High-efficiency Evaporation Research Articles

Thermo-adaptive interfacial solar evaporation enhanced by dynamic water gating

Solar-driven evaporation offers a sustainable solution for water purification, but efficiency losses due to heat dissipation and fouling limit its scalability. Herein, we present a bilayer-structured solar evaporator (SDWE) with dynamic fluidic flow mechanism, designed to ensure a thin water supply and self-cleaning capability. The porous polydopamine (PDA) layer on a nickel skeleton provides photothermal functionality and water microchannels, while the thermo-responsive sporopollenin layer on the bottom acts as a switchable water gate. Using confocal laser microscopy and micro-CT, we demonstrate that this unique structure ensures a steady supply of thin water layers, enhancing evaporation by minimizing latent heat at high temperatures. Additionally, the system initiates a self-cleaning process through bulk water convection when temperature drops due to salt accumulation, thus maintaining increased evaporation efficiency. Therefore, the optimized p-SDWE sample achieved a high evaporation rate of 3.58 kg m−2 h−1 using 93.9% solar energy from 1 sun irradiation, and produces 18–22 liters of purified water per square meter of SDWE per day from brine water. This dynamic water transport mechanism surpasses traditional day-night cycles, offering inherent thermal adaptability for continuous, high-efficiency evaporation.

Suppressed Droplet Splashing on Positively Skewed Surfaces for High-Efficiency Evaporation Cooling.

Two types of functional surfaces with the same roughness but completely different surface topographies are prepared, namely positively skewed surfaces filled with micropillar arrays (Sa ≈4.4µm, Ssk >0) and negatively skewed surfaces filled with microcavity arrays (Sa ≈4.4µm, Ssk <0), demonstrating promoting droplet splashing. Remarkably, the critical Weber number for generating satellite droplets on the negatively skewed surfaces is significantly lower than that on the positively skewed surfaces, indicating that the negatively skewed surface with microcavity arrays is more likely to promote droplet splashing. It is mainly attributed to the fact that air on the negatively skewed surface can make the liquid film take on a Cassie-Baxter state on the surface so that the stabilizing capillary force of the liquid film exceeds the destabilizing stress of the air film. Moreover, the surface topography promoting droplet spreading and the mechanical properties of three-phase moving contact lines are analyzed from the perspective of microscopic interface mechanics. Finally, it is demonstrated the designed positively skewed surfaces can be employed for large-area heat dissipation by means of high-efficiency evaporation.

Highly efficient MoS2/MXene aerogel for interfacial solar steam generation and wastewater treatment

Interfacial solar steam generation using aerogels holds great promise for seawater desalination and wastewater treatment. However, to achieve aerogels with both durable, high-efficiency evaporation performance and excellent salt resistance remains challenging. Here, a molybdenum disulphide (MoS2) and MXene composite aerogel with vertical pore channels is reported, which has outstanding advantages in mechanical properties, water transportation, photothermal conversion, and recycling stability. Benefiting from the plasmon resonance effect of MXene and the excellent photothermal conversion performance of MoS2, the aerogel exhibits excellent light absorption (96.58 %). The aerogel is resistant to deformation and able to rebound after water absorption, because of the support of an ordered vertical structure. Moreover, combined with the low water evaporation enthalpy, low thermal conductivity, and super hydrophilicity, the aerogel achieves an efficient and stable evaporation rate of about 2.75 kg m−2h−1 under one sun and exhibits excellent self-cleaning ability. Notably, the evaporator achieves removal rates of 99.9 % for heavy metal ions and 100 % for organic dyes, which has great potential in applications including seawater desalination and wastewater purification.

