Survey of Mechanical Durability of PV Backsheets

Kempe, Michael; Miller, David C.; Zielnik, Allen F.; Montiel-Chicharro, Daniel; Zhu, Jiang; Gottschalg, Ralph

doi:10.1109/pvsc.2017.8366198

Cited by 10 publications

(9 citation statements)

References 11 publications

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“…Operators and experts report multiple BS‐related issues of PV modules, most likely due to BS degradation over the years. There are external, visible signs of degradation; PV modules exhibit macroscopic cracks, peeling, corrosion, delamination, discoloration, blistering, burn marks, and so forth 1–9 . Dupont stated in their report from 2020 that a significant number of PV modules, 16% form 9 million analyzed PV modules, have BS defects 1…”

Section: Introductionmentioning

confidence: 99%

“…There are external, visible signs of degradation; PV modules exhibit macroscopic cracks, peeling, corrosion, delamination, discoloration, blistering, burn marks, and so forth. [1][2][3][4][5][6][7][8][9] Dupont stated in their report from 2020 that a significant number of PV modules, 16% form 9 million analyzed PV modules, have BS defects. 1 BS degradation may coincide with water ingress into the BS causing potentially high leakage currents and insulation issues.…”

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confidence: 99%

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Wet leakage resistance development of modules with various backsheet types

Buerhop‐Lutz

Stroyuk

Zöcklein

et al. 2021

Progress in Photovoltaics

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Over the last years, a significant number of inverter shutdowns most likely due to degraded backsheets have been reported by operators, investors, and manufacturers.We investigated water ingress into different backsheets, and the resulting risk for inverter shutdowns. For studying pending insulation issues of inverters, we analyzed exemplarily a 5-MWp photovoltaic (PV) power station with 20,530 PV modules and 314 inverters. For backsheet identification on-site near-infrared absorption spectroscopic measurements of 518 PV modules from 20 inverters were carried out. In the lab, wet leakage tests provide kinetic data of insulation resistances for different backsheet materials. Historic ground impedance data logged by the inverter were evaluated to show the temporal evolution of inverters with different backsheets. We observe different kinetics and drops in leakage resistance for different backsheet types based on polyamide (PA) and air-side fluorinated coating (FC), and distinguish between two types of behavior. "PA-like" is characterized by moderate leakage resistance loss and slower performance reduction with regard to insulation in the field. "FC-like" is characterized by high susceptibility to water and a high leakage resistance loss rate for PV modules after 6-8 years of operation. These characteristics are indicated when measuring inverter GI in dependence of temperature and humidity. For PA-based BSs, the reduction in ground impedance (GI) is steady over 8 years. We observe incidences with GI below the critical value of 400 kΩ on 2.8% of all days. For FC-based BSs, we also observe steady decrease of average GI initially, yet after 6 years in the field, we see a sudden and rapid decline for 20% of those inverters. GI falling below the critical value is observed on up to 5% of all days, with the trend increasing. Therefore we, expect this problem to become even more severe for longer operating times.

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

Wet leakage resistance development of modules with various backsheet types

Buerhop‐Lutz

Stroyuk

Zöcklein

et al. 2021

Progress in Photovoltaics

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“…The material was found to have a suitable RTI rating for tensile strength, likely due to the fiberglass content. After as little as 4 years of field exposure, 28–36 deep cracks formed all the way through the backsheet creating ground faults and consequent safety concerns. Post hoc testing revealed that thermal and/or UV aging caused a precipitous drop in elongation to break (that was not evaluated) but did not cause the tensile strength to decrease 35,36 …”

Section: Rti/rte/ti Testingmentioning

confidence: 99%

Standards development for modules in high temperature micro‐environments

Kempe

Holsapple

Whitfield³

et al. 2021

Progress in Photovoltaics

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Photovoltaic (PV) module qualification standards, IEC 61215 and IEC 61730, were designed to apply to “general open‐air climates” and IEC 61730 specifically indicated applicability of ambient air temperature of 40°C. Additionally, these standards provided allowances for so‐called “open rack mounted PV modules” without a clear definition of “open‐rack.” These implied restrictions and allowances meant that hotter climates or thermally restrictive installation methods may not be covered by these often customer‐mandated certification standards. This is particularly salient for the significant growth regions of the Middle East and India that would be expected to operate at significantly higher temperatures. The applicability of these documents raised issues over the definition of “open rack” and the fact that the geographic location is just as important as the mounting configuration in assessing the impact of the micro‐environment of a PV module. This work summarizes the scientific background for IEC Technical Specification 63126:2020 ED1, titled “Guidelines for qualifying PV modules components and materials for operation at high temperatures.” This standard was recently published by the IEC and is the first step in a systematic effort to rework these standards to address the question of temperature more directly. Instead of specifying a mounting condition, we specify different suites of tests suitable for a system (PV module, mounting style, and location) defined by the 98th percentile cell temperature. With a defined temperature regime to work from, this allowed us to use existing literature research combined with additional modeling work to determine, which tests would need to be modified. This resulted in suggested changes to material thermal indices, thermal cycling temperatures, hot spot testing, ultraviolet testing, and bypass diode testing among other tests and characteristics described herein.

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“…Various changes of the properties of polymer materials, in particular ethylene vinyl acetate (EVA) encapsulant and BSs of different types were detected in field-aged PV-modules and have been discussed in literature throughout the last years. Variations of BS modifications include discoloration (yellowing, browning), delamination, peeling, macroscopic crack structures, burn marks, corrosion, etc [1,2,[4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%