Learning about

Wind Power

(in India-2002)

CONTENTS

Wind resources: assessment,

monitoring, site selection

Energy conversion: wind turbine, gear,

generator, control

Tower : support at 50 m height with a

strong structure.

Potential in India :

Gross Potential :- 45,000 MW

Technical Potential :- 13,000 MW

Sites with Annual Average Wind Power

Density > 200 watts/m2 generally viable, 208

such sites in 13 states identified

States with high potential :

Gujarat, Andhra Pradesh, Tamil Nadu,

Karnataka, Kerala, Madhya Pradesh, and

Maharashtra.

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India’s Installed Wind Power Gen Capacity

at end of 2001 was about 1500 MW

State Installed capacity, MW

Tamil Nadu 828

Maharashtra 236

Gujarat 167

Andhra 92

Karnataka 50

M.P. 23

All Others 111 3

Wind energy basics

Kinetic energy >

Mechanical [Rotational] >

Electrical energy

Wind is created by the unequal

heating of the Earth’s surface by

the sun. Wind turbines convert

the kinetic energy in wind into

mechanical power that runs a

generator to produce electricity.

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Performance of WECS

Firstly,the availability of wind resources are

governed by the climatic conditions of the

region concerned- for which wind survey is

extremely important to exploit wind energy.

Performance of W E C S depends upon:

Subsystems like

wind turbine (aerodynamic),

gears (mechanical),

generator (electrical) and Control (electronic)

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Wind resources

Apart from having a good wind turbine, the

most critical aspects for the success of

investment in the wind energy sector are

having a good site and

an accurate assessment of the wind

resource at the site over a period of time.

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Wind Resource Monitoring

Site selection

Wind Monitoring

Wind Resource Mapping

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anemometer

An instrument for measuring the force or velocity of wind. There are various types:

A cup anemometer, is used to measure

the wind speed from the speed of rotation

of a windmill which consist of 3 or 4

hemispherical or conical cups, each fixed

to the ends of horizontal arms attached to

a vertical axis.

A Byram anemometer is a variety of cup

anemometer.

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A counting anemometer has cups or a fan

whose rotation is transmitted to a counter which integrates directly the air movement speed.

A hand anemometer is small portable anemometer held at arm's length by an observer making a wind speed measurement.

A pressure tube anemometer (Dines anemometer) is an instrument that derives wind speed from measurements of the dynamic wind pressures. Wind blowing into a tube develops a pressure greater than the static pressure, while wind blowing across a tube develops a pressure less than the static. This pressure difference is proportional to the square of the wind speed.

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WIND

Wind Speed at 10 m height

SPEED

Beaufort scale

SCALE

Wind

0.0-0.4 m/s (0.0-0.9 knots) 0 Calm

0.4-1.8 m/s (0.9-3.5 knots) 1 Light

1.8-3.6 m/s (3.5-7.0 knots) 2 Light

3.6-5.8 m/s (7-11 knots) 3 Light

5.8-8.5 m/s (11-17 knots) 4 Moderate

8.5-11 m/s (17-22 knots) 5 Fresh

11-14 m/s (22-28 knots) 6 Strong

14-17 m/s (28-34 knots) 7 Strong

17-21 m/s (34-41 knots) 8 Gale

21-25 m/s (41-48 knots) 9 Gale

25-29 m/s (48-56 knots) 10 Strong Gale

29-34 m/s (56-65 knots) 11

>34 m/s (>65 knots) 12 Hurricane 15

Some definitions….

1 m/s = 3.6 km/h = 2.237 mph = 1.944 knots

1 knot = 1 nautical mile per hour = 0.5144 m/s =

1.852 km/h = 1.125 mph

average wind speed: The mean wind speed over a

specified period of time.

PITCH CONROL: A method of controlling the

speed of a wind turbine by varying the orientation,

or pitch, of the blades, and thereby altering its

aerodynamics and efficiency.

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For wind data from selected stations,

essential attributes are:

Station location

Local topography

Anemometer height and exposure

Type of observation (instantaneous or

average)

Duration of record.

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Topographic maps

provide the analyst with a preliminary look

at other site attributes, including:

Available land area

Positions of existing roads and dwellings

Land cover (e.g., forests)

Political boundaries

Parks

Proximity to transmission lines.

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For verifying site conditions items of

importance include:

Available land area

Land use

Location of obstructions

Trees deformed by persistent strong winds (flagged

trees)

Accessibility into the site

Potential impact on local aesthetics

Cellular phone service reliability for data transfers

Possible wind monitoring locations.

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WIND RESOURCE ASSESSMENT-

India- Implemented through :

(i) State Nodal Agencies

(ii) Centre for Wind Energy Technology (C-

WET)

Financial Assistance :

(i) Full establishment costs of Wind Resource

Assessment Project (WRAP) of C-WET by

the Central Government.

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WIND RESOURCE ASSESSMENT

Implemented through…. :

(ii) The cost of setting up the wind monitoring

stations would be shared between MNES and

State Nodal agencies in 80:20 ratio, except

for North-eastern and hilly States, where it

would be in 90:10 ratio.

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Resource Survey in India

Centre for Wind Energy Technology (C-WET)

Chennai.

6 Volumes of “Wind Energy –Resource Survey in

India” , containing wind data have been published

Master Plans for 87 sites prepared and available

from C-WET at nominal cost.

Wind data available from C-WET on CD ROM.

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Government of India

Ministry of New and Renewable Energy

(Wind Power Division)

Block No.14, CGO Complex,

Lodhi Road, New Delhi – 110003

•C-WET would evaluate the eligibility of manufacturer, who approaches for Type. Certification, as per the evaluation criteria in vogue, which is being followed by C-WET. •Validity of Self-Certification facility for models specified in the List of Models and Manufacturers thereof issued by C-WET is extended up to 30th September, 2007. •Self-Certification facility would be available for a maximum period of 18 months from the date of signing of the agreement with C-WET for the models hereinafter including in the category "Model under Testing and Certification at C-WET" in the List to be issued by C-WET.

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Choosing an exact location for the

monitoring tower:

Place the tower as far away as possible

from local obstructions to the wind

Select a location that is representative of

the majority of the site.

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Horizontal Axis upwind

Wind Turbine

Most turbines today are Horizontal Axis

upwind machines with two or three blades,

made of a composite material like

fiberglass.

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•The amount of power a turbine will produce depends primarily on the diameter of its rotor. •The diameter of the rotor defines its “swept area,” or the quantity of wind intercepted by the turbine. •The turbine‟s frame is the structure onto which the rotor, generator, and tail are attached. The tail keeps the turbine facing into the wind.

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Small WECS for Pumping Water

One- to 10-kW turbines can be used

in applications such as pumping

water.

Wind-electric pumping systems can

be placed where the wind resource is

the best and connected to the pump

motor with an electric cable.

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Small wind turbines

Usually machines under about 10 kW in output.

In developing countries small wind turbines are used for rural energy applications, and there are many "off-grid" applications in the developed world as well - such as providing power for navigation beacons.

Since most are not connected to a grid, many use DC generators and run at variable speed. A typical 100 W battery-charging machine has a shipping weight of only 15 kg

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The formula for calculating the

power from a wind turbine is:

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Operating Characteristics

All wind machines share certain operating

characteristics, such as cut-in, rated and cut-out wind speeds.

Cut-in Speed Cut-in speed is the minimum wind speed at which the wind turbine will generate usable power. This wind speed is typically between 7 and 10 mph.

Rated Speed The rated speed is the minimum wind speed at which the wind turbine will generate its designated rated power. For example, a "10 kilowatt" wind turbine may not generate 10 kilowatts until wind speeds reach 25 mph. Rated speed for most machines is in the range of 25 to 35 mph.

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Rated Speed…

At wind speeds between cut-in and rated, the

power output from a wind turbine increases

as the wind increases. The output of most

machines levels off above the rated speed.

Most manufacturers provide graphs, called

"power curves," showing how their wind

turbine output varies with wind speed.

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Cut-out Speed

At very high wind speeds, typically between

45 and 80 mph, most wind turbines cease

power generation and shut down. The wind

speed at which shut down occurs is called

the cut-out speed. Having a cut-out speed is

a safety feature which protects the wind

turbine from damage. Shut down may occur

in one of several ways. In some machines an

automatic brake is activated by a wind speed

sensor.

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Cut out speed & yaw

Some machines twist or "pitch" the blades to

spill the wind. Still others use "spoilers," drag

flaps mounted on the blades or the hub which

are automatically activated by high rotor

rpm's, or mechanically activated by a spring

loaded device which turns the machine

sideways to the wind stream. Normal wind

turbine operation usually resumes when the

wind drops back to a safe level.

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Tip Speed Ratio

The tip-speed is the ratio of the rotational

speed of the blade to the wind speed. The

larger this ratio, the faster the rotation of the

wind turbine rotor at a given wind speed.

Electricity generation requires high rotational

speeds. Lift-type wind turbines have

maximum tip-speed ratios of around 10

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number of blades

The number of rotor blades and the total area they

cover affect wind turbine performance. For a lift-

type rotor to function effectively, the wind must flow

smoothly over the blades.

To avoid turbulence, spacing between blades

should be great enough so that one blade will not

encounter the disturbed, weaker air flow caused by

the blade which passed before it.

It is because of this requirement that most wind

turbines have only two or three blades on their

rotors

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The Practical Action small

wind turbine ©Practical Action

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Transmission

The number of revolutions per minute (rpm)

of a wind turbine rotor can range between

40 rpm and 400 rpm, depending on the

model and the wind speed.

