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Solar panel question  RSS feed

 
Phil spalletta
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I am designing a solar panel array for my home want to go off grid or reduce the utilities charges, but the costs and the budget make me ask this question. Is it better to have higher voltage and low amps or just enough voltage to trigger the string inverter and the rest of the panel in amps? ex: string inverter rated 3.3 kwh, trigger is 150 volts dc and 600 vdc max only have 16 165watt panels 36 vdc. = ?
 
Chris Wells
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Location: Zone 2b, Canadian Rockies
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forest garden hugelkultur solar
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Higher voltage, lower amperage will save you money. You'll need less equipment and less weight in copper wiring. It is easier to find cut off switches and breakers for low amperage high voltage DC than it is to find extreme amperage low voltage DC breakers and switches.

It is realistic to use low voltage high amperage DC only if you are energy sipping. An RV or shed might be suited. A residential home will not be.

Have you done everything you can to reduce power consumption? That is always the first step. You can't properly size a system otherwise.
 
frank li
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Location: Michigan
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If your module voltage is 36v, you could run two strings of 8 at 288v. This specification is important to have correct. You would need pv module voc and mppv and your historic low outdoor temperature to be sure, but it looks pretty safe as far as max voc and your inverter has wide input operating voltage range with a low strike voltage.

Chris always hits the point that higher voltage to a point, makes for lower cost in power handling across the entire system and especially any time distances are anything but short and/or the power requirement is high.

Your pv wiring will likely have 2x 15a breakers combined (sometimes combined at or near the control) onto a homerun capable of handling 30a and adjusted for voltage drop over its length.

The actual operating current per string might be around 4.5a-5a
Combined for a single set of conductors-home run, distances up to 250 (1% loss at 150') would have acceptable wire loss on #10 copper. This is economical.

For inverters, i run it high as your array architecture and equipment can without going over the inverters max voc.

 
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