How to use the Module Layout with very big PV plants ?

[André Mermoud]

The "Module Layout" tool, where you have to specify the position and the electrical wiring of each of your modules, is not practically useable for big installations (of, say, more than 500-1000 kWp).

On the one hand the positioning and attribution of all modules in the system may be tedious, and on the other hand the calculation time of the simulation will become prohibitive.

PVsyst advises a "reasonable" limit of 1 MW, and prevents to develop the ModuleLayout option for systems upper to 5 MW. However you can modify this limit in the Hidden parameters, topic "System Design Parameters, losses, shadings", item "Power limit for Module Layout error".

If you have a very big system, you are advised to perform your shading studies with the module layout option on a reduced representative part of your system.

This will give namely an electrical shading loss reference result.

After that, you can perform the calculation on the full system using the shading option "according to module strings", which is easy to define and fast.

This will give you another estimation of the electrical loss. With "Fraction for electrical losses" = 100%, this should represent an upper limit to this loss.

Finally, comparing with the loss obtained with your reduced system, you can adjust a realistic value for the "Fraction for electrical losses" parameter, in order to get the same relative loss.

With sheds (row) arrangement, the "Fraction for electrical losses" is usually 100%, even with by-pass diodes; because as soon as 30% of the submodules are shaded, the concerned string doesn't produce any more for beam component. See How to evaluate the effect of by-pass diodes in shaded arrays?

Therefore both calculations should give give close electrical shading loss results.