Abstract: A facility for the desalination and purification of sea water or brackish water by solar energy provided with a closed cycle including a thermal solar collector and a heat exchanger in which a heat transfer medium is circulating, and a basin for receiving the sea water or brackish water with the heat exchanger being placed in the basin for heating and evaporating water. A cooling surface is disposed above the basing for condensing the evaporated water which is then diverted to water collectors. The solar collector is located above the cooling surface so as to keep it in the shade.