Thermodynamic limits of atmospheric water harvesting with temperature-dependent adsorption

Adsorption-based atmospheric water harvesting (AWH) has vast potential for addressing global water shortage. Despite innovations in adsorbent materials, fundamental understanding of the physical processes involved in the AWH cycle and how material properties impact the theoretical limits of AWH is lacking. Here, we develop a generalized thermodynamic framework to elucidate the interplay between adsorbent properties and operating conditions for optimal AWH performance. Our analysis considers the temperature dependence of adsorption, which is critical but has largely been overlooked in past work. Using metal-organic framework (MOF) as an example, we show that the peak energy efficiencies of single-stage and dual-stage AWH devices, after considering temperature-dependent adsorption, increased by 30% and 100%, respectively, compared with previous studies. Moreover, in contrast to common understanding, we show that the adsorption enthalpy of MOFs can also be optimized to further improve the peak energy efficiency by 40%. This work bridges an important knowledge gap between adsorbent materials development and device design, providing insight toward high-performance adsorption-based AWH technologies. (C)2022 Author(s).

Automated summary

This study develops a generalized thermodynamic framework to elucidate the interplay between adsorbent properties and operating conditions for optimal performance of adsorption-based atmospheric water harvesting (AWH). It shows that considering temperature-dependent adsorption and optimizing the adsorption enthalpy can significantly improve the energy efficiency of AWH devices, using metal-organic frameworks (MOFs) as an example.