API field
Transparent fraction of the module plane
Light that passes through gaps in the modules to the ground
Unit %
What it is
The share of the module plane that lets the direct sunlight through to the ground in the shadow of the row: the gaps between modules and, on glass-glass modules, the spaces between the cells. The shaded ground receives this share of the direct and circumsolar light. The Unlimited sheds 2D and bifacialvf 1° sectors models use it. The bifacialvf (Marion 2017) and infinite sheds models do not. Under the PVWatts 8 fixed layout of the Rear-side geometry step the rear model takes 0.013 instead.
Typical values and how to get it
0 for modules with an opaque backsheet mounted without gaps. A few percent for glass-glass modules, from the cell layout of the datasheet drawing, plus the gaps between modules. If not given: 1.3 % (0.013 on the wire) under bifacialvf 1° sectors, the value of the model's reference code. 0 under Unlimited sheds 2D: no light passes between the modules.
API
bifacial.transmission_factor — sent as a fraction 0–1