外文翻译--来自太阳的能源

1、英文资料 ENERGYFROMTHESUN Thesunhasproducedenergyforbillionsofyears.Solarenergyisthesolarradiationthatreachestheearth.Solarenergycanbeconverteddirectlyorindirectlyintootherformsofenergy,suchasheatandelectricity.Themajordrawbacks(problems,orissuestoovercome)ofsolarenergyare:(1)theintermittentandvariablem

2、annerinwhichitarrivesattheearthssurfaceand,(2)thelargearearequiredtocollectitatausefulrate.Solarenergyisusedforheatingwaterfordomesticuse,spaceheatingofbuildings,dryingagriculturalproducts,andgeneratingelectricalenergy. Inthe1830s,theBritishastronomerJohnHerschelusedasolarcollectorboxtocookfooddurin

3、ganexpeditiontoAfrica.Now,peoplearetryingtousethesunsenergyforlotsofthings. Electricutilitiesaretryingphotovoltaics,aprocessbywhichsolarenergyisconverteddirectlytoelectricity.Electricitycanbeproduceddirectlyfromsolarenergyusingphotovoltaicdevicesorindirectlyfromsteamgeneratorsusingsolarthermalcollec

4、torstoheataworkingfluid.Outofthe14knownsolarelectricgeneratingunitsoperatingintheUSattheendof2004,10oftheseareinCalifornia,and4inArizona.Nostatisticsarebeingcollectedonsolarplantsthatproducelessthan1megawattofelectricity,sotheremaybesmallersolarplantsinanumberofotherstates.PHOTOVOLTAICENERGY Photovo

5、ltaicenergyistheconversionofsunlightintoelectricitythroughaphotovoltaic(PVs)cell,commonlycalledasolarcell.Aphotovoltaiccellisanonmechanicaldeviceusuallymadefromsiliconalloys. Sunlightiscomposedofphotons,orparticlesofsolarenergy.Thesephotonscontainvariousamountsofenergycorrespondingtothedifferentwave

6、lengthsofthesolarspectrum.Whenphotonsstrikeaphotovoltaiccell,theymaybereflected,passrightthrough,orbeabsorbed.Onlytheabsorbedphotonsprovideenergytogenerateelectricity.Whenenoughsunlight(energy)isabsorbedbythematerial(asemiconductor),electronsaredislodgedfromthematerialsatoms.Specialtreatmentofthemat

7、erialsurfaceduringmanufacturingmakesthefrontsurfaceofthecellmorereceptivetofreeelectrons,sotheelectronsnaturallymigratetothesurface. Whentheelectronsleavetheirposition,holesareformed.Whenmanyelectrons,eachcarryinganegativecharge,traveltowardthefrontsurfaceofthecell,theresultingimbalanceofchargebetwe

8、enthecellsfrontandbacksurfacescreatesavoltagepotentiallikethenegativeandpositiveterminalsofabattery.Whenthetwosurfacesareconnectedthroughanexternalload,electricityflows. ThephotovoltaiccellisthebasicbuildingblockofaPVsystem.Individualcellscanvaryinsizefromabout1cm(1/2inch)toabout10cm(4inches)across.

9、However,onecellonlyproduces1or2watts,whichisntenoughpowerformostapplications.Toincreasepoweroutput,cellsareelectricallyconnectedintoapackagedweather-tightmodule.Modulescanbefurtherconnectedtoformanarray.Thetermarrayreferstotheentiregeneratingplant,whetheritismadeupofoneorseveralthousandmodules.Asman

10、ymodulesasneededcanbeconnectedtoformthearraysize(poweroutput)needed. Theperformanceofaphotovoltaicarrayisdependentuponsunlight.Climateconditions(e.g.,clouds,fog)haveasignificanteffectontheamountofsolarenergyreceivedbyaPVarrayand,inturn,itsperformance.Mostcurrenttechnologyphotovoltaicmodulesareabout1

11、0percentefficientinconvertingsunlightwithfurtherresearchbeingconductedtoraisethisefficiencyto20percent. Thepvcellwasdiscoveredin1954byBellTelephoneresearchersexaminingthesensitivityofaproperlypreparedsiliconwafertosunlight.Beginninginthelate1950s,pvswereusedtopowerU.S.spacesatellites.ThesuccessofPVs

