Search Results (176)

Small multi-rotor UAVs face endurance limitations during long-range missions due to high rotor energy consumption and limited battery capacity. This paper proposes a folding-wing range extender integrating a sliding-rotating two-degree-of-freedom folding wing—which, when deployed, quadruples the fuselage length yet folds within its profile—and a tail-thrust propeller. The device can be rapidly installed on host small multi-rotor UAVs. During cruise, it utilizes wing unloading and incoming horizontal airflow to reduce rotor power consumption, significantly extending range while minimally impacting portability, operational convenience, and maneuverability. To evaluate its performance, a 1-kg-class quadrotor test platform and matching folding-wing extender were developed. An energy consumption model was established using Blade Element Momentum Theory, followed by simulation analysis of three flight conditions. Results show that after installation, the required rotor power decreases substantially with increasing speed, while total system power growth slows noticeably. Although the added weight and drag increase low-speed power consumption, net range extension emerges near 15 m/s and intensifies with speed. Subsequent parametric sensitivity analysis and mission profile analysis indicate that weight reduction and aerodynamic optimization can effectively enhance the device’s performance. Furthermore, computational fluid dynamics (CFD) analysis confirms the effectiveness of the dihedral wing design in mitigating mutual interference between the rotor and the wing. Flight tests covering five conditions validated the extender’s effectiveness, demonstrating at 20 m/s cruise: 20% reduction in total power, 25% improvement in endurance/range, 34% lower specific power, and 52% higher equivalent lift-to-drag ratio compared to the baseline UAV. Full article

Suction anchors are widely used in marine engineering because of their easy installation, cost-effectiveness, and excellent load-bearing capacity. However, existing research on their bearing capacity has primarily focused on homogeneous soils, which fails to adequately reflect the actual bearing capacity of layered seabed soils. Therefore, this study conducted a series of numerical simulations to investigate the pullout bearing capacity of suction anchors subjected to inclined loads in upper-stiff–lower-soft layered clay. By considering the clay strength (S_um/kD) and soil layer thickness ratio (T_h/L, T_c/L), this study systematically explores the influence of the optimal centerline loading depth (Z_cl,opt), uniaxial ultimate bearing capacity (H_ult and V_ult), and the VH failure envelope of suction anchors. The results indicate that the layer thickness ratio T_h/L of lightly overconsolidated clay (LOC) is the key factor influencing the Z_cl,opt and ultimate bearing capacity H_ult and V_ult. An increase in T_h/L significantly enhances the pullout resistance of suction anchors, which primarily results from the combined enhancement effect of lateral friction resistance and end resistance at the anchor–soil interface. The layered clay has a distinct influence on the horizontal and vertical bearing capacities of suction anchors. Based on the results of parameter analysis, a conservative analytical expression for the lower bound of the VH failure envelope curve is further proposed. The research conclusions provide a theoretical basis and engineering practice guidance for the optimized design and safety assessment of suction anchors in layered soil. Full article

Global restrictions related to climate change and the increasing demand for electricity are accelerating the transition from conventional energy sources, such as oil, gas, and coal, to renewable options like wind, solar, and biomass. Among these, solar photovoltaic (PV) systems are highly promising, offering clean and reliable electricity generation. In support of the Maldives’ target to achieve net-zero emissions by 2030, the deployment of PV systems has significantly increased. However, there is still a lack of detailed operational performance assessment specific to the Maldives. This study aims to address this gap and fulfill three main objectives. Firstly, to evaluate the real performance of six selected rooftop grid-connected PV systems installed in the Greater Malé region, Maldives. Secondly, the ideal performance ignoring shading, soiling, and aging effects of the selected systems on the islands are simulated, and the optimal orientation angles are estimated. Finally, the real and predicted performances are compared, and a module-level analysis is conducted to pinpoint the area for improving the performance of the rooftop PV systems installed on the island. The well-known International Electro-Technical Commission (IEC) standard, IEC 61724, is used for operational performance assessment, in addition, the PVsyst simulation tool and the S-Miles microinverters monitoring system are implemented for simulation and module-level analysis, respectively. In 2023, the six studied sites recorded annual daily averages of 2.52–4.45 kWh/kWp/day for yield factor, 0.98–2.9 h/day for total loss, 45.19–82.13% for performance ratio (PR), 10.51–18.55% for capacity utilization factor (CUF), and 7.69–15.94% for system efficiency. The actual performance was found to be lower than the simulated ideal values. The main reasons for this reduction were near-shading and microinverter connection issues. The orientation study showed that a 5° tilt angle with an azimuth between −25° and 5° gives the best results for fixed PV installations. These findings can guide better PV system design and operation in the Maldives and other similar climates. Full article

