Windmill question.

[RandomThoughts]

Why don't windmills have canvas funnels in front of them to direct a larger surface area of wind across rotors?

[harmonicon]

1. it doesn't work that way

[RandomThoughts]

4. why?

in fluid dynamics I think decreasing the size of one side of a tube would increase preassure at that point, although it might cause some back preassure. But thinking if used in winds the back preassure would be less then the gain.

[harmonicon]

5. how on earth could it be attached?

The windmill needs to catch the wind, which doesn't always come at the exact same direction.

[RandomThoughts]

7. well

the wind tube could be on an arc attached on the ground that turns with the windmill, or it could be extended outward from the windmill, with a counterbalance on other side.

Either way it would turn with windmill. However, thinking about it, tube would probably make turning tougher since it would create its own lift on inside of tube, more on faster side. just thinking about the why. Probably would be best in mostly stable wind direction areas.

[harmonicon]

10. that's not the only reason that it isn't practical

windmills don't only turn with wind coming straight at them - that's the basic point, and why they work so well. For the funnel to work, the wind has to be going straight into it, and then straight at the turbines.

[RandomThoughts]

11. Well

not straight wind would create lateral stress on funnel supports, but you could either turn the front into the wind, curving the tunnel. This could work for maybe 10 or 20 degrees, or more simply, retract winward side of tunnel a bit to make opening face wind, then the wind would always blow at the most efficiant directly at rotors direction.

You would have lateral stresses, but it would only be open in slower winds, since no gain is needed at +15 m/s

Or make the funnel, and the windmill head with rotors turn on the pole to always face wind. Then use the funnel to do the turning.

[harmonicon]

12. what would make it turn?

The windmill doesn't even have to turn. That's why it works, and why the funnel idea doesn't work.

If you really want to find out, build two models. Get two pinwheels. Blow on one in any direction you'd like. Put a funnel in front of one and blow at it in any direction you'd like, keeping the funnel in the same place, or attaching the funnel to the pinwheel if you want - it doesn't make a difference.

[RandomThoughts]

13. well

If they do not turn,

Then just scroll in one side or other of funnel, to catch a pretty good size arc of wind.

....0.......0
...|.|.....|.|_
../...\....|.....\_
./.....\...|
but the squiggly would be straight.

this would still catch wind from right side.

I think some of them do turn. Read at windpower.org today. I don't know much about windmills, just looked at it. But it speaks aboout yaw control to rotate wind head.

Or just make each side of funnel independant, that moves on arc around windmill. so it would be movable, possibly even redirecting wind at most efficient full face direction of windmill.

[harmonicon]

14. yes, some of them do turn, but that's not the point

what would turn the funnel!?!?!?! What on earth would power that? If you say "wind", I'll scream, because that same wind could be used to turn another turbine.

[RandomThoughts]

16. Ok.

The funnel would turn by wind, but would only turn when the wind direction changed for a set period of time. So in 24 hours, it would only be using wind to turn it a small fraction of production time. The only electric parts of canvas is a cable that moves canvas out or in when turning needed.

[RandomThoughts]

18. We are also talking about efficiency here.

Is it more efficiant to turn an entire other turban, or turn a funnel a few times a day, and because of that funnel get an increase in wind speed on one turban


2 turbans with two maintenance, and the power cost of the inertia of two sets of rotors. 200% power

versus

1 turban, and 1 funnel, that gets maybe 125% to 150% (guess, dependant on wind variation at location)

The real flaw is that it would only be of value when wind below 15 m/s So its use would be to be able to build same size Windmill in lower wind area, or to build windmill with smaller rotor which would be more efficiant.

It all depends on.

Is cost and maitenance of funnel less or more, then gains in power output of windmill. And more efficiant then adding another windmill.

[Rabrrrrrr]

2. What do you mean?

How would the funnels be placed, and where?

And how would a funnel direct a larger surface area, unless the wind went into the small end and out the big end, but then it would lose so much velocity it wouldn't freaking matter.

????

[RandomThoughts]

3. was thinking of it this way

well instead of making rotors bigger, just suspend a funnel with a big opening further away from rotors, and a small end near rotors.

since sides of canvas are smooth, their would only a little turblence, but an increase of windspeed at small end pointing at rotors?


if the amount of wind that hits the windmill is lets say 100 feet diamiter, and the front of canvas had 400 feet diamiter, the wind speed would increase when it reached the smaller end of funnel, and then the windmill.

[Rabrrrrrr]

6. One gigantic funnel with a small end big enough to cover all the rotors?

That is, if the "wingspan" of the windmill is 100 feet, then the small end of the funnel is 100 feet diameter as well? (or, let's say, 105 feet in diameter, just to be sure of coverage)?

And so the axis of the funnel is perpendicular to the plane of the rotors?

Is this what you mean?

Seriously, if you are going to ask complex questions like this, you need to add much more detail so that the people trying to answer you don't have to do all the work of also trying to figure out what your actual question is.

Anyway, it's not a workable idea, because it only works when the wind is coming in directly through the funnel or within about, say, 20-30 degrees of it. So you still have 330 or so wasted degrees of potential air movement.

You also have the material for the gigantic frakking funnel, and all the heavy framework necessary to keep it from blowing down or collapsing within itself because it will be collecting massive amounts of air volume, and setting incredible pressure differentials between the inside and outside of the funnel.

Probably cheaper and more efficient to just put up two or three windmills.

