Author Topic: VAWT Postings Welcome (Read 17606 times)

nvmike · « **on:** March 06, 2005, 03:28:59 AM »

A place to share ideas, comments, and anything related to VAWTs.

nvmike · « **Reply #1 on:** March 05, 2005, 09:14:11 PM »

I live in a low wind area and am trying to get a VAWT going with the idea of low speed, high torque, gear it up and hope to get something out of it. I am also limited to something I can build with hand tools and off the shelve parts, futher limited by living in a trailer park, so towers are out of the question.

I have built the dual rotor PMG from idea here and links posted here. Not spec. on the output yet.

Looking forward to sharing thoughts and ideas with you all.

Sincerely mike

arc · « **Reply #2 on:** March 05, 2005, 10:48:21 PM »

Hey Mike,

Looking forward to following your progress on this project.

Perhaps something mid sized, I was thinking of making a Savonius rotor VAWT using 5 Gallon paint buckets for the rotors, mine never got off the ground, it seemed like a pretty good size to get some usable power from, maybe charge a deep cycle or two, but they are pretty low speed (100 rpm or less usually).

My favorite design, however, is a DARRIEUS design, maybe with a center hub shape to speed air over the wings with a venturi effect.

Just some thoughts,

arc

nvmike · « **Reply #3 on:** March 05, 2005, 11:04:19 PM »

I would like to try the DARRIEUS design. Using 5 gal. paint buckets now, but hope to improve design later, just was in a hurry to get something up and turning.

nvmike · « **Reply #4 on:** March 05, 2005, 11:19:14 PM »

I would like to try the DARRIEUS design. Using 5 gal. paint buckets now, but hope to improve design later, just was in a hurry to get something up and turning.

nvmike · « **Reply #5 on:** March 05, 2005, 11:25:53 PM »

Arc, check out Windstuffnow for a nice Darrieus http://www.windstuffnow.com/main/darrieus_type.htm

arc · « **Reply #6 on:** March 06, 2005, 12:58:08 AM »

Ed's site is great, isn't it!

The quality of work that he does just blows me away every time, I only wish I had 1/100th the skills.

Yup, that's a pretty cool Darrieus all right, can't quite figure out how it works, I'll have to study up on that one.

Ya gotta love that Sterling Generator too, it is way cool.

Dave

DanB · « **Reply #7 on:** March 06, 2005, 06:18:42 AM »

Just a thought that I oftain tell folks when they talk about these sorts of machines. Swept area..

if we assume that the savonious machine is as efficient as a normal HAWT design, then it's interesting to consdider swept area. If we built a machine from say... big metal drums, 3' wide and 10' tall, we'd be sweeping 30 square feet. A 10' diameter HAWT sweeps about 75 square feet. I dont believe savonious wind turbine are as efficient - I think in most cases they are perhaps half as efficient. So to build a machine that would produce what we'd expect from a 'noarmal' 10' dia HAWT, we might need barrels that cover 150 square feet. (about 8' wide and 20' tall)

I think to get much power this way it needs to be huge and it would turn very slowly, and gettin it up 'into the wind' would be a daunting task because it would weigh a ton, so it would most likely be on the ground which hurts us even further.

Not to be a naysayer ; -), just something to consider which I think oftain gets overlooked with these. They surely have their place and for some applications I expect they may be the way to go.

electrondady1 · « **Reply #8 on:** March 06, 2005, 10:06:42 AM »

just wanted to let you know i am onboard and to see if i can post this image

electrondady1 · « **Reply #9 on:** March 06, 2005, 10:11:25 AM »

one more try

electrondady1 · « **Reply #10 on:** March 06, 2005, 10:14:04 AM »

sorry i tried to post a little video of my vawt spining can't get it in the post.

electrondady1 · « **Reply #11 on:** March 06, 2005, 10:46:52 AM »

well, i posted some thoughts in your "share ideas" posting mike before i noticed the new diary. just to reiterate, it's tough to generate currant at 0-150 rpm. a large dia mag rotor 1-2 meters would be sweet. but i dont have tec. right now to allow such a big disk to spin true within a few thousanth at the edge. i an a reluctant convert to a gear drive system. small genies turning off a large gear or sprocket might allow a modular system . as my knowlege and building skills improve the older less efficient units could be replaced/upgraded. also , if you could get the drive system working at about 1,000 rpm them ordinary auto alternators might become more viable.

nvmike · « **Reply #12 on:** March 06, 2005, 11:09:43 AM »

Dan, You made some good points on the efficiency between HAWT and VAWT and I agree with you. I am limited with resources and space as stated earlier and am mainly interested in getting something up and running. I am hoping that some where in the future I can build a HAWT using the great design help I have seen here on the discussion board. I will have to find someone in the country that will let me erect it on their property. Thanks again for taking the time to share with us.

nvmike · « **Reply #13 on:** March 06, 2005, 11:16:39 AM »

Arc,

Let me know if you figure out how Ed's cam design works, I think he has a patent on it, but I think we would be ok to try to duplicate for our own enjoyment.

