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WindEnergy--EnergyfromMovingAirWindissimpleairinmotion.Itiscausedbytheunevenheatingoftheearthsurfacebythesun.Sincetheearthsurfa

ceismadeofverydifferenttypesoflandandwater,itabsorbsthesunheatatdifferentrates.Duringtheday,theairabovethelandheat

supmorequicklythantheairoverwater.Thewarmairoverthelandexpandsandrises,andtheheavier,coolerairrushesintotakeitsplace,creatingwinds.A

tnight,thewindsarereversedbecausetheaircoolsmorerapidlyoverlandthanoverwater.Inthesameway,thelargeatmosphericwindsthatcircletheea

rtharecreatedbecausethelandneartheearth'sequatorisheatedmorebythesunthanthelandneartheNorthandSouthPoles.Today,winde

nergyismainlyusedtogenerateelectricity.Windiscalledarenewableenergysourcebecausethewindwillblowaslongasthesunshines.

TheHistoryofWindSinceancienttimes,peoplehaveharnessedthewindsenergy.Over5,000yearsago,theancientEgyptiansusedwi

ndtosailshipsontheNileRiver.Later,peoplebuiltwindmillstogrindwheatandothergrains.TheearliestknownwindmillswereinPer

sia(Iran).Theseearlywindmillslookedlikelargepaddlewheels.Centurieslater,thepeopleofHollandimprovedthebasicdesignofthewindmill.Theygaveitpropeller-ty

peblades,stillmadewithsails.Hollandisfamousforitswindmills.Americancolonistsusedwindmillstogrindwheatandcorn,topumpwater,andt

ocutwoodatsawmills.Aslateasthe1920s,Americansusedsmallwindmillstogenerateelectricityinruralareaswith

outelectricservice.Whenpowerlinesbegantotransportelectricitytoruralareasinthe1930s,localwindmillswereusedlessandless,thoughtheycanstillbeseenon

someWesternranches.Theoilshortagesofthe1970schangedtheenergypictureforthecountryandtheworld.Itcreatedaninterestinalte

rnativeenergysources,pavingthewayforthere-entryofthewindmilltogenerateelectricity.Intheearly1980swindenergyreallytookoffinCalifornia,p

artlybecauseofstatepoliciesthatencouragedrenewableenergysources.Supportforwinddevelopmenthassincespreadtootherstates,butCaliforniastillpr

oducesmorethantwiceasmuchwindenergyasanyotherstate.ThefirstoffshorewindparkintheUnitedStatesisplannedforanareaoffthecoastofCapeCod,M

assachusetts(readanarticleabouttheCapeCodWindProject).HowWindMachinesWorkLikeoldfashionedwindmills,todaywindmachinesusebladestocollectthewindkineti

cenergy.Windmillsworkbecausetheyslowdownthespeedofthewind.Thewindflowsovertheairfoilshapedbladescausinglift,liketheeffectona

irplanewings,causingthemtoturn.Thebladesareconnectedtoadriveshaftthatturnsanelectricgeneratortoproduceelectricity.Withthenewwindmachines,therei

sstilltheproblemofwhattodowhenthewindisblowing.Atthosetimes,othertypesofpowerplantsmustbeusedtomakeelectricity.WindPowerPlanWindp

owerplants,orwindfarmsastheyaresometimescalled,areclustersofwindmachinesusedtoproduceelectricity.Awindfarmusuallyhasdo

zensofwindmachinesscatteredoveralargearea.TheBigSpringWindPowerProjectinTexashas46windturbinesthatgenerateenoug

helectricitytopower7,300homes.Unlikepowerplants,manywindplantsarenotownedbypublicutilitycompanies.Insteadtheyareo

wnedandoperatedbybusinesspeoplewhoselltheelectricityproducedonthewindfarmtoelectricutilities.Theseprivatecompaniesareknownas

IndependentPowerProducers.Operatingawindpowerplantisnotassimpleasjustbuildingawindmillinawindyplace.Windplantownersmustca

refullyplanwheretolocatetheirmachines.Oneimportantthingtoconsiderishowfastandhowmuchthewindblows.Asarule,windspeedincreaseswithaltitudeandoverope

nareaswithnowindbreaks.Goodsitesforwindplantsarethetopsofsmooth,roundedhills,openplainsorshorelines,andmountaing

apsthatproducewindfunneling.Windspeedvariesthroughoutthecountry.Italsovariesfromseasontoseason.InTehachapi,

California,thewindblowsmorefromAprilthroughOctoberthanitdoesinthewinter.ThisisbecauseoftheextremeheatingoftheMojaveDesert

duringthesummermonths.Thehotairoverthedesertrises,andthecooler,denserairabovethePacificOceanrushesthroughtheTehachapimountainpasstotakeitsplace.I

nastatelikeMontana,ontheotherhand,thewindblowsmoreduringthewinter.Fortunately,theseseasonalvariationsareagoodmatchfortheelectricitydemandsofthe

regions.InCalifornia,peopleusemoreelectricityduringthesummerforairconditioners.InMontana,peopleusemoreelectricityd

uringthewintermonthsforheating.WindProductionAlltogether,windmachinesintheUnitedStatesgenerate17billionkWhpe

ryearofelectricity,enoughtoserve1.6millionhouseholds.ThisisenoughelectricitytopoweracitythesizeofChicago,butitisonlyas

mallfractionofthenation'stotalelectricityproduction,about0.4percent.Theamountofelectricitygeneratedfromwindhasbeengrowingfastinrecenty

ears,triplingsince1998.Newtechnologieshavedecreasedthecostofproducingelectricityfromwind,andgrowthinwindpowerhasb

eenencouragedbytaxbreaksforrenewableenergyandgreenpricingprograms.Manyutilitiesaroundthecountryoffergree

npricingoptionsthatallowcustomersthechoicetopaymoreforelectricitythatcomesfromrenewablesources.Windmachinesgenerateelectricityin30different

states.ThestateswiththemostwindproductionareCalifornia,Texas,Minnesota,Iowa,andWyoming.TheUnitedStatesranksthirdintheworldinwindpowercapacity,be

hindGermanyandSpain.MostofthewindpowerplantsintheworldarelocatedinEuropeandintheUnitedStateswheregovernmentprogramshavehelpedsupp

ortwindpowerdevelopment.WindandtheEnvironmentInthe1970s,oilshortagespushedthedevelopmentofalternativee

nergysources.Inthe1990s,thepushcamefromarenewedconcernfortheenvironmentinresponsetoscientificstudiesindicatingpotentialchangest

otheglobalclimateiftheuseoffossilfuelscontinuestoincrease.Windenergyoffersaviable,economicalalternativetoconven

tionalpowerplantsinmanyareasofthecountry.Windisacleanfuel;windfarmsproducenoairorwaterpollutionbecausenofuelisburned.Themostserious

environmentaldrawbackstowindmachinesmaybetheirnegativeeffectonwildbirdpopulationsandthevisualimpactonthelandscap

e.Tosome,theglisteningbladesofwindmillsonthehorizonareaneyesore;toothers,theyareabeautifulalternative

toconventionalpowerplants.