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Renewable Energy: Wake effects from large wind turbines?

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  1.  
    I've just got wind of a possible application for an 800kW turbine on a field near me. Unfortunately, it is down (prevailing) wind from my Gaia 11kW wind turbine at around 600m-800m away. I think it is just a speculative scheme but will the wake effects of such a turbine either reduce the performance of the Gaia or even destroy it?
    Any thoughts?.

    - I think my neighbours should be a bit more concerned than me because at least 6 of them are within 600m of it, 2 are 400m and I don't think turbulence will be their problem! :shocked:
    • CommentAuthorCWatters
    • CommentTimeJul 8th 2012
     
    I think the government say wake effects kick in at less then 5 diameters. Recall reading it in PPS22 or the companion.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJul 8th 2012
     
    There is also the local windspeed at different heights above the ground.
    Make sure you have some data from a local weather station that you can use to calibrate your turbine, then if change does happen, you can prove it. If there is no change, we have all learnt something.
    • CommentAuthorGavin_A
    • CommentTimeJul 8th 2012
     
    it won't have any effect at all.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJul 8th 2012
     
    That's my feeling, but would be interesting to know for sure.
    If it goes ahead, get the developer to pay for some decent monitoring equipment for you :wink:
  6.  
    Thanks,
    I did have a weather station that gave some good data (19% of the time the wind would go though the big turbine towards mine) but that was replaced by the Gaia - anyway thinking about it, I can't see how the neighbours site would be worth developing cos the wind speed can't be much better than my 5m/s (but I suppose i am 18m and they would be 50m AGL).
    I couldn't prove anything if the big turbine went up, for one I wouldn't have the money and don't think their developer would help with that! I think perhaps the GC Newts will prevail anyway!!!!!!
  7.  
    At 800 kW you would be looking at aroung a 50mtr rotor. That is way too far away to have any impact on your turbine. Industrial scale development have turbines closer than that to each other with no impact on neighbouring turbines. The term is called stacking. Look at some American sites if you are interested in stacking. I would not worry at all. Out of interest what turbine is proposed at 800 kW? I do not know of one that small from the major suppliers. The smallest being 850 kW.
    Gusty.
  8.  
    Thanks Gusty, that's reassuring and I think it's an Enercon 48. Not in planning or anything, just grapevine at this stage!
  9.  
    Having done the "internet search" seems that there is a demonstrated turbulent wake effect from single large wind turbines of 16 x blade diameter down wind of the turbine and at that distance the airflow would still not have returned to laminar/free flow (whatever this means!). Oh, apparently don't fly your microlight behind a big wind turbine because if you don't stall because of the 60% reduction in wind speed, you'll be mashed by the 500% increase in vortex velocity from the blade tips. They also say that the wind farms across the US have failed to adequately take account of the wake effects. Interesting.
    Seems, therefore, Gusty is right (just) in that I'm way too far away to have any impact at 16.6 x blade diameter!!
    • CommentAuthordjh
    • CommentTimeJul 9th 2012
     
    Posted By: windy lambUnfortunately, it is down (prevailing) wind from my Gaia 11kW wind turbine at around 600m-800m away.

    Is that a typo? If the new farm is downwind there won't be any wake effects at all. Well, actually the flow does start to change in advance of the obstruction, but not very far in advance.
  11.  
    djh,
    A typo I think however turbines tend to yaw through 360 degrees. Down wind one day up the next....:shocked:

    Enercon 48 eh. Very good turbine. They will generate up to 35m/s although the power curve does drop away.

