This work describes the evaluation of concentrated solar thermal (CST) in a conventional cement plant in order to replace from 40% to 100% of the thermal energy required in the process. By using CST at the calcination process in the cement production line, CO2 emissions can be reduced by 40%. The aim of the study is not to propose a detailed design of the solar process but to examine and quantify the various options in order to define the favorable economic conditions and the technical issues to face in a conventional cement plant aiming: substituting energy sources and achieving continuous operation of the cement plant employing a hybrid mode.