Venturi wind turbines

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?

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.

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

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.

1. There's not much wind at what looks from the photo to be about 8 meters off the ground. To get decent wind, one needs to be at least

1. Wind energy is proportional to the cube of the wind speed. The claimed 2 mph operating point (0.9 meters/sec) can deliver about 20 watts per square meter. My guess(tm) of the intake aperature is about

1. Hopefully, this horn of plenty has a one way flap valve for each intake. When the wind blows past a cylindrical obstruction, it creates a partial vacuum on the far side of the cylinder. Without the flap valves, the air will go in one intake, and out the others.
2. If this thing worked, I could install a big funnel on the front of my car, plumb a venturi to the aft end of the car, and use the compressed air flow to propel the car forward. Something about conservation of energy.
3. I can't wait to hear how much noise this thing makes. Whenever you change the direction of the wind, there's going to be noise.

See Fig 6 and 7:

I'm not an aero engineer but this looks like pie in the sky claims to me.

1. It appears that the intake area on this is significantly less than that of a propeller style windmill. Therefore it can't extract the same amount of wind energy. No?
2. There will be not insignificant loss of energy due to the aero drag on the walls of the venturi. Compressing the air will also add to the losses.

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

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.

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

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:

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

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.