Kosmas A. Kavadias, PhD, MSc, Mechanical Engineer, Associate Professor in the Energy Sector, Department of Mechanical Engineering of University of West Attica. His research interests, experience and expertise include design and optimization of solar energy systems, optimization of hybrid energy systems, design of RES-based hybrid energy systems, evaluation of energy storage systems, optimum management of autonomous energy systems and building integrated renewable energy systems, energy savings in buildings and industry. He has 20-year experience in teaching courses on Renewable Energy Sources, Hybrid Energy Systems, Buildings’ Energy Improvement and Energy Saving both in undergraduate and postgraduate students. Author and co-author of more than 30 papers in International peer reviewed Journals and more than 100 papers in National and International conferences. He is also a co-author in three books concerning Renewable Energy Sources and he has also contributed a chapter in the books entitled "Stand-Alone and Hybrid Wind Energy Systems", published by Woodhead Publishing Ltd., "Comprehensive Renewable Energy", published by Elsevier B.V. and "Advanced Power Engineering" published by CRC Press Taylor & Francis Group.