Researchers at the University of South Australia (UniSA) have unveiled a structure aimed at tackling the global issue of water shortages. The cost-effective technique uses a floating module and highly efficient solar evaporation to extract freshwater from contaminated or sea water, potentially eliminating water shortages for millions of people around the world.

It is estimated that 1.42 billion people around the world are living in areas of high water vulnerability – a figure which is expected to grow in the coming decades due to the pressures of climate change, pollution, and shifting population patterns. In response, researchers at the UniSA’s Future Industries Institute have focused their efforts on a solution for eliminating water stress, with a focus on areas housing vulnerable or disadvantaged communities.

Led by Associate Professor Haolan Xu, the team has unveiled a structure that derives freshwater from seawater, brackish water, or contaminated water, through highly efficient solar evaporation – delivering enough daily fresh drinking water for a family of four from one square meter of source water.

At the heart of the system is a highly efficient photothermal structure sitting on the surface of the water, converting sunlight to heat while focusing energy precisely on the surface to rapidly evaporate the uppermost portion of the water mass. While this technology has been used before, it has historically been hampered by energy loss, with heat passing through the source water and dissipating into the air above.

“Previously many of the experimental photothermal evaporators were basically two dimensional; they were just a flat surface, and they could lose 10 to 20 per cent of solar energy to the bulk water and the surrounding environment,” says Dr Xu. “We have developed a technique that not only prevents any loss of solar energy, but actually draws additional energy from the bulk water and surrounding environment, meaning the system operates at 100 per cent efficiency for the solar input and draws up to another 170 per cent energy from the water and environment.”

The system’s innovation lies in its use of a three-dimensional, fin-shaped, heatsink-like evaporator structure, which departs from the flat surfaces typically used by other researchers.  Under Xu’s system, the vertical fins retain heat which would otherwise have been lost to evaporation on the module’s surface; heat now used to further the system’s rate of freshwater evaporation. As a result, the team’s system can develop 10-20 litres of fresh water per square meter per day.

The structure is composed of everyday materials that are low cost, sustainable, and easily obtainable. “One of the main aims with our research was to deliver for practical applications, so the materials we used were just sourced from the hardware store or supermarket,” Assoc Prof Xu explains.

The team sees a future where such modules can be deployed in areas where local infrastructures are unable to keep pace with rising populations. “For instance, in remote communities with small populations, the infrastructure cost of systems like reverse osmosis is simply too great to ever justify, but our technique could deliver a very low cost alternative that would be easy to set up and basically free to run,” Xu says. “This technology really has the potential to provide a long-term clean water solution to people and communities who can’t afford other options, and these are the places such solutions are most needed.”