This country has a new way to make drinking water cheaper. Here's how

Chinese scientists have developed a new solar-powered desalination technology that could make drinking water from seawater cheaper than bottled water, according to a report by The South China Morning Post. 

The system runs only on sunlight, does not need electricity from the power grid, and remained stable during a year-long outdoor trial.

Researchers said that if the system operates for two years, the cost of producing fresh water would fall below the cost of bottled water. They added that the economic advantage "would become even more pronounced if the system were scaled up or used over the long term".

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The study was carried out by researchers from the Institute of Process Engineering (IPE) at the Chinese Academy of Sciences and Shenzhen University. It was published in the journal Advanced Materials on June 21.

How the new technology works

Desalination is the process of removing salt from seawater to make it safe for drinking. While it is already used in many countries, it is expensive because it requires large amounts of electricity and costly infrastructure.

To solve this problem, the researchers developed a new photothermal material that converts sunlight into heat to evaporate seawater and turn it into fresh water.

The team created an innovative way to weave nanoparticles into a three-dimensional structure. This improved the material's ability to absorb sunlight while preventing the tiny particles from clumping together.

The new material achieved a solar absorption rate of 90.2% and reduced the energy needed to evaporate the same amount of seawater by 45.7%.

Researchers said they took inspiration from buttons. They turned nanoparticles into individual "buttons" and used polymer "threads" to stitch them together, creating a strong three-dimensional framework. After cooling, the polymer chains locked billions of nanospheres together into what the researchers described as a three-dimensional "nanoforest".

Successful outdoor testing

The researchers built a 0.75-square-metre trial system powered by sunlight.

Solar panels operated a fan that carried water vapour into a condensation unit, where it was converted into fresh water.

The system produced more than 20 litres of drinking water every day using only natural sunlight. According to the researchers, this is enough to meet the basic daily drinking water needs of about 10 people.

An IPE press release said the water met World Health Organization drinking-water standards.

Also used for farming

The fresh water produced by the system was used to irrigate a 5-square-metre test plot, where spinach, corn and Chinese cabbage completed their full growth cycles.

The photothermal material also showed year-long stability during outdoor testing.

The researchers said that after two years of operation, the cost of producing water would be lower than bottled water. They added that the savings would increase further if the technology was used on a larger scale or for longer periods.

What happens next?

"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," the IPE said.