Search Results (33,496)

The marble extractive industry heavily depends on diesel-powered equipment, particularly wheel loaders and excavators used for block handling, resulting in high energy consumption and operating costs. In this study, the potential for fuel reduction through managerial and technological transitions was evaluated using the example of the marble quarry located in the Carrara basin. The energy demand of excavators, wheel loaders, and dumpers was characterized using telemetry data gathered through an Industry 4.0 methodology. A standard elementary cycle was modeled via the program evaluation and review technique (PERT) to map productive tasks and idling periods. To ensure comparability, a specific consumption coefficient (SCC) was defined. Subsequently, a novel fuel handling index (FHI) is proposed to prioritize investments by accounting for the uncertainties and production variables typical of quarry projects. Results demonstrate that while idle management offers a 4% fuel reduction, transitioning to hybrid wheel loaders represents a more significant strategy, achieving a 12% saving among the scenarios analyzed. The full-hybrid scenario leads to a cumulative 17% reduction. This framework supports decision-making for energy efficiency in high-yield extraction sectors, mitigating the economic risk associated with technological transitions. Full article

This study designs a novel modular prefabricated concrete foundation for cable termination supports in the power industry. This foundation is composed of prefabricated components including concrete segmented foundations, strut and connector via bolted connections, featuring convenient construction and a reduction of nearly 40% in concrete consumption. The finite element model was established using FEA software (Version ABAQUS 2020), and an economical and stable mesh size was selected through mesh convergence analysis. The settlement and bearing capacity of the foundation under axial compression were analyzed. Results show that this prefabricated foundation remains in the elastic stage under service load, with uniform settlement and excellent integrity. The stress of reinforcement bars and bolts is much lower than the material yield strength, and the concrete has ignorable damage. In addition, the safety margin is sufficient, and the force transfer path is clear. The research results can improve the prefabricated system for power facilities and provide technical support for the green and efficient construction of cable termination support foundations. Full article

To support the integration of high shares of renewable energy and enhance the operational flexibility of thermal power systems, thermosyphon have been considered as promising high-efficiency heat transfer components for thermal energy storage applications. In this study, a water-based thermosyphon motivated by molten-salt thermal energy storage scenarios is investigated numerically to clarify its internal heat-transfer behavior under different operating conditions. A two-dimensional CFD model is established based on the Volume-of-Fluid (VOF) multiphase approach coupled with the Lee phase-change model. The effects of heating power (3.5–5.0 kW) and liquid filling ratio (25–40%) on wall temperature distribution and thermal resistance characteristics are systematically analyzed. The results indicate that increasing the filling ratio improves the uniformity of the evaporator wall temperature, and a filling ratio of 40% leads to a relatively favorable liquid distribution and the lowest total thermal resistance within the investigated range. The evaporator thermal resistance exhibits a “decrease–increase” trend with heating power and reaches a minimum value of 1.019 × 10⁻⁴ K/W at 4.5 kW, while the condenser thermal resistance decreases monotonically with in-creasing heating power. This study provides comparative numerical insights into the coupled effects of heating power and filling ratio on thermosyphon performance, offering a reference for the component-level design and parameter selection of heat pipe heat exchangers in molten-salt-related thermal energy storage systems. Full article

With the expansion of urban rail transit, increased train operation density, and the large-scale grid integration of renewable energy such as offshore photovoltaic power, traction power supply systems face stricter requirements for operational safety, power supply reliability and energy utilization efficiency. Offshore photovoltaic power, integrated into the traction power supply network via flexible DC transmission technology, promotes renewable energy consumption, but its random and volatile output overlaps with time-varying traction loads, increasing the complexity of DC-side fault characteristics and protection control. Flexible DC technology is a core direction for next-generation traction substations, and three-level converters (key energy conversion units) have advantages over traditional two-level topologies. However, their P-O-N three-terminal DC-side topology introduces new faults (e.g., PO/ON bipolar short circuits, O-point-to-ground faults), making traditional protection strategies ineffective. In addition, wide system current fluctuation (0.5–3 kA) and offshore photovoltaic power fluctuation easily cause fixed-threshold protection maloperation, and the coupling mechanism among modulation strategies, DC bus capacitor voltage dynamics and fault current paths is unclear. To solve these bottlenecks, this paper establishes a simulation model of the system based on the PSCAD/EMTDC(A professional simulation software for electromagnetic transient analysis in power systems V4.5.3) platform, analyzes the transient electrical characteristics of three-level converters under traction and braking conditions for typical faults, clarifies the coupling mechanism, proposes a condition-adaptive fault identification strategy, and designs a reconfigurable fault energy handling system with bypass thyristors and adaptive crowbar circuits. Simulation and hardware-in-the-loop (HIL) experiments show that the proposed scheme completes fault identification and protection within 2–3 ms, suppresses fault peak current by more than 70%, limits DC bus overvoltage within ±10% of the rated voltage, and has good post-fault recovery performance. It provides a reliable and engineering-feasible protection solution for related systems and technical references for similar flexible DC system protection design. Full article

