question

jakudo avatar image
jakudo asked

1 MPPT - 2 roof sides

Hi,

I'd like to understand more about how does the MPPT work in combination with panels on different roof sides.

For example I have one MPPT 150/100 and 12x 450Wp panels distributed as follows (2S6P):

  • 2 panels on SE
  • 10 panels on SW

I know that it would be better to have them all oriented the same or have separated MPPT for each roof side. However, I don't really know why.

How does the 2 separated panels affect the total power? Why is it better to have them facing the same side?

What is the advantage of having all panels on one side? Or have 2 MPPTs for each side?

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Alexandra avatar image
Alexandra answered ·

@jakudo

In a honesty 2 separate in your case. How are you setting them up as in the number of strings voc etc?

If you are going for an east west split, then 2 mppts make sense. The two roof orientation increase the length of your solar day. And yeilds are better.

The two mppts allows for different tracking, as voltage and amps will be different from each set due to temperatures shading and irradiance.

There are always debates about using one for different facing directions it was definitely taboo a while ago, but there are blocking diodes in panels now. but this onky works for matching string voltages and setup.

In your case with so many on one roof and a few on another then 2 will be better.



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jakudo avatar image jakudo commented ·

I didn't set anything - some company did it for me :)

Since it is 2S6P, so one paralel string is on the SE side and 5 paralel string are on the SW side.

So now the "problem" might be that the two sides affects each other and the mppt cannot work for 100% because each side has a different voltage and amps.


To be honest, I'm going to change it in spring - I will put all 12 panels on SW side of the roof and buy another MPPT and 4 panels and put them on the SE side of the roof so at that time it should work well.


Thanks a lot for explanation.

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Alexandra avatar image Alexandra ♦ jakudo commented ·
@jakudo

It does work. We did it as an experiment for a while at home since we get asked funny questions like this especially when the customer wants to save money. And sometimes it works quite well like on a cloudy day where ther is no direct sun but diffused light so the irradiance is fairly even.

Do we install for customers like that - no.

Just make sure you are not over amping with your many parallel setup. (the mppt short circuit input limit.)

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jakudo avatar image jakudo Alexandra ♦ commented ·
Yes, I know, I will check all the date before expanding the installation. Since I'm not so happy with the work of the installing company, I'm gonna expand the system by myself. I read many articles and see hours of youtube of how to do that, how to calculate it etc, so I hope I will be fine :)
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