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Industrial heat converters are essential to meet the growing demand for thermal energy in industries. This demand can be met by designing solar heat absorbers which can be used as renewable energy sources for these industries. The effective solar absorber is built with the efficient three layers of top and based layer is constructed with the titanium (Ti), and the middle layer is demonstrated with the Gallium Arsenide (GaAs). The resonator (Ti) layer is in the mathematical sign divide and the proposed design can be effectively explored in the four different infrared light regions. The second layer of the GaAs layer is sandwiched between the two Ti-based and resonator layers. In this divide sign solar absorber, the proposed resulting percentage can be identified by using the four peak wavelengths in micrometers of 0.45 for λ 1, 0.8 for λ 2, 2.2 for λ 3, and 2.5 for λ 4 respectively. The resulting absorption rate can be presented in three sections of 700 nm bandwidth is above 95% in that rate and the section of 710 nm bandwidth is above 90%. The overall accepted rate from 0.2 to the highest rate of 3 µm is 2800 nm and explores the average rate of greater than 90% (90.16%). The expression of the proposed divided sign solar absorber, the building section's multistep inclusions, and the Air Mass (AM)1.5 situation in the different color sections can also be approved. The different studies of the design section can be expressed by changing the Ti-based and resonator layers, GaAs middle layer. Moreover, the amount of chemical potential and the TE and TM difference can also be analyzed with the degree changes from 0 to 50 degrees. The proposed dividend solar design can be used as a heat converter in industries as effective renewable energy such as cooling techniques, oil refining, recovery systems, air conditioning. [ABSTRACT FROM AUTHOR]

A U-shaped Metal-Insulator-Metal (MIM) solar energy absorber is simulated, and designed in this paper. Tungsten is utilized as the base metal layer because of its transmission blocking characteristics, the SiO 2 is used as a dielectric insulator and a U-shaped resonator made of titanium as a radiation absorber to achieve a near perfect Solar energy absorber as it provides the impedance matching abilities. The proposed structure is simulated over the solar spectrum which covers the wavelengths from 0.2 to 2.5 µm which includes the ultraviolet (UV) to near infrared (NIR) bands, the absorbed energy is of 94.52%, 97.06%, and 96.67%, respectively. Furthermore, the additional investigation under solar radiation is conducted and the proposed structure is absorbing most of the energy while the minimal amount is missed in visible range. The main contribution of this work lies in its broadband absorption spectrum which is achieved employing a very simple and easy to fabricate structure. In addition, the structure also achieves the angle and polarization insensitiveness. The major contribution is the prediction of absorption at an intermediate wavelengths with locally weighted linear regression with a R2 score of 0.9999. The proposed structure can be used for the efficiency enhancement of thermoelectric photovoltaic devices. [ABSTRACT FROM AUTHOR]

Solar absorbers are the heart of sustainable photothermal utilization. To obtain higher photothermal conversion efficiency, nanomultilayer absorbers with low emissivity are undoubtedly the best choice. However, the strategy of co-sputtering with at least two targets is usually employed, which makes the preparation process complex and costly, so it is necessary to develop a one-step sputtering preparation through a target. Herein, we propose preparation of Ti–TiO x nanomultilayer solar selective absorption coatings (SSACs) with a single metal Ti target by one-step sputtering. The self-doped Ti nanoparticles as well as the Ti2+, Ti3+ and Ti4+ oxides in TiO x matrix can easily customize the band gap from ultraviolet to visible light, resulting in a high absorption of 0.92 and a low thermal emissivity of 0.07 (298.15K). The obtained Ti – TiO x SSACs exhibit excellent thermal stability after heat treatment at 250 °C for 300 h in air. More significantly, the measured surface temperature reached 114.5 °C under 1.5 suns simulated illumination, indicating its outstanding solar-thermal conversion ability. This work extends the application range of the titanium oxide, developing a simple method for designing low-emissivity solar absorbers. [Display omitted] • Self-doped Ti–TiO x films with α of 0.92 and ε of 0.07 were constructed by one-step sputtering for selective absorption. • It shows good thermal stability after annealing at 250 °C and can reach 114.5 °C under indoor simulation of 1.5 suns. • This work provides an unprecedented method to achieve adjustment of selective absorption of broadband gap materials. [ABSTRACT FROM AUTHOR]

Solar energy conversion technologies attain enormous attention to create more efficient energy production sources to meet the current world's demand. The solar thermal conversion system converts solar energy to heat, and the receiver tube is crucial for achieving high photo-thermal conversion efficiency. The absorber coatings with high solar absorptance at normal and wide incidence angles of solar radiation improve the performance of concentrated and non-concentrated solar thermal systems. To achieve high photo-thermal conversion efficiency in the solar thermal conversion system, a novel spinel structured cobalt-rich transition metal oxide-based absorber coating was developed by a cost-effective wet chemical route. The developed absorber coatings with sub-micron scaled surface protrusions with porous structure (size 0.75 μm) exhibit an excellent spectral selectivity (α/ ε = 0.91/0.13). In addition, the coatings show an excellent wide angular solar absorptance of 0.97–0.96 at incidence angles of 10°–40°. Extensive characterization has been carried out to analyze the structural properties of the absorber coatings and correlated to the spectral selectivity and wide angular solar absorptance property. The stability of the absorber coating at 400 °C for 100 h in an open-air atmosphere assessed by the performance criteria (PC) function value of 0.015 indicates the ability of the optimized absorber coatings to employ in solar thermal systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Solar collectors have the potential for significant climate change mitigation by substituting heat produced with fossil fuels. To achieve this, collectors with highly efficient solar absorbers are essential. Carbon nanotubes are highly absorbing, sustainable, cheap, and thermally stable, making them a promising material for solar absorbers. However, achieving a high solar absorptance and low thermal emittance (solar selectivity), while maintaining good thermal stability and scalability is challenging. Here, we present a selective coating based on multi-walled carbon nanotubes and silica (SiO 2). A water-based dispersion enabled by carboxyl functionalization of the carbon nanotubes (CNT F) is spray coated on a stainless steel (SS) substrate and fixated with sol-gel dip coated silica. The SS/CNT F /SiO 2 surface exhibits an optical selectivity dependent on CNT F area load and with 0.83 g CNT m−2 a solar absorptance and thermal emittance of 0.94 and 0.40, respectively, is achieved. The coating also demonstrates excellent thermal stability, with an estimated lifetime of >25 years at working temperatures ≤222°C. All together, we show that by using scalable and cheap technology, concurrent with sustainable materials and a simple structural design, we can manufacture a coating that exhibits properties suitable for low-to-mid-temperature applications. Our study highlights the potential of carbon-based solar absorbers. [Display omitted] • We present a novel selective coating based on multi-walled carbon nanotubes and silica (SiO 2). • The SS/CNT F /SiO 2 surface exhibits a high solar absorptance and an optical selectivity. • The coating demonstrates good thermal stability, with an estimated lifetime of >25 years at working temperatures ≤222 °C. • The coating exhibits properties suitable for low-to mid-temperature applications. [ABSTRACT FROM AUTHOR]

The optimization of the solar absorber is very important to develop the efficiency of the solar absorber. We have designed here one solar absorber which is optimized using variation in different physical parameters. The design of this absorber is based on Cr-GaAS-Ag materials which is also based on a thin film graphene material. The designed solar structure is used for heating applications which can be applied in industrial use. The highest absorption of more than 99 % is achieved for different wavelengths. The design also shows the 97.1 % absorption for the 1000 nm wavelength. The optimization section is also provided in this research at the end of results section. The conclusions are obtained using absorption for the different layer structures in this research. Layer by layer analysis for the absorption is provided in this manuscript. The research is aimed at renewable energy use in the industries by providing sustainable heating applications. [ABSTRACT FROM AUTHOR]

With the invention of the photonics techniques, a new structural design for thermal energy absorber is designed which uses the multilayer structure to absorb the solar energy and this solar energy is converted to thermal energy which is possible to be utilized in industrial heating applications. The use of solar energy makes it a sustainable option to meet the high growing industrial output energy. Materials like Titanium (Ti), Titanium Carbide (TiC), Silicon (Si) are used for this purpose. The use of these materials makes it more cost-friendly compared to the other similar options. The higher absorption rate is achieved by optimizing the design layers. The flowchart for the optimization in materials as well as design is also shown in this research. The optimization makes the design more compact and handy for industrial use. The advantage of these designs over the other designs is the choice of materials as well as their compact size. The results are also analyzed for the wide angle of incidence and polarization. All the results obtained show that the design is highly efficient in the solar spectral range and can be a renewable energy option for industrial and domestic heating applications. [ABSTRACT FROM AUTHOR]

