In the video, if I heard this correct, it is stated that this device "will on average put out about 800W consistently in about a 6mph wind"
Now I believe that represents a claim that this device puts out 800W of continuous power in winds of 6 miles per hour. I didn't hear the specific diameter of the turbine in question, but it was listed at 65 inches above in this posting and my best estimate from the video is that it is in this neighborhood. Now it could be that they were referring to an unseen 30 foot turbine other than the one shown in the video, but for the example below I will go with 65 inch diameter rotor as an approximation.
Wind turbines convert the kinetic energy in wind to electrical energy at the output. There are other types of energy in the wind, such as thermal, the energy in the random motion of the molecules we measure when we measure temperature, but no turbine that I have ever heard of or seen has the ability to tap into that. Turbines are all limited to this kinetic energy. How much energy is in this wind? Well a turbines blades have to collect this energy from the wind passing over them. Betz figured out that you can't take all of it or the air would stop in its tracks and no more wind would move over the blades, he calculated a theoretical limit of 16/27 or 59.3% which bears his name. No turbine to date has ever been proven to exceed, or even come close to this limit. Even if there were no limit, there is still only a limited amount of kinetic energy.
In the case of a turbine with a 65 inch diameter rotor, and for winds of 6 miles per hour this can be calculated fairly easily.
Assuming there are no errors in my units or math, below are the calculations for such conditions. First, for me, I have to get everything into SI units, meters and Kilograms in order for my results to come out in Watts.
12.5 miles per hour * 5280 feet per mile * 12 inches per foot * 2.54 cm / inch * 1 meter /100 cm * 1 hour / 3600 seconds = 5.58 meters / second
65 inch diameter blades blades would have a radius of 65 inches/ 2 * 2.54cm/1 inch * 1 meter / 100 cm = .8255 meters
swept area = pi* square of radius, or 3.14 * .8255 meters squared = 2.14 square meters
volume of wind passing the blades in one second = swept area multiplied by the wind speed = 2.14 square meters * 5.58 meters per second = 11.94 cubic meters per second
from Wikipedia, density of air at sea level is approximately 1.29 kg / meter cubed at zero degrees celsius and at sea level
(it would be lower at higher temperatures and/or elevations)
mass of air passing through the swept area if it did not slow down at all while passing would be 11.94 cubic meters * 1.29 Kg / cubic meter = 15.4kg/second
total kinetic energy contained in the air passing through the swept area if the wind did not slow down at all in passing would be:
1/2 * the mass of air * the square of the velocity = 15.4kg/s * (5.58 meters) ^ 2 = 479.5 kg m^2/s^3 which = 479.5 Joules per second or 479.5 Watts
This would be the case with 100% efficiency, no Betz limit considerations, and no alternator inefficiencies.
The Betz Limit would put this at about 284.3 Watts, and at the efficiencies of the best utility scale wind turbines that I have heard of at about 47% would only be about 225 Watts or so. When you add reasonable inefficiencies common in small wind turbines you end up with figures about what Sparweb already posted.
If you are actually getting 800 Watts from such a setup, you have an overunity device that works and with a proper write up are a shoe in to win a nobel prize as none has ever been demonstrated. The most likely error for anyone honestly claiming such an output from such a machine would be a mismeasurement of wind speed, since the power available is a function of the cube of the wind speed, a small error there would be magnified when calculating the efficiency.
One other note is that I looked into grid tie in my area, and the inverter must be hard wired here, not connected by cord, and must be UL approved for the specific use for which it is applied. I doubt most utilities in the U.S. would feel much differently, but there may be coops or other providers out there with a more liberal attitude.
Lastly, although I am not attempting to call anyone out, only give a general example, since accusations of slander have already surfaced in this thread, I should point out that I am writing this in Illinois, and it is an affirmative defense here for defamation (slander) if what you write is determined to be the truth. While I do not claim to know all of the specifics of the particular wind turbine in question, I am stating that there is no way that a 65" diameter wind turbine can output 800Watts of continuous power in a 6 mile per hour wind, period.
