Potential of solar desalination in Israel and in its close vicinity

Recent studies dealing with the potential of Renewable Energy Sources (RES) for desalination along the Mediterranean Coast and in the Middle East choose to use RES to generate electricity first, and then use this electricity to power desalination. The present work eliminates the phase of electricity generation by using solar thermal energy directly for distillation by evaporation. Saving the thermal to mechanical conversion losses allows the proposed Multi Effect Distillation (MED) process to compete economically with Reverse Osmosis (RO) process of significantly lower energy consumption. The new opportunity to revive direct thermal evaporation, arises from a new collector technology developed by Solel Solar Systems, that is coupled to the familiar MED process modified by IDE Technologies to match the solar steam characteristics. Solel has applied its unique technique of selective coating to demonstrate a very efficient solar radiation collection, achieving high temperatures with relatively low installation costs. While the generated steam is not sufficient for efficient generation of electrical power to be used for RO — its quality far exceeds the minimum necessary for the existing methods of steam powered desalination by evaporation. Our analysis shows that a combination of a large number of effects of evaporation, together with high pressure saturated steam available for recycling, yields a dramatic improvement in the production rate of water desalination, accompanied by relatively modest increase in the desalination installation cost. For the specific case analyzed in detail, replacing the commonly used low temperature MED with the new combination, increases the Economic Ratio (ER) from 7 to 16 — a factor of 2.3, while the installation costs grew by only 60%. This implies that the distillate production costs are significantly lower with the new proposed combination. The cost increase is mainly due to the higher costs for the expansion of the desalination system, with relatively low additional costs for producing the high temperature solar steam. A basic assumption, drawn from economic considerations and technological constraints, is that the desalination system would operate continuously, while the solar system, which is limited to daytime operation, would feed a steam generator combined with a storage tank. Therefore utilization of solar energy requires either large and expensive heat storage capacity or fossil fuel backup – a hybrid plant. The effects of storage and fuel cost are presented. The paper refers to *Corresponding author. Presented at the European Conference on Desalination and the Environment: Water Shortage, Lemesos, Cyprus, 28–31 May 2001. 0011-9164/01/$– See front matter © 2001 Elsevier Science B.V. All rights reserved