Solar Thermal Evaporation Research Articles

A sustainable MXene/PVA/CNFs@Fabric roll-based 3D photothermal evaporator integrating efficient evaporation and anti-pollution design

Solar-driven interface evaporation is an effective approach towards achieving clean seawater desalination. The focus of research in this field lies in attaining sustained, stable, and efficient steam generation during the photothermal evaporation process. In this study, the proposed MPFR evaporator featured a 3D spiral conical groove design combined with a hydrophilic MXene/PVA/CNFs functional layer, which effectively enhanced light absorption (>97 %) through multistage reflection and absorption. This facilitated a body-phase absorption/body-phase heating process that effectively reduced the surface temperature of the illuminated area compared to a flat evaporator. Consequently, this was conducive to the absorption of environmental heat to supply water evaporation. Under 1.0 sun illumination, the evaporation rate and evaporation efficiency of MPFR-4 evaporator reached 3.84 kg m−2·h−1 and 156.29 % respectively. The introduction of the hydrophilic functional layer not only enabled water activation but also enhanced the water supply capacity of both yarn and fabric on the evaporator surface, forming a water layer that promoted high-salinity water diffusion and salt crystal dissolution while effectively inhibiting salt crystal pollution. Moreover, this water layer imparted oil-repellent characteristics to the evaporator, enabling it to resist oil-pollution from sea surfaces as well. Thus, this work provided novel insights into designing highly efficient and anti-pollution solar thermal evaporators that drove advancements within green and sustainable water generation.

A robust and low-cost blended-fiber-based evaporator with high efficiency for solar desalination

The solar-driven interfacial evaporation (SDIE) is a clean and efficient technology to mitigate freshwater shortages. A robust and low-cost evaporator is essential for the practical implementation of SDIE systems. Herein, we design a fantastic blended-fiber-based evaporator using weaving techniques. This mixture fabric is crafted using polyethylene terephthalate fibers and linen threads. It makes full use of the excellent light absorption, tensile strength, and corrosion resistance of polyethylene terephthalate fibers. Meanwhile, the mixture fabric reserves exceptional air permeability and water supply capability of linen thread. We optimize the density of the mixture fabric by adjusting the reed count and the weft count. It is found that the combination of the 40 reed and a single weft yarn produces the most effective and stable evaporator. The optimized mixture fabric makes a good trade-off between the water supply to the evaporator and solar-thermal evaporation. As a result, the evaporator achieves a high evaporation rate and efficiency (~1.53kg/m2/h, ~ 90%) under 1 sun illumination, which surpasses most of the existing two-dimensional evaporators based on metal nanomaterials, polymers, carbon-based materials, and fabrics. Our work opens a new horizon for the development of efficient, scalable, flexible, low-cost, corrosion-resistant, and stable evaporators.

Hydrovoltaic Electricity Generation from Potato Carbon Cake: Using an Interconnected Porous Solar Steam Generator

AbstractIntegrating two advanced techniques, such as solar thermal evaporation (STE) for freshwater production and hydrovoltaic (HV) for electricity generation, makes a considerable attempt to attain basic energy needs. Here in this work, a crisscross porous carbonized ethanol‐treated potato cake as a hydrovoltaic device (CHV) is fabricated. CHV device is a highly stable, portable, eco‐friendly device with a maximum output voltage of 0.23 V and current of 5 µA under ambient conditions. This is further raised to 0.5 V when exposing 1 sun illumination (1 kW m2). Voltage studies are done by varying the wind flow, relative humidity, and bulk water temperature to confirm the device's HV property and dependent factors. The potential application of the device is tested by glowing an LED light connected with 5 CHV devices in series. It is continuously delivered output till the bulk water is dry. The shelf‐life ability of CHV is also analyzed after 1 year of usage and provided nearly the same outcome. Therefore, this single device with dual‐energy harvesting gives a significant solution to society's energy and water crisis for a better tomorrow.

Bifunctional La0.5Sr0.5CoO3-δ-CuO foam ceramic for solar thermal evaporation and water purification

Solar steam generation is an efficiently strategy to obtain fresh water utilizing solar energy. However, without effective decontamination treatment, the volatile organic compounds in the contaminated raw water would be concentrated during the evaporation process. Herein, a bifunctional composite based on La0.5Sr0.5CoO3-δ (LSC5) foam ceramic decorated with acicular-like copper oxide (CuO) was designed. The outstanding degradation capacity of LSC5-CuO could be attributed to the extraordinary conductive property of photothermal LSC5 ceramic which could separate the photo-induced electron and hole pairs. The bifunctional LSC5-CuO foam ceramic may provide a new perspective to solar pure water generation system.

