Radiative cooling technology addresses the self-heating issue in solar cells, improving power output. However, dust accumulation poses a significant challenge for radiative cooling PV systems. This study theoretically explores the radiative properties and power efficiency of radiative cooling PV systems under dust accumulation, employing the Monte Carlo Ray Tracing method to simulate light transfer through dust with varying characteristics. The influence of dust particle size, coverage area, and solar incidence angle on system performance is examined. Results show that dust accumulation decreases solar transmittance and infrared emissivity of the radiative cooling covers, thereby reducing system efficiency. The effect of highly absorptive dust on the radiative cooling cover is more pronounced than that of non-absorptive dust. For every 1 g/m2 increase in deposition density, the power generation of RC-PVs covered with non-absorptive and absorptive dust accumulation decreases by approximately 0.96% and 4.01%, respectively. Functional relationships have been established between dust density and solar transmittance, infrared emissivity, and power generation. Additionally, optimal cleaning intervals for the systems under different dust conditions are determined. For full-automatic cleaning at a dust accumulation rate of 200 mg/m2/day, the recommended intervals for non-absorptive and absorptive dust are 44.2 and 22.1 days, respectively. These findings provide quantitative relationships between dust accumulation and its impacts on radiative cooling PV systems, highlighting the importance of regular maintenance to optimize system performance and associated costs. The results of this study offer valuable insights for the effective deployment, design, and maintenance of radiative cooling PV systems in practical applications, particularly in dusty environments.

Nanoporous structures play a critical role in a wide range of applications, including catalysis, thermoelectrics, energy storage, gas adsorption, and thermal insulation. However, their thermal instability remains a persistent challenge. Inspired by the extraordinary resilience of tardigrades, an “atomic armor” strategy is introduced to enhance the stability of nanoporous structures. Applied to mesoporous silica at parts-per-million levels, the atomic armor provides thermal resistance exceeding that of existing stabilization techniques. Thermal treatment at 1,000 °C for 168 h results in a fivefold increase in specific surface area, 66% lower thermal conductivity, and a sixfold increase in pore volume compared to untreated samples. Surface viscosity is linked to sintering resistance, and glass transition temperature and fragility are introduced as design parameters. Machine-learned interatomic potentials and metabasin escape algorithm-assisted molecular dynamics simulations are employed to reveal that materials traditionally classified as nonglass formers can exhibit glass transition temperatures and display intrinsic fragility. Alumina is identified as having a record-high glass transition temperature. By modulating the surface viscosity of nanoparticles, this approach stabilizes nanoporous structures effectively. The proposed method offers a simple and universal posttreatment process for improving the thermal stability of nanoporous structures.

Silica aerogels are widely used as thermal insulation materials, and their stable mechanical properties are essential for maintaining consistent thermal insulation performance, particularly at high temperatures. This study investigates two key mechanical parameters of silica aerogels: elastic modulus and Poisson's ratio. The results indicate that the Poisson's ratio is minimally influenced by changes in density and temperature, gradually converging to 0.2 with decreasing density or increasing temperature. To predict the sound velocity of silica aerogels, the Gibson-Ashby scaling formula was utilized. By refining the scaling exponent range to 1.1-1.4, an improvement over the previously reported range of 0.5-1.5, the prediction accuracy was significantly enhanced, as confirmed by available experimental validation. The study further explored the temperature-dependence of the elastic modulus. Below 623 K, the elastic modulus remains nearly temperature-independent. Between 673 and 1023 K, sintering effects in the aerogel cause a rapid increase in the elastic modulus. Beyond 1023 K, the growth rate decreases, eventually stabilizing at higher temperatures. This work provides critical insights into the mechanical behavior of silica aerogels under varying thermal conditions, offering valuable guidance for their applications in high-temperature environments.

