Lower energy output and PR after update from V7.4.8 to V8.0.5

[JIannace]

Hello, 

I ran the same project simulation in V7 and V8 of the software and V7 shows slightly higher produced energy, apparent energy and a slightly better performance ratio. I didn't change any settings but when I ran the V8 simulation it prompted me to recompute the shading tables because they were from an older version. 

The azimuth appears to have changed on its own from 8.2° (V7) to 10° (V8). The bifacial system also changed from "2D Calculation Unlimited Sheds" to "Unlimited Sheds 2D model". 

One big change I see on the loss diagram is that the Sky diffuse on the rear side decreased from +44% down to +20.6%. 

Are there any settings or parameters I can change to revert back to the higher production values?

Thank you,  

  

[Robin Vincent]

Regarding the bifacial contribution, please see this post : 

 

 

For the azimuth, are you using averaged orientations and/or do you have a specific field topography ? 

Since most of the reduction seems to come from the bifacial diffuse irradiance contribution, you can try manually setting the number of sheds in the bifacial menu.

Setting Number of sheds = 3 should give you a value similar to what you had in V7.

I'd suggest not to do so, as the V7.4 results were unrealistically high while results with the V8 should be closer to the reality. But you should be at least be able to validate the reason behind this change.