• A wind turbine with a 50 m diameter rotor is rotating at 25 rpm under steady winds at an average velocity of 10 m/s. The electrical power output from the turbine is 375 kW. The combined efficiency of the gearbox/generator is 90 percent. Taking the density of air to be 1.20 kg/m 3 , determine (a) the wind turbine efficiency, (b) the tip speed of the blade, in km/h, and (c) the air velocity at the turbine exit if the turbine operated ideally at the Betz limit.