wind turbine saurabh yadav

8/8/2019 Wind Turbine Saurabh Yadav

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Topic: Wind Turbine

Submit to:Ms.

Kulwinder Kaur

Submitted by:

Saurabh YadavSection: D6002

Roll No.:B70

Reg.No:11011367

CONTENTS:

HISTORY

WIND TURBINE

RAW MATERIALS

MANUFACTURERING PROCESS

ROTARY BLADES

TYPES OF WIND TURBINE

CYCLIC STRESS AND

VIBRATION:

MODERN WIND TURBINE

ADVANTAGEAND

DIS ADVANTAGE


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HISTORY:

The first large-scale wind turbine built in the

United States was conceived by Palmer

Cosslett Putnam in 1934. He completed it in

1941. The machine was huge. The tower

was 36.6 yards (33.5 meters) high, and its

two stainless steelblades had diameters of

58 yards (53 meters). Putnam's wind turbine

could produce 1,250 kilowatts of electricity,

or enough to meet the needs of a small town.

It was however abandoned in 1945 because

of mechanical failure.

With the 1970s oil embargo, the UnitedStates began once more to consider the

feasibility of producing cheap electricity

from wind turbines. In 1975 the prototype

Mod-O was in operation. This was a 100

kilowatt turbine with two 21-yard (19-

meter) blades. More prototypes followed

(Mod-OA, Mod-1, Mod-2, etc.), each larger

and more powerful than the one before.

Currently, the United States Department of

Energy is aiming to go beyond 3,200

kilowatts per machine.

WIND TURBINE:

A wind turbine is a machine that converts

the wind's kinetic energy into rotary

mechanical energy, which is then used to do

work. In more advanced models, the

rotational energy is converted into

electricity, the most versatile form of

energy, by using a generator.

A wind turbine is a rotary device that

extracts from the wind if the mechanical

energy is used directly by machinery, suchas for pumping water, cutting lumber or

grinding stones, the machine is called

awindmill. If the mechanical energy is

instead converted to electricity, the machine

is called a wind generator, wind

turbine, wind turbine generator

(WTG), wind power unit (WPU), wind

energy converter (WEC) or aerogenerator.

RAW MATERIALS:

A wind turbine consists of three basic parts:

the tower, the nacelle, and the rotor blades.

The tower is either a steel lattice tower

similar to electrical towers or a steel tubular

tower with an inside ladder to the nacelle.

The first step in constructing a wind turbine

is erecting the tower. Although the tower'ssteel parts are manufactured off site in a

factory, they are usually assembled on site.

The parts are bolted together before

erection, and the tower is kept horizontal

until placement. A crane lifts the tower into

position, all bolts are tightened, and stability
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is tested upon completion.

Next, the fiberglass nacelle is installed. Its

inner workingsmain drive shaft, gearbox,

and blade pitch and yaw controlsare

assembled and mounted onto a base frame ata factory. The nacelle is then bolted around

the equipment. At the site, the nacelle is

lifted onto the completed tower and bolted

into place.

Most towers do not have guys, which are

cables used for support, and most are made

of steel that has been coated with a zinc

alloy for protection, though some are

painted instead. The tower of a typicalAmerican-made turbine is approximately 80

feet tall and weighs about 19,000 pounds.

The nacelle is a strong, hollow shell that

contains the inner workings of the wind

turbine. Usually made of fiberglass, the

nacelle contains the main drive shaft and the

gearbox. It also contains the blade pitch

control, a hydraulic system that controls the

angle of the blades, and the yaw drive,

which controls the position of the turbine

relative to the wind. The generator and

electronic controls are standard equipment

whose main components are steel and

copper. A typical nacelle for a current

turbine weighs approximately 22,000

pounds.

The most diverse use of materials and themost experimentation with new materials

occur with the blades. Although the most

dominant material used for the blades in

commercial wind turbines is fiberglass with

a hollow core, other materials in use include

lightweight woods and aluminum. Wooden

blades are solid, but most blades consist of a

skin surrounding a core that is either hollow

or filled with a lightweight substance such

as plastic foam or honeycomb, or balsa

wood. A typical fiberglass blade is about 15meters in length and weighs approximately

2,500 pounds.

MANUFACTURERING

PROCESS:

Before consideration can be given to the construction

of individual wind turbines, manufacturers must

determine a proper area for the siting of

wind farms. Winds must be consistent, andtheir speed must be regularly over 15.5

miles per hour (25 kilometers per hour). If

the winds are stronger during certain

seasons, it is preferred that they be greatest

during periods of maximum electricity use.

