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Dew plant for bottling water
... Outdoor experiments on radiative cooling surfaces for dew collection have been widely performed since the 90's [4,5,6,7]. Here, we aim to develop their indoor counterpart, with the idea of getting rid of the outdoor disadvantages (weather variations, duration and cost of experiments). To our knowledge, indoor radiative devices have received very little attention, except more than 50 years ago and nearly exclusively from biologists. ...
... The flux is measured and controlled by the flowmeter (10). Radiative heat exchange between the dew collector and the cold source is performed by reflection on mirrors (7). The chamber (4) is separated from the cold source (1) by an IR transparent double windows (6). ...
... Note that during a 10 hours experiment, a total condensed-water volume of v ∼ = 0.5 L.m −2 would be obtained. As a comparison outdoor dew yield (for one night) is reported to range from 0.12 L.m −2 [40] in Ajaccio (France) to 0.6 L.m −2 [7] in Kothara (India). Our experiment thus produces an amount of dew comparable to natural dew condensation. ...
We describe a radiative cooling chamber which reproduces in the laboratory radiative cooling and subsequent dew formation. Based on radiative exchange with a cold source (at a temperature of nearly -80 °C), which acts as a cold black body, cooling power of at least 50 W.m⁻² is achieved. Radiative exchange is quantitively estimated. This original device permits to study under controlled air temperature and humidity the formation of dew on any system (material, biological) for which contact cooling is inefficient, and in particular investigate the influence of radiative and wetting surface properties on dew yield. It is applicable to the study of dew itself and its effects on plants and small animals, as well as dew atmospheric chemistry, and more generally of any natural radiative cooling application.
... Such decreases in fog frequency and dew yield will undoubtedly negatively affect nonrainfall water harvesting in these environments. Therefore, it is paramount that nonrainfall harvesters adopt designs and materials, for example, nanotechnology and biomimicry that will result in higher water yields per nonrainfall water event Park et al., 2013;Sharan et al., 2017), ensuring viability even under the threat of global climate change. At the same time, a few studies have indicated chemical and biological characteristics of nonrainfall water that may be of concern to public health. ...
... Therefore, fog harvesting technologies could benefit from the use of more efficient materials specifically designed for this purpose and this could increase yields by as much as fivefold (Park et al., 2013). Similarly, dew could also benefit from advancements in material science and collector designs developed specifically for passive dew collection (Beysens, 2018;Sharan et al., 2017). For example, origami-shaped roofs could increase dew yield efficiency by as much as 400% compared to planar surfaces for low yields (<0.02 ...
... However, according to Sharan et al. (2011), the cost of dew water per liter that had undergone treatment (0.07 US$/L) was still a third of the cost of market price bottled water (0.22US/L) in the Kutch region of Western India, and when rain was factored in because of the dual use of the equipment, the cost dropped to 0.006-0.0075 US$/L (Sharan et al., 2011;Sharan et al., 2017). Meanwhile, in Chile, fog provided better quality potable water at 0.0011-0.0017 ...
Abstract Fog and dew are often viewed as economic nuisances causing significant financial losses in the transportation industry and agricultural sector. However, they are also critical components of the hydrological cycle, especially in water scarce environments. Water scarcity is one of the major threats to mankind in the 21st century, and this can be due to development pressures, pollution, and/or expanding populations. In water scarce environments, fog and dew represent potentially exploitable ancillary water resources that could ameliorate the water scarce situation, if efficiently harvested. However, two important issues are often overlooked in relation to fog and dew harvesting and potability. First, current fog and dew harvesting technologies are low yielding with great potential for improvements. Second and more importantly, the potability of these water resources is often based on simple analyses that often omit trace metal and biological analyses. The few studies that report trace metal or biological measurements suggest elevated trace metal concentrations or biological contamination that could be of concern to public health. We discuss the potential for fog and dew harvesting technologies and the need for trace metal and biological analyses of these waters before use.
... Dew is an important hydrological input to many ecosystems especially in dry regions, and dew frequency could even exceed rain during extreme drought (Jacobs et al., 2006;Kaseke et al., 2017;Kidron et al., 2011;Stone, 1963;Uclés et al., 2015;Wang et al., 2017;Wang et al., 2022). The temperature of the substrate where the dew forms is lower than that of the ambient air due to the radiative cooling, and dew occurs when the temperature reaches a dew point (Sharan et al., 2017). Dew can provide up to 63% of plant water needs in certain environments (Hill et al., 2015). ...
... Previous studies show that there are mainly three sources of water vapour responsible for dew formation including from lower atmosphere, soil evaporation, and transpiration (Deser et al., 2017;Sharan et al., 2017;Wen et al., 2012). The water vapour in the lower atmosphere is the main source (Wen et al., 2012). ...
... (i) Thermal behavior of the radiative material and the insulation material, including its thermal conductivity, thermal expansion, density, heat capacity and emissivity in the atmospheric window whenever known (see Table 1). For simplicity, the radiative and insulation materials have been taken the same (Styrofoam) with emissivity 0.83 as in Sharan et al. (2017) simulation. (ii) Radiative cooling power, which depends on the condenser geometry and also on atmospheric conditions (condenser and sky emissivity, air temperature T a , cloud cover N). (iii) Incoming diffusive and convective (free or forced) heat exchange with air, which depends on wind speed V, wind speed direction and condenser geometry. ...
... Average for atmosphere, see Beysens (2018). (b) Value used in the simulation by Sharan et al. (2017). Heat transfer from the air to the surface of the condenser occurs by forced convection. ...
Dew condensation is the result of cooling by radiative deficit between a substrate and the atmosphere. Dew yield can be enhanced in hollow structures like hollow cones where the influence of wind is lowered. Corrugation increases the local tilt angle with horizontal and makes dew drop grow faster on edges, then drops detach sooner and act as natural wipers. However, corrugation increases the heat exchange with surrounding local air, which may reduce cooling.
In order to evaluate these effects on cooling and dew yield, a corrugated, W-shaped hollow cone is compared to the same, smooth structure (S-cone) by Computational Fluid Dynamics. Two softwares were used: Ansys CFX for a pre-study concerning detailed aerodynamics where the computational domain is modeled to obtain a fully developed wind profile assuming an unobstructed inlet and COMSOL Multiphysics for aerodynamics coupled with heat flux, including radiative exchange surface-to-sky and surface-to-surface. Local temperatures can be obtained, which can be related to the dew yield. Turbulence is seen at all speeds but stagnation of the flow is also observed, which limits the convective heat exchanges and facilitates dew formation. At low wind speed, convective heat exchange is similar for both smooth and corrugated surfaces, and corrugation increases cooling. At higher air flow velocities, convective heat exchange is larger for the W-cone but cooling is only slightly smaller than found on the S-cone. Corrugated W-cone should thus give larger yield than the corresponding smooth S-cone.
... In semi-arid areas, dew is one of the fundamental sources of water for the vegetation growth (Wang et al., 2017). Research focused on dew, as an alternative source of potable and service water for agriculture and land restoration, is emerging increasingly topical (Agam and Berliner, 2006;Beysens et al., 2003;Kogan and Trahtman, 2003;Li, 2002;Maestre-Valero et al., 2015;Nikolayev et al., 1996;Pan et al., 2010;Schemenauer and Cereceda, 1992;Sharan et al., 2017). The dew formation on dew collectors is caused by condensation of water vapour. ...
... The selection of the time period for the detailed analysis of the dump temperature conditions is based on the assumption of dew formation at the time of the highest air humidity and the lowest surface temperature at dew collector at night and towards morning (Sharan et al., 2017). The specific time from 2 a.m. to 8 a.m. was chosen based on the air humidity analysis of the weather station Ulaanbaatar (Weather Underground, 2019a) in the growing season 2015 (Fig. 4) combined with the percentage of cases where appropriate temperature conditions for dew formation were found at both dumps. ...
Waste rock dumps in the aftermath of pegmatite mining enable the growth of healthy populations of Larix sibirica in, for the forest unsuitable semi-arid steppe habitat, the Khentii Mountains, Mongolia. Trees can thrive in such extreme habitats due to water vapour condensation and adsorption in the topsoil of a dump. During the growing season 2015–2017, continual measurement of thermal regime (hourly) was carried out at the depths of 10, 30 and 60 cm in the dumps and surrounding steppes. At the depth of 10 cm, temperatures (up to 40% of cases) enabling dew formation in dumps, in the time period of the highest possible air humidity (2 a.m. to 8 a.m.) were confirmed there. The suitable temperature conditions to form dew were found primarily at the beginning of the growing season characterized by a low precipitation. Later in the growing season with the following increasing precipitation, the temperature potential of dumps for dew formation decreased continuously. The cross-correlation indicated active exchange of heat between the atmosphere and the dump up to the depth of 30 cm. The outcomes further indicate that water vapour adsorption shall contribute significantly to the moisture regime of dumps and the effective porosity of sandy soils of dumps is likely to form ideal conditions for it. The construction thickness of the cover soil material between the depths of 30 and 60 cm with the predefined physico-chemical properties can be recommended to augment the potential of the dew yield in future projects. Effective water vapour condensation and adsorption may support success of landscape afforestation or reclamation of mining areas in arid or semi-arid conditions.