Improving the efficiency of the main heat exchanger in gas wall-hung boilers is essential for energy conservation and carbon neutrality. However, limited space availability restricts heat transfer enhancement in these systems. This study firstly investigated the thermal-hydraulic performance of conventional dimple slotted finned-tube (FD) heat exchangers, revealing that insufficient fluid mixing and serious flow dead zones reduce heat transfer efficiency. To address these issues, an airfoil four-slotted fin design with integrated vortex generators (F-A) was proposed and evaluated through both numerical simulations and experimental testing. Three prototypes were examined: F-A design with 57 fins, and two configurations of F-D (57 fins and 74 fins, labeled F-D1 and F-D2, respectively). The results showed that the F-A design improves heat transfer performance by 14.4-21.2%, yielding an overall performance coefficient (PEC) of 1.1, a significant improvement over F-D1. In contrast, the denser fin structure of F-D2 resulted in a PEC below 1.0 at high Reynolds numbers. Additionally, empirical correlations for the Nusselt number (Nu) and friction factor (f) on the flue gas side were developed. The proposed high-efficiency finned-tube heat exchanger demonstrates substantial potential in improving energy efficiency of gas wall-hung boilers.

Thermal transport in amorphous silica (a-SiO2) and silica aerogel is critically important for thermal protection and microelectronics applications. However, notable disparities exist between the predicted and measured thermal conductivity of a-SiO 2 . Inspired by the dual-phonon theory proposed by Luo et al. [Nat. Commun. 2020, 11, 2554] for crystalline materials, this work introduces a dual-diffuson transport method for amorphous materials. The criterion based on the thermal diffusivity is employed to differentiate between normal diffusons and phonon-like diffusons. Herein, the thermal conductivity of a-SiO 2 is investigated by combining a modified Allen- Feldman (AF) theory with the dual-diffuson transport method. The present method is validated well by the measurement using the transient plane source (TPS) method. In addition, the results indicate that normal diffusons primarily govern the thermal transport in a-SiO 2 , with only a minor contribution from phonon-like diffusons. The temperature dependence of specific heat capacity and mode linewidth contributes to the positive temperature-dependent thermal conductivity. The quantum effect of specific heat capacity is the primary influencing factor in the temperature range of 100-1000 K, while the mode linewidth becomes dominant at higher temperatures. Finally, a theoretical framework for predicting the solid thermal conductivity of silica aerogel is introduced by including the temperature effect on the inherent thermophysical properties of the backbone. This work uncovers the physical mechanisms underlying temperature-dependent thermal transport in a-SiO 2 and silica aerogels.

High temperature exposure is commonly encountered in aerospace and industry, necessitating materials capable of providing both thermal insulation and thermal energy conversion. However, current thermoelectric aerogels often face dual challenges of constrained application temperatures (300-400 K) and prohibitively high costs due to substrate material limitations. In this study, a cost-effective graphite aerogel was fabricated using the directional freeze-drying method for integrated thermal insulation-thermoelectric applications across a wide temperature range. A pioneering Voronoi diagram-based electrical conductivity model featuring fractal lamellar structures was proposed with below 5% deviation between simulation and experimental data, which enables analysis of electrical transport properties under different densities of the lamellar structure, providing in-depth mechanism analysis of the interplay between microstructure and thermoelectric performance. By modulating the oriented lamellar skeletal structure, this aerogel achieved an efficient electrical carrier transportation of 48.28 S·cm-1 and an effective suppression of thermal conductivity to 0.585 W·m-1·K-1 at 923 K. Remarkably, the aerogel exhibits a 2-3 orders of magnitude enhancement in cost-normalized electrical conductivity over current-generation thermoelectric aerogels. Due to the band degeneracy effect, the Seebeck coefficient shows a significant increase when the temperature exceeds 773 K and reaches 96.84 μV·K-1 at 923 K. The hierarchically structured graphite aerogel exhibits exceptional high-temperature thermoelectric performance with a peak ZT value of 0.036, creating an innovative framework for high-temperature thermal management and energy conversion in extreme environments.