12、inspacegeneratedcommercialapplicationsforpvtechnology.Thesimplestphotovoltaicsystemspowermanyofthesmallcalculatorsandwristwatchesusedeveryday.Morecomplicatedsystemsprovideelectricitytopumpwater,powercommunicationsequipment,andevenprovideelectricitytoourhomes. Photovoltaicconversionisusefulforseveral

13、reasons.Conversionfromsunlighttoelectricityisdirect,sothatbulkymechanicalgeneratorsystemsareunnecessary.Themodularcharacteristicofphotovoltaicenergyallowsarraystobeinstalledquicklyandinanysizerequiredorallowed. Also,theenvironmentalimpactofaphotovoltaicsystemisminimal,requiringnowaterforsystemcoolin

14、gandgeneratingnoby-products.Photovoltaiccells,likebatteries,generatedirectcurrent(DC)whichisgenerallyusedforsmallloads(electronicequipment).WhenDCfromphotovoltaiccellsisusedforcommercialapplicationsorsoldtoelectricutilitiesusingtheelectricgrid,itmustbeconvertedtoalternatingcurrent(AC)usinginverters,

15、solidstatedevicesthatconvertDCpowertoAC.Historically,pvshavebeenusedatremotesitestoprovideelectricity.However,amarketfordistributedgenerationfromPVsmaybedevelopingwiththeunbundlingoftransmissionanddistributioncostsduetoelectricderegulation.Thesitingofnumeroussmall-scalegeneratorsinelectricdistributi

16、onfeederscouldimprovetheeconomicsandreliabilityofthedistributionsystem. SOLARTHERMALHEAT Themajorapplicationsofsolarthermalenergyatpresentareheatingswimmingpools,heatingwaterfordomesticuse,andspaceheatingofbuildings.Forthesepurposes,thegeneralpracticeistouseflat-platesolar-energycollectorswithafixed

17、orientation(position). Wherespaceheatingisthemainconsideration,thehighestefficiencywithafixedflat-platecollectorisobtainedifitfacesapproximatelysouthandslopesatanangletothehorizonequaltothelatitudeplusabout15degrees.Solarcollectorsfallintotwogeneralcategories:nonconcentratingandconcentrating.Intheno

18、nconcentratingtype,thecollectorarea(i.e.theareathatinterceptsthesolarradiation)isthesameastheabsorberarea(i.e.,theareaabsorbingtheradiation). Inconcentratingcollectors,theareainterceptingthesolarradiationisgreater,sometimeshundredsoftimesgreater,thantheabsorberarea.Wheretemperaturesbelowabout200oFar

19、esufficient,suchasforspaceheating,flat-platecollectorsofthenonconcentratingtypearegenerallyused. Therearemanyflat-platecollectordesignsbutgenerallyallconsistof(1)aflat-plateabsorber,whichinterceptsandabsorbsthesolarenergy,(2)atransparentcover(s)thatallowssolarenergytopassthroughbutreducesheatlossfro

20、mtheabsorber,(3)aheat-transportfluid(airorwater)flowingthroughtubestoremoveheatfromtheabsorber,and(4)aheatinsulatingbacking. Solarspaceheatingsystemscanbeclassifiedaspassiveoractive.Inpassiveheatingsystems,theairiscirculatedpastasolarheatsurface(s)andthroughthebuildingbyconvection(i.e.lessdensewarma

21、irtendstorisewhilemoredensecoolerairmovesdownward)withouttheuseofmechanicalequipment.Inactiveheatingsystems,fansandpumpsareusedtocirculatetheairortheheatabsorbingfluid. SOLARTHERMALPOWERPLANTS Solarthermalpowerplantsusethesunsraystoheatafluid,fromwhichheattransfersystemsmaybeusedtoproducesteam.Thest

22、eam,inturn,isconvertedintomechanicalenergyinaturbineandintoelectricityfromaconventionalgeneratorcoupledtotheturbine.Solarthermalpowergenerationisessentiallythesameasconventionaltechnologiesexceptthatinconventionaltechnologiestheenergysourceisfromthestoredenergyinfossilfuelsreleasedbycombustion.Solar

23、thermaltechnologiesuseconcentratorsystemsduetothehightemperaturesneededfortheworkingfluid. PARABOLICTROUGH TheparabolictroughisusedinthelargestsolarpowerfacilityintheworldlocatedintheMojaveDesertatKramerJunction,California.Thisfacilityhasoperatedsincethe1980andaccountedforthemajorityofsolarelectrici

