i know you have probably thought of these concerns
1. a 20 kwatt machine will require a massive set of blades, and with size comes all sorts of stresses that become unimaginable
especially when the wind gets gusty and turbulent, let alone high wind conditions.
2. the planetary gearbox is ok, but there will be some losses associated with its use, and
it will require frequent overhaul, most are not meant to run 24/7/365, where thousands of hours and jillions or rotations
are inevitable.
3. taming the voltage will require some rather expensive power electronics, because regulating voltage will be very important
4. a 20 kwatt dump load is a large project on its own
5. failure to any of the forementioned will lead to catastophic results, a serious threat to life and limb
6. you will likely need to attain about 1000rpm or so at the pm generator to get useful target power out of it
so at 10:1 you will need 100rpm at the blade/rotor,, that is pretty fast on a large rotor
centrifugal forces will be massive, throw a blade and i can see the dozer ending up on its side.
not meaning to rain on your parade, but a project approaching 20kwatts is hardly a first time project
at least for someone like me 
, an i have spent hundreds if not thousands of hours researching windpower.
how large in diameter do you figure your rotor to be?, without doing some research i would think maybe
25 or 30 feet?
the reason i am concerned is based on a delta kite a group of my friends and i built in the early 80's for an exhibition
it was 18ft high and 12 ft wide, it took 18mph to get aloft and took all a 454 duelly wrecker could do in granny gear
to get it up,, and when you stepped on the clutch the truck would stop dead in its tracks!
i can't imagine a 25plus foot rotor running at speed being anything less than that kite when it comes to the stresses involved.
however, i look forward to seeing how you come out with your planned monster (baby)
bob g
Bob,
The machine you describe was my original plan. 120 RPM, 36 foot, two blade propeller lift blade made of steel up on a horizontal shaft 75 feet in the air. I am not well enough to climb towers anymore so for that reason alone this became impossible.
The new machine concept is a much shorter vertical axis machine with the blade, a squirrel cage type affair, steel frame with aluminum skin airfoils and foamed core), beginning at the 25-28 foot level. I have a 3:1 truck differential in front of the 10:1 (to create the 90 degree flip to a vertical driveshaft) so I actually only have a turbine speed of about 60 RPM to spin the alternator at 1800. That is a nce leisurely one revolution per second.
The machine will be part drag part lift so not expecting or desiring a TSR above maybe 2 or 3:1 max. The squirrel cage may be as much as 22 feet tall and 16 feet in diameter'ish.
I will not have to climb any tower to service the guts of this baby as they will be at ground level in my heavy crawler chassis. The crawler will be stabilized with outriggers on pads and screw jacks.
If I get 10 kW in a good steady wind that will be considered a success. If I get 3-5 kW on average windy days that will be fine.
