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[Display omitted] • A biomimetic hollow structural C@CuO nanofibrous membrane was developed. • The hollow structure localized thermal energy in the membrane to suppress heat loss. • The C@CuO membrane exhibited a high and stable evaporation rate for saline/dye water. • The mechanisms of heat localization and high evaporation were proposed. The rational design of material structures can be an effective approach to enhance the performance of solar-driven clean water production. In this study, a hollow structural nanofibrous membrane was developed by mimicking the hollow structure of polar bear hair using coaxial electrospinning. The shell layer consisted of carbon nanoparticles (C NPs) decorated CuO nanosheets (C@CuO), that exhibited photothermal conversion capacity. Meanwhile, the core layer containing hydrophilic polyvinylpyrrolidone (PVP) was eliminated to generate the hollow structure. The C NPs enhanced the membrane's light absorption to increase thermal energy harvesting, while the CuO nanosheets improved the membrane's wettability enhancing the water supply. Furthermore, the hollow structure limited air convection, prevented heat conduction, and minimized heat radiation, enabling heat localization to be achieved inside the membrane to suppress heat loss during evaporation. For 3.5 wt% saline water and actual dye wastewater, the C@CuO nanofibrous membrane achieved high evaporation rates of 1.36 kg·m−2·h−1 and 1.31 kg·m−2·h−1, respectively, under 1 sun illumination. Moreover, even after continuous 6-h evaporation tests, the evaporation rate of the C@CuO membrane remained virtually unchanged, highlighting its long-term stability with regard to salt resistance in real-world applications. Additionally, the remarkable flexibility of the C@CuO membrane offers convenience during operation and guarantees dimensional stability when it is subjected to external stresses. These discoveries should inspire subsequent research on developing delicate architectural materials and exploring their potential applications in various fields, including energy generation, clean water production, and thermal insulation. [ABSTRACT FROM AUTHOR]

Interfacial solar steam generation is considered as economical and more effective implementation of Solar steam generation (SSG) where solar energy is concentrated at the liquid surface via the utilization of heat localization materials (HLM). Herein we report the fabrication of an HLM constituted of a nanocomposite absorber of graphitic carbon nitride (g-C3N4) and covellite copper sulfide (CuS) supported on a mixed cellulose ester membrane, with a substrate of air laid paper-wrapped polystyrene foam. This structure allowed for strong broad-spectrum absorbance, increased hydrophilic character and minimal thermal losses. The HLM system absorbed 98% of the material and had an evaporation rate of 2.58 kgs per square meter per hour. This is twice the evaporation rate of water tested under the same conditions. Moreover, as fabricated HLM was also incorporated in a solar still in order to assess its practical performance in solar distillation. Initial studies proved that HLM modified solar still was more effective than conventional solar stills.

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]

Solar-to-steam generation (SSG) for seawater desalination is emerging process which faces several technology challenges for successful scaling up. Floating solar-to-steam generation (SSG) sandwich-based systems using hydrophilic water bridges have been proved to be fascinating technology for seawater desalination. However, the mechanistic pathways of heat dissipation, mass diffusion and convection are still the key bottlenecks for reliable scaling up. To solve the heat loss and surface salt deactivation, we demonstrate herein the performance of novel SSG structure for seawater desalination via the incorporation of cellulosic sponge as water holder to play a role of water transit between hydrophilic bridge and the top surface. Two systems using low-cost materials were compared, namely graphite felt/hydrophilic paper/polystyrene (GF-HP-PS) and Graphite felt/Water receiver/hydrophilic paper/polystyrene (GF-HP-W R -PS). The process of heat generation and localization was maximum in the GF-W R -HP-PS system, reaching 68.2 °C under 0.5 sun. The photothermal conversion efficiency was found to be 92 and 114 % under 0.5 sun for GF-HP-PS and GF-HP-W R -PS, respectively. On top of that, GF-HP-W R -PS shows effective steadily salt rejection during the desalination of seawater. The W R layer plays a crucial role to govern the confined water, which boosts the dissolution of salt and its convection without significant heat downward convection. As a practical consideration, the cost of used components to fabricate this SSG system is very acceptable and without major restrictions. [Display omitted] • Design of novel multilayer sandwich solar-to-steam generation for seawater desalination. • The incorporated super water holding layer allows a continuous salt convection. • Localized heat production was found to be 68.2 °C under 0.5 sun. • Photothermal conversion efficiency was found to be 114 % under 0.5 sun. [ABSTRACT FROM AUTHOR]

Solar thermoelectric generators (STEGs) consisting of solar absorbers and thermoelectric generators (TEGs) can utilize solar energy to generate electrical power. However, performances of STEGs are limited by the heat losses of solar absorbers in air, which become more and more significant with an increase in the solar absorbing area. Herein, we describe the preparation of Au@AgPd nanostructure monolayer/poly(vinyl alcohol) (PVA) Janus photothermal films with broadband plasmonic absorption in the visible and near-infrared regions. By uniaxially stretching the Janus film, Au@AgPd can align along the stretching direction, which creates particle-in-cavity structures on the PVA surface. Benefiting from the oriented plasmonic particle-in-cavity configuration, the Janus films effectively convert sunlight into heat, trap the heat within their micrometer-depth structure, and facilitate its transfer along the direction of the nanostructure orientation. Integration of the Janus films with commercial TEGs allows thermal concentration onto a small thermoelectric surface, yielding an open-circuit voltage of 308 mV under 102 mW/cm 2 natural sunlight illumination. Heat losses in commercial TEGs integrated with Janus films are reduced by approximately 50% while maintaining the same voltage output. Furthermore, incorporating the Janus films into a conventional STEG with carbon-based solar absorbers significantly enhances solar-thermal-electric conversion performance, achieving an output power density of 1.3 W m -2 . Our design of Janus photothermal films with oriented particle-in-cavity surfaces can be extended to various solar-thermal systems for high-efficiency solar energy conversion and heat management.

