windmill additions

[moonhill]

http://www.alternative-energy-news.info/windcube-generates-electricity-in-moderate-wind/

Here is a link to a modified windmill, kind of like the fan shroud on the car, the car will over heat if it does not have the shroud in place.  It produces 8 times the power of a mill with out the shroud and in less wind.



Tim

[OneWithWood]

Interesting.

Any idea of cost to install one, say on a tower?

[moonhill]

OWW, I don't know the price of this unit.  From the responses below the article it sound very expensive.  From reading the responses it is questionable if the shroud is capable of producing what the designers have suggested it is capable of. 

Tim

[DanG]

That was an interesting read, particularly in the discussion that ensued.  Some really bright people joined in.  There was even a guy that mentioned building a sawmill! ;D  I'll be contacting him about visiting with us here.

I was a little bumfuzzled as to how the Bernoulli Principle was going to help increase airflow on that thing, at first.  After a brief period of cogitation, I concluded that they must be using the decreased pressure in the throat of the shroud to draw in additional air from some side ducts, essentially "making" wind from static air.  Interesting concept! :P

[Ianab]

What the bernouili primnciple says if that if the fluid is forced through a smaller diameter, it has to go faster.

Faster is better for windmills. So if you have a 10mph wind, thats pretty useless for a windmill, but with a shroud you might get 20mph at the blades, and much more power.

Another way of looking at it is you have effectivly increased the area of wind you are capturing without increasing the size of the blades. If the shroud blocks 3 times the volume of air, then it's reasonable to assume you might get twice the energy caputured.

Now is the cost more efficient that just making a bigger windmill? Dont know. But in an urban setting, a small square box on top of a building is probably preferable to a big whirling open blade machine?

Ian

[DanG]

The Bernoulli Principle stipulates that a fluid, in this case air, accelerates as it travels through a confined space, but what it states is that the pressure decreases as the air accelerates.  A pitot tube is a perfect and practical example of an internal Bernoulli device, and that is exactly what the wind cube is, as far as my limited understanding of the cube allows me to speculate.  As the tube within the cube narrows, the pressure is greatly reduced, which causes the side ducts to introduce more air into the tube, thereby increasing the volume of air at the exhaust end of the tube, where the turbine is.

Did you ever see one of those little compressed air vacuum pumps that they use to evacuate the air from an A/C system?  It is the same principle.  The highly acclerated air from the high pressure hose causes such an incredible lack of air pressure within the tube that almost all of the air from the side port is sucked into the windstream, leaving an almost complete vacuum in the space connected to the side port.  In that case, the purpose is to get rid of the air in the side port's limited source space, by exhausting it into the unlimited space beyond.  In the case of the cube, they are using the same principle to draw air from an unlimited space in order to force it into a limited space, which is the chamber in front of the turbine.

[moonhill]

DanG, is that the same principle for a leaky house?  The wind blowing form the north is not leaking in from the north side, but it creates a vacuum on the south side and pulls internal air out through the south side of the house, causing drafts.  The shroud creates a vacuum on the back side of the rig?   

Tim 

[DanG]

Yes, that would be the same principle, but it wouldn't only effect the south, or leeward side of the house.  As the air streams past the east and west sides, it creates a difference in pressure, relative to the pressure inside the house, and pulls that nice heated air out through any leak there is.  That, along with the airfoil or airplane wing are examples of external Bernoulli devices.

One thing that has me scratching my noggin is the question of just where this side source of air should be.  My thinking is that all of the air around the cube is going to be at reduced pressure already, because of the very wind they are trying to harness.  That is why, or at least one of the reasons they recommend placing a windmill away from other structures.  It looks to me like that cube would work a lot better if it were placed on a hollow enclosed tower, where you would use the tower as the duct, and pull the relatively high pressure air from ground level.

[moonhill]

I think they have done such a thing, down under somewhere.  A tall stack with a turbine near the top, surrounding the base is a green house of some kind, creating hot air which rises up the stack turning the turbine.   Maybe someone will enlighten. 

Tim

[SPIKER]

I think they have done such a thing, down under somewhere.  A tall stack with a turbine near the top, surrounding the base is a green house of some kind, creating hot air which rises up the stack turning the turbine.   Maybe someone will enlighten. 

Tim

there is one in-use down under now I think and a very large one in the planning stages.  it uses a vertical shaft with the fan/wind mill at the top so air rushing UP the shaft/pipe/tower.   the surrounding area is covered with clear tarp/glass and starts out lower to the ground at the edge.   as it goes in towards the tower it gets higher off the ground to create a natural draft.   the sun heats the dirt/ground and the natural draft pulls the hot air towards the center of the tower and up the tower.   there it hits the turbine and spins it.   

the NEW big one is planned to have multiple turbines all mounted on the ground like spokes of a wheel, for ease of maintenance all will have louvers so one turbine can be isolated.  then repair work can be done or to combine the heat/air flow down to smaller number of generators if there is not enough sunlight that day.   same principal as the fan shroud with the louvers to block the fan blades so no air moves, hence the generator does not turn...   very neat idea but takes  LOT of surface area and requires a very large tower/smoke stack/chimneys to make it work.

Mark

[metalspinner]

It seems to me they are missing out on an even more efficient system. Assuming the one they have works as described.  After the air has been accelerated through the initial fan, a second  stage fan should be set up behind the first to capture the accelerated air.  Then a third fan, etc. 

Set up in a series like this, they may have hurricane force winds shooting out the back unit.

[Ianab]

Umm.. not quite.  :P

The shroud speeds up the air, the turbine blades in the middle slow it down again. On average the air will be slowed down by the whole unit, thats where the energy comes from.

If you want to see the effect in action, stand on the street between two tall buildings on a windy day. The buildings partially block the wind just like the shroud does, and the wind is funnelled into the space between them.

So people walking on the street get blown over, even though the general wind speed in the area isn't that high.

Interestingly enough the big wind farm here in NZ is build in a natural pass in a range of hills. Taller hills on each side of the wind farm area channel the prevailing winds into the gap and increase the wind flow in that area.

Ian

[metalspinner]

 smiley_dizzy smiley_dizzy

Now I know why I hung out in the music building during college. :

So is the density of the air what we are talking about?  Like a bottle neck in a traffic situation?

[maple flats]

That looks like a project asking to be rednecked. I like the idea and think I will try something along that design in the future, scaled down of course.

[routestep]

I don't think any static air is allowed in from the sides. That would slow down the flow velocity at the throat where the spinning blades are located. Probable would introduce a lot of turbulence to the blades which might then start to flutter. The shroud is the front half of a venturi accelerating the flow. It also presents quit a large frontal area to the airstream (wind). The animation looks like it is on a turntable maybe to keep a strong wind from knocking it flat. Just turn it out of the wind.