An atmospheric water harvesting system based on the "Optimal Harvesting Window" design for worldwide water production.

Atmospheric water harvesting (AWH) is a promising solution to the water shortage problem. Current sorption-based AWH (SAWH) systems seldom obtain both wide climatic adaptability and high energy efficiency due to the lack of thermodynamic optimization. To achieve the ideal harvesting circulation in SAWH systems, the "optimal harvesting window" (OHW) design based on thermodynamic analysis was first proposed and validated by our prototype. The "OHW" theory indicates the water production rate and energy efficiency could be improved by properly reducing the adsorption temperature. As the humidity increases, the optimal adsorption temperature should be closer to the dew point of the environment. Experimental results revealed that, loaded with 3 kg widely adopted silica gel, the daily water production could reach 5.76-17.64 L/d with ultrahigh energy efficiency of 0.46-1.5 L/kWh. This prototype could also achieve optimal performance in wide climatic conditions in terms of 13-35 °C and 18%-72% RH. Lastly, the performance of photovoltaic (PV)-driven SAWH was evaluated. Results showed that a 1 m2 PV panel could generate 0.66-2 L water per day in Shanghai throughout the year, the highest in opening literature. Notably, this work introduces a promising concept that can help achieve large-scale, ultra-fast, energy-efficient AWH worldwide.

Exceptional water production yield enabled by batch-processed portable water harvester in semi-arid climate.

Sorption-based atmospheric water harvesting has the potential to realize water production anytime, anywhere, but reaching a hundred-gram high water yield in semi-arid climates is still challenging, although state-of-the-art sorbents have been used. Here, we report a portable and modularized water harvester with scalable, low-cost, and lightweight LiCl-based hygroscopic composite (Li-SHC) sorbents. Li-SHC achieves water uptake capacity of 1.18, 1.79, and 2.93 g g-1 at 15%, 30%, and 60% RH, respectively. Importantly, considering the large mismatch between water capture and release rates, a rationally designed batch processing mode is proposed to pursue maximum water yield in a single diurnal cycle. Together with the advanced thermal design, the water harvester shows an exceptional water yield of 311.69 g day-1 and 1.09 g gsorbent-1 day-1 in the semi-arid climate with the extremely low RH of ~15%, demonstrating the adaptability and possibility of achieving large-scale and reliable water production in real scenarios.

An encapsulation protocol of salt-based composite sorbents for atmospheric water harvesting.

Sorption-based atmospheric water harvesting (SAWH) is a feasible and sustainable approach to address water scarcity issues. Featuring the high affinity of hygroscopic salts with water vapor, salt-based composite sorbents have been widely used. However, the risk of salt solution leakage is still challenging. In this protocol, we introduce a porous waterproof and moisture-permeable membrane encapsulation technique to develop salt-based sorbents. The high salt content composites (HSCC-Ex) exhibit remarkably high salt content of 80 wt % without the risk of leakage. For complete details on the use and execution of this protocol, please refer to Shan et al. (2021).

Viability of a practical multicyclic sorption-based water harvester with improved water yield.

Sorption-based atmospheric water harvesting (SAWH) has emerged as an attractive way to relieve water scarcity. However, the daily water yield of currently reported SAWH devices remains low to satisfy the rising demand for drinking water. The sorption and desorption kinetics, long-term stability and especially facile scaling-fabrication of adsorbents and scaled-up device implementation have become the bottleneck to such large-scale SAWH application. To overcome these challenges, an air-cooled SAWH device was fabricated to investigate its atmospheric water harvesting (AWH) performance under real island climate and its feasibility of multicyclic operation. Under monocyclic operation, the device demonstrated the superior water productivity as much as 3.9 kg day-1, or 0.39 kgwater kgadsorbent-1 day-1, at 31 °C and 70% RH, with a thermal efficiency of 25.4% (desorption at 94 °C). The SAWH device demonstrated successful water production through 2 adsorption-desorption cycles within one day, with increased thermal efficiency to as high as 32.2% and increased water harvesting performance up to 0.42 kgwater kgadsorbent-1 day-1 by 20-90%. This is the first demonstration in multicyclic SAWH at large scales, holding the promise of large-scale and practical water supply in island areas while opening up new applications such as indoor dehumidification.