บทความวิจัยapheit.bu.ac.th/jounal/science-Jan-Jun-2562/...แดร เร ยส-ซาโวเน ยส มาเร ยงซ อนก นแบบ 2 ช

64 สมาคมสถาบันอุดมศึกษาเอกชนแห่งประเทศไทยในพระราชูปถัมภ์ สมเด็จพระเทพรัตนราชสุดาฯ สยามบรมราชกุมารี

Performance of Stacking a Darrieus-Savonius Wind Turbine for Low-Speed Operation

ประสิทธิภาพการท�างานที่ความเร็วลมต�่าของกังหันลม แดร์เรียส–ซาโวเนียส แบบซ้อนทับ

Suppachai Jina1, Montri Suklueng2, Wattana Ratismith3

Priwan Pongwan4, Chainuson Kasagepongsan5

FacultyofEngineering,PrinceofSongklaUniversity1,4

InterdisciplinaryGraduateSchoolofEnergySystem,PrinceofSongklaUniversity2,3

FacultyofScienceandTechnology,SuratthaniRajabhatUniversity5

ศุภชัย จินา1, มนตรี สุขเลื่อง2, วัฒนา รติสมิธ3, ไพรวัลย์ พงษ์หวาน4, ชัยนุสนธ์ เกษตรพงศ์ศาล5

คณะวิศวกรรมศาสตร์มหาวิทยาลัยสงขลานครินทร์1,4

บัณฑิตวิทยาลัยสหวิทยาการระบบพลังงานมหาวิทยาลัยสงขลานครินทร์2,3

คณะวิทยาศาสตร์และเทคโนโลยีมหาวิทยาลัยราชภัฏสุราษฎร์ธานี5

E-mail:[email protected]

Received: March 23, 2019; Revised: June 7, 2019; Accepted: June 7, 2019

ABSTRACT

Windpower is a formof green energy thatmakes nopollutionwhenused as an

operationalsystem.Thelow-speedwindturbineisveryinterestingforharvestingenergywith

awiderangeofapplications.DerrieusandSavoniusareverticalwindturbinesthatcanbe

operatedwithlowcomplications.Lightermaterialsusedforproducingthebladescanreduce

the gravitational force, leading to faster start-up of thewind turbine operation. Savonius

(Interferenceofshafttype)waslocatedattheupperandDarrieus(H-type)waslocatedatthe

lower(ModelB2)inaverticalturbinefabricatedbyacrylicplate,whichcouldstart-upatalow

speedof1.52m/s.Therefore,thenovelstackingofDarrieus–Savoniusturbineandlightweight

acrylicmaterialscouldpromotetheverticalaxiswindturbineforlow-speedoperation.

KEYWORDS: Savonius,Darrieus,VerticalAxisWindTurbine,LowWindSpeeds

บทความวิจัย

ปีที่ 8 ฉบับที่ 1 มกราคม-มิถุนายน 2562 65

บทคัดย่อ

พลังงานลมเป็นพลังงานท่ีอยู่ในรูปของพลังงานสะอาดซ่ึงไม่ก่อให้เกิดมลพิษเมื่อใช้เป็นแหล่งกำาเนิด

พลังงาน กังหันลมความเร็วลมตำ่าเป็นเทคโนโลยีที่น่าสนใจอย่างมากสำาหรับการนำามาเพื่อใช้ในการเก็บเกี่ยว

พลังงาน เนื่องจากสามารถใช้งานในย่านที่กว้างขึ้น กังหันลมแบบ แดร์เรียส และ ซาโวเนียส เป็นกังหันลม

แนวแกนตั้งที่สามารถทำางานได้ที่ความเร็วลมตำ่า การนำาเอาวัสดุที่มีนำ้าหนักเบามาใช้ในการสร้างใบกังหันลม

สามารถลดแรงกระทำาจากแรงโน้มถ่วงที่เกิดขึ้นกับตัวกังหันลมซึ่งมีผลทำาให้การออกตัวของใบกังหันลมง่ายขึ้น

กงัหนัลมแบบซาโวเนยีส(ลกัษณะการโค้งรอบเพลา)ตดิตัง้ไว้ด้านบนและตดิตัง้กงัหนัลมแบบแดร์เรยีส(ลกัษณะ

ทางกายภาพแบบตัวอักษรเฮช) ไว้ตำาแหน่งด้านล่าง (โมเดล B2) ใช้อะคริลิคเป็นวัสดุในการผลิตใบกังหันลม

