you have a good wind site?
Wind powered battery charging systems can be cost effective if the
average wind speed is nine miles per hour (mph) or more at the location
of the wind generator. If you are using wind in combination with
photovoltaic power, it may be cost effective if you have good wind
only during part of the year. The power available from the wind
is proportional to the cube of the wind speed. When the wind speed
doubles, the power delivered is eight times as great. Most wind
generators are designed to deliver maximum power at a wind speed
of 30 mph. At 15 mph, they will deliver about 1/8 their rated power.
A wind generator should be mounted at least 20 feet higher than
any obstruction within 300 feet to avoid turbulence.
Measuring Wind Speed
You can use one of the measuring devices in this section to determine
wind speed. The NRG Wind Totalizer acts like an odomet
er in a
car, giving you the total wind passage over time. Average wind
speed is calculated by the user by dividing the miles of wind
passage by the number of hours the machine has been running. This
unit can be installed and checked weekly or monthly. If you are
patient, you can measure for a year or two and get a good idea
of your potential power availability. The Dwyer and Kestrel wind
speed indicators are both like a speedometer, displaying wind
speed at the time you are looking at it, but it does not record
any information for future reference. The Dwyer and NRG can be
mounted on a tower to give you an idea of wind speed where the
generator will be located. If you measure wind speed at ground
level, you can expect about 1.5 times the wind speed 30 feet up,
which equates to about three times the power. At 120 feet above
the ground, wind speed will be twice what is measured at ground
level and power output will be more than twice the output at 30
feet. If you do not have a wind gauge, you can get a rough idea
of wind speed from the table below.
of wind shown by smoke drift, but not by wind vanes.
felt on face; leaves rustle; ordinary wind vane moved by wind.
and twigs in constant motion; wind extends a light flag.
dust, loose paper; small branches are moved.
trees in leaf begin to sway; crested wavelets form on inland
branches in motion; whistling heard in power lines; umbrella
use is difficult.
We do not recommend
mounting wind generators on roofs. Though it is possible with
wind generators of 500 watts or less output, it will be noisy.
Larger wind generators could cause severe damage to the building.
Freestanding towers, guyed towers or guyed poles may be used with
wind generators. Wind generators can be mounted on freestanding
towers designed for antennas. They require a large, engineered
concrete base for support, but since they do not require guy wires,
they can be installed in the smallest space. Guyed steel truss
towers, also designed for antenna mounting are less costly, but
require a large area for guy wire placement. A tilt-up pole tower
is the most economical and the easiest to install. Wiring and
mounting of the wind generator are done before the tower is erected.
No climbing is necessary.