pvlib.irradiance.extraradiation

pvlib.irradiance.extraradiation(datetime_or_doy, solar_constant=1366.1, method='spencer')[source]

Determine extraterrestrial radiation from day of year.

Parameters:

datetime_or_doy : int, float, array, pd.DatetimeIndex

Day of year, array of days of year e.g. pd.DatetimeIndex.dayofyear, or pd.DatetimeIndex.

solar_constant : float

The solar constant.

method : string

The method by which the ET radiation should be calculated. Options include 'pyephem', 'spencer', 'asce'.
Returns:

float or Series

The extraterrestrial radiation present in watts per square meter on a surface which is normal to the sun. Ea is of the same size as the input doy.

‘pyephem’ always returns a series.

See also

pvlib.clearsky.disc

Notes

The Spencer method contains a minus sign discrepancy between equation 12 of [1]. It’s unclear what the correct formula is.

References

[1] M. Reno, C. Hansen, and J. Stein, “Global Horizontal Irradiance Clear Sky Models: Implementation and Analysis”, Sandia National Laboratories, SAND2012-2389, 2012.

[2] <http://solardat.uoregon.edu/SolarRadiationBasics.html>, Eqs. SR1 and SR2

[3] Partridge, G. W. and Platt, C. M. R. 1976. Radiative Processes in Meteorology and Climatology.

[4] Duffie, J. A. and Beckman, W. A. 1991. Solar Engineering of Thermal Processes, 2nd edn. J. Wiley and Sons, New York.