It appears the cam which is connected to the tail controls the pitch but would be interested to know the airfoil design and where is the angle of attack changed as the air foils move around the circle.

Anyone have any suggestion or ideas on this?

nvmike · « **Reply #14 on:** March 06, 2005, 11:26:01 AM »

I have not posted pics yet, I hope someone comes back telling us how to post a animated pic. Electrondady, how about posting a still pic of your machine?

monte350c · « **Reply #15 on:** March 06, 2005, 12:02:57 PM »

Good observations Dan,

I spent a lot of time researching Darrieus turbines and even building a bunch of small versions. You're right about the area observations.

If we were to use your 10' diameter horizontal rotor as an example again, let's say there are 3 blades. Each one would be around 5 feet long.

So you would have to make or buy about 15 feet worth of blades.

If it was a Darrieus machine, to get the same swept area, each blade would need to be 15.7 feet long.

So for a 2 blade machine, you would need 31.4 feet of blades.

For a three blade machine, you would have to make or get 47 feet worth of blades, or over 3 times more blade length than with the horizontal rotor.

If you compare both turbine types to a wheel, the blades of a horizontal axis turbine are like the spokes of a wheel. Naturally enough with a Darrieus machine, the blades are like the wheel rim. Unless a guy greatly enjoys making blades it's hard to see the advantages...

However both types are fun to build!

Ted.

rotornuts · « **Reply #16 on:** March 06, 2005, 02:36:10 PM »

Dan certainly makes a good point regarding swept area but I'd like to point out another often overlooked factor, rotor efficiency. Buried in the equation used to determine potential power output is rotor efficiency and varying this variable also varies power. Many people claim hawt's have a higher efficiency so this could somwhat offset the smaller sweep in the equation. But the you may want to take that comment in the context that I'm attemping to build a single blade rotor!

Nuts,

TomW · « **Reply #17 on:** March 06, 2005, 03:53:13 PM »

Just click here to see that video:

http://www.otherpower.com/images/scimages/2793/little_erma_004.avi

T

electrondady1 · « **Reply #18 on:** March 06, 2005, 04:07:26 PM »

tom ,how did you do it?thats funny to see it on the screen when i was not expecting it thanks!!!

windstuffnow · « **Reply #19 on:** March 06, 2005, 04:48:58 PM »

The way I see it is the VAWT get a bad wrap because of the area involved. Anyone that has run through the numbers can easily prove that the VAWT blade is much more efficient than the HAWT. (that should bring up a bunch of contraversy)... Having said that, yes there is alot of collection area on the HAWT's and their much easier to build especially in the terms of manufacturing. But... when you calculate what the collection side is actually doing your actually meeting the Betz efficiency. Since the standard is measuring total area of the machine the VAWT's will fall short all the time. If you get into the nitty gritty of what the machine is really doing ( collecting from 1/2 the area )then you realize the actual efficiency of the downwind side. Try a couple formulas only using the downwind side, their pretty amazing. They have alot of potential but from an engineering/manufacturing standpoint they will never match the simplicity of the HAWT's

Have Fun

Windstuff Ed

windstuffnow · « **Reply #20 on:** March 06, 2005, 05:33:03 PM »

It's actually quite simple and can be used for an articulated darrieus or when the offset is large enough, a very powerful drag machine with very little opposing forces on the upwind side. And, no I don't mind you building them...

The diagram below shows the general layout with an exadurated wing angle. The wings and main shaft spin together of course and the cam has a bearing inside the hub and is mounted to the main shaft which allows it to run free of the main shaft. The wings are mounted on a pivot and the rods that control the wings extend to the offset pin in the cam hub. This offset determines the amount of angle the wings will achieve at any given point around rotation. The tail is mounted to the offset pin above the rods. Thats about all there is to it. When the wind picks up the tail will rotate into the wind and automatically positions the wings to catch the air. The cam stays still and the wings and rods rotate around the cam. It works quite well in both configurations. Remember the larger the wing angle the slower the blades will turn but the torque is increased considerably. Smaller wing movements will increase speed but lower torque... the power output is the same regardless with the exception of losses either way.

Have Fun

Windstuff Ed

rotornuts · « **Reply #21 on:** March 06, 2005, 05:35:56 PM »

make that vawt not hawt

arc · « **Reply #22 on:** March 06, 2005, 06:12:41 PM »

Hi Ed,

Thanks for the sketch, you've really captured my interest, I'm going to have to make a working model of this so I can see it in action.

It's great of you to post this ... Thanks!

arc (aka Dave)

monte350c · « **Reply #23 on:** March 06, 2005, 07:02:47 PM »

Hi Ed,

I followed along through another post by you some time ago on the calculations for a drag based unit, and it's not too hard to see you're right about the efficiency of the blade that's actually doing the work - since the blade traveling upwind is of course not contributing, and in fact actually opposing the energy collection process.