• Solar absorber; We introduce an absorber which worked in visible and mid-infrared spectrum. • Wideband absorption: Absorber has wideband absorption in this region. • Multilayered structure: The structure of solar absorber based on multilayers of different metamaterials. • FDTD: We simulated absorber by using finite difference time domain (FDTD) software. • Polarization insensitive: This absorber is polarization insensitive up to high oblique angle. We explore a new solar absorber via vertically structured metamaterials integrating 2D graphene, dielectric layers of silica (SiO 2), aluminum oxide (Al 2 O 3), and phase-transition vanadium dioxide (VO 2) graphene, dielectric, phase transition (GDPT), achieving broadband absorption and polarization independence. Applying the finite-difference time-domain (FDTD) method, the optical performance of the absorber is analyzed under the normal incidence of a plane wave spanning wavelengths from 250 to 4000 nm. Particularly, our investigation reveals a broad bandwidth exceeding 90 % absorption, spanning 3559 nm from 250 to 3809 nm, with an impressive average absorption efficiency of over 95.9 %. Significantly, the absorber demonstrates polarization independence and insensitivity to large angles of incidence, enhancing its practical capability. We illuminate the important role of Fabry-Perot resonance in absorption by precisely tuning layer thicknesses to induce interference effects. The integration of graphene, dielectric layers, and VO 2 , augmented by Fabry-Perot resonance, provides a vital foundation for high-performance solar energy conversion technology. This technology has important applications in efficient and broadband solar absorbers, and these absorbers can maintain high performance under different conditions. Our goal is to solve current technological challenges and contribute to the development of next-generation solar energy conversion for various photon technologies, such as energy harvesting, electromagnetic wave capture, and photovoltaic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • A cost-effective and environmentally benign Ag/NiO nanocoatings method was synthesized for solar thermal application. • The RBS was used to investigate the distribution of Ni, Ag, and O atoms throughout the coatings. • The morphology and optical response of Ag/NiO composites were studied by varying Ag content. • The incorporated Ag nanoparticle enhanced the spectral absorption. • The prepared NiO thin film exhibits an excellent solar absorptance (α) value of 0.95 and thermal emittance(ε) of 0.08. This study presents the synthesis of environmentally benign, single-layered spectrally selective Ag/NiO nanocoating absorbers using a green synthesis method. Various characterization techniques, including Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM), were used to examine the effects of plasmonic Ag concentration on the structural, chemical composition, and surface morphology of the nanocomposites. The optical properties of the deposited nanocoatings were investigated using a UV–Vis-NIR spectrophotometer in the solar spectrum region (300–2500 nm) and an FT-IR spectrophotometer in the infrared wavelength region (3000–20,000 nm). XRD results confirmed the coexistence of a face-centered cubic phase of Ag and NiO in the Ag/NiO nanocermet thin films. SEM and TEM topography revealed uniformly distributed nanosphere NiO thin films and cubic Ag metal with better dispersibility and crystallization. The RBS spectrum of the samples showed a homogeneous distribution of Ni, Ag, and O atoms throughout the coatings. Ag/NiO nanocoatings deposited with 8 wt% Ag content exhibited excellent solar absorptance (α) = 0.95 and thermal emittance of (ɛ) of 0.08. This enhancement is primarily attributed to the localized surface plasmon resonance (LSPR) effect associated with the embedded Ag nanoparticles, which facilitates more effective utilization of light. [ABSTRACT FROM AUTHOR]

In this article, nanostructured ultrawideband absorber is proposed for infrared to ultraviolet spectrum. The proposed three layered absorber structure formed of nickel, polyimide and nickel (Ni) material. The proposed unit cell volume is 90nm × 90 nm × 10.62 nm (0.0484 λ L × 0.0484 λ L × 0.00571 λ L nm 3 where, λ L is wavelength at lowest operating frequency). Absorption (A) ≥ 90 % is achieved from 161.48 THz (1857.81 nm) to 3894.58 THz (77.03 nm) which covers infrared, visible and ultraviolet frequency bands. The average absorption 98.08 % is achieved over the entire operating frequency band. The absorption is also analyzed in different resonating patch geometry and using different substrate material. Due to the symmetricity of the octagonal patch geometry, the proposed structure is polarization insensitive and has incident angle ( θ ◦ ) stability up to 60 ° for absorption more than 80 %. The proposed solar absorber achieves 96.82 % solar absorption efficiency (η A) and also achieves 94.61 %, 95.78 %, 96.31 % & 96.62 % thermal emission efficiency (η E) at temperature 2000K, 2500K, 3000K & 3500K respectively. The suggested nanostructure absorber design works well across infrared, visible, and ultraviolet (UV) light, making it an efficient absorber for various uses like solar panels, detectors, solar energy harvesters, thermal devices, cloaking, solar power, sensors, and UV protection. • Ultrathin single layer simple structure with unitcell volume of 0.0484 λ L × 0.0484 λ L × 0.00571 λ L nm3. • The proposed absorber has average peak absorption of 96.94 % from 161.22 THz (1861 nm) to more than 3100 THz (96.77 nm). • Polarization insensitive and Incident angle (θo) stability upto 40o for A≥90 % & 60o for A≥80 %. • Solar absorption efficiency of 96.82 % for AM 1.5 standard with A≥95% for visible, UV, NIR and MIR frequencies. • Thermal emission efficiency of 94.61 %, 95.78 %, 96.31 % & 96.62 % at temperature 2000K, 2500K, 3000K & 3500K respectively. [ABSTRACT FROM AUTHOR]

Perfect solar energy absorption is becoming more and more significant in the fields of carbon neutrality, the numerical study of various metamaterial solar absorbers is boosting but their fabrication is still challenging us a lot. In this study, we propose a unique type of metamaterial absorbers with cross shaped nanostructures achieving efficient absorptance in the wavelength range of 300–2400 nm with an equivalent solar energy absorption efficiency up to 0.94. In addition, the proposed solar absorber is fabricated by using electron beam lithography (EBL) method, and its nearly perfect absorption properties affected by morphology and geometric parameters are further experimentally studied. We also numerically study the effects of the material compositions, geometrical parameters and light sources on the absorption properties of the broadband metamaterial absorbers, and the absorption mechanisms are revealed by employing the electric field distributions. The results indicate that the nearly perfect absorption of solar energy of our metamaterials mainly depends on the surface plasmon resonances (SPRs) that occur between sub-wavelength nanostructures. The present metamaterial solar absorber enables the promising applications of solar vapor generation, solar desalination, wastewater treatment, thermophotovoltaic, etc., especially those working in high temperature and harsh environments because of the high melting point of titanium used in it. • The use of metamaterial absorbers with nanocrosses offers an innovative method for solar energy harvesting. • The simulation and experimental results providie robust evidence to support the effectiveness of the proposed metamaterial absorbers. • The metamaterial absorbers show high absorptance across the solar spectrum, indicating their potential for various solar photothermal applications. • The use EBL for fabricating the metamaterial absorbers demonstrates a practical approach to realizing these structures. [ABSTRACT FROM AUTHOR]

Solar absorbers are used in many different applications to collect solar energy. The Rectangular-Shaped with Thin Wire MXene-based resonator (RSWTWMR) is a unique solar absorber design that is proposed in this study. Aluminium and MXene are the materials used in the substrate and resonator layers of the RSWTWMR, respectively. MXene allows for the absorption of a large amount of solar light because of its remarkable absorption qualities and unique optical properties. The MXene-based resonator has a unique design with a thin wire and a rectangular box that makes it insensitive to polarization. RSWTWMR shows an astounding 95.67 % average absorption over three different wide bands. It is noteworthy that the absorption values in the 920 nm and 720 nm bandwidths exceed 90 % and 94 %, respectively. In addition, the absorption is more than 96 % at wavelengths of 550 nm. Additional research examined how well the system performs in air mass (AM1.5) conditions and examined how different factors, such as substrate and resonator thickness, affect absorption properties. Furthermore, the research looks at the impact of an angle of incidence, which is unaffected between 0 and 70°. This study suggests the RSWTWMR solar absorber has great promise for applications in solar energy harvesting. [ABSTRACT FROM AUTHOR]

• Broadband absorption efficiency of notched nanorings absorber is achieved. • The nearly perfect solar energy harvesting is attributed to the integration of multiple modes of resonances from the notched nanorings. • The incident angle of light significantly affects the absorptance of our absorber because of the notched nanorings. • The gap size and ring eccentricity make a big difference on broadband absorption of our absorbers. Various methods for solar energy utilisation are being developed for reducing the emission of CO 2 from fossil fuels, and perfect solar absorbers are attracting increasing attention. In the present study, a metamaterial solar absorber is proposed. The absorber consists of an array of Ni notched nanorings that are periodically arranged on a gold substrate with a layer of SiO 2 dielectric between the rings. The proposed absorber achieves nearly perfect harvesting of incident solar energy, which is attributed to the integration of multiple modes of resonances from the notched nanorings on the top, including electric and magnetic polaritons. However, the composition, geometries, and arrangement of the notched nanorings significantly affect the absorption properties of our absorbers with a small tolerance. Additionally, the incident angle of light significantly affects the absorptance of our absorber because of the non-rotationally symmetric notched nanorings. When submerged in water, the absorbers that totally harvest solar energy can act as solar evaporators, which in turn promise potential applications involving solar vapour generation, sterilisation, and seawater treatment that can be enabled by solar energy for producing freshwater. [ABSTRACT FROM AUTHOR]

