Search Results (13,023)

The integration of reversible solid oxide cell (rSOC) systems with industrial energy units can improve operational flexibility, but it also requires safe and efficient management of hydrogen-rich off-gas. This study presents the numerical design of an exhaust gas afterburner for a 10 kW rSOC stack, in which unreacted hydrogen mixed with steam is oxidized using the hot air stream employed for stack purging. A finite-volume CFD approach was applied using a non-premixed combustion model, a k– SST turbulence model, and GRI-Mech 3.0 chemistry, followed by a thermo-mechanical assessment of the chamber. For the reference case, the unreacted hydrogen stream was 1.16661 × 10⁻⁴ kg/s, corresponding to approximately 14 kW of chemical energy. The simulations predicted a localized reaction zone directly downstream of the burner outlet, accompanied by rapid hydrogen consumption and a fluid-temperature range of approximately 492–930 °C. The thermo-mechanical analysis predicted a maximum total deformation of 2.2189 mm and a maximum axial displacement of approximately 2.21 mm for the analyzed steady-state operating point. These results characterize the temperature, species, and deformation fields of the 10 kW reference configuration. The 100 kW and 1 MW variants should be treated only as preliminary geometric extrapolations, because they were not verified by separate CFD/CSD calculations. Full article

The increasing global demand for sustainable energy solutions has intensified the need for efficient and environmentally friendly biomass-conversion technologies. Among these, thermochemical processes, such as pyrolysis, gasification, and hydrothermal liquefaction, have emerged as promising pathways for transforming lignocellulosic and other organic waste materials into valuable biofuels and biochemicals. This paper presents a comprehensive evaluation of advanced thermochemical conversion and catalytic conversion methods, focusing on their operational mechanisms, catalytic enhancements, and product yields. The efficiency, environmental impact, and economic feasibility of various thermochemical platforms, including recent developments in catalyst design and process-integration strategies, are compared, and innovative approaches to optimize hydrogen generation, improve carbon efficiency, and minimize undesirable byproducts through tailored reaction conditions and bifunctional catalytic systems are explored. Recent advances as well as the current challenges related to feedstock variability, process scalability, and system sustainability are highlighted. By identifying critical research gaps, this study provides strategic insights aimed at guiding future improvements in thermochemical biomass utilization for clean energy production within a circular economy framework. Full article

Xylitol is a five-carbon sugar alcohol widely used in the food, pharmaceutical, oral healthcare, and personal care industries because of its low caloric value, low glycaemic index, and non-cariogenic properties. Industrial production is mainly based on catalytic hydrogenation of xylose, which provides high conversion efficiency but requires intensive energy input, costly catalysts, and complex purification processes. Microbial fermentation has emerged as a sustainable alternative for producing xylitol from renewable lignocellulosic biomass. This review summarizes recent advances in xylitol production, with a particular focus on microbial biomanufacturing. Key developments in lignocellulosic biomass utilization, metabolic engineering, cofactor balancing, oxygen regulation, and fermentation optimization are discussed. Chemical and biological production routes are critically compared in terms of efficiency, sustainability, and industrial applicability. Recent progress in downstream purification and biorefinery integration is also highlighted. Despite substantial advances, challenges including inhibitor toxicity, limited microbial robustness, low fermentation productivity, and high purification costs continue to hinder large-scale commercialization. Future research should focus on feedstock valorization, systems metabolic engineering, process intensification, and sustainable separation technologies to improve the economic and environmental sustainability of bio-based xylitol production. Full article

