Solar Water Desalination by Vapour Evacuation

Abstract

In the present investigation a vapor compressiOn desalination system driven by solar energy is considered. The vapor compression desalination system has the advantage of being suitable to the use of solar energy. In the systems operating under vacuum, generation of vacuum is achieved either mechanically (by vacuum pump) or thermally (by steam ejector) in small solar powered system. The difference in elevation is a practical way in order to produce vacuum. Another alternative is the use of a compressed water operated ejector. In the present work, a companson between the most commonly used desalination plants is made. This comparison is carried out from both technical and economical point of view. A detailed review of these desalination processes has revealed the harmful effect of scale formation and non-condensable gases on the existing systems. This harmful effect is seen to be minimized with the decrease in operating temperature (and hence the operating pressure). The system utilizing the elevation difference for vacuum generation is studied. Leakage represents the main problem in this system. Another system with compressed water operated ejector is investigated. This system is simple in both construction and operation and can be a good choice for rural areas. It consists mainly of a heatersimulating a solar flat plate collector, condenser, evaporator, heat exchanger and the ejector system to generate vacuum. The stage of the proposed system was theoretical and experimental analyses. The energy