We present and study a bidirectional metamaterial-perfect absorber based on TiO 2 -InAs regular hexagonal pattern thin films and gold grating. We employ the finite difference time domain approach for simulation. Multi-narrowband perfect absorption and ultra-wideband perfect absorption can alternate as the light source's direction changes. Four narrow-band absorption peaks developed at 987 nm, 1188 nm, 1510 nm, and 2091 nm, respectively, when the incident light struck the bottom. The corresponding absorption efficiencies were 99.69 %, 99.41 %, 98.54 %, and 98.97 %. The broadband region displays the properties of perfect absorption when incident light strikes the top. It should be noted that it is not affected by the polarization or angle of the incidence. With an average absorption efficiency of 96.02 %, the structure attains over 90 % absorption in the 3023 nm range (424–3447 nm). Second, the weighted absorption efficiency of the full spectrum is as high as 96.84 %, and the AM 1.5 solar radiation spectrum and the solar absorption spectrum are strongly coincident. Furthermore, the computation results show that the thermal radiation efficiency is greater than 95 % between 300 K and 1500 K. The electric field distribution revealed that the Fabry-Perot cavity resonance within the film, the surface plasmon resonance (SPR) on the surface of the InAs and TiO 2 regular hexagonal pattern films, the interstitial mode excitation between the films, and the excitation cavity coupling between cells of each unit were primarily responsible for the perfect absorption of broadband. The high-order resonant coupling in the FP cavity and the strong coupling between the local surface plasmon resonance and the FP cavity resonance in the metal grating's slit are the primary causes of the narrow band's perfect absorption. The suggested bidirectional metamaterial perfect absorber has significant promise for use in the disciplines of sensing, solar energy absorption, photoelectric detection, and photothermal conversion, as evidenced by its superb absorption and thermal radiation characteristics. Based on Au grating and TiO 2 -InAs regular hexagonal pattern sheets, a perfect metamaterial absorber capable of bidirectional switching between narrowband and broadband absorption is presented. When a light source illuminates the bottom of a bidirectional metamaterial perfect absorber (BDMPA), multi-narrow band perfect absorption occurs. Four resonant absorption peaks were seen at 987 nm, 1188 nm, 1510 nm, and 2091 nm, with absorption efficiencies of 99.69 %, 99.41 %, 98.54 %, and 98.97 %, respectively. When the light source illuminates the top of this BDMPA, it achieves perfect ultra-wideband absorption. The absorption rate exceeds 90 % between 424 and 3447 nm, the bandwidth reaches 3023 nm, and the average absorption efficiency is 96.02 %. [Display omitted] • > When incident light hits the bottom, four resonant peaks with absorption greater than 98 % are achieved. • > When incident light hits the top, the absorber achieves an absorption bandwidth of 3023 nm for efficiencies above 90 %, and 2283 nm for efficiencies above 95 %. • > The thermal radiation absorption efficiency is greater than 95 % in the range of 300–1500 K. [ABSTRACT FROM AUTHOR]

Sustainable and Renewable Energy is essential because it's non-polluted and available in nature. Solar energy is the most important of them all as its the essential of them all. Sun energy is a clean and finest alternative to renewable energy sources. The slotted cylinder-shaped Mxene-based resonator solar absorber (SCMRSA) achieved an average of 95.06 % efficient absorption. The MXene material is used as a resonating material above the titanium oxide layer based on the MXene layer. The wide angle of incidence is achieved which is analyzed by changing the different angles of incidence. The E-field response is also observed for the TE and TM modes. The results show a similar response for both TE and TM modes. The optimization of the structure is also observed for different variable variations and the final optimized design is used for the highly efficient absorptance results. The SCMRSA is also applicable for various solar thermal applications and energy harvesters. [ABSTRACT FROM AUTHOR]

Thermal Energy is required in the industries for various purposes like heating liquids, metals cause boiling of these materials is required to mold it to different shapes. This thermal energy generation required high electricity for its generation. We can reduce the electricity required by making it a self-sustainable model using solar energy. The solar absorber gives the best way to generate sustainable and renewable solar thermal energy. The new solar design investigation depends on the ring resonators with the inverted pyramid shape overlapping. The generated solar output is at the higher desired rate, and the current ring resonator design includes a thin layer of graphene, which can also be determined from the UV to MIR regime. To catch the best-resulted output, the ring resonator design is contributed by multilayered structured materials. The bandwidth contribution depends on the overall amount, the generated solar energy is higher than 97 % at a1500 nm, and more than 95 % for a500 nm. The current investigation of the ring resonator absorber can be used mainly in solar harvesting processes of heating liquids and metals in industries. [ABSTRACT FROM AUTHOR]

In this work, a metamaterial absorber with ultra-broadband, ultra-high absorption, polarization independence and high-temperature resistance for solar thermal energy harvesting applications is designed and numerically simulated. The proposed nanostructure is composed of four T-shaped strips and square ring nanoarray structures of tungsten (W) material deposited on Au substrate. The findings demonstrate that the solar metamaterial absorber can attain broadband absorption of solar energy with a bandwidth of 1.78 μm and the absorption rate of over 90% at the resonance wavelengths of 0.4 μm and 2.18 μm. Namely, the solar absorber exhibits excellent features of ultra-broadband and ultra-high absorption. The ultra-broadband and ultra-high absorption rate of solar absorbers are achieved by exciting surface plasmon resonance (SPR). In the design of solar absorber, the performance can be further enhanced by optimizing the geometry of the nanostructure (e.g., changing the geometric dimensions of T-shaped strips and square rings, and the period of array structures, etc.). Whether in TM mode or TE mode, solar metamaterial absorbers are insensitive to incident angles and can be used within the range of 0°–45° incident angles. The variation of the polarization angle also does not affect the absorption performance of the solar absorber with good polarization independence. Furthermore, at high temperatures from 300 °C to 1500 °C, the optical properties hardly change. It is found that the designed solar metamaterial absorber not only has ultra-broadband and ultra-high absorption, but also has excellent performance of polarization independence and high-temperature resistance. Consequently, this absorber has a promising application in solar cells, photothermal conversion and solar thermal energy harvesting applications. In this study, we designed a solar absorber that can achieve efficient absorption over an extremely wide spectrum, its performance is not affected by the polarization direction of the light and can maintain excellent absorption efficiency under high temperature conditions. [Display omitted] • The proposed solar metamaterial absorber achieved ultra-broadband absorption of 1.78 μm. • The change of the geometrical parameters of the nanostructure can affect the absorption performance of the solar absorber. • Whether in TE mode or TM mode, the absorption performance of solar absorbers does not change with the change of incident angle and has polarization independence. • The solar absorber can maintain stable and efficient absorption performance in high temperature environments. • Either Au can be used as the bottom material, or Ag, Al and Cu can be replaced. [ABSTRACT FROM AUTHOR]

This paper proposes an ultrawideband electromagnetic absorber operating in the infrared, visible light, and ultraviolet regime. The overall structure of the proposed absorber is made up of multiple square rings arranged in a symmetrical configuration. The absorber consists of three layers, the ground layer made of nickel, the intermediate substrate layer is made of polyimide and the top layer is constructed from nickel. The overall unit cell dimension of 119 nm × 119 nm × 31 nm has been proposed for the optimum performance of the absorber. It has absorption (A) of more than 90 % for the frequency range of 131.59 THz to more than 4500 THz. The proposed absorber is polarization-independent. The absorber shows more than 70 % absorption for incident angle<65° in both transverse electric and transverse magnetic modes. The absorber covers the range of infrared, visible, and ultraviolet frequencies. Using this proposed absorber, high solar absorption efficiency (η A) of 96.84 % and high thermal emission efficiency (η E) of 90.19 %, 92.54 %, 95 % and 96.64 % are achieved at 1000K, 1500K, and 2500K & 3500 K, respectively. Due to the ultrawideband characteristic of the proposed design in the infrared, visible, and ultraviolet regimes, the proposed design can be used as a highly efficient absorber in many applications such as photovoltaics, photo-detectors, thermal emitters, IR (Infrared) detectors, cloaking, solar energy harvesting, sensing, and UV (Ultra-Violet) protection. [ABSTRACT FROM AUTHOR]

