High frequency generation of coupled GHI and DNI based on clustered Dynamic Paths

Abstract

This Brief Note presents a general and efficient clustered-based methodology for the generation of high-frequency coupled global horizontal irradiance (GHI) and direct normal irradiance (DNI) series, based on the envelope clear sky and Dynamic Paths concepts. The procedure for generating 1-min synthetic irradiance data assumes that the effect of passing clouds on the fluctuations of both GHI and DNI can be dynamically reproduced using local variability patterns characterized by a 1-year ground measurements. This work presents for the first time synthetically generated 1-min GHI and DNI coupled datasets (156 months, from 1999 to 2011) generated from their corresponding low frequency series and local solar irradiance dynamics. The statistical parameters used for compare the measured and generated series perform well: mean absolute deviation is negligible, with averaged values of ∼0.3% and ∼0.2% for GHI and DNI, respectively. The KSI(%) values for DNI and GHI are lower than 100% in average. KSI(%) values of GHI series (in the range of 51.5–70.1% for averaged daily KSI(%) values at each month) are lower than the respective KSI(%) values of the DNI series (in the range of 75.0–110.8%). Finally, the generated 1-min solar irradiance series has the same autocorrelative structure as the observed, according to the similitude of their Ramp Rates.