[Cd]

I didn't read all of the postings here, so I may be repeating someone .... but .... I saw in Popular Science circa 1999 - 2000 that a company was experimenting with this idea.
A 'windmill' was placed on the roof of a van sideways. As the vehicle drove along, the wind would spin the blade and produce electricity.
What made their idea so clever was that the blades flattened out as they spun around creating far less drag than if they remained intact.

It was the issue that had "Detroits' 80MPG supercars". ( The Precept, Dodge intrepid ESX, Ford Prodigy.)

Like so many things in that magazine, it's promises never amount to anything.