PV panels located over 300M from batteries?

markaubin · September 2016

I have an off-grid power system that I've been using successfully for about 6 years.

8 - 6V Rolls S-530 batteries wired in series
Magnum Energy MS4448PAE inverter/charger
Midnite Solar EPanel
Winco PSS8B4W propane generator

I've always imagined that I would add PV to the system, but have put it off because there isn't good sun exposure near the power shed.

If I go up the hill about 300M or so, I can get excellent sun exposure. But I don't want to move any of my gear up the hill, just the panels.

Has anybody here had this sort of situation and can you share how you solved it? I did read over all the archives looking for a similar thread and couldn't find anything that matched this very well.

I realize it is not very practical to extend DC this distance. Most likely this means the voltage needs to be AC and boosted to minimize loss.

I'm wondering if I should be considering micro-inverters to get AC at the panels?

If I boost the AC, will I then need to drop it back down, requiring transformers at both ends, and conversion back to DC for the charge controller? Is there an integrated charge controller available that can handle high AC voltages?

Thanks for any advice!

Mark

jonr · September 2016

No need for AC - you can get 600V MPPT charge controllers (eg: TriStar MPPT 600V). How many watts are you thinking?

mike95490 · September 2016

jonr said:

No need for AC - you can get 600V MPPT charge controllers (eg: TriStar MPPT 600V). How many watts are you thinking?

Exactly.... That's what MPPT controllers are for. Run HV-DC the long distance, and then step down at the batteries.
You can get models at 150Vdc, a few companies make some 250 & 300V models, and then a couple make 600VDC models
I used 4ga alum wire in conduit for a 900' run, alum wire is OK if you use aluminum rated connectors with it, Much cheaper than copper, and wire does not care about AC or DC, just voltage on the insulation,
You will have to price out the difference between 150V models and heavier wire, vs 600V and thinner wire.

halfcrazy · September 2016

As Mike points out, Be aware when you make the leap to 600v that the breakers and disconnects get a lot more pricey and aluminum wire is cheap.

Looking at off the shelf prices I have run many exercises and rarely is the 600v controller and smaller wire actually cheaper if you consider a code compliant install with disconnect at the array AND MPPT. I don't want to post numbers here on the Distributors website but feel free to email me and I will share some white papers off line ryan@midnitesolar.com

jonr · September 2016

Also note that there is the option of adding more panels to make up for wire loss. To pick a random example, 300 meters of 12 gauge wire moving 1500 watts at 150V will have a 21% loss where 10 gauge would have 13%. It's cheaper to add another 120 watts of panel than to upgrade the wire.

Dave Angelini · September 2016

halfcrazy said:

As Mike points out, Be aware when you make the leap to 600v that the breakers and disconnects get a lot more pricey and aluminum wire is cheap.

Looking at off the shelf prices I have run many exercises and rarely is the 600v controller and smaller wire actually cheaper if you consider a code compliant install with disconnect at the array AND MPPT. I don't want to post numbers here on the Distributors website but feel free to email me and I will share some white papers off line ryan@midnitesolar.com

I'd like to see your numbers because I almost always use a 600V mppt. The labor saved and the flexibility to make easy changes later
are easily 5 times the cost of a 600vdc disconnect. I can get the square D and another make for less than $100.
300M ? a no brainer for the morningstar or schneider electric 600vdc mppt'.

https://www.amazon.com/HU361-SQUARE-safety-disconnect-switch/dp/B00A2BKD40/ref=pd_sbs_60_1?ie=UTF8&psc=1&refRID=STF0YSK16N1XZGMNGS1P

BB. · September 2016

Ryan/Halfcrazy--Please feel free to post the paper/link to the paper about high voltage arrays for off grid power systems (if you would like).

We are all about sharing the information here--And let the chips fall where they may.

Take care,
-Bill

jonr · September 2016

Dave, is that disconnect rated for DC use (I see only AC on the label)?

Dave Angelini · September 2016

Jon, I thought you were an engineer? Electrical or mechanical?
one can get these in NEMA 3 also for out in the rain or build a cover for this one under the eaves with a inverter shut down for the fire guys. I think these have been around since Tesla so nothing new here. With the industry going to 1000V and commercial going to 1500 DC. I have clients who place one inside the structure also because they are afraid to go out when the lightning is close. One can add a fuse kit and have 3 panel strings in one of these. I love the sound they make, sounds like the electric chair in one of those old movies or the one in Young Frankenstein.

Image: https://us.v-cdn.net/6024911/uploads/editor/vm/1lizjy6ny66f.png

markaubin · September 2016

Thanks everybody for all the great advice. Now that I have learned this will be possible my next step is to pick the actual spot for the panels and then measure the distance to the existing power shed. With real numbers then I can determine what panels & wiring combinations might work.

I'm still waiting for a private reply from halfcrazy/ryan@midnitesolar.com regarding the white papers.

Vic · September 2016

markaubin said:

Thanks everybody for all the great advice. Now that I have learned this will be possible my next step is to pick the actual spot for the panels and then measure the distance to the existing power shed. With real numbers then I can determine what panels & wiring combinations might work.

I'm still waiting for a private reply from halfcrazy/ryan@midnitesolar.com regarding the white papers.

Hi Mark,

In an attempt to be clear about Halfcrazy Ryan's e-mail address, you did send an e-mail, to:
ryan@midnitesolar.com ... NOT halfcrazy/ryan@midnitesolar.com ??

Just an easy question. FWIW, Vic

markaubin · September 2016

Vic said:

markaubin said:

Thanks everybody for all the great advice. Now that I have learned this will be possible my next step is to pick the actual spot for the panels and then measure the distance to the existing power shed. With real numbers then I can determine what panels & wiring combinations might work.

I'm still waiting for a private reply from halfcrazy/ryan@midnitesolar.com regarding the white papers.

Hi Mark,
In an attempt to be clear about Halfcrazy Ryan's e-mail address, you did send an e-mail, to:
ryan@midnitesolar.com ... NOT halfcrazy/ryan@midnitesolar.com ??
Just an easy question. FWIW, Vic

Yup I sent email to ryan@midnitesolar.com

Just sent another ping.

Vic · October 2016

OK, Thanks Mark, just checking. Good Luck, Vic

DaveB · July 2017

Was there any more technical info that could be shared about this? Was also looking at 10kw ~1000ft away. May use multiple lines to orient some panels in different directions (East to pick up morning sun, most South, and some West to pick up evening sun, all for off grid so reducing battery use in morning and evening beneficial).

jonr · July 2017

No problem with a voltage on the high side and the right size wire (probably aluminum). http://www.calculator.net/voltage-drop-calculator.html

BB. · July 2017

The actual wiring/breaker configuration will depend on the details... The MPPT charge controller(s) you choose, and the array/wiring configuration needed to support them.

You can get MPPT charge controllers that support ~400 Vmp-array-std (600 volt max input controller) from several vendors now. That would (probably) be the optimum configuration (price/performance).

However, I highly recommend that you do several paper designs and cost them out before you go and by (more) hardware.

-Bill

DaveB · July 2017

My missing piece was not realizing that aluminum cable is 2x-3x cheaper then copper now and it would be acceptable to use USE-2 in aluminum one gauge larger.

mike95490 · July 2017

DaveB said:

My missing piece was not realizing that aluminum cable is 2x-3x cheaper then copper now and it would be acceptable to use USE-2 in aluminum one gauge larger.

I thought it was 2 ga sizes larger, if #10 copper is good, # 8 aluminum is good too. #9 would not be large enough.

PV panels located over 300M from batteries?

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