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Int. J. Mech. Eng. & Rob. Res. 2014 Tipu Sultan et al., 2014

DIFFERENTIATION ANALYSIS OF SINGLE ANDDUAL ROTOR WIND TURBINE TORQUE

TRANSMISSION SYSTEM

Tipu Sultan1*, Anurag Gour1 and Mukeshpandey1

*Corresponding Author: Tipu Sultan, sultan.tipu59@yahoo.com

For the next leap in the sustainable technologies, we are under obligations not only to cope withthe warming global environment but also to conserve natural ecosystem and to coexist withnature this study aims to analyse the comparison analysis of single and dual rotor wind turbinetorque transmission. For this purpose, we had analysed the gearbox transmission system ofsingle and dual rotor wind turbine. In a single rotor wind turbine system the gear transmissionsystem has parallel or planetary gear box arrangement but the dual rotor wind turbine systemhad combination of planetary and parallel shaft gearbox arrangement.

Keywords: Wind power, Gears, CATIA, Torque, Betz limit, Wind speed, Shafts, Bearings

INTRODUCTIONWind is one of the clean energy sources, andits conversion to usable energy is important toreduce fossil fuel dependency. In order toobtain energy from wind, a lot of wind turbinesare being constructed. However, regionshaving high wind energy density are finite. It isone of the fastest growing energy resourcesand it is going to have remarkable share inthe energy market. Thus, the consequencesof the connection of wind turbine, specificallyin the form of a wind farm, to the electrical gridmust be investigated from steady state,dynamic and transient point of view. Different

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Int. J. Mech. Eng. & Rob. Res. 2014

1 School of Energy and Environmental Managment, UTD, RGPV Bhopal, MP, India.

approaches have been introduced to improvethe static and dynamic responses of the windturbines. Therefore, many researches toincrease energy efficiency of wind turbineshave been accomplished.Generally, horizontalaxis wind turbines having a single rotor areused for conventional wind turbine systems.According to Betz theory (Manwell et al.,2005), the maximum energy conversionefficiency of conventional wind turbines havinga single rotor is about 59%. Bycontrast, themaximum efficiency obtained by two rotorshaving the same area is increased to 64%.based on this results, in order to increase the

Research Paper

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Int. J. Mech. Eng. & Rob. Res. 2014 Tipu Sultan et al., 2014

energy efficiency of wind turbines, someresearches for Counter-Rotating WindTurbines (CRWT) that have two rotors rotatingopposite direction at the same axis have beenprogressed. Appa technology initiatives(Appa, 2002) have established a proto modelof 6 kW counter rotating wind turbine inCalifornia. the rotor performance data havebeen measured and numerical predictionsusing Blade Element Momentum (BEM)method have been accomplished. Jung et al.(2005) has constructed a 30 kW counterrotating wind turbine system and has obtainedpower curve experimentally and numerically.inaddition, the effects of distance and diameterratio between two rotors have beenconsidered by using BEM method. Shen et al.(2007) has used CFD code, ellipse 3d, topredict performance of a counter rotating windturbine having two Nordtank 500 kw rotors. Allthese researches mentioned above havecompared the performance of a counterrotating wind turbine with that of single rotorhaving half number of blades. However, thesecomparisons are unfair because each rotorconfiguration has different solidity (the ratio oftotal blade areato rotor disk area). In this study,for a fair comparison, aerodynamiccharacteristics of a counter rotating windturbine were compared with that of a singlerotor having equal solidity as well as a singlerotor having half solidity. Through numericalcalculations of induction factors and powercoefficients for each rotor configuration, theaerodynamic feasibility of a counter rotatingwind turbine was considered.

METHODOLOGYMechanical power transmission by multiplyingthe angular speed under a constant

transmission ratio represents the function of alarge group of products known asspeedmultipliers. Most wind turbines andhydro systems drive trains include a gearboxto increase the speed of the turbine shaft tothe generator. An increase in speed is neededbecause the turbines rotors turn at a muchlower speed than is required by most electricalgenerators. The range in which the inputangular speed must be increased is 25-30times the RPM.

Figure 1: Planetary Gearbox Arrangement

There are two basic types of gearboxesused in wind turbines applications: parallel-shaft gearboxes and planetary gearboxes. Inthe first case, in order to obtain higher valuesof the transmission ratio, multiple stages areplaced in series. This arrangement increasesthe multiplication ratio but, in the same time,increases the overall dimension. Unlike theparallel-shaft gearboxes, the planetarygearboxes have some significant differences:the input and output shafts are coaxial, thatreduces the radial and axial dimensions;there are sometimes multiple powerbranches, so the loads on each gear arereduced; the gearboxes are relatively lightand compact.