... A yearly average of 300 L m −2 of rain can be collected. 32 This reveals the limited added value of dew collection even in areas where rain falls only during a few days in a year. ...
... 37 Temporal water storage is needed to equilibrate supply and demand when using a dew, fog or even rainwater capturing approach. 32 Conductive heat loss to the underground is an alternative way of cooling a condensation surface. In a device operating according to this principle, air is forced to enter an underground metal coil connected to a reservoir for collecting the condensate. ...
Extraction of water vapour from atmospheric air and condensing it to liquid water for human usage is an imaginative solution to the water scarcity problem. Atmospheric water vapour is a large and readily accessible fresh water source able to fulfil human water needs. Many systems that draw water vapour from the air with water collecting surfaces, desiccant materials such as zeolites, silica gels, MOFs, polymers and salts and aids such as membranes have been proposed. Much progress has been made in increasing water harvesting efficiency, reducing cost and improving applicability especially in the extreme atmospheric conditions of arid regions. But all these systems are energy intensive and this energy demand for water production is an important element of the water-energy nexus. In this paper the intrinsic energy requirements of water vapour capturing processes in different atmospheric conditions are quantified as the specific water yield (L kW⁻¹ h⁻¹). Distinction is made between passive systems that use natural phenomena like solar energy directly, and active systems with human transformation of the energy vector. The generation of thermoelectric energy involves water use and may even lead to overall water consumption instead of production. Technologies involving air cooling to provoke condensation of the water vapour reach specific water yields of 1–4 L kW⁻¹ h⁻¹ but their application is strongly dependent on atmospheric conditions. A specific water yield of 0.1–1 L kW⁻¹ h⁻¹ is commonly achieved for an ad/absorption–desorption cycle with a desiccant material. Depending on climate conditions, either passive systems with desiccants or active cooling of condensation surfaces is energy wise the optimum choice. The intrinsic energy requirements of atmospheric water harvesting are more than hundred times larger than seawater desalination. Fundamentally new concepts are needed to make atmospheric water an affordable fresh water source.
... The main disadvantage of fog collection is that the efficiency of the water flowing through the collector meshes is proportional to the amount of water reaching the collector gutter [39]. Two main factors affect the efficiency of collection based on surface [27]. (b) Hybrid Surfaces for Improved Dew Collection [29]. ...
Life is dependent on water. However, in terms of the potential effects, water scarcity is quickly emerging as one of the most critical problems in the world. To access more fresh water for drinking, sanitation, and irrigation, water can be harvested from different forms of water on earth. Atmospheric harvesting is the best alternative for producing fresh water for everyday life and reducing global water shortages. To date, many modern technologies have been introduced for this application, with several prototypes being demonstrated. Thus, this study explores the potential benefits of the current atmospheric water harvesting systems in terms of their modes, atmospheric conditions, and production rate and examines the key factors that affect the efficiency of atmospheric water harvesting, such as temperature and humidity. According to the studies, there has been a significant advancement in energy harvesting and conversion technology, along with atmospheric water harvesting, over the past few years, including new mechanisms and technical paths. However, there are still many obstacles; in particular, most of the technologies depend on outdoor conditions. In order to overcome this issue, new directions need to be investigated. Here, we discuss the principles, advantages, limitations, and potential applications of these technologies.
... Vapour-harvesting processes can be classified into passive and active. The processes that do not need an artificial energy input are defined passive [8], and an example of such an approach is represented by the radiative cooling, such as that employed in the dew plant described in ref. [26], where panels with a particular emissivity and geometry are installed in the open air. The temperature gradient, caused by irradiation, between the environmental air and the panel surfaces, permits vapour condensation. ...
The water crisis is currently affecting billions of people. To mitigate the issue, unconven-tional water sources should be taken into account. Among them, atmosphere is a promising possibility , but it is still considered a novel source, and more studies, based on real results concerning the behaviour of the Atmospheric/Air-to Water Generator (AWG) systems, also known as Atmospheric Water Harvesting (AWH) systems, are needed to prove the water extraction sustainability. The current research work describes the real application of an integrated AWG system, based on a thermo-dynamic reverse cycle, designed to extract water from air and take advantage of the other useful effects of the cycle at the same time. The integrated machine was placed in Dubai, in a worker village , and tested. The machine is able to provide, at the same time, with the same energy consumption , water, heating and cooling energy. On the basis of onsite measurements, calculations about the efficiencies, using the Water Energy Transformation (WET), plastic savings, due to bottled water avoidance, and economic sustainability were carried out. The work answers to research questions concerning the potentiality of integrated systems in Heating Ventilation Air Conditioning (HVAC) plants revamping, the economic sustainability of water extraction from air and the lack of tests on real AWG machines of thousand-litre production capability (large size).
... In this corollary, atmospheric moisture such as dew can be an important contributor to the water cycle and supplement the existing water sources in arid and semi-arid ago-ecologies, especially during the dry winter season (Tomaszkiewicz et al., 2016;Wu et al., 2018). Dew is a natural phenomenon and occurs when humid air condenses on an object and converts into liquid water (Sharan et al., 2017). It occurs in almost all the ecosystems, from arid to humid climate, and adds a considerable amount to the terrestrial water budget (Gerlein-Safdi et al., 2018;Tomaszkiewicz et al., 2017). ...
Dew is a non-conventional and additional source of moisture which can alter the plant water balance by reducing leaf temperature, suppressing transpiration through evaporative cooling, and enhanced leaf albedo and emissivity and thus help to improve agronomic productivity under arid and semi-arid agro-ecologies. However, the significant role of dew in enhancing the agronomic yields of crops is the most neglected aspect in both arid and semi-arid agro-ecosystems. This study is about the dew accumulation and its significant contribution in improving productivity of mustard (Brassica juncea L.) during the dry rabi season, especially under rainfed conditions. The average dew accumulation was 22.8% higher than the average seasonal rainfall. The grain yield of mustard was 1.5 and 1.8 t ha-1 under rainfed and irrigated condition, respectively which is acceptable because of the saving of inputs and production cost by Rs. 5000-6000 ha-1. Thus, dew has a scope to improve the yield of crops besides enhancing fallow land utilization and augmenting income of the farmers in medium deep black soils of arid and semi-arid regions of India.
... Previous studies reported various AWG systems using both active and passive techniques including fog harvesting, [16]- [18] dewing, [19] direct-air cooling, [20] and desiccant-based methods. [21]- [23] Fog harvesting and dewing, despite being widely studied and practically implemented as conventional technologies over the decades, [24] suffer from several limitations thermodynamically, climatically, and geographically. ...
Globally, multiple efforts are made to develop active atmospheric water generation (AWG) or atmospheric water extraction (AWE) systems, particularly using direct-air cooling technology to produce water from ambient air. However, this legacy technique is highly energy-intensive, it can only be operated when the local dew point is above the freezing point of water, allows bacteria to grow within the system, and does not scale to create enough water to offer solutions for most industries, services, or agriculture. Liquid desiccant-based AWG methods show promising performance advantages and offer a versatile approach to help address the thermodynamic, health risks, and geographic constraints currently encountered by conventional active AWG systems. In this study, we performed a techno-economic analysis of a liquid desiccant-based AWG system with a continuous operating style. An energy balance was performed on a single design point of AWG system configuration while using LiCl liquid desiccant loaded with multi-walled carbon nanotubes (MWCNTs). We showed that the MWCNTs can be doped in LiCl for effective heat transfer during water desorption, resulting in a lowering of the sensible heat load by ≈ 49% on the AWG system. We demonstrated that the specific energy consumption (SEC) can currently be obtained as low as 0.67 kWh/gal while changing the inlet desiccant stream concentration of MWCNTs-doped LiCl at given conditions. While the production cost of water (COW) showed a significant dependency over the region, the economic analysis revealed that the cost of water can be produced at a minimum selling price of $0.085 per gallon based on the 2021 annual average wholesale electricity cost of $0.125 per kWh in the U.S., thereby, providing a strong foundation for future research to meet the desirable and competitive water costs by 2026 but before 2031.
