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Fluorescence imaging analysis of depth‐dependent degradation in photovoltaic laminates: insights to the failure
摘要： Accurate evaluation of the reliability of photovoltaic (PV) packaging materials is critically important for the long‐term safe operation of modules. However, the complexity of the laminated systems due to their multilayered and multicomponent structures and diverse aging mechanisms makes a thorough system evaluation very challenging, especially when the degradation is non‐uniform through the thickness. In such a case, neither surface nor bulk measurements can present a clear picture of the degradation profile. In this study, fluorescence imaging was developed to visualize the degradation depth‐profiles of an aged laminated PV system. A glass/ethylene vinyl acetate (EVA) encapsulant/poly(ethylene terephthalate) (PET)‐PET‐EVA (PPE) backsheet laminate was weathered with the glass‐side facing an ultra-violet (UV) light source for 3840 h. Cross‐sectional fluorescence images revealed a non‐uniform distribution of degradation species across the thickness of the EVA encapsulant, providing greater insight into the mechanisms of degradation, which are unavailable by traditional bulk‐based methods. In addition, strong fluorescence emissions were observed from the two thin adhesive layers of the aged backsheet, indicating severe degradation of the adhesives and a potential for interlayer delamination. This method is further confirmed with other microscale characterization techniques. The changes in optical (yellowness index), chemical (oxidation, UV absorber concentration), mechanical (Derjaguin‐Muller‐Toporov modulus), and thermal (melting enthalpy) properties of the EVA encapsulant were found to be related to fluorescence profiles, following the attenuation of UV light. This study highlights that fluorescence imaging is a spatially‐resolved and sensitive method for rapid failure assessment and in‐depth mechanism study for complex PV‐laminated system.
关键词： modulus,depth profile,UV aging,photovoltaic laminates,yellowness index,fluorescence imaging,degradation
更新于2025-09-16 10:30:52
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Evaluation of color changes in PV modules using reflectance measurements
摘要： The main objective of this paper is to investigate the possibility of evaluating the color changes in real photovoltaic modules from re?ectance measurements. To accomplish this main objective, the work has been organized into three main axis: (1). Exploring the possibility of using simpli?ed instrumentation and techniques for the measurement of color parameters in solar cells. (2). Identifying a simple parameter as an indicator of solar module color appearance and (3). Exploring the possibility of correlating that parameter with solar module degradation. It is explored the use of re?ectance and related magnitude Yellowness Index (YI) as an indicator of photovoltaic (PV) solar module surface color change and degradation. While spectrometric quantities as transmittance have been used as a measurement of separated encapsulant and backsheet characteristics, in the present paper re?ectance of the surface of real PV solar mono and polycrystalline modules are analyzed. With the objective of verifying the applicability of such measurements in real PV installations, the correctness of using simpli?ed measurement geometries and portable spectrometers is tested. It is found that 45°/45° and hemispheric re?ectance supply similar results. Consequently portable ?ber optic spectrometers and simple ?ber optic probes with their holders can be used. We found that 45°/45° and hemispheric re?ectance with their associated Yellowness Index can be used indistinctly in the cases analyzed as a good indicator of super?cial color changes. We have also concluded that Yellowness Index is a good indicator of changes in appearance in PV modules. It is observed an increase of Yellowness Index with ultraviolet dose supplied to a solar module and a reduction in its maximum power.
关键词： Re?ectance,Degradation,Yellowness index,Photovoltaic
更新于2025-09-10 09:29:36