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This paper presents the results of experimental, analytical, and numerical studies on determining the driving torque and power of a vertical-axis wind turbine (VAWT) with planetary blade motion forced by a carousel rotor. First, experimental studies in the wind tunnel laboratory were conducted to determine the tip speed ratio λ for the real-scale wind turbine model under self-starting conditions. Then, an analytical kinematic model of the turbine was developed. Finally, computational fluid dynamics (CFD) analysis was conducted to verify the analytical approach and examine aerodynamic interferences between particular turbine blades. The main objective of the study was to verify the accuracy of the simplified analytical approach to calculating the driving torque and turbine power compared to the numerical results based on 2D analysis using computational fluid dynamics. The obtained results showed good agreement considering the modeling of the motion of the three dual-coherent blades of the wind turbine. Comparing the analytical and CFD approaches, the error in determining the average driving torque and the average turbine power was about 1%. An additional objective of the study was to use the developed analytical method to calculate the starting torque and demonstrate the main advantage of the carousel wind rotor, which is its higher starting torque compared to the H-type Darrieus rotor. [ABSTRACT FROM AUTHOR]

This study covers the structural optimization of vertical axis wind turbines (VAWTs) that can operate reliably for long periods of time in marine environments, as well as simulation analysis to evaluate their fatigue and strain resistance. Due to the nature of the marine environment, strong wind speeds and constant wave loads are applied, and VAWTs are likely to suffer from fatigue build-up and deformation problems in the long term. In this study, detailed numerical simulations were performed using ANSYS software (2024 R2) to analyze the effects of different airfoil shapes, material choices, tip speed ratios (TSRs), and foundation types on the turbine's stress distribution and fatigue resistance. The results showed that NACA 0030 airfoil, composite steel, and single-pile foundation performed best under TSR 1.8 conditions, with the potential to reduce strain by approximately 30% and fatigue damage by approximately 25% compared to conventional structures. With this optimized combination, it was found that maintenance costs could be significantly reduced while maintaining structural stability at sea. These results could make an important contribution to the economical and durable design of VAWTs in the future. [ABSTRACT FROM AUTHOR]

This study aims to introduce a new optimization method for designing a vertical-axis wind turbine (VAWT) that dynamically morphs its blades as a function of the tip-speed ratio (TSR) and azimuthal angle. For this purpose, the Darrieus turbine is the subject of a dynamic study under transient aerodynamic loads. By resolving the two-dimensional unsteady incompressible Navier–Stokes equation, the aerodynamic torque is obtained with the k- ϵ  realizable turbulence model. A comparison between rotor operation at optimal and lower   C p  values is possible according to the investigation of flow-field characteristics for a variety of tip-speed ratio values, with experimental results so that a better understanding of the vertical-axis wind turbine's basic physics is obtained. Then, a multi-objective optimization technique is coupled with ANSYS Workbench to increase the energy generation of VAWT blades by reducing the drag coefficient and maximizing the power coefficient. The input variables were evaluated through a sensitivity analysis, and the most important one was chosen. The analysis results of the best compromise showed that the design methodology's output is feasible for manufacturing. [ABSTRACT FROM AUTHOR]

In the present situation and considering the dangers that affect human life and the environment, it is necessary to expand the use of renewable energy that is available in all geographical areas. Environmental pollution caused by urban life has attracted researchers' attention to the use of renewable energy such as vertical axis wind turbines (VAWTs) with the aim of urban application. Because of their unique features, these turbines can provide the electricity needed for the targets, but to date, less attention has been paid to their tower structure. A wind turbine tower is one of the main and costliest components of wind systems. In this paper, based on the standards of turbine design and its structure, an algorithm was presented to create more resistance and strength in the tower structure and control the tower's deflection caused by incoming loads. Different models of simple monopole towers, variable crosssection monopole towers, monopole towers with channel beam control, and monopole towers with lateral restraint in the case study of Iran were simulated. Results show that models with lateral restraint have the lowest deflection of about 3 to 5 cm and, in addition to passing all design standards, the members' stress ratio is allowed within the limit. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the accuracy of predicting the aerodynamic loads and investigate the aerodynamic wake characteristics of a vertical axis wind turbine (VAWT) rotor using a simplified two-dimensional numerical rotor model and an advanced numerical approach – the Scale Adaptive Simulation (SAS) coupled with the four-equation γ – Reθ turbulence model. The challenge for this approach lies in the operating conditions of the rotor, the blade pitch angles, and the very small geometric dimensions of the rotor. The rotor, with a diameter of 0.3 m, operates at a low tip speed ratio of 2.5 and an extremely low blade Reynolds number of approximately 22.000, whereas the pitch angles, β, are: -10, 0, and 10 degrees. Validation was conducted based on high-fidelity measurements obtained using the PIV technique at TU Delft. The obtained results of rotor loads and velocity profiles are surprisingly reliable for cases of β = 0° and β = –10°. However, the 2-D model is too imprecise to estimate both aerodynamic loads and velocity fields accurately. [ABSTRACT FROM AUTHOR]

