Lincolnshire wind farm incident

[fuzzyfelt]

http://news.bbc.co.uk/1/hi/england/lincolnshire/7817378.stm

Any thoughts?

[Andre]

One of the possibilities could be just a structural failure at the root of the missing blade, The latter may have hit the next blade.

Such a down to earth scenario is probably hard to imagine for the witnessing crowd. If you don't see where the departing blade was coming from, it's automatically an UFO, isn't it?

[matthyaouw]

It's a head scratcher. Look what happens when the thingamybob that limits the blade speed breaks:

http://uk.youtube.com/watch?v=7nSB1SdVHqQ

Something to think about.

[Ivan Seeking]

From what I've read, there is nothing to suggest that this was anything but a mechanical failure. The reports of strange lights in the area likely have no connection whatsoever.

[mgb_phys]

From what I've read, there is nothing to suggest that this was anything but a mechanical failure. The reports of strange lights in the area likely has no connection whatsoever.
in that case why did my and Evo's posts about aliens in Lincolnshire mysteriously disappear?
Because the matrix is controlled from Grantham - thats why!

[Ivan Seeking]

Posts disappeared? How strange!!! :biggrin:

[fuzzyfelt]

Thanks everyone for your thoughts, and thanks matthyaouw for the impressive broken blade speed limiting thingamybob causing explosion video.

[Ivan Seeking]

One question that I have not seen addressed is rather obvious: Was there any wind that night?

[fuzzyfelt]

As far as I have read, there was little wind, but there could have been ice.

[Ivan Seeking]

I did check last night and found one source showing a median wind speed of 5 kph that day, but it didn't provide an hourly graph. In order to do the damage seen to the blade that was bent, I would think that the blades must have been moving fairly quickly, which doesn't seem likely if the wind speed was in fact only a few mph.

[russ_watters]

Regarding the "UFO" phenomena, it wasn't clear to me from the articles whether anyone actually saw them that night. The way they read, no one witnessed the actual failure. So there isn't necessarily any corellation at all.

Also, if there is anywhere that one might expect to find ball lightning or other similar atmospheric electrical phenomena, a wind farm is the place due to the static electricity the rotor blades would produce.

[Ivan Seeking]

Regarding the "UFO" phenomena, it wasn't clear to me from the articles whether anyone actually saw them that night. The way they read, no one witnessed the actual failure. So there isn't necessarily any corellation at all.

That was my original point as well - I haven't heard anything to suggest that the reported lights had anything to do with it. But if there was no or little wind, it seems difficult to account for the damage. I am starting to suspect that there was no wind, which is why the wind turbine company keeps the UFO option open. Not to suggest that it was a UFO flown by aliens, but it does seem a bit more likely to me now that something actually hit the turbine.

Since one blade was bent [made of metal], it seems likely that the blades are grounded through the tower, which would prevent the accumulation of a static charge.

[matthyaouw]

I caught a snippet about this on the local news this morning. There is still no word from the owning company about what happened. They are investigating but so far undecided.

[glondor]

Similar damage on this one. Lightening strike.
http://www.youtube.com/watch?v=OyOiDQGn-6k&feature=related

[Ivan Seeking]

Similar damage on this one. Lightening strike.
http://www.youtube.com/watch?v=OyOiDQGn-6k&feature=related

Do you have any supporting information? YouTube is not a qualified source for explanations.

If it got hot enough to fail in that manner due to a lightning strike, I would expect to see signs of heat - scorched paint or discoloring, pitting or holes, etc.

[Orion1]

The report I read said that one of the blades was missing and was not located by search.

Where did the blade go?

[mgb_phys]

Where did the blade go?

1, Stolen by aliens
2, Nicked by locals
3, Somewhere in a ditch/long grass but it's too cold and wet to bother searching for it - especially when surrounded by farmers with shotguns shouting "oi, gerroff my land"

[Ivan Seeking]

The broken blade has been recovered and is being examined.
- from the OP

[Ivan Seeking]

The lookouts for little green men can go home. It wasn’t an unidentified flying object with octopus tentacles that caused a wind turbine blade in England to fall off last month, and damaged another blade. Rather, the problem was “material fatigue” in the turbine that caused bolts to come loose...
http://greeninc.blogs.nytimes.com/2009/02/11/damaged-wind-turbine-it-wasnt-aliens/

[fuzzyfelt]

http://greeninc.blogs.nytimes.com/2009/02/11/damaged-wind-turbine-it-wasnt-aliens/

I'm pleased to see it resolved, thanks all.

