The aim of this Capstone project is to study desalination technologies and the possibility to combine them with Renewable Energy Sources. The first part of the project is a literature review of the most advanced desalination technologies, the need for desalination and their combination with RES. The second part is an analysis of Reverse Osmosis systems. The third part is a case study of a small Reverse Osmosis plant powered by photovoltaics in the island of Iraklia, Greece. The last part includes the conclusions and a discussion about further research on the subject.