Running solar wires long distance

I'm curious if anyone has solar panels in a field approx 200+ feet away from their home.  What is the preferred method for transferring power to the home inverter and batteries?  Has anyone experimented with voltage drop at those distances?  I was recently watching a youtube video on a water generator and he said something interesting, "if transferring power at the same voltage, DC is actually more efficient than AC." This goes against what many of us believe but it seems there is some truth to it.  So it seems the higher the DC voltage I can transmit it at the more efficient it will be and I will also not have the restriction of eddy currents as I would in AC.  Has anyone ran high voltage solar DC wiring at length?  I am able to input 2 165V DV inputs into my unit, but I also understand at this point the DC voltage is getting to a "not safe" point.  Obviously roof mount is an option but requires a lot more code and inspection processes.

The reason AC has been the choice for so many long-distance transmission systems is because it's simple to step up and down the voltages with transformers. DC requires boost and buck circuitry, which is more complicated (and costly), but it's not impossible. The advantages include elimination of inductive losses.

You'll get voltage drop with a long cable run whether it's DC or AC, but at higher voltages you can use thinner wire and that is a cost savings. There will usually be a sweet spot where a higher voltage allows a conductor size that limits voltage drop but doesn't impose the need for extra insulation. So, if your panel configuration and inverter support higher voltage strings, that will give you better returns across distance.

If working with higher voltages is daunting to you, getting a qualified electrician to advise and do the hookup isn't a bad idea.

Bob Nall wrote:I'm curious if anyone has solar panels in a field approx 200+ feet away from their home.  What is the preferred method for transferring power to the home inverter and batteries?  Has anyone experimented with voltage drop at those distances?  I was recently watching a youtube video on a water generator and he said something interesting, "if transferring power at the same voltage, DC is actually more efficient than AC." This goes against what many of us believe but it seems there is some truth to it.  So it seems the higher the DC voltage I can transmit it at the more efficient it will be and I will also not have the restriction of eddy currents as I would in AC.  Has anyone ran high voltage solar DC wiring at length?  I am able to input 2 165V DV inputs into my unit, but I also understand at this point the DC voltage is getting to a "not safe" point.  Obviously roof mount is an option but requires a lot more code and inspection processes.

As a general rule modern systems are going to a higher and higher voltage coming in from the solar strings. Most all in one inverters are accepting a 300-500 VDC input charging a 48 volt battery. We regularly go out 200-300 ft from the inverter and stay bellow the 2percent loss we have to adhere to in Ontario. This is a big change from the older 150-200 volt charge controller based systems we used to use. The transformation happens at the inverter mounted near the end user. You should plan on a good steel jacketed teck cable and metal junction boxes or trays all the way to the inverter to minimize risk. Use a high voltage rated isolation switch at the array and high voltage rated Breakers at the inverter. It costs money but saves money in wiring and allows for much larger systems. It boils down to size of system, how far out you are and the level of loss you are willing to take.

David Baillie wrote:.............The transformation happens at the inverter mounted near the end user. You should plan on a good steel jacketed teck cable and metal junction boxes or trays all the way to the inverter to minimize risk. Use a high voltage rated isolation switch at the array and high voltage rated Breakers at the inverter. It costs money but saves money in wiring and allows for much larger systems. It boils down to size of system, how far out you are and the level of loss you are willing to take.

David B.,   Does this suggest that micro-inverters installed within each panel are going by the wayside now for the industry at large?  If I'm thinking about this right, micro-inverters would kick the DC voltage from the PV panels into 120VAC (yes?), which would reduce line loss (correct?) and possibly allow for less expensive cabling from panel to destination, although best not to skimp on that with any wiring exposed to the elements.  For battery charging, this would need to be converted back to DC at the destination point.  But I thought one advantage of micro-inverters was being able to grid-interie without an inverter positioned near the end-user.  Thanks....