Combined sensible heat and nano-enhanced latent heat energy storage for solar thermal evaporation: an experimental approach

Combined sensible heat and nano-enhanced latent heat energy storage for solar thermal evaporation: an experimental approach

Fabrication of novel water glass-based monolithic aerogels with fibrous skeleton under alkaline for oil sorption and thermal evaporation

We presented the fabrication of novel water glass-based monolithic aerogel reinforced with the electrospun SiO2 nanofibers (SNFs) by one-step acid catalysis in alkaline condition under ambient pressure drying (APD). Compared with the powder-like water glass-based aerogel (WAG), integrated monolithic aerogel composited with nanofibers (FWAG) was successfully constructed featured with core/shell fibrous skeleton, low density, high porosity, hydrophobic surface and enhanced mechanical property. The obtained FWAG exhibits compressive elastic modulus of 0.13 MPa for FWAG-3 and a sorption capacity of 11.83 g−1 for CH2Cl2, as well as good insulator performance used at high temperature of ∼460 °C without obvious damage. The low density, hydrophobicity and excellent insulation property enable the FWAG to be applied as insulator for solar thermal evaporation with a water evaporation rate of 1.35 kg m−2h−1 and conversion efficiency up to 88.4% at one solar intensity to produce fresh water.

Facile fabrication of compressive aerogels with novel core/shell fibrous skeleton for oil sorption and thermal evaporation

Due to the great size difference and poor interfacial compatibility, the traditional fiber reinforced aerogel composites mainly exist in form of particles deposited on the filled fibers with insufficient mechanical property. In this work, A novel compressive silica aerogel (SNAG) with electrospun SiO2 nanofibers (SNFs) as reinforcement was facilely established via a simple acid/base catalyzed two-step method under ambient pressure drying. The obtained SNAG is organized with unique fibrous core/shell skeletons to acquire excellent properties of low density, hydrophobicity, strong mechanical and effective insulation. The SNAG has a sorption capacity of 10.3 g g−1 for CH2Cl2 and can be repeatedly used through rapid compression and springback with a compressive ratio of 65%. The mechanical strength of the SNAG with 0.6 wt% SNFs can reach up to 0.23 MPa, which is 4.9 times higher than that of pure silica aerogel without addition of SNFs. Moreover, SNAG has been successfully employed as insulator for interfacial solar thermal evaporation with an evaporation rate of 1.31 kg m−2 h−1 to produce fresh water. It is believed that the obtained SNAG would be a prospective elastic aerogel for various applications and bring new insights into designing high-strengthen aerogels.

Patterned nanofibrous membrane via hot-pressing for enhanced solar thermal evaporation

Composited fibrous membrane has been demonstrated as a type of versatile and efficient photothermal material to produce fresh water by solar thermal desalination, but still suffers from some shortages such as weak mechanical property for reusability and insufficient investigations on the microstructure regulation for higher evaporation performance. In this work, a self-supported carbon black/polyacrylonitrile (CB/PAN) membrane with irregular patterns was facilely manufactured by simple hot-pressing (hp-CB/PAN) for highly efficient solar thermal evaporation. The hot-pressing induces the densification of the nanofibrous membrane and melt adhesion of partial membrane surface, leading to significant increase of the mechanical property and certain improvement of water diffusion, but no detected change of the nanofibrous components. Moreover, the hp-CB/PAN possesses optical absorption of 99.1% over the entire wavelength range of 250–2500 nm. Accordingly, the hp-CB/PAN exhibits an excellent evaporation rate of 1.33 kg m−2 h−1 and a superior photothermal conversion efficiency of 86% under one sun illumination (1000 W m−2), which are much higher than those of 1.27 kg m−2 h−1 and 82.8% for CB/PAN. The obtained hp-CB/PAN can also be utilized for purifying organic polluted solution and repeatedly solar thermal evaporation without attenuation of the evaporation performance.

