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
考研
At the moment, there are two reliable ways to make electricity from sunlight.【F1】You can use a panel of solar cells to create th
At the moment, there are two reliable ways to make electricity from sunlight.【F1】You can use a panel of solar cells to create th
admin
2016-03-22
34
问题
At the moment, there are two reliable ways to make electricity from sunlight.【F1】
You can use a panel of solar cells to create the current directly, by liberating electrons from a semiconducting material such as silicon. Or you can concentrate the sun’s rays using mirrors, boil water with them, and employ the steam to drive a generator.
Both work. But both are expensive. Gang Chen of the Massachusetts Institute of Technology and Zhifeng Ren of Boston College therefore propose, in a paper in Nature Materials, an alternative. They suggest that a phenomenon called the thermoelectric effect might be used instead—and they have built a prototype to show that the idea is practical.
In their view, three things are needed to create a workable solar-thermoelectric device. The first is to make sure that most of the sunlight which falls on it is absorbed, rather than being reflected. The second is to choose a thermoelectric material which conducts heat badly(so that different parts remain at different temperatures)but electricity well.【F2】
The third is to be certain that the temperature gradient which that badly conducting material creates is not frittered away by poor design.
The two researchers overcame these challenges through clever engineering. The first they dealt with by coating the top of the device with oxides of hafnium, molybdenum and titanium, in layers about 100 nanometres thick.【F3】
These layers acted like the anti-reflective coatings on spectacle lenses and caused almost all the sunlight falling on the device to be absorbed.
The second desideratum, of low thermal and high electrical conductivity, was achieved by dividing the bismuth telluride into pellets a few nanometres across.【F4】
That does not affect their electrical conductivity, but nanoscale particles like this are known to scatter and obstruct the passage of heat through imperfectly understood quantum-mechanical processes.
The third objective, efficient design, involved sandwiching the nanostructured bismuth telluride between two copper plates and then enclosing the upper plate(the one coated with the light-absorbing oxides)and the bismuth telluride in a vacuum. The copper plates conducted heat rapidly to and from the bismuth telluride, thus maintaining the temperature difference. The vacuum stopped the apparatus losing heat by convection. The upshot was a device that converts 4.6% of incident sunlight into electricity.【F5】
That is not great compared with the 20% and more achieved by a silicon-based solar cell, the 40% managed by a solar-thermal turbine, or even the 18-20% of one of the new generation of cheap and cheerful thin-film solar cells.
But it is enough, Dr Chen reckons, for the process to be worth considering for mass production.
【F3】
选项
答案
它们的作用类似玻璃眼镜上面防反射的覆盖层,使所有落到设备上的阳光都被吸收。
解析
转载请注明原文地址:https://kaotiyun.com/show/dOsZ777K
0
考研英语一
相关试题推荐
[A]TheLaborDepartmentexpectstwomillionnewjobsthisyearontopofthe1.7millioncreatedlastyear.Helpingtofuelwha
WhatIstheElectricityUsedfor?电力用来做什么?A.Studythechartcarefullyandwriteanessayof160-200words.B.Youressayshould
Whatmakesagreathighschool?Americansthinkalotofthingsdo,fromoutstandingacademicsorasupportiveenvironmentfors
Whatmakesagreathighschool?Americansthinkalotofthingsdo,fromoutstandingacademicsorasupportiveenvironmentfors
Athleteswhocheatbyinjectingthemselveswithstoredsuppliesoftheirownbloodmightsoonbecaughtout.Arevealingtrailo
Athleteswhocheatbyinjectingthemselveswithstoredsuppliesoftheirownbloodmightsoonbecaughtout.Arevealingtrailo
Iamaddictedtoelectricity.Soareyou.Andsoisyourbusiness.Weliveinan"alwayson"world—airconditioners,streetlight
随机试题
流行性感冒可表现为
某企业拟建一座10kV变电所,用电负荷如下:1)一般工作制大批量冷加工机床类设备152台,总功率448.6kW。2)焊接变压器组(εr=65%,功率因数0.5)6×23kV.A+3×32kV.A,总设备功率94.5kW,平均有功功率28.4kW,平均无
已知随机变量X~N(2,22),且Y=aX+b~N(0,1),则()。
A注册会计师负责审计甲公司2011年度财务报表,在制定审计计划考虑信息技术对审计影响时,A注册会计师遇到下列事项,请代为做出正确的专业判断。被审计单位的内部控制仅依赖手工控制,此类手工控制不依赖系统所生成的信息或报告,则注册会计师对内部控制应当设计的审
四位球迷在某球赛的晋级赛开始之前对几个队伍的赛况进行预测,他们比较关注其中的两支球队,分别做了如下预测:方某说:“如果甲队不能晋级,那么乙队也不能晋级。”白某说:“不管甲队能不能晋级,乙队都不能晋级。”夏某说:“乙队能晋级,但
Thepresidentspokeatthebusinessmeetingfornearlyanhourwithout______hisnotes.
()是农业结构性改革的基本底线。
不属于经济特区的城市是()。
(2012年下半年)某高校准备建设一个容纳50位学生上机的机房,假设每一计算机系统及其辅助设备的投影面积为1.5平方米,则该机房最小面积应该为(28)平方米。
______changedthespeaker’sfamilyfortunesdrasticallyinhischildhood.
最新回复
(
0
)