Help on matching alternator

[zenpi314]

Hello Everyone,

I'm getting ready to make my first alternator. I did make a small turbine with an ametek 30V generator, but would really like to match an alternator to my needs, restrictions, and available wind speed. I have been reading and searching this site for some time now and must say that it is a phenomenal resource. Thank you very much for that. But because I don't have any experience in mechanics and/or electronics, I still have some questions.

The questions are:

What diameter should the rotor and stator be?

How many windings of what # (two in hand) wire?

I live in Florida and would like to use this system as a backup for when the power goes out after a hurricane. The windspeed here is generally low, so I would like to start charging at fairly low speed (hopefully 5 or 6 mph winds) and I don't mind if I don't use all of the power of high winds. Since I live in the middle of town, I would like to keep the rpm's down in order to keep it safe. So, I will try to furl fairly early. When a hurricane hits, I will take the turbine of the tower (only about 22ft).

I have 6.8ft fiberglass blades (from ebay)

I have 24 magnets N42 (1.5 x 0.75 x 0.25). I was thinking about using 12 of these magnets (single rotor for simplicity) and 9 coils.

I have a 12volt battery bank.

I have a trailer hub with 4 on 4 and a 1.25" spindle.

Is there any other information that is important to supply?

I would appreciate any help.

[Flux]

I am not sure how much luck you will have. Wind power in the middle of a town is not likely to give much results unless you can get the thing way above the local buildings. here it would be impossible to obtain permission to get the sort of height needed but things may be easier without all the regulations that kill everything here.

I am not familiar with US wind conditions but I suspect Florida is one or the least impressive. This combined with the urban environment puts you in a poor starting point.

There is effectively nothing at 5 mph and even at 6 mph you need an extremely good machine to do much beyond supply its own losses. Low winds need large rotor diameters but large rotor diameters are much worse affected by turbulence that you will almost have in a town.

Unless you can get 20 ft above the surrounding objects and it is reasonably clear for 1/4 mile arr round with no major big factors to block the wind then you are really in the land of toys and toy windmills really come into their own on very windy sites.At 22ft in this country you would be down below useful wind, I don't know how tall buildings are in your part of the world.

If these low winds are regular and sustained for long periods then something in the size of 8ft may produce enough to keep you going for the odd power outage but it would do much less than a 4ft on a good site. I would be reluctant to try something large as a first attempt, at least at 8ft you would get a feel for the severity of the turbulence and decide if you could risk going bigger.

Your only chance is an air gap alternator and something like Hugh Piggot's 8ft with a few more turns or a grade higher magnets would make the best use of your low wind.

Flux

[cyplesma]

Hey Flux would the urban areas be better suited for a vawt?

[Flux]

I can't really answer that. I tend to regard urban areas as no go for wind power. I have seen nothing in the last 50 years to convince me that a VAWT has real virtues but when thing are close to impossible then possibly it may beat the HAWT.

Flux

[luv2weld]

ZenPi,

Obviously, you have done a lot of thinking about this.  So I want to ask,

why only 1 rotor???  It may be simple, but the output is reduced.  By adding

the second rotor, you can greatly increase the output for just a minor

investment in materials and labor.

The other question is "Why not follow the plans that are already published,

either by our hosts or Hugh Piggott, Ed Lentz, Randy Burmeister, etc.

Their plans are very easy to follow and if you work carefully, you know

what the output will be (or at least real close).  When you start asking

someone to recommend the size and number of windings, especially on your

first mill, you are venturing into the experimentation area.  You are also

asking them to take responsibility for the outcome.  If you don't make the

decision, then it's not your fault if it doesn't turn out exactly the way

you wanted.

Did you ask the questions because the blades you bought were not exactly

what was called for in the plans??  Then you have the opportunity to become

one of the "old hands" at this by using those blades and carefully

documenting and posting what you did and the results.

Without any testing, we can say that the 6.8 foot blades will probably spin

a little faster than 8 foot blades in the same wind speed.  Key word there

is "Probably".  Since we don't know how good the blades are, we can't say for sure.

As Flux already said, being in the middle of town, you are not in the

best environment.  So try to get as much height as you can because you need

"clean" air.

Now "jump in there" and get that genny in the air!!!  We all love it when

a new generator goes up!!!

Ralph

[Mary B]

TSR on those blades heavily loaded is 6, medium load is 8, light is 10 according to the manufacturer (in other words I might believe the TSR of 6, the rest???).

[windstuffnow]

  Here are the plans to build a 500 watt rated stator that will work very well with those blades from my site.... http://www.windstuffnow.com/turbine%20kit.pdf

  I reciently purchased a set myself to see how they would do and they are quite respectible.  It's been up and running with those blades for a few weeks now and I haven't seen any noticable difference in performance from the hand carved blades.  

  The kit uses a much larger surface area wedge magnet so it won't perform exactly the same using your smaller magnets.  It might be wise to read the instructions just to see and learn the process then make a test coil and experiment a bit to find the right combination.  That prop will produce some reasonable power so you want to make sure you match it up fairly well.   A runaway prop can lead to quite a bit of damage and/or liability.

