment from David Burns et. al.
 

6:	 Generate test procedure for accelerated UV aging. 

7: Perform laboratory verification of proposed test standard/failure mode. 

- mini-module study (Japan), SoPhia round-robin (Europe), Ea interlaboratory study (US) 

PVMRW 2015 3
 

 

 

 

 

 

 

 

 

 

Motivation for the Ea Interlaboratory Experiment (TG5 US) 

•	 Knowing Ea (for rate of change in a characteristic) is critical to prescribing and 

interpreting a UV- and temperature-mediated test.
 

•	 Unfortunately, Ea is not known for the UV degradation of common PV materials. 

n	  −Ea   T  

  k	 = A e RT   	 

T0 

The modified Arrhenius equation Critical unknowns 

(Goals for the interlaboratory experiment): 

1. Quantify Ea so that applied test conditions can be interpreted. 

2. Provide a sense of the range of Ea that may be present by examining “known bad,” 

“known good,” and “intermediate” material formulations. 

3. Determine if there is significant coupling between relevant aging factors,
 

i.e., UV, temperature, and humidity.
 

What factors does TG5 need to consider?
 

4. Investigate the spectral requirements for light sources by comparing specimens 

aged by different sources, i.e., Xe-arc, UVA-340, metal-halide. 

Is visible light required in addition to UV ? 

PVMRW 2015 4
 

 

 

 

 

 

 

 

The Materials Used in the Ea Experiment 

•Discoloration of encapsulation has been studied in the literature: 

We have a sense of the general rate of degradation.
 

We have a sense of the sorts of formulations used (historical and contemporary).
 

•6 Materials examined in interlaboratory study: 

Example: compare peroxide used for cross-linking. 

Example: compare type or use of UVA. 

A TPU formulation is chosen as a known bad material. 

INGREDIENT DESCRIPTION MAKER MASS {g} 

Elvax PV1400 EVA resin, 33 wt% Vac E. I. du Pont 100 100 100 100 100 N/A 

Z6030 silane primer, gama-methacroyloxy propyl 

trimethoxysilane Dow-Corning Corp. 0.25 0.25 0.25 0.25 0.25 ? 

TBEC curing agent, OO-Tertbutyl-O-(2-ethylhexyl)-peroxycarbonate Arkema Inc. N/A 1.5 1.5 1.5 1.5 ? 

Lupersol 101 curing agent, 2,5-Bis(tert-butylperoxy)-2,5-

dimethylhexane Arkema Inc. 1.5 N/A N/A N/A N/A ? 

Tinuvin 329 UV absorber (UVA), benzotriazole type BASF Corp. N/A N/A N/A 0.3 N/A ? 

Cyasorb 531 UVA, benzophenone type Cytech Industries Inc. 0.3 0.3 0.3 N/A N/A ? 

Tinuvin 770 hindered amine light stabilizer (HALS) BASF Corp. 0.1 0.1 0.1 N/A N/A ? 

Tinuvin 123 non-basic aminoether-hindered amine light 

stabilizer (NOR-HALS) BASF Corp. N/A N/A N/A 0.1 0.1 ? 

Naugard P anti-oxidant (AO), phosphite containing Chemtura Corp. 0.2 0.2 N/A N/A N/A ? 

Designation 

(Note) 

EVA A 

(known bad, 

"slow cure" ) 

EVA B 

(improved, 

"fast cure") 

EVA C EVA D 

(known 

good) 

EVA E 

(modern, 

no UVA) 

TPU 

(known 

bad) 

Encapsulation materials being compared in the transmittance (discoloration) experiment. 

The encapsulation adhesion experiment examines Material B only. 

PVMRW 2015 5
 


 

 

 

 

 

 

 

 

 

 

Interlaboratory Participation Enables a Wider Range of Study
 

•Indoor aging is expensive. No one institution has all the resources to apply the
 

complete set of factors we would like to examine.
 

•Discoloration and adhesion will be studied at (12) -volunteer- institutions. 

• Example: compare similar instrument makes and models (e.g., Ci5000 & QSUN XE3). 

•This overcomes the difficulty of limited availability of aging equipment. 

