Solar Irradiance (Global, Direct and Diffuse) Quality Control Methodologies Review: Application to Time Series Measured At LES/LNEG, Lisboa, Portugal

Solar irradiance spatial and temporal quantification is essential to the development, implementation, and operation of solar systems, being used throughout a solar project lifecycle. It is crucial to have good quality data measured in meteorological and radiometric ground stations in order to enable the calibration and validation of irradiance models and data series. The Solar Energy laboratory at LNEG operates a meteorological station gathering relevant parameters to characterize the solar irradiation profile for the city of Lisbon in Portugal. This work presents and compares the application of different methodologies used for quality control of solar irradiance measurements. Three methods - the CIE ( 1994) / Muneer and Fairooz (2002), the QCRad and the IEC - were tested against two synthetic data sets: a clear-sky year and a typical meteorological year randomly and uniformly infused with errors. IEC showed to have limitation regarding the extreme value criteria for beam normal irradiance and CIE for the diffuse horizontal irradiance. The QCRad presented the best performance, with total sensitivity above 80% and maximum specificity. This method was applied to the measured data of LES-LNEG between 2014 and 2018. Most of the detected errors were detected during the coherence test stage, having a higher prevalence between 2015 and mid-2016, highlighting the need to modify the diffuse horizontal irradiance measuring system.