Search Results (371)

This paper presents the mathematical modeling of the thermal state of a 1000 W wind turbine generator (WTG) integrated into a vertical-axis wind turbine (VAWT) system, taking into account external environmental factors, mechanical losses, and the operation of the cooling system. The developed model considers the influence of ambient temperature, wind speed, air humidity, ventilation openings, radiator cooling, and mechanical losses. An analysis was conducted over a range of operating conditions from −20 °C to 50 °C, with wind speeds from 0.5 m/s to 15 m/s and air humidity from 10% to 90%. The nonlinear dependence of the winding temperature on these factors was investigated, and critical operating conditions leading to potential overheating were identified. It was found that high humidity (>70%) increases the winding temperature by 5–10% compared to low humidity (<30%). The developed model can be used to optimize cooling systems and improve the reliability of wind turbines in various climatic conditions. In addition, the proposed model is intended to be integrated into fault detection and diagnosis systems for wind turbines, enabling the identification of potential faults related to thermal overload. Full article

Vertical axis turbines (VATs) have grown in popularity over the past decade, owing to their lower cost of energy (CoE) when installed in remote offshore locations. The Davidson Hill Venturi system, as a kind of vertical axis tidal turbine technology, has been tested and proved to increase the power generation by the effect from the venturi structure. Based on the Computational Fluid Dynamic simulation (Ansys 2021R1) software, the present project develops a complete and improved 3D model to calculate the influence from different parameter adjustments on the turbine. The angle of the hydrofoil on the side panel was investigated in a previous study, while the new hydrofoil and different number of blades on the centre rotor can also affect the power generation of the tidal turbines. With this accurately created design, a sizing procedure is developed, and several 3D turbine models with a new hydrofoil or different number of blades are established. Both three-dimensional and two-dimensional section results are compared with the model with adjusting parameters. The 2D section view obtained from a static 3D model without a centre rotor is used to compare with the previous research, while the different number of blades is simulated by the dynamic 3D model without the hydrofoil. An analytical optimisation demonstrates that the new hydrofoil GOE-222 performed better than the material used in a previous study. The optimal number of blades between four blades and eight blades for use in the DHV turbine is also confirmed to be four. Full article

Axial flux permanent magnet (AFPM) machines offer some advantages over conventional radial flux machines for the case of a limited space in the axial direction, such as high torque density, compact structure, and modular design ability. They, therefore, are increasingly used in wind power and electrical vehicles. This paper focuses on developing an effective analytical model and equivalent auto-finite element method (FEM), including rotor linear motion for the design of axial flux permanent magnet generators in vertical axis wind turbines. The initial design of a 1.35 kW-AFPM generator with an outer double rotor and double layer concentrated windings is based on analytical equations, and then it is refined using equivalent time-stepping transient FEM, including rotor linear motion to calculate voltage, electromagnetic force, and torque. The automatic generation of an equivalent transient 2D-FEM model to replace a time-consuming 3D-FEM model is investigated. As a consequence, the influence of slotting the effect on a 1.35 kW-AFPM machine’s performances, such as air gap flux density, internal voltage, and cogging torque, is announced. Full article

This article discusses the automated control of dynamic loads in drive systems using the example of a wind turbine screw drive. A mathematical model was developed, including differential equations of system motion, the voltage balance of the electric motor, and transfer functions of the control system. The Laplace transform was applied to obtain the system’s frequency and time characteristics. Numerical calculations and simulation results are presented, demonstrating the system’s stability and the effectiveness of the proposed control method. The generated amplitude–frequency and transient response graphs confirm the system’s operability. The proposed approach enhances the reliability of the screw drive, reduces mechanical loads, and extends the equipment’s service life. Full article

