[youtube=http://www.youtube.com/watch?v=dN_YLe3Ohjg&feature=player_embedded]
YouTube user ecodeasnet recorded a man in a town in Nepal driving a modified rickshaw. It had a steel drum that had been shaped to catch the wind and channel that power into the wheels. It doesn’t seem the most effective, his speed isn’t massively impressive, presumably because of what looks like quite thick sheet metal.
