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   notes
   India ranks fifth amongst the wind-energy-producing countries of the world
    after USA, China, Germany and Spain.

   India's position was 3rd in the World till September 96, thereafter it became
    4th upto December 98, 5th upto December 04, it was 4th upto December 08
     and now it is 5th again.

   Estimated potential is around 45000 MW at 50 m above ground level.

   Exhaustive wind resource assessment has been carried out in 650 stations
    spread over 27 States in the country. As on date 225 Wind Monitoring
    stations have indicated wind power density more than 200 W/m2 at 50 m
    above ground level.

   Micro Survey of Wind Resource for 97 Wind Monitoring Stations have been
    completed to know the zone of influence and Wind Power Potential around
    the stations to meet the requirement of wind energy developers in the

   Windfarms have been installed in 11 States.

   More than 95% of installed capacity belongs to Private Sector in seven states

   A good number of wind turbine manufacturers are active in India and
    producing Wind Electric Generators (WEGs) of rating 225 kW to 2100 kW.

   A large number of agencies have come up to supply components/spares/
    accessories and to provide services like Erection, O&M, Civil & Electrical
    Construction, Consultancy etc.

   A large number of water pumping windmills and small aero-generators have
    been installed in the country.

   Wind-Solar and Wind-Diesel Hybrid systems have also been installed at a
    few places.

   The Central Ministry and several State Nodal Agencies encourage growth of
    Wind Energy Sector through financial incentives and policy support.

   The Ministry of New & Renewable Energy (MNRE), Govt. of India has
    established a Centre for Wind Energy Technology at Chennai with field test
    station at Kayathar to act as technical focal point for wind power
    development in the country.
      Financial assistance for Renewable sources of energy is available through
       Indian Renewable Energy Development Agency (IREDA), a supporting arm
       of MNRE, GOI.

Figures aand facts
      Largest Rating of WEG installed
       2100 kW, Suzlon
      Highest Hub Height of WEG installed
       85 m, Regen PowerTech 1500 kW
      Maximum Rotor diameter of WEG installed
       88 m, Suzlon 2100 kW
      Maximum Installation in a State
       4875 MW, Tamil Nadu (as on 31 March 2010)
      Maximum Installed Capacity by a WEG Manufacturer
       5255 MW, Suzlon
      Maximum estimated gross wind power potential in a State
       9675 MW, Gujarat
      Maximum estimated technical wind power potential in a State
       3750 MW, Tamil Nadu
      Maximum extrapolated Mean Annual Wind Power Density of a Site at 50 m height amongst
       the MNRE notified sites
       721 W/m2, Perampukettimedu, Kerala
      Maximum No. of Wind Monitoring Stations Installed in a State
       119 Nos., Maharashtra
      Highest elevation at which windfarm Established
       1100 m.a.s.l. at Vankusawade, Maharashtra
      Highest elevation at which Wind Monitoring Station Established
       3360 m.a.s.l. at Basgo, J&K
      Highest elevation amongst the MNRE notified sites
       1768 m.a.s.l. at B.B. Hills, Karnataka
      Highest capacity addition in a financial year
       1778 MW during the year 2006-07
      Highest capacity addition in a financial year by a WEG Manufacturer
       929 MW during the year 2007-08, Suzlon
      Highest capacity addition in a financial year in a State
       861 MW during the year 2005-06, Tamil Nadu
      Largest Private Windfarm Developer
       MSPL Group of Companies, 191.60 MW
      Overall average rating of WEGs installed in India as on 31-03-2010
       644 kW
      Overall average rating of WEGs installed in India during 2009-10
       932 kW
      First Concrete Tower for WEG
       Enercon, 230 kW WEG at Gudimangalam, Dist : Coimbatore
      First WEG Installed under Demonstration projects
       55 kW & 110 kW, Micon make at Mandvi, Gujarat, commissioned on 15.01.1986
      First Private Windfarm Developer
       M/s.Pandian Chemicals, Madurai (T.N)
       250 kW WEGs, NEPC-Micon make at Kattadimalai (T.N) commissioned on 28.03.1990.
      First Wind Monitoring Station
       Sultanpet (T.N.) established on 28.07.1986
      First Wind-Diesel Project
       Sagar Island (WB), supplied by Auroville Wind Systems for WBREDA
      First Joint Sector Company
       M.P. Windfarms Ltd., Bhopal, M.P. (Promoted by Consolidated Energy Consultants Ltd.,
       IREDA & M.P. Urjavikas Nigam Ltd.) formed in the year 1994.
      First exclusive web-site on wind power programme in India
       www.windpowerindia.com developed by Consolidated Energy Consultants Ltd., Bhopal in
       the year 2000.
      First Directory on wind power programme in India
       Directory on Indian Wind Power published by Consolidated Energy Consultants Ltd.,
       Bhopal, in the year 2001

