Multiple Effect Desalination

Multiple Effect Desalination is more effecient than other evaporation techniques. 

A low temperature source of energy is used to power the system to obtain fresh water from sea water. Multiple vessels (also known as effects) are used in sequence to recover the vapours produced by boiling the brackish sea water. Only the first vessel is provided with an external energy source to heat the water into vapors, the vapors that boils off in one vessel can be used as a source of heat for the next. With a decrease in pressure, the boiling point also decreases and thus the temperature that needs to be maintained in each vessel is lower than the one that precedes it.