How about running at 36V

[force9BOAT]

Hello,

I've learned that the stator I built has way too many windings for 12V and even 24V.  I can hit fifty no-load volts turning the machine by hand as fast as I can.  But that is at higher RPMs than I think I could ever reach with local wind conditions.  So I'm wondering, how about 36V?  Most discussions appear to assume either 12, 24 or 48V.  Do batteries need to be connected in series of 2 or 4 or can I use a series of 3 to produce 36V cut-in?

Thanks all,

Rob

[dinges]

In itsself, 36 isn't better or worse than 24V or 48V (apart from the wiring losses/wire size needed). The batteries can be wired up fine for 36V.

The question boils down to whether you can find equipment to operate on 36V. 12V gear is plentifully and cheaply available; 24V and 48V are less common (but usually of higher quality, I understand). 36V? Can't remember ever having seen equipment for this voltage; which doesn't mean it doesn't exist, of course.

Remembering that your stator didn't earn a beauty prize, perhaps it may be wiser to simply rebuild one for the voltage you really need? Short pain now, when building, but I think you'll be happier in the long run.

Peter,

The Netherlands.

[Flux]

Yes you can use 36v . In past times 32v was common for lighting plant.

The snag is that the world seems to have standardised on 12, 24 and 48v for inverters. If you use 36v you will need a special inverter that will be expensive.

12v is common because many of the halogen lamps will run directly and you can also buy cfl lamps for 12v. You may be able to get these to order for 36v but the cost will be higher.

If your loads are modest you could use a voltage converter to 12 or 24v.

Charging at 36v and taking loads from taps on the battery has lots of problems but if you are prepared to swop batteries round and keep balancing the volts you could do that.

If you can reach 50v by hand you may not be that much too fast for 48v. It is difficult to crank at much over 250 rpm by hand. A fast prop at 48v may not be out of the question.

Flux

[wdyasq]

The 'new' auto voltage is claiming to be a '42V system' but are actually 18 - 2.2V lead acid cells.  The bad news it they aren't being built yet.  The good news it there will be good-sized efficient '42V' air-conditioning systems when they start making them.

Ron

[Flux]

If you are prepared to mount your rectifiers on the tower you can connect your alternator as 3 star windings for 12v and use 3 rectifiers. This comes out quite nicely with 3 coils per phase in each winding. You have the leads outside so you can do this.

I think 12v was your intended voltage so this should work out quite well.

Flux

[wooferhound]

Instead of wiring it up in star or delta

you could rectify each phase individually





then combine the voltage after the rectifiers

This will lower your voltage somewhat

while increasing the current somewhat

[force9BOAT]

Thanks Wooferhound and Fux,  I like both those ideas and will try it.

Rob

[Shadow]

I've often wondered why they did that, started out everything was 32 volt, light plants, wind generators, lots of equipment. Then along comes 110 volt from the power companys, which I can see being more feasible. But then off it went to 12, 24 or 48. 32 volt was lost and forgotton.  Why 32 volt in the first place? and why didnt it carry on, 12, 24, 32? Things that make you go hmmmm.

[electrondady1]

 i'm a bit confused, (not the first time) my understanding is that if the geni puts out more than than say 14 volts the battery some how holds the voltage down and amperage is increased.  if that is the case, why the concern with larger voltages ?

[Tom in NH]

I don't know much about wind energy, but I'm wondering, would a DC-DC converter be a solution to your problem? I use an MPPT controller on my solar panels, which is basically a DC-DC converter. The nice thing about it is it will accept as much as 100 volts and convert it down to 12 volts for my batteries. The downside is my particular unit does not provide for a dump load, which I imagine is quite important for a wind system. --tom

[Waterfront]

It's when you consider line loss to the battery that the difference comes out...

Line loss = R x I^2

So, comparing 12V and 48V for a same power output, for the 12V, the battery will take down the open circuit voltage and you'll get 4 times the current (I). When you come to calculate your line loss to the battery, that 4 times (I) is gonna get hammered by the square in the equation (4x4=16 times the lost). To make it up, R is gonna need to drop down considerably, and that will cost money!

For short battery runs, it's not much of an issue, but if your 300' away, and your using a 12V system voltage, and your batteries convert all that OC voltage into amps, your gonna get killed getting the output to your battery.