Dual-Effect Salt-Tolerant Slope-Suspended Solar Evaporators: High Evaporation Efficiency and Industrialized Implementation

Construction of Janus-wetting interfaces in solar thermal evaporation is one of the most widely applied strategies to overcome salt accumulation to prolong a system’s lifetime. Nevertheless, hydrophobicity and steam escape in traditional Janus floating evaporators are negatively correlated, resulting in the trade-off between salt resistance and the evaporation rate. Herein, a scalable suspended-slope evaporator (SSE) based on the inverse wettability polypyrrole (PPy) fabric is designed to surmount the long-term trade-off for achieving continuous and stable high-rate water desalination. Experiments and numerical simulations indicate that the suspended structure opens the “shackles” brought by the upper hydrophobic PPy fabric to steam escape, and the Marangoni convection induced by the inclined structure further enhances salt resistance performance. With this structure employed, SSEs present good salt tolerance (no obvious salt accumulation in 21 wt % brine for 5 h) and excellent solar evaporation performance (evaporation rate of 2.46 kg m–2 h–1 in 3.5 wt % brine, and the energy efficiency is 85.48%). Additionally, there is no need for special customized high-pressure equipment in the whole synthesis process, which has great significance for the widespread practical application. This work elucidates the intrinsic effects of the device structure on solar evaporators while providing insights for designing high-efficiency and salt-tolerant solar evaporators.

Dendritic Structure-Inspired Coating Strategy for Stable and Efficient Solar Evaporation of Salinity Brine

Solar thermal evaporation has been widely used to tackle the problem of freshwater shortage. The strategy to improve the evaporative performance of solar thermal evaporation by simple and effective methods is still a challenge. Herein, a dendritic structure-inspired coating strategy based on the dendritic structure of polyvinyl alcohol (PVA) colloids firmly grabbing titanium trioxide (Ti2O3) on the outer surface as a light-absorbing core–shell filler was prepared using the non-solvo-induced precipitation method. Such a core–shell structure was then coated on the PVA sponge to prepare the solar photothermal composite Ti2O3/PVA@PVA, which gave full play to the photothermal advantage of the filler itself and can be long-term stable. Meanwhile, a three-dimensional Ti2O3/PVA@PVA evaporator with an embossment-sawtooth structure was prepared, which enhances light absorption to 98% in the whole solar spectrum through folds. Under 1.0 solar irradiation, the evaporation rate reaches as high as 2.66 kg m–2 h–1 and the evaporator illustrates good stability in simulated seawater for 7 consecutive days. Such a design showed good salt resistance and self-cleaning ability and could be reliably used for seawater desalination. In addition, the evaporator illustrates good adsorption capacity for dye molecules and heavy metal ions. This work provides new insights into the development of simple, efficient, environmentally friendly, sustainable, and salt-resistant solar evaporators.

Freestanding Hydrophilic/Hydrophobic Janus Covalent Organic Framework Membranes for Highly Efficient Solar Steam Generation

Solar-powered clean water production has been considered an efficient and favorable way to address the global water shortage challenge. Herein, we design and synthesize a series of robust, porous, azo-rich covalent organic frameworks (COFs) that can directly form freestanding pure membranes via one-step interface polymerization for highly efficient solar steam generation. The abundant photoresponsive groups, highly ordered porous structure, and inherent hydrophilic/hydrophobic Janus membrane structures endow COF membranes with excellent solar energy absorption, solar thermal conversion effect, water transportation, and evaporation efficiency. Without any supporting substrate or post-treatment, the steam generation rate of COF membranes reaches up to 3.02 kg/m2/h under 1 sun irradiation, and the energy conversion efficiency is up to 94%. This performance is the best among all solar thermal evaporators using COFs as solar thermal materials. The evaporation system not only works for clean and pure water generation but also for solar desalination. The good performance and reusability of COF membranes make them promising platforms for solar-thermal water production from seawater.

A non-covalent supramolecular dual-network polyelectrolyte evaporator based on direct-ink-writing for stable solar thermal evaporation

Polymers possessing highly adjustable physicochemical properties have been accepted as ideal flexible materials for solar thermal evaporation, which is considered as an eco-friendly and progressive strategy for water reclamation.

Hybrid nanoarchitectonics of carbon/titanium carbide integrated hydrogel/melamine foam for highly efficient solar steam and thermoelectric power generation

