Dew Water Research Articles

All-day freshwater harvesting enabled by designing benzoxazine molecule with intrinsic photothermal conversion and radiation cooling ability

The importance of clean water resources for human health and economic development cannot be overlooked. Providing a way for fully passive all-day freshwater harvesting presents a significant challenge. Herein, we propose a strategy for all-day freshwater harvesting passively through a freestanding Janus film which combining solar-driven interfacial desalination during day time and dew water generation driven by passive radiative cooling at night. Specifically, the core of the strategy was a new bio-based benzoxazine which containing high-infrared emittance in the atmospheric window and the resultant cured black freestanding film owns a steady high light absorbance in the whole range of the solar irradiation wavelength. The home-made device made by the Janus film achieved a drinkable freshwater collection efficiency of 90.9 % when desalinating seawater under 1 sun illumination and achieved a dew water collection rate of 68.36 g m−2 day−1 at night. Moreover, the film has an excellent antibacterial effect, which ensures the quality of water collection and enhances the service life. Combining the advantages of bio-based raw materials, a simple fabrication process and scalability of the film, the all-day freshwater collection system makes a promising solution to alleviate freshwater shortage in many arid regions, islands and even boats sailing on the sea.

A techno-economic review of direct air capture of moisture processes: sustainable versus energy-intensive methods

AbstractOne of the biggest challenges that the world faces today is the availability of fresh and potable water in arid, semi-arid, and deprived regions. This is a challenge that concerns not only economic development but also social development spanning several UN SDGs. This article presents a detailed critical and systematic review of the technologies for producing industrial and potable water. Emphasis is made on direct air capture (DAC) methods as the next frontier in sustainable water production against the backdrop of traditional energy intensive methods such as desalination. Comparisons using a variety of techno-economic, scale, geographic, and environmental metrics are carried out. While market reports suggest that investments and market value of DAC technologies will continuously rise, these data only extend the next 5–10 years. However, using this data, a projection was made by the authors on various scenarios leading to 2050. At 2030, best projections fall short of UN SDG 6 predictions for a four-fold increase (from 2020 levels) required to sustain populations. The review notes that DAC has the potential to be an attractive solution for the current water crisis (in some cases drought) experienced in various regions on earth. The report finds that while several moisture DAC technologies (e.g., fog and dew water harvesting) are currently being developed, they are only being implemented on small scales around the world—with huge implications for arid and deprived regions of the world.

Condensation of water on PDMS-coated copper surfaces for fresh water harvesting

With an increased need to solve fresh water scarcity for humanity in many places around the world, dew water harvesting is one promising approach to improve the situation. While condensation from humid air has been a research topic for many years, it is still unclear how surface wettability influences the condensation efficiency and the fresh water harvest. In this work, we contribute to bridging this knowledge gap by comparing the condensation efficiency of PDMS-coated hydrophobic and uncoated hydrophilic surfaces. We characterize the humid air velocity field to enable comparability of the present results on condensation efficiency with the results gained at other conditions. In addition, the surface wetting behavior prior to and after the condensation experiment is investigated to analyze the PDMS-coating longevity and allow to draw conclusions on their suitability for long term use in condensation applications.

Study of the relative humidity effects on the water condensation performance of adsorption-based atmospheric water harvesting using passive radiative condensers

Adsorption-based atmospheric water harvesting (ABAWH) and passive radiative condensers are two examples of dew water collection. The application of passive radiative condensers to ABAWH has recently been demonstrated. However, ABAWH prefers high relative humidity (RH) for higher water uptake by adsorbents, while radiative condensers favor low RH for higher radiative cooling power, so there exists a desired RH for the water harvesting system under different conditions. However, this has not been previously studied. Therefore, we pioneer the development of a numerical model to obtain the desired RH for the water harvesting system and determine optimum operating parameters for maximum water production under different conditions. The adsorption isotherms are fit based on experimental results, and the effect of RH on radiative cooling power is mathematically predicted via cloud-cover fraction. Based on the numerical results, the desired RH ranges from 20 % to 29 % for 200 g MIL-101-Cr (HF) under certain conditions. Compared to other factors, the radiative condensation emitter and climate have a greater influence on the water condensation rate. Overall, this work provides guidelines on the design and setting of in-situ large-scale applications of ABAWH systems using passive radiative condensers for the greatest decentralized freshwater condensation performance under specific weather conditions.

