How dangerous are wind turbines when they fail?

[Cyrcle]

Hw dangerous are wind turbines when they fail? Seems like those big wooden blades could do some real damage.

[dnix71]

http://en.wikipedia.org/wiki/Smith-Putnam_wind_turbine

The world's first megawatt turbine threw a blade 750 feet. It wasn't properly constructed or maintained because of shortages during WW2.

http://www.youtube.com/watch?v=CqEccgR0q-o  This one sheared a few sheep when the brake failed in a storm. One of the failed Vestas turbines had been in service 19 years.

http://www.off-grid.net/2008/01/15/vestas-turbine-collapse/

[hayfarmer]

I have a  micro 6 footer at my farm and it came with galvanized blades.had a strong storm one nite with winds peaking 80 mph and found one of the blades 100 feet away buried 6 inches into the ground,replaced with  smaller blades and less surface area  and no worries for the last two years.have 2 other turbines no problems.

[Rover]

To me this is a troubling question.

"How dangerous are wind turbines when they fail?"

It depends on what you think is dangerous. To the generral public and bodily harm... extremely unlikely.. actually beyond extreme...probably beyond measurement 

Most of us worry about the battery banks , the destruction of the mill etc (for us that is the danger) .

 As far as population harm... you are by far  more likely to get hit by lightning.

[frackers]

The failure I had last week took out all 3 blades on a 3m mill and I'm still finding pieces of wood up to 80m away even though it was up only 12m high.

[taylorp035]

I think rover hit it on the head.  Chances of an industrial windmill exploding is very,very, very small.  Usually some one will clear the area if all of the brakes fail, so when it does blow, no one will get hurt. 

For us people who like to play with our windmills, the most dangerous times are when you don't have a good tower (or lack there of).  I found that out the hard way my self.  An 8ft diameter turbine on a 6ft step ladder can produce way more force than two people can hold, especially in the 40 mph winds that the thrill seekers inside of us love.  Mine blew up when the blades hit the ladder.  Many of the pieces flew a good 60 yards behind me.  The tip speeds were in the 100's of mph.

Be safe out there.  There are more fun ways to die than getting hit on the head with windmill blade.

[wooferhound]

Wind Turbine Fires for your viewing pleasure . . .
http://fieldlines.com/board/index.php/topic,140851.0.html

[jarrod9155]

I just lost my 18 footer this morning 80 mph winds , turnbuckle snapped in half and it was a chain reaction still haven't found one of the blades what a mess . But no one was hurt had a buffer of 120 feet around the mill so if it did fail it wouldn't hit anything . Rip 18 footer

[fabricator]

The danger is directly proportional to the proximity of any individual person or persons and the chances of a failure at any given time, however you must also remember that failures of wind turbines usually happen during exceptional weather periods, during which people are the least likely to be in the vicinity of a turbine.
Those stupid aliens in that UFO that crashed into that turbine in Europe were just morons.

[Cyrcle]

Seems like it should be pretty safe 100+ yards from the house. Guess I'd better start saving for the thick wire for that distance!

[Flux]

I think this question is fairly closely related to your other post about starting big.

If it is your own property and there is no other people within a safe distance then as long as you have a clear fall zone then there is not too much problem. I think you must assume that any tower will fall down, you build it in such a way that it can't and make it twice as strong as is needed to do that but still act on the assumption that it will fall.

Flying blades is the worst problem as you never know where they are going to go, but if it is your property and things go wrong in a storm just keep out of the flight path. With a well designed and built machine the chances of blade failure is really very low but that may not be the case if you don't have the experience to avoid stupid things.

If you make furling work properly and you don't have any electrical failures to cause a loss of load then runaway is not likely. If it doesn't furl and it seeks the wind then at best expect a terrible fright, but I have to say that well made wooden blades properly mounted will survive some incredible conditions even though the noise will drive you a mile away from the scene.

I have never built a machine bigger than 5ft diameter without some form of control to stop it in the event of an electrical failure but I have always had people too close to the danger area to risk it. Nearly everything here relies on electrical braking and that is normally fine but if you loose the load you have to sit it out in a storm. If you are aware of the danger and take precautions when it goes wrong then the danger is not as bad as it first seems.

Wind is a pretty uncontrollable thing and during storms things happen but a decent wind machine is probably no more dangerous than a building or roof but you can never say that something won't go wrong.

Flux

[Cyrcle]

I have never built a machine bigger than 5ft diameter without some form of control to stop it in the event of an electrical failure but I have always had people too close to the danger area to risk it.

What kind of controls help keep it from running away without a load?

Thanks everyone for all the great info!

[fabricator]

A switch to short out the phases at the base of the tower or in the control room, or both, or some kind of mechanical device, Jacobs has been putting cable crank systems to pull the tail into furl for many years, my 17 foot machine has a mechanical brake operated by an air cylinder, these are just a few of many different things that can be done.

[SparWeb]

One member of the forum reported a few years ago that his turbine shed a blade, and it went through the skylight in the roof of his house.
Of course it was his idea to attach the turbine on a TV tower attached to the wall of his house, instead of a modest distance away.
My own bade experience:  the two cable let go while I was lowering it once.  Destroyed the turbine, but nothing but the tower was negligibly damaged in that incident.

There are common safety practices that, if learned and followed, can eliminate most possible failure modes.  The other side of the coin: abuse and poor maintenance will cause things do degrade quickly.  Unsafe conditions can be caused.

[imsmooth]

My first turbine had a week tail boom.  During a storm the boom snapped and the tail fell into the blades.  Pieces flew everywhere, but there was no other damage.  I built an axial flux with bigger pipe and strong welds.  For the last two years and several +60mph winds I have had no problems.  If my tower does fall it is situated far enough away that it won't hit the house.  I also have a braking switch to short all three phases.