Solar driven interface water evaporation, a feasible approach to solve the global water crisis, requires a rational combination of high efficiency photothermal material and evaporation structure. In this paper, carbon/titanium carbide (C/TiC) nanohybrids from Ti-based metal-organic framework (Ti-MOF) were controllable synthesized and applied for highly efficient solar steam and thermoelectric power generation. Considering inherent defects of single-component materials, the synthesized unique porous C/TiC nanohybrids exhibit both lattice resonance and plasmonic absorption properties, achieving a high solar-steam conversion efficiency of 90 %. Further, a multi-structured hydrogel (TMH) was prepared by dipping porous melamine foam in gel containing porous C/TiC nanohybrids, and a high evaporation rate of 1.93 kg m−2 h−1 under one sun irradiation has been achieved for its excellent light absorption performance and thermal management ability. Long-term desalting experiments exhibit TMH presents desirable self-cleaning characteristic and can meet its performance requirements in 3.5–20 wt% brine. More importantly, as a proof-of-concept demonstration of synergistic solar steam and thermoelectric power generation, the synergistic system simultaneously realized a high evaporation rate of 0.93 kg m−2 h−1 and produced a stable voltage up to 150 mV under one sun irradiation. This solar-thermal evaporation and thermoelectric generation technology provides a promising avenue for practical desalination and thermoelectric power generation.

Double-Layer MWCNTs@HPPS Photothermal Paper for Water Purification with Strong Acid-Alkali Corrosion Resistance.

Solar-driven interfacial evaporation technology has been identified as a promising method to relieve the global water crisis, and it is particularly important to design an ideal structure of the solar thermal conversion evaporation device. In this paper, hydrophilic polyphenylene sulfide (HPPS) paper with loose structure and appropriate water transmission performance was designed as the based-material, and multi-walled carbon nanotubes (MWCNTs) layer with excellent photothermal conversion performance was constructed to realize the high-efficiency solar-driven evaporation. Under tail swabbing mode, the cold evaporation surface on the back of the evaporator greatly improved the evaporation rate, cut off the heat transfer channel to bulk water, and achieved the maximum evaporation rate of 1.23 L/m2·h. Ethyl cellulose (EC) was introduced to adjust the water supply performance of HPPS layer, and a large specific surface area of cold evaporation was obtained, thus improving the water evaporation rate. In the simulation experiment of seawater desalination and dye wastewater treatment, it showed good water purification capacity and acid/alkali-resistance, which had great practical application significance.

Activated carbon-cement composite coated polyurethane foam as a cost-efficient solar steam generator

Solar thermal evaporation (STE) is a promising advanced technique to purify contaminated water under the influence of solar light. Naturally, cement has served as a binder in masonry-related applications and possesses light-absorbing properties. Herein, we fabricated a cost-effective high-durable cement/carbon/polyurethane foam (CCPF) composite material as a solar-driven evaporator. It provided an excellent evaporation rate of ∼2.4 kg m−2 h−1 under one sun (1 kW/m2) illumination. The CCPF exhibits a high solar light absorbance due to the presence of carbon. Also, the high-interconnected porous foam provides the self-floating ability to maximize heat localization. Simultaneously, the interconnected crisscross porous foam and the porous activated carbon coat on the air-water interface behave like a highly concentrated dye water filter, salt-water filter, and high density muddy water filter. Moreover, the super hydrophilic surface of CCPF and the addition of polyurethane (PU) foam ensure adequate water supply. Complete wastewater filtering ability was confirmed by UV–Vis spectral analysis. As-fabricated composite can attain the maximum surface temperature of 62 °C under one sun illumination for 1 h. The stability and adhesive strength of the coating were confirmed from successive 60 days of water treatment. No carbon was excreted from the device even after 60 days of the experiment. The small size solar still setup was fabricated with an area of 30 × 30 cm2 to show the performance of the device under ambient conditions. Collection of 140–180 ml ultrapure water from the device under ∼0.6 kW/m2 (variable solar intensity) at environment temperature 30–32 °C in 4–5 h. Therefore, this easily fabricated, cost-effective, highly stable CCPF solar-driven evaporator can be used as a strategy for high water production on a potential scale for the long term.

Effect of electric field on water free energy in graphene nanochannel

Graphene nanochannels and nanostructures have been of great interest to applications like nanofluidics and solar-thermal evaporation since nanoconfinement can lead to altered liquid properties. In this article, we employ molecular dynamics simulations combined with the free energy perturbation method to study the influence of external electric fields on the free energy of water molecules in graphene nanochannels. We observe a decrease in the water free energy difference (ΔG1−0=G0−G1, where 0 is the reference vacuum state and 1 is the solvated state) with the increasing electric field, suggesting that the application of an electric field may reduce the thermal energy needed to evaporate water from graphene nanochannels. Our analysis reveals that the reduction in free energy difference is related to more aligned water molecules along the electric field direction in the nanochannels, which leads to a decrease in the water inter-molecular potential energy and, thus, reduces the free energy difference.

