NSolV8 Shading Calculations

“We have a customer that, due to local constraints, had to install a system in an area that is shaded for part of the day by a permanent obstruction. I’d like to incorporate that obstruction into the analysis.

What is your recommendation for how to do that in NSol?”

Shading losses are a complex issue and I have never figured out a way to calculate them accurately. Some comments:

  1. The losses depend on the array configuration – how big is it, which parts are being shaded at what times, what are string lengths and how does shading affect them? Varies by month as well.

Also what type of modules – are they traditional modules or half-cell? And if they are shaded, they are still “seeing” diffuse irradiance, so there is partial output.

  • Solmetric makes a device called the SunEye which can accurately calculate shading losses. Residential installers use this and it is apparently pretty good.
  • NSolV8 generates a sun elevation chart and table. With a little effort you could draw a “shading horizon” and try to estimate how much shading would occurs during each month. This is only somewhat accurate due to issues mentioned in #1.
  • Apparently, some of the more advanced programs calculate shading for every single module in a system and determine losses based on this. To do this in NSol, we would have at add information on physical array layout and shading horizon.
  • Once you know the losses by month, you can enter them into seasonal losses in the factors page. Make sure you upgrade to V8.1.10 (currently the latest) – someone recently pointed out that seasonal losses were not updating properly so I fixed it.