I think they mean that the blades are not visible from ground level. A big problem with wind turbines in residential areas is the motion is really distracting a

I think they mean that the blades are not visible from ground level. A big problem with wind turbines in residential areas is the motion is really distracting and shadows on windows can be annoying as heck. Although looking at the patent, this thing would be stopped up with dead squirrels on my house in ten minutes unless they added some grating to the inlet.