Multifunctional graphene/Ag hydrogel with antimicrobial and catalytic properties for efficient solar-driven desalination and wastewater purification

The increasing shortage of freshwater resources needs to be addressed urgently. Solar-driven desalination and wastewater purification are efficient and green methods to obtain freshwater resources. However, it is still a challenge to obtain efficient, stable, salt-resistant, antimicrobial, and antifouling evaporators. To address this challenge, in this study, polyacrylamide-based reduced graphene oxide hydrogels with a porous structure were synthesized in situ by a one-step radiative reduction method, and silver nanoparticles were introduced on this basis. Graphene/silver composite hydrogel (ArG-Ag) exhibits fast water transport, thermal localization, and low enthalpy of water evaporation, achieving an excellent evaporation rate of 3.089 kg m-2h−1 (one sun) and an evaporation efficiency of 122.7 %, as well as good mechanical stability, salt resistance, and salt ion purification after 8 cycles of evaporation. The ArG-Ag evaporator exhibits 99 % 24 h bacterial inhibition against E. coli and 210-day long-term mold resistance, effectively resisting biological contamination of seawater. In this study, multifunctional evaporators with integrated high efficiency evaporation performance, salt resistance, antimicrobial, antifungal, antifouling, and catalytic properties are proposed, which are expected to be used for seawater desalination and wastewater purification.

Engineering of 0D/1D architectures in 3D networks over CDs/PPy-CPP biomass foam with high efficiency on seawater evaporation

Converting waste biomass into solar evaporator foam has been recognized as an effective strategy for waste recycling and solving the problem of water shortage, but problems of salt deposition and mechanical stability seriously hinder their practical application. Herein, this work proposes a sustainable and high mechanical strength biomass foam (CDs/PPy-CPP) evaporator with zero-dimensional/one-dimensional (0D/1D) hierarchical structure by hydrophilic carbon dots (CDs) and tubular polypyrrole (PPy) are seamlessly integrated into the outer surface of the three-dimensional (3D) carbonized pomelo peel (CPP) biomass foam. The evaporator achieved a high-efficient evaporation rate of up to 2.46 kg m−2 h−1 in 3.5 wt% NaCl solution at 1 sun irradiation, and similarly exhibited outstanding salient evaporation efficiency and resistance to salt deposition in 25 wt% NaCl solution, as well as prominent swage purification ability. Excellent photothermal conversion efficiency is demonstrated attributed to the 0D/1D structure in 3D networks of the CDs/PPy-CPP evaporator, as well as superior mechanical and water transport properties based on the multilayer mesh structure and microscopic water transport pores. The research intends to offer a low-cost, energy-efficient, and environmentally friendly approach to obtain multifunctional photothermal biomass foams and demonstrate the potential applications in seawater desalinization and swage purification.

An Experimental Study on the Cooling Performance of Refrigerant (R134a/R1234yf) in Automobile HVAC System

The present work deals with the experimental investigation on the performance evaluation of R134a and R1234yf as automotive HVAC refrigerants. As the usage of R134a increases environmental issues due to its higher global warming potential (GWP), it is necessary to find an alternative without compromising the performance of the HVAC system. R1234yf having low GWP is one such drop-in alternative. But the COP of the system using R1234yf is observed to be low. Hence this work investigates on the effects of using an internal heat exchanger (IHX) with the conventional automotive HVAC system in the performance enhancement. The results indicate acceptable range of cooling capacity, COP and compressor discharge temperature for R1234yf when integrated with IHX and a high efficiency evaporator. COP of the R1234yf IHX system is observed to higher than the COP of R134a baseline system. The results of cooling capacity and compression discharge temperature of R1234yf IHX system also shows an enhancement and matches with the corresponding values of R134a baseline system.

An ecofriendly and efficient wood-based polyoxovanadate solar evaporation generator

Currently, freshwater scarcity is a global challenge, and developing low-cost methods for purifying, desalinating, and distilling seawater is crucial. Natural wood, owing to its advantages of high hydrophilicity, low density, microporous channels, and low thermal conductivity, is widely considered a vehicle for solar evaporation. However, the majority of the reported wood-based solar evaporation generators have been economically inefficient, with limited evaporation rates under low-power solar irradiation. Herein, we developed an ecofriendly and efficient wood-based solar evaporation generator comprising a material with excellent photothermal conversion efficiency, polyoxovanadate, loaded on the wood surface with a natural channel structure. The solar evaporation generator exhibited high light absorption capacity (∼98%) in the wide wavelength range of 200–1200 nm, rapid water transport through the wood channels, minimal heat dissipation due to the adiabaticity of the wood, and reduced evaporation enthalpy. Therefore, the overall evaporation efficiency was increased, and a high evaporation rate of 2.23 kg m−2 h−1 and solar-vapor efficiency of 90% under 1 Sun was observed. This environment-friendly, low-cost, and high-efficiency evaporation generator has enormous potential for practical applications in solar desalination and water purification.