The Darrieus are a totally different animal and it wouldn't surprise me in the slightest to see a revitalised Darrieus variant get a lot closer to the 59% limit.

I still like them in spite of the extra blade building required. I have in mind another 'hare-brained' scheme that involves a sort of diamond shaped Darrieus that can kneel to reduce its swept area, for wind speed control. I read an old patent with a similar idea and that's got me thinking.

I'm currently working on a home brew router table that will hopefully allow easy production of multiple blades in some longer lengths. Once that's done I will probably give this idea a whirl.

Ted.

nvmike · « **Reply #24 on:** March 06, 2005, 07:03:52 PM »

Thanks for the information Ed. Very nice design with the cam.

wooferhound · « **Reply #25 on:** March 06, 2005, 07:37:24 PM »

I was playing with smaller sizes of PVC Pipe to make Savinous rotors.

Here's a picture...

And heres the story...

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

windstuffnow · « **Reply #26 on:** March 06, 2005, 07:54:49 PM »

Have you built a darrieus yet? I've built a couple small ones and to be honest their downright scarry. Calculating wing loads its easy to see its critical to be able to control them. The cam is one way to control the speed, basically turning into a cycloturbine.

Have you seen the VAWT's built from standard wind turbine blades? Their a bit scarry also, but can be built with spring loaded pivots at the root which allow the blades to flatten out in high winds. I saw a darrieus built similar to this where the blades were pivoted in the center and the bottom of the unit had a weight. When they started to overspeed the wings would pick up the weight and flatten out decreasing area as well as increasing diameter and slow themselves down. Similar to a flyball governor arrangement. Always wanted to build one...it's in the circular to do list.

so many fun projects.... so little time...

Have Fun

Windstuff Ed

monte350c · « **Reply #27 on:** March 06, 2005, 08:13:53 PM »

Hi Ed,

I built 3 little ones (just about 3 feet in diameter) and that's enough to see some pretty interesting potential. They sort of poke along for a bit then just take off. The last one was a little model of this diamond shaped unit. I put a ring of magnets on an empty wire spool at the bottom so I could track rpm, and a string wrapped around the empty spool, pulled on by a spring scale gave me some torque figures.

I recorded around 25% efficiency which didn't disappoint me too much since at this small size (this model has 36" blades, about 4 feet diameter, diamond shape) the blades are not getting into any sort of decent Reynolds number. Bigger will be better.

I hinged the outer ends of the diamond so it can kneel and this effectively controls the maximum rpms quite nicely. When it kneels the swept area goes down to practically nothing. Adding weight delays this action and increases rpm.

It ran at over 600 rpm unloaded in a 15 mph wind.

Fun and I can't wait to try this in a real size!

Ted.

monte350c · « **Reply #28 on:** March 06, 2005, 08:28:18 PM »

Here's one of the diamond shaped models. I'm hoping to be able to test a 15 or 20 foot diameter full scale model this summer. All the tests on the little guys look pretty good.

Ted.

ghurd · « **Reply #29 on:** March 07, 2005, 01:00:48 AM »

Wow.

New to me. The 'fold down' idea.

Regarding the lower area. How much wire do you go through? Looks like a 500' spool of 14ga to me.

G-

monte350c · « **Reply #30 on:** March 07, 2005, 08:20:25 AM »

Hi ghurd,

This will sound really dumb. I don't know how many feet of wire were on that spool. I made friends with a guy at a motor rewind shop last year, and when I need wire, I just go there. He takes an empty spool, like the one in the picture and fills it with whatever guage I ask for.

That one was a spool full of 18.

So, when I am winding something I just keep going and hope I have enough wire. When the spool starts to look a bit empty I go get some more. Pretty unscientific!

Ted.

finnsawyer · « **Reply #31 on:** March 07, 2005, 08:42:53 AM »

Since a VAWT has a large diameter any way, might I suggest the following: Place a hoop or ring around the outside of the VAWT that extends a short way below it. Place a pneumatic tire on the end of your alternator and drive that off of the inside of the hoop (makes better contact). This should allow a considerable speedup with little loss of power. You control the tension of the drive by adjusting the air pressure in the tire.

windstuffnow · « **Reply #32 on:** March 07, 2005, 12:21:49 PM »

Very nice! That's pretty much what I was talking about... I had seen one engineered this way ( flyball reference ). The top was secure and the bottom had the weight. It was some time ago so I don't remember any specifics about the unit.

A large unit may need to be "coaxed" into the TSR of 2 range to get it up to speed. I've seen a couple large units that the alternator was also a starter to bring it up to speed when the wind was there.

Great work! I'm looking forward to seeing a larger one. Keep in mind the stress loads on those things when designing it... they can go critical very quickly in wind gusts.

Have Fun

Windstuff Ed

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Author Topic: VAWT Postings Welcome (Read 17606 times)