I remember reading an article in popular mechanics about them years ago (found it [1]) and it seemed like a superior turbine…
[1]: https://www.popularmechanics.com/technology/gadgets/a246/128...
This had me really scratching my head for way too long, I laughed out loud when I realised my error.
“They are bolted down surely?”
Where it will land is still up in the air
Me: "Well, thats f**ing no good"
In the early days of California wind power, there were some Darrieus turbines at Pacheco Pass. They're probably gone now. In those days, 30KW was a big turbine.
Efficiency in price per kwH is more important and big turbines have claimed their crown here. Given that stresses are behind size limits the strategy is clear here.
It's a "perfect is the enemy of good enough" thing. Better designs along one axis with a multi axis problem won't be best overall.
Vertical still only makes sense in limited space.
The horizontal turbines put the pole behind the blades. The pole does make a bow wave, but it is not as bad as the VAT wake. The pole/blade interaction is not as severe.
The standard horizontal three-blade upwind turbine design seems to have been the one that scaled up the best; you can just keep making them larger and larger and they get more cost-effective.
Source: I worked for a micro generation helical VAWT startup for 5 years.