This study presents a novel numerical framework that elucidates the critical, yet previously underexplored, role of Marangoni vortex dynamics in determining the final surface quality during the laser polishing of Ti6Al4V (TC4). TC4 titanium alloy is widely used in aerospace, biomedicine, and other high-precision applications due to its excellent specific strength, corrosion resistance, and biocompatibility. However, its surface quality directly affects the fatigue life and service performance of parts, and traditional polishing methods suffer from low efficiency and high pollution. As a non-contact, controllable surface treatment technology, nanosecond laser polishing has demonstrated unique advantages in balancing processing efficiency and surface quality. This study systematically discussed the influence of key process parameters (spot overlap rate, laser power, and scanning times) on the nanosecond laser polishing of TC4 titanium alloy. It revealed the internal physical mechanism by analyzing the temperature and velocity fields and vortex dynamics during molten-pool evolution. It is found that the polishing effect is determined by the process parameters, which adjust the thermal–fluid coupling physical field (temperature distribution, melt flow, and vortex structure) in the molten pool. There is an optimal combination of parameters (spot overlap rate of 79%, laser power of 0.8 W, scanning speed of 5 m/min, scanning 3 times) that can place the molten pool in an optimal dynamic balance state and achieve effective flatness. The experimental results show that, under this parameter, the surface roughness of the specimen with an initial roughness of 1.223 μm is reduced by about 32%. The research further clarified the mechanism by which the initial roughness of the base metal influences the molten pool: the greater the initial roughness, the more pronounced the “peak shaving and valley filling” effect. Under the same parameters, the improvement rate of the specimen with the initial roughness of 1.623 μm could reach about 40%. This study not only establishes the optimized process window but also reveals the essential relationship between “process parameters–bath behavior–surface quality” from the level of the physical field of the molten pool. The findings provide a practical guideline for parameter optimization, directly applicable to the high-precision laser finishing of critical titanium components in the aerospace and biomedical industries. Full article

This study introduces a novel transcritical CO₂ pumpless Rankine power generation cycle based on the thermal compression concept, utilizing low-temperature renewable sources. The investigated theoretical system consists of a 5 kW_e unit incorporating the aforementioned working cycle coupled with a 50 m² evacuated tube solar collector arrangement installed on the rooftop of a multifamily house in Athens, Greece. The proposed innovative configuration is parametrically analyzed for different hot water inlet temperature levels ranging from 70 to 120 °C and its efficiency is compared to the typical Organic Rankine Cycle (ORC) topology employing different conventional refrigerants. The energetic assessment is made using validated mathematical models developed in MATLAB integrating the CoolProp library. The derived results show that the investigated topology increases the performance figures compared to the baseline system for all the examined refrigerants, leading up to over 15% thermal efficiency enhancement for operation under low heat source temperatures. Finally, the year-round operation of the proposed system generates up to 5221 kWh/year for the building. Full article

