Low-cost, low-energy desalination

A low-cost water desalination system developed by NMSU engineers can convert saltwater to pure drinking water on a round-the-clock basis – and its energy needs are so low it can be powered by the waste heat of an air conditioning system.

A prototype built on the Las Cruces campus can produce enough pure water continuously to supply a four-person household, said Nirmala Khandan, an environmental engineering professor.

New Mexico and other parts of the world have extensive brackish groundwater resources that could be tapped and purified to augment limited freshwater supplies, but traditional desalination processes such as reverse osmosis and electrodialysis consume significant amounts of energy.

This research project explores the feasibility of using low-grade heat – such as solar energy or waste heat from a process such as refrigeration or air conditioning – to run a desalination process.

Khandan said the project builds on a process, first developed by researchers in Florida, that makes distillation of saline water possible at relatively low temperatures: 45 to 50 degrees Celsius (113 to 122 degrees Fahrenheit) rather than the 60 to 100 C (140 to 212 F) required by most distillation processes.

The system utilizes the natural effects of gravity and atmospheric pressure to create a vacuum in which water can evaporate and condense at near-ambient temperatures.