With sheds on a tilted roof, PVsyst changes my orientation

[André Mermoud]

Yes, this is quite normal.

When you tilt the baseline of a collector (rotating around the azimuth line), the plane "true" orientation will change.

For understanding this: please take a cardboard as collector, and position it at, say, 30°south.

Then give a tilt to the base (baseline slope). Now the plane azimuth is defined as the perpendicular to the intersection of your cardboard and the horizontal plane.

And the plane tilt is the tilt accounted perpendiculary to this horizontal line (i.e. the angle between the plane of your cardboard and the horizontal plane)

At the limit of a vertical base line, the azimuth will be (90°-plane tilt) (by respect to original Azimuth if not south).

The calculation of these new orientation angles is not straightforward: it implies 3D rotations matrices. But you can trust the proposition of PVsyst...

This arises on a roof when the tables are set perpendicularly to the slope, and also when you put tables on a sloped terrain (hill).

In the case of a hill, you have usually many different slopes, and PVsyst performs an average for the incident irradiance calculation.

You have a detailed tool for analyzing this situation in the 3D shadings editor, menu "Tools > Edit orientations".