Proceedings of ES2008 Energy Sustainability 2008 August 10-14, 2008, Jacksonville, Florida, USA ES2008-54075 SOLAR FLASH DESALINATION UNDER HYDROSTATICALLY SUSTAINED VACUUM Mohammad Abutayeh Department of Chemical Engineering, University of South Florida, Tampa, FL 33620, USA Yogi Goswami Clean Energy Research Center, University of South Florida, Tampa, FL 33620, USA ABSTRACT Creating vacuum conditions above liquids will increase their evaporation rates. This phenomenon can be integrated into a practical continuous desalination process by repeatedly flashing sea water in vacuumed chambers to produce water vapor that will be condensed producing fresh water. Gravity can be used to balance the hydrostatic pressure inside the flash chambers with the outdoor atmospheric pressure to maintain that vacuum, while low grade solar radiation can be used to add heat to sea water before flashing. The proposed desalination system consists of a saline water tank, a concentrated brine tank, and a fresh water tank placed on ground level plus an evaporator and a condenser located several meters above ground. The evaporator-condenser assembly, or flash chamber, is initially filled with saline water that later drops into the ground tanks by gravity creating a vacuum above the water surface in the unit without any mechanical work. The vacuum is maintained by the hydrostatic pressure balance between the connected vessels. The ground tanks are open to the atmosphere, while the flash chamber is insulated and sealed to retain heat and vacuum. Keywords: desalination, flash desalination, low grade heat desalination, solar desalination, vacuum desalination. INTRODUCTION The need for new water supplies is increasing as populations around the world keep growing and as existing fresh water reserves keep decreasing due to consumption and pollution. Saline water represents an infinite water source since 97.5% of global water is present in oceans. Consequently, seawater desalination is the logical answer to the scarce fresh water reserves due to its relative infinite abundance. As the world is becoming more industrialized, the energy demand is continually increasing. Oil and gas remain the principal source of energy for most of the world; however, their reserves are dwindling, their production is peaking, and their consumption is harming the environment. Serious economic and social disruptions are beginning to unfold over the finite energy resources; hence, developing a solution to the energy crisis will help avoid catastrophic conflicts, continue modern lifestyles, and preserve an increasingly warming and polluting environment [1]. Solar energy is becoming a very important source of energy due to its infinity and renewability; moreover it’s harmless for the environment. A lot of research is underway to better use this free form of energy to develop more efficient processes such as desalination and power generation. Several desalination processes have been developed over the years to economically produce fresh water from seawater. These processes can be classified according to the applied separation scheme into thermal, physical, and chemical processes. Selecting a suitable desalination process requires several considerations such as: start up time, seawater quality, seawater supply, maintenance requirements, energy efficiency, capital cost, operating cost, and other site specific factors [1]. The objective of this study is to theoretically simulate a solar flash desalination process under a hydrostatically sustained vacuum and analyze its controlling variables. The simulation can be achieved by building a rigorous thermodynamic model of the proposed unit employing the fundamental physical relationships to describe the process complimented by reliable empirical correlations to estimate the physical and the instrumental parameters. This approach will increase the applicability of the model over exclusively empirical models. 1 Copyright © 2008 by ASME