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Solar steam generation (SSG) is an extremely promising desalination technology that meets the global demand for clean water. Herein, we report a facile and effective method that utilizes absorbed heat to evaporate limited water while minimize heat loss. The top layer is a hydrophilic photothermal layer that allows for uniform distribution of water on the photothermal layer, whereas the bottom layer is a hydrophobic insulating layer that provides excellent insulation and heat preservation. Water is supplied by dripping from the top to thoroughly avoid heat loss caused by contact between the photothermal layer and water body. We achieve a high evaporation rate of 1.622 kg/m2h and energy conversion efficiency of 90.8 % under 1 sun irradiation. [ABSTRACT FROM AUTHOR]

The generalization of Samarskii–Sobol' solution in the mode of heat exacerbation and localization is obtained for a quasilinear heat equation in half-space. The analogy of this solution with summer heating of moisture-saturated soil in the permafrost zone is discussed. [ABSTRACT FROM AUTHOR]

A chemically treated luffa sponge (LS) derived from the ripe fruit of the Luffa cylindrica (LC) plant is investigated as an efficient solar photothermal conversion material for water purification applications for the very first time. Hydrophilicity and solar absorbance of the LS are enhanced by dopamine treatment and candle soot surface coating. The fabricated surface modified LS (SM‐LS) leads to a superb solar evaporation rate of water as high as 1.30 kg m−2 h−1, which is five times higher than that of the freshwater under 1 sun illumination. The outdoor experiment shows an excellent solar evaporation efficiency of 79.98%, which is significantly higher than other low‐cost materials. Such SM‐LS can be further applied to desalinate seawater, where it is shown that 1 m2 of surface‐modified LS can produce 7.5–8 L of freshwater per day. Hence, the proposed system can be utilized in remote areas and refugee camps. [ABSTRACT FROM AUTHOR]

Solar steam generation is an efficient way for water purification. However, it is still challenging to establish a steam generation system possessing high evaporation efficiency under natural sunlight condition with good durability. Herein a novel, free‐floating nanoplatform is constructed by a gas foaming strategy, embedding plasmonic Cu7S4‐MoS2‐Au nanoparticles (CMA NPs) in porous polydimethylsiloxane (PDMS) matrix. The gas diffusion process creates 3D porous PDMS matrix with low thermal conductivity and open channels, which allows for efficient energy confinement and fast water supply in an integral matrix, beneficial to mechanical strength of the system. By taking advantage of broadband absorption and high photothermal efficiency of CMA NPs and structural design of the matrix, the nanoplatform achieves a high evaporation rate (3.824 kg m−2 h−1) and photothermal conversion efficiency (96.6%) under one‐sun illumination (1 kW m−2). Moreover, such performance maintains stable even under harsh conditions in the presence of strong acid, strong base, strong oxidants, and high salinity, suggesting a broad prospect in seawater desalination, sewage treatment, sterilization and so on. [ABSTRACT FROM AUTHOR]

Transient thermo-mechanical analysis of welding problem requires tremendous computation cost. To accelerate the thermal analysis of large-scale welded structures, an efficient computation scheme based on heat transfer localization and dual meshes was proposed. The computation accuracy is guaranteed by a local fine mesh model with size determined by a theoretical solution and a global coarse mesh model with equivalent heat input. The validity and accuracy of the dual-mesh method were verified using an experimental bead-on-plate model. By extending the weld length, the computation time of the proposed method was proved to be almost linearly dependent on the model scale. The thermal analysis of fillet welding of a large panel structure with 6-m-long weld was accelerated by 10 times over conventional finite element analysis and 2.2 times over adaptive mesh method. Meanwhile, the physical memory consumption was also greatly reduced by the dual-mesh method. Such efficient computation method enables fast evaluation of welding stress and distortion which are vital for manufacturing process and structure performance. [ABSTRACT FROM AUTHOR]

Plasmonic nanostructures with strong light-matter interactions have been intensively explored in the past decades. The plasmonic photothermal effect has garnered significant research interest and triggered plenty of applications, such as photothermal therapy, photothermal imaging, and photocatalysis. Recently, plasmonic nanostructures are emerging as one of the most exciting candidates for solar vapor generation, inspiring the revival of solar-thermal-based water purification technologies. Here we present a review of state-of-the-art plasmonic-enhanced solar evaporation, including the theoretical background, various designs of plasmonic materials and structures, and their potential applications. The current challenges and future perspective are outlined as well. [ABSTRACT FROM AUTHOR]

