Vertical Bifacial East-West: received irradiance from each side

[Hung MAI]

Hello PVsyst!

I have a vertical bifacial East-West system, and I want to make sure that the irradiance received from the East-side should be the same whether I use east-front facing or west-front facing config. Same for West-side.

Therefore, I made 2 simulations with the above 2 config, then compare just the Ressource losses (top part of the Loss Diagram). The results are attached as images.

I don't think the horizon loss and soiling loss is integrated in the backside losses, hence I excluded these 2 losses from the front-side. The structure shading loss BackShd is also excluded for the back-side, in hope of a fair comparison.

For the result, I expect the "Global Irradiance on front side (no soiling, no horizon shading)" of one configuration (East/West) to be more or less similar with the "Global Irradiance on rear side (no soiling, no structure shading)" of the other config (West/East). I highlight the 2 couples values in green and orange. 

West front-facing result:

East front-facing result:

 

Only the green pair seems to be similar (1.1% difference), the orange pair is 4.5% difference. This is already much better than some previous version of PVsyst, but I still want to know if my expectation is logical and if yes, what are the reason for this difference (the orange pair).

Thank you!

[Maïlys B]

Hi ! I'm also doing a simulation with bifacial vertical PV and I'd like to know to what extend PVsyst is accurate. From what I understand : soiling, far shading and near shading from the 3D scene are not considered for the back face thus the production is overestimated. Also, if the nominal energy is not accurate, then most of the other following losses will also be wrong (inverter behavior, ohmic losses, grid limitation, etc.). Are you confident with your results ? Or are you planning on improving the calculation ?

Many thanks