Measurement procedures for materials used in photovoltaic modules - Part 1-7: Encapsulants - Test procedure of optical durability

IEC 61215-2 provides a set of qualification tests that indicate that a PV module design is likely
to be free of flaws that will result in early failure. However, IEC 61215-2 does not address the
long term wear-out of PV modules. This part of IEC 62788-1 is designed as a more rigorous
qualification test, using accelerated UV exposure at elevated temperature to determine whether
polymeric encapsulants can suffer loss of optical transmittance. IEC 61215-2 already includes
a UV preconditioning test (MQT 10), however, the parameters for that test only represent a
limited level of exposure (~weeks of UV dose). This test procedure is intended for
representative coupon specimens, applying stress at a greater intensity (designed relative to
Phoenix, AZ), using a radiation spectrum that is more similar to the terrestrial solar spectrum,
and using a duration of exposure that is more relevant to the PV application (i.e., equivalent to
several years of outdoor exposure). This test quantifies the degradation rate of encapsulants
so that the risk of the materials losing optical transmittance during operation in the terrestrial
environments can be managed. The quantitative correlation between climate (or location of use),
a specific application (utility-installation, residential-installation, roof-mount, rack-mount, use of
a tracker, the system electrical configuration and its operation), and the test can be established
for each specific encapsulant material, but is beyond the scope of this document.
The method herein is intended to qualify encapsulants for use in a PV module. This document
is intended to apply to encapsulants used in PV modules deployed under temperature
conditions of normal use, as defined in IEC TS 63126. The use of this method for encapsulants
in modules deployed under conditions of higher temperature is specified elsewhere, for example
IEC TS 63126. The method here is intended to be used to examine a particular encapsulant
and does not cover incompatibilities between the encapsulant and other packaging materials.
This document covers PV technology constructed using a transparent incident
surface/encapsulant/photovoltaic device construction, the relevance to other geometries where
the encapsulant layer is located behind the photovoltaic device layer, is outside the scope of
this document. In the case of bifacial cell technology, the module can accept light from its front
and back surfaces – the transmittance of a frontsheet (if used), encapsulant, and transparent
backsheet (if used) is relevant for both active surfaces. The optical durability of frontsheets and
backsheets, however, is addressed separately in the IEC TS 62788-2. Thin coatings that might
be added for antireflection or anti-soiling purposes are outside the scope of this document. The
method in this document can be used for other purposes (e.g., research and development);
many details of alternate uses of the method (e.g., alternate test durations or measurement
increments) are not described here.

Messverfahren für Werkstoffe, die in Photovoltaik-Modulen verwendet werden - Teil 1-7: Verkapselungsstoffe - Testverfahren der optischen Beständigkeit

Procédures de mesure des matériaux utilisés dans les modules photovoltaïques - Part 1-7: Encapsulants - Procédure d’essai de la durabilité optique

l’IEC 62788-1-7:2020 est conçue comme un essai de qualification plus rigoureux, qui utilise une exposition aux UV accélérée à température élevée destinée à déterminer si les encapsulants polymérisés peuvent présenter une perte de facteur de transmission optique. L’IEC 61215-2 comprend déjà un essai de préconditionnement aux UV (MQT 10), toutefois, les paramètres de cet essai ne représentent qu’un niveau limité d’exposition (~semaines de dose d’UV). La présente procédure d'essai concerne les éprouvettes de coupon représentatives et applique des contraintes d’une plus grande intensité (conçues par rapport à Phoenix, AZ), en utilisant un spectre de rayonnement qui est plus proche du spectre lumineux solaire terrestre et une durée d'exposition plus pertinente pour l’application PV (c’est à dire équivalente à plusieurs années d'exposition en extérieur). Cet essai quantifie la vitesse de dégradation des encapsulants de manière à pouvoir gérer le risque de perte de facteur de transmission optique des matériaux au cours du fonctionnement dans l’environnement terrestre. La corrélation quantitative entre le climat (ou le lieu d'utilisation), une application spécifique (installation de service public, installation résidentielle, montage sur toit, montage sur châssis, utilisation d'un traqueur, configuration électrique du système et son fonctionnement) et l’essai peut être établie pour chaque matériau d’encapsulation spécifique mais n’entre pas dans le domaine d’application du présent document.

