Search Results (2,438)

The conversion of low-grade heat into storable electrical energy using nanoporous carbon materials represents an efficient energy harvesting strategy. In this study, a reduced graphene oxide (RGO) and carbon nanotube (CNT) composite with a rich microporous structure was synthesized. A symmetrical thermoelectric cell was constructed to harvest thermal energy. The application of a temperature difference (ΔT) generated a stable equilibrium voltage (U_s), which scaled linearly with ΔT. The resulting thermoelectric coefficient (U_s/ΔT) increased markedly with the carbon nanotube (CNT) content, underscoring the effectiveness of CNT incorporation for improving thermoelectric properties. It also shows a non-monotonic dependence on KCl concentration, first increasing and then decreasing, with a maximum value of 4.17 mV/°C achieved in 0.1 M KCl using the RGO-5%CNTs electrode. When connected to an external load, the discharge voltage and current decay rapidly before stabilizing within seconds. Circuit analysis reveals that the incorporation of CNTs reduces internal resistance and increases the equivalent capacitance. Although instantaneous discharge power declines quickly, the addition of CNTs elevates its initial value and slows the decay rate. Both the average output power and thermoelectric conversion efficiency improve with increasing ΔT and are further enhanced at higher CNT content. Overall, the RGO-CNT composite demonstrates significantly superior thermoelectric performance compared to pure RGO. Full article

Various studies on the envelope renovation of existing residential buildings have quantified energy savings effects across various climate conditions and building types yet have also reported discrepancies between predicted and actual energy savings performance. Given that identical technical improvements can yield substantially different actual outcomes depending on occupants’ behavioral adaptation patterns, renovation effect evaluation requires a multifaceted approach incorporating occupant behavioral changes. This case study empirically analyzed the effects of envelope renovation on occupants’ actual heating operation patterns. Envelope renovation effects applied to a 30-year-old apartment were analyzed by subdividing temperature conditions, with comparative evaluation using a non-renovated adjacent unit within the same building as a reference. While recognizing the inherent limitations of single-case analysis, this study presents a novel methodological framework for capturing subtle behavioral shifts through high-resolution temperature-specific analysis. Change-point models utilizing utility billing data were employed to analyze threshold temperature changes, and daily heating water-consumption estimation algorithms were applied to track heating pattern changes according to outdoor temperature variations. Results showed heating energy reduction despite more severe climate conditions post-renovation, with particularly pronounced savings under mild conditions. The upper limit of temperature ranges showing high heating dependency shifted downward from pre-renovation levels, improving to levels lower than the reference unit’s upper limit, demonstrating envelope performance enhancement effects. These results provide quantitative evidence that envelope improvements directly influence occupants’ heating decision-making criteria, though broader validation across multiple cases would strengthen these findings. This study quantifies envelope renovation effects not only in terms of energy savings, but also from the perspectives of occupant behavioral changes and comparison with reference units, presenting a novel evaluation methodology for effective energy efficiency improvements in aging buildings. Full article

This article focuses on the utilization of the supramolecular self-assembly of renewable materials derivatives to obtain functional compounds. Novel bio-based amphiphile molecules (CALAH and PALAH) were synthesized through a tailored process, involving Williamson ether synthesis and amidation reactions, employing renewable amino acid and cashew nut shell liquid (CNSL) derivatives as essential reactants. Their molecular structures were confirmed by nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS), and Fourier-transform infrared spectroscopy (FT-IR). Notably, these compounds self-assemble into nanofibers that organize into a fibrous network, unexpectedly exhibiting two distinct morphologies: curved and rigid nanostructures. These structures were characterized by scanning electron microscopy (SEM), and their formation mechanisms were elucidated through temperature-dependent NMR studies and density functional theory (DFT) calculations. The sodium salts of the compounds (PALA and CALA) exhibited fundamental surfactant properties, exhibiting a hydrophilic lipophilic balance (HLB) value of 13.7 and critical micelle concentration (CMC) values of 1.05 × 10⁻⁵ M and 4.10 × 10⁻⁶ M. They also demonstrated low cytotoxicity, suggesting potential suitability in consumer applications. Furthermore, the compounds exhibited multi-functional performance as effective inhibitors of Staphylococcus aureus and efficient adsorbents for gaseous pollutants. Full article

