Degradation of photovoltaic backsheets: Comparison of the aging induced changes on module and component level

Knausz, Marlene; Eder, Gabriele; Voronko, Yuliya; Duscher, Bernadette; Koch, Thomas; Pinter, Gerald; Berger, Karl

doi:10.1002/app.42093

Cited by 45 publications

(49 citation statements)

References 21 publications

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“…It is worthwhile to note that the samples aged in UV humid conditions for 700 hours randomly presented an early sign of delamination during the tensile testing. The increase of elastic moduli after aging (Figure C) was probably because of the combination of physical annealing, chemical aging, and chemocrystallization at elevated temperature . The competition between recrystallization and PET degradation depends on the stress level of aging condition and time.…”

Section: Resultsmentioning

confidence: 99%

“…Extensive efforts have been made to characterize the backsheet degradation based on changes in yellowing, chemical structure and microstructure, tensile strength, adhesion strength, and other bulk thermo or mechanical properties . However, limited studies have investigated backsheet cracking, probably because it is challenging to reproduce the cracking observed in the field using accelerated aging tests.…”

Section: Introductionmentioning

confidence: 99%

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A novel test method for quantifying cracking propensity of photovoltaic backsheets after ultraviolet exposure

Lin

Jacobs

et al. 2018

Progress in Photovoltaics

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Surface cracking in multilayered backsheets is one of the common failure modes for field photovoltaic (PV) modules, leading to safety concerns. However, the current IEC qualification tests such as IEC 61215 cannot adequately predict the backsheet cracking in fielded modules. Moreover, little is known about effect of key environmental factors on the cracking behaviors of backsheets. In this study, a novel test method combining accelerated weathering with in situ surface cracking monitoring during tensile deformation is developed to quantify cracking propensity of backsheets after aging. A polyester‐based backsheet was selected, and 4 environmental conditions (UV/85°C/5% relative humidity (RH), UV/85°C/60% RH, 85°C/5% RH, 85°C/60% RH) were used for backsheet aging. The relationship between material degradation and crack formation of the backsheet under different environmental conditions is discussed. The channel cracks (fragmentation) perpendicular to the loading direction were only observed on the UV‐aged samples, not on those unaged or aged without UV irradiation. Moisture played a synergistic role with UV in the formation of surface cracking. Mode I fracture toughness (KIC) of the embrittled surface layer obtained from this test dropped by 98% relative to fresh samples, indicating a much higher cracking propensity of this backsheet after UV exposure. The proposed method was further validated by fragmentation tests of outdoor‐exposed backsheet samples. This method can serve as a quantitative tool to evaluate the cracking propensity of backsheets for a better material selection and lifetime prediction of PV modules.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A novel test method for quantifying cracking propensity of photovoltaic backsheets after ultraviolet exposure

Lin

Jacobs

et al. 2018

Progress in Photovoltaics

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“…The FTIR spectra of the outer surface of the backsheet of the modules exposed to ageing action moderate1 indicate that the additional irradiation initiated a beginning photo‐degradation of the backsheets PET surface (changes in the relative intensities and shift in the absorption maxima of the bands typical for the ester group at 1714, 1244, 1119, and 1098 cm −1 ) …”

Section: Resultsmentioning

confidence: 99%

Climate specific accelerated ageing tests and evaluation of ageing induced electrical, physical, and chemical changes

