At the Faculty of Civil Engineering, University of Belgrade, from June 18-21, 2024, the third training school within the COST Action (COST ACTION CA20109) MODENERLANDS (Modular Energy Islands for Sustainability and Resilience) was held. The theme was the conceptual design of floating energy islands from traditional concepts to digital-twins driven design. The head of the COST Action is Prof. Dr. Carlos Rebelo from the University of Coimbra. Asst. Prof. Dr Anina Glumac, with the help of colleagues Asst. Prof. Dr Miloš Jočković, Kristina Kostadinović Vranešević, and Milica Koprivica from the Faculty of Civil Engineering in Belgrade gathered participants from over 10 countries with prestigious European universities, including: University of Birmingham, University of Coimbra, Liverpool John Moores University, TU Delft, Università Politecnica delle Marche, University College Dublin, Technical University of Crete, Polytechnic University of Tirana, Atlantic Technological University, ERC, Bursa Technical University, University of La Coruna, IUSS Pavia, University of Florence, University of Nis, Faculty of Electrical Engineering and Information Technology North Macedonia, and Middle East Technical University. Training school aims to connect and systematise the work of European research groups on the development of sustainable energy technologies, with a special focus on wind and wave energy. The training school tends to develop initial ideas and projects through training, targeted lectures presented by experienced lecturers, and the synergy of the research areas of the participants. The main topic is the application of sustainable energy principles to ensure the maximum collection and conversion of renewable energy sources and their efficient integration into the grid with the latest technologies for energy storage and transport. As part of the Training school, a visit to the Čibuk 1 wind farm was organized. The general manager of Vetroelektrane Balkana, Rade Roganovic, and his team guided them through the wind farm and provided practical information on the maintenance and management of the wind power plant, as well as the environmental aspects of wind energy production.