Geothermal Desalination

Geothermal desalination uses geothermal heat, or the electricity generated from it, to convert salt water into fresh water, and is offered as a potentially more energy efficient and lower emission alternative to conventional desalination methods such as reverse osmosis, though its overall environmental impact is not yet fully established. The technology works in two general ways: a direct approach heats seawater in an evaporator until it boils, then condenses the resulting steam back into fresh water, drawing on established thermal desalination methods such as multistage flash, multi effect distillation and thermal vapor compression, while an indirect approach instead converts geothermal energy into electricity that powers membrane based desalination equipment; both approaches can also supply surplus heat or electricity for other uses. Bechtel Group scientist Leon Awerbuch first proposed powering desalination with geothermal energy in 1972, a Caldor-Marseille prototype produced several cubic meters of fresh water a day in 1994, and Tunisia brought an early documented plant online in 1995 producing about three cubic meters a day at roughly 1.20 dollars per cubic meter. The approach has since been applied at the Balcova-Naridere geothermal field in Turkey for agricultural irrigation and at the Milos Island project in Greece for drinking water production.