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Microflappers
Windmills only work well with laminar flowing air. Can we get energy from the turbulence instead? | |
So I've been reading about windmills, and they work most efficiently high up in the air with all the nearby trees cleared away, because they like a nice flow of air that is going in the same direction all across its cross-section. So it made me wonder if we could extract energy from turbulent air instead.
My
half-baked idea is, of course, lots of little micro-generators. I've seen ideas like this here before but I'm thinking more of a mass-manufactured thing that takes up a large volume instead of wasting your life taping piezos to a tree or coating just a surface with piezoelectric bendy things.
I'm visualizing lots of vertical rods with segments and roughly hand-sized flaps sticking out of each segment to be pushed back and forth as the wind... um... turbulates.
How to get power out of this? Not sure. Typical electromagnetic generators would be pretty expensive I think, although they would also be mass-manufactured. But probably not too efficient. Can you run a piezoelectric motor in reverse and turn it into a generator? Probably not. It would turn wind energy into electrical energy, but I don't know how efficiently.
(?) An illustration
http://img178.echo....icroflappers7ze.png
This is really what I wanted to show [omegatron, May 28 2005]
Nature's flappers
http://www.fotosearch.com/EYW745/ev01110/
(Run the little movie clip) [Ling, May 31 2005]
Brownian Motors
http://www.google.c...en&q=brownian+motor
Rotary motion from random motion [half, Jun 01 2005]
Piezo fan
http://www.piezo.com/prodfan0nav.html
Correct link [omegatron, Jun 02 2005]
Brownian motors
http://en.wikipedia...wiki/Brownian_motor
They are real, but useful? [omegatron, Jun 02 2005]
Wind belt
http://www.physics....uredetail.asp?id=47
Because the original link has gone bad [Vernon, Jan 03 2017]
[link]
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// Yes, you can generate eletricty with piezo electric crystals. |
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I know. But from rotary movement? I thought maybe you could use a piezo motor (that has lots of little piezo elements that take turns rotating the shaft) in reverse. |
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// That's why its more efficient to grow organic fuel crops. |
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Yes. That's a very good idea. Biodiesel and the like, right? But that's not converting wind energy into electrical energy. This would be used in places like rooftops and such, where growing crops is kind of impractical. |
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//rooftops... where growing crops is kind of impractical// |
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Not sure I understand what makes them flap. It'd need very choppy wind I think. |
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See link. I imagine a series of horizontal layers, each covered with mechanical grass (for want of a better description). |
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I notice that the grass seems to make it's own "turbulence". |
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But I am stumped on how to collect the energy. Maybe each blade is like a lever, with the pivot at the ground, and below the ground the blade continues for a short distance (therefore increasing available force).
Could it pump water? Grass seems to ripple, following the action of a wave. |
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// But I am stumped on how to collect the energy. // |
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I'm seeing some kind of implementation of the triboelectric effect. Like a bimetallic strip that bends when the two metals expand at different rates. Except in this case the two materials making up the blade of grass rub against each other, and electrons are preferentially moved from one to the other through triboelectricity. Whether you can then get those electrons to move in a current or not, I don't know. I don't think tribo materials are conductive. |
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omegatron, see link. "Bi metallic" piezo. |
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The Brownian motor concept might be relevant. On a vastly different scale, so maybe it's not relevant, but that's what popped in to my head. (link) |
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half, has anyone actually made a Brownian motor that works? I can find plenty of theories, and they seem to require that the ratchet is turned on and off. I wonder if the energy required to turn the ratchet on and off is more than the energy gained. |
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Brownian motors are real science. They are used for moving in a specific direction in a very viscous fluid. I'm not sure how applicable they are. |
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The piezo fans are a good idea. The piezo isn't the bendy part, though; they have mylar blades. It could probably work, though. Just use some schottky rectifiers and put a whole bunch in series? |
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The general concept of creating directed motion from random motion for the purpose of doing work seemed like it might be relevant to this present discussion which involves converting the fairly random motion of turbulence in to a usable energy source, but I'm not a physicist. I don't even play one on TV. |
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omegatron, first of all, sorry about the wayward link.
You mentioned that the peizo isn't the bendy part: I think it does bend a little (but is amplified by the blade).
The piezo fan consists of a piezo construction which wiggles the mylar blade. The peizo construction consists of two piezo elements which work in opposite directions when a voltage is applied across them. One contracts, and the other expands. Much like a bi-metallic strip. |
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The wikipedia link for Brownian motors describes what they are, but there are no references to any real Brownian motors. My ether-tour revealed plenty of theories, but nothing real and working. Did I miss something? |
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// I think it does bend a little (but is amplified by the blade). |
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Well, yeah. It bends a *little*. Typical piezo materials change width on the order of nanometers. I guess if it's in bending mode instead of "thickening" mode, that small change could become a large bend... |
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// The general concept of creating directed motion from random motion for the purpose... |
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Here's a good description I found: |
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Can we get work out of unbiased fluctuation? It is possible for macroscopic fluctuations. However, the situation is more subtle for microscopic fluctuations. We know from the second law of thermodynamics that is is impossible to get work in a repetitive cyclic manner from a single heat bath at equilibrium. But nothing forbids the appearance of Maxwell demon in the case of *nonequilibrium* fluctuations. |
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With these flappers, the macroscopically turbulent air is broken down into lots of small laminar currents changing directions all the time, and the movement of each small current is captured and rectified into useful work. |
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Now I am humming the Charleston. |
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