Jump to content
Science Forums

Recommended Posts

I have in mind to try building a small windmill for electrical generation, :) and the simplest rotor looks like the Savonius rotor. The biggest drawback is the air resistance of the backsides of the cups, and I already have some design modifications in mind to offset this. :)

 

Here's a bit of a read-up on rotors and the power of wind in general. Practical Wind Generated Electricity

Interestingly, the Wicki article on Savonius rotors is auf Deutsch und meine wortsprache sind klein. Plenty of reading out there if you just search 'Savonius rotor'.

 

Any of you have any practical experience with this design? :) Any of you have any impractical experience with this design? :cup: I'll be back in a while with some little drawerings. :eek: :cup: :eek:

 

PS Found a wicki auf Englishe >>Savonius wind turbine - Wikipedia, the free encyclopedia

 

auf Deutsch >>Savonius-Rotor - Wikipedia

Link to post
Share on other sites
How does the air that gets in their efficiently escape?

 

I think it spills out the out-board edge as the rotor turns. I have a little one made of a pop can, a couple straws, and corrugated paper; however, we have no wind just now and my little fan is insufficient to turn it.

 

I saw one article in which the writer suggested using fabric rather than solid material; I like that idea.

 

This little bit is what I have in mind more or less. >> IngentaConnect Valve-Aided Twisted Savonius Rotor

...Another proposition for increasing specific output is to place non-return valves inside the concave side of the blades....

 

I'm thinking vanes on axles like a shutter to act as the valves; when the convex side is facing the wind the shutters close and full force is applied, and when the convex side comes into the wind the shutters open and let the air through. :cap: :shrug: :shrug: Admittedly more moving parts, and I can only imagine what it would sound like operating, but it might overcome the main inefficiency of the Savonius rotor. :eek: :shrug: :D :hyper:

 

We'll see how jazzed I get when I get some wind (without rain) & try my little model. I'll put up a vid on u-tube of it. :cup: :turtle:

Link to post
Share on other sites
I think it spills out the out-board edge as the rotor turns. I have a little one made of a pop can, a couple straws, and corrugated paper; however, we have no wind just now and my little fan is insufficient to turn it.

 

Take it to the Columbia! :)

I saw one article in which the writer suggested using fabric rather than solid material; I like that idea.

 

Don Quixote Style! :D :eek:

 

I'm thinking vanes on axles like a shutter to act as the valves; when the convex side is facing the wind the shutters close and full force is applied, and when the convex side comes into the wind the shutters open and let the air through. :cap: :shrug: :shrug: Admittedly more moving parts, and I can only imagine what it would sound like operating, but it might overcome the main inefficiency of the Savonius rotor. :eek: :shrug: :turtle: :cup:

 

What if the "shutters" could be angled in such a way to create lift as well as provide for the system you suggest. The vertical motion could be converted into lateral motion, thus accelerating the axle even more (retention of efficiency, maybe?).

I'm envisioning something similar to those toys in which you spin the stick and the toy fans out and floats/accelerates up (they look like umbrellas, can't remember the name).

Or perhaps more to the topic, aerodynamic ridges within the semi-cylinders that correlate with helicopter blades, or perhaps a different 'lateral lift' approach. :cap:

 

Or perhaps I'm bonkers... :hihi:

I love brainstorming though. :)

 

Come to think of it, perhaps a Mobius strip holds the answer. :D

This makes me think of the correlation that was drawn between Mr. Fuller and the phenomena observed on the north pole of Saturn. Perhaps convex and concave are not the best. :hyper:

Link to post
Share on other sites
Take it to the Columbia! :cap:

 

 

Don Quixote Style! :eek: :shrug:

 

 

 

What if the "shutters" could be angled in such a way to create lift as well as provide for the system you suggest. The vertical motion could be converted into lateral motion, thus accelerating the axle even more (retention of efficiency, maybe?).

I'm envisioning something similar to those toys in which you spin the stick and the toy fans out and floats/accelerates up (they look like umbrellas, can't remember the name).

Or perhaps more to the topic, aerodynamic ridges within the semi-cylinders that correlate with helicopter blades, or perhaps a different 'lateral lift' approach. :shrug:

 

Or perhaps I'm bonkers... :eek:

I love brainstorming though. :hihi:

 

Come to think of it, perhaps a Mobius strip holds the answer. :shrug:

This makes me think of the correlation that was drawn between Mr. Fuller and the phenomena observed on the north pole of Saturn. Perhaps convex and concave are not the best. :turtle:

 

Try as I might, I can't edit one iota of your post to quote. :hyper:

 

I tried the Mobius strip, but it acts as a wind vane (with an axle down the long axis) rather than a rotor. That is to say it rotates 'into' the wind and stays there until wind direction changes. Great minds think alike though. :cap:

 

Here's a little vid of my pop-can getup. The spinning is by hand just to show rotation. Wind tests to follow, weather permitting. >> YouTube - savonius rotor http://www.youtube.com/watch?v=FfZs3w5abrk

 

I thought about giving the vanes/shutters and airfoil cross-section too, but for now expect any model I make to be a down-n'-dirty version.

 

By all means please submit drawings and or models of your own design ideas. One source I read said this is the oldest type of windmill on Earth, which makes improving it practically, something of a unique challenge. :cup: :D

Link to post
Share on other sites
...

I thought about giving the vanes/shutters and airfoil cross-section too, but for now expect any model I make to be a down-n'-dirty version.

