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Generating Clean Water from Solar-Powered Technology

Team from the University of Science and Technology of China have developed a biomimetic hierarchical solar steam generator based on bacterial cellulose nanocomposites.

The demand for clean drinking water across the world remains high, especially for areas lacking in electricity supply. Today, 20 percent of the world’s population live in water-deficient areas and access to clean drinking water is limited. This proves an urgent need for efficient, low-cost, sustainable and accessible technologies to generate clean water to meet the demands for such areas in the world.

Solar-powered water purification technology is one option, with its simple and efficient process to obtain clean drinking water from non-potable sources such as lake water, sewage or seawater.

A team led by Professor Yu Shu-Hong from the University of Science and Technology of China have found an efficient and sustainable method of leveraging on solar energy to generating clean water. The system known as a biometric hierarchical solar steam generator (HSSG) was formed using a one-step aerosol-assisted biosynthesis process.

Scientists formulated the microbial synthesis process through the combination of deposited nanomaterials and a sophisticated biomimetic hierarchical structure. This structure composes of three continuous layers catering different functions.

Within the HSSG, its three-dimensional cellulose nanofiber network demonstrated to reduce energy consumption when converting liquid water into vapour and accelerate the vaporization of water. Energy efficiency was attributed to the hierarchical structure design.

The hierarchical structure nanocomposites grow on the wood substrate and are tightly combined with the wood substrate through the bacterial cellulose (BC) network of nanofibers. These nanofibers crosslink with the cellulose of wood forming infiltrating layer in wood, which acts as a strong binder between wood and BC nanocomposite layers. These layers together with glass bubble provide the basis of thermal insulation and water transportation.

On the top of the device, the carbon nanotubes and BC nanocomposite layer have sophisticated interlaced structure where carbon nanotubes and cellulose nanofibers form double-network of nanofibers.

In this double-network, carbon nanotubes function as highly effective solar light absorber and BC nanofibers are used to transport water and reduce the energy consumption of evaporation. This multi-layered structure design helps to achieve fast water transportation, thermal management, effective light absorption and reduced vaporization energy consumption.

The researchers systematically investigated the relation between evaporation rate, energy efficiency and energy consumption of evaporation. Providing a novel two-dimension chart with guide lines showing different enthalpy of vaporization. This theoretical analysis method shows potential for analysing the contributions of different functional parts in solar steam generator devices for evaporation rate.

Comparing with other technology of solar powered water purification, HSSG has great potential to be a promising technology in water purification and meeting the increasing demand for clean drinkable water across the world. [APBN]