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HydroelectricPowerUnit31Content4.1IntroductiontoHydroenergy4.2Hydroelectricpowergeneration4.3Environmentalimpact4.4subject-verbStructures4.5Threegorgesdam23Hydroenergyreferstosumofthekineticenergy,potentialandpressureenergyofwater.Generalizedhydroenergyresourcesincludingriverwater,tidalenergy（潮汐能）,waveenergy(波浪能)，oceanenergyetal.

Throughhydropower,theenergyinfallingwaterisconvertedintoelectricitywithout“usingup”thewater.

Hydroelectricpower/hydropower:水力發(fā)電

4.1IntroductiontoHydroenergyHydroenergy:水能

Humansfirstlearnedtoharnessthekineticenergyinwaterbyusingwaterwheels.Awaterwheelisarevolvingwheelfittedwithblades（槳葉）,buckets（斗葉）,orvanes（葉片）.

Waterwheelsconvertthekineticenergyofflowingwatertomechanicalenergy.Waterwheel：水車Earlywaterwheelsusedmechanicalenergytogrindgrainsandtodrivemachinerysuchassawmills（鋸木頭）andblacksmith（打鐵）equipment.TypesofWaterWheels（水車）TypesofwaterwheelsarebaseduponwherethewaterstrikesitPitchback–后流式水車Overshot–上沖式水車Undershot–下沖式水車WaterWheels:PitchbackandOvershotAsurroundstructurecouldforcethewateragainstthewheelasitfallsandincreasetheweightofthewaterinthewheel.Pitchback

（后流式水車）–waterdropsfromtopandisdeflectedbackwardstofallbacktowardsthedamOvershot

（上沖式水車）–shootsoverthetopontothewheel;theusualkindWaterWheels:Undershot（下沖式）TheundershotwheelissimplyplacedinastreamwiththebottomofthewheelpushedbythecurrentWorkswellwherethereislittledepthandnoheadInefficient,butworkswhereotherswon’tWaterwheeltechnologyadvancedovertime.Turbinesareadvanced,veryefficientwaterwheels.Turbine：渦輪機(jī)、水輪機(jī)、汽輪機(jī)Waterwheelsturnslowlycomparedwithturbines:onetofiftyrpmTurbinesrpm:revolutionsperminute轉(zhuǎn)數(shù)/分10ClassificationofHydroTurbinesReactionTurbines：反擊式水輪機(jī)TotallyimmersedinwaterCombiningactionofpressureenergyandkineticenergyofthewaterPropeller(槳葉式)andFrancis（混流式或法蘭西式）turbinesPropellerTurbineSmallversionsofthePropellerturbinecanbeloweredintoastreambyhandtopoweraremotehomehttp://www.hitachi.co.jp/Div/hitachi/hydraulic-turbine/BULB.htm050322Ampair'sAquairUWsubmersiblepropellerturbine

30ftdiameter 0.8ftdiameterFrancisTurbineWaterflowsthroughtherunnertospintheturbine.

水流從四周徑向流入轉(zhuǎn)輪，然后近似軸向流出轉(zhuǎn)輪，混流式水輪機(jī)結(jié)構(gòu)緊湊，效率較高，能適應(yīng)很寬的水頭范圍

03032313ImpulseTurbines：沖擊式水輪機(jī)ConvertkineticenergyofwaterjethittingbucketsNopressuredropacrossturbinesImpulseTurbinesThesedoublecupscatchthewaterfromtheinputwaterjetsandreflectitformaximumthrusttospintherotorImpulseTurbinesarepopularformicroturbinesproducingenergy.http://www.hitachi.co.jp/Div/hitachi/hydraulic-turbine/others.htm050322美國(guó)的佩爾頓最早發(fā)明的水斗式水輪機(jī)。它有流線型的收縮噴嘴，能把水流能量高效率地轉(zhuǎn)變?yōu)楦咚偕淞鞯膭?dòng)能。Notlongafterthediscoveryofelectricity,itwasrealizedthataturbine’smechanicalenergycouldbeusedtoactivateageneratorandproduceelectricity.Thefirsthydroelectricpowerplantwasconstructedin1882inAppleton（阿普爾頓）,Wisconsin（威斯康星州）.

