Considering DIY Long distance from panels

[georgia088]

I have a house that sits about 400-500 feet from an open 1 acre field. I live in area where (as far as I can tell) does not offer net metering services. I use approximately approximately 40kwh - 50kwh per day. The house is surrounded by trees and I would prefer not to add panels on the roof. I do however have a relatively flat portion of roof that I would consider adding panels to that covers about 350 square feet and would receive about 4-5 hours of sun I am guessing. I have some knowledge of lithium batteries and have built several 48v battery packs that I have been very pleased with. I have a couple of questions as to IF I would ever see monetary gains by going "off grid" and what would be the best method. I am in georgia. The only way I would consider doing it is if I did it myself.

If I were to try to go off grid, I realize 400-500 feet is a long ways. I already have wire buried from this 1 acre field to my panel. The wire I believe is 4 gauge aluminum. Because AC voltage travels better with less voltage loss than DC, would I be better off with the inverter near the panels? Or, would the DC voltage from the panels be ok traveling this distance and the inverter close to the house/panel/battery pack?

What size/ kind of inverter would I need?

Would I ever come out financially?

Any input is appreciated!

Thanks

 

[hwy17]

4awg or 4/0 aluminum?

Generally you run DC over the long distance since it's higher voltage and for 4awg I would run several strings of combined DC. If it's 4/0, 240V AC might be an option.

 

[pvgirl]

You'd be better off running the DC for the panels the long distance, although depending on array and inverter sizing you may need multiple DC PV circuits and to run additional wire.

 

[georgia088]

4awg or 4/0 aluminum?

Generally you run DC over the long distance since it's higher voltage and for 4awg I would run several strings of combined DC. If it's 4/0, 240V AC might be an option.

4/0 aluminum.... Sorry.

 

[Hedges]

DC travels just as well as 60 Hz AC.

The voltage drop in AC would cause difficulty staring motors. Voltage drop in PV DC doesn't really matter; even if as high as 25% of DC voltage during peak sun, the system will work OK.

Get an inverter or SCC that supports the highest PV voltage possible. Typically that is 600V maximum. My PV strings with a number panels such that Voc never exceeds 600V in the coldest weather are about 480Voc in nominal conditions and 380 Vmp.

How many wires? Two 4 awg is good for a lot of current, takes care of PV+ & PV- for multiple strings. You need one more wire to ground PV panel frames back to the inverter to prevent shocks.

Financial benefit depends on what you pay for utility power. I estimate that grid tied PV system hardware costs $0.025/kWh over 20 years. If you make a battery system you have to include cost of batteries. Without net metering, if backfeed is not allowed, zero-export with inverter power blending with grid power could let you make it most cost effective. Or you can make an off-grid system that connects to grid and uses it as "generator" when needed.

 

[Hedges]

Since the topic concerns voltage drop for AC and DC here is a handy calculator:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

Something I learned to do by hand in High School, if not Junior High.

The bigger question is, how much voltage drop can you tolerate?
For 120VAC, I'd say about 6V.
For 380Vmp DC, I'd say I could even live with 190V drop (assuming wide MPPT range), I'd be OK with 95V drop, I wouldn't be terribly upset with 38V drop.

Also see if 1000V max is a possibility. Many panels support it and some inverters do.

The only question is, what costs more, silicon or copper (aluminum if you like.) You can offset the loss, within limits, by putting up more panels. That can make sense with 500' or 1000' distance.


For OP, 1000' for 4 awg aluminum is 0.5 ohms.
If he uses 4 strings of 10 amp panels, 40A will produce 20V drop.
An 80 Vmp system would drop to low for charging 48V battery but would work for 24V battery.
A 200Vmp system would work fine, lose 10% only during times of highest production (which usually doesn't matter if not grid-tied.)
A 400 Vmp system would only lose 5%, close to the guidelines others recommend.

 

[hwy17]

4/0 Aluminum is adequate for 60 amps AC at 500ft with less than 3% drop.

