A Physically Inspired Model for Estimating Clear-Sky Solar Irradiance

The estimation of solar irradiance under clear sky conditions is still a research topic. Many times, accessible empirical models are applied in practice, even if more uncertainty is expected than in the case of complex models. This paper reports a class of innovative empirical models for estimating clear sky global solar irradiance. Although the models are of an empirical nature, the mathematical equations are inspired by the physics behind the radiative transfer in the atmosphere. The models are developed with high-quality data recorded on the Solar Platform of the West University of Timisoara, Romania. Considering the local character of the empirical models, the development process is described in detail so that it can be replicated in other locations. Having only deterministic quantities as input, the proposed models harmoniously combine the two key requirements for practical applications: accessibility and accuracy.