UV-Fluorescence Imaging of Silicon PV Modules After Outdoor Aging and Accelerated Stress Testing

Sulas‐Kern, Dana B.; Johnston, Steve; Owen‐Bellini, Michael; Terwilliger, K. M.; Meydbray, Jenya; Spinella, Laura; Sinha, Archana; Schelhas, Laura T.; Jordan, Dirk

doi:10.1109/pvsc45281.2020.9300901

Cited by 8 publications

(12 citation statements)

References 10 publications

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“…One such emergent method involves the fluorescence of the encapsulant excited by ultraviolet light (UVF), which promises rapid cell cracking identification in the field. Fluorescent species develop in the encapsulant as the degradation of the constituent polymer and/or additives occur [37], as shown in Figure 5a. Before the thermal stress is applied, the entire area of the solar cell nearly shows one dotted area corresponds to the actual crack.…”

Section: Detection and Characteristics Of Pv Microcracksmentioning

confidence: 99%

“…A crack that causes an electrical separation of an important part of the cell can significantly reduce the power output of the module [42]. As a result, by observing Figure 5b, microcrack orientation is commonly defined with respect to busbars as: (right) images after either damp heat or thermal cycling [37]; (b) different microcrack orientations indicated by red circles as described by [33].…”

Section: Detection and Characteristics Of Pv Microcracksmentioning

confidence: 99%

“…Figure 5. Solar cell cracks: (a) UVF images after outdoor exposure, but before stress testing, and(right) images after either damp heat or thermal cycling[37]; (b) different microcrack orientations indicated by red circles as described by[33].…”

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confidence: 99%

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A Review of Models for Photovoltaic Crack and Hotspot Prediction

2022

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The accurate prediction of the performance output of photovoltaic (PV) installations is becoming ever more prominent. Its success can provide a considerable economic benefit, which can be adopted in maintenance, installation, and when calculating levelized cost. However, modelling the long-term performance output of PV modules is quite complex, particularly because multiple factors are involved. This article investigates the available literature relevant to the modelling of PV module performance drop and failure. A particular focus is placed on cracks and hotspots, as these are deemed to be the most influential. Thus, the key aspects affecting the accuracy of performance simulations were identified and the perceived relevant gaps in the literature were outlined. One of the findings demonstrates that microcrack position, orientation, and the severity of a microcrack determines its impact on the PV cell’s performance. Therefore, this aspect needs to be categorized and considered accordingly, for achieving accurate predictions. Additionally, it has been identified that physical modelling of microcracks is currently a considerable challenge that can provide beneficial results if executed appropriately. As a result, suggestions have been made towards achieving this, through the use of methods and software such as XFEM and Griddler.

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Section: Detection and Characteristics Of Pv Microcracksmentioning

confidence: 99%

Section: Detection and Characteristics Of Pv Microcracksmentioning

confidence: 99%

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A Review of Models for Photovoltaic Crack and Hotspot Prediction

2022

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“…The fluorescent response of EVA has been previously examined in the literature. [18][19][20]24,25,[40][41][42][43][44][45][46][47][48][49] The local fluorescence intensity and spectra have been found to vary across the cells within a module, as well as with between geographic locations and combined UV, temperature, and humidity module histories. The fluorescent response of encapsulants forms the basis for the recently popularized, qualitative method of fluorescence imaging of PV modules, for example, for identification of cracked cells, based on the localized destruction of fluorophores from reaction with oxygen and/or water at the cracks.…”

Section: Introductionmentioning

confidence: 99%

“…This is because the fluorescent intensity is proportional to the lumophore concentration, and the wavelength is characteristic of the lumophore species. The fluorescent response of EVA has been previously examined in the literature 18–20,24,25,40–49 . The local fluorescence intensity and spectra have been found to vary across the cells within a module, as well as with between geographic locations and combined UV, temperature, and humidity module histories.…”

Section: Introductionmentioning

confidence: 99%

Degradation in photovoltaic encapsulant transmittance: Results of the second PVQAT TG5 artificial weathering study

