VBPV system calculation process of beam and diffuse component for rear-side

[Luis Zimmermann]

Hello together, 

is the calculation process of the beam and diffuse component on the rear side of a VBPV system (bifacial model) the same as for the front-side?

If not, please explain me the simplification and differences. 

[Linda Thoren]

Hello Luis Zimmermann,

In PVsyst, the beam and diffuse components and the rear side of a vertical bifacial PV system are calculated similarly as on the front side, by computing the integral of the visible sky. For the rear side irradiance, this is done using a 2D intersection method, same as the "unlimited shed" field type. If the layout is done in the 3D scene, the visible sky is instead in 3D. 

With bifacial systems, the view factor model also estimates the contribution of ground reflection to the front and rear side (not considered in mono facial simulations). 

[Luis Zimmermann]

Can you please explain a bit more detailed the difference between the calculation of beam and diffuse components for the front and for the rear side?
And what about the AlbInc (reflected irradiance from the far ground), how is this component calculated for the front and for the rear side?

[Linda Thoren]

This is further explained in the following help page:
https://www.pvsyst.com/help/project-design/bifacial-systems/index.html#irradiance-on-the-rear-side-view-factor