[jacquesm]

It is the tower occlusion that sets off the problematic resonance, which ends up eating the base bearings.

[bigiain]

There are a couple of (small, obviously academic/experimental) vertical axis wind turbines near me which both have helical blades. I wonder what the tradeoffs for that design are?

Here's a picture (not mine) one of them: https://www.flickr.com/photos/nicephotog/25044930672/

[hasmanean]

For very tall VAWTs in a grid, could you dampen the resonances by tying the tops of the masts together with guy wires?

[jacquesm]

That will make it worse, not better. You want to decouple as much as you can so you don't end up creating a giant resonant structure.

[jacquesm]

They're sexy toys, not turbines.

See also: Windtree and other scams.