South African small, medium and micro enterprises, particularly township-based spaza shops, face barriers to adopting solar photovoltaic systems due to upfront costs, regulatory uncertainty, and limited technical capacity. This article presents a reproducible methodology for evaluating and selecting solar photovoltaic systems that jointly considers economic, technological, and legal/policy criteria for such enterprises. We apply multi-criteria decision making using the Multi-Objective Optimization by the Ratio Analysis method, integrating simulation-derived techno-economic metrics with a formal policy-alignment score that reflects registration requirements, tax incentives, and access to green finance. Ten representative system configurations are assessed across cost and benefit criteria using vector normalization and weighted aggregation to enable transparent, like-for-like comparison. The analysis indicates that configurations aligned with interconnection and incentive frameworks are preferred over non-compliant options, reflecting the practical influence of policy eligibility on investability and risk. The framework is lightweight and auditable, designed so that institutional actors can prepare shared inputs while installers, lenders, and shop owners apply the ranking to guide decisions. Although demonstrated in a South African context, the procedure generalizes by substituting local tariffs, irradiance, load profiles, and jurisdiction-specific rules, providing a portable decision aid for small enterprise energy transitions. Full article

This study investigates the axial performance of continuous helix screw piles compared to helical piles through full-scale compression and tension load testing in layered soils. Twenty-three piles were installed and tested. The results demonstrate that screw piles can achieve considerable axial capacity with lower installation torque than helical piles, particularly under tensile loading. The capacity-torque relationship for screw piles was more consistent across both compression and tension, likely due to reduced soil disturbance from the smaller helix projection. Strain gauge measurements indicated that screw piles act primarily as friction piles with the threaded shaft carrying most of the load, especially in stiff clay. On the other hand, the smooth portion of the pile shaft contributed only marginally to resistance in compression and none in tension. The calculated capacity based on theoretical equations aligned well with field results in compression, with screw piles best represented by cylindrical shear failure in sand and a combination of cylindrical shear and individual bearing failure in clay. However, there is greater variability between calculated and measured uplift capacity, possibly due to soil disturbance effects. Additionally, the commonly used helix spacing ratio (S/D) was found to be less applicable to screw piles in predicting failure mode due to their smaller shaft-to-helix diameter difference. Full article

With the growing global deployment of Fiber-to-the-Home (FTTH) networks driven by the demand for ensuring high-capacity broadband services, mobile network operators (MNOs) face challenges of excessive energy consumption (EC) of wired optical access networks (OANs). This paper presents a comprehensive review of methods aimed at improving the energy efficiency (EE) of wired access passive optical networks (PONs) and active optical networks (AONs). The most important energy management and power-saving methods for Optical Line Terminals (OLTs) and Optical Network Units (ONUs), as key OAN components, are overviewed in the paper. Special attention in the paper is further given to analyzing the impact of a constant increase in the number of subscribers and average data rate per subscriber on global instantaneous power and annual energy consumption trends of FTTH Gigabit PONs (GPONs) and FTTH point-to-point (P-t-P) networks. The analysis combines the real ONU/OLT device-level power profiles and the number of installed OLT and ONU devices with data traffic and subscriber growth projections for the period 2025–2035. A comparative EE analysis is performed for different MNO FTTH OAN architectures and technologies, point-of-presence (PoP) subscriber capacities, and GPON-to-P-t-P subscriber distribution ratios. The findings indicate that different FTTH PON and AON architectures, FTTH technologies, and PON-to-AON subscriber distributions can yield significantly different EE gains in the future. This review paper can serve as a decision-making guide for MNOs in balancing performance and sustainability goals, and as a reference for researchers, engineers, and policymakers engaged in designing next-generation wired optical access networks with minimized environmental impact. Full article

