Large difference of irradiance on the back of bifacial PV with different pitch

[hohai]

Hello, bifacial PV components of the back irradiance algorithm is there pitch increasing irradiance is also increasing the error?

For example, I tested a 4-meter spacing, the irradiance was 209205, and when the spacing was 400 meters, the irradiance became 653899.5, Nearly three times, is there a problem here? When the spacing increases to a certain extent, the irradiance should not change much.

Looking forward to a reply.

Thks！

[Michele Oliosi]

Did you try other distances? I don't see a problem because you show just two instances. At 4 meters there may be still a lot of impact from mutual shadings.