...The company claims the unit starts spinning from winds of a mere 0.5 mph—with electricity generated from only 3 mph. Traditional gearbox wind turbines, said the company, require at least 7.5-mph winds to start generating power.
A tool on Windtronics' website had calculated we'd get 1,155 kWh per year at the 12-mph average it predicted for our area of Yonkers, New York. And the authorized installer, during his initial visit, didn't say the roof of our headquarters might generate any less, but that rating is at a height of 164 feet, not the 33 feet WindTronics requires for rooftop installations.
In the 15 months since the turbine was installed, though, it has delivered less than 4 kWh—enough only to power a 12,000 btu window air conditioner for one afternoon. A company representative in charge of installations worldwide recently visited our offices and confirmed that our test model was correctly installed. What's more, he told us that while the WT6500 should start generating power at about 3 mph, the initial juice goes just to power the system's inverter, which must be running before it supplies any AC power elsewhere. The true wind speed needed to start producing AC while the inverter is on is 6 mph, not far from the 7.5 mph needed by a traditional gearbox wind turbine.
I have had an Air-X Marine wind generator in Baja California for over 12 years and came to the conclusion that it's best function was to warn when winds start to pick up. I was surprised when I mentioned this to other sailors who laughed and said they had come to the same conclusion. Definitely not a reliable source of power in Baja - which has fairly low winds other than the occasional storm or hurricane. As someone in the thread noted, I concluded I could have got better value by spending my money on solar panels. The figures are there for people to digest, but not in an obvious form. It's easy to be wowed by impressive "30 KWh/month" claims while not connecting that is probably less than one tenth of the power needs of an average household. And that drops significantly when "real" winds are used. In Baja, a single $200 solar panel generates more power than the Air-X.
If you go by the Air-X power output vs windspeed chart and convert from monthly KWh to amps or the windspeed vs output chart and convert watts to amps you get just over 1 amp in a 10 mph wind, 5 amps in a 15 mph wind. Max output at about 30 mph is about 37 amps. In Baja just one modest solar panel put out more than 5 amps.
HOWEVER: The wind generator usually provided more than enough power on many cloudy/stormy days and in that sense was a good backup for when solar wasn't producing much.
My Air-X is still running after 12 years, although it 'failed' due to corrosion between the aluminum hub and the blade roots. The expanding corrosion products literally pushed the blades off the bolts holding them to hub. The fix was an easy replacement blade kit but it could have been prevented by better maintenance.
A couple of responses to some thread comments -
"* A windmill receiving an average wind speed of 4.5 meters per second produces 7 times more energy than a windmill receiving an average wind speed of 3 meters per second."
That sounds wrong to me. The same thread correctly notes a cubic power relationship between windspeed and power output. That would put the power output at 4.5 m/s at just under 3.5 fold - half of the suggested change.
"add to that the air x will upon hitting 28mph will shut itself down from production for about 5 minutes meaning that the 20mph winds if producing gusts will render the thing useless for production"
According to their specs, my Air-X is rated to 22 m/s (49 m/h). I recall mine operated well in 50mph winds without shutting down, although it would cut out in larger gusts but didn't take 5 minutes to restart. Perhaps the 28 mph shutdown is a fault in the device and requires some adjustment. Air-x have an output chart up to 60 mph here which shows outputs are limited at around 25-28 mph but still with outputs of 100 or 200 watts (8 or 17 watts) depending on the model.