In this work, a pioneering approach is proposed to enhance the efficacy of vertical axis wind turbines within the aerodynamic field. This innovative method involves integrating a bionic airfoil, inspired by the tail fin of a swordfish, along the trailing edge of the airfoil. To evaluate the impact of these biomimetic airfoils on wind turbine functionality, applications such as numerical simulations facilitated by computational fluid dynamics (CFD) and design of experiments (DOE) were employed. The primary objective of this study is to mitigate the flow separation phenomenon that occurs when wind turbines operate at low tip speed ratios (TSR < 4). The results indicate that the addition of the bionic tail delays the angle at which the peak torque appears, and enhances positive torque generation effectively within the phase angle range of 60° to 150°, suggesting successful suppression of the flow separation phenomenon. The presence of the tail also postpones the occurrence of dynamic stall, particularly near the trailing edge of the airfoil, and reduces losses associated with the expansion and shedding of dynamic stall vortices. As the tip speed ratio increases, the average power coefficient of the bionic airfoil exhibits a positive trend. Notably, at a tip speed ratio of 2.63, a significant increase in the average power coefficient of approximately 17% was observed. The analysis of the downstream wake of the wind turbine reveals that the bionic tail enhances the speed loss in the wake. This indicates that the blades can generate greater lift at a lower tip speed ratio, allowing the vertical axis wind turbine to operate effectively at low wind speeds, particularly in urban areas with significant development potential. [ABSTRACT FROM AUTHOR]

The operation of vertical axis wind turbines (VAWTs) to generate low-carbon electricity is growing in popularity. Their advantages over the widely used horizontal axis wind turbine (HAWT) include their low tip speed, which reduces noise, and their cost-effective installation and maintenance. A Farrah turbine equipped with 12 blades was designed to enhance performance and was recently the subject of experimental investigation. However, little research has been focused on turbine configurations with more than three blades. The objective of this study is to employ numerical methods to analyse the performance of the Farrah wind turbine and to validate the findings in comparison with experimental results. The investigated blade pitch angles included both positive and negative angles of 7, 15, 20 and 40 degrees. The k-ω SST model with the sliding mesh technique was used to perform simulations of a 14.4 million element unstructured mesh. Comparable trends of power output results in the experimental investigation were obtained and the assumptions of mechanical losses discussed. Wake recovery was determined at an approximate distance of nine times the turbine diameter. Two large complex quasi-symmetric vortical structures were observed between positive and negative blade pitch angles, located in the near wake region of the turbine and remaining present throughout its rotation. It is demonstrated that a number of recognised vortical structures are transferred towards the wake region, further contributing to its formation. Additional notable vortical formations are examined, along with a recirculation zone located in the turbine's core, which is described to exhibit quasi-symmetric behaviour between positive and negative rotations. [ABSTRACT FROM AUTHOR]

While the wind turbine industry has been primarily dominated by horizontal-axis wind turbines, the forefront of knowledge of these turbines has revealed significant challenges in various aspects, including manufacturing, structural design, cost, and maintenance. On the other hand, the advantages associated with Darrieus vertical-axis wind turbines (VAWTs) demonstrate significant potential that can address the existing challenges of the wind turbine industry. Current work aims to investigate the practicality of this potential for the wind energy sector. To this end, the benefits of employing Darrieus turbines for domestic and industrial applications, isolated operation, and on/offshore windfarm applications have been explored. It is apparent that Darrieus VAWTs are better suited to a wide range of environments, whether they are deployed in isolation or integrated systems, and whether they are utilized on a small or large scale. Darrieus VAWTs are adaptable to urban unsteady variable wind, are less expensive on large scales, provide higher power density at the windfarm level, and provide stability for offshore platforms. Nevertheless, challenges remain in fully harnessing VAWT potential rooted in their complex aerodynamics. This serves as a primary challenge for VAWTs to address the challenges of the wind turbine industry in line with the 2050 roadmap. [ABSTRACT FROM AUTHOR]

