Scientists in China recently announced proof of concept of an efficient solar-powered thermal desalination process. The news was reported by IEEE Spectrum.

The graphene-based absorber may solve a problem that plagues other solar-powered technology: the need to use thermal insulation to prevent heat loss. Additional advantages include portability and low cost. The graphene absorber is easy to transport, making it potentially attractive to use in remote areas and in developing countries.

The graphene absorber is easy to transport.Unlike existing solar-based thermal absorbers, the new absorber does not come in direct contact with the bulk of the water. Current technology requires that the absorber be immersed in the water being desalinated to ensure efficient transfer of energy.

However, these desalinators require both optical concentrators and thermal insulation. Immersing the absorber in a large quantity of unheated water can lead to thermal loss. Preventing thermal loss requires adding a lot of insulation. The resulting desalinating device then becomes neither easily portable nor efficient.

Jia Zhu’s laboratory designed a novel graphene-oxide solar absorber to avoid both problems. A thermal insulator made from polystyrene foam separates the absorber from the water. A 2D cellulose channel wraps around the insulator. The bottom of the channel rests on the water and the solar absorber is on top. Water circulates by capillary action and is heated by the absorber.

This design depends on unique qualities of graphene oxide. First, it is an excellent solar absorber, says Zhu. It has low thermal conductivity in the direction perpendicular to the material’s plane; it has pores that act as channels for water vapor; it can be folded, and it is relatively low cost, Zhu says.

Researchers will need to test this system’s long-term stability outside the laboratory. The Chinese team says it is enthusiastic about its potential to bring safe water and power generation to remote parts of the world.