Wind power is a great source of energy in
locations with adequate potential. Before you dream any further
however, it takes a lot of windy days and nights to make it a
reliable source of power. Average wind speeds of 10 miles per hour
or 4.5 meters per second or greater are required at the location of
the wind turbine. To put that into perspective, that means 7 times
out of 10 your are struck by the force of the wind when you head out
the door (that is if you didn’t grow-up east of the divide). 3 times
out of 10 you have to lock your hat down or pull your clothes in.
Another way I like to describe how much wind it takes to be a
reliable source of power at your location is for you to go outside
daily with a hard back book you like and try to read. If you are
forced to go somewhere out of the wind to read in order to avoid
tearing your pages 4 days in 5, you have a good location for wind.
In good wind locations trees will look sculpted by the prevailing
wind. While these are not scientifically proven methods they do help
put into perspective how much wind potential you might have.
There are instruments available used to monitor
wind potential at your site. They can be a simple as a hand held
observation tool used for repeated measures costing only $85 or wind
data loggers costing around $1000.
Simple facts about physics and wind:
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When winds speed doubles, the force increases
by 8 times.
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Most turbines produce 1/8th their
rated output at 15 mph or 6.75 mps.
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Most turbines produce max. power at 30 mph or
13.4 mps wind speeds
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Multiply surface wind speed by 1.5 to get
speeds at 30 feet above ground level and equates to 3 times the
power.
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Multiply surface wind speed by 2.0 to get speed
at 120 feet above ground level and six times the power.
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Due to decreases in air pressure wind force
declines at a rate of 3% per thousand feet.
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Turbines need to be located 10 meters above
obstructions for 300 feet to avoid turbulence.
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Our Southwest Windpower H80(1000 watt turbine)
has to be rotating 4 times per second to even start producing
measurable power.
There are a lot of wind turbines to chose from.
Some are grid-tied capable from right at the turbine and others operate
with battery based systems and a dump load for those excessively windy
periods. A dump load can be as simple as a hot water heater element or a
baseboard type resistive load heater. Wind is often combined with solar
for assured power during non-windy periods.
In a location with adequate wind resources the cost
of the wind system could be less than for a similar sized harvest from
solar. While wind turbines are not hugely expensive relative to their
harvest potential, the tower and its installation can exceed the cost of
the turbine so be wary about posted prices.
For those potential customers living in the valleys
west of the Continental Divide in BC and Montana, there are few
locations where wind will beat out solar for reliability and price per
kWH harvested over the long run. If you have a location in an exposed
saddle, or close to a ridge top then buy a wind data logger and get some
good data before you spent thousands of dollars.
All this being sound and sobering advice, there are
smaller less expensive wind turbines that work on a sail boat or during
stormy weather. They are very enchanting and magical to watch knowing
they are making even little energy.
In Cuba they employ homemade wind turbines to
charge electric fences. They are recycle from old automobile wiper
motors and home made wooden blades. There are service organizations that
arrange trainings in 3rd world coastal villages to show the
local residents how to build and maintain their own wind turbines, from
recycled motors and hand made blades. This maybe be more than you want
to know, but we just wanted to share how simple it can be to harness the
wind.
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