What is Wind Power and How Does It
Wind Power Generates Clean, Renewable Energy
Is Wind Power the Answer?
When Bob Dylan first sang Blowin’ in the Wind in the early 1960s, he probably
wasn’t talking about wind power as the answer to the world’s ever-increasing need
for electricity and sources of clean, renewable energy. But that is what wind has
come to represent for millions of people, who see wind power as a better way to
generate electricity than plants fueled by coal, hydro (water) or nuclear power.

Wind Power Starts with the Sun
Wind power is actually a form of solar power, because wind is caused by heat from
the sun. Solar radiation heats every part of the Earth’s surface, but not evenly or at
the same speed. Different surfaces—sand, water, stone and various types of soil—
absorb, retain, reflect and release heat at different rates, and the Earth generally
gets warmer during daylight hours and cooler at night.

As a result, the air above the Earth’s surface also warms and cools at different rates.
Hot air rises, reducing the atmospheric pressure near the Earth’s surface, which
draws in cooler air to replace it. That movement of air is what we call wind.

Wind Power is Versatile
When air moves, causing wind, it has kinetic energy—the energy created whenever
mass is in motion. With the right technology, the wind’s kinetic energy can be
captured and converted to other forms of energy such as electricity or mechanical
power. That’s wind power.

Just as the earliest windmills in Persia, China and Europe used wind power to pump
water or grind grain, today’s utility-connected wind turbines and multi-turbine
wind farms use wind power to generate clean, renewable energy to power homes
and businesses.

Wind Power is Clean and Renewable
Wind power should be considered an important component of any long-term energy
strategy, because wind power generation uses a natural and virtually inexhaustible
source of power—the wind—to produce electricity. That is a stark contrast to
traditional power plants that rely on fossil fuels.

And wind power generation is clean; it doesn’t cause air, soil or water pollution.
That’s an important difference between wind power and some other renewable
energy sources, such as nuclear power, which produces a vast amount of hard-to-
manage waste.

Wind Power Sometimes Conflicts with Other Priorities
One obstacle to increasing worldwide use of wind power is that wind farms must be
located on large tracts of land or along coastlines to capture the greatest wind

Devoting those areas to wind power generation sometimes conflicts with other
priorities, such as agriculture, urban development, or waterfront views from
expensive homes in prime locations.

The Future Growth of Wind Power
As the need for clean, renewable energy increases, and the world more urgently
seeks alternatives to finite supplies of oil, coal and natural gas, priorities will change.

And as the cost of wind power continues to decline, due to technology improvements
and better generation techniques, wind power will become increasingly feasible as a
major source of electricity and mechanical power.


         A wind turbine is a machine that converts the kinetic energy in wind into
         mechanical energy. If the mechanical energy is used directly by machinery, such
         as a pump or grinding stones, the machine is usually called a windmill. If the
         mechanical energy is converted to electricity, the machine is called a wind
         generator, or more commonly a wind turbine (wind energy converter WEC).

         A wind turbine is old technology applied to meet new challenges. We need to
         adapt and use every means at our disposal to combat global warming and
         carbon dioxide build up, yet still provide energy for our modern (lavish)
         lifestyles. Whatever your views as to the use of alternative energy, as an
         engineering student you will probably want to know how these beautiful
         machines work. I know I have always been fascinated by them. NK
                        Find Out How the Turbine Works

This aerial view of a wind power plant shows how a group of wind turbines can
make electricity for the utility grid. The electricity is sent through transmission
and distribution lines to homes, businesses, schools, and so on.

These three-bladed wind turbines are operated "upwind," with the blades
facing into the wind. The other common wind turbine type is the two-bladed,
downwind turbine.

