Stand-alone solar desalination plant

The paper presents research to design and develop an efficient stand-alone modular desalination system able to provide sufficient non potable water to satisfy the needs of an average family of four living in Mediterranean regions. The system comprises a solar thermal collector for providing thermal energy for the desalination process and photovoltaic (PV) elements to provide electrical energy for the pumping operations. The analysis given here starts by presenting the functional scheme of designing a multi-stage flash (MSF) desalination thermal plant where the saltwater is warmed to about 90 degrees C and supplied to several chambers in turn, where the pressure reduces sequentially from one space to the next. It is clear from the analysis that the plant requires large surfaces to provide sufficient evaporation of the seawater; in view of this, an alternative approach based on using several spray-nozzles together with only one flash chamber is proposed. This substantially improves the heat exchange between the seawater and the internal air for the evaporation of the saltwater. The electric power to pump the seawater supply through the solar collector and through the spray nozzle as well as the pumping requirements of the fresh water and brine extracting pumps will be supplied by PV panels. The surface area of the thermal collector will be about 6 m(2) with an optimal tilt angle for summer.