So you really have either option if you want it, inverter at the array or inverter at the house. If it's at the array, the 60 amps will be a design limitation, but most people are not running more than 60 amps of inverter anyway. And you can't really run hybrid then either.

@SeaGal Do you have a history with that user? Without any backstory I gotta tell you the correction sounds too aggressive.

 

[georgia088]

@Solarcabin Channel

There will be less power loss if you run the high-voltage DC from the panels to the house, rather than invert to 110V and transmit a low voltage.

I can see there is apparent bad blood here. It was not my intent to stir up problems. Can you explain this? My understanding is there is less power loss when transmitting at a higher voltage and then reducing the voltage down to the needed amount as close to the load as possible. Am I wrong? Am I understanding that the panels in series would create a much higher voltage than the 120/240VAC that I would need at the house. This higher voltage would transmit with less loss than inverting to the lower voltage and then transmitting. I think it started to make sense as I typed it out.

Something I learned to do by hand in High School, if not Junior High.

The bigger question is, how much voltage drop can you tolerate?
For 120VAC, I'd say about 6V.
For 380Vmp DC, I'd say I could even live with 190V drop (assuming wide MPPT range), I'd be OK with 95V drop, I wouldn't be terribly upset with 38V drop.

Also see if 1000V max is a possibility. Many panels support it and some inverters do.

The only question is, what costs more, silicon or copper (aluminum if you like.) You can offset the loss, within limits, by putting up more panels. That can make sense with 500' or 1000' distance.


For OP, 1000' for 4 awg aluminum is 0.5 ohms.
If he uses 4 strings of 10 amp panels, 40A will produce 20V drop.
An 80 Vmp system would drop to low for charging 48V battery but would work for 24V battery.
A 200Vmp system would work fine, lose 10% only during times of highest production (which usually doesn't matter if not grid-tied.)
A 400 Vmp system would only lose 5%, close to the guidelines others recommend.

I am still on the first grade level so bare with me. What would a 200Vmp system or 400Vmp system look like? I think I would prefer to stay with 48v battery packs. I have materials to build them. How many panels/what kind voltage type etc. would I need to produce this?

Thanks

 

[Jim in Florida]

There are several voltage drop calculators out there.

Voltage Drop Calculator | Southwire

www.southwire.com

Is one you can play with to work out your solution.

 

[SeaGal]

My understanding is there is less power loss when transmitting at a higher voltage and then reducing the voltage down to the needed amount as close to the load as possible. Am I wrong? Am I understanding that the panels in series would create a much higher voltage than the 120/240VAC that I would need at the house. This higher voltage would transmit with less loss than inverting to the lower voltage and then transmitting. I think it started to make sense as I typed it out.

Not wrong... absolutely correct

I am still on the first grade level so bare with me. What would a 200Vmp system or 400Vmp system look like? I think I would prefer to stay with 48v battery packs. I have materials to build them. How many panels/what kind voltage type etc. would I need to produce this?

Thanks

Typically 8 panels in series would get you to about 300V. My inverter handles up to about 500V - but you'll need to look at the specs of the inverter to match suitable panels to it. To go off-grid with a usage of 40+kWh is a large system.

 

[WindWizard]

Use the calculator and set it for any distance and wire gauge you want.

Thanks for the voltage calculator. It seems to work great. I ran it with more realistic numbers.

400 Volts DC 30 Amps 500 feet 4/0 Aluminum wire

Voltage loss 3.29 Volts.

 

[Hedges]

500 feet is a long run so HVDC might be a better choice but more expensive install and my recommendation was in general for smaller installs.

True for a small system, and AGM is simple, just have temperature compensated charging.
Couple of PV panels, and run 120V back to the house. Should work fine up to 12A at 120V, which would cause 6V drop (5%)

OP said 50 kWh/day so I'd figure 10kW PV (if that consumption was summer not winter.)
My original 10kW system was four strings of PV panels, about 7.5A each at 380 Vmp so 30A on the home run wire.

Some where in between, might have 150V or 250V PV string to an AIO.

 

[georgia088]

It seems to make a lot of sense to put a large solar array in the open field and then use the 4/0 aluminum wire as the carrier for the PV.