  I wouldn't put that prop on a single rotor machine

 

[dastardlydan]

    Zen:

Where abouts in Florida ??

I am in Tampa.

 You mite chech out my posting

Hurricane Electric.

http://www.fieldlines.com/story/2007/4/4/03657/23609

Just finish a 10 Ft made for low wind

here in Florida.

Send your e-mail I am at

dasrardlydan1@verizon.net

PS hope to here from you.

+++++++++++++++++++++++++++++++++++++

[zenpi314]

Hi Flux, Luv2weld, MaryAlana, and Ed

Thanks for the quick responses.

The reason I went with this design is because I did not want it to get too large. I thought that the 6.8ft blades were as much as I could get away with. I really live in the metropolis of Ft. Lauderdale, so size and height are restricted. Flux, neighbors do need to remain friendly;) I kind of took the one rotor idea from the 7 foot turbine being displayed on the otherpower website. But I could get talked into a two rotor design (probably have been already) I also understand the point about making my own decisions, but I was hoping to at least have an idea what wire to purchase, and not have to buy 3 different sizes. So... with a two rotor design, what wire # should I use? I will then experiment with winding count.

I realize that I will not get huge amounts of energy out of my turbine and that it will not be a good investment, but that is not really the point. I would really like to produce some of my own power, just out of principle. Everyone else around here is buying noisy generators for hurricane backup, but I refuse to do that. My solar panel and turbine will have to be enough to charge my 12 volt battery, so that we can watch some tv, listen to the emergency radio, and have a small fan blowing.

Again, thank you everyone for the advice.

Zenpi314

(Ed... thank you for the detailed design. Your website has already been visited by me many times.)

[luv2weld]

ZenPi,

A quick check of my 3 "bibles" shows---

Our hosts (otherpower) recommends for 12 volts--2 in hand of # 14 and 36 turns

Remember that this is for a different size magnet and blade set

Windstuff Ed recommends for 12 volts---single strand # 14 wire and 44 turns

This is for low wind. Again different magnet set. But they are the same

thickness, just more surface area.

Hugh Piggott's book says for 12 volts---single strand # 15 wire and 80 turns

or 2 in hand # 18 wire and 70 turns

This was for an 8 foot blade set and different magnets

Because of the magnet size that you chose, your output will be lower than

the things I have referenced.

There are about a million options. If you already have wire on hand, (as an

example, # 17 wire) you could use it. You just have to adjust the number in

hand and number of turns. Keep in mind 12 volts needs a larger conductor

than 24 volt, etc. So, if you have to buy wire, buy larger rather than smaller.

Sorry I can't give you any firm numbers for your coils, but I have not used

the magnets that you have. Maybe someone here has. NTL, tecker, willib are

some that I seem to remember as experimenting with smaller magnets.

I also only have 24 volt systems, so that's another wrench thrown in the

works.

If you're not firmly convinced to stay at 12 volts, you might consider going

for a higher voltage system. The wiring can be smaller which can save

some money.

I did visit your site. Thanks for posting it. Neat stuff!!

Keep us posted on your progress. Since you already have one generator

flying, you have probably already become the "resident expert" in your area.

Remember that you never really know or understand a subject until you

start to teach it!!

Ralph

[zenpi314]

Hi Ralph,

Thanks again. Very helpful.

I understand that probably nobody has done the exact same thing as I'm doing and therefore nobody will have a ready-made answer. But do you know of a good site or thread on this forum that goes over the basics for wiring? What are the differences in voltage systems, what does adding more windings do, what is the relationship between the different wire sizes, resistence, magnets, etc. Sorry for the ignorance. I saw many threads talking about it, but don't recall a 'how to basics'. I am mentally converted to a two rotor plan, so I can just slightly modify existing plans.

Thank,

Arno

[luv2weld]

Arno,

  "Sorry for the ignorance." Nobody is born knowing this stuff!! Or anything

else for that matter. Everybody has to learn somewhere. So no need to apologize

for not knowing.

I'm going to recommend a reading list. If you haven't read them yet, maybe you

can pick up a few tidbits. If you have already read them, read the parts pertaining

to coils and winding again. I printed them out so I could reread them whenever

something crossed my mind.

1. Hugh Piggott's PMG (Permanent Magnet Generator) booklet--you need Adobe Reader

http://www.scoraigwind.com/pmgbooklet/itpmg.pdf

2. Hugh Piggott's Windpower Workshop or How to Build a wind Turbine.
   
3. otherpower has several pages that should be read and reread
   
   

http://www.otherpower.com/otherpower_wind_tips.html

http://otherpower.com/7windturbine.html

http://www.otherpower.com/woodmill.html

http://otherpower.com/stator.html

4. Windstuff Ed gave you his site earlier. Check the part that has to do

with coils and winding.

This is a quote from Hugh's book "How to build a Wind Turbine"

"The voltage produced at a given rpm is proportional to the number of turns

per coil, so you can double the voltage output by doubling that number of turns

and using thinner wire. (However the also halves the current it can carry

with the same heating effect).