Generators typically require rpm's of 1,200

to 1,800. As a result, most wind turbines

require a gear-box transmission to increase

the rotation of the generator to the speeds

necessary for efficient electricity production.

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Generators

It converts the turning motion of a wind

turbine's blades into electricity. Inside

this component, coils of wire are rotated

in a magnetic field to produce electricity.

Different generator designs produce

either alternating current (AC) or direct

current (DC),

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range of output power ratings.

Generators are available in a large range of

output power ratings.

The generator's rating, or size, is dependent

on the length of the wind turbine's blades

because more energy is captured by longer

blades.

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Applications adapted to run on

DC.

• Storage systems using batteries store DC

and usually are configured at voltages of

between 12 volts and 120 volts in USA.

A typical 100 W battery-charging machine

has a shipping weight of only 15 kg.

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Generators…..

• Generators that produce AC are generally

equipped with features to produce the correct

voltage (120 or 240 V) and

• constant frequency (60 / 50 cycles) of

electricity, even when the wind speed is

fluctuating.

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Induction generator

Induction generator offers many advantages over a

conventional synchronous generator as a source of

isolated power supply.

Reduced unit cost, ruggedness, brush less (in

squirrel cage construction), reduced size, absence

of separate DC source and ease of maintenance,

self-protection against severe overloads and short

circuits, are the main advantages

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induction generator…

Further induction generators are loosely

coupled devices, i.e. they are heavily damped

and therefore have the ability to absorb slight

change in rotor speed and drive train

transient to some extent can therefore be

absorbed.

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drawback of the induction

generator

Reactive power consumption and poor

voltage regulation under varying speed are

the major drawback of the induction

generators, but the development of static

power converters has facilitated the control of

induction generator, regarding output voltage

and frequency.

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Synchronous generator

Synchronous generators are closely coupled

devices and when they are used in wind

turbines which is subjected to turbulence and

requires additional damping devices such as

flexible couplings in the drive train or to

mount gearbox assembly on springs and

dampers.

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Towers

Tower on which a wind turbine is mounted is

not just a support structure. It also raises the

wind turbine so that its blades safely clear

the ground and so it can reach the stronger

winds at higher elevations.

Maximum tower height is optional in most

cases, except where zoning restrictions

apply. The decision of what height tower to

use will be based on the cost of taller towers

versus the value of the increase in energy

production resulting from their use.

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The tower must be strong enough to

support the wind turbine and to sustain

vibration, wind loading and the overall

weather elements for the lifetime of the

wind turbine.

Tower costs will vary widely as a function

of design and height.

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Towers….

Studies have shown that the added

cost of increasing tower height is often

justified by the added power generated

from the stronger winds.

Larger wind turbines are usually

mounted on towers ranging from 40 to 70

meters tall.

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Environmental Aspects of

Power Generation Using WECs

Wind turbines are most environment friendly method

of producing electricity.

They do not pose any adverse effect on the global

environment, unlike the conventional coal or oil-fired

power plants. The pollution that can be saved per

year from a typical 200 kW wind turbine, involving of

substitution of 120 - 200 tonnes of coal which

contain pollution contents as, Sulphur dioxide

(SO2): 2 –3 tonnes, Nitrogen oxide (NOX): 1.2 to

2.4 tonnes, and other particulates of 150-300 kg. .

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Audible noise

The wind turbine is generally quiet. The wind turbine

manufacturers generally supply the noise level data

in dB versus the distance from the tower.

A typical 600 kW wind turbine may produce 55 dB

noise at 50 meter distance from the turbine and 40

dB at a 250 meter distance [4, 22] comparable with

the noise level in motor car which may be

approximately 75 dB.

This noise is, however, is a steady state noise. The

wind turbine makes loud noise while yawing under

the changing wind direction. Local noise ordinance

must be compiled with.

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Research and development

Research and development is going on to make wind power competitive with fossil fuel and nuclear power in strict sense, without taking into account of wind power‟s social factors such as environment benefits.

Efforts are being made to reduce the cost of wind power by: design improvement, better manufacturing technology, finding new sites for wind systems, development of better control strategies (for output and power quality control), development of policy and instruments, human resource development, etc

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About Enercon- E-30-230 kW-

Gearless type--1

Variable speed drive, Continuous pitch regulation,

Starts gen. at low speed of 2.5 m/s,

Gearless construction, no transmission loss,

Synchronous gen., draws < one % reactive power from grid,

By using AC_DC_AC conversion, pumps the power at „grid frequency‟,

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About Enercon - E-30-230 kW-

Gearless type--2

Produces power at all loads at near unity

power factor without using capacitors

Supply reactive power to the grid to improve

grid power factor

Slow speed generator of maximum 50 rpm

Three independent air breaks, no

mechanical breaks

Lightning protection

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