In California's Altamont Pass, for instance,

site of the world's largest wind farm, wind

speed peaks in the summer when demand is

high. In some areas of New England wherewind farms are being considered, winds are

strongest in the winter, when the need for


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The nacelle is a strong, hollow shell that

contains the inner workings of the wind

turbine, such as the main drive shaft and the

gearbox. It also contains the blade pitch

control, a hydraulic system that controls theangle of the blades, and the yaw drive,

which controls the position of the turbine

relative to the wind. A typical nacelle for a

current turbine weighs approximately

22,000 pounds. Heating increases the

consumption of electrical power. Wind farms

work best in open areas of slightly rolling land

surrounded by mountains. These areas are

preferred because the wind turbines can be

placed on ridges and remain unobstructed by

trees and buildings, and the mountains

concentrate the air flow, creating a natural wind

tunnel of stronger, faster winds. Wind farms

must also be placed near utility lines to facilitate

the transfer of the electricity to the local power

plant.

ROTARY BLADES:

1. Aluminum blades are created by bolting

sheets of aluminum together, while wooden

blades are carved to form an aerodynamic

propeller similar in cross-section to an

airplane wing.

2. By far the greatest number of blades,

however, are formed from fiberglass. Themanufacture of fiberglass is a painstaking

operation. First, a mold that is in two halves

like a clam shell, yet shaped like a blade is

prepared. Next, a fiberglass-resin composite

mixture is applied to the inner surfaces of

the mold, which is then closed. The

fiberglass mixture must then dry for several

hours, while it does, an air-filled bladder

within the mold helps the blade keep its

shape. After the fiber glass is dry, the mold

is then opened and the bladder is removed.Final preparation of the blade involves

cleaning, sanding sealing the two halves,

and painting.

3. The blades are usually bolted onto the

nacelle after it has been placed onto the

tower. Because assembly is easier to

accomplish on the ground, occasionally a

three-pronged blade has two blades bolted

onto the nacelle before it is lifted, and the

third blade is bolted on after the nacelle is in

place.

Wind turbines also include a utility box,

which converts the wind energy into

electricity and which is located at the base of

the tower. Various cables connect the utility

box to the nacelle, while others connect the

whole turbine to nearby turbines and to a

transformer.


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TYPES OF WIND TURBINE

Wind turbines can rotate about either a

horizontal or a vertical axis, the former

being both older and more common.

The 3 primary types of HAWT and VAWT

as they appear in operation.

HORIZONTAL WIND TURBINES

Horizontal-axis wind turbines (HAWT) have

the main rotorshaft and electrical

generatorat the top of a tower, and must be

pointed into the wind. Small turbines are

pointed by a simple wind vane, while large

turbines generally use a wind sensor coupled

with a servo motor. Most have a gearbox,

which turns the slow rotation of the blades

into a quicker rotation that is more suitable

to drive an electrical generator.

COMPONENTS OF

HORIZONTALAXIS-WINDTURBINE:

Wind turbines are designed to exploit the

wind energy that exists at a

location. Aerodynamic modeling is used to
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determine the optimum tower height, control

systems, number of blades and blade shape.

Wind turbines convert wind energy to

electricity for distribution. Conventional

horizontal axis turbines can be divided

into three components.

1. The rotor component, which is

approximately 20% of the wind turbine cost,

includes the blades for converting wind

energy to low speed rotational energy.

2. The generator component, which is

approximately 34% of the wind turbine cost,

includes the electrical generator, the control

electronics, and most likely

agearbox component for converting the low

speed incoming rotation to high speed

rotation suitable for generating electricity.

3. The structural support component, which

is approximately 15% of the wind turbine

cost, includes the tower and rotor yaw

mechanism.

Small wind turbines may be as small as a

fifty-watt generator for boat or caravan use.

Small units often have direct drive

generators, direct current output, aero elastic

blades, lifetime bearings and use a vane to

point into the wind.

Larger, more costly turbines generally have

geared power trains, alternating current

output, flaps and are actively pointed into

the wind. Direct drive generators and aero

elastic blades for large wind turbines are

being researched.