Dew Water of Tamarisk Leafs (Salt Cedar) for Treating Warts Infection in Libya

Warts are caused by Human papiloma virus which causes a skin infection in all ages, it is un-convenient, if not treated by using the relevant medicine. Tamarisk is a plant commonly known as Salt cedar or, (Athal in Arabic region), which belongs to the Tamaricaece species, the presence of high content of phytochemical compounds like polyphenolics and flavonoids, is a potential source of antioxidant, anti-inflammatory and antiproliferative properties, that seems to have secrete medication effect on warts infection. A study to dew water of tamarisk leafs effect on warts infection have showed magic results, seven cases used dew water as remedy irregularly once per day for four to seven times per month, all cases totally healed from warts infection and responded positively 100% to the use of tamarisk leafs dew water.

Understanding inland fog and dew dynamics for assessing potential non-rainfall water use in the Atacama

In (semi-)arid regions, harvesting fog and dew can become a complementary solution to traditional water supply. In the Atacama region, a territory of key and water-dependent economic activities, both fog and dew are driven by the advection of marine moisture from the Pacific. Still, little is described regarding the dynamics and water potential of these events. In this study, we analyze the spatiotemporal variability of fog and dew in the Atacama Desert to assess the potential of non-rainfall atmospheric water harvesting. Our research strategy combines three methods to achieve a comprehensive understanding of these phenomena: a satellite-spatial analysis of fog and low cloud frequencies; a thermodynamic characterization of the fog cloud vertical structure; and an observational analysis of fog and dew water collection. Our findings reveal that fog is a regular phenomenon in the area, occurring from 3% to 20% of the year. We estimate that fog cloud reaches 50 km inland and up to ∼1100 m ASL, covering a vast territory where it can be harvested. Fog and dew represent 72% and 28% of the total collected atmospheric water (∼0.2 L m−2 day−1). Both fog and dew represent a complementary natural water source with multiple uses for local industries.

Application of membrane electrode assembly for water hydrogen isotope exchange

Hydrogen isotope separation will be important for future hydrogen energy applications. The materials used in polymer electrolyte fuel cells (PEFCs), such as the hydrophobic support and Pt catalyst, are essentially the same to those used in the conventional isotope-separation method of water hydrogen chemical exchange. Hereby, deuterium (D) separation was performed with a PEFC. The separation was improved with increasing the water vapor and temperature. D was enriched into the dew water in the cell. The quantities of D conversion from the gas through the vapor to the dew water was measured. The conversion values were less than the simulated ones. This was attributed to the vapor pressure drop and the wetted catalyst surface by the water condensation.

Plastic foil micro-grooved by embossing enhances dew collection without aging effects

Low-tech, radiative, and recyclable plastic foil is considered for the passive collection of dew water. Fashioning micro-grooves at their surface by hot embossing improves by a large factor the collection of even tiny water drops. We show that this improvement is conserved under harsh outdoor conditions. The ability of the micro-grooved foil to collect condensed water is measured by the latency time (tl) to collect the first drop at the bottom of a vertical substrate. Compared to the same smooth foil, tl is smaller for the micro-grooved foil by an order of magnitude. Under severe outdoor conditions (dust storm, heat waves) the properties of the micro-grooved foil are preserved after 6 months, whereas the collection properties of the smooth foil have decreased by 50%. The basic reason is the insensitivity of the water collection mode to the evolution of surface wetting and roughness properties. Such a low-cost, scalable, and robust material should find applications in passive water harvesting devices to supply supplementary fresh water in regions where water is, or is becoming, a scarce resource.

Surfaces with modified morphology and wettability arrangement: a potential medium for water harvesting in desertification areas

Abstract The cost of water transport for irrigating drought-endurable plants in desertification areas makes it important to develop other water sources. Research shows that freshwater produced by dewing could satisfy the water requirement during germination of desert plants, therefore, functional materials that promote dew formation provide solutions for reduction of plant irrigation costs in desertification regions. In this review, feasibility of utilizing trace irrigation for ensuring survival of desert plants has been demonstrated. The technologies of preparing water harvesting materials with modified microstructure and wettability arrangement have been introduced, it has been shown that surface embedded with a bump array which has counter wettability compared with its plane section is a common morphology adopted by current works. After comparing climates in desertification regions with those in dewing chambers, it has been found that currently, the expected values of dew productivities of most water harvesting materials in deserted areas will not be as efficient as they performed in experiments due to low relative humidity. However, hydrophobic surface with submicron scale hydrophilic spherical cavity array produced by nanosphere lithography has shown reliable prospects in reducing the energy barrier of heterogeneous nucleation and thus become a more potential medium in dew water production.

Dew benefits on alpine grasslands are cancelled out by combined heatwave and drought stress.

