This type of turbine is simple to build, but is not nearly
as efficient as a well-designed horizontal axis turbine.
The Savonius turbine relies solely on drag to produce the
force that turns their shaft. One side of the turbine catches
the moving air more than the other, causing the turbine
to spin. This design does not allow the turbine to spin
faster than the oncoming wind, which makes them a poor choice
in areas where winds are light.
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| A
Savonius wind turbine.
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Horizontal axis turbines are by far the most common kind
of wind turbine. They can be seen at several places across
Canada and the United States. They are also becoming common
in Europe and many other countries around the world. These
turbines feature wing-like blades that generate aerodynamic
lift as the wind blows past them, causing the central shaft
to turn. To operate at peak efficiency, this type of turbine
must always face directly into the wind. Many horizontal
turbines have a large wind vane that acts like a sail, helping
them to stay pointed in the right direction.
Making electricity
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| A
horizontal axis turbine.
Courtesy
Vision Quest Wind Electric.
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|
We are surrounded by hundreds of appliances that use electricity
to do work. But what is electricity? Basically, electricity
is a flow of electrons in a metal wire, or some other conductor.
Electrons are tiny particles found inside atoms, one of the
basic building blocks of all matter. We call the flow of electrons
through any conductor a "current of electricity."
Each electron carries a tiny negative charge. When they
move through a conductor, they produce an invisible field
of magnetic force, similar to that found around a magnet.
The strength of that field depends on how many electrons
are in motion. You can concentrate this field by winding
the wire in which the electrons move into a tight coil with
many turns. This causes many more electrons to be in motion
in a small space, resulting in a stronger field. If you
then place a piece of iron in the middle of the coil, the
electromagnetic field will turn the iron into a powerful
magnet.
While it is true that electrons moving through a conductor
produce a magnetic field, the reverse is also true. You
can make electrons move in a wire by "pushing" them with
a moving magnet. This is in fact how an electrical generator
works. Electrical generators usually contain powerful magnets
that rotate very close to dense coils of insulated wire.
The coils develop a flow of electrons that becomes an electrical
current when the generator is connected to an electric circuit.
You will be building an electrical generator as part of
this project. It uses moving magnets to create a current
of electricity in coils of wire. This generator is technically
called an alternator because the electrons move back and
forth in the wire, rather than flowing in just one direction
as they do from a battery. A meter connected to the wire
would show that the charge of the wire switches or alternates
between positive and negative as the electrons change directions.
Such an electrical current is called alternating current
or AC. Household electrical current is alternating current.
Appliances have to be specially designed to use it. The
other type of current is called direct current, because
the electrons move in one direction only. Most battery-powered
appliances such as calculators and portable CD players use
direct current.
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