Rational Design of Biomass-Derived Composite Aerogels for Solar-Driven Seawater Desalination and Sewage Treatment

To combat the water crisis, on-site reclamation of freshwater from seawater and sewage is urgently desired, in which solar-driven interfacial evaporation has been recognized as an emerging strategy. However, potentially costly fabrication, salt accumulation, and contaminant influence still hinder the real-world application of solar–thermal evaporators. Herein, a biomass-derived composite aerogel is constructed through the Schiff base reaction of chitosan and polyethylenimine and freeze assembly and further loaded with CuS/rGO nanoheterostructures via a spray stacking strategy. Because of the reverse transport of vertical-channel arrays, the lower part enables excellent salt-resistant properties during long-term desalination in parallel to upward water supply. The upper part promotes the thermal localization by controlling the spatial distribution of CuS/rGO, providing high solar spectrum absorption for efficient water evaporation. Notably, the composite aerogel exhibits great superiority in sewage treatment benefiting from its adsorption and photocatalytic capabilities, thus harvesting freshwater resources that meet drinking water standards. The rational design of this cost-effective evaporator may inspire new paradigms for boosting the combination of solar–thermal utilization and freshwater access.

Janus interpenetrating structure based on optimized water supply for solar-driven water evaporation

Realizing a balance between water supply and the evaporation of photothermal evaporators is a valuable means to enhance the solar–thermal evaporation rate, but practical obstacles remain. The interfacial mechanics of a Janus evaporator with an interpenetrating structure are proposed to achieve a dramatic improvement in the solar–thermal evaporation rate. The Janus evaporator is composed of a membrane material of Cu1.96S grown in situ on a foamed copper skeleton (CF@Cu1.96S) and a graphene oxide/sodium alginate aerogel (GA), through an interfacial freeze-drying shape technology. In this unique architecture, the superhydrophilic GA can be stretched into the hydrophobic CF@Cu1.96S interior to build an interpenetrating network architecture (CF@Cu1.96S/GA), thereby adjusting the Laplace pressure and constraining capillarity. Due to the optimized water supply of interfacial mechanics, the CF@Cu1.96S/GA evaporator achieves an evaporation rate of 1.79 kg m−2 h−1 under 1 sun irradiation and exhibits superior salt resistance. This provides a rationale for the reasonable design of the structure of the solar–thermal evaporators.

Spontaneous water-on-water spreading of polyelectrolyte membranes inspired by skin formation

Stable interfaces between immiscible solvents are crucial for chemical synthesis and assembly, but interfaces between miscible solvents have been less explored. Here the authors report the spontaneous water-on-water spreading and self-assembly of polyelectrolyte membranes. An aqueous mixture solution containing poly(ethyleneimine) and poly(sodium 4-styrenesulfonate) spreads efficiently on acidic water, leading to the formation of hierarchically porous membranes. The reduced surface tension of the polyelectrolyte mixture solution drives the surface spreading, while the interfacial polyelectrolytes complexation triggered by the low pH of water mitigates water-in-water mixing. The synergy of surface tension and pH-dependent complexation represents a generic mechanism governing interfaces between miscible solvents for materials engineering, without the need for surfactants or sophisticated equipment. As a proof-of-concept, porous polyelectrolyte hybrid membranes are prepared by surface spreading, exhibiting exceptional solar thermal evaporation performance (2.8 kg/m2h) under 1-sun irradiation.

Multifunctional integrated sandwich-structured evaporator based on nanofibrous membrane for efficient photothermal seawater desalination

Solar steam generation has gained considerable amount of attention due to its popularity in recent studies around seawater desalination. Herein, we suggest a sandwich-structured nanofibrous membrane that excels at highly efficient seawater evaporation desalination. The top thin layer made with MXene (Ti3C2Tx) to improve membrane's photothermal conversion efficiency. The highly hydrophobic electrospun Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) fibers in the middle allow membrane to self-float on the seawater. Its highly interconnected nanofiber network structure provides an ideal environment for the transport of water vapors. The hydrophilic bottom layer is prepared by depositing cross-linked polydopamine and polyethyleneimine (PDA/PEI) on the PVDF-HFP fibers surface, which is designed to be in direct contact with seawater. Under three sun (3 kW m−2), the solar thermal conversion efficiency and evaporation rate of the membrane could reach 95.45% and 3.782 kg m−2 h−1. This multifunctional integrated sandwich-structured evaporator based on nanofibrous membrane provides a new strategy for water purification.