Urban turbine with concentrators

[jamesjones]

I had an idea a while back to increase the power output of small scale HAWTs that are mounted on houses. Build a metal funnel on the side of the house (or two, one for each side of the HAWT) that focus the wind onto the HAWT and increase the speed.

Would this be the same as having a HAWT the same size as the large end of the funnel?

I have a simple garden windmill mounted on a pole by the side of my house, and this turns almost all the time (about 7 feet off the ground). I realise that mounting the HAWT inside a funnel means that it won't receive wind from all directions, but then, if it's in the middle of a 30 feet long wall, there isn't going to be much wind blowing directly onto the wall (if you choose the right side of your house!), and winds that are, say, 20 degrees off the side of the wall will still go into the funnel and most of their energy will be preserved until they hit the turbine, (correct me if I'm wrong).

It would also be possible to build houses next to each other with an angle of 10 or 20 degrees, with, say, a 2 feet gap between them at one end, where you put a line of turbines up the wall. The other end might be 30 feet apart, and you would then get very high wind speeds through the narrow gap.

You then have all the benefits of a large turbine (i.e. a 30 foot one) but by using 7 or 8 with a 2 foot diameter.

Small is beautiful, as Schumacher said.

Do any of you know of any research into concentrating devices like this, on HAWTs or VAWTs?

[jamesjones]

I found a bit of research here:

http://www.eru.rl.ac.uk/web.htm

But I'm thinking of a complete funnel, which would also serve to hide most of the view of the turbines from any 'anti wind brigaders' who might not want them in their neighbourhood. I'll try and draw up a simple diagram tonight to illustrate what I'm getting at.

As an alternative, you could mount the turbines at the top of the roof, and have a flat board parallel to the ground, running from about two feet above the roof, straight out. The wind would then hit the roof and be concentrated into the turbines. (I realise the structure would have to be extremely strong to cope with high winds though! All those drag forces, you see...)

[kitno455]

i design racing car bits. one of the things we deal with is air to water heat exchangers (radiators).

it has been shown, in wind tunnels and in actual experience, that you actually want exactly the opposite of what you propose.

because the surface of the exchanger is half metal, and there is lots of drag in each of those little channels for the air, you only need an grille openning that is ~ 1/3 the size of the exchangers core. you need the angle from the openning to the core to open at no greater than 12 to 15 degrees from horizontal, to avoid turbulence in this 'mouth'.

if you try to cure an over-heating condition by openning the mouth into a funnel, or even just make it straight, the air just piles up, and spills out of the front, increasing drag for the whole car, but not doing much for the overheating.

now, yes, the venturies in a carb do accelerate the air, and the effect is certainly used in wind tunnels all the time. but the windmill is trying to slow the air. the booster in the carb, and the object in the wind tunnel generally are not.

allan

[jamesjones]

http://www.bdsp.com/web/pdfs/Project%20WEB%20Summary%20(2002).pdf

More info. here.