Author Topic: VAWT fiddling started...  (Read 6971 times)

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DamonHD

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VAWT fiddling started...
« on: October 03, 2007, 01:18:31 PM »
Hi,


Although I'm more a programmer than a carpenter (or whatever the equivalent in plastic is), I'm having a small go at understanding a simple drag-type S-VAWT made from an empty drink bottle.  Not to drive any sort of generator, just to move.


At the moment my little prototype is becalmed by a complete absence of wind (and a poor bearing) though I'm sure I saw it twitch a few mm in the right direction when we had a little puff of breeze.


* * *


My moderate idea is this: for small VAWTs, rather than have them sat on the ground with the motor bearing taking the weight (ie in compression) would an alternative to be to suspend the VAWT blades from the motor spindle (ie in tension) with the motor on a universal joint and/or the blades suspended on a piece of slightly twistable cord to avoid some of the side-to-side wear/torque?  Getting everything slightly off the ground is likely to improve wind speed/flow a little, just to start with.


The bottom of the blades at the centre could be fixed to the floor via another cird and bearing, or simply allowed to hang free, maybe with a small weight.


I'm think of constructions from the size of a Chinese lantern up to a plastic barrel VAWT.  Maybe good for Watts through to tens of Watts in low wind speed.


Any chance of it being do-able or sensible?


Rgds


Damon

« Last Edit: October 03, 2007, 01:18:31 PM by (unknown) »

disaray1

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Re: VAWT fiddling started...
« Reply #1 on: October 03, 2007, 08:11:09 AM »
 Ahhh. Damon has the fever. Who's got a thermometer? BTW, the only difference between a oral thermometer and rectal thermometer, is the taste. :-P


 I think your moderate idea would work, and as an experiment would be fine. Maybe FeralAir can chime in about his current experience with hanging the rotor from the top. I'm in the process of putting a S type together that'll be heavy. I scrounged a  clutch throw-out bearing from a Porsche 930 for the rig to sit atop and not transfer any compression loads onto the outputshaft. I think these things need solid top and bottom support to be safe and stable.


 Height- the higher the better- just like hawt, it wants clean air.


 Think low speed with Savonius. Your gen will either need to be able to produce at low rpm, or gearing will need to be implemented to get the alt speed up. I think Ghurd suggested a stepper motor for small units.


 Fiddle-on, dude.


 David

« Last Edit: October 03, 2007, 08:11:09 AM by disaray1 »

gotwind2

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Re: VAWT fiddling started...
« Reply #2 on: October 03, 2007, 10:45:35 AM »
Hi Damon.

I think you might like this mini vawt constructed from a 'Pringles' tube...


There's even a design for a mini single rotor air core axial alternator.

http://www.instructables.com/id/Pringles-Wind-Turbine-Pleech---Version-One/?ALLSTEPS


There is also a more robust version on the same site - Instructables (it's a bit childish, I love it)

http://www.instructables.com/id/Build-a-Savonius-Wind-Turbine-or-VAWT-to-make-elec/?ALLSTEPS


Have fun.


Ben.

« Last Edit: October 03, 2007, 10:45:35 AM by gotwind2 »

ghurd

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Re: VAWT fiddling started...
« Reply #3 on: October 03, 2007, 11:07:18 AM »
Imagine how much better the Pringles can would work if he has steel behind the magnets, and wasted less in "too thick" coils beyond the flux.


I am playing with McDonald's soda cups now.  :-)  Same idea.

G-

« Last Edit: October 03, 2007, 11:07:18 AM by ghurd »
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DamonHD

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Re: VAWT fiddling started...
« Reply #4 on: October 03, 2007, 11:16:19 AM »
I'm so far off attaching a generator to it you'd never guess.


No, at the moment I'm just trying to make something mechanically workable.


Then I'll probably cheat and try to buy a motor/gen...


My tweaking is coming along, and I may even have something that I can put in the garden  to spin by itself tomorrow...  What I believe TomW may call "yard art" but in this case becomes "educational toy"!


Rgds


Damon

« Last Edit: October 03, 2007, 11:16:19 AM by DamonHD »

DamonHD

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Re: VAWT fiddling started...
« Reply #5 on: October 03, 2007, 11:42:21 AM »
Well, goodness!  I have something that turns quite well: a lungful of air has it turn at least 2 or 3 times.  Any most of it should survive rain, though is otherwise quite fragile.


