Solar Vapor Generation Research Articles

High-Efficiency Solar Vapor Generation Boosted by a Solar-Induced Updraft with Biomimetic 3D Structures.

Sunlight-based desalination is one of the most environment-friendly, low-cost methods for obtaining freshwater on the planet. We implemented a biomimetic three-dimensional (3D) solar evaporator, improved by a solar-induced air-flow updraft. A carbon-coated polyvinyl alcohol (PVA) foam allowed us to achieve perfect absorption of ultrabroadband sunlight and continuously provide water to tall 3D structures. Integrating the convection flower (Amorphophallus titanum) and solar chimney structure, we proposed a bio-inspired 3D solar evaporator system that generates an updraft airflow. This updraft replaces saturated vapor between neighboring PVA foams with dry air, resulting in a significant increase in the effectiveness of dry air-water contact interfaces. Under the 1 sun condition (1 kW m-2), we achieve a high solar-vapor conversion efficiency of 95.9%.

Carbon Materials for Solar Water Evaporation and Desalination.

Seawater desalination is viewed as a promising solution to world freshwater scarcity. Solar assisted desalination is proposed to overcome the high energy consumption in current desalination technologies, as it uses abundant and sustainable solar energy as the only energy input. Interfacial solar vapor generation (SVG) has attracted considerable research interest due to its high energy conversion efficiency, simple implementation, and cost-effectiveness. Among all the candidate materials for solar evaporators, carbon-based materials stand out due to their intrinsic high solar absorption, highly tunable structure, easy preparation, low cost, and earth-abundancy. In this review, the recent progress on carbon-based materials for the development of interfacial SVG is summarized. First, a brief introduction to the basic design principles of the interfacial SVG system is presented. Then, recent efforts in carbon-based solar evaporators, from artificial structures to bioinspired configurations, focusing on their structure-function relationship are highlighted. Strategies for designing antisalt-fouling desalination systems are also summarized. Last, the challenges and opportunities of carbon-based materials for solar evaporation technology are elaborated.

Polypyrrole‐Reinforced N,S‐Doping Graphene Foam for Efficient Solar Purification of Wastewater

Solar vapor generation is a sustainable and cost‐effective approach to addressing the issue of water shortage. However, the challenges of solar steam generation still exist for achieving a high evaporation efficiency combined with long‐term stability in the wastewater containing heavy metal ions and wide degrees of acidity and alkalinity (pH = 1–14). Herein, polypyrrole (PPy) loading on the N,S‐doped graphene oxide (N,S‐GO) foam is used for high‐efficiency solar evaporation of treating wastewater. With the advantages of excellent broadband solar absorption ( >97%), extremely low emissivity (0.70), and outstanding hydrophilicity, the N,S‐GO/PPy foam achieves a high evaporation efficiency of 90.5% under 1 sun illumination. More notably, the N,S‐GO/PPy foam has strong adsorption of heavy metal ions (Fe3+, Cu2+, and Cr6+) for treating wastewater synchronously evaporates at higher efficiencies of 94.7–98.4%. Interestingly, the high‐toxicity Cr6+ can be reduced to low‐toxicity Cr3+ effectively by the synergistic effect of N,S‐GO and PPy. In addition, the N,S‐GO foam shows a better long‐term resistance of acidity and alkalinity for 45 days. A new insight is offered into high‐efficiency solar evaporation for treating wastewater and water purification.

A high-performing single-stage invert-structured solar water purifier through enhanced absorption and condensation

<h2>Summary</h2> Interfacial solar vapor generation is an emerging technology for producing purified water with a minimized carbon footprint. While the evaporation rate has been significantly increased, the rate of water collection has been limited because of ineffective heat transfer during condensation and compromised light absorption in the conventionally designed solar still. In this work, an invert-structured, single-stage solar water purifier (ISWP) is elaborately designed and fabricated and consists of a top selective absorber and a honeycombed bottom water condenser based on hydrophobic nanostructured copper. This inverted structure not only avoids optical loss due to the vapor condensation but also realizes enhanced heat transfer and condensation. As a result, it can achieve a high water-collection rate of 1.063 kg m⁻² h⁻¹ and an overall efficiency of solar collected water of ∼70% for single-stage solar purification systems.