    :wink:
  12.  
    Yes - typo I meant up wind but you all knew that anyway.
    The Encercon 48 is a good turbine but not necessarily when you put it 400m from houses! Might upset the neighbours especially when the landowner lives a few miles away!
  13.  
    There proposing 3 Enercon 48 on moorland near us but have told planning that there only 500kw turbines. It will be interesting to find out whether they get planning as the local councillor is adamant thou shall not build on the moors.
  14.  
    I suppose an Enercon 48 just refers to the diameter of the blades so could accommodate a variety of generator sizes in the nacelle. Whether it's 500 or 850kW still would be 48m blades diameter on a 48-60m tower. Generator size would be the last thing you notice!
    •  
      CommentAuthorSteamyTea
    • CommentTimeJul 10th 2012
     
    Would they fit a smaller generator because of the lower windspeed?
  16.  
    Posted By: SteamyTeaWould they fit a smaller generator because of the lower windspeed?


    Its just a con to get through planning. The turbine is still a 850kw but restricted electronically to 500kw as that is the maximum the grid will currently accept. Once the turbines are in the grid can be upgraded to the full 850kw per turbine. Windspeed is quite high at average 6.5 m/s.
    •  
      CommentAuthorted
    • CommentTimeJul 10th 2012 edited
     
    Posted By: windy lamb16.6x blade diameter


    Any chance of a link for that reference, please Dave? Very relevant to something I am looking at. I've read a few papers on turbine wake but haven't seen that figure quoted.
    • CommentAuthorwindy lamb
    • CommentTimeJul 10th 2012
     
    Ted, here's that paper - not sure how well respected the author is but I'm sure it'll lead you in the right direction. http://www.arising.com.au/aviation/windturbines/wind-turbine.html
  19.  
    Surely planning are interested in tip height and not generation. I would imagine the 500 kW limit would be from the grid provider and not planning. Yes turbine rotor diameter can be increased for low wind speed sites to increase capacity factor. You would not buy an 800 kW turbine and restrict to 500 kW though. That does not happen. You would but a different turbine that would fit the site output. The manufacturer would not put a smaller generator in hence making the turbine slightly cheaper, it would be the same generator restricted by software. The turbine would have an 800 kWprice for 500 kW. NO way. This is rubbish. I am pro wind in the correct locations and those that know me have can confirm I do not twist the truth. Some of this thread is total rubbish though,
    Gusty.

    very upset by cobblers. :cry:
  20.  
    Would you construct an 800 kW turbine with the possibility of increasing the power with grid upgrades. What a gamble. I would request evidence that this has ever happened on any UK site. Evidence mind you, not gossip.:sad:
    • CommentAuthorJoiner
    • CommentTimeJul 11th 2012 edited
     
    Gusty, you're right that planners will NOW only consider arguments concerning the physical appearance and consequent landscape impact (big "Oh yeah?" from those opposing certain developments) and not the generation since the NPPF came out. All they have to do now is turn and you're away.

    The issue of how the developer decides which generator to fit according to whether the grid can accept whatever the developer wants to put in is new to me. I had no idea they could keep their options open in anticipation of future changes to grid limitations. I wonder how many others were surprised by what you've just said?

    This place is a little cosmic FE college.
    • CommentAuthorwindy lamb
    • CommentTimeJul 11th 2012
     
    Gusty and Joiner, of course you're both right but it does seem that there are a lot of very speculative applications going in which really don't make much sense (economically or otherwise), many of which are withdrawn after objections. I can think of a couple in the next parish. Anyway, electronically limiting an 850kW turbine to 500kW in the planning application stage really is immaterial when a grid connection of any capacity has not been confirmed/established to the site.
    So you get planning for your 500kW turbine (which you can upgrade to 850kW by pressing a few buttons) but that's useless when the 4 landowners that your grid connection has to cross all decline permission to the DNO. Can the DNO force the landowners to give access for what is not a national infrastructure project? I know we had to get permission from our neighbours to connect to the grid a few years ago. I'd suggest you establish whether a connection is possible before you apply for planning for any size of turbine. Many seem not to - that's the cobblers that upsets me.
    FE college but without the spots and silly hair cuts!
  23.  
    Gusty

    Unfortunately our planners are becoming paranoid in respect of even small wind turbines.

