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Comparison of pv capability


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I need your comment please and advice please. I have the following: 2x 5kva axpert kings in parallel. 12 x 345watt solar panels on each inverter, 24 in total. Installation done in May 2020. The max power from the panels to date varied between 4000 and 5000 watts for the combined system. To me this sounds a bit low, I was expecting around 6000 watts. Array is 3 in series, with 4 parallel banks. 6mm sq wires used throughout. What is the norm for similar installations? Many thanks for any input. Regards, Kobus

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Hi,

That does sound on the low side.  I have 12x 335w panels which are peaking just below 3500wh.

20201019_170836.thumb.jpg.3887efeb218315b6fcb0a0fba7f4d409.jpg

It could that your Solar charger is running hot and thus degrading the performance.  The King doesn't like 3 panels in series as this results in the MPTT running on the upper end of the voltage limits causing additional heat.  Many on the forum would suggest rewiring your panels rather run in 2 panels in series

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1 hour ago, Kobus van Eeden said:

What is the norm for similar installations?

I have a very similar installation (12x365W on each of my Kings). I ran them in 3S4P initially and subsequently changed them to 2S6P.  This made them run very much more reliably - they are VERY fussy about the max voltage, and 3 72-cell panels in series is simply too much.  High temperatures and SCC trips no longer happen at all since I changed them.

Having said all that, your problem seems to be more than that.  My change to 2S had no discernible effect on peak production - I regularly got 4000W from each set of panels in good conditions, and still do.

What is your location and the direction and inclination of your panels?  I have software that can produce some graphs that will show you what your production should be.

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1 hour ago, Kobus van Eeden said:

Thanks for your prompt response. I am based in Witbank, mpumalanga. 12 panels 3s4p face north and connected to inverter1. 6 panels 3s face west and 6 panels 3s face east and connected to inverter 2 all strings in parallel.

That might be your issue right there. At peak sunlight at midday you've got only 12x345W angled towards the sun. The other inverter with East and West-facing panels will spread your generation to the morning and afternoon, which is useful if that's the time you need power, but it reduces your peak and total generation. Also, if those 6 West and 6 East panels are on the same MPPT, you may be reducing your output further.

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1 hour ago, GreenFields said:

if those 6 West and 6 East panels are on the same MPPT, you may be reducing your output further

There was a study done that show only a 1% reduction for east/west panels. In my set up I see almost no reduction. It just adds and works very well.

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On 2020/10/20 at 10:36 PM, Louisvdw said:

There was a study done that show only a 1% reduction for east/west panels.

I bet that's only with a dual MPPT system (two trackers).

I wonder if it might work better to connect half the N and the E set to one inverter, and the other half of the N and the W set to the other inverter.

 

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On 2020/10/20 at 10:47 AM, Kobus van Eeden said:

I am based in Witbank, mpumalanga. 12 panels 3s4p face north and connected to inverter1. 6 panels 3s face west and 6 panels 3s face east and connected to inverter 2 all strings in parallel.

Below your maximum yield for the 12 panels facing North.

image.png.0c04284994a511caeebd9670707ba847.png

 

And for the 12 Panels facing East and West

image.png.fd0bb75ec8528d9238888fb1f386a42d.png

Note that this is the maximum that could be achieved, assuming perfect conversion.  It does not make allowance for thermal coefficient or MPPT losses, which could reduce peak yield by 10-13% on a hot day.  The output from the East-West panels would be further reduced if the are on a single MPPT.

You can see that the biggest drawback of the East-West combination is the terrible performance in mid-winter. Annual average is 5.3 vs 6.5, a 18% reduction.

Below is the graph for your combined system

image.png.1125e2008188febd648bdfd3bae542b0.png

 

 

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48 minutes ago, Erastus said:

Is that for a split system on all the panels?

These graphs are the sum of the solar insolation (the total PV energy hitting the panels) for the panels and orientations listed in each. So, they would approximate what you would get with a separate MPPT controller for each bank. 

Although, from the link @Louisvdw posted above, the losses from combining different sets on one controller is less than one might expect.

Edited by Calvin
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