LIGHT SOURCE, FILTER Xe Arc (right-light/cira filter) or (Suga-Q/#295/Ircut) 

Xe Arc 

(right-light/cira filter) UVA 340 fluorescent (no filter) 

UVA 340 fluorescent 

(no filter) Metal-Halide No light 

field deployment 

(outdoors) 

UV LIGHT INTENSITY NOMINAL (102 W•m-2 for 300≤λ≤400) 

STANDARD 

(0.8 W•m-2@ 340 nm) 

NOMINAL 

(1.0 W•m-2@ 340 nm) 

NOMINAL 

(~150 W•m-2 for 300≤λ≤400) 0 W•m-2 

CHAMBER RELATIVE HUMIDITY {%} 30 ("low") 50 ("high") 20 ("low") ~7% ("very low") 60 ("high") 30 ("low") 30 ("low") ambient 

CHAMBER TEMEPRATURE {°C} 40 60 80 40 60 80 40 60 60→ 80 → 40 60 40 60 80 ambient 

PARTICIPANT 

(INSTRUMENT MODEL) 

3M (Ci5000) 3M (Ci5000) 3M (Ci5000) Mitsui (SX120) NREL (Ci5000) Fraunhofer CSE 

(Ci4000) QLAB (QUV) QLAB (QUV) Fraunhofer ISE (custom) EPFL NIST (custom) 

NIST 

(custom) 

NIST 

(custom) ATLAS (EMMA in Phoenix) 

QLAB (QSUN XE3) QLAB (QSUN XE3) ATLAS (UVTEST) NREL (custom UV suitcase) CWRU (5x in Cleveland) 

ATLAS (SunTest XXL) Fraunhofer ISE (custom) ATLAS (rack in Phoenix) 

Suga (SX75) Suga (FDP) ATLAS (rack in Miami 

CWRU (QUV)@1.55 W·m-2 @ 340 nm NREL (rack in Golden) 

KACST (rack in Riyadh) 

Summary of participating laboratories and test conditions 

•	 A standard condition (60°C chamber ambient) allows a broad variety of light 

sources to be compared. 

•	 Rate of degradation will be compared against field data to allow site-specific 

acceleration factors to be determined. 

•	 Outdoor data will verify the validity of the indoor test. 

•	 Separate experiment at NIST (EVA-A & EVA-B) will examine action spectrum. 

PVMRW 2015 6
 

 

 

 

 

 

 

 

 

 

 

 

Details of the Ea Methods and Experiment: Encapsulation Transmittance Test
 

•	 Glass/polymer/glass coupon specimens measured using a spectrophotometer 

(with integrating sphere) 

•	 Measure at specimen center (anaerobic, no O2) and edge (aerobic) 

•	 Analyze: solar-weighted transmittance, yellowness index, and UV cut-off wavelength. Hemispherical transmittance {%} 

Th vs. Wavelength, material averages, unaged 

100 

90 

80 EVA A 70 EVA B 60 EVA C 50 EVA D 40 EVA E 30 

TPU 20 

Td_silica 10
 

Solite
 0 

200 250 300 350 400 450 500 

Wavelength {nm} 

Transmittance will be examined 

using silica/polymer/silica samples. 

User summary: 

Specimen in sample holder for 

indoor aging at NREL. 

Specimens on outdoor rack, aging 

in Golden, CO at NREL. 

•	 Geometry: glass/polymer/glass (3.2 mm/0.5 mm/3.2 mm) 

•	 Size: 2” x 2” 

•	 Quantity: 3 replicates of 6 materials (pre-conditioned), and 1 reference (not pre-conditioned) 

•	 Aging: 0, 15, 30, 45, 60, 75, 90, 120, 150, 180 cumulative days (indoors) 

or 0, 1, 2, 3, 4, 5 years (outdoors) 

•	 Measurements (non-destructive): repeatedly age and measure at each laboratory/test site 

PVMRW 2015 7
 

 

 

 

 

 

 

 

 

 

 

 

Formulation Specific Results Emerging From the Ea Experiment
 

5 cm
 

Visual appearance of the UV Suitcase aged 

specimens at NREL at 180 days. Specimens 

arranged in columns for EVA-A, EVA-B, EVAC, EVA-D, EVA-E, and TPU. 

Comparison of the spectral transmittance at 180 days
 

(dashed lines) relative to unaged specimens (solid) for
 

the UV Suitcase (UVA-340 fluorescent) aged specimens at NREL. 

