New Guy..System Upgrade (actually system replacement) question

[ard]

Hi all.

Nice forum, new member, etc etc. Did an intro in the new member sub...

The Ask: Would like comments/advice on a system upgrade.

Background: Self-installed current set up about 12 years ago..so not an idiot. But a lot has changed since then...


Current:
Ground Mount; 36x215W Sunpower panels (7.7KW). State of the art back then, knew a rep. Odd positive ground system too. Sunnyboy inverter.

Perfect south exposure. Maybe a slight chance of some tree shading at low angles (winter and very early am). 4 strings of 9, combined out at the array

I have a tesla dual powerwall system, it is NOT integrated with the solar system (yes, the tesla system reports power flows in and out, but they are not interlinked with controllers etc. The Tesla gateway just has current sensors on the wire from the inverter and also senses power pulled from the grid.)

Location: East-Northeast of Sacramento CA. HOT in the summer, 30-40 days over 100F. Rarely freezes. Once every 20 years snow. FWIW.
Powerwalls, gateway, Sunnyboy inverters all live in the garage, so out of the sun and rain. (BTW, I inputted this into the solaredge designer tool, so calcs on hot and cold and the impact on the module output and invert inputs have been done, based on historical weather.)

Future:

Replace panels (w optimizers). Slight modification to racking- add a bit and longer rails.
Looking at 36x400 Panasonic panels (EVPV400H). Size is a minor constraint, want 40" max by ~71". (Will be able to increase rack size a bit w two more legs and replacing tracks up to 164 inch long.)

Replace Inverter

Replace wire between panels to Inverter (~245 ft, in conduit)


The asks:
I assume with a 14.4kw system I want an inverter that will handle 14.4kw. Is this accurate? (I have someone telling me the solaredge 11.4 will be fine?...) Ive read up on oversizing PV arrays.... still not sure why a -say- 14.4Kw inverter wouldn't give me more, even only on some days at some times. Running the SolarEdge Designer tool, my system comes up as "126%" oversized.

What inverter to use? (Not married to SolarEdge. Might like more input power and 4 string inputs. My sunnyboy has been bullet proof..)

What optimizers to use? (I get the sense that same mfg for optimizer and inverter is a good idea..)

I think I want to run each string back to the inverter, 245 feet away. Current system just slaps them together in a nema disconnect/fuse box at the array.) I also suspect that 4 strings of 9 would be a good idea, which means I need an inverter that has 4 string input. Is this accurate? Or, since I have optimizers, 3x12 would work just as well? Is a 4x9 or 3x12 better? Why?

On the racks, these will be placed in landscape mode- 4 high and 9 across (4 on one rack, 5 on the next rack)

What numbers should I use for voltage and current calcs to size the wire from array to inverter? Vpm and Ipm? Or Voc and Isc?? This is for sizing the wires back to the inverter, and for running voltage drop calcs? (and is 3% VD ok?)


Oh, is that a poor choice for panel? All ears. I'm trying to read as much as I can here, so bear with me...

Thanks in advance for any feedback. Im sure more will come up, in fact I bet Im asking some of the wrong questions!

ard

PS Sorry for the super long post...but figured it would tend to get better

[ard]

Im confused..why is the post truncated? Some moderation thing??? FWIW I run several VBulletin forums, yes spamming is a pita

and after editing the post 6 times and scrubbing it for ANY signs of odd content, it finally gave me a warning and said it was being moderated....

[SunEagle]

Im confused..why is the post truncated? Some moderation thing??? FWIW I run several VBulletin forums, yes spamming is a pita

and after editing the post 6 times and scrubbing it for ANY signs of odd content, it finally gave me a warning and said it was being moderated....

The anti spam software will note that if someone modifies an early or first post the post will go to moderation. If you plan on causing issues then you get banned and the posts deleted.

[ard]

It worked!

[SunEagle]

Im confused as to why it truncated my post.

I tried to fix it- editing and searching for anything in the text that would cause it to truncate

I dont 'plan on causing issues'

Im really at quite a loss here. Please give me a suggestion as to how I post and not run afoul of rules or 'anti spam software'. I admin, design and moderate 4 other Vbulleting forums- happy to comply with whatever you need.

thx

I would suggest you not modify any post for a while. The anti-spam software may take that as someone getting in and then adding a spam link.

