Wind electronics diy??

[CaptainElectrode]

Hi all, I am new to wind generators.  I have a few basic questions but I have been reading for days now and can not find my answers.  

1. I intend to build a generator, what is the differences between 12v 24v or 72v or higher volt systems?  Would it be better to go high volt?
   
2. I want to run the wind generator and any thing not used I want to put it back on the grid for net billing.  How do I convert the electricity to put it on the grid and I do not want to use batteries.  Are there plans that I can make my own converter (if that is what you call it).
   
3. I can not find exact specs for coils?  Where can I find that information?  I want to  build something big and powerful. Any information about the coils is much needed.
   
   

I am new to this list and I want to thank everyone in advance for any help that you may send my way.  

[spinningmagnets]

Hello CaptainElectrode, There is nothing wrong with putting together an odd-volt system, but if you do, you wont be able to use off-the-shelf components (inverters, charge controllers, etc), it will be more expensive than neccessary, and when you have a problem, few people will be able to advise you.

1. The common system voltages are 12, 24, and 48. Each with their own benefits and drawbacks. A Watt is a measurement of power, and it is Volts X Amps (Ohms Law) If you use higher volts, you will need less amps to get the same power. Higher volts travel father distances better, and using less amps means you can use thinner (cheaper) wire safely without overheating. The best wind site may be a hill 100 yards from your house
   
2. Electricity from the city utility is "the grid", and you need to ask them if your city allows "net metering". If yes, they will give you a list of approved grid-tie inverters that have net metering which you can purchase. After installation, an approved electrician will inspect it. Spec out the entire system before buying anything, there is a lot to it.
   
3. On the home-page of otherpower.com there are several popular projects, one is a 10-foot diameter PMA wind-gen, and also a 17-footer (considered very big for DIY). Before spending any money on parts, you should do a lot of reading here. Find out if you can get permission to erect a tower for a wind-gen that is at least 60 feet tall.
   
   

If you're not using a battery for storage, the widely varying "wild" power from wind has sometimes been used to heat water. If you are only net metering to off-set your electric bill, you might spend a lot of money (a LOT) and also time/effort to not have an electric bill, but they will NOT pay you any profit if you give more than you use (and trust me, you use more than you think).  

You need to know what kind of wind you have (difficult to make higher voltage in low winds), and what voltage you want to generate with it before you can spec the coils. It is apparently common to make up the magnet plates and spin them at your sites projected wind RPM's over one test coil. At that point, the coil specs can be altered to adjust its output caracteristics based on a wide set of compromises before making the whole stator.

Read the diaries...(disclaimer: I haven't built one yet)

[vawtman]

Hi Spinninmags

 For a newbie that hasn't built anything.You sure seem to know your stuff from reading.More or less the ultimate newbie.

 Good Job! from me at least.

 Mark

[spinningmagnets]

Dear sir, you are too kind!

I read quite a bit from many sources, but as you must already know, the posting archives here are a goldmine!

My wife is not very "green", and the city does not allow me to have a HAWT here, so I am "chomping at the bit", and I must live vicariously through the many excellent posters here. Many here have graciously helped me with much patience, and I am grateful.

[finnsawyer]

Let's say you build your alternator to provide 24 volts at some RPM.  It has an effective resistance of R.  When connected across a 12 volt battery the current into the battery is I = (24 - 12)/R  = 12/R from Ohm's Law.  The power flowing into the battery is then:  P = 144/R.  Now suppose we rewind the coils keeping the total amount of copper the same to get four times the voltage to charge a 48 volt battery.  To get four times the voltage we need four times as many turns of wire in the coils, which means the wire must be four times as long.  To get that with the same total amount of copper means the wire must have half the diameter (1/4 the cross section).  With 1/2 the diameter the resistance per unit length of the wire will be four times as large.  Since we now have four times the length of the wire the resistance is now 16 times R (16R).  So the current into the 48 volt battery now becomes (96 - 48)/16R = 3/R.  The power flowing into the battery is now:

      P = 48x3/R = 144/R, the same as before.  The total power going into the battery has not changed, but the current has decreased by a factor of four for the given RPM.

