System-level Design, Fabrication, and Optimization of Sorbent-based Atmospheric Water Harvesting Devices

Abstract

Sorption-based atmospheric water harvesting (SAWH) has been demonstrated as a promising avenue to addressing the increasing problem of water scarcity, especially in arid inland regions where alternative technologies are limited. However, current sorbent materials are often limited in their applicability due to system integration and device design constraints. In this thesis, we present advancement of atmospheric water harvesting technologies in both the passive and active design space by leveraging a system-level approach to modelling and optimization of devices. First, we discuss SAWH device fundamentals in terms of heat, mass, and fluid transport, and identify key components which impact device performance for both passive (solar) and active (electrical/chemical) systems, as quantified by our proposed performance metrics. Next, we develop a coupled heat and mass transport model of a passive, solar-driven atmospheric water harvesting device and quantify the impact of system variables on device operation. We use this model to fabricate an optimal system that efficiently utilizes a hydrogel-salt composite sorbent for record passive water production in the Atacama Desert. Furthermore, we propose an underlying mechanism for observed system-level degradation of our hydrogel-salt composite and demonstrate successful lifetime elongation of the sorbent in SAWH operation. Additionally, we use our fundamental understanding of SAWH to design an active device for portable use. Highly compact, lightweight, and energy dense, this system operates independent of external environment conditions and produces more than 2 L/day of potable water. Finally, a generalized topology optimization approach is proposed for sorbent scaffolding structures to further improve system water output while reducing power consumption and packing of atmospheric water harvesting devices.