Plasmonic silver nanoparticle-decorated electrospun nanofiber membrane for interfacial solar vapor generation

Interfacial solar vapor generation as an emerging technique has great potential in solving water shortage and pollution problems. Electrospun nanofiber membrane with high porosity, mechanical flexibility, numerous microsized channels for fast water transport, and low thermal conductivity offers an ideal platform for solar vapor generation. In this research work, plasmonic silver nanoparticles (Ag NPs) were utilized as photothermal materials and electrospun polyacrylonitrile (PAN) nanofiber membranes as substrates to fabricate Ag nanoparticles-uniformly decorated PAN (Ag@PAN) nanofiber membranes by electroless plating method. The morphology and chemical composition of the membranes were characterized by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffractometry. By varying the volume ratios of glucose and silver ammonia solution, the sizes of Ag NPs as well as the light-absorption ability of corresponding nanofiber membrane were regulated. As a result, the optimal Ag@PAN nanofiber membrane demonstrated a high light-absorption efficiency of 92.8% in the range of 280–2500 nm wavelength. The evaporation rate reached 1.34 kg m−2 h−1 and 5.83 kg m−2 h−1 under 1 sun and 5 sun irradiations, respectively. The plasmonic nanofiber membrane also exhibited long-term use stability, without any degradation in solar vapor generation performance even after 10 cycle tests. This work paves the way for the design and development of plasmonic nanofiber membranes as high-performance interfacial solar vapor generators.

Controllable synthesis of sea urchin-like carbon from metal-organic frameworks for advanced solar vapor generators

Solar evaporation is considered as a hopeful technology for producing freshwater from non-potable water using inexhaustible solar energy. However, solar evaporators with high performance and good scalability are still urgently needed. Herein, a bilayer solar evaporator is prepared by facilely coating natural wood with carbon materials pyrolyzed from sea urchin-like metal–organic frameworks (MOFs). The carbon materials inherit the sea urchin-like morphology and grow bamboo-like carbon nanotubes wrapping Ni nanoparticles, which synergistically contribute to the efficient light trapping and thermal harvesting. Meanwhile, the doped nitrogen and oxygen enhance the hydrophilicity of carbon materials. In another aspect, wood not only provides abundant hydrophilic channels for sufficient water supply, but also reduces the water evaporation enthalpy by 26% through the hydrogen bonds between water and hydrophilic groups of wood. With the combined merits above, the bilayer solar evaporator achieves high sunlight absorption (98%), low thermal conductivity (0.17 W m−1 K−1), rapid water transport, and low vaporization enthalpy. Consequently, the solar evaporator exhibits a notable water evaporation rate of 2.07 kg m-2 h−1 under 1 Sun irradiation, surpassing that of reported MOFs or wood-based evaporators. Importantly, a large-scale solar desalination device is developed for outdoor experiments to obtain freshwater from seawater. The daily freshwater production amount per unit area (2.74 kg) meets the daily water consumptionrequirement of one adult. This work states the great potential of MOFs-derived carbons for efficient solar vapor generation and opens an avenue for application in energy storage and conversion.

Artificial Phototropic Systems for Enhanced Light Harvesting Based on a Liquid Crystal Elastomer

Oblique‐incidence‐induced energy‐density loss (OEL) is a universal problem which affects nearly all processes involving electromagnetic waves, especially sunlight harvesting. Technologies (solar concentrating plants, large scale systems, etc.) are developed to address this issue, albeit with limitations such as complex design, large size, and high cost. Inspired by nature, artificial phototropism is developed to accurately follow the light direction without complex motors system and electronical control. However, the existing systems are limited by small tracking operation windows, low robustness, or the requirement of high‐power input. Herein, a system is reported that is versatile, low cost, mechanically strong, and can achieve large‐angle reorientation driven by unconcentrated sunlight. This system is demonstrated to be able to recover the OEL for photovoltaics as well as solar vapor generation (SVG) processes. Compared with the nonphototropic system, it can achieve 447% output in lab and 155% in real‐life applications. The principle behind our artificial phototropic system is universal and can be extended to many optical applications, especially sunlight harvesting.

Solar vapor generator: A natural all-in-one 3D system derived from cattail

Solar-driven interfacial water evaporation is a promising strategy to produce fresh water by effectively converting abundant solar energy into localized heat. In this work, a natural all-in-one three-dimensional (3D) solar vapor generator (SVG) with low-cost and large-scale production based on Cattail (CT) has been proposed. The simple carbonized CT (CCT) as a photothermal material (PM) to construct the 3D SVG exhibited outstanding steam vapor generation performance due to its unique hierarchical porous architecture, rapid water transportation, high water storage capacity, enough steam escape channels and high light capture capability. When the height of CCT exposed to the environment was adjusted to be 10 cm, SVG showed an amazing water evaporation rate of 4.12 kg m −2 h −1 under 1 kW m −2 light intensity, which was higher than those of reported 3D devices, and the photothermal conversion efficiency was as high as 105.8%. The environmental energy was utilized to enhance the water evaporation performance by forming a cold evaporation surface. In addition, a device for collecting evaporated water outdoors has been designed, with an average evaporation rate of 1.04 kg m −2 h −1 , about 8.32 kg m −2 ·day −1 , demonstrating an excellent application prospect in the field of producing fresh water. • A natural all-in-one 3D solar vapor generator derived from cattail was designed. • The carbonized cattail (CCT) exhibits excellent water transmission performance. • The side surface of the CCT solar vapor generator as a cold evaporation surface can obtain energy from the environment to enhance water evaporation performance. • The high water evaporation rate of 4.12 kg m −2 h −1 was achieved under one sun.

