AC versus DC cable, energy loss

[(unknown)]

 I have building a VAWT for a while, just beginer there. I put my turbine on the shed and run AC wires for about 30 ft. to my basement.

 I just want to ask which AC or DC curent loses more energy versus travel, because I could build bridge rectifier on turbine frame if AC loses more of it's curent.

 I am not very good at it, so any advice would be helpful.

Thank you

Vilius

[birdhouse]

vilius-

AC current travels much better over distance.  if your turbine is AC (guessing it is) then you would be better rectifying just before the battery bank.  what kind of power have you seen out of you VAWT?  just curious.

let us know how it turns out!

birdhouse

[independent]

My understanding is AC is better for changing voltage and up and down as transformers can be used. However, voltage loss over distance is decided more by how many volts you have in relation to cable size. That is relatively high voltage will lose far less potential energy over a long distance compared to a relatively low voltage (depending on cable size) whether it's AC or DC. Because AC is usually higher voltage then it follows that it travels well and as an added advantage will be able to be transformed to a lower voltage with little loss and simply.

[joestue]

Rectify at the turbine and save yourself 33% on the copper.

Better yet use aluminum, its cheaper.

[DanB]

I had a feeling this one would be controversial.  I think you got it wrong birdhouse...

If the voltage is the same, DC will have less line loss.  If you want to save on cable then run DC.  With AC, (especially a battery charging system), much of the time there is 0 current in the line ~ and other times high current.  With DC it's less current and fairly constant.  The I^2R losses are greater in the AC line.  Most folks think AC is better but that is a misconception.  AC is better in many cases because transformers are easily used to increase the voltage for long lines and decrease it at hte end where it's used, and of course the high voltage helps greatly.

  I still prefer to run AC actually, because I like the rectifiers and the stop switch to be located indoors near the battery.

[tanner0441]

Hi

Transformers are OK if the frequency is fairly constant around the design frequency, outside that range they become very ineficient and can turn all your power to heat.

As for aliminium you are stuck with compression connections ie. you can't solder joins in the cable easily to extend it. Brass nuts and bolts are prone to electrolitic corrosion.

Brian.

[vilekas]

Thank you all guys for advices

My VAWT is producing 5V-7V (don't know AMPs) at about 5-9MPH wind, the peak was about 12V on really windy day. I have 12 AWG AC cable.So still not so satisfying.

 So I build new stator(much more wire) and new rotor assembly, so I will double stack over old one, and going to do some changes on blade design, and later change wire to 6 AWG.

 The reason why VAWT is not much wind up there in PA where I live. I had homemade HAWT, but that was not much performance...

 After all changes done, maybe I will put it on the house roof... don't know how.. the thing is heavy enough... but someday

 all projets still await's at least for snow melt... we got plenty of it there in PA

Thank you all again

 Vilius

[REdiculous]

Another thing: You can't pull lengths of aluminum through conduit that bends because you'll stretch and probably break the wire. This can really (really!) suck if you ever have to pull the wire back out.

The line to our well-house used to be aluminum. It took 3 people and 2 full days to get all the dead wire out.

[birdhouse]

dan-  i stand corrected.  thanks for the detailed explanation!  

birdhouse

[joestue]

Good point about the conduit.

To the GP, Transformers work a lot better when you have a tap changer set properly.

Transformers cause starting problems due to the cubic wind loading, not because the iron losses are high, but because volts/hz is highest at startup and there is no power available. Depending how you look at it, iron losses are actually almost zero at startup and will climb with hz to the 1.6 power ( silicon steel) or as high as 1.9 or so with newer amorphous iron.

The solution is to just use at least 2 sets of primary coils. If your alternator is very efficient then you may be able to get away with a WYE/Delta switch on the primary.

Or just get a bigger transformer and accept 4 times the losses overall. (50% efficient alternator, full load at .6T, startup at 1.2T)

I suspect that most of these axial flux alternators are mostly sine wave machines, in which case there would also be a 5-10% benefit to wiring up a 12 pulse rectifier.