... Total water recoveries for MD and MDC for the three salts are shown in Fig. 6. At large scale, the water evaporated from the crystallizer would be captured using a low-energy condensate collection system [49,50], thus the evaporated water was included in the total water recovery reported. In all cases, higher total water recoveries were measured for the MDC system than for MD alone. ...
Membrane distillation crystallization (MDC) is a promising technique for treatment of inland desalination brines due to its ability to recover clean water and solid salts. The MDC system developed in this study used a six-tray cascading crystallizer with extended mesh surfaces to provide nucleation sites and support for crystal growth. Sodium chloride (NaCl), potassium chloride (KCl), and sodium nitrate (NaNO3) brines were used to investigate clean water and solid salt recovery using MDC, as well as brine volume reduction. When compared to MD alone, MDC achieved higher water and solid salt recovery under the same operating conditions, resulting in greater reductions in brine volume, while retaining >99.8% rejection for all three salt species. Solid salts were recovered from all three feed solutions, with NaNO3 feed solution, which has the strongest temperature-solubility relationship, having the highest yield (126.55 ± 6.65 g).
... where temperature is inside temperature of the j-surface and is the outside temperature. Heat exchange with air strongly depends on air flow configuration above the condensing surface, as seen in CFD simulations [34][35][36]. Typical values were 5-8 W.m 2 .K −1 for natural air convection and 20-30 W.m 2 .K −1 for forced air convection [37]. ...
The metal surfaces of a car exhibit favorable properties for the passive condensation of atmospheric water. Under certain nocturnal climatic conditions (high relative humidity, weak windspeed, and total nebulosity), dew is often observed on cars, and it is appropriate to ask the question of using a vehicle as a standard condenser for estimating the dew yield. In order to see whether cars can be used as reference dew condensers, we report a detailed study of radiative cooling and dew formation on cars in the presence of radiating obstacles and for various windspeeds. Measurements of temperature and condensed dew mass on different car parts (rooftop, front and back hoods, windshield, lateral and back windows, inside and outside air) are compared with the same data obtained on a horizontal, thermally isolated planar film. The paper concludes that heat transfer coefficients, evaluated from temperature and dew yield measurements, are found nearly independent of windspeed and tilt angles. Moreover, this work describes the relation between cooling and dew condensation with the presence or not of thermal isolation. This dependence varies with the surface tilt angle according to the angular dependence of the atmosphere radiation. This work also confirms that cars can be used to estimate the dew yields in a given site. A visual observation scale h = Kn, with h the dew yield (mm) and n = 0, 1 2, 3 an index, which depends whether dew forms or not on rooftop, windshield, and lateral windows, is successfully tested with 8 different cars in 5 sites with three different climates, using K = (0.067 ± 0.0036) mm.day−1.
... Dew water offers a potential renewable and complementary source of water for rainfed, arid and semiarid climate (Sharan et al., 2016). The water balance of plants can be altered by interference of dew droplets with the leaf energy balance, which leads to reduced leaf temperature and suppression of transpiration through evaporative cooling and increased leaf albedo and emissivity (Lakatos et al., 2012;Gerlein-Safdi et al., 2018). ...
In the present scenario of climate change, increasing demand and competition for
freshwater among agriculture and non-agricultural sectors drive our attention towards dew as
a supplementary source of water. Dew can be a significant substitute to overcome the
problem of water scarcity up to some extent, especially under rainfed agro-ecosystems.
Therefore, the present study was conducted at ICAR-Indian Institute of Soil and Water
Conservation, Research Centre, Kota (Rajasthan) to analyze and demonstrate the trend of
dewfall over the year, its frequency and total accumulation. The dew observations for a
period of 27 years (1993-94 to 2019-20) were collected with the help of dew gauge installed
in agro meteorology station at the research farm. Statistical analysis was performed to assess
any significant difference in dew deposition patterns in different months and years under
study. The highest annual dew deposition was 54.8 mm and the lowest was 14.8 mm. Linear
regression analysis revealed an upward and downward trend in the years under study but
statistically non-significant. The maximum dew deposition was recorded in the months of
December and January. Hence, an effort was made to assess the extent of dew accumulation
that could mitigate water deficiency and augment soil moisture for possible agronomic
exploitation in the future in rainfed, arid and semi-arid regions.
Keywords: Dew, Dew trend, Rainfed, Regression, South-eastern Rajasthan
... However, there has been recent renewed interest in dew as a supplemental water source (Muselli et al., 2002;Beysens et al., 2007;Sharan et al., 2011;Sharan, 2011;Tomaszkiewicz et al., 2015;Khalil et al., 2016) as our understanding of condenser physics (Nikolayev et al., 1996), radiative cooling (Head, 1959;Bliss, 1961;Nilsson et al., 1992;Hossain and Gu, 2016;Zeyghami et al., 2018;Zhou et al., 2018;Dong et al., 1961;Zhao et al., 2019), and dew formation (Beysens, 1995;Agam and Berliner, 2006) have improved, and high-yield materials have come to bear (Beysens et al., 2003;Maestre-Valero et al., 2011;Maestre-Valero et al., 2012;Chen et al., 2016;Zhai et al., 2017;Bintein et al., 2019;Bao et al., 2017;Guan et al., 2013;Al-Khayat et al., 2017). In an effort to optimize dew yields, many parameters have been studied including: wind speed (Clus et al., 2008;Muselli et al., 2009), angle of the collector (Kidron, 2005;Beysens et al., 2003), shape of the apparatus (Jacobs et al., 2008;Ziatdinov et al., 2019;Beysens et al., 2013;Kotzen, 2015;Beysens et al., 2021) and scaling of dew collectors (Carvajal et al., 2018;Sharan et al., 2017) to name a few. ...
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, YYYY. 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.
... Dew water harvesting by using passive radiative cooling provides excellent benefits over its simplicity of use and installation. In the last decades, studies have been conducted to maximize the amount of water collected by using passive radiative cooling with hydrophilic materials, which favors the condensation of water vapor (Sharan et al. 2017). Additionally, it is a technology that does not use active energy, and it can be used in different regions of the planet Sharan 2011;Khalil et al. 2015;Ernesto & Jasson 2016;Jarimi et al. 2020). ...
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 evaluate the dew yield through passive radiative cooling in Vicosa city, Minas Gerais, Brazil by using standard white plastic for dew harvesting, developed by the International Organization for Dew Utilization (OPUR), polypropylene plastic, black plastic, packaging tape, and anodized aluminum as condensing surfaces during two different periods. The polypropylene plastic and packing tape materials used in this present research have not been researched before in the literature. However, they have demonstrated potential for harvesting dew. As a result, the average water collected was, respectively, 0.151, 0.135, 0.140, 0.127, and 0.046 mm/night using the OPUR standard plastic, polypropylene plastic, black plastic, and packaging tape, and anodized aluminum as condensing surfaces. Although relatively small water volumes were harvested, this water should not be neglected since it can supplement the water demand for irrigation, human and animal consumption, among other uses in drought periods. HIGHLIGHTS
Water vapor can be harvested to supplement traditional water sources using low-cost materials.;
We analyzed two low-cost materials that have not been studied for dew harvesting yet.;
There is no statistically significant difference between the amount harvested by each low-cost material and the amount harvested by the OPUR standard plastic.;
... Dew formation, normally at night, is favored by windless and clear sky conditions when the temperature of the surface on which condensation occurs reaches the dew point temperature (Agam & Berliner, 2006). Although dewfall represents small amounts of liquid water compared to rainfall, in some regions, it may reach a maximum potential of 0.6 mm (0.6 L/m² or 6000 L/ ha) per night (Sharan et al., 2017). In dry environments (or in dry seasons as analyzed), dew can be the only liquid water source for sessile organisms and for species with low vagility, thus having a significant ecological importance for biodiversity. ...
The Brazilian Cerrado is a global biodiversity hotspot with notoriously high rates of native vegetation suppression and wildfires over the past three decades. As a result, climate change can already be detected at both local and regional scales. In this study, we used three different approaches based on independent datasets to investigate possible changes in the daytime and nighttime temperature and air humidity between the peak of the dry season and the beginning of the rainy season in the Brazilian Cerrado. Additionally, we evaluated the tendency of dew point depression, considering it as a proxy to assess impacts on biodiversity. Monthly increases of 2.2-4.0°C in the maximum temperatures and 2.4-2.8°C in the minimum temperatures between 1961 and 2019 were recorded, supported by all analyzed datasets which included direct observations, remote sensing and modeling data. The warming raised the vapor pressure deficit, and although we recorded an upward trend in absolute humidity, relative humidity has reduced by ~15%. If these tendencies are maintained, gradual air warming will make nightly cooling insufficient to reach the dew point in the early hours of the night. Therefore, it will progressively reduce both the amount and duration of nocturnal dewfall, which is the main source of water for numerous plants and animal species of the Brazilian Cerrado during the dry season. Through several examples, we hypothesize that these climate changes can have a high impact on biodiversity and potentially cause ecosystems to collapse. We emphasize that the effects of temperature and humidity on Cerrado ecosystems cannot be neglected and should be further explored from a land-use perspective.
