Whirly windy things!

[archeraddict]

Can any one tell me what the 'round metal things' (about 10 foot high) do, that you see on some verges or near some shops. They look like mini turbines and I have wondered if they generate electricity, but they turn at a steady pace. It's been driving me mad and can't find any one who knows.

[Solarjunkie]

Some form of extractor fan, or air movement?

[Ethel]

Where I live in the Midlands these contraptions safely dispel trapped methane gasses from underground - where old landfill sites have been built on and so on.

You sometimes see flames in back gardens. :)

[sddsddean]

Do you mean the small wind turbines that power road signs in remote areas? There is usually a small solar panel by them as well. These are used on big electronic display signs that say something like 'Slow Down. Junction Ahead' when you approach too fast. Is this the sort of thing?
http://www.surreycc.gov.uk/SCCWebsite/SCCWSIma ges.nsf/WebLookupImageByUNID/docid348BD8314DE6 4C358025726500498966/$FILE/VAS+Power+Supply.jp g

[archeraddict]

Thanks, but no, that's not them. They sit on top of a post and look as if they are circular, with individual metal sheets that all meet in the middle and rotate horizontaly. A bit like a globe cut in half, with the flat bit on the pole. Wish I could explain myself better! I see lots of them around on the side of roads and near shops that are out of town, like drive through Macdonalds.

[sddsddean]

Do you mean a cowl like this?
http://www.stovesonline.co.uk/Flue/img/rotorve nt.jpg
They are quite often on old landfill sites to vent the methane build up. I know one of our local McD's in Northampton (along with the whole Sixfields area) is built on an old landfill and there are loads of vents and cowls all over the site.

[archeraddict]

Yes yes yes! Thank you so much. I had pictured it on a non hollow stand, but the top is absolutely right! Thanks to Ethel aswell - you were right.
I can now sleep at night with my new found knowledge!