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F.j. Pern - One of the best experts on this subject based on the ideXlab platform.
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encapsulation of pv modules using ethylene vinyl acetate copolymer as a pottant a critical review
Solar Energy Materials and Solar Cells, 1996Co-Authors: Al W. Czanderna, F.j. PernAbstract:Abstract The primary purpose of this work is to review the literature about what is and is not known about using ethylene vinyl acetate (EVA0 copolymer as the encapsulant (or pottant) material in photovoltaic (PV) modules. Secondary purposes include elucidating the complexity of the encapsulation problem, providing an overview about encapsulation of PV cells and modules, providing a historical overview of the relevant research and development on EVA, summarizing performance losses reported for PV systems deployed since ca. 1981, and summarizing the general problems of polymer stability in a solar environment. We also provide a critical review of aspects of reported work for cases that we believe are important. Failure modes resolved in the early work to establish reliability of deployed modules and the purposes and properties of pottants, are summarized. Typical performance losses in large field-deployed, large-scale systems ranging from 1% to 10% per year are given quantitatively, and qualitative reports of EVA Discoloration are summarized with respect to ultraviolet (UV), world-wide location and site dependence. The general stability of polymers and their desirable bulk properties for solar utilization are given. The stabilization formulation for EVA, its effectiveness, and changes in it during degradation are discussed. The degradation mechanisms for the base resin, e.g., unstabilized Elvax 150 TM , and stabilized EVA are indicated for literature dating to the early 1950s, and the role played by unsaturated chromophores is indicated. The limited number of studies relating Discoloration and PV cell efficiency are summarized. Observed degradation of EVA or the unstabilized base resin in the laboratory and examples used to measure the degradation are summarized in sections entitled: (1) thermally-induced degradation; (2) photodegradation and photothermal degradation of EVA in different temperature regimes; (3) photobleaching and photodegradation of the UV absorber and cross-linking agent; (4) acetic acid and metal and metal-oxide catalyzed oxidative degradation; and (5) discolaration and PV cell efficiency losses. Processing effects/influences on EVA stability are discussed in sections entitled: (1) EVA raw materials and extruded, uncured films; (2) thermal encapsulation processes; (3) effects of lamination, curing, and curing peroxide on gel content and chromophores formed; and (4) incomplete shielding of curing-generated chromophores. A summary is given for the limited number of accelerated lifetime testing efforts and examples of erroneous service lifetime predictions for EVA are discussed. The known factors that effect the Discoloration rate of several EVA formulations are discussed in which the reduction in rate by using UV-absorbing superstrates is a prime example. A summary is given of what is and is not known about EVA degradation mechanisms, degradation from exposures in field-deployed modeules and/or laboratory testing, and factors that contribute to EVA stability or degradation. Finally, conclusions about using Elvax 150 in EVA formulations are summarized, and future prospects for developing the next-generation pottant for encapsulating PV modules are discussed.
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encapsulation of pv modules using ethylene vinyl acetate copolymer as a pottant a critical review
Solar Energy Materials and Solar Cells, 1996Co-Authors: Al W. Czanderna, F.j. PernAbstract:Abstract The primary purpose of this work is to review the literature about what is and is not known about using ethylene vinyl acetate (EVA0 copolymer as the encapsulant (or pottant) material in photovoltaic (PV) modules. Secondary purposes include elucidating the complexity of the encapsulation problem, providing an overview about encapsulation of PV cells and modules, providing a historical overview of the relevant research and development on EVA, summarizing performance losses reported for PV systems deployed since ca. 1981, and summarizing the general problems of polymer stability in a solar environment. We also provide a critical review of aspects of reported work for cases that we believe are important. Failure modes resolved in the early work to establish reliability of deployed modules and the purposes and properties of pottants, are summarized. Typical performance losses in large field-deployed, large-scale systems ranging from 1% to 10% per year are given quantitatively, and qualitative reports of EVA Discoloration are summarized with respect to ultraviolet (UV), world-wide location and site dependence. The general stability of polymers and their desirable bulk properties for solar utilization are given. The stabilization formulation for EVA, its effectiveness, and changes in it during degradation are discussed. The degradation mechanisms for the base resin, e.g., unstabilized Elvax 150 TM , and stabilized EVA are indicated for literature dating to the early 1950s, and the role played by unsaturated chromophores is indicated. The limited number of studies relating Discoloration and PV cell efficiency are summarized. Observed degradation of EVA or the unstabilized base resin in the laboratory and examples used to measure the degradation are summarized in sections entitled: (1) thermally-induced degradation; (2) photodegradation and photothermal degradation of EVA in different temperature regimes; (3) photobleaching and photodegradation of the UV absorber and cross-linking agent; (4) acetic acid and metal and metal-oxide catalyzed oxidative degradation; and (5) discolaration and PV cell efficiency losses. Processing effects/influences on EVA stability are discussed in sections entitled: (1) EVA raw materials and extruded, uncured films; (2) thermal encapsulation processes; (3) effects of lamination, curing, and curing peroxide on gel content and chromophores formed; and (4) incomplete shielding of curing-generated chromophores. A summary is given for the limited number of accelerated lifetime testing efforts and examples of erroneous service lifetime predictions for EVA are discussed. The known factors that effect the Discoloration rate of several EVA formulations are discussed in which the reduction in rate by using UV-absorbing superstrates is a prime example. A summary is given of what is and is not known about EVA degradation mechanisms, degradation from exposures in field-deployed modeules and/or laboratory testing, and factors that contribute to EVA stability or degradation. Finally, conclusions about using Elvax 150 in EVA formulations are summarized, and future prospects for developing the next-generation pottant for encapsulating PV modules are discussed.
