wind turb lecture full

8/3/2019 Wind Turb Lecture Full

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WindPowerSystems

Fall2010


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HistoryofWindPowerDevelopment

WindPower'sBeginnings

(1000B.C.

1300

A.D.)

SailBoat

PersianPanemone

500900A.D.

Verticalaxiswindstructureforseed

grindingorwaterpump

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WindmillsintheWesternWorld

(13001875

A.D.)

ThefirstwindmillstoappearinwesternEurope

wereofthehorizontalaxisconfiguration.

Thereasonforthesuddenevolutionfromthe

verticalaxisPersiandesignapproachisunknown

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Mediterraneanwindmill(Hills:1996)

Itusestheconceptofsailboat

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TheDutchman

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Asteel

bladed

water

pumping

windmill

in

the

American

Midwest(late1800's).

Between1850and1970,oversixmillionmostlysmall(1

horsepowerorless)mechanicaloutputwindmachineswere

installedintheU.S.alone.Theprimaryusewaswater

pumpingandthemainapplicationswerestockwateringand

farmhomewaterneeds.Verylargewindmills,withrotorsup

to18metersindiameter,wereusedtopumpwaterforthe

steamrailroadtrainsthatprovidedtheprimarysourceofcommercialtransportationinareaswheretherewereno

navigablerivers.

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Waterpumpusingwindenergy

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From:DevelopingWindPower

ProjectsbyToreWizelius (2007)

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Disaster

Palmer

Putnam's

1.25

megawatt

wind

turbine

wasoneoftheengineeringmarvelsofthelate

1930's,butthejumpinscalewastoogreatfor

availablematerials.

Thishorizontalaxisdesignfeaturedatwobladed,175footdiameterrotororienteddownwindof

thetower.The16tonstainlesssteelrotorused

fullspanbladepitchcontroltomaintainoperation

at28RPM.In1945,afteronlyseveralhundred

hoursofintermittentoperation,oneoftheblades

brokeoffnearthehub,apparentlyasaresultof

metalfatigue.

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Typicala3bladeturbine

system

Lowspeed;1530RPM

Noticethepoleheight;50m

Rotordiameter=oneblade

lengthx2

Sweptarea= (D/2)2

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ThebiggesteggbeaterDarrieus,thenearly

100mheight60mdiameter4MWratedgiganticeggbeaterEOLE,asshownintheleftpicture,locatedatCapChat,Quebec,Canada.Thegiantwasoperatedatlowerspeednowtoensure

longevitythusoutputreducedto2.5MW.AnotherEole pictureishere.

The42mheight34mdiameter625kWSandiaLaboratoryprototype wasbuiltspeciallyforresearchatBushland,Texas.ItcanbeidentifiedeasilyfromthefatcolumnwithUSDA,DOE,andaneaglelogoonit.

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http://rotor.fb12.tu-berlin.de/picture.eole.htmlhttp://rotor.fb12.tu-berlin.de/picture.eole.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://telosnet.com/wind/govprog.htmlhttp://rotor.fb12.tu-berlin.de/picture.eole.html


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From:Mukund Patel

WindandSolarPower

System(2006)

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NationalRenewableEnergy

Laboratory(NREL)Mt.Newall,Antarctica(NREL)

4NEGMicon225kW,Ascension

IslandinmidAtlanticOcean(NREL)16


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HornsRev Denmark'sLargestWindFarm HornsRevissituatedofthecoastof,Blvandhuk,themostwesternpointofDenmark.

ThelargestwindfarminDenmarkistheoffshorewindfarmofHornsRev,whichwascompletedin2002.ItissituatedintheNorthSea,1420kmoffthecoastofJutland.Withits80Vestas 2MWturbines,thewindfarmhasatotalcapacityof160MW.Thatmakesitthelargestoffshorewindfarmin

theworldtoday(2003).Thefarmsuppliestheequivalentof150,000(Danish)households.ThelargerproductioncomparedtoNysted isduetobetterwindconditions.Learnmoreatwww.hornsrev.dk

(PhotographClausBjle Mller,2003DWIA)

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http://www.hornsrev.dk/Engelsk/default_ie.htmhttp://www.hornsrev.dk/Engelsk/default_ie.htmhttp://www.hornsrev.dk/Engelsk/default_ie.htm


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InBrunsbuttel,Germany(2006),two5megawatts

offshorewindturbineswereonline.Theblade

diameterof126meterssweepinganareaof

12,000m2.

Maximumpoweriswhenthewindspeedis30

mph.Therotorsstarttoturnfor7mphwindspeed.

Fewmegawattsduringfreshbreeze.