Based on the ab initio molecular dynamics (AIMD), the temperature and velocity statistics of diatomic semiconductors were proposed to be classified by atomic species. The phase differences resulting from lattice vibrations of different atoms indicated the presence of anharmonicity at finite atomic temperatures. To further explore the electronic properties, the effect of temperature on electrostatic potential field vibrations in semiconductors was studied, and the concept of electrostatic potential oscillation (EPO) at finite atomic temperature was introduced. It was confirmed that EPO in semiconductors was driven by lattice vibrations at finite temperatures. As the temperature increased, both the intensity of EPO and the rate of EPO change in heavy and light atoms increased, influencing electron thermal transport. To characterize the uncertainties in atomic lattice vibrations and EPO, the entropies of atomic EPO, atomic velocity of EPO (VEPO), atomic temperature, and atomic velocity were defined, with results consistent with the principle of entropy increase. This study not only aids in understanding the fundamental physical picture of electronic properties in semiconductors at finite temperatures but also provides a method for describing their uncertainties. The new theoretical concepts and statistical methods presented here can advance the understanding of electron thermal transport issues in semiconductor devices.

Thermoelectric (TE) materials have great potential in the energy recovery and environmental protection. Single crystal tin selenide (SnSe) demonstrates advantaged TE performance across a broad temperature range, but it is easy to form mechanical cracks and difficult to apply in devices. Poly-crystallization effectively enhances its mechanical properties but severely limits the hole transport reducing TE performance. Here, we provide an efficient strategy to increase hole concentration and introduce intermediate band for enhancing the electrical performance of polycrystalline SnSe in its advantaged temperature range via Al/Na co-doping. Specifically, Na dopant increases the hole concentration from 2.60 x 10(17) cm(-3) to 1.20 x 10(19) cm(-3), while Al dopant introduces intermediate band to reduce the thermal excitation temperature and promote the hole transition. As a result, the power factor of Al0.01Na0.01Sn0.98Se reaches to 10.78 mu W cm(-1) K-2 at 823 K. In addition, we used the volatilization of carbonate to introduce dislocations and point defects in SnSe. The multi-scale defects effectively scattered phonons, making the thermal conductivity of 0.39 W m(-1) K-1 is achieved in Al0.03Na0.01Sn0.96Se. Benefit from the optimization strategies of both electrical and thermal performance, a state-of-the-art peak ZT of similar to 1.73 is achieved in Al0.01Na0.01Sn0.98Se. This work reveals the key roles of intermediate bands and dislocations in regulating the thermal excitation temperature and anisotropic thermal conductivity of SnSe, and it provides a new idea for improving the TE performance of SnSe-based materials.

Due to the fragile characteristic of silica aerogel, it is difficult to achieve large-scale preparation of large-sized and multi-shaped silica aerogels through the simple and low-cost ambient drying method to meet the needs of various application fields. In this study, we present a novel approach that combines ambient and freeze drying methods to synthesize fiber composite silica aerogels with excellent formability and thermal insulation performance. Rock-wool fibers and TiO2/ZrO2 fibers produced by electrostatic spinning were employed to fabricate composite in various shapes. The rock-wool fiber composite aerogel exhibits high thermal insulation performance with a thermal conductivity of 0.0283 W m- 1 K- 1 at room temperature. The TiO2/ZrO2 fiber composite aerogel demonstrates a high specific surface area of 792.26 m2 g- 1 and outstanding temperature resistance up to 800 degrees C. The Mie scattering simulations demonstrate that the TiO2/ZrO2 composite fibers exhibit high radiative shielding properties at high temperature and the measured thermal conductivity of the TiO2/ZrO2 fiber composite aerogel powder is 0.0538 W m- 1 K- 1 at 800 degrees C in an argon atmosphere. This study introduces a novel method for integrating silica aerogel with various types of fibers, expanding the potential applications of ambient drying aerogels.

