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Alternator design for big LENZ
By filipeandremail, Section Wind Posted on Thu Aug 28th, 2008 at 11:47:27 AM MST
yes

Hi,
I want to build a 4,92 x 8,20 feet tall (1,5 x 2,5 meters ) lenz turbine designed by Ed Lenz.
My problem is to understand how to build a good alternator for it. I've been mailing Ed about this. He his great and very helpfull. He gave me some tools and formulas to make the math for number of turns per coil etc but I feel I need to learn a lot more about this in order to be confident enough to design and build an alternator for a lenz of that size.
As I'm running out of time (I have till 25 september this year to build it) I give up trying to design it myself and I'm asking if any generous soul could tell me how should I design the alternator for that lenz. :)
I'm posting in this forum instead of mailing Ed again because I feel bad annoying Ed with so many mails and this way the information is shared.
My only limitation is in buying magnets. I live in Portugal and I want to buy the magnets from a European Union country to avoid customs taxes. The best price I found are the magnets selling in http://www.solbergavind.se/ (sweden) or the pack of Grade N40 46 x 30 x 10 Phosphate Coating from http://www.cermag.co.uk/magnet_online_shop/old_online_shop/Buy_Neodymium_Magnets_Online.htm (UK). Unless anyone knows other place to buy cheap magnets in Europe the alternator should be designed with one of those kind of magnets.
I need to know how many magnets, the size of them, the rotor diameter. Also the number of coils, wire diameter, number of turns, shape of the coil and any other information usefull.
I was thinking to build it based on the methods used in the otherpower plans.
Sorry for asking to have the work done for me. In return I promise I will do my best to take photos and videos when I'm building and running it and share all the data I can collect.
special thanks to Ed lenz for all the help so far
Best regards to all.

Alternator design for big LENZ | 10 comments (10 topical, 0 editorial)

Re: Alternator design for big LENZ (3.00 / 0) (#1)
by Stonebrain on Thu Aug 28th, 2008 at 07:54:34 AM MST
(User Info)

have a look here
http://www.neotexx.com/
maybe they are competetive.

I hope people who built a lenz can give more help

cheers,
stonebrain

Re: Alternator design for big LENZ (3.00 / 0) (#2)
by Ungrounded Lightning Rod on Thu Aug 28th, 2008 at 02:12:43 PM MST
(User Info)

Has Ed given you the TSR under load and enough to figure the amount of mechanical power available from the cross-section you plan to build? Those two - plus a guesstimate of your local wind speed distribution - are all you need to to design a matching alternator.

(You can do adequately with just the TSR and a wild guess at the power, such as "about 2/3 the power of a HAWT of the same cross-section" - which might be low if Ed's design is better than the improved Savonius types.)

Re: Alternator design for big LENZ (3.00 / 0) (#3)
by vawtman (vawtman(at)charter(dot)net) on Thu Aug 28th, 2008 at 04:31:03 PM MST
(User Info)

Hi Filipe

What will happen to you if you don't get it done by that date? Not sure where your from.

Take a deep breath and relax a bit.

Mark

Re: Alternator design for big LENZ (3.00 / 0) (#4)
by filipeandremail on Thu Aug 28th, 2008 at 05:55:51 PM MST
(User Info)

lol, nothing special happens really. I'm just going to study to poland in october and the project would have to wait a year and I don't know if I'll have the time.
Now would be the perfect timing for me special because I'm going to received around 500 dollars from adsense from my 6 months revenue with my blog lol (someday I'll get rich with that) and if I don't spend them now with the wind turbine I might just wast them in Poland :)

Anyway, I'm not stressed. If get plans for a project that I'm confident it will work I'll do it. If not, no problem.

[ Parent ]

Re: Alternator design for big LENZ (3.00 / 0) (#5)
by vawtman (vawtman(at)charter(dot)net) on Thu Aug 28th, 2008 at 06:06:04 PM MST
(User Info)

Take the year and build up your gear :)

[ Parent ]

Re: Alternator design for big LENZ (3.00 / 0) (#6)
by Stonebrain on Fri Aug 29th, 2008 at 02:17:42 PM MST
(User Info)

I think indeed you're a bit optimistic thinking that you can figure out an alternator in 15 days.
If you're copying an existing proven design,it might be doable.
But in you're case,even if you're can do guestimations the way ulr explained,you must be ready to do some tweaking like making testcoils and adjusting the airgap.You need to understand how to do a trade off between cut-in speed and high wind performance.
If you want to do these things right,you need to understand what you're doing.

Be aware that even if the theoretical poweryield from a lenz can be good,it's still a relative low rpm-machine,what means that if you want to extract all the power of your lenzrotor,you need a quite big,or even huge alternator or a gear.

