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Scientists at New Mexico State University have a prototype for a new technique for changing salt water to water that’s drinkable.

Environmental engineer Nirmala Khandan told Earth & Sky that the new system consumes less energy – and is less costly – than existing desalination technologies(海水淡化技术）. There are two primary ways to desalinate water. You can use high pressure to push water through a membrane（薄膜）, thereby removing the salt. Or you can boil water and collect the salt-free steam（无盐蒸汽，纯蒸汽） that results.

Nirmala Khandan: Water can boil at low temperatures if the pressure is low enough. So our trick is to bring down the pressure by building two columns that are about 30 feet tall.

This prototype consists of two 10-meter, or 30-foot vertical towers – one rising from a tank of salt water and the other from a tank of fresh water. The two are connected by a horizontal tube. The barometric pressure（气压） of the tall water columns creates a vacuum at the top of the tubes. Under those conditions, Khandan said, it’s possible to boil water at room temperature（室温） to produce salt-free steam. And that means an energy savings.

Khandan said his system could help communities near coasts purify salt water. The technology is so efficient, he said, it could run on waste heat produced by air conditioners and other appliances.