How Do Windmills Generate Electricity?
Windmills. What comes to mind on
hearing the term are the interesting adventures of Don
Quixote! What a fascinating sight they make, these huge arms
rotating in the wind. And this rotation produces energy that
is used productively. Windmills are ancient inventions, they
have been around for a long time. Wind
turbines began to be used to produce electricity on a large
scale after the 1970s.
Windmills are mills which use sails or vanes, which,
when wind acts upon them, drive
machinery that perform functions like pumping water or
grinding grains or other materials.
The history of windmills dates back to ancient times. They were
initially used in the East, and in
Europe they were first used in Germany and the Netherlands in
the 12th century. Windmills were also used for pumping
seawater from land below sea level, sawing wood and pressing
oil from seeds. A windmill is like a huge propeller and its
source of power is the wind. The fans of early windmills were
made of wood over which canvas was stretched. Ropes attached
to the fan were used for making adjustments as required by the
force of the wind. The length of the fans would often extend
to 40 feet.
Different types of
windmills were used in different parts of the world. One such
traditional type of mill is the post mill, which turned around
a post when the direction of the wind changed.
Another type is the tower mill that has a revolving turret on
top. In order to keep its sails pointing into the wind, it
also has a fantail. The fantail was invented in 1745 and was a
mechanism that automatically rotated the sails into the wind.
In 1772, the spring sail was developed. This type of sail had
wood shutters, the openings of which were controlled either
manually or automatically to maintain a constant sail speed in
winds of varying speeds. Other improvements were air brakes to
stop the sails from rotating and the use of propeller like
airfoils instead of sails, due to which the windmills could be
used even in light winds.
The tower windmill was
first used in Europe in the 14th century. One type of windmill used
on farms in the USA is very light and has steel sails supported on a
long steel girder shaft. In Holland, a very different type of
windmill is used. Here the roof
revolves. To do this, there is a small windmill located on the roof
on the opposite side of and at right angles to the bigger windmill.
When the small windmill rotates, it activates a device that moves
the roof. The roof rotates till the bigger windmill faces the wind.
The improved windmills that are used today
are made of galvanized steel. An improvement in design has led to
the inclusion of a rudder, which swings the wheel on a pivot to
catch the wind from every direction and optimize the force of the
wind. Windmills are a cheap source of power and
are used to irrigate fields or provide water for cattle in pastures.
Wind power is also harnessed for
generation of electric power. This is done by using a wind turbine.
The movement of the turbine drives a generator for producing
electricity. This power is also used to drive fuel pumps, wireless
Wind turbines are
generally of two types. One type of turbine has large propeller-type
rotors mounted on a tall tower and the second type has flexible
metal strips fixed to a vertical axle at the top and bottom. The
world's largest wind turbine is in
Hawaii, in the Pacific Ocean. It has two blades, 50 meters long, on
top of a high tower. An array of
windmills or wind turbines are used for generating electrical power.
The world's largest wind farm at Altamont Pass, California, USA,
consists of 6,000 wind turbines.
And how are wind
turbines made in today's tech savvy world? Before a turbine is
built, entire systems are modeled using sophisticated computer
programs that allow trials of advanced components in different
configurations. Then, tests are conducted and the final design is
decided upon. Modern blades are specially designed to capture more
energy from the wind. They are made from light composite materials
that increase their efficiency but at the same time are strong
enough to withstand gusty winds. Speed is controlled with the use of
aerodynamic controls or "brakes". The latest rotor hub designs are
flexible and allow increased rotor
efficiency; at the same time, they minimize operational damages.
Innovative designs allow a wind turbine to produce power at variable
rotor speeds. As a result, the machines are more efficient and
easier to control. Special tower designs and construction materials
allow the turbine to be placed higher, where the wind is stronger
and which means more energy.