The Basic Idea

The following drawing illustrates the basic idea.  Assume we have an airfoil with a Lift to Drag ratio of 10.  (We probably can do much better than that.)  Then, if we look at the end of a spinning airfoil, we will have 1 unit of a Drag force and 10 units of Lift force as shown below.

The blue motors that spin the airfoils only need to consume enough power to overcome the Drag force.  On the other hand, a very large Lift force creates a large torque which propels the beam, motors and shaft which is the rotor of the MOTOR shown below.  The airfoils are like propellers that propel airplanes except, in this case, they are propelling something that has no wings and no body as an airplane does.