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
2013-01-29
59
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 hy 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 I 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 mentions which of the following as advantages of amorphous materials for solar cells over silicon crystals?
选项
A、The relative thinness of amorphous materials.
B、The cost of amorphous materials.
C、The size of solar ceils which can be made of amorphous materials.
D、All of the above.
答案
D
解析
作者在第三段的后半部分提到了非结晶材料胜过硅晶体的三个优点;答案A,B和C均是非结晶材料的优点,所以答案应选D(All of the above)。
转载请注明原文地址:https://kaotiyun.com/show/FM1O777K
0
考博英语
相关试题推荐
Thisprogramwilltakekidswhohaveamanifesthistoryofviolentacts.
Mostpeoplewhotravellongdistancecomplainofjetlag.Jetlagmakesbusinesstravelerslessproductiveandmoreprone【21】makin
Influenzashouldnotbedismissedasatrivialdisease.Itkillsthousandsofpeopleeveryyearataveryhighcosttotheecono
Researcherswhorefusetosharedatawithothersmay【51】otherstowithholdresultsfromthem,【52】astudybyhealth-policyanalys
Researcherswhorefusetosharedatawithothersmay【51】otherstowithholdresultsfromthem,【52】astudybyhealth-policyanalys
Don’tcallhimjustacollegeprofessor.Internetentrepreneur,TVpersonality,advisortopresidents,andfriendtotherichan
"Popularan"hasanumberofmeanings,impossibletodefinewithanyprecision,whichrangefromfolkloretojunk.Thepolesare
Tofundthe______eventandalsopromotethemarketingvalueoftheNationalGames,theorganizingcommitteesetuptheMarketi
FirstlaunchedinAprilthisyear,NetMySingaporealsoincludeseffortsthattraining,development,andtheexplorationofnew
He______somuchworkthathecouldn’treallydoitefficiently.
随机试题
下列不属于中央银行“国家的银行”职能的是()
外科最常见的休克是________和________。
下列财产可以抵押的有( )。
将3个小球随机地投到4个大盒子中,则一个盒子中至多有一个球的概率为()。
Therepairpersoncouldnotfindthespecificproblem____hadcausedthecomputertocrash.
关于ATM机描述不符合规定的是()。
关于违约责任,下列说法不正确的是()
Thelimestonewaserodedbythe______wateruntilonlyathinshellremained.
RenownedChinesedirectorZhangYimou’slatestfilm,RidingAloneforThousandsofMiles,heldatrialpremiereinthesouthern
ThewordYogaitselfcomesfromanancientSanskritwordmeaning"union".Whatkindofuniondoyouthinkthewordrefersto?Wh
最新回复
(
0
)