Microinverters will continue to be a worthwhile option for roof-mounted installations, I think. Ease of expansion and tolerance of variation between panels are selling points and I certainly see the benefit this time of year when the afternoon sun gets occluded on the lower panels first. But for any situation where you've got distance to cover, HVDC looks like more of a winner to me.

John Weiland wrote:

David Baillie wrote:.............The transformation happens at the inverter mounted near the end user. You should plan on a good steel jacketed teck cable and metal junction boxes or trays all the way to the inverter to minimize risk. Use a high voltage rated isolation switch at the array and high voltage rated Breakers at the inverter. It costs money but saves money in wiring and allows for much larger systems. It boils down to size of system, how far out you are and the level of loss you are willing to take.

David B.,   Does this suggest that micro-inverters installed within each panel are going by the wayside now for the industry at large?  If I'm thinking about this right, micro-inverters would kick the DC voltage from the PV panels into 120VAC (yes?), which would reduce line loss (correct?) and possibly allow for less expensive cabling from panel to destination, although best not to skimp on that with any wiring exposed to the elements.  For battery charging, this would need to be converted back to DC at the destination point.  But I thought one advantage of micro-inverters was being able to grid-interie without an inverter positioned near the end-user.  Thanks....

I would agree with phil,
The only situation where micro inverters still have a role is on roof mounted arrays or ground arrays close to the house that face shading issues. Micro inverters convert from say 40 volts dc to 240 volts AC but nobody would run a single panel voltage string unless it was a one panel trailer system so there is no advantage there. A 500 volt dc string will have half the power loss of a 240 volt ac feed from the micro inverters. Even on roof mounts a more common solution is becoming panel installed rapid shutdown receivers and a ground mounted transmitter and again a 500 volt dc feed... Design is getting to be more and more site specific as the solutions multiply. For the original scenario of 200 ft from the house a high voltage all in one inverter like the solark or the lux would be the usual solution if you are pairing with batteries,  If you are just feeding the grid a fronius or a sollis or a solar edge would be my choices.

Wow, I'm shocked to discover I'm waaaay behind when it comes to the current state of solar. Thanks for the updates guys!

Douglas Alpenstock wrote:Wow, I'm shocked to discover I'm waaaay behind when it comes to the current state of solar. Thanks for the updates guys!

Douglas, for the longest time you could just spec out a magnum inverter a midnite solar charge controller and 3-5kW of solar and go home. Then China decided to push solar hard. Its impossible to overstate how completely they now own the industry. Cheap lithium options, panels and incredibly powerful inverters have turned everything upside down and halved prices... Solar arrays are now huge, lithium batteries last for 20 years the sky is the limit. Unfortunately there is also a proliferation of low end junk as well. Its now the wild west. I'm fairly conservative in my design choices sticking to companies with a North American presence for support.
Cheers,  David

David Baillie wrote: .....Unfortunately there is also a proliferation of low end junk as well. Its now the wild west. I'm fairly conservative in my design choices sticking to companies with a North American presence for support.  

^^^ This!   I'm possibly being overly cautious with expenditures and the rate of installation, but prefer not to end up with useless piles of electronics destined for the scrap heap or landfill.  Trying to be as modular as possible with installations and buying used PV panels that I can test locally on-sight first before buying on-line as an option.  Still, with a Permie approach to energy needs, PV/wind/hydro seems like such a sensible route for home power.

Nobody has actually posted any kind of voltage drop calculator.  I use this one.

https://www.calculator.net/voltage-drop-calculator.html

For my own system, I'm running about 8A a total distance of 130 feet at 120VDC, with no measurable voltage drop through 10 gauge copper wire.  Just plug in your numbers into the calculator to see what you get.

I'd suggest that wiring 5-6 large 250W residential solar panels in series would give you between 150-180VDC that would cross that 200 foot distance with less than 2% voltage drop.

Of course, you need a charge controller (or AiO) that can handle voltage that high.

