A team of materials scientists in China have developed a solar-powered device that can produce freshwater from seawater with better economics than bottled water.
By creating a weave of nanomaterials and organic polymers which were both durable and highly reflective, they created a device that could absorb 90.2% of incoming sunlight and use it to evaporate water with 47.5% less energy.
After it generated 5 gallons of fresh water every day for a year of testing, the scientists say that at scale it would be cheaper than producing bottled water.
It wasn’t a coincidence that after seawater desalination plants were threatened with destruction during the recent war in the Persian Gulf, virtually all belligerents came to the negotiating table.
The some-400 desalination plants located along the Gulf’s shoreline represent most of the world’s R&D into the technology, which for decades has been stuck with an energy-intensive process known as membrane or reverse osmosis desalination.
Engineering teams around the world have been attempting to develop new methods of seawater desalination to improve drinking water economies around the world’s arid regions; GNN has reported on several.
This new method, pioneered from a team from Beijing-based Institute of Process Engineering (IPE) at the Chinese Academy of Sciences and Shenzhen University, was used in a test to irrigate 50-square feet of vegetables year round.
Membrane desalination forces seawater through a thin membrane that catches the salt particles. It sounds simple, but other steps drive the energy use up to the point that only energy-rich countries like Saudi Arabia can afford to base their entire water supplies around it.
Solar-powered evaporation is another potential method—the one used by the Chinese scientists—but it had been plagued with materials failures. Ultrafine solar-absorbing powders clumped like flour; organic polymers cracked like cheap plastic.
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Drawing inspiration from a shirt button, the Chinese scientists constructed nanoparticle spheres that could be threaded together with polymer like yarn pulled through the holes in a button. The resulting structure consisted of billions of these microspheres, and proved extremely robust and durable, even in conditions that simulated a squally coastline.
All the individual spheres reflected light out into each other, boosting the solar-thermal capacity to 90.2%, ensuring the heat radiating out into the water was hot enough to drive evaporation at the highest rate possible.
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This device was able to produce 5.3 gallons of WHO-grade drinking water every day to irrigate bok choi, beans, and corn for a year. According to their calculations, the system could do far more if scaled up exponentially, to the point where it would produce, after 2 years of use, drinking water for less than a bottled water plant.
“The team is now working to improve condensation efficiency and reduce system costs, with the aim of scaling up the technology for use in water-scarce coastal areas, islands and remote regions,” SCMP reported.
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