4th European Conference on Renewable Energy Systems, jointly organized by Gazi University and Yıldız Technical University, took place between 28-31 August 2016 at Yıldız Technical University Davutpaşa Convention Centre. Researchers and academicians from 30 different countries who speacialize mainly in areas such as hydrogen energy, hydro-energy and biomass energy contributed to the conference with oral presentations and posters. Our Rector, Prof. Dr. Bahri ŞAHİN, were present at the conference, welcomed the participants, attented some of the sessions and expressed his thanks to the orginizing committee of the conference.