Traditional multiple-input multiple-output (MIMO) systems are confronted with significant challenges in realizing ubiquitous connectivity for sixth-generation (6G) networks, particularly in environments characterized by severe signal blockage and dynamic co-mobility. While aerial intelligent reflecting surfaces (AIRS) offer a promising paradigm to address these difficulties, the existing channel models often fail to capture fast channel changes, thereby leading to inefficient phase optimization in time-varying scenarios. To address these limitations, a geometric MIMO channel model is proposed for AIRS-assisted communications. This model comprises an indirect link from the base station (BS) via the AIRS to the receiver (Rx) and a direct BS-Rx link, whose direct propagation environment is rigorously characterized by a one-cylinder model specifically designed to tackle the complexities of dynamic co-mobility and intricate propagation. A joint optimization problem is formulated to maximize the achievable rate by optimizing the transmitted signal’s covariance matrix and the AIRS phase shift. Subsequently, an iterative algorithm employing the projected gradient method (PGM) is proposed for its solution, which is tailored for efficient operation in time-varying environments. Furthermore, expressions for the space–time correlation function and Doppler power spectrum are derived to evaluate the overall channel properties. Significant enhancements in achievable rates are demonstrated by AIRS, with substantial gains being observed even for a small number of reflecting elements. Consequently, crucial guidance for the design of robust AIRS-assisted MIMO systems is provided by these findings, and the broad applicability of the proposed algorithm is thereby confirmed. Full article

With the core advantages of high energy efficiency, high power density, and reliable operation, high-voltage permanent magnet motors have become the mainstream development direction of modern motor technology. However, the risk of demagnetization caused by excessive temperature increases in permanent magnets has become a key bottleneck restricting motor performance and operational reliability, which makes research on the flow and heat transfer characteristics of motor cooling systems of great engineering value. Taking the 710 kW high-voltage permanent magnet motors as the research object, this study established a global flow field mathematical model covering the internal and external air duct cooling systems of the motor based on the theories of computational fluid dynamics and numerical heat transfer, and systematically analyzed the flow characteristics and distribution laws of cooling air. The thermal–fluid coupling numerical method was employed to simulate the temperature field of the motor, and the overall temperature distribution of the motor, temperature gradient of key components, and maximum temperature value were accurately obtained. To verify the validity of the established model, a test platform for the cooling system performance was designed and built. Measuring points for wind speed, air temperature, and component temperature were arranged at key positions, such as the stator radial ventilation ducts, and experimental tests were conducted under the rated operating conditions. The results show that the flow field distribution of the internal and external air ducts of the motor is reasonable and that the cooling air flows uniformly, with the external and internal circulating air volumes reaching 1.2 m³/s and 0.6 m³/s, respectively, which meets the heat dissipation requirements. The maximum temperature of 95 °C occurs in the stator winding area, and the maximum temperature of the permanent magnets is controlled within the safe range of 65 °C. The simulation results were in good agreement with the experimental data, with an average relative error of only 4%, which fell within the engineering allowable range, thus verifying the accuracy and reliability of the established global model and thermal–fluid coupling calculation method. This study reveals the thermal–fluid coupling transfer mechanism of high-voltage permanent magnet motors and provides a theoretical basis and engineering reference for the optimal design, precise temperature rise control, and reliability improvement of motor cooling systems. Full article

The assessment of reliability in non-repairable subsystems of mining electronic equipment represents a computationally challenging problem, particularly for complex and highly connected structures. This study presents a systematic comparative analysis of several deterministic approaches for reliability estimation, focusing on their computational efficiency, accuracy, and applicability. The investigated methods include classical boundary techniques (minimal paths and cuts), analytical decomposition based on the Bayes theorem, the logic–probabilistic method (LPM) employing triangle–star transformations, and the algorithmic Structure Convolution Method (SCM), which is based on matrix reduction of the system’s connectivity graph. The reliability problem is formally represented using graph theory, where each element is modeled as a binary variable with independent failures, which is a standard and practically justified assumption for power electronic subsystems operating without common-cause coupling. Numerical experiments were carried out on canonical benchmark topologies—bridge, tree, grid, and random connected graphs—representing different levels of structural complexity. The results demonstrate that the SCM achieves exact reliability values with up to six orders of magnitude acceleration compared to the LPM for systems containing more than 20 elements, while maintaining polynomial computational complexity. Qualitatively, the compared approaches differ in the nature of the output and practical applicability: boundary methods provide fast interval estimates suitable for preliminary screening, whereas decomposition may exhibit a systematic bias for highly connected (non-series–parallel) topologies. In contrast, the SCM consistently preserves exactness while remaining computationally tractable for medium and large sparse-to-moderately dense graphs, making it preferable for repeated recalculations in design and optimization workflows. The methods were implemented in Python 3.7 using NumPy and NetworkX, ensuring transparency and reproducibility. The findings confirm that the SCM is an efficient, scalable, and mathematically rigorous tool for reliability assessment and structural optimization of large-scale non-repairable systems. The presented methodology provides practical guidelines for selecting appropriate reliability evaluation techniques based on system complexity and computational resource constraints. Full article

