Author Topic: VAWT (Read 2496 times)

ffoegw · « **on:** February 05, 2006, 01:33:21 AM »

Ok,

I will now confess that I am preparing to build a VAWT.

My intention is to build it just high enough that it will not come near anyones head or any other favorite body parts.

This means that I don't realy have to buy or run up a tower which gives some nice advantages.

I should be able to couple a Power Take Off to any store bought generator I want.

Initial questions are.

Which one and how large?

Also I have not seen any vawt on the net or anywhere else similar to the one I have in mind.

Are there any windmill ideas which are presently patented?

What I am imagining is a vawt which has sails instead of blades.

Has the laughter stopped yet?

I promise that if there are any engineers here who say it can't be done I will listen very carefully.

Here is another quetion.

How much power does a very large Sail Ship take from the wind?

One something like this:

http://en.wikipedia.org/wiki/Tall_ship

Any guesses?

This is the kind of power which I am expecting a fully blown version of my vawt idea should be able to provide however, I will probably start with something with the power of a dinghy or sloop and then work towards a full blown clipper type size of power.

I am imagining something which is much slower than the more popular wind turbines and yet has enormous amounts of power.

That's about 5 or 6 questions however, I am certain there will be many more and I am really looking forward to whatever you have to say.

Geoff

vawtman · « **Reply #1 on:** February 04, 2006, 06:59:42 PM »

Cloth blades in a low turbulant area is not a good idea.In the ocean the design would work.Good Luck and just test different designs.Fun.

theTinker · « **Reply #2 on:** February 04, 2006, 07:02:10 PM »

i myself have no experience with this so i cant be any help but here is a link to a post which had a similar small scale version.

click or copy me :

http://www.fieldlines.com/story/2006/1/30/143452/124

wdyasq · « **Reply #3 on:** February 04, 2006, 07:04:51 PM »

There are several sail designs for VAWT. Some are actually self furling.

Large vessels need 2 HP per to make 'hull speed', ~1.34 X the square root of the length along water. The largest of the 'P-Line' was ~400' long and would do near 20kn - I think, from old memory, it was near 8,000 tons which would mean that speed took 8,000HP or so.

Ron

ffoegw · « **Reply #4 on:** February 04, 2006, 07:06:34 PM »

Thanks vawtman.

I was thinking more of a rigid sail rather than a blade.

Perhaps start with 2' by 4' by 1/8" and cut 4 out of a 4' x 8' sheet.

So here is another question that perhaps someone may know how to calculate.

If a 2' x 4' rigid sheet was held against a 10mph wind how much enegry would it be stopping?

any idea's.

Geoff

(a wannabe vawtman)

ffoegw · « **Reply #5 on:** February 04, 2006, 07:09:57 PM »

WOW!

8000 hp

How many watts could 8000hp make?

Geoff

ffoegw · « **Reply #6 on:** February 04, 2006, 07:16:31 PM »

Actually, I noticed yesterday at Home Depot that a 10kw construction site generator was matched to a 17hp gas engine.

So if I do the math.

8000hp/17hp x 10k = 470kw

hhhhhhhhmmmmmmm

maybe I should patent it.

Geoff

vawtman · « **Reply #7 on:** February 04, 2006, 07:30:51 PM »

Its not so much the energy you can get.You have to get it started first and flat blade designs are horrible for starting.You need an airfoil shape to cut through turbulant winds.Its worth the extra effort.Trust me, I tested many designs when I was at your stage.

ghurd · « **Reply #8 on:** February 04, 2006, 07:36:28 PM »

Almost 6 megawatts. 746W = 1hp.

G-

windstuffnow · « **Reply #9 on:** February 04, 2006, 08:04:27 PM »

The pressure can be found using this formula...

.00492 x area x windspeed^2 = pressure in pounds

A 2ft by 4ft section in a 20 mph wind would create...

.00492 x 8 x 20^2 = 15.74 lbs of pressure

multiply that by the arm length in feet to find ft/lbs. So if the section was on a 10ft diameter the arm length would be 5 ft or making about 78 ft/lbs of torque, if it were running at 50 rpms it would be making aproximately .75 hp or 559 watts. ( torque x rpm / 5252 = hp ) This, of course, is assuming its making that amount of torque constantly through the entire 360 degree of rotation which is highly unlikely.

Sounds like a fun project!

.

mlz · « **Reply #10 on:** February 04, 2006, 08:23:33 PM »

However the vessal that Ron is alluding to has some massive sails... If you have that much room and are willing to build that tall, you must have some major bucks...

wdyasq · « **Reply #11 on:** February 04, 2006, 08:54:03 PM »

About 2 acres of sail Mike....IIRC. There are very few successful VAWT projects. There has been a bunch of money trying to get them to work properly.