24、typroducedbytheelectricpowersectorin2004. Aparabolictroughcollectorhasalinearparabolic-shapedreflectorthatfocusesthesunsradiationonalinearreceiverlocatedatthefocusoftheparabola.Thecollectortracksthesunalongoneaxisfromeasttowestduringthedaytoensurethatthesuniscontinuouslyfocusedonthereceiver.Becauseo

25、fitsparabolicshape,atroughcanfocusthesunat30to100timesitsnormalintensity(concentrationratio)onareceiverpipelocatedalongthefocallineofthetrough,achievingoperatingtemperaturesover400degreesCelcius. Acollectorfieldconsistsofalargefieldofsingle-axistrackingparabolictroughcollectors.Thesolarfieldismodula

26、rinnatureandiscomposedofmanyparallelrowsofsolarcollectorsalignedonanorth-southhorizontalaxis.Aworking(heattransfer)fluidisheatedasitcirculatesthroughthereceiversandreturnstoaseriesofheatexchangersatacentrallocationwherethefluidisusedtogeneratehigh-pressuresuperheatedsteam.Thesteamisthenfedtoaconvent

27、ionalsteamturbine/generatortoproduceelectricity.Aftertheworkingfluidpassesthroughtheheatexchangers,thecooledfluidisrecirculatedthroughthesolarfield.Theplantisusuallydesignedtooperateatfullratedpowerusingsolarenergyalone,givensufficientsolarenergy.However,allplantsarehybridsolar/fossilplantsthathavea

28、fossil-firedcapabilitythatcanbeusedtosupplementthesolaroutputduringperiodsoflowsolarenergy.TheLuzplantisanaturalgashybrid. SOLARDISH Asolardish/enginesystemutilizesconcentratingsolarcollectorsthattrackthesunontwoaxes,concentratingtheenergyatthefocalpointofthedishbecauseitisalwayspointedatthesun.Thes

29、olardishsconcentrationratioismuchhigherthatthesolartrough,typicallyover2,000,withaworkingfluidtemperatureover750C.Thepower-generatingequipmentusedwithasolardishcanbemountedatthefocalpointofthedish,makingitwellsuitedforremoteoperationsor,aswiththesolartrough,theenergymaybecollectedfromanumberofinstal

30、lationsandconvertedtoelectricityatacentralpoint.Theengineinasolardish/enginesystemconvertsheattomechanicalpowerbycompressingtheworkingfluidwhenitiscold,heatingthecompressedworkingfluid,andthenexpandingthefluidthroughaturbineorwithapistontoproducework.Theengineiscoupledtoanelectricgeneratortoconvertt

31、hemechanicalpowertoelectricpower.SOLARPOWERTOWER Asolarpowertowerorcentralreceivergenerateselectricityfromsunlightbyfocusingconcentratedsolarenergyonatower-mountedheatexchanger(receiver).Thissystemuseshundredstothousandsofflatsun-trackingmirrorscalledheliostatstoreflectandconcentratethesunsenergyont

32、oacentralreceivertower.Theenergycanbeconcentratedasmuchas1,500timesthatoftheenergycominginfromthesun.Energylossesfromthermal-energytransportareminimizedassolarenergyisbeingdirectlytransferredbyreflectionfromtheheliostatstoasinglereceiver,ratherthanbeingmovedthroughatransfermediumtoonecentrallocation

33、,aswithparabolictroughs.Powertowersmustbelargetobeeconomical.Thisisapromisingtechnologyforlarge-scalegrid-connectedpowerplants.Thoughpowertowersareintheearlystagesofdevelopmentcomparedwithparabolictroughtechnology,anumberoftestfacilitieshavebeenconstructedaroundtheworld. LastRevised:July2008 Sources

34、:EnergyInformationAdministration,ElectricPowerAnnual,FormEIA-860,AnnualElectricGeneratorReportdatabase.来自太阳的能源 太阳产生能量已有数十亿年，太阳能是太阳辐射到地球的能量。太阳能可以直接或间接地转换为其他形式的能源，如热能和电能。主要缺点（问题，或者问题有待克服）太阳能是：（1 1）间歇方式到达地球表面，（2 2）大面积收集在一个大容器中。 太阳能被用于加热家庭用水，供暖建筑物，干燥农产品，发电和电力能源。在 18301830年代， 英国天文学家约翰赫在一个探险队到非洲在烹调食物时采用太阳