And, through ham-fistedly running out of other alternatives, the bearing is at the top, with the whole device hanging down from a 'sprung' pillar.  A very small gen could fit in there at the top of the post, with wires running down the post.


I'll take its photograph 'planted' in my garden tomorrow, and see how long it takes to fall apart.


Then I can think about a real VAWT generating my usual milliWatts, when we get any breeze at all...


In any case, I'll see how quickly this one rotates.


What's the relationship between rpm, windspeed, and other design parameters for a simple Savonius VAWT?  (I'm gonna Google anyway, but I'm sure that you guys know it off by heart...)


Rgds


Damon

« Last Edit: October 03, 2007, 11:42:21 AM by DamonHD »

wooferhound

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Re: VAWT fiddling started...
« Reply #6 on: October 03, 2007, 11:50:31 AM »
I made this Vertical Turbine in a rather unique way. It's been hanging in the yard for 3 years now and it's always spinning. Never went past this point in the design, and never tried to make power with it. I think it would work really well with a shroud.


http://www.fieldlines.com/story/2003/12/1/122243/608

« Last Edit: October 03, 2007, 11:50:31 AM by wooferhound »

feral air

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Re: VAWT fiddling started...
« Reply #7 on: October 03, 2007, 12:02:30 PM »
Sure, I'll chime in...good of you to think of me and my, uh, experiment...


Hanging it like that doesn't really work unfortunately. When I hung my pb-vawt from a (crude) u-joint the swinging motion took up a lot of the wind's power and it looked like it was slowing the rotation every time it swung back. It's now got top and bottom bearings and spins much faster/nicer.


I think a good-sized weight at the bottom would help a little if the weight wasn't being spun. You might be able to use a couple of magnets as bearings for that part.


If you plan to trying this out on a larger scale and more permanently then consider the stress on the bearings over time. Maybe bike wheel hubs would last a few years...that's what I'm using on my big one and I'm crossing my fingers.


If you go with gearing I think 1:10 is about right. When I hooked a radiator fan motor to my pb-vawt the ratio was 1:5 and I got a tickle-on-the-tongue for output - not quite the bite of a 9v battery. The vawt was spinning around 36rpm or so, so the motor would've only been spinning around 180rpm...


With a 1:10 ratio, when your vawt hits 100rpm the motor will spin at 1000rpm. That seems decent. If it's smaller and faster then maybe 1:8...I dunno, it's variable and needs to be done on a case-by-case basis, I think.


This came out longer than I thought it would...I'm just glad I'm not the only one with the bug!

« Last Edit: October 03, 2007, 12:02:30 PM by feral air »

DamonHD

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Re: VAWT fiddling started...
« Reply #8 on: October 03, 2007, 12:14:13 PM »
Ben, thanks for those links.  I had already seen them, and my current pathetic prototype borrows from them and others.


Next thing I'll be asking you where to get the magnets in the UK!  B^>


Rgds


Damon

« Last Edit: October 03, 2007, 12:14:13 PM by DamonHD »

ghurd

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Re: VAWT fiddling started...
« Reply #9 on: October 03, 2007, 01:38:10 PM »
Is this optimism, pessimism, or "Heading you off at the pass"?  I don't know.


I won't put any more time or money into a small VAWT.  A 40cm diameter HAWT is cheaper, easier, and I got at least measurable power.

I certainly wouldn't bother building it dual-rotor PMA!


It is probably best suited to an 8V stepper motor for LEDs or AA nicd/nimh.

Meaning TomW's 'yard art' or a useful "educational toy".  Don't be offended. TomW is a realist looking from the perspective of powering a household instead of powering a digital camera.


It will be big fun. It could be usable, in a small sort of way.  It won't cost much (with a stepper motor).

Build a similar HAWT, be it similar in cost or swept area or whatever.

It will show why nobody has a proven commercial 50+W VAWT.

Ed might do it, but that is a completely different animal.