This paper presents the development and evaluation of an autonomous solar dryer designed to enhance the drying efficiency of bee bread granules. In contrast to natural open-air drying, the proposed system utilizes solar energy in an oscillating operational mode to achieve a controlled and accelerated drying process. The dryer comprises a solar collector integrated into the base of the drying chamber, which facilitates convective heating of the drying agent (air). The system is further equipped with a photovoltaic panel to generate electricity for powering and controlling the operation of air extraction fans. The methodology combines numerical modeling with experimental studies, structured by an experimental design framework. The modeling component simulates variations in temperature (288–315 K) and relative humidity within a layer of bee bread granules subjected to a convective air flow. The numerical simulation enabled the determination of the following: the time required to achieve a stationary operating mode in the dryer chamber (20 min); and the rate of change in moisture content within the granule layer during conventional drying (18 h) and solar drying treatment (6 h). The experimental investigations focused on determining the effects of granule mass, air flow rate, and drying time on the moisture content and temperature of the granular layer of Bee Bread. A statistically grounded analysis, based on the design of experiments (DoE), demonstrated a reduction in moisture content from an initial 16.2–18.26% to a final 11.1–12.1% under optimized conditions. Linear regression models were developed to describe the dependencies for both natural and forced convection drying. A comparative evaluation using enthalpy–humidity (I-d) diagrams revealed a notable improvement in the drying efficiency of the proposed method compared to natural drying. This enhanced performance is attributed to the system’s intermittent operational mode and its ability to actively remove moist air. The results confirm the potential of the developed system for sustainable and energy-efficient drying of bee bread granules in remote areas with limited access to a conventional power grid. Full article

The increasing frequency of extreme heat events poses significant challenges to buildings in terms of escalating thermal stress, while courtyards, as a traditional passive cooling strategy, demonstrate considerable potential in improving building thermal performance and in energy savings for cooling. Although existing studies have revealed the role of courtyards in enhancing their internal microclimate, an in-depth understanding of how design parameters regulate the microclimate and thereby affect the thermal performance of adjacent buildings remains limited, constraining their effective application in coping with extreme heat. This study conducts an exploration of relevant research aiming to elucidate the mechanisms of courtyard microclimate regulation, the quantitative methods employed, and effective design strategies in addressing high temperatures. The findings indicate that courtyards influence the building thermal performance through four mechanisms: solar radiation control, airflow organization, evaporative cooling, and thermal buffering. Their effectiveness depends on the optimized combination of geometry, material properties, and landscape configuration. Moreover, different quantitative methods exhibit notable differences in scale, accuracy, and applicability. Finally, based on the identified key factors and their interactions, this study proposes optimization pathways to bridge the gap between design expectations and practical outcomes, thereby providing both a theoretical framework and practical guidance for advancing the scientific application of courtyards in enhancing building thermal performance and energy efficiency. Full article

The economic viability of solar drying mainly depends on the appropriate design of air collectors, which are the main parts of a solar dryer. Although the V-groove collector has been reported to have one of the highest efficiencies, no comprehensive parameter analysis on this collector has been reported in the literature. This detailed study investigates the influence of different operating and design variables on the outlet temperature and the efficiency of the air collector. The parameter analysis also contributed to the development of the most effective design guidelines. The parameters examined include solar radiation, airflow rate, incoming air temperature, collector length, height of the vee, the spacing between the top of the vee and the transparent cover, number of such covers, and the thickness of the back insulation. The airflow rate is identified to be the essential operating parameter that affects the efficiency, and a better heat transfer rate is noticed in the intermediate flow state. It is also found that to achieve the best performance, it is necessary to maintain a mass airflow rate between 0.015 and 0.055 kg/m²s, to have incoming air at a near-atmospheric temperature, and to have two transparent covers on top. Full article

This study presents a numerical investigation of a solar dryer prototype integrated with microencapsulated phase change material (MPCM) for rice drying under tropical climatic conditions. The thermal and drying behavior of the system was evaluated under the following four configurations: a baseline solar dryer, a dryer with MPCM only, a dryer with an auxiliary heater, and a combined system using both MPCM and auxiliary heating. The prototype was also tested with rice layers of 25 mm and 45 mm to assess the influence of layer thickness on drying performance. The results showed that the use of MPCM reduced temperature fluctuations from about $\Delta T\approx 70$ °C in the baseline case to stabilized values near 33–34 °C (MPCM only) and 35–38 °C (MPCM + heater), contributing to a more stable thermal environment. In thinner layers (25 mm), MPCM helped prevent localized overheating, while in thicker layers (45 mm), it promoted more uniform moisture reduction. However, the overall improvement in drying performance was marginal, as efficiency remained strongly dependent on heater support. The study points out the need for improved integration of PCM within dryer design. Enhanced thermal contact and strategic preheating of MPCM could improve heat discharge during non-solar periods. Future work will focus on experimental validation, design optimization, and the development of preheating strategies to maximize the benefits of PCM-assisted solar drying systems. Full article

Recovering waste heat is widely seen as an effective way to improve energy efficiency. Because of its potential to lower both energy costs and greenhouse gas emissions, it has been used for many years in industries with high energy demand. While several technologies are already available for this purpose, most of them require relatively high temperatures to achieve high performance. One approach that can make use of lower temperature heat sources is the thermally regenerative electrochemical cycle (TREC). Systems based on this principle can be a cost-effective option for capturing heat from sources such as fuel cells, although their efficiency depends on several factors. This study applies parameter sensitivity analysis to support more efficient system design. The results show that chemical properties, especially the thermal coefficients of redox pairs, have the strongest effect on performance. Geometric aspects, particularly the size of the active membrane area, also play an important role. Full article

In this study, we investigated the performance of iron-loaded biochar (Fe-BC) derived from mulberry branches in activating persulfate (PS) for the efficient degradation of sulfamethoxazole (SMX). The Fe-BC/PS system exhibited superior catalytic activity towards SMX degradation, achieving 97% removal within 60 min. The degradation efficiency was found to be highly dependent on preparation conditions, including calcination temperature, the type of iron salt, and biomass feedstock. Reactive species such as hydroxyl radicals (^•OH), sulfate radicals (SO₄^•−), and iron (IV) (Fe(IV)) were identified as key contributors to SMX degradation, with Fe(IV) playing a dominant role. The influence of water quality parameters, such as inorganic ions, pH, and natural organic matter (NOM), on the degradation of SMX was also examined. Proposed degradation pathways revealed the stepwise oxidation of SMX into smaller intermediates, ultimately leading to mineralization. Our findings highlight the potential of Fe-BC/PS systems as a sustainable and effective approach for the remediation of sulfonamide antibiotics in aquatic environments. Full article

This study presents the fabrication and performance optimization of porous fly ash-based geopolymer (FAGP)–polyethersulfone (PES) composite fibers with tunable FAGP loading for the multivariate adsorption of heavy-metal ions from aqueous solutions. Fibers containing 20 wt%, 40 wt%, and 60 wt% FAGP were prepared using phase inversion method and were characterized using X-ray computed tomography and mechanical testing. Adsorption experiments were conducted to assess the removal efficiencies of Pb²⁺, Cd²⁺, Cu²⁺, and Ni²⁺ at different pH values, temperatures, contact times, adsorbent dosage and initial metal-ion concentrations. The composite containing 60 wt% FAGP exhibited the high performance for all ions, and its performance was especially high for Pb²⁺. The isotherm and kinetic modeling revealed that the adsorption process followed Freundlich and Redlich–Peterson models, with mixed chemisorption–physisorption mechanisms depending on the metal-ion type. Compared with conventional adsorbents, the optimized composite fibers exhibited high adsorption capacity, enhanced handling suitability, and scalability in addition to their sustainability owing to the use of industrial by-products as precursors. These findings provide new insights into the structure–function relationships of FAGP composite fiber adsorbents and their potential for wastewater treatment applications. Full article

This study conducted a systematic investigation of the degradation pathway and process optimization of strong acid cation exchange resins subjected to SCWO. Controlled experiments evaluated the effects of operating temperature, oxidant stoichiometry, initial organic concentration, and residence time. RSM was utilized to refine the operating parameters, and a second-order regression model (R² = 0.9951) was established to predict COD removal (R_COD), valid within experimental ranges: reaction temperature 400–500 °C, oxidant stoichiometry 80–150%, initial COD 10,000–100,000 mg·L⁻¹, and residence time 1–10 min. COD-dependent NaOH addition could enhance degradation efficiency. The R_COD was sensitive to operating temperature, oxidant stoichiometry, and residence time. Under the optimized conditions of 472 °C, oxidant stoichiometry of 137%, initial COD of 77,216 mg·L⁻¹, and residence time of 4.9 min with the addition of 1.74 wt% NaOH, the R_COD reached 99.92%, which was in close agreement with model predictions. GC-MS analysis of intermediates revealed that sulfonic groups dissociated early, followed by aromatic compounds, particularly phenol, undergoing ring-opening and oxidation to small carboxylic acids and aliphatic species, which were ultimately mineralized to CO₂ and H₂O. These findings provide mechanistic insight into resin decomposition and offer a scientific basis for the safe treatment of radioactive waste resins using SCWO. Full article