Microgears enable mechanical power transmission, speed reduction, motion conversion, and synchronization in compact devices ranging from microelectromechanical systems to miniature robots and optically driven micromachines. Their behavior cannot, however, be inferred by geometrically scaling conventional gears alone. As size decreases, relative manufacturing errors, surface forces, friction, adhesion, environmental sensitivity, and metrological uncertainty become increasingly important, while torque capacity and stored kinetic energy decrease rapidly. This critical review integrates the design, manufacture, tribology, and system-level performance of microgears and microgear trains. It first clarifies dimensional terminology and derives the principal scaling relationships. It then compares external, internal, planetary, worm, bevel, compliant, and reconfigurable transmission architectures; evaluates silicon micromachining, electroforming, micro powder injection molding, microforming, micro-electrical discharge machining, ultrashort-pulse laser ablation, and additive microfabrication; and examines adhesion, friction, wear, lubrication, and environmental effects. Particular attention is paid to transmission efficiency, starting torque, backlash, transmission error, lifetime, and the influence of the measuring instrument on the observed response. The literature remains strongly weighted toward manufacturability and isolated components, whereas reproducible, loaded, system-level tests are comparatively scarce. On this basis, the review proposes a unified hierarchy of validation, a minimum functional test matrix, and scale-aware design indicators. The central conclusion is that successful microgear transmissions require concurrent design of geometry, process, surface condition, environment, load path, and measurement strategy. Full article

Autonomous robotic systems designed for extraterrestrial in situ resource utilization (ISRU) will play a central role in enabling a sustained human presence on the Moon and Mars. These robots are expected to perform tasks such as regolith excavation, water extraction, oxygen production, and propellant generation under extremely harsh environmental conditions, including large temperature variations, abrasive dust, high radiation levels, and significant communication delays with Earth. Consequently, their onboard electrical systems must operate with high reliability, autonomy, and fault tolerance. A critical enabling technology for these systems is the isolated power conversion architecture, which distributes energy from primary power sources to multiple robotic subsystems, including mobility actuators, drilling systems, sensors, computing units, and thermal management modules. Future lunar and Martian missions are expected to rely on a combination of alternative energy sources, including solar photovoltaic arrays with energy storage, fuel cells, radioisotope power systems, and nuclear surface power reactors, which can provide continuous and high-density energy independent of sunlight availability. These diverse power sources require flexible and highly efficient isolated DC–DC power conversion architectures capable of managing wide input voltage ranges while ensuring electrical isolation, safety, and system stability across distributed robotic platforms. This literature review surveys recent developments in autonomous isolated power conversion architectures suitable for lunar and Martian resource extraction robots. The review examines advanced converter topologies such as resonant converters, phase-shifted full-bridge converters, dual-active bridge converters, and modular multiport power converters designed for high efficiency, high power density, and scalable power distribution. Emphasis is placed on converter architectures capable of interfacing with nuclear-powered systems and other high-energy-density sources while supporting distributed loads in robotic mining and processing systems. In addition, the paper reviews emerging autonomous control strategies, including adaptive digital control, intelligent power management, fault detection and self-recovery mechanisms, and distributed power architectures capable of maintaining stable operation under dynamic load conditions. The role of wide-bandgap semiconductor technologies, including silicon carbide (SiC) and gallium nitride (GaN), is also examined, highlighting their potential to enable higher switching frequencies, improved efficiency, reduced system mass, and enhanced thermal performance in vacuum environments. Finally, system-level considerations for integrating isolated power conversion within robotic ISRU platforms are discussed, including redundancy strategies, power bus architectures, electromagnetic compatibility, thermal management, and long-duration reliability requirements. By consolidating advances across power electronics, autonomous control, and space power systems, this review identifies key research gaps and outlines design directions for next-generation autonomous power conversion systems capable of supporting scalable lunar and Martian resource extraction infrastructures powered by both renewable and nuclear energy sources. Full article

Natural gas hydrates, with their vast reserves and high gas storage density, have emerged as a highly promising alternative energy source and technology for gas storage and transportation. Wettability, as a core surface property of porous media, directly influences hydrate nucleation, growth, occurrence morphology, and flow behavior. In this study, quartz sand with varying surface properties was prepared with the octyltrimethoxysilane (OTMS) silane coupling agent via surface chemical reactions. The methane hydrate (MH) equilibrium conditions as well as the formation kinetics in silica sand were measured, and the mechanism and potential of the surface modification for enhancing methane hydrate storage capacity were analyzed. The experimental results indicate that surface modification of quartz sand has no significant effect on the MH equilibrium condition. Hydrophobic modification of quartz sand provides more gas–liquid interfaces, increases the contact area, and thereby significantly enhances mass transfer under high-water-saturation conditions and accelerates the MH formation rate. However, excessively high surface hydrophobicity may reduce the effective gas–liquid interfacial area and limit the overall hydrate formation rate. Due to the influences of the hydrate distribution and aggregation, as well as gas diffusion on hydrate formation, the effect of the initial formation pressure on MH formation is only observed during the early stages of MH formation, while the temperature effect is less pronounced than that of formation pressure. It is suggested to further consider combining stirring with continuous gas injection to enhance gas–liquid flow and improve gas–liquid contact, thereby increasing the formation rate of hydrates. Full article