Putting the equipment in a shed in the field sounds like a lot of future trouble in the works.

I like to keep all the Charge Controllers and other equipment in the house where you can monitor them.

I am also a big fan of off grid sense you are not in the power companies back pocket plus you can do your own work without all of the permits required for grid tie. The LFP Cells are reasonable and putting together a DIY pack is fun and saves money.

I like the idea of not having to get permits etc. However, if I do not go fully "off grid" Is there a way to do this to reduce my utility costs and have the luxury of being able to run some equipment if ever a blackout? If I am understanding correctly, to only be "partially" off grid, I would still need to be "grid tied". Is there a way to still have grid power, but utilize what you have?

Typically 8 panels in series would get you to about 300V. My inverter handles up to about 500V - but you'll need to look at the specs of the inverter to match suitable panels to it. To go off-grid with a usage of 40+kWh is a large system.

I just grabbed some data off the net of a 450 watt panel. 8 of these would give me about 278V when in series? Which would mean I would need to find a inverter that could handle 500vish? What else would I need to look for in an inverter? What about specs for a Charge Controller? Again, this is IF I used 2 48v 100AH lithium packs.

 

[Hedges]

My understanding is there is less power loss when transmitting at a higher voltage and then reducing the voltage down to the needed amount as close to the load as possible. Am I wrong? Am I understanding that the panels in series would create a much higher voltage than the 120/240VAC that I would need at the house. This higher voltage would transmit with less loss than inverting to the lower voltage and then transmitting. I think it started to make sense as I typed it out.

Exactly

I am still on the first grade level so bare with me. What would a 200Vmp system or 400Vmp system look like? I think I would prefer to stay with 48v battery packs. I have materials to build them. How many panels/what kind voltage type etc. would I need to produce this?

Transformers can convert AC to higher or lower voltage. For an isolation transformer, same efficiency regardless of voltage ratio.

DC/DC converters use square wave pulses into an inductor to accomplish similar.
Greater power loss for greater voltage ratio, e.g. some equipment is 98% efficient with optimal input voltage, 96% efficient (twice the loss) with voltage near limits.


Here's the first inverter that popped up (not necessarily a recommendation for your needs)

Refurbished | EG4 6K Off-Grid Split Phase Inverter | 6000EX-48HV | 6000W Output | 7500W PV Input | 500V VOC Input | Split Phase 120/240VAC | All In One Solar Inverter

Signature Solar provides solar panels, off-grid solar systems, grid-tie, and hybrid systems. Quality solar inverters, bifacial solar panels, complete solar kits, solar batteries. Featuring brands such as EG4 Electronics with their solar battery, LifePower4 and EG4 LLifePower4 and EG4 LL

signaturesolar.com

Produces 120/240VAC, accepts up to 500V input. Using 16% margin for cold weather, a PV string up to 430Voc according to label would be fine.

Many other AIO or hybrid have lower PV voltage spec. Efficiency and no-load loss (which it burns 24/7) differ, and need to be supplied by PV and battery. A number of factors to consider selecting your inverter.

 

[WindWizard]

I like the idea of not having to get permits etc. However, if I do not go fully "off grid" Is there a way to do this to reduce my utility costs and have the luxury of being able to run some equipment if ever a blackout? If I am understanding correctly, to only be "partially" off grid, I would still need to be "grid tied". Is there a way to still have grid power, but utilize what you have?

I originally setup my system to do just that. I plunked down a few panels and then ran them into a charge controller and then ran that into some LFP's that were connected to a Inverter to run the house. I had it setup so that when the LFP's had enough charge, then the inverter would run the house and then when the voltage dropped on the LFP's then it would flip the relay on a transfer switch and then go back to grid power.

It worked great and I was able to reduce the power bill. Then I decided to expand and expand and now I am pretty well off grid.

 

[georgia088]

I originally setup my system to do just that. I plunked down a few panels and then ran them into a charge controller and then ran that into some LFP's that were connected to a Inverter to run the house. I had it setup so that when the LFP's had enough charge, then the inverter would run the house and then when the voltage dropped on the LFP's then it would flip the relay on a transfer switch and then go back to grid power.