The development of green technologies in recent years in the field of wind energy conversion into electricity implies a technology transfer from the static switching field to the energy field. This paper presents a wind turbine simulator using a hardware solution following the energy conversion of a real turbine. We implemented this solution for educational and research purposes to train students in the process of electrical conversion in wind turbines. For the simulation, we chose an E82/2300 turbine, installed by ENERCON in a nearby geographical area. The turbine has the capacity to generate 2300 kW of electricity into grids. It has a direct coupling structure of the propeller to the generator. The solution is implemented on a multi-processor architecture with analog signal processing. The structure of a wind turbine is divided into three consecutive blocks, namely TUGEN, DCDC4X, and SIN3F. Each block of the simulator is designed with electronic components. The input and output signals of these blocks have similar waveforms to real signals, and their succession is interconditioned by process parameters. The innovation of the proposed solution is provided by software engineering applied to a hardware structure. The ratio between the simulated and real values is 1:60 in order to visualize the signals on a digital oscilloscope, mainly for educational purposes. Full article

To address voltage stability challenges in power grids with high penetration of distributed generation (DG), this paper proposes an optimal configuration method for reactive power compensation devices. Voltage-weak nodes are first identified using a novel short-circuit ratio (SCR) index. An average electrical distance metric is then introduced to determine optimal installation nodes by computing distances between candidate nodes and weak nodes. Subject to constraints on maximum compensation capacity and allowable DG disconnection limits, MATLAB simulations validate the optimal configuration. Case studies on modified IEEE 9, 14 and 39 bus systems confirm the method’s efficacy: DG tripping due to low-/high-voltage ride-through failures is effectively mitigated, with minimum fault voltage increasing by 0.05–0.08 p.u. and voltage recovery time reduced by 0.15–0.8 s. Full article

Many existing reinforced concrete (RC) frames with brick infill walls are vulnerable to earthquake damage, particularly when the walls contain window openings that reduce the lateral resistance. This study aims to examine the seismic performance of RC frames strengthened with U-shaped precast concrete (PC) wall panels. In the proposed method, the window-containing brick infill walls within the RC frames are replaced with factory-fabricated U-shaped PC wall panels, thereby converting the infill into a strong and rigid structural element while preserving the openings. The panels are anchored to the RC frame using post-installed anchors inserted through predrilled holes, allowing for rapid and secure installation with minimal on-site work. To validate the method, five full-scale, one-bay, one-story RC frames were constructed and tested under reversed cyclic lateral loading. Three frames were strengthened with U-shaped PC wall panels of varying thicknesses and large openings. Displacement-controlled cycles following ACI 374.1-05 (R7.0) were applied, with three cycles at each drift ratio stage, and no axial load was applied to the columns. Compared with the reference specimen with a U-shaped brick wall, the strengthened frames exhibited up to 3.29 times higher lateral strength, 4.39 times higher initial stiffness, and 4.33 times greater energy dissipation capacity. These findings demonstrate that the proposed strengthening technique significantly enhances seismic resistance while maintaining the architectural openings, offering a practical and efficient solution for upgrading low-rise RC buildings. Full article

