Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
If there is a shadow on an exterior surface, the shadowing algorithm calculates the sunlit area of the surface. It doesn't know, where exactly the shadow is on the surface, just the beam component is multiplied with the Surface Outside Face Sunlit Fraction. The effect of the shadow is uniformly distributed over thesurface of the PV. This is the best case scenario in terms of power output and since module level mismaches cannot be modeled in e+ directly, this means that e+ will probably overestimate the power output, in case there is partial shading on the modeled surface. The extent of the overestimation depends on the power system layout of the real PV system you model. A system with individual power optimizers or microinverters is less sensitive to partial shading than a system with series-connected modules with a central inverter.
tl;dr: e+ gives an upper limit for the power output of the PV. (see e+ I/O reference pg. 2205)