Do some reading.Be studiing.This costs time.

In the ideal case you would be able to guestimate a powercurve.
What I mean by this is that you guess for some windspeeds the optimum rpm and poweryield.If you know the powercurve,you're nearly there.
Then you just ask the best alternator-guestimator of the web,named 'flux'(we're lucky he is living on this board)what you're alternator have to be like.
As long as you can't say anything about your rotor,even flux can't help you very much.

cheers,
stonebrain

Re: Alternator design for big LENZ (3.00 / 0) (#7)
by vawtman (vawtman(at)charter(dot)net) on Fri Aug 29th, 2008 at 03:37:00 PM MST
(User Info)

Hi Stone

I think Ed(windstuff) already gave him the most professional opinion.Flux is not much of a vawt fan.

[ Parent ]

Re: Alternator design for big LENZ (3.00 / 0) (#8)
by windstuffnow (elenz(at)windstuffnow(dot)com) on Fri Aug 29th, 2008 at 04:46:41 PM MST
(User Info) http://www.windstuffnow.com/main

I really don't have time to sit down and calculate it out right now... been swamped with projects all year...

The rpm it will run can be calculated using the following formula...

Windspeed x 88 / ( diameter x 3.14 ) x TSR = rpm

windspeed in mph, diameter in feet

When the unit is loaded it seems to like a TSR of around 0.8 for the best performance

Calculating output can be done with the usual formula...

.00508 x Area x windspeed^3 x efficiency ( turbine and alternator combined) = watts

again area in sq ft, windspeed in mph. The efficiency of the blades runs in the 38-40% range, this is shaft power the alternator efficiency will determine the "overall efficiency" of the unit.

As an example your unit 4.92 diameter x 8.2 tall is about 40 sq ft so in a 20mph wind it might make in the range of 450 to 500 watts...

.00508 x 40 x 20^3 x .4 x .75 = 487 watts

It would run at a speed of around 90 rpm in that wind loaded...

20 mph x 88 / ( 4.92 x 3.14 ) x .8 = 91 rpm

The cut in speed, assuming around 6 mph the unit would be running at or around 30 rpm ( same formula with out the TSR... it will run faster wthout a load.

Not perfect but will get you in the ballpark for performance in different winds...

You didn't mention what voltage your going to use for charging, that would make a big difference on turns and wire size.

Hope that helps... when I get more time I can help a little more with all these projects going on around the world..

.
Have Fun! Windstuff Ed

Re: Alternator design for big LENZ (3.00 / 0) (#9)
by filipeandremail on Sat Aug 30th, 2008 at 11:08:42 AM MST
(User Info)

hi,
I have 8-12 mph winds in the summer but in the winter 20-25.
12 volts output would be fine

Thanks

Re: Alternator design for big LENZ (3.00 / 0) (#10)
by Todd a on Sun Aug 31st, 2008 at 10:11:39 AM MST
(User Info)

drag type VAWT are very limitted on the speed. They can not move faster than the wind... resulting in the low TSR. A lift type VAWT can have a higher RPM as it can go faster than the wind (like a VAWT), but has a poor start-up speed. A combination is best really for the DIY. It also sounds like those numbers are for HAWT and likely will not give you as accurate of numbers. VAWT have a larger surface area than what the the area covered for a HAWT has. and depending on the design, you can get a power stroke out of 25 to 75% of the stroke depending on design.

It just can not take into acount design differences like...

http://www.youtube.com/watch?v=Uj2c4NreTSY&feature=related

http://www.youtube.com/watch?v=dl6m4emdeBI

http://www.youtube.com/watch?v=q7ffNWkefyY&feature=related

http://www.youtube.com/watch?v=8FbiPI1iYSk&feature=related

http://www.youtube.com/watch?v=CZ1KN0fKqyA&feature=related

http://www.youtube.com/watch?v=RPN_oZf1DSc&feature=related

http://www.youtube.com/watch?v=UdoKEYNfoVE&feature=related

http://www.youtube.com/watch?v=q9flSPAdOLk&feature=related

http://www.youtube.com/watch?v=CkIX3_O8sWg&feature=related

http://www.youtube.com/watch?v=ZXYUBNpa4Hg

These are a wide range of designs, ranging from about half the size of yours up to probably 2 times. Not all give ratings, but some say from 500w to 5kw. Now the Lenz type do not seem to be the best of the ones I show above, but you might be able to get a 1Kw if you can gear up your generator as the speed of 91mph at 20mph wind is actually probably a bit high. For VAWT they lower the diameter the higher the RPM for drag types.

[ Parent ]

Alternator design for big LENZ | 10 comments (10 topical, 0 editorial)

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