Unmet Hours

Shading calculations

asked 2018-04-16 17:13:27 -0600

RChidwick

519 ●2 ●9

updated 2018-04-17 06:48:32 -0600

__AmirRoth__

4446 ●5 ●17 http://bleedinggreenna...

Hello everyone,

I am wondering how shading calculations are performed on a wide surface with PV. Specifically, if a shadow is cast over part of the surface, how does that affect the performance of that whole surface? I am simulating a row of panels with a single surface (to avoid having to draw 1000's of surfaces, it's a large system), but I am concerned that generation numbers are lower than they should be due to the whole surface being 'shaded' when only a part of it is.

I hope that was clear, please comment if I need to clarify.

Thank you

answered 2018-04-17 07:00:14 -0600

adambgnr

759 ●1 ●2 ●7 http://www.linkedin.co...

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)