A 2-D Lattice Boltzmann Method, designed to ensure stability at high Reynolds numbers, is combined with an Actuator Line Model to compute the loads on a two-bladed vertical axis wind turbine. Tests on the kernel size at a high mesh resolution reveal that a size equal to half of the full chord length yields the most accurate results. The aerodynamic load solution is validated against a fully resolved Scale-Adaptive Simulation (SAS) output, demonstrating high correlation, and enabling an assessment of near wake and downstream effects. The model's adaptability to various rotor operating conditions is confirmed through tests at high and low tip-speed ratios. Additionally, a Biot–Savart-based Vortex Model (VM) is employed for further comparison, showing good agreement with the Lattice Boltzmann output. The results indicate that the Highly Stable Lattice Boltzmann Method integrated with the Actuator Line Model enhances the accuracy of flow field resolution and effectively captures complex aerodynamic phenomena, making it a valuable tool for simulating vertical axis wind turbines. [ABSTRACT FROM AUTHOR]

Abstract Controlling wind flow on vertical axis wind turbine blades is an effective technique for enhancing their performance. Modern equipment such as plasma actuators have gained significant attention for their ability to control, and improve the flow behavior in wind turbines. Previous studies have primarily focused on investigating plasma actuators with constant force. In this study, plasma actuators with varying forces over time were applied to the turbine blades. An unsteady 2D model was used to analyze the wind turbine. The sliding mesh model was employed to simulate rotor rotation, and the SST $$k-\omega $$ k - ω model was utilized for turbulence modeling. Initially, the performance of the clean turbine was examined. In the next step, the plasma actuators with different force waveforms were applied to the wind turbine blades, including constant, sine, cosine, positive ramp, negative ramp, pulse in the first half-cycle, and pulse in the last half-cycle waveforms. The results indicated that the cosine, and sinusoidal waveforms, led to the greatest improvement with 37.28% and 35.59% increase in the net energy produced by the turbine, respectively, compared to the baseline case.

Studies demonstrate that the reduced frequency k is influenced by the incoming wind speed U0 and the rotor speed n. As a dimensionless parameter, k characterizes the stability of the flow field, which is a critical factor affecting the performance of vertical-axis wind turbines (VAWTs). This paper investigates the impact of k on the performance of straight-blade vertical-axis wind turbines (H-VAWT). The findings indicate that 0.05 is the critical value of k. The same k results in a similar flow field structure, yet the performance changes vary with different U0. A decrease in n or an increase in U0 leads to an increase in the average value and fluctuation of k, which subsequently reduces the rotor rotation torque Cm and decreases the maximum wind energy utilization rate Cpmax. This reduction in Cpmax weakens the stability of the flow field. Additionally, the high-speed area of the blade's trailing edge velocity trajectory at  θ = 0 ° ,  θ = 120 ° , and  θ = 240 °  expands with increasing range. Velocity dissipation in the high-speed area of the trailing edge affects the stability of the flow field within the rotor. [ABSTRACT FROM AUTHOR]

Omnidirectionality and simple design make VAWTs more attractive compared to HAWTs in highly turbulent and harsh operational environments including low wind speed conditions where this technology shines more. However, the performance of VAWTs is lacking compared to HAWTs due to low turbine efficiency at downstream caused by large wake vortices generated by advancing blades in the upstream position. Introducing variable design methods on VAWT provides better adaptability to the various oncoming wind conditions. This paper presents state-of-the-art variable methods for performance enhancement of VAWTs to provide better direction for the wind industry. The variable VAWT design can increase the lift and torque, especially at the downstream regions by managing the blade-to-wake interaction and blade angle of attack (AoA) well, hence contributing to the performance enhancement of VAWTs. In addition, the self-starting capabilities have also been found to improve by employing variable methods with a better angle of attack on the turbine blades. Nevertheless, the complexity of varying mechanisms and structural rigidity are the main challenges in adopting this idea. Yet, it possesses great potential to develop higher-efficiency VAWT systems that can operate in a wide range of wind speeds. [ABSTRACT FROM AUTHOR]