An energy conservative air-conditioning system is critical to promoting energy conservation and emission reduction. One promising alternative is liquid desiccant cooling system (LDCS), which can be driven by low-grade heat and has superior dehumidification performance. However, energy waste from traditional regeneration process restricts its application from widespread use. To overcome this disadvantage, a wood-based heat localization regenerator is presented: it localizes the thermal energy on the regeneration surface avoiding the unnecessary heating of bulk solution. The real performance of this new regenerator has been investigated theoretically and experimentally in this paper. The regeneration process of desiccant solution has been analyzed and a regeneration performance prediction model has been developed. Some performance indexes have been derived from experimental data. A regeneration performance comparison has been conducted between the heat localization method and the traditional heating method. The results show that the new method improves regeneration thermal efficiency by above 50% and the maximum value can achieve 43.6%. Besides higher performance, the reduction of energy consumption, initial cost and complexity has achieved with the heat localization regenerator. The overall improvement makes LDCS such a competitive alternative to the current air-conditioning system. [Display omitted] • A wood-based heat localization regenerator is presented for efficient regeneration. • The actual performance of heat localization regeneration method has been revealed. • The heat localization method improves regeneration thermal efficiency by more than 50%. • The heat localization based LDCS has advantages on performance, initial cost and complexity. [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]

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.

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]

Solar-driven interfacial evaporation is recognized as an energy-efficient and sustainable approach to combat the global freshwater crisis, particularly in rural areas where continuous energy inputs are limited. Additionally, these regions often lack effective sterilization methods for their water sources. By incorporating photothermal materials with inherent antibacterial properties, water purification can be enhanced without relying on external sterilization steps. Herein, we designed a multi-functional photothermal (MFP) evaporator based on a Cu dendrite@ CuO with abundant nanowires via a template-free method for solar-thermal clean water production. Compared to flat-type structures, the MPF evaporator with its dendritic architecture not only exhibits efficient photon absorption but also expands the evaporation area by over sevenfold, facilitating enhanced water evaporation with an efficient pathway for water transfer. Under 1 kW m−2, the MFP evaporator achieves an impressive evaporation rate of 1.40 kg m−2 h−1 and an efficiency of 87.8 %. Furthermore, the MFP evaporator demonstrates remarkable antibacterial capabilities, effectively inhibiting bacterial growth in raw water by damaging bacterial cell walls. Hence, the as-prepared MFP evaporator exhibits tremendous potential as an innovative system for solar-driven interfacial water evaporation and purification. We proposed a multi-functional photothermal (MFP) evaporator for solar-thermal clean water production which realized a photothermal evaporation temperature of 40.6 °C and an evaporation rate of >1.40 kg m−2 h−1 via ∼ 87.8 % solar conversion under 1 sunlight illumination, originating from the large photo-thermal evaporation area, narrow heat conduction path, and efficient water transfer. Besides, the MFP evaporator was fabricated through a simple process of low cost and can be connected together to form large-scale floating networks for water evaporation. Moreover, the MFP evaporator possessed a great antibacterial ability, inhibiting the growth of bacteria in raw water by destroying the cell wall of bacteria. Thus, the as-prepared MFP evaporator has great potential serves as a novel system for implementing solar-driven interfacial water evaporation and water purification. [Display omitted] • A multi-functional photothermal evaporator was designed for solar water evaporation. • Enhanced light trapping and large evaporation area contributed an excellent evaporator. • The MFP evaporator with inherent antibacterial properties (rejection rate exceeded 99.9 %). • The conversion efficiency of the setup reaches as high as 87.8 % under 1 sun. • A low-cost and well-controllable fabrication process enables for large-scale applications. [ABSTRACT FROM AUTHOR]

Abstract 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 Utilizing solar energy to evaporate water is a green and promising approach in addressing the issue of global freshwater shortage and water pollution. Carbon materials have gained extensive research attention as efficient solar absorbers for solar steam generation owing to the non-toxic nature and environmental friendliness. In this work, the metal-organic framework (MOF) derived porous carbon (MDPC) materials were first employed as solar absorbers for enhancing water evaporation. An efficient surface heating and evaporation system was designed by coating the leaf-like two-dimensional (2D) MOF precursor on stainless steel mesh followed by calcination (MDPC/SS mesh), and then in conjunction with a floating air-laid paper wrapped polyethylene (EPE) foam. The prepared solar evaporator with unique light trapping structures shows a high solar absorption (>97%), excellent hydrophilicity, and great surface heat localization for solar steam generation. Consequently, a photo-thermal conversion efficiency of 84.3% with an evaporation rate of 1.222 kg m−2 h−1 was achieved under one sun illumination. Furthermore, the MDPC/SS mesh shows good recyclability and durability. This work opens a new avenue for the application of MOF derived carbon as photo-thermal material in the field of solar steam generation. Highlights • First demonstration of MOF derived carbon for solar steam generation. • The MDPC/SS mesh supported by EPE foam was applied as solar evaporator. • A photo-thermal conversion efficiency of 84.3% was obtained under 1 kW m−2. • The light trapping structures of MDPC/SS mesh enhanced solar absorption. [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]