In salt cavern compressed air energy storage (CAES) systems, slag particles entrained by high-pressure airflow can cause pipeline wear and flow instability, posing challenges to long-term operational safety. However, direct experimental studies are constrained by high-pressure, large-scale conditions and transient multiphase flow complexities. This study uses Fluent, a numerical simulation method based on gas–solid two-phase flow theory, to investigate the flow characteristics, particle dynamics, and erosion behavior in the above-ground pipeline of CAES system. Results reveal uneven gas velocity distribution, with the lowest flow (≤2.3 (m/s)) in the main pipeline favoring particle deposition, and complex vortex structures at branch connections. Particles accumulate on the outer wall of 90° elbows due to centrifugal effects, leading to localized erosion, with severe wear occurring at impact angles of 20–30°. Over a 30-year operational cycle, the predicted maximum wear depth is 0.38 mm, which remains below the existing protective cladding thickness of 0.5 mm. The findings not only provide a theoretical basis and design insights for optimizing wear protection strategies, but also hold positive implications for enhancing the economic sustainability and environmental benefits of large-scale energy storage systems. Full article

Reversible solid oxide cells (ReSOCs) represent one of the most promising electrochemical technologies for sustainable energy conversion and storage, yet their large-scale deployment remains constrained by electrode materials capable of sustaining stable performance under alternating oxidizing and reducing conditions. Reversible solid oxide cells require electrode materials that combine phase stability, chemical compatibility, redox tolerance and a microstructure suitable for gas transport and surface reactions. However, the relationships among cation composition, thermal processing, phase formation and local chemical homogeneity remain insufficiently understood, particularly for compositionally complex perovskite-related oxides. In this work, this problem was addressed through a comparative physicochemical screening of three candidate electrode materials synthesized by a simple co-precipitation route: two co-doped lanthanum ferrites, (La_0.8Sr_1.2) (Fe_0.9Co_0.1)O_6+δ (LSFC) and (La_0.8Ca_1.2) (Fe_0.9Co_0.1)O_6+δ (LCFC), and one high-entropy praseodymium nickelate, Pr(Ba_0.8Ca_0.2)(Fe_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)₂O_6+δ (PBC-HEO). DTA–TG analysis was used to determine the thermal decomposition and crystallization ranges of the precipitated precursors. Phase evolution as a function of calcination temperature was investigated by X-ray diffraction, while Raman and FTIR spectroscopy were employed to examine the local metal–oxygen environment and structural disorder. Raman spectroscopy confirmed the formation of perovskite-type metal–oxygen frameworks in all samples and revealed distinct redistributions of spectral weight between apical/equatorial (or symmetry-related) BO₆ stretching sub-modes and bending/tilting modes, reflecting different local defect-chemical mechanisms associated with A-site doping (Sr vs. Ca) in the Ruddlesden–Popper ferrites and B-site multi-cation occupancy in the double-perovskite PBC-HEO. Bulk and local elemental compositions were assessed by ICP-MS and SEM-EDS, respectively, and SEM was used to compare particle morphology and porosity. SEM-EDS analysis showed that PBC-HEO developed the most open and interconnected microstructure among the investigated powders, although accompanied by residual compositional heterogeneity. This morphology may favor gas accessibility; however, its effective impact on electrocatalytic performance requires dedicated surface area, porosimetry, electrical, and electrochemical measurements. LSFC formed a single major Ruddlesden–Popper phase only after high-temperature calcination, whereas LCFC retained calcium-containing secondary phases. PBC-HEO developed a major perovskite-related phase at 700 °C, accompanied by minor Zn-rich segregation. Under the selected processing conditions, PBC-HEO retained the finest and most interconnected porous microstructure, although it also displayed the highest local compositional heterogeneity. These results demonstrate that cation selection and thermal history jointly control phase stability, local disorder and microstructure, providing a basis for the subsequent electrochemical evaluation and optimization of perovskite-related ReSOC electrode materials. Full article

