A unique technique to remove salt from seawater using solar power

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Floating desalination unit
Floating desalination unit "Hydriada" powered by wind and solar energy in Irakleia, Greece, the first of its kind (Credits - Wikimedia Commons)

Researchers have recently discovered a new convenient nanoscale method of removing salt from sea-water which is likely to benefit 844 Million people globally who don’t have regular access to clean water. The findings have been published in the journal Energy & Environmental Science.

The device completely operates on sunlight and uses a small disc made of super-hydrophilic filter paper laminated with carbon nanotubes for light absorption and is able to remove 100% salt from the original liquid. The new method will turn water into steam using solar energy and solar thermal materials and is based on the traditional way of heating water until it steams, leaving salt and impurities behind. It also maintains a constant rate of water evaporation as the salts are collected and removed to avoid the system to halt because of the covering of salt crystals.

Devices using desalination method powered by sunlight can be used in those places with no access to electricity because it is economical and effective. Chemical engineer Xiwang Zhang, from Monash University in Australia said that the study results progress one step towards solar steam generation technology in seawater desalination, resource recovery from sewage and zero fluid discharge. Moreover, he added that this research can be building brick for future researches in energy-passive methods to supply clean and safe water to millions of people, illuminating environment effects from waste and recovering resource from waste.

A cotton thread of 1-millimetre (0.04 inch) diameter is used to carry saline water to the evaporation disk where clean water is collected, pushing out salt towards the edges. Researchers during testing found out that it makes good use of solar energy that is available with over 94 percent light absorption throughout the entire solar spectrum. Zhang told that this creative method is able to generate 6-8 litres (or 1.6-2.1 gallons) per square metre (10.8 square feet) of surface area of clean water per day. The next target is to increase the production rate.

Last year, a group from US have developed a one more fascinating and powerful desalination method to remove salt from Dead Sea using hydrogel-based, solar powered technique. However, the challenge is to put the systems in place and scaling up the methods so that sufficient amount of water can be processed.

Zhang said that water protection is the greatest challenge globally in the 21st Century as population grows and climate varies, especially for developing and under-developed communities. He also said that one of the permanent and eco-friendly solution for scarcity of clean water is production by utilising solar energy.

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