[Andre]

One of the possibilities could be just a structural failure at the root of the missing blade, The latter may have hit the next blade.

Such a down to earth scenario is probably hard to imagine for the witnessing crowd. If you don't see where the departing blade was coming from, it's automatically an UFO, isn't it?

You see?

Metal fatique is a serious liability in aviation with ever changing loads on the components. Seems that these lessons learned with the Comet (http://en.wikipedia.org/wiki/De_Havilland_Comet) are unknown in the wind turbine industry.

It could be start of something similar, if one bold fails due to fatique, all are subject to the same load variation.

[Ivan Seeking]

You see?

I think what made people suspect something else was that strange lights had been reported in the area. But I still want to know how it failed if there was little to no wind.

Under normal circumstances, fatigue would be a bit of a no-brainer. But a good bit of force was involved in causing the damage to the second blade, which would seem to be inconsistent with the weather report. Presumably the wind had kicked up but this wasn't reflected in the weather logs.

[Andre]

the force of the failed blade while falling hitting the second damaged blade, which was just going up?

The last load on a fatique crack doesn't need to be big, it's only the last load.

[fuzzyfelt]

the force of the failed blade while falling hitting the second damaged blade, which was just going up?

The last load on a fatique crack doesn't need to be big, it's only the last load.

I see.

[Ivan Seeking]

the force of the failed blade while falling hitting the second damaged blade, which was just going up?

I think you are missing the point: According to the weather data that I was able to find, there was little to no wind. I don't see how the damage present - the bent blade - was possible unless the turbine was turning at a good clip. But, I was only able to find mean values for the wind, which was listed at about 5mph that day. My next thought was that the wind is usually calm at 4am unless a storm is moving in - ie the land to sea temp differential is near its minimum.

[redargon]

I haven't looked at the pics (they get blocked here at work, which i should probably be doing, but hey, it's lunch time) but most wind turbines have three blades (i'm looking at some out of my office window). We have a wind of 2km/h (1.2mph) and the are spinning at... 1 rotation every 6 seconds (10RPM). If tangential velocity is w*r (rotational velocity mulitplied by radius) and these blades are a good 30m long. Then the tangential velocity at the tip is: 300m/min or 5m/s or about 11.25mph.

Now consider that the blade that is fatigued breaks when it is in the horizontal position (pretty decent to assume, because this should be when the torque about the fatigue crack due to the blade's weight is largest). When it comes free, there is a weight imbalance and the other two blades will swing more under their weight towards the falling broken-off blade. Collision and whammo, 2nd blade is damaged.

This is just a rough idea of how this could have happened, I assume no responsibility for actually being correct :wink:

[Ivan Seeking]

I guess the point was this: It was not a case of people picking a UFO strike [which could mean something like UAV strike] out of the blue; to suggest it was is rather silly. There had been strange lights reported in the area and the company couldn't initially explain what had happend - they even specified that something could have hit the turbine. The wind conditions then caught my attention, but given that the company has determined that fatigue caused the initial failure, I would expect that there is no mystery.

[fuzzyfelt]

Thanks too, redargon and Ivan Seeking.

[Andre]

I think you are missing the point:.

Most definitely not, the last of the fatique bends is just the last, regardless of the forces involved. It can be just nothing.

[physicsmum]

Hi I was just browsing when this thread caught my eye. My daughter and I have actually seen the red balls of light that were reportedly seen before the incident. There was two of them one was bigger than the other and they seemed to be white hot in the centre. they moved pretty fast and there was no sound

[fuzzyfelt]

Fascinating! Interesting that these lights were reported some time before.

[matthyaouw]

Hi I was just browsing when this thread caught my eye. My daughter and I have actually seen the red balls of light that were reportedly seen before the incident. There was two of them one was bigger than the other and they seemed to be white hot in the centre. they moved pretty fast and there was no sound

I am intrigued- How would you be able to deduce this?