Increasing frequencies of heatwaves combined with simultaneous drought stress in Europe threaten the ecosystem water and carbon budgets of alpine grasslands. Dew as an additional water source can promote ecosystem carbon assimilation. It is known that grassland ecosystems keep high evapotranspiration as long as soil water is available. However, it is rarely being investigated whether dew can mitigate the impact of such extreme climatic events on grassland ecosystem carbon and water exchange. Here we use stable isotopes in meteoric waters and leaf sugars, eddy covariance fluxes for H2O vapor and CO2, in combination with meteorological and plant physiological measurements, to investigate the combined effect of dew and heat-drought stress on plant water status and net ecosystem production (NEP) in an alpine grassland (2000m elevation) during the June 2019 European heatwave. Before the heatwave, enhanced NEP in the early morning hours can be attributed to leaf wetting by dew. However, dew benefits on NEP were cancelled out by the heatwave, due to the minor contribution of dew in leaf water. Heat-induced reduction in NEP was intensified by the combined effect of drought stress. The recovery of NEP after the peak of the heatwave could be linked to the refilling of plant tissues during nighttime. Among-genera differences of plant water status affected by dew and heat-drought stress can be attributed to differences in their foliar dew water uptake, and their reliance on soil moisture or the impact of the atmospheric evaporative demand. Our results indicate that dew influence on alpine grassland ecosystems varies according to the environmental stress and plant physiology.

Physical and Chemical Characteristics of Dew and Rain in North-West Africa with Focus on Morocco: Mapping Past and Future Evolution (2005–2100)

In the context of global warming and a reduction in fresh water availability, this study presents the evolution of dew, rain and evapotranspiration in the North-West (NW) of Africa. This study is followed by a chemical analysis of dew and rain data in a representative site. The time periods are concerned with the years 2005–2020 using existing data, and years 2020–2100 using the low and high emissions representative concentration pathway scenarios RCP 2.6/8.5 from the coordinated regional climate downscaling experiment database. A continuous decrease in rain precipitation is observed, on the order of −14 mm·decade−1 for the more credible scenario RCP 8.5. The amplitude is maximum on the coast and on the foothills of Atlas. A clear decrease in dew yields (up to 7%) is also observed along a NW/SE axis. It is strongly correlated with a corresponding decrease in relative humidity. Chemical dew and rain data in the representative site of Mirleft correspond to the major cations of Na+ > Ca2+ > Mg2+ > K+, similar to local spring water. The concentrations in rain are about two times less than in dew water. Ionic concentrations are compatible with the World Health Organization standards. The seasonal variations of the ionic concentrations in dew and rain follow a volume dilution dependence. In the future, the expected diminution in dew and rain volumes according to the RCPs 2.6 and 8.5 should increase the dew and rain ionic concentrations.

Atmospheric Corrosion Evolution of Carbon Steel AISI 1020 along a Longitude Transect in the Atacama Desert

Carbon steel AISI 1020 was exposed to environmental conditions along a transect of the Atacama Desert to gather experimental evidence to identify the local atmospheric mechanism that triggers corrosion through a buildup of water layer formation on the metal surface in addition to corrosion evolution. Coupons initially left in selected sites were periodically collected to determine weight loss and surface attributes by scanning electron microscopy and X-ray diffraction. In addition, meteorological conditions were measured in addition to a fog water collector in one site. During the study period, the predominant conditions were the absence of rain, clear skies, and large daily oscillations in temperature and relative humidity. The evidence indicates a water film formation on a metal surface either from a vertical water flux as fog water droplets and/or by the dew water harvesting mechanism. The uptakes of oxygen and chlorides during the corrosion process were highest in the coastal site P0 and gradually decreased with the increasing distance from the coast. This is attributed to both humidity and saline marine fog intrusion from the coast. The oxide layer evolved to form a compact layer with main constituents of lepidocrocite, goethite, and lesser amounts of akageneite. The corrosion depth can be modelled by a simple power function d=AtB with B < 1, indicating a deceleration process.

New approach towards mitigating photovoltaic panels soiling by dew flowing.

Soiling has a crucial importance regarding its impact mainly for countries that have high soiling levels, dust storms, water scarcity and a great solar energy potential as the case of Morocco. Soiling mitigation is therefore mostly required during spring, due to higher pollen concentration, and summer, due to the lack of heavy precipitation. In this work, systematic measurements of soiling ratio were made in Rabat, city of north-western Morocco, during almost 1year. Soiling has been evaluated considering the effect of dual-axis tracking that was compared to photovoltaic (PV) on fixed structure. A soiling rate of about 0.22%/day has been found for static PV while only 0.1% was found for PV on tracker. An additional approach of cleaning has been proposed in this paper which aims to use dew water. Using glass samples that were exposed to real environmental conditions, similar to the exposure conditions of PV panels, the soiling ratio was determined. At sunrise time, the subsequent change of the glass sample, from the horizontal position at night into the position of 30° tilt angle during the day, is performed to promote dew flow by the force of gravity acting on the droplets of dew. It has been found that relying only on the change of tilt angle, the average soiling losses were only 3.8% compared with 11.8% for fixed PV. This approach can reduce soiling similarly to solar trackers.

