Importing POA data with tilted trackers

[afiala634]

Hi all, I'm working to import measured POA irradiance measurements into PVsyst version 6.8.3. Looking at the measured versus modeled data, I'm seeing a large discrepancy in both POA and GHI values, particularly around noon. I believe I've narrowed this down to an issue with how I'm inputting axis tilt when importing the custom ASCII file. If I enter the axis tilt as the negative of the system axis tilt is entered (i.e. entering in -2 during the file import orientation definition whereas the orientation is defined with a 2 degree tilt), this seems to produce well matching results between measured and modeled data. I'm hoping to understand why this is however. Does PVsyst require a 0 degree axis tilt to be most accurate in its transposition calculation?

Thanks,

Alec

[skrhee]

I would also like to know the answer to this question.