Search Results (184)

The increasing demand for sustainable and lightweight structural systems has motivated the development of alternative materials for wind turbine tower applications, where conventional steel structures are associated with high material consumption and environmental impact. In this study, a novel steel-reinforced recycled thermoplastic composite system is proposed as an alternative structural solution. To enable the design and practical application of such composite systems, the mechanical properties of the recycled thermoplastic matrix were experimentally characterized. Compression and tensile tests revealed average yield strengths of approximately 32 MPa in compression and 7.8 MPa in tension. To account for the environmental conditions encountered in field applications, the temperature-dependent mechanical behavior of the material was investigated. Since the critical mechanical response of the thermoplastic matrix in the composite system is governed by compression rather than tension, the study was limited to compression tests under elevated temperatures. The results show that the compressive yield strength decreases to approximately 31 MPa at 55 °C. An analytical model based on the transformed-section approach was also developed to predict the flexural behavior of the composite section and was validated through three-point bending tests, with an analytically predicted yield load of approximately 31.5 kN showing good agreement with experimental results. To assess structural applicability at a larger scale, a full-scale composite wind turbine tower was designed and manufactured, and its dynamic performance was evaluated through field measurements under natural wind loading conditions. The results indicate that the composite tower exhibits comparable dynamic behavior to a conventional steel tower, with a first natural frequency of approximately 3.08 Hz compared to 2.89 Hz for the steel tower, along with enhanced damping characteristics. These findings demonstrate that steel-reinforced recycled thermoplastic composites offer a promising and sustainable alternative for wind turbine tower applications, with potential for broader use in structural systems. Full article

Turbulent wind conditions pose significant challenges to the blade structural reliability of small wind turbines. Different from the authors’ previous work, which mainly focused on the output characteristics of the same 5 kW prototype under variable inflow conditions, this study combines field-test observations with numerical simulations to further investigate the blade structural dynamic responses of a 5 kW variable-pitch wind turbine under both uniform inflow and extreme wind conditions. Owing to the unique pitch-regulation mechanism of the proposed turbine, two pitch-control modes, namely conventional power-limited pitch control and active stall pitch control, are comparatively analyzed to clarify their effects on blade load, stress, and displacement responses. The results indicate that, under uniform inflow conditions, stresses are concentrated near the leading edge of the blade mid-span, while the maximum displacement occurs at the blade tip. Both stress and displacement decrease with increasing conventional pitch angle. Under extreme wind conditions, increasing gust intensity causes a nonlinear growth in blade loads and aggravates blade structural response. During active stall pitch control, the load distribution pattern is generally consistent with that under conventional pitch control, whereas the blade structural response first decreases and then increases as the pitch angle is adjusted toward negative values. Under uniform inflow at the rated wind speed of 11 m/s, the blade-tip maximum displacement decreased from 56.51 mm under the +6° power-limited/reference pitch condition to 48.42 mm under the −6° active-stall-related pitch condition, corresponding to a reduction of approximately 14.3%. These results provide a useful reference for the blade structural design and control optimization of distributed small wind turbines under complex inflow conditions. Full article

Grid-forming converters, with their voltage-source characteristics, can independently provide voltage support and thus have become a critical supporting technology for new-type power systems. However, they suffer from overcurrent risks and insufficient voltage support capability during grid faults. To overcome these shortcomings, this paper proposes an adaptive transient-voltage support strategy for grid-forming PMSG wind turbines based on DC capacitor-voltage synchronization. First, the inertia synchronization and autonomous-voltage support mechanisms of such grid-forming wind turbines are analyzed. Second, based on power-flow equations and the grid-forming topology, key factors affecting the grid-connected voltage during faults are identified, and an adaptive voltage-support strategy using fuzzy control is developed. Finally, a grid-forming wind power system is modeled on the PSCAD/EMTDC platform, where the proposed strategy raises the minimum PCC voltage to 0.62 p.u. and increases reactive power injection by 0.13 p.u. under a 70% deep sag, successfully fulfilling low-voltage ride-through requirements. Full article

During the worldwide energy transition, wind power has become a leading development direction. Compared to large-scale horizontal-axis wind turbines (HAWTs), small-scale vertical-axis wind turbines (VAWTs) show potential, lack yaw mechanisms, adapt to wind direction changes, and are cost-effective. However, small-scale VAWTs operate in the near-surface atmospheric boundary layer and are sensitive to low-temperature and high-humidity climates, which cause blade icing. Ice buildup leads to fluctuations in aerodynamic loads, reduces power output, and diminishes stability. This study focuses on the NACA-0018 airfoil, using a low-temperature wind tunnel platform to simulate freezing durations to obtain ice characteristics on the blade surface. Based on ice profiles, numerical models were developed. Computational fluid dynamics (CFD) techniques were used to perform unsteady simulations of aerodynamic performance at various icing durations, investigating the influence on the power coefficient. The results indicate that the effect of icing duration on the average power coefficient depends on TSR. At the 5 min icing stage, the optimal tip-speed ratio decreases. Icing deteriorates aerodynamic performance at high tip-speed ratios, while producing positive optimization effects at low tip-speed ratios. This paper reveals the variation patterns of aerodynamic performance and differentiated mechanisms during the icing process of small vertical-axis wind turbine blades, providing a theoretical basis and data support for the development of surface anti-icing technologies and safe, efficient operation in low-temperature environments. Full article