Solar steam generation, combining the most abundant resources of solar energy and unpurified water, has been regarded as one of the most promising techniques for water purification. Here, an artificial tree with a reverse-tree design is demonstrated as a cost-effective, scalable yet highly efficient steamgeneration device. The reverse-tree design implies that the wood is placed on the water with the tree-growth direction parallel to the water surface; accordingly, water is transported in a direction perpendicular to what occurs in natural tree. The artificial tree is fabricated by cutting the natural tree along the longitudinal direction followed by surface carbonization (called as C-L-Wood). The nature-made 3D interconnected micro-/nanochannels enable efficient water transpiration, while the layered channels block the heat effectively. A much lower thermal conductivity (0.11 W m-1 K-1) thus can be achieved, only 1/3 of that of the horizontally cut wood. Meanwhile, the carbonized surface can absorb almost all the incident light. The simultaneous optimizations of water transpiration, thermal management, and light absorption results in a high efficiency of 89% at 10 kW m-2, among the highest values in literature. Such wood-based high-performance, cost-effective, scalable steam-generation device can provide an attractive solution to the pressing global clean water shortage problem. [ABSTRACT FROM AUTHOR]

Abstract: Solar steam generation, combining the most abundant resources of solar energy and unpurified water, has been regarded as one of the most promising techniques for water purification. Here, an artificial tree with a reverse‐tree design is demonstrated as a cost‐effective, scalable yet highly efficient steam‐generation device. The reverse‐tree design implies that the wood is placed on the water with the tree‐growth direction parallel to the water surface; accordingly, water is transported in a direction perpendicular to what occurs in natural tree. The artificial tree is fabricated by cutting the natural tree along the longitudinal direction followed by surface carbonization (called as C‐L‐Wood). The nature‐made 3D interconnected micro‐/nanochannels enable efficient water transpiration, while the layered channels block the heat effectively. A much lower thermal conductivity (0.11 W m−1 K−1) thus can be achieved, only 1/3 of that of the horizontally cut wood. Meanwhile, the carbonized surface can absorb almost all the incident light. The simultaneous optimizations of water transpiration, thermal management, and light absorption results in a high efficiency of 89% at 10 kW m−2, among the highest values in literature. Such wood‐based high‐performance, cost‐effective, scalable steam‐generation device can provide an attractive solution to the pressing global clean water shortage problem. [ABSTRACT FROM AUTHOR]

Because it is able to produce desalinated water directly using solar energy with minimum carbon footprint, solar steam generation and desalination is considered one of the most important technologies to address the increasingly pressing global water scarcity. Despite tremendous progress in the past few years, efficient solar steam generation and desalination can only be achieved for rather limited water quantity with the assistance of concentrators and thermal insulation, not feasible for large-scale applications. The fundamental paradox is that the conventional design of direct absorber-bulk water contact ensures efficient energy transfer and water supply but also has intrinsic thermal loss through bulk water. Here, enabled by a confined 2D water path, we report an efficient (80% under one-sun illumination) and effective (four orders salinity decrement) solar desalination device. More strikingly, because of minimized heat loss, high efficiency of solar desalination is independent of the water quantity and can be maintained without thermal insulation of the container. A foldable graphene oxide film, fabricated by a scalable process, serves as efficient solar absorbers (>94%), vapor channels, and thermal insulators. With unique structure designs fabricated by scalable processes and high and stable efficiency achieved under normal solar illumination independent of water quantity without any supporting systems, our device represents a concrete step for solar desalination to emerge as a complementary portable and personalized clean water solution. [ABSTRACT FROM AUTHOR]

Absorption air-conditioning systems have a great advantage in terms of energy conservation and environmental protection. However, the large amount of energy waste in the thermal regeneration process leads to lower efficiency and impedes its development. To reduce energy loss and improve performance, a local heating regeneration method is proposed in this paper. The main principle is reducing the volume of the liquid participating regeneration. Including the solar steam mode, two modes are introduced and configured. Theoretical and experimental research has been made on the new methods. Models have been developed for comparison analysis. Experiments have been conducted on water and absorbent solution with different modes. Performance has been evaluated based on the experimental data. The results expose the influence of different parameters, like liquid volume and solution concentration, on the regeneration process. The local heating method improved the regeneration efficiency by 40% in the no solar steam mode and the performance tripled in the solar steam mode. The COP (the ratio of cooling load to energy consumption) of the absorption system with the solar steam mode is more than two times of that with the traditional regeneration mode. It shows the local heating regeneration method has good potential in future application. [ABSTRACT FROM AUTHOR]

