Coils, windings, gauge, voltage.

[zowwie438]

All,

Thanks to everyone who has replied in the past... And thanks for everyone participating in the group.

I have a few questions that I can't find answers to.

I am almost ready to build, but I can't find an answer to how many coils, winds I need for my proposed PM.

Here are the stats:

Diam: 20"

Thick: 7/8"

Material: Steel

See LARGE bearing assembly here: http://www.fieldlines.com/story/2004/8/7/113757/0426

Intended purpose:

1. Drive heating element for water heater(s).
   
2. Use excess voltage when heaters have reached temp to charge batteries for landscaping lights, fountains, etc.
   
   

My concerns are this:

High Voltage:

   a) Nice because I don't have to be too concerned with distance.

   b) How can I throttle the voltage coming from the PM... What a regulator?

   c) Voltage must be "pulsed" to heating element to prevent abnormal load and the adverse effects such a high load oculd place on the mill.

Magnets: Plan on purchasing some 2" X 2" X 1/2" NEO's.

Dependency:

   Average wind speeds are only 10 MPH or so... So it's very important that I get MAX volts/current from device.

Wire Size:  

   Should I purchase some 18gauge or 20 gauage?

Blades:

  System will sport a three or four blade assembly that is 8'.

If anyone has any input, links or else related... Please give me some ballpark numbers so I can start experimenting.

[DanOpto]

http://www.windstuffnow.com/main/formulas.htm

Buy the design program from windstuff now.  It is far cheaper than making a mill and finding it doesn't work.

You can input different sizes of blades to see what power you need.

Electricity (in Ontario} costs about 14 cents per kilowatt hour delivered.(rising soon)

The windstuff now has a 16 foot mill producing

 160 watts at 10 mph   worth  2.2 cents per hour  or   53 cents per day    

 440 watts at 14 mph   worth  6   cents per hour  or  $1.47 per day

I suggest that your design is too small for your suggested use.

A small 110 volt electric heater uses 1500 watts.

You would need multiple heaters to heat a house in winter.

A 25 foot diameter mill will produce

 371 watts at 10 mph worth  5.1 cents per hour or  $1.24  per day  or $37 per month

1017 watts at 14 mph worth  14 cents per hour  or  $3.36  per day  or $100 per month

If you are going to all the effort of putting up a wind generator, make it big enought to generate a reasonable amount of power.

My power bill is about $150 per month.

If my average wind speed is 10 mph then my savings will be $37 per month or $446 per year.

If I am only saving $446 per year, I cannot afford to put $1500 into my complete system for it to pay for itself in 3 years.

I would encourage you to look at larger machines if you are in need of anything more than a hobby.

This is the rub that I see with wind power.

A wind generator has to be much bigger than the units we are currently experimenting with in order to be truly a cost saving or competitive with the grid.

[old55olds]

This seems to be a hard concept for most people to accept. This is a good hobby but if you think that you are going to do better than the utility, you gotta remember that they have deeper pockets than most of us, and more politicians in their pocket too. The payback time is greater than most people are willing to live. Typically with my 1Kw genny in similar winds I can produce 153Kw per month in similar wind conditions. I have long ago learned to do without the electric drier, stove, hot water heater (all on propane) When the sun goes down the outdoor decor lights go off too. I would thind that you will need rather heaverier wire.  Mine uses 9 gauge wire and 1.5 X 2 inch neo's. 3phase  12 poles. 8foot prop..  For your size you probably will need 10 times that.

[zowwie438]

Guys,

First... Thanks for the cost break down.   I have seen tons of data here and there the past month or so, but I have never seen it broken down like that.   GREAT! :-)

I know that 10MPH winds are at the bottom of the food chain, but I was hoping to make up for the low winds by using a 20" diam stator.

I figure if I can't get that many RPM's out of the machine (due to large blades and low windws) I would have to double up or tripple up my coils.  (Am I correct here guys?)

I have read that a stator should have at least 12 coils to be worth much, so I was thinking about 48 or 96 coils.