The speed required to produce a certain voltage is proportional to the

number of turns, so you can halve the cut-in speed by doubling the number

of turns per coil.

American wire gauge (AWG) numbers are arranged such that when you add

3 to the number you halve the wire size. For example #14 is half the

weight of #11, and you can fit twice as many turns using #14, or you could

wind with two in hand.

There are lots of other sites and books that I just can't think of right now.

I will keep looking and will update the list as I find them.

Ralph

[zenpi314]

Wow,

Well, of course, thanks again.

That was a crash course in windings. This should certainly help me in the decision making process. I will let you know what I decide to do, and will post it on this site somewhere.

One last question (probably not, but ok), most rotors are 12 inches across for the larger magnets, do you think I can get away with 10 inch diameter for my magnets?

Arno

[luv2weld]

Take a look at windstuff ed's site again. You'll see that he is using 8" rotors.

You can make it as small as you want (provided you can still arrange things

properly). Most of us use 12" or larger rotors because we want "More Power"!!!

Larger magnets require thicker steel. But it sure looks goofy to have a 2"

diameter, 1/2" thick rotor!!! A steel hockey puck!! Larger diameter usually means slower turning. The smaller diameter (such as an Air 403) has to really get

"cranking" before it generates usable power. You can control this by the wire size

and number of turns. Just remember that the smaller you go, the less "real estate"

you have to work with.

I hope you continue with the reading on each section as you build. It's kind of

like a jig saw puzzle. The first time you look at it, nothing seems to fit. Then

when you manage to get 2 or 3 pieces together, you look at it again and you

see where another piece fits in.

Another reason for reading and rereading everything you can find about wind

generators, is you will pick up tips that other people have discovered and

are using to make things easier and cheaper. Examples are--

1. using baby powder as a filler in the resin for the stator and rotors. It is

a lot cheaper than resin and it helps keep the temperature down.

 (Here is where I get hammered because everybody has their own ideas

about the use of fillers.)

2. Using a cake frosting plastic tub to mix your resin in. It was the proper size

(windstuff ed said he needed 19 oz of resin for that particular project)and it was

disposable.

Thanks Ed.

One other thing we haven't mentioned yet---offset. Make sure you have the proper

offset of the generator from the yaw tube center or it WILL NOT furl. I'm

assuming you are going to have a furling mechanism??? Here is a good explanation--

http://www.thebackshed.com/windmill/Docs/Furling.asp

This should be enough to chew on for right now.

Ralph

[zenpi314]

Hi Ralph,

Well... thanks a lot for filling up my day even more with all that information;)

Although I have seen most of the sites, you are entirely correct, each time you look at them you seem to be ready for new information from them. Great resources. I really liked the furling site. Those pictures made it so clear. I almost think I understand it:)

I'll be quite for a while now, while I'm reading and learning. I'll be back with results, a huge mess, and/or more questions. Thanks again.

Arno

[luv2weld]

"I almost think I understand it:)"

Now there's a scary statement!!!

I really doubt that you'll have a huge mess. You seem to be getting a grasp on this

disease/madness. No need to be quiet either. You can now help answer questions

from others because you have a much better understanding.

I'm constantly adding to my bookmarks when someone recommends a new site. I could

probably spend the whole day on the computer reading, and still not be caught up!!

Ralph

[luv2weld]

Arno,

I almost forgot. Sparweb posted a real good basics. Here is the link---

http://www.sparweb.ca/Forum/AXIAL_FLUX_HowItWorks.pdf

Ralph

[zenpi314]

Ralph,

Again ,the right info at the right time.

I just ordered the 2x1x0.5 magnets and 2 12" rotor plates. I figure that I should stay on the proven path and built a somewhat common design. When the rotors are done, I want to start experimenting with wire size and coil count. In the mean time I need to practice my welding skills. I just bought a small one, and am a first time user. I did some welding on my tower and a scooter frame which came out decent. Hopefully it will develop enough to create a safe turbine. I also just bought a cheap tachometer so that I can relate windspeed to rpm and do some safe testing on a low test stand.

Thanks for steering me in the right direction (hopefully).

Arno

[luv2weld]

Arno,

The best advice I can give you on your welding is---

get a tablet and a flat washer and a pencil. No joke!!!

Put the pencil point inside the washer and drag the washer around the

the tablet without making any marks on the paper. It's practice for holding

the stinger at a constant height above the work. When you can drag the washer

around without making any marks, you're ready for the next step. And the

next step is to practice welding. And keep practicing. The more you practice,

the better you'll get. Did you get a wire welder or stick??

You already have a tower??? Give us some more info.

I really think you'll be surprised how easy and simple your generator will

go together. I can just about guarantee a smile from ear to ear when it's

finished. One of the secrets is to focus on only one thing at a time. It's

a lot like lifting the hood of a car and looking at the engine compartment.

Most people get overwhelmed when they do that. But if you focus on only one

thing at a time, it becomes simple. It's just a lot of small pieces working

together. Just don't try to look at everything at the same time!!

If you need help, or just have a question, email me direct--luv2weld at

hughes dot net.

Ralph