Innovative energy-efficient desiccant-based atmospheric-water-harvesting system for sustainable freshwater production: Numerical investigation and experimental validation

Atmospheric water harvesting is a promising decentralized source of freshwater. Yet, its adoption is limited by the high energy demand of desiccant regeneration and the substantial thermodynamic irreversibility in current systems, resulting in elevated entropy generation and poor specific energy consumption. To address this challenge, this study proposes a heat-pump-assisted, zero-liquid-discharge atmospheric water-harvesting system that integrates liquid desiccant absorption with a closed-loop regeneration cycle and a heat-and-mass-recovery exchanger. A key novelty of the configuration is the introduction of a single-point air extraction and injection strategy, which achieves thermodynamic balancing by aligning temperature gradients and reducing local enthalpy pinch, yielding significant energy savings. A comprehensive mathematical model is developed incorporating temperature–enthalpy balancing for both zero- and single-extraction configurations. The model is validated against experimental data, showing strong agreement. Results demonstrate that single air extraction substantially enhances system performance by lowering thermodynamic irreversibility. At a zero enthalpy pinch, the specific energy consumption decreases from approximately 280 kJ kg⁻¹ of freshwater in the zero-extraction configuration to about 114 kJ kg⁻¹ in the single-extraction configuration, an improvement of 59 %. Even at moderate pinch values, the single-extraction configuration consistently outperforms the baseline case, with benefits diminishing only beyond a critical pinch of around 46 kJ kg⁻¹.