They are less efficient and require larger/more robust bearings than standard horizontal turbines. They look neat, but a "standard" turbine will produce more power in the same footprint and require less material to produce. One advantage of the vertical axis turbines is that the "business end" is at the bottom, making it easier to maintain without climbing up a tower. They just stink at the one thing they are supposed to do.

My dad used to work as an electrician at the "Wind Research Institute" in Romania, back when the communists were still in power. So of course, I was regaled with all sorts of stories on wind turbine deployments all throughout childhood.

One of them was when this huge vertical axis turbine research prototype suffered a destructive failure while he was in the control room underneath because of a flaw in the emergency braking system. Apparently, when the blades (that normally are under tension) break off they make a loud noise and having that thing fall on you is super dangerous.

Only mildly related, but thought I'd share since only now, as a grownup, I realize it's actually interesting, whereas as a small child I really did not appreciate it. And, well, not sure how many times vertical wind turbines come into discussion.

Can't wait for my kid to roll his eyes at my stories.