IEC TR 63279:2020

Derisking photovoltaic modules - Sequential and combined accelerated stress testing

IEC TR 63279:2020 reviews research into sequential and combined accelerated stress tests that have been devised to determine the potential for degradation modes in PV modules that occur in the field that single-factor and steady-state tests do not show. This document is intended to provide data and theory-based motivation and help visualize the next steps for improved accelerated stress tests that will derisk PV module materials and designs. Any incremental savings as a result of increased reliability and reduced risk translates into lower levelized cost of electricity for PV. Lower costs will result in faster adoption of PV and the associated benefits of renewable energy.

General Information

• Status: Published
• Publication Date: 20-Aug-2020
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Current Stage: PPUB - Publication issued
• Start Date: 04-Sep-2020
• Completion Date: 21-Aug-2020

Standards Content (Sample)

IEC TR 63279 ®
Edition 1.0 2020-08
TECHNICAL
REPORT
colour
inside
Derisking photovoltaic modules – Sequential and combined accelerated stress
testing
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IEC TR 63279 ®
Edition 1.0 2020-08
TECHNICAL
REPORT
colour
inside
Derisking photovoltaic modules – Sequential and combined accelerated stress

testing
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-8737-8

– 2 – IEC TR 63279:2020 © IEC:2020
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 Framework for sequential and combined stress testing . 8
5 Sequential and cyclic sequential test methods . 9
5.1 Extended damp heat and addition of ultraviolet light . 9
5.2 Sequential/combined testing with damp-heat, thermal cycling and ultraviolet
light . 10
5.3 Consideration of interaction of UV radiation and damp heat . 12
5.4 Test-to-failure—A sequential test protocol . 13
5.5 Sequential test protocol optimized for differentiating backsheets . 16
5.6 Mechanical stress testing in combination with damp-heat, humidity-freeze,
and thermal-cycling tests for examining cell cracking and its effects . 20
6 Mechanism-specific multi-factor stress tests . 22
6.1 General . 22
6.2 Testing for delamination . 22
6.2.1 General . 22
6.2.2 Delamination – UV irradiation with high-temperature stress . 22
6.2.3 Delamination – UV irradiation with thermal-cycling stress and humidity
freeze . 23
6.2.4 Delamination – UV irradiation with cyclic dynamic mechanical loading,
thermal cycling stress, and humidity freeze . 24
6.2.5 Delamination – Temperature, humidity, and electric field associated with
system voltage . 25
6.3 Testing for potential-induced degradation . 28
6.3.1 General . 28
6.3.2 Testing for potential-induced degradation with humidity, voltage, bias,
and light . 28
6.3.3 Factor of salt mist . 29
6.4 Testing in damp heat with current injection and as a function of temperature . 30
6.5 Cell cracking and propagation in cyclic loading at various temperatures. 31
7 Combined-accelerated stress testing . 33
7.1 Combined-accelerated stress testing for tropical environments . 33
7.2 Combined-accelerated stress testing for multiple environments . 36
8 Future directions. 39
Annex A (informative) Overview of degradation modes and causal stress factors . 41
Annex B (informative) Failure modes plotted on a failure tree diagram for selected
clauses in this document . 43
Annex C (informative) Summary table of sequential and combined testing: Samples,
factors, combination, and stress-test results . 44
Bibliography . 49

Figure 1 – Framework for sequential and combined stress testing, showing three axes
of comprehensiveness – testing samples, the number of stress factors of the natural
environment, and their sequence or combination of application. . 9
Figure 2 – Fraction power loss of modules though stress testing . 10

Figure 3 – (a) Combined test sequence, and resulting (b) normalized power loss,
(c) short-circuit current (I ), and (d) fill factor (FF) [1] . 11
SC
Figure 4 – Power degradation of modules in 85 °C and 85 % relative humidity as a

function of extent of preconditioning under Xe light [9] . 13
Figure 5 – (a) Overview of the test-to-failure sequences, and (b) results showing
module power normalized to their post-light-soak values for seven module types. 14
Figure 6 – Examples of field-relevant degradation modes seen in modules tested in
the test-to-failure protocol . 15
Figure 7 – Module accelerated sequential tests (MAST) . 17
Figure 8 – Degradation modes from MAST and fielded modules . 19
Figure 9 – (a) Front-side mini-module exposure in a xenon weathering chamber with
water spray; (b) fielded module with six years of service in North America with 30 %
power loss [21] . 20
Figure 10 – (a) Test-stage description; (b) relative change in standard test condition
(STC) module parameters as a function of stage and maximum  power determined at

STC [23] . 21
Figure 11 – (a) Stress testing at 65 °C combined with UV radiation dose of 180 W/m
in the range of 300–400 nm, 900 h; (b) 75 °C without UV radiation, 1 000 h [28] . 23
Figure 12 – Delamination in sequential test . 25
Figure 13 – Delamination associated with system voltage . 27
Figure 14 – Degradation of three modules with and without UV-A light irradiance in
chamber at 60 °C, 85 % RH, and 1 000 V (positive or negative polarity depending on
the sample) . 29
Figure 15 – Sheet resistance measured on glass surfaces with various soil types, as a
function of relative humidity (RH %), at 60 °C [41] . 30
Figure 16 – Cyclic unidirectional 4-point bending with loading alternating between 0 N
and 500 N at different temperatures as shown, with duration of 4 s at each of the high-
and low-pressure dwells, 10 000 to 30 000 cycles with pressure (“Press”) from the
front-glass side or backsheet side [49] . 32
Figure 17 – Example of 24 h PV module combined accelerated stress-testing protocol
modified from ASTM D7869 . 34
Figure 18 – Shrinkage of polymer C backsheet leading to delamination and cracking . 35
Figure 19 – Multiple-environment C-AST sequence . 37
Figure 20 – Failure of two mini-modules with a polymer B outer-layer backsheet type
undergoing different multiple-environment C-AST sequences . 38

Table 1 – Extended damp heat and ultraviolet light . 10
Table 2 – Sequential/combined testing with damp-heat thermal cycling and ultraviolet
radiation . 12
Table 3 – Ultraviolet light and damp-heat interaction . 13
Table 4 – Test-to-failure – Sequential test protocol . 16
Table 5 – Module accelerated stress test 1 (MAST #1) . 18
Table 6 – Module accelerated stress test 2 (MAST #2) . 18
Table 7 – Module accelerated stress test 3 (MAST #3) . 18
Table 8 – SML-TC-HF sequential test . 21
Table 9 – UV irradiation under high-temperature conditions . 23
Table 10 – UV irradiation with TC stress . 24
Table 11 – UV irradiation with DML-TC-HF sequential test . 25

– 4 – IEC TR 63279:2020 © IEC:2020
Table 12 – DH – Negative system bias stress sequential test . 28
Table 13 – UV irradiation – negative system bias stress combined test . 29
Table 14 – Bending load test at various temperatures . 33
Table 15 – Partial list of observed degradation modes, attributed mechanisms, and
stress factors seen in the first application of the combined accelerated stress-testing

protocol based on ASTM D7869 . 35
Table 16 – Combined-accelerated stress test (Tropical 24 h ASTM D7869-based
sequence) . 36
Table 17 – Multiple-environment combined-accelerated stress test . 38
Table A.1 – Degradation modes and potential stress factors that can lead to their
manifestation . 42
Table C.1 – Table summarizing sequential and combined stress testing . 44

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