ซึง่การทำางานของระบบกงัหนัสามารถเริม่ต้นทีค่วามเร็วลม1.52เมตรต่อวนิาทีด้วยเหตนุี้การนำากงัหนัลมแบบ

แดร์เรียส-ซาโวเนียสมาเรียงซ้อนกันแบบ2ชั้นแบบใหม่และรวมถึงการใช้วัสดุอะคริลิคที่มีนำ้าหนักเบาสามารถ

ช่วยให้กังหันลมแนวแกนตั้งทำางานได้ที่ความเร็วลมตำ่า

ค�าส�าคัญ:ซาโวเนียสแดร์เรียสกังหันลมแนวแกนตั้งความเร็วลมตำ่า

Introduction

Fossil fuel pollution and related

energyresourcedepletioncreatesinteresting

challengestodecreaseemissionsthroughthe

application of alternative energies (Tahani,

Rabbani, Kasaeian, Mehrpooya, &Mirhos-

seini,2017).Energyhasbeenessentialforthe

continuous advancements and economic

expansionseeninrecentdecades.Providing

suitable and low-cost energy sources is

essential to reduce poverty, develop

human satisfaction, and improve living

standards worldwide (Ramadan, Yousef,

Said, & Mohamed, 2018). Alternative

renewable energy resources have been

reported to emit low pollution and be

friendlier to the environment, such as

solar,wind,biomass,tidal,oceanwavesand

soon.

Wind energy is one of the most

interesting alternative energy technologies.

It is well known as being pollution-free,

excessively available in the atmospheric

earth,andlocallytransformed.Itcansupport

decreaseddependencyonfossilfuelssuch

as gas and oil.Many developing countries

havealready realisedthehighpotentialof

windpowerasaresourceforenergygenera-

tionsinceitiseffectivefortheutilisationof

powerproduction(Mohamed,Janiga,Pap,&

Thévenin,2010).

Windenergy transforms free kinetic

energy in thewind intoelectricity, through

pollution-free process.Wind turbine tech-

nologies are categorised into various sizes

dependent on their energy generating

capacity.Therearealsodifferenttypeswith

distinctrotordesigns.


Smallwind turbines are defined as

those that have a capacity rating of less

than10kW,whichissignificantlylowerthan

utility-scale turbines which have capacity

ratingsrangingfrom100kW-5MW.Small-scale

windturbineshaveexcellentcharacteristics

suchaslowprice,relativelyshortpay-back

periods,andhighperformanceandreliability.

Theyarecomfortable foruse inanumber

of locations including offshore platforms,

sailboats, telecommunications transmitters

andremotemilitaryposts(Liang,Fu,Ou,Wu,

Chao,&Pi,2017).

Generally,windturbinetechnologies

can be divided into vertical-axiswind tur-

bines (VAWTs)andhorizontal-axiswindtur-

bines(HAWTs).However,theybothperform

withthesameidealefficiency.Themajority

productsavailableonthetradeareoftenthe

HAWTtype.

The producing level of VAWTs

(Savonius-Darrieus) isobviouslylowmature

than those for HAWT.On the other hand,

thedisadvantagesofHAWTarerepresented

such as high-cost, noise, highwind speed

forcut-in.Previousreports(Gsänger&Pitte-

loud,2014)forHAWTs,thedevelopmentof

18%producedinVAWTs(Savonius-Darrieus)

that has numerous advantages including

easymaintenance, omni-directionality, and

reducednoise.Therefore,VAWTs(Savonius-

Darrieus) have more development and

researchprovidedintermsofwindturbine

platforms for novel small-scale energy

generation,whencomparedbyHAWTsystem.

Based on the VAWTs rotor, VAWTs

rotors comprise different types such as

Savonius, helical Savonius, Eggbeater

Darrieus,H-Darrieus,combinedconfiguration

ofSavoniusandDarrieusrotor.

Purpose

Inthisinvestigation,focusingonthe

vertical axis wind turbine is conducted in

low-speedwind.Darrieus-Savoniusrotorsare

combinedwiththeperformanceof3-blades

forinitialstart-upatlow-speedwind.Studyof

thepropertieswasoperatedwhencombined

betweenDarrieusandSavoniusatdifferent

positions, which are switched between

the upper and lower, as shown in Figure

1-2.Comparisonoftheweightofmaterials

wascarriedoutforallfabricatedbladesand

measuredpropertiesofthewindturbineto

bethebestlow-speedVAWTs.

