DC module deviation from STC

Hi Karthik,

Yes, the GCR of 0.954 is for very closely spaced rows with just 11.5 cm of ground between rows. My diagram for GCR = 0.514 is for 1.75 m of ground between rows, or a distance between the bottom of rows of 3.385 m.

Best regards,
Paul.

Hi Karthik,

Comparing results between SAM's Detailed PV model and other PV performance models requires ensuring that the input assumptions are the same for all of the models. This is described in the NREL comparisons I referenced above, which are available at sam.nrel.gov/photovoltaic/pv-validation.

The difference here may be in differences in the way SAM and the other models calculate self shading losses. You might want to try the comparison with GCR = 0.3, and for both the linear and non-linear self shading option.

Note that for the non-linear shading option, SAM models the reduction in beam irradiance as a DC loss that is applied to the array's DC electrical output rather than to the incident beam irradiance. This DC loss represents the response of a crystalline Silicon module with three bypass diodes to partial shading. The linear self shading model models self shading as a uniform reduction in the beam irradiance incident on the array. These approaches are described in Chapter 9 of the Photovoltaic Reference Manual (2018) available at sam.nrel.gov/photovoltaic/pv-sub-page-2.

Thanks,
Paul.

Hi Gabriel,

The source code for the "Module deviation from STC" calculation is here:

github.com/NREL/ssc/blob/7b84c5b5eb73ab77bc72e081277c6c27a3a00f31/ssc/cmod_pvsamv1.cpp#L3042

The images in your post did not come through. If you want to use images in your post, please attach them as files and then insert them in  your post instead of copying and pasting them into the editor.

Best regards,
Paul.