Does BkGlobInc variable include Rear Side Shading loss?

[sneakypete92]

Does the BkGlobInc output variable account for the Rear Side Shading loss already? Or is BkGlobInc the unobstructed backside irradiance and the Rear Side Shading loss is then applied to it?

[dtarin]

The variable name in PVsyst is GlobBak and it is the rear irradiance after shading, before the bifaciality factor is applied. The shading loss on rear side has its own output variable.

[johank]

Thanks dtarin. I only recently learned that GlobBak is after shading (and IAM?).

Would it be possible to split out irradiance before / after losses are applied?

As far as I'm aware then there's currently not a rear-side parameter that corresponds to GlobInc. Having that would be very useful for performance monitoring & the like.

See also this post by jmallineni.

[johank]

Thanks! So just confirming - it is after shadings, but no other losses are taken out of GlobBak?

Would it be possible to add an "after losses" variable, something like GlobBakEff? And have GlobBak be the "before losses" rear irradiance, analogous to GlobInc. That seems more in line with how the front irradiance chain is handled.

In the meantime seems just adding BackShd to GlobBak gives you the before shadings irradiance. I think it'd be worth clarifying in the variables definition in the help that GlobBak is after shadings.

[dtarin]

There is also an IAM loss accounted for in GlobBak.

[johank]

Got it, thanks. Is the rear IAM loss captured in one of the output variables?

Finally found the help section discussing it, sounds like it always uses the "Fresnel-Glass" (non-AR) profile to calculate rear IAM loss.

[dtarin]

Only shows for beam component.