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Factors that affect the EVA encapsulant Discoloration rate upon accelerated exposure
Proceedings of 1994 IEEE 1st World Conference on Photovoltaic Energy Conversion - WCPEC (A Joint Conference of PVSC PVSEC and PSEC), 1994Co-Authors: F.j. PernAbstract:Several factors that may affect the net Discoloration rate of the ethylene-vinyl acetate (EVA) copolymer encapsulants used in crystalline-Si photovoltaic (c-Si PV) modules upon accelerated exposure have been investigated by employing UV-visible spectrophotometry, spectrocolorimetry, and fluorescence analysis. A number of laminated films, including the two typical EVA formulations, A9918 and 15295, were studied. The results indicate that the rate of EVA Discoloration is affected by the: (1) curing agent and curing conditions; (2) presence and concentration of curing-generated, UV-excitable chromophores; (3) UV light intensity; (4) loss rate of the UV absorber, Cyasorb UV 5311; (5) lamination; (6) film thickness; and (7) photobleaching rate due to the diffusion of air into the laminated films. In general, the loss rate of the UV absorber and the rate of Discoloration from light yellow to brown follow a sigmoidal pattern. A reasonable correlation for net changes in transmittance at 420 nm, yellowness index, and fluorescence peak area (or intensity) ratio is obtained as the extent of EVA Discoloration progressed.
Susan Agro - One of the best experts on this subject based on the ideXlab platform.
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investigation of the degradation and stabilization of eva based encapsulant in field aged solar energy modules
Polymer Degradation and Stability, 1997Co-Authors: Peter P Klemchuk, Myer Ezrin, Gary Lavigne, William Holley, James Galica, Susan AgroAbstract:Abstract The Discoloration of EVA-based encapsulant in some solar photovoltaic modules, most notably a mirror-enhanced module and others recovered from Carrisa Plains, CA, has been investigated in order to understand the causes of the phenomenon and to find solutions to the problem of reduced electrical output. The Discoloration has been found to be due to interactions between cross-linking peroxide and some stabilizing additives, and is also likely to be due to oxidation of the encapsulant. No evidence could be found in field-aged, discolored EVA encapsulant for conjugated double bonds, which has been implicated as the cause of Discoloration in earlier publications. Reformulated encapsulant and the use of cerium-oxide-containing glass as the top cover of PV modules have dramatically reduced Discoloration. Additional benefit should be derived by excluding oxygen from the modules.
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investigation of the degradation and stabilization of eva based encapsulant in field aged solar energy modules
Polymer Degradation and Stability, 1997Co-Authors: Peter P Klemchuk, Myer Ezrin, Gary Lavigne, William Holley, James Galica, Susan AgroAbstract:Abstract The Discoloration of EVA-based encapsulant in some solar photovoltaic modules, most notably a mirror-enhanced module and others recovered from Carrisa Plains, CA, has been investigated in order to understand the causes of the phenomenon and to find solutions to the problem of reduced electrical output. The Discoloration has been found to be due to interactions between cross-linking peroxide and some stabilizing additives, and is also likely to be due to oxidation of the encapsulant. No evidence could be found in field-aged, discolored EVA encapsulant for conjugated double bonds, which has been implicated as the cause of Discoloration in earlier publications. Reformulated encapsulant and the use of cerium-oxide-containing glass as the top cover of PV modules have dramatically reduced Discoloration. Additional benefit should be derived by excluding oxygen from the modules.