Hope that helped,

[Nando]

ROB:

You do not need to rebuild the stator windings -- as a matter of fact, with higher voltage and a charger controller you will be able to harvest higher energy levels since you are not clamping the alternator to the battery voltage.

Instead of attaining around 50 % maximum power harvesting at the peak power you may obtain 85 to 90 % efficiency.

Send me a message directly and I explain what to do.

Nando

[Flux]

Rob

Woof's suggestion of rectifying phase separately is equivalent to delta and may not be slow enough to get you down to 12v.

For now connect as 3 parallel star windings with individual rectifiers.

If you have a bit of electronic experience take up Nando's offer, the electronic solution is effective but it will not happen instantly. You can always re-connect the coils back in series star when you have the electronics running.

90% is too optimistic, you will not achieve that from your alternator into a rectifier and you will have converter loss. There will however be a fair improvement over the normal resistive matched connection. It will also remove most of the problem of line losses between mill and battery.

Flux

[Flux]

Yes the battery will hold the volts down and it will work, but a winding designed for a higher than necessary voltage will not match a low voltage properly, there will be too much resistance in the windings and you will bring the prop operating point down into the region of stall.

You will get poor blade performance and poor alternator performance.

Flux

[Nando]

Flux:

Well the 90 % it is not optimistic if the generator produces voltages about 3 to 5 times greater than the battery bank.

Normally, if one can measure the internal resistance of the generator and the external load is at least 9 times higher impedance than the generator's then one can calculate the power transfer and at the same time define what voltage level is needed to attain the % efficiency.

85 % efficiency is not difficult to attain, let's say a 1 KW generator with a peak voltage of 250 volts which represents 4 amps output.

Let's say the 10 % is lost in the generator or 100 watts which makes 100 watts / 4 amps= 25 volts drop internally in the generator and 225 volts going out at 4 amps rate, let say that the converter takes this 900 watts ( 225 volts @ 4 amps) and converts it to any desired voltage, like a 48 volts bank ( charging a 56 volts level with a current transfer of (225 / 56 ) * 4 amps = 16.07 Amps.

In addition let's say that this convert has an efficiency of 94 %, instead or 16.07 amps the current would be 16.07 * 0.94 = 15.1 amps for a total wattage of 15.1 * 56 = 845.6 watts

Generated power = 1000 watts

Delivery power = 845.6 watts

Over-all efficiency = 84.56 %

IN ADDITION this generator can start producing energy at a much lower wind regime, like at 80 volts, without boosting if the controller is well done with MPPT capabilities.

I have worked some 10 and 20 KW Wind Mills that produced around 87+ % efficiency with generators producing much higher voltage, charging high voltage battery banks.

Nando

[Flux]

Nando

Your 90% should be quite possible at 10kW but it is difficult to maintain such efficiencies with smaller machines.

The biggest snag I found is the drastic increase in size and cost of the alternator to gain the full benefit.

For a small machine the saving on size and materials for 50% is considerable and the gain is easily made up with a bit bigger prop.

With larger sizes dissipating 50% in the stator is not possible and the situation changes rapidly.

At present I feel that the idea will be limited to those who can build it themselves and who want the best possible from a given size machine.

If you can produce it at a low enough price or make it so simple that anyone can build it then it will not be long before everyone uses it.

Keep up the good work.

Flux

[Nando]

Flux:

This efficiency is not limited to high power, it is defined by the way that the generator is designed and its output voltage..

I have two Wind mills in South America, using a F & P generators that are used without any wiring change (one 100 and one 80 wire sizes) with high voltage charge controllers that, at the present time, are working and generating 80 to 82 % efficiency with MPPT.

They are in furling mills and soon will be in Pitch controlled mills to see if higher conversion efficiency is obtained at higher constant power levels.

I tried with in this group to interest some of the builders but nobody has accepted the idea.

Nando

[coldspot]

"for inverters. If you use 36v you will need a special inverter that will be expensive."

In my "P-Rat, itus" Findings-

I found an Inverter that wasn't that special and was expensive I'm sure,

Also not that old by some standards,

Maybe 1980-ish, "Best" Brand

B-est

E-nergy

S-ystems for

T-omorrow Inc.

Model # B 32-3000

States Input V.D.C. as, 28 to 38

Just my

$0.02