Adding panels to my 18kpv, Canadian Solar 400w bifacials. 4s2p or 8s. Shading expected

[y0bailey]

Alright...now that I've figured out my EG4 18kpv install (still awaiting delivery), I'm thinking about the next project...which is 2 of the 4 panel Signature Solar Brightmounts thrown in my side yard, with some sort of bifacial setup of 8 panels. They will be facing the same direction and roughly in the same area, but will experience some shading at different times in the AM/PM as the sun comes over the trees.

Right now the Canadian Solar 400w bifacial split cell panels are in the lead, but that can change. I just cannot exceed 44inches wide on the panels.

Their operating voltage is ~39v. So 4 in series will be around 155v.

The spec sheet on the 18kpv has the following for the DC inputs, which I admit to not fully understanding:

Full Power MPPT Voltage Range 230–500V
DC Nominal MPPT Tracker DC Voltage 360V
DC Nominal DC Voltage Range 100–600 V
DCMPP Operating Voltage Range 120–500 VDC

1) So is the 150v a bit low and I am better off running them in series?

2) Or will paralleling them by using the 1st PV input (the parallel input ) in the 18kpv handle this for me?

3) Will my shading issues + 8s potentially negate the benefit (if there is any...see question #2) and I'm better off keeping 4s2p?


Early in my research but any input is appreciated!

 

[prometheanfire]

are you willing to use optimizers?

 

[y0bailey]

are you willing to use optimizers?

Trying to avoid it

 

[Quattrohead]

If you are into scientific experiments this would be a fantastic one, however if you are not set them up whichever way is easiest and as long as you get roundabout what you expect in production you should be fine. Actually it would be a really interesting test of the mppt to see how it handles the two different scenarios.

 

[y0bailey]

If you are into scientific experiments this would be a fantastic one, however if you are not set them up whichever way is easiest and as long as you get roundabout what you expect in production you should be fine. Actually it would be a really interesting test of the mppt to see how it handles the two different scenarios.

I am into science experiments, I'm just a beginner.

Can you help me understand what all of this means a bit so I can better grasp what I'm "studying"? I'm thinking there is just increased efficiency if I'm in the "Full Power range" vs. the "Nominal range"? But both will work?

Full Power MPPT Voltage Range 230–500V
DC Nominal MPPT Tracker DC Voltage 360V
DC Nominal DC Voltage Range 100–600 V
DCMPP Operating Voltage Range 120–500 VDC


Science experiment wise, I feel like there are 3 things to test, so correct me if I'm wrong.
Test 1 = 8s into any MPPT input on the 18kpv
Test 2 = 4s2p into any two MPPT ports on the 18kpv
Test 3 = 4s2p into the first ports (the parallel ports) on the 18kpv.

Super easy to just bury two wire runs and use one/both during the testing phase. I also have a DC disconnect that can handle it as well.

 

[Quattrohead]

Sounds good to me, you will be testing two different things, one will be the efficiency of the mppt depending on voltage and current it gets and secondly will be how the panels react to being partially shaded depending whether they're all in series or in parallel. You will also be chasing the change in season but you might see some trends that are worthy of note.

 

[y0bailey]

Reporting back in with some updated information! I've been doing some testing between 4s2p and 8s on my solar array.


DRUMROLL!

Parallel wins!

I do get about 5% lower "peak" wattage in 4s2p. I'm assuming either because it's outside of the "full power MPPT voltage range", or more loss in the 100+ foot wire run at the lower voltage.

With my shading the parallel setup gets an extra almost 60 minutes of 1000+watt production compared to 200-300 watt production in series. This happens every morning when the right array stays shading and the left array has full sun, and every evening when the left array has shading while the right array has full sun.

It's at least 1-2 KWH difference between the configurations over the past few experiments.

I may repeat the experiment at peak sun-hours, but so far parallel has never lost on comparable days! My one worry about the heat of summer is if my voltage in 4s2p will drop below the dreaded 120v...but we shall see.