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Sandia Savonius design
By RobD, Section Homebrewed Electricity Posted on Tue Apr 20th, 2004 at 12:27:35 PM MST
I built the Sandia Savonius from their patent

Ted (Monte350) directed me to this patent and I built a small prototype that was quite impressive.
I posted this info on another post but somehow it was lost so I'll repost it here with the ratios laid out so some of you can give it a try.

Here are the dimensions for this mill that I made from step flashing that is sold in packages of 100 at my local building supply.

finally here are the Sandia ratios. They claim 37% eff and since this was a gov. project they are probably accurate.

Savonius have some good benefits:
No tail
No furling
No yoke
Easy to make blades
I'm going to make a larger version to see how it does with real power.
RobD

Sandia Savonius design | 16 comments (16 topical, 0 editorial)

Re: Sandia Savonius design (3.00 / 0) (#14)
by pdvjak on Wed Aug 25th, 2004 at 10:06:16 AM MST
(User Info)

Hi;

A few months ago, this post inspired me to also build that design.... my version is from ply and thin fiberglass-sheet... about 2' dimater and 6 ' tall..... All epoxied together on top of a bamboo pole.... spins like a dream with the slightest breezes from any direction.... silent too....

I'll be making the whole thing 'retractable' (for securing during storms) and will couple two of them (at right angles), with a bicycle chain/sprocket, on to one shaft.... to either drive a small alternator (for which I'm looking for a simple, cheap, 'developing world' solution), as 'stand-alone' charging a 12V battery, or as 'assistance' to a PV installation, providing 'some' charging for when the sun's not working.

I'm in Jakarta, Indonesia and looking for ways to turn the tropical sun and winds here into 'usable' sources for lighting and, most of all, refrigeration, especially in remote locations where services and parts are difficult... The idea is to keep the whole thing on the 'bycicle-technology' level so that a local bicycle repair shop can understand and repair and maintain them and parts are always available...

As a Dutchman, have grown up a long time ago cycling into the wind to school, and mostly also into the wind on the way back, I'm inclined to respect both wind-power and bicycle 'technology', plus I note that even Olympic cyclists still use chain/sprocket, so it can't be that 'outdated' a tech for transferring (small) work from one shaft to another (and maybe gearing it)....

Anyway.... Thoughts, ideas, suggestions, experiences, are invited....

Re: Sandia Savonius design (3.00 / 0) (#15)
by chris psmith on Sun Nov 11th, 2007 at 03:13:54 AM MST
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RobD,

Like the design, any recent progress on it? Mulling it over I couldn't help thinking that placing a half round on the front of the trailing edge would give you less drag as it comes round, so a hlaf round from the centre point out to meet up with the outer curve of the blade?

What sort of rpm are you seeing in light winds with this size of rotor? I had in mind a much bigger one but the largest half rounds i can get easy acces to are 116mm diameter gutter, so by the ratios it would have a diameter of about 200mm.

Any thoughts on the optimum height of the rotor with these ratios?

Regards
Chris

Re: Sandia Savonius design (3.00 / 0) (#16)
by chris psmith on Sun Nov 11th, 2007 at 06:36:21 AM MST
(User Info)

RobD,
Like the design, any recent progress on it? Mulling it over I couldn't help thinking that placing a half round on the front of the trailing edge would give you less drag as it comes round, so a hlaf round from the centre point out to meet up with the outer curve of the blade?

Any thoughts on the optimum height of the rotor with these ratios?

Regards
Chris

Re: Sandia Savonius design (none / 0) (#1)
by DanB (danb@*no spam*otherpower.com) on Tue Apr 20th, 2004 at 12:41:35 PM MST
(User Info) http://www.otherpower.com/

Looks neat RobD! It'll be fun to hear some results... I hope you or someone else here builds a larger one and gets some data! 37% efficient would be impressive!

Regarding the benifits... I think tails are fun!
And Im not sure no furling is a benifit - I think perhaps the difficulty in furling/governing these machines is actually one of the problems that needs to be sorted out in a reliable way.

Its fun to see all these homebrew projects/ideas moving foward!!