The self-starting capability of straight-bladed H-type Darrieus Vertical Axis Wind Turbines (VAWTs) remains a major constraint for deployment, particularly in urban, low speed, and turbulent environments. We conducted a systematic review of technological strategies to improve self-starting, grouped into five categories: (1) aerodynamic airfoil design, (2) rotor configuration, (3) passive flow control, (4) active flow control, and (5) incident flow augmentation. Searches in Scopus and IEEE Xplore (last search 20 August 2025) covered the period from 2019 to 2026 and included peer-reviewed journal articles in English reporting experimental or numerical interventions on H-type Darrieus VAWTs with at least one start-up metric. From 1212 records, 53 studies met the eligibility after title/abstract screening and full-text assessment. Data were synthesized qualitatively using a comparative thematic approach, highlighting design parameters, operating conditions, and performance metrics (torque and power coefficients) during start-up. Quantitatively, studies reported typical start-up torque gains of 20–30% for airfoil optimization and passive devices, about 25% for incident-flow augmentation, and larger but less certain improvements (around 30%) for active control. Among the strategies, airfoil optimization and passive devices consistently improved start-up torque at low TSR with minimal added systems; rotor-configuration tuning and incident-flow devices further reduced start-up time where structural or siting constraints allowed; and active control showed the largest laboratory gains but with uncertain regarding energy and durability. However, limitations included heterogeneity in designs and metrics, predominance of 2D-Computational Fluid Dynamics (CFDs), and limited 3D/field validation restricted quantitative pooling. Risk of bias was assessed using an ad hoc matrix; overall certainty was rated as low to moderate due to limited validation and inconsistent uncertainty reporting. In conclusions, no single solution is universally optimal; hybrid strategies, combining optimized airfoils with targeted passive or active control, appear most promising. Future work should standardize start-up metrics, adopt validated 3D Fluid–Structure Interaction (FSI) models, and expand wind-tunnel/field trials. Full article

As wind energy development continues to expand toward nearshore and deep-sea regions, enhancing the aerodynamic efficiency of vertical axis wind turbines (VAWTs) in complex marine environments has become a critical challenge. To address this, a composite flow control strategy combining leading-edge suction and trailing-edge gurney flap is proposed. A two-dimensional unsteady numerical simulation framework is established based on CFD and the four-equation Transition SST (TSST) transition model. The key control parameters, including the suction slot position and width as well as the gurney flap height and width, are systematically optimized through orthogonal experimental design. The aerodynamic performance under single (suction or gurney flap) and composite control schemes is comprehensively evaluated. Results show that leading-edge suction effectively delays flow separation, while the gurney flap improves aerodynamic characteristics in the downwind region. Their synergistic effect significantly suppresses blade load fluctuations and enhances the wake structure, thereby improving wind energy capture. Compared to all other configurations, including suction-only and gurney flap-only blades, the composite control blade achieves the most significant increase in power coefficient across the entire tip speed ratio range, with an average improvement of 67.24%, demonstrating superior aerodynamic stability and strong potential for offshore applications. Full article

Micro and small wind turbines (MAWTs) are increasingly integrated into residential and prosumer hybrid energy systems. However, their real-world performance often falls short of catalog specifications due to mismatched wind resources, siting limitations, and insufficient attention to human comfort. This paper presents a comprehensive decision-support framework for selecting the type and scale of MAWTs under actual local conditions. The energy assessment module combines aerodynamic performance scaling, wind speed-frequency modeling based on Weibull distributions, turbulence intensity adjustments, and component-level efficiency factors for both horizontal and vertical axis turbines. The framework addresses three key design objectives: efficiency—aligning turbine geometry and control strategies with local wind regimes to maximize energy yield; comfort—evaluating candidate designs for noise emissions, shadow flicker, and visual impact near buildings; and climate adaptation—linking turbine siting, hub height, and rotor type to terrain roughness, turbulence, and built environment characteristics. Case studies from low and moderate wind locations in Central Europe demonstrate how multi-criteria filtering avoids oversizing, improves the autonomy of hybrid PV–wind systems, and identifies configurations that may exceed permissible limits for noise or flicker. The proposed methodology enables evidence-based deployment of MAWTs in decentralized energy systems that balance technical performance, resilience, and occupant well-being. Full article

