pvlib.snow.dc_loss_nrel(snow_coverage, num_strings)[source]

Calculates the fraction of DC capacity lost due to snow coverage.

DC capacity loss assumes that if a string is partially covered by snow, the string’s capacity is lost; see 1, Eq. 11.8.

Module orientation is accounted for by specifying the number of cell strings in parallel along the slant height. For example, a typical 60-cell module has 3 parallel strings, each comprising 20 cells in series, with the cells arranged in 6 columns of 10 cells each. For a row consisting of single modules, if the module is mounted in portrait orientation, i.e., the row slant height is along a column of 10 cells, there is 1 string in parallel along the row slant height, so num_strings=1. In contrast, if the module is mounted in landscape orientation with the row slant height comprising 6 cells, there are 3 parallel strings along the row slant height, so num_strings=3.

  • snow_coverage (numeric) – The fraction of row slant height covered by snow at each time step.

  • num_strings (int) – The number of parallel-connected strings along a row slant height.


loss (numeric) – fraction of DC capacity loss due to snow coverage at each time step.



Gilman, P. et al., (2018). “SAM Photovoltaic Model Technical Reference Update”, NREL Technical Report NREL/TP-6A20-67399. Available at https://www.nrel.gov/docs/fy18osti/67399.pdf