pvlib.irradiance.dni

pvlib.irradiance.dni(ghi, dhi, zenith, dni_clear=None, clearsky_tolerance=1.1, zenith_threshold_for_zero_dni=88.0, zenith_threshold_for_clearsky_limit=80.0)

Determine DNI from GHI and DHI.

When calculating the DNI from GHI and DHI the calculated DNI may be unreasonably high or negative for zenith angles close to 90 degrees (sunrise/sunset transitions). This function identifies unreasonable DNI values and sets them to NaN. If the clearsky DNI is given unreasonably high values are cut off.

Parameters:

• ghi (Series) – Global horizontal irradiance. See ghi. [Wm⁻²]

• dhi (Series) – Diffuse horizontal irradiance. See dhi. [Wm⁻²]

• zenith (Series) – True (not refraction-corrected) zenith angles. See solar_zenith. [°]

• dni_clear (Series, optional) –

  Clearsky direct normal irradiance. See dni_clear. [Wm⁻²]

  Changed in version 0.11.2: Renamed from clearsky_dni to dni_clear.

• clearsky_tolerance (float, default 1.1) – If dni_clear is given this parameter can be used to allow a tolerance by how much the calculated DNI value can be greater than the clearsky value before it is identified as an unreasonable value.

• zenith_threshold_for_zero_dni (float, default 88.0) – Non-zero DNI values for zenith angles greater than or equal to ‘zenith_threshold_for_zero_dni’ will be set to NaN.

• zenith_threshold_for_clearsky_limit (float, default 80.0) – DNI values for zenith angles greater than or equal to ‘zenith_threshold_for_clearsky_limit’ and smaller the ‘zenith_threshold_for_zero_dni’ that are greater than the clearsky DNI (times allowed tolerance) will be corrected. Only applies if dni_clear is not None.

Returns:

dni (Series) – The modeled direct normal irradiance. See dni. [Wm⁻²]