Solar Installation By Previous Owner - Advice Sought

[Xhumeka]

Good photos, I think they are very helpful. I'm looking at the empty spot to the left of your main cabin, and above and slightly to the right of your small structure. That appears to be in full sun most of the day, finally getting deep shade late in the afternoon.

That looks like the best spot to position a ground array. I think you could easily squeeze in 1500W there. I can see that one big tree to the left of the main cabin, and directly above the small building. Would it be acceptable to cut that tree down? Could you pole off a few of the south-facing branches and squeeze in even more panels.

What exactly is the smaller structure? Mother-in-law cabin, or just for the kids? What I would envision using for is make it the main repository for your solar system, with batteries, electronics, and stuff placed in there, then sending the AC power to both the small structure, and the main cabin.

Unfortunately we are losing that structure - the municipality has deemed it "illegal", so it's being demolished sometime this summer. Not sure what we are planning to / allowed to replace it with, but I like this idea a lot and will try to incorporate it into whatever we end up doing with that space.

For now, I'm going to have to stick to a temporary roof-top solution until I want to replace everything like I want to. That means I'm limited to my 12V inverter, midnite classic 150 charge controller, and 12 volt battery bank (2s2p configuration of 6CS25PS, 6v, Surrette/Rolls, 1156 Ahr@100hr, 820Ah @20hr batteries) for now.

With that in mind, here's what I'm thinking of doing (bearing in mind power limitations of midnite classic, and fact that it's most efficient to run lower array voltages for 12V systems):

With option #1, here's what the midnite solar sizing tool shows:

Basically it maxes out the capability of the midnight classic in full sun with 6 of my panels. My thoughts for option #2 are that all 8 would never be in full sun together, and at any point in time will likely never go above 1500Watts. I will have each string on a separate breaker so I can experiment once in place.

And finally here is where I'm thinking of laying out the 8 panels (assuming I go with option #2):

Thoughts? Thanks!

 

[Hedges]

Multiple orientations (all strings same Voc/Vmp) connected in parallel will be lower peak watts, so the SCC can handle more panels, produce over more hours.

 

[Xhumeka]

Multiple orientations (all strings same Voc/Vmp) connected in parallel will be lower peak watts, so the SCC can handle more panels, produce over more hours.

Thanks - I guess my question is more directed to my specific plan, and if you think it could possibly overload my controller. I know it's hard to tell without testing it in-place, but any gut-feelings?

 

[Wellbuilt]

It looks as if the panels where laying flat on the roof you would be ok .
You lose a lot of power have panels facing different directions .
Just thinking but if your panels are facing in diffrent directions your mppt controler can’t lock on it’s power point
and you lose power .
i have 5 885watt strings and this time of year I can turn off 2 strings and still get to float by 200 pm

 

[Hedges]

Thanks - I guess my question is more directed to my specific plan, and if you think it could possibly overload my controller. I know it's hard to tell without testing it in-place, but any gut-feelings?

We expect an MPPT charge controller to limit its output current and its temperature. If PV array offers extra wattage, the SCC should simply never draw PV voltage down to where that much is produced.
Some devices specify a maximum short-circuit current. That is probably because they have a backwards diode across the input, so if PV is connected backwards the voltage is clamped to a diode drop. That diode has a maximum current.

I didn't find a spec for max PV wattage or max current related to the Classic. Send an inquiry to Midnight if it is OK to over-panel to the extent you're considering.

You lose a lot of power have panels facing different directions .
Just thinking but if your panels are facing in diffrent directions your mppt controler can’t lock on it’s power point
and you lose power .

The MPPT will lock on to something.

Where they may do poorly is if the I/V curve has multiple peaks. That can occur if two strings are in parallel and one has several panels shaded. Such a condition will result in not getting power from all unshaded panels. For instance, 10s2p, with 5 panels of one string shaded. There is a peak from 10 in series, and no current is drawn from the other string with 5 receiving sun. There is another peak at the Vmp of those 5 receiving sun, with the 10 unshaded panels pulled down to that voltage and adding slightly more current than 5 produce. Some SCC search and find both peaks, selecting the higher. Some do not. If only one panel out of a string of 10 is shaded, only about one panel's output is lost. Penalty for two strings in parallel is negligible.