This study investigates the acoustic emission (AE) response and damage mode characteristics of ±45° glass fiber-reinforced polymer (GFRP) composites used in wind turbine blade shear webs under quasi-static tensile loading. It aims to establish the relationship between AE features and three typical damage mechanisms—matrix cracking, interfacial debonding, and fiber fracture—to support damage assessment and structural health monitoring. Quasi-static uniaxial tensile tests with synchronous AE monitoring are conducted on specimens with three orientations (0°, 45°, and 90°). AE features are selected using correlation analysis and principal component analysis, and the HAC-initialized K-means clustering method is employed for damage mode identification. The optimal number of clusters is determined to be three, according to the Davies–Bouldin index (DBI) and the Silhouette index (SI). The resulting low-, mid-, and high-frequency clusters are associated with matrix cracking, interfacial debonding, and fiber fracture, respectively. These interpretations are further supported by wavelet-based time–frequency analysis and microscopic fracture surface observations. Full article

This wind farm study provides a detailed and deep investigation into numerous aspects of both wind dynamics and the associated wind turbine performance via a wind data analysis utilizing an extrapolated timeframe of 50 years. The major wind characteristics assessed included wind speed and direction, flow inclination, turbulence intensity, and wind speed (average based on extremes) over the entire duration of the evaluated data set. A majority of study results indicated only narrow wind speed ranges (6.3 m/s to 7.0 m/s) for turbine operation within the wind farm. Higher turbine operation speeds than the average measured wind speed may significantly increase turbine energy output. Turbines were evaluated across numerous geographic locations, resulting in average flow inclination (−4.12° to 1.57°) from the vertical to horizontal directions. The variation in flow inclination indicates that there is a geographic component that likely creates a localized terrain impact on turbine performance. Similarly, the measurement of turbulence intensity was also assessed, which indicated elevated levels of turbine mechanical stress and additional requirements for turbine maintenance. Energy production analyses from each turbine in the wind farm exhibited various regions of energy loss, with the highest energy losses associated with select turbines. Full article

This work presents the development and validation of a modular low-power wind turbine emulator (WTE) specifically designed for academic research and distributed generation applications. The primary objective is to provide a flexible and cost-effective test bench capable of replicating the aerodynamic and mechanical performance of a bladed rotor without the need for wind tunnels or specific field conditions. The emulator integrates a 4.5 kW three-phase induction machine as the motor and a 1 kW permanent magnet synchronous generator (PMSG). The system is managed by an ARM Cortex M7 microcontroller, which gives instructions to a Siemens Sinamics Variable Frequency Drive (VFD) that is used for torque vector control, offering superior dynamic response to wind speed variations. The aerodynamic characteristics were previously derived using blade element momentum (BEM) theory and validated using MATLAB/Simulink simulations. Unlike traditional steady-state emulators, this study addresses dynamic behavior through an autonomous control algorithm that reduces mechanical stress and compensates for inertia differences. Experimental tests conducted in a grid-connected scenario using a commercial on-grid inverter showed high correlation between the emulator’s output and the field data of a real EOLOCAL AG1000 turbine. The results confirm the system’s reliability as a platform for evaluating power conversion systems and for future expansions, such as blade pitch control emulation. Full article

This paper aims to investigate the aerodynamic variation patterns of twin-rotor vertical-axis wind turbines (TR-VAWTs) considering phase interference under different solidities, and to reveal the interactive mechanism between solidity, phase interference, and aerodynamic loads of TR-VAWTs. This paper first establishes a phase interference aerodynamic analysis model for TR-VAWTs based on two-dimensional computational fluid dynamics (CFD) methods. Secondly, experimental results are used to verify the accuracy of the numerical model. Finally, the variation patterns of aerodynamic forces and wake characteristics of TR-VAWTs under different parameters (solidity, initial phase angle) are explored. The results show that: (1) Each turbine of the side-by-side TR-VAWTs exhibits an increase in the energy utilization coefficient (C_P) in comparison with a single rotor. (2) The phase angle exhibits similar influence patterns on the efficiency of TR-VAWTs with different solidities. As the phase angle varies within the range of 30° to 60°, the efficiencies of rotor 1 and rotor 2 under medium-to-high tip speed ratios are both improved, while within the range of 60° to 90°, the efficiencies of each rotor generally decrease. (3) When TR-VAWTs with different solidities are at intermediate phase angles (90° for two blades, 60° for three blades, and 45° for four blades), the efficiencies of each rotor are basically consistent, which is conducive to power transmission. (4) If the intermediate phase angle is adopted as the reference configuration, the pressure influence on the turbines is minimized, which can not only make the power output more balanced but also improve the wake characteristics to a certain extent. Full article