•For EVA-A, EVA-D, and TPU, a significant discoloration is observed that may be 

correlated to a rounding of the UV cut-off and increased yellowness. 

•Result corresponds to the formation of chromophore species. 

•For EVA-B, EVA-C, EVA-E, the UV cut-off wavelength is instead decreased and there is 

an increase in the transmittance. The transmittance is increased broadly for EVA-C. 

•Result may be explained by the loss of additive(s) with age. 

PVMRW 2015 8
 

 

 

 

 

 

 

Effect of Temperature Stands Out in Early Comparison
 

•Effect of T examined directly at 3M: same irradiance, RH applied
 

using 3 similar chambers (Ci5000 , Xe lamp with Right Light filter).
 

•Effect of aging is increased 

with temperature. 

•Same trend observed for 

EVA-A and TPU (not shown). 

•Coupling anticipated from 

field observation, e.g., 

increased discoloration at local 

hot spots in modules. 

•Ea can be determined from 

experiment. 

EVA-A: comparison of change in transmittance with 

aging temperature (aged at 3M, with Xe lamp). The 

default temperature and humidity conditions were 

applied in separate chambers. 

PVMRW 2015 9
 

 

 

 

 

 

 

 

Dark Chamber Aging: UV Facilitated Degradation
 •Control experiment in environmental chambers at NIST. 

•Apply default T and RH, with no UV present. 

•No discoloration visually 

observed to date for EVA 

formulations. 

•Some rounding of UV 

cut-off for EVA-E 

(no UVA). 

•Slight discoloration 

observed with time for 

TPU at 80°C, both center 

and edge. (∆YI~2). 

•Implication: ∆τ results 

from UV degradation.
 PVMRW 2015 10

EVA-A: comparison of change in transmittance in dark 

chambers (aged at NIST, with no UV) for the default 

temperature and humidity conditions. 
 

 

 

 

 

 

 

 

Formulation Specific Results Emerging From the Ea Experiment
 

Specimen Edge Specimen Center 

Change in representative solar weighted Change in representative solar weighted 

transmittance (300≤λ≤1250 nm) for the transmittance (300≤λ≤1250 nm) for the 

encapsulation specimens at their center. Results encapsulation specimens at their edge. Results 

shown for UV Suitcase (fluorescent) at NREL. shown for UV Suitcase (fluorescent) at NREL. 

•The effects of aging are less significant at the specimen periphery (except TPU). 

•In EVA, a photobleaching effect occurs at edges, but is limited by rate of O2 diffusion. 

Here and previous slides:
 

EVA’s ⇒ effects of aging are dominated by interactions between additives.
 PVMRW 2015 11
 

 

 

Ea Experiment Examines Relevant Source Spectra
 

•Will compare Xe, UVA-340, M-H, and terrestrial light sources for all 

formulations examined. 

•Depending on specimen’s action spectrum (damage susceptibility), 

UV source (e.g., 360-400) could render different results. 

•Aged EVA’s have not yet 

varied significantly between 

sources. 

•Other base materials or 

components (backsheet) 

may have stronger spectral 

dependence. 

•NIST SPHERE experiment 

(passband filters) will 

provide additional insight. 

•Also method: ASTM G178. 

Overlay of representative common artificial UV sources, relative to the AM1.5 global spectrum.
 

PVMRW 2015 12
 

 

 

 

 

 

 

 

 

 

 

Beginning to Compare Between Artificial Light Sources
 •A common metric for H must be 

agreed upon when comparing Xe-arc 

and UVA-340 fluorescent sources. 

•One might think to overlay data 

(τ of EVA-A and TPU) at a similar 

aging condition (chamber 60 °C) 

for the total UV, 300≤λ≤400 nm. 

•But: UVA-340 lacks emission from 

∆τ: Shown for Ci5000 and UV Suitcase, H from 300≤λ≤400 nm. 360≤λ≤400nm. 

TPU: similar slope! 

RH may not matter? 

Fowler, “Developing Steady State Exposure Conditions
 

in an ASTM G154 Fluorescent UV Test Chamber for
 

Backsheet Materials.”
 

•295≤λ≤360nm: may be best criteria 

between Xe and UVA-340 fluorescent. 

•Comparing figures implies different 

action spectrum. 

