I have never been able to get my brain around this. The relationship between mass and power being linear. If you move X mass of air with a mechanical fan, and X mass with an electromechanical fan. the power required to move the mass (rotating force to rotate the fan blades) should be identical. Belt turning fan or belt turning an alternator. Actually the electric fan should be a little less efficient, with losses in the alternator and resistance in the low voltage wiring, 2 sets of bearings vs. 1 etc... Some one help me out here.