    I have just found this site which appears to be set up by the council although claimed to be by local residents. Main anti wind person in the village is the local councillor.

    http://westpenninesprotectiontrust.co.uk/research/turbines/

    As for the 500kw debacle it was rejected by planners for reasons I cannot understand but the refusal notice is on the Blackburn & Darwen planning site under Lower Aushaw farm
    • CommentAuthorwindy lamb
    • CommentTimeJul 11th 2012
     
    And I was worried about turbulence affecting my Gaia - the bloke from Birch Farm (see the westpenninesprotection link) has 2 Gaias and wants to put an Enercon smack-bang next to them! He's got some money burning a hole.
    • CommentAuthorwindy lamb
    • CommentTimeJul 16th 2012
     
    Gusty -
    There's plenty of Enercon 48s going up which have been "downgraded" to 500kW, in the UK and overseas. Don't know why but just do an internet search to see planning applications. So why would you buy an 800kW turbine then restrict it to 500kW? - if the grid can't handle that, then why not put up a 250kW turbine that's been rated as 250kW? Seems someone somewhere is making too much money.
    It's a bit like "the inappropriate siting of wind turbines being the industry's own worst enemy", again.
    •  
      CommentAuthorDamonHD
    • CommentTimeJul 16th 2012 edited
     
    Hi,

    I can think of two reasons why an electronically-limited turbine would make sense:

    1) Expectation that local grid capacity will increase.

    2) Making better use of a low-wind site. (In the same way I have 5.2kWp of PV but the abs max output of my inverters is a shade under 4.5kWp: the available power is so rarely going to exceed that figure that the extra infrastructure to harvest the rest is not worth it.)

    Rgds

    Damon
  27.  
    Windy Lamb,
    Very interesting. I would guess that this pattern then must be speculative to try and increase the output with grid upgrades as Damon stated. I would want to be certain that the future upgrade was going to happen though as turbine cost are around the £1.1 million installed per MW. What a gamble to take. So a 500kW turbine with grid connection etc could cost £550,000 (ball park figure) and the 800 kW could cost £850,000 or so. Then you rectrict your generation after paying over the odds for the turbine. Are these in areas that the grid work has already had the green light? Enercon are very expensive too by the way. Before you restrict the output.
    I have never seen this pracice before in my 13 years working in the wind indusrty. Just goes to show that I am a novice...........:shamed::cry:
    I have seen larger rotors going on turbines to increase capacity factor in lighter wind areas but this is from design stage and has always been the intention.
    Gusty.
    •  
      CommentAuthorSteamyTea
    • CommentTimeJul 16th 2012 edited
     
    Damon
    How have you got around the G83 restriction of 16A/3.68kW?

    Is there a 500 kW turbine that would suit the wind regime for that area (may be very skewed) and cost less than the Encon.
    At that sort of money I am sure people have checked it a few times.
    •  
      CommentAuthorDamonHD
    • CommentTimeJul 16th 2012
     
    The local DNO simply granted us a waiver at my house and basically said "submit the new system as if G83 and we'll accept it". If we hadn't been the first PV system for at least many streets (possibly the first on our substation) they might have been a little more tetchy.

    At the school the (same) DNO asked us to fill in the G59 forms for the second system we commissioned but didn't ask for any extra technical steps over G83, so we have two identical ~8kW (3ph) inverters feeding in, one technically covered by G83 and its twin by G59.

    A friendly DNO makes a big difference.

    Rgds

    Damon
    • CommentAuthorwindy lamb
    • CommentTimeJul 16th 2012
     
    Steamy - I'm not entirely sure whether the "rent a field" wind turbine type company has looked into any other 500kW turbines. I get the impression they just deal with Enercon so they just deal with Enercon turbines. This is all a bit second hand, so my info may be a bit ..well, who knows. Anyway, having had long discussions with the planners about an 11kW turbine, I would have thought permission for an Enercon would be a long shot. Perhaps these companies send in 50 planning applications for sites only expecting permission for 5. Seems a bit of a waste of time and money but someone must be making on it.

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