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VAWT land | 25 comments (25 topical, 0 editorial)

Re: VAWT land (3.00 / 0) (#4)
by wooferhound (tim((NoSpamAt))wooferhound.com) on Sat Aug 30th, 2008 at 05:27:47 PM MST
(User Info) http://wooferhound.com

I never saw a savinous with 3 blades like that
makes me wonder . . .

W o o f -={(

Re: VAWT land (3.00 / 0) (#5)
by tecker on Sat Aug 30th, 2008 at 05:44:24 PM MST
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I worked this out on a small scale and with two tiers it starts well and gyros about 110rpm The 15 has motor coils in the genset this one will also .

[ Parent ]

Re: VAWT land (3.00 / 0) (#14)
by tecker on Sun Aug 31st, 2008 at 01:38:35 PM MST
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The problem i've seen is that the air swirls inside and doesn't exit as the rpm increases Low rpm the air passes thru .

[ Parent ]

Re: VAWT land (3.00 / 0) (#15)
by windstuffnow (elenz(at)windstuffnow(dot)com) on Sun Aug 31st, 2008 at 04:42:05 PM MST
(User Info) http://www.windstuffnow.com/main

For maximum extraction, on a drag machine, the turbine needs to be loaded to a TSR of 0.33 or 1/3 of the wind speed. The closer it gets to a TSR of 1 the less power it can extract.

For instance, if the blade, or drum, is moving away from the wind as fast as the wind is commng in then there can't be any power extraction.

On another note, the efficiency of the savonius type blade is very close to the Betz limit when loaded if you consider the actual wind it's extracting from. As an example, the wind is moving at 10mph the turbine is loaded to a TSR of .33 or moving away from the wind at 3.3 mph your actually extracting energy from a 6.7 mph wind. Unfortunately, after you subtract the up wind blade drag and other machine inefficiencies the power is considerably lower. Since your only extracting energy from one side of the turbine it makes it look like it's not very efficient overall when in reality the blade or drum is actually extracting energy more efficiently than alot of "good" turbines that are out there.

Put that 1/2 drum on a linear alternator and run it in a straight line for a mile or two it would have better efficiencies than almost all the turbines being built. You may need to run the return drums in a tunnel below the main run to reduce the losses.

Unfortunately they just don't do so well in a circle...

;O)
.
Have Fun! Windstuff Ed
[ Parent ]

Re: VAWT land (3.00 / 0) (#16)
by tecker on Sun Aug 31st, 2008 at 05:26:11 PM MST
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Yep the half drum will start backward untill it hits the entry point the drag there has very little lift to reguage .

[ Parent ]

Re: VAWT land (3.00 / 0) (#17)
by tecker on Sun Aug 31st, 2008 at 06:19:10 PM MST
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I 've watched the air on the upwind side of the two halves the air gets split as the work cycle starts . In misty weather you see the air gush to the outside and there's not as much air that goes through the turbine as the model shows . I've seen some videos of darius Halve drum combos that look powerful

[ Parent ]

Re: VAWT land (3.00 / 0) (#18)
by vawtman (vawtman(at)charter(dot)net) on Sun Aug 31st, 2008 at 06:45:38 PM MST
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Darrius half drum combo's ?

[ Parent ]

Re: VAWT land (3.00 / 0) (#19)
by tecker on Sun Aug 31st, 2008 at 10:48:10 PM MST
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This one
http://www.youtube.com/watch?v=Lbiqrpjy-f4

[ Parent ]

Re: VAWT land (3.00 / 0) (#22)
by colej (colej@castle-ranch.com) on Tue Sep 2nd, 2008 at 09:03:04 PM MST
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Could you block the wind from acting against the back barrel and somewhat direct it into the scoop with a vain driven cowling type rig?
the Vain would keep the cowling in front of the oncoming half reducing the backforce

Whats the drawbacks to this?
In theory it sounds like it would work.

[ Parent ]

Re: VAWT land (3.00 / 0) (#23)
by tecker on Wed Sep 3rd, 2008 at 07:09:45 AM MST
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Rediirecting the around the upwind is a good idea . I've been trying to do this with the rotor but still have a bit going around the other direction but there is lift there now starting at 40 rpm .

[ Parent ]

Re: VAWT land (3.00 / 0) (#24)
by colej (colej@castle-ranch.com) on Wed Sep 3rd, 2008 at 05:04:29 PM MST
(User Info)

here is an idea I had last night after reading your post. My theory is that the "cowling" would not only block the wind from the Leeward edge, but also focus some wind into the Windward edge boosting the efficiency (at least in theory). As wind direction changes so would the cowling to always block the leeward edge from oncoming force.
I'm sure there will be some turbulance within (design idea for another day) but just maybe the benefit of blocking the drag side would still be beneficial.
Comments please.

<img

[ Parent ]

Re: VAWT land (3.00 / 0) (#10)
by Norm (peppysue@suite224.net) on Sun Aug 31st, 2008 at 07:43:58 AM MST
(User Info)

I've tried 3 blades on a small scale (plastic
cups) 2 tiered, 2 blades per tier, offset 90
degrees from the other tier seems to work better
for me.
( :>) Norm
[ Parent ]

Re: VAWT land (3.00 / 0) (#11)
by tecker on Sun Aug 31st, 2008 at 08:48:49 AM MST
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The jurys's still out on 90 second tier offset it depends on how the air enters the inner vortex if the second tier is blocked say with a plate between its effective but if the air goes from one tier to the other then the pressure exchange between the two interfears .

[ Parent ]

Re: VAWT land (3.00 / 0) (#13)
by windstuffnow (elenz(at)windstuffnow(dot)com) on Sun Aug 31st, 2008 at 11:19:52 AM MST
(User Info) http://www.windstuffnow.com/main

The ones I've tested I found the torque is that of 1 tier for the entire machine. What it does is offset the torque pulse from 180 degrees to 90 degrees. You have lower torque but a more continuous torque.

I built a 4 tier unit with the blades offset by only 22.5 degrees, very similar to the "twisted" or "helix" savonius. This actually seemed to remove the torque pulse but still only carried the torque of one tier or slightly above.

Overall I never achieved much more than 20% efficiency with any of the units I built. They provide a very good torque at low rpm and would be well suited for pumping water, running an air compressor and such but for electric they present a number of challenges. It can be done...

.
Have Fun! Windstuff Ed
[ Parent ]

VAWT land | 25 comments (25 topical, 0 editorial)

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