With the growth of urban zones and the increasing need for energy, the use of renewable energy solutions in the built environment becomes a must. Due to their small size and the ability to capture wind from any direction, vertical-axis wind turbines are an alternative to conventional wind energy generators. However, the use of these turbines in the built environment faces difficulties due to performance inefficiencies, particularly because of the intricate aerodynamic characteristics of the blades. This work investigates a method for increasing the efficiency of VAWTs by addressing blade-to-blade interactions using Computational Fluid Dynamics simulations. The research aims to improve turbine design for urban locations, which motivates the application context of the study. The present numerical model employs a uniform inflow to isolate blade–blade interaction mechanisms under controlled conditions. The paper presents a design that minimizes aerodynamic losses, decreases turbulence-induced drag, and increases overall energy capture efficiency by modeling different blade configurations and their interactions. The performance of four asymmetric configurations of blade chord and radius was numerically studied and compared to a symmetric configuration. Full article

For geotechnical structures with a strict control requirement of deformation, the high modulus and non-linear attenuation characteristics of the surrounding soil under small-strain conditions cannot be ignored during performance evaluation; the HSS constitutive model offers significant advantages over conventional approaches (e.g., Mohr–Coulomb) to describe the above soil behaviors. In this study, the theoretical framework of the HSS model, i.e., the yield function, hardening laws, and flow rule, is first elucidated. Subsequently, it is numerically implemented into the finite element software FssiCAS. The reliability of the FssiCAS software (Version 3.5) incorporating the HSS model is validated through a triaxial test and a physical test involving the horizontal loading of the monopile. Finally, taking the four-monopile jacket foundation of an offshore wind turbine (OWT) in Lianjiang County, China, as a representative, the HSS model is adopted to describe the mechanical behaviors of a seabed foundation. The horizontal bearing characteristics of the jacket foundation–seabed system under multi-angle horizontal loading are investigated, and the influence of the horizontal loading angle on the horizontal bearing capacity, jacket displacement, and seabed deformation is quantitatively elucidated. The results indicate that (1) the horizontal bearing capacity of the jacket is minimal when horizontal loading is along the diagonal of the four piles, representing the most severe loading case, and therefore, the horizontal bearing capacity of the jacket foundation–seabed system should be evaluated based on this case; and (2) the FE software FssiCAS has good reliability when dealing with pile–soil interaction problems involving complex geometries and complex mechanical behaviors of seabed soils. This study could provide technical support and an analysis platform for the design of jacket foundations for complex marine structures, such as OWTs. Full article

Seabed response and local scouring around pile groups under combined wave–current loading pose critical threats to the stability and long-term performance of offshore structures, particularly those supporting offshore renewable energy infrastructures. In this study, we present a systematic experimental investigation on the pore-water pressure and local scour around pile groups subjected to regular waves, combined regular wave–current conditions, and irregular waves generated using the JONSWAP spectrum under wave-only conditions. Pore-water pressures and seabed morphology were analyzed for different hydrodynamic conditions, pile spacings, and pile arrangements. The experimental results demonstrate that the presence and magnitude of current are the dominant factors controlling scour development. Increasing the current velocity from 0 to 0.25 m/s leads to a three (3) to five (5) times increase in maximum scour depth, whereas comparable variations in wave height and wave period produce relatively small effects. The direction of a current affects the location of maximum scour, with the wave–forward current condition promoting the development of an interconnected scour area within the pile array and wave–opposing current condition, shifting local scour toward downstream piles. Small-spaced piles ($G/D$ = 1) intensify hydrodynamic interactions and increase scour depth by approximately 30–40% compared with wider spacing. Irregular waves generate more spatially distributed but shallower scour than regular waves of comparable wave characteristics. These findings provide insights into the mechanisms governing seabed instability around pile group foundations and contribute to more sustainable design and operation of offshore infrastructure, such as offshore wind turbine foundations. Full article

