- It's cheaper per KWh (they claim 40%, IIRC, but that was in 2015)
- It requires less maintenance (no moving parts)
- It doesn't kill birds
- It's silent (no frequencies >20 Hz)
- It's 30% less efficient than a blade design but you can put twice as many in the same area
- It doesn't cause the alternating light/shadow effects that huge blades do
They are no rotating parts, but some parts are moving.
A 100W conventional turbine also only has a couple of moving parts, won't kill birds and is effectively silent. I'm unsure on wether these claims are still true as the device scales up. A device 100m or so tall will have a fast velocity at the tip perhaps as much as 50m/s at a few Hz which is similar to the blade tip speed of a conventional turbine thus having similar potential to kill birds and make noise.
(purchase + installation) / average_life_span + maintenance per time unit
So, even at triple the cost it could still be worthwhile.
I hope there also isn't much noise below 20 Hz, as infrasounds are uncomfortable and potentially dangerous.
But we can tell they don't care about bird because they don't complain about glass buildings, cars, power lines or cats, all of which kill more birds than wind turbines.
http://theconversation.com/wind-farms-are-hardly-the-bird-sl...