• The embrittlement X factor for weld metal is 45, which is three times more than the recommended value (≤15). • It is apprehended that the fractured metal part could be susceptible to temper embrittlement. • The Charpy impact energy absorbed by the fractured metal is 13 J, which is lower than impact energy absorbed by the base metal 300 J. • The scanning electron microscopy demonstrated intergranular crack propagation, discontinuous cracking along grain boundaries, and blunted cracks at grain interiors. • The fractography is performed on the fracture surface of the impact test specimens and it indicated heavily cavitated intergranular facets along the grain boundaries and deep secondary cracks on the fracture surface. • These findings suggested that the severe cracking observed in the fire tube at the U-bend is likely due to temper embrittlement (TE) induced by exposure of the fire tube material to elevated temperatures. Overheating, corrosive degradation, hydrogen embrittlement, creep, erosion, and corrosion are the cause of most failure problems in fire tubes. Herein, we have evaluated the macrostructural, microstructural, and mechanical properties at welded U-bend of the fractured fire tube to analyze the failure of the SA 387 grade 22 steel heater treater fire tube that has been under continuous use for 18 years at an oil refinery. We have found that the embrittlement factor at U-bend proved to be the most significant factor in its failure. The embrittlement X factor for weld metal is 45, which is three times more than the recommended value (≤15). It is apprehended that the fractured metal part could be susceptible to temper embrittlement. There is a significant higher hardness value of weld metal as compared to base metal, which is due to metallic phase transition at high temperature. The Charpy impact energy absorbed by the fractured metal is 13 J, which is lower than impact energy absorbed by the base metal 300 J. The macroscopic examination reveals that the crack initiated on the emulsion side and propagated radially in welded U-bend before extending further into the base metal in the axial direction. The scanning electron microscopy demonstrated intergranular crack propagation, discontinuous cracking along grain boundaries, and blunted cracks at grain interiors. The fractography is performed on the fracture surface of the impact test specimens, and it indicated heavily cavitated intergranular facets along the grain boundaries and deep secondary cracks on the fracture surface. Energy disperse spectroscopy identified the carbides formation at the U-bend cracking parts, which counter confirm the microstructural phase transition. These findings suggested that the severe cracking observed in the fire tube at the U-bend is likely due to temper embrittlement (TE) induced by exposure of the fire tube material to elevated temperatures. [ABSTRACT FROM AUTHOR]

Abstract The sun is considered as the most promising abundant renewable energy source that can be exploited to solve many of human beings' challenges such as energy and water scarcity. Solar energy can be utilized in steam and vapor generation processes which has a great importance in many engineering applications such as water desalination, domestic water heating, and power generation. However, dilute solar flux (∼1000 W/m2) cannot supply the absorber with enough power required to overcome water latent heat of vaporization to evaporate water. Optical concentrators such as parabolic trough collector, parabolic dish reflector, and circular Fresnel lens can be used to concentrate the solar radiation to achieve the required power however they suffer from complexity and high cost. Moreover, the efficiency of the conventional solar desalination devices such as solar stills decreases dramatically with increasing bulk water quantity, due to the heat loss to bulk water. Therefore, the need to solar steam generation (SG) devices, that localize heating on a thin layer of water rather than the water bulk, arises. Thin film technology has shown promising progress in SG in which solar energy is utilized to wastewater desalination. The past five years have seen a significant surge in the development of thin film based SG devices. In this review, recently developed thin film-based SG devices are scrutinized with respect to their physical mechanisms, fabrication methods, structure, advantages, and disadvantages. Different types of thin-film materials, including: metal-based nanoparticles, metal oxides, carbon-based materials, polymers, etc.; as well as different substrates materials, including: wood, paper, cotton fabric, carbon fabric, polystyrene foam, and gauze, have been discussed. Moreover, different preparation and synthetization methods of the steam generation devices have been discussed. Suggestions for future research directions are also presented. [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]

The problem of worldwide scarcity of clean water can be resolved efficiently by utilizing the significant heat localizing capability of the solar-driven interfacial evaporator with a nominal impact on the environment. A novel flexible, recyclable, hydrophilic photothermal composite membrane containing a blend of mesoporous Co 3 O 4 nanorod and nanoporous nitrogen-doped graphitic carbon hollow spheres has been proposed. The composite membrane exhibits an enhanced broadband optical absorption which leads to a high interfacial evaporation rate (2.28 kg m−2 h−1) and a notable solar-to-steam generation efficiency (93%) under sunlight (900 W/m2) at 3.5 wt% NaCl salinity. The lower salt accumulation on the evaporation surface and the remarkable recyclability of the photothermal membrane under sunlight prove its practical usability in the desalination of seawater, water purification, salt production, and solar energy harvesting. [Display omitted] • Significant heat localizing ability of porous C–Co 3 O 4 nanocomposite based membrane. • An evaporation rate of 2.28 kg m−2 h−1 at 900 W/m2 at 3.5 wt% salinity was found. • Solar-thermal conversion efficiency around 93% at 900 W/m2 was found. • High surface temperature around 47 °C indicates remarkable heat-localizing ability. • Remarkable synergistic impact in optical absorption is observed in composites. [ABSTRACT FROM AUTHOR]

• A novel regeneration method based on solar heat localization was investigated. • Evaporators for seawater desalination and desiccant regeneration were developed. • Evaporation rate of 1.496 kgm−2 h−1 for pure water at 22 °C was achieved. • Regeneration efficiency of 40 wt% CaCl 2 remains stable under 3-sun irradiation. • Excellent salt-rejecting is conducive to improving regeneration performance. Liquid desiccant air conditioning systems (LDAC) have attracted increasing interest for the high efficiency of temperature and humidity control. Improving the regeneration performance with low-grade energy could make LDAC systems more competitive. In this work, by combining Chinese ink and lignocellulose sponge, we developed an inexpensive, efficient and large-scale evaporator that allows regeneration of desiccant via solar energy. Results show that the evaporator exhibits remarkable salt-resistance capacity, rendering it suitable for effective seawater desalination and regeneration of high-concentration desiccant. Even for the 40 wt% desiccant at about 22 °C, the regeneration rate can reach 0.63 kgm−2 h−1 under 1-sun irradiation. The outdoor experiments further confirmed the high regeneration rate of the evaporator. Additionally, concentrated desiccant presents an alternative means of solar energy storage. Considering the high efficiency, easy preparation, and remarkable salt resistance, the lignocellulose sponge-based evaporators could advance the practical application of solar heat localization for seawater desalination and desiccant regeneration. [ABSTRACT FROM AUTHOR]