So how do wind turbines make electricity? Simply stated, a wind turbine works
the opposite of a fan. Instead of using electricity to make wind, like a fan, wind
turbines use wind to make electricity. The wind turns the blades, which spin a
shaft, which connects to a generator and makes electricity. Utility-scale turbines
range in size from 50 to 750 kilowatts. Single small turbines, below 50 kilowatts,
are used for homes, telecommunications dishes, or water pumping.

                       Look at the Wind Turbine Close Up
Wind turbines can be separated into two types based on the axis about which
the turbine rotates. Turbines that rotate around a horizontal axis are more
common. Vertical-axis turbines are less frequently used.

Wind turbines can also be classified by the location in which they are to be used.
Onshore, offshore, or even aerial wind turbines have unique design

Wind turbines may also be used in conjunction with a solar collector to extract
the energy due to air heated by the Sun and rising through a large vertical solar
updraft tower.

Horizontal axis

Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical
generator at 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 for
generating electricity.

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 up a small

Downwind machines have been built, despite the problem of turbulence,
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. Because turbulence
leads to fatigue failures and reliability is so important, most HAWTs are
upwind machines.

                 Doesburger windmill, Ede, The Netherlands

There are several types of HAWT:

These four- (or more) bladed squat structures, 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 to grind grain. In the
Netherlands they were also used to pump water from low-lying land, and were
instrumental in keeping its polders dry. Windmills were also located throughout
the USA, especially in the Northeastern region.

Modern Rural Windmills
These windmills, invented in 1876 by Griffiths Bros and Co (Australia), were
used by Australian and later American farmers to pump water and to generate
electricity. They typically had many blades, operated at tip speed ratios (defined
below) not better than one, and had good starting torque. Some had small
direct-current generators used to charge storage batteries, to provide a few
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 in the 1950's. Such devices are still
used in locations where it is too costly to bring in commercial power.

                   Wind turbines near Aalborg, Denmark
       A standard doorway can be seen at the base of the pylon for scale

Common modern wind turbines

Usually three-bladed, sometimes two-bladed or even one-bladed (and
counterbalanced), and pointed into the wind by computer-controlled motors.
The rugged three-bladed turbine type has been championed by Danish turbine
manufacturers. These have high tip speeds of up to 6x wind speed, high
efficiency, and low torque ripple which contributes to good reliability. This is
the type of turbine that is used commercially to produce electricity. The blades
are usually colored light gray to blend in with the clouds and range in length
from 20 to 40 metres (60 to 120 feet) or more.
Cyclic stresses and vibration

Cyclic stresses fatigue the blade, axle and bearing material, and 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.

When the turbine turns to face the wind, the rotating blades act like a
gyroscope. As it pivots, gyroscopic precession tries to twist the turbine into a
forward or backward somersault. For each blade on a wind generator's turbine,
precessive force is at a minimum when the blade is horizontal and at a
maximum when the blade is vertical. This cyclic twisting can quickly fatigue
and crack the blade roots, hub and axle of the turbine.

Vertical axis

12 m Windmill with rotational sails in the Osijek CroatiaVertical-axis wind
turbines (or VAWTs) have the main rotor shaft running vertically. Key
advantages of this arrangement are that the generator and/or gearbox can be
placed at the bottom, near the ground, so the tower doesn't need to support it,
and that the turbine doesn't need to be pointed into the wind. Drawbacks are
usually pulsating torque that can be produced during each revolution and drag
created when the blade rotates into the wind. It is also difficult to mount
vertical-axis turbines on towers, meaning they must operate in the often slower,
more turbulent air flow near the ground, resulting in lower energy extraction

Windmill with rotational sails

This is a new invention. This windmillstarts making electricity above a
windspeed of 2m/s. Its sails contract and expand as the wind speed changes.
This windmill has three sails of variable surface area. The speed is controlled
through a magnetic rev counter that expands or contracts the sails according to
windspeed. A (microprocessor type) control unit controls the sails either
manually or automatically. In case of a control unit failure, strong winds would
tear the sails, but the frame would remain intact.