Furling canbeachievedeithermanually(bytheturbineownerhimselfphysicallycrankingthe

turbineoutandawayfromthewind),or

automatically(withhydraulicsandspringsfor

example)withthegoalofturningtheturbine

bladeedgesintothewindwhenthewindisdangerouslystrongandgusty.

WhatIsWindTurbineFurling

Ifthewindistoostrong,thepitchof

individualbladewillberotatedto

preventthewholestructurebeingdamaged(Furling)

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WindSpeedandEnergy

Mukund R.Patel(WindandSolar)

Joules

m =massflows

Thevolumetricflowrateis AV

Themassflowrateis AV kg/sec

SpeedandPowerRelations

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Thetotalmechanicalpowerontheupstream

windinwatts:

Sometimethesiteselectionisbasedon

thepowerdensityorspecificwind

power(watts/m2)or

NoticeonV3 variation

Theupstreamwindwillberetarded/slowdownbythe

bladesandhenceextractingtheenergy.However,notall

thewindenergywillberemoved;thedownstreamair

stillmovesatalowerspeed.

W/m2

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=therotorefficiency=Neverreach1.0

= Maxvalueis0.593

Canbearrangedintheform

Powerfromthebladesisexpressedintermsofupstreamwind(watts)

Where

Comparingtheaboveequationto

Notice: Cp isthefractionoftheupstreamwind

powerthatisextractedbytherotorbladesandfed

tothegenerators(usefulpower).

V=upstreamwindvelocityattheentranceoftherotorblades

V0 =downstreamwindvelocityattheexitofrotorblades

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28.97g/mol=Molecularweight(MW)

ofgas

Warmerairhaslessdensityandhence

produceslesspower.


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http://docs.engineeringtoolbox.com/documents/600/air_density_specific_we

ight_chart.pdf
http://docs.engineeringtoolbox.com/documents/600/air_density_specific_weight_chart.pdfhttp://docs.engineeringtoolbox.com/documents/600/air_density_specific_weight_chart.pdfhttp://docs.engineeringtoolbox.com/documents/600/air_density_specific_weight_chart.pdfhttp://docs.engineeringtoolbox.com/documents/600/air_density_specific_weight_chart.pdf


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Theratiocanbeusedto

determinetherotorstress,as

inExample6.6P322.

P0 isthereferenceheightat10m


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FromFig3.3,thetheoretical

maximumvalueofCp is0.59

happenedwhenV0/Vof

about0.033or(1/3).

Cp canbeexpressedintermsof

therotortipspeedratio(TSR),whichisdefinedasthelinear

speedoftherotorstiptothe

upstreamwindspeed.

Whathappenatextremev0/vratio?

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InpracticaldesignsCpranges:

0.40.47formodernhighspeedtwobladeturbines

0.40.42forModernthreebladeturbines

FromFig3.4,wecanseethatuptonowthemaxvalueis0.47or

about0.5(50%efficiency).HenceaPracticalmaxpoweroutputis

Watts/m2 ofsweptarea

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Rotorsweptareaforthehorizontalaxis

turbineis:

whereDistherotor

diameter.

Sweptareaforverticalaxisturbine,like

Darrieus design,isverycomplicatedto

calculate.Theapproximationwithblade

shapeasaparabolagives:

Areaofparabola=2/3XbaseXheight

For33mdiameterand33mhalf

oftherotor,sweptarea=726m2

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AirDensity

Theairdensityatsealevelat1atm (14.7

psi)and60Fis1.225kg/m3.

ThefollowingtwoapproximatedEqs are

validupto6000m(~20,000ft):

OR

where,Hm isthesiteelevationinmeters.

Thetemperatureisrelatedtoelevationin Cas:

Varieswithpressureandtemperature

(GasLaw)

ToconvertCto F=multiply Cby9/5,thenadd32

Forthereverse,subtract32to F,thenmultiply5/9 20 C=68 F 34


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LargesyncgeneratorrequiresDCcurrentfeedingthefieldwindings.

DCsupplyusuallyobtainsfromacpowergridthroughrectifierand

capacitor.

TheinternalfieldingwindingsareexcitedbytheexternalDCcurrent

throughthesliprings(attachedontherotorshaft)andbrushes.

SmallgeneratorcanusetheresidualDCmagneticfieldleftover

insidethemachine.


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Thespeedforwindapplicationdoesnotturnasafixedspeed(asynchronousgenerator).

RotatingMagneticfield

Resultantmagneticfield

rotatesClockwise(CW)


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Inthistext,thesenseofpositiveflowofcurrentis

shownbelow:

Magnetic field


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SquirrelCageRotorMagneticfield

rotatesCWandat

thestartingthecage

aswellasthecrosswiresarestandstill.

Twomainequations:

F=i (lXB)e=(VXB).L

Toapplythe

equations,themagneticfieldis

stationaryandthe

wiresmoveacross

thefield.Todothis,

weviewfromthe

movingwireandthe

fieldappears

standstill.


