The power available from a wind turbine is calculated by the following equation: P=1/2A ρv^3
where P 5 power [watts], A=sweep area (circular) of the blades [square meters], ρ=air density [kilograms per cubic meter], and v=velocity [meters per second]. The world’s largest sweep area wind turbine generator in Spain has a blade diameter of 420 feet [ft]. The specific gravity of air is 0.00123. Assuming a velocity of 30 miles per hour [ mi/h] and the power produced is 5 megawatts [MW], determine the efficiency of this turbine.