35、能集热箱。 现在，人们正试图用太阳的能量做很多东西。电力部门正试图利用光伏发电，是太阳能直接转化为电能一个过程。电流可以直接由太阳能利用光电器件或间接从蒸汽发生器产生，使用太阳能热收藏家一一热工质收藏。 在美国 20042004 年年底已出现的 1414 个已知太阳能发电营运单位，其中主要在加州和亚利桑那州。统计数据显示正在收集的太阳能，可以产生小于 1 1 兆瓦的电力，因此，在其他一些国家可以应用较小的太阳能电厂。 光伏发电 光伏发电是把太阳光转换为电能，通过光伏（PVPV 州勺电池板，即俗称的太阳能电池。光伏电池是一个非机械装置，通常制成硅合金。日光是由光子或粒子组成的太阳能，这些光子含有

36、不同量的能量相应于不同波长的太阳光谱。当光子通过光伏电池可以反映出来，穿过的，或者被吸收，利用吸收光子的能量来发电。 当阳光不足（能源）时将所吸收的材料（半导体），利用电子赶出了材料的原子。特殊处理的材料表面在制造使得锋面的细胞更容易接受自由电子，所以电子自然迁移到地表。当电子离开自己的位置，就形成空穴。当许多电子，带负电荷的 电子运动形成电流，由此产生的不平衡电荷之间产生电位从而由负极流向正极。两个电极通过外部负载形成回路而产生电流。 光伏电池的基本构造光伏系统。电池板规模可大可小，可从 1 1 厘米（1/21/2 英寸）到1010 厘米（4 4 英寸）。但是，一块小的电池板只产生 1 1

37、或 2 2 瓦特，这对于大多数负载来说是远远不够用的。需要增加输出功率，将许多小的电池板模块连接成一个紧凑模块。模块可以进一步连接组成一个电池板组。任期阵列指的是整个发电厂的，不论它是由一个或几个单元组成。正如很多模块需要连接组成一定大小的阵列。光伏阵列受到阳光的影响。气候条件（例如，云雾）对光伏阵列收到的太阳能有重大影响。目前大多数科技光伏组件约有 10%10%高效日光转换，进一步的研究正在进行中，以把效率为提高为 20%20%。 在 19541954 年由贝尔电话研究者研究的敏感性，发明光伏电池，利用硅片吸收阳光。5050年代后期，被用于美国在太空的卫星。由于在太空的成功应用，光伏技术逐渐

38、应用于商业。许多小型计算器和手表都用最简单的光伏电源系统。更为复杂的系统，提供 fe 力抽水，电力通讯设备，甚至向用户提供电力。光电转换是有很多优点。利用阳光直接产生电力，使得笨重机械发电机系统逐渐被取代。模块化特性光伏发电阵列很快发展成可以满足任何尺寸要求。同时，光伏发电系统对环境的影响是非常小的，它无需水冷却系统，也不会产生副作用。光伏电池，产生直流电，即一般用于小负载（电子设备）。当直流的光伏电池用于商业应用或利用电力网出售给电力企业，它必须用逆变器转换成交流电，固莅装置转换成直流电源空调。 在过去，光伏电池已用于在远程站点提供电力。然而，根据市场分布，使开发与分拆输电和配电成本上涨。

39、无数小型发电机， 配电馈线能改善经济性和可靠性的分配制度。 热力太阳能 目前供暖游泳池，热水供国内使用，和空间加热建筑物大量应用太阳能热能。为实现上述目的，一般的做法是使用平板型太阳能储藏提供一个固定的方向（位置）。如供暖主要是考虑效率最高，用固定平板式集热器获得，可以放到向南斜坡上的一个角到地平线约 1515 度。 太阳能集热器可分为两大类：非集中和集中。 在非集中型中的集热器面积（即该地区拦截太阳辐射）是相同的吸热面积（即该地区吸收的辐射）。在集中收藏，该地区拦截太阳辐射较大，比吸热面积有时高几百倍。在温度低的情况下，如供暖，平板集热器的类型非集中普遍使用。有很多平板式集热器的设计，但一般都包括下列内容：（1 1）平板式减震器，拦截，又吸收了太阳能，（2 2）透明覆盖板，使太阳能通过，降温的吸收剂，（3 3）传热流体（空气或水），流经管道，以消除热量的吸收，（4 4）有保温的后盾。