QA TG5: UV, temperature and 

http://pvqataskforceqarating.pbworks.com/

 goto 5. UV, tempera

Wednesday, February 27, 11:00-11:15

Task-Force coordinated by:

Michael Köhl, Fraunhofer ISE, Germany

michael.koehl@ise.fraunhofer.de

Kusato Hirota, Toray Industries, Inc., Japan

Kusato_Hirota@nts.toray.co.jp

Jasbir Bath, SEMA, USA

*

jasbir_bath@yahoo.com

NREL/PR-5200-58372

*Presented by David Miller, NREL, David.Miller@nr
Needs and Approaches

 Service life assessment needs to take UV-degradation 

account (up to 3000 kWh/m2 in the desert for 25 years)

 Different suitable artificial UV radiation sources are ava

with varying spectral distribution of the irradiation

 Different spectral sensitivities of the tested materials ha

expected

 Are comparable tests in different labs possible ? Can we accelerate tests by increasing UV intensity? Can we accelerate tests by increasing the sample temp
Present Activities

 Comparison of different light sources Test protocols for mini-modules in Japan Round Robin testing of encapsulants Round Robin testing of light sources and back-sheets Modelling the UV – irradiation locally and globally
UV – Round Robin Light and 

 Aim: Comparison of the effect of different UV- sources on glass/encapsulant/backsheet laminates with different materials

 Spectral distribution of different UV-light sources leads to 

degradation on different materials

 Stronger UV testing needs better definition of the test coSpectra of radiation sources used in PV testing 280 290 300 3

0

50

100150200250300350400450500550

μW/cm2nm

UV-spectrum meon a German mo
UV – Round Robin Samples

 Samples: 

 manufacturers provide different back-sheet types ISE produces laminates (usual glass and EVA, 13x20 cm

and 300 sample holders (till end of February)

3 long-pass filters

2 neutral density filters 

Un
UV – Round Robin Procedure

 Time frame: September 2013 Samples: 

 manufacturers provide different backsheet types  ISE produces laminates (usual glass and EVA, 13x20 cm direct radiation on the back side and on the front glazing

 Testing procedure:

 2 temperature levels: 60°C, 80°C (e.g.) (Assessment 

sample temperatures)

 Irradiation: integral UV dose: min. 120 kWh/m2 Light sources and (spectral distribution) characterised 

radiometrically (Fluorescence, Metal-halide, Xenon)

 3 longpass and 2 neutral density filters provided by ISE
UV – Round Robin Proced

 Characterisation procedures after 0, 30, 60, 120 kWh (when 

 Spectral hemispherical reflectance (UV-VIS-NIR)

Calculation of Yellowness Index or adequate degradation 

 Raman / Micro-Raman spectroscopy FTIR-ATR measurements for BS

Calculation of carbonyl-index

 Optical microscopy/AFM investigation for microcracks in  Fluorescence for encapsulants And .....?
UV – Round Robin Participa

 Backsheet manufacturers

 Krempel Toray Feron Coveme Dupont Toppan printing Dunmore

 Test labs

 ISE JRC Fiti ITRI KTI NREL Ametek

 Encapsulant: UV  Small number of 

adherence to ba

 Glass: Interfloat
UV – Round Robin Proced

 Results

 Differences of degradation in different labs Rough idea about spectral sensitivity of materials Proven UV-stability Acceleration possibilities by temperature increase Base for new materials/modules standard
UV – Round Robin Schedule

 Preparation and Testing

Purchasing of components (filters, etc) is finishedBack-sheet materials are collectedProduction of Mini-modules and filter-holders in March 2Distribution of samples to test labs beginning of April 20Testing till August 2013 (at least 120 kW/m2)intermediadte telecons or meetings at NRELMRW, TC8

 Final characterisation of the samples and evaluation of 

Fraunhofer ISE August - September 2013

 Final discussion of the results during PVSEC2013 or fa

TC82 WG2 
Overview of the QA TG5-Japan Ac

Objectives:

(1) Develop the procedure for a suitable UV weathering test us

Factors during the test: irradiation intensity, temperature, humExperiment will help determine: test duration + characteristics 

(2) A combination test or a sequential test series (if appropriate

UV weathering + Dynamic Mechanical load test UV weathering + DH Test 

Provisional schedule:4 cell mini-module test 2000 cumulative hours: 2013 June  Examination of UV weather resistant test of 1 cell module: 201 Examination of a compound or sequential test: 2013 October  International proposal for a new comparative UV weathering tecertification including the test of a full-size module, a mini modu2014 May. 
UV weathering test of 4-cells small size module 

