Sotirios Karellas is Professor at the School of Mechanical Engineering of NTUA, Director of the laboratory of Thermal Processes, and visiting Professor at the Technische Universität München and the Universität Bayreuth Germany. He is currently member of the European Hydrogen Sustainability and Circularity Panel (EHS&CP). Member of the Greek delegation to the Programme Committee “Secure Clean and Efficient Energy” (2014-2021) and to the Coal and Steel Committee (COSCO) (2014 – 2019). His research is focusing on central and decentralized energy systems, Carbon Capture Storage and Utilisation, energy storage, Hydrogen energy, Zero Energy Buildings, co-, poly-generation, solar-thermal energy, biomass, Organic Rankine Cycle technology and heat pumps, Waste to energy. He has over 150 relevant publications in scientific Journals and Conferences and more than 5000 citations. He has supervised 7 Ph.Ds and he is currently supervising 6 Ph.D students at NTUA working in the field of CCU, energy conversion systems for Electricity, Heating and Cooling. He has participated in a large number of projects in NTUA (2006-present) and in Technische Universität München (2001-2006), having both technical and coordination responsibilities. He has significant industrial experience in power production plants, co/tri-generation systems, heat pumps, building heating systems and chillers. He is full member of the editorial board of 4 scientific journals dealing with central-decentralised energy systems and renewable energy sources.