Wind Turbine Technology VIII Sem

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A Project Report on

Vertical Wind Turbine

Prepared byAbhishek AggarwalUjjwal KumarNiraj Kumar

Under the guidance of 

Ajay Kumar

Department of Mechanical Engineering,Laxmi Devi Institute of Engineering & Technology, Chikani, Alwar

Session: 2010-2011 

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Vertical Axis Wind Turbine

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A windmill is an engine powered by the wind to produceenergy. It is a device that converts kinetic energy from thewind into mechanical energy. If the mechanical energy isused to produce electricity, the device may be called a windgenerator or wind charger. If the mechanical energy isused to drive machinery, such as for grinding grain orpumping water, the device is called a windmill or wind

pump. Developed for over a millennium, today's windturbines are manufactured in a range of vertical andhorizontal axis types. The smallest turbines are used forapplications such as battery charging or auxiliary power onsailing boats; while large grid-connected arrays of turbinesare becoming an increasingly large source of commercialelectric power.

Introduction

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• Windmills were used in Persia (present-day Iran) as early as 200 B.C..

• The first known practical windmills were built in Sistan, a region between Afghanistan andIran, from the 7th century. These “Panemore” were vertical axle windmills, which had longvertical drive shafts with rectangular blades.

• Windmills first appeared in Europe during the middle ages. The first historical records fortheir use in England date to the 11th or 12th centuries and there are reports of German crusaders taking their windmill-making skills to Syria around 1190.

• By the 14th century, Dutch windmills were in use to drain areas of the Rhine delta. • First electricity generating wind turbine, was a battery charging machine installed in July1887 by Scottish academic.

• In Denmark by 1900, there were about 2500 windmills for mechanical loads such aspumps and mills, producing an estimated combined peak power of about 30 MW. The largest

machines were on 24-metre (79 ft) towers with four-bladed 23-metre (75 ft) diameterrotors. By 1908 there were 72 wind-driven electric generators operating in the US from5 kW to 25 kW.

• In the fall of 1941, the first megawatt-class wind turbine was synchronized to a utility gridin Vermont. The Smith-Putnam wind turbine only ran for 1,100 hours before suffering acritical failure. The unit was not repaired because of shortage of materials during the war.

• The first utility grid-connected wind turbine to operate in the U.K. was built by John Brown& Company in 1951.

History

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A quantitative measure of the wind energy available at any location is calledthe Wind Power Density (WPD) It is a calculation of the mean annual poweravailable per square meter of swept area of a turbine, and is tabulated fordifferent heights above ground. Calculation of wind power density includes theeffect of wind velocity and air density. Color-coded maps are prepared for aparticular area described, for example, as "Mean Annual Power Density at 50Meters.

Betz Limit 

All wind power cannot be captured by rotor or air would be completely still behindrotor and not allow more wind to pass through. Theoretical limit of rotor efficiencyis 59%.

5926.

27

16C max, p ==

Resources

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 Types

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 Turbines can be categorized into two overarching classes based on theorientation of the rotor.

• Vertical Axis

• Horizontal Axis

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Horizontal Axis TurbineHorizontal-axis wind turbines (HAWT) have the

main rotor shaft and electrical generator at thetop of a tower, and must be pointed into thewind.

Most have a gearbox, which turns the slowrotation of the blades into a quicker rotation thatis more suitable to drive an electrical generator.

Since a tower produces turbulence behind it, theturbine is usually positioned upwind of itssupporting tower.

 Turbine blades are made stiff to prevent theblades from being pushed into the tower by highwinds.

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Vertical Axis Turbine• Vertical-Axis Wind Turbines (or VAWTs) have the main rotor shaft arranged

vertically.

• Key advantages of this arrangement are that the turbine does not need to bepointed into the wind to be effective. This is an advantage on sites where thewind direction is highly variable, for example when integrated into buildings.

• The key disadvantages include:• The low rotational speed with the consequential higher torque and

hence higher cost of the drive train,• The inherently lower power coefficient, the 360 degree rotation of 

the aerofoil within the wind flow during each cycle and hence thehighly dynamic loading on the blade,

• The pulsating torque generated by some rotor designs on the drivetrain, and the difficulty of modelling the wind flow accurately.

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With a vertical axis, the generator and gearbox can be placed

near the ground, hence avoiding the need of a tower andimproving accessibility for maintenance. Drawbacks of thisconfiguration include(i) wind speeds are lower close to the ground, so less wind

energy is available for a given size turbine, and(ii) wind shear is more severe close to the ground, so the rotor

experiences higher loads.

