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Old 11 February 2004, 17:49   #11
nik
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Its a bugger as Portland Harbour Authority seems determined to wipe out diving in the harbour.
They had a pretty good go at trying to banish windsurfing in the harbour as well.
Nick
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Old 11 February 2004, 17:56   #12
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I did my degree project on Wind Turbine blades - hence the interest and why I was looking on the Crown Estates web site in the first place - but (way back) then they all talked about siting them 'far away from land' to reduce the 'environmental' impact (on us humans I assume).

That looks like what they are trying to do in the North West - at least they're a few klicks offshore. I wonder if the planning for building them takes into account previous usage and stuff like that?

It does seem a bit odd that they want to do it in Portland Harbour, and on top of known, good, dive sites. There is a lot of sea-bed between the low-water and the 12 km line - I'm sure they could find a bit no-one was THAT bothered about if they tried.

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Old 11 February 2004, 18:00   #13
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turbines

Hello DGR,
can you tell me this? Most windfarm turbines I have seen have 3 blades, if more blades were added to the turbine, would it not generate more power?
Nick.
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Old 12 February 2004, 05:24   #14
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Blades...

The turbines are designed to produce a specific amount of power (i.e. 1MW etc) within a specific windspeed range, and then the blades are designed to produce the required amount of effort to drive the turbine.

You tend to see 2 and 3 bladed designs, but a 2 bladed design needs longer blades to generate the same power as a 3 bladed one - from (very hazy) memory, a 1MW (big) turbine had a similar wingspan to a Boeing 747 if you use a 2 bladed design. A 3 blade design means significantly shorter blades, and therefore a much shorter (and cheaper) tower for the same power generation and ground clearance.

From there I think you get diminishing returns on extra blades - the additional costs of the blades, the extra control mechanism and the interference effects of the blades negates any of the benefits (slightly shorter span and slighty shorter towers). The biggest benefit seems to come from 3 blades - so that's what most are.

I also seem to remember that 3 bladed turbines are quieter than 2 bladed ones as well - the tip speeds are lower so they don't "whoomp" as much as they go round.

It's a long time since I did any of this - and a lot may have changed since I looked at it - not least of which is probably my memory!!

Dylan...
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Old 12 February 2004, 06:49   #15
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Thanks Dylan,
This has puzzled me for a while. I can remember in westrns, seeing wind driven water pumps for wells which had loads of blades. But that could be down to limited quality of materiels and limited technology.
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Old 12 February 2004, 07:19   #16
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Yes - I guess all those wind turbines in the movies did was just pump up water from a well, so just as long as it was powerful enough to go round and drive the pump then it was OK. Modern wind turbines are trying to extract as much energy out of the moving air as they can - so use technology/modern materials to do that.

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