Controlling wind flow on vertical axis wind turbine blades is an effective technique for enhancing their performance. Modern equipment such as plasma actuators have gained significant attention for their ability to control, and improve the flow behavior in wind turbines. Previous studies have primarily focused on investigating plasma actuators with constant force. In this study, plasma actuators with varying forces over time were applied to the turbine blades. An unsteady 2D model was used to analyze the wind turbine. The sliding mesh model was employed to simulate rotor rotation, and the SST k - ω model was utilized for turbulence modeling. Initially, the performance of the clean turbine was examined. In the next step, the plasma actuators with different force waveforms were applied to the wind turbine blades, including constant, sine, cosine, positive ramp, negative ramp, pulse in the first half-cycle, and pulse in the last half-cycle waveforms. The results indicated that the cosine, and sinusoidal waveforms, led to the greatest improvement with 37.28% and 35.59% increase in the net energy produced by the turbine, respectively, compared to the baseline case. [ABSTRACT FROM AUTHOR]

Advances in non‐conventional energy technologies and increasing fossil fuel prices along with environmental concerns have made hybrid renewable energy systems important. In view of this scenario, solar panel mounted on a vertical axis wind turbine (called as solar‐wind tower) can be utilized to produce more electric energy than individual one. This solar‐wind tower will be located in the space available between two opposite roads of expressways/highways. Solar‐wind tower located in such a manner that the air velocity produced from driving vehicles on both sides of the road is adequate to cut the turbine blades which will produce unidirectional torque. A battery energy storage system (BESS) stores the power produced by the solar‐wind tower so that it can subsequently be used for local loads and electric vehicle charging stations (EVCS) and remaining energy can be supplied to the grid. In this work, a hybrid system composed of wind and solar is designed and modelled in Simulink (MATLAB) and tested on real data of wind speed and validated by Opal‐RT simulator. From the simulation result, it is estimated that total electrical power output of a single solar‐wind tower is around 15 to 20 kWh in a day under the assumed conditions. [ABSTRACT FROM AUTHOR]

A modeling technique for a nearshore hybrid wind–wave energy converter system (HWWECS) is presented in this research. The model consists of the buoy, wind system, and generator, allowing simulation of the HWWECS's behavior in response to varied wave circumstances, such as different wave heights and periods. The HWWECS is made up of two buoy units and a wind system that work together to power a generator. The Wave Analysis at Massachusetts Institute of Technology (WAMIT) software is used to calculate the hydrodynamic forces. A variable inertia hydraulic flywheel is used to bring the system into resonance with incident wave frequencies in order to improve power production. [ABSTRACT FROM AUTHOR]

Abstract This work introduces and explores the use of secondary rotors for vertical axis wind turbine power take‐off. A parametric framework based on optimally designed secondary rotors is developed which calculates the maximum achievable efficiency of power conversion between the primary and secondary rotors. It is shown that practicable rotor designs can convert between 87% and 90% of primary rotor power to the secondary rotors whilst facilitating nacelle mass reductions between 85% and 87% compared to traditional reference turbine drivetrains.

Wind turbines are a solution for sustainable energy, significantly reducing carbon emissions and fostering a circular economy for more cost-effective and cleaner power generation, in line with worldwide environmental aspirations. In this context, this research aims to explore a novel two-stage, twisted-blade micro-Vertical-Axis Wind Turbine (μ -VAWT)alternative inspired by the Savonius Rotor (SR). This investigation utilizes the κ − ω SST turbulence model to explore the power coefficient ( C P ) and torque coefficient ( C T ), finding C P values ranging from 0.02 to 0.08 across the turbine by altering the free stream velocity (V). C T analysis further delves into four specific sections, highlighting areas of particular interest. These results are validated by examining velocity contours, pressure contours, and streamlines in four horizontal sections, demonstrating that the proposed turbine model exhibits minimal torque fluctuation. Moreover, the analysis of vertical wind streamlines illustrates very low interference with various wind turbine proposals, underscoring the turbine's efficiency and potential for integration into diverse wind energy projects. [ABSTRACT FROM AUTHOR]