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Int. J. Mech. Eng. & Rob. Res. 2014 Tipu Sultan et al., 2014

S. No.

1.

2.

3.

4.

5.

6.

Specification

GearboxArrangement

Gearbox Structuraldesign view

Power and Torque

Cut in speed

Efficiency

Cost

Single Rotor Wind Turbine

It may be planetary or parallel shaftgearbox.

In single rotor wind Turbine thewind energy we received is equalto

3

21 AVP

NPT

260*

This wind energy is converted intorotating energy by the help of rotorblades. Single rotor wind turbinecan only convert about 1/3 rd ofenergy. Other 2/3rd of wind energyis wasted.

The cut in speed of a small singlerotor wind turbine is about 2.5-4m/s but for large wind turbine thisincreases up to 7-9 m/s.

According to the Betz limit themaximum energy we can extractfrom a single rotor wind turbine is59% of the total captured windenergy. But practically only 30-40%of wind energy can be converted toelectricity.

Gearbox is one of the mostexpensive part of the wind turbine.Single rotor wind turbine gearboxcost about 100000 dollars for a unitMW. This is about 11% of the totalcost of the wind turbine.

Dual Rotor Wind Turbine

In this wind turbine Gearbox they are thecombination of both planetary and parallel shaftgearbox

Dual rotor wind turbine has advantage of extraenergy capture.

The wind energy which is wasted by the Frontrotor can be used by rear rotor. Thus we get doubletorque from front and rear rotor.

Total Torque on the Gearbox = Torque from Frontrotor + Torque on the Rear rotor.

Dual rotor wind turbine has advantage of reducein cut in speed since the input torque of gearboxis doubled.

The wind energy from the front and rear rotorcaptures more energy than single rotor windturbine. Different new Researches and studieshave found that Dual rotor wind turbine had 5%more efficiency than a single rotor wind turbine. .In case of single rotor only single front rotor canconvert wind energy into useful energy but in thisresearch paper had designed a dual rotor windturbine gearbox on CATIA which can generateabout 5% more power than conventional windturbine system.

Since in the Dual rotor wind turbine the designcomplication and Size of the gearbox is more thansingle rotor wind turbine hence the cost will begreater. But since it has been proofed inresearches that about 5% of increase in efficiencyin Dual rotor wind turbine hence payback periodwill also reduce.

Table 1: Comparison Analysis Table of Single and Dual Rotor Wind Turbine

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Int. J. Mech. Eng. & Rob. Res. 2014 Tipu Sultan et al., 2014

CONCLUSIONIn this Research paper we have studied thedesigning of the Gearbox of dual rotor windturbine system. We have used CATIA softwarefor the designing of the gearbox. Butcalculation for the dimensions of gear is doneby basic formulae’s. We assumed that thespeed of wind in front rotors is reduced by2/3rd times the original wind speed. Basicformulae’s for calculating gear dimensions arediscussed and tables of gear dimensions aredrawn in this paper. This gearbox has two inputshafts and one output shaft. The dual rotors infront and rear side capture wind energy. Thecaptured wind energy is transformed into highspeed rotational energy by transmissionsystem. In case of single rotor only single frontrotor can convert wind energy into usefulenergy but in this research paper had designeda dual rotor wind turbine gearbox on CATIAwhich can generate about 5% more power thanconventional wind turbine system.

REFERENCES1. Appa K (2002), “Energy Innovations Small

Grant (EISG) Program (Counter RotatingWind Turbine System)”, EISG FinalReport, California, US.

2. Jung S N, No T S and Ryu K W (2005),“Aerodynamic Performance Prediction ofa 30 kW Counter-Rotating Wind TurbineSystem”, Renewable Energy, Vol. 30,pp. 631-644.

3. Manwell J F, Mcgowan J G and Rogers AL (2005), Windenergy Explained, JohnWiley & Sons.

4. Shen W Z, Zakkam V A K, Sørensen J Nand Appa K (2007), “Analysis of Counter-Rotating Wind Turbines: The Science ofMaking Torque from Wind”, Journal ofPhysics: Conference Series, Vol. 75.