• Machine learning optimized Solar thermal absorber is designed for solar thermal applications. • The absorption is more than 97 % achieved in the visible region. • The absorption is more than 93 % and 90 % absorption achieved in the wavelength range of 3000–4000 nm and 400–5000 nm. • The prediction accuracy is good. The highest R2 value is 0.999592. Harvesting solar energy into other useful energy sources are essential now a days, hance there are many systems available for that, such as solar absorbers, solar PV, etc. In this study, we have investigated four different solar absorber designs. Out of that four, the Hash-Shaped Solar Absorber (HSSA) structure is more effective for absorbing solar radiation and converting it into heat energy. With the broad response range this structure absorb more than 90 % of the radiation in observed range (100–5000 nm). The HSSA structure demonstrates absorption > 99 % at specific wavelength peaks, including 170 nm, 550 nm, 1790 nm, 2750 nm, 3090 nm, and 3700 nm within the solar spectrum. With this the HSSA structure is having more than 93 % absorption in the 3000–4000 nm range, whereas more than 97 % absorption is achieved in the visible region. Further, the HSSA structure is treated with the Machine Learning model as the parameter optimization. The greatest R2 value for this structure is 0.999592 with a test size of 0.25, and the mean squared error is 1.79801 × 10−4. The ML reduces time (takes ¼ of the traditional time) and other simulation requirements. Additionally, the structure is polarization insensitive and up to 60° incident angle insensitive. Due to these characteristics, the HSSA structures find usage in various applications, including solar thermal energy harvesting systems, plasmonic sensors, and detectors. [ABSTRACT FROM AUTHOR]

A high-temperature stable solar absorber is crucial for next-generation (Gen3) concentrating solar power (CSP) plants, to enable high temperature operation, maximize power generation efficiency, and thereby reduce the levelized cost of energy. This study presents novel, fractal-textured solar absorber coatings whose multiscale feature scales effectively match the visible region of the solar spectrum, leading to superb absorptive properties. Single and bimetallic oxide coatings of copper, cobalt and manganese were prepared on Inconel 625 substrates using electrodeposition. The effect of electrodeposition parameters and annealing temperature are systematically studied to optimize the morphology and properties of the oxide coatings. Multiscale textured bimetallic coatings of copper manganese oxide and copper cobalt oxide demonstrate a superior absorptance of 0.985, a remarkably low emittance <0.45 and an exceptional optical efficiency of ∼96 % under Gen3 CSP operating conditions, surpassing previously reported values in the literature by about 5 %. Durability tests confirmed the coatings' steadfast endurance of mechanical and environmental stress, making them suitable for long-term application in harsh CSP environments. [Display omitted] • Highly textured solar absorber coating developed by simple electrodeposition. • Bimetallic coatings showed higher optical efficiency than their single counterparts. • Optimum preparation conditions are determined for the maximum optical efficiency. • Great mechanical durability of coatings on Inconel substrate. • Highest optical efficiency in class for bimetallic coatings. [ABSTRACT FROM AUTHOR]

In this work, we explore the possibility that a hexagonal ring structure can be used as a solar absorber and a thermal emitter for multiple applications. By using FDTD (finite-difference time-domain) Solutions for numerical simulation, the light source is set to 280 nm–2500 nm, and the following properties of the structure are studied. Firstly, the structure achieves an average absorption efficiency of 92.57 % and 97.88 % at AM (Air Mass) 1.5, and the bandwidth is 283 nm–2006 nm (absorption efficiency greater than 90 %), which achieves ultra-broadband perfect absorption. Secondly, the structure can theoretically work at 1500 K, at which the thermal radiation efficiency is 89.13 %. When considering the oxidation and decomposition of materials in practical applications, the structure can work up to 700 K, and the thermal radiation efficiency decreases to 77.07 %. Therefore, the structure has excellent absorption and radiation performance, and has a wide range of applications as a solar absorber or thermal emitter. We studied the absorption and thermal radiation properties of a structure using refractory metals and TMDCs. The average absorption efficiency of the structure in 280–2500 nm reaches 93.19 %, and the bandwidth of A>90 % reaches 1747 nm. In addition, the average absorption efficiency under AM 1.5 is 98.64 %. We also studied the thermal radiation properties of the structure. Theoretically, the structure can work stably at a high temperature of 1500 K; in practical applications, it can also withstand a high temperature of 700 K, and the thermal radiation efficiency reaches 90.59 % and 79.98 %, respectively. In summary, the structure achieves ultra-broadband perfect absorption, can work at high temperatures theoretically and practically, and has high thermal radiation efficiency. Therefore, it has a very wide range of applications, such as thermal management, energy utilization, thermal and optical applications. [Display omitted] • A hexagonal ring structure obtains an average absorption efficiency of 93.19 % in 280–2500 nm. • The structure obtains an average absorption efficiency of 98.64 % at AM1.5. • The structure has an ultra-high thermal emission efficiency of 90.59 % at 1500 K and 79.98 % at 700 K. • The multilayer structure can be used as a solar absorber and a thermal emitter. [ABSTRACT FROM AUTHOR]

Solar absorbers enable the use of solar energy, a renewable and plentiful resource, minimizing reliance on finite fossil fuels and contributing to sustainable energy practices. The solar absorber that is studied here has an average absorptance of 96.85 % with a simple design and inexpensive materials. This design has two layers of resonator and active layer Block Ring Base Solar Absorber (BRBSA) structure. This study employs tungsten (W) as a resonator and titanium carbide (TiC) as a dielectric layer. The absorption spans from 100 to 3200 nm, with an average absorption exceeding 94 % across the entire structure. Notably, over 97 % of absorption occurs within the range of 210–710 nm, and the highest absorption, reaching 99.9 %, is observed in the wavelength range of 1510–1650 nm. The structure demonstrates high absorption rates across various regions, including 95.85 % in the UV region, 97.89 % in the visible, 95.73 % in the near-infrared, 95.87 % in the mid-infrared, and 89.56 % in the far-infrared region. After analyzing various potential variations of the proposed structure, an optimal design was identified. The parametric study was conducted to determine the optimal physical properties. Additionally, the electric field intensity analysis confirmed the proposed structure's broadband and constant absorption response. This Block Ring Base Solar Absorber has various uses, including solar drying systems, cookers, vaporizers, and warmers. [ABSTRACT FROM AUTHOR]

Antimony selenide (Sb 2 Se 3) is emerging as a promising material for optoelectronic applications owing to its exceptional properties. Achieving c-axis oriented [001] Sb 2 Se 3 films, which is crucial for optimizing charge carrier transport has consistently been challenging. In this work, a facile route involving reactive selenization of antimony films deposited on glass substrates via thermal evaporation was employed to obtain [001] oriented Sb 2 Se 3 thin films. The resultant films were comprehensively characterized using X-ray diffraction, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy to confirm phase purity and compositional homogeneity, elucidating the role of selenization temperature in the formation of Sb 2 Se 3 through this method. XPS analysis was carried out to confirm the oxidation states of Sb and Se. Optical analysis revealed a high absorption coefficient of ∼1.75 × 105 cm−1 with the desired direct band gap values in the range of 1.23 eV–1.20 eV. All these favourable properties, steered to observe a photocurrent of 143 nA at a 5V applied bias in 375°C selenized films under AM1.5 G illumination conditions. An n-Si/Sb 2 Se 3 heterojunction was fabricated and a photocurrent of 2.8 μA was observed with responsivity and detectivity values of 8.18 × 10−5 A/W and 4.26 × 109 Jones respectively at zero applied bias and AM1.5 illumination conditions, showing the favourable prospects of Sb 2 Se 3 thin films prepared via the selenization of antimony films in optoelectronic applications. [Display omitted] • Selenization induced Sb 2 Se 3 films. • [001] Oriented films for easy charge carrier transportation. • High optical absorption coefficient. • Strong photosensing properties. • Self-biased photo detecting n-Si/Sb 2 Se 3 heterojunction. [ABSTRACT FROM AUTHOR]

Most of the solar absorbers are absorbing visible spectrum energy and are not focused on the ultraviolet spectrum and infrared spectrum energies. Here we propose a solar absorber that absorbs most of the energy of the available solar spectrum including visible spectrum and ultraviolet spectrum energies. The multilayer metasurface solar absorber design is analyzed and its results are compared with the single-layer metasurface solar absorber design. Both design results are also compared with AM 1.5 solar spectral irradiance plot for a wavelength range of 0.2 μm–1.5 μm. The graphene is used as a spacer to increase the absorption response of the proposed structure. The efficiency of multilayer design is high in both visible spectrum regions and ultraviolet spectrum regions compared to single-layer design. The parameter optimization for substrate thickness and resonator thickness is analyzed for improvement of absorption of the proposed design. The design results in the form of absorption, a normalized electric field. The proposed solar absorber with its high efficiency in visible and ultraviolet regions can be used in solar energy harvesting devices. The novel part of this research is predicting absorption values for assorted variations in substrate thickness, resonator thickness for forthcoming wavelengths using a Long Short-Term Memory model. The results of the experiments show that prediction may accurately anticipate absorption values, reducing simulation time and resource requirements. The visual comparison of simulated and predicted values is also presented in the paper. [ABSTRACT FROM AUTHOR]