Re: Sandia Savonius design (none / 0) (#2)
by RobD on Tue Apr 20th, 2004 at 01:03:45 PM MST
(User Info) http://www.dsgnspec.com

Hi Dan,
Yep! tails are fun especially the neat ones you guys make. I never thought about the furling issue on larger machines but I will address it, this was my first real Savonius.
I did stick it out my car window while doing about 50 and it sure zipped along!
By the way this one is going to power my remote anemometer. I have most of the parts and it should transmit over 200' when done. I'll post the circuits. Also I've located some linear hall devices that I hope will make good gauss meters. We'll see.
RobD

Re: Sandia Savonius design (none / 0) (#6)
by Norm (peppysue@suite224.net) on Tue Apr 20th, 2004 at 05:52:29 PM MST
(User Info)

Do you think if you had a couple of these hooked onto a couple of car heater blower motors in an apparent wind speed of about 80mph that they would turn the motors over fast enough to charge 12 volt batteries?
( :>) Norm.
( :>) Norm
[ Parent ]

Re: Sandia Savonius design (none / 0) (#7)
by DanB (danb@*no spam*otherpower.com) on Tue Apr 20th, 2004 at 06:02:04 PM MST
(User Info) http://www.otherpower.com/

I think probably not. I believe car heater motors probably have to get up to over 1000 rpm (or more) to charge 12 volts. Thats one problem with these... they turn so slowly - that you need to build a large, and expensive alternator in order to get much power from the low rpm - or - use belts and gears which have significant losses.

[ Parent ]

Re: Sandia Savonius design (none / 0) (#9)
by RobD on Tue Apr 20th, 2004 at 06:26:40 PM MST
(User Info) http://www.dsgnspec.com

Dan,
This mill runs quite well and I'd estimate the rpms at over 2k in a 30 mph wind although I haven't put a tach on it yet. Power? I'll have to do more tests but this is only about .25 sq.' surface area and I'm seeing reasonable power out. 80 mphs, there's a lot of power in that kind of wind.
I think the slow speeds attached with these machines is in the wide designs. When you start putting two oil drums together things get very slow and heavy. This machine is all alu. and only 5" wide if I can make it strong it should be quite good. I was surprised to see it hold up to 50 mph. I thought it would blow apart with the .010 thick alu. blades. You can't see from the picture but the bottom curved outside edge is bolted to the base while the top edge isn't. The upper edge expands in high winds and maybe this is the answer to the furling problem. When it's done and 'beefed' up I'll run it up to 75 or 80 mph to see if it can take it. I won't worry about any furling if it holds up to, say, about 85 mph wind speed.

[ Parent ]

Re: Sandia Savonius design (none / 0) (#8)
by RobD on Tue Apr 20th, 2004 at 06:04:08 PM MST
(User Info) http://www.dsgnspec.com

Norm,
When I ran the mill outside my car going 50 mph it roared. How much power? Can't tell, depends on your alternators and load but off hand I'd say there's a good chance it would give you what you need. I'd build it down a bit or beef up the blades to take the high wind speed though. Perhaps a bearing on the top plate for further stability. When I started this design I was only looking for 5 volts at 25 ma. to drive my circuit. It will do much better.
RobD

[ Parent ]

Re: Sandia Savonius design (none / 0) (#3)
by monte350c on Tue Apr 20th, 2004 at 01:07:20 PM MST
(User Info)

Hi Rob,

Looks really good! It will be interesting to see the circuit you've worked up for tracking wind speed, and how this little Savonius performs at collecting it. Sometimes I find making a little one is even more challenging than a larger version!

Keep us posted on your findings!

Fun!

Ted.

Re: Sandia Savonius design (none / 0) (#4)
by windstuffnow (elenz(at)windstuffnow(dot)com) on Tue Apr 20th, 2004 at 01:30:43 PM MST
(User Info) http://www.windstuffnow.com/main

Nice job Rob!!! It will be interesting so see some numbers on it. How did they come up with the 37%? dyno?

