Chinese researchers reported on the 21st of the National Academy of Sciences that an efficient and portable solar desalination technology can convert seawater into high quality drinking water with energy conversion efficiencies of up to 80%.
Professor Zhu Jia of the School of Modern Engineering and Applied Science at Nanjing University, who is in charge of the study, told the reporter that solar desalination uses the principle of light distillation and can produce fresh water without other energy. Therefore, it is an ideal seawater desalination scheme, but it has always been due to low energy conversion efficiency. Can not be applied on a large scale.
To this end, Zhu Jia's research group proposed a new idea, which has two major innovations: First, the use of graphene made of a collapsible and lightweight film, used to absorb solar distilled sea water, greatly increased the portability; Second, Separation of graphene absorbers from seawater reduces thermal conductivity losses.
Zhu Jia said that in the past most of the work, the absorber was in direct contact with water, causing the energy to dissipate through the heat of the water itself. Therefore, optical focusing, thermal insulation, and other means were required to maintain the thermal balance. Their work has designed a special two-dimensional water channel that does not allow the absorber to be in direct contact with the seawater, so efficient conversion can be achieved without external assistance.
Specifically, they designed a thermal insulator in the shape of a cylinder, made of foamed polystyrene. The outer layer of thermal insulation was coated with a woven cellulose coating to form a special water channel, and the top of the cylinder was covered with a graphene film. At work, woven cellulose absorbs water from the lower pool by capillary action, supplies the upper film and heats it to steam, and collects fresh water.
Zhu Jia said that before the energy conversion efficiency of light to steam is generally about 60% under the same conditions, and their devices can reach 80%, the water quality after the conversion has passed the preliminary test of the World Health Organization and other international standards. With the fact that the film is foldable and lightweight, the manufacturing cost is low, so that the scope of application is greatly improved. Of course, the stability of the long-term operation of this device requires time and inspection under different application scenarios.
Talking about the significance of this work, Zhu Jia said that the shortage of water resources is a worldwide problem, and it is also closely linked with energy and environmental issues. Where there is a shortage of water resources, it is often a lot of special places (desert, islands), poor areas of poverty, or places that suffer from natural disasters. Green, portable, and efficient water treatment technologies are often needed in such areas. The desalination of seawater is more efficient, while reducing costs and increasing its scope of application may provide a different method and idea for solving this problem."
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