Dual-hydrophilic Janus evaporator for Long-term and efficient Bimode solar evaporation

Solar steam generation has emerged as a promising and sustainable technology to solve the global water scarcity. However, the fabrication of low-cost and high-efficiency evaporator with long-term stability remains a great challenge. Herein, a dual-hydrophilic Janus evaporator coupled with inclined isolating structure is fabricated to realize long-term efficient solar evaporation and flexible salt manipulating, where the upper electrospun Mo2C-C@PAN membrane serves as the evaporation layer and the bottom nonwoven fabric functions is used as mass transporting layer. The encapsulating feature of the Mo2C-C@PAN enables better energy confinement and reduces the usage of solar absorber by ∼50 % without deteriorating the evaporation performance. The hydraulic conductivity difference prevents the Marangoni effect inner the Janus evaporator, while the inclined isolating structure enables unidirectional ions transporting. With features of adequate water transport, enhancement of energy confinement, and salt manipulation, the constructed inclined Janus evaporators can not only work stably for 200 h in 10 wt% NaCl solution without salt accumulation, but also achieve efficient salt harvesting with rate of ∼260 g m−2 d−1 under one sun. This study provides new possibilities for a dual-hydrophilic Janus evaporator for a long-term, efficient, and synergistic extraction of fresh water and mineral salt resources.

Development of MXene-decorated sodium alginate/SiO2@n-docosane hierarchical phase-change microcapsules for solar-driven sustainable seawater desalination

A novel type of MXene-decorated and sodium alginate (SA)-coated phase-change microcapsules (hereafter named “MXene/SA/SiO2-MEPCM”) was designed as a bifunctional solar absorber for the interfacial evaporator to realize sustainable seawater desalination. The MXene/SA/SiO2-MEPCM was fabricated by encapsulating n-docosane as a phase change material (PCM) in the SiO2 shell, followed by depositing a SA layer and decorating MXene nanosheets. An innovative integration of SA and MXene nanosheets enables the microcapsules to achieve a high light absorption capability of over 97 % together with good wettability, promoting a high evaporation rate of 2.11 kg·m−2·h−1 under one-sun illumination. The MXene/SA/SiO2-MEPCM exhibits a high latent heat capacity of over 150 J·g−1 for consecutive and high-efficient evaporation under intermittent solar illumination. Compared to the evaporator without a PCM core, the MXene/SA/SiO2-MEPCM-based evaporator achieved an increase in evaporation mass by 1.4 kg·m−2 through 5-cycle consecutive evaporation processes under solar illumination and natural cooling. Furthermore, its total water production was increased by 1.01 kg·m−2 under natural solar illumination for 7.5 h on a semi-cloudy day. The MXene/SA/SiO2-MEPCM also exhibits good recyclability for long-term use in solar-driven seawater desalination thanks to the good structural stability of its shell and highly stable reversible phase transitions of its PCM core.

Fabrication of a Highly Efficient Wood-Based Solar Interfacial Evaporator with Self-Desalting and Sterilization Performance.

Solar interfacial evaporation based on wood-derived materials has been considered a promising strategy for desalination and wastewater purification. Herein, we adopted delignified wood (DW) as the water transport substrate and lignosulfonate (LS)-modified narrow-band gap semiconductor nickel disulfide (NiS2) as the light-absorbing agent (LS-NiS2) to fabricate a high-efficiency evaporator (LS-NiS2@DW). On the one hand, the high absorbance (>95%) within a broad wavelength range and excellent photothermal conversion efficiency of LS-NiS2 endow efficient solar energy utilization. On the other hand, the hydrophilicity of DW facilitates water activation, which results in a lower evaporation enthalpy of LS-NiS2@DW (1274.4 kJ kg-1) than that of pure water. By combining LS-NiS2 and DW, LS-NiS2@DW achieved an evaporation rate as high as 2.80 kg m-2 h-1 under one sun irradiation (1 kW m-2), and the evaporation efficiency reached 87.4%. Notably, LS-NiS2@DW exhibits a high evaporation rate (2.42-2.69 kg m-2 h-1) in simulated seawater for 24 h with no salt crystals formed on the surface. Moreover, LS-NiS2@DW shows high antibacterial activity with about 90% reduction in bacterial survival rate. This work could provide new perspectives for the design of a high-efficiency wood-based photothermal evaporator.

