You need an efficient boost/buck converter with a low
A cheap one from e-bay this one
is about 18mA which is a good percentage of what you'll be generating.
I made a turbine using 4 x PC fans, in a decent wind it would generate enough power to run 1 x PC fan at a little more than half speed. Not very efficient but it worked. Much better at charging 2 x AA batteries, then using a joule thief to power a 1W LED.
Used a 5 gallon bucket for the head, rope tied to top hole and a tree branch, another rope tied to bottom hole and a concrete block on the ground.