> Does anyone know why vertical wind turbines didn’t take off?

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?”

One of the reasons may be a problem with "disabling" vertical turbines during high winds. With properller-like turbines, blade can rotate to move edge-on towards the wind direction or move parts of blades in the opposite direction, so that the overall torque in each blade is zero regardless of the wind speed.

Reminds me of a report about the floating decision for the UK's first spaceport:

Where it will land is still up in the air

Me: "Well, thats f**ing no good"

Great joke :D

There are a whole series of problems. Darrieus turbines and their variations are fun to watch.[1] But they have structural strength problems. Also, they're hard to stop. Large bladed turbines have variable pitch, and are set to neutral during high wind conditions to prevent overspeeding. Most of the vertical designs can't do that.

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.

[1] https://en.wikipedia.org/wiki/Darrieus_wind_turbine

They face more turbulence and greater stresses, and less efficient combined with being more expensive from the start.

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.

what about vertical turbines in the water & bolted to the sea floor?

All engineering at sea costs more. Seabed anchoring is a thing, and a higher degree of wind offshore is a thing, but if you do the linear optimisation of the different cost benefit lines I suspect scaling up traditional fan style 3 blades just wins.

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.

Doesn't change a thing on how stresses damage the turbine.

Vertical still only makes sense in limited space.

Interestingly, vertical designs have been proposed for Mars, because space for shipping them is at a serious premium, and the much lower atmospheric density reduces the stress considerably. (Hollywood depictions of destructive Martian sandstorms are quite exaggerated for effect.)

Mars is a good example of differing constraints leading to choice of different technologies, indeed.

what are the stressors? mechanical failure, too much kinetic energy in the waves?

The pole in the center of the VAT generates a turbulent wake that the blades pass through once every rotation. This wake shakes the blade and causes extra stress. The blades themselves make a wake also, though not as much as the pole.

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.

thank you

There's a nice video compairing vertical and horisontal axis wind turbines here: https://www.youtube.com/watch?v=EM-gCvhQhPU

They look cool, but the standard three blade turbine is by far the best for engineering reasons. With vertical turbines you always have a blade going against the wind. With vertical turbines you get variable power from the wind depending on where the blade is in relation to the wind. Engineering can work around these to make the work, but in the end the standard 3 blade turbine is more efficient in both theory and practice.

Structural issues: https://www.modernpowersystems.com/features/featurewhatever-...

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.

I don't know anything more than what Wikipedia would tell you but I was driving out east one summer when I saw the largest one ever built in Cap-Chat, Québec. Very cool looking, I thought I was seeing the future. Apparently not though.

They are considerably more complicated to build and their main benefit is efficiency in turbulent flows, however it turns out that also turbulent flows tend to be slower in practice so there's less energy to get out of them anyway. This reduces your margins to zero if not negative unless you scale them up to sizes that are not practical for places that actually do have turbulent wind conditions. (e.g. cities.)

Source: I worked for a micro generation helical VAWT startup for 5 years.