radiation on vertical surface

Hi Marco,

I assume you used the same weather file and array tilt and azimuth values for your comparison between SAM and PVsyst.

Could you reply with a copy of the .sam file and weather file you used for this analysis?

Best regards,
Paul.

Hi Marco,

Thank you for emailing your files.

I have a qualitative explanation for the results you are seeing. The following heat map shows the hourly DNI data from your weather file. I added a green horizontal line to emphasize Noon. You can see that more solar energy is available over the year in the morning than in the afternoon, so I would expect an east-facing array to collect more energy over the year than a west facing one.



I have to look into the rear-side calculations for the bifacial model with tilt = 90 and azmiuth = 90 or 270. The model was originally developed based on data from arrays with tilt angles between 15 and 45 degrees and facing the equator, so I am not sure it was tested for vertical east- and west-facing arrays.

In any case, if you compare the monthly electrical output of the two arrays, the difference is much smaller than the difference in monthly plane-of-array front-side and rear-side irradiance values. I will follow up when I've had time to investigate further.

Best regards,
Paul.

Hi Marco,

Sorry about that! I forgot to attach and insert the picture -- it should be there now.

Best regards,
Paul.