VAWT

[bluehunter40]

Hello everyone,

I am going to build a VAWT. I know they are not too popular but for me it fits. I am going to try to make a single rotor alternator. I am going to do a squirrel cage design. Blades mounted around two round pieces of plywood. I will us a spindle and hub. I expect this will need to work at very low speeds and not always even catch wind. In a perfect world I would love to shoot for 500wats on a 12 volt system. But I don't think that will work. I need some idea of what size magnets and wire size/length to use? I will try to do a little drawing of what I have in mind.

I had this idea: It seems the main complaint with vawt is the slow speed, or the speed in which the magnets pass the coils. I was considering that, if I am using a large round vawt base, I could have the magnets on the outer edge, thus spinning the magnets much faster across the coils. I was thinking of 6 or 9 coils at 3 phase? If I could get 200 watts it would be a great success.

Tim

[electrondady1]

good idea

[ADMIN]

Hi Tim --

The big trick of designing wind turbines is matching the alternator power curve to the shaft power curve from the blades. Until you actually build your blades and measure shaft power at different wind speeds and RPMs, there's no way to answer your question.

DAN F

[electrondady1]

the amount of energy your mill will produce,

 is directly related to it's swept area.

the maximum theoretical power a windmill can produce

 is 59%(bets limit) of the energy in the wind.

a squirrel cage design will produce perhaps 25% of that.

it will produce x amount of torque @ x rpm.

that will be the maximum electrical load it can carry.

creating a mag rotor the same dia. as your mill will allow you the use lots of magnet

 poles and as a  result a higher frequency.

(thats the good idea)

[spinningmagnets]

I like VAWTs, but anyone who wants to play with them must be realistic about whats possible. They have higher torque, but less RPM's if placed in the same wind with a prop-style of HAWT (and both have the same swept area)

They have a narrower RPM range, because even though they have early start-up, as soon as wind starts to pick up, a high pressure area builds in front of them, and a lot of wind volume simply goes around it instead of through it.

Very similar characteristics to the high-solidity water-pumping wind-mills farmers/ranchers use. Early start-up in light winds enchant the inexperienced public into daydreaming that there 'must' be a way to make lots of power from them.

In electrical generation, RPM's count. Higher RPM's are a case where 1 + 1 = 4

I am in the middle of a move to Kansas City, but I plan to make a flash-light battery charger from a coffee-table sized VAWT, and Ghurd sent me 2 stepper motors from trash-day copiers along with diodes and a wiring diagram (Thanks Glen in Ohio!).

I have purchased a camping LED lantern for testing, but it might take a few months to settle in and finish. Have fun...

[ghurd]

The basic design you propose limits itself to about non functional, or at least very expensive.

Single rotor is about half as powerful as the same thing in dual rotor.

The 6 or 9 coils, with magnets in a large OD pattern, takes a LOT of magnets.  Otherwise it will just make an occasional spike of power. The coil only makes power when the magnet is passing.

If all those magnets are there anyway, may as well make a lot of coils, which allows for bigger wire more efficiently used in a single rotor.

The low speed of a VAWT like that needs to be as efficient as possible.

Then go to what E-Daddy said.

The thing will be lucky to get 10% of what power is in the wind, or 25% of Betz Limit.

If you want 200W, decide the wind speed where you want that 200W, then figure out the size it needs to be.

This is about the place most people stop.

Quick math (maybe wrong), I get 200W at 20MPH needing a 48.5 square foot VAWT.

That's about 5' dia x 10' tall.

G-

[bluehunter40]

Well thank you all for your comments. I now realize that this is not the best way to go. I live in South Florida a few miles from the coast. I have hopes of moving to a hobby farm in the future and really just wanted to have a project. But I see now that what I need is a HAWT. However I have very limited room to fly one, that was why I liked the VAWT idea. I not a welder or a wood craftsman either. Plus our wind here is not constant nor always from the same direction. While we see SE Sea breeze at 10-15 on the coast, over most of summer, we tend to have north and south winds in the winter months. Plus I cant got too high, I live in a townhouse, I have a court yard but not much room for guy wires, plus the HOA would be all over me for the VAWT they will have a fit with a HAWT. I was planning on building something that I can take with me should I move anyway, so I will try this: I will still need a smaller HAWT but I think I can make one with duel rotors, the trick for me will be slightly downsizing the alternator? I was thinking about the chispito? But with a real alternator? Also maybe 4 blades? and will the PVC blades work if I make then a little longer and use 10 or 12 inch sewer pipe?

Thanks for being so kind in my education

Tim  

[electrondady1]

i didn't mean to discourage you in any way.

just be realistic.

i think a squirrel cage design is the best looking

that may not be important when you get your hobby farm

 but for an urban environment and happy neighbors it's a good idea.

 a nice one from one of the members

http://www.fieldlines.com/story/2007/10/5/1192/20143

[bluehunter40]

I think its just a question of being realistic. I need to get my feet wet, so to speak, and I have read many posts where the message seems to be "build something tried and true". Having said that I still like the looks of a VAWT but I now think I should do something proven then venture into design work. However I must say that link you posted was impressive, very nice work. Like I said, I would be happy to get just a few hundred watts at 12v. I think the key is to get my hands dirty for now. I have seen some posts about a 4 footer, do you know where I can get plans for something like that? Must I buy them? I would have thought people would give away this kind of information in this type of setting. Don't get me wrong I will buy if I must. I thank all of you for your comments. Oh and can I use a simple stick welder for this kind of construction? I think some are around on craigslist pretty cheap. I guess I could find some scrap and learn to weld. I looked for classes in the local schools but there aren't any starting soon. As an a/c tech long ago I used gas torches to braze and think I could pick it up.

Tim  

[electrondady1]

hugh piggott is the guy that started all this back in the 70's

google his name and it will get you to his site

he's written lots of books about it

[ghurd]

Might look at some of Jerry's posts for PVC blades and different twists to alternators.

If the PVC blades are longer, they will turn slower.

And be careful what you wish for.

If it makes 200W (14A) on a semi-regular basis,

you need batteries able to accept that much charging rate,

you need a dump load able to handle more than 20A,

etc.

The items not yet considered can get pretty expensive pretty fast.

G-

[bluehunter40]

Well I would use some 6v golf cart batteries. As for the load dumping, I was very interested in the 12v heating element that is placed into the drain hole of an electric water heater. A few years ago I picked up a 1500 watt inverter that I used to run my fridge on battery power during the hurricanes. That was when my interests peaked. I found a 75watt solar panel and I made a portable charger from 3 vw panels. In fact, I have seen some many people do so much with those vw panels, I work for a car rental company for a while, we had hundreds of them from cars we sold. I was told to toss them in the dumpster. What a waste!

So in the end the system I want would have some PV panels (not VW) and some wind. I can't make enough to grid tie, but for emergencies and possibly powering my shed/tools would be useful. If I am able to move, I want to be off the grid or tied but provide most of my power needs.  

Tim

[bluehunter40]

Okay I bought it, its on the way !

[ghurd]

"we had hundreds of them from cars we sold. I was told to toss them in the dumpster"

And now I am feeling a little ill.

G-

[garison]

you might what to google builders corner everyone has a little different view on

the VAWT. I like them. the one on builders corner is only a 63 watt but I added

 another wing and 6 foot long wings at a 36 in diameter and got 130 watts. and the best part about it  is i learned a lot for the next one. so stick in there.( get her

done).