The current tiny turbine I have is supplying a suitably tiny amount of charging current to my battery, but is mainly there to establish if there is any harvestable energy at all in my urban environment.
We're just getting to get some blowy autumn weather, with our nearest weather station reporting winds a little over 10mph, and today so far, more than 30 of my 2-minute samples report generated power...
http://www.earth.org.uk/off-grid-stats.html
Just got to get up to another 12 hours or so per day for this to be sensible!
Rgds
Damon