Carbon aerogels, owing to the high-temperature durability and low thermal conductivity, are promising candidates for high-temperature thermal insulation used in inert atmospheres. However, significant drying shrinkage poses challenges in fabricating large-sized carbon aerogels and optimizing their thermal insulation properties. Herein, we report the synthesis of monolithic carbon aerogels with low drying shrinkage and controllable nanostructures by adding self-crosslinked chitosan to provide reaction sites and three-dimensional network support based on the traditional resorcinol-formaldehyde method in an acetic acid environment. Owing to the increased cross-linking degree of resorcinol-formaldehyde gel from the polymerization and hydrogen bonding between chitosan and resorcinol-formaldehyde oligomers, the skeleton of gel network is strengthened and the shrinkage during supercritical drying is as low as 1.51 %, resulting in a good monolithic shape of carbon aerogel (130 x 130 x 15 mm). Besides, they exhibit typical nanoporous characteristics with uniform and small particle size (9-130 nm) and low density (0.070-0.221 g center dot cm- 3), achieving a low thermal conductivity of 0.047 W center dot m- 1 center dot K- 1 at 1100 degrees C and high compressive strength of 1.80 MPa (density of 0.138 g center dot cm- 3). This method facilitates the production of carbon aerogels with low shrinkage, minimal defects, low density, and small pore size, rendering them suitable for applications requiring large dimensions and low defect levels, such as fiber-reinforced composites and high-performance thermal insulators.

Polybenzoxazine-based aerogel composites have attracted much attention as intrinsic fire-retardant thermal insulation materials. However, their promotion in the thermal management field is currently constrained by the prevalent use of hazardous solvents and the requirement of high temperatures or high-active catalysts during preparation. Herein, a novel needle quartz fiber felt-enhanced polybenzoxazine aerogel composite (NQF/ WPBzAC) was prepared using deionized water as the solvent combined with ambient pressure drying, wherein a binary monomer gelation strategy was employed to induce the sol-gel transition occurred under mild and catalyst-free conditions. The resultant NQF/WPBzAC exhibited integrated characterizes of lightweight (0.324 g cm- 3), efficient thermal insulation (0.055 W m-1 K-1), good compressive and flexural resistance, and excellent fire retardance. Repeated water immersion tests and high-temperature exposure tests were carried out to assess the durability of NQF/WPBzAC in harsh environments. This research provides insights into the green and gentle preparation of polybenzoxazine-based aerogel composites applicable for fire resistance and thermal insulation.

Constructing a lunar base is strategically vital for deep space exploration, resource development, and future interstellar migration. However, the absence of atmospheric protection exposes the lunar surface to extremely complex thermal management issues and intense ultraviolet (UV) radiation challenges. For the first time, this study presents a multifunctional composite silica aerogel to enhance UV shielding, thermal insulation, and plant photosynthesis for sustainability in lunar base. The doping scheme is based on the numerical simulation combining Mie scattering, discrete dipoles approximation (DDA) and Monte Carlo method. The optimized UVopacifier TiO2 has 0.005 % volume fraction and 30 nm particle radius. ITO infrared opacifiers, with volume fraction of 0.05 % and radius of 20 nm, reduce infrared radiative dissipation, thereby enhancing thermal insulation. Ag nanorods with volume fraction of 0.001 %, length-to-diameter ratio of 3.5, and radius of 10 nm, can filter green light, promoting plant photosynthesis and sustainability. Synthesized with a one-step basecatalyzed sol-gel method, this composite aerogel demonstrates 18.4 % improvement in UV resistance compared with traditional transparent aerogels, while maintaining visible light transmittance of 75.2 %. The thermal conductivity is 0.0409 W m-1 K-1 at 400 K. Its exceptional thermal insulation properties achieve energy savings up to 87.1 % under extreme temperature fluctuations on the lunar surface. This composite aerogel can provide crucial solution to the sustainable development of lunar bases.