... Dew water offers a potential renewable and complementary source of water for rainfed, arid and semiarid climate (Sharan et al., 2016). The water balance of plants can be altered by interference of dew droplets with the leaf energy balance, which leads to reduced leaf temperature and suppression of transpiration through evaporative cooling and increased leaf albedo and emissivity (Lakatos et al., 2012;Gerlein-Safdi et al., 2018). ...
... Their model could be used to predict dew formation at 15 other major cities in Morocco. Sharan et al. [44] described the construction and functioning of a combined rain and dew harvesting plant for drinking water. The design and evaluation were performed via CFD simulation, and the dew yield was calculated using meteorological data. ...
... A partir du stade 2 de la condensation, le prol moyen de concentration de la vapeur d'eau devient perpendiculaire à la surface (ux diusif (1.8) [21] Jerusalem, Israel 1 m 2 0.2 − 0.5 [21] Kothara, Inde 540 m 2 0.6 [93] Panandhro, Inde 850 m 2 0.3 [92] Paris, France 1 m 2 0.19 [20] Bisevo, Croatie 15.1 m 2 0.18 [31] En pratique les surfaces sont rarement complètement lisses. Une première conséquence est que l'angle de contact mesuré est compris dans un intervalle θ r < θ < θ a avec θ a l'angle d'avancée et θ r l'angle de reculée. ...
Ce travail est une contribution à l’amélioration de la condensation et de la collecte passive de l’eau de rosée. Dans une première partie, une surface traitée par sablage est utilisée pour la condensation en laboratoire. Sur cette surface rugueuse, refroidie par contact, les gouttes condensées se détachent plus vite que sur la surface non-traitée, et la collecte passive par gravité des gouttes est augmentée. Les expériences montrent que la combinaison du sablage et des effets de bord peut augmenter considérablement la collecte passive par gravité à partir d'un substrat. Des gains d'environ 30% par rapport au même support lisse sont obtenus. Dans une deuxième partie, un dispositif original de refroidissement radiatif en laboratoire est développé, qui réalise des échanges radiatifs entre un objet de petite taille et une source froide. Ce dispositif permet d’étudier de manière contrôlée l’influence des propriétés radiatives des matériaux sur les performances des condenseurs passifs de rosée. En environnement humide, la condensation est obtenue sur des objets de géométries variées, y compris des géométries peu compactes et/ou de faibles conductivités thermiques pour lesquelles le refroidissement par contact est peu efficace. Un résultat important a été obtenu par cette technique : l’émissivité de la surface de condensation ne joue un rôle important qu'au début de la condensation, puis la surface se couvre de gouttes condensées qui déterminent son émissivité globale. Un modèle simple des échanges radiatifs entre une goutte posée sur une surface plane et son environnement est proposé afin d'établir une expression de l'émissivité moyenne d'une surface couverte de gouttes.
... Total water recoveries for MD and MDC for the three salts are shown in Fig. 6. At large scale, the water evaporated from the crystallizer would be captured using a low-energy condensate collection system [49,50], thus the evaporated water was included in the total water recovery reported. In all cases, higher total water recoveries were measured for the MDC system than for MD alone. ...
This work investigates the process of Membrane Distillation-Crystallization (MDC) for treating inland brackish waters to maximize the clean water and salt recovery.
... The process of predicting the fog and its persistence limits the practical use of this design [12]. Among the alternative technologies, dew water collectors have always been one of the major candidates due to their low geographical constraints [13][14][15]. With the development of chillers, active condensers were designed as a replacement for dew collectors. ...
An office drinking water cooler is converted to a humidity absorption device. The reservoir-type evaporator of the water cooler is separated and a finned-tube evaporator is installed. A channel is installed at the inlet of the evaporator. A fan, a cool-mist humidifier, and a heater are installed inside this channel, where the amount of humidity and heat production can be adjusted. Several pressure gauges are installed at different locations of the cycle and monitor cycle performance while working. Pressure variations in different locations of the cycle are measured at various inlet air conditions. The MHI is defined as the ratio of condensation enthalpy to the total given heat. Changes of this index are evaluated by changing the input conditions. Results show that with increasing the air temperature, the condenser and evaporator pressure increases. Results of absorbed water in various MHIs show that with increasing this index, the amount of absorbed water increases. The graph of the absorbed water based on the MHI can be used to estimate the amount of water collected from this device under different climatic conditions. The amounts of collected water from this device for several different cities of Iran are presented. Results show that in high MHIs for a device with a quarter horsepower, the water production rate can reach to 250 g/h. Also, if the device is working continuously in these conditions, it can produce about 4 kg of water per day.
... Total water recoveries for MD and MDC for the three salts are shown in Fig. 6. At large scale, the water evaporated from the crystallizer would be captured using a low-energy condensate collection system [49,50], thus the evaporated water was included in the total water recovery reported. In all cases, higher total water recoveries were measured for the MDC system than for MD alone. ...
... On the other hand, dew condensers do it passively. They consist of arrangements of surfaces that at night cool below dew point causing condensation over them [8]. ...
Fog water is a valuable resource in places were fresh water is scarce and fog events occur frequently. Fog collectors (FCs) are the technology currently used for harvesting it. In this work we present an electrostatic method for achieving this. A radial electric field is generated between two electrodes which exerts electric forces over the fog droplets that guide them to a collection place. A prototype with a novel design was built and tested on laboratory and field conditions proving that the method works and even outperforms standard FCs with collection rates per unit cross-sectional area about 60% higher.
... With the advance of chillers, active condensers 24,44,45 were designed as an alternative method for dew collection that produces more water by using additional energy inputs. Early active dew condensers were developed in the 1930s, but rapid and wide innovations did not occur until the commercialization of mechanical refrigeration after the 1980s. ...
Even if people live in an arid desert, they know that plenty of water exists in the air they breathe. However, the reality tells us the atmospheric water cannot help to slake the world's thirst. Thus an important question occurs: what are the fundamental limits of atmospheric water harvesting that can be achieved in typical arid and semi-arid areas? Here, through a thorough review on the present advances of atmospheric water-harvesting technologies, we identify the achievements that have been acquired and evaluate the challenges and barriers that retard their applications. Lastly, we clarify our perspectives on how to search for a simple, scalable, yet cost-effective way to produce atmospheric water for the community and forecast the application of atmospheric water harvesting in evaporative cooling, such as electronic cooling, power plant cooling, and passive building cooling.
... Amongst the papers dealing with Water issues, the access to fresh water and its management in arid and semi-arid areas, where rain and dew water can have a significant impact as new sources of water, were investigated by Sharan et al. (2017). Urban factors affecting water consumption in Italy was studied by Romano et al. (2016). ...
Following the 2015 Paris Agreement, the main challenge for world economies nowadays is to commit themselves to long-term reforms aimed at increasing and promoting sustainable, inclusive and balanced development. An adequate response to this challenge will certainly require using the best available scientific knowledge and constant re-evaluation of the development process in light of the scientific findings. To ensure that the sciences are responsive to the emerging needs and to address sustainable development issues. This Virtual Special Issue of the Journal of Cleaner Production is dedicated to both Sustainable Development of Energy, Water and Environment Systems 2016 Conferences – 2nd South East European Sustainable Development of Energy, Water and Environment Systems Conference and 11th Sustainable Development of Energy, Water and Environment Systems Conference. The Virtual Special Issue is focused on four main fields: Energy issues, Water issues, Environmental engineering and management, and Sustainable engineering solutions and large-scale sustainability approaches. The division of selected papers follows the previous Journal of Cleaner Production Special Sections and Volumes dedicated to the Sustainable Development of Energy, Water and Environment Systems Conference series.
Arid regions are classified on the basis of severe lack of available water which further affects the growth as well as the development of flora, fauna, and human life. The idea of recovering water from atmosphere has remained quite a problem in arid regions. AWH defined as atmospheric water harvesting, is a prominent way to overcome water scarcity. It is considered as an alternative source of fresh water regardless of the physical conditions prevailing in a certain area. Various techniques are used to harvest atmospheric water that comprises adsorption-based technology, fog collector, atmospheric water generator and few other models in other to harvest atmospheric water. In this chapter, our focus will mainly be based on potential behind harvesting atmospheric water in arid regions and we will be going through different case studies to have in-depth knowledge and information regarding it.
