# Windmill with Funnel/Cone

1. Feb 21, 2012

### Blast12345

[I have been searching for an answer to this puzzling question for the past two hours. (To no avail.) A few search results lead me hear, but nobody had raised the question that is in my mind]

Would building a funnel/cone improve the power output of a given windmill?

Let us say, for example, that we have a windmill with a 3 meter diameter. The windmill would only capture the energy from the wind within the area [approx. 7 square meters] of its rotation (give or take), correct?

So, if you were to build a cone (or a pyramidal funnel) with an area of 28 square meters, wouldn't the energy from the entire area (the 28 square meters) be exerted on the windmill?

(I understand the increase wouldn't be perfect, as there are many variables to consider.)

Also, does the change in angle (thus altering the length) have any effect on the efficiency of the process? (More efficient compression?)

I do apologize if my terminology (and general understanding of fluid dynamics) is not up to snuff. I am only in 12th grade physics - no college craziness :P

2. Feb 22, 2012

### fleebell

Yes, you will get more power but if you make one big enough to justify adding it you lose the ability to turn the wind turbine.

Many ancient cultures used vertical windmills mounted on the ground or hill with a built structure to funnel the wind into them. These areas also tend to have months of wind from the same direction also.

Just look up ancient wind turbines or wind mills and you will get all kinds of examples.

3. Feb 22, 2012

### A.T.

You don't have to build a funnel much larger in area than the turbine. You just need the right shape to increase the pressure difference.

It acts similar to the fan shrouding below, but it's not quite the same thing:

4. Feb 22, 2012

### Blast12345

@Fleebell: Why would I loose the ability to turn the turbine with a large cone?

@A.T.: Thanks for the suggestion :)
Do you happen to know how much more energy a shaped "shroud" will capture in comparison to the cone? [estimate?]

Also, the Dyson fan video is interesting (and I looked up some more information about them online), but what are you specifically suggesting? Are you referring to only its shape, or the way that it functions as well?

5. Feb 22, 2012

### rcgldr

What the large cone effectively does is bring most of the moving wind it captures to a stop, with some of the wind flowing through the turbine and some of the wind flowing around the outer edges of the cone. There's a slight increase in pressure due to ram effect (dynamic pressure) when stopping the wind, but it's not much at normal wind speeds.

I'm thinking that just increasing windmill diameter somewhat will have more benefit than using a large funnel (cone).

6. Feb 22, 2012

### Blast12345

I know, but it just seems too easy

Anyways, thanks for helping me with this idea. Shame it wouldn't work (as well) as I had hoped, however I am not terribly surprised.

7. Feb 23, 2012

### A.T.

No, but you should be able to find data online.
It has a similar shape, but the flow is generated differently of course. The shroud has the profile of a wing, and creates under-pressure on the inside, which sucks more air in.