This has an airfoil base designed to harness the kinetic energy of the fluid flow
via an artificial current around its center. It is differentiated from others by its
capability to unitize most of the air mass passing through redirecting it to flow
over the upper chamber of the airfoils, and causing a lift force all around. It is
applicable not only to wind, but also to a variety of hydroelectric applications,
including free-flow (rivers, creeks), tidal, oceanic currents and wave motion, via
ocean wave surface currents. Views of Hydro model, :Portable aero model

              30 m Darrieus wind turbine in the Magdalen Islands

Darrieus wind turbine

"Eggbeater" turbines. They have good efficiency, but produce large torque
ripple and cyclic stress on the tower, which contributes to poor reliability. Also,
they 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 3 or more blades which results in a higher solidity for
the rotor. Solidity is measured by blade area over 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 type of Darrieus turbine, these lift-type devices have vertical blades. The
cycloturbine variety have variable pitch to reduce the torque pulsation and are
self-starting [1]. 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.

Savonius wind turbine

These are drag-type devices with two- (or more) scoops that are used in
anemometers, the Flettner vents (commonly seen on bus and van roofs), and in
some high-reliability low-efficiency power turbines. They always self-starting if
there are at least three scoops. They sometimes have long helical scoops to give a
smooth torque. The Banesh rotor and especially the Rahai rotor improve
efficiency with blades shaped to produce significant lift as well as drag.

Windstar turbines

These lift-type devices made by Wind Harvest have straight, extruded
aluminum blades attached at each end to a central rotating shaft and are
operated as Linear Array Vortex Turbine Systems (LAVTS). Vertical-axis
rotors each with their own 50-75kW generator are placed in three to any
number of rotors in linear arrays with each rotor’s blades passing within two
feet of its neighbor. In this configuration, the center rotors gain an increase in
output and efficiency (reaching the high efficiencies of HAWTs). This increased
efficiency is protected under patent (number 6784566) as the "vortex effect".
Each rotor unit has a dual braking system of pneumatic disc brakes and blade
pitch. The newest Windstar LAVTS stand 50 feet tall, have 1500 and 3000
square feet of swept area per rotor and are designed to be placed in the
turbulent winds within the understory of wind farms.


Offshore wind turbines near CopenhagenOffshore wind development zones are
generally considered to be ten kilometers or more from land. Offshore wind
turbines are less obtrusive than turbines on land, as their apparent size and
noise can be mitigated by distance. Because water has less surface roughness
than land (especially deeper water), the average wind speed is usually
considerably higher over open water. Capacity factors (utilisation rates) are
considerably higher than for onshore and near-shore locations which allows
offshore turbines to use shorter towers, making them less visible.

In stormy areas with extended shallow continental shelves (such as Denmark),
turbines are practical to install — Denmark's wind generation provides about
25-30% of total electricity demand in the country, with many offshore
windfarms. Denmark plans to increase wind energy's contribution to as much
as half of its electrical supply.

Locations have begun to be developed in the North American Great Lakes -
with one project by Trillium Power approximately 20 km from shore and over
700 MW in size. Ontario, Canada is aggressively pursuing wind power
development and has many onshore wind farms and several proposed near-
shore locations but presently only one offshore development.

In most cases offshore environment is more expensive than onshore. Offshore
towers are generally taller than onshore towers once the submerged height is
included, and offshore foundations are more difficult to build and more
expensive. Power transmission from offshore turbines is generally through
undersea cable, which is more expensive to install than cables on land, and may
use high voltage direct current operation if significant distance is to be covered
— which then requires yet more equipment. The offshore environment can also
be corrosive and abrasive in salt water locations but locations such as the Great
Lakes are in fresh water and do not have many of the issues found in the ocean
or sea. Repairs and maintenance are usually much more difficult, and generally
more costly, than on onshore turbines. Offshore wind turbines are outfitted
with extensive corrosion protection measures like coatings and cathodic
protection however some of these measures may not be required in fresh water

While there is a significant market for small land-based windmills, offshore
wind turbines have recently been and will probably continue to be the largest
wind turbines in operation, because larger turbines allow for the spread of the
high fixed costs involved in offshore operation over a greater quantity of
generation, reducing the average cost. For similar reasons, offshore wind farms
tend to be quite large—often involving over 100 turbines—as opposed to
onshore wind farms which can operate competitively even with much smaller

There are some conceptual designs that might make use of the unique offshore
environment. For example, a floating turbine might orient itself downwind of its
anchor, and thus avoid the need for a yawing mechanism. One concept for
offshore turbines has them generate rain, instead of electricity. The turbines
would create a fine aerosol, which is envisioned to increase evaporation and
induce rainfall, hopefully on land.


