 Basic Wind Concepts & Rules
When the wind speed doubles, the power available increases by a factor of 8. That means there’s very little power available in low winds. Increase the wind speed for any rotor from 5 mph to 10 mph and you get EIGHT TIMES the power you would get from the 5 mph wind. For example, a small 5-foot diameter turbine at 5 mph: Power available (Watts) = ½ * 1.23 * 1.8241 * 2.23521 = 12.53 Watts Increase to 10 mph (8.9408 m/s) and you get Power available (Watts) = ½ * 1.23 * 1.8241 * 4.47043 = 100.22 Watts Keep in mind that multiplies into a 20 mph wind generating Power available (Watts) = ½ * 1.23 * 1.8241 * 8.94083 = 802 Watts The best way to increase the available power in low winds is by sweeping a larger area with the blades. Power available increases by a factor of FOUR when the diameter of the blades doubles. If we use a 5-foot diameter turbine in a 10 mph wind: 5 feet = 1.524 m swept area = pi * r2 = 1.8241m2 wind Speed = 10 mph = 4.4704 m/s Power available (Watts) = ½ * 1.23 * 1.8241 * 4.47043 = 100.22 Watts If we use a 10-foot (3.048 m) diameter rotor for a 7.30 m2 swept area in a 10 mph wind, we get: Power available (Watts) = ½ * 1.23 * 7.30 * 4.47043 = 401 Watts 
The combination of increased sweep area AND increased wind speed can produce astounding improvements. This means locating the wind machine in the best wind speed area (usually high above buildings and tree effects and perhaps on a hill AND using the largest windmill available. Multiply 64 x 4 and you get 256 times the power of the small low wind machine. So, a good result is 256 times better, or conversly; a BAD solution only gives you far less than ONE PERCENT of a GOOD solution. So a 10-foot (3.048 m) diameter rotor for a 7.30 m2 swept area in a 20 mph wind: Power available (Watts) = ½ * 1.23 * 7.30 * 8.94083 = 3209 Watts The definition of a 10 mph wind is really supposed to mean AVERAGE wind speed of 10 mph. AVERAGE means that there could be a lot of 5 mph with some gusting of 20 mph winds. Turbulance might not be much help, and may actually damage the wind machine and eliminate the higher wind benefits. The farther you transmit energy, the more energy is already used. If your Power Controls and Fuse Box are far from the wind generator, less energy will be available. The more distance used, the more important to consider using AC instead of DC to transverse the distance. There is a significant loss during DC transport, and very little loss during AC transport. The faster the movement, the more noise produced. Nothing mechanical will last without maintenance. Preventive maintenance will always be less expensive than repairs. The lifespan of the components and the whole system can be easily cut short by a vibration creating a loose bolt, or failing to lubricate a gear, or cover a component from rain. There is no way to harvest ALL of this available energy and turn it into electricity. In 1919 a man named Betz calculated that there is a limit to how much power can be extracted from the wind. Beyond the Betz Limit of  |