So you see the only substantial change has been a decrease in current.  The power can be the same.  The decrease in current also can mean a decrease in line losses since the power loss in a transmission line goes as I^2xRl.  Reducing I by a factor of four (in this case) reduces the line loss or allows a longer transmission line.

You should, however, chose a voltage that would be the most useful to you.

[CaptainElectrode]

Thank you very much! That is the kind of information I am seeking.  One more thing.... I have seen people talking about winding coils using two strands of wire instead of one lone long strand.  What is the advantage of that and why do it?  Also, you said to figure out the right system for my needs.  Either 12 or 24 or 48.  What is the differences between these systems and how do I discover what is right for me.  

FYI..... I am now in the process of building a wind mill that has high torque and will also spin in very low wind speeds.  However, if high winds occur then I have high torque.  I dont know if that effects the type of system i should choose or not.

Thanks once again for your input.

[spinningmagnets]

Dear CE, you are covering some of the basic problems and compromises encountered when contemplating windpower. The classic old-west water-pumping windmill has many thin blades that presents to the wind a fairly solid disc.

It has high torque in a low wind, but as wind speed rises, much of the approaching wind will build up pressure in front of this "high-solidity" propellor, and actually pass around it. To get the most possible power from the wind you have at your site, there's a formula from a guy named "Betz", and a certain amount of wind has to go through the prop.

There is nothing wrong with an even number of blades in a wind-gen prop, but odd numbered blades are apparently easier to balance, and have less of a problem with high-RPM harmonic frequency vibration (don't ask me what that is, it involves math and physics, and apparently cannot be fixed by getting a bigger sledge-hammer).

Therefore most windgens use 3-blades, and some small low-wind gens have had moderate success with 5-ish blades. Some sites are just not very good for harvesting wind, but you need to find out if you can have a high tower (60+ feet high). Measure the wind at the height of tower you're allowed, and can afford.

I "think" that designing a wind-gen to get your target volts at around 300-450 RPM, in the type of wind you have, is a fairly efficient goal. Must balance the prop size against anticipated load.

I believe wiring a coil with several strands "in-hand" has benefits, but I don't yet completely understand it. Two/three thin wires cheaper and easier to wind than one fat wire? free wire salvaged from old TV's? Anyone?

12/24/48? What do you want to do with it? Charge a battery? What devices do you want to run off the battery? What kind of wind do you have? How many questions can I squeeze into one paragraph?

[wpowokal]

An even number of blades is generally not used because when the unit yaws (rotates to changing wind) with an even number of blades will have two in the horozontal plane and this is very stressful on them, uneven number never has two in the horozontal plane.

Hold an angle grinder with the disc horozontal and running and try to rotate it side to side, it resists, so do the blades.

Winding two in hand is generally done for ease of winding and making a neat compact coil, a single large wire is hard to use and leaves a greater air gap between layers, that simple realy.

allan down under

[finnsawyer]

If you keep the coil size and wire the same and go to a two in hand winding with the windings connected in parallel externally, you would get half the voltage per coil and 1/4 the resistance.  Three in hand gives 1/3 the voltage and 1/9 the resistance as compared to the single strand.  Two in hand allows you to use lighter wire to get the same output and resistance.

Don't put too much emphasis on torque.  The power you get out also depends on the RPM of the blade assembly.  Since you can only expect at best around 35% of the power hitting the turbine from the wind anyway, higher torque would mean a lower RPM, which in turn may not be enough to drive the alternator to give the desired voltage.  There isn't much power available at the low wind speeds anyway.

Don't bother responding to this comment as I will be away from the site for the foreseeable future.  I wish you and everyone else the best of luck and may all your winds be fair!

[spinningmagnets]

Thanks Allan! your posts have always been helpful to me.

[wooferhound]

Hey finnsawyer

What's Up ?

could we be nicer to you . . .