Apr 16, 2019 10:15 AM EDT
One of the major problems around the world is the lack of access to safe drinking water, and about a billion people suffer from this. One of the ways that can help to fill this critical gap is to desalinate salty water into drinking water. The problem remains that the traditional desalination systems are far too expensive to install and operate in many locations, particularly in low-income countries and remote areas.
University of Maryland's researchers has then demonstrated a successful prototype of one crucial component for affordable small-scale desalination: an inexpensive solar evaporator, made of wood. As explained by the associate professor of materials science and engineering and affiliate of the Maryland Energy Innovation Institute, Liangbing Hu said that the evaporator generates steam with high efficiency and minimal need for maintenance.
Hu further explained that the design made use of a technique known as interfacial evaporation which shows excellent potential in response to global water scarcity due to its high solar-to-vapor efficiency, low environmental impact, and portable device design with low cost. The features of the device make it suitable for off-grid water generation and purification, particularly for low-income countries.
Furthermore, Hu explained that they used thin materials that float on saline water to make interfacial evaporators. While it can absorb the heat on top, the evaporators continually pull up the saline water from below and convert it to steam on their top surface, leaving behind the salt.
He added that over time, however, salt can build upon this evaporative surface and gradually degrading performance until it is removed.
The team worked on minimizing the need for this maintenance with a device made out of basswood that exploits the wood's natural structure of the micron-wide channels that carry water and nutrients up to the tree.
A lead author of the paper who is also a visiting scholar, Yudi Kuang said that to supplement these natural channels, the researchers drilled a second array of millimeter-wide channels through a thin cross-section of the wood. Next, they exposed the top surface to high heat which then carbonizes the surface for excellent solar absorption.
The function of the device makes it absorb solar energy and draws up salty water through the wood's natural micron-wide channels. There will be an automatic exchange of salt from these tiny channels through natural openings along their sides to the vastly broader drilled channels, and then easily dissolves back into the water below.
According to Kuang, they have successfully demonstrated excellent anti-fouling in the lab in large range salt concentrations with the stable steam generation of about 75 percent efficiency. The device is also useful in other types of wood with the same natural channels. The researchers are now optimizing their system for higher efficiency, lower capital cost, and integration with a steam condenser to complete the desalination cycle.
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