DESIGN AND FABRICATION OF COMBINED SAVONIUS AND DARRIEUS WIND TURBINE
SARAVANAKUMAR M1 , NAGARAJ A2
1,2Lecturer, Department of Mechanical Engineering, PSG Polytechnic College, Coimbatore, Tamilnadu
Abstract – In this design, an attempt is made to use the advantage of Darrieus and Savonius rotors, to work on the overall effectiveness of the affair power. This combined wind turbine with a Darrieus rotor provides the main power, starting power is handed by the Savonius rotor. At low wind pets the Savonius rotor starts rotating, pullingalongsideitthe Darrieus rotor. At the point when the Darrieus rotor reaches its critical speed, it starts rotating at a faster speed. Presently, for a analogous low wind speed, both the Savonius rotor and Darrieus rotors rotate at their own pets, the affair of which will be fed to a one input epicyclic gear box, so that an enhanced affair will be attained from the gear box. The combined Savonius- Darrieus rotor can increase the wind turbine effectiveness in low wind speed and also enable tonestarting in Darrieus turbine. Hence, analysis of this design performance of the system is done.
Key Words: DarrieusandSavoniusrotor,Criticalspeed,,etc (Minimum5to8keywords)…
1. INTRODUCTION
Winds are an outcome due to the earth’s equatorial regions receiving more alternative solar energy than the PolarRegionsandthesesetsupenormousconvectionflows intheatmosphere.Infewareasoftheplanet,windenergy has proactively developed to be thought asa mainstream energy source. It is the most economical solution to the world’severrisingenergyrequirements.It’sacleanenergy andconsumesnofuel.Windenergycancontributemajorly in satisfying the world’s need for clean and renewable energy in the coming years. The energy that may be extractedfromthewindisdirectlyproportionaltothecube of the wind speed. Thus, an understanding of the wind characteristics(likevelocity,direction,andvariation)adds to every aspects of wind energy generation, from the identification of suitable places to predictions of the economicviabilityofwindfarms,tothedesignofthewind turbinesthemselves.Themoststrikingwindcharacteristicis its random nature. The wind varies highly in, both geographicallyandtemporally.
1.1 Wind Turbines
Awindturbineisadevicethatconvertsthewind'skinetic energy into electrical energy. Wind turbines can be
manufacturedinwidescopesofsizes,witheitherhorizontal orverticalconfigurationoftheaxes.Itisassessedthathuge number of large wind turbines, wheninstalled grouply knownaswindfarms,cangeneratemorethan700Gigawatts ofpower,with70GWaddingeveryyear.Windenergyarean increasinglycrucialsourceofintermittentrenewableenergy, and are utilized in several countries to bring down the energy costs and diminish the reliance on fossil fuels, for generatingelectricalenergy.
1.2 Vertical Axis Wind Turbine
Windturbinesthataresetonaverticalaxis,freetorotate, arecalledasverticalaxiswindturbines(VAWT).Recently, VAWTsaregainingpopularityduetotheinterestofpeople inproducingeco-friendlyenergysolutions.Smallcompanies, allovertheworldhavebeenadvertisingthesenewdevices suchasHelixWind,UrbanGreenEnergy,andWindspire.As, VAWTsaresmall,quiet,easytoinstall,cantakewindfrom any direction, and operate efficiently in turbulent wind conditions,anewareainwindturbineresearchhasopened uptomeettheenergydemandsofindividuals,willingtotake control and put resources into small wind energy technology.
Averticalaxiswindturbinesareclassifiedintotwotypes, theyare
SavoniusWindTurbine
DarrieusWindTurbine
1.3 Savonius Wind Turbine
Savonius wind turbines shown in Fig 1, are a type of vertical-axiswindturbine(VAWT),usedforconvertingthe wind’sforceintorotationaltorque,onarotatingshaft.The turbine consists of a number of aero foiled shaped leaves usually, but not always vertically mounted on a rotating shaft. They are either ground stationed or connected in several airborne systems. Savonius turbines extract much lessofthewind'spower,thanothersimilarly-sizedlift-type turbines.MuchofthesweptareaofaSavoniusrotormaybe
around the ground, if it has a small mount without an extended post, making the overall energy extraction less efficient due to the lower wind speeds available at lower altitudes. Savonius turbines are used whenever cost or reliability is much more considerable parameters than efficiency.Theyarealsousedfortheself-startingmechanism ofaturbinewithoutanyexternalmechanicalaid.