This work introduces and explores the use of secondary rotors for vertical axis wind turbine power take‐off. A parametric framework based on optimally designed secondary rotors is developed which calculates the maximum achievable efficiency of power conversion between the primary and secondary rotors. It is shown that practicable rotor designs can convert between 87% and 90% of primary rotor power to the secondary rotors whilst facilitating nacelle mass reductions between 85% and 87% compared to traditional reference turbine drivetrains. [ABSTRACT FROM AUTHOR]

Wind energy is one of the most abundantly available renewable energy, which is clean and promising source for electric energy conversion. Vertical Axis Wind Turbine (VAWT) possesses technological, environmental, and economic benefits over Horizontal Axis Wind Turbine. Thus, the present work investigates on the design and analysis of two airfoil profiles (NACA 0012 & NACA 0018) with VAWT using ANSYS Fluent 2020 R2 solver. The structural stability (deformation) of Aluminum blades at varied wind speeds throughout the energy conversion is the prime focus of the present work. Developed airfoil models showed the structural stability even at extreme pressure, with minimal deformation, stress and strain. The velocity and pressure contours at diverse wind speeds (3, 5 and 10 m/s) are analyzed. It is evident that, the turbine blade were with uniform rotation even under turbulent flow. The outcomes of the analysis on the developed models showed good agreement to predict the torque and power. Therefore, it can be practically implemented to form and join using Friction Stir Processing. [ABSTRACT FROM AUTHOR]

The performance of a new vertical-axis wind turbine rotor based on the mathematical equation of the cycloid is analyzed and compared through simulation and experimental testing against a semicircular or S-type rotor, which is widely used. The study examines three cases: equalizing the diameter, chord length and the area under the curve. Computational Fluid Dynamics (CFD) was used to simulate these cases and evaluate moment, angular velocity and power. Experimental validation was carried out in a wind tunnel that was designed and optimized with the support of CFD. The rotors for all three cases were 3D printed in resin to analyze their experimental performance as a function of wind speed. The moment and Maximum Power Point (MPP) were determined in each case. The simulation results indicate that the cycloid-type rotor outperforms the semicircular or S-type rotor by 15%. Additionally, experimental evidence confirms that the cycloid-type rotor performs better in all three cases. In the MPP analysis, the cycloid-type rotor achieved an efficiency of 10.8% which was 38% better than the S-type rotor. [ABSTRACT FROM AUTHOR]

Abstract The wind energy market is currently dominated by horizontal axis wind turbines (HAWTs); however, vertical axis wind turbines (VAWTs) are emerging as a design alternative, especially for deep‐water offshore siting due to their low center of gravity, ease of access to drivetrain components, and overall simplicity. Due to the absence of a pitch mechanism in large‐scale Darrieus VAWTs, stall control has often been used to manage power and loads. Introducing a pitching mechanism in H‐type VAWTs has been studied, but this diminishes the mechanical simplicity advantage, and the use of a pitching mechanism in a large‐scale Darrieus‐type VAWT is not practical. This work examines an innovative, alternative method to control the rotor dynamics of a large‐scale 5 MW VAWT to maximize power while constraining loads without introducing any new or complex mechanical elements. This control strategy is termed intracycle revolution per minute (RPM) control, where the rotational speed of the turbine is allowed to vary in an optimal fashion with the azimuthal location of blades as opposed to typical constant RPM operation. An optimization framework is formulated for an open‐loop optimal control problem and solved to maximize power subject to constraints on aerodynamic design loads. Results are presented to demonstrate the benefits and the performance limits of intracycle RPM control for large‐scale 5 MW Darrieus VAWTs, namely, (1) power production (quantified in terms of AEP) that can be increased subject to baseline load limits and (2) opportunities to significantly increase AEP or decrease loads via intracycle RPM control that are examined for both two‐bladed and three‐bladed VAWTs.

This study covers the structural optimization of vertical axis wind turbines (VAWTs) that can operate reliably for long periods of time in marine environments, as well as simulation analysis to evaluate their fatigue and strain resistance. Due to the nature of the marine environment, strong wind speeds and constant wave loads are applied, and VAWTs are likely to suffer from fatigue build-up and deformation problems in the long term. In this study, detailed numerical simulations were performed using ANSYS software (2024 R2) to analyze the effects of different airfoil shapes, material choices, tip speed ratios (TSRs), and foundation types on the turbine’s stress distribution and fatigue resistance. The results showed that NACA 0030 airfoil, composite steel, and single-pile foundation performed best under TSR 1.8 conditions, with the potential to reduce strain by approximately 30% and fatigue damage by approximately 25% compared to conventional structures. With this optimized combination, it was found that maintenance costs could be significantly reduced while maintaining structural stability at sea. These results could make an important contribution to the economical and durable design of VAWTs in the future.

