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WindEnergy--EnergyfromMovingAirWindissimpleairinmotion.Itiscausedbytheunevenheatingoftheearthsurfacebythesun.Sincetheearthsurfaceismadeofve

rydifferenttypesoflandandwater,itabsorbsthesunheatatdifferentrates.Duringtheday,theairabovethelandheatsupmorequicklythantheairoverw

ater.Thewarmairoverthelandexpandsandrises,andtheheavier,coolerairrushesintotakeitsplace,creatingwinds.Atnight,thewindsarereversedbecausetheai

rcoolsmorerapidlyoverlandthanoverwater.Inthesameway,thelargeatmosphericwindsthatcircletheeartharecreatedbecausethela

ndneartheearth'sequatorisheatedmorebythesunthanthelandneartheNorthandSouthPoles.Today,windenergyismainlyusedtogenerateelectricity.Windiscalleda

renewableenergysourcebecausethewindwillblowaslongasthesunshines.TheHistoryofWindSinceancienttimes,peoplehaveha

rnessedthewindsenergy.Over5,000yearsago,theancientEgyptiansusedwindtosailshipsontheNileRiver.Later,peoplebuilt

windmillstogrindwheatandothergrains.TheearliestknownwindmillswereinPersia(Iran).Theseearlywindmillslookedlikelarge

paddlewheels.Centurieslater,thepeopleofHollandimprovedthebasicdesignofthewindmill.Theygaveitpropeller-typeblades,sti

llmadewithsails.Hollandisfamousforitswindmills.Americancolonistsusedwindmillstogrindwheatandcorn,topumpwater,andtocutw

oodatsawmills.Aslateasthe1920s,Americansusedsmallwindmillstogenerateelectricityinruralareaswithoutelectricserv

ice.Whenpowerlinesbegantotransportelectricitytoruralareasinthe1930s,localwindmillswereusedlessandless,thought

heycanstillbeseenonsomeWesternranches.Theoilshortagesofthe1970schangedtheenergypictureforthecountryandtheworld.Itcreatedaninte

restinalternativeenergysources,pavingthewayforthere-entryofthewindmilltogenerateelectricity.Intheearly1980swindenergyreallytookoffinCalif

ornia,partlybecauseofstatepoliciesthatencouragedrenewableenergysources.Supportforwinddevelopmenthassincespreadtoothe

rstates,butCaliforniastillproducesmorethantwiceasmuchwindenergyasanyotherstate.ThefirstoffshorewindparkintheUnitedStatesisplan

nedforanareaoffthecoastofCapeCod,Massachusetts(readanarticleabouttheCapeCodWindProject).HowWindMachinesWorkLikeoldfa

shionedwindmills,todaywindmachinesusebladestocollectthewindkineticenergy.Windmillsworkbecausetheyslowdownthespeedofthewind.Thewindflowsove

rtheairfoilshapedbladescausinglift,liketheeffectonairplanewings,causingthemtoturn.Thebladesareconnectedtoadriveshaftthatturnsanele

ctricgeneratortoproduceelectricity.Withthenewwindmachines,thereisstilltheproblemofwhattodowhenthewindisblow

ing.Atthosetimes,othertypesofpowerplantsmustbeusedtomakeelectricity.WindPowerPlanWindpowerplants,orwin

dfarmsastheyaresometimescalled,areclustersofwindmachinesusedtoproduceelectricity.Awindfarmusuallyhasdozensof

windmachinesscatteredoveralargearea.TheBigSpringWindPowerProjectinTexashas46windturbinesthatgenerateenough

electricitytopower7,300homes.Unlikepowerplants,manywindplantsarenotownedbypublicutilitycompanies.Insteadtheyareownedandoperatedbybusinesspeoplewhose

lltheelectricityproducedonthewindfarmtoelectricutilities.TheseprivatecompaniesareknownasIndependentPowerProducers.Operatingawin

dpowerplantisnotassimpleasjustbuildingawindmillinawindyplace.Windplantownersmustcarefullyplanwheretolocatetheirmachines.Oneimpor

tantthingtoconsiderishowfastandhowmuchthewindblows.Asarule,windspeedincreaseswithaltitudeandoveropenareaswithnowindbre

aks.Goodsitesforwindplantsarethetopsofsmooth,roundedhills,openplainsorshorelines,andmountaingapsthatproducewindfunneling

.Windspeedvariesthroughoutthecountry.Italsovariesfromseasontoseason.InTehachapi,California,thewindblowsmorefromAprilthroughOctob

erthanitdoesinthewinter.ThisisbecauseoftheextremeheatingoftheMojaveDesertduringthesummermonths.Thehotairoverthedesertrises,andthecool

er,denserairabovethePacificOceanrushesthroughtheTehachapimountainpasstotakeitsplace.InastatelikeMontana,ontheot

herhand,thewindblowsmoreduringthewinter.Fortunately,theseseasonalvariationsareagoodmatchfortheelectric

itydemandsoftheregions.InCalifornia,peopleusemoreelectricityduringthesummerforairconditioners.InMontana,people

usemoreelectricityduringthewintermonthsforheating.WindProductionAlltogether,windmachinesintheUnitedStatesgenerate17billionkWhperyearofelectrici

ty,enoughtoserve1.6millionhouseholds.ThisisenoughelectricitytopoweracitythesizeofChicago,butitisonlyasmallfracti

onofthenation'stotalelectricityproduction,about0.4percent.Theamountofelectricitygeneratedfromwindhasbeengrowingfastin

recentyears,triplingsince1998.Newtechnologieshavedecreasedthecostofproducingelectricityfromwind,andgrowthinwindpowerhasbeenencouragedbytaxbrea

ksforrenewableenergyandgreenpricingprograms.Manyutilitiesaroundthecountryoffergreenpricingoptionsthatallowc

ustomersthechoicetopaymoreforelectricitythatcomesfromrenewablesources.Windmachinesgenerateelectricityin30differentstates.Thestate

swiththemostwindproductionareCalifornia,Texas,Minnesota,Iowa,andWyoming.TheUnitedStatesranksthirdintheworldinwindpowercapacity,behindGe

rmanyandSpain.MostofthewindpowerplantsintheworldarelocatedinEuropeandintheUnitedStateswheregovernmentprogramshavehelpedsupportwindpowerdevelopm

ent.WindandtheEnvironmentInthe1970s,oilshortagespushedthedevelopmentofalternativeenergysources.Inthe1990s,thepushcamefromarenewedconcernfortheenvi

ronmentinresponsetoscientificstudiesindicatingpotentialchangestotheglobalclimateiftheuseoffossilfuelscontinuestoincrease.Windenergy

offersaviable,economicalalternativetoconventionalpowerplantsinmanyareasofthecountry.Windisacleanfuel;win

dfarmsproducenoairorwaterpollutionbecausenofuelisburned.Themostseriousenvironmentaldrawbackstowindmachinesmaybetheirn

egativeeffectonwildbirdpopulationsandthevisualimpactonthelandscape.Tosome,theglisteningbladesofwindmillsontheh

orizonareaneyesore;toothers,theyareabeautifulalternativetoconventionalpowerplants.