Eder

Voronko

Dimitriadis³

et al. 2018

Progress in Photovoltaics

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As the PV market shows enormous potential with huge growth rates especially in climatic‐sensible regions, specific artificial ageing test procedures are a key point for an efficient and fast product development of new PV modules/materials optimized for the use in specific climatic regions. Based on the definition of four climate profiles (dry and hot—arid, moderate, humid, and hot—tropical and high irradiation—alpine), a program was worked out with 14 climate specific test conditions for accelerated ageing tests. The big challenge in this respect was the adaption/advancement of existing standard procedures for PV modules/components testing in a way that reliable testing for certain climatic conditions optimized PV modules is possible. The time‐dependent repeated application of combined climatic and environmental stresses (temperature, temperature cycles, humidity, irradiation, mechanical load, salt mist) was used to induce performance losses, material degradation, and failures in test modules which resemble those effects occurring in real‐life PV installations under comparable climatic and environmental conditions. For this demanding task, a large number of identical test modules with respect to composition and module design was manufactured. A detailed nondestructive analysis/characterization of all modules was performed: (1) before; (2) during (six intermediate stages); and (3) after the accelerated ageing test. The nondestructive characterization methods used to follow the module's ageing processes throughout the whole accelerated ageing procedure were current‐voltage characteristics measurements and electroluminiscence images for the electrical performance evaluation and ultraviolet fluorescence (spectroscopic and imaging) measurements, Fourier transform infrared spectroscopy as well as colour measurements of the backsheets outer layer for recording of chemical changes of the encapsulant and backsheet. The electrical and material characterization data were incorporated in an optimized database. As stated above, a set of three identical modules was exposed together in the respective climate specific ageing tests and subsequently characterized in order to increase statistical reliability of the measuring results. The analysis of the data and first approaches of advanced data treatment have already clearly shown that the electrical and material degradation of the test modules is dependent on (1) the type and combination, (2) duration, and (3) mode (sequential versus constant) of the stresses applied. On the one hand, the simulation of environmental stresses like heavy snow and wind load and enhanced frequency of temperature cycling resulting in cell cracks and cell connector breakage could be demonstrated. Additional treatment in salty atmosphere, on the other hand, did not show an accelerating effect on degradation on the electrical or material side. The accelerating effect of enhanced temperature, humidity, or additional irradiation on the degradation of power and materials could be shown very well. D...

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“…The outer layers have to be resistant against various weathering impact factors (e.g., irradiance, humidity etc.) Often used protection layers are fluoropolymers, such as polyvinylfluoride (PVF), polyamide (PA) or polyethylene terephthalate (PET) [15].…”

Section: Adhesion Loss Of the Backsheet Filmsmentioning

confidence: 99%

Development of a GIS Tool for High Precision PV Degradation Monitoring and Supervision: Feasibility Analysis in Large and Small PV Plants

et al. 2017

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Abstract:It is well known that working photovoltaic (PV) plants show several maintenance needs due to wiring and module degradation, mismatches, dust, and PV cell defects and faults. There are a wide range of theoretical studies as well as some laboratory tests that show how these circumstances may affect the PV production. Thus, it is mandatory to evaluate the whole PV plant performance and, then, its payback time, profitability, and environmental impact or carbon footprint. However, very few studies include a systematic procedure to quantify and supervise the real degradation effects and fault impacts on the field. In this paper, the authors first conducted a brief review of the most frequent PV faults and the degradation that can be found under real conditions of operation of PV plants. Then, they proposed and developed an innovative Geographic Information System (GIS) application to locate and supervise them. The designed tool was applied to both a large PV plant of 108 kWp and a small PV plant of 9 kWp installed on a home rooftop. For the large PV plant, 24 strings of PV modules were modelized and introduced into the GIS application and every module in the power plant was studied including voltage, current, power, series and parallel resistances, fill factor, normalized PV curve to standard test conditions (STC), thermography and visual analysis. For the small PV installation three strings of PV panels were studied identically. It must be noted that PV modules in this case included power optimizers. The precision of the study enabled the researchers to locate and supervise up to a third part of every PV cell in the system, which can be adequately georeferenced. The developed tool allows both the researchers and the investors to increase control of the PV plant performance, to lead to better planning of maintenance actuations, and to evaluate several PV module replacement strategies in a preventive maintenance program. The PV faults found include hot spots, snail tracks, ethylene vinyl acetate (EVA) discoloration, PV cell fractures, busbar discoloration, bubbles and Si discoloration.

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Degradation of photovoltaic backsheets: Comparison of the aging induced changes on module and component level

Cited by 45 publications

References 21 publications

A novel test method for quantifying cracking propensity of photovoltaic backsheets after ultraviolet exposure

A novel test method for quantifying cracking propensity of photovoltaic backsheets after ultraviolet exposure

Climate specific accelerated ageing tests and evaluation of ageing induced electrical, physical, and chemical changes

Development of a GIS Tool for High Precision PV Degradation Monitoring and Supervision: Feasibility Analysis in Large and Small PV Plants

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