Near-shore turbines are generally considered to be within a zone that is on land
three kilometers of a shoreline and on water within ten kilometers of land.
Wind speeds in these zones share wind speed characteristics of both onshore
wind and offshore wind. Issues that are shared within near-shore wind
development zones are ornithological (including bird migration and nesting),
aquatic habitat, transportation (including shipping and boating) and visual

Sea shores also tend to be windy areas and good sites for turbine installation,
because a primary source of wind is convection from the differential heating
and cooling of land and sea over the course of day and night. Winds at sea level
carry somewhat more energy than winds of the same speed in mountainous
areas because the air at sea level is denser.

Near-shore wind farm siting can sometimes be highly controversial as coastal
sites are often picturesque and environmentally sensitive (for instance, having
substantial bird life).


Wind turbines near Walla Walla in WashingtonOnshore turbine installations in
hilly or mountainous regions tend to be on ridgelines generally three kilometers
or more inland from the nearest shoreline. This is done to exploit the
topographic acceleration where the hill or ridge causes the wind to accelerate as
it is forced over it. The additional wind speeds gained in this way make large
differences to the amount of energy that is produced. Great attention must be
paid to the exact positions of the turbines (a process known as micro-siting)
because a difference of 30 m can sometimes mean a doubling in output. Local
winds are often monitored for a year or more with anemometers and detailed
wind maps constructed before wind generators are installed.

For smaller installations where such data collection is too expensive or time
consuming, the normal way of prospecting for wind-power sites is to directly
look for trees or vegetation that are permanently "cast" or deformed by the
prevailing winds. Another way is to use a wind-speed survey map, or historical
data from a nearby meteorological station, although these methods are less

Wind farm siting can sometimes be controversial, particularly as the hilltop,
often coastal sites preferred are often picturesque and environmentally sensitive
(for instance, having substantial bird life). Local residents in a number of
potential sites have strongly opposed the installation of wind farms, and
political support has resulted in the blocking of construction of some

    Turbine blade at Southampton docks - Nelson Kruschandl in foreground
Turbine design and construction

Advantages of vertical wind turbines

Easier to maintain because most of their moving parts are located near the
ground. This is due to the vertical wind turbine’s shape. The airfoils or rotor
blades are connected by arms to a shaft that sits on a bearing and drives a
generator below, usually by first connecting to a gearbox. As the rotor blades
are vertical, a yaw device is not needed, reducing the need for this bearing and
its cost.

Vertical wind turbines have a higher airfoil pitch angle, giving improved
aerodynamics while decreasing drag at low and high pressures. Mesas, hilltops,
ridgelines and passes can have higher and more powerful winds near the
ground than up high because of the speed up effect of winds moving up a slope
or funneling into a pass combining with the winds moving directly into the site.
In these places, VAWTs placed close to the ground can produce more power
than HAWTs placed higher up.

Low height useful where laws do not permit structures to be placed high.
Smaller VAWTs can be much easier to transport and install.

Does not need a free standing tower so is much less expensive and stronger in
high winds that are close to the ground. Usually have a lower Tip-Speed ratio so
less likely to break in high winds.

Disadvantages of vertical wind turbines

Most VAWTs produce energy at only 50% of the efficiency of HAWTs in large
part because of the additional drag that they have as their blades rotate into the
wind. This can be overcome by using structures to funnel more and align the
wind into the rotor (e.g. "stators" on early Windstar turbines) or the "vortex"
effect of placing straight bladed VAWTs closely together (e.g. Patent #

There may be a height limitation to how tall a vertical wind turbine can be built
and how much sweep area it can have.

Most VAWTS need to be installed on a relatively flat piece of land and some
sites could be too steep for them but are still usable by HAWTs.

Most VAWTs have low starting torque.

