Thermodynamic evaluation of advanced adsorbents for thermally-driven atmospheric water harvesting system in diverse climatic conditions.

In the context of freshwater scarcity, the current research aims to evaluate silica-gel, zeolite, ionogel, and metalorganic framework (MOF) based four types of advanced adsorbents for thermally-driven adsorption-based atmospheric water harvesting (AWH) system. Thermodynamic modeling framework is executed for performance evaluation of studied adsorbents by means of water production potential (WPP), energy consumption (EC), and thermal efficiency (TE) with respect to different operating conditions like ambient/adsorption temperature (Tamb/ads)/relative humidity (RHamb/ads) and desorption T (Tdes)/RH (RHdes). According to results, ionogel and MOF-based adsorbents observed maximum WPP of 1.28 kg/kg/cycle and 0.95 kg/kg/cycle, respectively at Tamb/ ads of 25 ◦C, Tdes of 100 ◦C and RHdes of 20 %. Consequently, the EC computed as 4350.91 kJ/kg/cycle and 4650.67 kJ/kg/cycle with TE of 0.52 and 0.49, respectively. Keeping in view optimized operating conditions, the studied adsorbents are further evaluated for five major cities of Pakistan and South Africa having diverse climatic conditions (arid, semi-arid and humid subtropical). Average WPP of 7.10 L/kg/day and 19.85 L/kg/day is observed by ionogel and MOF, respectively throughout the year with EC of 4647.49 kJ/kg/cycle, and 4331.86 kJ/kg/cycle as well as TE of 0.49 and 0.51, respectively. This research underscores feasibility of advanced adsorbents in diverse climatic conditions from thermodynamic point of view and presents valuable insights on integrating low-grade thermal energy options for the AWH systems. Moreover, the integration of AWH systems could be a potential option in building façades and green roofs for water-resilient urban development in water stressed regions.