1.4 Overlapping Savonius Rotors
A simple modification, done to the Savonius rotor is to overlaptheleavesofthewindturbineorrotors,permitting air to flow between each of the sides, which dominantly increasesthewindturbine’sefficiency.Thisstudyconcluded that,thetwostageoverlappingSavoniusrotorasshownin Fig 2 was the most efficient wind turbine among the differentcombinationsoftheSavoniuswindturbinerotors tested.Thisalsoallowstheturbinetobestartedwithwind from any direction because the offsetting rotors or stages ensures that either one of the buckets are usually in the directionofthewind.
1.5 Darrieus Wind Turbine
It is type of vertical axis wind turbine (VAWT) used to produce electricity from the wind energy. The turbine containsseveralcurvedaerofoilshapedblades,mountedon afreetorotateshaft.Thecurvatureofthebladespermitsthe bladetobestressedonlyathighrotatingspeeds.Thereare many difficulties in safe guarding the Darrieus type wind turbinefromextremewindconditionsandinmakingitselfstarting.TheshapeoftheleavespresentintheDarrieustype windturbinescouldbeoftwotypes
Egg-Beatertype
rotors
H-rotortyperotors
1.6 Egg-Beater Type Darrieus Wind Turbine
ThistypeofDarrieuswindturbineconsistsoftwocurved bladesthatareverticallypositionedandrotatingarounda verticalshaft.ThisDarrieuswindturbineisakindofVAWT. UnliketheSavoniustypewindturbine,theDarrieustypeisa lift-typeVAWT.Insteadofgatheringtheairstreamswithin its cups, the turbines will drag around along with wind. Darrieustypewindturbineutilizestheliftforceofthewind which is created through the air stream striking the aero foiledshapedrotorstomakerotationsaroundtheshaft.
TheH-rotortypeDarrieuswindturbinecontainsstraight and vertically oriented rotors rather than the standard shapes that have curved blades directly, horizontal structures connect the blades or rotors and the shaft. The orientationofthesestructuresistypicallyontheendsorthe centerofthebladesasshowninFig4.Oneofthemajorand crucialcharacteristicsofthistypeverticalaxiswindturbine is that it has the ability to collect the wind from different directions.Moreover,straightforwardandsimpledesignof therotorsleadstoeasymanufacturingofthewindturbine, whichultimatelyleadstoeasyinstallationandmaintenance.
1.8 Methodology
2. LITERATURE SURVEY
[1]Anurag Kumar et al describes brieflyabout thehybrid rotor system which has been available in different configurations.Manyattemptshavebeenmadetoachievea good start-up torque for the hybrid rotor consisting the Savoniustyperotor.Hence,Savoniusrotorsprovidetheselfstartingability.
[2]Nawfal M.Ali etal studies showedexperimentallyand numericallywhatistheeffectofthecombinationbetween thetwotypesofwindturbines(SavoniusandDarrieus).The mainconclusionswere“TheperformanceofthehybridWind millcaseisbetterthantheothercases.Atlowwindvelocity, thereisincreasedpowerco-efficientandtorqueco-efficient and can be self-started at a lower wind velocity too. The overall efficiency of extracting the wind power for the Hybrid Wind mill is economically feasible for larger structures”.
[3] Parth Rathod et al evident that the power output of verticalaxiswindturbinefortwoblades(Savoniusrotors) withtwostages,ismaximum.Itisalsoobservedthatwhen Darrieus H type rotors are constructed above the S type Savoniusrotors,thenpoweroutputincreaseswithrespectto thevelocityofwind.
[4] Mr.Jaimin Patel et al shows that Vertical axis wind turbine(Savoniuswindturbine)iseasiertoconstruct,low costinmanufacture,requireslessmaintenance,lessspace availability and most important provides free & green energy.Theresultfromtheliteratureshowsthattwoblade Savoniusrotorismoreefficientthanthethreebladesetup.It can play an important role in villages for producing renewableandfreeenergy.Also,itcanreducethepollution createdbythefossilfuelstoproduceelectricity.Hence,itis veryusefulforhouseholdapplication.
[5]M.Douak,Zetalconcludesthat“Therotorheightdoes not affect the power coefficient as it appears in the expressionsof boththeproducedandmaximumavailable power. However, it does affect the value of the starting torqueandthepower.Bothofthesevaluesincreasewiththe value of height.” Hence, Darrieus Rotors require external starting power or aid, with increased rotor height, to generateelectricityefficiently.