A flywheel energy storage system (FESS) is a device that employs a high-speed rotating flywheel for energy storage, where the motor is a core component enabling the energy conversion. Since the motor rotor is integrated onto the flywheel rotor (FR), when the FESS operates, the vortex motion of the FR causes misalignment between the motor rotor and stator, and the resulting unbalanced magnetic pull (UMP) will induce changes in the vibration characteristics of the FR. This paper presents a permanent magnet synchronous motor (PMSM) designed for a FESS and analyzes the variation pattern of the UMP induced by rotor eccentricity in this motor utilizing the finite element method. Furthermore, the UMP is equivalently modeled using the motor stiffness, and a dynamic model of an active magnetically suspended rigid flywheel rotor that considers the UMP in the motor is established. In this study, the motor position offset ratio β is defined to quantify the axial distance between the motor position and the FR mass center. This paper analyzes the variation law of the vibration characteristics of the FR with the magnitudes of the UMP and the motor position offset ratio β using numerical calculations. Finally, the correctness of the calculated results is verified using experimental testing. This investigation demonstrates that the value of UMP fluctuates as the rotor’s rotation angle increases, while its average value exhibits a linear increasing trend with the growth in rotor eccentricity. As UMP and β increase, the first- and second-order critical speeds of FR exhibit a clear decreasing trend. Meanwhile, variations in these two factors also exert different influences on the vibration amplitude induced by the mass imbalance response of the FR. Therefore, when designing an active magnetically levitated flywheel energy storage system, the influence of motor parameters on the vibration characteristics of FR should be taken into consideration. Full article

In population health the highly cited Atherosclerosis Risk in Communities study indicated a U-shaped association between carbohydrate intake and mortality, whilst the Prospective Urban Rural Epidemiology study linked higher fat intake to lower mortality risks. The Malaysia Lipid Study reported high-fat and high-carbohydrate dietary patterns were associated with increased cardiometabolic risks, including insulin resistance and small dense LDL particles generation. This animal model study therefore was purposely designed to evaluate metabolic outcomes of carbohydrate–fat permutations in Zucker diabetic fatty (ZDF) and Zucker lean (Z_lean) rats by using ¹H Nuclear Magnetic Resonance (NMR) metabolomics. Twenty-four ZDF rats were randomly divided into four groups (n = 6 per group): control (standard diet), Diet A (54%-energy carbohydrate, 32%-energy fat, 14%-energy protein) mimicking a recommended adult Malaysian diet, Diet B (49%-energy carbohydrate, 37%-energy fat, 14%-energy protein) mimicking a low-carbohydrate, moderate high-fat diet, and metformin treatment (100 mg/kg), which effectively represents a 5%-energy exchange in isocaloric meals. An additional six Z_lean were given Diet A (n = 3) and Diet B (n = 3). The intervention lasted eight weeks. Using log-transformed data, analysis of variance (ANOVA) revealed significant differences between the groups for eleven metabolites (1,6-anhydro-β-D-glucose, 2-hydroxyvalerate, acetate, 3-aminoisobutyrate, 3-hydroxybutyrate, carnitine, choline, citrate, creatine, lactate, and N-methylhydantoin) (all p < 0.05) which remained significant even after false discovery rate (FDR) correction. Majorly elevated metabolites in both ZDF and Z_lean rats were 3-hydroxybutyrate, N-methylhydantoin, 3-aminoisobutyrate, and carnitine, indicating dietary influences independent of diabetes status. Conversely, citrate and 1,6-anhydro-β-D-glucose levels showed distinct patterns across the groups, with Z_lean rats exhibiting lower levels and ZDF rats showing higher levels compared to healthy controls, suggesting potential genetic or physiological influences. Other metabolites such as creatine, acetate, choline and 2-hydroxyvalerate showed varied trends, highlighting metabolic complexities. Compared to the control group, metformin treatment generally resulted in lower levels of metabolites, except for acetate, which was higher, indicating improved insulin sensitivity. The findings indicated moderate high-fat diets may exacerbate metabolic disturbances as seen in both ZDF and Z_lean rats, while metformin treatment generally improved metabolic profiles. Full article

