Longish run, bad idea to parallel the panels and split?

[dudeinthewoods]

Apologies if this is too basic or in the wrong place.

So I'm considering another 30kw in panels (120) about 150' from my breakers / inverters etc.

I'm not too worried about wire size etc I'll calculate that shortly. I'm more concerned if the concept is dumb.

Exact number in series pending SCC/inverter.
So let's say I'm running 30voc x 6 panels for 180v in series.

Then I can run 20 sets of wires to my house. Could I just parallel those 20 sets of panels? Would it make more sense to just run 1 fatter set say 0000awg and then split it when it's inside?

I'm concerned with then splitting it up when its in the house. I could take that 0000awg and run it to a panel that splits it to 1awg lines and 6 x 6kw sunnyboy for example.

My concern here is that one pulls too much for it's wiring or something but maybe I'm over thinking it. If they're all parallel on their output I guess it should be fine.

I haven't seen this since I've been reading the site but my apologies if I missed it.

 

[Hedges]

Once they are parallel, you can't split to separate Sunny Boy. They need to see only the I/V curve they produce, and perhaps to do leakage tests independently. You could do some combining in the field but you need a pair for each Sunny Boy.

If the Sunny Boys have multiple MPPT inputs, for at least some models those can be paralleled. Some may have multiple fused inputs which should be kept separate.

Running a bunch of separate pairs of wires gives you flexibility to reassign later to different inverters. Also easier to pull. A downside is NEC derating for 40 current-carrying conductors in a conduit. I may use 12A fuses on my 12 awg wires, each of which has one string of panels. I do have one 8 awg pair; for that I'll parallel 3 strings of panels with fuses.

 

[dudeinthewoods]

Great thanks.

Even splitting it in to 6 pairs would be more economical. I suppose I could do that.

I'll have to decide on models and then voltage / amperage etc to know how many pairs so that's not dialed in yet. Just trying to decide on the concept.

I also didn't look in to any larger systems that could possibly handle more volts/amps. I'll do that now.

 

[Hedges]

What do you have for a system so far?

I use about 380Vmp, 480Voc at ambient into 600V max Sunny Boy, AC coupled to Sunny Island.

Have you checked out SanTan Solar for panels?

For DC coupled there may be some high voltage options. Midnight Classic is 150V, 200V, 250V. I think you get more watts per dollar with the 150V. I think they have the ability to withstand excess Voc on a cold morning so you can design a bit higher.

 

[dudeinthewoods]

I've heard good things about santan. I've looked at them but undecided yet on where to get the new panels.

I'm running DC coupled currently on make sky blue blue SCCs and a "reliable" chinese inverter. I've currently got (40) 10kw in panels.

I also have batrium on my lifepo4 bank that I built (48v).

I'm really pretty flexible on how I do all this. I am really set on sunnyboy/island ac coupling. It seems like the ideal set up but I'd also be all for a higher volt / amp solution if it made sense or anything else really.

 

[the_colorist]

Apologies if it's already been discussed but what size are these panels? Looks like you are considering 250W panels with a VOC of 30V? Seems low to me but maybe I'm guessing wrong on the panel size you're considering.

It would be recommended to keep the strings separate just like @Hedges mentioned. That said, with SB's you may not need that many.

The following is based on Santan's 250W panel specs and assuming 120 panels.

If you put 15 in series (3,750W, assuming 250W panels @30.3VMP), you'll end out with 8 strings @ 454.5 VMP roughly. 8.27 ISC per string.

If you put 10 in series (2500W, assuming 250W panels @30.3VMP), you'll end out with 12 strings @ 303 VMP roughly. 8.27 ISC per string.

As you can see you could get it down to either 16 or 24 wires rather than 40. Neither voltage is what I would call perfectly optimum (see efficiency curves below) but overall probably the best you'll get per watt assuming 4x 7.7 SB's. The newer transformerless SB's are more efficient at slightly higher voltages than the older transformer-based models. If you're using older SB's the max eff curve is usually lower, closer to the 240V output.



