Wind speed statement of?

[Shen]

Hi,

This is probably a very si8lly question but at least I am honest about it.

I read about m/s speeds.

I have worked offshore for many years and we rate wind in knots /hour.

If the wind is moving at 50 knots per hour, constantly, for arguments sake, then it is at any given second in that hour moving at 50 knots per second.

If a turbine cannot cope with more than 25 metres / second at what speed is it tripping out? In other words what does this speed really mean? Does 25m/sec mean 1500m/min which in turn would mean 90k/hr? Or in my basic language, 56mph?

Am I anywhere right or wildly out? If it is 56 mph, that does seem a bit feeble? I am quite used to 100 mph gusts out here you see.

All comments welcome..

Shen

[Alan]

Hello Shen

50 Knots per hour relates to 57.53897 Mph or  0.01388 Knots per sec

The quoted survival wind speed for the 10 K.W. unit is 60 metre per sec  which equates to 116.63 Knots. ( Survival normally means, don’t expect it to work but big bits should not fall off )

It is designed to start to turn out of the wind at speeds greater than  48.596 knots.

That’s the theory. Practice is some what different

Regards

Alan

[martin]

being a pedant, "knots per hour" is incorrect! - the word "knots" has the "per hour" bit built in!
Blame my old yachtmaster's course!

[Bargeman]

Hello,

The following statement is extracted from "Energy Efficiency Best Practice Installing small wind powered electricity generating systems" (CE72), published by EST.

"Wind loading

The UK has a good wind resource, but severe winds occur occasionally.The turbine and tower must not become a health and safety risk due to mechanical failure caused by high winds.

The wind turbine and tower should at least be rated to withstand wind speeds that average 35m/s (78mph) over a 10 minute period without any damage to its operation.

The wind turbine and its support structure should be designed to survive a gust of at least 50m/s (112mph) without suffering
any damage that might result in any or all parts of the turbine or tower falling to the ground.

Gusts of 50m/s are rare, but they must not result in catastrophic mechanical or structural damage; although it is accepted that
systems may not function correctly afterwards. Manufacturers' instructions will normally require turbine inspection following
severe winds.Wind speeds of 35m/s are more common and it is important that the turbine is designed to return to normal
reliable operation after such events (in accordance with BS EN 61400-2). Some particularly exposed sites, or installations
in public areas, may need to meet more stringent design requirements."

Given the problems folk have been having with the recent rather breezy weather, where wind speeds have been up around these upper limits, is this 'best practice' sufficiently rigorours ?

regards

[Ivan]

Buildings clearly do not have to comply with the same level - as many buildings suffered damage - slates and tiles blown off, chimeny stacks fallen, walls falling down and killing people. And all of this in regions we know are subject to lower wind speeds than the turbines atop towers!