Molecular Insights into Dissolved Organic Matter in Natural Dew Water: Biogrime Films on Leaf Surfaces

Dew water serves as a temporary reservoir of dissolved organic molecules that are released in the morning when the dew evaporates. Many locations allow for direct sunlight on the dew water in the morning, raising the possibility for photolysis-driven chemical reactions. The majority of prior works looking at dew water chemical composition has targeted freshly deposited dew on clean surfaces like Teflon. However, the dissolved organic material in dew is a mixture of compounds deposited during the night, as well as water-soluble compounds already present on the surface. Here, we analyzed six separate dew or frost water samples collected off grass and bush leaf surfaces in Southeast Virginia in the fall of 2020 and found evidence for a water-soluble surface grime layer that we term biogrime. The chemical composition and photoactivity of the mixtures were probed using Fourier transform ion cyclotron resonance mass spectrometry, offline-aerosol mass spectrometry, and UV/vis spectroscopy. Complex organic mixtures were found in all the samples with a total of ∼9600 identified molecular formulae containing C, H, N, O, S, and P. Many samples had strong absorption in the visible region, and all showed an initially rapid photodecay. The composition varied between samples with possible sources including plant guttation and microbial waste as well as deposition of atmospheric organic aerosol particles, soil particles, and fog droplets. The composition of organic molecules, combined with their photoactivity, suggests that dew water may be a complex source for water-soluble gases as it evaporates.

Ecological cleaning of PV panels by exploitation of dew water in Morocco

This work presents an ecological solution for cleaning of photovoltaic (PV) modules and a continuity of our first experience. It consists on using the dew water formed on the surface of the front glass. The study site is in Rabat city in the Northwest of Morocco, at the RDI (Research, Development and Innovation) Solar Energy Platform of ENS. In order to examine the effect of the angle change combined with the formation of dew water, and consequently on the cleaning of PV modules, systematic measurements of soiling ratio were made. The experiments were performed on glass plates that were exposed in real outdoor conditions. The soiling ratio was calculated by measuring the transmitted and received irradiance by the glass. At approximately sunrise, the subsequent permutation of the glass from the horizontal position to a 30° tilt angle promotes the dew droplets flow. The efficiency of cleaning is then investigated. A comparison of the soiling losses of fixed glass and variable glass with dew water flow was presented. It was found that the soiling losses for fixed glass averaged 9.3% during the exposure period while variable glass only marked 3.3%. In other words, the losses due to soiling for the fixed glass generate three times the losses compared to a variable glass with cleaning using dew water.

Oiling low temperature separation process for dehydration and de-hydrocarbon of natural gas and practical application

In order to reach the specification of water and hydrocarbon dew point, most of the water and C3 and heavier hydrocarbons need to be removed from natural gas. Low Temperature Separation (LTS) process by throttling expansion or refrigeration is commonly employed for natural gas dehydration and de-hydrocarbon as the most economical method. In case of some special natural gas which contains small quantity of the wax (mainly C16+ components), wax is easily deposited in the throttling facilities that leads the blockage of internals of low temperature separator and affects safety operation. Oiling LTS process, a novel process for this kind of special natural gas, is investigated in this work. The oil is injected into the natural gas to reduce the wax precipitation temperature and thus to avoid wax blockage. It is a kind of improvement and innovation process based on conventional treatment ones. According to the simulation analysis and practical application for a natural gas processing plant in Aksu, China, the new process presents good performance. Also, it is found that the best injection point is at the inlet pipe of raw gas pre-cooler and the optimal injecting stream is from the three-phase separator. Also, the injection oil flowrate is determined by refrigerating temperature and the concentration of wax. Meanwhile, the detailed economic analysis of oiling LTS process was involved. Comparing the conventional process, its adding investment is around 423,583$ accounting on 5% total capital cost of this unit. However, from the comprehensive aspects, this optimized process presents a good economic benefit.