Merilni postopki za materiale, uporabljene v fotonapetostnih modulih - 1-7. del: Enkapsulanti - Preskusni postopki za optično trajnost

General Information

Status
Published
Publication Date
20-Jul-2020
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
07-Jul-2020
Due Date
11-Sep-2020
Completion Date
21-Jul-2020

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SLOVENSKI STANDARD
SIST EN IEC 62788-1-7:2020
01-september-2020
Merilni postopki za materiale, uporabljene v fotonapetostnih modulih - 1-7. del:
Enkapsulanti - Preskusni postopki za optično trajnost
Measurement procedures for materials used in photovoltaic modules - Part 1-7:
Encapsulants - Test procedure of optical durability

Messverfahren für Werkstoffe, die in Photovoltaik-Modulen verwendet werden - Teil 1-7:

Verkapselungsstoffe - Testverfahren der optischen Beständigkeit

Procédures de mesure des matériaux utilisés dans les modules photovoltaïques - Part 1-

7: Encapsulants - Procédure d’essai de la durabilité optique
Ta slovenski standard je istoveten z: EN IEC 62788-1-7:2020
ICS:
27.160 Sončna energija Solar energy engineering
SIST EN IEC 62788-1-7:2020 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN IEC 62788-1-7:2020
---------------------- Page: 2 ----------------------
SIST EN IEC 62788-1-7:2020
EUROPEAN STANDARD EN IEC 62788-1-7
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2020
ICS 27.160
English Version
Measurement procedures for materials used in photovoltaic
modules - Part 1-7: Encapsulants - Test procedure of optical
durability
(IEC 62788-1-7:2020)
Procédures de mesure des matériaux utilisés dans les To be completed
modules photovoltaïques - Part 1-7: Encapsulants - (IEC 62788-1-7:2020)
Procédure d'essai de la durabilité optique
(IEC 62788-1-7:2020)

This European Standard was approved by CENELEC on 2020-05-26. CENELEC members are bound to comply with the CEN/CENELEC

Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC

Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the

Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 62788-1-7:2020 E
---------------------- Page: 3 ----------------------
SIST EN IEC 62788-1-7:2020
EN IEC 62788-1-7:2020 (E)
European foreword

The text of document 82/1669/FDIS, future edition 1 of IEC 62788-1-7, prepared by IEC/TC 82 "Solar

photovoltaic energy systems" was submitted to the IEC-CENELEC parallel vote and approved by

CENELEC as EN IEC 62788-1-7:2020.
The following dates are fixed:

• latest date by which the document has to be implemented at national (dop) 2021-02-26

level by publication of an identical national standard or by endorsement

• latest date by which the national standards conflicting with the (dow) 2023-05-26

document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice

The text of the International Standard IEC 62788-1-7:2020 was approved by CENELEC as a

European Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards

indicated:
IEC 60904-3 NOTE Harmonized as EN IEC 60904-3
IEC 61730-2 NOTE Harmonized as EN IEC 61730-2
IEC 62788-2 (series) NOTE Harmonized as EN IEC 62788-2 (series)
---------------------- Page: 4 ----------------------
SIST EN IEC 62788-1-7:2020
EN IEC 62788-1-7:2020 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments)

applies.

NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the relevant

EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available here:

www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 61215-2 - Terrestrial photovoltaic (PV) modules - EN 61215-2 -
Design qualification and type approval -
Part 2: Test procedures
IEC 61730-1 - Photovoltaic (PV) module safety EN IEC 61730-1 -
qualification - Part 1: Requirements for
construction
IEC/TS 61836 - Solar photovoltaic energy systems - - -
Terms, definitions and symbols
IEC 62788-1-4 - Measurement procedures for materials EN 62788-1-4 -
used in photovoltaic modules - Part 1-4:
Encapsulants - Measurement of optical
transmittance and calculation of the solar-
weighted photon transmittance,
yellowness index, and UV cut-off
wavelength
IEC/TS 62788-7-2 - Measurement procedures for materials - -
used in photovoltaic modules - Part 7-2:
Environmental exposures - Accelerated
weathering tests of polymeric materials
IEC/TS 62915 - Photovoltaic (PV) modules - Type - -
approval, design and safety qualification -
Retesting
IEC/TS 63126 - Guidelines for qualifying PV modules, - -
components, and materials for operation
at high temperatures
Under preparation. Stage at the time of publication: IEC/DTS 63126:2019.
---------------------- Page: 5 ----------------------
SIST EN IEC 62788-1-7:2020
EN IEC 62788-1-7:2020 (E)
ISO 291 - Plastics - Standard atmospheres for EN ISO 291 -
conditioning and testing
ASTM G7 - Standard practice for atmospheric - -
environmental exposure testing of
nonmetallic materials
---------------------- Page: 6 ----------------------
SIST EN IEC 62788-1-7:2020
IEC 62788-1-7
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Measurement procedures for materials used in photovoltaic modules –
Part 1-7: Encapsulants – Test procedure of optical durability
Procédures de mesure des matériaux utilisés dans les modules
photovoltaïques –
Partie 1-7: Encapsulants – Procédure d’essai de la durabilité optique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-8035-5

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 7 ----------------------
SIST EN IEC 62788-1-7:2020
– 2 – IEC 62788-1-7:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 3

INTRODUCTION ..................................................................................................................... 5

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 7

4 Principle .......................................................................................................................... 7

5 Apparatus ........................................................................................................................ 7

5.1 Spectrophotometer for transmittance measurements ............................................... 7

5.2 Environmental chamber for weathering ................................................................... 7

6 Test specimens ............................................................................................................... 8

6.1 Specimen components and general considerations for all material types ................ 8

6.2 Test specimens for datasheet reporting .................................................................. 8

6.3 Use of alternate superstrate and substrate materials .............................................. 8

6.4 Witness specimens and experimental control .......................................................... 9

7 Measurement procedure .................................................................................................. 9

8 Artificial accelerated weathering ...................................................................................... 9

9 Calculation and expression of results .............................................................................. 9

10 Test procedure .............................................................................................................. 10

11 Pass/fail criteria ............................................................................................................. 10

12 Test report ..................................................................................................................... 11

Bibliography .......................................................................................................................... 13

---------------------- Page: 8 ----------------------
SIST EN IEC 62788-1-7:2020
IEC 62788-1-7:2020 © IEC 2020 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEASUREMENT PROCEDURES FOR
MATERIALS USED IN PHOTOVOLTAIC MODULES –
Part 1-7: Encapsulants –
Test procedure of optical durability
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international

co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and

in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,

Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their

preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with

may participate in this preparatory work. International, governmental and non-governmental organizations liaising

with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for

Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence between

any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent

rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 62788-1-7 has been prepared by IEC technical committee 82: Solar

photovoltaic energy systems.
The text of this International Standard is based on the following documents:
FDIS Report on voting
82/1669/FDIS 82/1704/RVD

Full information on the voting for the approval of this International Standard can be found in the

report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 62788 series, published under the general title Measurement

procedures for materials used in photovoltaic modules, can be found on the IEC website.

