Unlimited Sheds vs Near shading partition in module chains

[Jeremyw]

Curious to know the explanation for the following obsveration.

Simulation A: only modified variable is rather than a near shadings 3-d model created, under "orientation", the field type of unlimiated sheds is selected. Same pitch, inactive band widths, electrical effect is selected with 2 modules in width.

Simulation B: only modified variable is rather than unlimited sheds selected, "fixed tilted plane' is chosen. And a 3-d model is created in the near shadings option. Pv plane in sheds is created. Same pitch, inactive band widths, etc. Partition in module chains is selected as well with 2 strings in height.

*all other system losses and configurations are held the same. I'm observing a varied lower outputs from Simulation B when compared to Simulation A. Sometimes as small as .38%, but other times greater. I'm guessing the Simulation B could be considered a more "accurate" representation?

Your insight would be appreciated.

[sebstein]

With "unlimited sheds", the string power decreased linearily while the buttom cell row is being shaded. The beam component of radiation is reduced by the ratio of the shaded cell area to the full cell area.

This is the correct electrical behaviour if unshaded and shaded strings are connected in parallel (MPP voltage is determined by the unshaded string, no bypass diodes are involved)

With 3D, the irradiance of the buttom string will be reduced immediately by the beam component as soon as the buttom cell row is affected by a shadow.

In PVsyst 6.0, "According to module layout" combines the best of 3D and "unlimited sheds".