From what little I know the output of a wind turbine increases in proportion to the cube of the blade length. Which mans that bigger is much much much better. And conversely, smaller is much much much worse.
So, from my relatively ignorant position, I'd have thought that a small turbine isn't of much use at all unless it's ... say ... to keep the battery topped up in a remote weather station or something like that, and even then I think you'd be better off with a solar cell of some description.
Still speaking from my position of total ignorance, I'd have thought that a dynamo hub on the bike would be zillions* of times more efficient than lugging around a windmill. Although this could possibly be handy if you had a semi-permanent base camp in a windy location.
*at least.
I could be wrong. I sometimes often usually am.