Benefit of Research

The stacking Savonius and Darrieus

starteddevelopingverticalaxiswindturbines

that can start at low speeds of around 2

m/s. This low speed operation broadened

theapplicationssuitableThailand’slocation.

Meanwhile,thelighterbladeweightsreduce

theforceofgravityforceallowingittostart

running at lowwind speeds and generate

highperformance.


Research Process

Thisinvestigationprovidedthedesign

ofthebladesofaverticalwindturbinethat

focusedontheSavoniusandDarrieusrotors

for cut-inat lowwind speedsofaround2

m/s. Savonius (Interference of shaft type)

(Akwa,Vielmo,&Petry, 2012)andDarrieus

(H-typ) (Hashem &Mohamed, 2018) were

usedtoexamthepropertiesof theblade.

Inordertostudytheproperties,theywere

classifiedinto2models,asshowninTable

1.Savonius(Interferenceofshafttype)was

producedfromstainlesssheetsteel.Darrieus

(H-type)wasproducedfromnaturalrubber

combinedwithglassfiberandresin,called

ModelA.Basedontheinvestigations,both

ofthesebladeswereswitchedforlocation

betweenupperandlower,asshowninFigure1.

Savonius was located at the lower and

Darrieuswas located at the upper, called

Model A1. Savonius was located at the

upperandDarrieuswaslocatedatthelower,

calledModelA2,whileSavonius(Interference

of shaft type) and Darrieus (H-type) were

producedfromacrylic,calledModelB.When

operatingthesystem,bothoftheseblades

were switched for location between the

upper and lower, as shown in Figure 2.

Savonius was located at the lower and

Darrieuswas located at the upper, called

Model B1. Savonius was located at the

upperandDarrieuswaslocatedatthelower,

calledModelB2.

Instruments

Thewind tunnel experimentswere

conducted with an open test using the

facilities at the Department of Electrical

Engineering, Prince of Songkla University,

wherethewindtunnelstructureismadefrom

ironsheets.Thewindtunnelisdrivenbyan

invertedspeedACmotor.Thetestsection

hadalengthof2.4mandoffereda1.2m

×1.2mcross-section.Theinletofthewind

tunnelhadahoneycombstructureinstalled

inordertoreduceturbulenceandmakethe

windmorestreamlinedbeforereachingthe

wind turbine. Themaximumwind velocity

generatedreached4m/s,buttheseexperi-

mentswerecarriedoutinthelowrangeof

windspeedsat1.5-4.0m/s.Thisinvestigation

measured the flow field around thewind

turbinebyanemometerbrandUNI-Tmodel

UT363witharangebetween0-30m/s(±5%

rdg+0.5). The Digiton Photo Tachometer

modelDT-2234C+withanaccuracyof±0.1

RPMwasusedtorecordtherotationalspeed.

Inthesectiontorqueoftherotorwasused

torque transducer, unhurried loads were

appliedtotheturbineshaftthroughanaxis

connectedtothetorquetransducer;model

WSC3-030CNwiththerangeandaccuracyat

6-30Nm,±3%(CW),experimentalapparatus

asshowninFigure3.


Table 1 GeometricaldetailsfortheSavoniusandDarrieuswindturbines

Geometrical

structure

Values

Model A Model B

Savonius Darrieus H-type Savonius Darrieus H-type

Numberofblades 3 3 3 3

Bladeheight(H) 0.45m. 0.60m. 0.45m. 0.60m.

Bladedimension(D) 0.80m. 0.72m. 0.72m. 0.72m.

Bladethickness(t) 1×10-3m. 2×10-3m. 2×10-3m. 2×10-3m.

Materials Stainless

sheetsteel

NaturalRubber

+Fiberglass

Acrylic Acrylic

Weight 17.70kg. 8.90kg.

Figure 1Vertical axiswind turbine,denotedasModelA.Darrieus (H-type)was fabricated

bystainlesssheetsteel,whileSavonius(Interferenceofshafttype)wasfabricated

usingstainlesssheetsteel(A1).Darrieus(H-type)waslocatedattheupper,while

Savonius (Interference of shaft type) was located at the lower. (A2) Savonius

(Interferenceofshafttype)waslocatedattheupper,whileDarrieus(H-type)was

locatedatthelower


Figure 2 Vertical axiswind turbine, denoted asModel B. Darrieus (H-type) and Savonius

(Interferenceofshafttype)werefabricatedbyacrylic(B1)Darrieus(H-type)located

attheupper.Savonius(Interferenceofshafttype)waslocatedatthelower.(B2)

