I would think the drag is considerable.

I would also worry about stability in a strong side wind.

As a result, I would not like to ride the 2-wheeled version in strong side wind. The 3-wheeled version looks OK, but also suffers from drag.

Besides, to generate power from wind while parking, you would have to choose your parking direction. But you can’t always choose the parking direction - location dictates it often. That kind of a wind generator on a vehicle looks severely half-assed. They should have though two steps ahead.