Frictional heat is generated on the rubbing surface and various types of thermal localization occur during sliding contact in braking on disk and pad surfaces. Thermoelastic expansion affects the contact pressure distribution due to the frictional heat generation. The surface temperature is sometimes localized, and the thermal behavior causes surface damage. To evaluate this phenomenon, braking tests were conducted and the localized temperature on the disk surface was observed with an infrared camera. The localized temperature was found to correlate with frequency response for contact force variation. To investigate localized temperature on the disk surface, FEM analysis of the braking test was conducted. The FEM analysis method combined with contact analysis and heat transfer/thermal stress analysis was applied. Heat flux distributions were calculated by contact analysis in consideration of the frictional heating introducing the actual contact force and the friction coefficient variation. The disk surface temperature was then evaluated by the coupled heat transfer/thermal stress analysis using the heat flux distributions obtained from the results of contact analysis. The disk surface temperature obtained from FEM analysis almost coincided with that measured during the braking test. Moreover, the new method could greatly reduce the calculation time compared to the method using the contact analysis alone. Therefore, the proposed method is believed to be useful for evaluation of the rubbing surface temperature.

The abundant waste polyurethane sponge, commonly considered as one of the municipal wastes, can be recycled and converted into the valuable resources of environment. The increasing landfill cost and air-pollutions have made it a great urgent to develop the effective applications of waste polyurethane sponge. Recently, solar vapor generation has attracted extensive attentions, since energy shortage and water scarcity along with water pollution are becoming alarming global issues to be addressed. The solar vapor generation relies on the performance of the solar absorbers which convert the solar energy into heat for the vaporization process. A low cost, efficient and durable solar absorber is vital for the development of solar vapor generation. Here, we report that the recycled self-floating black polyurethane sponges are very promising solar absorber materials. which can efficiently generate water vapor after a simple one-step hydrophilic treatment with dopamine hydrochloride. The evaporating rate was more than 3.5 times higher compared to that of the existing natural evaporation process, exhibiting an evaporation efficiency of above 50%. Furthermore, this black polyurethane sponge can also drive solar ethanol distillation, yielding up to 25 wt% concentration promotion under each distillation cycle. [ABSTRACT FROM AUTHOR]

Efficient solar-enabled evaporation plays a critical role in solar power-based concentration systems, photochemical plants, seawater desalination technologies, etc. However, traditional processes for solar steam generation usually depend on high-temperature heating of the bulk liquid, which requires highly concentrated solar power and suffers from high energy and optical losses. Therefore, the enhancement of solar steam generation by bio-inspired interface solar heating is proposed in this work. In this study, easy-to-prepare, flexible, and reusable plasmonic membranes (PMs) were fabricated for realizing the bio-inspired interface solar heating and continuous steam transportation through the micropores of the membranes. A solar steam generation efficiency of ∼85% was achieved at an illumination power of 10 kW m −2 . The effects of Au concentration in the membranes and optical power on the steam generation efficiency were systemically studied. The observed high evaporation rate and efficiency were attributed to three main factors: high (∼90%) and broadband solar absorption, efficient photo-thermal conversion due to high plasmon dissipation losses, and fast capillary flow in the membrane micropores. Finally, the application of PMs in a single basin solar still system for seawater desalination was investigated and the PMs exhibited great performance on enhancing the productivity of clean water. [ABSTRACT FROM AUTHOR]

Solar-based interfacial vapor generation techniques have received fresh attention lately, for generating potable drinking water for remote regions application. However, fouling due to salt accumulation and low water productivity has limited their commercialization. Decoupling of the solar irradiation absorbing surface and the vapor generating surface, is a technique recently preferred to address the above shortcomings. A thermosyphon-based decoupling strategy, enabling provision for latent heat recovery, and which is not prone to salt-fouling, is proposed here for the first time. In this strategy, the evaporator section is used for absorbing the solar irradiation energy whereas, the condenser section attached with a wick is the vapor generating surface. The optimal filling ratio (40 %) of the working fluid, for the operation of thermosyphon with the least thermal resistance, to achieve maximum solar-to-vapor conversion efficiency (81 % for 1-Sun) is identified. The proposed strategy is then made to undergo a 7-Day trial with 8-h of operation (with external input heat flux) followed by a 16-h of nighttime (without any external heat flux). Thus, the proposed strategy can successfully generate vapor continuously with a reasonable solar-to-vapor conversion efficiency of ~73 %, better than the recently reported studies that have shown long-term reliability. [Display omitted] • Novel thermosyphon-based solar heat-localization strategy for desalination • Provision for latent heat recovery in a 'front-side evaporation system' • Easily scalable, fabric based wicking material requiring no advanced wick coating material • Suitable for incorporation of commercially developed technologies, like flat-plate solar collectors • Continuous, reliable vapor generation for 1-Sun without accumulation of salt deposits in the wick [ABSTRACT FROM AUTHOR]

