The performance of a solar thermal power converter is closely related to the occurrence of beam solar irradiance on the collector surface. In this thought, the present study deals with modeling the beam solar irradiance component, studying the influence of different atmospheric parameters (ozone column content, Ångström turbidity coefficient, water vapor column content) on its magnitude. The occurrence of beam solar irradiance at a given moment is indicated by the sunshine number Boolean parameter stating whether the sun is shining or not. The tests show that the estimation accuracy is strongly influenced by the stability of the radiative regime. © 2014 Taylor and Francis Group, LLC.