The actual power curve of a wind turbine is essential for performance evaluation and operational optimization. However, SCADA data frequently contain various abnormal data points that limit their direct and effective use. Existing methods often fail to provide high-quality data for accurate power-curve fitting. Therefore, this paper proposes a comprehensive outlier cleaning method (QRD). This method incorporates the operational mechanisms of wind turbines and establishes preprocessing rules to effectively remove extreme outliers and bottom horizontal accumulation exhibiting distinct numerical characteristics. By leveraging the data distribution features in pitch angle–power and wind speed–power relationships, it implements horizontal and vertical quartile methods to eliminate mid-level accumulation and discrete outliers. A segmented regression-based outlier detection method with metrics adaptive to the power-curve distribution characteristics is proposed to clean residual outliers. Comparative results demonstrate that, relative to the Bins, CPQ, CIF, and TTLOF methods, the QRD method achieves a cleaning speed of 0.152 s per 10,000 data points, improving the average dispersion difference by 32.94%, 11.74%, 13.05%, and 9.67%, respectively. In terms of power-curve fitting accuracy, the average NMAE decreases by 8.65%, 5.07%, 7.57%, and 4.06%, while the average NRMSE decreases by 10.78%, 7.99%, 7.66%, and 5.16% and R² increases by 1.74%, 1.62%, 1.57%, and 1.03%, respectively. Overall, QRD demonstrates superior efficiency and accuracy in identifying abnormal wind power values, providing reliable support for high-quality power-curve modeling. Full article

Under extreme fault conditions or during maintenance restarts, DC collection wind farms may experience a total blackout due to protective isolation. Addressing the black-start challenges arising from the unidirectional power flow structure and weak damping characteristics inherent to DC step-up collection wind farms, this paper proposes a sequential black-start control scheme predicated on grid-source coordination. A representative topology and an equivalent black-start model of the DC collection system are established to analyze the start-up mechanism and to design an active voltage build-up strategy with virtual impedance for the grid-side Modular Multilevel Converter (MMC). Meanwhile, generator-side permanent-magnet direct-drive wind turbines exploit their self-excitation capability and optimized pitch control to realize islanded self-bootstrapping and stable rotational speed. In addition, we develop a two-stage soft cut-in strategy that combines open-loop voltage scanning for pre-synchronization with closed-loop constant-current ramping of DC/DC converters, together with control logic for sequentially connecting multiple units to the DC grid. Simulation results show that the proposed approach smoothly restores the system from a zero-energy state to the rated operating point without external power sources, confirming the feasibility of full-farm start-up using the grid-side converter station and unit self-bootstrapping. Full article

This study investigates the aerodynamic and structural behavior of a traditional horizontal-axis windmill equipped with a passively controlled fabric-sail rotor system, representative of the historic Lasithi Plateau windmills of Crete. The traditional windmill of the Lasithi Plateau, historically employed for water pumping to support irrigation and domestic water supply, constituted the conceptual basis for its further development into a wind energy system capable of electrical power generation. To this end, the structural and constructional characteristics of the traditional windmill are thoroughly investigated, with the objective of defining the technical specifications required for the design of a new product, namely a small-scale wind turbine incorporating a sail-based rotor configuration. First, the local meteorological conditions in the area are assessed using a long-term mesoscale to microclimatic approach. These parameters determine the operational and extreme working conditions of the windmill. Then emphasis is placed on understanding how important design features—such as the sail geometry, the supporting framework, and the passive aeroelastic deformation mechanism—govern the rotor’s performance and operational robustness. The sail’s ability to deform substantially plays a central role in regulating aerodynamic loading, serving as an inherent load-shedding mechanism that enhances survivability during high-wind events up to 40 m/s. The observed nonlinear trends in torque and thrust with increasing wind speed highlight the importance of aeroelastic effects in the functional design of fabric-sail rotors. Particular attention is given to the behavior of the woven polyester sail material, which enables large reversible deformations without mechanical failure, thereby preserving structural integrity and operational continuity. Overall, this study provides insight into the design principles and operational characteristics of flexible-sail windmills, illustrating how traditional configurations can inform the development of resilient, low-cost wind-driven systems. Full article

As offshore wind power development advances into deeper waters, tension leg platform (TLP) floating wind turbines stand out for their excellent motion performance, lightweight structure design, and minimal seabed footprint. This paper reviews the advancements in TLP technology, covering structural configurations, dynamic characteristics and control strategies. Particular emphasis is given to analyzing dynamic response under combined environmental loads, including nonlinear motions induced by higher-order wave forces and parametric excitations, as well as the multiphysics coupling mechanisms involving aerodynamics, hydrodynamics, servo control, and structural dynamics. The review concludes by outlining future trends in platform scaling, intelligent operation and maintenance, and multi-energy integration. Overall, this review provides strategic insights for further research and engineering applications of TLP floating wind turbines. Full article