Multiple Stage Flash Distillation (MSF)
Multiple Stage Flash Distillation is one of the predominant conventional phase change methods of achieving desalination. It accounts for roughly 45% of the total world desalination capacity and 93% of all thermal methods.
Solar derivatives have been studied and in some cases implemented in small and medium scale plants around the world. In Margarita de Savoya, Italy there is a 50-60 m3/d MSF plant with a salinity gradient solar pond providing its thermal energy and storage capacity. In El Paso, Texas there is a similar project in operation that produces 19 m3/d. In Kuwait a MSF facility has been built using parabolic trough collectors to provide the necessary solar thermal energy to produce 100 m3 of fresh water a day. And in Northern China there is an experimental, automatic, unmanned operation that uses 80 m2 of vacuum tube solar collectors coupled with a 1 kW wind turbine (to drive several small pumps) to produce 0.8 m3/d.
Production data shows that MSF solar distillation has an output capacity of 6-60 L/m2/d versus the 3-4 L/m2/d standard output of a solar still. MSF experience very poor efficiency during start up or low energy periods. In order to achieve the highest efficiency MSF requires carefully controlled pressure drops across each stage and a steady energy input. As a result, solar applications require some form of thermal energy storage to deal with cloud interference, varying solar patterns, night time operation, and seasonal changes in ambient air temperature. As thermal energy storage capacity increases a more continuous process can be achieved and production rates approach maximum efficiency.
Read more about this topic: Solar Desalination
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