---------------------- Page: 9 ----------------------
SIST EN IEC 62788-1-7:2020
– 4 – IEC 62788-1-7:2020 © IEC 2020

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 10 ----------------------
SIST EN IEC 62788-1-7:2020
IEC 62788-1-7:2020 © IEC 2020 – 5 –
INTRODUCTION

IEC 61215-2 (covering module design qualification and type approval) specifies a UV

-2 -2

preconditioning of 54 MJ⋅m (15 kWh⋅m ), which would be encountered after ~40 ideal sunny

days of exposure to the AM1.5G UV spectrum in IEC 60904-3. IEC 61730-2 presently specifies

4x the same UV exposure, i.e., 5 months UV dose. The International PV Quality Assurance

Task Force (PVQAT) leads global efforts to craft quality and reliability standards for solar

energy technologies. These standards will allow stakeholders to quickly assess a solar

photovoltaic (PV) module's performance and ability to withstand weather stresses, thereby

reducing risk and adding confidence for those developing products, designing incentive

programs, and determining private investments. As developed in conjunction with PVQAT, this

part of IEC 62788-1 is intended to supplement module qualification, which typically covers

reliability issues related to infant mortality, i.e., the first months of field use. This part of

IEC 62788-1 may also facilitate the pre-qualification of encapsulation materials using coupon

specimens, because long term weathering is not practical for larger module specimens. This

part of IEC 62788-1 also importantly uses high fidelity UV irradiation (relative to the terrestrial

solar spectrum), which is not practical to apply to module specimens (due to the lack of available

commercial equipment and the anticipated cost of operation).This part of IEC 62788-1 is not

presently specified for pre-qualification purposes in other standards, but may be used for that

purpose by module manufacturers.

The optical performance (transmittance) of polymeric frontsheets and backsheets is not covered

in this part of IEC 62788-1. These components are addressed in the IEC TS 62788-2.

---------------------- Page: 11 ----------------------
SIST EN IEC 62788-1-7:2020
– 6 – IEC 62788-1-7:2020 © IEC 2020
MEASUREMENT PROCEDURES FOR
MATERIALS USED IN PHOTOVOLTAIC MODULES –
Part 1-7: Encapsulants –
Test procedure of optical durability
1 Scope

IEC 61215-2 provides a set of qualification tests that indicate that a PV module design is likely

to be free of flaws that will result in early failure. However, IEC 61215-2 does not address the

long term wear-out of PV modules. This part of IEC 62788-1 is designed as a more rigorous

qualification test, using accelerated UV exposure at elevated temperature to determine whether

polymeric encapsulants can suffer loss of optical transmittance. IEC 61215-2 already includes

a UV preconditioning test (MQT 10), however, the parameters for that test only represent a

limited level of exposure (~weeks of UV dose). This test procedure is intended for

representative coupon specimens, applying stress at a greater intensity (designed relative to

Phoenix, AZ), using a radiation spectrum that is more similar to the terrestrial solar spectrum,

and using a duration of exposure that is more relevant to the PV application (i.e., equivalent to

several years of outdoor exposure). This test quantifies the degradation rate of encapsulants

so that the risk of the materials losing optical transmittance during operation in the terrestrial

environments can be managed. The quantitative correlation between climate (or location of use),

a specific application (utility-installation, residential-installation, roof-mount, rack-mount, use of

a tracker, the system electrical configuration and its operation), and the test can be established

for each specific encapsulant material, but is beyond the scope of this document.

The method herein is intended to qualify encapsulants for use in a PV module. This document

is intended to apply to encapsulants used in PV modules deployed under temperature

conditions of normal use, as defined in IEC TS 63126. The use of this method for encapsulants

in modules deployed under conditions of higher temperature is specified elsewhere, for example

IEC TS 63126. The method here is intended to be used to examine a particular encapsulant

and does not cover incompatibilities between the encapsulant and other packaging materials.

This document covers PV technology constructed using a transparent incident

surface/encapsulant/photovoltaic device construction, the relevance to other geometries where

the encapsulant layer is located behind the photovoltaic device layer, is outside the scope of

this document. In the case of bifacial cell technology, the module can accept light from its front

and back s
...

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