Hierarchical unidirectional fluidic solar-electro-thermal evaporator for all-day efficient water purification

Constructing a high-efficiency evaporation system with all-day operation capability remains a great challenge for the emerging solar water purification technologies due to the accompanied salt-fouling problem and uncertain natural sunlight conditions. Here, a hierarchical solar-electro-thermal evaporator with serpentine and unidirectional fluidic structure is developed by in situ assembling MoS2 nanosheet arrays on activated Ti mesh to integrate solar-thermal desalination and electro-thermal desalination for all-day efficient clean water production. The serpentine structure serves as controllable current channels for efficient Joule heating, whereas the unidirectional fluidic structure functions as water pathways for manipulating the salt migration. As a result, the fabricated device realizes continuous water extraction from 6.0% of concentrated brine under 3 sun for 8 h without salt accumulation, and the evaporator can achieve extremely high water evaporation rate of 7.88 kg/m2/h under solar-electro-thermal mode based on the critical synergistic effect (1 sun-2.0 A). As a proof-of-concept application, the 3D printing desalination system can achieve continuous clean water extraction from seawater and/or wastewater with high production rate of 7.4 kg/m2/d and salt ions concentration far below the drinking standards defined by the World Health Organization.

The mechanism for solar irradiation enhanced evaporation and electricity generation

Generating electricity via natural water evaporation from porous materials is a promising energy-harvesting strategy and solar irradiation is a feasible and sustainable way to accelerate water evaporation. However, it is hard to enhance the evaporation-induced electricity by solar irradiation due to the lack of understanding on the working mechanism. Here we demonstrate that a tilted structure design with cheap carbon black materials can achieve about 180% enhancement in water-evaporation-induced power generation at a high-efficiency evaporation rate of up to 3.94 kg m-2 h-1 under one sun illumination. The enhanced water evaporation from the porous structure can continuously generate a voltage of up to 1.39 V with a maximum power density of about 0.103 mW m-2 without active electrodes involved. Detailed experimental results reveal that solar irradiation and thermal energy in the environment play a synergistic role in enhancing the output performance mainly through the electrokinetic effect of streaming potential. The facile structure design, easy-to-access materials and tilt angle dependent enhancement in evaporation and output performance in this work open a viable way to simultaneously harvest solar and environmental energy for cogeneration of freshwater and electric power.

Engineering a superhydrophilic TiC/C absorber with multiscale pore network for stable and efficient solar evaporation of high-salinity brine

Achieving stable and efficient solar-driven evaporation of high-salinity brine is highly desirable while challenging because of salt inevitably blocking the evaporator surface during vapor generation. One of the effective resolvents is to construct macropores to ensure sufficient diffusion and convection of concentrated salt back into the bulk water. Herein, inspired by the interconnected pores of the balsa wood, superhydrophilic porous TiC/C absorber (SPTCA) with macro-/micro-/nano-pores network is successfully built by carbothermic reduction. The macropores channel plays the role of water transport, steam overflow, and salt ion diffusion backflow. The micro-/nano-pores channel enables broadband light absorption and keeps the moisture in a small range to achieve high-efficiency evaporation. With this rational design, the evaporator alloys for a stabilized evaporation of 1.78 kg/m2 h from simulated seawater for over 100 days and 1.75 kg/m2 h from high-salinity brine (15 wt.% NaCl) for over 50 days under 1 sun irradiation. The SPTCA provides a promising avenue for architecting the multiscale-pores network for solar desalination of high-salinity brine.

