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philwzen
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Joined: 21/09/2013
Location: Fiji
Posts: 2

Posted: 06:42pm 21 Sep 2013

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hi everyone,
this is just an idea i had a while ago. not really had a chance to test it but what i have done looks promising.
Basically to do with power transmission, trying to get away from having heavy exspensive cables from power source to batteries/controller. i live off grid , have done for years mainly solar but a small 600w windmill also. thinking about rearanging my equipment for optimum placement gave me a problem as controls and batteries would be approx equidistant from panels and wind mill. id need a lot (130 meters+) of heavy duty cable for the 12v side!!! particulary as the windmill is 3 phase ac output .

this got me to thinking , we all know you want to have high voltage to travel long distance to minimise cable loss. so how about inverting at the panels and at the mill sending it down the line then drop down to 12v again rectify and regulate for controllers and charging. I know people will say loss in inverter but try this ! get cheap chinese inverter . only use the first half of the circuit which chops the dc at a high frequency and transforms it up to around 250v, dont bother with second stage 50hz chopper as we actually want a high freq ac for transformer so it will be smaller, (higher freq ac needs smaller transformer for same power apparently!).this voltage can then be fed down the line or even transformed higher,(this is as far as ive got testing the idea) we may run into problems from RF perhaps would need to use a coax cable after all its not different from a high power radio transmitter. at the batteries use same ratio transformer to drop down then rectify it and away you go! for the windmill i would 3 phase rectify to get single dc source to invert up.

sounds mad but i think it would work, and save a fortune in cableing! please any comments. its just an idea for people to play with. ill also post this on otherpower.com for some ideas .
regards
phil. in the jungle Fiji!.

norcold

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Joined: 06/02/2011
Location: Australia
Posts: 670

Posted: 07:50pm 21 Sep 2013

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Copper is expensive, but why not just have your solar panels in series, say to 120 volts, then the solar controller converts back to your battery voltage right at your batteries. Todays controllers are designed with this in mind.

Your wind turbine, run the three phase right to the rectifier again at the batteries.

Of course I may not be in complete understanding of your thoughts here, but it is a simple and effective solution. Edited by norcold 2013-09-23

We come from the land downunder.
Vic

Tinker

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Joined: 07/11/2007
Location: Australia
Posts: 1904

Posted: 03:48am 22 Sep 2013

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Phil, I suspect you may be kidding yourself in thinking that 130m of high quality low loss coax cable is cheaper than rusing adequate DC cables without the RF paraphernalia in the first place.

Norcolds suggestion above is what I would do in your situation. But keep in mind that 120V DC is as dangerous as mains voltage AC.

Klaus

philwzen
Newbie

Joined: 21/09/2013
Location: Fiji
Posts: 2

Posted: 10:35am 22 Sep 2013

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i understand what your both saying but two things. we wont really be in rf territory only around 5khz i think so might well be able to get away with bell wire!. also im in FIJI stuff here is horendously exspensive and often totally impossible to obtain . you cant even buy replacement capicitors when they blow!. as for seriesing the panells great idea hadnt thought of it , i have 14 12 volt, never seen a controller here that will take that and if it was here it would be in the thousands of dollars range, i will investigate. thanks for the input.

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