Flat maximum energy production

[smbunn]

I know this has been mentioned before but wanted some clarity on what I can expect in terms of maximum production from my panels throughout the year. I am in the southern hemisphere (NZ) and my panels point due north. They are inclined on a flat roof with a tilt up from flat of about 20 degrees.
Panel theoretical maximum production is 10 kW. This is from 20 of 500 watt panels into two SolaX 5 kW inverters. 10 panels per inverter in a single string each.

It's winter and my production is flat lining during the day at around 6.6 kW. Is this normal? What could I expect in Summer?


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I generated a solar incidence report for my house, and it is shown below. It seems to indicate that in September I can expect 4.32 kW-hr/m2 and in peak summer 5.73. So thats 75% now. At 75% I should be getting 7.5 kW max or am I mis-calculating this?

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[Ampster]

My only guess is that flat lining looks similar to the inverter clipping that I have on some of my systems. On the surface one would not expect that with two 5kW inverters and 10 kW of panels. That is a DC to AC ratio of one to one. Is there anything in the specs or perhaps a setting that would explain that clipping?

[scrambler]

Something is clearly off here, so you will need to dig deeper in the monitoring and settings.
Can you pull separate monitoring for each inverter?
Can you pull individual panel monitoring for each array of each inverter?

[smbunn]

Here are the two separate output files for my two inverters.

solar2.png

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The second set of panels is about 25 degrees the first row about 17 degrees so in Winter I am getting slighlty more power from the panels with more tilt.

[scrambler]

So each 5kW Inverter is clipping at 3500W.

I assume they each are connected to the same number of panels or 10 x 500W panels.

So the nest question is what are exactly these 500Watts panels (brand Model specs...)?

Do you have anything on them like optimizers or other things that would provide monitoring?

Have you checked the Inverter settings in case there is an Output limit setting on them?

[smbunn]

Solar panels are Trina TSM-DE18M(495). Attached is spec sheet (https://static.trinasolar.com/sites/...II)_202011.pdf)

10 panels per inverter. Two panels on one set and one on the other have 'optimizers' as there is potential shading from a chimney. I checked and this shading only occurs after about 5:30 pm in Winter so unlikely to be an issue.

SolaX settings are all default except one unit has a 5 kW export clip function using a CT on my grid connection. The other has no export limit. The theory being if my export goes above 5kW then that single unit with the CT will ramp down and eventualy if required shut down. I temporarily disabled this export limit and saw no change in the output which stayed at about 6.8 kW. (I have the installers passcode so can get into all settings)

[scrambler]

You are going to need and speak with the installer, because the shape of the curve indicates that without clipping, it would peak around 4300W which would be normal for 10 x 500W panels at this time of year in full exposure.

This to me looks like the Inverters are clipping the array production, so some setting in there has to be responsible for that...

Have you tried to shutdown one inverter and see what happens, and if the only one remaining continues to clip at 3500W?

[scrambler]

Also, if you are subject to Rule 21 (like in CA), try deactivating that in one inverter for a while to see if it makes a difference.

[smbunn]

I am in New Zealand. The only restriction is max export of 5kW. I did deactivate this and it made no difference.

I do like your idea of shutting one down and seeing if I get 4300 out of the other...

My installer company (largest in New Zealand) has their technical lead send me an email saying this is perfectly normal output and just wait for summer.

[scrambler]

My installer company (largest in New Zealand) has their technical lead send me an email saying this is perfectly normal output and just wait for summer.

This is just complete bull****....
If this was due to winter, the whole curve would be low but have a regular bell shape.

What that curve says is that there is a lot of production potential, but it is Clipped at 3500W.That flat top in the production curve Cannot be explained by a natural phenomenon, not low sun production, not shade etc....

I just hate when installers/Solar providers give us that kind of BS, they are just adding Insult to injury....

[scrambler]

Also, Rule 21 does not apply in New Zealand but I am pretty sure New Zealand does have Smart Inverter regulations.

These basically define various ways the inverter would reduce production based on specific Grid circumstances.
The ones that could affect DC production would be Volt Watt and Frequency Watt modulations.
I don't know in New Zealand, but here and as part of Rule 21, Volt watt is triggered by high grid voltage and Freq Watt by high grid frequency
So it may be useful to investigate what type of smart remote controls are mandatory in smart inverters over there, and if so what settings activate them

That said, the fact this is a consistent daily thing does not really match the above which would normally be occasional.

One other test worth trying (after trying to shutdown one), is try to set the max export of one inverter to something like 2500W, see if it does clip at that to confirm the option works, then if it does, change it to 4500W and see what happens.

[nerdralph]

Solar panels are Trina TSM-DE18M(495). Attached is spec sheet (https://static.trinasolar.com/sites/...II)_202011.pdf)

That link is for 380W panels. I think the DE18M are 210mm cell high-power panels with high MPPT current (13-14A). If your inverter has a 10A MPPT limit per string, that would explain the clipping you are seeing.

[scrambler]

Good point, we do need to check what is the MPPT range of the inverter to see if it matches the string current and voltage.

Please give us the exact model of the inverter and spec sheet, so we can find what is the acceptable range of the MPPT for both Volts and Amps
And we do need the correct spec sheet for the panels to be sure of their output...

[smbunn]

wrong link, sorry, this is my panel https://static.trinasolar.com/sites/...(II)_2021B.pdf
I had the right name but wrong link

[scrambler]

We may have cross posted, we need the inverter model and spec sheet too to verify the MPPT acceptable input range