Honeycomb-structured fabric with enhanced photothermal management and site-specific salt crystallization enables sustainable solar steam generation

The emerging of solar-driven interfacial evaporation provides new opportunities to alleviate the shortage of fresh water resource. Nevertheless, in practical solar desalination, salt precipitation will lead to the decrease of evaporation rate due to reduced light absorption and blocked evaporation channels of evaporator. It still remains a challenge to eliminate salt accumulation and simultaneously maintain high-efficient evaporation. In this work, a solar evaporator was prepared based on reduced graphene oxide and chitosan coated honeycomb-structured fabric (rCHF). The rCHF showed a high light absorbance of 97.2% due to enhanced light trapping of the honeycomb structure and ultra-low thermal conductivity of 0.044 W m−1 K−1. Furthermore, the temperature gradient generated inside the honeycomb unit can induce the Marangoni effect, which led to the site-specific salt crystallization on rCHF in seawater evaporation. As a result, the rCHF realized an excellent solar evaporation rate of 2.02 kg m-2h−1 under one sun irradiation (1 kW m−2). The site-specific salt crystallization on the surface of rCHF ensured stable evaporation even in 20% brine, and the isolated salt can be removed by natural dissolution owing to the excellent hydrophilicity of rCHF. This work provides a new perspective for the design of solar evaporator for practical solar seawater desalination.

Numerical simulation of flow pattern for non-Newtonian flow in agitated thin film evaporator

Agitated thin film evaporator (ATFE) is a new type of high-efficiency evaporator where a film is forced to form through a rotating scraper and the high-viscosity non-Newtonian flow materials can be evaporated smoothly. The flow distribution and transmission mechanism of the material in the evaporator directly determine the evaporation efficiency and power consumption of the evaporator. Unlike previous study that was based mainly on Newtonian flow, this paper establishes a three-dimensional computational fluid dynamics model of ATFE for non-Newtonian flow with different viscosities, and systematically probes the flow field distribution characteristics and film forming mechanism in the evaporator. The results show that the flow field distribution characteristics of low-viscosity non-Newtonian flow are similar to those of Newtonian flow, the material can form a uniform and continuous liquid film on the wall; as the viscosity increases, the uniformity and continuity of the liquid film gradually deteriorate. Through studying the flow field distribution and transmission form of the materials, and combining the liquid film distribution, velocity distribution, shear strain rate distribution, and viscosity distribution, it is found that the shear field and viscosity distribution formed by the internal structure and operating state of the evaporator are the key to the good film formation. In addition, it is proposed that the bending of the leading edge of the scraper can assist the spreading of high viscous fluid liquid film, and the best bending angle is explored. This research provides theoretical guidance and basis for the design and application of ATFE.

A waste biomass-derived photothermic material with high salt-resistance for efficient solar evaporation

Effective use of solar energy to produce steam for solving the problem of global shortage of fresh water is considered to be a promising technology. In this work, we reported a low-cost, high-efficient, waste biomass-derived solar evaporator with Janus structure was readily constructed from porous pomelo peel (PP). This multifunctional photothermal sponge has a hydrophobic top layer and a hydrophilic bottom layer to prevent the accumulation of salt on the surface of the evaporator, ensuring high efficiency and stable water vapor output. After hydrophobic modification of one side of freeze-dried PP, MXene was sprayed on the Janus PP (JPP), the interfacial solar energy driven water evaporation can be effectively realized for seawater desalination. The evaporation rate and solar thermal conversion efficiency of JPP@MXene (JPP@M) under simulated sunlight irradiation with one sun (1 kW m−2) were 1.48 kg m−2·h−1 and 92.3% respectively. Under simulated sunlight irradiation of 1 sun, a high efficiency evaporation performance could be maintained after 50 cycles. In addition, JPP@M could be used to effectively reduce the viscosity of heavy crude oil through solar-assisted heating, resulting in effective purification. Moreover, JPP@M exhibited excellent antibacterial property, which is more important for biomass samples. This cost-efficient, sustainable and eco-friendly photothermic sponge is expected to be used for large-scale wastewater treatment and clean water generation.

