pvlib.snow.coverage_nrel

pvlib.snow.coverage_nrel(snowfall, poa_irradiance, temp_air, surface_tilt, initial_coverage=0, threshold_snowfall=1.0, can_slide_coefficient=-80.0, slide_amount_coefficient=0.197)[source]

Calculates the fraction of the slant height of a row of modules covered by snow at every time step.

Implements the model described in [1] with minor improvements in [2], with the change that the output is in fraction of the row’s slant height rather than in tenths of the row slant height. As described in [1], model validation focused on fixed tilt systems.

Parameters:
  • snowfall (Series) – Accumulated snowfall within each time period. [cm]
  • poa_irradiance (Series) – Total in-plane irradiance [W/m^2]
  • temp_air (Series) – Ambient air temperature [C]
  • surface_tilt (numeric) – Tilt of module’s from horizontal, e.g. surface facing up = 0, surface facing horizon = 90. [degrees]
  • initial_coverage (float, default 0) – Fraction of row’s slant height that is covered with snow at the beginning of the simulation. [unitless]
  • threshold_snowfall (float, default 1.0) – Hourly snowfall above which snow coverage is set to the row’s slant height. [cm/hr]
  • can_slide_coefficient (float, default -80.) – Coefficient to determine if snow can slide given irradiance and air temperature. [W/(m^2 C)]
  • slide_amount_coefficient (float, default 0.197) – Coefficient to determine fraction of snow that slides off in one hour. [unitless]
Returns:

snow_coverage (Series) – The fraction of the slant height of a row of modules that is covered by snow at each time step.

Notes

In [1], can_slide_coefficient is termed m, and the value of slide_amount_coefficient is given in tenths of a module’s slant height.

References

[1](1, 2, 3) Marion, B.; Schaefer, R.; Caine, H.; Sanchez, G. (2013). “Measured and modeled photovoltaic system energy losses from snow for Colorado and Wisconsin locations.” Solar Energy 97; pp.112-121.
[2]Ryberg, D; Freeman, J. (2017). “Integration, Validation, and Application of a PV Snow Coverage Model in SAM” NREL Technical Report NREL/TP-6A20-68705