Seawater into fresh water with solar power
Researchers from the University of Waterloo have created an energy-efficient device that turns seawater into drinking water using solar power. Desalination is vital in many coastal and island nations in providing fresh water, especially with population growth and increasing water consumption globally.
Around 2.2 billion people around the world have no access to clean water, highlighting a need for new technology to generate fresh water, the UN World Water Development Report 2024 finds.
Current desalination systems pump seawater through membranes that separate the salt from the water. But this process uses a lot of energy and salt can accumulate on the surface of the device, obstructing the flow of the water and reducing its efficiency. As a result, these systems need maintenance and cannot work continuously.
To solve this, Waterloo researchers took inspiration from the natural water cycle to build a device that mirrors how trees transport water from their root up to their leaves. The new technology can continuously desalinate water without the need for major maintenance.
“Our inspiration comes from observing how nature sustains itself and the way water evaporates and condenses in the environment,” said Dr. Michael Tam, a professor in Waterloo’s Department of Chemical Engineering. “The system we’ve engineered induces water to evaporate, transports it to the surface, and condenses it in a closed cycle, effectively preventing the accumulation of salt that reduces the efficiency of the device.”
The device is also solar-powered. It is capable of turning around 93% of sunlight it receives into energy, five times better than current desalination systems. It also produces around 20 litres of fresh water per square meter, the same amount recommended by the World Health Organization for each person every day for basic drinking and hygiene.
The team made the device using nickel foam coated with a conductive polymer and thermoresponsive pollen particles. This material can absorb sunlight and convert it into heat. A thin layer of salt water on the polymer is heated up and transported upward. This is similar to the process employed in capillaries in trees. As it evaporates, the remaining salt falls to the bottom layer, similar to a backwash system in swimming pools, preventing any potential blockages and allowing for a continuous operation.