In a world of over 8.2 billion people, the land footprint of any infrastructure has become a critical factor in sustainable spatial planning. In the case of wind energy deployment, land use primarily involves hardstands, access roads, and interconnection infrastructure. This study focuses on Greece, a country with complex mountainous terrain, where Wind Power Stations are predominantly installed along ridgelines and slopes. Using GIS analysis based on digitization of actual on-site infrastructure, we measured the land coverage of wind energy facilities with a total installed capacity of nearly 2.6 GW. We found an average land-use intensity of 0.33 hectares per megawatt (ha/MW), placing it near the lower end of the range reported in international literature. For the subset of projects with available energy yield data, the value was 1.58 square meters per megawatt-hour (m²/MWh). This approach provides one of the largest, nationally representative, infrastructure-based estimates of actual wind energy land use in complex terrain. Applying these findings to the onshore wind deployment targets of Greece’s National Energy and Climate Plan (NECP) for 2030 and 2050, we estimate that only 0.02–0.03% of the country’s land area will be occupied by wind energy infrastructure. By comparison, lignite mining has already transformed approximately 0.13% of the national territory—almost four times more land than projected for wind energy use in 2050. Further spatial analysis was conducted to identify the land use categories associated with wind energy infrastructure, while for the subset of projects located within Natura 2000 protected areas, the types of affected habitats were also examined. Treating land coverage as a standalone proxy for environmental impact should be avoided; the study demonstrates the need for a context-sensitive interpretation of land use, accounting for ecological context, land-use compatibility, and positive co-benefits, such as improved forest accessibility, fire prevention works and recreation parks. Repowering maximizes land efficiency by extending wind farm lifetimes without expanding their footprint. Full article

Direct solar photovoltaic to electrolyser systems offer a promising pathway for producing low-carbon hydrogen, yet their performance and scalability remain limited by challenges that arise when variable solar generation is coupled to electrochemical conversion, with unresolved implications for electrolyser lifetime and hydrogen production cost. This review synthesises recent advances in photovoltaic technologies, electrolyser development and emerging deployment configurations to evaluate the technical, operational and environmental factors that shape system feasibility. The assessment draws on findings from experimental studies, modelling frameworks and techno-economic analyses to examine photovoltaic efficiency losses, thermal and material degradation, high-resolution intermittency effects, electrolyser dynamics, degradation mechanisms and storage interactions, and their combined influence on usage-dependent lifetime and cost behaviour. The results show that fluctuating solar input reduces conversion efficiency, increases transient overpotentials and accelerates degradation in both photovoltaic modules and electrolyser stacks. Technology-specific trade-offs persist, with alkaline water electrolysis constrained by limited flexibility, proton exchange membrane electrolysis by reliance on scarce catalyst materials, and anion exchange membrane and solid oxide electrolysis systems requiring further validation under real-world variability. Floating photovoltaic systems and agrivoltaics expand deployment opportunities but introduce additional constraints related to water quality, ecological impacts and power variability. Overall, the review finds that system-level integration, dynamic modelling, degradation-aware design and coordinated storage strategies are essential to unlocking reliable and scalable solar-to-hydrogen production. Full article

Battery-electric residential storage systems can increase the self-consumption of photovoltaic (PV) generation; however, economical sizing typically requires a high-resolution time series of PV production and household load behind the meter. In practice, such data are often unavailable. This work therefore presents a simulation model for determining the economically optimal residential storage capacity based exclusively on smart-meter data at the point of common coupling (PCC), i.e., hourly import and export time series. Economic performance is assessed using net present value (NPV) over a multi-year evaluation horizon. In addition, technical constraints (SoC limits, power limits, charging/discharging efficiencies) as well as capacity degradation are considered via a semi-empirical aging model. For validation, a reproducible reference scenario is constructed using PVGIS generation data and the standard load profile H23, enabling a direct comparison between the conventional approach (consumption/generation) and the PCC approach (import/export). The results show that the capacity optimum can be reproduced consistently using PCC data, even under smart-meter-like integer kWh quantization. At the same time, large parts of the investigated parameter space indicate that, under the assumed scenarios, foregoing a storage system is often not economically sensible. Sensitivity analyses further highlight the strong impact of load shifting, in particular due to the charging time of electric vehicles. A case study using real PCC measurement data, together with a two-week-window analysis, demonstrates practical applicability and robustness under limited measurement durations. Full article

