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Unusual VAWT design
By baggo, Section Wind Posted on Wed Jul 21, 2004 at 09:53:11 AM MST
Unusual VAWT design

I came across this VAWT some time ago during one of my frequent ramblings through RE sites on the web.
http://www.rainbowtradingpost.com/crescent_gen.html
It sounds as though this is still under development but suggests it uses an AWP 3.6 alternator. The idea of having fixed vanes around the inner rotor seems interesting. As well as protecting the rotor from damage by external objects (and vice versa), presumably the vanes will 'funnel' the wind onto the rotor inside perhaps increasing performance? They will also shield the non power side of the rotor when it is travelling towards the wind and reduce drag there. Maybe produce a low pressure area at the front of the rotor? Looks like an interesting project to have a play with when I get time. Does anybody have any ideas about the possible design of the internal rotor? The description on the website is pretty vague and it is difficult to get any idea of size etc.
Thanks in advance for any ideas and comments,
John

Unusual VAWT design | 9 comments (9 topical)

Re: Unusual VAWT design (3.00 / 0) (#1)
by Gary D on Wed Jul 21, 2004 at 10:46:28 AM MST

Looks very similar to Dan B's crossflow/banki hydro. Could be an interesting project for someone so inclined. No windspeed data included tho.... just rpm's. Foolish thought here.... Gary D.

Re: Unusual VAWT design (3.00 / 0) (#2)
by Dutch on Wed Jul 21, 2004 at 11:03:48 AM MST

For me it's not clear how this thing converts energy in the wind to a rotating movement. The vanes/wings seems to be very small. It wouldn't have much torque. Why not give some more information about the concept? Is it lift- or drag based? The powercurve is from the AWP-generator. But will the thing meets the revelutions?
Too much questions I guess...

Re: Unusual VAWT design (3.00 / 0) (#3)
by hvirtane on Wed Jul 21, 2004 at 03:09:17 PM MST

I think that there is a savonius inside.
I think that the design is good.

Here living not so far from me, Erkki Nousiainen has built 14m tall Savonius with that kind of fixed 'guide vanes' outside the rotor.

His machine looks really special. I will send later some photos. In this photo it isn't ready yet. The 'guide vanes' aren't there yet.

- Hannu

Re: Unusual VAWT design (3.00 / 0) (#4)
by RobD on Wed Jul 21, 2004 at 08:07:03 PM MST

Wow! Hannu,
The neighbors must love him!
RobD

Re: Unusual VAWT design (3.00 / 0) (#5)
by DanB on Thu Jul 22, 2004 at 07:43:03 AM MST

Not to sounds grouchy...
but it seems like every VAWT page I see (especially for those machines which are under development) starts out with a long list of all the "advantages" of that particular machine. At least this page doesnt list all the drawbacks (noise, reliability issues, killing birds etc etc... ) associated with proven workable designs.

But this machine is talking 1KW @ 400 rpm. To actually get 1KW from such a machine, I think it would have to be HUGE (I could be wrong..) - and at that size, I'm very doubtful it would spin anywhere near the 400 rpm that the AWP 3.6 needs to see.

It's neat looking, and interesting though... I think at some point after seeing so many "under development" VAWT wind turbine pages out there - most of them completely unrealistic... I have become skeptical.

Interesting page though and thankyou for pointing it out!

Re: Unusual VAWT design (3.00 / 0) (#6)
by baggo on Thu Jul 22, 2004 at 12:19:49 PM MST

Hi all,
thanks for your comments. Have just come across this which seems to explain the basic design:http://members.axion.net/~enrique/windgenerator.html

I agree with DanB that the machine would probably have to be very large to produce 1kW.

John

Re: Unusual VAWT design (3.00 / 0) (#7)
by Dutch on Thu Jul 22, 2004 at 02:04:40 PM MST

So the device has a Savonius inside. It's impossible for a Savonius to have a TSR > 1.

Reasoning:

The Savonius is a 100 percent drag based device. If the wings of a Savonius rotate with a TSR = 1 - what will mean that the device rotate with windspeed - there is no pressure anymore from the wind against the wings. Because the Savonius also has drag from the bearings and one of the wings have to move against the wind the actual TSR will be far less then 1.

If and only if my reasoning is correct, then, assume that the Savonius has a TSR = 1, and that it's diameter is 2 meters.
The circumference is then 2 x 3.14 = 6.28 m.
With 400 revolutions the windspeed will be 400 x 6.28 / 60 = 42 m/s.
So you need at least a typhoon or a hurricane to get 1 KWatt ;-)

Re: Unusual VAWT design (3.00 / 0) (#8)
by baggo on Thu Jul 22, 2004 at 02:29:28 PM MST

Thanks for that Dutch,
That's probably why the design is still 'under developement' They probably can't get it to work! As Dan B suggests it's probably another impractical design however interesting it appears to be. I might have a go at building a small version just for the hell of it though if only to see if the external vanes do actually make any difference. Looks like a job for some plastic pipe!

John

Re: Unusual VAWT design (3.00 / 0) (#9)
by DanB on Sat Jul 24, 2004 at 08:18:00 PM MST

yes, Ive seen that other page too...
I tend to remain skeptical about - but hard to say. At any rate, I do think its a bit deceptive to buy an alternator (from the AWP 3.6) and copy their power curve graph, and call that the power curve for the wind turbine... it seems quite unlikely.

Here's another page... they have a bit more info, but not much. Quick to discuss the advantages of their design, and the drawbacks of other designs, but absolutely no real information regarding actual power output.

http://aerotecture.com/

[ Parent ]

Unusual VAWT design | 9 comments (9 topical)

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