To mitigate the global water shortage problem, interfacial solar steam generation (ISSG) technology, an eco-friendly desalination technology, has been actively studied. ISSG technology could be appropriate for practical seawater desalination technology when achieving a high evaporation rate. Hydrogels have been used as platforms for solar absorbers because they can provide high evaporation rates. This study proposes a thermoresponsive polypyrrole/alginate/poly(n-isopropylacrylamide) (PAP) hydrogel composed of alginate, poly(N-isopropylacrylamide) (PNIP), and polypyrrole (PPy) for ISSG. The proposed PAP hydrogel has high water absorption and releases water rapidly, which can facilitate active evaporation. Additionally, the PAP hydrogel was fabricated into a three-dimensional (3D) structure to maximize the total area of the water–air interface and in turn maximize solar evaporation. The effect of the 3D geometric shape on the solar evaporation rate was investigated by varying its aspect ratio. The experimental results indicate that a hydrogel with a high aspect ratio gives rise to a progressively higher evaporation rate. The highest evaporation rate was 4.145 kg m−2 h−1 under 1 sun irradiation (solar intensity of 1 kW m−2). To confirm the evaporation rate on the top and side surfaces in a 3D form, a ratio calculation based on the aspect ratio was also performed. [Display omitted] • PNIPAm, a thermoresponsive polymer, has a great water release ability above LCST. • Ferric chloride can be used to synthesize alginate and pyrrole simultaneously. • Hydrogel-based 3D solar absorber has achieved high evaporation rate. • The contribution of photothermal heating gently declines as the height increases. • The side surface area engaging in evaporation can gather environmental energy. [ABSTRACT FROM AUTHOR]

Solar evaporation by heat localization has drawn intensive research interest recent years, because this potential desalination technology is free of fossil fuel consumption and carbon dioxide emission. With various materials and innovative structures being explored, many recently-proposed systems could achieve a solar-thermal evaporation efficiency (solar-to-vapor energy efficiency) higher than 90 %. However, the upper limit of the solar-thermal evaporation efficiency is not bounded by 100 %. In this work, the thermodynamic limit of the solar-thermal evaporation efficiency is analyzed, which is much higher than all reported evaporation efficiencies in previous works. There is still much room for further improvement in the evaporation efficiency, which would count on system-level regulation of the energy and substance transport processes. At the same time, taking advantage of the solar-driven transport of energy and substances, some hybrid devices that integrates new functions like power generation into the heat-localized solar evaporators have been emerging. However, the complexity of coupled heat and substance transports have imposed great challenges for optimization of both heat-localized solar evaporation and their hybrid systems. To inspire strategies for improving the performance of heat-localized solar evaporation and their hybrid systems at a system level, this article critically reviews heat-localized solar evaporation from the perspective of energy and substance transport. This review first discusses the energy transport processes including solar-heat absorption, energy conversion in the phase transition, heat dissipation to the ambient, and the corresponding strategies for higher solar energy utilization efficiency. We then discuss the substance transport processes including vapor, water, and salt in those devices, which reveals the importance of several structure parameters including the surface area, thickness and pore diameter of the evaporator. Hybrid applications beyond water desalination are discussed, including electricity generation, solar photocatalysis, and superheated steam generation. Finally, we give directions for further performance improvement of the heat-localized solar evaporation and their extended hybrid systems, as well as unresolved challenges, such as efficient vapor-power co-generation and large-scale vapor condensation for fresh water. [Display omitted] • Thermodynamic limit of the heat-localized solar desalination systems is analyzed. • Energy and substance transports in heat-localized solar evaporators are elucidated. • Tradeoffs in designing high-efficiency heat-localized solar evaporators are analyzed • Progress and future opportunities in heat-localized solar evaporation are presented. [ABSTRACT FROM AUTHOR]

Liquid desiccant air-conditioning (LDAC) system is a promising alternative to the traditional vapor compression system. The most energy-consuming part of LDAC system is desiccant regeneration. An urgent issue that needs to be addressed is the inefficiency of traditional regeneration method. Solar heat localization is a novel and high-efficiency strategy for seawater desalination. However, the wide application is confined due to the low-efficient of water condensation and harvesting. In this work, the regeneration performance of heat localization method was investigated and an electric heating sheet was adopted to circumvent the effect of solar reflection. Compared with traditional heating method, the regeneration performance can be significantly improved by heat localization method. The regeneration efficiency of desiccant with 40 % concentration was significantly improved by 6 times (about 23.15 %) through heat localization method. Heat localization method allows immediate concentration of high-concentration desiccant with a low-temperature rise of regenerated desiccant. The low-temperature rise is beneficial for LDAC system due to less cooling energy is needed. This work is expected to extend the application of solar heat localization and provide some new information for liquid desiccant regeneration. [Display omitted] • An electric heating sheet was adopted to study regeneration performance of heat localization. • Regeneration efficiency can be improved by 6 times with heat localization methods. • The desiccant temperature regenerated by heat localization methods is the lowest. • Heat localization methods are more conducive to the regeneration of high concentration solution. [ABSTRACT FROM AUTHOR]

Facing the global water shortage challenge, solar-driven desalination is considered a sustainable technology to obtain freshwater from seawater. However, the trade-off between the salt cycle and heat localization of existing solar evaporators (SE) hinders its further practical applications. Here, inspired by water hyacinth, a self-standing and self-floating 3D SE with adiabatic foam particles and aligned water channels is built through a continuous directional freeze-casting technique. With the help of the heat insulation effect of foam particles and the efficient water transport of aligned water channels, this new SE can cut off the heat transfer from the top photothermal area to the bulk water without affecting the water supply, breaking the long-standing trade-off between salt cycle and heat localization of traditional SEs. Additionally, its self-standing and self-floating features can reduce human maintenance. Its large exposure height can increase evaporation area and collect environmental energy, breaking the long-standing limitation of solar-to-vapor efficiency of conventional SEs. With the novel structure employed, an evaporation flux of 2.25 kg m -2 h -1 , and apparent solar-to-vapor efficiency of 136.7% are achieved under 1 sun illumination. This work demonstrates a new evaporator structure, and also provides a key insight into the structural design of next-generation salt-tolerant and high-efficiency SEs., (© 2023 Wiley-VCH GmbH.)

