Approximately 1.5 billion people worldwide lack regular access to fresh water, which makes up only 3% of the world’s water sources. Most of these people live in arid environments where there’s plenty of sunshine.
To address this issue, a team of scientists at the University of Southern Australia (UniSA) has improved a process that derives freshwater from seawater (or dirty water) via highly efficient solar evaporation.
The system is based on a 3D photothermal structure placed on the water’s surface to convert sunlight to heat and assist in the evaporation of the liquid’s top layer, which then turns into freshwater. This technique enables a family of four to get sufficient fresh drinking water daily from one square meter of polluted water, seawater, or any salty water.
While similar photothermal technologies have been designed before, the Australian team claims their new fin-shaped, three-dimensional, heatsink-like evaporator is far more efficient. “The new design shifts surplus heat away from the evaporator’s top surfaces, distributing heat to the fin surface for water evaporation, thus cooling the top evaporation surface and realizing zero energy loss during solar evaporation,” the scientists explained.
The UniSA team added:
This heatsink technique means all surfaces of the evaporator remain at a lower temperature than the surrounding water and air, so additional energy flows from the higher-energy external environment into the lower-energy evaporator.
Impressively, the new system can derive anywhere between 10 liters to 20 liters of fresh drinking water per square meter of water daily.
Associate Professor Haolan Xu, from UniSA, explained:
Previously, many of the experimental photothermal evaporators were basically two dimensional; they were just a flat surface, and they could lose 10 to 20% of solar energy to the bulk water and the surrounding environment.
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% efficiency for the solar input and draws up to another 170% energy from the water and environment.
As a bonus, the 3D photothermal evaporators can be produced from inexpensive materials and are easy to construct and deploy, providing a low-cost alternative to more expensive desalination techniques.
The photothermal structure’s design prevents salt and other contaminants from building up on the evaporator surface, making maintenance super easy. “It is so simple and requires virtually no maintenance, there is no technical expertise needed to keep it running, and upkeep costs are minimal,” Xu added.
Xu stresses:
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.
Earlier this year, we saw some clever devices that turn seawater or dirty water into clean, drinkable water. These include a skylight dubbed ‘Solar Desalination Skylight’ that makes seawater drinkable and provides free lighting; and Princeton University scientists’ cheap, flat, sponge-like device that absorbs water from a pond or lake, then releases purified water when placed under the sunlight.
Last year, scientists at Australia’s Monash University developed new water purification and desalination technology that transforms seawater into clean drinking water in under half an hour.
