Engineering news
According to the UN, a fifth of the world’s population lives in areas where water is scarce – so we urgently need clean, affordable technologies to make undrinkable water from the sea or contaminated sources potable.
Researchers from the University of Science and Technology of China have developed a new type of solar steam generator, which can separate pure water from contaminants using evaporation. Lots of these devices have been created in the past – and to improve them, researchers must find ways of increasing light absorption, and improving heat management, water transport and evaporation.
In the latest development, Shu-Hong Yu and colleagues decided to use wood, which is sustainable and has a porous structure that allows rapid water transport.
They used a type of bacteria that produced long cellulose nanofibres, which bound the different layers of the device together. They added that bacteria to the surface of a wooden block and allowed them to ferment. Then, they sprayed tiny glass bubbles – hollow spheres that provide thermal insulation – onto the same surface.
The bubbles became embedded in the nanofibres which had been produced by the bacteria, forming a ‘hydrogel’. The final step was to add carbon nanotubes, which also tangled with the nanofibres, creating a top layer that absorbed light but allowed water to evaporate.
Contaminated water is transported upwards through the wood to the light-absorbing layer, which is heated by the sun. That creates evaporation, which is then collected and condensed to create pure water. The layer of glass bubbles keeps the heat in the top layer, and the nanoscale structure increases the surface area and lowers the energy required for evaporation.
The device therefore has a higher evaporation and greater efficiency than existing solar steam generators.
Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.