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]

• The performance of solar interfacial regeneration method was investigated. • Drilling holes of wood regenerator can promote the salt resistance ability. • Sunlight absorption ability can be enhanced by drilling holes. • Regeneration rate can reach 0.64 kgm−2h−1 for 40 wt% CaCl 2 solution at 30 °C. Liquid desiccant air-conditioning (LDAC) systems are one of the most promising alternatives to conventional air conditioning systems due to the high energy efficiency. The most energy-consuming part of LDAS system is desiccant regeneration, while traditional regeneration methods often fail to balance the energy grade and energy efficiency. Inspired by solar heat localization for seawater desalination, the regeneration performance of this novel method has been investigated. Here, we fabricated a wood-based regenerator by drilling holes and spaying Chinese ink, which features high sunlight absorption and strong water transportation ability. Owing to the high hydraulic conductivity of drilled holes and low thermal conductivity of wood substrate, liquid desiccant can be regenerated efficiently with a low-temperature rise. Even for 40 wt% CaCl 2 solution at 30 °C, the regeneration rate and efficiency can reach 0.64 kg·m−2·h−1 and 43.2 %. Comparisons between solar interfacial regeneration method and other traditional regeneration methods were also conducted. Results show that the solar interfacial method can significantly improve the regeneration rate at the same temperature. Given the low manufacturing cost and operating cost, high regeneration rate and efficiency, superior salt-rejecting property, and low-temperature rise, the wood regenerators based on solar interfacial regeneration show great potential in LDAC systems. [ABSTRACT FROM AUTHOR]

Solar-driven interfacial evaporation is regarded as one of the most promising technologies to address the critical issue of global water scarcity. However, a great deal of energy is lost via conduction during the interfacial evaporation process. Herein, a self-floating Janus evaporator containing micron-sized isolated bubbles that can enhance heat localization is designed. The evaporator is synthesized by gas foaming polyacrylonitrile (PAN) nanofibers and subsequently depositing polypyrrole (PPy). The hydrophilic PAN nanofiber layer on the bottom of the evaporator with abundant macropores can continuously pump water upward through the capillary force. The hydrophobic PAN@PPy composite nanofiber layer on the top possesses a broadband solar absorption property, converting solar irradiation to heat efficiently. The low thermal conductivity of the isolated micron-sized bubbles enhances the thermal insulation of the obtained PAN foam@PPy Janus evaporator, while the stretching and expanding of the nanofibers induced by the bubbles contribute to its increased mechanical stability. This work offers a simple route to fabricate evaporators that can continuously produce drinking water from brine under sunlight, and provides a fresh idea to enhance the thermal insulation and mechanical properties of the conventional electrospinning-based fiber scaffold. [Display omitted] • A Janus evaporator is designed by gas-foaming and liquid-phase depositing techniques. • The isolated micron-sized bubbles can enhance the thermal insulation of the evaporator. • The evaporator is easy to achieve mass production. [ABSTRACT FROM AUTHOR]

Interfacial solar-driven water evaporation is an effective strategy to solve freshwater scarcity. Efficient interfacial evaporation comes from excellent photothermal material. Herein, we developed a multilayer carbon-fiber fabric (MCF) evaporator with excellent mechanical properties for efficient solar-driven water purification. The all‑carbon composition and multilayer honeycomb structure endows the MCF with a high broadband light absorption (97%), rapid water transport, and good thermal management. As a result, the MCF shows an impressive purification capacity for seawater and organic wastewater and a good inhibition for the volatilization of low-boiling-point organic components. Under 1 sun irradiation, the evaporation rate can reach 3.39 kg∙m−2∙h−1. The outstanding salt-rejecting property also enables perfect stability and reusability. Even 20 wt% brine has no impact on the evaporation process and energy efficiency. More importantly, the MCF can effectively resist mechanical destruction from the environment, maintain its structural integrity. The concept of MCF with a hierarchical structure and multiple attributes will stimulate more inspiration for the development of solar-energy desalination and sewage treatment. [Display omitted] • The multilayer CF evaporator has excellent mechanical properties and purification capacity. • The enthalpy of interfacial water evaporation decreases from 2392.53 to 1094.28 J∙g−1 • Under 1 sun irradiation, the evaporation rate can reach 3.39 kg∙m−2∙h−1. • The multilayer structure of CF fabrics supply outstanding salt-rejecting properties and inhibition of organic volatilization. [ABSTRACT FROM AUTHOR]

Seawater desalination has a strong potential for solving global water shortage problem, and solar-based evaporative desalination technology has received increased attention. For successful solar steam generation (SSG), solar energy should be utilized in a balanced manner through heat localization. In this study, we propose a sucrose‑carbonized sugar-templating polydimethylsiloxane (PDMS) sponge sealed with ethyl vinyl acetate (EVA) foam, called as C-STP sponge. The C-STP sponge consists of a double-layered porous structure with carbonaceous material on the top surface. The C-STP sponge exhibits high SSG performance in long-term operation with anti-salt fouling ability by its self-cleaning feature. Several factors governing the C-STP sponge were optimized by examining two different kinds of sugar with different porosity levels and carbonized layer thicknesses. The porous C-STP sponge has numerous micropores caused by sugar-leaching, thereby decreasing the thermal conductivity to improve the evaporation rate. The heat localization aspects of PDMS were also investigated. The highest solar evaporation was 1.53 kg m−2 h−1 during long-term operation up to water depletion. The C-STP sponge is easy to fabricate as a solar evaporator and has much room for enhancing solar evaporation efficiency in the future. This work on dual-insulation sponge-based SSG system will provide insights for practical applications. [Display omitted] • The structure was fabricated by carbonizing sugar based on the porous PDMS structure. • The effect of carbonization thickness and porosity were investigated. • The sponge could be used for a long time with a constant evaporation rate. • The sponge has a self-cleaning surface when not in use. • The bilayer sponge with insulation foam could minimize the heat loss. [ABSTRACT FROM AUTHOR]