To summarize, slap a stepper on it and be happy.  :-)

G-

« Last Edit: October 03, 2007, 01:38:10 PM by ghurd »
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fcfcfc

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Re: VAWT fiddling started...
« Reply #10 on: October 03, 2007, 03:18:39 PM »
Hello All:

I am in the process of designing my own VAWT and was just looking at the posts searched by VAWT in the "wind" cat.. I ended up designing my own gen, PM disk type 3 phase. It is going to be a bear to build, but I wanted something that could be direct drive and produce good power at even 1 RPS. I was looking at Ed's stuff, interesting but tailored for higher RPS's, not efficient enough, but good to re-engineer from.

I live in a low wind spot... Don't see much over 10 MPH most of the time, so I need to take advantage of the 5 to 8 MPH market. Basically, the helix will be 4' in "diameter" and 16' tall, on top of my new barn roof starting 20' off the ground, top of helix at 40' from ground zero. I am going to use three baffles at 120 degrees to intensify the wind a bit, but the main "edge" I hope will be in the gen design..

I am just starting so I am going to build a small 32" high model first to experiment with the baffles, a "thin" airfoil design.


.....Bill

« Last Edit: October 03, 2007, 03:18:39 PM by fcfcfc »

electrondady1

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Re: VAWT fiddling started...
« Reply #11 on: October 03, 2007, 03:27:18 PM »
gurd have you forgotten about windside in finland ?

they have been in busness for a long time and i beleave they make a great deal more than 50 watts.

« Last Edit: October 03, 2007, 03:27:18 PM by electrondady1 »

RP

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Re: VAWT fiddling started...
« Reply #12 on: October 03, 2007, 03:32:06 PM »
The outer edge of a drag type rotor like a savonius will be essentially the same as the windspeed when it's unloaded.


For a 1 foot diameter rotor the circumference will be 3.14 feet so in a windspeed of 10mph, the outer edge of the rotor will be going 52800 feet/hour or 88 feet/minute.


Dividing the circumferencial speed by the actual circumference gives you 88/3.14=28rpm


I believe optimum loading for a savonius is when it's running at a tsr of 1/3 so to extract maximum power you'd want your alternator to hold it down to a little over 9rpm in a 10mph wind.


Hope this helps

« Last Edit: October 03, 2007, 03:32:06 PM by RP »

feral air

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Re: VAWT fiddling started...
« Reply #13 on: October 03, 2007, 03:54:13 PM »
S-vawts are hard to break down with numbers. I don't know of any way to sit down with a piece of paper and figure out exactly what size/configuration of an s-vawt you need to build get a given amount of power out. I think it's ok to go by 'feel' though...


You can't really say an s-vawt made from 6" pipe will spin this fast in this wind. Besides the height, you've got weight, air gap, bearings, general build quality, load, etc....lots of things play a part, even with a simple-S design.


Then, are you really talking about a simple Savonius? To me that means each blade is a half circle, the gap is about 18%, the blades don't overlap, there's likely a center rod and you've got end plates. Or are you talking about a modified simple S?..


I consider my quick vawt to be a modified simple S...the blades aren't half circles (though they could be), they do overlap a little, there's no center rod, the gap is totally configurable and a bottom plate is all that's really mandatory (to protect the bottom bearings from the weather).


Past about that point you get into the more complicated designs/problems and all hell breaks loose. Then you start pondering the aspect ratio..wider is better for low winds but is lower rpm, tall and skinny for high winds and high rpms. Oh, should I use those "J" looking blades?..those are more efficient. Etc.


There's just so many variables.

« Last Edit: October 03, 2007, 03:54:13 PM by feral air »

wdyasq

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Re: VAWT fiddling started...
« Reply #14 on: October 03, 2007, 08:12:40 PM »
Sandia labs did several million dollars of research on VAWTs of all descriptions. They figured out many of the problems. They built many prototype mills. A great amount of data was published.


Ron

« Last Edit: October 03, 2007, 08:12:40 PM by wdyasq »
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DamonHD

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Re: VAWT fiddling started...
« Reply #15 on: October 03, 2007, 11:54:44 PM »
That's a very good starting point.


I might just have the materials for a 1ft diam S to hand, so expecting ~1rpm/mph/ftdiam is a decent rule of thumb at least.  Hideously un-metric though!  B^>


Rgds


Damon

« Last Edit: October 03, 2007, 11:54:44 PM by DamonHD »

DamonHD

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Re: VAWT fiddling started...
« Reply #16 on: October 04, 2007, 12:12:45 AM »
Yes, they look actually plausible for me at the low end...


