Technical Director
written by Dan Fink , October 15, 2007
Hmmm....
this is basically a small toy. Their math is OK, but it won't make a useful amount of power -- look at their own power curves printed on the site. Their claims about the disadvantages of 'normal' 3 bladed wind turbines don't add up either. Unfortunately, the facts are that wind turbines of *any* design perform very poorly when mounted on rooftops or below the trees (as shown on their website).
Any wind turbine needs to fly at least 30 feet above anything within 300 feet, no matter what hype you hear--urban, rooftop wind turbines are like mounting solar panels in the shade. Solar panels are the way to go for urban areas, since most cities won't allow tall towers for wind turbines.
Average windspeeds in most locations range from 10-15 mph (4.47 to 6.71 m/s). The modal wind speed (the most common) at most locations, on a tall tower, is about 15 mph.
From their power curve:
http://www.loopwing.co.jp/images/00en/i ... pc1500.gif, you can expect about 25 watts at 10 mph, and 75 watts at 15 mph. Ouch, that only runs a couple light bulbs! You'll get the rated output (438w at 2 m/s), at most sites that are 30 feet above anything within 300 feet, for fewer than 150 hours per year (ref: Paul Gipe, also NREL).
Just don't let anyone hype you into thinking a tiny wind turbine at rooftop level will make significant amounts of power--solar panels are MUCH better for that. In case anyone tries to scam you with their wind turbine output math, here's how to detect a scam:
Power available in moving air= 1/2 * air density (kg/m^3)* swept area (m^2)* wind velocity^3 (m/s)
then times coefficient of performance (cP) to get actual output. They claim a cP of 0.43, far more than any other small wind turbine. I doubt it, but if you do the math, you'll see that such a tiny turbine won't help you much on your electric bills.
The average US home in a good wind location would require a 23 ft diameter turbine flying 100 feet in the air to offset their power bill.DAN FINK
Technical Director
http://www.otherpower.com/