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Tree Wind Generator

Discussion in 'Electronic Design' started by Dirk Bruere at NeoPax, Apr 16, 2010.

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  1. An idea I've had for years, but never tried and never seen anyone else
    do it either.
    Simple idea - capture the energy of a tall tree swaying in the wind.
    Rough numbers: 200kg force (2kN) through 0.3m every 2 seconds is
    potentially around 330W.

    Tie a line to the top of the tree to ground via a spring. Use the
    movement of the tether to drive a ratchet connected to a generator.

    Anyone know of anything similar?
     
  2. Tim Williams

    Tim Williams Guest

    It would be pretty cool if you put the trees on a merry-go-round. Put up
    some sort of wind screen so they only sway on the windward side. Instead of
    200kg through 0.3m, you get maybe 100kg through 20m/s!

    Moving/living sculpture projects aside, sway has the advantage of working in
    place. Can't say I've heard of it before though.

    Invent it, then market it to nut orchards -- turn the generator around and
    it doubles as a tree shaker for harvest. :)

    Tim
     
  3. By attaching two lines at right angles it would not matter which way the
    wind is blowing. All the material needed are pretty cheap on a per watt
    basis (as well as absolute)
     
  4. Sjouke Burry

    Sjouke Burry Guest

    Wave generator, same principle.
     
  5. The question is how to turn massive force short stroke, low velocity
    movement into energy efficiently. A simple magnet and coil would not
    work well at all.
     
  6. But a tree is a lot cheaper than a wind turbine on all counts.
    It would be quite easy to make a portable unit for camping, or
    recharging batteries off-grid. A cheap fill-in for PV.
     
  7. What kind of trees are you thinking about ?

    I have wire antennas hanging from pine trees and if the movement and
    forces would be as large as stated, the antennas would have snapped a
    long time ago.
    Possibly a usable system to power some flea power meteorological
    station that transmits the cumulated data a few times a day.

    For any real power production (e.g. summer cottage) this is
    unfortunately a bad idea.

    The kinetic energy of the wind is proportional to the third power of
    wind speed and directly proportional to the cross section area and air
    density. While there are quite stable winds above 600 m, the surface
    roughness will drop the wind speed close to the ground.

    On a small low island in the middle of a sea or a moderate tower in
    the middle of a crass land will produce some usable power levels. In
    areas with trees and bushes within a few kilometer, the wind turbine
    would have to be well above the tree tops to produce usable levels of
    power.

    This tree spring idea was compared to wave power, however, the density
    of water is about 800 times larger, so the extracted power density
    would also vary in the same way.
     
  8. The question is, how much sag do you accept in calm warm environment ?
    With sufficient sag, the wire will not snap.

    I have a multiband inverted-V dipole hanging from the tallest pine
    tree with the ends of the element suspension wires suspended via other
    pine tree branches "pulleys" into small trees acting as "springs".

    Anyway, most of the dipole radiation is created close to the high
    current point, i.e. close to the dipole feed-point, so the wire
    sagging does not drop the radiated power in a significant way.
    Thus 10 .. 25 kg and 0.7 .. 1 m with unspecified cycle.

    The original poster claimed
    Thus up to an order of magnitude less and then only during a storm.
    Using trees swaying in the wind to produce a small amount of
    electricity might be an interesting way of powering micro-power
    electric gadgets and hence very much on topic in this news group.

    Unfortunately, I have became quite allergic to some "green" claims
    that if something works in a very specific environment, it will also
    work for a whole family or solve the national or even global energy
    needs :).
     
  9. Just because the stroke is moving 25kg does not mean that it could not
    move something 10x heavier.
    After all, the above poster was adding weight merely to tension his lines.
     
  10. Do you expect that the amplitude of the tree oscillation will remain
    the same, when you put say, 250 kg hanging from the line ?
     
  11. No, I assume it will probably be in line with my example ie around 30cm
    stroke in moderate wind. That's what I observe.
     
  12. I've seen cylindrical turbines placed at the edges of buildings where
    bad aerodynamics causes extreme winds. I found this for the turbines on
    Park Ave. in San Jose, CA:

    http://www.mercurynews.com/breaking-news/ci_14191622
     
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