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WindEnergy--EnergyfromMovingAirWindissimpleairinmotion.Itiscausedbytheunevenheatingoftheearthsurfacebythes

un.Sincetheearthsurfaceismadeofverydifferenttypesoflandandwater,itabsorbsthesunheatatdifferentrates.Duringtheday,t

heairabovethelandheatsupmorequicklythantheairoverwater.Thewarmairoverthelandexpandsandrises,andtheheavier,coolerairrushesint

otakeitsplace,creatingwinds.Atnight,thewindsarereversedbecausetheaircoolsmorerapidlyoverlandthanoverwater.Inthesameway,thelargeatmosphericw

indsthatcircletheeartharecreatedbecausethelandneartheearth'sequatorisheatedmorebythesunthanthelandneartheNorthandSouthPoles.Today,windenergyi

smainlyusedtogenerateelectricity.Windiscalledarenewableenergysourcebecausethewindwillblowaslongasthesunshines.TheHi

storyofWindSinceancienttimes,peoplehaveharnessedthewindsenergy.Over5,000yearsago,theancientEgyptiansusedwin

dtosailshipsontheNileRiver.Later,peoplebuiltwindmillstogrindwheatandothergrains.TheearliestknownwindmillswereinPersi

a(Iran).Theseearlywindmillslookedlikelargepaddlewheels.Centurieslater,thepeopleofHollandimprovedthebasicdesignofthewindmill.Theygaveitpropeller-type

blades,stillmadewithsails.Hollandisfamousforitswindmills.Americancolonistsusedwindmillstogrindwheatandcorn,topumpwater,a

ndtocutwoodatsawmills.Aslateasthe1920s,Americansusedsmallwindmillstogenerateelectricityinruralareaswithoutelect

ricservice.Whenpowerlinesbegantotransportelectricitytoruralareasinthe1930s,localwindmillswereusedlessandless,thoughtheycanstillbeseenonsomeWeste

rnranches.Theoilshortagesofthe1970schangedtheenergypictureforthecountryandtheworld.Itcreatedaninterestinalternativeener

gysources,pavingthewayforthere-entryofthewindmilltogenerateelectricity.Intheearly1980swindenergyreallytookoffinCalifornia,partlybec

auseofstatepoliciesthatencouragedrenewableenergysources.Supportforwinddevelopmenthassincespreadtootherstates,butCaliforniastillproducesmoret

hantwiceasmuchwindenergyasanyotherstate.ThefirstoffshorewindparkintheUnitedStatesisplannedforanareaofft

hecoastofCapeCod,Massachusetts(readanarticleabouttheCapeCodWindProject).HowWindMachinesWorkLikeoldfashionedwindmills,todaywindmachines

usebladestocollectthewindkineticenergy.Windmillsworkbecausetheyslowdownthespeedofthewind.Thewindflowsovertheairfoilshapedbladescausing

lift,liketheeffectonairplanewings,causingthemtoturn.Thebladesareconnectedtoadriveshaftthatturnsanelectricgeneratortoproduceelectricity.Wi

ththenewwindmachines,thereisstilltheproblemofwhattodowhenthewindisblowing.Atthosetimes,othertypesofpowerplantsmustbeused

tomakeelectricity.WindPowerPlanWindpowerplants,orwindfarmsastheyaresometimescalled,areclustersofwindm

achinesusedtoproduceelectricity.Awindfarmusuallyhasdozensofwindmachinesscatteredoveralargearea.TheBigSpringWin

dPowerProjectinTexashas46windturbinesthatgenerateenoughelectricitytopower7,300homes.Unlikepowerplants,manywindplantsarenotownedbypublicutilitycompan

ies.Insteadtheyareownedandoperatedbybusinesspeoplewhoselltheelectricityproducedonthewindfarmtoelectricutilities.Theseprivatecompa

niesareknownasIndependentPowerProducers.Operatingawindpowerplantisnotassimpleasjustbuildingawindmillinawindyplace.Windplantownersmustcarefullyplan

wheretolocatetheirmachines.Oneimportantthingtoconsiderishowfastandhowmuchthewindblows.Asarule,windspeedincreaseswithaltitudeandoverope

nareaswithnowindbreaks.Goodsitesforwindplantsarethetopsofsmooth,roundedhills,openplainsorshorelines,andmountaing

apsthatproducewindfunneling.Windspeedvariesthroughoutthecountry.Italsovariesfromseasontoseason.InTehachapi,California,thewindblowsmorefromApril

throughOctoberthanitdoesinthewinter.ThisisbecauseoftheextremeheatingoftheMojaveDesertduringthesummermonths.Thehotairoverthedesertrises,an

dthecooler,denserairabovethePacificOceanrushesthroughtheTehachapimountainpasstotakeitsplace.InastatelikeMontana,ontheotherhand,thewindblowsmoredurin

gthewinter.Fortunately,theseseasonalvariationsareagoodmatchfortheelectricitydemandsoftheregions.InCalifornia,peopleusemoreelectricity

duringthesummerforairconditioners.InMontana,peopleusemoreelectricityduringthewintermonthsforheating.WindProductionA

lltogether,windmachinesintheUnitedStatesgenerate17billionkWhperyearofelectricity,enoughtoserve1.6millionhouseholds.Thisi

senoughelectricitytopoweracitythesizeofChicago,butitisonlyasmallfractionofthenation'stotalelectricityp

roduction,about0.4percent.Theamountofelectricitygeneratedfromwindhasbeengrowingfastinrecentyears,triplingsince1998.Newtechnologieshavedecre

asedthecostofproducingelectricityfromwind,andgrowthinwindpowerhasbeenencouragedbytaxbreaksforrenewableenergyandgreenpricing

programs.Manyutilitiesaroundthecountryoffergreenpricingoptionsthatallowcustomersthechoicetopaymorefore

lectricitythatcomesfromrenewablesources.Windmachinesgenerateelectricityin30differentstates.ThestateswiththemostwindproductionareCalifornia,Texa

s,Minnesota,Iowa,andWyoming.TheUnitedStatesranksthirdintheworldinwindpowercapacity,behindGermanyandSpain.Mostofthewindpower

plantsintheworldarelocatedinEuropeandintheUnitedStateswheregovernmentprogramshavehelpedsupportwindpowerdevel

opment.WindandtheEnvironmentInthe1970s,oilshortagespushedthedevelopmentofalternativeenergysources.Inthe1990s,thepushcamefromarenewedconcernforth

eenvironmentinresponsetoscientificstudiesindicatingpotentialchangestotheglobalclimateiftheuseoffossilfuelscontinuestoin

crease.Windenergyoffersaviable,economicalalternativetoconventionalpowerplantsinmanyareasofthecountry.Windisa

cleanfuel;windfarmsproducenoairorwaterpollutionbecausenofuelisburned.Themostseriousenvironmentaldrawbackstowind

machinesmaybetheirnegativeeffectonwildbirdpopulationsandthevisualimpactonthelandscape.Tosome,theglisteningbladesofwindmillsonthehorizonareaneyes

ore;toothers,theyareabeautifulalternativetoconventionalpowerplants.