Savonius (Interference of shaft type) was located at the upper, while Darrieus

(H-type)waslocatedatThelower

Figure 3 Schematicdiagramofexperimentalapparatus

Source:Elkhoury,Kiwata,&Aoun(2015)


Figure 4 Anexperimentalwindtunnelmeasuringaverticalwindturbine

Figure 5 Verticalwindturbinebehaviourshowing(a)therelationshipbetweenwindvelocity

androtationalspeedand(b)therelationshipbetweenwindvelocityandtorque

Data Analysis

Figure4showstherealexperimental

windtunnelmeasuringverticalwindturbines

withbladesconstructedfromacrylic,stainless

sheetsteel,andnaturalrubber+fiberglass.

Figure5(a)showstherelationshipbetween

wind velocity and rotational speed for

comparing the vertical wind turbine of 3

models including Model A1, Model A2,

ModelB1,andModelB2.Basedonthelow

speedwindturbine,thewindturbineneeds

tooperateatlowerthan2m/s.Thisresult


indicatedthatModelA2andModelB2had

higherperformancethanModelA1andModel

B1.ThestructuresofModelA2andB2were

fabricatedbySavoniuslocatedattheupper

positionandDarrieus locatedat the lower

position.Additionally,Figure5(b)showsthe

relationship between wind velocity and

torque,which indicates thatModel A per-

formedbetterthanModelB,leadingtoModel

A being heavier thanModel B by approxi-

mately50%.However,thelowspeedcondi-

tionofthis investigationfocusedonModel

A2andModelB2(Savoniuswaslocatedat

upper,Darrieuswaslocatedatlower),which

had start-up low speed ranges between

1.52-1.60m/s. The best start-up at a low

speedof1.52m/swasoccupiedbyModelB2

producedfromlightweightmaterials.

Blade-fluid interaction confirms the

expandedclearlyconcentrationofvortices

on the downstream of the Darrieus rotor

in comparison to the downstream of the

SavoniusrotorthatcanproducetheCoanda

effect. This reaction is associatedwith the

squeezingofthevorticesonthedownstream

ofDarrieusrotorduetoforcingtherotorinto

this rotation. Therefore, this situation can

produce power (Ghosh, Biswas, Sharma, &

Gupta, 2015). A Darrieus turbine requires

low-speedwind to produce theminimum

rotational speed,while a Savonius turbine

locatedonthetop isattributedtoturbine

self-startatlowwindspeed(Abidetal.2015),

asshowninFigure5(a).

The development of wind turbine

technologies has been increasing for the

purposeofharvestinghigherenergy.Increased

rotorbladeweightinturnincreasesthesize.

Thus, gravitational loads become create

drivers(MacPhee&Beyene,2019;Mishnaevsky

et al., 2017). For this reason, the blade

materialneedstobelightweightinorderto

reducegravitationalloadsinlowspeedwind

turbines,asconveyedinFigure5(b).

Generally, the performance of

verticalaxiswindturbinesisrepresentedby

thetorquecoefficient(Ct),powercoefficient

(Cp),andstatictorquecoefficient(Cts).

Ct=

CP=

Cts=

(1)

(2)=

(3)

T

TѠPTurbine

Ts

0.5ρAV2R

0.5ρAV3PAvailable

0.5ρAV2R

WhereVisthefreestreamvelocity,

ρ isairdensity,A is thesweptareaof the

turbine,R is the radiusof the turbine,TSR

is the tip speed ratio, T represents the

dynamictorque,Ѡisrotationalspeed,Tsisthe

statictorque,andPTurbine

andPAvailable

represent

the power resulting from the turbine

andavailablewindpower,respectively.


Figure 6(a) shows the relationship

between the tip speed ratio (TSR) and

coefficient of power (Cp), which indicated

thatModelB1-B2serieswashigherforTSR

thanModel A1-A2. Model A1-A2 initially

showedinitiallyadifferenttrendatarange

0.2-0.5 TSR and then overlapping trends

wereperformedatarangebetween0.5-0.6

TSR.Onother hand,Model B1-B2 showed

initially overlapping trends in a range

between 0.3-0.5 TSR and then the trends

were clearly split at a range between

0.5-0.9TSR.ModelsAandBwererevealed

at approximately 0.23 Cp. However,Model

B2hadthehighestperformancewith0.27Cp

and0.9TSR.