3. COMPONENTS DESCRIPTION
3.1 Bearing
HereDeepGrooveBallBearingisselectedasneededfor withstanding the desired load.BallbearingSKF6201with 20 mm bore diameter is selected to fit the shaft size (20 mm).
Shaftwithdiameter20mmisselectedforourprojectas thissizeofrodweighslightandcanwithstandconsiderable stressesandstrains.
TheframeforourprojectiscreatedbyweldinginLangles accordingtoourrequirements.
MSPlatesareusedinourprojecttomountthe Darrieus typeverticalwindturbine.MildsteelPlatesareusedasthey areductile,weldableandeasytoinstall.Theplateisdrilled toproduceaholeofabout20mmtofititintheshaft.
Lead acid batteries are generally used because of their powertoweightratioandtheirlowcost.Insidealead-acid battery, the positive and negative electrodes consist of a groupofplatesweldedtoaconnectingstrap.Theplatesare immersedintheelectrolyte,consistingof8partsofwaterto
3partsofconcentratedsulfuricacid.Thebatteryusedinour projectisAP-BTX5L lead acidbattery withVoltage – 12 V andPowerOutputat5A-h.
4. DESIGN OF THE TURBINE
Fig-16: DesignofthecombinedSavoniusandDarrieus WindTurbine
4. 1 Assembled view of the turbine
WindTurbineAssembly
5.
The wind turbine setup was tested from wind speeds varyingfrom 5m/sto35 m/sand wasalsotested forits starting wind speed also The test run results for both Savonius setup alone and the combined Savonius and Darrieuswindturbineisasshowninthetable1and2below.
We can clearly see that the combined Savonius and Darrieuswindturbinesetupautomaticallystartsupatthe wind speed of 7.5 m/s. The starting speed of combined SavoniusandDarrieuswindturbineisalittlebithigherthan Savoniuswind turbinesetupalone,isbecauseoftheadded weightoftheDarrieus windturbinesetupmade.Darrieus wind turbine require even more higher wind speed and a largesweptareaordiameteroftherotor,forprovidingeven morehigherrotationalspeedsandhigherefficiency.Having recordedthesevalues,theEfficiencyoftheWindturbineis foundoutbyCalculations.
5.2 Efficiency Calculation
Trail 1 (For Velocity 10 m/s)
Pavail
Pavail
Pavail
ConsideringpowerfactortobeCp =0.4, Pactual
Pactual =317.806x0.4= 127.122 watts
Consideringthepowerlossesintheturbine, Wakeloss–1%;MechanicalLoss–2%;ElectricalLoss–1.5 %;otherlosses–1%
Total Power Loss = 127.122 x 4.5 % = 127.122 x 0.045 = 5.72 watts
Therefore,theactualpowerafterallthelossesis, Pactual =127.122–5.72=121.402watts
Therefore, Efficiency of the wind turbine = 38.18%
From this test run we can clearly conclude that the Savoniuswindturbinesetupalone, automaticallystartsto rotate at the wind speed of 5 m/s. Though the Savonius windturbinesetuphelpstoself-starttheentirewindturbine withoutanystartingup mechanical aid,itdoesn’tperform well at higher wind speeds. Next, the Combined Savonius and Darrieus wind turbine setup was tested at the wind tunnel.Theresultswereasshowninthetable2below.
Trail 2 (For Velocity 15m/s)
Pavail
Pavail
Pavail
ConsideringpowerfactortobeCp =0.4, Pactual
Pactual =1072.598x0.4= 429.039 watts
Consideringthepowerlossesintheturbine,
Wakeloss–1%
MechanicalLoss–2%
ElectricalLoss–1.5%
Otherlosses–1%
TotalPowerLoss=429.039x4.5%=429.039x0.045= 19.30 watts
Therefore,theactualpowerafterallthelossesis, Pactual =429.039–19.30=409.739watts
Therefore,Efficiencyofthewindturbine = 38.20%
5.3 Torque Calculation
Torquegeneratedbythewindturbineisfoundoutusingthe Tipspeedratioofthewindturbineandbydeterminingits angularvelocity.Weknowthat,
Bladetipspeed
Then, theangularvelocity ofthe wind turbineatdifferent windspeedsisfoundoutanditisthentabulated.