It depends on where you buy from but the 7.7's are usually the cheapest per watt.

Make sure and call Santan if you choose to go with them. We recently ordered a shipment of thier 250W snail trail panels. They were pristine, Tier 1 Trina Solar to boot. I also got them lower than the listed price. Less than $0.14 per watt. BUT I only got that by calling them and discussing a discount.

So far I've found Germany to have the cheapest second-life panels but coordinating shipping is an issue for anything less than a FCL (Full Container Load). Before shipping, you can be looking at ~$0.07 per watt or so.

Are you wanting to go (or are you currently) completely off-grid? Just curious.

 

[dudeinthewoods]

The 30voc was off the top of my head and honestly probably is a bit low. I'm talking about the panels that I currently have not the ones I intend to buy.

I'm currently off grid power wise which is all that matters for this discussion I suppose haha. They've still got me on water and I'm not sure how you can be "off grid" and "on internet" haha.

I assume you meant 16 or 24 (not 22) wires above or I'm confused.

Thanks for the advice on santan panels. I'll absolutely keep that in mind.

I've got a bit to digest. I suppose I'm trying pretty hard to fight the extra cables and they're not so horribly expensive at the end of the day.

I'm going to dig in some more. I've got 40 panels now which I'll probably switch over to sunnyboys even though my makeskyblue is working just fine. I'd like to test the SB before I go even bigger with them.

I am going to pull up tbe data sheets. I didn't realize the 7.7s could push that many watts. That probably makes sense.

Thanks again both of you.


Long shot on this one but do you know how well the SB play together and if one CAN bus out to something like my batrium BMS can control all the sunny? I've been looking and haven't got a good answer on that.

 

[the_colorist]

Yikes yes, I meant 24 (typo). I've fixed that now.

The command/control system works like this:

BMS -> Sunny Island -> Sunny Boy

BMS sends commands to the Sunny Island master over CAN. The SI's then control the SB's via Frequency Shifting or droop control as it's known in Europe and other countries.

Again I'm not familiar with your system layout but if you're just considering replacing your makeskyblue controllers with SB's, you'll need the SI's or another frequency shifting voltage-source battery inverter first. I'm sure you're aware of that but just mentioning.

 

[Hedges]

Off grid, you can do Sunny Island 2s2p like me, or 3-phase Y. With 3-phase you can link multiple clusters for your own multi-building village, if desired.
You can install Sunny Boy totaling about 2x the wattage of Sunny Island.

Sunny Boy respond to frequency shift of Sunny Island.
Sunny Island has CAN bus and interface is available to Midnight Classic SCC.
REC is a BMS available with Sunny Island protocol.

For grid-backup, the recent -40 and -41 SB (including that 7.7 kW) aren't officially supported. Only on-grid or entirely off grid. They should work for grid-backup but with a setting not formally approved in SMA documentation (I would get the workaround recommendation in writing from SMA before implementing it.)

 

[the_colorist]

Not to contradict at all but according to the latest documentation, SMA states the latest SB's are officially compatible if the country data set CA Rule 21 is set.

BUT perhaps I'm missing something here? Never had to deal with this (yet).

https://files.sma.de/downloads/SB-OffGrid-TI-US-en-22.pdf

 

[dudeinthewoods]

Yikes yes, I meant 24 (typo). I've fixed that now.

The command/control system works like this:

BMS -> Sunny Island -> Sunny Boy

BMS sends commands to the Sunny Island master over CAN. The SI's then control the SB's via Frequency Shifting or droop control as it's known in Europe and other countries.

Again I'm not familiar with your system layout but if you're just considering replacing your makeskyblue controllers with SB's, you'll need the SI's or another frequency shifting voltage-source battery inverter first. I'm sure you're aware of that but just mentioning.

Yep what I was thinking. Wasn't sure if I can connect to one SI and it talks to the others or if I have to connect to each.

Thanks again. No plans on grid backup but it's always nice to be have it as an option. Really looking forward to playing with these SI and SB soon.

