Would like help designing my solar layout please.

[rogerdw]

We live in South Australia ... on grid ... but want to put in an off-grid system ... retaining the grid for backup and for battery charging when necessary.

I've collected 12.6Kw of used panels (6Kw of 250 watt panels and 6.6Kw of 275 watt).

I've organised a 14Kw LF inverter and am chasing up a large 48V traction or forklift battery.

What I'd like some help with is in deciding where to locate all the ancillary equipment ... and what extra bits I need to plan locations for.

The diagram shows the property layout, orientation and some dimensions.

There's not much doubt that the panels would be best on the north facing roof of the shed, which fortunately has zero shading due to a large empty paddock alongside.

My main question is around the best location for charge controllers, inverter and battery etc.

There are several options for where they could go but I'm leaning towards inside the shed and below the panels ... position 1.

There is an adjoining shed (large farm style shed) with open front that would be 'safer' perhaps ... but with the extra distance from the panels would add considerably to cable expenses and voltage drop. Especially as we'll have lots of strings of just 3 or 4 panels.

The last option would be to locate them at the opposite corner of that 2nd shed where the meter box is ... but thats another 20 metres or so ... and while it'd save on AC cabling, the DC cabling would be a major issue.

I plan to employ a solar tech to do the installation but I really want to have worked out the best locations for everything in advance ... rather than potentially getting talked into changing things and regretting it later.

 

[MichaelK]

Have niece in Adelaide, and I love going there. California is just like it. Even smells the same.

First question, is each "shed" weather tight? Are their walls between each of the 1A, 1B, and 1C sections?

I like your position 1 for the batteries. Fork lift batteries would be a great choice, though having a wall between the battery and the electronics would be the very best choice. I would say please the battery on the West wall of shed 1B, and the electronics on the East wall of shed 1A. Then the battery to electronic distance is only going to be cm instead of m. Once you convert the DC to AC, you'll be able to run the 230VAC significant distances with no issues.

Are you planning on incorporating a generator into your system? You might also have that positioned in shed 1A if you are able to safely plumb the exhaust gas outside for carbon monoxoide safety.

It appears that you have the panels in groups of 6/12? How will you intend to wire them? With a good quality MPPT controller like the Outback 300V, you could wire 6 in series for 180VDC. At freezing, the Voc of your panels might be ~40Voc, so that would reach 240V at 0C. Other cheaper Outback controllers have a 150V limit, so that means only 3 panels in series.

Voltage drop for the distances you have is not going to be an issue. You can use this drop calculator to reconfirm.

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

I'm running 4 panels like yours in series for 120VDC, and I'm measuring no drop at all with American 10 gauge wire over a 40m distance. I'm running that to a Midnight200 controller. Which inverter are you planning on?

 

[rogerdw]

Have niece in Adelaide, and I love going there. California is just like it. Even smells the same.

Wow, small world. I have a friend who lived in California for 15 years but is back here now.

First question, is each "shed" weather tight? Are their walls between each of the 1A, 1B, and 1C sections?

Shed 1 is totally weather tight and there are corrugated iron walls between the sections. Shed 1A is lined and insulated and is where I work.

Shed 2 has an open front on the eastern side, like a farm machinery shed.

I like your position 1 for the batteries. Fork lift batteries would be a great choice, though having a wall between the battery and the electronics would be the very best choice. I would say please the battery on the West wall of shed 1B, and the electronics on the East wall of shed 1A. Then the battery to electronic distance is only going to be cm instead of m. Once you convert the DC to AC, you'll be able to run the 230VAC significant distances with no issues.

That is my preferred positioning for the battery too ... though because I spend my working hours in 1A, I was a little concerned that any fan noise could become a nuisance. ... so having the inverter in 2A was also preferable.

I'm assuming the main reason for seperation between the batteries and the electronics is because of the risk of fuming and corrosion or even fire perhaps?

Our mains feed in from the road is over 400 metres and seems to work ok, though when the big aircon kicks in we see a dimming of the lights for an instant. The AC feed from inverter to meter box should only be 30 odd metres so should be fine ... and is only one line rather than the multiples of DC wires if the battery/inverter were over at the meter box.

We'll also need a second AC line from the meter box across to the battery area so we can charge the battery with mains if/whenever the need arises.

Are you planning on incorporating a generator into your system? You might also have that positioned in shed 1A if you are able to safely plumb the exhaust gas outside for carbon monoxoide safety.

I do have an old 5Kw Honda generator that I would use for emergencies ... but despite many peoples opinions of our Sth Aus power system, we rarely have any outages ... at least where we are. So at this stage I don't see a need to set up a permanent arrangement. That may come later.

It appears that you have the panels in groups of 6/12? How will you intend to wire them? With a good quality MPPT controller like the Outback 300V, you could wire 6 in series for 180VDC. At freezing, the Voc of your panels might be ~40Voc, so that would reach 240V at 0C. Other cheaper Outback controllers have a 150V limit, so that means only 3 panels in series.

This is something I haven't worked out yet. I have 24 x 250w panels and 24 x 275w panels but wasn't sure on the configuration I should use.

I've never really thought about it too much (or understand properly yet) ... but can a higher voltage input charge controller (like an Outback 300V) charge a 48V battery happily enough or efficiently enough ... or should I be aiming for something lower?

I also need to do a bit more research on temperatures here, but it is very rare for us to get down to 0°C even overnight ... and certainly not once the sun comes up ... so I'm not sure how critical that will be.

I'm running 4 panels like yours in series for 120VDC, and I'm measuring no drop at all with American 10 gauge wire over a 40m distance. I'm running that to a Midnight200 controller. Which inverter are you planning on?

Thanks for the link to the calculator, I'll have a bit of a play. And thanks for your real world example too.

I'm building a Warpverter. It's nearly finished after a long couple of years.