Bifacial
The user can enable bifacial modules which can collect light from the both surfaces. The same Decomposition, Transposition, and View Factors are used for the backside to determine the backside irradiance. Currently only the simple shading model can be used with bifacial modules as the full shading model does not support shading of the backside or shading of the ground. After completing the near shading model we have a backside component, in addition to the frontside, denoted \(G_{poa,near,back}\).
The soiling loss, incidence angle modifier and spectral effects are not modelled for the backside irradiance. The backside irradiance is a small part of the total irradiance, so these ommiting this small effects from what is already a small effect should not introduce a significant error.
Two additional irradiance effects are modelled for bifacial modules, structural shading loss and transmission loss. They are both simple loss factor models where the user must specify the loss parameter.
$$G_{\text{back,shade}} = G_{poa,near,back} \bullet \left( 1 + K_{\text{shade}} \right)$$ $$G_{\text{back,transmission}} = G_{back,shade} \bullet \left( 1 + K_{\text{transmission}} \right)$$
This backside irradiance is then combined with the front-side irradiance.
$$G_\text{eff,back} = G_\text{spectral} + G_{poa,near,back}$$
$$G_\text{eff,back,shade} = G_\text{spectral} + G_{back,shade}$$
$$G_\text{eff,back,transmission} = G_\text{spectral} + G_{back,transmission}$$