You no longer need to become a nerd to find out how wind energy
Wind is caused by the uneven heating of the Earth by the sun
and the fact that temperatures are invariably attempting to reach
an equilibrium (heat is always moving to a cooler area). With the
rising expense of energy and the damage to the environment from
standard fuels, it is more and more equitable to harvest this
Some great benefits of wind energy are that it is virtually
free (in case you buy the equipment) and there is no pollution.
The disadvantages include the fact that it's not a consistent
source (the velocity varies and many times it is insufficient to
make electricity) and it typically requires about one acre of
How Wind Energy Works
The quantity of power that's available varies by wind speed.
The amount available is termed it's power density and it is
measured in watts per square meter. That is why, the U.S. Doe has
separated wind energy into classes from 1 to 7. The normal wind
speed for class 1 is 9.8 mph or less while the average for a class
7 is 21.1 or even more. For effective power production, class 2
winds (11.5 mph average speed) are frequently required.
Usually, wind speeds increase as you get higher above the
Earth. Due to this, the typical wind generator is a component of a
tower at least 30 feet above obstructions. That there are two
basic kinds of towers used for residential wind power systems
(free standing and guyed). Free standing towers are self
supporting and are usually heavier meaning they take special
equipment (cranes) to erect them. Guyed towers are supported on a
concrete base and anchored by wires for support. They typically
are not as heavy and most manufacturer's produce tilt down models
which is often easily raised and lowered for maintenance.
The kinetic (moving energy) from the winds is harnessed by a
device known as the turbine. This turbine includes airfoils
(blades) that capture the energy of the wind and use it to turn
the shaft of an alternator (like you have on a car only bigger).
There are two basic kinds of blades (drag style and lifting
style). We all have seen pictures of old windmills with the large
flat blades which are an example of the drag style of airfoil.
Lifting style blades are twisted rather than flat and resemble the
propellor of a small airplane.
A turbine is classified as to whether it is built to be
installed with the rotor in a horizontal or vertical position and
whether the wind strikes the blades or the tower first. A vertical
turbine typically requires less land for it's installation and is
a much better option for the more urban areas around the globe. An
upwind turbine is created for the wind to impact the airfoils
before it does the tower.
These units ordinarily have a tail on the turbine which is
required to keep the unit pointed into the wind. A downwind
turbine does not require a tail as the wind acting on the blades
tends to keep it oriented properly.
These turbine systems would be damaged if they were to be
allowed to turn at excessive speeds. Therefore, units will need to
have automatic over-speed governing systems. Some systems use
electrical braking systems while others use mechanical type
The output electricity from the alternator is sent to a
controller which conditions it for use in the home. The usage of
residential wind power systems requires the home to either remain
tied to the utility grid or store electricity in a battery for use
when the wind doesn't blow sufficiently.
When the home is linked with the grid, the surplus electricity
that is made by the residential wind power system can be sold to
the utility company to reduce and sometimes even eliminate your
electric bill. During periods with not enough wind, the home is
supplied power from the utility company.
The price of Wind Energy
Small residential wind power turbines can be an attractive
alternative, or addition, to those people needing more than
100-200 watts of power for their home, business, or remote
facility. Unlike PV's, which stay at basically a similar cost per
watt independent of array size, wind turbines get more affordable
with increasing system size. At the 50 watt size level, for
example, a small residential power windmill would cost about
$8.00/watt compared to approximately $6.00/watt for a Photovoltaic
This is why, everything being equal, Photovoltaic is less
expensive for very small loads. As the system size gets larger,
however, this "rule-of-thumb" reverses itself.
At 300 watts the wind turbine costs are down to $2.50/watt,
while the PV costs are still at $6.00/watt. For a 1,500 watt wind
system the cost is down to $2.00/watt and at 10,000 watts the cost
of a wind generator (excluding electronics) is down to $1.50/watt.
Copyright Mary J. 2010
Presented with permission of the author
About the Author
www.residentialwindturbines.org to help You get info to make
the transition from a full-time energy dependent to successful
energy efficiency. She started
www.residentialwindturbines.org in 2008 to help people
who want to save energy using wind power or deal with the
sometimes overwhelming prospect of starting a wind turbine system.
Prior to raising her family, she spent over 3 years as a teacher
and workshop leader.
To contact her, please email at info [AT]