Long distance power loss question.

[KenandDeb]

So which would be preferable?

The guy I bought all my solar stuff supplied a 50' cable to go from the panel array to the 3in1 controller at the bus. The problem is the tall trees blocking the sun at various times of the day. I doubt I will get more than 3-4 hours of strong sunlight in a day without cutting down a few trees. However, up higher on our land is a clearing that would be a perfect place for a "solar farm" but it's 300-400' feet from the bus. As a side note, we found a spring up there today so maybe that will pan out as a better gravity fed option than we currently have. I digress.

If you had a $500-$1000 budget would it be better spent cutting down trees or buying wire to cross the distance? I'm assuming having it already converted to AC would be better for that distance.

[DeMac]

One used saw. Then trees fall for free.



In my experience, the sweat expense is cheap yet offers value.









Even if I had to dig the stumps out by hand, I know what I'd do. I chose to remove the trees. That's my advise.

[Jono14]

Originally Posted by KenandDeb

So which would be preferable?
If you had a $500-$1000 budget would it be better spent cutting down trees or buying wire to cross the distance? I'm assuming having it already converted to AC would be better for that distance.

Last week I literally, jokingly asked my wife: "is it OK to cut down trees to get better sun on your solar panels?" I guess I can see both sides, but cool to keep trees around if you can.

Voltage drop is based on current (lower the better) wire gauge (bigger the better but also more expensive) and distance (shorter is better). So for example, lets assume 400' is the fixed distance and all panels are in series so made up current is 15A and voltage is 150V for the string (curious what your actual panel set is like).
10 AWG wire causes a 11.7 volt drop which is ~8% drop from the 150V.
8 AWG wire = 7.3V (5%)
Doubling the amps would double the voltage drop.

Bulk TEMco 10AWG Solar wire is ~$0.45/ft so ~$360 for 800 ft round trip
8 AWG = ~$0.75/ft = ~$600
Not sure what your panels and SCC specifics are but this looks possible on a first approximation.

I don't think converting to AC helps the power loss specifically, and I have seen some arguments that DC is more efficient at the same voltages - others here will know more about this.
But higher voltage and (more importantly but related) lower amps, keep voltage drop lower. This may be limited by your panels and what your SCC can accept for max voltage.

[KenandDeb]

I have 8 JA Solar 380 panels.


https://www.solarreviews.com/manufac...rjam72s09380pr

[Jono14]

What is the input voltage limit and the max output current of your SCC?

[KenandDeb]

EG4

Rated Power:3,000W
Max PV Input:5000W
Battery Voltage:48V
Max Charging Current:80A
Max MPPT Operating Voltage:500V
DCRated AC Output Power:120V

[KenandDeb]

Btw, we measured today and the distance is only 260'

[Jono14]

Originally Posted by KenandDeb

Btw, we measured today and the distance is only 260'

Well to the best of my calculations, If all panels are in series Voc goes to 390V (8 x 48.75) and Imp is 9.6 so you could expect just a ~5V (1.25%) drop using 10 AWG wire (520 ft seems doable for <$300 in wire).

Not sure how cold it might get where you are (colder panels increase the voltage) and adding a typical headroom of 25% gets 390V to 488V which is getting close to 500V max which can damage the SCC if crossed. So, another option would be 2 parallel strings of 4 series panels each, which puts volts to 195 and amps to 19.2 resulting in a voltage drop of ~9.7V = 5% which also seems totally fine. (6V and 3% drop using 8 AWG wire).

Disclaimer: I am working from theory and have not actually built such a system. Lots of smart folks here, but maybe not as much experience with long runs. The DIY Solar Power forum has a bunch of people powering cabins in the woods and may be able to confirm these ideas.

You can play with your own voltage drop estimates on this wire calculator - their numbers are quite close to mine but not exactly the same.

Good luck, let us know what you end up doing!

[KenandDeb]

Thanks for the info.

[powderskier]

I agree with Jono 14 increase the output voltage put in temp variance it'll be on the panel specs. understanding that dust and angle etc always diminish max output. Today's newer systems of high voltage DC to the mppt are so much better than the old 12v way.
At the same time depending on where you live cutting down trees may be good. Fire and all. Good luck. I've been off grid over 12 years now. A lot of learning to buy quality not cheap. Have fun.

[HamSkoolie]

Also don't forget to calculate available solar energy for your lattitude. Panel specs are a LAB spec and are supposed to reflect maximum production at the equator with the sun directly overhead. Any latitude north of south of the equator reduces production so unless you're on the equator, your panel specs are high.


Higher voltage through a given size wire will result in lower drop because the current is lower (OHM's LAW). However, high voltages are more dangerous though the current (AMPS) flowing is what will do the damage. A million volts with no current is harmless....but if you manage to become the link to ground, there'll be a million volts going through you and that's just not good. Food for thought there.


I'd go with the highest voltage your SCC can handle (and I'd use the panel specs for a safety margin). I'd also put properly rated disconnect switches at EACH end as well as the appropriate fuses on the panel (supply) end. Remember, while you don't want nuisance failures of your fuses, you definitely want them to blow quickly if there's a short.

[Rock-N-Ruth]

Originally Posted by KenandDeb

So which would be preferable?

The guy I bought all my solar stuff supplied a 50' cable to go from the panel array to the 3in1 controller at the bus. The problem is the tall trees blocking the sun at various times of the day. I doubt I will get more than 3-4 hours of strong sunlight in a day without cutting down a few trees. However, up higher on our land is a clearing that would be a perfect place for a "solar farm" but it's 300-400' feet from the bus. As a side note, we found a spring up there today so maybe that will pan out as a better gravity fed option than we currently have. I digress.

If you had a $500-$1000 budget would it be better spent cutting down trees or buying wire to cross the distance? I'm assuming having it already converted to AC would be better for that distance.

If you put your inverter at the solar array, alternating current, AC, suffers less loss over distance. High voltage AC loses even less allowing smaller diameter wire. 220/240v can be carried with standard aluminum transmission cable 400' with negligible voltage drop.
https://inspectapedia.com/electric/L...able-Sizes.php