Theoretically, the moisture in the air could stand in for an infinite supply of potable water. Kyle E. Cordova and colleagues at the Advanced Research Centre of the Royal Scientific Society in Amman, Jordan, have developed an atmospheric water harvesting device that can automatically adjust its operation to adapt to shifting environmental conditions in order to extract as much water as possible from the air. This adaptable layout increases water production with less energy use, making the technology more feasible for application in places where clean water is scarce.
Condensing Steam from Water
The process of creating liquid water from atmospheric water is called “atmospheric water creation.” The concept relies on the fact that at or below the dew point (the temperature at which the relative humidity of the air is 100%, in other words, when the air is entirely saturated), water vapour in the air will condense on the surface. Although the dew point rarely falls below freezing, it can get close when the relative humidity of the air falls below 30%. Consequently, in arid regions, this technique is now impracticable due to high cooling costs and inadequate water supply.
Materials that are hygroscopic and porous can be used to solve this problem since they absorb huge amounts of moisture from the air and then release it when heated. Because the water vapour is concentrated so well, it can be collected even in dry locations. MOF-801 (shown), a zirconium-based metal-organic framework, is one of the best materials for atmospheric water collection at low humidity. Although it has been used in desert areas as a prototype, the cost of its water production and the energy required to run it make it impractical for widespread use.
Rather than focusing on inventing new and more efficient extraction materials, the team looked for ways to save energy during the operation itself to increase the efficiency of atmospheric water collecting. Cordova recognised the sorption material’s reaction to environmental variables as a critical area for optimization. To activate the gadget, air must be forced through it at specific intervals. No thought is given to the natural world, he says.
Dew Point Swings
The group found that the saturating time of the adsorbing substance changed with the relative humidity and temperature. However, both characteristics vary throughout the day, with high relative humidity and low temperatures at night and low relative humidity and high temperatures in the day. Researchers concluded that adsorption and desorption periods in each cycle should be regulated depending on temperature and humidity since these two environmental characteristics together give the dew point, which in turn defines the material’s ability to take up water.
The group set up two sensors to monitor the air temperature and relative humidity of the entering air during the adsorption phase and the air data within the condensation chamber to continuously evaluate the dew points for the sorption material and condenser. One algorithm uses the sensor data to determine the best time for the adsorption phase, while another determines the desorption time and condenser cooling temperature.
Optimization by Itself
As a result, the device could automatically adjust its cycle periods in response to changes in the surrounding conditions, such as when relative humidity was low (during the day), the cycles were shorter, and when humidity was high (at night), the cycles were longer. This adaptive procedure reduced the number of cycles run each day by 1.5, but increased output by 26% while reducing energy use by 44%. The adaptive-mode device performed better than its rivals in atmospheric water harvesting systems and materials, particularly at relative air humidities below 30%.
Applying the findings to real-world scenarios, the researchers determined that, in a desert area, 1.9 kg of material are required to create 3.5 L of clean, drinkable water per day, the recommended daily intake for one person. The amount of energy required to manufacture this volume is comparable to what is needed to drive an electric vehicle between 60 and 120 kilometres. The group also notes that the cost of one litre of this air-harvested water may be roughly equal to half of the going rate for potable water.
The research demonstrates that moisture harvesting devices in arid regions can operate at peak efficiency when smart modes of operation are employed. This is very promising for a sector that has put a lot of resources into materials development. Researchers like Guihua Yu of the University of Texas at Austin, who are looking at superhygroscopic polymers for this purpose, are excited about this fresh viewpoint. How to maximise the daily practical yield of water production using next-generation sorbent materials is discussed.
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