• Cactus extract was used as reducing and stabilising agent to synthesise Cr 2 O 3. • Cost-effective green synthesis method was used to prepare Cr 2 O 3 nanocoatings. • Drop and spin coatings were used to prepare the thin films. • A single layer of Cr 2 O 3 on Cu substrate was found to be spectrally selective. • High solar absorptance of 0.93 and low emittance of 0.23 was achieved. Cost-effective and eco-friendly Cr 2 O 3 spectrally selective solar absorber nanocoatings prepared by an entirely green process on polished Copper (Cu) substrate is presented. The green synthesized Cr 2 O 3 was deposited by using drop and spin coatings at rotational speeds (RS) of 600, 800, 1000, and 1200 rpm onto Cu substrate. The crystal structure of the nanocoatings investigated by XRD showed merely Eskolite Cr 2 O 3 crystalline phase, implying no other chromium oxide phases were observed. The topological investigations using AFM showed a columnar growth with an average surface roughness of 16.7 nm and 16.3 nm for the drop coat and spin-coated at 600 rpm samples, respectively. SEM analysis revealed quasi-spherical, nanorod, and meso spherical shaped nanocoatings, corresponding to drop coat and spin coatings, respectively. XPS analysis confirmed the presence of Cr3+ 2p 3/2 , Cr3+ 2p 1/2, and O1s, which represent Cr 2 O 3 in all samples. Raman analysis also revealed vibrational modes corresponding to 5E g and 1A g symmetries in Cr 2 O 3 , which agrees with previously reported XPS results. The optical properties of the Cr 2 O 3 nanocoatings exhibited a high solar absorptance (α) value of 0.93 and thermal emittance (ε) of 0.23 for the drop coated and spin coated at 600 rpm samples, confirming the two basic characteristics of a spectrally selective solar absorber coating. The obtained optical properties of the Cr 2 O 3 nanocoatings can be attributed to the multiple reflections trapped by the surface morphology and intrinsic phenomena of the nanocoatings. One can observe that this cost-effective and environmentally friendly green synthesized Cr 2 O 3 nanocoatings deposited onto Cu substrate is a potential candidate for spectrally selective solar absorber applications. [ABSTRACT FROM AUTHOR]

A low cost and feasible fabrication of novel photothermal conversion material and solar absorber was widely studied for enhanced solar-to-vapor performance in solar driven vapor generation. In this work, a novel hybrid carbonized sawdust/barium titanate composite was fabricated by sol-gel method, where it was later incorporated with a cotton towel using a dip-coating process to produce a solar absorber. The solar driven seawater desalination setup was made up of i) solar absorber where heat was localized and the evaporation occurs, ii) thermal insulation using polystyrene foam and air gap to minimize the heat loss, and iii) water pathway for continuous supply of seawater to the solar absorber. Carbonized sawdust/barium titanate composite solar absorber was tested under direct solar radiation for about 2 h using seawater collected from the beach coast of Universiti Malaysia Sabah, where it was repeated three times to observe the stability of the solar absorber. The average efficiency of the carbonized sawdust/barium titanate composite solar absorber was about 72.04% with average evaporation rate of 1.32 kg/m2 h. Salinity of the clean water was significantly reduced about 99.8% from the initial seawater salinity at 29300 ppm to 50 ppm, and the pH value was observed at 7.40. The salinity and pH value of the generated clean water was within the safe water limit based on the World Health Organization (WHO) standard. [ABSTRACT FROM AUTHOR]

• Spectral normal emittance of SiC, TaB 2 and ZrB 2 ceramics is measured up to 850 °C temperature. • Surface features of samples affect the temperature–dependent emittance. • The size of surface features is key parameter. • Borides show a thermal emittance significantly lower than silicon carbide. In this work, for the first time, we studied the temperature-dependent spectral emittance of highly refractory ceramics, e.g. silicon carbide (SiC) and two ultra-high temperature ceramics (tantalum diboride (TaB 2), zirconium diboride (ZrB 2)) to evaluate their potential for solar tower receivers applications. We measured the spectral normal emittance from 1 µm to 21 µm at temperatures up to 850 °C, in vacuum, by means of a novel experimental setup composed by an electric furnace connected to a FT-IR spectrometer. Comparison with previously published data collected with a different setup was also carried out to validate the results. In addition, the experimental spectral emittance was also compared with the values calculated from hemispherical reflectance at room temperature by means of Kirchhoff's law. The results show that surface features play a fundamental role in the emittance of investigated ceramics. [ABSTRACT FROM AUTHOR]

Molybdenum oxide (MoO x) film has attracted increasing research attention owing to its superior solar energy absorption. Herein, a series of monolayer MoO x films were fabricated on aluminium substrates through the reactive sputtering of single molybdenum targets. The reflectance spectra reveal that the spectral absorbance can be highly tuned by controlling the film thickness. Such monolayers exhibit high absorptivity and low emissivity of 0.83 and 0.05, respectively, at a partial pressure of 0.6 Pa, indicating their excellent selective absorption property. The scanning electron microscopy images show a morphological evolution from needle-like to spherical particles that may be responsible for the varying spectral absorption. In addition, X-ray diffraction and variable angle spectroscopic ellipsometry analyses confirm the films' semi-absorbing states. A MoO x /SiO 2 solar absorber suggests that the resulting MoO x films have significant potential in solar energy harvesting. [ABSTRACT FROM AUTHOR]

Industrial heating applications required renewable energy-based solutions to meet his high demands. The recent design exhibition is a three-layer type solar absorber with an effective graphene compilation; Gallium Arsenide (GaAs) in the top (resonator), Aluminium (Al) in the middle (substrate), and Zirconium (Zr) in the ground (based) layer respectively. To show the extinct variation analysis for the used parameters of the design, the perfect six points are selected (micrometers) such as λ 1 = 0.35, λ 2 = 0.6, λ 3 = 0.7, λ 4 = 2.3, λ 5 = 2.65, and λ 6 = 2.85 respectively. In this case of absorption, the whole design absorption rate is 94.36% with the overall wavelength description of 2800 nm, 98.2% is achieved in 700 nm bandwidth, and 96.1% in 1000 nm respectively in this structure absorption area. According to the perfect development of the recent structure, the absorption situation can be expressed in the ultraviolet area, visible spectrum, and near and middle (NIR and MIR) regions. To increase the study of the absorber, the various sections; designs and parameter demonstration, construction design and lithography, absorption ranges and Air Mass (AM) exploration, parameter analysis and color results, Electric and Magnetic field intensities, incident angle changes (0–60°), are presented in the manuscript. The displayed solar design can apply the applications of thermal energy systems usually in the particular area of heating and cooling processes. With the recent solar absorber as a renewable thermal system, the services of heating and cooling, geothermal, and biogenics are also can be performed. Moreover, thermal energy systems of agricultural processes and heat provide applications for industries and buildings that can be also used. [ABSTRACT FROM AUTHOR]

Among the various types of solar cells, thin film solar cells stand out for their affordability, durability, and lightness. CuSbS 2 as an absorber in thin film solar cells holds a particular appeal due to its unique characteristics such as high absorption coefficient, suitable band gap, and high p-type carrier concentrations. One of the major challenges in the production of CuSbS 2 thin films is related to the probability of different phases/materials formation including Cu–Sb–S ternary and S –Sb, Cu–S binary compounds. Consequently, a competition arises among the formation of aforementioned system compounds, which can be affected by the growth conditions. The aim of this study was to understand the evolution of the formation of different binary and ternary compounds during the growth of the CuSbS 2 layer by the spray pyrolysis technique, which is essential for tailoring the material's properties for solar applications. To this end, the effect of different growth conditions including Cu:Sb ratio, substrate temperature, and spraying rate were investigated. It has been demonstrated that these growth parameters significantly influence the microstructural and optical properties of CuSbS 2 layers. The experimental approach presented in this study is of general interest for the fabrication of CuSbS 2 layers by spray pyrolysis technique, and it can shed light on the relationship between synthesizing conditions and binary and/or ternary crystalline phase evolution. [Display omitted] • There is a correlation between the CuSbS 2 layer's growth conditions and crystalline phase evolution. • The spraying rate has an essential role in the microstructural and micro-morphological properties of CuSbS 2 thin films. • The precursor solution is prepared with limited additional chemicals to minimize residual contamination in the layers. [ABSTRACT FROM AUTHOR]

Industrial heaters nowadays work on renewable energy concepts and one of the important green energy sources is solar energy and we have used solar energy to design industrial heaters. The solar absorber converts the solar energy into heat which is used for industrial heaters. We developed a new solar absorber construction with three different layers by using different materials for each layer construction. Aluminium (Al) is for the top (resonator) layer, iron (III) oxide (Fe 2 O 3) is for the middle (substrate), and silicon is used in the ground (based) layer respectively. A thin graphene layer is constructed between the Al resonator and the Fe 2 O 3 substrate sections to develop better absorption by this design. In the wavelength range (μm) of 1.86 and 3, the explored absorption rate is 95.43 % with a 1740 nm bandwidth. The absorption rate performs above 97 % (97.23 %) at a 540 nm bandwidth with a wavelength (μm) difference between 1.96 and 2.5. The overall absorption for design explores 91.23 % (greater than 90 %) with a 2800 nm bandwidth range by the wavelength contribution from 0.2 to 3 μm. To highlight the explored amounts in variation, the four high wavelengths (in micrometers) are selected with λ 1 = 0.45, λ 2 = 1.1, λ 3 = 2.1, and λ 4 = 2.5 respectively. Concerning the presentation of this design, the construction steps from the beginning to the complete stage distribution, Air Mass (AM) exploration and equations, parameter analysis with the respective color extractions, polarization situation by changing incident angle (degree) from 0 to 80, electric and magnetic field analysis section, and a comparison table will be included in this work. This design can be achieved in the development of renewable energy such as the large amount of electricity generation by solar energy (green energy) systems, the process of heating and cooling systems of water, and multiple transportation systems. [ABSTRACT FROM AUTHOR]

A concentrated solar absorber with finned phase change materials was experimentally studied using a Scheffler type parabolic dish concentrator. The absorber's inner surface was fixed with hollow cylindrical containers filled with phase change material (PCM) for heat transfer augmentation. The absorber's selected PCM was acetanilide (Melting point of 116 °C)—the cylindrical capsules protruding into the fluid side to create turbulence and mixing and acting as fins. The absorber surface temperature was observed to be about 130–150 °C during the outdoor tests while passing fluid through the absorber. The fluid flow rate varied from 60 to 100 kg/h during the outdoor experiments. The peak energy and exergy efficiency of parabolic dish collector (PDC) at the fluid flow rate of 80 kg/h with PCM integrated solar absorber was found to be about 67.88% and 6.96%, respectively. The integration of cylindrical PCM containers resulted in more heat transfer augmentation in the solar absorbers. The optimized solar absorber could be suitable for various applications like steam generation, biomass gasification, space heating, and hydrogen generation. • Uniform heat output of PCM integrated solar absorber attained due to PCM. • Heat storage is effective after the complete melting of the PCM in the absorber. • Cylindrical PCM containers assist the smooth fluid flow inside the solar absorbers. • The energy efficiency of concentrated solar absorber with PCM reaches up to 67.88%. • The exergy efficiency of concentrated solar absorber with PCM reaches up to 7%. [ABSTRACT FROM AUTHOR]

• Vacuum Flat Plate Enclosures were fabricated involving Ultrasonic Soldering techniques. • Tin-based alloy, Cerasolzer 217, used to create the vacuum seal. • Mechanical structural analysis undertaken to study stresses. • Digital Image Correlation (DIC) used to study the strain profile. • Helium mass spectrometer leak detector used to investigate the hermeticity of edge seal. Vacuum flat plate (VFP) solar thermal collectors exhibit excellent optical and thermal characteristics due to a combination of wide surface area and high vacuum thermal insulation offering a high performance and architecturally versatile collector with a variety of applications for industrial process heat and building integration. A vacuum flat plate solar collector consists of a solar absorber in a flat vacuum enclosure comprising glass or glass and metal covers sealed around the periphery with an array of support pillars to maintain the separation of the enclosure under atmospheric pressure. The edge seal must be both mechanically strong and hermetic to ensure the durability of the internal vacuum over collector lifetime. This presents several challenges for the fabrication of flat vacuum enclosures. In this study a novel sealing technique is presented using a tin-based alloy, Cerasolzer 217, to create the vacuum seal between two glass panes and an edge separating spacer. The sealing process is undertaken at temperatures ≤250 °C allowing the use of thermally tempered glass panes. The mechanical strength of the edge seal was investigated using a tensometer. It was demonstrated that the bond between glass and edge spacer was sufficiently strong to withstand induced stresses in the edge seal region. The edge seal was leak tested using a conventional Helium mass spectrometer leak detector and was shown to possess leak rates low enough to maintain an adequate vacuum pressure to supress conductive and convective heat transfer in the collector. A finite element method (FEM) is developed and validated against the experimental results and employed to predict the stresses in different regions of the enclosure. It was found that the mechanical strength limits of the seal and glass are higher than the stresses in the edge seal region and on the glass surface, respectively. [ABSTRACT FROM AUTHOR]

Electromagnetic wave absorbers with very long absorption spectra have become an important target for optoelectronic materials and technology. In this paper, we propose a titan-based resonator to achieve near-perfect wide spectrum absorption of solar radiation. In the whole spectrum of the study, the average absorption of the absorber is up to 93.17%. Using surface plasmon resonance, up to 1759 nm in the range of absorption over 90% in the absorption spectrum studied (166.8–1926.6 nm). Furthermore, the absorption spectrum of the absorber is not sensitive to polarization. Since the material constituting the absorber is a mainly refractory metal, it can work under a complex electromagnetic environment (solar radiation) and high-temperature conditions. Later, the influence of various parameters on the absorption spectrum and the mechanism of forming broadband absorption was explored. It is also found that other refractory metals similar to titanium have a good effect on the absorber with this structure. We report a numerical study of an ideal solar broadband absorber based on refractory titanium. By optimizing the design, the average solar absorption efficiency of the absorber in the studied wavelength range (100–2000 nm) is as high as 93.17%. Image 1 • The absorber is capable of obtaining ultra-wide spectrum absorption of solar energy. • The absorbency of the absorber can be adjusted by optimizing the structural parameters. • The absorber is insensitive to changes in the angle of incidence and polarization. • The absorber has certain versatility to other refractory materials. [ABSTRACT FROM AUTHOR]

• A low cost, low environmental impact and easy to make solar absorber coating was developed. • The coating is highly absorbent in the solar spectrum. • The structural characterization of the functional material of the solar absorbent coating was performed. • The optical and thermal properties of the solar absorber coating were estimated. • The coating was evaluated in a solar cooker, generating better results than conventional paints. This paper discusses the development of a coating made of solid waste and residual biomass and its application as ecological solar absorber coating. This absorbent solar coating is made with a binder that consists of essential grapefruit rind oil and expanded polystyrene, both obtained from waste materials, as well as forest biomass soot (FBS) processed by mechanical grinding and used as a functional photothermal material. This mixture produces a paint that can be applied to metallic substrates to form a solar energy-absorbing surface. The characterization and evaluation is shown in three steps: (a) Characterization of the materials using XRD, SEM, TEM, XPS, Raman spectroscopy and IR; (b) coating evaluation using AFM, optical characterization to measure solar absorption, TG to determine the operating temperature and laser flash analysis to determine thermal conductivity; and (c) a testing with thermosolar technology to determine the thermal parameters of solar cookers. It has been identified that the pseudo-amorphous carbon in FBS has solar energy absorption capacity due to the sp2-sp3 bonds present in this kind of carbon, associated with the material's graphitic domain. Also, results show that the coating can be used with thermosolar technologies operating above 250 °C with a solar absorption index above 96%, and it has thermally-efficient properties. In addition, the coating, it shows better results with solar cookers than other coatings used with this technology, increasing cooking power, so it can potentially be employed with various thermosolar technologies due to the replicability of its materials, its low environmental impact and low economic cost. [ABSTRACT FROM AUTHOR]

A phase change material (PCM) can be used for thermal management of photovoltaics and thermal energy storage. This paper presents a photovoltaic thermal (PVT) system integrated with a PCM as a thermal storage medium for managing the photovoltaic temperature and together with a ventilation duct for preheating supply air or natural ventilation of a building. The novelty of the integrated PVT/PCM system lies in using the PCM as a passive technique not only for PV cooling but also for building heating and ventilation. Experiments have been carried out on a prototype PVT system for different sizes of PCM. The results show that a 30 mm thick PCM layer with a phase change temperature of 25 °C can maintain the PV temperature below 45 °C and improve the PV electrical efficiency by 10% for about 210 min under 600 W/m2 insolation. Increasing the PCM thickness by 10 mm increases the time for thermal control by 60–70 min. The PVT/PCM system is able to generate a 15 L/s ventilation rate in a vertical duct of 1100 mm wide, 1200 mm high and 100 mm deep during the melting phase and at least 20 L/s during the solidification phase. Use of metal fins to enhance heat transfer in the PCM can increase the PV electrical efficiency further by 3% and the ventilation rate by 30%. • Photovoltaic thermal collector for thermal control, storage and natural ventilation. • The capacity of thermal control increases with the thickness of phase change material. • Integration of phase change material increases photovoltaic efficiency by 10%. • A 1.1 m wide x 1.2 m high PV thermal collector can generate a 15 L ventilation rate. • Metal fins in phase change material increase ventilation rate by 30%. [ABSTRACT FROM AUTHOR]

