>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 08 November 2005 17:53
>To: Microcontroller discussion list - Public.
>Subject: RE: [OT] Savonious turbines
>
>
>> I believe the anemometers we built for weather spotters 25 years ago
>would
>> be an example. Back in those days L'eggs Panty hose came in an egg
>shaped
>> container that provided the wind catchers!
>> Cheap Radio Shack DC motors were the generator part.
>
>It's a form of S-rotor.   They are used for that because of their
>minimal tendency to overspin when the wind drops off. Which is 
>part and parcel of being inefficient.  Remember when you see 
>one spinning, that the act of spinning is expending all the 
>energy it's extracting from the wind.

You can extract energy from them, though they are quite inefficient. Googling for "savonius efficiency" (note spelling!) shows a few small DIY designs that have managed to get usefull amounts of power e.g. a 3' diamater x 4' tall rotor delivering 52 Watts at 12.5mph wind speed:

http://www.windstuffnow.com/main/vawt.htm

Regards

Mike

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