Atmospheric water harvesting (AWH) has consistently emerged as a possible source of fresh water, especially in regions where water and energy are scarce. Harvesting water from ambient air has the potential to be largely powered by renewable energy sources. Renewable energy has demonstrated a greater potential to produce water in arid regions using adsorption-based atmospheric water harvesting (ABAWH). Adsorbent is the only component in the ABAWH process that converts ambient air or moisture to water. In this direction, metal–organic frameworks (MOFs) have recently emerged as effective AWH adsorbents. The chapter focuses on the development of MOF-based adsorbents with excellent adsorption performance. Various parameters, such as adsorption kinetics, climatic conditions, and adsorption–desorption rate, have been covered in this chapter. This chapter also looks at the current advancements in AWH technologies and achievements. It is expected that this chapter will provide the reader with challenges that have been identified that retard the potential practical application of MOFs in AWH technology.
Water production by underground condensation is a low-capacity water-gathering technology for hot, humid climates. Hot, humid air is routed to subterranean pipes where it is progressively cooled and the vapor within the pipes appears as water droplets on the pipe surface. The goal of this paper is to quantify the amount of water extracted in the condensation system of humid and hot air. The water produced from humid air in buried pipes in the ground at a 0.5 m depth with different lengths is evaluated using MATLAB software, and optimal pipe length is established. Numerical findings show that water production is about 1 kilogram per day. It has been investigated how air temperature, pipe material, soil temperature, air humidity, and input speed influence underground condensation water production. It has been determined that 20 meters is the optimal length of the pipe. According to studies, Sandstone soil can produce 86%more water than other types of soil. It is also revealed that copper pipes could improve efficiency by 31%. The impact of effective factors on the efficiency of the condensation system, such as intake air temperature and humidity, inlet air velocity, and soil temperature, has also been assessed.
Globally, multiple efforts are being made to develop active atmospheric water generation (AWG) or atmospheric water extraction (AWE) systems, particularly using direct air-cooling technology to produce water from ambient air. However, this legacy technique is highly energy-intensive; it can only be operated when the local dew point is above the freezing point of water, and does not scale to create enough water to offer solutions for most industries, services, or agriculture. Liquid-desiccant-based AWG methods show promising performance advantages, and offer a versatile approach to help address the thermodynamics, health risks, and geographic constraints currently encountered by conventional active AWG systems. In this study, we performed a techno-economic analysis of a liquid-desiccant-based AWG system with a continuous operating style. An energy balance was performed on a single design point of the AWG system configuration while using a LiCl liquid desiccant loaded with multiwalled carbon nanotubes (MWCNTs). We showed that the MWCNTs can be doped in LiCl for effective heat transfer during water desorption, resulting in lowering of the sensible heat load by ≈49% on the AWG system. We demonstrated that the specific energy consumption (SEC) can currently be obtained as low as 0.67 kWh per US gallon, while changing the inlet desiccant stream concentration of MWCNT-doped LiCl under the given conditions. While the production cost of water (COW) showed a significant regional dependency, economic analysis revealed that water can be produced at a minimum selling price of USD 0.085 per US gallon, based on the 2021 annual average wholesale electricity cost of USD 0.125 per kWh in the U.S.A., thereby providing a strong foundation for future research to meet desirable and competitive water costs by 2026, but before 2031.
The current climate emergency has already impacted life on Earth with increasingly extreme, prolonged, and frequent weather events. One of the most critical consequences is the progressive desertification of lands, leading to a scarcity of safe and sustainably sourced freshwater supplies. Water availability is entwined with regional economic and social benefits, as well as environmental and ecosystem security. Today, about 4.5 billion people have inadequate access to clean water, pushing to find alternative solutions for providing safe water to all. Localized atmospheric water harvesting (AWH) may represent an economical and efficient alternative, and some case studies already demonstrate its small-scale viability. Nonetheless, its large-scale applicability in urban environments and its related impacts and barriers are significantly under-explored.
This paper proposes a systematic review of the main AWH technologies from the literature. It evaluates their potential for application on building façade components by identifying the technology readiness level (TRL) and undertaking a Strengths-Weaknesses-Opportunities-Threats (SWOT) analysis. Results indicate that the currently available technologies, despite their infancy on the TRL scale, offer significant potential for application at the building scale. Future research should investigate the boundary conditions necessary for AWH technologies to work in urban environments to identify a roadmap for large-scale uptake from the construction industry.
In the context of global water scarcity, water vapor available in air is a non-negligible supplementary fresh water resource. Current and potential energetically passive procedures for improving atmospheric water harvesting (AWH) capabilities involve different strategies and dedicated materials, which are reviewed in this paper, from the perspective of morphology and wettability optimization, substrate cooling, and sorbent assistance. The advantages and limitations of different AWH strategies are respectively discussed, as well as their water harvesting performance. The various applications based on advanced AWH technologies are also demonstrated. A prospective concept of multifunctional water vapor harvesting panel based on promising cooling material, inspired by silicon-based solar energy panels, is finally proposed with a brief outlook of its advantages and challenges.
The maximizing daily freshwater yield on the ocean surface necessitates all‐day water harvesting technologies and materials. This is realizable by taking advantage of the natural sunlight and humid air, which can drive daytime solar desalination and nighttime fog collection, respectively. To this end, two types of hierarchically porous microneedle array structures, which demonstrate superior capabilities for efficient fog capturing and photothermal evaporation, respectively, are prepared. The gel‐forged microneedle arrays with Janus wettability are fabricated via a simple and controllable top‐down micro‐molding process on a porous platform, and porosity within microneedles is further achieved readily by additional freeze‐drying treatment. The developed microneedle structure shows an ultrahigh fog harvesting rate up to 30.5 kg m⁻² h⁻¹, enabling high flux water droplet harvesting from moisture during nighttime. In the daytime, a solar evaporation rate of 2.46 kg m⁻² h⁻¹ is realized due to the increased evaporative area of the porous microneedle arrays and enhanced photothermal conversion. By uniting these two water‐harvesting routes, a daily cycle can ideally deliver an overall water yield close to 200 kg m⁻², which will offer a promising solution for sustaining future low‐cost and decentralized clean water production.
The availability of freshwater is persistently changing, and the current trends indicate that it is declining very rapidly, both quantitatively and qualitatively around the globe. Therefore, the shortage of freshwater will pose the biggest threat to mankind, and hence, there is an urgent need to develop and demonstrate new and sustainable technologies to address the issue. Atmospheric water generation technologies, which generate water from the air, has been untapped so far and could be an emerging alternative to tackle this issue. However, these technologies have been energy-intensive, which actually limits their widespread deployment in the field. The performance of various technologies has been summarized and compared in terms of their important performance parameters, constraints and advancements. The technological solutions to some of the current issues, retarding the growth of these technology have also been identified and discussed. Further, it is found that the advancement of some of these technologies is still in the nascent stage, and could not emerge as an economically viable solution. Thus, there is immense scope to explore atmospheric water generation and transform it into a feasible futuristic solution to water scarcity. Therefore, this review aims to provide the technical insight to re-examine the available technologies, research gaps and scope for further advancements.
Water is indispensable for human survival. Freshwater scarcity and unsustainable water are the main growing concerns in the world. It is estimated that about 800 million people worldwide do not have basic access to drinking water and about 2.2 billion people do not have access to safe water supply. Southeast Asia is most likely to experience water scarcity and water demand as a result of climate change. Climate change and the increasing water demand that eventually contribute to water scarcity are focused upon here. For Southeast Asia to adapt to the adverse consequences of global climate change and the growing concern of environmental water demand, fog water harvesting is considered as the most promising method to overcome water scarcity or drought. Fog water collection technique is a passive, low maintenance, and sustainable option that can supply fresh drinking water to communities where fog is a common phenomenon. Fog water harvesting system involves the use of mesh nets to collect water as fog passes through them. Only minimal cost is required for the operation and maintenance. In conclusion, fog water harvesting seems to be a promising method that can be implemented to overcome water scarcity and water demand in Southeast Asia. Water scarcity is the main growing concern in the world. During prolonged drought seasons, fog‐to‐water is one close‐at‐hand freshwater resource. A pilot study on fog‐to‐water solutions in climate‐change hazard hotspots in Southeast Asia is provided. The outcome makes a significant difference to sparse populations in many arid regions specially the archipelago nations in Southeast Asia.