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InductionmachineasaMotor

Therotorspeedisabitslowerthan

synchronousspeed,duetoeitherfriction,coolingblades,orloadatthe

shaft.

Ex.6.8P333


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InductionMachineasaGenerator

Therotor/shaftspeedisabitfasterthanthesynchronousmagneticfield.

TheslipconceptisstillappliedbutonlythesignbecomesNEGATIVE.

(Rotorspeedismovingfasterthansynchronousspeed)

For60Hz,2polemachine,synchspeedis120f/p=3600rpm.

Theslipofgridconnectedgeneratoris


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Selfexcitedgenerator:

Useresonanceconcept

Makeuseoftheresidual

magneticfield

AdvantageusingInductionGeneratorforwindturbine

application


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http://livelypictures.blogspot.com/2008/05/inductionmotor.html

http://www.electricmotors.machinedesign.com/guiEdits/Co

ntent/bdeee11/bdeee11_7.aspx

Moreoninductionmachines

http://www.allaboutcircuits.com/vol_2/chpt_13/9.html
http://livelypictures.blogspot.com/2008/05/induction-motor.htmlhttp://livelypictures.blogspot.com/2008/05/induction-motor.htmlhttp://livelypictures.blogspot.com/2008/05/induction-motor.htmlhttp://www.electricmotors.machinedesign.com/guiEdits/Content/bdeee11/bdeee11_7.aspxhttp://www.electricmotors.machinedesign.com/guiEdits/Content/bdeee11/bdeee11_7.aspxhttp://www.allaboutcircuits.com/vol_2/chpt_13/9.htmlhttp://www.allaboutcircuits.com/vol_2/chpt_13/9.htmlhttp://www.electricmotors.machinedesign.com/guiEdits/Content/bdeee11/bdeee11_7.aspxhttp://www.electricmotors.machinedesign.com/guiEdits/Content/bdeee11/bdeee11_7.aspxhttp://livelypictures.blogspot.com/2008/05/induction-motor.html


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Modern3bladesystem,Cp workswell

whenthetipspeed

ratioisbetween3

to5.5,with4being

thebest.


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PowerdeliveredbyModern3Bladesystem


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Rememberwindpowervariesasv3

DiscreteProbability


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Windstatisticinoneyear=8760hrs

Thissitehaswindat6m/sfor946hrs

Previousslide


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Hoursinayear Average


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Continuouscase

8760hr/yristhenormalized

factor


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Whenk=2,thep.d.f hasa

specialnamewhichweall

recognizeas,Rayleighpdf

Forthebestguessofthe

windpdf,usingk=2for

initialdesign.


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Shapefactor(k)=2

Rayleighpdf

Vistheaveragewindspeed

=0.886Xscaleparameter


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OnP342,thecorrectpowerdensityisabout1.9times

more.Thisisduetothefactthattheauthorusedthe

windhistogramthatfitsRayleighpdf.


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Sincewedontknowtheblade

sweptarea,thenwehavetoexpressthewindpowerinterms

ofW/m2

P 52 f th f ll i t Th fitti i W ib ll


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http://www.offshorewindenergy.org/reports/report_043.pdf

Page52ofthefollowingreport.ThecurvefittingusingWeibull

pdf andrealmeasureddata.
http://www.offshorewindenergy.org/reports/report_043.pdfhttp://www.offshorewindenergy.org/reports/report_043.pdfhttp://www.offshorewindenergy.org/reports/report_043.pdf


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FormulacommonlyusedinEurope

RoughnessClass1


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Sweptarea= r2 =

D2/4

Diameter=48m

Usuallywedeterminethe

energyperyear

Optimum Spacing of Towers for Wind farm


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OptimumSpacing ofTowersforWindfarm


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Twostrategies:increaserotordiameterorincreasethegeneratorsize

Increaserotorsize:theoutputpowerreachesmaxatlower

windspeed(SeeFig.6.33a)

IncreaseGensize:Thiswillincreasetheoutputpoweratthe

sitewherethereishighwindmostofthetime.


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k=2andC=6

Theavg.windspeed=5.32m/s


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Wh t i th b bilit th t th i d bl


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Whatistheprobability thatthewindblows

between


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Histogramoftheexceldata


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BasedonRayleighstatistic


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WecanestimatetheCapacityFactor

(CF)usingalinearequation,

Slope(m)=(0.40.13)/(85)

=0.09~0.087

Intersection=

7


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Energyproductionperyear

Onlyapproximation

Usingthisapproximation,theannualpoweris

2,899,560kWh/yrAscomparedto2,851,109kWh/yr(page365give

moreaccuratepower)


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wind turb lecture full

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