Tunable Sponge-Like Hierarchically Porous Hydrogels with Simultaneously Enhanced Diffusivity and Mechanical Properties.

Crosslinked polymers and gels are important in soft robotics, solar vapor generation, energy storage, drug delivery, catalysis, and biosensing. However, their attractive mass transport and volume-changing abilities are diffusion-limited, requiring miniaturization to avoid slow response. Typical approaches to improving diffusion in hydrogels sacrifice mechanical properties by increasing porosity or limit the total volumetric flux by directionally confining the pores. Despite tremendous efforts, simultaneous enhancement of diffusion and mechanical properties remains a long-standing challenge hindering broader practical applications of hydrogels. In this work, cononsolvency photopolymerization is developed as a universal approach to overcome this swelling-mechanical property trade-off. The as-synthesized poly(N-isopropylacrylamide) hydrogel, as an exemplary system, presents a unique open porous network with continuous microchannels, leading to record-high volumetric (de)swelling speeds, almost an order of magnitude higher than reported previously. This swelling enhancement comes with a simultaneous improvement in Young's modulus and toughness over conventional hydrogels fabricated in pure solvents. The resulting fast mass transport enables in-air operation of the hydrogel via rapid water replenishment and ultrafast actuation. The method is compatible with 3D printing. The generalizability is demonstrated by extending the technique to poly(N-tertbutylacrylamide-co-polyacrylamide) and polyacrylamide hydrogels, non-temperature-responsive polymer systems, validating the present hypothesis that cononsolvency is a generic phenomenon driven by competitive adsorption.

Cu3BiS3/MXenes with Excellent Solar-Thermal Conversion for Continuous and Efficient Seawater Desalination.

Two-dimensional materials with unique physical and chemical properties have recently attracted widespread attention in the field of solar thermal conversion. However, affected by the Fresnel effect, traditional two-dimensional materials such as MXenes, graphene, transition metal disulfide often have relatively significant light reflection losses at the solid-liquid or gas interface. So how to improve the light absorption of the two-dimensional material performance has become a new challenge in photothermal conversion. Here, we use an improved thermal-injection method to uniformly grow Tricopper(I) Bismuth Sulfide (Cu3BiS3, CBS) on the surface of Ti3C2 nanosheets in a nonaqueous polar solvent environment. A three-dimensional nanoflower-nanosheet structure CBS-Ti3C2 for photothermal conversion has been constructed successfully. Owing to the excellent photothermal performance of Cu3BiS3 in the near-infrared region, the good thermal conductivity of Ti3C2, and the unique porous structure of the composite material, the composite achieves broadband absorption of light (more than 90% in the visible light region, more than 80% in the near-infrared region), which optical model and finite element simulation have theoretically verified. The composite material has obtained higher solar-to-heat conversion performance than similar material systems, and the steady-state temperature can reach 62.3 °C under 1 sun incident light intensity. CBS-Ti3C2 is expected to become a light-absorbing layer material for solar vapor generation devices due to its excellent light-to-heat conversion performance and good material flexibility. It still guarantees a reasonably high steam generation rate (1.32 kg·m-2·h-1) even with a thinner material thickness (0.48 mg·cm-2) and a comprehensive conversion efficiency higher than 90%. Besides, CBS-Ti3C2 also exhibits the characteristics of resisting surface salt accumulation, which is conducive to maintaining the long-lasting photothermal seawater evaporation process. The material's electronic structure and the charge transfer process of the heterojunction interface have been studied with the first-principles calculation. The high light absorption performance and good thermal conductivity of the composite material are theoretically explained and supported.

