Now here's something you don't see every day.
- posted
11 years ago
Now here's something you don't see every day.
I can see that taking off ! ( but not in a bad way :) )
It's freaking genius. I can see the EPA maybe requiring a 2-inch-square mesh to prevent hummingbirds from being caught in the draft, but... wow. Wow. And wow. US$0.02/kw-hr, huh.
Looks expensive. And it will blow away in a good thunderstorm.
Does that actually work, necking down a pipe to increase air velocity?
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
It does, but total air flow Q = velocity * cross-sectional area, similar I guess to how total power = voltage * current.
And, yeah, the cross sectional area at the generator is quite a bit smaller than at the intake.
Sure looks interesting though.
It's a clever idea if it works. It'll probably be easier to make the upper works stout when there's no moving parts -- that might offset the extra cost of making them so _big_. Having the moving parts at ground level means that your maintenance guys are exposed to a lot less risk, too.
Time will tell. It'll probably garner some gov'mint money, no matter what.
-- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
om&YM_MID=1375571&sfvc4enews=42
lar
I can see it being less noisy and not so many complaints from neighbors that don't like their house and garden turned in to a blinking disco when the sun is low
-Lasse
r I guess to how total power = voltage * current.
er than at the intake.
Ah, extractable power is more like 1/2 * (density of air) * (cross-sectiona l area) * (velocity^3).
I vaguely remember power is proportional to the cube of the velocity, and t here are some really nasty equations we had to use/derive back in fluid mec hanics classes, but this is a good distillation of the relevant equations ( and quite elegant, I must add). No macroscopic mechanical energy balances required, haha.
Michael
Neato, and as obvious as hindsight makes it look, it's about time!
Seems to me it would suck rather than blow. If you do the old blow-across-the-open-end-of-a-pipe trick, you get lift from the Bernoulli effect. Specifically, the difference in wind velocity between ground level (especially if you hide the intake within a dense forest or something like that) and altitude causes a pressure difference
I suppose the catcher part is baffled and, perhaps, equipped with throttle plates to shut off the non-windward sides, so only ram air travels through. A passive structure would be possible with lightly sprung check valves (air pressure might also provide the action), or perhaps simply taking advantage of fluid flow (Coanda effect). If this is the case, it leaves much of the head underutilized. I expect further improvements are possible, and in development.
Tim
-- Deep Friar: a very philosophical monk. Website: http://seventransistorlabs.com wrote in message news:0d341c3d-b898-4e92-bb6a-2ae660938b8e@googlegroups.com... > Now here's something you don't see every day. > > http://machinedesign.com/article/no-more-windmills-wind-catchers-use-venturi-technique-to-generate-power-0222?NL=EET-01&Issue=EET-01_20130225_EET-01_543&YM_RID=mrdarrett@gmail.com&YM_MID=1375571&sfvc4enews=42
The website looks interesting, but it looks like they won't have product shipped until later this year...
Minnesota... that's pretty close to you, Tim, right?
Michael
No test results, simulations, numbers, or calculations to be found anywhere. Hmmmm...
A few problems.
See Fig 6 and 7:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I'm not an aero engineer but this looks like pie in the sky claims to me.
There do appear to be some benefits, but efficiency isn't one of them. Art
In a relative sense, yes. Digikey (Thief River Falls) ships practically next day. But it's also a six hour drive.
For being mostly flat and midwestern, WI gets enough wind that they've installed some turbines in various areas. As I recall there's a few around the capitol.
Tim
-- Deep Friar: a very philosophical monk. Website: http://seventransistorlabs.com
On a sunny day (Mon, 25 Feb 2013 14:00:28 -0800 (PST)) it happened snipped-for-privacy@gmail.com wrote in :
Bit of a storm and that whole thing will blow away. Windmil poles do not catch much wind, and the propellor blades can be put in neutral position.
The energy of the wind is directly proportional to the air density and cross section area and relative to the third power of wind speed.
The cross section area can be the area covered by a conventional horizontal axis wind turbine or the area covered by some vertical construction or even the classical Savonius design.
If the structure shown in the picture is 30 m high and maybe 10 m wide, the cross section area is only 900 m², why would anyone expect it to generate 1.8 MW ? In a lossless system, that would require at least 18 m/s wind, which is rare at 30 m above ground in most parts of the world. The situation might be realistic a few hundred meters above ground.
The basic flaw in arguing that a small structure would concentrate the air into the turbine. The air is not "so stupid" that it would go through the turbine, while it can more easily go around the structure:-).
The situation is different, when the structure is kilometers wide and/or hundreds of meters tall, e.g. a valley between two mountains or when the air flow above a high hill, in which case the speed of air is increased (compare this to the faster air flow above the wing of an airplane).
Right. The necking down will increase velocity, but also make back pressure that will reduce the intake volume.
Seems silly.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Hey Jeff, it does say they tested a 0.3 watt unit. :-)
"The first small scale field unit, rated 300 mW was designed and constructed last year and validated the CFD models predictions. A larger scale field demo unit rated 1.5 kW to 5 kW also went live last year. "
I wonder if the pictures shown are the 1.5 kW unit mentioned above.
Mikek
Well there you go. Obozo will fund it if they kick some of the money back.
Milliwatts, Megawatts... what's a few zeros worth these days?
Let's do the math. The question is 1.5 KW at what wind speed? My guess(tm) is that the aperture size is 3 x 3 meters or 9 square meters. Ignoring all losses and inefficiencies, in order to produce
1.5 KW, one needs a wind speed of approx: Watts/sq-meter = 0.6 * (meters/sec)^3 (meters/sec)^3 = (1500 / 9 / 0.6)^0.333 = 6.5 meters/sec wind (15 mph) at about 8 meters altitude. That's possible, but not easy at such a low intake altitude, I doubt that there would be too many places where such a minimum wind speed could be sustained 24x7x365. Perhaps a few days per year on some mountain top (conveniently lacking trees) might work. Ignoring losses is also a bad idea as I suspect the backpressure from using wind as an air compressor is substantial.Average wind speed for various US airports. Airports usually don't have trees obstructing the approach. The anemometer is usually on the control tower roof, which might be a bit higher than the Sheerwind thing, but close enough:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I'd ask 'em the same thing I'd ask Rossi, "why is it so difficult to prove it?"
Build a uni-directional one out of plywood. Bolt it to a flatbed truck, or on top of a bus. Drive it down the road. Measure volume/pressure with speed as a parameter. If you like the numbers, stick a generator in it. Then go solve all those pesky issues with omnidirectional behavior.
If you can't make it work on a truck driving down the road at
2 or 20 or 60 MPH, there's no need to pursue it further.That'd be far more useful than a 300mW prototype. And you could work on it where there's no wind. And it'd cost far less and take less time than setting up their website. But it'd garner fewer greedy/uninformed investors.
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