DC module deviation from STC

Good Day Paul,

Decreasing GCR reduced the module loss. But I would like to keep a row spacing of 1.75 m between two arrays.
Attached the PV system design for reference.
And I kept the same pitch: 1.75 m and GCR: 95.4% in PVsyst and I got less module loss and more Annual energy output under same conditions.

Thanks,
Karthik.

Hi all,
How exactly the "DC module deviation from STC" is calculated? I cannot find a good reference and in some of my calculations this parameter enhances the performance of the pv-system and I don't understand why.
Best regards,
Konrad

Hi Konrad,

There is a long discussion about the module loss value in this issue on GitHub (see also the link to Issue #197 mentioned in the comments):

github.com/NREL/ssc/issues/205

Best regards,
Paul.

Hi Karthik,

Based on the information you provided, I calculate GCR = 0.51:



GCR = 1.74 / ( 1.74 * cos( 20 ) + 1.75 ) = 0.514

I used SAM's parametric simulations in the attached .sam file to generate this table showing the annual output and "module deviation from STC" loss for a range of GCR values:



Best regards,
Paul.

Hallo Paul,

Thanks a lot for the simulation.
But in SAM row spacing of 1.75 m is different from the one you calculated (1.74 * cos( 20 ) + 1.75 ).

And also in the attached PV system design, the arrays are closer with a total pitch(row spacing) of 1.75 m only, this leads to GCR 0.954 (same in case of PVSyst)


Thanks,
Karthik.

Thank you Paul, very interesting discussion indeed!

Best,
Konrad