Vertical axis wind turbines (VAWTs) are increasingly utilized for decentralized power generation in urban and low-wind settings because of their omnidirectional wind capture and compact form. This study numerically investigates the aerodynamic performance of Darrieus-type VAWT blades as their curvature varies systematically from deeply convex (−50 mm) to strongly concave (+50 mm) across seven configurations. Using steady-state computational fluid dynamics (CFD) with the frozen rotor method, simulations were conducted over a low Reynolds number range of 25 to 300, representative of small-scale and rooftop wind scenarios. The results indicate that deeply convex blades achieve the highest lift-to-drag ratio (Cl/Cd), peaking at 1.65 at Re = 25 and decreasing to 0.76 at Re = 300, whereas strongly concave blades show lower and more stable values ranging from 0.95 to 0.86. The power coefficient (Cp) and torque coefficient (Ct) similarly favor convex shapes, with Cp starting at 0.040 and remaining above 0.030, and Ct sustaining a robust 0.067 at low Re. Convex blades also maintain higher tip speed ratios (TSR), exceeding 1.30 at Re = 300. Velocity and pressure analyses reveal that convex profiles promote stable laminar flows and compact wakes, whereas concave geometries experience early flow separation and fluctuating torque. These findings demonstrate that optimizing the blade curvature toward convexity enhances the start-up, torque stability, and power output, providing essential design guidance for urban VAWTs operating under low Reynolds number conditions. Full article

This study investigates the aerodynamic performance of vertical axis wind turbines (VAWTs), focusing on a novel dual-airfoil morphing mechanism for H-type Darrieus turbines. By leveraging the aerodynamic benefits of two distinct airfoil profiles, the proposed design adapts dynamically to varying wind speeds, enhancing overall efficiency. The methodology includes airfoil selection and aerodynamic analysis using the Double Multiple Stream Tube (DMST) model, simulated in QBlade software. The numerical model was validated against established benchmark data, confirming its accuracy. Key findings reveal that among all tested airfoils, the NACA 64(2)-415 airfoil achieves the highest power coefficient at low wind speeds, while the FX 84-W-127 airfoil performs optimally at higher wind speeds. Inspired by biomimetic principles, a morphing strategy and mechanism is proposed to transition seamlessly between these two profiles and enable broader operational adaptability. This innovative approach demonstrates significant potential for improving the energy capture efficiency and viability of VAWTs, contributing to the advancement of renewable wind energy technologies. Full article

To enhance the aerodynamic performance of vertical axis wind turbines (VAWTs) under complex gust conditions, the design parameters of the flap were optimized using the computational fluid dynamics (CFD) method combined with orthogonal experimental design and the SHERPA algorithm, and two gust models with mainly high and low wind speeds were generated by a self-compiling program to investigate the effects of three combinations of the chordwise mounting position of the flap, the moment of inertia, and the maximum deflection angle on the aerodynamic performance of the vertical axis wind turbine. The results demonstrated that adaptive flaps reduced the flow separation region and suppressed the formation and development of separation vortices, thereby enhancing aerodynamic performance. The adaptive flap was found to be more effective in high-speed gust environments than in low-speed ones. The optimal configuration—chordwise position at 0.4C, moment of inertia at 6.12 × 10⁻⁵ kg·m², and a maximum deflection angle of 40°—led to a 57.24% improvement relative to the original airfoil. Full article

To address the low wind energy utilization efficiency of vertical axis wind turbines (VAWTs) and enhance their engineering applicability, cavity and groove-flap structures were incorporated into turbine blades. Numerical simulations were performed to optimize these configurations, followed by wind tunnel experiments investigating output power variations of three VAWT types under different wind speeds at installation angles of 0°, 2°, 4°, and 6°. The Omega criterion was employed to comparatively analyze vortex evolution patterns at the leading and trailing edges for installation angles of 0°, 3°, and 5°. Experimental results demonstrated nonlinear growth in output power with increasing wind speed and rotational velocity, with groove-flap VAWTs exhibiting superior performance. The optimal installation angle was identified within 2.5–3.5°, where appropriate angles reduced adverse pressure gradients, delayed boundary layer separation, and mitigated vortex shedding effects. Excessive angles induced vortex accumulation and wake disturbances, compromising flow field stability. This study provides critical insights for optimizing VAWT aerodynamic performance through structural modifications and installation angle adjustments. Full article

