Researchers have significantly boosted the output from a system that can extract drinkable water directly from the air even in dry regions, using heat from the sun or another source. The system brings the system, designed three years ago, closer to something that could become a practical water source for remote regions.
The earlier device from researchers at MIT provided a proof of concept for the system, which harnesses a temperature difference within the device to allow an adsorbent material that collects liquid on its surface to draw in moisture from the air at night and release it the next day.
When the material is heated by sunlight, the difference in temperature between the heated top and the shaded underside makes the water release back out of the adsorbent material. The water then gets condensed on a collection plate.
But that device required the use of specialized materials called metal organic frameworks, or MOFs, which are expensive and limited in supply, and the system’s water output was not sufficient for a practical system.
Now, by incorporating a second stage of desorption and condensation, and by using a readily available adsorbent material, the device’s output has been significantly increased, and its scalability as a potentially widespread product is greatly improved, the researchers say in a statement.
Instead of the MOFs, the new design uses an adsorbent material called a zeolite, which in this case is composed of a microporous iron aluminophosphate. The material is widely available, stable, and has the right adsorbent properties to provide an efficient water production system based just on typical day-night temperature fluctuations and heating with sunlight.
The overall productivity of the system, in terms of its potential liters per day per square meter of solar collecting area (LMD), is approximately doubled compared to the earlier version, though exact rates depend on local temperature variations, solar flux, and humidity levels.
The team is continuing work on refining the materials and design of the device and adapting it to specific applications, such as a portable version for military field operations.
Image credit: philografy, flickr/Creative Commons
