Breakthrough System Improves Solar Still And Offers Low-Cost Desal

Desalination takes salt and other contaminants out of water. Now scientists are looking to take the prohibitive costs out of desalination.

“Researchers have come up with a solar-powered technique that could make small-scale desalination systems affordable, even for individual households. The approach is a new take on an old technology known as a solar still. These stills — large containers covered by clear plastic tarps or glass enclosures — direct sunlight onto a basin of salty water,” Science journal reported.

Normally, solar stills, which rely on evaporation, are too slow and do not produce enough water, but researchers at Nanjing University in China are trying to change that. They created a solar absorber that works on aluminum. Aluminum is mainly useful for soaking up ultraviolet light, but the scientists tried a twist on usual procedures in their study published last month by Nature Phonetics.

“First, they perforated the foil with a regular array of holes, each 300 nanometers across. The array prevents light from reflecting off the surface and scatters it through the film, increasing the odds it will be absorbed. The researchers also misted the aluminum oxide foil with an extra dose of vaporized aluminum. The additional aluminum formed a thin layer on top. But in the pores, the aluminum atoms bunched up into tiny ‘islands’ that increased the foil’s odds of absorbing sunlight,” Science reported.

“The aluminum islands worked like gold particles, creating energy-funneling hotspots that boosted water evaporation at those sites. The approach worked so well that the researchers were able to purify salt water up to three times faster than without the foil,” the report said.

Using the new system, a square meter of foil produced 2 to 8 liters of water per hour.

“The combination of the significant desalination effect, the abundance and low cost of the materials, and the scalable production processes suggest that this type of plasmon-enhanced solar desalination device could provide a portable desalination solution,” the study said.

Researchers still need to prove that their system can hold up during years of repeat use, and they need to figure out what to do with the leftover brine, Science reported.

Lowering the cost of desalination could be useful for water-scarce nations around the world. Globally, one in ten people lack access to safe drinking water, according to the international nonprofit Water.org. That’s 663 million people.

To read more about modern desalination solutions visit Water Online’s Desalination Solutions Center.