Irradiance ・・・ 90 W / m

2 (UV 300-400nm)

Nearly 2x UV (ASTM G173 Xenon Lamp)

Chamber temp. ・・・ ・ ・ 65 

Ԩ

Chamber humidity. ・・・ No Control

( typical 1 –10

%RH)

Test Modules ・・・ 4-cells, polycrystalline SiTermination ・・・ Open circuit

Backsheet ・・・ Multilayer laminated PETEncapusulant ・・・ EVA (all: fast cure)

EVA A ・・・ Within the shelf life 

EVA B ・・・ Over the shelf life

Sample ID and Test sequence

120410-02120710-01

* The front or back side is irradiated 

Module layout 

X: Thermocoup□:Junction BO
0%

20%40%60%80%

100%120%

Initial UV330h UV660h UV990h UV1314h

Isc Change 120410-02(CH1)

120410-03(CH4)120710-01(CH2)120710-02(CH3)

0%

20%40%60%80%

100%120%

Initial UV330h UV660h UV990h UV1314h

Voc Change 120410-02(CH1)

120410-03(CH4)120710-01(CH2)120710-02(CH3)

0%

20%40%60%80%

100%120%

Initial UV330h UV660h UV990h UV1314h

Pmax Change 120410-02(CH1)

120410-03(CH4)120710-01(CH2)120710-02(CH3)

0%

20%40%60%80%

100%120%

Initial UV330h UV660h UV990h UV1314h

FF Change

120410-02(CH1)120410-03(CH4)120710-01(CH2)120710-02(CH3)

C

[]

Current

[

A

]

Current

[

A

]

[]

Output power performance Q

Irradiation on Front :990h + on Back :324h

Isc decreased

1.5 to 2% approximately

Pmax decreased

1.5 to 2% approximately

No major performance loss. Isc with Pmax  is consistent with encapsulation discoloration.
Discoloration of the Backsheet QA 

6

Measurement position

7 Glass

BS

7

6

Measurement position(Cross sectional view)

Test sequence I :Front side 990h

→ + Back side 324h

Slight yellowing oYellowing of BS dof a cell.When UV light irrout on the front sback side, yellowincreased signific

Cell

→ Result: higher 

Test sequence II :Back side 330h

→ 

*

7 measured at 

990hrs,1314 hrs only

offof cell +UV324h +UV330

on cell
Motivation for the Ea Interlaboratory 

As in Kempe, “Group 3: Understanding the Temperature and Environment Inside a PV Module ”, knowing Ea is critical to pr

interpreting a <UV and temperature> mediated test.Unfortunately, Ea is not known for the common UV PV degra

The modified Arrhenius 

     

n 

e TT Ak Critical unknowns 0

(Goals for the interlaboratory experiment):1. Quantify Ea, so that applied test conditions can be interpret

2. Provide a sense of the range of Ea that may be present by 

bad”, “known good”, and “intermediate” material formulations.3. Determine if there is significant coupling between relevant i.e., UV, temperature, and humidity.What factors does TG5 need to consider?4. Investigate the spectral requirements for light sources by comparing Ea for different sources, i.e., Xe-arc, UVA 340. 

Is visible light required in addition to UV light?
Degradation Mechanisms for Crys

Failure/degradation mechanisms from the lite

• Corrosion of AR coating on glass (Group3/Group 5)• Corrosion of cells (Group 3/Group 5)• Corrosion of electrical interconnects (Group 3/Group 5)• Crazing of glass. Crazing/roughening of front surface (Gro• Delamination of encapsulation (Group3/Group 5)• Diode failure during “hot spots” (Group 4)• Discoloration of encapsulation (Group 5)• Embrittlement of back sheet (Group 5)• Embrittlement of encapsulation (Group 5)• Embrittlement of junction box material and wire insulation • Fatigue of solder bonds (Group 2)• Fatigue of interconnects [open circuits/arcing ] (Group 2)• Fracture of cells (Group 2)• Fracture of glass/superstrate (Group 2)• Ground faults (Group3/Group 5)• Junction box and module connection failures (Group 2)• Soiling of glass/superstrate (TBD)• Structural failures (TBD)

† based on Wohlgemuth, “PV Modules: Validating Reliability, Safety and Service Life”, Intersola*e.g., D. C. Jordan and S. R. Kurtz, “Photovoltaic Degradation Rates—an Analytical Review”, PILiterature

*, site inspections, and industry feedback suggest these ar

St
Details of the Ea Test Specim

(4) custom EVA formulations, (1) TPU product proposed for  EVA to be extruded at NREL; specimens to be laminated at 

quartz/EVA/quartz specimen

Kempe et. al., Proc. PVSC 2009, 1826-1831.

