Progress and Expectation of Atmospheric Water Harvesting

Tu, Yaodong; Wang, Ruzhu; Zhang, Yannan; Wang, Jiayun

doi:10.1016/j.joule.2018.07.015

Cited by 535 publications

(380 citation statements)

References 101 publications

(168 reference statements)

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“…Thus, any efforts that increase access to water in these rural or remote areas will dramatically improves the life quality of human beings. Recently, there is a renewed interest to harvest atmospheric water using sorption methods . While solid sorbents, such as anhydrous salt, hybrid hydrogel, silica gel, zeolite, activated alumina, clay, and metal–organic frameworks, have been heavily investigated for water harvesting, liquid sorbents with high capability of sorption also have many other advantages in terms of durability, system continuity, and cost .…”

Section: Methodsmentioning

confidence: 99%

An Interfacial Solar Heating Assisted Liquid Sorbent Atmospheric Water Generator

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Harvesting water from air is a promising strategy for fresh‐water production, and it is particularly desirable for areas that lack direct access to clean water. While high‐concentration liquid sorbent is well‐known for high sorption, it has not been widely used for atmospheric water collection, being primarily limited by the difficulty in desorption. Interfacial solar heating based on a salt‐resistant GO‐based aerogel is now shown to enable a high‐concentration liquid sorbent (CaCl2 50 wt % solution) based atmospheric water generator. Fresh water (2.89 kg m−2 day−1) can be produced at about 70 % relative humidity, with only solar energy input and energy efficiency of desorption as high as 66.9 %. This low‐cost and effective approach provides an attractive pathway to extract water from air, to relieve the thirst of arid, land‐locked, and other areas where fresh water is scarce.

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Section: Methodsmentioning

confidence: 99%

An Interfacial Solar Heating Assisted Liquid Sorbent Atmospheric Water Generator

et al. 2019

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“…In this context, hygroscopic materials based on surface water adsorption, such as molecular sieves, silica gels, and polymeric desiccants, can serve as the moisture absorber over a wide range of RH . However, the hygroscopic materials designed for moisture capturing exhibit strong interaction with water that significantly hinders the water releasing, blunting their opportunity to be used as atmospheric water harvesters …”

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confidence: 99%

Super Moisture‐Absorbent Gels for All‐Weather Atmospheric Water Harvesting

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demonstrated the possibility of directly collecting liquid water from air with the assistance of water condensation at ultrahigh relative humidity (RH = 100%, e.g., fog capture and dew collection). [3][4][5][6][7][8] Due to the dependence of RH on the temperature of the air, such a process requires either periodic temperature drop or artificial cooling systems to raise the RH to be supersaturated. [9] A recent report presents an AWH material functioning at low RH levels down to 20% to harvest moisture (water vapor) from air, enabling the moisture as a promising water source for potential next-generation AWH systems. [10] In view of the seasonal and climatic variation, the RH of the droughty region (such as the Namib Desert) varies between 30% and 90% for most of the years. [3,11] Since such modest RH (at given temperature and air pressure) indicates a relatively large water reservoir in the air, the highly efficient AWH toward this "rich ore" of water, which, however, remains elusive, is vital to both fundamental research and practical applications. In this context, hygroscopic materials based on surface water adsorption, such as molecular sieves, silica gels, and polymeric desiccants, can serve as the moisture absorber over a wide range of RH. [12][13][14] However, the hygroscopic materials designed for moisture capturing exhibit strong interaction with water that significantly hinders the water releasing, blunting their opportunity to be used as atmospheric water harvesters. [15,16] In line with the design of super water-absorbent gels, which are capable of absorbing tens of times its own weight in liquid water, [17,18] we present here a super moisture-absorbent gel (SMAG) that synergistically combines the moisture-absorbing hygroscopic polymer with the water-storing hydrophilic gel, which substantially outperforms other AWH materials. We demonstrate a rationally designed hybrid gel that integrates the hygroscopic chloride-doped polypyrrole (PPy-Cl) and the poly(Nisopropylacrylamide) (poly-NIPAM) with switchable hydrophilicity. [19][20][21] Such an SMAG realizes the polymeric-network-enabled moisture capturing, rather than active-surface-based vapor adsorption as in other AWH materials, and hence exhibits highly efficient AWH in broad humidity range. Moreover, to explore the potential application, we further demonstrate the outdoor experiments by a scalable SMAG prototype with low-cost accessories to simulate the AWH in the natural environment.The critical steps of SMAG-based AWH are (I) water capturing and (II) water releasing. As shown in Figure 1a, the Atmospheric water harvesting (AWH)-producing fresh water via collecting moisture from air-enables sustainable water delivery without geographical and hydrologic limitations. However, the fundamental design principle to prepare materials that can convert the water vapor in the air to collectible liquid water is still mostly unknown. Here, a super moisture-absorbent gel, which is composed of hygroscopic polypyrrole chloride penetrating in hydrophilicityswitchabl...