Itproduced12.5kilowattsofelectricitywhichwasusedtolighttwopapermills（紙廠）andonehome.4.2Hydroelectricpowergeneration16Flowingwaterisdirectedataturbine(rememberturbinesarejustadvancedwaterwheels).Theflowingwatercausestheturbinetorotate,convertingthewater’skineticenergyintomechanicalenergy.Themechanicalenergyproducedbytheturbineisconvertedintoelectricenergyusingaturbinegenerator.Insidethegenerator,theshaftoftheturbinespinsamagnetinsidecoils（銅線圈）ofcopperwire.

Itisafactofnaturethatmovingamagnetnearaconductorcausesanelectriccurrent.

HowaHydroelectricPowerSystemWorksPotential

EnergyKinetic

EnergyElectrical

EnergyMechanicalEnergyElectricityTheamountofelectricitythatcanbegeneratedbyahydropowerplantdependsontwofactors:

flowrate

-thequantityofwaterflowinginagiventime;

head-theheightfromdamthewaterfalls.Thegreatertheflowrateandhead,themoreelectricityproduced.Howmuchelectricitycanbegeneratedbyahydroelectricpowerplant?flowrate：流量

Head：水頭Whenmorewaterflowsthroughaturbine,moreelectricitycanbeproduced.Theflowratedependsonthesizeoftheriverandtheamountofwaterflowinginit.Powerproductionisconsideredtobedirectlyproportionaltoriverflow.Thatis,twiceasmuchwaterflowingwillproducetwiceasmuchelectricity.FlowRate=thequantityofwaterflowinginagiventimeThehigherthedam,thefartherthewaterfalls,producingmorehydroelectricpower.Powerproductionisalsodirectlyproportionaltohead.Thatis,waterfallingtwiceasfarwillproducetwiceasmuchelectricity.Head=theheightfromdamwaterfallsPower=theelectricpowerinkilowattsorkWHead=thedistancethewaterfalls(measuredinfeet（英尺）)Flow=theamountofwaterflowing(measuredincubicfeetpersecond orcfs)Efficiency=Howwelltheturbineandgeneratorconvertthepowerof fallingwaterintoelectricpower.Thiscanrangefrom60% (0.60)forolder,poorlymaintainedhydroplantsto90% (0.90)fornewer,wellmaintainedplants.11.8=Indexthatconvertsunitsoffeetandsecondsintokilowatts

Astandardequationforcalculatingenergyproduction:Power=(Head)x(Flow)x(Efficiency)11.8

feet：英尺

Thetwoprimarytypesofhydropowerfacilitiesaretheimpoundmentsystem

(ordam)andtherun-of-the-riversystem.TypesofHydropowerFacilitiesimpoundmentsystem：蓄水系統(tǒng)

run-of-the-riversystem：運(yùn)行的河流系統(tǒng)Animpoundmentissimplyadamthatholdswaterinareservoir.Thewaterisreleasedwhenneededthroughapenstock（水渠）,todrivetheturbine.Thisillustrationshowsthepartsofastandardhydroelectricdam.Mostlarge,high-headhydropowerfacilitiesuseimpoundments.ImpoundmentSystemArun-of-the-river

systemusestheriver’snaturalflowandrequireslittleornoimpoundment.Itmayinvolveadiversionofthestreamthroughacanal（管道）orpenstock（水渠）,anditmayinvolveplacementofaturbinerightinthestreamchannel.Run-of-the-riversystemsareoftenlow-head.Run-of-the-RiverHydropowerSystem運(yùn)行的河流系統(tǒng)發(fā)電系統(tǒng)Therearelargepowerplantsthatproducehundredsofmegawattsofelectricityandservethousandsoffamilies.Therearealsosmallandmicrohydropowerplantsthatindividualscanoperatefortheirownenergyneeds.HydropowerPlantsAlsoVaryinSizeAlargehydropowerfacilityhasthecapacitytoproducemorethan30,000kilowatts(kW)ofelectricity.