I don't think I am going to get 96 coils on a 20" disc, but I could go with a large disc array... but then it would catch too much wind.   Such a disc could be fixed horizontally though.

Keep the comments coming.   I want to hear more.

PS:  I stated heat, but I am not driving "heaters" with this unit, I am driving heating elements for the hot water heaters OR I am going to heat another type of liquid that retains heat longer and cycle the water from the hot water heaters through a heat exchanger.

I must still figure out the best method with minimal loss and expense.

I still love this group and I wish I would have found it before we closed on our house.... If I knew I would have the mill fever like this, I would have got something with a larger plot of land. :-)

[DanOpto]

You are correct in thinking that a large stator will give you more output at low windspeeds.

A large stator increases the velocity of the magnets over the coils. This increases the output.

You must have enough torque to move the large stator.

That means you must have POWER.

If you build a large stator, you will need a large prop.

http://www.otherpower.com/bigmills2.html

Look at the 14 foot mill on otherpower.

The large stator stalled the prop until the airgap was increased to 1 inch.

If the same rotor was on a 20 foot mill and the airgap was narrowed to 1/8 on an inch, it would really be impressive.

There is no advantage in storing heat in another medium and then transferring it to water. Every extra step adds cost. Water sucks up tremendous heat and is a good storage medium in itself. Just insulate your tank.

You don't need to double or triple your coils.  Just use a bigger, stronger magnet.

When you consider the cost of your tower, the work to build the blades and the wire and epoxy, the cost of another $100 to buy the mother of all magnets will be a bargain.

Wind coils big enough to span the full magnet length and width.

Hot water heating elements are usually 110 volts or 220 volts.

They run on DC just as well as AC.

High voltage coils use smaller wire, drop less in resistance losses and it costs less to get it to your house.

You must increase the voltage to run your heating elements.

Higher voltage coils will reduce the amount you have to boost your output to match your heater.

Hot water heat is "low quality" power"  You may be able to get much cheaper hot water by building a solar collector.  They are very low tech, reliable and they work.

Keep your electricity for lights, and quality power use through an inverter.

You will get much better value for your work by replacing your 110 volt loads.

Propane will give you fast, easy hot water if you need it. And the propane will wait in the bottle till you need it, not like wind.

[DanB]

"You don't need to double or triple your coils.  Just use a bigger, stronger magnet.

When you consider the cost of your tower, the work to build the blades and the wire and epoxy, the cost of another $100 to buy the mother of all magnets will be a bargain.

Wind coils big enough to span the full magnet length and width."

I used those nice big wedge magnets on those and they worked pretty well...

I think, with a dual rotor machine, there is a minimum size a magnet can be to still get good flux through the coils.  Those were way more than big enough...

But it may be more cost effective to use an even larger rotor - and keep with smaller magnets which are still big enough to create a good strong field through the stator.  Hughs latest project is using 28 magnets per rotor I think - they are the normal 1" x 2" X 1/2" blocks (or darned close anyhow).  I figure, on that machine - hes got about the same overall "mass" of magnets that I do in mine.  His goal is a 16' prop - and his alternator is producing 4000 watts @ 200 rpm.  (I think mine produced something like 2KW @250 rpm or so...)

So in this case, using smaller magnets  - more of them - and a larger diameter rotor pays off.  Of course... I think doing it the way I did may make for a more compact machine which may also have its benifits.  

The whole trick though is matching the alternator to the prop.  To do it most efficiently (cost wise) we need to pick appropriate magnet rotors and pack as much copper as possible into the stator.  If the magnets are too many - or too large - then we can match it to the prop by opening the airgap... or perhaps putting a bit less copper in the stator, but in either case it means we bought more magnets than we actually needed.  It's better to have too much alternator than too little though... you can always "detune" (Add resistance and/or open the airgap) a big alternator to match up with a smaller prop.  If the alternator is too little.. you've either got to cut the prop down or watch it burn up.

At least thats my take on it all...

I think the next large machine I build may have lots more... and somewhat smaller magnets in it, we'll see.