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WindEnergy--EnergyfromMovingAirWindissimpleairinmotion.Itiscausedbytheunevenheatingoftheearthsurfacebythesun.Sinceth

eearthsurfaceismadeofverydifferenttypesoflandandwater,itabsorbsthesunheatatdifferentrates.Duringtheday,theairabo

vethelandheatsupmorequicklythantheairoverwater.Thewarmairoverthelandexpandsandrises,andtheheavier,coolerairrushesintot

akeitsplace,creatingwinds.Atnight,thewindsarereversedbecausetheaircoolsmorerapidlyoverlandthanoverwater.Inthesameway,thelargeatmosphericwindsthatcirc

letheeartharecreatedbecausethelandneartheearth'sequatorisheatedmorebythesunthanthelandneartheNorthand

SouthPoles.Today,windenergyismainlyusedtogenerateelectricity.Windiscalledarenewableenergysourcebecausethewindwill

blowaslongasthesunshines.TheHistoryofWindSinceancienttimes,peoplehaveharnessedthewindsenergy.Over5,000yearsago,theancientE

gyptiansusedwindtosailshipsontheNileRiver.Later,peoplebuiltwindmillstogrindwheatandothergrains.TheearliestknownwindmillswereinPersia(Iran).Theseea

rlywindmillslookedlikelargepaddlewheels.Centurieslater,thepeopleofHollandimprovedthebasicdesignofthewindmi

ll.Theygaveitpropeller-typeblades,stillmadewithsails.Hollandisfamousforitswindmills.Americancolonistsusedwindmillstogri

ndwheatandcorn,topumpwater,andtocutwoodatsawmills.Aslateasthe1920s,Americansusedsmallwindmillstogenerate

electricityinruralareaswithoutelectricservice.Whenpowerlinesbegantotransportelectricitytoruralareasinthe1930s,localwindmillswereuse

dlessandless,thoughtheycanstillbeseenonsomeWesternranches.Theoilshortagesofthe1970schangedtheenergypicturefor

thecountryandtheworld.Itcreatedaninterestinalternativeenergysources,pavingthewayforthere-entryofthewindmilltogenerat

eelectricity.Intheearly1980swindenergyreallytookoffinCalifornia,partlybecauseofstatepoliciesthatencouragedrenewableenergyso

urces.Supportforwinddevelopmenthassincespreadtootherstates,butCaliforniastillproducesmorethantwiceasmuchwindenergyasanyotherstate.Thefirstoffshorew

indparkintheUnitedStatesisplannedforanareaoffthecoastofCapeCod,Massachusetts(readanarticleabouttheCapeCodWindProject)

.HowWindMachinesWorkLikeoldfashionedwindmills,todaywindmachinesusebladestocollectthewindkineticenergy.Windmillsworkbe

causetheyslowdownthespeedofthewind.Thewindflowsovertheairfoilshapedbladescausinglift,liketheeffecton

airplanewings,causingthemtoturn.Thebladesareconnectedtoadriveshaftthatturnsanelectricgeneratortoproduceelectricity.With

thenewwindmachines,thereisstilltheproblemofwhattodowhenthewindisblowing.Atthosetimes,othertypesofpowerplants

mustbeusedtomakeelectricity.WindPowerPlanWindpowerplants,orwindfarmsastheyaresometimescalled,areclustersofwindmachinesuse

dtoproduceelectricity.Awindfarmusuallyhasdozensofwindmachinesscatteredoveralargearea.TheBigSpringWindPowerProjectinTexashas46windturbinesthatgenerat

eenoughelectricitytopower7,300homes.Unlikepowerplants,manywindplantsarenotownedbypublicutilitycompanie

s.Insteadtheyareownedandoperatedbybusinesspeoplewhoselltheelectricityproducedonthewindfarmtoelectricutilities.Thesepr

ivatecompaniesareknownasIndependentPowerProducers.Operatingawindpowerplantisnotassimpleasjustbuildingawindm

illinawindyplace.Windplantownersmustcarefullyplanwheretolocatetheirmachines.Oneimportantthingtoconsideri

showfastandhowmuchthewindblows.Asarule,windspeedincreaseswithaltitudeandoveropenareaswithnowindbreaks.Goodsitesforwind

plantsarethetopsofsmooth,roundedhills,openplainsorshorelines,andmountaingapsthatproducewindfunneling.Windspeedvariesthroughoutthecountry.Itals

ovariesfromseasontoseason.InTehachapi,California,thewindblowsmorefromAprilthroughOctoberthanitdoesinthew

inter.ThisisbecauseoftheextremeheatingoftheMojaveDesertduringthesummermonths.Thehotairoverthedesertrises,andthecooler,denserairabovethePacificOc

eanrushesthroughtheTehachapimountainpasstotakeitsplace.InastatelikeMontana,ontheotherhand,thewindblowsmoreduringthewinter.Fortunately,t

heseseasonalvariationsareagoodmatchfortheelectricitydemandsoftheregions.InCalifornia,peopleusemoreelectricityduringthesummerforairco

nditioners.InMontana,peopleusemoreelectricityduringthewintermonthsforheating.WindProductionAlltogether,windmachinesintheUnitedStatesgenerate1

7billionkWhperyearofelectricity,enoughtoserve1.6millionhouseholds.ThisisenoughelectricitytopoweracitythesizeofChicago,butitisonlyasmallfractionofth

enation'stotalelectricityproduction,about0.4percent.Theamountofelectricitygeneratedfromwindhasbeengrowingfastinrecentyears,triplingsince1998.Newte

chnologieshavedecreasedthecostofproducingelectricityfromwind,andgrowthinwindpowerhasbeenencouragedbytaxbreaksforrenewableenerg

yandgreenpricingprograms.Manyutilitiesaroundthecountryoffergreenpricingoptionsthatallowcustomersthecho

icetopaymoreforelectricitythatcomesfromrenewablesources.Windmachinesgenerateelectricityin30differentstates.Thestateswith

themostwindproductionareCalifornia,Texas,Minnesota,Iowa,andWyoming.TheUnitedStatesranksthirdintheworldinwindpowercapacity,behindGermanyandSpain.Mo

stofthewindpowerplantsintheworldarelocatedinEuropeandintheUnitedStateswheregovernmentprogramshavehelpedsuppo

rtwindpowerdevelopment.WindandtheEnvironmentInthe1970s,oilshortagespushedthedevelopmentofalternativeenergysources.Inthe1990s,thepushcamefr

omarenewedconcernfortheenvironmentinresponsetoscientificstudiesindicatingpotentialchangestotheglobalcl

imateiftheuseoffossilfuelscontinuestoincrease.Windenergyoffersaviable,economicalalternativetoconventionalpowerplantsinmanyareasofthecountr

y.Windisacleanfuel;windfarmsproducenoairorwaterpollutionbecausenofuelisburned.Themostseriousenvironmentaldrawbackstowindmachinesmaybetheirnega

tiveeffectonwildbirdpopulationsandthevisualimpactonthelandscape.Tosome,theglisteningbladesofwindmillsonthehorizonareaneyesore;tooth

ers,theyareabeautifulalternativetoconventionalpowerplants.