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“…With increasing population and degrading environment, freshwater scarcity is becoming a major global challenge . As atmospheric water is estimated to be ≈10% of all fresh water on earth, water harvesting from air is attracting significant attention with several strategies such as fog water capture and dewing collection . Recently, solar‐driven atmospheric water generator based on a sequential adsorption–desorption process is emerging as a promising option.…”

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confidence: 99%

An Interfacial Solar‐Driven Atmospheric Water Generator Based on a Liquid Sorbent with Simultaneous Adsorption–Desorption

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atmospheric water at night, desorbs under the sunlight to generate vapor, which condenses into liquid water (Figure 1a). For example, Kim et al. [11] demonstrated that with metal-organic framework (MOF) materials as solid sorbent, 1.2 kg m −2 d −1 of water production can be achieved. William et al. [22] utilized 30% calcium chloride (CaCl 2 ) solution as liquid sorbent to get a total evaporated water of 2.32 kg m −2 d −1 . In most if not all the previous studies, the adsorption and desorption processes are separated and sequential steps, which happen at night and daytime, respectively ( Figure 1a). Desorption is considered as the bottleneck of the entire process particularly for liquid sorbents, because of two main reasons. First, conventional solar heating method heats up the significant volume of water, while desorption typically happens at interface. As a result, part of input solar energy is wasted to increase temperature of bulk solution, rather than breaking interaction force between sorbent and water molecules directly to promote water evaporation. Hence, it leads to inefficient energy utilization and insufficient energy to drive desorption. Second, in most of previous atmospheric water generators, as the adsorption and desorption processes are sequential, there will be no water supplement during daytime desorption. Consequentially, water content in the sorbents gradually decreases during desorption, which decreases the driving force of the process. As a result, in typical atmospheric water generator, the water desorption rate drops very quickly (Figure 1b), ultimately causing incomplete desorption and limited water production.Recently, interfacial solar heating with high solar energy utilization efficiency has been widely applied for enhancing evaporation in various fields, such as desalination, wastewater treatment, and power generation. [23][24][25][26][27][28] Evaporation rate over 1.8 kg m −2 h −1 based on interfacial solar heating has been reported by several groups. [29][30][31][32][33][34][35][36][37][38] Herein, we demonstrate that combining tailored interfacial solar absorbers with ionic-liquid-based sorbents can enable interfacial solar-driven atmospheric water generator (ISAWG). With effective desorption and a simultaneous adsorption-desorption process, it can maintain high desorption rate and increased water production each day. Water scarcity is one of the greatest challenges facing human society.Because of the abundant amount of water present in the atmosphere, there are significant efforts to harvest water from air. Particularly, solar-driven atmospheric water generators based on sequential adsorption-desorption processes are attracting much attention. However, incomplete daytime desorption is the limiting factor for final water production, as the rate of water desorption typically decreases very quickly with decreased water content in the sorbents. Hereby combining tailored interfacial solar absorbers with an ionicliquid-based sorbent, an atmospheric water generator with a simultaneous ads...

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Progress and Expectation of Atmospheric Water Harvesting

Cited by 535 publications

References 101 publications

An Interfacial Solar Heating Assisted Liquid Sorbent Atmospheric Water Generator

An Interfacial Solar Heating Assisted Liquid Sorbent Atmospheric Water Generator

Super Moisture‐Absorbent Gels for All‐Weather Atmospheric Water Harvesting

An Interfacial Solar‐Driven Atmospheric Water Generator Based on a Liquid Sorbent with Simultaneous Adsorption–Desorption

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