Renewable energy systems are highly complex and dynamic systems. A first estimation of their behaviour can be carried out in many cases with relatively simplified modelling approaches. A detailed assessment and prediction of their behavior and performance might require instead significantly more complex models. The aim of this course is to provide a sound overview on different modelling approaches relevant for renewable energy systems: from steady-state to dynamic models, from continous to discrete models. Additionally some statistic modelling approaches are introduced. Students will programm models following these approaches and try to identify and critically assess their streghts and weaknesses as well as the main research questions that can be answered with them. Octave/Matlab is used as programming language/environment in this course.