Pultrusion is a manufacturing process used to produce fiber-reinforced polymer composites with excellent mechanical, thermal, and chemical properties. The resulting materials are lightweight, durable, and corrosion-resistant, making them valuable in aerospace, automotive, construction, and energy sectors. However, conventional thermoset composites remain difficult to recycle due to their infusible and insoluble cross-linked structure. This review explores integrating vitrimer technology a novel class of recyclable thermosets with dynamic covalent adaptive networks into the pultrusion process. As only limited studies have directly reported vitrimer pultrusion to date, this review provides a forward-looking perspective, highlighting fundamental principles, challenges, and opportunities that can guide future development of recyclable high-performance composites. Vitrimers combine the mechanical strength (tensile strength and modulus) of thermosets with the reprocessability and reshaping of thermoplastics through dynamic bond exchange mechanisms. These polymers offer high-temperature reprocessability, self-healing, and closed-loop recyclability, where recycling efficiency can be evaluated by the recovery yield retention of mechanical properties and reuse cycles meeting the demand for sustainable manufacturing. Key aspects discussed include resin formulation, fiber impregnation, curing cycles, and die design for vitrimer systems. The temperature-dependent bond exchange reactions present challenges in achieving optimal curing and strong fiber–matrix adhesion. Recent studies indicate that vitrimer-based composites can maintain structural integrity while enabling recycling and repair, with mechanical performance such as flexural and tensile strength comparable to conventional composites. Incorporating vitrimer materials into pultrusion could enable high-performance, lightweight products for a circular economy. The remaining challenges include optimizing curing kinetics, improving interfacial adhesion, and scaling production for widespread industrial adoption. Full article

Cross-linked polyethylene (XLPE) has been widely used in high-voltage cables due to its superior properties, but its thermoset cross-linked structure makes it difficult to recycle. Catalytic pyrolysis offers a feasible pathway for converting XLPE into high-value chemicals. In this study, a systematic study on the catalytic cracking of XLPE using metal ion-loaded ZSM-5 nanosheets was conducted, and ZSM-5 nanosheets loaded with Ag, Mo, Ni, and Ce were prepared via ion exchange. After metal loading, ZSM-5 retained the MFI framework structure, but the specific surface area and mesopore volume varied depending on the type of metal. Temperature-Programmed Desorption of Ammonia results indicated that metal–support interactions enhanced the acidity of ZSM-5. Among the catalysts, Ag-loaded ZSM-5 exhibited the highest efficiency: with 10 wt% Ag, at 380 °C, the conversion reached 94.1%, with 52.5% light olefins in the gas phase and 59.4% benzene, toluene, and xylene (BTX) in the liquid products. Further studies on different Ag loadings revealed that moderate Ag loading (5 wt%) provided the best overall balance, maintaining 92.3% conversion, 56.1% selectivity to light olefins, and 58.2% BTX in the liquid fraction. These findings demonstrate that tuning the metal loading effectively optimizes the acidity and pore structure of ZSM-5, thereby enabling controlled regulation of XLPE pyrolysis product distribution. Full article

This paper proposes a new family of robust estimators of means, depending on the Orthogonalized Gnanadesikan–Kettenring (OGK) covariance matrix. These estimators are computationally feasible and robust replacements of the Minimum Covariance Determinant (MCD) estimator in survey sampling contexts involving auxiliary information. With the growing popularity of outliers in environmental data, as in the case of measuring solar radiation, conventional estimators like the sample mean or the Ordinary Least Squares (OLS) regression-based estimators are both biased and unreliable. The suggested OGK-based exponential-type estimators combine robust measures of location and dispersion and have a considerable advantage in the estimation of the population mean when auxiliary variables such as temperature are highly correlated with the variable of interest. The MSE property of OGK-based estimators is also obtained through a detailed theoretical derivation with the expressions of optimal weights. Performance was further proved using real-world and simulated data on solar radiation, as well as by demonstrating lower MSEs and higher PREs in comparison to MCD-based estimators. These results show that OGK-based estimators are highly efficient and robust in actual and artificially contaminated situations and hence are a good option in robust survey sampling and environmental data analysis. Full article

Municipal solid waste incineration promotes sustainable development by reducing waste, recovering resources, and minimizing environmental impact, with furnace temperature control playing a key role in maximizing efficiency. Accurate real-time temperature prediction is crucial in developing countries to optimize incineration, re-duce emissions, and enhance energy recovery for global sustainability. To address this, we propose a method integrating an improved whale optimization algorithm (IWOA) with a self-attention gated recurrent unit (SAGRU). Using the maximal information coefficient (MIC) to identify key factors, we optimize SAGRU parameters with IWOA, enhancing prediction accuracy by capturing temporal dependencies. Experimental validation from an MSWI plant in China demonstrates that the proposed model significantly enhances prediction accuracy under complex conditions. When compared with the Elman and LSTM models, the error is reduced by 0.7146 and 0.4689, respectively, highlighting its strong potential for practical applications in waste incineration temperature control. Full article