Can PVsyst please comment on this post? I have the same question and want to add that there are a lot of sources that recommend calculating the structure shade factor simply by taking the ratio of the width of the racking (or torque tube) on the rear side by the length of the module (assuming it's in portrait orientation). My concern is that this is not taking into account the electrical effect of shading a row of cells that is in series with the rest of the cells, i.e. the current will be reduced in the entire module if you shade just a single row of cells.
So the calculation should be the width of the row of cells divided by the width of the racking or torque tube, correct? This is in line with PVsyst's instructions, "the current in a string is the current in the worst cell, if this mechanics covers x% of one cell, the shading effect will be x% for the concerned string. This loss may be reduced by a factor of 2 if the mechanics is covering half a cell (i.e., the shade is distributed on 2 cells). "
In summary, following these instructions, assuming the racking above shades 40% of the row of cells behind it, even if it's only 10% of the length of the module, would the Structure Shading Factor be 40%? Or 10%?