The global energy crisis driven by an 80% reliance on fossil fuels and the urgent need to reduce greenhouse gas emissions demands the exploration of sustainable biotechnological alternatives. This study addresses a critical knowledge gap regarding the integration of fungal secondary metabolites into bioelectrochemical energy systems, as these compounds have traditionally been investigated for pharmacological purposes. The methodology involved a documentary analysis using the Scopus database (2000–2025), applying a search equation that combined terms such as “secondary metabolite”, “fungi”, and “bioenergy”. Data processing was conducted using R Studio (R 3.6.0+), VOSviewer (1.6.20) for collaboration networks, and Plotly Studio (v6.5.0) for interactive visualizations. Key findings revealed that redox mediators such as quinones and organic acids derived from Aspergillus niger enhanced electron transfer efficiency by 35%, achieving power densities of 1.2 W/m². Meanwhile, Penicillium chrysogenum reduced internal electrode resistance by 40%. Additionally, the “xeno-fungosphere” system achieved 97.9% herbicide removal and generated 9.3 µW/cm². Notably, biosynthesized bis-quinones were successfully applied in redox flow batteries, reaching a capacity of 1.58 Ah/L. In conclusion, the study identified a scientific shift from pharmacological applications toward energy metabolism and sustainability, positioning fungi as critical components for the future efficiency of bioelectrical technologies. Full article

Crawler cranes suffer from power mismatch in their electro-mechanical–hydraulic main drive system under sudden load variations and multi-action coupling conditions, which results in low energy utilization efficiency. This study establishes an electro-hydraulic closed-loop transfer function model and proposes a synthetic deviation-driven proportional–integral–derivative power matching control strategy to regulate hydraulic pump displacement. Experiments on a 1250 t crawler crane show that the model is reliable, with the coefficient of determination R² between simulation and experimental data exceeding 0.94. The strategy improves power matching by 27.33% for the engine–pump link and 18.9% for the full link in single-action conditions, and 12.67% and 8.7% in compound-action conditions. After control, the engine–pump power matching coefficient stabilizes around 1.04 and the full-link coefficient stabilizes within 1.05 to 1.21 under single-action conditions, while under compound-action conditions, the engine–pump coefficient stabilizes within 1.05 to 1.15 and the full-link coefficient stabilizes within 1.0 to 1.25. The control strategy suppresses power mismatch and optimizes system stability and energy efficiency, which provides a technical reference for the optimization of electro-mechanical–hydraulic drive systems in heavy machinery. Full article

European bioeconomy policies stress the need for responsible, efficient feedstock use and timely, comprehensive data on ecosystems and bioeconomic activities. This paper addresses the data gap by: (i) providing holistic county-level (sub-NUTS3) biomass maps for the Republic of Ireland (RoI), covering primary feedstocks (PFs) and secondary feedstocks (SFs, i.e., by-products and waste); (ii) identifying feedstock uses during the study period. In total, 221 feedstocks were mapped: 85 solid PFs (approx. 43 million tonnes dry matter (tDM) nationally) and 136 solid SFs (approx. 6 million tDM nationally), plus 6 liquid PFs (approx. 18 thousand million m³ nationally) and 8 liquid SFs (approx. 39 thousand million m³ nationally). The mapping indicates that environmentally sustainable bio-based value chains (BBVCs) requiring large amounts of solid or liquid SF should prioritise processing sites near major feedstock sources in the southeast and southwest of the RoI. The northwest and east coast have the lowest availability, while the west and midlands have the most variety in quantity and type of feedstock. Counties with abundant feedstocks do not necessarily have high feedstock diversity, except for Cork. Granular sub-NUTS3 mapping of quantities and fate provides a powerful foundation for future feedstock strategies and empowers stakeholders to design innovative BBVCs. Full article