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South-Facing Solar Array Underperforming: Seeking Advice and Expansion Tips

Fahmula

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I have 20 solar panels (400W each, total 8kW) with 2.4kW facing east (6 panels in series) and 5.6kW facing south (7 panels in series, 2 strings in parallel) connected to a Deye 8k inverter.

**Panel Specs:**
- **Model:** CanadianSolar CS1U-400
- **Voc:** 53.4 V
- **Isc:** 9.60 A
- **Vmp:** 44.1 V
- **Imp:** 9.08 A

These panels were installed three years ago. I'm not sure if this is an issue, but my south-facing array isn’t performing as well as the east-facing array. There is a bit of shading on the south array in the morning, which you'll see in the pictures. This has always been the case, but I thought it might be due to the panels getting warmer throughout the day.

Additionally, I would like to add more panels, as my load regularly hits 60kWh or more, while the panels max out at 40kWh on most days. I'll attach pictures of the panels and data from Home Assistant showing the panel performance on 05/18/2024.

PV1 is east and PV2 is south.
 

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For improving the output of the south-facing array, I would suggest adding DC optimizers, which you can add just one to the panel that has the shading which will effectively bypass that panel and reduce the drag on the string restoring optimal output in a DC string.


I believe you can install the TS4 solo without the Tigo TAP or transmitter since it doesn't have rapid shutdown, you'll have to confirm that if this solution looks desirable.

Edit: The Tigo with optimization also has rapid shutdown so you will need more Tigo devices to tell it when it should be on or off.
 
Last edited:
For improving the output of the south-facing array, I would suggest adding DC optimizers, which you can add just one to the panel that has the shading which will effectively bypass that panel and reduce the drag on the string restoring optimal output in a DC string.


I believe you can install the TS4 solo without the Tigo TAP or transmitter since it doesn't have rapid shutdown, you'll have to confirm that if this solution looks desirable.

Edit: The Tigo with optimization also has rapid shutdown so you will need more Tigo devices to tell it when it should be on or off.
I thought about using optimizer but It just doesn't seem worth the effort and cost. I'm leaning towards just adding more panels.
 
Upon closer look, that entire panel is shaded across the bottom section which during that shading event effectively reduces the output very close to zero on that panel and impacts the whole string. If you don't want to add an optimizer, I would at least consider moving that panel perhaps to the far left.

1716494217060.png
 
Upon closer look, that entire panel is shaded across the bottom section which during that shading event effectively reduces the output very close to zero on that panel and impacts the whole string. If you don't want to add an optimizer, I would at least consider moving that panel perhaps to the far left.

View attachment 217227
If I added an optimizer to that one panel would it help? Also would three be worth it for the additional shaded panels?

I looked into the optimizers and it seems they can work without the tap but it looses a lot of functionality tho it'll do it's main purpose.
 
The optimizers are supposed to work without the TAP, I believe they call it blind mode or something like that. I believe your warranty/support changes if you run in that mode. I recently did a full install with the Tigo optimizers, tap and all. They seem to help.
1716515839465.png

Is 5kWh over 87.4kWh worth it? It's hard to say but I'm happy with the way they're working and the install was very easy. Plus I have RSD now if it's needed.
 
The optimizers are supposed to work without the TAP, I believe they call it blind mode or something like that. I believe your warranty/support changes if you run in that mode. I recently did a full install with the Tigo optimizers, tap and all. They seem to help.
View attachment 217260

Is 5kWh over 87.4kWh worth it? It's hard to say but I'm happy with the way they're working and the install was very easy. Plus I have RSD now if it's needed.
If RSD is needed then it's definitely worth it. I mainly need it for the shadow on the panels but it's only last about 1-2 hours so I'm not sure how much of a different the optimizer would make.
 
They're about $50 ea, you could try it on a single panel and see if makes much of a difference. If not, I bet it would be fairly easy to resale.
 
Any panels that have shading at any time throughout the day would be beneficial to bypass the degraded panel and improve the overall string. However, panels do have some inner workings that allow them to handle slight shading, but any panels where an entire section of the panel is shaded from left-to-right or top-to-bottom would receive the most benefit from an optimizer.
 
This picture was taken at noon today with no shades on the panels by this time. It even hit 7300 but it doesn't hold just a peek. Does this means the panels are too hot?

1000001059.jpg
 
Any panels that have shading at any time throughout the day would be beneficial to bypass the degraded panel and improve the overall string. However, panels do have some inner workings that allow them to handle slight shading, but any panels where an entire section of the panel is shaded from left-to-right or top-to-bottom would receive the most benefit from an optimizer.
I see. I'll definitely test out a few of them to see if it helps.
 
I would recommend doing some research on your particular panel to see if they utilize bypass diodes. Bypass diodes allow a shaded panel to be bypassed so that it doesn’t drag the whole string down with it. If your panels utilize bypass diodes then the realized effectiveness of an optimizer will be reduced significantly. I currently have an array laying on the ground and for most of the morning one of the panels is shaded on the top half only by the A/C condenser (these panels are 395w half cell with bypass diodes). Looking at the graph you can see that once that panel no longer is shaded the power jumps up about 200w suddenly when the bypass diode kicks out, which shows that the rest of the string including the lower half of the panel in question isn’t being affected by the shading. In any case at close to $50 per panel optimizer plus the supporting equipment your money may be much better spent on additional panels, unless you would like the added benefits of optimizers, which are:
1. Every panel will produce its full potential regardless of the others in the string.
2. Panel level monitoring. When setup properly optimizers give you stats on each individual panel, much like microinverters do which can come in handy to prove a panel warranty claim for degradation or otherwise alert you to issues.
3. RSD. RSD is required for new installations in most US jurisdictions. This is for human safety (reducing PV wire voltage to safe levels at the panel) as well as fire safety (panel output can be reduced to effectively zero in the case of an emergency, wire arcing, or inverter fault).
The only major downside besides upfront cost is it introduces several additional failure points to the system.
 
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