TheReynoldsnumberisoneofthe

factor parameters forcing the rotation of

velocity and inflow velocity, at which the

turbineoccupiesitsmaximumperformance

coefficient (Cp). The lift produced by the

blades is dependent on the Reynolds

number,whichinturndependsonthewind

speed (Elkhoury, Kiwata, & Aoun, 2015; Li

etal.,2016).

Re= (4)

Wherec is thebladechord length,

ν isthekinematicairviscosity,andWisthe

resultantvelocitytoblade.

ThearchitecturalModelB1-B2leads

tothehighCpperformanceoftheresultant

velocitytotheblade(W)andthelightweight

ofModelB1-B2canreducethegravitational

force that affects high Reynolds number.

A higher Reynolds number enables better

turbine performance. It is indicated that

stronger torque is generated on the rotor

foragreaterReynoldsnumber,causingthe

enhancementof the liftcoefficient for the

blades(Lietal.,2016;MacPhee,&Beyene,

2019;Mishnaevskyetal.,2017).

Figure 6(b) shows the relationship

between the tip speed ratio (TSR) and

coefficient of torque (Ct), which displays

almost the same trends as the trends in

Figure 6(a). TheModel B1-B2 represented

also TSR value higher thanModel A1-A2.

Contrastingly, coefficient of torque (Ct) for

ModelA1-A2wasthehighestwhencompared

withothersaround0.35Ct.

Based on equat ion (1-2) , the

corresponding ratio between Cp and C

t is

shown.TheCtinverticalaxis2bladeswind

turbinetheefficiencydependsonthepith

anglewithamaximumof18%Cp(Lietal.,

2016).InthecaseofDarrieus(H-type),how-

ever, this investigationwasperformedβ=

80o and stackedwithSavonius rotorblade

thatcanproducehigherefficiency.

Wcν


However, the double-step rotor is

obviouslymentionedtobe lightlysuperior

toarelatedsingle-stepturbine(conventional

Savoniusrotor)inbothpowercharacteristics

andtorque(Akwa,Vielmo,&Petry,2012).

Conclusion

Experiments were carried out that

focusedon the cut-inof lowwind speeds

ofaround2m/s.Windtunnelexperiments

were used for testing the VAWT rotor

combinedbetweentheSavoniusandDarrieus

rotors.Bothbladeswereswitchedbetween

locationsatupper-lower.Thepropertiesof

the blades in the studywere classified as

2models. Performance investigations of

combining Savonius-Darrieus rotors were

also carried outwith the same conditions

to compare the 2models. The effects of

the weight and switching from 2models

were discussed with the rotation speed,

torquevalue,coefficientofpower(Cp)and

coefficient of torque (Ct) at different

velocities and tip speed ratios.The results

from the study may be summarised as

follows:

• Inthepresentstudy,itwasfound

that the position of both the

Savonius and Darr ieus types

affectedtheperformanceofwind

turbines.TheSavoniuswaslocated

attheupperpositionandDarrieus

located at the lower position as

ModelA2.ModelB2showedhigher

performance thanModel A1 and

ModelB1.

•Theexperimentalresultsrevealed

thattheweightofthewindturbine

will become gravitational loads.

The cut-in of the wind turbines

Figure 6Verticalwindturbinebehaviourfor(a)therelationshipbetweentipspeedratioand

coefficientofpowerand(b)therelationshipbetweentipspeedratioandcoefficient

oftorque


increaseswiththeincreasingweight

of the wind turbine. The best

start-upoccursatalowspeedof

1.52m/sasoccupiedtoModelB2

duetoModelB2beingfabricated

fromlightweightacrylicmaterials.

•The rotational speed (RPM) and

torque value combined between

the Savon ius and Dar r ieus

rotors for all 4models increase

with the increasing of velocity.

Also, the coefficient of power

(Cp),coefficientoftorque(C

t)and

no-load tip speed ratio increase

withanincreaseoftipspeedratio

(TSR).

Therefore,theSavoniuswaslocated

attheupperpositionwhiletheDarrieuswas

locatedatthelowerpositionwhichallows

it to start-up at low speeds and can also

increase efficiencywhen using lightweight

acrylicmaterials, such as Model B2. The

ModelB2verticalwindturbineshowedhigh

performanceduringthisstudy.

Acknowledgements

Theworkisfinanciallysupportedby

ElectricityGeneratingAuthorityofThailand:

EGAT(61-F405000-11-IO.SS03F3008347).

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Documents

บทความวิจัยapheit.bu.ac.th/jounal/science-Jan-Jun-2562/...แดร เร ยส-ซาโวเน ยส มาเร ยงซ อนก นแบบ 2 ช