Underground condensation water production system is a low capacity water harvesting method that is suitable for hot and humid climate regions. In this method, the hot and humid airflow is directed to the buried pipes in the ground and, the air is gradually cooled down and the vapor contained therein appears as droplets of water on the pipe surface. The assessment of the amount of water extraction in the condensation system of hot and humid air is the main objective of this investigation. A computational code using MATLAB software is developed to evaluate the amount of water production from humid air in the buried pipes into the ground at a depth of 0.5 m with various lengths and obtain the optimal length of the pipe. Numerical results indicate that water production by considering the initial conditions in this study is about 1 kg per day. The influence of important and effective parameters in underground condensation water production system such as pipes material, air temperature, air humidity, soil temperature, input speed have been investigated. Also, the influence of effective parameters on the performance of the condensation system, including temperature and humidity of inlet air, soil temperature and inlet air velocity, have been evaluated.
Water scarcity is one of the greatest global challenges at this time. Significant efforts have been made to harvest water from the air, due to widely available water sources present in the atmosphere. Particularly, solar‐driven hygroscopic water harvesting based on the adsorption–desorption process has gained tremendous attention because of the abundance of solar energy in combination with substantial improvements in conversion efficiency enabled by advanced sorbents, improved photothermal materials, interfacial heating system designs, and thermal management in recent years. Here, recent developments in atmospheric water harvesting are discussed, with a focus on solar‐driven hygroscopic water harvesting. The diverse structural designs and engineering strategies that are being used to improve the rate of the water production, including the design principles for sorbents with high adsorption capacity, high‐efficiency light‐to‐heat conversion, optimization of thermal management, vapor condensation, and water collection, are also explored. The current challenges and future research opportunities are also discussed, providing a roadmap for the future development of solar‐driven hygroscopic water harvesting technology.
Atmospheric water harvesting (AWH) is emerging as a promising technique of water production in remote and isolated areas away from natural water resources. The present study describes potential of the AWH from low-humid regions under the climatic conditions of Hail city (27.64° N, 41.75° E) in Saudi Arabia. Trapezoidal prism solar still of 5-shelves is developed, where the shelves are filled with black cotton cloth bed saturated with calcium chloride solution. The solar still is opened during night hours, enabling the descant to absorb humidity from humid air (absorption process) and closed during day hours causing desorption of water under higher temperatures (regeneration process). The vapor condensates on a glass surface and is collected in a bottle. Under low-humid conditions of the Hail city, the desiccant balanced approximately at 48% saturation concentration. The water production of the device reaches 1.06 l/m2day by consuming 22.96 MJ solar energy/l of water with a cost of $0.055 per liter. The present study has demonstrated high potential of the AWH technique from low-humid regions up to 26.5%. The proposed device is standalone with promising performance, which needs neither the natural water resources nor the infrastructure. The device is suitable for remote and isolated small communities.
The purpose of compiling this manuscript is to draw attention of young researchers on portable devices that yield drinkable water. The various techniques for potable water collection include solar stills, water distiller/condenser from air using radiative technique or desiccant material, bio-sand filter and steam generation by solar absorber materials are discussed in detail. The main vital parameters like solar radiations, type of material used, thickness of glass cover and its inclination, type of filter, diameter in case of nanoparticles, depth of water, pH of water, evaporation rate are under considerations for determining the performance of unit. Conventional desalination processes are not enough to fulfil remote area water requirements, so the utilization of solar energy is perceived solution using portable devices. Subsequently economic analysis of portable device is also presented for determining the performance of unit.
For the first time and as alternative source of bootable water, water extraction from atmospheric air using tubular solar still was tested experimentally under extremely low humid air conditions (12%) of Hail city, Saudi Arabia (27.64 oN, 41.75 oE). A rectangular trough filled with black cotton cloth bed filled with calcium chloride desiccant was used. The device is equipped with a small air fan to circulate ambient air inside tube at night hours (absorption process). The absorption process was tested under 5 different air speed conditions (natural, 0.5, 1, 3 and 4 m/s). The fan removed and the tube sides closed during day hours causing evaporation of the water from desiccant solution, the vapour condensed on the inner tube surface (regeneration process) and extracted outside the device. The evaporated water was measured at the end of the regeneration process. Results revealed a maximum water production of 467 mL/m²day for 4 m/s air speed with 25% thermal efficiency, while the minimum production was 230 mL/m²day for natural air circulation with 12.2% thermal efficiency. The water production cost was US $0.4/L for natural air circulation and US $0.2/L for 4 m/s air speed. The present study proofed the feasibility of water extraction from low humid regions in desert places. The proposed device still needs more research effort to be mature enough. The proposed device can be used directly in desert places without any need for infrastructure.
Drought limits plants growth. In many parts of the world, crop productions depend on water availability. Seed germination is a sensitive and low water stage in plants. A pot experiment was designed to test the effect of dew-irrigation on seed germination percentage of fennel, flax, and fenugreek. Irrigation treatments included dew-irrigation and control (non-irrigation). Results showed that dew-irrigation increased seed germination compared to control. Treatment of dew-irrigation had seed germination of 92.7%, 78.7% and 63.5% for flax, fenugreek, and fennel, respectively. But none of the seeds of control treatment germinated. Among plants studied, flax which is a cold season plant had the highest percentage of germination by dew-irrigation, and the plants that are the most heat-sensitive, such as fenugreek and fennel, had the lowest germination percentage. Results of this experiment determined that the moisture content in the air is capable to provide the necessary moisture for seed germination of the plants studied. In conclusion, dew-irrigation, due to supply low water, is better to be used at stages with lower water requirement such as germination. The ability of water supply by dew-irrigation at whole plant stage can be studied at the next experiments.
This study characterized different polyethylene (PE) and polyvinyl chloride (PVC) plastic foil materials effectiveness for dew collection in arid field-conditions in Kenya. Dew yields were collected daily for one year. Ten dew collectors with four different plastic foils were setup in the experimental field. The cumulated dew yields ranged from 18.9 to 25.3 mm. The greatest cumulated dew yields were 25.3 mm (nightly mean 0.096 mm) and 24.3 mm (nightly mean 0.093) measured with PVC and OPUR coated collectors respectively. The lowest cumulated dew yields 18.9 mm (nightly mean 0.075 mm) and 19.1 mm (nightly mean 0.074 mm) were measured with PVC and PE coated collectors respectively. Dew provided a continuous water source during the dry season. The type of the surface material was not found to be a determining factor for the collected dew yield. The location of the collector at the experimental field had impact on the collected dew yields. We also compared harvested dew yields to measured meteorological parameters and calculated dew yields with the use of a diffusion model using the measured surface temperatures and coefficient of mass diffusion to evaluate the dew collecting potential under the prevailing conditions.
Dew harvesting can be a supplementary source of freshwater in semiarid and arid areas. Several experiments on small-scale dew condensers (usually of 1 m²) have been carried out in many places in the world; however, few experiments have been conducted on large-scale collectors integrated into buildings. This work aims to assess one year of dew water harvesting in Combarbalá (Chile) using a painted galvanised steel roof as collecting surface. The roof (36 m²) was coated with a high-infrared-emissivity paint containing aluminosilicate minerals (OPUR, France). Dew measurements were conducted daily from September 2014 to August 2015. The dew yield and its relationship with meteorological variables were analysed. The results show that despite the low nocturnal relative humidity throughout the year (average: 48%), dew collection occurred on 56.1% of the recorded days. The daily average collection rate was 1.9 L d¹, with a maximum of 15 L d¹. The maximum daily dew yield is correlated strongly with relative humidity and correlated weakly with air temperature and wind speed. Considering the same rooftop can collect dew and rain, it was estimated that over one year dew water could contribute to roughly 8.2% of the total water collected, considering both sources.
Due to climate change concerns, various environmental stresses and social inequality among the people, the welfare of mankind is increasingly being viewed through the prism of sustainable development. Sustainable development is a highly multi-disciplinary field of research that has been extensively studied during last two decades. Therefore, from the beginning of the 21st century, a series of Sustainable Development of Energy, Water and Environment Systems (SDEWES) Conferences were founded to address sustainable development issues. This Journal of Cleaner Production Special Volume (SV) is dedicated to the 10th SDEWES Conference. The SV is focused on three main fields that are of strategic importance to sustainable development: energy issues, water issues, and environmental engineering and management. The division of selected papers according to the named research fields was established following the previous Journal of Cleaner Production Special Sections and Volumes dedicated to the SDEWES Conferences. Therefore, this Special Volume builds upon the previously generated SDEWES knowledge base.
Over the last 20 years, dew harvesting has evolved to fruition due to a better understanding of its physics, thermodynamics, and the radiative cooling process of condensing substrates. Although resultant yields are relatively small, dew positions itself as a viable water resources supplement because it occurs naturally and frequently in many locations globally, particularly in the absence of precipitation or when more traditional water sources are subject to depletion. Moreover, dew water is generally potable, especially in rural locations, where it is most beneficial. This review summarizes dew harvesting research achievements to date including formation processes, collection in various environments, prediction models, water quality, and applications. The paper concludes with outlining existing gaps and future research needs to improve the understanding and performance of dew harvesting in the context of adaptation to climate change.
