khain wrote:I'd be interested to see if a wind-powered battery charger would be any use on a bike. It would obviously be low output but the advantage over a dynamo is that the drag would decrease to negligible levels when climbing. The problem is obviously that you would need very small rotors but it might be possible to use several on the down tube. I don't know, just an idea.
But with a hub dynamo the drag is reduced the slower you go too. The wind-powered generator would not be as effective in a tailwind, whereas the hub dynamo would work at the same rate as with a headwind. In addition the hub dynamo has electrical drag when in use and slight magnetic drag when not in use but otherwise the bearings create as much drag as any front hub would. The wind generator would add aerodynamic drag plus drag from another set of bearings plus the weight of the generator, a suitably robust mounting and rotor protection.
On the plus side, the wind generator would also work whilst you slept. But then again you could turn your bike over, fit a couple of stiff sheets of plastic to the spokes on your front wheel and turn it into a windmill generating power as you sleep.