A damage‐free dewatering method, without centrifugation, mechanical squeezing, and solar irradiation, is important for separating solids from pure water and can be used for the production of biomass‐derived renewable fine chemicals, fertilizers, and fuels in biotechnological applications. Herein a damage‐free steam generator constructed by a single sheet of nitrogen‐doped nanoporous graphene and nitrogen‐doped porous graphene foam as hierarchical structures is reported. The multifunctional hierarchical graphene steam generator has a high water evaporation rate (1.54 kg m−2 h−1) accompanied by a high energy conversion efficiency (82.2%). Furthermore, it exhibits excellent persistence in dewatering performance over multiple uses, unlike the graphene foam that shows marked reduction in performance after several reuses. Therefore, the multifunctional hierarchical graphene steam generator is a cost‐effective material for accelerating both the harvesting of biomass concentrates and the production of pure water. [ABSTRACT FROM AUTHOR]

Solar Vapor Generation: Low-Cost and High-Efficiency Solar-Driven Vapor Generation Using a 3D Dyed Cotton Towel (Global Challenges 9/2019) Keywords: dyed cotton towels; heat localization; solar-driven evaporation; water purification Dyed cotton towels, heat localization, solar-driven evaporation, water purification, water purification. [Extracted from the article]

Solar‐driven vapor generation is a promising method to mitigate freshwater shortage and water contamination. However, most of the current highly efficient solar evaporators suffer from low robustness, tedious preparation procedures, and high cost. In this study, an easy‐to‐manufacture, low‐cost, and high‐reliability solar‐driven evaporator is designed using a black cotton towel with a hollow conical shape. The reactive dye molecules diffuse into the cotton and form strong covalent bonds with the fiber after dyeing, which firmly fixes light‐absorbing materials on the substrate. The looped pile structure of towels and hierarchical structure of yarns enable the evaporator enlarged surface area. The hollow conical shape of the cotton towel can effectively suppress the heat loss to the environment without compromising light absorption. The 3D vapor generator exhibits an evaporation rate of 1.40 and 1.27 kg m−2 h−1 for pure water and saline water, respectively. Meanwhile, this towel‐based solar‐driven evaporator exhibits a promising antifouling property as well as superior reusability and provides a reliable pathway in dealing with realistic waters, such as seawater and dyeing sewage. Therefore, the low‐cost, solar‐driven water evaporation system offers a complementary approach for high‐efficiency vapor generation and water purification in practical application. [ABSTRACT FROM AUTHOR]

Solar steam/vapor generation is a promising approach to produce clean water and solve water scarcity and energy shortage issues. Most of steam/vapor generation devices can only be used on surface water from oceans, lakes, or rivers. Groundwater is another essential resource for public water supply. Acquiring clean water directly from groundwater is important, especially for countries and regions that lack surface water. A natural, plant‐inspired solar steam/vapor generation device is developed in this work by coating a thin layer of carbon nanotubes (CNTs) on the top surface of a tree stump with roots to extract water directly from groundwater. The 3D interconnected channels/pores in the roots and stump enable fast water transportation within the plant. Under sunlight irradiation, the surface‐coated CNT layer can convert solar energy into heat, and the water is continuously supplied to the heat‐localized interfacial layer of the top surface and is evaporated into vapor upon heating. The evaporation efficiency of such steam/vapor evaporation device for extracting water from groundwater is as high as ≈86% under 10 kW m−2, which approaches the best performance achieved by devices for surface water extraction, providing an attractive method to utilize groundwater. A natural, plant‐inspired solar steam/vapor generation device is developed for the acquisition of clean water directly from groundwater. The 3D interconnected porous microstructures in the roots and stump enable water uptake from soil moisture and water transport within the plant, which enable a high evaporation efficiency of ≈86% under 10 kW m−2. [ABSTRACT FROM AUTHOR]