OT Knackered wind turbine

I predict we will see more. A bit of a boring failure compared to a combusting generator and gearbox. Google Images for "burning wind turbine".

ARW snipped-for-privacy@blueyonder.co.uk> wrote in news:y4flI.329750$E75e.213251 @fx21.ams4:

Bird strike by the look of it . . .

Nasty scratch that. Car body filler?

Wind damage, blown the blade back into the tower. Maybe not feathered in time, or properly.

What you cannot see on that photo (as I was driving when I took it) is that the blade has split into two. Half of it is hanging down the front of the tower but as it is white on white you cannot see it.

Manufacturing defect, bird-strike, overspeed, or any combination of these by the sound of it.

The blades are in the furled position.

It's pretty difficult to come up with a brake for these things.

The small wind turbines, they have a mechanical brake. When the wind gets at those, it causes the mechanical brake to heat up so much, the generator casing catches fire.

On the larger ones, you can short out the generator to make a braking effect, but then if the wind gets at it, it can overheat and destroy the generator.

Even if furled, it's probably spinning in some direction, and if no brake was used, anything could happen.

Paul

If you were an engineer, where would you most not want to put a large dangerous piece of rotating machinery?

On the end of a cantilever shaft, out in the elements, subject to bird strikes, insect build up, ice build up, marine spray in a high intensity magnetic field, subject to gust loading and going in and out of multispeed boundary layers. And 100 meters up in the air and from any maintenance staff and equipment.

Especially when the alternative was in a nice environmentally stable turbine hall, on finely balanced beam and centre bearing mounted shafts, fully enclosed and subject to a constant onrush of steam...and with a gantry crane already there to replace it if anything goes wrong...

Fibreglass yacht masts fail like that sometimes

Better shot from today's journey

Makes you wonder what that blade is made out of.

Paul

How can you tell, I've no idea what your picture shows, does it have a blade missing and by the way why do turbines not use more blades? Brian

Glass or carbon fibre, epoxy resins in the high stress regions.

Googling "why do wind turbines have three blades" will give you a number of interesting articles.

NASA made an experimental turbine, with just one blade, and a counterweight. Someone has tested that idea.

They do have turbines with two blades. The tower wobbles more, when the top blade is in full wind, the bottom blade is shielded by the tower. That torques the hub and tower.

Apparently, adding the third blade only adds 3% more power. But the torque ripple in the tower is less.

Additional blades would only add more mass and drag. The next number of practical blades would be five.

One article on wind turbines, mentions that the design is all about "number of flexures". And the blades are only good for about 100 million flexures. Each rotation counts as a flexure for the blade, it is constantly being worked (and ruined). Same goes for the tower, it takes a lot of abuse too.

The Dutch windmills are different. There's an entire article on "Windmill Sail" design and mechanisms for automating the furling in high wind (spring-loaded shutters).

How many horsepower does a dutch windmill generate ?

The wind turbines are currently 2MW to as much as 9MW.

"How much horsepower did the average traditional Dutch windmill/wind pump generate?"

So a factor of 40 or so.

Paul

some dont

The Natural Philosopher formulated on Sunday :

And of course these exotic composited can't be recycled.

Green aren't they?

Andy