flocking windmills
Locked
 
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Same power production as existing wind farms in 100th the land area.
-- rec --
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Now what a blithering moment. Cyclists flock to reduce friction. Ditto fish, I suppose.
So, turbines want less friction with the wind?????
Something screwy here.
N
Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([hidden email])
http://www.cusf.org [City University of Santa Fe]
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What they lack is mobility - lacking some sort of mobile platform maybe
they could get together and decide where the next best placement would
be and tell the manufacturing and installation people. Some sort of
distributed instantiation - Group orders another member, turbine shows
up in the mail, speaks up, says, "I am a wind turbine, the group has
determined that it will be most efficient if you place me over there."
And the humans would go do that, since the turbine family was usually
right about such things.
So maybe the turbines "want" some particular configuration, the friction is just one criteria. If they were a phased array antenna (in addition to being a group of wind turbines) then they would have additional criteria. C Nicholas Thompson wrote:
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In reply to this post by Roger Critchlow-2
Sorry, everybody. What I meant to write was, "Wait a blithering moment!!!", suggesting, at least, that the metaphor between bunching up cyclists and bunching up windturbines was backwards. Don't you WANT your turbines to "feel" the "headwind"?
Of course I am wrong about this, but I sure would like to understand why.
Nick
Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([hidden email])
http://www.cusf.org [City University of Santa Fe]
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It looks to me the article addresses this.
When windmills are in a conventional "face to the wind" position, they do need
to be well spread out in order to catch as much wind as possible. But if
you rotate the position 90 of the fans degrees so that they are spinning
"sideways", they spin with greater efficiency when lined up behind each
other in zones of lower air resistance. The article appears to
refer to this fan position as a "vertical" rotation. The photo shows
"vertically" rotating tube like structures, which are much like long fans turned
on their sides. Aligning them in fish school formation evidently is the
most efficient in terms of space and maximal wattage generation. That's
how it all appears to me in any event.
Hugh Trenchard
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In reply to this post by Nick Thompson
Speculation:
It seemed to me that, based on the picture, they are arranging the turbines something like bowling pins. With that, they can funnel the wind between them, as when they spin fast enough they start to act, in some ways, like solid cylinders. Now, its not quite that straight, because the fans make the wind come out at an angle (which is why you alternate the direction of rotation). Of course, the bowling pin metaphor works for me, but I'm not sure what any of that has to do with schooling fish, the latter analogy is equally puzzling to me. My only guess, perhaps, that the schooling fish want the water to be moving really fast right next to them, but not at all directly as a headwind. So, if you can get the wind to hit one side of the fan pretty hard, but the direct head of the fan not at all, you get an increase in turbine speed?!? Eric On Wed, Nov 25, 2009 12:45 AM, "Nicholas Thompson" <[hidden email]> wrote: Eric Charles Professional Student and Assistant Professor of Psychology Penn State University Altoona, PA 16601 ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
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In reply to this post by Hugh Trenchard
...that should read "rotate the position of the
fans 90 degrees" (it was late and I should have been in bed).
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In reply to this post by Roger Critchlow-2
Hugh,
Thanks for explaining this to me. I figured it was something like that.
But the logic IS backwards with respect to the bike racer model. The Bike racer pod is trying to protect the lead racer from wind resistance, the wind mills are trying to pass that resistance through to ever member of the pod.
We could shrink-wrap the bike-pod, and it would do its job even better. Not so the windmill pod.
Right?
N
Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([hidden email])
http://www.cusf.org [City University of Santa Fe]
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No, the pelaton uses the lead rider to break a bow wave through the air, but the eddies from each rider's passage also curl around to give some lift to the subsequent riders in the pelaton. If you smoothed it out into one long cylinder, it wouldn't work as well.
The vertical wind turbines work as a flock because they induce a sort of do-si-do of the wind through the flock, where each rank of turbines is positioned to catch the eddy from the preceding rank and throw it back to the next rank. Because the wind takes a longer than straight path through the flock, it has to move faster than the unimpeded wind. If you just set up a stonehenge in the same arrangement as the flock of turbines, you'd get the same sort of velocity effect.
