pvlib.bifacial.infinite_sheds.get_irradiance#

pvlib.bifacial.infinite_sheds.get_irradiance(surface_tilt, surface_azimuth, solar_zenith, solar_azimuth, gcr, height, pitch, ghi, dhi, dni, albedo, model='isotropic', dni_extra=None, iam_front=1.0, iam_back=1.0, bifaciality=0.8, shade_factor=- 0.02, transmission_factor=0, npoints=100, vectorize=False)[source]#

Get front and rear irradiance using the infinite sheds model.

The infinite sheds model [1] assumes the PV system comprises parallel, evenly spaced rows on a level, horizontal surface. Rows can be on fixed racking or single axis trackers. The model calculates irradiance at a location far from the ends of any rows, in effect, assuming that the rows (sheds) are infinitely long.

The model accounts for the following effects:

  • restricted view of the sky from module surfaces due to the nearby rows.

  • restricted view of the ground from module surfaces due to nearby rows.

  • restricted view of the sky from the ground due to rows.

  • shading of module surfaces by nearby rows.

  • shading of rear cells of a module by mounting structure and by module features.

The model implicitly assumes that diffuse irradiance from the sky is isotropic, and that module surfaces do not allow irradiance to transmit through the module to the ground through gaps between cells.

Parameters
  • surface_tilt (numeric) – Tilt from horizontal of the front-side surface. [degree]

  • surface_azimuth (numeric) – Surface azimuth in decimal degrees east of north (e.g. North = 0, South = 180, East = 90, West = 270). [degree]

  • solar_zenith (numeric) – Refraction-corrected solar zenith. [degree]

  • solar_azimuth (numeric) – Solar azimuth. [degree]

  • gcr (float) – Ground coverage ratio, ratio of row slant length to row spacing. [unitless]

  • height (float) – Height of the center point of the row above the ground; must be in the same units as pitch.

  • pitch (float) – Distance between two rows; must be in the same units as height.

  • ghi (numeric) – Global horizontal irradiance. [W/m2]

  • dhi (numeric) – Diffuse horizontal irradiance. [W/m2]

  • dni (numeric) – Direct normal irradiance. [W/m2]

  • albedo (numeric) – Surface albedo. [unitless]

  • model (str, default 'isotropic') – Irradiance model - can be one of ‘isotropic’ or ‘haydavies’.

  • dni_extra (numeric, optional) – Extraterrestrial direct normal irradiance. Required when model='haydavies'. [W/m2]

  • iam_front (numeric, default 1.0) – Incidence angle modifier, the fraction of direct irradiance incident on the front surface that is not reflected away. [unitless]

  • iam_back (numeric, default 1.0) – Incidence angle modifier, the fraction of direct irradiance incident on the back surface that is not reflected away. [unitless]

  • bifaciality (numeric, default 0.8) – Ratio of the efficiency of the module’s rear surface to the efficiency of the front surface. [unitless]

  • shade_factor (numeric, default -0.02) – Fraction of back surface irradiance that is blocked by array mounting structures. Negative value is a reduction in back irradiance. [unitless]

  • transmission_factor (numeric, default 0.0) – Fraction of irradiance on the back surface that does not reach the module’s cells due to module features such as busbars, junction box, etc. A negative value is a reduction in back irradiance. [unitless]

  • npoints (int, default 100) – Number of discretization points for calculating integrated view factors.

  • vectorize (bool, default False) – If True, vectorize the view factor calculation across surface_tilt. This increases speed with the cost of increased memory usage.

Returns

output (dict or DataFrame) – Output is a DataFrame when input ghi is a Series. See Notes for descriptions of content.

Notes

output includes:

  • poa_global : total irradiance reaching the module cells from both front and back surfaces. [W/m^2]

  • poa_front : total irradiance reaching the module cells from the front surface. [W/m^2]

  • poa_back : total irradiance reaching the module cells from the back surface. [W/m^2]

  • poa_front_direct : direct irradiance reaching the module cells from the front surface. [W/m^2]

  • poa_front_diffuse : total diffuse irradiance reaching the module cells from the front surface. [W/m^2]

  • poa_front_sky_diffuse : sky diffuse irradiance reaching the module cells from the front surface. [W/m^2]

  • poa_front_ground_diffuse : ground-reflected diffuse irradiance reaching the module cells from the front surface. [W/m^2]

  • shaded_fraction_front : fraction of row slant height from the bottom that is shaded from direct irradiance on the front surface by adjacent rows. [unitless]

  • poa_back_direct : direct irradiance reaching the module cells from the back surface. [W/m^2]

  • poa_back_diffuse : total diffuse irradiance reaching the module cells from the back surface. [W/m^2]

  • poa_back_sky_diffuse : sky diffuse irradiance reaching the module cells from the back surface. [W/m^2]

  • poa_back_ground_diffuse : ground-reflected diffuse irradiance reaching the module cells from the back surface. [W/m^2]

  • shaded_fraction_back : fraction of row slant height from the bottom that is shaded from direct irradiance on the back surface by adjacent rows. [unitless]

References

1

Mikofski, M., Darawali, R., Hamer, M., Neubert, A., and Newmiller, J. “Bifacial Performance Modeling in Large Arrays”. 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC), 2019, pp. 1282-1287. DOI: 10.1109/PVSC40753.2019.8980572.