Reviewed by Lexie CornerSep 12 2024
In a study published in Nature Communications, researchers at the University of Waterloo developed an energy-efficient device that produces drinking water from seawater using an evaporation process primarily powered by the sun.
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Mock-up of solar desalination system. Image Credit: University of Waterloo
Desalination is vital for many coastal and island nations to provide access to fresh water, given concerns about water shortages caused by rapid population growth and increasing global water usage. According to the UN World Water Development Report 2024, approximately 2.2 billion people worldwide lack access to clean water, emphasizing the urgent need for new methods of freshwater production.
Current desalination systems typically pump seawater over membranes to separate salt from water. This process is energy-intensive, and salt often accumulates on the device's surface, blocking water flow and reducing efficiency. Consequently, these systems require frequent maintenance and cannot operate continuously.
To tackle this problem, researchers at the University of Waterloo designed a device inspired by the natural water cycle, mimicking how plants transport water from roots to leaves. This innovative system can desalinate water continuously with minimal maintenance.
Our inspiration comes from observing how nature sustains itself and the way water evaporates and condenses in the environment. The system we have 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.
Dr. Michael Tam, Professor, Department of Chemical Engineering, University of Waterloo
The device is also solar-powered, converting around 93 % of the sun's energy into electricity—five times more efficient than conventional desalination devices. It can produce around 20 liters of fresh water per square meter, meeting the World Health Organization's daily recommended water intake for drinking and hygiene.
The device was created by a research team that included Ph.D. students Eva Wang and Weinan Zhao. They used nickel foam covered with a conductive polymer and thermoresponsive pollen particles. This substance absorbs sunlight across the solar radiation spectrum, converting its energy into heat. A thin layer of saltwater is heated and moves upward, mimicking the natural movement of water through tree capillaries.
As the water evaporates, the remaining salt flows to the bottom layer, functioning similarly to a backwash mechanism in a swimming pool. This prevents salt buildup and ensures continuous operation.
Dr. Yuning Li, a professor in Waterloo's Department of Chemical Engineering, assisted the team by using a solar tester to evaluate the device's light-harvesting capabilities for optimal solar energy conversion.
This new device is not only efficient but also portable, making it ideal for use in remote regions where access to fresh water is limited. This technology offers a sustainable solution to the emerging water crisis.
Yuning Li, Professor, Department of Chemical Engineering, University of Waterloo
Moving forward, the Waterloo researchers plan to develop a prototype of their device that can be deployed at sea to test the technology on a larger scale.
“If the test is proven successful, the technology can sustainably supply fresh water to coastal communities and advance UN Sustainable Development goals three, six, ten, and twelve,” Tam concluded.
Journal Reference:
Wang, Y., et al. (2024) Thermo-adaptive interfacial solar evaporation enhanced by dynamic water gating. Nature Communications. doi.org/10.1038/s41467-024-50279-z.