The solar evaporator offers a new way of access to fresh water

About one billion people in the world do not have access to drinking water. Desalination of salt water in drinking water can help fill this dangerous gap. However, traditional desalination systems are far too expensive to install and use in many places, particularly in low-income countries and remote areas.

Researchers from the A. James Clark School of Engineering at the University of Maryland have demonstrated the success of a prototype of an essential component for small-scale, affordable desalination: an inexpensive solar evaporator made of wood. The evaporator generates steam with high efficiency and minimal maintenance, says Liangbing Hu, an associate professor of science and materials engineering and a member of the Maryland Energy Innovation Institute.

The design uses a technique known as interfacial evaporation, "which has significant potential in response to water scarcity due to its high solar-vapor efficiency, low environmental impact and the design of low-cost portable devices, "Hu said. "These features make it suitable for off-grid water production and purification, especially for low-income countries."

Interfacial evaporators consist of thin materials that float on saline water. By absorbing solar heat at the top, the evaporators continuously extract saline water from below and convert it to steam on the upper surface, leaving behind the salt, explains Hu, lead author in an article describing the work done at Advanced Materials.

However, over time, salt can accumulate on this evaporative surface, progressively degrading performance until it is eliminated, he says.

Hu and his colleagues downplayed the need for this interview with an American Basswood rig that harnesses the natural structure of wood, made up of multi-micron channels, that carry water and nutrients into the water. ;tree.

The researchers complement these natural channels by digging a second row of channels one millimeter wide in a thin cross section of the wood, says Yudi Kuang, guest researcher and lead author of the journal. Investigators then briefly expose the upper surface to a high heat, which carbonizes the surface for greater sun absorption.

In operation, when the device absorbs solar energy, it sucks up salt water through the natural channels of wood, of a width of several microns. The salt is spontaneously exchanged from these tiny channels through natural openings along their sides to the much larger drilled channels, and then dissolves easily in the water.

"In the laboratory, we have successfully demonstrated excellent anti-fouling in a wide range of salt concentrations, with stable steam generation with an efficiency of about 75%," said Kuang.

"By using natural wood as the only starting material, the solar salt rejection evaporator should be inexpensive," adds Chaoji Chen, research associate. The evaporator approach is also effective in other types of wood with similar natural channels. Researchers are now optimizing their system for greater efficiency, reduced investment costs and integration with a steam condenser to complete the desalination cycle.

Hu's laboratory recently developed another solar-heated prototype device that takes advantage of the ability of carbonized wood to absorb and distribute solar energy – the latter was created to help clean spills of heavy oils difficult to collect. "Our carbonized wood material exhibits fast and efficient absorption of crude oil, as well as a low manufacturing cost and upgradeable manufacturing potential," said Kuang, lead author of an article on research on advanced functional materials.

"Wood is an intriguing material scaffolding, with its unique hierarchical porous structure, and it's a renewable, abundant and profitable resource," Hu said. "In our laboratory, the fundamental understanding of biomaterials (especially wood) leads us to achieve extraordinary competitive performance over widely used but unsustainable materials."

Among other projects, his laboratory has created light and efficient insulating materials based on "nanowood". He also made "super wood" that is 12 times stronger and 10 times stronger than natural wood, and could potentially replace steel, titanium or carbon fiber in some applications, he says.