Solar Panel String Advice - Blocking concerns?

[kronic24601]

Hi. I'm a newbie here and have just DIY installed my first Solar system on my residential home in Los Angeles. LADWP gave me the go ahead to turn it on just a few days ago so I don't have a lot of info. However, one thing I am observing is that I'm generating less than I was originally anticipating. I have been contemplating adding 3 more panels to the back-side of my house, but I have some concerns. Can anyone give me advice based on the setup and information below (primary questions below)?

Setup (current):
- Solaria 360W modules (25)
- SolarEdge HD-Wave SE7600H-US Inverter
- SolarEdge P370 Optimizers

All modules in full sun on the front of my house. 8 modules over garage 17 modules over main house. But due to String voltage limitations per strong (6000) I separated the north most 4 panels over the house with the garage panels for the first string (12) and the others for string 2 (13)

Fixed at ~14 degrees.

On the roof is 9,000 potential watts of power, but due to orientation, height to roof (minimal), sub-optimal tilt, optimizer and module efficiencies ... I didn't expect to generate near this and opted for the 7.6Kw inverter ...

However, based on current readings I'm peaking at just over 7.1kw (hovering over 7Kw for like an hour)... and this is summer. Given the longest day of the year was June 21 --- I'll be getting less and less sun for quite some time.


Questions:
1) Does my generation and loss seem normal to everyone? Is this ~21% loss from panel DC to inverted AC seem right given my situation? (I attached an image of the solar production, it's not at peek power yet, but getting close)

2) To produce a little more and take advantage of the Fed credit while it lasts, I was considering adding three more panels on the back of the house (picture attached for reference). However, this area is going to get more shade than the other areas. In the summer a tree shades it until about 10:30 before they would all be in full sun. In the winter a chimney will shade the south most panel as the in the noon-3ish time frame. Since I cannot put those three on their own string, I'll have to bring them into the panel strings I already have... but I'm concerned that there might be blocking going on ... somewhat brining down the voltage of the other panels on that string in the front of the house. Does anyone have any thoughts or suggestions about adding 3 new partial shaded panels to my existing setup?


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[Ampster]

Questions:
1) Does my generation and loss seem normal to everyone? Is this ~21% loss from panel DC to inverted AC seem right given my situation? (I attached an image of the solar production, it's not at peek power yet, but getting close)

I am not sure how you calculated loss from DC to AC. Are you expecting the panels to produce 9,000 Watts at Noon? Unless you have perfect conditions of all panels facing due South at Solar Noon on a cool day with a tilt putting the panels exactly perpendicular to the sun then you will have less. Even if you got 7800 Watts, your inverter will clip the excess power. Does your chart of generation show a flat top around solar Noon? It looks like you are quite a ways off a South facing array if I read your diagram correctly.

2) To produce a little more and take advantage of the Fed credit while it lasts, I was considering adding three more panels on the back of the house (picture attached for reference). However, this area is going to get more shade than the other areas. In the summer a tree shades it until about 10:30 before they would all be in full sun. In the winter a chimney will shade the south most panel as the in the noon-3ish time frame. Since I cannot put those three on their own string, I'll have to bring them into the panel strings I already have... but I'm concerned that there might be blocking going on ... somewhat brining down the voltage of the other panels on that string in the front of the house. Does anyone have any thoughts or suggestions about adding 3 new partial shaded panels to my existing setup?

You are already at a DC to AC ratio of 1.18 to one, Adding 3 more panels will bring it up to 1.36, which is still below the manufacturers maximum. Would the additional paneIs be facing Northeast? If you are clipping the only benefit from more panels is you will get an steeper ramp up in the morning and a steeper ramp down in the evening. Other than the shadows in the winter you should see no clipping and some additional production. The Optimizers should prevent the shadows from affecting the other panels assuming you string correctly. That is their purpose. When I say additional production, I only mean in reference to a smaller system. Your winter generation will be a lot less because the sun is lower in the sky and the days are shorter.
Have you simulated your system using PVWatts? That should give you a benchmark and also a sense for how much production to expect for the entire year. You can even get a simulation from the proposed panels. You haven't mentioned your expected consumption and that is an important factor in determining whether to increase the size of a system.

[ButchDeal]

Questions:
1) Does my generation and loss seem normal to everyone? Is this ~21% loss from panel DC to inverted AC seem right given my situation? (I attached an image of the solar production, it's not at peek power yet, but getting close)

What makes you think you have ~21% loss from your PV modules to your inverter? Your PV modules never generated it. The sun is not a constant and from your image it looks like the northern most modules have some evening shadows thus limiting their production. This is effecting the northern most WEST facing more than the more northern but SW facing modules.

2) To produce a little more and take advantage of the Fed credit while it lasts, I was considering adding three more panels on the back of the house (picture attached for reference). However, this area is going to get more shade than the other areas. In the summer a tree shades it until about 10:30 before they would all be in full sun. In the winter a chimney will shade the south most panel as the in the noon-3ish time frame. Since I cannot put those three on their own string, I'll have to bring them into the panel strings I already have... but I'm concerned that there might be blocking going on ... somewhat brining down the voltage of the other panels on that string in the front of the house. Does anyone have any thoughts or suggestions about adding 3 new partial shaded panels to my existing setup?

