Answer Happy

Suppose that you have a wind turbine that is operating at 41% total efficiency, with a wind speed of 25 km/hour and an air density of 0.51 kg/m^3. Which of the following would be possible ways of roughly doubling the electrical power output of the turbine? Select one or more: Increasing the wind speed to 50 km/hour Increasing the wind speed to 31 km/hour Doubling the number of blades on the turbine. Increasing the air density to 1.02 kg/m^3 Increasing the overall efficiency from 41 to 82%.
Calculate the power output from a horizontal axis wind turbine with two 12m blades, in a 35 kph wind, operating at 65% of the theoretical maximum efficiency. Assume the air density is 1.15 kg/m^3. Give your answer as a number, with units (e.g., W, kW, MW, etc) Answer:
Calculate the speed of the tip of a 67m blade on a horizontal axis wind turbine rotating at 20 revolutions per minute. Express your answer as a Mach number, ie, the fraction of the speed of sound (340 m/s). Do not give units. Answer:
In designing a horizontal axis wind turbine, which of the following factors would lead to a preference for fewer numbers of blades? Select one or more: Lower turbulence produced by the blades. Lower cost. Lower variations in moment of inertia about the vertical axis. Higher efficiency.