Tipspeedratioofthewindturbine
Hence, using the Angular velocity, found above, and the wind speed, the tip speed ratioforvariouswindspeedsis foundandthentabulated.
RadiusoftheWindturbine=0.4064m
Table -3: Tipspeedratioforrespectivewindspeeds
Table -4: TorqueProducedforrespectivewindspeeds
Thetorquegeneratedbythewindturbineiscalculatedby thegivenformula,
Thus, we have calculated and found out the Torque producedbythewindmillatvariouswindspeeds,andthe efficiencyoftheCombinedWindturbinewasfoundout.
6. ADVANTAGES AND APPLICATIONS
6.1 Advantages
It is a renewable source of energy.
Better utilization of wind power.
TheSavoniuswind turbine setup attached in the combined wind turbine, helpsin the Self-starting of the wind turbine at a wind speed of 7.5 m/s, hence startingtoproduceelectricityatwindspeed around 10 m/s only.
Themajoradvantageofthiswindturbinedesign is thatit can acceptwind fromanydirection, hence eliminating steering the setup into the wind.
The Combination of Savonius and Darrieus wind turbine has helped to achieve higher efficiency than usual vertical axis windturbines.
As this machine has vertical axis symmetry, it eliminatesyawcontrolrequirementforitsrotorto capturewindenergy.Acomparativelysimpleshaft axis support is required as well as ground level power output delivery due to the presence of a vertical shaft. Hence, allowing easier access and serviceability.
The tip speed ratio and power coefficient are considerablybetterthanthoseoftheSavoniuswind turbines setup alone but are still less than the values of a modern horizontal-axis, three-bladed propellerrotor
Construction and manufacturing of this wind turbineissimple.
VAWT’s can be installed in more versatile locations such as - on roofs, alonghighways,in parkinglots,etc.
Combined Wind turbine can be scaled more easily – designs for producing frommilli-wattsto mega-wattsofpower.
Combined Wind turbine on a small scale setup can be utilized to produce a fewkilowatts of electricity,andislesscostlytoo.
Combined wind turbine on a large scale setup, costs can be competitive higher andlower costs couldbeattainedbymassproduction.
It can have low maintenance downtime, as the wind turbine is closer to ground and can be accessedeasily.
6.2 Applications
Wind-turbinegeneratorshavebeenbuiltonawide scope ofpoweroutputs, rangingfromkilowatttoa few thousand mega-watts.
Windturbinesproducing lowpowercangenerate sufficient electricity for spaceheating or cooling and for can be utilized for domestic applications.
Applications of more powerful wind turbines producing power up to about 50 kW, can be utilized for operating irrigation pumps, navigational signal, etc.
Windturbinesproducingpowerintheintermediate power range, roughly about 5 to50 kW can supplyelectricityto isolated areas.
7. CONCLUSIONS
Windturbinetechnologyhasdemonstratedthepotential toharnesselectricityfromthewindpower,andtocontribute totheever-risingenergydemandsoftheworld.Ifthecorrect locations with suitable wind characteristics were fully utilized, they could contribute to the production of electricity, and supply the ever growing demand for electricityinthisgrowingworld.
Our Project is designed, fabricated and tested for performanceatvariouswindspeeds,onthebasistoproduce a combined vertical axis wind turbine, to create its own characteristics.Theadvantageoftheself-startingSavonius typewindturbineiscombinedalongwiththehighlyefficient Darrieuswindturbine,toincreaseitsefficiencyatlowwind speeds.Thisdesignhas helpedtomaketheDarrieuswind turbineself-startingatlowwindspeedssuchas7.5m/sand
produce uninterrupted electricity supply at a speed of 10 m/s. Thus, the project of designing and Fabrication of the Combined Savonius and Darrieus wind turbine has been successfullydone.
Future Scope
The design of the wind turbine leaves can be changedintoamoreefficientaerofoilstructureto increaseitsefficiency.
Differentmaterials,withlesseroverallweight,can be selected and used to create the structural featuresofthewindturbine,tobemoreefficientat evenlowerwindspeeds.
Total area of wind capture can be increased by scalingthemodel, to captureevenmorewindand produceelectricityatgreaterefficiency.
Larger generators can be coupled with the up scaled model of the wind turbine toproduce morepower.
REFERENCES
[1] Anurag Kumar and Alok Nikhade “Hybrid kinematic turbine rotor: A review,” International Journal of EngineeringScienceandAdvancedTechnology,vol.4, 2014,Issue6,pp.453-463
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