It worked great and I was able to reduce the power bill. Then I decided to expand and expand and now I am pretty well off grid.

This sounds exactly like what I would like to do! Start relatively small and get my feet wet, but allow myself room to expand if desired later. Could you give me more detail of your setup? I would love to see what others are using (panels, inverters, charge controllers, etc.)

 

[Hedges]

Thanks for the voltage calculator. It seems to work great. I ran it with more realistic numbers.

400 Volts DC 30 Amps 500 feet 4/0 Aluminum wire

Voltage loss 3.29 Volts.

"Length of cable run (feet)"
500' run, 1000' of wire.

OP said 4 gauge, not 4/0.
that returns 3.27% or 13V, still fine.

 

[Hedges]

I like the idea of not having to get permits etc. However, if I do not go fully "off grid" Is there a way to do this to reduce my utility costs and have the luxury of being able to run some equipment if ever a blackout? If I am understanding correctly, to only be "partially" off grid, I would still need to be "grid tied". Is there a way to still have grid power, but utilize what you have?

If you get equipment that is utility interactive (synchronizes inverter output to grid), and use current transformers for zero backfeed, maybe even minimum 100W or 200W draw from grid, that might ensure you never backfeed noticeably. If inverter is feeding 3kW to a load that suddenly shuts off, might backfeed momentarily but hopefully total over the seconds logged by meter is still net consumption.

I'm allowed to backfeed, so I have Sunny Island as a UPS and Sunny Boy downstream from it. There are other lower cost, high frequency, all in one units which could work for you.

To absolutely prevent backfeed, you can do a double-conversion UPS. Something like EG4 Chargeverter uses grid power to keep battery charged to a minimum level, PV charges battery fully, EG4 inverter always supplies loads from battery. You then have transistors always working to supply loads, and inverter + battery must supply starting surge.

 

[WindWizard]

This sounds exactly like what I would like to do! Start relatively small and get my feet wet, but allow myself room to expand if desired later. Could you give me more detail of your setup? I would love to see what others are using (panels, inverters, charge controllers, etc.)

I only like Tier 1 equipment. It works and it works well, and you do not have to keep diddling with it. I personally have looked at the AIO's and have found them to be lacking.

1- If something goes wrong you replace the whole unit
2- The amount of power that is wasted due high idle current
3- Equipment that is built in China or reversed engineered lacks support and quality

Now I used that approach when designing my System. It has to work without my tweaking it every day and it has to be fully automatic.

Start with the panels. I bought the cheapest panels I could find on Market place and Craigslist. I bought them for around $100 each. Solar Panels are designed to last at least 20 years. My panels are producing very well and at $100 they can be replaced easy. I went with ground mount because I really are to old to be crawling on the roof.

The panels are easy once you get them mounted. Just connect up the MC4 cables and run them into your house with a wire.

The next thing you will need is a Charge Controller. If you want simplicity, then go with an AIO. I chose not to for the reasons above. Again, quality is the most important thing. Victron is really the only Charge Controller I would even consider. The 250/100 is the one I chose. It has built in Bluetooth and no fan so it runs silent. All of your setting can be set with your phone.

I chose a 48 Volt Tier 1 Inverter. I wanted a Low Frequency because they have a very large transformer and a rugged and can handle a lot of surge. To switch between Grid and Battery I just used a heavy-duty relay. I used the signal from the Charge Controller to control it.

I know I am leaving out a whole lot of fuses wires and disconnects and other things, but this gives you an idea. Spend your money on quality stuff and it will last for years.

 

[Supervstech]

Your personal attacks like the one above and continual trolling is why you are being ignored.

Hopefully the moderator has taken notice.

End of discussion and putting you back on ignore.

ADDED: By the way my "shed" as you referred to it has been featured in Mother Earth News, Treehugger, and in Lloyd Kahns book and was built for cash. No house payments, no utility bills and freedom!

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