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joyt12k

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Joined: 12/05/2009
Location: Australia
Posts: 49

Posted: 03:19am 11 Sep 2010

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Hi everyone, does anyone know how to work out swept area for my VAWT.
I've included a picture. there are 3 blades which, when flat measure 1200mm X 100mm. The diameter at fixing points is 600mm and in the middle is 750mm.
I cant try it out because when making the 'C' frame I forgot to allow for the extension of the blades beyond the fixing point, anyway no wind today.

jasmine

fillm

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Joined: 10/02/2007
Location: Australia
Posts: 730

Posted: 04:14am 11 Sep 2010

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Hi Jasmine,

Thats a beautiful piece of work that you have created there. Please keep the pics and story going when you sort the frame out .

What stator/rotor config are you using ?

Edited by fillm 2010-09-12

PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits

VK4AYQ
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Joined: 02/12/2009
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Posted: 04:34am 11 Sep 2010

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Hi Jasmine

Very nice work I am glad to see the VAWT being promoted as there has been so much negative said about them.

All the best

Bob

Foolin Around

joyt12k

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Joined: 12/05/2009
Location: Australia
Posts: 49

Posted: 05:11am 11 Sep 2010

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Thanks guys it's not my design entirely , I saw three of these on top of a 6 storey
building in the U/K and took some pictures, the actual ones at a guess were about
3metres high. The stator on there at the moment is wired for 24v low wind, until I know how it performs I can't decide. Hope to have it going at ground level next weekend for trials.

jasmine

Downwind

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Joined: 09/09/2009
Location: Australia
Posts: 2333

Posted: 05:22am 11 Sep 2010

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Now thats a try piece of mechanical windmill art, it looks great

It even looks as though it should work, and should it not preform as desired will still look great as a yard feature.

Look forward to seeing the results once you get it flying.

Pete.

Ps:- your work bench looks like mine, but mine is messier

Edited by Downwind 2010-09-12

Sometimes it just works

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 06:06am 11 Sep 2010

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Swept area is only used on HAWT's. What we really need to work out is the area facing the wind, so for a HAWT, we can use swept area to work out the area of the turbine, since its facing directly into the wind.

For a VAWT its different, cause the turbine is side on to the wind. So we need to work out how big the side of the turbine is. Using some approximations, your width is about 700mm, and your hight is about 1200, give or take. Thats a area of 700 * 1200, or 0.7 * 1.2m, about 0.84m2. A HAWT with a 2 meter diameter has a area of 3.14m2 as a comparison.

Its a nice looking turbine, but I'm afraid to say your going to have a couple of problems if you want to use it with that F&P motor. First up, that design doesn't have a lot of startup power, and I think it would be lucky to overcome he cogging of the F&P, unless you go for a cogless 7 phase or later model 36 pole motor. You may have to attach a pull rope to get it started. The other problem is it wont make a lot of power once running, due to its small size, and the F&P will waste most of it in iron losses.

However, it should work very well with a smaller alternator/generator. A DC treadmill motor comes to mind, I think it would match up well to that turbine.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Greenbelt

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Joined: 11/01/2009
Location: United States
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Posted: 07:04am 11 Sep 2010

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Time has proven that I am blind to the Obvious, some of the above may be True?

Gizmo

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Posted: 07:52am 11 Sep 2010

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Thanks Greenbelt, spot on.

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

itsandbits1
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Joined: 13/08/2010
Location: Canada
Posts: 81

Posted: 05:00am 12 Sep 2010

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the calculation is fine until you take into account the other 3.14 because once it goes into lift it produces power all the way round

joyt12k

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Posted: 07:01am 12 Sep 2010

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Can you explain what you mean the other 3.14 please?

jasmine

itsandbits1
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Posted: 02:41pm 12 Sep 2010

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the circumference. the vawt is much more limited by the type of blade i think because it has so much more blade area. But it also has as a benefit the full rotation of the blades to get lift from once it is in the lift zone as it gets pushed around the circle. the high efficiency models I have heard have a runaway lift preventer brake to stop this from going too far. It is the same as the hawt blades; if you watch them you can see when they get lift and take off.

joyt12k

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Location: Australia
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Posted: 08:56am 18 Sep 2010

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I have just finished putting the VAWT up, this is just a temporary position for it
as it's close to the garage, where my battery bank is, as usual, no wind at present,
but we have had strong easterlies the last three nights, the stator is not on as yet,because I'm waiting to see how it performs, will update tomorrow if I get some results.

jasmine

Downwind

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Joined: 09/09/2009
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Posted: 11:07am 18 Sep 2010

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At least you have the right sex toy in the garage

Pete.

Sometimes it just works

itsandbits1
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Posts: 81

Posted: 02:05am 19 Sep 2010

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Yea, that should be good for another 500 watts at least. should put it on a tipping pole and get it up above the roof line at least. the wind is gonna hit the house and the underside of the portch and really get slowed down and messy. The vawts can deal with it but you are going to loose a lot of power.

joyt12k

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Joined: 12/05/2009
Location: Australia
Posts: 49

Posted: 01:25am 02 Oct 2010

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Well have had some strong easterlies recently with really strong gusts and guess what? It did'nt budge not even when I tried giving it a helping hand. It looks just the real ones that I saw in the U/K, and it's in propotion, just cant figure it out.

jasmine

fillm

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Posted: 02:48am 02 Oct 2010

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I would think it is a combination of two things , the blades being flat aluminum are not aerofoils in there design and are not creating enough lift and drag, the second is the cogging effect of the F&P, unless you have used one of the coggless 7 phase mods, then that could be discounted.

PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits

joyt12k

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Joined: 12/05/2009
Location: Australia
Posts: 49

Posted: 05:56am 02 Oct 2010

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The F&P was'nt even on at the time, anyway it's on the bottom of my list at the moment, I'm waiting on my PMA and blades from the States, and want to get that going.

jasmine

KarlJ

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Joined: 19/05/2008
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Posted: 07:20am 02 Oct 2010

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INdeed very nice piece of Garden Artwork.

I'm afraid a 2m diameter F&P will do 300W if you're lucky hence at 1/4 the swept area
you're looking at ~80W.

I wouldnt be doing any re-wire at all and a 60S stator would be the pick.
If it runs faster than expected then a quick jumper into delta might solve it.
next step would be the 80S again I'd try unrewired first.

Blade at its extremity facing the wind should have an angle of attack of about 5deg.
if there is little or no angle it will never start.

Twist those poles on the stator and round the edges of the poles as well, this should make it almost cogless without re-wire to 7 phase and another magnet rotor.

Karl

Luck favours the well prepared

itsandbits1
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Joined: 13/08/2010
Location: Canada
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Posted: 07:33am 02 Oct 2010

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I thought you said somewhere those were helicopter blades. they should have some airfoil if that is the case. if you spin them up to close to tsr1 with a stick they should take off somewhat even if they are flat in a stiff; 20kph-up breeze. I run my symetrical naca0015 modified blades at 0 degrees aoa and that is the sweet spot for them . they are all different though. a test was just done on the naca4415 at 8 degrees aoa and it almost made the betz limit so you never know

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