Desalination technology has a long way to go, as most methods require 10-1000 times more energy than traditional methods of collecting freshwater. However, a new technology from a team of engineers from the Department of Energy of Politecnico di Torino might provide a more efficient and low-cost option using solar power. Their research was published in the journal Nature Sustainability.
This passive technology is based on spontaneous processes and is currently capable of doubling the amount of water produced from solar energy, though future room for improvement might make it even more efficient. Researchers Matteo Fasano and Matteo Morciano explain how their system works:
"Inspired by plants, which transport water from roots to leaves by capillarity and transpiration, our floating device is able to collect seawater using a low-cost porous material, thus avoiding the use of expensive and cumbersome pumps. The collected seawater is then heated up by solar energy, which sustains the separation of salt from the evaporating water. 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 (for example the mangroves)."
The technology is inexpensive and installation and repair are easy. Furthermore, the fact that the system does not require specialized pumps or infrastructure or even specialists to set it up (as most other desalination systems require) makes it appealing for less-developed regions.
Additionally, the system is actually quite energy efficient (a characteristic which other passive strategies have lacked). "While previous studies focused on how to maximize the solar energy absorption, we have shifted the attention to more efficient management of the absorbed solar thermal energy. In this way, we have been able to reach record values of productivity up to 20 liters per day of drinking water per square meter exposed to the Sun. The reason behind the performance increase is the 'recycling' of solar heat in several cascade evaporation processes, in line with the philosophy of 'doing more, with less'. Technologies based on this process are typically called 'multi-effect', and here we provide the first evidence that this strategy can be very effective for 'passive' desalination technologies as well."
FAO estimates that within the next six years, almost 2 billion people may not have enough drinking water on a daily basis. The researchers hope the technology will be able to reduce this number; they say it will be particularly helpful in providing freshwater-relief in emergency situations in coastal areas with a lot of sun.