A VAWT that uses guyed wires to hold it in place puts stress on the bottom
bearing as all the weight of the rotor is on the bearing. Guyed wires attached to
the top bearing increase downward thrust in wind gusts. Solving this problem
requires a superstructure to hold a top bearing in place to eliminate the
downward thrusts of gust events in guyed wired models.

Advantages of horizontal wind turbines

Blades are to the side of the turbine's center of gravity, helping stability.
Ability to wing warp, which gives the turbine blades the best 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.
Ability to pitch the rotor blades in a storm, to minimize damage.
Tall tower allows access to stronger wind in sites with wind shear. In some wind
shear sites, every ten meters up, the wind speed can increase by 20% and the
power output by 34%.
Tall tower allows placement on uneven land or in offshore locations.
Can be sited in forests above the treeline.
Most are self-starting.
Can be cheaper because of higher production volume, larger sizes and, in
general higher capacity factors and efficiencies.

Disadvantages of horizontal wind turbines

HAWTs have difficulty operating in near ground, turbulent winds because their
yaw and blade bearing need smoother, more laminar wind flows.

The tall towers and long blades (up to 180 feet long) are difficult to transport on
the sea and on land. Transportation can now cost 20% of equipment costs. Tall
HAWTs are difficult to install, needing very tall and expensive cranes and
skilled operators.

Supply of HAWTs is less than demand and between 2004 and 2006, turbine
prices increased up to 60%. At the end of 2006, all major manufacturers were
booked up with orders through 2008. The FAA has raised concerns about tall
HAWTs effects on radar in proximity to air force bases. Their height can create
local opposition based on impacts to viewsheds.

Offshore towers can be a navigation problem and must be installed in shallow
seas. HAWTs can't be floated on barges.

Downwind variants suffer from fatigue and structural failure caused by

Horizontal-axis wind turbine aerodynamics

The aerodynamics of a horizontal-axis wind turbine are complex. The air flow
at the blades is not the same as the airflow far away from the turbine. The very
nature of the way in which energy is extracted from the air also causes air to be
deflected by the turbine. In addition, the aerodynamics of a wind turbine at the
rotor surface include effects that are rarely seen in other aerodynamic fields.

Special wind turbines

One E-66 wind turbine at Windpark Holtriem, Germany carries an observation
deck, open for visitors to see. Another turbine of the same type, with an
observation deck, can be located in Swaffham, England.

A series of floating wind turbines utilizing the Magnus Effect are in
development in Canada by Magenn Power. They deliver power to the ground
by a tether system.

The world's first megawatt wind turbine on Grandpa's Knob, Castleton,
VermontWind machines were used for grinding grain in Persia as early as 200
B.C. This type of machine was introduced into the Roman Empire by 250 A.D.
By the 14th century Dutch windmills were in use to drain areas of the Rhine
River delta. In Denmark by 1900 there were about 2500 windmills for
mechanical loads such as pumps and mills, producing an estimated combined
peak power of about 30 MW. The first windmill for electricity production was
built in Cleveland, Ohio by Charles F Brush in 1888, and in 1908 there were 72
wind-driven electric generators from 5 kW to 25 kW. The largest machines
were on 24 m (79 ft) towers with four-bladed 23 m (75 ft) diameter rotors.

By the 1930s windmills were mainly used to generate electricity on farms,
mostly in the United States where distribution systems had not yet been
installed. In this period, high-tensile steel was cheap, and windmills were placed
atop prefabricated open steel lattice towers. A forerunner of modern horizontal-
axis wind generators was in service at Yalta, USSR in 1931. This was a 100 kW
generator on a 30 m (100 ft) tower, connected to the local 6.3 kV distribution
system. It was reported to have an annual load factor of 32 per cent, not much
different from current wind machines.


The world's largest turbines are manufactured by the Northern German
companies Enercon and REpower. The Enercon E112 delivers up to 6 MW , has
an overall height of 186 m (610 ft) and a diameter of 114 m (374 ft). The
REpower 5M delivers up to 5 MW , has an overall height of 183 m (600 ft) and a
diameter of 126 m (413 ft).

The turbine closest to the North Pole is a Nordex N-80 in Havoygalven near
Hammerfest, Norway. The ones closest to the South Pole are two Enercon E-30
in Antarctica, used to power the Australian Research Division's Mawson

                      Offshore wind farm off Danish coast
Wind Turbine Glossary

Anemometer: Measures the wind speed and transmits wind speed data to the

Blades: Most turbines have either two or three blades. Wind blowing over the
blades causes the blades to "lift" and rotate.