[RandomThoughts]

8. yea, probably could have added more.

yes, you got what I was thinking.

well, I was thinking what is more efficiant, canvas with only moving part the closing in high winds, and extra cost of turning. Or an entire new set of rotors, with the extra drag of the weight of two sets of rotors.

And most importantly, it could be extended only during that high extra gain period from 2 to 10 m/s wind speed. It could be like ship sails, so relatively light weight, and on shower curtain like rings and just rolled in and out with cable to turn the whole windmill when needed. Retract one side or the other to get the turning of entire contraption, then lock and reextend.

[RandomThoughts]

9. It would look like a light house.

but imagine the light beam as the funnel(but fatter), and the turning only done when wind changes direction. And the light house light lens would be the rotors (but bigger).

[RandomThoughts]

15. k/r

[mainegreen]

17. Because it's cheaper to place a second windmill.

Trust me, I'm Dutch.

[RandomThoughts]

19. Well thats possible.

I think the real bad part is it would take up more space, and cover more area. So would not be real appreciated since it would block views, in areas people live.

[billyskank]

20. Because it would be fucking huge?

[RandomThoughts]

21. Yup

Wouldn't have to be huge, but the bigger the funnel, the more it would increase speed. But it would work in non residentials.

Figure it would be the radius of the rotors X 2 in diamiter at end of funnel. And maybe Radius x 3 outward from rotors. But if you were building it at sea in less populated areas, might be worth it.

http://www.fredolsen-renewables.com/?aid=9045949

Make these twice as high, and you could slap a funnel on those bad boys, and see what happens.

:)

[pokerfan]

22. You mean like this?

http://www.freepatentsonline.com/y2007/0001465.html

[RandomThoughts]

23. yea! Like that!

See I was wondering why it was not being done.


:rofl:

I didn't get idea from there. But yup just like that.

[pokerfan]

25. It's been a while since I've studied fluids

and even that was just part of a senior level heat transfer course. My guess is probably cost. It's just easier to make ginormous, lightweight blades and locate the windmills where nature provides a natural venturi effect, like a ridge top. And as already pointed out, the entire structure must rotate.

[RandomThoughts]

27. I actually would guess that is the why,

plus the eye sore, and how the more complicated, you add cost.

As far as rotating, that would be easy, the sides of the funnel could even be used to do the rotating. Since unless wind is actually outside of either flank, just unlocking would move one side while other side is unextended, and other side could be cabled to proper or wanted angle, then lock and re extend.

In case where both sides are outside of rotation, withdraw both flanks, and let small trailing tail move it.


Or better yet, Have the whole thing be an X with the tower in the center. Then if you need to do a more then 90% wind change, just pull the sail across the tower center access to the other side.
Hmm that might not work, since head would then be backwards. LOL
But there could be a back vine just for adjustments. So it would be a Y not an X (from top view)

Although the shower curtain attachments would have to be replaced with more ski lift type ones :rofl:

[RandomThoughts]

24. His patent is for fixed directional windmills.

It does not seem to have the added, nifty little cables to draw in and out, for high winds and yaw adjustments. Does not have mounting on circular platform at base of windmill, or on arc on ground. Nor does it even mention the use of different extended sizes to catch wind at different angles.

That really seems a bit vague.

[pokerfan]

26. That eliminates the need for rotation

There's some discussion here:

http://www.whynot.net/ideas/4044

[RandomThoughts]

28. yup, but to salvage idea

Nobody there adressed the use of the funnel to actually rotate itself and protect it from high winds.

So I still got some uniqueness. thanks for link.

[RandomThoughts]

29. Windmill Drawings

I posted some drawings to explain idea, its fun to think, so any comments are welcome

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x178276

[crimsonblue]

30. because it would be ridiculously cumbersome,

impractical, and not effective. Windmills can actually rotate to best catch the wind. There's no need for a funnel. Plus, a funnel may make the air flow turbulent, diminishing the efficiency of the windmill.

[RandomThoughts]

32. Thanks for comment.

You are right on turbulence, but I think that would only occur for windmills further back in wind farm. So spacing might need to increased, or heights varied. And if used in offshore deep sea usage, spacing is fairly irrelevant. Lots of ocean space.

But as a stand alone, the airflow within the funnel itself, should be non turbulant, since there would not be any rough obstruction.

Funnel would not add rotation capability, vains been used for years for that, but the idea would not be dissalowed by lack of rotation capabiity. The funnel is only usefull if it rotates also, and its greater mass would require a larger surface to facilitate rotation. So added that canvas vain to compensate for the greater turning difficulty of the contraption.

[crimsonblue]

35. okay, I get what you're saying

Some windfarms on the front range use natural valleys to direct air to their farms. It would be feasable, but only in places with a steady wind direction. A place like Kansas, where the wind can change direction every day, this wouldn't be feasable. But then again, in most of the wind farms in western kansas, they are running near full speed most of the year.

[Jamastiene]

31. This probably belongs in the Science Forum, but I'm really glad

you posted it here. I wish more people would have discussions like this. I learn a lot. :)

[RandomThoughts]

33. I posted it over in energy.

Did some sketches to better explain the thought.

the link is a couple posts up. Or here :)
http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x178276

Posted it in Lounge, cause it was at first more of just a thought, still don't know if it is ridiculous, or actually has some limited application.

And because lots of people in lounge :)

[Jamastiene]

34. Yes. Actually, that is a smart idea.

I don't think people venture out of the "Big 5" quite enough to see something like this. I'm sure the idea has some useful application. It is good to know you are thinking. :thumbsup: