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This solar-powered device produces energy and cleans water at the same time

Still a prototype, the machine could one day help curb electricity and freshwater shortages

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8:00am, July 12, 2019
solar panels

UNDER THE SUN  Solar panels with water purification devices mounted on their backs (illustrated) could produce freshwater and electricity simultaneously.

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By mounting a water distillation system on the back of a solar cell, engineers have constructed a device that doubles as an energy generator and water purifier.

While the solar cell harvests sunlight for electricity, heat from the solar panel drives evaporation in the water distiller below. That vapor wafts through a porous polystyrene membrane that filters out salt and other contaminants, allowing clean water to condense on the other side. “It doesn’t affect the electricity production by the [solar cell]. And at the same time, it gives you bonus freshwater,” says study coauthor Peng Wang, an engineer at King Abdullah University of Science and Technology in Thuwal, Saudi Arabia.

Solar farms that install these two-for-one machines could help meet the increasing global demand for freshwater while cranking out electricity, researchers report online July 9 in Nature Communications.

Using this kind of technology to tackle two big challenges at once “is a great idea,” says Jun Zhou, a materials scientist at Huazhong University of Science and Technology in Wuhan, China, not involved in the work.

In lab experiments under a lamp whose illumination mimics the sun, a prototype device converted about 11 percent of incoming light into electricity. That’s comparable to commercial solar cells, which usually transform some 10 to 20 percent of the sunlight they soak up into usable energy (SN: 8/5/17, p. 22). The researchers tested how well their prototype purified water by feeding saltwater and dirty water laced with heavy metals into the distiller. Based on those experiments, a device about a meter across is estimated to pump out about 1.7 kilograms of clean water per hour.

“It’s really good engineering work,” says George Ni, an engineer who worked on water distillation while a graduate student at MIT, but was not involved in the new study.

“The next step is, how are you going to deploy this?” Ni says. “Is it going to be on a roof? If so, how do you get a source of water to it? If it’s going to be [floating] in the ocean, how do you keep it steady” so that it isn’t toppled by waves? Such practical considerations would need to be hammered out for the device to enter real-world use.

Citations

W. Wang et al. Simultaneous production of fresh water and electricity via multistage solar photovoltaic membrane distillation. Nature Communications. Published online July 9, 2019. doi:10.1038/s41467-019-10817-6.

Further Reading

J. Rehm. A new 2-D material uses light to quickly and safely purify water. Science News. Vol. 195, March 16, 2019, p. 15.

A. Witze. More than 2 billion people lack safe drinking water. That number will only growScience News. Vol. 194, August 18, 2018, p. 14.

M. Temming. A new way to turn saltwater fresh can kill germs and avoid gunk buildupScience News Online, December 11, 2018.

L. Hamers. Perovskites power up the solar industryScience News. Vol. 192, August 5, 2017, p. 22.

T. Sumner. New desalination tech could help quench global thirstScience News. Vol. 190, August 20, 2016, p. 22.

T. Sumner. Solar panels are poised to be truly green. Science News Online, December 6, 2016.

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