•Quantitative analysis (e.g., Ea) will 

provide greatest insight. ∆τ: Shown for Ci5000 and UV Suitcase, H from 295≤λ≤360 nm. 

PVMRW 2015 13 

EVA: more similar slope 
 

 

 

 

 

 

 

 

 

 

Fluorescence Spectroscopy: Xe and UVA-340 Affect Similarly 

•Photoactive electronic structure evolves significantly with age at the specimen center. 

(less profound changes seen at periphery). 

•Distinct signatures between EVA’s suggests interaction between formulation additives. 

•Similar profiles suggest specimen chemistry affected similarly for UVA-340 & Ci5000. 

•EVA-A: Verify signature at end of the experiment. 

Base scan spectra for NREL 

unaged specimens. 

Base scan spectra (specimen center) for NREL Base scan spectra (specimen center) for NREL 

UV Suitcase (UVA-340 @2x, 60°C) at 120 days. Ci5000 (Xe @2x, 60°C, 50%RH) at 120 days. 

PVMRW 2015 14
 

 

 

 

 

 

 

 

 

 

 

 

 

Transmittance: Comparison to Historic & Outdoor Data
 •Historically, yellowness index has been 

used to compare between indoor- and fieldaged encapsulation. 

•We examine 2 of the classic formulations,
 

using a modern version of the same glass.
 

•∆YI, EVA-A: ~8 (Xe, 60°C) vs. ~55 (Xe, 70°C).
 

•Contiued verification & analysis to follow.
 

•Same & similar formulations deployed at
 

APS in 1996.
 

⇒Conclusion: discoloration resulted from
 

additive interactions (as in Ea experiment).
 

•Location specific results
 

(center vs. periphery) as in Ea experiment.
 

•TG5 will determine location specific
 

acceleration factor for Cleveland,	 Localized discoloration of EVA 

(known formulation in module) at the APS site. Golden, Miami, Phoenix, & Riyadh.	 Wohlgemuth et. al., Proc IEEE PVSC, 2013, 3260-3265. 

PVMRW 2015	 15 

Assessing degradation from change in YI. 

Reid et. al., Proc SPIE, 2013, 8825-7. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

Details of the Ea Methods and Experiment: Encapsulation CST Adhesion Test 

•	 Better physics-based methods being developed as IEC standard. 

• 25 mm square specimens (diced, after aging) examined using loadframe. 

• Pristine edge quality is critical. Dice using abrasive water jet cutter. 

Specimens on outdoor rack, 

aging in Golden, CO at NREL. 

User summary: 

• Geometry: glass/polymer/glass (3.2 mm/0.5 mm/3.2 mm) 

• Size: 3” x 3” 

•	 Quantity: 10 replicates of 1 material (pre-conditioned), 

plus 5 extras (not pre-conditioned)
 

•	 Aging: 15, 30, 45, 90, and 180 cumulative days (indoors), 

or 1, 2, 3, 4, 5 years (outdoors)
 

• Remove 2 coupons at each increment 

•	 Measurements(destructive): age at each laboratory/test site,
 

then sent to NREL for measurement
 

Sample holder configuration
 

for indoor aging at NREL.
 

Samples are diced after aging.
 

The CST will be used to examine
 

the attachment of EVA.
 

Method from: Chapuis et al.,
 

PIP, 22 (4), 2014, pp.405–41.
 

(EPFL)
 

PVMRW 2015 16
 

 

 

 

 

 

 

 

 

 

 

 

Profound Reduction in Attachment Strength Initially Observed
 

•Examining EVA-B (STR 15295 P/UF), found in many veteran PV installations. 

•Strength and resilience were seen to decrease significantly (by 66%) in the first 90 

days aging at Fraunhofer ISE. 

•Similar magnitude of effect observed for specimens aged at NREL. 

•This change exceeds the rule of 50% for pass/fail, typically applied in relative 

thermal index (RTI) tests. 

•Experiment will verify if the strength is maintained after prolonged aging, e.g., as in 

an absolute minimum requirement. 

Change in strength of attachment and resilience for Change in maximum strength of attachment 

fluorescent UV Custom Chamber at Fraunhofer ISE. and resilience for Xe Chamber at NREL. 