This study focuses on optimizing the flow field uniformity within a vertical honeycomb wet electrostatic precipitator (WESP), which is a critical prerequisite for achieving high particulate removal efficiency. For a vertical honeycomb WESP with an air capacity of 25,000 m³/h, the internal flow field is optimized by adjusting the opening ratio and aperture ratio of the airflow equalizing plate, installing additional deflector plates, and adding additional airflow equalizing plates at strategic locations. The optimization reduces the velocity relative standard deviation at the anode inlet section to 0.14. Through 1:1-scale equipment construction and testing, the particle concentration at the outlet is stabilized below 10 mg/Nm³, with an average removal efficiency of 95.88%—a 5.7% improvement over the original model. This study solves the design dependency on empirical guidance for vertical honeycomb WESP in the food industry, providing a green technology paradigm for low-carbon industrial emissions. Full article

Addressing the issue of stress concentration at the toe of steel plate shear walls, which is susceptible to local buckling and brittle failure under seismic loading, this paper innovatively proposes a disc spring-laminated rubber energy dissipation device (DSLRDD) newly designed for application at the wall toe of the shear wall structures. Firstly, the structure characteristics and energy dissipation principle of the DSLRDD are described. Secondly, the finite element model of the DSLRDD is established in ABAQUS. Furthermore, the optimal design parameters’ values of DSLRDD are analyzed and given by taking the stacking arrangement of disc springs, the thickness ratio of steel plate to rubber layer, and the yield strength of steel plate as three main parameters. It is recommended that in DSLRDD, the disc spring stacking arrangement adopts either two pieces in series or a composite of series–parallel. At the same time, the range of the thickness ratio between the steel plate and the rubber layer is defined as being between 1.25 and 2.5, and the yield strength value of the steel plate is determined as 400 MPa. Finally, to verify the energy dissipation capacity of the DSLRDD, a double corrugated steel plate shear wall (DCSPSW) is taken as the experimental structure. The model has been verified against the test data, with a maximum damping force error of 14.4%, ensuring reliable modeling. DSLRDD models with the disc spring stacking arrangements of two pieces in series and composite of series–parallel were established, respectively, and they were installed at the toe of the DCSPSW. The seismic performance of the DCSPSW before and after the installation of two different DSLRDDs is studied. The results show that the DSLRDDs have obvious energy absorption capabilities. The energy dissipation factors of DCSPSW before and after installing DSLRDD were increased by 10.0% and 8.9%, respectively. DCSPSW with DSLRDD exhibits better plasticity and bearing capacity under seismic action, and the stress and deformation are mainly concentrated on the DSLRDD instead of the wall toe. Moreover, it is recommended to use the stacking arrangement of two series disc springs with a simple structure. In conclusion, the DSLRDD has excellent energy dissipation capacity and can be fully applied to practical projects. Full article

This paper investigates whether carbon payments are sufficient to entice private landholders to invest in the rehabilitation and protection of coastal wetlands as a nature-based climate solution. Ecologically intact coastal wetlands, such as mangroves and saltmarshes, are capable of sequestering and storing large amounts of carbon. Reinstating ecological functionality of degraded coastal wetlands may be achieved by installing conservation fences that exclude hard-hoofed domestic and feral animals. This research integrates ecological, technical and economic data to ascertain whether conservation fencing could represent a financially viable investment for coastal landholders in the Australian context, if restored wetlands attracted carbon payments. Data gleaned through literature review and expert interviews about technical fencing requirements, contemporary costs and potential blue carbon income are consolidated into scenarios and tested using cost–benefit analysis. Payback periods are calculated using deterministic parameters. Risk-based cost–benefit analysis accounts for uncertainty of ecological and price parameters; it provides probability distributions of benefit–cost ratios assuming an expert-agreed economic lifespan of conservation fences. The results demonstrate that the payback period and benefit–cost ratio are highly sensitive to wetlands’ carbon sequestration capacity, fencing costs and the carbon price going forward. In general, carbon payments on their own are likely insufficient to entice private landholders to protect coastal wetlands through conservation fencing, except in circumstances where restored wetlands achieve high additional carbon sequestration rates. Policy measures that reduce up-front costs and risk and remuneration of multiple ecosystem services provided by restored wetlands are required to upscale blue carbon solutions using conservation fencing. The research findings bear relevance for other conservation and land-use contexts that use fencing to achieve sustainability goals and generate payments for ecosystem services. Full article