Brake: A disc brake which can be applied mechanically, electrically, or
hydraulically to stop the rotor in emergencies.

Controller: The controller starts up the machine at wind speeds of about 8 to 16
miles per hour (mph) and shuts off the machine at about 65 mph. Turbines
cannot operate at wind speeds above about 65 mph because their generators
could overheat.
Gear box: Gears connect the low-speed shaft to the high-speed shaft and
increase the rotational speeds from about 30 to 60 rotations per minute (rpm) to
about 1200 to 1500 rpm, the rotational speed required by most generators to
produce electricity. The gear box is a costly (and heavy) part of the wind
turbine and engineers are exploring "direct-drive" generators that operate at
lower rotational speeds and don't need gear boxes.

Generator: Usually an off-the-shelf induction generator that produces 60-cycle
AC electricity.

High-speed shaft: Drives the generator.

Low-speed shaft: The rotor turns the low-speed shaft at about 30 to 60 rotations
per minute.

Nacelle: The rotor attaches to the nacelle, which sits atop the tower and includes
the gear box, low- and high-speed shafts, generator, controller, and brake. A
cover protects the components inside the nacelle. Some nacelles are large
enough for a technician to stand inside while working.

Pitch: Blades are turned, or pitched, out of the wind to keep the rotor from
turning in winds that are too high or too low to produce electricity.

Rotor: The blades and the hub together are called the rotor.

Tower: Towers are made from tubular steel (shown here) or steel lattice.
Because wind speed increases with height, taller towers enable turbines to
capture more energy and generate more electricity.

Wind direction: This is an "upwind" turbine, so-called because it operates
facing into the wind. Other turbines are designed to run "downwind", facing
away from the wind.

Wind vane: Measures wind direction and communicates with the yaw drive to
orient the turbine properly with respect to the wind.

Yaw drive: Upwind turbines face into the wind; the yaw drive is used to keep
the rotor facing into the wind as the wind direction changes. Downwind
turbines don't require a yaw drive, the wind blows the rotor downwind.

Yaw motor: Powers the yaw drive.

1. The wind is free and with modern technology it can be captured efficiently.
2. Once the wind turbine is built the energy it produces does not cause green house gases or other pollutants.
3. Although wind turbines can be very tall each takes up only a small plot of land. This means that the land below
can still be used. This is especially the case in agricultural areas as farming can still continue.
4. Many people find wind farms an interesting feature of the landscape.
5. Remote areas that are not connected to the electricity power grid can use wind turbines to produce their own
6. Wind turbines have a role to play in both the developed and third world.
7. Wind turbines are available in a range of sizes which means a vast range of people and businesses can use them.
Single households to small towns and villages can make good use of range of wind turbines available today.


1. The strength of the wind is not constant and it varies from zero to storm force. This means that wind turbines do
not produce the same amount of electricity all the time. There will be times when they produce no electricity at all.
2. Many people feel that the countryside should be left untouched, without these large structures being built. The
landscape should left in its natural form for everyone to enjoy.
3. Wind turbines are noisy. Each one can generate the same level of noise as a family car travelling at 70 mph.
4. Many people see large wind turbines as unsightly structures and not pleasant or interesting to look at. They
disfigure the countryside and are generally ugly.
5. When wind turbines are being manufactured some pollution is produced. Therefore wind power does produce
some pollution.
6. Large wind farms are needed to provide entire communities with enough electricity. For example, the largest
single turbine available today can only provide enough electricity for 475 homes, when running at full capacity. How
many would be needed for a town of 100 000 people?
erate the same level of noise as a family car travelling at 70 mph.
4. Many people see large wind turbines as unsightly structures and not pleasant or interesting to look at. They
disfigure the countryside and are generally ugly.
5. When wind turbines are being manufactured some pollution is produced. The refore wind powe r does produce
some pollution.
6. Large wind farms are needed to provide entire communities with enough electricity. For example, the largest
single turbine available today can only provide enough electricity for 475 homes, when running at full capacity. How
many would be needed for a town of 100 000 people?

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