Investigation of a solar-powered desalination system employing regeneration

The objective of this research project was to develop a process that makes use of low-grade heat provided from solar irradiation to drive a distillation-desalination process. An optimized distillation process re-uses input heat, by using the heat-of-condensation as the heat source for pre-heating the incoming cold saline water. This research project was concerned with examining the physical and thermodynamic characteristics of this process so as to optimize the efficiency of a solar powered water distiller employing heat recovery. The study was primarily concerned with understanding the natural convection driving the evaporation-condensation process and the other physical and geometric considerations that affect the distillation process in multi effect humidification (MEH) systems. A new term, coined “GOR of an ideal MEH device - GORMEHi” is described and used. In contrast to other projects investigating low temperature distillation devices employing regeneration, this research project incorporated a CFD analysis that formed the base for the optimization process. By using such an analysis the optimum geometry for a distillation enclosure was determined to be an ”ovalized rectangle”. This basic geometry with CFD-optimized dimensions, along with some additional features was incorporated into a fully operational laboratory distillation system. The distillation system was tested for its functionality and thermal efficiency. The device tested is capable of distilling salty water (≈23,000 ppm) to very low levels (≈17 ppm) of dissolved salt content at thermal efficiencies comparable to the theoretically possible.