According to the UN Food and Agriculture Organisation, massive water shortages could affect almost 2 billion people around the world by 2025, meaning that more than a quarter of the world‘s population could be lacking potable water necessary to meet their basic needs in just 7 years from now.
The most obvious solution to the problem, namely – the desalination of seawater, faces the challenge of requiring as many as 10 to 1,000 times more energy than regular methods of freshwater supply, such as pumping water from rivers or wells.
Fortunately, a group of young engineers from the Department of Energy of Politecnico di Torino has recently come up with a new, sustainable and low-cost technique for removing salt from seawater by using solar energy.
Writing in a paper out in the prestigious journal Nature Sustainability, the group details their invention, which operates in a manner similar to plants – rather than relying on expensive and cumbersome pumps, the floating device collects seawater using a low-cost porous material.
Solar energy then heats up the collected water, thereby separating salt from the evaporating H2O. “This process can be facilitated by membranes inserted between contaminated and drinking water to avoid their mixing, similarly to some plants able to survive in marine environments,” explained co-authors Matteo Fasano and Matteo Morciano.
Since the new “passive” desalination technology requires neither costly mechanical or electrical components, nor specialised technicians for installation and maintenance, it could be particularly attractive in isolated coastal regions which lack comprehensive water supply infrastructures, but have solar energy in spades.
To bring the efficiency of the technology closer to that of “active” desalination methods, rather than focusing on maximising solar energy absorption, researchers looked into superior ways of its management.
By “recycling” solar heat in several cascade evaporation processes, the team was able to “reach record values of productivity” – tests conducted in the Ligurian Sea have demonstrated the device to be capable of generating “up to 20 litres per day of drinking water per square meter exposed to the Sun”.
The team is now looking for industrial partners to make the prototype more durable, scalable, and versatile.