Looks like your having fun!!!
Windstuff Ed

Have Fun! Windstuff Ed

Re: Sandia Savonius design (none / 0) (#5)
by RobD on Tue Apr 20th, 2004 at 05:47:00 PM MST
(User Info) http://www.dsgnspec.com

I did set it on a ladder in my field to check the charging ability.It charged the caps even in light breezes during the day with no appreciable wind. Here's what I'm doing:
I'm using two 1 Farad caps as the storage and I built a high voltage air gap alternator (you can just see it under the mill in the picture) that starts giving me power at in mild breeze. Once the caps are charged they will hold the power for a day or so according to my tests and I'm designing a circuit to send pulses through a Radiotronix RCT-433-as transmitter that will be picked up in the house by a receiver converter. So in the end there are no wires on the anemometer and no need to replace batteries so I can run it all over for data collection. The anemometer will resemble the Sav. alternator and have one hall sensor sensing its speed. I have to figure out the conversion to wind speed from rpms but I don't think that will be a problem.

The .37 efficiency was stated on their patent with .24 for a standard Savonius but watching this thing run I believe it as it spun right along with my props. A larger version would most likely be longer and my guess is that longer and narrower would still keep the high rpms. I don't think I'd make it any wider than 8" and any longer than 5'. As Dan said I'd have to figure out a furling system as I think this machine might have problems over 50 mph but I just don't know yet.
cool stuff!
RobD

Re: Sandia Savonius design (none / 0) (#10)
by hvirtane (hannu_markus_virtanen(at)yahoo(dot)com) on Wed Apr 21st, 2004 at 12:34:08 PM MST
(User Info) http://web.archive.org/web/20050404022706/www.cc.jyu.fi/~hvirtane/cooker/

Really nice!

Thank you a lot for publishing here
the exact dimensions.

Please tell about the performance,
after you built a bigger one.

The shape is very similar to that
of www.picoturbine.com 250 watt.

I have no doubt over the claimed
efficiency.

In fact Dr. Johnson is
telling quite the same efficiencies
as measured at his university.
Please see my post about
'Savonius efficiency.
http://www.fieldlines.com/story/2003/7/29/131857/998

- Hannu

Re: Sandia Savonius design (none / 0) (#11)
by RobD on Wed Apr 21st, 2004 at 04:00:30 PM MST
(User Info) http://www.dsgnspec.com

Hi Hannu,
I reread your post and I'm getting some of the same results as Sandia. I'm still working out the size but I'm in favor of several 6-8"(15-20cm) machines tied together. I have to do more work on the system to keep it from blowing up at high rpm but again, these are not slow machines and the speed is very close to the blade HAWT which really surprised me! I think this is a very good design for the low tech builders who want to start getting power. I'll post my final designs when they are done and working.
Rob

Re: Sandia Savonius design (none / 0) (#12)
by monte350c on Wed Apr 21st, 2004 at 06:32:16 PM MST
(User Info)

Hi All,

Once in a while I see Dr. Gary Johnson's book crop up in discussions.

I downloaded this excellent book last summer - I started to read it and basically couldn't put it down. He released it into the public domain (read free!) and you can download your own copy here:

http://www.eece.ksu.edu/~gjohnson/

As Hannu mentioned, it really makes a good read and is packed with all sorts of info about wind, horizontal and vertical turbines, fuel cells and etc.

It's written in a style that's very easy to read - but it also includes all the formulas and math to do your own calculating.

For a newcomer to this field like me it's an excellent reference...

Ted.

[ Parent ]

Re: Sandia Savonius design (none / 0) (#13)
by RogerAS (theropod at yahoo dot com) on Thu Apr 22nd, 2004 at 07:34:26 AM MST
(User Info)

Hi,

Couldn't one use aluminum irrigation pipe? You know the kind, made to take apart and move in a field, often with sprinkler heads attached. I've seen these up to 6" dia. Wonder if these would work, split long ways? Heck that would make a 20' tall version, or 4-5 footers, or...

RogerAS
Roger AS
8 Years off-grid & counting
[ Parent ]

Sandia Savonius design | 16 comments (16 topical, 0 editorial)

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