Wind turbine "bites the dust" in low winds
 

http://www.dailymail.co.uk/news/arti...ph-breeze.html

What do you think about this story ?

Metal failure ?

Wind speed much higher than gauge showed ?

Fill in the blank....

Act of *od ?

Hi there,

something along that line would be my guess. Maybe a yet undetected small damage at the shaft base. Just consider the shaft's height in relation to its diameter, and you get an imagination of how much force there is at its base. A small material fault or some imbalance of the system ...

Don't think so. There would have been at least some noticeable effect on the other turbines standing nearby. But there's no mention of that.

[X] Doc CPU

There's a lot of "voodoo mechanics" in those things. I'm amazed that they don't fail more often than they do.

I knew a fellow who lived in the wind-swept plains of the midwest, and his "off the grid" solution for his home was infinitely simpler: he had a row of (antique ...) windmills at the edge of his property, each one of them driving one or more car alternators. In a nearby well-insulated shed he had rows of car batteries stacked on neat shelves. The usual controlling electronics. This gave him more 12-volt (and 110-volt) power than he needed.

The biggest problem with wind (and solar ...) power thinking right now, in America at least, is that people are still thinking in terms of "the grid." Centralized generating plants driving what is actually a very leaky and inefficient power-distribution system, most of it from the 1940's. Sunlight falls everywhere at once.

The usual culprit for such things is a faulty governor. Unless you regulate the speed of the blades properly, you'd never get one to operate AT ALL. Think about something with a span as large as those blades...consider what would happen if they just SPUN at whatever speed the wind blew. It would fly apart from the centrifugal force. You need fairly constant rotation to produce 'clean' power, that's not spiking or dropping wildly every time the wind gusts or dies.

Once the governor starts to die, it introduces a slight wobble...the wobble leads to tower fatigue. Once that starts, and the governor isn't fixed, the amount of drag on the blades goes up (they stop spinning at the design spec, and go over drag limits), leading to greater force against the nacell and the already-fatigued tower. Down she comes....lots of weight balanced at the top of a long pole.

There's typically software to monitor such things, which 'calls home' to the company, who sends techs out. Lots of potential for failure there, including overworked techs who just didn't get there in time.

Living in Wind Farmville. Here in West Texas.

http://www.getsmartenergy.com/images/Brake.jpg

http://isaacbrana.files.wordpress.co...peed-shaft.jpg

I think TBone is on to something. Edit: Because here. On a Windy day. You will see lots of Wind
Turbines not spinning because down for maintenance.

And to think, only a few years ago I couldn't spell "engineer", and now I are one. :)

Wind turbines do not have a speed governor. Most turbines have a gearbox to speed up the axis speed. The axis drives a synchronous generator. The generator is in sync with the grid. That is a very, very tight coupling. With generators like the failed type the power generation is regulated by blade pitch adjustment. Even if the adjustment would fail completely, the rotor can never overspeed.

Another type of generator is slow-turning, direct-drive. AC is rectified and the DC is coupled to the grid through an inverter. The speed is limited by the power the generator delivers to the grid.

There are newer developments like generators with variable frequency excitation but the principle remains the same of generator-grid sync remains the same.

Only in the case a turbine generator is not loaded and the safety system fails to detect that, and fails to detect a too high rotational speed, or the nacelle rotation mechanism fails it could lead to an overspeed condition.

That is not to say an overspeed is impossible. It is possible. But not due to a governor failure. Turbines do not have a governor.

jlinkels

You can see that the shaft bent down in a area were the bending moment is the highest. And if you look at the kink there seems no material on the inside, like a drinking straw. Make test with a drinking straw you will see failor like this.

And if this happens like this it could be that the the shaft is not stong enough against bending. The fatigue strength is much lower then the static strenth. If you make tests on a test bench you will see that some parts brake earlier and some later. I made a lot tests for automotive parts. There are some words for this: fatigue limit; endurance limit; fatigue strength; dynamic strength. They have to look for this.

Informative info.

I think that the biggest problem with these designs is that they're trying to create a stable-power generating device for "the (1940's) grid." They want a single generator to produce a lot of power, and steady power, just like a steam or hydro generator does. Similarly, they want big solar "farms" which can collectively (ahem ...) generate enough power to interest "the grid."

But the real potential of these power sources will require a complete re-thinking of "the grid." These are inherently power sources that will produce a variable amount of power and, most easily, a small amount of power. Solar panels on your roof, for example, to supply your house.

And another problem is that "the 1940's grid" must have an approximately-equal sink of electrical demand to match (consume) its electrical supply at the instant it is generated. If load is suddenly taken off of a turbine, it will explode. If a large number of people actually did start to employ "individual" sources of power, "the 1940's grid" would become unbalanced.

But we need to be thinking in those terms anyway.

Perhaps "governor" was an oversimplified term...but there IS a system to prevent overspeed, which DOES fail, and they have many times in the past:
https://www.youtube.com/watch?v=7nSB1SdVHqQ

...is just one example. There are many more of them catching fire from the loads places on the transmissions between the rotors and the rest of the system further in the nacell.

Talking to some of the crews out here. I fix their Harley Davidsons. They say blade failure is a big problem with these things.

http://www.gcube-insurance.com/en/ne...wntime-events/

Taming nature will always be impossible. :-)

I wrote that a turbine will never overspeed by a failing pitch control
It will overspeed when the electrical or mechanical load is removed for whatever reason, and the nacelle is not turned out of the wind.

jlinkels

Given that the story is from the Daily Mail and that paper ran with the headline "Hurrah for the Blackshirts!" in 1934 in support of Hilter's fledgling Nazi party and also ran many anti-Semitic pieces in the 1940s, I don't think we should pay any attention to that disgusting rag...
http://tompride.wordpress.com/2014/0...-semitic-past/