首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The need for solar electricity is clear. It is safe, ecologically sound, efficient, continuously available, and is has no moving
The need for solar electricity is clear. It is safe, ecologically sound, efficient, continuously available, and is has no moving
admin
2013-01-18
39
问题
The need for solar electricity is clear. It is safe, ecologically sound, efficient, continuously available, and is has no moving parts. The basic problem with the use of solar photovoltaic devices is economics, but until recently very little progress has been made toward the development of low-cost photovoltaic devices. The larger part of research funding has been devoted to study of single-crystal silicon solar cells, despite the evidence, including that of the leading manufacturers of crystalline silicon, that the technique holds little promise. The reason for this pattern is understandable and historical. Crystalline silicon is the active element in the Very successful semiconductor industry, and virtually all of the solid state devices contain silicon transistors and diodes. Crystalline silicon, however, is particularly unsuitable to terrestrial solar cells.
Crystalline silicon solar cells work well and are successfully used in the space program, where cost is not an issue. While single-crystal silicon has been proven in extraterrestrial use with efficiencies as high as 18 percent, and other more expensive and scarce materials such as gallium arsenide can have even higher efficiencies, costs must be reduced by a factor of more than 100 to make them practical for commercial use. Beside the fact that the starting crystalline silicon is expensive, 95 percent of it is wasted and does not appear in the final device. Recently, there have been some imaginative attempts to make polycrystalline and ribbon silicon, which are lower in cost than high-quality single crystals. But to date the efficiencies of these apparently lower-cost arrays have been unacceptably small. Moreover, these materials are cheaper only because of the introduction of disordering in crystalline semiconductors, and disorder degrades the efficiency of crystalline solar cells.
This dilemma can be avoided by preparing completely disordered or amorphous materials. Amorphous materials have disordered atomic structure as compared to crystalline materials. That is, they have only short-range order rather than the long-range periodicity of crystals. The advantages of amorphous solar cells are impressive. Whereas crystals can be grown as wafers about four inches in diameter, amorphous materials can be grown over large areas in a single process. Whereas crystalline silicon must be made 200 microns thick to absorb a sufficient, amount of sunlight for efficient energy conversion, only 1 micron of the proper amorphous materials is necessary. Crystalline silicon solar cells cost in excess of $100 per square foot, but amorphous films can be created at a cost of about 50 per square foot.
Although many scientists were aware of the very low cost of amorphous solar cells, they felt that they could never be manufactured with the efficiencies necessary to contribute significantly to the demand for electric power. This was based on a misconception about the feature which determines efficiency. For example, it is not the conductivity of the material in the dark which is relevant, but only the photoconductivity, that is the conductivity in the presence of sunlight. Already, solar cells with efficiencies well above 6 percent have been developed using amorphous materials, and further research will doubtless find even less costly amorphous materials with higher efficiencies.
The author is primarily concerned with ______.
选项
A、discussing the importance of solar energy
B、explaining the functioning of solar cells
C、presenting a history of research on energy sources
D、describing a possible solution to the problem of the cost of photovoltaic cells
答案
D
解析
作者在开头指出,太阳能非常重要,进一步指出,太阳能电池显然是太阳能技术的重要组成部分,其成本高的问题尚未解决。作者接下来讨论对太阳能电池的研究以及生产硅电池遇到的困难。在第三段,作者指出,有一种解决问题的办法,那就是非结晶材料 (amorphous materials)。因此,全文的主要目的是把非结晶材料作为一种有可能解决太阳能电池成本高的问题。
转载请注明原文地址:https://kaotiyun.com/show/ZU2O777K
0
考博英语
相关试题推荐
ThenewtechnologicalrevolutioninAmericannewspapershasbroughtincreased______,awiderrangeofpublicationsandanexpa
Manyparentsareconcernedthattheirchildrendonotconsumetheproperfoodstheyneedtostaystrongandhealthy.Thetruthi
DuringMcDonald’searlyyearsFrenchfriesweremadefromscratcheveryday.RussetBurbankpotatoeswere【1】,cutintoshoestrin
Ifyoudon’t______smoking,you’llnevergetbetter.
LastyearFrenchdriverskilled【C1】_____than5,000peopleontheroadsforthefirsttimeindecades.Creditgoeslargely【C2】___
LastyearFrenchdriverskilled【C1】_____than5,000peopleontheroadsforthefirsttimeindecades.Creditgoeslargely【C2】___
LastyearFrenchdriverskilled【C1】_____than5,000peopleontheroadsforthefirsttimeindecades.Creditgoeslargely【C2】___
Stocksarenotgoods—theymerelyare_____.exchangingcurrentcashflowsforfutureones.
Humanchoice,nottheintrinsiccontentofscience,determinestheoutcomeandscientists,ashumanbeings,thereforehaveaspe
Notcontentto______alonginignoranceandonherown,Pattybeganreadingeverythingshecouldgetandimmediatelysetoutto
随机试题
_______是人力资源管理的前提与主要职能()
下列短语都属于联合短语的是()
Atthistimenextweek,we______thematterwithourfriends.
人体维生素B1缺乏人体铁缺乏
下列资产中,属于企业流动资产的是()。
黄山公司系上市公司,在2014年至2016年发生的与长期股权投资有关的交易或事项如下:(1)2014年1月1日,黄山公司以发行普通股和一项作为固定资产核算的厂房为对价,从非关联方取得甲公司25%股权,对甲公司具有重大影响,采用权益法核算,并于当日办妥相关
甲、乙两公司采用合同书形式订立了一份买卖合同,双方约定由甲公司向乙公司提供100台精密仪器,甲公司于8月31日前交货,并负责将货物运至乙公司,乙公司在收到货物后10日内付清货款。合同订立后双方均未签字盖章。7月28日,甲公司与丙运输公司订立货物运输合同,双
案例:李老师在进行“表格数据的图形化”这节课时,提出一个情境:“中国网民有多少?有网瘾的有多少?占的百分比是多少?网络给我们带来了很大的便利,如果不能正确使用它,我们的生活就会受到影响。”很多同学都微微点头,李老师接着说:“我们今天就开展关于中小学学生上
阅读以下短文。回答下列问题:中国传统审美文化是与它的社会形态相一致的。中国自古以来就是农业国度,决定了它的文化精神重视天人合一与人人相合,礼乐便是这个系统的体现。礼不仅包含宗教仪式,而且包括各种典章制度;乐则是调和礼制内人与人之间的思想感情。美善
百度在一直努力创新,通过大数据分析的优势帮助我们寻求未来技术解决方案,应对社会和环境问题。
最新回复
(
0
)