Ron

electrondady1 · « **Reply #12 on:** February 05, 2006, 09:08:27 AM »

ffoegw, if you can think of air as a fluid and build your vawt in a suitable maner you will find the wind will be happy to spin just about anything you care to put up. the push is to get the thing to spin quickly. a vawt based on the shape of a sailboats sail could be a thing of beauty and as a by product create a decorative surface. were as a propeller is a propeller is a propeller. the coils are were the power is created and the copper does not know it is connected to a vawt. it can only react to the frequency of the changing magnetic polarity.if you can accept the idea that to create usable power you must use a transmision of some sort or go with a large dia.mag rotor with lots of poles you will be free to create any sort of devise you can imagine.

shawn

DanB · « **Reply #13 on:** February 05, 2006, 09:34:37 AM »

Hi - welcome to the fieldlines! I don't usually get into VAWT discussions because I honestly have no experience with it. There have been a few interesting developments here though over the course of time, but I'm not sure there have been any really successful machines other than perhaps Ed's design (windstuffnow) which seems to still be in the experimental stage - but very interesting! Micheal posted a fun story about an H Rotor he's working on a few days back, that's worth a read for sure!

Some comments:

"This means that I don't realy have to buy or run up a tower which gives some nice advantages."

All wind turbines like good clean non-turbulant wind. I think it's a misconception that VAWTS can live near the ground. I think folks like to believe that (because it's so hard to get them up into the air sometimes). You can put a HAWT near the ground too - it just wont work nearly as well (neither will a VAWT). To roughly quote Mick Sagrillo 'you may as well just leave it in the box if your not planning a tower', think this applies to either type of machine.

"I should be able to couple a Power Take Off to any store bought generator I want."

If your talking sails then I expect your talking a pretty slow machine, you'd really have to gear things way up. Probably feasable if you build it pretty big - probably not cost effective... hopefully lots of fun though!

Initial questions are.

"Which one and how large?"

Ed's design is pretty neat - look up postings and diaries by 'windstuffnow'. I also think the H Rotor probably holds some promise although I'd still not personally go the VAWT route (Id rather wait and let somebody else figure out all the problems for me first ;-) )

"Also I have not seen any vawt on the net or anywhere else similar to the one I have in mind."

There may be a reason for that!

Are there any windmill ideas which are presently patented?

"What I am imagining is a vawt which has sails instead of blades."

I think it would be very slow, and the changing wind direction every rotation would be very hard on sails.

"Has the laughter stopped yet?"

Hopefully not! Laughter is a healthy thing!

Try building a miniature version first. Years ago up here we were playing with a similar idea. It had sails. The bottoms of the sails were hooked to stationary 'arms' (4 of them) that were hooked to the bearing, and the tops of the sails were hooked to moving arms, which moved up and down according to a cam shaft which could rotate in the wind via a tail - so the blades always opened for the wind, and closed when they were coming into the wind. We called it the 'flapper' - and it was lots of fun. The first one we made was only 12" in diameter and it was quite amazing when you'd blow into it, itd spin up quickly and it was fun to watch the sails opening and closing just like they should. The next one was 4' in diameter and didn't work very well at all, it was very slow and didn't have much power (barely enough to turn itself around because there's quite a bit of work in opening and closing sails plus we had a lousy bearing).... but it was lots of fun.

ffoegw · « **Reply #14 on:** February 05, 2006, 10:09:23 AM »

Thanks Windstuff now.

You certainly seem to know your stuff.

Playing around with your formula's above it seems the further away from center the 2' x 4' section is then the more power is generated.

The further away from center however, the more the structural components become important.

Now I am wondering how far away from center I could get without the weight of the structure collapsing itself.

HHHHHHHHHHHmmmmmmmmmm

Geoff

ffoegw · « **Reply #15 on:** February 05, 2006, 10:12:01 AM »

VAWT,

You certainly seem commited.

Thanks for providing wisdom and encouragement.

Geoff

ffoegw · « **Reply #16 on:** February 05, 2006, 10:19:06 AM »

VAWT,

Sorry, no major bucks.

I am seriously thinking about selling up and moving to a couple hundred acre hunting camp where I could have some space and won't endanger or offend neighbours.

In Northern Ontario they go for between $30,000 and about $50,000 CDN a hundred acres.

I live in Southern Ontario, not far from Toronto where I work as a database programmer / logistics analyst.

I am able to work from home on my computer most of the week and so hope to be able to find some ways to also do this when I expect to be "off the grid".

Regards

Geoff

ffoegw · « **Reply #17 on:** February 05, 2006, 10:22:32 AM »

2 acres of sail!

Now I am wondering if there is a way to actually support the perimeter arms of a major size vawt with some kind of wheels?

What do you think?

Too bizarre?

Geoff

ffoegw · « **Reply #18 on:** February 05, 2006, 10:28:29 AM »

Shawn,

Thats what I am thinking also.

There are enough gears, pulleys, axles, differentials, transmissions and drive shafts in the world that I should be able to make a generator spin up to spec as long as I have the power.

That brings me back to my original question.

Which generator should I buy.

Regards

Geoff

ffoegw · « **Reply #19 on:** February 05, 2006, 10:45:33 AM »

DanB,

Thanks for the advice.

Do you have any pics or drawings of your vawt(s)?

