Hi,
How much POWER are you going to get out of your Savonius (vertical axis) wind turbine?
Can you post its specs/data, and/or a picture please.
For flea power systems the Joule Thief works well, you may have to check how reliably it starts with slow power level changes.
The Joule Thief is basically an oscillator, so to start, it may need a proper step ON to reliably function.
You will need to experiment to check it suitability.
Interesting project.
Tom... 