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Components of Turbine

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 Active v/s Passive Yaw

• Active Yaw (all medium & largeturbines produced today, &some small turbines fromEurope)

 –

Anemometer on nacelle tellscontroller which way to pointrotor into the wind

 – Yaw drive turns gears topoint rotor into wind

• Passive Yaw (Most small

turbines) – Wind forces alone direct rotor

• Tail vanes

• Downwind turbines

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 Aerofoil Nomenclature

Wind turbines use the same aerodynamic principals as aircraft

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•  The Lift Force isperpendicular to the directionof motion. We want to makethis force BIG.

•  The Drag Force is parallel tothe direction of motion. Wewant to make this forcesmall.

α = low

α = medium<10 degrees

α = HighStall!!

Lift & Drag Forces

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α

VR =RelativeWind

V

ΩR Ωr 

V

= angle of attack = angle between theαchord line and the direction of the relativewind, VR .

VR = wind speed seen by the airfoil – vectorsum of V (free stream wind) and ΩR (tipspeed).

 Apparent Wind & Angle of Attack 

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• Rotor must move more rapidly tocapture same amount of wind – Gearbox ratio reduced – Added weight of 

counterbalance negatessome benefits of lighterdesign

 – Higher speed means morenoise, visual, and wildlifeimpacts

• Blades easier to install becauseentire rotor can be assembled onground

• Captures 10% less energy thantwo blade design

• Ultimately provide no costsavings

Number of Blades – One Blade

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• Advantages & disadvantagessimilar to one blade

• Need teetering hub and orshock absorbers because of gyroscopic imbalances

• Capture 5% less energy thanthree blade designs

Number of Blades – Two Blades

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• Balance of gyroscopic forces

• Slower rotation

 – increases gearbox &transmission costs

 – More aesthetic, less noise,

fewer bird strikes

Number of Blades – Three Blades

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Wind energy price is competitive. Offshore wind energy is becoming more andmore realizable.

Present European Price of Wind Energy

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India and China account for 28 percent of world energyconsumption by 2030 – Indian wind power needs to growfaster than in Europe

World Electricity Source Mix

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Currently more than 50% of the

electricity is generated through coal

The biggest source of renewableenergy is wind energy and currenttargets are modest in their numbers.

Current Energy Scenario in India

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10240MW

0 2 4 6 8 10 120

2

4

6

8

10

12

YEAR 

INSTALLE

DCAPACITY(MW)

Wind Energy installed capacity, India

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Even with an advanced or optimistic realization in 2020, GWEC is projectingonly an 18% share of electricity for wind energy in India, requiring 134 GWof wind power capacity.

Comparison of Global and India Wind EnergyScenario

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• Most of the wind speeds

between 5.5 -7m/s

•Large parts of the countryshown in white with lowwind speeds.

•

Current map is with 50mmasts or less, largerheights necessary formodern MW turbines.

Wind Power Density of INDIA

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Wind maps: Mean (annual andseasonal) wind speed andpower density at 50m and80m.

Verification: Can compare

generalized wind climatesderived from observationalwind atlas method andnumerical wind atlasmethod.

Application data: Generalizedwind climate in WAsP .libfile format for all of India;50 from observational windatlas and 200,000+ fromnumerical wind atlas, allowsapplication at very high

resolutions (~10m)

Wind Resource Mapping for INDIA

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Failures

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Conclusion

Inexpensive, reliable, simple, the hallmarks of the Helix system make it thebest choice for low wind speed residential and commercial applications. TheSavonius turbine based design catches wind from all directions creatingsmooth powerful torque to spin the electric generator. Mounted up to 35 feethigh, in winds as low as 10 mph the Helix system creates electricity to poweryour home or business.

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References• Ahmad Y Hassan, Donald Routledge Hill (1986). Islamic Technology:

 An illustrated history , p. 54. Cambridge University Press, ISBN 0-0-521-42239-6.

• Donald Routledge Hill, "Mechanical Engineering in the Medieval NearEast", Scientific American, May 1991, p. 64-69.

•

Alan Wyatt: Electric Power: Challenges and Choices. Book Press Ltd., Toronto 1986,ISBN 0-920650-00-7.

•http://www.nrel.gov/gis/wind/html - Dynamic Maps, GIS Data and Tools

• http://www.windpower.org/en/tour/utrb/comp/index/htmWind turbine

components retrieved November 8, 2008.

• "Wind Turbine Design Cost and Scaling Model," Technical ReportNREL/TP-500-40566, December, 2006, page35,36. http://www.nrel.gov/docs/fy07asti/40566.pdf 

•

A Wind Energy Pioneer: Charles F.BrushDanish Wind IndustryAssociation. Retrieved 2008-12-28

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Thank You

RegardsAbhishek AggarwalUjjwal KumarNiraj Kumar

VIII Semester