ThemajorityofhydropowersystemsintheU.S.fitinthiscategory.Largehydropowersystemstypicallyrequireadam.LargeHydropowerSmallHydropowerSmallhydropowerfacilitiescanproduce100–30,000kilowatts(kW)ofelectricity.Smallhydropowerfacilitiesmayinvolveasmalldam,orbeadiversionofthemainstream,orbearun-of-the-riversystem.Microhydropowerplantshavethecapacitytoproduce100kilowatts(kW)orless.Micro-hydrofacilitiestypicallyusearun-of-the-riversystem.MicroHydropower4.3EnvironmentalConsiderationsHigh-headhydropowersystemscanproduceatremendousamountofpower.However,largehydropowerfacilities,whileessentiallypollution-freetooperate,stillhaveundesirableeffectsontheenvironment.Installationofnewlargehydropowerprojectstodayisverycontroversial（有爭(zhēng)議的）becauseoftheirnegativeenvironmentalimpacts.Theseinclude:upstreamfloodingdecliningfishpopulationsdecreasedwaterqualityandflowreducedqualityofupstreamanddownstreamenvironmentsScientiststodayareseekingwaystodevelophydropowerplantsthathavelessimpactontheenvironment.Onewayisthroughlow-headhydropower.Low-headhydropowerprojectsareusuallylowimpactaswell—thatis,theyhavefewernegativeeffectsontheenvironment.Low-headandLowImpactHydropower4.3subject-verbStructures在英語(yǔ)閱讀中，句子主謂結(jié)構(gòu)的識(shí)別是最基本的閱讀技巧：

句子的中心內(nèi)容句子的主干識(shí)別主謂結(jié)構(gòu)是分析句子的第一步。

英語(yǔ)的主謂次序：主語(yǔ)在前，謂語(yǔ)在后。主語(yǔ)和謂語(yǔ)之間常插入定語(yǔ)和狀語(yǔ)。33(1)Thepotentialenergypossessedbywateristheproductofitsweightandausabledifferenceinelevationcalledhead.(2)Thepowerplant,withatotalinstalledcapacityof1800MW,

isapuredaily-regulatedpumpedstoragepowerplant.(3)Thewaterpossessinglargeenergystrikestherunnerandcausesittorotate.Economiesofscaleandthegreatergeneratingefficiencyachievedashighersteamtemperaturesandpressureswereattainedbothreinforcedthistendency.34Economiesofscaleandthegreatergeneratingefficiencyachievedashighersteamtemperaturesandpressureswereattained

bothreinforcedthistendency.大多情況下，主語(yǔ)相對(duì)比較容易確定，但識(shí)別主謂結(jié)構(gòu)的關(guān)鍵是找謂語(yǔ)動(dòng)詞。有時(shí)主語(yǔ)與謂語(yǔ)之間插入的內(nèi)容較多，正確找出謂語(yǔ)就會(huì)比較困難。主語(yǔ)謂語(yǔ)后置定語(yǔ)從句謂語(yǔ)獲得更高的蒸汽溫度和壓強(qiáng)可以得到更高的發(fā)電效率，規(guī)模經(jīng)濟(jì)和更高的發(fā)電效率加強(qiáng)了這種（電力增長(zhǎng)的）趨勢(shì)。35Theexpandinggascomingfromtheturbineandmovingalongthejetnozzles（噴嘴）

continuestoexpandandacceleratetoformahighvelocity.英語(yǔ)主謂結(jié)構(gòu)這一問(wèn)題可以從英語(yǔ)名詞的數(shù)、基本的英語(yǔ)主謂結(jié)構(gòu)類型以及定語(yǔ)從句主謂結(jié)構(gòu)的識(shí)別等三方面來(lái)判斷。（1）英語(yǔ)名詞的數(shù):謂語(yǔ)動(dòng)詞根據(jù)主語(yǔ)的單復(fù)數(shù)的不同發(fā)生單復(fù)數(shù)的變化。-s結(jié)尾的名詞不一定是復(fù)數(shù)(如一些表示學(xué)科的名詞、專有名詞)Electronics(電子學(xué))isthebasisofallcommunicationssystem.Mechanics(力學(xué))hasdevelopedalotinmoderntimes

又如：thermodynamics，physics,optics.36Generalmotors(通用汽車公司)producesmanydifferenttypesofcars.（2）基本的英語(yǔ)主謂結(jié)構(gòu)類型

單個(gè)名詞+謂語(yǔ)動(dòng)詞并列名詞+謂語(yǔ)動(dòng)詞名詞+后置定語(yǔ)/狀語(yǔ)+謂語(yǔ)動(dòng)詞謂語(yǔ)動(dòng)詞+名詞（倒裝句）另外，還有非謂語(yǔ)動(dòng)詞或從句充當(dāng)主語(yǔ)

