This could very well prove to be the most efficient bird killer ever devised.
> This could very well prove to be the most efficient bird killer ever devised.
Oh, geez.... Same old bird-shredder argument. No matter how many times the facts are presented (such as, the number of birds injured by large wind machines is miniscule compared to the population; it's a negligible cause-of-death among healthy birds), this still comes up.
It's just not a significant problem, because the prop rotates so slowly. Do the math, don't just parrot falsehoods.
The blade tips must stay well below Mach 1 (the speed of sound), which is a little over 1000 feet/sec. A 120-foot radius means the circumference of the rotor is about (120 * PI * 2) or about 750 feet. This means that the prop won't be turning faster than about 1 rev per second tops.
Say a large bird (couple feet front to back) flies straight into the swept area of the rotor. Say it's going, 30 feet per second (slow-average speed of big birds in open windy areas). The chances that it'll encounter the blade are less than 1:10 -- that's flying directly into it. Smaller bird, even smaller chance. Faster bird, even smaller chance.
(And as a different matter, any bird that can't see (and get out of the way of) something turning that slowly probably isn't long for this world anyway.)
As for "efficient", you'd do better with a BB-gun, at much lower cost.
Or if you really want to kill birds with wind-machines, get a small one that turns really quickly, a backyard unit with 10-15-foot blades. Those turn fast enough that they might actually shred a couple of local avians.