Encapsulation of PV modules using ethylene vinyl acetate copolymer as a pottant: A critical review

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.     

影响塑料模压制件内应力的因素分析

主要讨论了造成塑料模压制件内应力的主要因素,包括制件造型设计不合理、模具设计不合理、成型工艺条件不正确等,并针对不同情况给出了相应的解决办法     

狭缝中生存——浅谈影响建筑师理想实现的因素

本文根据作者最近所参与“北大附中重庆实验学校”的工程项目中的所见所闻,结合国内建筑市场的实际情况,探讨了中国建筑师在理想实现过程中,所面临的各种困难及其背后深刻的社会原因,希望借此启发一些正在为自己的理想而在日夜奋斗着的年轻建筑师们。为了形象地说明这些因素对一项优秀建筑项目的产生所起的作用,文中采用了量化的百分比评价体系。     

Determination of non-methane hydrocarbon emission factors from vehicles in a Tunnel in Seoul in May 2000

Measurements of non-methane hydrocarbons (NMHC) were performed at the entrance and exit of the Sangdo tunnel to estimate emission factors (EF) of NMHC from vehicles in May 2000. About 50 species were analyzed by a combined GC/FID and GC/MS system. Ethylene was the most abundant compound, followed by n-butane and acetylene, respectively. Based on the measurement data, the real world vehicular EF in Seoul was estimated. The highest EF value was 89.8 mg (veh-mile)^-1 for n-butane, followed by ethylene and toluene.     

Psychophysical basis for maximum pushing and pulling forces: A review and recommendations

The objective of this paper was to perform a comprehensive review of psychophysically determined maximum acceptable pushing and pulling forces. Factors affecting pushing and pulling forces are identified and discussed. Recent studies show a significant decrease (compared to previous studies) in maximum acceptable forces for males but not for females when pushing and pulling on a treadmill. A comparison of pushing and pulling forces measured using a high inertia cart with those measured on a treadmill shows that the pushing and pulling forces using high inertia cart are higher for males but are about the same for females. It is concluded that the recommendations of Snook and Ciriello (1991) for pushing and pulling forces are still valid and provide reasonable recommendations for ergonomics practitioners. Regression equations as a function of handle height, frequency of exertion and pushing/pulling distance are provided to estimate maximum initial and sustained forces for pushing and pulling acceptable to 75% male and female workers.     

酚醛泡沫塑料研究

针对影响酚醛泡沫性能的诸多因紊的不确定性，对树脂粘度、发泡剂、固化剂、表面活性剂、工艺温度及其他因素对泡沫性能的影响进行了讨论。研究表明：当树脂粘度控制在2000-10000cps，发泡剂用量为3．7％-9．5％，固化剂用量为7．5%-2．5％，表面活性剂用量为3．5％-8.5％，发泡温度控制在70℃-80℃之间时，可制得质量较好的酚醛泡沫塑料。     

学校信息化应用的影响因素研究

要推进学校信息化应用的步伐,其中一个重要步骤就是明确影响学校信息化应用的相关影响因素,只有明确了这些影响因素,才能有助于学校制定出有效的推进策略.笔者对近年来学者对学校教育信息化影响因素方面的相关研究情况进行了整理和总结,得出影响学校信息化应用的因素很多,且这些因素之间存在较为复杂的关系.本文现围绕学校信息化应用影响因素展开论述,先分析了学校信息化的具体应用情况,然后总结了影响学校信息化应用的影响因素.     

论港口危险货物运输装卸作业安全问题

危险货物作业安全越来越受到人们的关注，从危险货物的分类谈起，分析了危险货物港口运输装卸作业中易引发事故的诸因素和安全作业中应特别注意的几个问题，强调从业单位、从业人员的资质、法律意识和业务素质，制定危险货物事故应急预案等。提出了加强港口危险货物安全管理的有关建议：开展危险源与事故隐患的多层次监控；推进港航危险货物企业建立安全质量标准化体系；创建“抓小放大”的安全管理机制。     

八面河地区孔店组油气成藏条件与勘探方向

在剖析了八面河地区孔店组的地层和沉积特征及其油源、储层、储盖组合条件等油气成藏条件的基础上,认为研究区西北部为有利勘探区带,东北部为较有利勘探区带,南部为潜在勘探区带。     

利他行为的启动因素

结合当前人们的现实表现和社会风气,分析利他行为的启动因素。人格因素包括移情能力、积极体验、责任心等;情境因素包括旁观者效应和应急反应等;文化因素包括传统文化对日常生活的渗透以及“施报观”等独特的社会心理。