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WIND ENERGY
In the past, windmills were used to convert wind energy into mechanical
energy. The mechanical energy was then used to run machinery. For
thousands of years, human beings have tried many different designs
to get as much power as possible from the wind.
 The
Greeks made windmills with cloth blades, so they would be very light
and fast, like the sail on a boat. To get the most energy out of
the wind, the sails were angled so that the wind hit them from the
side.
The more common design, that we all think of when we imagine a
windmill is the Dutch design.
 In
the north the winds are much stronger, so cloth sails couldn't be
used. The Dutch design uses wooden sails. Windmills such as these
are still used today all over Holland to pump water, and were used
in Northern Ireland to grind corn. One such example, pictured left,
is at Ballycopeland near Millisle in Co. Down.
Using Windmills to Make Electricity
Today instead of turning wind energy into mechanical energy we
turn it into electrical energy. The way to make a generator make
electricity is to make it spin very fast. Using windmills is a good
way to do this.
 A
windmill that produces electricity is called a wind turbine or a
wind energy convertor. They are much taller than ordinary windmills
and are made from metal and plastic to make them very light and
strong. They turn a turbine connected to a generator to produce
electricity.
The amount of energy a turbine can produce depends on how strong
the wind is, but also on the size of the blades. Longer blades are
better so modern wind turbines are very tall so that they can have
long blades. If the wind is too strong the turbine must be shut
down.
The wind changes direction all the time, so the top of the wind
turbine rotates around so that the wind can always spin the blades.
The box behind the blades contains the turbine. As the blades turn
the turbine spins a shaft, which spins the generator and produces
electricity.
 This
map shows the location of wind farms in Northern Ireland. Most of
the wind farms have only 10 or so turbines, however in other countries
vast areas of land are used for 100's of wind turbines. The turbines
on Rathlin Island are the only supply of electricity for the island.
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