# Irradiance loss in module layout and corners

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Hi,

I am currently trying to understand well the impact of shadows on PV cells.

I am using the “Shading mismatch loss calculation in PVsyst 6” presentation written by Mr. André Mermoud. And also the PVsyst online help.

When using the Module Layout option, the Irradiance or Linear shading factor is defined as the ratio of the number of shaded sub module over the total number of sub modules.

Or in the same slide the shaded percentage of sub module are defined : 1 corner = 25%, etc.

So, how the linear shading factor is calculated?

Let’s say I have a system with 1 string of 5 panels (3 bypass diodes per panel). One panel is partially shaded on 5 cells. 3 of these 5 cells are on one sub module (SUBMOD1), the others 2 on the above sub module (SUBMOD2). The SUBMOD1 has 2 corners shaded, the SUBMOD2 one corner shaded.

The SUBMOD1 is then supposed 50% shaded and the SUBMOD2 25% shaded.

What’s the calculation? 50 + 25 % = equivalent of 1 sub module shaded 75% and then the ratio is equal to 0.75*1/(5*3) ?

Or is it simply 2/(5*3) ? In this case what’s the aim of the definition of the corners and the shading percentage extrapolated for the whole sub module?

Best regards, Loic A