Desalination system could produce freshwater that is cheaper than tap water

Good news! Desalination is salvation! It does not have to be solar powered as in this case.

"Engineers at MIT and in China are aiming to turn seawater into drinking water with a completely passive device that is inspired by the ocean, and powered by the sun. ...

The configuration of the device allows water to circulate in swirling eddies, in a manner similar to the much larger “thermohaline” circulation of the ocean. This circulation, combined with the sun’s heat, drives water to evaporate, leaving salt behind. The resulting water vapor can then be condensed and collected as pure, drinkable water. In the meantime, the leftover salt continues to circulate through and out of the device, rather than accumulating and clogging the system. ...

The researchers estimate that if the system is scaled up to the size of a small suitcase, it could produce about 4 to 6 liters of drinking water per hour and last several years before requiring replacement parts. At this scale and performance, the system could produce drinking water at a rate and price that is cheaper than tap water. ..."

From the highlights and abstract:

"Highlights

• Thermohaline convection is initiated in confined-saline-layer evaporation

• Record-high efficiencies are achieved in the salinity range of 0–20 wt %

• 180-h continuous distillation of 20 wt % concentrated seawater is realized

Summary

Recent advances in multistage solar distillation are promising for the sustainable supply of freshwater. However, significant performance degradation due to salt accumulation has posed a challenge for both long-term reliability of solar desalination and efficient treatment of hypersaline discharge. Here, inspired by a natural phenomenon, thermohaline convection, we demonstrate a solar-powered multistage membrane distillation with extreme salt-resisting performance. Using a confined saline layer as an evaporator, we initiate strong thermohaline convection to mitigate salt accumulation and enhance heat transfer. With a ten-stage device, we achieve record-high solar-to-water efficiencies of 322%–121% in the salinity range of 0–20 wt % under one-sun illumination. More importantly, we demonstrate an extreme resistance to salt accumulation with 180-h continuous desalination of 20 wt % concentrated seawater. With high freshwater production and extreme salt endurance, our device significantly reduces the water production cost, paving a pathway toward the practical adoption of passive solar desalination for sustainable water economy."

Desalination system could produce freshwater that is cheaper than tap water | MIT News | Massachusetts Institute of Technology MIT engineers and collaborators developed a solar-powered device that avoids salt-clogging issues of other designs.

Extreme salt-resisting multistage solar distillation with thermohaline convection (no public access)

Graphical abstract: