Tree-Inspired Aerogel Comprising Nonoxidized Graphene Flakes and Cellulose as Solar Absorber for Efficient Water Generation.

As global freshwater shortages worsen, solar steam generation (SSG) emerges as a promising, eco-friendly, and cost-effective solution for water purification. However, widespread SSG implementation requires efficient photothermal materials and solar evaporators that integrate enhanced light-to-heat conversion, rapid water transportation, and optimal thermal management. This study investigates using nonoxidized graphene flakes (NOGF) with negligible defects as photothermal materials capable of absorbing over 98% of sunlight. By combining NOGF with cellulose nanofibers (CNF) through bidirectional freeze casting, we created a vertically and radially aligned solar evaporator. The hybrid aerogel exhibited exceptional solar absorption, efficient solar-to-thermal conversion, and improved surface wettability. Inspired by tree structures, our design ensures rapid water supply while minimizing heat loss. With low NOGF content (∼10.0%), the NOGF/CNF aerogel achieves a solar steam generation rate of 2.39 kg m-2 h-1 with an energy conversion efficiency of 93.7% under 1-sun illumination, promising applications in seawater desalination and wastewater purification.

Performance optimization of energy-efficient solar absorbers for thermal energy harvesting in modern industrial environments using a solar deep learning model.

Thermal energy harvesting has seen a rise in popularity in recent years due to its potential to generate renewable energy from the sun. One of the key components of this process is the solar absorber, which is responsible for converting solar radiation into thermal energy. In this paper, a smart performance optimization of energy efficient solar absorber for thermal energy harvesting is proposed for modern industrial environments using solar deep learning model. In this model, data is collected from multiple sensors over time that measure various environmental factors such as temperature, humidity, wind speed, atmospheric pressure, and solar radiation. This data is then used to train a machine learning algorithm to make predictions on how much thermal energy can be harvested from a particular panel or system. In a computational range, the proposed solar deep learning model (SDLM) reached 83.22 % of testing and 91.72 % of training results of false positive absorption rate, 69.88 % of testing and 81.48 % of training results of false absorption discovery rate, 81.40 % of testing and 72.08 % of training results of false absorption omission rate, 75.04 % of testing and 73.19 % of training results of absorbance prevalence threshold, and 90.81 % of testing and 78.09 % of training results of critical success index. The model also incorporates components such as insulation and orientation to further improve its accuracy in predicting the amount of thermal energy that can be harvested. Solar absorbers are used in industrial environments to absorb the sun's radiation and turn it into thermal energy. This thermal energy can then be used to power things such as heating and cooling systems, air compressors, and even some types of manufacturing operations. By using a solar deep learning model, businesses can accurately predict how much thermal energy can be harvested from a particular solar absorber before making an investment in a system.

Design of a High-Performance Titanium Nitride Metastructure-Based Solar Absorber Using Quantum Computing-Assisted Optimization.

Metastructures of titanium nitride (TiN), a plasmonic refractory material, can potentially achieve high solar absorptance while operating at elevated temperatures, but the design has been driven by expert intuition. Here, we design a high-performance solar absorber based on TiN metastructures using quantum computing-assisted optimization. The optimization scheme includes machine learning, quantum annealing, and optical simulation in an iterative cycle. It designs an optimal structure with solar absorptance > 95% within 40 h, much faster than an exhaustive search. Analysis of electric field distributions demonstrates that combined effects of Fabry-Perot interferences and surface plasmonic resonances contribute to the broadband high absorption efficiency of the optimally designed metastructure. The designed absorber may exhibit great potential for solar energy harvesting applications, and the optimization scheme can be applied to the design of other complex functional materials.

Ultra-Wideband High-Efficiency Solar Absorber and Thermal Emitter Based on Semiconductor InAs Microstructures.

Since the use of chemical fuels is permanently damaging the environment, the need for new energy sources is urgent for mankind. Given that solar energy is a clean and sustainable energy source, this study investigates and proposes a six-layer composite ultra-wideband high-efficiency solar absorber with an annular microstructure. It achieves this by using a combination of the properties of metamaterials and the quantum confinement effects of semiconductor materials. The substrate is W-Ti-Al2O3, and the microstructure is an annular InAs-square InAs film-Ti film combination. We used Lumerical Solutions' FDTD solution program to simulate the absorber and calculate the model's absorption, field distribution, and thermal radiation efficiency (when it is used as a thermal emitter), and further explored the physical mechanism of the model's ultra-broadband absorption. Our model has an average absorption of 95.80% in the 283-3615 nm band, 95.66% in the 280-4000 nm band, and a weighted average absorption efficiency of 95.78% under AM1.5 illumination. Meanwhile, the reflectance of the model in the 5586-20,000 nm band is all higher than 80%, with an average reflectance of 94.52%, which has a good thermal infrared suppression performance. It is 95.42% under thermal radiation at 1000 K. It has outstanding performance when employed as a thermal emitter as well. Additionally, simulation results show that the absorber has good polarization and incidence angle insensitivity. The model may be applied to photodetection, thermophotovoltaics, bio-detection, imaging, thermal ion emission, and solar water evaporation for water purification.

Thin-Film Solar Energy Absorber Structure for Window Coatings for Self-Sufficient Futuristic Buildings.

Energy-efficient buildings are a new demand in the current era. In this paper, we present a novel metamaterial design aimed at achieving efficient solar energy absorption through a periodic MMA structure composed of a W-GaAs-W. The proposed structure can be implemented as the window coating and in turn it can absorb the incident solar energy and, then, this energy can be used to fulfill the energy demand of the building. Our results reveal significant improvements, achieving an average absorptance of 96.94% in the spectral range. Furthermore, we explore the influence of the angle of incidence on the absorber's response, demonstrating its angle-insensitive behavior with high absorption levels (above 90%) for incidence angles up to 60° for TE polarization and 40° for TM polarization. The proposed structure presents a significant advancement in metamaterial-based solar energy absorption. By exploring the effects of structural parameters and incident angles, we have demonstrated the optimized version of our proposed absorber. The potential applications of this metamaterial absorber in self-sufficient futuristic building technologies and self-sustaining systems offer new opportunities for harnessing solar energy and are a valuable contribution to future developments in the fields of metamaterials and renewable energy.

Emergence of the Janus-MOF (J-MOF) Boat as a Nascent Amalgamation in the Arena of Photothermal Desalination.

The diminution of potable water is a pressing issue in several countries and is the most prioritized obligation of environmental scientists. Thence, the ardent emergence of photothermal interfacial evaporation (PTIE) is seen as a neoteric horizon in the avenue of water remediation. Consequently, for the first time, the decoration of metal-organic frameworks (MOFs) over a Janus architecture as an avant-garde marriage was explored in the domain of photothermal desalination. In this study, a solar absorber was developed by inducing phase change to Ni-doped HKUST-1 (Cu-MOF) via high-temperature calcination to create biphasic CuO/Cu2O caged in N-doped graphene oxide (NGO) sheets. The doping of Ni in the framework demonstrated to enhance the pyrrolic nitrogen (PN) of NGO sheets, which improved the photothermal feature of the solar absorber in union with promoting Cu2+ species as well as enriching the p-type nature of the biphasic configuration for augmented nonradiative relaxation of electrons. In order to take advantage of the robust potential of the designed solar absorber, it was coated over a Janus membrane prepared via the facile approach, composed of poly(methyl methacrylate) (PMMA) and agarose gel having opposing wettability, referred to as the J-MOF boat. This nascent amalgamation recorded a maximum evaporation rate of 1.5 kg/m2 h with pure water and 1.3 kg/m2 h with simulated seawater under 1 sun irradiation. This phenomenon was ascribed to the highly porous agarose layer to facilitate extraordinary water pumping, while concomitantly rejecting salts via capillary action in a nature-mimicking fashion as seen in mangrove trees. The boat-like feature arises from the PMMA layer to conduct PTIE at the water/air interface by uniformly dispersing the localized heat from the solar absorber owing to its low thermal conductivity and three-dimensional (3D) porous structure. Thus, it is believed that this nascent strategy could push the boundaries of solar-driven desalination.

Modulating the Combinatorial Target Power of MgSnN2 via RF Magnetron Sputtering for Enhanced Optoelectronic Performance: Mechanistic Insights from DFT Studies.

The unique structural features of many ternary nitride materials with strong chemical bonding and band gaps above 2.0 eV are limited and are experimentally unexplored. It is important to identify candidate materials for optoelectronic devices, particularly for light-emitting diodes (LEDs) and absorbers in tandem photovoltaics. Here, we fabricated MgSnN2 thin films, as promising II-IV-N2 semiconductors, on stainless-steel, glass, and silicon substrates via combinatorial radio-frequency magnetron sputtering. The structural defects of the MgSnN2 films were studied as a function of the Sn power density, while the Mg and Sn atomic ratios remained constant. Polycrystalline orthorhombic MgSnN2 was grown on the (120) orientation within a wide optical band gap range of ∼2.20-2.17 eV. The carrier densities of 2.18× 1020 to 1.02 × 1021 cm-3, mobilities between 3.75 and 2.24 cm2/Vs, and a decrease in resistivity from 7.64 to 2.73 × 10-3 Ω cm were confirmed by Hall-effect measurements. These high carrier concentrations suggested that the optical band gap measurements were affected by a Burstein-Moss shift. Furthermore, the electrochemical capacitance properties of the optimal MgSnN2 film exhibited an areal capacitance of 152.5 mF/cm2 at 10 mV/s with high retention stability. The experimental and theoretical results showed that MgSnN2 films were effective semiconductor nitrides toward the progression of solar absorbers and LEDs.

Carbonized rice husk coated solar absorber for clean water generation from seawater with a solar still.

This study demonstrated the generation of clean water from seawater collected at the beach coast in Universiti Malaysia Sabah, Malaysia, with carbonized rice husk coated melamine sponge as solar absorber by a solar still. Melamine sponge was utilized as a seawater transportation medium since its porous structure is excellent in channelling the seawater. Whereas carbonized rice husk was used as the photothermal conversion material for its efficient heat absorption due to its black colour and porous structure. Implementing air gap between the seawater body and solar absorber, and restricted water pathway assisted in localizing heat on the top surface of the solar absorber. Clean water was generated under direct solar radiation during the day at an open space with average solar intensity around 1.1∼1.2 kW/m2 (slightly higher than 1 sun) for about 4 h. Efficiency of the solar absorber was calculated, while the quality of the generated clean water was observed in terms of salinity and pH value. Insulated solar still with carbon-coated sponge showed the highest efficiency at about 54.74%. Salinity of the collected clean water significantly reduced to consumable level which was approximately 55 ppm, and the pH value at about 6.73 where it was within the safe limit of the drinkable water pH.

Effect of Argon on the Properties of Copper Nitride Fabricated by Magnetron Sputtering for the Next Generation of Solar Absorbers.

Copper nitride, a metastable semiconductor material with high stability at room temperature, is attracting considerable attention as a potential next-generation earth-abundant thin-film solar absorber. Moreover, its non-toxicity makes it an interesting eco-friendly material. In this work, copper nitride films were fabricated using reactive radio frequency (RF) magnetron sputtering at room temperature, 50 W of RF power, and partial nitrogen pressures of 0.8 and 1.0 on glass and silicon substrates. The role of argon in both the microstructure and the optoelectronic properties of the films was investigated with the aim of achieving a low-cost absorber material with suitable properties to replace the conventional silicon in solar cells. The results showed a change in the preferential orientation from (100) to (111) planes when argon was introduced in the sputtering process. Additionally, no structural changes were observed in the films deposited in a pure nitrogen environment. Fourier transform infrared (FTIR) spectroscopy measurements confirmed the presence of Cu-N bonds, regardless of the gas environment used, and XPS indicated that the material was mainly N-rich. Finally, optical properties such as band gap energy and refractive index were assessed to establish the capability of this material as a solar absorber. The direct and indirect band gap energies were evaluated and found to be in the range of 1.70-1.90 eV and 1.05-1.65 eV, respectively, highlighting a slight blue shift when the films were deposited in the mixed gaseous environment as the total pressure increased.

Enabling Highly Enhanced Solar Thermoelectric Generator Efficiency by a CuCrMnCoAlN-Based Spectrally Selective Absorber.

Harvesting solar energy to enhance thermoelectric generator efficiency is a highly effective strategy. However, it is a grand challenge but essential to increase solar-thermal conversion efficiency. A spectrally selective absorber, which is capable of boosting solar absorptance (α) while suppressing thermal emittance (ε), shows great potential to elevate the solar-thermal conversion efficiency. Herein, we fabricate a multilayer spectrally selective absorber with the assistance of high-entropy nitrides, which shows outstanding spectral selectivity (α/ε = 95.2/10.9%). Benefitting from the high-entropy nitrides, it is experimentally demonstrated that the as-deposited absorber exhibits superior thermal stability, which is crucial to ensure service life. Under 1000 W·m-2 simulated solar illumination, it achieves a very high surface temperature of 109.6 °C, making it suitable to enhance the efficiency of solar thermoelectric generators. Impressively, the integration of the proposed absorber with a commercial thermoelectric generator efficiently reinforces thermoelectric performance, offering a high output power of 1.99 mW. More importantly, by taking advantage of a thermal concentration strategy, it enables a further increase of the output power by 2.98 mW. This work provides a promising solar-thermal material to boost high thermoelectric performance and extends the application category of high-entropy nitrides.

Tunable Color-Variable Solar Absorber Based on Phase Change Material Sb2Se3.

In this paper, a dynamic color-variable solar absorber is designed based on the phase change material Sb2Se3. High absorption is maintained under both amorphous Sb2Se3 (aSb2Se3) and crystalline Sb2Se3 (cSb2Se3). Before and after the phase transition leading to the peak change, the structure shows a clear color contrast. Due to peak displacement, the color change is also evident for different crystalline fractions during the phase transition. Different incident angles irradiate the structure, which can also cause the structure to show rich color variations. The structure is insensitive to the polarization angle because of the high symmetry. At the same time, different geometric parameters enable different color displays, so the structure can have good application prospects.

Selective Solar Harvesting Windows for Full-Spectrum Utilization.

Smart windows can selectively regulate excess solar radiation to reduce heating and cooling energy consumption in the built environment. However, the inevitable dissipation of ultraviolet and near-infrared into waste heat results in inefficient solar utilization. Herein, a dual-band selective solar harvesting (SSH) window is developed to realize full-spectrum utilization. A transparent photovoltaic, converting ultraviolet into electricity, and a transparent solar absorber, converting near-infrared into thermal energy, are integrated and coupled with a ventilation system to extract heat for indoor use. Compared with common transparent photovoltaics, the SSH window increases solar harvesting efficiency up to threefold while maintaining a considerable visible transmittance. Simulations suggest that the SSH window, besides generating electricity, delivers energy savings by over 30% higher than common smart windows. This is the first integration of transparent photovoltaic and transparent solar absorber into a window, which may open up a new avenue for the development of energy-efficient buildings.

Experimental and analytical datasets for pressure drop and flow distribution in a Z-type flat-plate solar absorber.

This data article provides two dataset types for total pressure drop and parallel-flow distribution in a Z-type flat-plate solar thermal absorber with water as the working fluid. The first dataset consists of high-resolution pressure drop measurements at different temperatures under laminar and turbulent flow conditions obtained experimentally using a state-of-the-art hydraulic test rig. The second dataset comprises analytical data on flow distribution in the absorber. Conducting high-resolution pressure measurements, essential for evaluating thermo-hydraulic models, is a sensitive and time-demanding process requiring a relatively elaborated test rig to accurately measure pressure drop at different temperatures and flow rates in the presence of thermal equilibrium. In this context, engineers and researchers can use these datasets to compare and verify developed numerical models for thermo-hydraulic evaluation of pressure drop and flow distribution in flat-plate solar collectors under both laminar and turbulent flow regimes. The article also comprises analytical data for flow distribution in the absorber for several header configurations presented by dimensionless-flow-rate and non-uniformity. This data article is related to the research article (Shantia et al., 2022 ). The datasets are accessible in the supplementary files accompanied by the online version of this article and in the Mendeley Data repository.

Operation of Wearable Thermoelectric Generators Using Dual Sources of Heat and Light.

A wearable thermoelectric generator (WTEG) that utilizes human body heat can be a promising candidate for the wearable power generators. The temperature difference (ΔT) between the body and the environment is a stable source driving the WTEG, but this driving force is limited by the ambient temperature itself at the same time. Here, a novel WTEG that can be operated using the dual source of body heat and light with exceptionally high driving force is fabricated. The printable solar absorbing layer attached to the bottom of the WTEG absorbs ≈95% of the light from ultraviolet to far infrared and converts it into heat. To optimize the power density of WTEGs, the fill factor of the thermoelectric (TE) leg/electrode is considered through finite-difference time-domain (FDTD) simulation. When operated by the dual sources, the WTEG exhibits a power density of 15.33 µW cm-2 , which is the highest under "actual operating conditions" among all kinds of WTEGs. In addition, unlike conventional WTEGs, the WTEG retains 83.1% of its output power at an ambient temperature of 35 °C compared to its output power at room temperature. This study will accelerate the commercialization of WTEGs by introducing a novel method to overcome their limitations.

Hydrophobic and porous carbon nanofiber membrane for high performance solar-driven interfacial evaporation with excellent salt resistance.

Interfacial evaporation has recently received great interest from both academia and industry to harvest fresh water from seawater, due to its low cost, sustainability and high efficiency. However, state-of-the-art solar absorbers usually face several issues such as weak corrosion resistance, salt accumulation and hence poor long-term evaporation stability. Herein, a hydrophobic and porous carbon nanofiber (HPCNF) is prepared by combination of the porogen sublimation and fluorination. The HPCNF possessing a macro/meso porous structure exhibits large contact angles (as high as 145°), strong light absorption and outstanding photo-thermal conversion performance. When the HPCNF is used as the solar absorber, the evaporation rate and efficiency can reach up to 1.43 kg m-2h-1 and 87.5% under one sunlight irradiation, respectively. More importantly, the outstanding water proof endows the absorber with superior corrosion resistance and salt rejection performance, and hence the interfacial evaporation can maintain a long-term stability and proceed in a variety of complex conditions. The HPCNFs based interfacial evaporation provides a new avenue to the high efficiency solar steam generation.

A Scalable Solution Route to Porous Networks of Nanostructured Black Tungsten.

This paper studied the feasibility of a new solution-processed method to manufacture black tungsten nanostructures by laser conversion of tungsten hexacarbonyl precursor on the Inconel 625 substrate under argon atmosphere at ambient pressure. The results show that sublimation of the precursor can be prevented if the decomposition temperature (>170 °C) is achieved using the laser heating method. Three different laser powers from 60-400 W were used to investigate the role of laser parameters on the conversion. It was found that lower laser power of 60 W resulted in a mixture of unconverted precursor and converted tungsten. Higher laser powers >200 W resulted in α-W (BCC) in one step without further heat treatment. Different oxygen concentrations from 0.5 ppm to 21 vol% were used in the laser canister to investigate the effect of oxygen concentration on the conversion. It was found that the hard vacuum (>10-4 torr) or hydrogen is not necessary to obtain α-W (BCC). The solar absorptance varied from 63-97%, depending on the amount of precursor deposited on the substrate and oxygen content in the laser canister. This solution-based laser conversion of tungsten precursor is a scalable method to manufacture tungsten coatings for high-temperature applications.

Broadband Solar Absorber Based on Square Ring cross Arrays of ZnS.

Solar energy is an inexhaustible clean energy. However, how to improve the absorption efficiency in the visible band is a long-term problem for researchers. Therefore, an electromagnetic wave absorber with an ultra-long absorption spectrum has been widely considered by researchers of optoelectronic materials. A kind of absorbing material based on ZnS material is presented in this paper. Our purpose is for the absorber to achieve a good and wide spectrum of visible light absorption performance. In the wide spectrum band (553.0 THz-793.0 THz) of the absorption spectrum, the average absorption rate of the absorber is above 94%. Using surface plasmon resonance (SPR) and gap surface plasmon mode, the metamaterial absorber was studied in visible light. In particular, the absorber is insensitive to both electric and magnetic absorption. The absorber can operate in complex electromagnetic environments and at high temperatures. This is because the absorber is made of refractory metals. Finally, we discuss and analyze the influence of the parameters regulating the absorber on the absorber absorption efficiency. We have tried to explain why the absorber can produce wideband absorption.

Physicochemical and Optical Characterization of Citrus aurantium Derived Biochar for Solar Absorber Applications.

Agro-industrial waste valorization is an attractive approach that offers new alternatives to deal with shrinkage and residue problems. One of these approaches is the synthesis of advanced carbon materials. Current research has shown that citrus waste, mainly orange peel, can be a precursor for the synthesis of high-quality carbon materials for chemical adsorption and energy storage applications. A recent approach to the utilization of advanced carbon materials based on lignocellulosic biomass is their use in solar absorber coatings for solar-thermal applications. This study focused on the production of biochar from Citrus aurantium orange peel by a pyrolysis process at different temperatures. Biochars were characterized by SEM, elemental analysis, TGA-DSC, FTIR, DRX, Raman, and XPS spectroscopies. Optical properties such as diffuse reflectance in the UV-VIS-NIR region was also determined. Physical-chemical characterization revealed that the pyrolysis temperature had a negative effect in yield of biochars, whereas biochars with a higher carbon content, aromaticity, thermal stability, and structural order were produced as the temperature increased. Diffuse reflectance measurements revealed that it is possible to reduce the reflectance of the material by controlling its pyrolysis temperature, producing a material with physicochemical and optical properties that could be attractive for use as a pigment in solar absorber coatings.

A Thermoelectric Energy Harvester Based on Microstructured Quasicrystalline Solar Absorber.

As solar radiation is the most plentiful energy source on earth, thermoelectric energy harvesting emerges as an interesting solution for the Internet of Things (IoTs) in outdoor applications, particularly using semiconductor thermoelectric generators (TEGs) to power IoT devices. However, when a TEG is under solar radiation, the temperature gradient through TEG is minor, meaning that the TEG is useless. A method to keep a significant temperature gradient on a TEG is by using a solar absorber on one side for heating and a heat sink on the other side. In this paper, a compact TEG-based energy harvester that features a solar absorber based on a new class of solid matter, the so-called quasicrystal (QC), is presented. In addition, a water-cooled heat sink to improve the temperature gradient on the TEG is also proposed. The harvester is connected to a power management circuit that can provide an output voltage of 3 V and store up to 1.38 J in a supercapacitor per day. An experimental evaluation was carried out to compare the performance of the proposed QC-based harvester with another similar harvester but with a solar absorber based on conventional black paint. As a result, the QC-based harvester achieved 28.6% more efficient energy generation and achieved full charge of a supercapacitor around two hours earlier. At last, a study on how much the harvested energy can supply power to a sensor node for Smart agriculture during a day while considering a trade-off between the maximum number of measurements and the maximum number of transmission per day is presented.

Molecular Engineering of Pure 2D Lead-Iodide Perovskite Solar Absorbers Displaying Reduced Band Gaps and Dielectric Confinement.

Pure 2D lead-iodide perovskites typically demonstrate poor charge transport and compromised visible light absorption, relative to their 3D congeners. This hinders their potential use as solar absorbers. Herein, the systematic tuning of pyridinium-based templating cations is reported to introduce intermolecular interactions that provide access to a series of new 2D lead-iodide perovskites with reduced inter-octahedral distortions (largest Pb-(µ-I)-Pb bond angles of 170-179°) and very short inorganic interlayer separations (shortest I⋅⋅⋅I contacts ≤4.278-4.447 Å). These features manifest in reduced band gaps (2.35-2.46 eV) and relaxed dielectric confinement (excitonic binding energies of 130-200 meV). As a consequence, they demonstrate (more than ten-fold) improved photo- and electrical conductivities relative to conventional 2D lead-iodide perovskites, such as that templated by 2-(1-naphthyl)ethylammonium. Through computational studies, the origin of this behavior was shown to derive from a combination of short iodoplumbate layer separations and the aromaticity of the organic dications.