CYCLIC STRESS AND

VIBRATION:

Cyclic stresses fatigue the

blade, axle and bearing resulting in material

failures that were a major cause of turbine

failure for many years. Because wind

velocity often increases at higher altitudes,

the backward force and torque on a

horizontal-axis wind turbine (HAWT) blade

peaks as it turns through the highest point in

its circle. The tower hinders the airflow at

the lowest point in the circle, which

produces a local dip in force and torque.

These effects produce a cyclic twist on the

main bearings of a HAWT. The combined

twist is worst in machines with an even

number of blades, where one is straight up

when another is straight down. To improve

reliability, teetering hubs have been used

which allow the main shaft to rock through a

few degrees, so that the main bearings do

not have to resist the torque peaks.

The rotating blades of a wind turbine act like

a gyroscope. As it pivots along its vertical

axis to face the wind, gyroscopic

precession tries to twist the turbine disc

along its horizontal axis. For each blade on a

wind generator's turbine, precessive force is

at a minimum when the blade is horizontal
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and at a maximum when the blade is

vertical. The cyclic loading affects the

design of the mechanical elements,

structure, and foundation of the wind

turbine.

VERTICAL AXIS DESIGN:

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 be pointed into the wind to be

effective. This is an advantage on sites

where the wind direction is highly variable.

With a vertical axis, the generator and

gearbox can be placed near the ground, so

the tower doesn't need to support it, and it is

more accessible for maintenance.

Drawbacks are that some designs produce

pulsating torque.

It is difficult to mount vertical-axis turbines

on towers meaning they are often installed

nearer to the base on which they rest, such

as the ground or a building rooftop. The

wind speed is slower at a lower altitude, so

less wind energy is available for a given size

turbine. Air flow near the ground and other

objects can create turbulent flow, which can

introduce issues of vibration, including noise

and bearing wear which may increase the

maintenance or shorten the service life.

However, when a turbine is mounted on a

rooftop, the building generally redirects

wind over the roof and this can double the

wind speed at the turbine. If the height of the

rooftop mounted turbine tower is

approximately 50% of the building height,

this is near the optimum for maximum wind

energy and minimum wind turbulence.

Since a tower produces turbulence behind it,

the turbine is usually pointed upwind of the

tower. Turbine blades are made stiff to

prevent the blades from being pushed into

the tower by high winds. Additionally, the

blades are placed a considerable distance in

front of the tower and are sometimes tilted

forward into the wind a small amount.

Downwind machines have been built,

despite the problem of turbulence (mast

wake), because they don't need an additional

mechanism for keeping them in line with the

wind, and because in high winds the blades

can be allowed to bend which reduces their

swept area and thus their wind resistance.

Since cyclic (that is repetitive) turbulence

may lead to fatigue failures most HAWTs

are upwind machines.

12th-century windmills:

These squat structures, typically (at least)four bladed, usually with wooden shutters or

fabric sails, were developed in Europe.

These windmills were pointed into the wind

manually or via a tail-fan and were typically

used for grinding grain. In the
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Netherlands they were also used for

pumping water from low-lying land, and

were instrumental in keeping itspolders dry.

In Schiedam, the Netherlands, a traditional

style windmill (the Noletmolen) was built in

2005 to generate electricity. The mill is one

of the tallest Tower mills in the world, being

some 42.5 metres (139 ft) tall.

19th-century windmills

The Eclipse windmill factory was set up

around 1866 in Beloit, Wisconsin and soon

became successful building mills for

pumping water on farms and for filling

railroad tanks. Other firms like Star,

Dempster, and Aero motor also entered the

market. Hundreds of thousands of these

mills were produced before rural

electrification and small numbers continue

to be made. They typically had many blades,

operated at tip speed ratios not better than

one, and had good starting torque. Some hadsmall direct-current generators used for

charging storage batteries, to provide power

to lights, or to operate a radio receiver. The

American rural electrification connected

many farms to centrally generated power

and replaced individual windmills as a

primary source of farm power by the 1950s.

They were also produced in other countries

like South Africa and Australia (where an

American design was copied in 1876. Such

devices are still used in locations where it is

too costly to bring in commercial power.

AIRBORNE WIND TURBINE:

An airborne wind turbine is a design concept

for a wind turbine that is supported in the air

without a tower. Airborne wind turbines

may operate in low or high altitudes; they

are part of a wider class of airborne windenergy systems (AWE) addressed by high

altitude wind power. When the generator is

on the ground, then the tethered aircraft need

not carry the generator mass or have a

conductive tether. When the generator is

aloft, then a conductive tether would be used

to transmit energy to the ground or used

aloft or beamed to receivers using

microwave or laser. Air borned turbine

systems would have the advantage of

tapping an almost constant wind, without

requirements forslip rings oryaw

mechanism, and without the expense of

tower construction. Kites and 'helicopters'

come down when there is insufficient wind

kytoons and blimps resolve the matter.