Self-Healing Hydrophilic Porous Photothermal Membranes for Durable and Highly Efficient Solar-Driven Interfacial Water Evaporation

Self-Healing Hydrophilic Porous Photothermal Membranes for Durable and Highly Efficient Solar-Driven Interfacial Water Evaporation

Synergistic adjustment of water channels and light absorption pathways to co-generate salt collection and clean water production

Solar-driven interface evaporation for clean water production has attracted significant concern due to its energy-saving and environmental protection. However, it is still challenging for the evaporator to continuously and efficiently produce clean water in practical applications because of salt particle deposits and insufficient water supply. Here, an improved and easy-to-manufacture solar evaporator device (Co-NCNT-GO system) enhances water supply and light absorption by introducing a water supply layer (melamine sponge) and bamboo-like structure carbon nanotubes embedded with metal cobalt particles (Co-NCNT). The salt accumulation on the edge of the Co-NCNT-GO film is achieved by controlling the concentration gradient of brine in the center area and the edge area of the film. This paper aims to study the photothermal mechanism of the Co-NCNT-GO system through a series of characterization and theoretical calculations (DFT) and discuss the influence of different water supply areas on the salt recovery capacity. The results show that Co-NCNT-GO significantly reduces the band (0.054 au) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUNO) by graphite nitrogen-doped CNTs, which is beneficial to improve the light-to-heat conversion capability. Furthermore, the Co-NCNT-GO film has good water wettability due to the higher adsorption energy of pyridine nitrogen and water molecules in Co-NCNT (−9.33 kcal/mol). Simultaneously, it is found that the water evaporation capacity and water supply capacity significantly affect whether the salt can be continuously crystallized at the edge of the film. When the ratio of water supply area to light and heat area is 4:2.5, the salt recovery rate is 46.54 g m−2 h−1 during 108 h continuous desalination under one sun illumination. This rationally designed structure and adjustable water transport channel can simultaneously meet high-efficiency evaporation and salt recovery, which can have great potential in practical applications.

Self-regulating and asymmetric evaporator for efficient solar water-electricity generation

Water evaporation is a ubiquitous natural process than can be applied to generate electricity through hydrovoltaic effect. However, it remains a great challenge to construct an evaporation system that can satisfy both high-efficiency evaporation and stable power output due to their differences in water managements. Herein, we demonstrate a sandwich membrane strategy to construct a three-dimensional (3D) asymmetric evaporator for efficient tandem solar water-electricity generation by coating two carbon black (CB)/polyvinyl alcohol (PVA) functional films with different channel structures and water uptake at two opposite sides of a wood chip. Owing to the smart self-regulating property of the thin PVA skin and the superior thermal utilization performance of the 3D structure, the fabricated device achieves high evaporation rate of 1.93 kg m −2 h −1 . More importantly, the asymmetric water distribution of the evaporation unit and the confined nanochannels of the dense PVA network render the generator with stable and efficient power output, and the simple connections of several units in series and/or parallel can easily power a commercial calculator, electrolyze methylene blue solution, and light up light emitting diodes, which well proves the conception of combining solar water evaporation and electricity generation in an integrated device. • A sandwich evaporator was for the first time fabricated to achieve efficient solar water-electricity generation. • The fabricated device achieves high water evaporation rate of 1.93 kg m −2 h −1 . • The evaporation unit has asymmetric water distribution and confined nanochannels for stable and efficient power output. • The integrated device can easily power a commercial calculator, electrolyze methylene blue solution, and LEDs.

Sandwich Photothermal Membrane with Confined Hierarchical Carbon Cells Enabling High-Efficiency Solar Steam Generation.

Solar-driven vaporization is a sustainable solution to water and energy scarcity. However, most of the present evaporators are still suffering from inefficient utilization of converted thermal energy. Herein, a universal sandwich membrane strategy is demonstrated by confining the hierarchical porous carbon cells in two energy barriers to obtain a high-efficiency evaporator with a rapid water evaporation rate of 1.87 kg m-2 h-1 under 1 sun illumination, which is among the highest performance for carbon-based and wood-based evaporators. The significantly enhanced evaporation rate is mainly attributed to the inherently optimized porous evaporation mode derived from the hierarchical hollow structures of pollen carbon cells, and the synergistically regulated water transporting and thermal management performance of the sandwich membrane. Moreover, the constructed sandwich membrane also exhibits excellent self-regenerating performance in simulated seawater and high salinity water. The developed device can maintain an average evaporation rate of 4.3 L m-2 day-1 in a 25 day consecutive outdoor test.