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Due to water shortages in several places in the world, alternative water sources such as atmospheric water and greywater have been studied. Dew water harvesting by passive radiative cooling is an unconventional water source that is easy to use, install, and shows great potential in several places in the world. This paper aims to experimentally eval...
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... Da silva et al. [66] in 2022 studied and evaluated the potential of passive radiative cooling for dew water harvesting in Vicosa city, Minas Gerais, Brazil, using different materials as condensing surfaces. They utilized (OPUR), polypropylene, black plastic, packaging tape, and anodized aluminium. ...
Water scarcity is one of the most challenging problems that the world has ever faced. There are numerous methods to remedy the water crises. One is using atmospheric water harvesting (AWH) to provide water. So far, there is much research on the subject of AWH. However, there is still a lack of establishing an extensive comparison between different technologies and methods used to harvest atmospheric water. In this review, we provide details on the thermodynamic performance of the AWH system. The systems are categorized into both active and passive systems. Heat pumps, membranes, thermoelectric solar systems, and adsorption systems are some atmospheric harvesting technologies that will be thoroughly discussed. Based on the comparison that had been made, it was found that TEC systems are the best for small applications. In contrast, systems such as vapour recompression can meet great demands as they can be integrated with different types of energy, such as natural gas and biogas. Solar systems as passive systems can also be coupled with active systems to boost the efficiency of vapour recompres-sion systems and reduce energy consumption. Furthermore, this review will focus on recent development for each category, the utilization of different advanced materials, and the prospect and challenges associated with AWH.
Radiative cooling and low-emissivity coatings are promising strategies for building energy savings. Despite their potential, comprehensive assessments across diverse climate zones remain limited. This study addresses this gap by investigating the potential energy performance associated with these coatings in buildings at 250 locations worldwide, spanning all ASHRAE climate zones. To quantitatively assess the energy efficiency benefits, this study employs EnergyPlus simulations to analyse annual thermal energy needs in two-floor, single-family detached apartments with varying levels of thermal transmittance. Results indicate that radiative cooling coatings provide considerable energy-saving effects for most locations, including those with higher heating demands than cooling demands. For buildings with poor insulation, low-emissivity coatings provide substantial annual energy savings in over 74% of the case locations. Moreover, the study also assesses heating penalties due to overcooling effects, revealing that these are generally less critical than the cooling energy savings in most climate zones. Furthermore, a strong linear correlation was found between yearly energy savings and the annual average outdoor temperature for each coating type in zones 0 to 6. The insights from this study have broad implications for the applicability of radiative cooling and low-emissivity coatings in new constructions and existing building retrofits across various climate zones.
Water scarcity is a major global challenge, with 2.3 billion people living in water-stressed countries and the potential for 700 million people to be displaced by 2030 due to widespread water scarcity. The increasing effects of climate change and overpopulation are exacerbating the problem, particularly in arid and remote regions. One potential solution is the harvesting of atmospheric water, which is estimated to be a vast source of freshwater at 12,900 km3. This study aims to provide a comprehensive and up-to-date review of the latest research in the field of atmospheric water harvesting systems. The purpose of this review is to present the various types of harvested water, the use of solar energy, the methods of gathering it, and the mathematical models used in the literature. The paper has covered numerous types of atmospheric water harvesting techniques, including harvesting dew and fog. In addition, the paper has also discussed water harvesting technologies that rely on sorbent materials. The primary focus of the paper is to present recent advances in water harvesting systems, such as dehumidifying, condensing, vapor compression refrigeration cycles (VCRCs), thermoelectric coolers (TECs), air conditioning units, fuel cells, and integrated systems. The paper aims to provide a comprehensive understanding of the latest developments in atmospheric water harvesting systems. The paper also presents an assessment of the efficiency and effectiveness of these water harvesting systems. The paper concludes by comparing various approaches to provide accurate descriptive information regarding the amount of water harvested. Additionally, the article proposes suggestions to enhance current water harvesting systems and outlines potential future initiatives.
Hypothesis:
Biphilic surfaces, namely surfaces comprising hydrophilic areas with a (super)hydrophobic background, are used in nature and engineering for controlled dropwise condensation and liquid transport. These, however, are highly dependent on the surface temperature and subcooling.
Experiments:
Here, biphilic surfaces were cooled inside a rotatable environmental chamber under controlled humidity. The condensation dynamics on the surface was quantified, depending on the subcooling, and compared to uniform superhydrophobic (USH) surfaces. Rates of condensation and transport were analyzed in terms of droplet number and size, covered area and fluid volume over several length scales. Specifically, from microscale condensation to macroscale droplet roll-off.
Findings:
Four phases of condensation were identified: a) initial nucleation, b) droplets on single patches, c) droplets covering adjacent patches and d) multi-patch droplets. Only the latter become mobile and roll off the surface. Cooling the surface to temperatures between T = 2-16 °C shows that lowering the temperature shortens some of the condensation parameters linearly, while others follow a power law, as expected from the theory of condensation. The temperature dependent condensation dynamics on (super)biphilic surfaces is faster in comparison to uniform superhydrophobic surfaces. Nevertheless, within time intervals of a few hours, droplets are mostly immobile. This sets guiding lines for using biphilic surfaces in applications such as water collection, heat transfer and separation processes. Generally, biphilic surfaces are suitable for applications in which fluids should be collected, concentrated and immobilized in specific areas.
Atmospheric water harvesting appears to be a potential way to address water scarcity, particularly in locations where liquid water is scarce. Rainwater harvesting (RWH) is a low-cost, easy approach that requires little special expertise or understanding and has numerous advantages in remote areas. The purpose of this chapter is to examine various types of sustainable atmospheric water harvesting techniques. AWH appears to be a potential methodology for decentralized water production, overcoming the difficulties of long-term conveyance and supply of fresh drinking water in remote areas. Structural designs of innovative materials enable moisture harvesters to have desirable characteristics including high water uptake, durable recyclability, and easy collection of water, accelerating the next generation development of AWH. In this chapter, we first show the sorption mechanism for moisture-harvesting materials, including absorption and adsorption, and then review essential needs and moisture harvester design concepts. The development of an atmospheric water harvester that can generate water irrespective of geographical location, humidity level, low cost, and can be manufactured using local materials is the primary goal of all methods.
