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On wind energy

  1. Jun 2, 2009 #1
    As I live not far from Altamont Pass and often hike the wind energy area, I see the damage windmill blades do to birds by the number of dead ones on the ground. Also, these windmills are truly Star Wars ugly and insulting to the environment visually, not even considering what they do to birds. Ugh, overall.

    Are wind turbines better energy producers, all things considered? With turbines, at least screens can be put on them, but as a naturalist I do understand that a bird hitting a screen in flight is almost as bad as hitting a blade. Both near 100% fatality, but even a few percentage points better saves birds.

    Turbines can be grouped closer and are perhaps more space efficient(?), and are not as architecturally offensive as I have actually seen some online that look sculpted and are quite cool. Are they less deceptive to flying birds with their unmoving support structure, as birds know to avoid the support structure but not the moving blades of a windmill?

    Thanks for any learned input.
     
  2. jcsd
  3. Jun 2, 2009 #2

    berkeman

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    But you also see the newer, larger turbines there in the pass as well, right? The newer ones are bigger with longer, slower blades, and are said to be much less of a problem for birds. They are also more attractive, IMO. Do you see piles of birds around the newer ones?
     
  4. Jun 2, 2009 #3
    The newer wind turbines are much higher and have much longer blades. The wind speeds are higher 100 meters up, so making the turbines taller makes sense. Also, the output power increases as the square of the blade length, and the cube of wind velocity. But the blades are not slower. The blades are airfoils, like airplane wings, and are most efficient when the HAWT (horizontal axis wind turbine) blade-tip is moving at about 5-6 times the wind speed. See
    http://en.wikipedia.org/wiki/Wind_turbine_design
     
  5. Jun 2, 2009 #4
    This is incorrect. The larger the blade, the slower the speed. What you mentioned is the tip speed ratio (TSR) which is the relation of the tip speed of the blade divided by the wind velocity.

    TSR = R * w / V

    So, if you assume a constant tip speed of 6.5, wind velocity of 10m/s, and blade lengths of 50 and 100m;

    w = 6.5*10m/s / 50m = 1.3 rad/sec (12rpm)

    w = 6.5*10m/s / 100m = 0.65 rad/sec (6rpm)

    Also, your link says the 6-7, not 5-6.

    The TSR and rotational speed of the wind turbine can actually vary greatly in order to achieve maximum efficiency if its a variable pitch design. 6-7 is typical for a fixed pitch turbine but for a turbine operating in varying wind conditions with variable pitch I have seen designs that operate from 2 - 8.
     
  6. Jun 3, 2009 #5
    Bob S said
    The newer wind turbines are much higher and have much longer blades..... But the blades are not slower.
    Not true. As per your calculation, the blade tip speed for both your examples above is the same; 65 meters per second. If I were talking about racecars going around in a circle, I would measure their speed in meters per sec, not radians per sec. In any case, a bird will be blind-sided by a blade moving at 65 m/s in a wind speed of only 10 m/s.
     
  7. Jun 3, 2009 #6
    When you said "don't move slower", I assumed you meant a lower RPM and were not referring to their tangential speed. My mistake. Anyway, I concur, tip speed is the same and RPM is slower.
     
  8. Jun 3, 2009 #7

    russ_watters

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    Note, though, that since it is only the tip speed you guys are talking about, a larger turbine would be safer due to the fact that there are fewer of them needed: there are fewer objects to hit a bird flying through a field.
     
  9. Jun 3, 2009 #8

    mheslep

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    The AWEA shows ratio of bird kills from everything else man related to wind turbine kills as 10000:1, and 1000:1 from house cats alone.
    http://www.awea.org/pubs/factsheets/050629_Myths_vs_Facts_Fact_Sheet.pdf [Broken], pg 4.
     
    Last edited by a moderator: May 4, 2017
  10. Jun 3, 2009 #9

    russ_watters

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    Lol, that's good to know! I wonder what the ratio of bird kills by other birds is!

    Still, we may just be looking to increase the number of wind turbines out there by a factor of 1000.
     
  11. Jun 4, 2009 #10
    Not pleased with the above responses as most don't even speak to my original question, and one justified wind mills as being less deadly on birds than cats. Incredibly ignorant and biased, or worse, and not relative at all to my question re: mills or turbines.

    Stick to the original question or PLEASE do not respond.
     
  12. Jun 4, 2009 #11

    berkeman

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    Well you were gone for a couple of days, so yes, we did get a bit off on our own. What was your question again? I re-read your OP, and didn't really understand what you are asking. Can you post a couple pictures of the devices that you are trying to contrast? Do you have any links to information about their relative efficiencies?
     
  13. Jun 4, 2009 #12

    RonL

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    I think you might be over reacting, I think the posts were close to being in line with your question.
    Something to consider might be the fact that birds seem to take chances by flying close to moving objects (sort of a daring challange, quite like humans) have you ever noticed how birds seem to swoop down and just barely miss an automobile as it is moving down the road, this has always been a thing of curiosity to me.
    I have a piece of property that has power lines over one end, there has always been a few birds, that have over the years flown into the stationary lines and fallen to their death on the ground below, much to the local cats delight.

    RonL
     
  14. Jun 4, 2009 #13

    russ_watters

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    Your post reads like a generic gripe as much as a question and contains many unrleated elements that don't lend themselves to a tightly focused discussion. If you want a tightly focused discussion, construct a tightly focused question!
     
  15. Jun 5, 2009 #14

    Redbelly98

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    They are less ugly, and less insulting to the environment, than the consequences of staying chiefly with fossil fuels to produce electricity.

    I don't understand this. Isn't a screen stationary and visible, therefore avoidable?
     
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