不定式（短語(yǔ)）+謂語(yǔ)動(dòng)詞動(dòng)名詞（短語(yǔ)）+謂語(yǔ)動(dòng)詞主語(yǔ)從句+謂語(yǔ)動(dòng)詞37單個(gè)名詞+謂語(yǔ)動(dòng)詞The20thcenturyhaswitnessedabigexpansionofelectricalpowergenerationanddistribution。并列名詞+謂語(yǔ)動(dòng)詞并列名詞有三類：and、or單個(gè)并列連接詞連接起來(lái)作主語(yǔ)的名詞。Notonly…butalso,neither…nor,either…or組合并列連接詞連接起來(lái)作主語(yǔ)的名詞。Aswellas,alongwith,togetherwith,inadditionto等介詞短語(yǔ)連接起來(lái)的名詞。Therotorshaftand

thefieldstructurearemadeofasolidalloysteel（固體合金鋼）forging（鍛造）inwhichslots（槽）aremachinedtoacceptthefieldcoils（勵(lì)磁線圈）,asshowninFigure2.And用復(fù)數(shù)，or由后面的名詞決定。Notonlycoalandoilbutalsofallingwaterisbeingusedtoproduceelectircity.Neither….nor,either…or…由后面的名詞決定。并列名詞+謂語(yǔ)動(dòng)詞39Thevariousmanifestations（表現(xiàn)形式）

ofelectricityaretheresultoftheaccumulationormotionofelectrons.名詞+后置定語(yǔ)/狀語(yǔ)+謂語(yǔ)動(dòng)詞Themachineaswellasitsauxiliarydevicesisimported.Aswellas,alongwith由后面的名詞決定。40Thehydroelectricpowerusingafallofwatertodrivewaterturbines

hasbeendevelopedtogenerateelectricity.Anotherimportantfactortobetakenintoconsiderationisthatcurrentstrengthisequalatcertainpointsinaseriescircuit.41Thereare

fourwaysfortransmittingpowerfromtheelectricmotortothespindle.謂語(yǔ)動(dòng)詞+名詞are是謂語(yǔ)動(dòng)詞，are提示主語(yǔ)是后面的復(fù)數(shù)名詞ways.Touseanyofthesefuelsneedsourseriousconsideration.不定式（短語(yǔ)）+謂語(yǔ)動(dòng)詞主語(yǔ)是不定式短語(yǔ)，而不是fuels.Generatingcurrentatalowerfrequencyandthenboostingittoahigherfrequencyaremoreefficient.動(dòng)名詞（短語(yǔ)）+謂語(yǔ)動(dòng)詞主語(yǔ)是兩個(gè)并列的動(dòng)名詞42Whetherthisunitwilloperateefficientlyremainstobeseen.Whatpotentialenergyandkineticenergymeansandhowweexplainthesetwoterms

havebeenmentionedinthisarticle.（3）定語(yǔ)從句的主謂結(jié)構(gòu)的判別

由于定語(yǔ)從句的主語(yǔ)可能是由that或which等連接詞來(lái)充當(dāng)，that或which到底指代什么，有時(shí)需要通過(guò)主謂結(jié)構(gòu)的分析才能搞清。主語(yǔ)從句+謂語(yǔ)動(dòng)詞Thisprocessenhancestheoverallthermalefficiencyofenergyconversiontoabout50percent-asopposedtoconventionalprocesses,whichhaveanefficiencyofabout36to38percent.Thisprocessenhances

theoverallthermalefficiencyofenergyconversiontoabout50percent-asopposedtoconventionalprocesses,whichhaveanefficiencyofabout36to38percent.43高壓輸電線路通常是由銅、鋁或包銅的線組成，這些線通過(guò)一連串瓷制絕緣體，懸掛于高高的鋼鐵格子塔架上。Thelineofhigh-voltagetransmissionsystemsareusuallycomposedofwiresofcopper,aluminum,orcopper-clad,whicharesuspended（懸浮于）fromtalllatticeworktowersofsteelbystringsofporcelaininsulators（瓷制絕緣體）.Thelineofhigh-voltagetransmissionsystemsareusuallycomposedofwiresofcopper,aluminum,orcopper-clad,whicharesuspended（懸浮于）fromtalllatticeworktowe