Structure shading factor

What it is

The fraction of the rear-side light blocked by the mounting structure behind the modules, such as torque tubes and rails. Under the PVWatts 8 fixed layout of the Rear-side geometry step the rear model takes 0.

Typical values and how to get it

5 % for a light structure and 10 % for a heavy one are common design values; the default is 5 %.

How it is applied

$$G_{\text{rear}} = (1 - f_{\text{struct}})\,G_{\text{rear,0}}$$

where

Symbol	Meaning	Unit
$G_{\text{rear}}$	the rear irradiance after the structure shading	W/m²
$f_{\text{struct}}$	this input as a fraction	—
$G_{\text{rear,0}}$	the rear irradiance from the ground, the sky and the sun before it	W/m²

API

bifacial.structure_shade_factor — sent as a fraction 0–1

Symbols follow the symbol registry.