Advise on panel optimization

[Jdcarrol]

We’re finally up and running and have enjoyed the setup thus far, but I need advise on two things, but first, context:

context 1: I’m working with the 18kPV inverter. I have 3 series functioning right now. I have a place on my roof where I’d like to put a 4th series which would run in parallel with the 3rd string.

Context 2: The panels spec sheet is attached.

Context 3: my I am using Tigo 2-for-1 RSD, not optimizers.

Question 1. I separated my series two to account for the immediate shade it would get from the chimney. In the later afternoon my series 1 is then shaded. If I use optimizers on the panels that are shaded in my series 1, would that help account for the late afternoon shading?

Question 2: I purchased my panels from SanTan Solar new but the are not willing to restock that panel. Because my 4th series needs to be identical to the 3rd due to those being paralleled, what advice do yall have on specific panels or configuration? I understand the series need to be identical, but I can’t get them unless i want to buy a whole pallet from Santan’s source.

 

[sunshine_eggo]

counting:
10 panels in string 1
8 panels in string 2
10 panels in string 3

Q1: if you put optimizers on shaded panels, it will improve string performance.

Q2:


whelp, I have good news.

You don't need identical panels. You need panels that have series Vmp of 410V ±10%

Generally speaking, you need to match Vmp within about 10% to ensure the panels will perform normally; however, both strings may experience that 10% penalty to rated output (there will be a penalty, but it may not be the full 10%). You can also use different panels in series, but they will operate at the current of the lowest rated panel.

Generally speaking, while you may pay a penalty for dissimilar panels, it is almost always worth it if it enables you to add another string.

 

[GXMnow]

Another idea...
Connect the new string with a separate MPPT charge controller straight to the battery bank.

 

[Jdcarrol]

counting:
10 panels in string 1
8 panels in string 2
10 panels in string 3

Q1: if you put optimizers on shaded panels, it will improve string performance.

Q2:


whelp, I have good news.

You don't need identical panels. You need panels that have series Vmp of 410V ±10%

Generally speaking, you need to match Vmp within about 10% to ensure the panels will perform normally; however, both strings may experience that 10% penalty to rated output (there will be a penalty, but it may not be the full 10%). You can also use different panels in series, but they will operate at the current of the lowest rated panel.

Generally speaking, while you may pay a penalty for dissimilar panels, it is almost always worth it if it enables you to add another string.

What if I put series 1 and series 3 in parrarel into the 1st port? I think I’m reading elsewhere that orientation doesn’t matter if it will take the average of the two?

I guess I need to find panels that can get me to that 410v that also satisfy the wife’s aesthetics review

 

[Jdcarrol]

Another idea...
Connect the new string with a separate MPPT charge controller straight to the battery bank.

yea that could work, I’m trying to keep it simple with just the eg418k inverter and power wall though

 

[sunshine_eggo]

What if I put series 1 and series 3 in parrarel into the 1st port? I think I’m reading elsewhere that orientation doesn’t matter if it will take the average of the two?

It's important that all panels in a single string be facing the same direction. Unshaded parallel strings can be at different orientations with little to no penalty; however shading on a single string in that scenario will have adverse effects on the overall. Optimizers will help.

 

[Jdcarrol]

It's important that all panels in a single string be facing the same direction. Unshaded parallel strings can be at different orientations with little to no penalty; however shading on a single string in that scenario will have adverse effects on the overall. Optimizers will help.

Ok, I think I’m going to run the east facing 10pv string with the west facing 10pv string and place optimizers on few that get shaded. Thanks!

 

[zanydroid]

Read the installation notes for paralleled strings of optimizers . I am not sure that Tigo, for instance, allows “partial deployment” in that case. I have placed their jargon in quotes, search for tigo partial deployment for more details.

 

[sunshine_eggo]

Ok, I think I’m going to run the east facing 10pv string with the west facing 10pv string and place optimizers on few that get shaded. Thanks!

Even with optimizers note that if you have two shaded panels on one string, you may effectively lose the performance equivalent to two panels on the unshaded string. To bypass a panel, the voltage of that panel is lost. If you lose the voltage of the two shaded panels, the MPPT moves down to the -2 panel voltage of the string.