Concentrating solar power is one of the most promising solar energy exploitation technologies. Its efficiency improvement needs a significant increase of operating temperatures, from the current 500°C to 900°C. Alumina (Al 2 O 3) ceramics are refractory materials characterized by a huge industrial interest, mature production techniques and low cost. In the present work, we successfully synthesized dark ceramic Al 2 O 3 bulks, to evaluate their potential as high-temperature solar absorbers for CSP. We investigated process-dependent ceramics composition, microstructure and optical properties, obtaining pellets with a solar absorbance even higher than that of SiC. Image, graphical abstract [ABSTRACT FROM AUTHOR]

MXene has received a lot of attention from researchers in the fields of photothermal and photovoltaic due to its excellent optical properties. However, research on MXene-based solar absorbers has rarely been carried out. In this work, we proposed a MXene-based solar absorber with absorption broadband, wide-angle, and polarization insensitive. The absorber has excellent light capture capability, with its average absorption in the solar band as high as 97.8 % and an energy absorption ratio of 98.9 % in the AM1.5 solar radiation spectrum. The electric and magnetic field distributions indicate that the unique hierarchical nanohole design can effectively excite multiple resonance couplings of surface plasmon resonance, cavity resonance, and guided mode resonance. The proposed absorber can still maintain the broadband absorption characteristics within a certain manufacturing tolerances. Moreover, the absorber is insensitive to polarization and has a high light absorption under a large incident angle. We believe that this work holds great promise for solar thermal conversion and heat utilization. [ABSTRACT FROM AUTHOR]

The challenging development/modification of particles to meet the requirements of thermal stability, high absorptance and mechanical resistance with minimal economical cost is a key point to attain for the next particle receivers of concentrated solar power plants. The properties of the particles influence the performance of the system, since the concentrated solar radiation is absorbed and stored in these solid materials. In this work, resulting from the studies carried out within the HORIZON 2020 COMPASsCO2 project, the deposition of black-coloured transition-metal oxides with spinel-like structure coatings on different particles is proven. Five different particles (state-of-the-art and innovative) developed by Saint-Gobain have been coated, studied and compared. The coating deposition was adapted to the dip-coating methodology, ensuring high and good reproducibility. The composition of solid particles as well as the composition of the precursor solution, the curing methodology and the number of deposited spinel layers demonstrate that they have a great influence on the solar absorptance value and the abrasion resistance. Therefore, it is essential to find the perfect balance between all these different parameters in order to achieve the best performance of the particles. The addition of silica nanoparticles in the precursor solution provides rougher layers with enhanced absorptance, up to 0.980, on newly developed particles with excellent thermal stability and abrasion resistance. [Display omitted] • Performance improvement of the CSP particle-supercritical CO 2 systems. • High absorptance coatings deposition on particles for solar receivers. • Innovative adapted deposition methodology with novel precursor solutions. • Solar absorptance of 0.979 with new ceramic particles coated with SiO 2 /CuCoMnOx. • Proven resistance to abrasion of coated particles. [ABSTRACT FROM AUTHOR]

• An ultra-broadband, high-absorption lithography-free metamaterial absorber. • Optimization used multi-objective PSO and FDTD. • Ultrabroadband due to FP resonance and anti-reflection property. • LFMA achieves efficient, omnidirectional, polarization-insensitive absorption. • With excellent photothermal conversion, it shows great potential for solar thermal collection. In the pursuit of improved solar energy conversion, the construction of solar absorbers with high omnidirectional absorption has been a preferred approach. Here, we present an almost perfect broadband absorber with multilayer planar films that can absorb incident light from the whole solar spectrum (300–2500 nm). By employing the particle swarm optimization and finite-difference time-domain (PSO/FDTD) algorithm, we have meticulously designed the materials and thickness of the multi-layer structure, resulting in outstanding performance. Our novel absorber exhibits high absorption of 98.51 % over the entire solar spectral range. The reason for its extraordinary absorption is inseparable from the excellent anti-reflection characteristics of the top dielectric stacks coating. This cutting-edge absorber holds immense potential, with the capacity to yield annual energy savings of up to 1727 kW·h/m2 in regions blessed with abundant solar radiation resources. Because of having numerous virtues, such as using different non-noble metals, stacking with fewer layers, exhibiting an extraordinary angular tolerance, and having ideal absorption for entire solar spectrum, our proposed absorber is a promising candidate in application of solar thermal energy harvesting. [ABSTRACT FROM AUTHOR]

The proposed solar thermal absorber consists of sandwich structure-inspired Ti–SiO 2 –Ti (Titanium–Silicon Dioxide -Titanium) Metal-insulator-Metal (MIM) material. Here proposed thermal absorber has materials, Ti as ground, SiO 2 as substrate and Ti as resonator. The design of solar thermal absorber is well-versed with the modern theory of absorption and made up on a nanometre basis with each parameter being less than 500 nm. An average absorption of 96.34 % has been achieved throughout the wavelength range of 0.2–3 μm including various regions including UV, Visible, NIR, and MIR with an average absorptance 92.72 %, 93.81 %, 96.58 %, 98.55 % respectively. The proposed nanoscale solar absorber also has 1920 nm of wavelength range above 95 % with an average absorptance of 97.985 % and 2730 nm of wavelength range above 90%with an average absorptance of 96.6 %, although transverse electric (TE) and magnetic (TM) modes achieved an average absorptance of 96.34 % and 94.1 % respectively. We also have noticed characteristics like large angular and polarization-independent in the proposed solar energy absorber structure which eventually benefitted the applications of optoelectronics. [ABSTRACT FROM AUTHOR]

The purpose of compiling this manuscript is to draw attention of young researchers on portable devices that yield drinkable water. The various techniques for potable water collection include solar stills, water distiller/condenser from air using radiative technique or desiccant material, bio-sand filter and steam generation by solar absorber materials are discussed in detail. The main vital parameters like solar radiations, type of material used, thickness of glass cover and its inclination, type of filter, diameter in case of nanoparticles, depth of water, pH of water, evaporation rate are under considerations for determining the performance of unit. Conventional desalination processes are not enough to fulfil remote area water requirements, so the utilization of solar energy is perceived solution using portable devices. Subsequently economic analysis of portable device is also presented for determining the performance of unit. [ABSTRACT FROM AUTHOR]

Abstract Optimal coatings on receivers for concentrated solar power plants (CSP) not only need to have high solar absorptance, but should also possess superior stability in air at elevated temperatures. For next-generation CSP plants, the surface temperature of the receivers is expected to exceed 750 °C. In this work, we systematically studied optical properties and long term thermal stability of solar absorbing coatings (SACs) made from various Cu(II) containing spinel oxide nanoparticles, including CuCr 2 O 4 , Cu 0 · 5 Cr 1 · 1 Mn 1 · 4 O 4 , CuFeMnO 4 , and compared these properties to those of the state-of-the-art Pyromark 2500 coating. The solar absorptance of each sample was measured after isothermal annealing at 800 °C in air for durations of 100, 300, 1000, and 2000 h. We found that porous Cu 0 · 5 Cr 1 · 1 Mn 1 · 4 O 4 had the highest solar absorptance at 97.1% before the thermal annealing and remained the highest throughout thermal testing, remained at 97.2% after 2000 h, whereas Pyromark 2500 exhibited considerable degradation in solar absorptance, from 96.4% to 94.6%. We analyzed the chemical composition, microstructures, and particle sizes of all the samples before and after the thermal annealing and discussed their implications on optical properties and thermal stability. Highlights • Copper-containing spinel oxides display excellent thermal stability due to Jahn-Teller effect. • A porous structure for light trapping improves solar absorptance. • Porous Cu 0 · 5 Cr 1 · 1 Mn 1 · 4 O 4 exhibited a record-high solar absorptance of 97.1% after 2000-h annealing. [ABSTRACT FROM AUTHOR]

Abstract Three semi-closed open cell ceramic foams, namely mullite, brown alumina and ceria-based materials, were subjected to thermal cycles by direct concentrated solar irradiation to study their thermal resistance in view of their potential application as photothermal devices, such as volumetric solar absorbers. After cycling, the extent of the damage in the samples was determined by measuring the retained crushing (compressive) strength. The extent of the damage was found to depend on the composition, the applied surface temperature difference (ΔT) of thermal cycling and the temperature gradient across the foams. It was found that the retained crushing strength gradually decreased with an increase in ΔT and was independent of the number of thermal cycles in the range investigated. The ceria foams displayed the poorest thermal shock resistance. Experimental data fit the Gibson-Ashby model for the thermal shock resistance of ceramic foams, for a constant C = 0.65. Graphical abstract fx1 Highlights • Brown alumina and ceria foams for solar absorbers were developed for this study. • Iron-coated mullite foams showed excellent performance upon thermal cycling. • Ceria foams had poor resistance to thermal shock. • At ΔT ≥ 400 K brown alumina performs better than anticipated albeit its color change. • Good agreement of thermal shock data with Gibson-Ashby model for C = 0.65. [ABSTRACT FROM AUTHOR]