 

By all means please submit drawings and or models of your own design ideas. One source I read said this is the oldest type of windmill on Earth, which makes improving it practically, something of a unique challenge. :cup: :D

 

Sweet Mother of Betty!!:hyper: Can I make an understatemnt or what!? When I think 'proof of concept' or 'model' I never would have imagined this!!! :eek: :shrug: >> YouTube - Encore Clean Energy SideWinder Wind Turbine http://www.youtube.com/watch?v=MZhHCyuEEDk&mode=related&search=

 

That is apparently just the beginning of videos of Savonius rotors gone wild. Oh lordy! :shrug: :turtle:

 

addendum (ok;more dum'b than adden' :shrug: )

 

YouTube - Neo-Aerodynamic 1 at low wind Wind Turbine http://www.youtube.com/watch?v=H_fGuI0hOk8&mode=related&search=

 

YouTube - 50lb Savonius Wind Turbine http://www.youtube.com/watch?v=68pNF5728S8&mode=related&search=

Link to post
Share on other sites
Hey check this one out! I dont know if it counts as savonius, but its cool :eek:

 

 

it looks like they tapered the ends, maybe that helps with the air getting out..

 

Getting the air out has never been a problem in this household. :eek_big: :eek2:

 

Per Jay's suggestion, here is another link with more:

 

Aerotecture International - Products

Link to post
Share on other sites
Getting the air out has never been a problem in this household. :shrug: :cup:

 

Per Jay's suggestion, here is another link with more:

 

Aerotecture International - Products

 

I saw the vid when I was surfin'; thanks for the link too. My only qualifying remark is that it's not a Savonius rotor as it uses airfoils.

 

I'm starting to think about how to incorporate a laminar flow housing to collect wind over a larger surface area (intake duct) and deliver it to the Savonius rotor at a higher pressure and lower surface area (cross-section of delivery duct.) We'll see. :cup: :turtle:

Link to post
Share on other sites

If it was my effort going into the project, I’d make a Darrieus wind turbine. It has a simplicity and vertical orientation similar to the Savonius, but is much more efficient – better, ultimately, than a traditional propeller windmill design. There are quite a few interesting variations of the design, including modifications to get around the design’s chief limitation of not being self starting.

Link to post
Share on other sites
If it was my effort going into the project, I’d make a Darrieus wind turbine. It has a simplicity and vertical orientation similar to the Savonius, but is much more efficient – better, ultimately, than a traditional propeller windmill design. There are quite a few interesting variations of the design, including modifications to get around the design’s chief limitation of not being self starting.

 

I see it matched often with a Savonius to make a hybrid. This adds self-starting to the Darrieus. Here's a vid of a Savonius/Darrieus hybrid in operation. :turtle:

YouTube - Hi-Energy Vertical Axis Wind Turbine Power System http://www.youtube.com/watch?v=nKIkzAnbihI

Link to post
Share on other sites
how much energy do you think one that size could generate?

 

There's the rub mate! :juggle: :cup: They don't say. With so many variations on these homebuilt jobs, unless they specifically say how much power they get then your guess is as good as mine. I did see one Savonius rotor a couple feet tall that the guy had attached magnets to and surrounded with coils rather than connect the shaft to a conventional alternator/generator. He said he was getting a steady 16VAC output and 28VAC in higher winds.

 

Just the voltage isn't enough to give a power output rating though; we don't know the amperage.

 

In general these Savonius rotors are so much lower in efficiency and higher in vibration than other existing designs that they are more something for home enthusiasts rather than any kind of large scale commercial generation scheme.

 

I was thinking instead of making a single large rotor, I could make a bank of the little pop-can jobs connected to common shafts. I think 100 to 150 ought to be enough. :knit: :magic: :evil:

Link to post
Share on other sites
for some reason I think it would be more efficient if the center was not overlapped, possibly even minorly seperated. Ponder ponder...

 

Yeah, a lot about these rotors seem counterintuitive. If you think about a cup anemometer, which is a type of Savonius rotor, there is wide open separation through the middle and usually 3 cups rather than 2; however, efficiency is not a concern for the operation of the instrument once it is calibrated.

 

In reading a variety of material I consistantly find statements indicating the overlap in a 2-vane rotor is more efficient. :) Then again, the most consistant theme with these rotors seems to be a wide avenue of disagreement on what works 'best'. :cup: ;)

Link to post
Share on other sites
  • 11 months later...

For a Darrieus turbine and certain wind direction only one foil works. The other one give DRAG. that means that the hub is solicitated and will not last long. In fact this is why the Darrieus turbine is less in use than the HORIZONTAL axis turbine.For a such a turbine we have to assure optimal PIVOTATION of the plan of rotation in order to catch the wind.

Probably that at the end an HORIZONTAL axis turbine last longer and this is why it is used for traction and lift in aeroplanes powered by gas.

Another issue is that we have not disturbe the wind too much. That means thiny airfoil although, intuitively speaking, we may thing that the best is to capture a maximum amount of wind by increasing the foil area. In fact this is why Savonius turbine is so not efficient at high speed winds.

When you look at two turbines, one a Darrieus and the orher a Savonius turbine you see that the first one rotates much slower meaning less disturbance to the original wind. This is in fact equivalent to less drag and, therefore, an increased efficiency.

Savonius turbine is not efficient at high speed wind, but may be better than Darrieus at low speed wind. Why? Because the drag is lower at low speed wind.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...