This has been a most interesting topic but, I am left with a nagging question:
All I have seen here seems to emphasize the disadvantages of VATs (fatigue stress, noise, vibration, poor self starting etc.). I wonder then why not simply go with the ubiquitous, tried and proven 3 blade HAT??
I also note that, AFAIK, pretty much all commercial "wind farm" turbines are of the 3 blade HAT type (and I've never seen or heard of any other).