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1.
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 150TM, 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. 相似文献
2.
采用添加引发剂过氧化二异丙苯(DCP)和提高熔融挤出过程中双螺杆挤出机螺杆转速的机械力引发方法研究了马来酸酐(MAH)官能化乙烯一醋酸乙烯酯共聚物(EVA)的熔融挤出反应.研究了引发剂用量和螺杆转速对产物的接枝率和熔体流动速率的影响.结果表明,随着DCP用量的增加,产物接枝率出现峰值,而随着螺杆转速的增加,产物接枝率出现先下降后增大的变化,接枝产物的熔体质量流动速率(MFR)在螺杆转速达到300r/min时出现显著增大,在一定的配方条件下,通过改变螺杆转速,可以抑制EVA在接枝过程中的交联副反应,控制制得具有较高接枝率(0.29%~0.8%)和较好熔体质量流动速率(0.7~1.2g/10 min)的接枝产物(EVA-g-MAH).力学性能测试表明,此复合引发接枝产物对尼龙66具有较好的增韧效果. 相似文献
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本文介绍用特殊悬浮法合成共聚掺混树脂的方法,并讨论了粒经、掺混树脂含量等因素对糊性能的影响.结果表明,通过使用多元混合引发剂和悬浮剂及加入适量的助分散剂、界面活性剂、调粒剂等,并通过控制搅拌速率、温度等工艺条件能有效地控制粒子的粒径、粒度分布及粒子形状,从而制得具有良好性能和粒度均匀的掺混树脂;在一定的粒径范围内(25~40μm),掺混树脂的平均粒径越大,对降低糊粘度的效果越好;增加掺混树脂的含量对降低初始糊粘度更为有利,在PVC糊树脂中加入一定量的掺混树脂可降低塑化温度,缩短塑化时间,从而改善了PVC糊树脂的加工性能. 相似文献
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氧化还原引发乳液聚合单体水溶性与动力学之间的关系 总被引:1,自引:0,他引:1
本文研究了以过硫酸钾/焦亚硫酸钠为氧化还原引发体系,在苯乙烯、醋酸乙烯酯为具体单体的乳液聚合中,单体水溶性与动力学之间的关系。通过实验考察了聚合温度、搅拌速率、电解质浓度对聚合反应转化率~时间关系的影响,并讨论了单体水溶性、自由基水相反应和聚合速率等之间的内在联系。同时得出该氧化还原引发下苯乙烯和醋酸乙烯酯体系的表观活化能分别为47.06kj/mol和约70kJ/mol。 相似文献
7.
马菲 《自动化与仪器仪表》2012,(5):169-170
针对生产过程的控制需要,采用JX-300XP型DCS作为乙酸乙酯操作控制的系统核心,实现了乙酸乙酯的过程控制,运行效果良好. 相似文献
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《International Journal of Hydrogen Energy》2020,45(20):11550-11558
Anaerobic digestion is a multi-step biotechnological process, in which H2 is not detected as it is consumed immediately e.g. by hydrogenotrophic methanogens to produce CH4 and CO2. Recently a two-stage AD concept consisting of hydrogenic process followed by methanogenic process was suggested. However, only few models of this process are known. In this study a mathematical model of a continuous process of AD with production of hydrogen and methane in a cascade of two bioreactors, including some intermediate products in the first bioreactor was developed and investigated. 相似文献
10.
Waste organics conversion to algal lipid is environmentally friendly and it promotes sustainability. Achieving high-lipid content in cells is crucial to the economic feasibility of algal lipid production and collection. Here, a phagotrophic microalga Ochromonas danica was grown on waste ketchup and then stimulated to accumulate high-lipid content using glycerol and acetate. Individually, glycerol and acetate could increase lipid synthesis. Sequential glycerol-then-acetate addition was more effective; for an O. danica culture with 0.25 g L−1 cells, the intracellular lipid content was increased to 70–80% (w/w) in 6–12 hours. However, acetate added at >1 g L−1 damaged cells. For high-density (25 g L−1) fermentations, glycerol and acetate addition strategies were evaluated to overcome this inhibition. Results indicated that glycerol could be added in batches or continuously as long as the amount was sufficient to satisfy the glycerol consumption rate of 6 mg (g cells-hour)−1 while acetic acid needed to be added continuously, optimal at a rate of 0.27–0.30 g hour−1 or 12–14 mg (g cells-hour)−1. Intracellular lipid content could reach 70–80% after 2-day supplementation of glycerol and acetic acid. The methods of glycerol/acetate additions developed here enhance algal lipid production and enable effective conversion of organic wastes to algal lipids as sustainable bioproducts. 相似文献