I am presently working on a very simple flash animation of what I have in mind.

Is there a way to post a flash file into a thread on this forum?

The vawt design I have in mind would not need a tail.

In fact it should work well in turbulent wind as I am expecting that each sail would make it's own independant adjustment.

In this way I really could add as many sails and build it as large as its own structrue could endure.

I am thinking it could be designed in such a way that add on modules or extensions would be possible so that anyone could start affordably and small while working towards providing power for their entire community ;-).

Regards

Geoff

DanB · « **Reply #20 on:** February 05, 2006, 10:57:03 AM »

Hi Geoff -

"Do you have any pics or drawings of your vawt(s)?"

No - like I said I have no experience with them at all, I've not made one. yet. (except for the 'flapper' we made years (maybe 15 years) ago and that was really just for fun)

I kind of like the H Rotor design though because it seems easier and simpler than some, and I can imagine it's the easiest to get up on a reasonable tower.

"I am presently working on a very simple flash animation of what I have in mind."

Maybe post it as a .mpg and keep it small for the sake of bandwidth. I don't care for flash myself (I dont have the stuff to look at them and I think many others don't). Perhaps I'm just a luddite ;-)

"Is there a way to post a flash file into a thread on this forum?"

I dont know that its ever been tried, but a .mpg would be fine if you keep it small.

"The vawt design I have in mind would not need a tail."

Most dont. It shouldn't be necessary. We used a tail on ours to orient the cam that opened and closed the sails. That was just a silly project though... (were still laughing about that one)

"In fact it should work well in turbulent wind as I am expecting that each sail would make it's own independant adjustment."

Hard for me to say anything with my lack of experience and lack of information about your design.

"In this way I really could add as many sails and build it as large as its own structrue could endure.

I am thinking it could be designed in such a way that add on modules or extensions would be possible so that anyone could start affordably and small while working towards providing power for their entire community ;-)."

Best of luck! Take pictures if you can along the way - Im sure itll be fun!

vawtman · « **Reply #21 on:** February 05, 2006, 12:26:21 PM »

Hi Dan,Am I reading you right,you might build a vawt?You should and I would love it if you copied my design.

BigBreaker · « **Reply #22 on:** February 06, 2006, 11:33:46 AM »

Same power... It's easy to trade rpm off against torque but the same power is there - just in a different form.

RPM is generally better than torque because it makes the generator smaller. High torque requires either gearing or a big genie. I also think RPM is generally more mechanically efficient, to a point.

VAWTs often run slower and torqu"ier" than HAWTs. I'd start thinking about how you'll transform that mechanical action into power sooner rather than later.

Slingshot · « **Reply #23 on:** February 06, 2006, 03:21:51 PM »

Actually, wouldn't the power be less? As soon as you let the wind-blocking area move, the force becomes less because the relative wind slows. A corollary of this would be to observe that a flat blocking area could never move at the speed of the wind and extract power, because the force would drop to zero.

One time I was looking at an undershoot water wheel, and ran some calculations. It seems like the extracted power was maximized when the wheel slowed the water by 50%, but I'm not sure.

windstuffnow · « **Reply #24 on:** February 06, 2006, 04:20:08 PM »

Your quite right slingshot, the formula will either give you the rough lift of a given wing area or the force against the wing ( or flat board for that matter ). In general there are much more complicated formulas to closely predict the output of a turbine, as well, there are different types of VAWT's that operate in different forms. A machine that extracts energy primarily from drag would need to be calculated from the size of wing on the downwind side and the movement away from the wind has to be considered. Also, you have to consider the upwind side moving into the wind and the drag that is taking away from the extraction... such as the savonius. A lift machine is quite different and there are a lot of variables that effect its extraction. The Lenz turbine is a hybrid of both lift and drag.

.

ffoegw · « **Reply #25 on:** February 17, 2006, 03:28:35 AM »

Hey Bigbreaker,

"I'd start thinking about how you'll transform that mechanical action into power sooner rather than later."

I've been thinking along the same lines.

How about taking an old rear end out of a truck and mounting it vertically in concrete.

Attach the axis of the vawt to the extended hub and take power off the drive shaft to either some gears or directly to a generator?

Any other idea's for doing it on the cheap?

regards

Geoff

ffoegw · « **Reply #26 on:** February 17, 2006, 03:38:49 AM »

Bigbreaker,

Thanks for this.

"Same power... It's easy to trade rpm off against torque but the same power is there - just in a different form."

The further out from the center the power remains the same however, at lower wind speeds there is more chance of starting some RPM in the first place.

Please advise if the above statement is correct and any other good or bad consequence of extending the radius.

Regards

Geoff

ffoegw · « **Reply #27 on:** February 17, 2006, 03:45:19 AM »

Hey Slingshot

"Actually, wouldn't the power be less? As soon as you let the wind-blocking area move, the force becomes less because the relative wind slows. "

Isn't the difference in the power actually going through the generator once "the wind-blocking area moves".

Thats a good thing isn't it?

Regards

Geoff

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Author Topic: VAWT (Read 2496 times)