Page 39 - AW SEPOCT 2019

MAKING WAVES

Using solar power to separate salt

from water

cientists at Australia’s Monash University Melbourne builds up on the disc while pushing the salt to the edge.
Shave put forward one rather promising solution, In this way, the device removes almost 100 percent
developing a new kind of system that heats up and purifies of salt from the water, a level that leader of the team
water using only the power of the Sun. Professor Xiwang Zhang assures us is “high enough for
As current approaches to water desalination are practical applications.” The salts that accumulate at the
tremendously expensive and energy-intensive, so the edges, meanwhile, can also be harvested for use.
search is very much on for new technologies that can Zhang and his team tested out the device using salty
get the job done more efficiently. water from a bay in South Australia, and found that it
Like other researchers around the globe, they have absorbed 94 percent of the light across the solar spectrum.
turned to sunlight to try and lighten the load, this time It worked whether wet or dry, with light exposure heating
directing it toward what is known as a solar steam up the device from 25 to 50° C (77 to 122° F) when dry
generator. and from 17.5 to 30° C (63.5 to 86° F) when wet, within just
In simple terms, these devices concentrate sunlight one minute.
onto a body of water, heating it up and causing it to “This device can produce six to eight liters (1.6 to 2.1
evaporate. The resulting steam can then be used to gal) of clean water per square meter (of surface area) per
drive turbines that produce electricity in concentrated day,” Zhang tells New Atlas. “We are working to further
solar power plants, perhaps sterilize medical equipment improve the water production rate.”
cheaply for the developing world, or simply to separate Zhang and his colleagues hope that with further
salt from water. work, the device could be put to use providing clean
But one problem with the lattermost application is that water to remote communities that are currently without
the salt tends to gather on the surface of the material, access. But its value mightn’t end there. The technology
which makes it difficult to produce pure water. The Monash could be used in other areas where more efficient water
University researchers worked around this problem with an purification methods might come in handy, such as mining
intricately designed solar steam generator that prevents and wastewater treatment.
the salt from spoiling the broth. “We hope this research can be the starting point for
It consists of a disc crafted from super-hydrophilic filter further research in energy-passive ways of providing
paper, a material that attracts water, which is coated with clean and safe water to millions of people, illuminating
a layer of carbon nanotubes that convert sunlight into environmental impact of waste and recovering resource
heat. Water is fed into the center of the disc via a simple from waste,” says Zhang. AW
cotton thread, where the heat turns it into steam that

Asian Water SEPTEMBER/OCTOBER 2019 37