This paper presents the results of experimental, analytical, and numerical studies on determining the driving torque and power of a vertical-axis wind turbine (VAWT) with planetary blade motion forced by a carousel rotor. First, experimental studies in the wind tunnel laboratory were conducted to determine the tip speed ratio λ for the real-scale wind turbine model under self-starting conditions. Then, an analytical kinematic model of the turbine was developed. Finally, computational fluid dynamics (CFD) analysis was conducted to verify the analytical approach and examine aerodynamic interferences between particular turbine blades. The main objective of the study was to verify the accuracy of the simplified analytical approach to calculating the driving torque and turbine power compared to the numerical results based on 2D analysis using computational fluid dynamics. The obtained results showed good agreement considering the modeling of the motion of the three dual-coherent blades of the wind turbine. Comparing the analytical and CFD approaches, the error in determining the average driving torque and the average turbine power was about 1%. An additional objective of the study was to use the developed analytical method to calculate the starting torque and demonstrate the main advantage of the carousel wind rotor, which is its higher starting torque compared to the H-type Darrieus rotor.

The operation of vertical axis wind turbines (VAWTs) to generate low-carbon electricity is growing in popularity. Their advantages over the widely used horizontal axis wind turbine (HAWT) include their low tip speed, which reduces noise, and their cost-effective installation and maintenance. A Farrah turbine equipped with 12 blades was designed to enhance performance and was recently the subject of experimental investigation. However, little research has been focused on turbine configurations with more than three blades. The objective of this study is to employ numerical methods to analyse the performance of the Farrah wind turbine and to validate the findings in comparison with experimental results. The investigated blade pitch angles included both positive and negative angles of 7, 15, 20 and 40 degrees. The k-ω SST model with the sliding mesh technique was used to perform simulations of a 14.4 million element unstructured mesh. Comparable trends of power output results in the experimental investigation were obtained and the assumptions of mechanical losses discussed. Wake recovery was determined at an approximate distance of nine times the turbine diameter. Two large complex quasi-symmetric vortical structures were observed between positive and negative blade pitch angles, located in the near wake region of the turbine and remaining present throughout its rotation. It is demonstrated that a number of recognised vortical structures are transferred towards the wake region, further contributing to its formation. Additional notable vortical formations are examined, along with a recirculation zone located in the turbine’s core, which is described to exhibit quasi-symmetric behaviour between positive and negative rotations.

In this work, metamodeling was performed to conduct efficiency-based design optimization (EBDO) of an H-rotor VAWT coupled with fixed guiding-walls surrounding its rotor. A design of experiments (DoE) created sampling points from the desired design space. Kriging generated surrogate models using input and output pairs calculated by CFD analyses. The Nelder–Mead Downhill Simplex optimization technique was used to determine the optimal design which satisfied the stated constraints. An estimated level of uncertainty was assigned to each random design variable for the efficiency analyses. Designing of guiding walls were considered, with different geometrical parameters. The results of the surrogate model were compared with those of the CFD, and an optimal solution was selected. The Open Darrieus VAWT and Optimal Darrieus​ VAWT with guiding-walls comparison revealed a considerable improvement of up to 177% at λ=3. It was evident that the enhancement in power coefficient due to augmentation of airflow velocity when VAWT is equipped with guiding walls. As a result, the placement and formation of the guiding walls has a significant role in the amount of power produced.

The objective of this work is to conduct a stress analysis of an H-rotor vertical axis wind turbine (VAWT) blade under aerodynamic loads. The rotor blade is designed based on the maximum deflection and bending stresses at extreme loading conditions, specifically the maximum radial force acting on the blade. The impact of the tip speed ratio and blade pitch angle on the bending stress of the H-rotor VAWT is presented. Analytical beam theories are used to determine the maximum deformation and bending stress, which are then validated numerically using the finite element method (FEM) with ANSYS software. The blade is composed of S-2 fiberglass/Epoxy composite material. The stress analysis is performed on both a solid cross-section blade and a hollow blade with varying wall thickness. A comparison is made between the S-2 fiberglass/Epoxy and carbon fiber/Epoxy composites, revealing that carbon fiber composites induce greater deflection in the rotor blade compared to S-2 fiberglass blades. Additionally, it is concluded that the tip speed ratio directly affects both the bending stress and total deflection of the blade.

Offshore floating wind foundations supporting a large wind turbine require a large yard facility or significant facility upgrades for their fabrication. To overcome the cost increase associated with facility upgrades, an innovative lightweight modular floating foundation is developed. The foundation comprises multiple modules to enable their assembly on water, offering many benefits and expanding fabrication options for a reduction in the overall cost of the platform. In this paper, the foundation modules and their assembly are briefly described, and an analysis of the platform’s dynamic responses is presented. The modular foundation includes a modular and lightweight tension leg platform (TLP) called “MarsVAWT” which supports a Darrieus 10 MW vertical axis wind turbine (VAWT). The platform is moored with highly pretensioned wire rope tendons. The responses of the platform are analyzed in the time domain in a semi-coupled manner under the turbine operating and parked conditions for an offshore site in the US Northeast. The tower base shear forces and bending moments increase considerably with the combination of wind and waves, compared to those with wind only. The tendon tensions on the weatherside in the operating condition at high wind speeds are comparable to the values of the 50-year extreme (parked). The tendon tension increases are highly correlated to the platform pitch, as well as the horizontal and vertical velocities and vertical acceleration at the tendon porch. The modular platform performances and tendon designs are confirmed to comply with industry standards and practices.

Abstract In recent urban buildings, there is an interest in using wind turbines inside the buildings. Thus, the rotors of wind turbines are shrouded by the walls of the buildings. A design for using wind turbines in urban areas is to use shrouded turbines on the roof of a building. Since vertical axis wind turbines (VAWTs) with low environmental impacts are recommended for energy supply in urban areas, here, the interaction of two shrouded VAWTs has been studied numerically. Based on the effects of different shroud parts, the diffuser‐shrouded turbines are selected. The arrangement of diffuser‐shrouded VAWTs has been optimized using the response surface method optimization with the Kriging model. The optimization samples are chosen by the design of experiment method to reduce the number of simulations and increase optimization accuracy. The total power coefficient of the optimized cluster is 46.2% higher than the sum of the same individual diffuser‐shrouded turbines and 149.6% higher than the sum of individual bare VAWTs. The economic assessment shows that the levelized cost of energy of the optimized cluster of two diffuser‐shrouded VAWTs is reduced by about 40% compared to two bare VAWTs.

The present study treats numerically the performance of a straight-bladed, vertical axis, Darieus wind turbine. A two-dimensional (2D), Unsteady Reynolds-averaged Navier–Stokes (URANS) simulations were performed out by the solver ANSYS/FLUENT using the sliding mesh method. Four turbulence models, namely the one-equation Spalart– Almaras (SA) model, the two-equation Shear Stress Transport (SST) k-ω, the Transitional Shear Stress Transport (TSST), and the realizable k-ϵ models, with low Reynolds number capabilities, were tested.The dependency of the power curve upon the torque coefficient and the Tip Speed Ratio (TSR) was evaluated under identical conditions to previously published experimental studies. The results suggest that the realizable k-ϵ model outperformed other turbulence models and matched better with the experimental data. Further numerical investigations were performed to determine the conditions for an optimal performance of the VAWT in question.

The wind energy market is currently dominated by horizontal axis wind turbines (HAWTs); however, vertical axis wind turbines (VAWTs) are emerging as a design alternative, especially for deep‐water offshore siting due to their low center of gravity, ease of access to drivetrain components, and overall simplicity. Due to the absence of a pitch mechanism in large‐scale Darrieus VAWTs, stall control has often been used to manage power and loads. Introducing a pitching mechanism in H‐type VAWTs has been studied, but this diminishes the mechanical simplicity advantage, and the use of a pitching mechanism in a large‐scale Darrieus‐type VAWT is not practical. This work examines an innovative, alternative method to control the rotor dynamics of a large‐scale 5 MW VAWT to maximize power while constraining loads without introducing any new or complex mechanical elements. This control strategy is termed intracycle revolution per minute (RPM) control, where the rotational speed of the turbine is allowed to vary in an optimal fashion with the azimuthal location of blades as opposed to typical constant RPM operation. An optimization framework is formulated for an open‐loop optimal control problem and solved to maximize power subject to constraints on aerodynamic design loads. Results are presented to demonstrate the benefits and the performance limits of intracycle RPM control for large‐scale 5 MW Darrieus VAWTs, namely, (1) power production (quantified in terms of AEP) that can be increased subject to baseline load limits and (2) opportunities to significantly increase AEP or decrease loads via intracycle RPM control that are examined for both two‐bladed and three‐bladed VAWTs. [ABSTRACT FROM AUTHOR]