 

[Hedges]

Not to contradict at all but according to the latest documentation, SMA states the latest SB's are officially compatible if the country data set CA Rule 21 is set.

BUT perhaps I'm missing something here? Never had to deal with this (yet).

https://files.sma.de/downloads/SB-OffGrid-TI-US-en-22.pdf

I've been waiting for that documentation update.
In the spring I bought SB 10000TLUS-12 because it was listed as compatible for grid-backup.
After experimentation, I informed SMA it was not and explained exactly what was wrong.
After review of firmware, they agreed and said the list would be updated.
(They also gave me the workaround of setting it to off-grid, when operated with Sunny Island between SB and the grid.)

So they say SB7.7-1-SP-US-4x is now "Compatible if country data set CA Rule 21 is set"
I think the European Sunny Island is able to talk to this SB by Speedwire (or similar). But no such interface supported for US models, even though hardware exists for their gateway.

I'll believe compatibility when I see it.
Rule 21 requires inverter to remain on-line for 299 seconds for a certain frequency range. It requires inverter to drop off after 300 seconds.
I think it is then required to say offline for 5 minutes/300 seconds?
I don't call that compatible.

 

[dudeinthewoods]

You guys are getting a bit out of anything I've studied but it's interesting.

I'm curious about the sunny tripower and why we don't hear more about it.

Seem like for 5k~ we can get an inverter that will do 30kw.

Now that I assume takes the place of the Sunny Boy and we still fees it to Sunny Island units?

I'd love to have one just fees it 800v or whatever.

I searched and haven't found much mention at all on here.

What are your guys thoughts on: https://www.sma-america.com/products/solarinverters/sunny-tripower-core1.html

Pretty late here calling it a night.

Thanks again.

 

[Hedges]

You guys are getting a bit out of anything I've studied but it's interesting.

I'm curious about the sunny tripower and why we don't hear more about it.

Seem like for 5k~ we can get an inverter that will do 30kw.

Now that I assume takes the place of the Sunny Boy and we still fees it to Sunny Island units?

I'd love to have one just fees it 800v or whatever.

I searched and haven't found much mention at all on here.

What are your guys thoughts on: https://www.sma-america.com/products/solarinverters/sunny-tripower-core1.html

Pretty late here calling it a night.

Thanks again.

I like the idea of one 3-phase inverter rather than 3 single-phase, because it doesn't impose 60 Hz ripple currents on its capacitors.
I'm not clear how nicely Tripower plays with Sunny Island. I don't have any documentation which mentions "island" or "off grid"

"Sunny Tripower in off-grid systems and in battery-backup systems
A three-phase off-grid or battery-backup system with Sunny Island 4548-US / 6048-US provides an AC grid voltage of 127 V / 208 V. However, the Sunny Tripower operates at a nominal AC voltage of 277 V / 480 V.
• When using a Sunny Tripower in off-grid systems or battery-backup systems with Sunny Island 4548-US /6048-US, always use a transformer.*

* The use of a generator has no effect on the Frequency Shift Power Control (FSPC) function."

I'm not sure if they meant "use of a generator" or "use of a transformer"
Of course a transformer wouldn't interfere with frequency slowly shifting between 55 Hz and 65 Hz.

You could consider the Tripower if building that size system, but there are benefits to having multiple Sunny Boys - if one goes down you still have the rest.
I noted the really cheap price I saw for some Tripower. Maybe it is a liquidation of older models.
I've bought some older Sunny Boys, new and used, for about $0.10 to $0.12/watt.

If you wanted a transformer to boost voltage for longer distances or certain equipment, that might make the tripower more attractive.
If you're just using 120/208Y it would be additional losses.
I don't worry as much about losses in PV wiring because PV is practically free. But losses in AC continue at night and are a demand on batteries.

For really interesting stuff, look what's available in Europe: 75 kVA Sunny Tripower Storage

Sunny Tripower Storage 60 (Successor: SMA Commercial Storage Solution) | SMA Solar

Information on the Sunny Tripower Storage 60 (no longer sold by SMA) ► discover the successor here!

www.sma.de