Polybenzoxazine (PBz) aerogels are promising candidates for high-performance thermal insulation due to their lightweight nature and excellent thermal stability. However, the preparation of non-green solvents and their non-hydrophobic nature result in poor thermal insulation properties during application, which seriously hinders the development of PBz aerogels. Herein, we report a green, one-pot strategy to fabricate a novel polybenzoxazine-based (BPBz/SiO2) hybrid aerogels with inherent hydrophobicity by incorporating boric acid and methyltrimethoxysilane. The prepared aerogels exhibit low density (0.144 g·cm−3), low thermal conductivity (0.0355 W·m−1·K−1), and excellent fire resistance. Remarkably, the BPBz/SiO2 hybrid aerogels exhibit outstanding intrinsic hydrophobicity (a water contact angle of 144°) and effectively prevent the adhesion of contaminants on the surface. This work is expected to play a significant role in advancing green synthesis technologies, innovating aerogel structural design, and developing high-performance thermal insulation materials.

The thermal insulation performance of windows is crucial for energy-efficient buildings. Windows are typically the weakest part of the building envelope, regarding thermal insulation. Due to its excellent thermal insulation and high transparency, silica aerogel shows great promise as a window material. However, moisture can impact the effectiveness of the aerogel, leading to poor visibility and reduced thermal insulation. This study simulated a silica aerogel with varying moisture levels using the combination of diffusion-limited cluster aggregation, discrete dipole approximation, and Monte Carlo methods. The effects of the moisture content, thickness, porosity, and particle size on thermal conductivity, solar transmittance, and haze were analyzed. Visual properties of the aerogels were also considered. The energy consumption of a 30 m2 room under different climates was simulated using TRNSYS to assess the energy-saving potential of silica aerogel glass. The findings indicate that a higher moisture content leads to decreased solar transmittance and increased thermal conductivity of aerogels. Silica aerogel glass is more energy efficient than single-layer float glass, with the dry aerogel performing better in cold climates but worse in hot climates. This study provides insights for designing aerogel glass that optimizes solar transmittance and thermal insulation to enhance building comfort and energy efficiency.

Soaring solar cell temperature hindered photovoltaic (PV) efficiency, but a novel radiative cooling (RC) cover developed in this study offered a cost-effective solution. Using a randomly particle-doping structure, the radiative cooling cover achieved a high ”sky window” emissivity of 95.3% while maintaining a high solar transmittance of 94.8%. The RC-PV system reached a peak power output of 147.6 W/m2. A field study to explore its potential in various provinces in China revealed significant efficiency improvements, with yearly electricity outputs surpassing those of ordinary PV systems by a relative improvement of 2.78%–3.72%. The largest increases were observed under clear skies and in dry, cool climates, highlighting the potential of RC-PV systems under real weather and environmental conditions. This work provided the theoretical foundation for designing scalable radiative cooling films for PV systems, unlocking the full potential of solar energy.

Ceramic nanofibrous aerogel (CNA) has received tremendous interest recently due to its advantageous properties and potential applications. However, modeling its gas-contributed thermal conductivity is quite difficult due to the intricate gas-solid coupling heat transfer mechanism and complex structure. Herein, based on an equivalent method used for a gas in free space, a model for predicting gas-contributed thermal conductivity in its nanopores is built to provide a straightforward solution to the above-mentioned issues. We study both gas and gas-solid coupling effects on the effective thermal conductivity of the randomly distributed Al2O3-carbon core-shell nanofiber aerogel. The coupled term demonstrates low gas-contributed and effective thermal conductivity of 0.022 and 0.065 W m_ 1 K_ 1 at 1500 K, respectively. It is shown that the coupling effect of gas-solid interaction is noticeable and should not be ignored when the gas pressure pg <= 0.1 bar. The predicted effective thermal conductivity demonstrates good consistency with available experimental data, which could provide direction for quick and accurate design and optimization of high-temperature thermal insulation materials.

