Every wonder why wind generators just keep getting bigger and bigger? Most people out west have been able to watch the size grow over the last 20 years from 10 foot blades to now over 100 foot lengths.
The formula for calculating power from wind generators is: Annual Output (KWH/year) = 0.01328 (D^2) (V^3) For the variables “D” is the diameter of the blade and “V” is the average wind velocity.
Every time you double the length of the blades you end up with four times as much power. If you compare a 10 foot diameter system to a 100 foot diameter system the energy difference is massive. The larger size generates 100 times as much power.
Let’s walk through the calculations quickly, assuming an 8 MPH average wind speed. For the 10 foot wind generator the formula is 0.0138 x 10^2 x 8^3 which gives us about 700 KWH per year. For the 100 foot system the calculation is 0.0138 x 100^2 x 8^3 yielding over 70,000 KWH per year.
Now, I know you may not be able to build a 100 foot system in your back yard, but going from 10 feet to 20 feet may be feasible. That generates four times the power with the same amount of wind. Certainly worth considering before you start building.