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Polystring option (mixed orientation within a string)


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Good morning,

I was reading this post in the FAQ from 2012 by Andre Mermoud:



However when putting modules of a same string in 2 different orientations leads to a the mismatch in current (due to different irradiances), which may be very important. This would be a very bad system and PVsyst doesn't allow it. This configuration would only be acceptable when using optimizers performing MPPT at the module level, but this is not yet implemented in PVsyst.

However, I do know of some installations in Perth in Australia, with different orientations on the same string(for example, when the roof facades are pretty small and there are only 3 modules on one side -> this is not enough in terms of voltage to make it a separate string, hence, it's connected with the other roof side which has 8 modules for example, making it a "polystring" of 11 modules with mixed orientation).

I acknowledge that this might be a bad design, however, sometimes the house constraints don't allow another option, and it would still be interesting to know the production and the losses in that situation, and be able to compare a variant with just the 8 modules on a single orientation vs. the 11 modules with mixed orientation, and see what's the benefit.

Finally, we are asked more and more to design systems with SolarEdge optimizers and inverters, it would be interesting if we could simulate a single string with mixed orientation and optimizers. Any update on this?


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To allow PV modules with different orientations within the same string, would mean a profound modification in the way PVsyst models the PV arrays. Therefore it is unlikely that this will be implemented sometime soon.

The situation might be different for the SolarEdge architecture. These systems are already handled in a special way by the simulation, and here it might be easier to add the complexity of multi-orientation strings. This is a topic that is being discussed within our team, but there is no timeline yet for an implementation.

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  • 3 months later...

I have just spent most of the day trying to set up a mixed orientation string SolarEdge system with optimizers. I can understand the reluctance to undertake the work needed to allow this option but it cannot be too great an effort to bring up an understandable error message if such a thing is attempted.

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  • 3 weeks later...


I have the same problem : I am asked to cover the maximum surface of the roofs and therefore I have 3 small sub-arrays with different shades but all the Solaredge optimizers will be in a single string.

If I select only 1 string per inverter, PVsyst proposes 3 inverters.

If I leave 3 strings per inverter, then PVSyst refuses to launch the computation, stating that the string voltage will be too small !

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  • 2 weeks later...

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