Dew water is water vapour that passively condenses from air. Once properly collected, it can provide a useful supplementary water resource for plants and humans. Its production can be significantly improved by using specific materials and particular geometry. In this context, new shapes for dew collectors are presented and their water yields are compared with those of a 1 m(2), 30 degrees, inclined planar condenser used as a standard. The experiments were carried out in Pessac (SW France), situated about 45 km from the Atlantic Ocean, during summer and fall 2009. In addition to conical shapes, which have 30 % larger yields than the planar reference condenser and whose functioning was simulated numerically, two new families of forms are considered: egg-box and origami types. The egg-box shape yields 9 % more water as compared to the reference planar condenser, a result nearly independent of the dew yield. In contrast, the origami shape gives yields 150 % larger than the reference planar condenser for events with high dew volumes and can show 400 % greater yields for low dew volumes. These results are analysed and discussed in terms of (i) radiative effects correlated with the angular variation of sky emissivity, (ii) heat losses by free and forced (wind) air convection and (iii) gravity water flow. General rules to increase dew collection are outlined.
This paper describes the development of dew harvesting systems for use in the semi-arid coastal region of northwest India. These systems were developed to ameliorate the drinking water problem in the region, especially for the people living near the coast where groundwater is of poor quality and surface sources are scarce. Although the amount of dew is much less (20-30 mm) than the rains (200-300 mm), it is a more consistent water source. Dew nights number approximately 100 while rainy days number 15-20. Dew occurs over a seven month period (October to April), while rain occurs over a four month period (June -September). Although engineered specifically to harvest dew, the designed systems also harvest rain, providing varying amounts of potable water throughout the year. A four-year R&D program led to development of three types of systems -condenser-on-roof (CoR), condenser-on-ground (CoG) and Roof-as-Condenser (RaC). The CoR and CoGs systems employ condensers made of plastic film insulated on the underside. CoRs are constructed over the roof of buildings while CoGs are constructed on open ground. The RaCs use the metal roof of buildings as the condenser itself. The CoR and CoGs gave higher output but required higher investment. The RaCs gave lower output but required only a small investment in collection and storage. Examples of working installations are presented. The benefits to the region, the learning accrued, and the partnerships created in the course of work are briefly discussed.
The world’s largest dew and rain collecting system, comprised of ridge-and-trough modules, was constructed in March 2006 at Panandhro in the semi-arid area of Kutch (NW India). The main goals were (i) to collect dew on a scale that could be beneficial to the local population (ii) to determine the efficiency of this new module shape, (iii) to determine whether results obtained from small measurement condensers can be projected to large condensers, (iv) to apply a computational fluid dynamic simulation to improve the condenser set-up. Preliminary studies performed with four standard plane condensers of 1 m2 surface area, inclined 30° from horizontal, identified Panandhro as a promising site. The cumulated dew water during 192 days was 12.6 mm with a maximum of 0.556 mm/night. A large dew condenser (850 m2 net total surface) was designed with 10 ridge-and-trough modules. The ridges are trapezoidal, 33 m long, 0.5 m wide at the top, 2.2 m wide at the base and sloping 30° from horizontal. The depth of the troughs between the ridges is 0.5 m. A 2.5 cm thick polystyrene foam rests on the surface as insulation with a radiative foil on top (similar to that developed by OPUR, see www.opur.fr).
The annual amount of dew input to the water budget in the midlatitudes is mostly neglected, possibly because direct dew measurements are very difficult and time-consuming. As the Netherlands has a very high frequency of dew events, a grassland area was selected to determine whether dew input could be significant. The study site is situated within the Wageningen University meteorological station. Dew measurement experiments were carried out in 2004. Data were used to verify a surface energy dew model, which was then applied to an 11-year data set. A mean annual dew amount of 37 mm was obtained with a standard deviation of 8 mm, while the mean annual precipitation was 830 mm with a standard deviation of 200 mm. Dew contributed about 4.5% of the mean annual precipitation. The average number of dew nights per year was 250 (70%) with a standard deviation of 25 nights. This frequency significantly affects leaf wetness and possible vegetation diseases.
There is a general need to determine dew yield in any place of the world. However, its determination requires systematic measurements that are not available everywhere. In addition, it depends on the particularities of the dew collector. A simple analytical formula valid for planar dew collectors is elaborated here. It is based on laboratory experiments where it is established that heat loss with surrounding air is the dominant parameter that limits dew condensation. A simple analytical formulation is then derived, which only needs cloud coverage, wind velocity, air and dew point temperature data to be collected, at least once in a day before sunrise. The formulation is tested in several places in the world with different climates. Agreement within typically 30% is found with dew measurements. Such an analytical relationship can thus provide a useful tool to obtain a worldwide estimation of the dew potential.
The arid, coastal region of northwest India is chronically short of drinking water. At the same time, measurements have shown the presence of significant dew resources. To access dew for human, the use of large condensers will be required. Mounting large condensers on frames is expensive in windy areas. One way to reduce the costs is to mount the condensers on roofs of large buildings-Condenser-on-Roof or (CoR). Many schools and warehouses provide such an opportunity. A project was accordingly carried out to demonstrate this. A 360 m 2 roof of a school was equipped with a special condensing foil similar to Nilsson' and OPUR' in village Sayara near the coast. Condensation does not occur on bare surfaces of reinforced concrete of which the roof was made. It was therefore, thermally isolated. The dew yield was measured during the dry season-October 2005 to May 2006. The objective was to determine the quantity of useful water that can be harvested and to compare it with yield from another large roof nearby in village Suthari, made of (un-insulated) galvanized iron sheets. The metal sheet itself was used as condenser without the foil. During the period, the cumulative dew yield from the school roof was 3107 L (8.6 mm). This value is nearly two times of that obtained on galvanized iron roof (4.7 mm). In addition, the use of thermal insulation led to reduced heat gain by the class rooms during the day, making these more comfortable. The yield from iron roof was less but so was the cost of installation which only required gutters. Both the examples indicate the potential of using existing roofs to make cost-effective dew harvesters.
PREFACE TO THE SECOND EDITION LIST OF SYMBOLS 1. SCOPE OF ENVIRONMENTAL PHYSICS 2. GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases 3. TRANSPORT LAWS General transfer equation Molecular transfer processes Diffusion coefficients Radiation laws 4. RADIATION ENVIRONMENT Solar radiation Terrestrial radiation Net radiation 5. MICROCLIMATOLOGY OF RADIATION (i) Interception Direct solar radiation Diffuse radiation Radiation in crop canopies 6. MICROCLIMATOLOGY OF RADIATION (ii) Absorption and reflection Radiative properties of natural materials Net radiation 7. MOMENTUM TRANSFER Boundary layers Wind profiles and drag on uniform surfaces Lodging and windthrow 8. HEAT TRANSFER Convection Non-dimensional groups Measurements of convection Conduction Insulation of animals 9. MASS TRANSFER (i) Gases and water vapour Non-dimensional groups Measurement of mass transfer Ventilation Mass transfer through pores Coats and clothing 10.MASS TRANSFER (ii) Particles Steady motion 11.STEADY STATE HEAT BALANCE (i) Water surfaces and vegetation Heat balance equation Heat balance of thermometers Heat balance of surfaces Developments from the Penman Equation 12.STEADY STATE HEAT BALANCE (ii) Animals Heat balance components The thermo-neutral diagram Specification of the environment Case studies 13.TRANSIENT HEAT BALANCE Time constant General cases Heat flow in soil 14.CROP MICROMETEOROLOGY (i) Profiles and fluxes Profiles Profile equations and stability Measurement of flux above the canopy 15.CROP MICROMETEOROLOGY (ii) Interpretation of measurements Resistance analogues Case studies: Water vapour and transpiration Carbon dioxide and growth Sulphur dioxide and pollutant fluxes to crops Transport within canopies APPENDIX BIBLIOGRAPHY REFERENCES INDEX
A dew collection project was carried out in Kothara, NW India, during the dry season between October 2004 and May 2005. One of the goals was to determine the amount of dew water that could be collected with little investment by adapting plain, uninsulated, corrugated galvanized iron roofs that are common in most rural regions of India. During the study period, the cumulative dew yield on an 18m2 double—sloped (30°) test roof was 113.5L (6.3mm). The west-facing side gave 35% higher water yields than the east-facing side. The use of thermal insulation and more IR radiative materials would have increased this yield by 40% (8.9mm or 160L). The cumulative dew water yield remains modest when compared with the average annual rainfall (300mm). But dew occurs far more frequently than rain and is available precisely during the dry season when water is most scarce. Dew events were correlated with meteorological data; relative humidity (the most important parameter) is strongly correlated with the monsoon.