Thermoelectric materials have great potential in the energy recovery and environmental protection, and thermoelectric films can also effectively achieve heat dissipation of the chip through thermoelectric refrigeration. WS2 films show good thermoelectric performance in prediction, but the figure of merit (ZT) of the synthesized WS2 films still needs improvement. In this work, Cu was doped into WS2 films by magnetron sputtering combined with chemical vapor deposition and sulfurization annealing. Cu doping narrowed the band gap and increased the hole concentration from 5.6 x 10(19) cm(-3) to 2.2 x 10(21) cm(-3), greatly improved the electrical properties of WS2 film. At 300 K, the electrical conductivity and power factor of Cu-doped films increased by 1086 % and 575 % compared to pristine WS2, respectively. In addition, Cu doping reduced the grain size and introduced more grain boundaries, which decreased the in-plane thermal conductivity to as low as 0.22 W m(-1) K-1 at 300 K. The coupling of the electrical and thermal properties optimization greatly improved ZT. The ZT value of Cu-5.5-WS2 films is as high as 0.181 at 425 K. This work provides a new idea for improving the thermoelectric performance of transition metal dichalcogenides (TMDCs) films.

The pore structure is a critical determinant of the properties of silica aerogels. However, the highly random nature of pore structures and their distribution pose significant challenges for designing the nanostructure of silica aerogels using a bottom-up approach. In this work, we propose utilizing faults in the silica backbone as "initial merging points"to adjust the pore structure of silica aerogels through heat treatment. Additionally, we present an atomic-scale visualization of pore structure evolution across various temperatures using large-scale molecular dynamics simulations (100 ns). Notably, this work is the first to propose anatomic model of the pore structure of silica aerogels. Our findings reveal that minor faults (tensile strain < 20%) have a limited impact on the pore structure, while significant faults (tensile strain > 30%) serve as "initial merging points", driving mass transfer and leading to the minimization of adjacent pores. Furthermore, two distinct types of pore structures were identified in the aerogel before mass transfer. After heat treatment, the specific surface area of silica aerogels with faults was found to increase compared to those without. These results offer valuable insights into the nanostructure design of silica aerogels in 3D technologies.

Icing plays an important role in various physical-chemical process. Although the formation of two-dimensional ice requires nanoscale confinement, two-dimensional bilayer ice in coexistence with three-dimensional ice without confinement remains poorly understood. Here, a critical value of a surface energy parameter is identified to characterize the liquid-solid interface interaction, above which two-dimensional and three-dimensional coexisting ice can surprisingly form on the surface. The two-dimensional ice growth mechanisms could be revealed by capturing the growth and merged of the metastable edge structures. The phase diagram about temperature and pressure vs energy parameters is predicted to distinguish liquid water, two-dimensional ice and three-dimensional ice. Furthermore, the deicing characteristics of coexisting ice demonstrate that the ice adhesion strength is linearly related to the ratio of ice-surface interaction energy to ice temperature. In addition, for gas-solid phase transition, the phase diagram about temperature and energy parameters is predicted to distinguish gas, liquid water, two-dimensional ice and three-dimensional ice. This work gives a perspective for studying the singular structure and dynamics of ice in nanoscale and provides a guide for future experimental realization of the coexisting ice.

High-stability thermal management is critical for the measurements of high sensitivity for temperature, but also challenging because any small thermal disturbances could lead to unacceptable temperature fluctuations. The present work delivers a design for passive temperature control, customized for a component in the satellites for gravitational wave detection. A novel sandwichlike structure is proposed with the configurations of proper materials, consisting of a layer of insulation material and two layers of nanocomposite phase change materials, bringing an integration of heat insulation and absorption/storage. Its performance is examined using an improved thermal network model and the revised transfer function method (TFM). The basic results of the two methods are validated by present COMSOL simulations and available numerical and experimental data in the literature. An effective reduction of temperature fluctuation is achieved to the scale of 0.1 K, even under two thermal disturbances from different directions: a radiative heat flux of 20 W m-2 (inside) and a temperature fluctuation of about 20 K (outside). Moreover, the TFM is employed to analyze the effects of the frequency of thermal disturbance: excellent damping performance is obtained for over 3.2 mHz and the underlying mechanism is discussed. Overall, the present design is expected to be combined with active temperature control to explore more possible ways for temperature control with higher stability.