A new low-cost technology where seawater turns into freshwater through solar energy!
FAO estimates that by 2025, almost 2 billion people may not have sufficient drinking water to meet their daily needs.Desalination is one of the possible solutions to this problem, namely, the treatment of sea water to make it drinkable.However, the elimination of salt from seawater requires 10 to 1000 times more energy than traditional freshwater supply methods, namely water pumping from rivers or wells.
Motivated by this problem, a team of engineers from Politecnico di Torino ‘s Department of Energy have developed a new prototype for the sustainable and low- cost desalination of sea water using solar energy more efficiently. Compared with previous solutions, the technology developed can actually double the amount of water produced by solar energy and can be subject to further improvements in efficiency in the near future.These results were recently published in the journal Nature Sustainability by a group of young researchers consisting of Eliodoro Chiavazzo, Matteo Morciano, Francesca Viglino and Matteo Fasano and Pietro Asinari (Multi-Scale Modeling Lab).
The working principle of the technology proposed is very simple: “”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),” explain Matteo Morciano and Matteo Fasano.
While conventional’ active’ desalination technologies require expensive mechanical or electrical components( such as pumps and/or control systems) and require technicians specialized in installation and maintenance, the desalination approach proposed by the Politecnico di Torino team is based on spontaneous processes without the help of auxiliary machinery and therefore, can be referred to as’ passive’ technology. All of this inherently makes the device cheap and easy to install and repair.The latter features are especially attractive in coastal regions that suffer from chronic drinking water shortages and are not yet reached through centralized infrastructure and investment.
To date, a well-known disadvantage of’ passive’ desalination technologies has been the low energy efficiency compared to’ active’ technologies. Researchers at Politecnico di Torino have faced this obstacle and dealt with it creatively: “While previous studies have focused on how to maximize solar energy absorption, we have focused our attention on managing solar thermal energy more efficiently. This enabled us to achieve record productivity values of up to 20 liters a day of drinking water per square meter exposed to the Sun. The reason for the increase in performance is that solar heat is “recycled “in several cascade evaporation processes, in line with the philosophy of “doing more, witless. ” Technologies based on this process are usually referred to as’ multi-effects,’ and here we provide the first evidence that this strategy can also be very effective in passive desalination technologies. ”
After developing the prototype for more than two years and testing it directly in the Ligurian Sea (Varazze, Italy), the engineers of Politecnico claim that this technology could have an impact in isolated coastal areas with little drinking water but plenty of solar energy, particularly in developing countries.In addition, the technology is particularly suitable for providing safe and low-cost drinking water in emergency situations such as in areas hit by floods or tsunamis and left isolated from the electricity grid and aqueduct for days or weeks. Floating gardens for food production are also intended for this technology, an interesting option especially in overpopulated areas. The researchers who continue to work on this issue at Politecnico di Torino ‘s Clean Water Center are now looking for potential industrial partners to make the prototype more durable, scalable and versatile. For example, engineered versions of the device could be used in coastal areas where over-exploitation of groundwater causes the intrusion of saline water into freshwater aquifers (a particularly serious problem in some parts of Southern Italy) or where water polluted by industrial or mining plants could be treated.