# Solar panel proximity to point of use



## Anonymooose

How close do the panels need to be to the house? Our best solar panel location is at least 200-300 feet away- but do you loose efficiency by running line that far?

Cutting down trees around the house is not an option.


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## wy_white_wolf

Yes you loose alot of power running that far or you spend big dollars on very big cables.

Are you trying to do a grid-tied or off-grid system?

WWW


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## Anonymooose

It would be off grid. 

What sort of distance are we looking for? (in an ideal world


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## artificer

In an ideal world... as close as possible.

There are several factors involved. The lower the solar panel voltage, the shorter the run needs to be to keep losses low. If you have a 12v battery bank, a pwm solar controller, and a bunch of 18v panels, you need either really big wire, or a short run.

An alternative is to get a MPPT charge controller. The Midnite Classic 250 will accept up to 250v input. String the solar panels in series, and feed it to the charge controller. Even if your battery bank is 12V, the run from the solar panels to the charge controller is at high voltage, so your long run is doable.

To get a better response, you need to provide the size/voltage of the battery bank, the controller you intend to use, and the size/number of solar panels in the system.

Michael


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## nosqrls

Or do battery bank as close to panels as possible. And dc/ac inverter and run ac line to house or where ever. Because ac travels farther with less power loss.


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## TnAndy

Anonymooose said:


> How close do the panels need to be to the house? Our best solar panel location is at least 200-300 feet away- but do you loose efficiency by running line that far?
> 
> Cutting down trees around the house is not an option.


First question is:

Are you using the panel power as low voltage DC, or inverting it to 120/240 AC ?


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## SolarGary

Hi,
There is a voltage drop calculator here: http://www.electrician2.com/calculators/vd_calculator_initial.html


For example if you had a 2000 watt PV array and the voltage between house and array was 48 Volts, then the current could be about 2000/48 = 42 amps.
Using the calculator and 200 ft distance from house to array, you have to go up to 2/0 AWG to get down to a 3% voltage drop. That would be a pricey set of wire. Home Depot lists 500 ft of 2/0 copper for $1140.

Seems to me you need to get the voltage up some to reduce the current. If you could put the battery bank at the array and take the power to the house via an inverter at the battery pack that was 240 VAC output, then the current drops to 2000/240 = 8.3 amps, and the wire size for an about 3% voltage drop is 8 AWG -- Home Depot lists 500 ft of 8 AWG for $159.

Note that in addition to the wire you would have the cost of conduit and trenching -- bigger conduit for the 2/0 wire than for the #8 wire.

Gary


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## PorkChopsMmm

Our panels are ~225 feet away from the house. You can definitely put the panels that far from the house but I would recommend you store all of your solar equipment out there, too. With most modern solar equipment you can monitor the system from afar. We have an Outback Power system and you can use the MATE display to control and monitor functionality. 

We built a small barn because we needed storage but you could build a small powershed near your panels. Then you run AC over thicker cables. I found that there is something called "mobile home feeder cable" which is a bundle of 2-2-2-4 gauge wires. It is cheaper than other wire combos and already comes twisted together. -- FYI I think i paid ~$300 for 225 feet of 2-2-2-4.

I rented a trencher and ran multiple wires in the trench -- coax for a cell phone extender, 2 RJ45 (one for solar equipment control and one for security cameras), and the 2-2-2-4. I also ran out some poly pipe for a water hose so I could wash off the panels or wash off equipment stored in the barn. I placed some metal detectable metal foil that you will also hit if you are digging. That way if we are long gone people won't dig into the trench.

Hope this helps!


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## Anonymooose

Ok, I'm back. 

Zowie. You guys are way over my head already. I know nothing about solar here, though my husband wired the last house we lived in, so he's got the basic ability to do electric wiring. 

Application: What we're hoping to do is run the small circulator pump for our outdoor boiler, so we're not dependent on electric for our heat. The amount of power necessary is really pretty small, but we'd like to leave our options open for future needs too. It is possible to put them on our roof, but they would be shaded by pines for part of the day. 



nosqrls said:


> Or do battery bank as close to panels as possible. And dc/ac inverter and run ac line to house or where ever. Because ac travels farther with less power loss.


^^This is sort of what I was thinking. Gary, what do you mean by "get the voltage up"? 

Next question, can the battery bank be kept in an insulated, but unheated shed? Our winters are cold, as in 30 below cold. Or would that kill the batteries?

Sorry if this is vague. We're really just in the initial phase here, casting a line in the water to see if it's even feasible. Thanks so much.


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## SpaceCadet12364

Yes, It can inverters will keep it warm. If using lead acid batteries it needs to be vented h2 buildup can ruin your week. Gel batteries are safer but allot more $. You can even run 3 phase ac to house by adding one lead and arranging inverters to supply it or a 3 phase inverter.


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## Jim-mi

As long as your keeping a charge on the batteries no the 30 below wont "kill" them
BUT . . .30 below does put those batteries down on their knees as far as output.
In other words battery capacity drops a big bunch in very cold weather. . . .Just when you need that circ. pump running constantly.
Don't kid your self about the pump "not using much" . . . . .Remember it will be running 24/7

Yes a battery box could be built with a small heat supply (think plumbing heat tape) that would make the batteries much happier against that 30 F below..

I would suggest you go with at least a 24v system.
And look at that circ. pump to see what the pump requires for electric (running currant).

Yes what you want is do-able . . . . .But it will take more than a few bucks to make it happen.


