Water Harvesting

Many regions with severe and persistent water scarcity due to groundwater depletion, limited infrastructure, and drought are found in geographic regions with an annual relative humidity (RH) at or below 30% (e.g. North Africa, Northern China). These remote and landlocked areas eliminate the practicality of desalination technologies. Water vapor harvested from the air presents a potential drinking water resource for these regions.

State-of-the-art atmospheric water generators, or dewing systems, utilize refrigeration cycles to cool air below the dew point in order to condense into a liquid. However, these systems are costly, require significant electrical energy consumption for cooling, and are inefficient or inoperable in arid climates with low RH or low temperature. Atmospheric water harvesters utilizing adsorbents present a potential solution to this problem.

In operation, the adsorbent is exposed to air to collect water vapor. During desorption, low grade heat, such as direct sunlight, is applied to release the water molecules. The concentrated vapor is then condensed at ambient temperature. Proof-of-concept testing utilizing metal organic frameworks highlighted the potential of using novel adsorbents to passively harvest water in low RH environments. The promising results have paved the way for current research to examine a variety of novel adsorbent materials for their water harvesting performance. In our approach, we take advantage of micro/nanoporous materials which exhibit sharp uptakes at low RH, favorable kinetics, hydrothermal stability, and relatively low desorption temperature. This project focuses on the characterization of metal organic frameworks and other adsorbent materials, as well as the design and development of a large-scale water harvesting system with optimized heat and mass transport.