Pressure Swing Assisted Desorption for Atmospheric Water Collection

Abstract

Ensuring water equity is an urgent and challenging issue in the light of climate change, global conflict, and socioeconomic disparities. Atmospheric water harvesting provides a promising option to collect water from the air, even in considerably dry conditions (RH < 40%), expanding the reach of this application to areas that would be particularly prone to clean water scarcity. The MIT Device Research Lab is developing a device for such applications that would be capable of producing drinkable water in even extremely dry environments. Current methods of atmospheric water harvesting focus on thermal desorption, where heat is applied to release the water vapor from the sorbent. Another method worth exploring is utilizing pressure swings to release this water vapor, and seeing how a combined method of thermal and depressurized desorption would affect the efficiency of this device. An initial MATLAB model showed that the methods, in order of slowest to fastest, should be (1) solely pressure swing desorption, (2) solely temperature swing desorption, and (3) the combined method using simultaneous pressure and temperature swings. The results from the experiment using the MOF UiO-66 as the sorbent showed that the combined procedure would indeed be the fastest, potentially twice as fast as a purely thermal desorption method and five times faster than a purely depressurized desorption method. The next step following this project would be the assembly of a vacuum-grade enclosure in which a small scale test unit of the device the MIT DRL is developing. A detailed design and brief procedure is included in the final section of this thesis.