I am not sure what you mean by blocking that your concerned with. With SolarEdge it doesn't matter if these produce at all as the optimizers have Buck/Boost voltage regulation.
That said your production from these 3 modules is going to be pretty minimal as they will be east facing but shadowed till 10:30 and out of sun shortly after noon, and even worse in winter.
Can you mount them closer to the north AND thus closer to the ridge, avoiding the chimney and more of the tree shadow?

[kronic24601]

I am not sure how you calculated loss from DC to AC. Are you expecting the panels to produce 9,000 Watts at Noon? Unless you have perfect conditions of all panels facing due South at Solar Noon on a cool day with a tilt putting the panels exactly perpendicular to the sun then you will have less. Even if you got 7800 Watts, your inverter will clip the excess power. Does your chart of generation show a flat top around solar Noon? It looks like you are quite a ways off a South facing array if I read your diagram correctly.

Ya I got that. My PVWatts calculation had me anticipating somewhat more generation. Even with my SouthWest and West facing modules, I had hoped/expected to see some clipping at the peak periods at the middle of the day. It appears that is unlikely to ever occur as I max out at about 7.1 kWh at 1pm-ish.

Last year I used about 12.5K kWh, and I expect my electric usage to increase over the years.

---

As for the feedback on the east facing modules. I suppose it may not be a great investment. I'm not very informed on how much of an impacted partially shaded modules has on production. Is there a good calculator for deducing this? I roughly was calculating a 1/2 as efficient as my full sun modules ... but that was just an estimate to calculate pay-off period.

[Ampster]

Ya I got that. My PVWatts calculation had me anticipating somewhat more generation. Even with my SouthWest and West facing modules, I had hoped/expected to see some clipping at the peak periods at the middle of the day. It appears that is unlikely to ever occur as I max out at about 7.1 kWh at 1pm-ish.

What did PVWatts say your annual production might be? I dont know anything about your latitude or other locational factors so it would be difficult to say whether you will generate as much as you consume.

Last year I used about 12.5K kWh, and I expect my electric usage to increase over the years.

Then I would size or increase accordingly to offset that anticipated consumption. The only thing that would change that would be any energy conservation reductions in consumption that you can make. You will get a better return on doing those before adding more solar.

As for the feedback on the east facing modules. I suppose it may not be a great investment. I'm not very informed on how much of an impacted partially shaded modules has on production. Is there a good calculator for deducing this? I roughly was calculating a 1/2 as efficient as my full sun modules ... but that was just an estimate to calculate pay-off period.

It may be a good investment depending some of the answers above. I think some installers have the tools to tell you how much production you might get out of that east facing partially shaded situation. There is probably not enough profit in a 3 panel installation for anyone that does have those tools to spend the time. The best advice is from ButchDeal to try to locate them near the ridge.

[kronic24601]

- PVWatts calculated over 13K kWh for the year, but I also wasn't entirely sure if I filled it out correctly. I left the default losses of 14% and didn't mess with the advanced params. Half of my is wondering if the SolarEdge inverter has some special configuration options to better optimize things, but that doesn't look to be the case.

- Right now, I was trying to maximize based on my inverter size. Since I'm still using more than I'm making, I figure I have a 7.6 kw inverter, why not ensure I can generate that amount ... at least at peak, if not with some minimal clipping? But then again I need to do the math to see if additional solar panels will be worth the investment (and time).

- Right now, I have too many other roof protrusions to move them closer to the ridge, I could move them south on the house and get them up higher ... but I think that puts them in a more shaded spot due to a large tree just south of my house. Alas ... this probably isn't worth the time.

I had read in a review of SolarEdge here: https://mcelectrical.com.au/blog/sol...imiser-review/ that there was some concerns with partial string location (see PRODUCTION LOSS AND "BLOCKING" section). So I was concerned that If I did go through the trouble of adding these additional panels, it might do more harm than good... but it sounds like I should not be concerned there?

[Ampster]

Are there any energy conservation measures that you can take? What are your largest loads? Are you on a Time of Use rate?
Based on what you have said, you maybe close to break even and time or money invested on energy conservation may provide more certainty than adding a few NorthEast facing panels.

[kronic24601]

Technically these "planned" additional would be true east facing. At this point I've done most other standard energy conservation measures that appear cost effective. I have been contemplating radiant barrier ... but I had new attic insulation, cool roof, new AC, and incrementally changing out for LEDs when bulbs go out (everything else is fluorescent). Largest load is prob still AC, and electric cars, pool, etc...

I haven't yet researched a TOU rate yet. My wife is home all day (so lots of peak usage in the past) but once I get a few bills I guess I'll be able to tell if the existing solar makes that a no-brainer.

At the end of the day I "think" I have my answer. If I assume a 30% loss from what my full sun modules are getting now (due to the shading), then it's about an 8 year payback based on the costs. What kind of a pay-back is to-be expected with these systems in general?

[Ampster]

It varies depending on rates. 8 years is acceptable. In Cslifornia, with solar I am required to be on TOU rate. Depending on the differential between getting paid for generation and paying for charging I can break even financially even though my consumption is greater than my generation. Most of that is because I charge the cars late at night and shift other loads to less costly periods. Someting to consider.