As an efficient method of seawater desalination, multi-stage solar distillation based on interfacial heat localization is facing to the problems of salt ions accumulation and crystallization that hard to discharge, which makes it difficult to obtain scalable and sustainable water production. Here we proposed and explored a fully passive and extra efficient discharge mechanism of concentrated brine based on open siphoning flow. Nano fiber is used as the super-hydrophilic membranous wick to analyze open siphoning flow. It is found the siphoning flowrate tends to the same value when each of suction height and short transverse flow length is large enough, which makes it possible to match the siphoning flowrate and heat capacity among multiple evaporation-condensation interfaces. A three-stage solar distiller was constructed and studied theoretically and experimentally. Under one sun (1000 W/m2), the water productivity is 238 g/h, which is nearly 82% of the total seawater flowing in, and the remaining 18% flows out as strong brine with a salinity of 19.6%. In addition, a water production of 940 g is obtained with an average gained-output ratio of 1.5 in a whole-day test, namely, 11.99 kg/(d·m2). This study may improve large-scale interfacial evaporation with efficient salt rejection. • Salt accumulation hinders interfacial evaporation of heat localization. • Super-hydrophilic wick can form siphonage between two water containers. • Both interfacial evaporation and brine discharge can be obtained by open siphonage. • Brine discharged by siphonage has salinity of 19.6% under one sun. • The daily water productivity is 11.99 kg/m2 with average gained-output ratio of 1.5. [ABSTRACT FROM AUTHOR]

Solar evaporation is a sustainable and green strategy to relieve the growing global freshwater crisis. In this strategy, a solar irradiation absorber platform absorbs the sunlight and converts it into heat for water evaporation. Herein, a new class of nitrogen-doped graphene quantum dots (N-GQDs) hydrogels has been developed for highly efficient solar water evaporation via the heat localization mechanism. N-GQDs hydrogels are fabricated via the hydrothermal self-assembly process. Using N-GQDs with different lateral size ranges as the precursor, hydrogels with different structural properties and solar water evaporation efficiencies are prepared. The highest achieved solar steam generation efficiency in this work is 89.7% obtained by employing N-GQDs with the smallest lateral size range in the precursor solution. The steam generation efficiency of hydrogels reduces with increasing the lateral size of synthesized N-GQDs in precursors. The colloidal morphology, high hydrophilicity, hierarchical pore structure, and low thermal conductivity of prepared N-GQDs hydrogels result in the high performance of these structures in solar water evaporation applications. [Display omitted] • Nitrogen-doped GQDs hydrogels are prepared via the hydrothermal reduction process. • Prepared hydrogels have colloidal structures with interconnected hierarchical porosities. • Solar steam generation efficiencies as high as 89.7% is achieved via prepared hydrogels. [ABSTRACT FROM AUTHOR]

Solar steam generation as a green and sustainable technology has recently attracted significant interest for relieving the longstanding challenge of clean water resources. However, the large-scale preparation of low cost photothermal materials for solar steam generators is highly desired yet still challenging. Herein, semi-coke (SC), a solid byproduct of coal industrial, was first demonstrated as an efficient photothermal material and successfully applied in solar steam generation system by depositing SC on melamine sponge with the assistance of polydopamine. Then, the modified melamine sponge was functionalized by hydrophobic methyl trichlorosilane to fabricate the self-floating semi-coke/polydopamine@photothermal melamine sponge (SPMS). Based on their outstanding light absorption, good wettability, and effective thermal location, the SPMS performs a high evaporation rate of 1.41 kg m−2 h−1 with a solar thermal conversion efficiency of 90.56% under 1 sun irradiation. Meanwhile, the SPMS has remarkable cycle stability and water purification abilities for seawater, dyeing wastewater and heavy metal solution. By turning "waste" to "wealth", the SPMS shows great potential for sustainable applications in synergetic solar clean water production. [Display omitted] • The waste semi-coke was first applied for solar steam generation. • A self-floating system inspired by ducks was fabricated. • Extremely low cost and abundant resources made this absorber stand out. • Excellent water purification capacity. [ABSTRACT FROM AUTHOR]

• As high as 124.14% of evaporation efficiency was achieved by 2D photothermal membrane. • The PSf substrate possessed ultra-low thermal conductivity of 0.04 W m−1 K−1. • The CB/rGO/PS layer provided dual-function including light absorption and water path. • The introduction of rough structure enhanced light absorption to 96.25%. Solar steam generation was widely considered as a promising desalination method due to its pollution-free, coordination and sustainability. In the present work, we proposed a new fabrication strategy for photothermal composite membrane, which was composed of hydrophobic polysulfone (PSf) membrane substrate and top hydrophilic functional layer involved reduced graphene oxide (rGO) and polystyrene (PS) microspheres. The PSf membrane obtained via the solvent volatilization process had ultra-low thermal conductivity by virtue of the enclosed cellular-like pore structure, which effectively restrained the heat diffusion from the absorption surface to the bottom water and ensured that the heat energy was confined to the evaporation surface. The rGO/PS layer acquired by introducing PS microspheres into the light absorbing layer showed high broadband solar absorption capacity depending on multiple scattering effects, and also provided efficient and continuous water transportation path by right of strong capillarity. Finally, the rGO/PS@PSf composite membrane showed excellent solar water evaporation rate of 1.06 kg m−2h−1 and evaporation efficiency of 69.58% under one sunlight. Further, with the addition of carbon black (CB) into rGO/PS functional layer and breaking the membrane into several pieces, the solar evaporation rate and efficiency had been further improved up to 1.86 kg m−2h−1 and 124.14%, respectively. This composite structure makes it a promising material for efficient seawater desalination. [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]

