The amount of energy output from bifacial vertical mounting!

[Amirhossein]

Greetings

I have a problem with the results from a vertical structure equipped with bifacial modules.

It is strange that PVSYST underestimates the energy output from this condition compared to PVSOL software (the results are much lower than PVSOL, up to 17% in hourly resolution for our setting) for the same inputs. I have used a bifacial module at a height from the ground of 70 cm, an albedo factor of 25%, a pitch of 10 m, and a bifacial module with a bifaciality factor of 80%, a tilt of 90 degrees, and an azimuth of -90 degrees (the front side of the PV module faces totally to the East) for Italy. We believe that it is unusual and unacceptable compared to the real condition and running/on-going vertical system. I've double-checked everything, but the results are still unexpected even with the latest version of PVsyst (Version 7.4.3). Could you please fix this issue?

Thanks for your support in advance

Best regards,

[André Mermoud]

I don't know what you are waiting for.

Our calculation model is the better way we can imagine for the evaluation of the Bifacial yield. We have deeply checked for the version 7.4.3, that the rear side incidence irradiance  is equivalent to the front side (up to about 1-2%). If the bifacial results were false, this would mean that the whole simulation of PVsyst (front and rear side) is erroneous, i.e. that the transposition models themselves are incorrect.  

I don't know with which data in real conditions you are comparing the PVsyst simulations, and what you consider as acceptable.

NB: If you have really measured data on the field, we would be happy to get them for analysing the discrepancies.

I don't know how PV*SOL evaluates the vertical bifacial systems, but we don't have any reason of being quite compatible with their resuts.