This study presents the design, fabrication, and performance assessment of a novel, small-scale (30–70 W), hybrid ocean energy system that captures energy from wave-induced heave motion using a point-absorber buoy and from ocean currents via a vertical axis water turbine (VAWT). Key innovations include a custom designed and built dual-rotor generator that accepts independent mechanical input from both subsystems without requiring complex mechanical coupling and a bi-directional mechanical motion rectifier with an overdrive. Numerical simulations using ANSYS AQWA (2024R2) and QBLADE(2.0.4) guided the design optimization of the buoy and turbine, respectively. Wave resource assessment for the Khobar coastline, Saudi Arabia, was conducted using both historical data and field measurements. The prototype was designed and built using readily available 3D-printed components, ensuring cost-effective construction. This mechanically simple system was tested in both laboratory and outdoor conditions. Results showed reliable operation and stable power generation under simultaneous wave and current input. The performance is comparable to that of existing hybrid ocean wave–current energy converters that employ more complex flywheel or dual degree-of-freedom systems. This work provides a validated pathway for low-cost, compact, and modular hybrid ocean energy systems suited for remote coastal applications or distributed marine sensing platforms. Full article

This article uses the sailfish outline as an airfoil profile to create a dual vertical-axis water turbine model for capturing wave and tidal current energy. A parametric water turbine model is built with the shape function perturbation and characteristic parameter description methods. Optimized by the multi-island genetic algorithm on the Isight platform, a CNC sample of the optimized model is made. Its torque and pressure are measured in a wind tunnel and compared with CFD numerical analysis results. The results show small differences between the numerical and experimental results. Both indicate that the relevant performance parameters of the turbine improved after optimization. During constant flow velocity measurement, the optimized axial-flow turbine has a pressure increase of 55% and a torque increase of 40%, while for the centrifugal turbine, the pressure increases by 60% and the torque by 12.5%. During constant rotational speed measurement, the axial-flow turbine’s pressure increases by 16.7%, with an unobvious torque increase. The Q-criterion diagram shows more vortices after optimization. This proves the method can quickly and effectively optimize the dual vertical-axis water turbine. Full article

As with wind turbines, marine tidal turbines are expected to be deployed in arrays of multiple turbines. To optimize these arrays, a more profound understanding of the interactions between turbines is necessary. This paper employs the Actuator Line Method alongside the Lattice Boltzmann Method and Large Eddy Simulation to develop a numerical model of tidal turbine arrays. It studies a vertical-axis turbine manufactured by HydroQuest/CMN that is equipped with two counter-rotating columns, each comprising two rotors. The ambient turbulence and upstream velocity profiles correspond to the characteristics of a tidal site such as the Alderney Race. Six turbine layouts are modeled: three aligned layouts with three turbines and three staggered layouts with four turbines. The spacing between turbines varies depending on the layout. This study yields several observations regarding array configuration. A minimum distance of 300 m, or $12D_{eq}$, between aligned turbines is necessary for full wake recovery. At shorter distances, the accumulation of velocity deficits significantly decreases the efficiency of the third turbine in the array. Pairs of counter-rotating vortices are observed in the wake of turbines. The evolution of these vortices and their influence on the wake depend greatly on the array configuration. An optimal configuration is observed in which the overall averaged power is not impaired by the interactions. Full article

This study provides a comprehensive overview of vertical-axis wind turbines (VAWTs) for emerging energy applications by combining a bibliometric analysis and a thematic mini-review. Scopus-indexed publications from 1979 to 2025 were analyzed using PRISMA guidelines and bibliometric tools (Bibliometrix, CiteSpace, and VOSviewer) to map global research trends, and a parallel mini-review distilled recent advances into five thematic areas: aerodynamic strategies, advanced materials, urban integration, hybrid systems, and floating offshore platforms. The results reveal that VAWT research output has surged since 2006, led by China with strong contributions from Europe and North America, and is concentrated in leading renewable energy journals. Dominant topics include computational fluid dynamics (CFD) simulations, performance optimization, wind–solar hybrid integration, and adaptation to turbulent urban environments. Technologically, active and passive aerodynamic innovations have boosted performance albeit with added complexity, remaining mostly at moderate technology readiness (TRL 3–5), while advanced composite materials are improving durability and fatigue life. Emerging applications in microgrids, building-integrated systems, and offshore floating platforms leverage VAWTs’ omnidirectional, low-noise operation, although challenges persist in scaling up, control integration, and long-term field validation. Overall, VAWTs are gaining relevance as a complement to conventional turbines in the sustainable energy transition, and this study’s integrated approach identifies critical gaps and high-priority research directions to accelerate VAWT development and help transition these turbines from niche prototypes to mainstream renewable solutions. Full article