PVMRW 2015 17
 

 

 

 

 

Additional Aging Conditions Suggest More Complicated Story
 

•3M samples aged with Xe at 2x UV and 30% RH, T = 45, 60, or 80 °C.
 

•3M: little or no effect seen at 45 & 60 °C. 

•Fraunhofer ISE & EPFL: minimal effect seen at 40°C (3x) or 60°C (1x).
 

Explanations: 

•Threshold of UV, T, or RH required to invoke substantial damage? 

•Effect is due only to absorbed moisture (polymer plasticization)? 

•Comment: Tm~60°C for EVA. 

•Additional results (at 80 °C or in dark) should elucidate. 

(a) (b) (c) 

45°C 60°C 80°C 

CST results for 3M Ci5000 chambers, Xe @ 2x and 30%RH: (a) 45 °C; (b) 60 °C; and (c) 80 °C.
 

PVMRW 2015 18
 

 

 

 

 

 

 

Adhesion: Comparison to Historic and Outdoor Data

•No good systematic quantitative study of 

adhesion in the PV literature. 

•e.g., accelerated conditions and duration 

to examine delamination not established.
 

Anecdotally then: 

•Encapsulation/cell interface often weakest. 

•Delamination often precedes corrosion. 

•May not be tightly correlated with Si cell module at TEP Springerville facility. 

encapsulation discoloration. 

Refer also to: 

•Adhesion test method: refer to Bosco et. al., “A 

Fracture Mechanics Based Approach to Adhesion 

Testing in the PV Module”, Proc. PVMRW 2015. 

•Site data: refer to Silverman et. al., “Review of 

observed degradation modes and mechanisms from Delamination at cell-corners and -interconnect fielded modules”, Proc. PVMRW 2015. 

PVMRW 2015 19 

Delmaination and subsequent corrosion in EFGribbons in mono-Si module at SMUD Hedges facility.
 
 

 

 

 

 

 

 

 

Application of the UV Test 

Direct application: 

•IEC 62792 (climate- & configuration-specific aging sequences) 

This is the primary application forTG5 effort. 

•IEC 62788 (PV module materials and components) 

-1 = Encapsulation; -2 = Backsheets; -... (tests of characteristics) 

-7 =Weathering 

(may draw directly upon the TG5 results in a UV test) 

Indirect or perhaps future influence: 

•IEC 61730-1 (module materials & components safety tests) 

•IEC 61730-2 (PV module safety tests) 

•IEC 61215 (PV module qualification tests) 

PVMRW 2015 20
 

 

Timeline of Activities for TG5
 • NREL specimens are presently at 150 days (Ci5000) and 180 days (UV suitcase). 

• Results will be used to assign t, T, %RH for a climate- & configuration-specific UV test. 

PVMRW 2015 21
 

 

 

 

 

 

 

 

 

Summary

•”Ea” interlaboratory experiment being conducted to provide a quantitative 

basis for climate- and configuration-specific UV weathering test. 

•Preliminary (qualitative) observations presented. 

Encapsulation transmittance: 

•Have replicated behaviors of fielded materials 

(specimen location- and formulation additive-specific discoloration). 

•T coupling observed for UV aging. 

•∆τ degradation in EVA results from UV aging. 

•Good qualitative comparison between Xe and UVA-340 sources for EVA. 

Encapsulation adhesion: 

•Attachment strength can decrease drastically (>50%) with age. 

•Early results suggest significant factor (UV, T, RH) dependence. 

•Much to be learned about adhesion. 

•We look forward to the quantitative values from the experiment.
 

PVMRW 2015 22
 

 

 

Acknowledgements 

There has been fantastic participation in TG5. 

Thank you to the many participants for their ongoing support!!!
 

• If interested in TG5 or the experiments, please contact the 

corresponding regional TG5 leader. (See title slide) 

• Future publication, “Degradation in PV Encapsulation 

Transmittance: An Interlaboratory Study Towards a ClimateSpecific Test”, submitted Proc. IEEE PVSC. 

Your questions and feedback are 

much appreciated. Please help me 

to cover the important details & 

perspectives. 

This work was supported by the U.S.
 

Department of Energy under Contract 

No. DE-AC36-08-GO28308 with the
 

National Renewable Energy Laboratory.
 NREL STM campus, Dennis Schroeder 

PVMRW 2015 23