The inherent problem with low level windmills regardless of type is
the land surface drag and there's no way around it.
None the less, I see all kinds of upgrades to get around that problem.
, essentially, a horizontal tube 20' in diameter and
200' long with jet engine like vanes running the full length. As the
wind traverses the interior of the tube pressure builds causing the
Bernouli principle on the vanes. Thus a 5 mph wind could cause the
movement of a 50 mph wind. Stacked ball bearings and graphite races,
in other words, extreme efficiency. Pressure switches and high speed
equalization vents throughout. This could generate 100,000 RPM's so
noise could be an issue.
The units on aerotecture's site remind of the Wright flyer - wind
power in its infancy.