the problem is not in building a large alternator, or even carving large blades, but
most folks have no clue as to the issues surrounding the safe mounting, tower, control and other issues,, let alone what do you do with large amounts of power.
certainly have to have a team of engineers along with their stamp on just about every item, bonded construction teams, certified welders, certified fasteners,
certified wood or whatever for the blades, insurance to erect, and insurance in operation, a good legal team, blah blah blah. before too long it stops being fun
and becomes a real job, a real business. and once built and put into operation your
on the hook for whatever it hurts/mames/kills from cradle to grave,, the insurance company will pay for losses but will come after the manufacture to recover its losses.
then to use the kind of power possible would require grid tie, and that will become a very expensive problem as well.
just seems like there is much more to be done in the kwatt class before moving up to the C/kwatt class.
mppt for wind being one area that needs development and widespread application, along with cambered blades, both of which would likely be needed for the larger versions anyway.
20 footers are as large as i would wanna be around, and quite frankly even those are too big for 95% of folks in my opinion.
just my opinions others likely will vary
bob g