pvlib.irradiance.dirint

pvlib.irradiance.dirint(ghi, zenith, times, pressure=101325.0, use_delta_kt_prime=True, temp_dew=None)[source]

Determine DNI from GHI using the DIRINT modification of the DISC model.

Implements the modified DISC model known as “DIRINT” introduced in [1]. DIRINT predicts direct normal irradiance (DNI) from measured global horizontal irradiance (GHI). DIRINT improves upon the DISC model by using time-series GHI data and dew point temperature information. The effectiveness of the DIRINT model improves with each piece of information provided.

Parameters:

ghi : array-like

Global horizontal irradiance in W/m^2.

zenith : array-like

True (not refraction-corrected) zenith angles in decimal degrees. If Z is a vector it must be of the same size as all other vector inputs. Z must be >=0 and <=180.

times : DatetimeIndex

pressure : float or array-like

The site pressure in Pascal. Pressure may be measured or an average pressure may be calculated from site altitude.

use_delta_kt_prime : bool

Indicates if the user would like to utilize the time-series nature of the GHI measurements. A value of False will not use the time-series improvements, any other numeric value will use time-series improvements. It is recommended that time-series data only be used if the time between measured data points is less than 1.5 hours. If none of the input arguments are vectors, then time-series improvements are not used (because it’s not a time-series). If True, input data must be Series.

temp_dew : None, float, or array-like

Surface dew point temperatures, in degrees C. Values of temp_dew may be numeric or NaN. Any single time period point with a DewPtTemp=NaN does not have dew point improvements applied. If DewPtTemp is not provided, then dew point improvements are not applied.

Returns:

dni : array-like

The modeled direct normal irradiance in W/m^2 provided by the DIRINT model.

Notes

DIRINT model requires time series data (ie. one of the inputs must be a vector of length > 2.

References

[1] Perez, R., P. Ineichen, E. Maxwell, R. Seals and A. Zelenka, (1992). “Dynamic Global-to-Direct Irradiance Conversion Models”. ASHRAE Transactions-Research Series, pp. 354-369

[2] Maxwell, E. L., “A Quasi-Physical Model for Converting Hourly Global Horizontal to Direct Normal Insolation”, Technical Report No. SERI/TR-215-3087, Golden, CO: Solar Energy Research Institute, 1987.