Total solar irradiance's effect on the performance of empirical models for estimating global solar radiation: An empirical-based review

Resumen

Many Total Solar Irradiance (TSI) and Solar Constant (SC) values are given and used in the literature, sometimes leading to confusion. The TSI value is relevant and has great importance in engineering and scientific research in energy. In this study, a review has been done to study the TSI and SC concepts. A reevaluation of the TSI and SC is undertaken to consider state of the art. The effect of three different TSI values concerning different locations is studied for estimating global radiation with the Ångström-Prescott (A-P) formulation over Spain. New seasonal A-P coefficient sets are developed for Spain. The good performance for all the 29 stations and seasons and the slight differences observed for the different TSI values employed ensure global solar radiation (GSR) accuracy with the A-P model. The results highlight the local and seasonal A-P coefficient calibration relevance instead of using a single general pair of calibration coefficients. Based on the TSI study, we recommended calculations of solar radiation models to adopt the TSI value equal to 1361 W m−2. The revised TSI is lower than the previous values proposed. Therefore, it is highly recommended to review the value and concept of TSI.