Graphical abstract We fabricated multilayer structures in which TiN x serves as an IR reflector, TiN x O y serves as the solar absorber, and a bi-layer N-doped TiO 2 /SiO 2 or HfO 2 layer for surface anti-reflection. Our study showed the excellent absorption up to 600 °C for the coating having SiO 2 layer and up to 800 °C for the coating having HfO 2 layer. Abstract In this work, we have investigated multilayer structures in which TiN x as an IR reflector on the substrate due to its high infrared reflectivity, TiN x O y coatings serve as the solar absorbers, and a bi-layer N-doped TiO 2 /SiO 2 or HfO 2 layer for surface anti-reflection. Both the TiN x and TiN x O y layers were first optimized. Selected TiN x and TiN x O y layers were then used to fabricate the multilayered structures. Optical properties were assessed at room temperature and high temperatures up to 800 °C. While the multilayered structures having bi-layer N-doped TiO 2 /SiO 2 as the anti-reflection layer show excellent absorption and emission up to 600 °C, much reduced absorption where obtained at 800 °C. The use of HfO 2 layer to replace SiO 2 improves the absorption at 800 °C. The relationship between material characteristics and optical performance, which has not been understood, is addressed in this study. Excellent high temperature selectivity is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract CSP (Concentrated Solar Power) plants technologies use the concentration of solar energy on a receiver to produce heat and then electricity by a thermodynamical process. A solar absorber material is used to convert the energy carried by light into heat. This type of material works at high temperatures (up to 1000 °C) under a highly concentrated solar flux (up to x1000 or more). Optical properties determine the performance of absorbers and it is thus necessary to measure their spectral absorptance and emittance. Solar absorptance is directly linked to the capacity of the absorber material to convert the solar flux into heat. Emittance drives the radiative thermal losses for the heated absorber and depends on the absorber temperature. The characterization of a material in operational conditions at high temperatures requires advanced apparatuses, and different measurement methods exist for the characterization of these two quantities of relevance regarding an absorber. A Round Robin Test (RRT) was conducted with the objective of comparing different new optical apparatuses and methods for measuring the emittance or luminance of various solar absorbers in air. Measurements were carried out directly at temperatures up to 560 °C while heating the samples, and also indirectly by hemispherical reflectance measurements at room temperature. In this paper, the Round Robin Test procedure to compare apparatuses is described, as well as the corresponding reflectance and emittance results on four types of materials. In addition, a discussion of some factors of influence over high temperature measurements in air and of the observed discrepancies among results from the evaluators is presented. The reliability of reflectance/emittance measurements is also demonstrated and statistics of deviations from the mean value are analysed. These allow us to infer information about measurement reproducibility. The reflectance spectra of all samples after high temperature measurements in air (up to 500 °C) do not show any significant changes. Highlights • Round Robin Test conducted with nine partners. • Apparatuses comparison for measuring the thermal emittance of various solar absorbers. • Direct thermal measurements up to 560 °C while heating the samples. • Emittance calculation assuming Kirchhoff's law of radiation. [ABSTRACT FROM AUTHOR]

Abstract Despite its high solar absorbance and surface coating abilities, pristine graphene as a semimetal is not promising for photovoltaic applications. In this study, we predict that Glycine (Gly), an amino acid, which is normally bound to pristine graphene by a weak van der Waals attraction, can form an organic coating durable to ambient condition when adsorbed on vacancy patterned graphene surface. Moreover, adsorbed Gly coating induces metal-insulator transition and concomitantly increases the solar absorbance of pristine graphene more than three times. This way, graphene attain critical functionalities to be used in solar energy and photovoltaic applications. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • C-TiO 2 solar absorber with a good photo-thermal conversion property was prepared. • Separating photo-thermal conversion and steam generation process was designed. • The film enhancement effect with different evaporation areas was investigated. • The changed thermal gradient between the film and evaporation region was verified. Abstract Solar steam generation is an effective method combining solar energy utilization with water treatment. Photo-thermal conversion and steam generation are typically integrated to enhance the evaporation process, which have wide applications in seawater desalination, waste water treatment, sterilization and power plant fields. However, the photo-thermal enhancement for different evaporation areas remains unclear, and there are a number of important issues for membrane process (e.g., blockage of pore structures and contamination of nanoparticles). To overcome these issues, we herein propose a separating design involving a C-TiO 2 absorber and a polyvinyl alcohol fiber material as the photo-thermal and steam generation units, respectively. A C-TiO 2 absorber with good spectral and photo-thermal conversion characteristics was prepared. And the evaporation enhancement effect was investigated with different evaporation areas by experiments and simulations. The equivalent evaporation rate reached the maxima with the evaporation area and decreased thereafter for this separating design. The optimum behavior was achieved when the evaporation region area to photo-thermal area ratio of ca. 2.06, providing guidance for large-scale use. These results can be explained in terms of the changed thermal gradient generated between the center C-TiO 2 film and the evaporation region. The design achieved equivalent evaporation rates and evaporation efficiencies of 1.24 kg·m−2·h−1 and 77.83%, respectively, paving the way for the further improvement of solar steam generation processes. [ABSTRACT FROM AUTHOR]

Abstract The design of sub-wavelength structure with full-spectrum near-unity solar absorption is a long-sought-after goal of crucial importance for optoelectronic materials and technology. To date, numerous attempts to tackle this problem consisted either of using stronger absorption-but narrowband or the broader spectrum-but moderate light trapping mechanisms. Herein, a novel strategy that achieves perfect absorption for solar energy in the full-spectrum range of the sun's radiance is presented by the thin-film refractory metal resonators. This impressive absorption mainly stems from the cooperative effect of strong plasmonic resonances and the intrinsic broadband spectral responses by the refractory metals, such as Ti, V, W, etc. The full-spectrum weighted solar absorption efficiency is exceeding 98%, showing a near-unity light trapping for the sun's radiation. Moreover, excellent thermal emitting with the spectral averaged efficiency ~ 91% is achieved in the wavelength range (280–4000 nm) by the W-based absorber, suggesting a platform for near-perfect blackbody emitting source. More importantly, the investigations on achieving full-spectrum solar absorbers and thermal emitters provide new insight on the mechanism and philosophy for the design. Just like the proverb, in order to catch bandits, the first thing is to catch the ringleader. As for the purpose of achieving full-spectrum near-unity absorbers or radiators, the key point is to perfectly trap or excite the solar/thermal power in the main distribution ranges for the sunlight or the blackbody radiation. Accordingly, these attractive properties and findings suggest that the investigation and the related full-spectrum solar absorbers and blackbody radiator might have promising applications in the fields related to energy harvesting and conversion. Graphical abstract fx1 Highlights • A feasible way is demonstrated for achieving full-spectrum thin-film solar absorbers. • The averaged solar absorption efficiency η A is > 98% for the sunlight (280–4000 nm). • Near-perfect thermal emitter with similar properties to the ideal blackbody radiator is demonstrated. • The key important factor for designing near-unity full-spectrum absorber/ emitter is obtained. [ABSTRACT FROM AUTHOR]

Highlights • New solar façade concept is proposed, tested and contrasted with conventional type. • Comparative analysis of selective absorber applying of transparent insulation material. • Validated building energy performance prediction model was developed using a BES tool. • Selective absorbent and transparent insulation properties improve overall thermal properties. • BES modeling limitations in surface radiant heat exchange with the low emissivity absorber. Abstract Solar thermal façade concepts for building integration have a relevant contribution in the field of renewable solar energy exploitation. This study is focused on an experimental analysis of a transparent insulation façade (TIF) concept and the options for the prediction of its performance using building energy simulation (BES) modelling. A TIF prototype based on a transparent insulation material (TIM) and a selective absorber is tested and compared with a nonselective type of absorber. An experimental study was conducted involving full-scale climatic chamber and dynamic outdoor tests. The proposed TIF concept with a selective absorber and its solar effective layers provides the same thermal performance as conventional types of thermal insulation. As the TIM integration is potentially limited by overheating phenomena, a maximum cooling energy load obtained by dynamic outdoor conditions provides its real outdoor performance. The results show that a significant difference is measured when compared with the nonselective absorber type. Finally, a detailed comparative investigation of the thermal performance of both TIFs was conducted using the BES method. When applying the low-e functionality of the solar absorber, significant limitations were found specifically concerning the surface radiant heat exchange with the low emissivity surface affecting the air cavity enclosed zone. [ABSTRACT FROM AUTHOR]