Small Wind capture has a Big Future in urban communities, globally.The nominal operating principle of a lift type VAWT is shown in the figure below. For a rotating turbine, the blades will observe a rotating wind velocity and an incoming wind velocity. Combining these wind velocities yields a total apparent wind at an incoming angle of attack. An incoming flow not parallel to the blade yields high and low pressure regions on the blade, yielding overall lift and drag forces. These forces can be decomposed into the turbines frame of reference, yielding radial and thrust forces. Summing the forces over the rotation of the turbine yields an overall positive thrust which can be extracted as electrical power through the generator.
Schematic depiction of the operating principles of a VAWT.