Having the flock adjust its geometry could be a big win. A fixed installation would be tuned to the most likely wind speed and direction. -- rec --
On Wed, Nov 25, 2009 at 9:58 AM, Nicholas Thompson <[hidden email]> wrote:
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In reply to this post by Roger Critchlow-2
Cyclists want lift??!! How do they maintain contact with the road?
N
Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology,
Clark University ([hidden email])
http://www.cusf.org [City University of Santa Fe]
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Sorry for the confusion. it's sailor talk, a "lift" is an impulse in the direction you're trying to go.
-- rec --
On Wed, Nov 25, 2009 at 10:43 AM, Nicholas Thompson <[hidden email]> wrote:
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In reply to this post by Roger Critchlow-2
As others have already said, this is about Vertical Axis Wind Turbines
(VAWT) rather than Horizontal Axis Wind Turbines (HAWT) like you see in eastern New Mexico and west Texas. The article is incorrect about VAWTs being a new idea - Sandia developed the idea in the '70s and you can see one of our surplused prototypes out at Clines Corner. VAWTs have three advantages - they are agnostic with respect to wind direction, the machinery is less complex as the turbine is at the bottom and there's no need for the machinery and complexity of the rotating head, and they can operate over a greater spread of windspeeds (HAWT are limited by the blade tip speed - if it exceeds the speed of sound they will break up). The reason HAWT have succeeded in the marketplace is that the blades can be lifted up into the best wind area - the Sandia egg-beater VAWTs are closer to the ground. The turbines in the article look like they beat that limitation by spinning around a tall mast. If I understand the article correctly, the concept of fish schooling formation undoes one of the benefits of VAWT - being agnostic with respect to wind direction. Ray Parks [hidden email] Consilient Heuristician Voice: 505-844-4024 ATA Department Mobile: 505-238-9359 http://www.sandia.gov/scada Fax: 505-844-9641 http://www.sandia.gov/idart Pager:505-951-6084 Roger Critchlow wrote: > Same power production as existing wind farms in 100th the land area. > > http://sciencenow.sciencemag.org/cgi/content/full/2009/1124/1 > > -- rec -- > ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
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In reply to this post by Hugh Trenchard
I've always wondered how sophisticated the algorithms for arranging
windmills might be.
A 0th-order one would seem to be to estimate the region where one windmill disturbs the airflow and avoid placing another in it. Another involves deferring to the topography (Tohachapi pass for example) and maximizing the ground-effects of air flowing over ridges, etc. It would seem that the problem should bend fairly well to computer simulation. My mother-in-law just signed over her 640 acre chunk of Northern Iowa, currently under cultivation for Soy, to be used for wind-farming (as well). There is not a place I know more flat than this land... I assume a large grid of windmills will sweep over the landscape with her 640 acres a tiny spot within the larger grid. Each windmill would seem to create a rough "cone" of disturbance leeward. That "cone" would probably consist of multiple scales of compression waves... it would seem that the natural period of the larger waves would be primarily a function of wind-speed while the structure of the turbine blades (blade pitch, width, length, cross-section) and the amount of resistance the blades(drag, bearing resistance, generator back-force, etc.) would inform the other structures. A simple euclidean grid would seem to be less than optimal, with a hexagonal grid (intuitively) seeming closest to optimal. One might imagine that freeing some assumed constraints might offer more opportunities for "tuning" such an array. Deliberately canting (in yaw) some of the mills relative to the wind might reduce their own effeciency to the gain of others "downwind" as might deliberately detuning the "pitch" (dynamically or statically.. at time of install/manufacture). Similarly, the height and pitch of the mill heads might be varied slightly over the array. One would expect some low order "standing waves" behind a single mill. Interesting (but distracting) question... How to tune a flock of windmills (statically, dynamically, ???). For many reasons, I expect wind "mills" to be replaced by something more like giant Cilia someday... maybe just for this very reason... that it should be easier to "tune" an array of such things than a bunch of "fans". Cilia-like energy extracting elements would seem suitable for hydro-power as well. You can tell I still love the "idea of" macro-engineering projects... but I'm pretty sure they are intrinsically bad for the health of the planet/humanity. - Steve
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Roger Critchlow wrote:
> if you had a flock of egg-beater generators on a piece of Iowa > farmland, could you run them as mixers and give a tornado a leg up > over the next town down wind? Why should Iowa have all the fun? Howzabout making waterspouts with flocking tidal turbines? :-) ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
Re: flocking windmills - bike race model
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In reply to this post by Nick Thompson
My understanding of drafting in the peloton is that
there is a low pressure area induced behind riders, meaning there is less air
resistance to the riders following, and hence less energy is expended by
riders following in low pressure areas (1,2). It's not lift, like it is in the bird vee formation (as Peter Lissaman
points out). There has been some suggestion that the lead rider also
benefits by a "nudge" from the rider behind who fills the low pressure
zone (3), but this is disputed (4). So energy savings in pelotons is not
strictly due to eddies either.