Remember though you are NOT measuring the working voltage making power, called the Vmp.  You need to be looking at the open-circuit voltage, which is what you measure when the array is disconnected from the controller.  That will be ~25% higher then the Vmp.  Also remember that the voltage of the panels goes up as the temperature goes down.  So, the panel Voc will be higher in below freezing winter weather then in summer.  You MUST take that into account when you are designing your system.  What are your winter lows like?

This guy goes through line losses

I'm sorry, but why is this considered to be a solar myth?  Why does it need disproving?  Everyone in the solar community today knows about raising voltage to cross long distances.  I myself have recommended this in just about every solar conversation on this board.  Why is this guy acting like "he" discovered the secret?

Because the “algorithm” rewards yellow journalism.

R Scott wrote:Because the “algorithm” rewards yellow journalism.

Yup, It's high school math. His reasoning for why we use larger cables is also dead wrong. We don't use thicker cables to carry the amps in this case we do it to reduce voltage loss to a low enough percentage to pass an inspection. Here it is under 2 percent some places in the States its 3 percent I'm told. If he had used the 12 gauge he was commenting about he would have been way over that over 400 ft.
I'm sure if it gets enough views someone else will remake the same damn video and "discover" it all over again. It's not a bad video. I don't see a disconnect at the array so that would be an automatic fail here, He is using an anker Solix which is a portable unit which I would not recommend for permanent install. Those all change with jurisdiction of course. I am also finicky about this stuff...

Bringing this one back up because I'm curious if anyone has tried using microinverters at the panel site for this setup. They might offer a decent solution by converting DC to AC right at the source and could make the longer distance transmission safer and more efficient. Plus, it could allow for system flexibility by working with lower voltage DC. Thoughts?

Hannah Garcia wrote:Bringing this one back up because I'm curious if anyone has tried using microinverters at the panel site for this setup. They might offer a decent solution by converting DC to AC right at the source and could make the longer distance transmission safer and more efficient. Plus, it could allow for system flexibility by working with lower voltage DC. Thoughts?

hi Hannah, if by "at source" you mean at the solar panel that is how it is usually done. The solar panel puts out roughly 28-40 volts depending on size as dc voltage. The micro inverter converts it to 240 volts Ac (in North America). So you have between 1/8th to 1/6th of the power loss if you were to bring that dc voltage to the house. Those losses add up with higher amperage as well. The pattern now is to create high voltage dc strings of 280-500 volts and send that to a larger charge controller to convert to ac... Now with the Dc voltage being higher than the final AC voltage the line losses are lower keeping it as DC. It depends on the situation. If all you are doing is net metering to the grid and all you have is your roof then Micro inverters still make sense. When you involve batteries you are almost always better of using a string inverter. I almost never put arrays on roofs here since the roof angle is wrong for winter and snow clearing is much harder so its been years since ive specked a micro inverter setup.
Cheers,   David

Bob Nall wrote:I'm curious if anyone has solar panels in a field approx 200+ feet away from their home.  What is the preferred method for transferring power to the home inverter and batteries?  Has anyone experimented with voltage drop at those distances?  I was recently watching a youtube video on a water generator and he said something interesting, "if transferring power at the same voltage, DC is actually more efficient than AC." This goes against what many of us believe but it seems there is some truth to it.  So it seems the higher the DC voltage I can transmit it at the more efficient it will be and I will also not have the restriction of eddy currents as I would in AC.  Has anyone ran high voltage solar DC wiring at length?  I am able to input 2 165V DV inputs into my unit, but I also understand at this point the DC voltage is getting to a "not safe" point.  Obviously roof mount is an option but requires a lot more code and inspection processes.

At 200+ feet, the biggest factor is keeping the current low since that's what really reduces voltage drop. That's why higher voltage DC from the panels to the inverter is a common approach. Once the power is converted, keep the battery bank as close to the inverter as possible.

Just keep in mind that 165V DC is definitely in the range where you need to take safety seriously. Proper wire sizing, disconnects, overcurrent protection, and code compliant installation become very important. If you're planning a long run like that, it's worth doing the voltage drop calculations before buying cable.