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.     

浅谈ispLSI及其应用

本文以ｉｓｐＬＩＳＩ１０００系列为例，对ｉｓｐ技术及ｉｓｐＬＳＩ器件进行了较为详细的介绍，并结合具体设计实例，介绍ｉｓｐＬＳ开发工具的使用。     

高水位地基处理实例

介绍高水位(距槽底300)条件下,地基处理的方法、检测及效果验证。为在此条件下进行施工作业提供依据。     

An exploratory study on ontology engineering for software architecture documentation

The usefulness of Software Architecture (SA) documentation depends on how well its Architectural Knowledge (AK) can be retrieved by the stakeholders in a software project. Recent findings show that the use of ontology-based SA documentation is promising. However, different roles in software development have different needs for AK, and building an ontology to suit these needs is challenging. In this paper we describe an approach to build an ontology for SA documentation. This approach involves the use of typical questions for eliciting and constructing an ontology. We outline eight contextual factors, which influence the successful construction of an ontology, especially in complex software projects with diverse AK users. We tested our ‘typical question’ approach in a case study and report how it can be used for acquiring and modeling AK needs.     

跨文化交际中的词汇空缺现象分析

语言是跨文化交流中最主要的手段,而词汇又是语言中最活跃的因素。由于受各自民族文化的影响,在跨文化交际过程中,会出现词汇空缺现象,给跨文化交际带来障碍。研究词汇空缺现象,了解并掌握造成词汇空缺现象的原因,明白其内涵,就可以避免在跨文化交际中产生误解,减少障碍,从而使跨文化交际得以顺利进行。     

基于遗传算法的自动组卷系统研究与实现

自动组卷系统是在已有的题库基础上,按照考核目的,按一定算法生成一份满足一定要求的试卷管理系统。计算机如何自动选题形成一套科学合理的试卷算法是最关键的问题,本文首先比较了几种常见的自动组卷方法,然后介绍了遗传算法组卷算法,最后给出了实现方法。     

电刷摩擦系数测量

本文介绍电刷摩擦系数的测量装置－电刷试验转台。由正压力给定系统测量电刷的正压力,力矩反馈系统测量摩擦力对旋转中心产生的转矩,游标尺测量电刷至旋转中心距离,从而得出摩擦力。摩擦力除以正压力即摩擦系数。文中给出二个测量系统之测试结果。     

一种基于案例推理的报价决策模型

在建筑行业的投标报价过程中,如何确定对最终投标报价决策影响较大的几项因素以及如何确定这些因素与最终投标报价决策之间的关系是一个棘手的问题。为此提出了基于案例推理的报价决策模型,并研究了该模型的可行性,使报价过程规则的自动提取成为可能。     

刍议先秦工艺造物思想中的“功能主义”

设计是人类的文化性物质创造活动。由于设计的终极目标永远是功能性与审美性,因此对设计的功能与形式等问题的讨论,有着极为悠久的历史。春秋战国时代,诸子百家对于"文"与"质"、"用"与"美"、自然与环境等诸方面都展开过热烈的争论,"功能主义"设计理念已经体现于诸子的理论学说之中。     

天地有大美而不言——论中国传统艺术审美精神

中国文化的主流,是人间的性格,是现世的性格,而中国艺术则是在人的具体生命的心、性中发掘艺术的根源,把握到精神自由解放的关键,在中国传统绘画、书法等艺术创作中无一不是这种精神自由解放的体现,本文就试图从社会与自然、情感与形式、天与人等关系中探求中国传统艺术审美精神。