With two different orientations (one series string all one orientation, another all a different orientation), those have different maximum power point voltages. But, pulled to the same voltage, total Wh/day is only reduced about 2% compared to each having its own MPPT (according to tests performed by SMA.) So you lose 2%, but you can squeeze 40% more power out of the same charge controller. Decide if you want to add 2% more PV panels or 40% more charge controller to accomplish the same energy harvesting.

If one of those two strings gets a lot of shade, refer back to previous paragraph.

 

[Wellbuilt]

O cool , great explanation I’ve never tried it .
2% is not bad at all

 

[Hedges]

How to design East/West polystring PV arrays - Sunny. SMA Corporate Blog

Have you ever heard about polystrings? Did you know that PV plants with this special plant design benefit from more energy yield over the course of the day? Sunny Design Web will help you easily design a polystring PV Array. Find out all you need to know about this key but often overlooked feature.

www.sma-sunny.com

What they didn't highlight is that you can over-panel a bit without losing out on production. Their example had 2x 3kW vs. one 6kW. Each 3kW would hit maximum at some point in the day, but the 6kW never will.

I figure if 90 degree angle between arrays (e.g. 10:00 AM and 4:00 PM sun orientation), max area presented is 0.71 times what a single orientation would be, so about 1.4x as much PV can be installed. These angles do each produce less total power than an optimum 12:00 Noon (or 1:00 PM daylight savings time) South orientation.

 

[rin67630]

With option #1, here's what the midnite solar sizing tool shows:

Midnight solar, what an oxymoron!
Basically the fat red "excessive" isn't appropriate.

There is nothing wrong with having more panel (tag) power installed that your SCC can handle, as long as maximum voltage is not exceeded.
Overpaneling is good and recommended in higher latitudes.
You will practically never get the tag power.

Can someone explain to me what "Temperature The Classic Will" is supposed to mean?
I would nominate this company for the Nobel prize for the breathtaking -290°C, -495°C and even -701°C!
That would have been EXCESSIVE and were simply revolutionizing the generally known physics!
?

 

[Hedges]

"Temperature The Classic Will"
... enter Hyper VOC

That's where input voltage is higher that it can handle, but it has a protection mechanism.
Manual says it will tolerate normal spec input voltage + battery voltage.
What they could do is have a FET that grounds negative side of input capacitors. If voltage exceeds capacitor rating, turn off the FET.

Software. I make fun of it all the time.
But if their sizing program guides people to valid designs and keeps them from killing hardware, I'll let it slide this time.

 

[rin67630]

Unfortunately we are losing that structure - the municipality has deemed it "illegal", so it's being demolished sometime this summer. Not sure what we are planning to / allowed to replace it with, but I like this idea a lot and will try to incorporate it into whatever we end up doing with that space.

For now, I'm going to have to stick to a temporary roof-top solution until I want to replace everything like I want to. That means I'm limited to my 12V inverter, midnite classic 150 charge controller, and 12 volt battery bank (2s2p configuration of 6CS25PS, 6v, Surrette/Rolls, 1156 Ahr@100hr, 820Ah @20hr batteries) for now.

With that in mind, here's what I'm thinking of doing (bearing in mind power limitations of midnite classic, and fact that it's most efficient to run lower array voltages for 12V systems):

With option #1, here's what the midnite solar sizing tool shows:

Basically it maxes out the capability of the midnight classic in full sun with 6 of my panels. My thoughts for option #2 are that all 8 would never be in full sun together, and at any point in time will likely never go above 1500Watts. I will have each string on a separate breaker so I can experiment once in place.

And finally here is where I'm thinking of laying out the 8 panels (assuming I go with option #2):

Thoughts? Thanks!

Maybe look, if you can mount 1, 3, 4 with some slope towards south since you are at a higher latitude, it will surely pay off.

 

[Xhumeka]

Update:

Well, I was finally able to get 3 buddies to help me remove the old panels and install 8 new ones this past weekend... ROOF WORK SUCKS!!! Next array I install will definitely be ground mounted, but for now I have a 2KW array on my roof (1KW on East side, 1KW on West side) that should tide me over.

Decided to use the "FastRack" system for mounting:

My next project will be to swap out my inverter for the Growatt 24v spf 3000tl lvm, but I need to wait for my 2 new batteries to arrive since I'm only 12v at the moment. Here are some pics of the work:

 

[12VoltInstalls]

Nice little mansion

 

[740GLE]

I feel for refinishing that deck, offff!!!

Congrats on the new system