Large-scale Vertical Axis Wind Turbines Research Articles

Blade Structure Analysis of 2 MW V-Shaped Vertical Axis Wind Turbine Using Numerical Simulation

The intensive research on large-scale Vertical Axis Wind Turbine (VAWT) couldprovide an alternative to Horizontal Axis Wind Turbine (HAWT) in offshore deployment for the future. Regarding this fact, this article develops a conceptual design of the VAWT blade structure and analyzes its feasibility using numerical simulation. The blade structure is designed for 2 MW Darrieus type V- shaped VAWT. The blade is tapered, 90m long, and inclined at 35° to the vertical axis. Initially, the blade design is tested for ultimate strength test according to IEC 61400-01 standard using aluminum alloy and homogenized composite material. In doing so, maximum aerodynamic loading on the blade is calculated after steady state 3-D RANS CFD simulation of the blade in ANSYS Fluent. The Finite Element Method (FEM) model of the blade is created using shell element in ANSYS Static Structural with structured meshing strategy, and tested with the aerodynamic load using the one-way Fluid-Structure Interaction (FSI) technique, to obtain mesh independent solution. The impact of the using 2, 3, and 4 number of shear webs is then analyzed on the selected mesh model of the blade. Finally, a four-shear web model of the blade is tested under extreme conditions. The thickness of the blade surface and shear web are varied to test maximum deflection at the tip, and maximum allowable strain of the blade. After obtaining the required blade structure, the deformation, maximum equivalent stress, and maximum equivalent strain for the blade are studied at rotation Tip Speed Ratio (TSR) of 5 under aerodynamic and gravitational loading, using both materials. The study showed significant deflection at the tip of the blade for the tower-less V-VAWT blade, suggesting an alternative support mechanism for the blade. Also, the study concluded that better structural robustness is achieved while using a composite material instead of an aluminum alloy. This article provides basis to study structural behavior of the novel V-VAWT blades and contribute to continuing research on obtaining optimized blade structure for such turbine.

Three-dimensional computational fluid dynamic analysis of a large-scale vertical axis wind turbine

The vertical axis wind turbine (VAWT) configuration has many advantages for an offshore wind turbine Installation. In this paper, the three dimensional (3D) computational fluid dynamics analysis of a large-scale 5 MW VAWT is conducted. At the optimum tip-speed ratio (TSR), the VAWT maximum inline force was 75% larger than the maximum lateral force. It was found the dynamic stall effects cause the VAWT flow field to become increasingly asymmetrical at the mid-span plane, when the TSR is reduced. The attachment of end plates to the blade tips, resulted in a performance improvement during the upwind phase with the average blade torque coefficient in this range being increased by 4.71%. Conversely, during the blade downwind phase a reduction in performance was found due to the increase in drag from the end plates and the average blade torque coefficient in this phase was reduced by 23.1%.

Employing Computational Fluid Dynamics to Derive Beddoes–Leishman Model Airfoil Parameters for Vertical Axis Wind Turbines

AbstractThe blades of a vertical axis wind turbine (VAWT) experience large variations in the angle of attack at low tip-speed ratios and induce blade force oscillation. These unsteady aerodynamic effects must be considered in the VAWT aerodynamic modelling methodology by utilizing a dynamic stall model. The Beddoes–Leishman (B–L) dynamic stall model is a popular method to simulate the unsteady VAWT blade dynamic stall aerodynamics. However, a limitation of the B–L dynamic stall model is the number of the airfoil dependent parameters derived from both steady and unsteady experimental measurements. In this paper, a methodology is described to compute these B–L dynamic stall model airfoil coefficients utilizing a computational fluid dynamics (CFD) model. This method permits the calculation of the blade dynamic stall characteristics over a range of reduced pitch rates by employing a user-defined sliding mesh motion technique. Furthermore, the variation in the blade Reynolds number is accounted for by conducting simulations at the maximum and minimum VAWT envelope operating limits. Aerodynamic blade force experimental measurements are used to compare the predictions from a low-order model with airfoil data extracted CFD and experiments. This approach expands the applicability of the B–L dynamic stall model for large-scale VAWTs.

Review on the Evolution of Darrieus Vertical Axis Wind Turbine: Large Wind Turbines

The objective of the current review is to present the development of a large vertical axis wind turbine (VAWT) since its naissance to its current applications. The turbines are critically reviewed in terms of performance, blade configuration, tower design, and mode of failure. The early VAWTs mostly failed due to metal fatigue since the composites were not developed. Revisiting those configurations could yield insight into the future development of VAWT. The challenges faced by horizontal axis wind turbine (HAWT), especially in the megawatt capacity, renewed interest in large scale VAWT. VAWT provides a solution for some of the immediate challenges faced by HAWT in the offshore environment in terms of reliability, maintenance, and cost. The current rate of research and development on VAWT could lead to potential and economical alternatives for HAWT. The current summary on VAWT is envisioned to be an information hub about the growth of the Darrieus turbine from the kW capacity to megawatt scale.