Investigation of zeolitic imidazolate frameworks–derived carbon nanotubes thin film in solar vapor generation

Solar vapor generation is considered a green and practical approach to take advantage of solar energy as a renewable source and provide pure water. However, developing suitable materials with high efficiency and long-term stability under one sun illumination is challenging. Consequently, in this paper, we manifested two-dimensional Zn/Co zeolitic imidazolate framework (ZIF)-L as a sacrificial template to prepare carbon nanotube (CNT) through carbonization of the ZIF-L (Z-CNT). This porous Z-CNT as the solar absorber was deposited on a low-cost fiber paper, as a carrier for water transport by the capillary effect. A polystyrene foam was placed under the provided film, which prevents the heat loss to bulk water. By utilizing this solar vapor generator, a high water evaporation rate of 1.44 kg m2 h−1 and a photothermal conversion efficiency of 84% was achieved under one sun. Beside the porosity, high light adsorption of carbon nano tubes (CNT) due to having black colour and low thermal conductivity of this material incorporate the high achieved efficiency.

Designing Carbonized Loofah Sponge Architectures with Plasmonic Cu Nanoparticles Encapsulated in Graphitic Layers for Highly Efficient Solar Vapor Generation.

Solar vapor generation represents a promising approach to alleviate water shortage for producing fresh water from undrinkable water resources. Although Cu-based plasmonics have attracted tremendous interest due to efficient light-to-heat conversion, their application faces great challenges in the oxidation resistance of Cu and low evaporation rate. Herein, a hybrid of three-dimensional carbonized loofah sponges and graphene layers encapsulated Cu nanoparticles is successfully synthesized via a facile pyrolysis method. In addition to effective light harvesting, the localized heating effect of stabilized Cu nanoparticles remarkably elevated the surface temperature of Cu@C/CLS to 72 °C, and a vapor generation rate as high as 1.54 kg m-2 h-1 with solar thermal efficiency reaching 90.2% under 1 Sun illumination was achieved. A study in the purification of sewage and muddy water with Cu@C/CLS demonstrates a promising perspective in a practical application. These results may offer a new inspiration for the design of efficient nonprecious Cu-based photothermal materials.

A scalable broadband plasmonic cuprous telluride nanowire-based hybrid photothermal membrane for efficient solar vapor generation

Abstract Solar vapor generation utilizes ubiquitous solar energy to address the issue of global water shortage. However, its large-scale field deployment is greatly hampered by inefficient solar absorption, moderate evaporation efficiency and high cost. Here, we report a new hybrid photothermal membrane, named broadband plasmonic Cu2−xTe nanowire (bpCu2−xTe) membrane, for interfacial solar evaporation to produce freshwater from various water sources. The bpCu2−xTe membrane features excellent broadband solar absorption (~95.9%), high porosity and hydrophilicity, and low thermal conductivity (0.55 W/(m K)), which enables a water evaporation rate as high as 4.3 kg/(m2 h) with the evaporation efficiency of up to 96% under 3 kW/m2 solar irradiation. The evaporation performance of the present Cu2−xTe membrane can be maintained even after it recycles multiple times under various solar irradiance, indicating excellent durability and stability. Efficient solar desalination of seawater is further demonstrated with the bpCu2−xTe membrane to deliver drinkable water. The combination of scalable fabrication ability, low cost and excellent solar evaporation performance of the bpCu2−xTe membrane highlights the potential for seawater purification and desalination in field applications.

Ultra-thin dark amorphous TiOx hollow nanotubes for full spectrum solar energy harvesting and conversion‡

Dark titania (TiOx) have been widely used for solar energy harvesting and conversion applications due to its excellent light absorbing performance throughout the ultraviolet to near infrared wavelength band, low cost, and non-toxic nature. However, the synthesis methods of dark TiOx are usually complicated and time-consuming. Here we report a facile and rapid method to fabricate dark amorphous TiOx (am-TiOx) hollow nanotube arrays on nanoporous anodic alumina oxide (AAO) templates using atomic layer deposition. Systematic investigation was performed to demonstrate that Ti3+ and O- species in the am-TiOx ultra-thin films, as well as the spatial distribution of these am-TiOx ultra-thin films on the vertical side walls of AAO templates are two major mechanisms of the black color. Importantly, the film deposition took ~18 min only to produce the optimized ~4‐nm‐thick am-TiOx film. Representative applications were demonstrated using photocatalytic reduction of silver nitrate and photothermal solar vapor generation, revealing the potential of these ultra-thin dark am-TiOx/AAO structures for full spectrum solar energy harvesting and conversion.