• Modeling framework of thermally-localized multistage solar stills (TMSS) is developed. • Heat and mass transfer in the TMSS are analyzed in detail. • Optimization strategies for the TMSS are presented. • Ultrahigh solar-thermal cumulative efficiency over 700% is predicted. Seawater desalination is a promising solution to global water shortage. Commercially available desalination technologies typically require large installations which can be impractical for developing regions without well-developed infrastructure. Passive solar desalination promises a viable solution, but can suffer from low efficiencies. Recent advances in the thermal design of small-scale solar desalination systems have demonstrated the potential for high-efficiency solar desalination in portable systems. In particular, the concept of a thermally-localized multistage solar still (TMSS) – which combines localized heating of a capillary flow with condensation heat recycling – has been experimentally demonstrated very recently and achieved over 100% solar-thermal cumulative efficiency. However, a fundamental understanding of the heat and mass transfer, efficiency limits and optimization strategies are missing in the literature. This work presents a modeling framework that evaluates the thermal and vapor transport in a model TMSS system with varying device configuration and predicts its solar desalination efficiency. We demonstrate that an ultrahigh solar-thermal cumulative efficiency, many times higher than that of conventional solar stills, can be achieved by optimizing the number of stages and device geometry. Specifically, our modeling shows that the efficiency of the capillary fed TMSS is limited by the dissipation of thermal energy to the environment during condensation and significant gains in efficiency can be achieved by minimizing this loss. This work provides insights into physical processes critical for thermally-localized portable solar distillation which could lead to high-performance desalination or water purification technologies. [ABSTRACT FROM AUTHOR]

Solar-thermal water evaporation is a promising technology for pure water production. However, the design of low-cost systems for efficient antifouling solar-thermal water evaporation remains a challenge. Herein, an evaporator based on metal oxy-hydroxides with a hierarchical and hollow structure is rationally designed through material selection and structural engineering. The obtained evaporator possesses good light absorption performance, excellent antifouling property against oil, and enhanced heat localization ability. Consequently, the water evaporation rate reaches as high as 1.65 kg m -2 h -1 with a solar-thermal conversion efficiency up to 82.3% under 1 sun illumination. More importantly, the evaporator exhibits almost identical evaporation performance in oily wastewater and natural seawater due to its superhydrophilicity and underwater superoleophobicity. This work provides a worth-adopted approach to prepare solar-thermal evaporators with high efficiency and anti-oil-fouling property, highlighting the new application of metal oxy-hydroxide-based materials and the importance of a hierarchical and hollow structure for efficient solar-thermal water evaporation.

Heat propagation in quasi-one-dimensional materials (Q1DMs) often appears puzzling. For example, while an isolated Q1DM, such as a nanowire, a carbon nanotube, or a polymer, can exhibit a high thermal conductivity κ, forests of the same materials can show a reduction in κ. Until now, the complex structures of these assemblies have hindered the emergence of a clear molecular picture for this intriguing phenomenon. We combine coarse-grained simulations with concepts known from polymer physics and thermal transport to unveil a generic microscopic picture of κ reduction in molecular forests. We show that a delicate balance among the persistence length of the Q1DM, the segment orientations, and the flexural vibrations governs the reduction in κ.

Solar steam generation is receiving considerable interest because of its potential application in wastewater treatment and desalination. Many devices with various photothermal materials and structures have been demonstrated to be solar steam evaporators by improving their light absorption, heat loss, water transportation, and vapor escape. However, developing a biomass-based evaporator with heat localization and rapid water transportation is highly desired yet still challenging. Here, corncobs, a kind of agricultural waste with vascular bundle and "vesiculose" structures, are used to fabricate solar steam-generation devices. After high-temperature treatment, the carbonized corncobs maintain the highly anisotropic porous framework and favorable hydrophilicity and thereby have excellent thermal management and water transportation. With efficient solar absorption, heat localization, and rapid water transportation, the lightweight carbonized corncobs can float on water and generate water vapor with a high steam generation efficiency of 86.7% under 1 sun.

Heat localization has been proposed as a new strategy to utilize solar energy efficiently. In the past few years, extensive research on heat localization has been limited to solar-steam generation. Many devices have been designed to improve the efficiency of photothermal conversion, but the complex preparation processes and the cycle instability limit its large-scale practical application. Herein, we fixed reduced graphene oxide and silver nanoparticles on a melamine sponge skeleton by a simple coating method. The modified sponge retained the high porosity of the sponge substrate and exhibited photothermal properties and hydrophobicity. Consequently, the modified sponge showed a high solar-steam evaporation efficiency (86.8%) under one-sun irradiation and an excellent adsorption capacity to organic solvents and low viscosity oils (54.0–123.0 g/g). The modified sponge also reduced the viscosity of the heavy crude oil under the driving of solar energy to achieve a high adsorption capacity of heavy crude oil (68.0 g/g under one sun). Because of the excellent mechanical properties of the melamine sponge substrate, the modified sponge had great reusable performances, and met the simple and scalable manufacturing requirements in practical applications. This material provides a new idea for the recovery of heavy crude oil and provides new applications for photothermal-conversion materials. Image 1 • An efficient photothermal conversion sponge was prepared via a facile method based on reduced graphene oxide and silver nanoparticles. • High solar steam generation efficiency of 86.8% achieved under one-sun irradiation. • The clean-up of crude oil spills under the driving of solar energy was greatly accelerated. [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]