Also, bad weather suchas lightning orthunderstorms, could

temporarily suspend use of the machines,

probably requiring them to be brought back

down to the ground and covered. Some

schemes require a long power cable and, if
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the turbine is high enough, an aircraft

exclusion zone. As of 2008, no commercial

airborne wind turbines are in regular

operation.

MODERN WIND TURBINE

Turbines used in wind farms for commercial

production of electric power are

usually three-bladed and pointed

into the wind by computer-

controlled motors. These have hightip speeds of over 320 kilo metres

per hour (200 mph), high

efficiency, and low torque ripple,

which contribute to good

reliability. The blades are usually

colored light gray to blend in with

the clouds and range in length from

20 to 40 metres (66 to 130 ft) or

more. The tubular steel towers

range from 60 to 90 metres (200 to

300 ft) tall. The blades rotate at 10-

22 revolutions per minute. At 22

rotations per minute the tip speed

exceeds 300 feet per second (91

m/s). A gear box is commonly used

for stepping up the speed of the

generator, although designs may

also use direct drive of an annular

generator. Some models operate at

constant speed, but more energy

can be collected by variable-speedturbines which use a solid-state

power converter to interface to the

transmission system. All turbines

are equipped with protective

features to avoid damage at high

wind speeds, byfeatheringthe

blades into the wind which ceases

their rotation, supplemented

bybrakes.
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Subtypes:

Darrieus wind turbine:"Eggbeater" turbines, or Darrieus turbines,

were named after the French inventor,

Georges Darrieus. They have good

efficiency, but produce large torque ripple

and cyclical stress on the tower, which

contributes to poor reliability. They also

generally require some external power

source, or an additional Savonius rotor to

start turning, because the starting torque is

very low. The torque ripple is reduced by

using three or more blades which results in a

higher solidity for the rotor. Solidity is

measured by blade area divided by the rotor

area. Newer Darrieus type turbines are not

held up by guy-wires but have an external

superstructure connected to the top bearing.

A helical twisted VAWT.

Giromill:

A subtype of Darrieus turbine with straight,

as opposed to curved, blades. The cyclo

turbine variety has variable pitch to reduce

the torque pulsation and is self-starting. The

advantages of variable pitch are: high

starting torque; a wide, relatively flat torque

curve; a lower blade speed ratio; a higher

coefficient of performance; more efficient

operation in turbulent winds; and a lower

blade speed ratio which lowers blade

bending stresses. Straight, V or curved

blades may be used.
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Windmill with rotating sails

Savonius wind turbine:

These are drag-type devices with two (or

more) scoops that are used in

anemometers, Flettner vents (commonly

seen on bus and van roofs), and in some

high-reliability low-efficiency power

turbines. They are always self-starting if

there are at least three scoops. They

sometimes have long helical scoops to give

a smooth torque.

Environmental Benefits:

A wind turbine that produces electricity

from inexhaustible winds creates no

pollution. By comparison, coal, oil, and

natural gas produce one to two pounds of

carbon dioxide (an emission that contributes

to the greenhouse effect and global

warming) per kilowatt-hour produced. When

wind energy is used for electrical needs,

dependence on fossil fuels for this purposeis reduced. The current annual production of

electricity by wind turbines (3.7 billion

kilowatt-hours) is equivalent to four million

barrels of oil or one million tons of coal.

Drawbacks:

Wind turbines are not completely free of

environmental drawbacks. Many people

consider them to be unaesthetic, especiallywhen huge wind farms are built near pristine

wilderness areas. Bird kills have been

documented, and the whirring blades do

produce quite a bit of noise. Efforts to

reduce these effects include selecting sites

that do not coincide with wilderness areas or

bird migration routes and researching ways

to reduce noise.

The Future of Wind Turbine:

The future can only get better for wind

turbines. The potential for wind energy is

largely untapped. The United States

Department of Energy estimates that ten

times the amount of electricity currently

being produced can be achieved by 1995. By

2005, seventy times current production is possible. If this is accomplished, wind

turbines would account for 10 percent of the

United States' electricity production.