Yoshinori Kawase - One of the best experts on this subject based on the ideXlab platform.
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hydroxyl radical concentration profile in photo fenton oxidation process generation and consumption of hydroxyl radicals during the Discoloration of azo dye orange ii
Chemosphere, 2011Co-Authors: Takuya Maezono, Makoto Sekine, Masahiro Tokumura, Yoshinori KawaseAbstract:Dynamic behaviors of hydroxyl (OH) radical generation and consumption in photo-Fenton oxidation process were investigated by measuring OH radical concentration during the Discoloration of azo-dye Orange II. The effects of operating parameters for photo-Fenton Discoloration, i.e. dosages of H2O2 and Fe, initial dye concentration, solution pH and UV irradiation, on the generation and consumption of OH radicals playing the main role in advanced oxidation processes were extensively studied. The scavenger probe or trapping technique in which coumarin is scavenger of OH radical was applied to estimate OH radical concentration in the photoreactor during the photo-Fenton Discoloration process. The OH radical generation was enhanced with increasing the dosages of Fenton regents, H2O2 and Fe. At the initial stage of photo-Fenton Discoloration of Orange II, the OH radical concentration rapidly increased (Phase-I) and the OH radical concentration decreased after reaching of OH radical concentration at maximum value (Phase-II). The decrease in OH radical concentration started when the complete Discoloration of Orange II was nearly achieved and the H2O2 concentration became rather low. The dynamic behavior of OH radical concentration during the Discoloration of Orange II was found to be strongly linked with the change in H2O2 concentration. The generation of OH radical was maximum at solution pH of 3.0 and decreased with an increase of solution pH. The OH radical generation rate in the Fenton Process was rather slower than that in the photo-Fenton process.
Lei Wang - One of the best experts on this subject based on the ideXlab platform.
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aqueous organic dye Discoloration induced by contact glow discharge electrolysis
Journal of Hazardous Materials, 2009Co-Authors: Lei WangAbstract:In this study, effects of applied voltage, types of electrolytes, initial substrate concentration, radical scavengers and iron salts on the aqueous polar brilliant B (PBB) Discoloration induced by contact glow discharge electrolysis (CGDE) were examined. Experimental results showed that the PBB Discoloration proceeded faster in chloride solution than in phosphate or sulfate solutions. Increasing the applied voltage from 450V to 550V did not enhance the Discoloration when the applied current was kept constant. Addition of a small amount of hydroxyl scavengers (methanol) to the solution decreased the Discoloration, whereas addition of a large amount of methanol increased the Discoloration. During the treatment, TOC of the solution smoothly decreased whereas COD of the solution gradually increased due to the production of H(2)O(2) in the liquid phase. Iron salts enhanced the Discoloration significantly due to the additional Fenton reaction. Higher initial PBB concentration resulted in lower color removal efficiency, indicating that the PBB Discoloration by CGDE did not observe the first-order reaction kinetics in inert electrolytic solutions.
Didier Brissaud - One of the best experts on this subject based on the ideXlab platform.
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The pink staircase of Sully-sur-Loire castle: Even bacteria like historic stonework
International Biodeterioration and Biodegradation, 2019Co-Authors: Johann Leplat, Faisl Bousta, Alexandre François, Mikael Guiavarc'h, Jean-didier Mertz, Didier BrissaudAbstract:Rosy Discoloration has affected the stone steps in the main spiral staircase of the Sully-sur-Loire castle donjon for many years now. This study monitors the development of the coloration and the environmental climatic conditions in the staircase to understand the conditions favoring the presence of this rosy Discoloration. High-throughput sequencing was performed on healthy stone and on pink pigmented stone to identify the agent responsible for this Discoloration. The results suggest that the rosy Discoloration is the mark of a former degradation process which is now inactive, and that bacteria were the main agent of the pink patina formation. Nitiliruptor was the main genus identified in the pink parts of the staircase. This is the first time that this bacterial genus has been linked to a cultural heritage biodeterioration process. There was no evidence that this bacterial genus was responsible for the development of the pink patina, but it could have replaced it as a subsequent evolution of the process.