Effective substrate emissivity during dew water condensation

Dew water condensation is due to the radiative cooling of a surface and is hence promoted on surfaces with high emissivity in the IR spectrum. The search for surfaces with enhanced radiative properties is usually carried out without considering the contribution of water condensation. On a condensing substrate, however, water droplets can occupy more than 55 % of the surface. Given the high emissivity of water (∼ 0.98), condensed water is thus expected to modify the condensation efficiency. The present study aims to investigate the interplay between water condensation and mean surface emissivity. Radiative cooling experiments in a humid air environment are performed using two substrates of contrasted emissivities (0.88 and 0.05). Although the condensation yield is initially larger on the high emissivity substrate, after a transient the condensation rate appears essentially the same for both substrates. A simple geometrical model taking into account the surface wetting properties reveals, in addition to the expected effect of droplet surface coverage, the existence of a threshold in drop thickness where water droplets effectively contribute to the radiative cooling process. The results are of conceptual and practical importance and can be generalized to any process involving vapor condensation induced by radiative cooling.

How Different Are Fog Collection and Dew Water Harvesting on Surfaces with Different Wetting Behaviors?

As the clean water shortage becomes a serious problem for mankind, atmospheric water harvesting has emerged as a viable solution. Two main approaches to collect water from the atmosphere exist: the first is to capture it from fog, whereas the second is through condensation of vapor on surfaces with a temperature below the dew point. The water collection mechanism in these two modes is completely different. In this work, we develop a deeper understanding of the effect of surface wettability on gravity-assisted atmospheric water harvesting and a comparative study of the two collection modes (fog and dew). First, we present theoretical estimates for the maximum water mass available in each mode and introduce an efficiency factor η which enables the direct comparison among surfaces in different setups and modes. Then we fabricate a series of micronanostructured surfaces with different surface wetting properties from hydrophilic to superhydrophobic. Our results demonstrate that drop mobility, derived from the surface superhydrophobic properties and micronanotopography, is the most important factor affecting fog collection: superhydrophobic surfaces show 40-65% higher fog collection rates compared to flat hydrophilic surfaces, with the more mobile among superhydrophobic surfaces (hysteresis 2°, and air-liquid fraction fA-L > 0.9) showing higher water collection. On the other hand, dew harvesting efficiency depends on the combination of drop mobility and nucleation rate, with superhydrophobic surfaces exhibiting 40% higher water collection rate compared to the flat hydrophilic or hydrophobic surfaces due to their low hysteresis as well as high surface area available for nucleation.

Generalized nighttime radiative deficits

We derive a general, tilt-dependent, nighttime, radiative deficit model with an eye towards improved dew collection. The model incorporates atmospheric/environmental incoming radiation, a linear precipitable water vapor transmittance function dependent on local meteo data and the influence of near-horizon obstacles. A brief discussion of cloud cover is given. The model is then used more specifically to predict radiative deficits for an ideal blackbody emitter in an environment with an isotropic temperature. Knowing the tilt angle, near-horizon obstacles and local meteo-data, it is then possible to estimate the radiative deficit of a given emitter. We consider errors resulting from the assumption that the ground and obstacles are at the same temperature as the air. We also analyze the errors arising from the linear precipitable water vapor transmittance function by comparing the results against high-resolution, full-spectrum Modtran® data Modtran, 2021. We show that for typical tilt angles, the isotropic temperature model is a reasonable approximation as long as the above-horizon environmental heating is small. We believe these results will be broadly valuable for the field of radiative cooling where a general radiative treatment has yet to be made and in particular the field of dew water harvesting.

Foliar water uptake of four shrub species in a semi-arid desert

Dew water plays an important role in supporting biological processes in desert ecosystems. Although some mechanisms underlying how plants survive in water-limited environments have been investigated, the water-use strategies of most desert plants remain unclear. We investigated whether foliar uptake of dew water occurs in four dominant shrub species (Artemisia ordosica, Hedysarum mongolicum, Salix psammophila, and Caragana korshinskii), in the Mu Us Desert of northern China. A fluorescent tracing experiment indicated that all four species absorbed water via leaf trichomes and cuticles, and A. ordosica also absorbed water via the stomata. A dew water exposure experiment and isotopic tracing revealed that water entered the leaves and stems of the four species, thereby enhancing their water potential. The relative contribution of dew water to the total water in the leaves of A. ordosica, H. mongolicum, S. psammophila, and C. korshinskii was 20.0 ± 7.0%, 8.4 ± 6.4%, 7.8 ± 1.9%, 3.1 ± 2.3%, respectively. The results demonstrated that all four species had the capacity to absorb water by their leaves, and the absorbed water could be transported to the stems. Our findings suggest that foliar water uptake may be one of the survival mechanisms by shrubs in the desert environment.