Structural Analysis of Large-Scale Vertical-Axis Wind Turbines, Part I: Wind Load Simulation

When compared with horizontal-axis wind turbines, vertical-axis wind turbines (VAWTs) have the primary advantages of insensitivity to wind direction and turbulent wind, simple structural configuration, less fatigue loading, and easy maintenance. In recent years, large-scale VAWTs have attracted considerable attention. Wind loads on a VAWT must be determined prior to structural analyses. However, traditional blade element momentum theory cannot consider the effects of turbulence and other structural components. Moreover, a large VAWT cannot simply be regarded as a planar structure, and 3D computational fluid dynamics (CFD) simulation is computationally prohibitive. In this regard, a practical wind load simulation method for VAWTs based on the strip analysis method and 2D shear stress transport (SST) k-ω model is proposed. A comparison shows that the wind pressure and aerodynamic forces simulated by the 2D SST k-ω model match well with those obtained by 2.5D large eddy simulation (LES). The influences of mean wind speed profile, turbulence, and interaction of all structural components are considered. A large straight-bladed VAWT is taken as a case study. Wind loads obtained in this study will be applied to the fatigue and ultimate strength analyses of the VAWT in the companion paper.

Field measurement, model updating, and response prediction of a large-scale straight-bladed vertical axis wind turbine structure

A renewed interest in vertical-axis wind turbines (VAWTs), especially straight-bladed VAWT (SB-VAWT), has been observed in recent years. Large-scale VAWTs were briefly explored in the 1980s, but have since been the subject of limited research. Thus, this paper presents a systematic investigation of the structural system of a large-scale SB-VAWT recently developed by Hopewell Holdings Limited of Hong Kong. The structural system, field measurement, finite element (FE) modeling, and model updating of the SB-VAWT is introduced sequentially. The proposed structural monitoring system can successfully identify the modal frequencies of the SB-VAWT below 10 Hz. The structural responses of the SB-VAWT are computed with the updated FE model and the simulated wind loads. The comparison between the computed and measured structural responses in the frequency domain shows satisfactory agreement. The results indicate that the proposed dynamic simulation approach based on a well-designed structural monitoring system can reproduce the structural responses of large-scale SB-VAWTs satisfactorily. This approach will shed light on the future analysis and optimization of this type of structure.

Aerodynamic modeling methods for a large-scale vertical axis wind turbine: A comparative study

Abstract Vertical axis wind turbines (VAWTs) are experiencing a renewed interest for large-scale offshore wind energy generation. However, the three-dimensional (3D) modeling of VAWT aerodynamics is a challenging task using computational fluid dynamics (CFD), owing to the high computational costs entailed. To alleviate this computational burden and improve design process efficiency, an alternative low-order model (LOM) is presented that incorporates key VAWT aerodynamic effects. These coupled sub-models account for the influence of dynamic stall, tower shadow, parasitic drag, flow curvature and finite blade effects. A two-step approach is adopted to investigate two-dimensional (2D) and 3D VAWT aerodynamics separately with experimental data. A CFD model was created and both modeling strategies were compared. The LOM showed good agreement with the CFD model and the measurements with a low computational cost requirement. The CFD results identified that as the tip-speed ratio (TSR) was increased, the tower's downwind wake became increasingly more skewed. Finally, both the LOM and the CFD model were employed in predicting the VAWT aerodynamic efficiency. It was established 3D effects must be included to provide an accurate prediction of VAWT performance especially at high TSRs. For VAWT analysts, modeling recommendations and limitations are discussed regarding the LOM.

Aeroelastic Stability Investigations for Large-scale Vertical Axis Wind Turbines

The availability of offshore wind resources in coastal regions, along with a high concentration of load centers in these areas, makes offshore wind energy an attractive opportunity for clean renewable electricity production. High infrastructure costs such as the offshore support structure and operation and maintenance costs for offshore wind technology, however, are significant obstacles that need to be overcome to make offshore wind a more cost-effective option. A vertical-axis wind turbine (VAWT) rotor configuration offers a potential transformative technology solution that significantly lowers cost of energy for offshore wind due to its inherent advantages for the offshore market. However, several potential challenges exist for VAWTs and this paper addresses one of them with an initial investigation of dynamic aeroelastic stability for large-scale, multi-megawatt VAWTs. The aeroelastic formulation and solution method from the BLade Aeroelastic STability Tool (BLAST) for HAWT blades was employed to extend the analysis capability of a newly developed structural dynamics design tool for VAWTs. This investigation considers the effect of configuration geometry, material system choice, and number of blades on the aeroelastic stability of a VAWT, and provides an initial scoping for potential aeroelastic instabilities in large-scale VAWT designs.