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## SolarGary

Anonymooose said:


> Ok, I'm back.
> 
> 
> 
> 
> ^^This is sort of what I was thinking. Gary, what do you mean by "get the voltage up"?


Hi,
On the long line between the PV array and the house, its important to choose a system that results in a high voltage on this line. 
The line of reasoning is:

- The power carried by this line is the product to the voltage times the current in the line. Power = (voltage)*(current).

- The voltage drop (basically the power lost in transmitting the electricity to the house) depends only on the current -- for a given wire size, the greater the current, the more the power loss. 

- So, you end up with two options that both transfer the same amount of power to the house: 1) A low voltage combined with a high current -- this solution works, but since the current is high, the wire size has to be large to keep the transmission loss on the line low enough so it does not eat up all your power on the way to the house. 2) A high voltage on the line combined with a low current --this transfers the same amount of power, but since the current is low, the wire size can be much smaller and still keep the power loss in transmission to the house low.

There are a couple of system designs that keep the voltage on the line from the array to the house high. You could have the inverters and the batteries at the array. In this case, the voltage on the line from the array to the house is the inverter output (basically house power) -- this would be either 120VAC or 240VAC -- if you can find an inverter that outputs 240VAC, this would allow a smaller wire size between house and array than an inverter that outputs 120VAC.

Another solution would be to locate the batteries and inverter at the house, and use a string inverter in which several PV panels are wired in series to produce a relatively high voltage. This would also result in a high voltage on the line from array to house and a relatively small wire size. There are lots of string inverters out there, and the manufacturers show the string voltage. 
I guess this 2nd one is not a common way to go, but I don't see any reason why it would not work as long as the string voltage does not exceed the wire's voltage rating -- maybe others have thoughts on this?

Gary


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## artificer

SolarGary said:


> Hi,
> ...
> There are lots of string inverters out there, and the manufacturers show the string voltage.
> I guess this 2nd one is not a common way to go, but I don't see any reason why it would not work as long as the string voltage does not exceed the wire's voltage rating -- maybe others have thoughts on this?
> 
> Gary


I looked into the micro/string inverters for my system. Power room is in the north east corner of the 80' long shed, but the solar panels are south of the shed. At about $200/inverter/panel it gets expensive quickly. Then you have to convert back to DC to charge the batteries, so more losses. My problem with them in an off-grid situation is that you still need batteries for night time power. They're great for grid-tie, however.

For me, the best bang for the buck seemed to be a Midnite Classic MPPT controller, with the batteries in the power room. (150v solar input) Losses should be minimized with the higher voltage, and mobile home feeder wire is cheap and allows for direct burial. For line loss, its about the same as two gauge smaller copper wire.


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## Jim-mi

String inverters are more often than not associated with a grid tied system.
And decent string inverters are a bit pricy.
If you want to go with batteries, then do the panels in series for high voltage and I would recommend going with the very best controller on the market today the Midnight Classic.
Yes that controller costs $750 bucks but it is really worth it. It is the best.

Using that controller and going with the high voltage solves many of your distance problems.


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## SolarGary

Jim-mi said:


> String inverters are more often than not associated with a grid tied system.
> And decent string inverters are a bit pricy.
> If you want to go with batteries, then do the panels in series for high voltage and I would recommend going with the very best controller on the market today the Midnight Classic.
> Yes that controller costs $750 bucks but it is really worth it. It is the best.
> 
> Using that controller and going with the high voltage solves many of your distance problems.


I agree -- did not have my brain engaged when I suggested the string inverter.

If you settle on an array size and a charge controller, we can help you with the wire size between house and array.

Gary


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## Anonymooose

Thanks, I appreciate it. When we get to that point, I'll be back with more questions!


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## TnAndy

Note: The Midnite Classic has a 250v input limit, not 150. Outback's controllers have the 150 limit......which is probably why the Midnite is another 150-200 bucks over Outback.

Also remember both of those have to be de-rated to compensate for temperature decreases which INCREASE voltage from your panels, so depending on your location, you many have a 10-15% lower input limit than stated. Here, I don't push an Outback over 140 panel rated volts......about strings of three 250-275w panels.


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## artificer

The Midnite Classic comes in a 150, 200, 250, and 250KS models. The model number is the max input voltage. The actual max VOC is higher with these units, so increased voltage at colder temps is already somewhat taken into account. (198V, 248V, 298V with 98V battery)

The higher the input rating, the lower the current cappacity. If you have a 12V battery bank, you'll be more limited on the power/size of the solar array. I went with the 150 because of my 12v battery bank. ($610 from Northern Arizona Wind & Sun)

You can also get the Midnite Classic Lite, which costs about $110 less. Only difference is the display. Led's instead of the LCD. Can still program it over ethernet.

Michael


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## Gray Wolf

If your heat is dependant on this system, how / where will your battery charging generator fit in?


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## LincTex

Gray Wolf said:


> If your heat is dependent on this system, how / where will your battery charging generator fit in?


Gray Wolf, are you referring to a CHP (combined heat and power) generator system?

If so, you need the generator close to the house to get the heat from it easily. The power to charge the batteries is best transmitted as A/C power out to the distant battery building under the remote solar array. Once there, the A/C power is run through a typical battery charger to charge the batteries. This is similar to what we are doing.

However, we have dual D/C systems so I am never sending juice back out to the batteries in the remote location - it sends inverted A/C only to the house. A separate (smaller) battery bank at the house runs all our night-time loads, and a D/C generator charges those batteries only (if it is needed).


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