This paper presents an energy-management and state-of-charge (SoC) balancing scheme, denoted OEMSS, for a DC microgrid comprising photovoltaic generation, a fuel-cell source, two energy storage systems (ESSs), and six household loads. A demand-driven power-allocation layer first determines whether generation is sufficient, ESS support is required, or priority-based load scheduling must be activated. A supervisory balancing layer then allocates the fleet charging or discharging request by using a capacity-weighted average SoC and separate mode-dependent correction laws. The balancing command is dimensionally expressed as an energy-capacity deviation divided by the control interval and is projected onto the SoC and power limits. A Python simulation driven by recorded generation profiles is used to evaluate four seasonal operating conditions. In the tested equal-capacity case, the maximum inter-ESS SoC deviation is reduced from 18% to 4.8%, synchronization is reached within approximately 2 to 4 h, and simulated over-discharge events are avoided. The reported increase from 45% to approximately 70% is interpreted as a 25-percentage-point increase in the ESS storage contribution rate, rather than an increase in conversion efficiency. During shortage intervals, the retained priority demand is supplied, whereas satisfaction of the original uncurtailed demand is not claimed. A discrete-time Lyapunov analysis gives the nominal convergence condition $0<{\gamma }_b<2$, and the online implementation has $\mathcal{O}(J+K+H)$ time complexity. The study provides simulation evidence for a simple coordinated allocation rule; hardware performance, battery-life extension, converter-level stability, and global optimality remain to be established. Full article

This study explores the utilization of local biomass through slow pyrolysis in a multifunctional domestic reactor, with a view to producing renewable energy and improving soil quality in arid regions. Four underutilized biomass sources were studied: millet stalks, cashew shells, cashew shell meal, and rumen contents. Thermal monitoring using thermocouples showed pyrolysis temperatures ranging from 270 to 350 °C, while the combustion chamber reached up to 800 °C depending on the biomass. Four thermal phases were identified (heating, devolatilization, stabilization, and cooling), confirming stable reactor operation. Gas analyses revealed a predominance of CO (approximately 1000 ppm) as well as variations in O₂, H₂S, and hydrocarbons, indicating a conversion process dependent on the type of biomass and interactions between chambers. Mass and energy balances show that performance depends heavily on the physicochemical properties of the feedstocks, particularly the content of volatiles, lignin, and ash. Cashew shells exhibited the highest energy efficiency (approximately 42.9%), followed by rumen contents (approximately 34.4%), while cashew shell meal showed lower performance due to prior extraction of volatiles. Biochar yields and energy distribution vary significantly depending on the biomass, highlighting the importance of feedstock selection in decentralized pyrolysis systems. Overall, household pyrolysis enables simultaneous energy recovery and biochar production under realistic, non-optimized conditions. These results provide new insights into biomass–reactor interactions and support the development of decentralized bioenergy solutions tailored to sub-Saharan regions. Full article

This study presents a comprehensive experimental and numerical investigation of a rotating propeller using three-dimensional Digital Image Correlation (3D DIC), Computational Fluid Dynamics (CFD), and Finite Element Method (FEM) analysis. The main objective was to assess the applicability and accuracy of 3D DIC for full-field displacement and strain measurements under centrifugal loading conditions. The propeller geometry was reconstructed using 3D scanning and implemented in a numerical model with material parameters identified through mechanical testing. Experimental measurements were carried out on a dedicated test stand, enabling controlled rotational speed and synchronized image acquisition. Particular attention was devoted to measurement uncertainty, including calibration errors, motion effects, and coordinate system alignment. The obtained displacement and strain fields were compared with FEM predictions after proper spatial transformation for rotational speeds of 4110, 6045, and 6940 rpm. The results demonstrate good agreement between numerical and experimental data in selected regions, confirming the potential of 3D DIC for validation of rotating structures, while also highlighting limitations related to dynamic effects and optical constraints. Full article