Rgds


Damon

« Last Edit: October 04, 2007, 12:12:45 AM by DamonHD »

DamonHD

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Re: VAWT fiddling started...
« Reply #17 on: October 04, 2007, 12:29:50 AM »
Hi,


I don't do build quality!  What do you take me for: a civil engineer?  B^>


Anyway, my little prototype does at least turn in a tiny breeze: I'll try and get a little video before it falls apart...


Rgds


Damon

« Last Edit: October 04, 2007, 12:29:50 AM by DamonHD »

DamonHD

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Re: VAWT fiddling started...
« Reply #18 on: October 04, 2007, 06:10:46 AM »
OK, some pics of this first S-VAWT prototype.  Yes it's all wrong, etc, but it's a start!


http://gallery.hd.org/_virtual/ByCategory/mechanoids/turbine/wind/tiny/vawt/


Rgds


Damon

« Last Edit: October 04, 2007, 06:10:46 AM by DamonHD »

finnsawyer

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Re: VAWT fiddling started...
« Reply #19 on: October 04, 2007, 06:44:56 AM »
Can you give us a link for this company, Windside?
« Last Edit: October 04, 2007, 06:44:56 AM by finnsawyer »

DamonHD

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Re: VAWT fiddling started...
« Reply #20 on: October 04, 2007, 06:48:58 AM »
windside.com


Rgds


Damon

« Last Edit: October 04, 2007, 06:48:58 AM by DamonHD »

ghurd

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Re: VAWT fiddling started...
« Reply #21 on: October 04, 2007, 07:29:31 AM »
Not sure I ever saw them. Interesting how the twisted blades have internal fins with bypass in the depths.

Can't figure out the charts format.  20W at 22.4 mph for the 100W version?

But "starting at $6500" for a 100W windmill head and blades sounds a bit... uh, much.

That makes solar panels look cheap!

G-
« Last Edit: October 04, 2007, 07:29:31 AM by ghurd »
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DamonHD

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Re: VAWT fiddling started...
« Reply #22 on: October 04, 2007, 07:49:00 AM »
Yes, most of the worldwide distributors were coy with pricing, which is usually a bad sign.


The 0.3m swept area one that I was looking at was ~$9k from the US distributor.


I'm waiting for pricing from the UK distributor.


Rgds


Damon

« Last Edit: October 04, 2007, 07:49:00 AM by DamonHD »

feral air

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Re: VAWT fiddling started...
« Reply #23 on: October 04, 2007, 08:25:45 AM »
For s-vawts it's easier to build the rotor first. Then you can figure out how much spinnage there is and how best to use it.


Having a good 'feel' will get you as close as running the numbers can anyway, all things considered.

« Last Edit: October 04, 2007, 08:25:45 AM by feral air »

feral air

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Re: VAWT fiddling started...
« Reply #24 on: October 04, 2007, 08:30:43 AM »
Do you have a direct link? I don't know what I'm looking at on that page, it's all kinds of crazy...


If it's a vid, can you post it on youtube?

« Last Edit: October 04, 2007, 08:30:43 AM by feral air »

DamonHD

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Re: VAWT fiddling started...
« Reply #25 on: October 04, 2007, 08:53:19 AM »
Try this page and click on the 'full' link under the 'bunny' icon, for example:


http://gallery.hd.org/_c/mechanoids/_more2007/_more10/turbine-wind-tiny-VAWT-Savonius-SVAWT-prototyp
e-blades-made-from-2l-two-litre-plastic-bottle-and-CD-and-garden-stake-and-drawing-pin-thumbtack-vid
eo-7-DHD.avi.html


There are JPEG stills as well, look further down the page and click on the thumbnails.


Rgds


Damon

« Last Edit: October 04, 2007, 08:53:19 AM by DamonHD »

DamonHD

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Re: VAWT fiddling started...
« Reply #26 on: October 04, 2007, 09:01:55 AM »
I think that that has to be rpm = mph / ft diameter
« Last Edit: October 04, 2007, 09:01:55 AM by DamonHD »