Efficiencies in bicycle
racing (ie. increasing speed for least possible power output) increase
as the peloton becomes denser, because greater energy
savings occur the closer a cyclist behind can get to the wheel in
front (1,2,4). This must be balanced against the increased risk for
collision cyclists undergo as peloton density
increases. The notion of a "shrink-wrapped" peloton well
describes the correlation between optimal peloton speed and density, and
seems to me a better description than the eddie model Roger C is
describing.
The staggering of cyclists in a peloton is due to
its dynamical nature and the necessity for cyclists to avoid collision, and not
because it is the theoretical absolute optimal energy savings
formation. That is to say that the maximum drafting benefit is directly
behind others (excluding cross-winds for the moment) (1,4), which does
not practically occur in a peloton (except in what I call a "stretched"
phase, which I won't get into here). Rather, a
dynamical arrowhead, rounded, or rotational effect to the peloton
occurs at a certain power output threshold (which is within a narrow
range for all riders) as riders rotate through positions at the front,
each seeking to save energy by drafting; optimal collective output occurs
during this phase (based on personal observation and analysis).
I don't profess a good understanding of the eddy
principles that Roger is describing in the windmill formation, but as I gather
them, the principles he describes do not seem to closely describe the
peloton formation, as you've pointed out. Also, unlike the static windmill
formation, the peloton is a dynamical system, and so its collective
output optimization also depends on the movements of the agents within
the system as they respond to each other and environmental
parameters. So, in that respect, the article may be a bit loose in
referring to the peloton as an analog.
However, it seems to me the main idea is that
there is overall energy saved by a particular collective formation.
Whether it's drafting or by creating eddies or by lift, the mechanism may
be different, but these principles of energy savings allow for generalized
flocking phenomena to occur in natural systems, which is, in general principle,
what the windmill engineers are exploiting.
Refs
1. Kyle C. 1979 "Reduction of wind resistance and
power output of racing cyclists and runners travelling in groups" Ergonomics
22: 387-397;
2. McCole et al 1990 "Energy expenditure during
bicycling" Journal of Applied Physiology 68: 748-753
3. Cycling Performance Tips. Excercise
Physiology - Energy Requirements of Bicycling http://www.cptips.com/energy.htm
4. Olds, T. 1998 "The mathematics of breaking
away and chasing in cycling" 77. Eur J App Phiol 492-497
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In reply to this post by Marcus G. Daniels
Well, I better keep my voodoo fluid dynamics speculations to myself in the future.
Here's more information about the reported effect, written by someone who'd seen a vertical axis windmill before.
"The reason, they say, is that the presence of neighbouring turbines concentrates and accelerates the wind."
The reports are all based off an oral presentation made Monday in Minneapolis at the annual meeting of the American Physical Society's Division of Fluid Dynamics.
-- rec --
On Wed, Nov 25, 2009 at 2:32 PM, Marcus G. Daniels <[hidden email]> wrote:
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Roger Critchlow wrote:
> Well, I better keep my voodoo fluid dynamics speculations to myself in > the future. > Nah. The venue for objection was the APS meeting in Minneapolis... ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
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