This lecture introduces the EPFL project based learning approach, focusing on the theory, project tasks, and tools used for optimizing energy systems. The course covers topics such as energy demand analysis, equations and solving methods, and thermo-economic analysis. Students work in teams to propose system configurations, estimate investments, and prepare reports on the solutions proposed. The lecture emphasizes the application of knowledge and theory to real projects, with a structured approach involving theory lectures, discussion forums, and team presentations.