50x50mm2 quartz/encapsulation/quartz geometry for transm

Details of adhesion experiment to be determined.

? ?

Ingredient Comment Mass {g} Mass {

Elvax PV1400 Dupont EVA resin, 33 wt% VAc 100 100 

Dow Corning Z6030 Silane primer, gama-methacroyloxy propyl trimethoxysilane 0.5 0.5 

Tinuvin 770 Hindered amine light stabilizer (HALS) 0.13 0.13 Tinuvin 123 Non-basic aminoether-hindered amine light stabilizer (NOR-HALS) N/A N/A 

TBEC Curing agent, OO-Tertbutyl-O-(2-ethyl-hexyl)-peroxycarbonate, 0.133kPa at 20C. N/A 1.5 

Lupersol 101 Curing agent, 2,5-Bis(tert-butylperoxy)-2,5-dimethylhexane 1.5 N/A 

Naugard P Phosphite anti-oxidant (AO) 0.25 0.25 

Tinuvin 328 Benotriazole UV absorber (UVA) N/A N/A 

Cyasorb 531 Benzophenone UV absorber 0.3 0.3 

Comments "Known bad", "slow cure" "Intermed

"fast cu
The Ea Interlaboratory Experiment Enables a Wid

Discoloration & adhesion will be studied in detail at different the same make & model of instrument (i.e., Ci5000, QUV).This overcomes the difficulty of limitedly-available aging equA standard condition (70C in chamber) allows a broad varieinstruments to also be compared.Rate of degradation will be compared against field data to alacceleration factors to be computed.Outdoor data should help verify validity of the test.Separate experiment at NIST (same EVA’s) will determine ac

LIGHT SOURCE, FILTER 

UV LIGHT INTENSITY 

CHAMBER RELATIVE HUMIDITY {%}

match for

"very low"

(~7%) 

CHAMBER TEMEPRATURE {°C} 50 70 90 50 70 70 50 60 70 50 

3M (Ci5000) 3M(Ci5000) 3M(Ci5000) ATLAS (Ci5000) Mitsui(SX120) NREL (Ci5000) CWRU(QUV)ATLAS (UVTEST) QLAB (QUV)

Fraunhofe

(custom

QLAB (QSUN XE3) QLAB (QSUN XE3) NREL (XR260) NREL (UV suitcase) 

ATLAS (SunTest XXL) Fraunhofer (custom) 

Suga (SX75) Suga (FDP) 

PARTICIPANT

(INSTRUMENT MODEL)

UVA 34

NOMINAL (

Xe Arc (right‐light/cira filter)

NOMINAL (92 W•m‐2 for 300400)

20 ("low") 50 ("high") ~7% ("very low")

UVA 340 fluorescent (no filter)

NOMINAL (0.92 W•m‐2@ 340 nm)

Summary of participaconditions
Summary of QA TG5 (UV, T

Goal develop UV & temperature facilitated test protocol(s) that may materials, components, and modules relative to a 25 year field deploRound-robin (under Sophia project)

Emphasis on backsheet materialsExamination of source (spectral) dependence

Mini-module round-robin (QA Task-5 Japan)

Examining backsheet and encapsulationApply a combination or series of aging plus dynamic mech

Ea interlaboratory study

Examining discoloration and delamination of encapsulatioQuantify coupled and (irradiation) source dependent effec

Upcoming talks in QA TG5 session:

David Burns and Kurt Scott, “Light Sources for Reproduc

Sunlight in the Natural Weathering of PV Materials, Components an

(light sources, indoor weathering equipment, spectral effec

Charlie Reid, Jayesh Bokria, and Joseph Woods, “Accele

Correlation with Outdoor Exposure of EVA Based PV Encapsulants”

(results of a field study)
Goal and Activities for QA TG5 (

IEC qualification tests (61215, 61646, 61730-2) presently prescribe equivalent (IEC 60904-3 AM 1.5) UV-B doseGoal develop UV & temperature facilitated test protocol(s) that may materials, components, and modules relative to a 25 year field deploCore Activities:1: (weathering and climates... location dependent information)

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

2: (standards from other fields of work) 

summary exists from Kurt Scott et. al.

3: (test conditions) 4-1 (collect information about observed failure mechanism)

e.g., the literature, site inspections

4-2 (find appropriate models for ALT procedures)5: (suitable UV sources) 

summary exists from David Burns et. al.

6: (proposal for accelerated service testing) 7: (laboratory verification of acceleration of proposed test standard/fa

Japan mini-module study, Sophia round-robin, 

Ea interlabo