Two methods of the evaluation of the amount of the atmospheric humidity condensed naturally are proposed. The comparison of these two methods is done from climatological considerations. The results in a hot and humid climate are very close; but in a hot and dry climate there is gap of 4% between the two methods.Experiments were conducted in three different climates; the results are similar to those of the theory. But the dew collected represents about 40% of which must be obtained.This paper describes the study and presents the results.
Using a numerical integration (Lowtran 6 code) stopped at several arbitrary base altitudes, in association with measurements from sounding balloons, clear sky radiation is determined as a function of the altitude parameter. The relations established, and the properties attached, are studied. In application, a natural system to obtain dew in dry climates is explained.
In many regions and geographical settings, dew water collection can serve as a water source, supplementing rain and fog water collection. This is particularly useful when precipitation is low or lacking, especially in remote areas and islands in the dry season. A project called Dew Equipment for Water (DEW) was initiated for a 15.1m2 roof in the island of Biševo (Croatia), equipped with commercial plastic cover selected for its superior dew collection properties. Measurements of both rain and dew water will be performed over several years and data will be correlated with meteorological data collected in situ. Preliminary measurements during the period 21 April–21 October 2005 showed that dew water contributed significantly, 26% of the total collected water.
Passive dew collection experiments were initiated in late 2003 in the centre of The Netherlands within a grassland area. A specially designed 1 m2 insulated planar dew collector, set at a 30° angle from horizontal, was covered with a thin (0.39 mm) polyethylene foil and subsequently replaced with 4 mm polyvinyl chloride. A second dew collector, in the shape of an inverted pyramid, was constructed to reduce the view angle to only the nighttime sky. A simple surface energy-budget model and an aerodynamic model were used to simulate the dew collected by both collectors. The planar collector collected about 90% of the dew at the grass cover while the pyramid collector collected about 1.20% of the grass cover. The aerodynamic model was able to predict the amount of collector data to within 50% for the planar collector and 60% for the inverted pyramid collector. The pyramid collector design was able to collect about 20% more dew than the inclined planar collector.
Radiation-cooled dew water condensers can serve as a complementary potable water source. In order to enhance passive dew collection water yield, a Computational Fluid Dynamics (CFD) software, PHOENICS, was used to simulate several innovative condenser structures. The sky radiation is calculated for each of the geometries. Several types of condensers under typical meteorological conditions were investigated using their average radiating surface temperature. The simulations were compared with dew yield measurements from a 1 m2 30°-inclined planar condenser used as a reference. A robust correlation between the condenser cooling ability and the corresponding dew yield was found. The following four shapes were studied: (1) a 7.3 m2 funnel shape, whose best performance is for a cone half-angle of 60°. Compared to the reference condenser, the cooling efficiency improved by 40%, (2) 0.16 m2 flat planar condenser (another dew standard), giving a 35% lower efficiency than the 30° 1 m2 inclined reference condenser, (3) a 30 m2 30°-inclined planar condenser (representing one side of a dew condensing roof), whose yield is the same as the reference collector, and (4) a 255 m2 multi-ridge condenser at the ground surface provided results similar to the reference collector at wind speeds below 1.5 m s− 1 but about 40% higher yields at wind speeds above 1.5 m s− 1.
The recovery of clean water from dew has remained a longstanding challenge in many places all around the world. It is currently believed that the ancient Greeks succeeded in recovering atmospheric water vapour on a scale large enough to supply water to the city of Theodosia (presently Feodosia, Crimea, Ukraine). Several attempts were made in the early 20th century to build artificial dew-catching constructions which were subsequently abandoned because of their low yield. The idea of dew collection is revised in the fight of recent investigations of the basic physical phenomena involved in the formation of dew. A model for calculating condensation rates on real dew condensers is proposed. Some suggestions for the ‘ideal’ condenser are formulated.
Moisture in the air can be condensed as dew and used for drinking and irrigation. The radiative cooling properties of polymer foils can enhance the performance of dew collecting surfaces. The main restrictions in condensing water in warm and arid locations are climatic factors, the dew collector design, and the optically selective and adhesive properties of the condensing surface itself. This paper concerns observations of dew formation on radiatively cooled pigmented polyethylene foils. The experiments were carried out in Sweden and in arid Dodoma, Tanzania. The results are in agreement with thermodynamical calculations, though the variation is large in the daily measured dew water volumes. This variation is caused by the hourly and daily changes in wind-speed, cloud cover, dry bulb temperature, and dew point temperature. The results are compared with earlier outdoor observations in Tanzania.
An inexpensive radiative condenser for collecting atmospheric vapor (dew) was tested in Grenoble (France). The surface temperature measurements are correlated with meteorological data (wind velocity, air temperature) and compared to the corresponding surface temperature of a horizontal Polymethylmethacrylate (Plexiglas) reference plate located nearby. The condenser surface is a rectangular foil (1×0.3 m2) made of TiO2 and BaSO4 microspheres embedded in polyethylene. The foil has an angle θ with respect to horizontal. The under-side of the device, thermally isolated, faces the direction of the dominant nocturnal wind. Both a 2D numerical simulation of the air circulation around the foil and experimental measurements shows that the angle θ=30° is a good compromise between weak wind influence, large light-emission solid angle and easy drop collection. The study was conducted from November 25, 1999 to January 23, 2001. In comparison to the reference plate, it is found that water yield can be increased by up to 20% and water collection greatly facilitated.
We compare the characteristics of dew at nearly the same latitude (42–45°N) for the Mediterranean island of Corsica (Ajaccio, France) and two continental locations (Bordeaux, France, Atlantic coastal area; Grenoble, France, alpine valley). Dew amount was measured on a horizontal reference plate made of polymethylmethacrylate (PMMA) and placed at 1 m above the ground. Data are correlated with plate and air temperature, air relative humidity, wind speed and cloud cover during the period from 14-08-1999 to 15-01-2003.General features as well as particularities of the sampling sites are discussed. The average daily dew yield is higher for the island station at Ajaccio (0.070 mm) than the Bordeaux coastal area (0.046 mm) or the Grenoble valley (0.036 mm). However, the accumulated dew yield was highest for the coastal station (9.8 mm/year) as compared to the island (8.4 mm/year), and much larger than in the alpine valley (4 mm/year). The difference between cumulated and average dew yield stems from the greater number of dew days in the coastal area (58%) versus 33% for the island and 30% in the valley. The higher wind speeds at the island station (average wind during dew is 2 m/s) and lower relative humidity explain the smaller number of dew days. The dew rate seasonal variation is negligible in Bordeaux and exhibits during summer a maximum in Ajaccio and a minimum in Grenoble.A computer model that includes simple meteorological data (air temperature and relative humidity, wind speed, cloud cover) is used to determine the thermal balance and fit to dew mass evolution. Two parameters that account for heat and mass exchange can be adjusted. It was found that, within the uncertainties, these two numbers are the same for the two continental sites, thus allowing dew formation on plates to be evaluated from only simple meteorological measurements. Somewhat larger values are found for the island, due to limitations in the model, which are discussed.
Air Wells: Myths and Realities or Russian & Soviet Works on the Production of Water from the Air
- I Mylymuk-Melnytchouk
- D Beysens
Mylymuk-Melnytchouk, I., Beysens, D., 2016. Air Wells: Myths and Realities or
Russian & Soviet Works on the Production of Water from the Air (in French).
Organization for Dew Utilization avalaible at
- Opur Web
Web references
OPUR, 2016. Organization for Dew Utilization avalaible at. http://www.opur.fr
(accessed April 2016).
Handbook of Applied Thermal Design
- E C Guyer
- D L Brownell
Guyer, E.C., Brownell, D.L., 1999. Handbook of Applied Thermal Design, 1st ed. Taylor
and Francis, London.
Indian Standard, 2012. IS 10500, Bureau of Indian Standards, 2nd revision, New
Delhi.
The case for alternative fresh water sources (in French)
- D Beysens
- I Milimouk
Beysens, D., Milimouk, I., 2001. The case for alternative fresh water sources (in
French). Secheresse 11, 281e288.
Roofs as dew Collectors: III. Special polyethylene foil on a school in Sayara (NW India)
- G Sharan
- S Singh
- I Millimouk-Melnythouk
- M Muselli
- D Beysens
Sharan, G., Singh, S., Millimouk-Melnythouk, I., Muselli, M., Beysens, D., 2007b.
Roofs as dew Collectors: III. Special polyethylene foil on a school in Sayara (NW
India). In: Proc. 4th Conference on Fog, Fog Collection and Dew (La Serena,
Chile, July 23-27, 2007), pp. 253e255.