Piezoelectric Energy Harvesting (PEH) has been increasingly adopted due to its substantial potential to harness unutilized vibrations for multiple small- and large-scale real-life applications. Various publications have discussed the PEH rationale and operating principles. Nonetheless, there is a considerable knowledge gap, reflected in a limited number of peer-reviewed articles, involving the selection of optimal PEH location during real-time operational excitations, like wind turbines. Subsequently, this paper considers the Vertical-Axis Wind Turbines (VAWTs) to accumulate vibrations realized mainly at the turbine's tower. Experimental Modal Analysis (EMA) and Operational Deflection Shape (ODS) analysis were employed to predict the natural frequency behavior, vibrational intensity, and electrical power output at various locations along the VAWT's tower. The tower was divided into eight zones to determine which region could yield the maximum power output from the VAWT-PEH system. Many publications have suggested that the region closer to the fixed base of the VAWT would experience the maximum deflection. Yet, this research has shown that the zone nearer the top of the VAWT tower exhibited the highest deflection rates and greater turbulence, resulting in better electrical power production. Consequently, region No. 1 gave the highest deflection, corresponding to a maximum electrical power from excitations with a peak-to-peak voltage of 2.834 V compared with 2.754 V for point No. 8. These lower charges could be practical for powering small-power consumption devices, such as sensors and LEDs, especially when they need a permanent power supply. [ABSTRACT FROM AUTHOR]

The current strong global consensus on reducing carbon emissions is a motivation to develop more efficient means of harnessing sustainable sources of energy. Accordingly, research efforts toward the development of more efficient wind turbine designs are desirable. With this motivation, we present a set of numerical studies on flows past vertical axis wind turbines (VAWTs). We perform large eddy simulations (LES) of flows past several VAWT configurations. A uniform inflow is set for our simulations. The influence of turbine blades on the flow field is modeled using the actuator line method (ALM). Our focus is on a twin rotor configuration, wherein the rotors are placed close enough, so that the separation between the centers of the two rotors is less than the diameter of the two individual turbines (the overlapping configuration). We demonstrate that such a configuration indeed results in (a) the enhanced power coefficient (ratio of power extracted by the turbine configuration to the power available in the freestream) and (b) better power density (power extracted by a turbine configuration per unit ground area occupied by the VAWT) compared to a single rotor VAWT configuration. Based on our findings, we conclude that the overlapping twin rotor arrangement can prove to be the preferred configuration for large-scale VAWT-based wind farms. [ABSTRACT FROM AUTHOR]

Given the state of the world nowadays, renewable energy is becoming more and more essential rendering wind turbine electricity quite important. Its shape and the fact that the Savonius vertical axis wind turbine runs at relatively low wind speeds with high torque values makes it suitable for practical uses such as that of an irrigation system in agriculture industry. This paper utilizes numerical research with Computational Fluid Dynamics (CFD) to investigate the performance of a vertical-axis wind turbine. The ANSYS CFD program was engaged to construct the simulations during the pre- and post-processing stages. Wind speed remained constant while the angular velocity was altered to enable analysis of the flow through the wind turbine. Because of its mechanical simplicity, the primary profile of a semicircle has remained a typical option for turbines that generate high torque based on drag force. The effects of using elliptical curves and the fluctuation in thickness along the profile chord were both examined in this study. Equivalently, an attempt to optimize the rotor's design was made. After the performance of a numerical simulation, a geometry consisting of simple circle arcs was developed, with a 10.9% improvement in the power coefficient, analogous to prior optimizations with more complicated geometries. The numerical results derived include the torque coefficient evolution throughout a full rotation as well as the distribution of vorticity magnitude at different rotor points. [ABSTRACT FROM AUTHOR]