This study evaluates the effect of homofermentative and heterofermentative inoculants used independently or in combination on the quality of fermentation, chemical composition, fiber digestion, and nutritional value of silage made from four wheat varieties (Bayraktar 2000, Kızıltan 91, Bezostaja 1, and Tosun bey). Four treatments were applied within each variety: an untreated control group; a homofermentative inoculant (HMF group; Lactiplantibacillus plantarum, formerly Lactobacillus plantarum, and Enterococcus faecium, applied at 1.0 × 10⁵ cfu/g fresh weight); a heterofermentative inoculant (HTF group; Lentilactobacillus buchneri, formerly Lactobacillus buchneri, applied at 5.0 × 10⁴ cfu/g fresh weight); and their combination (HMF+HTF; group 1.5 × 10⁵ cfu/g fresh weight). The whole-crop wheat silage collected at the dough stage was allowed to ferment for 120 days using a 4 × 2 × 2 factorial design having four replications. Statistically significant differences between varieties and inoculation treatments were seen in most of the recorded characteristics (p < 0.001), demonstrating that inoculant responses were significantly impacted by genotype. In Kızıltan 91, dry matter (DM) did not differ significantly among treatments (p > 0.05). In Bayraktar 2000, DM was reduced only by HTF applied alone (36.56% vs. 43.23% in the control), while HMF and HMF+HTF did not differ from the control. In Bezostaja 1, both HTF and HMF+HTF decreased DM relative to the control, whereas HMF alone had no effect. In Tosun bey, all LAB treatments increased DM relative to the control, with the homofermentative inoculant producing the greatest increase. Homofermentative inoculants demonstrated improved fermentation characteristics by lowering silage pH and ammonia-nitrogen concentrations and enhancing physical traits, while Heterofermentative inoculants reduced butyrate accumulation and raised acetic acid concentration, which reached 3.50 g/kg DM in Kızıltan 91 during combined inoculation. According to genotype, the application of inoculants varied the amount of fiber and digestibility. In vitro dry matter and organic matter digestibility, net energy of lactation, total digestible nutrient, and relative feed value (RFV) were frequently reduced by the combination HMF+HTF treatment. In Bayraktar 2000, RFV was found to have decreased the most, from 166.79 to 106.51. Conversely, Bezostaja 1 showed comparatively constant levels of energy content and digestibility regardless of the treatment, suggesting greater adaptability to the effects of microbial inoculants. In general, wheat genotype was the main factor influencing the nutritional value and quality of silage, and varietal characteristics had a significant impact on the efficacy of microbial inoculation. These results show how essential it is to choose inoculant methods according to variety in order to maximize fermentation quality and maintain feeding value in the production of wheat silage. Full article

Low-grade thermal energy is widely available in industrial waste-heat streams and natural temperature fluctuations, yet its utilization remains limited because of weak thermodynamic driving forces and the complexity of conventional heat-engine technologies. This study presents a physics-based framework for modular thermoelastic energy harvesting using the reversible thermal expansion and contraction of structural materials. Analytical models are established to quantify thermoelastic work, structural constraints, thermodynamic and exergy efficiencies, and long-term energy production. Material selection and thermo-mechanical limitations are evaluated through parametric analysis and finite-element verification. The results indicate that extractable work is fundamentally constrained by yield strength, buckling resistance, temperature swing, and the limited exergy content of low-grade heat. Scaling laws show that annual energy generation scales approximately linearly with active structural mass while remaining strongly dependent on column diameter, thermal-cycle frequency, and material performance indices. Thermodynamic and exergy efficiencies remain well below the Carnot limit, highlighting the inherent limitations of solid-state thermoelastic conversion. A techno-economic assessment further indicates that economic viability depends primarily on multi-cycle operation and low-cost implementation. Although the achievable energy density remains modest compared with conventional renewable technologies, the proposed framework provides quantitative performance limits and practical design guidelines for evaluating thermoelastic energy harvesting from low-grade heat. Full article