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PICList Thread
'[OT] Savonious turbines'
2005\11\08@115842 by Alex Harford

face picon face
Like the wikipedia article says, you may see these being used to
create a 2-frame animation in front of stores:

http://en.wikipedia.org/wiki/Savonious_wind_turbine

http://www.picoturbine.com/projectlist.htm

I wonder what the efficiencies are like, does anyone have experience
with these for power generation?

Alex

2005\11\08@123254 by John Ferrell

face picon face
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.

John Ferrell
http://DixieNC.US

{Original Message removed}

2005\11\08@123442 by David Van Horn

picon face
> I wonder what the efficiencies are like, does anyone have experience
> with these for power generation?

Low.. They are cheap to fab, but on the large scale, impractical.




2005\11\08@123633 by D. Daniel McGlothin

flavicon
face


> I wonder what the efficiencies are like, does anyone have experience
> with these for power generation?

I first ran across S-rotors in Mother Earth News.  Here are a couple of old
articles (might have to scroll down several pages to get to the text).  The
second is a sort of analysis of the construction discussed in the first.

www.motherearthnews.com/Alternative_Energy/1974_March_April/The_Savon
ius_Super_Rotor

www.motherearthnews.com/library/1974_July_August/More_On_The_Savonius
_Super_Rotor

I'm sure that there are more recent analyses.

Daniel

2005\11\08@124546 by David Van Horn

picon face
> 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.





2005\11\08@130109 by Bob Axtell

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David Van Horn wrote:

>>I wonder what the efficiencies are like, does anyone have experience
>>with these for power generation?
>>    
>>
>
>Low.. They are cheap to fab, but on the large scale, impractical.
>
>
>
>
>  
>
Agreed. Wind turbines work best when 100 feet or more above ground, and the
Savonius Rotor is very hard to get that high, because of the weight. I
did see a
pleasure boat driven by a Savonius Rotor/Main Mast, it was in an old copy of
Popular Mechanics, that's the only commercial application I am aware of.

I have seen a few made from cut & welded 50 gallon drums, and they do
generate
some power, but the weight is enormous.

My interest right now is solar power; we have so much sun here in So
Arizona that
we don't even need Daylight Savings Time (don't need to save any). Build
a nuclear
power plant, then throw out the nuclear part, and concentrate the sun
onto the
boiler. Can't imagine why it isn't being done already, acres of sunlight
gone to waste.
Too easy, I guess, no place to employ out-of-work nuclear bomb
engineers, I guess.

--Bob

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2005\11\08@134635 by Wouter van Ooijen

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>>I wonder what the efficiencies are like, does anyone have experience
>>with these for power generation?
>Low.. They are cheap to fab, but on the large scale, impractical.

For a more efficient type check its cousin, the Darius rotor.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu



2005\11\08@141920 by David Van Horn

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> For a more efficient type check its cousin, the Darius rotor.

A much prettier cousin, although she needs some help getting started,
she does put out well.



2005\11\09@055316 by Michael Rigby-Jones

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>-----Original Message-----
>From: .....piclist-bouncesKILLspamspam@spam@mit.edu [piclist-bouncesspamKILLspammit.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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2005\11\09@062229 by Wouter van Ooijen

face picon face
> 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

That does not look like a real Savionius (drag-type) rotor to me, more
like a Darius (lift-type)!

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


2005\11\09@063722 by Michael Rigby-Jones

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>-----Original Message-----
>From: .....piclist-bouncesKILLspamspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTspamTakeThisOuTmit.edu]
>Sent: 09 November 2005 11:23
>To: 'Microcontroller discussion list - Public.'
>Subject: RE: [OT] Savonious turbines
>
>
>> 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
>
>That does not look like a real Savionius (drag-type) rotor to
>me, more like a Darius (lift-type)!

I'm pretty sure it's still a drag type design, just more efficient than the classical S shaped rotor.  A first glance tt looks as like the design uses aerofoil shaped blades; however in reality they are just a modified cup shape to provide a better forward/back drag ratio (for want of a better description).

Regards

Mike

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2005\11\09@080131 by Wouter van Ooijen

face picon face
> I'm pretty sure it's still a drag type design, just more
> efficient than the classical S shaped rotor.  A first glance
> tt looks as like the design uses aerofoil shaped blades;
> however in reality they are just a modified cup shape to
> provide a better forward/back drag ratio (for want of a
> better description).

I am sure the design was meant to do drag only, but from the shape I
suspect it will actually work (partially) on lift. Conclusive evidence
would be the (unloaded) radial speed: if it is ever higher than the
windspeed it works (at least parially) on lift.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu


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