Research is now being done to increase the

knowledge of wind resources. This involves
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the testing of more and more areas for the

possibility of placing wind farms where the

wind is reliable and strong. Plans are in

effect to increase the life span of the

machine from five years to 20 to 30 years,improve the efficiency of the blades, provide

better controls, develop drive trains that last

longer, and allow for better surge protection

and grounding. The United States

Department of Energy has recently set up a

schedule to implement the latest research in

order to build wind turbines with a higher

efficiency rating than is now possible. (The

efficiency of an ideal wind turbine is 59.3

percent. That is, 59.3 percent of the wind's

energy can be captured. Turbines in actual

use are about 30 percent efficient.) The

United States Department of Energy has also

contracted with three corporations to

research ways to reduce mechanical failure.

This project began in the spring of 1992 and

will extend to the end of the century.

Advantages:

Variable blade pitch, which gives the turbine

blades the optimum angle of attack.

Allowing the angle of attack to be

remotely adjusted gives greater

control, so the turbine collects the

maximum amount of wind energy

for the time of day and season.

1. The tall tower base allows access to

stronger wind in sites with wind shear. In

some wind shear sites, the wind speed can

increaseby 20% and the power output by

34% for every 10 meters in elevation.

2. High efficiency, since the blades always

move perpendicular to the wind, receiving

power through the whole rotation. In

contrast, all vertical axis wind turbines, and

most proposed airborne wind

turbine designs, involve various types of

reciprocating actions, requiring airfoil

surfaces to backtrack against the wind for

part of the cycle. Backtracking against the

wind leads to inherently lower efficiency.

3. The face of a horizontal axis blade is

struck by the wind at a consistent angleregardless of the position in its rotation. This

results in a consistent lateral wind loading

over the course of a rotation,

4. Reducing vibration and audible noise

coupled to the tower or mount.

Disadvantages:

1. The tall towers and blades up to 45 meters

long are difficult to transport. Transportation

can now amount to 20% of equipment costs.

2. Tall HAWTs are difficult to install,

needing very tall and expensive cranes and

skilled operators.

3. Massive tower construction is required to

support the heavy blades, gearbox, and

generator.

4. Reflections from tall HAWTs may affect

side lobes ofradarinstallations creating
http://en.wikipedia.org/wiki/Wind_shearhttp://en.wikipedia.org/wiki/Wind_profile_power_lawhttp://en.wikipedia.org/wiki/Wind_profile_power_lawhttp://en.wikipedia.org/wiki/Airborne_wind_turbinehttp://en.wikipedia.org/wiki/Airborne_wind_turbinehttp://en.wikipedia.org/wiki/Radarhttp://en.wikipedia.org/wiki/Wind_shearhttp://en.wikipedia.org/wiki/Wind_profile_power_lawhttp://en.wikipedia.org/wiki/Wind_profile_power_lawhttp://en.wikipedia.org/wiki/Airborne_wind_turbinehttp://en.wikipedia.org/wiki/Airborne_wind_turbinehttp://en.wikipedia.org/wiki/Radar


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signal clutter, although filtering can suppress

it.

5. Their height makes them obtrusively

visible across large areas, disrupting the

appearance of the landscape and

sometimes creating local opposition.

6. Downwind variants suffer from

fatigue and structural failure caused by

turbulence when a blade passes through

the tower's wind shadow (for this reason,

the majority of HAWTs use an upwind

design, with the rotor facing the wind infront of the tower).

7. HAWTs require an

additional yaw control mechanism to

turn the blades and nacelle toward the

wind.

8. In order to minimize fatigue loads

due to wake turbulence, wind turbines

are usually sited a distance of 5 rotor

diameters away from each other, but the

spacing depends on the manufacturer

and the turbine model.

REFERENCE:

www.Cengage.co.in

www.greenandwhite.com

Amazon.com

BOOKS:

Wind Turbines: Fundamentals,

Technologies, Application

Wind Turbines Economics Book
http://en.wikipedia.org/wiki/Yaw_drivehttp://www.cengage.co.in/http://www.greenandwhite.com/http://www.amazon.com/Turbine-Engineering-Design-David-Eggleston/dp/0442221959http://en.wikipedia.org/wiki/Yaw_drivehttp://www.cengage.co.in/http://www.greenandwhite.com/http://www.amazon.com/Turbine-Engineering-Design-David-Eggleston/dp/0442221959

wind turbine saurabh yadav

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