[Ampster]

I would suggest you not modify any post for a while. The anti-spam software may take that as someone getting in and then adding a spam link.

I have had similar issues with making grammar changes with posts which contain links. They go to moderation.

[SunEagle]

I have had similar issues with making grammar changes with posts which contain links. They go to moderation.

I guess our Admin felt the anti spam software was better then having to deal with spammers. Although it seems to catch just about anyone that the software feels is not right.

[bcroe]

I find, check your posts carefully before hitting POST REPLY. Going back
to fix some trivial error may send it to moderation, but not if you wait a
couple hours.

I also had trouble writing something off line and then using copy and paste
here. But I just type a couple letters AND THEN paste, works. Delete those
extra letters.

Bruce Roe

[ard]

Thanks all.

I did compose the post in an outlook email editor, then pasted it. But scrubbed it by pasting into notepad, looking for anything hidden....

I'll get it fixed tonight, again appreciate to hear im not crazy. (interesting tip from bruce- the 'paste first' might indeed be the kind of action spammers might use....)

I did a few things:

Didnt paste the whole thing.... left the first couple of sentences as is, added content after that.... did the paste in pieces, not all at once.

The gods smiled!

[Ampster]

I guess our Admin felt the anti spam software was better then having to deal with spammers. Although it seems to catch just about anyone that the software feels is not right.

Yes it is a reasonable compromise.

[ard]

First post updated.... any inputs much appreciated.

[SolTex]

Hello from a fairly new-to-solar forum member. Our system has been up and running for just over 1 year, and we are very pleased with the performance. I only feel qualified to respond one of your questions:

"I assume with a 14.4kw system I want an inverter that will handle 14.4kw. Is this accurate? (I have someone telling me the solaredge 11.4 will be fine?...) Ive read up on oversizing PV arrays.... still not sure why a -say- 14.4Kw inverter wouldn't give me more, even only on some days at some times. Running the SolarEdge Designer tool, my system comes up as "126%" oversized."

If you have read up on oversizing PV arrays, then you have probably heard the justification for doing so. Whether you believe the justification is what matters. I fall into the camp that believes...but I'm always open to reasonable arguments pro and con. I've learned that "one size does NOT fit all" when it comes to solar design. What I can say is that our system works great, and it has a oversized PV array.

We have 40 LG380 panels, so our nominal STC (DC) system size is 15.2kW. The total peak (AC) output rating of our 40 IQ7+ inverters is (40 x 295W) 11.8kW. We see our system clip at the 11.8kW level for a few hours around noon every (sunny) day. In spite of this, our system exactly meets our design criteria to offset our annual consumption 100% so we are happy campers.

IF you wish to oversize your PV array (or undersize your inverter) then one widely accepted rule-of-thumb is to shoot for a DC/AC ratio of around 1.25 to achieve optimum annual performance. So for your proposed 14.4kW system a 11.4kW inverter would be (as someone told you) just fine. I can't tell you that this ILR (Inverter Loading Ratio) works for every situation, but it does work for us, and we have conditions very similar to what you describe (HOT in the summer, 30-40 days over 100F. Rarely freezes. Once a year snow).

[J.P.M.]

Ard:

Welcome to the neighborhood and the forum of few(er) illusions.

Q's:
1.) What's your zip?
2.) What panel orientation(s) are you considering for the new array(s) ?
3.) Are you familiar with SAM?
4.) Are you familiar with PVWatts ?
5.) Who is your utility provider ?
7.) What are your design goals for the new, proposed PV system ?

J.P.M.

[ard]

1. 95682
2. Arrays are placed due south. Dont want to alter this, holes and concrete and all...
3. No. And google isn't helping....
4. PVWatts looks to be the NREL tool for estimating solar production? Have not used it, just found it- and will start plugging away..
5. PGE
6. ?
7. My current sunpower 7.7kw system results in an annual true up of $3000 a year. Id like it to be much less.... Large home, two ACs, shop, pool, landscaping- on a well, so all water is pumped from 400ft down. And will probably by an EV in the next year. Presently it seems that my system is meeting 50% of my (current) power needs

[ard]

Hmmm. Inputting my system in PVWatts, then downloading the excel spreadsheet for hourly production... looking at how many days I would be production over 11,400W

Is that the idea?

Just took a quick spin. Getting late, will drill down tomorrow.

thx