Friday, 15 May 2015

fluid dynamics - Do wind turbines convert the kinetic energy of air?


It is often said that wind turbines convert the kinetic energy of the wind into electricity. But in respect to horizontal wind turbines with airfoil shaped blades this is imho not the case.



Wind turbine designers try to minimize drag. A perfect wind turbine has an infinite lift-to-drag-ratio (drag is infinitesimal) where the kinetic energy of the air molecules behind the rotor is equal to the kinetic energy in front of the rotor.


Unlike traditional windmills and most vertical axis wind turbines, horizontal wind turbines with airfoil blades do not try to "catch the wind" (try to transfer the kinetic energy of the air onto the blades) but use lift to induce rotation.


What is really happening?




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