Ferroelectric Resonator—An Energy-Efficient Alternative to Heat for Water Extraction

Many communities worldwide experience a shortage of freshwater resources, which severely inhibits their land development and creates harsh humanitarian conditions for their populations. There is a need for atmospheric water harvesting (AWH) technologies that can operate in arid or semi-arid climates or in regions where large-scale installations are impractical for economic or security reasons. However, the state-of-the-art technology has prohibitively high energy consumption due to the high heat of water desorption from AWH materials. We present a novel approach to extracting liquid water from atmospheric water harvesting hydrogels (AWGs) using a 1.5W ferroelectric resonator. Our results show that this method is at least ~5x more energy-efficient compared to the current state-of-the-art, which predominantly relies on heating-induced evaporation. Using commercially available ferroelectric polycrystalline material, we designed, prototyped, and tested a lab-made resonator with a capacitance of 3000 pF, which simultaneously induces mechanical strain and Joule heating in AWGs under an AC voltage. Our work demonstrates that the resonator can achieve quick and efficient water release from polyacrylamide (PAM) AWGs synthesized in our lab, which incorporate lithium (Li) and chloride ions (Cl) as essential elements for their ability to adsorb water molecules from the atmosphere. Further, a complex electronic sensor system was used to sense the mechanical wave produced by the actuator that transmitted through the PAM-LiCl, allowing us to effectively study the influence of moduli and thickness of AWGs to be used with our resonator for effective water extraction. Based on the recent thermodynamic models of sorption-based atmospheric water production with AWGs, the lowest amount of energy recorded so far is 22.5 MJ/kg, whereas our proposed system demonstrated an exceptional efficiency of 4.8 and 5.25 MJ/kg for extracting water from HG-M and PAM-LiCl, representing a paradigm shift in the field of water extraction from AWGs.