Wind contains power from kinetic energy equal to:
E = 0.5 * (rho) * V3 * (pi) * R2.
RHO= air density. V= wind speed.
Wind Speed | Horsepower per Exposed Sq Ft | 10 ft. Windmill Exposed Area Sq Ft (approx) | Horsepower Exposed to
| At 30% Efficiency: Usable HP |
| 10 MPH | .007 | 75 | .5 | .16 |
| 20 MPH | .06 | 75 | 4.5 | 1.5 |
| 40 MPH | .42 | 75 | 31.5 | 10.4 |
A 10-mph wind contains about 4 ft-lb/sec.
Or about .007 Horsepower per square foot of wind area.
--------------------------
A 20-mph wind has about 8 times as much power as a 10-mph wind - .06 HP
----------------------------
A 40-mph wind has about 64 times as much power - .42 HP
---------------------------
A 60-mph wind contains about 810 ft-lb/sec.
Or about 1.5 HP per square foot of wind area.
A 10 foot windmill intercepts about 75 square feet of wind area.
And performs, at best, at 30% efficiency.
A 10 mph wind x 75 sq.ft. = about 0.5 horsepower.
At 30% efficiency, about 0.16 horsepower
A 20 mph wind x 75 sq.ft. = about 4.5 horsepower.
At 30% efficiency, about 1.5 horsepower
A 40 mph wind x 75 sq.ft. = about 31.5 horsepower.
At 30% efficiency, about 10.4 horsepower
Fuel Cost -- Per Horsepower -- In Dollars
$0.00!