Photovoltaic (PV) modules undergo comprehensive testing to validate their electrical and thermal properties prior to market entry. These evaluations consist of durability and efficiency tests performed under realistic outdoor conditions with natural climatic influences, as well as in controlled laboratory settings. The overall performance of PV cells is affected by several factors, including solar irradiance, operating temperature, installation site parameters, prevailing weather, and shading effects. In the presented study, three distinct PV modules were analyzed using a sophisticated large-scale steady-state solar simulator. The current–voltage (I-V) characteristics of each module were precisely measured and subsequently scrutinized. To augment the analysis, a three-layer artificial neural network, specifically the multilayer perceptron (MLP), was developed. The experimental measurements, along with the outputs derived from the MLP model, served as the foundation for a comprehensive global sensitivity analysis (GSA). The experimental results revealed variances between the manufacturer’s declared values and those recorded during testing. The first module achieved a maximum power point that exceeded the manufacturer’s specification. Conversely, the second and third modules delivered power values corresponding to only 85–87% and 95–98% of their stated capacities, respectively. The global sensitivity analysis further indicated that while certain parameters, such as efficiency and the ratio of V_oc/V, played a dominant role in influencing the power-voltage relationship, another parameter, U, exhibited a comparatively minor effect. These results highlight the significant potential of integrating machine learning techniques into the performance evaluation and predictive analysis of photovoltaic modules. Full article

Helical piles are widely used in geotechnical engineering, and their rapid installation and service reliability have attracted significant interest from the offshore wind industry. These piles are frequently subjected to cyclic loading in complex marine environments. Although the cyclic bearing behavior of helical piles has been studied, most research has focused on soil properties and loading conditions, with a limited systematic analysis of plate parameters. Moreover, the selection of plate parameters is not explicitly defined. As a crucial preliminary step in the capacity calculation, it is vital for the design of helical piles. To address this gap, the present study combines physical modeling tests and finite element simulations to systematically evaluate the influence of plate parameters on their cyclic bearing behavior. The parameters investigated include the plate depth, the plate diameter, plate spacing, and the number of plates. The results indicate that, under the same embedment conditions, cumulative displacement increases with the plate depth, with a critical embedment depth ratio of H_cr/D = 6 under cyclic loading conditions, but decreases with the number of plates. Axial stiffness increases with the plate depth, diameter, and number of plates, with an increase ranging from 0.5 to 3.0. However, the normalized axial stiffness decreases with these parameters, reaching a minimum value of 1.63. The plate spacing has a minimal influence on cyclic bearing behavior. Additionally, this study examines the evolution of displacement and stiffness parameters over repeated cycles in numerical simulations, as well as the post-cyclic pullout capacity of the helical pile foundation, which varies between −5% and +12%. Full article

Given the widespread use of gas-fired boilers and combined heat and power (CHP) units in existing district heating (DH) systems, this study investigates the integration of medium-scale heat pumps (HPs) into such configurations. Fifteen DH system variants were analysed, differing in installed HP capacity, operational strategies, and the synchronisation of heat and electricity production with thermal demand. A dynamic simulation model incorporating real-world equipment performance was developed to assess energy efficiency, environmental impact, and economic viability under three distinct energy price scenarios. The results demonstrate that an HP sized to 17% of the total heating capacity of the DH system achieves a 54% decrease in primary energy consumption and a 68% decrease in emissions compared to the base system. Larger HP capacities enhance environmental performance and increase the share of renewable energy but also entail higher investment. An economic analysis reveals that electricity-to-gas price ratios strongly influence the cost-effectiveness of HP integration. Under favourable electricity pricing conditions, systems with HP operational priority achieve the lowest levelized cost of heating. The most economically viable configuration consists of 600 kW HP and achieves a payback period of 4.7 years. The findings highlight the potential for HPs to decarbonize DH systems while emphasising the importance of market conditions and system design in ensuring economic feasibility. Full article