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Small
Wind Factsheets
What
is Small Wind?
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For
many people, the term "wind energy" conjures up an image
of utility-scale wind farms, large arrays of industrial-sized 750-kW
turbines with 150-foot rotors mounted on 200-foot tall towers. But
wind energy systems come in small packages as well. A typical residential
wind energy system includes a 10kW turbine, with rotors measuring
perhaps 23 feet in diameter, mounted on an 80-foot tower. Such a
system is suitable for meeting the electricity needs of a household
or small business. Turbines as small as 400 watts, with rotors only
46 inches in diameter, may be employed for specific purposes, such
as pumping water (for stock or irrigation) or running lights and
appliances in a remote cabin or recreational vehicle. Wind energy
may be used to complement a solar photovoltaic (PV) system, or by
itself. It may be set up as a stand-alone system, or it may be interconnected
with the utility grid.
Why
Install a Small Wind System?
For
over a hundred years, people have captured the wind's energy using
mechanical windmills. Before rural electrification programs were
instituted by the Federal government, farm families throughout the
Midwestern U.S. used 200-3,000 watt wind generators to power lights,
radios, and kitchen appliances. Today, small wind energy systems
are still used to bring power to remote locations, but they are
also increasingly being used as an independent, clean, affordable
alternative to fossil- or nuclear-fueled, utility-generated electricity.
How
Does a Small Wind Turbine Work?
Wind
energy is a form of solar energy created by the uneven heating of
the Earth's surface by the sun. Most small wind turbines use a horizontal
axis propeller, or rotor, to capture the kinetic energy of the wind
and convert it into rotary motion to drive a generator, which usually
is designed specifically for the wind turbine. The rotor consists
of two or three blades, usually made from wood or fiberglass. (These
materials give the turbine the needed strength and flexibility,
and have the added advantage of not interfering with television
signals.) The structural backbone of the wind turbine is called
the mainframe, and it includes the "slip-rings" that connect
the wind turbine - which rotates as it points itself into changing
wind directions - and the fixed tower wiring. The tail aligns the
rotor into the wind.
To avoid turbulence and capture greater wind energy, turbines are
mounted on towers. As a rule of thumb, turbines should be mounted
at least 30 feet above any structures or natural features within
300 feet of the installation. Smaller turbines can go on shorter
towers. For example, a 250-watt turbine may be mounted on a 30-50
foot tower, while a 10 kW turbine will usually need a tower of 80-120
feet. Towers come in a variety of designs, including tubular or
latticed, guyed or self-supporting. Wind turbine manufacturers also
offer towers, and can ensure that the tower meets required building
and safety specifications as well as being compatible with the turbine.
References
Adapted from a Small Wind Energy Primer
by Michael Bergey, Bergey Windpower Co., previously published in
Home Power and Backwoods magazines
Other
Fact Sheets Available on Small Wind Energy:
How Much Noise do Small
Wind Systems Make?
What About Visual Impact?
Small Wind Systems and Public Safety
How Do Small Wind Systems Affect Property
Values?
The Economics
of Small Wind
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