Siemens 21MW prototype machine

[Mart]

Thing is, if you can build a taller tower, you can then also fit longer blades, which means you then need a bigger generator machine otherwise it's energy you could have turned to electricity not being made... and so on

Very true. I was just wondering if when we reach the limit of what the blades can cope with, and also the economic limit on building ones bigger (twice the length will mean ~8x the mass), would it then be possible to mount that max size WT higher in the air?

I suspect that too brings limitations, as the stronger wind will apply more force, so the blades need to be stronger, and we start going in circles (WT pun intended).


Time will tell, and the economics will shine through in the end. Maybe a 50MW WT is the technical limitation (purely as an example), but two 30MW WT's at a 50% capacity factor, are cheaper to build, install and maintain, than one 50MW WT with a 60% cf.

Maybe let the Chinese find the physical and economic limitations, and then simply copy them?

[Stinsy]

Thing is, if you can build a taller tower, you can then also fit longer blades, which means you then need a bigger generator machine otherwise it's energy you could have turned to electricity not being made... and so on

Very true. I was just wondering if when we reach the limit of what the blades can cope with, and also the economic limit on building ones bigger (twice the length will mean ~8x the mass), would it then be possible to mount that max size WT higher in the air?

I suspect that too brings limitations, as the stronger wind will apply more force, so the blades need to be stronger, and we start going in circles (WT pun intended).


Time will tell, and the economics will shine through in the end. Maybe a 50MW WT is the technical limitation (purely as an example), but two 30MW WT's at a 50% capacity factor, are cheaper to build, install and maintain, than one 50MW WT with a 60% cf.

Maybe let the Chinese find the physical and economic limitations, and then simply copy them?

I distinctly remember thinking we’d hit that limit when 1MW turbines appeared.

Your “let us copy the Chinese” plan is an interesting reversal.

[AE-NMidlands]

Very true. I was just wondering if when we reach the limit of what the blades can cope with, and also the economic limit on building ones bigger (twice the length will mean ~8x the mass), would it then be possible to mount that max size WT higher in the air?

I suspect that too brings limitations, as the stronger wind will apply more force, so the blades need to be stronger, and we start going in circles (WT pun intended).

I was wondering whether twice the length would double or square the "centrifugal" force? Acting on 8 x the mass...
Maybe huge blades would turn slower but have a higher-geared generator... which transfers the challenge to the gearbox instead!

[Countrypaul]

Very true. I was just wondering if when we reach the limit of what the blades can cope with, and also the economic limit on building ones bigger (twice the length will mean ~8x the mass), would it then be possible to mount that max size WT higher in the air?

I suspect that too brings limitations, as the stronger wind will apply more force, so the blades need to be stronger, and we start going in circles (WT pun intended).

I was wondering whether twice the length would double or square the "centrifugal" force? Acting on 8 x the mass...
Maybe huge blades would turn slower but have a higher-geared generator... which transfers the challenge to the gearbox instead!

Perhaps that is a motivating factor for the Direct Drive that Siemens are using.

I wonder if the blades could be made in 2 (or more) pieces and fitted togethr on site or even during the assembly phase

[Adokforme]

Very true. I was just wondering if when we reach the limit of what the blades can cope with, and also the economic limit on building ones bigger (twice the length will mean ~8x the mass), would it then be possible to mount that max size WT higher in the air?

I suspect that too brings limitations, as the stronger wind will apply more force, so the blades need to be stronger, and we start going in circles (WT pun intended).

I was wondering whether twice the length would double or square the "centrifugal" force? Acting on 8 x the mass...
Maybe huge blades would turn slower but have a higher-geared generator... which transfers the challenge to the gearbox instead!

Perhaps that is a motivating factor for the Direct Drive that Siemens are using.

I wonder if the blades could be made in 2 (or more) pieces and fitted togethr on site or even during the assembly phase

Prior to this monster I believe blade tips were approaching speeds of 550mph at max rpm. I wonder if the sound barrier will come into play at any point?

[dan_b]

Looks like that's what GE is doing, or prototyping at least - and they're made with carbon-fibre too

https://www.lmwindpower.com/en/stories- ... n-launched

I wonder if the blades could be made in 2 (or more) pieces and fitted togethr on site or even during the assembly phase

[Stinsy]

I wonder if the blades could be made in 2 (or more) pieces and fitted togethr on site or even during the assembly phase

This is the problem! Blades cannot be manufactured in several parts, the stresses are simply too high.

[Stinsy]

Prior to this monster I believe blade tips were approaching speeds of 550mph at max rpm. I wonder if the sound barrier will come into play at any point?

The sound barrier would indeed be a huge problem.

Even one revolution every 10 seconds (6RPM) is over 300mph. Engineering any kind of gearbox that can handle the almost-unimaginable torque sounds like a very tricky undertaking indeed!

[Marcus]

.....
Prior to this monster I believe blade tips were approaching speeds of 550mph at max rpm. I wonder if the sound barrier will come into play at any point?

IIRC some of the very early 2 blade windmills did go supersonic, which causes some noise nuisance ( if your standing in the plane of the mill, such that the supersonic tips are travelling towards you then you hear that heavy "thud, thud, thud" as you do when a fast moving helicopter is coming towards you - for the same reason of course: the tip of the advancing blade of the helicopter is going supersonic)

My thought was that they design them to stay below the speed of sound (~750mph? It varies a bit) for that reason. But if they're only up to 550mph I think there's some headroom.

[nowty]

Tip speeds of around 200mph seems to be the max on large wind turbines (3 blade) as they wear out to quickly over that.