Wind Turbine Power Output

Power in the wind P = ½·ρ·A·v³ where A = π(D/2)². A turbine can capture at most 59.3% (Betz limit); real turbines achieve a power coefficient C_p of 0.35–0.45. Output rises with the cube of wind speed, so doubling wind speed gives 8× the power. Annual energy = output × the hours per year the wind blows at about that speed.