Morse

Thuis

Holsapple

et al. 2022

Progress in Photovoltaics

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The optical degradation of encapsulants from ultraviolet (UV) radiation has historically resulted in a significant loss in performance throughout the life of a photovoltaic (PV) module. International Electrotechnical Commission (IEC) test methods have recently been developed to screen for PV encapsulants prone to loss in optical performance. The present study was performed to benchmark polymeric packaging materials relative to IEC 62788‐1‐4 (covering the measurement of optical transmittance) and IEC 62788‐1‐7 (on the durability of transmittance), provide feedback toward improvement of the methods, and develop insight regarding optical degradation. Contemporary materials were examined, including poly(ethylene‐co‐vinyl acetate) (EVA), thermoplastic polyolefin (TPO), polyolefin elastomer (POE), and polyvinyl butyral (PVB) encapsulants; a poly(ethene‐co‐tetrafluoroethene)/poly(ethylene terephthalate) (ETFE/PET) transparent backsheet; and a polystyrene (PS) working reference material. The use of silica‐, specialty‐, and rolled‐glass was also compared in laminated coupons. Specimen size was separately examined from 2.5 to 12.5 cm. Weathering was performed with a xenon source, using IEC TS 62788‐7‐2 methods A2, A3, A4, and A5 (chamber temperature of 55°C, 65°C, 75°C, or 85°C), respectively. Characterizations were made using a UV–visible–near‐infrared (UV–VIS–NIR) spectrophotometer (transmittance and reflectance, with and without an integrating sphere), a UV–VIS fluorescence spectrophotometer, a camera, and an optical microscope. Performance was analyzed, including solar weighted transmittance, yellowness index, UV cut‐off wavelength, and haze (scattering). Separate Arrhenius analyses were performed to assess retention of transmittance and changes in yellowness index. The activation energy for both characteristics was found to range from 15–80 kJ·mol−1, with an average of 48 kJ·mol−1, similar to the average of 45 kJ·mol−1 identified in the previous international PV Quality Assurance Task Force (PVQAT) Task Group 5 (TG5) study of more traditional encapsulants. The separate degradation modes of discoloration and scattering were distinguished in the encapsulants using a comprehensive spectral characterization. Based on these results, the IEC 62788‐1‐7 pass/fail criteria of 5% change in transmittance was confirmed to identify a known bad encapsulant.

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Electrochemical degradation modes in bifacial silicon photovoltaic modules

Sulas‐Kern

Owen‐Bellini

Ndione

et al. 2021

Progress in Photovoltaics

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Motivated by the rapidly rising deployment of bifacial monocrystalline‐silicon photovoltaics (PV), we investigate the durability of various PV module packaging configurations with transparent coverings on both the front and rear sides of the module. We use a series of bifacial passivated emitter and rear cell (p‐PERC) mini‐modules with systematically varying outer cover materials (glass/glass, G/G, or glass/transparent backsheet, G/TB) and encapsulant chemistries (poly [ethylene‐co‐vinyl acetate], EVA; or polyolefin, POE). We study degradation modes over 1,000 hours of combined damp heat (DH) exposure and high system voltages that can cause potential‐induced degradation (PID) under positive, zero, or negative 1,000 V cell‐to‐frame bias. We analyze the degradation modes using a combination of current–voltage measurements, impedance spectroscopy, external quantum efficiency, and spatially resolved luminescence and thermal imaging. Our results highlight various types of degradation including shunting, enhanced recombination, and series resistance increases, and we use spatially resolved characterization to separately identify the localized effects. We show that multiple PID and moisture‐ingress degradation modes severely affect EVA‐containing modules, with previously reported PID processes under negative‐bias DH and a unique observation of rear‐side surface recombination in G/EVA/G modules under positive‐bias DH. We observe significantly less degradation in POE‐containing modules, where the G/POE/G configuration exhibits minimal degradation under all stress conditions that we employ.

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UV-Fluorescence Imaging of Silicon PV Modules After Outdoor Aging and Accelerated Stress Testing

Cited by 8 publications

References 10 publications

A Review of Models for Photovoltaic Crack and Hotspot Prediction

A Review of Models for Photovoltaic Crack and Hotspot Prediction

Degradation in photovoltaic encapsulant transmittance: Results of the second PVQAT TG5 artificial weathering study

Electrochemical degradation modes in bifacial silicon photovoltaic modules

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