Boosting solar steam generation by photothermal enhanced polydopamine/wood composites

Solar steam generation is an emerging strategy for water desalination using renewable solar energy and seawater resources. In order to convert solar energy into heat for seawater evaporation, we developed a bi-layered structure composite for high-efficient solar evaporation based on photothermal-enhanced arginine-doped polydopamine (APDA) and raw wood, which are biodegradable and sustainable. Note that the APDA coating layer exhibited improved optical absorption and photothermal conversion ability compared with conventional polydopamine (PDA) coating on account of the construction of donor-acceptor pairs within the APDA microstructure system. Density functional theory (DTF) calculation further confirmed that the energy bandgap of APDA could be narrowed though donor-acceptor microstructures and then enhanced the absorption spectrum. The resulting APDA-wood composite performed a solar vapor generation efficiency of ~77% on the condition of 1 sun illumination. The water evaporation process was quite stable over 100 cycles and the metal ions in seawater were almost eliminated after desalination. This amino acid-initiated cost-effective and facile coating method provided new opportunities to fabricate photothermal-enhanced coating materials for solar evaporation applications.

Solar thermal evaporation using bubbly nanofluids with recyclable magnetic particles

Nanofluids have been extensively studied as light absorption and heat transfer medium for solar energy harvesting. In this work, we, for the first time, investigate the convective bubbly flow in recyclable Fe3O4 nanofluids for solar steam generation. The low-cost nanoparticles inherently exhibit broadband light harvesting properties and facile recyclability. The great amount of dispersed bubbles not only work as light transfer center to amplify solar flux, but also provide large areas for mass transport across the interfaces. Our experimental results show that the bubbly nanofluid can significantly enhance the solar thermal evaporation. The coupling effect from light harvesting nanoparticles and dispersed air bubbles finally results in 2.48 times enhancement of the evaporation rate compared to base water. Based on the experimental results, a fully discussion on heat transfer mechanisms around the coupling of nanoparticles and bubbles is additionally provided, in which the thermal boundary layers induced by the particle chain around bubbles played significant roles. This work opens an economic and efficient way for accelerating solar vapor generation, and such concept and methods can be translated into industrial applications such as solar desalination and wastewater treatment.

Broadband Meta‐Absorber with Au/Ni Core–Shell Nanowires for Solar Vapor Generator

AbstractSolar energy has the advantages of being eco‐friendly, practically infinite, and nonreliant on chemical fuels. A solar vapor generator uses sunlight to transform a liquid stream into a vapor stream to operate a turbine for generating electricity. For efficient vapor generation, it should absorb the sunlight in broad spectrum with high absorption, and also have high photothermal conversion efficiency. In this work, Ni nanowires and Au/Ni core–shell nanowire absorbers which meet the relevant conditions are fabricated using a cost‐effective process for efficient solar vapor generation. The light is scattered and trapped in the nanowires and the electrical field is enhanced between the nanowires by the surface plasmonic gap resonance, resulting in high absorption. Also, the adiabatic nanofocusing structure generates heat at hot spots, resulting in efficient photothermal conversion. As a result, the Ni and Au/Ni core–shell nanowire absorbers respectively, absorb over 98% and 91% of the incident light in the solar spectrum. Further, the efficiency of photothermal conversion of the Au–Ni absorber under 1 Sun is found to be ≈33%. These absorbers have the potential to be applied to diverse fields, such as desalination, solar thermophotovoltaics, and metamaterials.

Sustainable Solar Evaporation while Salt Accumulation.

Solar-driven water evaporation, as a cost-effective and eco-friendly way to produce high-quality freshwater from saline water, is a burgeoning and promising force in the battle against global thirst. However, unsustainable vapor generation caused by salt accumulation has always plagued researchers. Here, it is revealed that a solar thermal photo vapor generator (STPV), which utilizes infrared photons as a heat source, can evaporate water stably in the presence of salt accumulation. Thanks to the low reflection of the wet salt in the infrared band and the porous structure of the salt layer, the energy can be used effectively and the vapor escapes without hindrance. The STPV evaporates water at a stable rate of 1.04-1.19 kg m-2 h-1 under 2 sun illumination for 8 h in a highly concentrated sea salt solution (20 wt %). In contrast, the evaporation rate of conventional solar thermal vapor generators (STVs) decreased by >50% in 1 h and ≈70% in 8 h. This finding could inspire the future development of more advanced solar evaporators so as to ease the global water scarcity.

An environmental pollutant to an efficient solar vapor generator: an eco-friendly method for freshwater production

The solar-driven water evaporation technique has shown enormous potential for freshwater generation. Solar vapor generator made of carbonized coconut husk shows an evaporation rate of 3.6 kg m−2h−1with the ability to purify seawater and sewage.

A solar evaporator based on hollow polydopamine nanotubes with all-in-one synergic design for highly-efficient water purification

An all-in-one synergic strategy to prepare solar evaporators considering four sub-processes during solar vapor generation.