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Title: Defining Threshold Values of Encapsulant and Backsheet Adhesion for PV Module Reliability: Preprint

Abstract

The width-tapered cantilever beam method is used to quantify the debond energy (adhesion) of encapsulant and backsheet structures of 27 modules collected from the field. The collected population of modules contains both those that have remained in-tact and those with instances of either or both encapsulant and backsheet delamination. From this survey, initial threshold values (an adhesion value above which a module should remain intact throughout its lifetime) for encapsulant and backsheet interfaces are proposed. For encapsulants this value is about 60 J/m2 and for backsheets about 20 J/m2. It is expected that these values will continue to be refined and evolve as the width-tapered cantilever beam method becomes adopted by the PV industry, and that they may aid in the future improvement of accelerated lifetime tests and the development of new, low-cost materials.

Authors:
 [1];  [1];  [1];  [2];  [2]
  1. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
  2. Stanford University
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
OSTI Identifier:
1378265
Report Number(s):
NREL/CP-5J00-67767
Journal ID: ISSN 2156--3381
DOE Contract Number:
AC36-08GO28308
Resource Type:
Conference
Resource Relation:
Journal Volume: 7; Journal Issue: 6; Conference: Presented at the 2017 IEEE 44th Photovoltaic Specialists Conference (PVSC), 25-30 June 2017, Washington, DC
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; PV module reliability; encapsulant; backsheet; adhesion

Citation Formats

Bosco, Nicholas S, Kurtz, Sarah, Eafanti, Joshua, Tracy, Jared, and Dauskardt, Reinhold. Defining Threshold Values of Encapsulant and Backsheet Adhesion for PV Module Reliability: Preprint. United States: N. p., 2017. Web. doi:10.1109/JPHOTOV.2017.2746682.
Bosco, Nicholas S, Kurtz, Sarah, Eafanti, Joshua, Tracy, Jared, & Dauskardt, Reinhold. Defining Threshold Values of Encapsulant and Backsheet Adhesion for PV Module Reliability: Preprint. United States. doi:10.1109/JPHOTOV.2017.2746682.
Bosco, Nicholas S, Kurtz, Sarah, Eafanti, Joshua, Tracy, Jared, and Dauskardt, Reinhold. Mon . "Defining Threshold Values of Encapsulant and Backsheet Adhesion for PV Module Reliability: Preprint". United States. doi:10.1109/JPHOTOV.2017.2746682. https://www.osti.gov/servlets/purl/1378265.
@article{osti_1378265,
title = {Defining Threshold Values of Encapsulant and Backsheet Adhesion for PV Module Reliability: Preprint},
author = {Bosco, Nicholas S and Kurtz, Sarah and Eafanti, Joshua and Tracy, Jared and Dauskardt, Reinhold},
abstractNote = {The width-tapered cantilever beam method is used to quantify the debond energy (adhesion) of encapsulant and backsheet structures of 27 modules collected from the field. The collected population of modules contains both those that have remained in-tact and those with instances of either or both encapsulant and backsheet delamination. From this survey, initial threshold values (an adhesion value above which a module should remain intact throughout its lifetime) for encapsulant and backsheet interfaces are proposed. For encapsulants this value is about 60 J/m2 and for backsheets about 20 J/m2. It is expected that these values will continue to be refined and evolve as the width-tapered cantilever beam method becomes adopted by the PV industry, and that they may aid in the future improvement of accelerated lifetime tests and the development of new, low-cost materials.},
doi = {10.1109/JPHOTOV.2017.2746682},
journal = {},
number = 6,
volume = 7,
place = {United States},
year = {Mon Aug 28 00:00:00 EDT 2017},
month = {Mon Aug 28 00:00:00 EDT 2017}
}

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  • The width-tapered cantilever beam method is used to quantify the debond energy (adhesion) of encapsulant and backsheet structures of 32 modules collected from the field. The collected population of modules contains both those that have remained intact and those with instances of either or both encapsulant and backsheet delamination. From this survey, initial threshold values (an adhesion value above which a module should remain intact throughout its lifetime) for encapsulant and backsheet interfaces are proposed. For encapsulants this value is ~ 160J/m 2 and for backsheets ~ 10J/m 2. Here, it is expected that these values will continue to bemore » refined and evolve as the width-tapered cantilever beam method gets adopted by the PV industry, and that they may aid in the future improvement of accelerated lifetime tests and the development of new, low-cost materials.« less
  • Presented at the 2001 NCPV Program Review Meeting: Measurements of backsheet moisture permeation and encapsulant-substrate adhesion. At the March 2001 NCPV workshop on ''Moisture Ingress and High-Voltage Isolation'', industry participants identified several properties associated with PV module durability that are critical for commercial success. These include interface conductivity, adhesion of encapsulants to substrate materials as a function of in-service exposure conditions, and moisture permeation through backsheet materials as a function of temperature. Electrical data is discussed in a companion paper; adhesion and water vapor transmission rate (WVTR) measurements are presented herein.
  • Among the infrequently measured but essential properties for thin-film (T-F) module reliability are the interlayer adhesion and cohesion within a layer. These can be cell contact layers to glass, contact layers to the semiconductor, encapsulant to cell, glass, or backsheet, etc. We use an Instron mechanical testing unit to measure peel strengths at 90{sup o} or 180{sup o} and, in some cases, a scratch and tape pull test to evaluate inter-cell layer adhesion strengths. We present peel strength data for test specimens laminated from the three T-F technologies, before and after damp heat, and in one instance at elevated temperatures.more » On laminated T-F cell samples, failure can occur uniformly at any one of the many interfaces, or non-uniformly across the peel area at more than one interface. Some peel strengths are << 1 N/mm. This is far below the normal Instron mechanical testing unit Instron mechanical testing unit; glass interface values of >10 N/mm. We measure a wide range of adhesion strengths and suggest that adhesion measured under higher temperature and relative humidity conditions is more relevant for module reliability.« less
  • Performance of a photovoltaic (PV) module is related to the micro-environment around the module. The position of photovoltaic modules in an array row have a large effect on the yellowing and gloss of PV module backsheet exposed in Dfa climatic zone (Gaithersburg, MD) with a polyethylene naphthalate (PEN) outer layer. Stress/Response models of yellowing and gloss-losing as function of location parameters of module, including the shed, row, measurement position in a same module and the distance of module location to the row center, are under development. The module installation height had the greatest influence on degradation of PEN PV backsheetmore » in the Dfa climatic zone. The module backsheets at the end of an array have higher degradation rate (edge effect). The edge effect decreases with increasing of module installation heights.« less
  • MDRC Techniques are used for the detection of the vulnerability in specific regions in a PV module. They can also be useful as quality control tools. PV modules were selected randomly at the factory floor over a sixteen month period. Adequate number of samples were extracted at predetermined locations in the middle, periphery, and bus line regions from a selected cells of each module. Adhesive shear strength was measured during the extraction of the samples. Care was taken to verify that the data was statistically significant. Consistently high values of adhesive strength are desirable in all the regions. There wasmore » a smaller spread of values in the batches with higher adhesive strengths. On the other hand, the data showed wider fluctuations in the batches of lower average values of adhesive shear strength showing that inhomogeneity from one region to other may be leading to overall low values. The techniques were found to be useful for assuring quality. The information may be useful for determining warranty period. {copyright} {ital 1999 American Institute of Physics.}« less