scholarly journals Theoretical Modeling of Vertical-Axis Wind Turbine Wakes

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 10 ◽  
Author(s):  
Mahdi Abkar
Keyword(s):  
Wind Turbine ◽  
Wind Velocity ◽  
Measurement Data ◽  
Vertical Axis ◽  
Theoretical Models ◽  
Momentum Balance ◽  
Vertical Axis Wind Turbine ◽  
Gaussian Shape ◽  
Velocity Defect ◽  
Wake Model

In this work, two different theoretical models for predicting the wind velocity downwind of an H-rotor vertical-axis wind turbine are presented. The first model uses mass conservation together with the momentum theory and assumes a top-hat distribution for the wind velocity deficit. The second model considers a two-dimensional Gaussian shape for the velocity defect and satisfies mass continuity and the momentum balance. Both approaches are consistent with the existing and widely-used theoretical wake models for horizontal-axis wind turbines and, thus, can be implemented in the current numerical codes utilized for optimization and real-time applications. To assess and compare the two proposed models, we use large eddy simulation as well as field measurement data of vertical-axis wind turbine wakes. The results show that, although both models are generally capable of predicting the velocity defect, the prediction from the Gaussian-based wake model is more accurate compared to the top-hat counterpart. This is mainly related to the consistency of the assumptions used in the Gaussian-based wake model with the physics of the turbulent wake development downwind of the turbine.

Experimental Study of Vertical Axis Wind Turbine with Wind Speed Self-Adapting

2012 ◽  
Vol 215-216 ◽  
pp. 1323-1326
Author(s):  
Ming Wei Xu ◽  
Jian Jun Qu ◽  
Han Zhang
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Velocity ◽  
Vertical Axis ◽  
Maximum Power ◽  
The Self ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Opening And Closing

A small vertical axis wind turbine with wind speed self-adapting was designed. The diameter and height of the turbine were both 0.7m. It featured that the blades were composed of movable and fixed blades, and the opening and closing of the movable blades realized the wind speed self-adapting. Aerodynamic performance of this new kind turbine was tested in a simple wind tunnel. Then the self-starting and power coefficient of the turbine were studied. The turbine with load could reliably self-start and operate stably even when the wind velocity was only 3.6 m/s. When the wind velocity was 8 m/s and the load torque was 0.1Nm, the movable blades no longer opened and the wind turbine realized the conversion from drag mode to lift mode. With the increase of wind speed, the maximum power coefficient of the turbine also improves gradually. Under 8 m/s wind speed, the maximum power coefficient of the turbine reaches to 12.26%. The experimental results showed that the new turbine not only improved the self-starting ability of the lift-style turbine, but also had a higher power coefficient in low tip speed ratio.

Coupled Dynamics of a Vertical Axis Wind Turbine (VAWT) With Active Blade Pitch Control on a Semi-Submersible Floater

2018 ◽  
Author(s):  
Ebert Vlasveld ◽  
Fons Huijs ◽  
Feike Savenije ◽  
Benoît Paillard
Keyword(s):  
Wind Turbine ◽  
Wind Velocity ◽  
Vertical Axis ◽  
Power Production ◽  
Mooring Line ◽  
Vertical Axis Wind Turbine ◽  
Coupled Dynamics ◽  
Low Frequencies ◽  
Pitch Control ◽  
Thrust And Torque

A vertical axis wind turbine (VAWT) typically has a low position of the center of gravity and a large allowable tilt angle, which could allow for a relatively small floating support structure. Normally however, the drawback of large loads on the VAWT rotor during parked survival conditions limits the extent to which the floater size can be reduced. If active blade pitch control is applied to the VAWT, this drawback can be mitigated and the benefits can be fully utilized. The coupled dynamics of a 6 MW VAWT with active blade pitch control supported by a GustoMSC Tri-Floater semi-submersible floater have been simulated using coupled aero-hydro-servo-elastic software. The applied blade pitch control during power production results in a steady-state thrust curve which is more comparable to a HAWT, with the maximum thrust occurring at rated wind velocity. During power production, floater motions occur predominantly at low frequencies. These low frequency motions are caused by variations in the wind velocity and consequently the rotor thrust and torque. For the parked survival condition, it is illustrated that active blade pitch control can be used to effectively reduce dynamic load variations on the rotor and minimize floater motions and mooring line tensions.

Concepts Developed for a Multi-Phased, Vertical Axis Wind Turbine System With an Adjustable Inlet Air Scoop and Exit Drag Curtain

2010 ◽  
Author(s):  
Brett C. Krippene ◽  
Ira Sorensen
Keyword(s):  
Wind Turbine ◽  
Wind Velocity ◽  
Tall Buildings ◽  
Vertical Axis ◽  
Vertical Axis Wind Turbine ◽  
Flow Tube ◽  
Technical Feasibility ◽  
Essential Information ◽  
Wind Turbine System ◽  
Air Turbine

A conceptual design is presented of a roof-top type, MULTI-PHASED VERTICAL AXIS WIND TURBINE SYSTEM with an ADJUSTABLE INLET AIR SCOOP and EXIT DRAG CURTAIN at a 100 Watt to 50 kWe commercial scale. The MULTI-PHASED VERTICAL AXIS WIND TURBINE (MVAWT) SYSTEM is cost effective in an environmentally friendly manner. It is especially useful in areas where it can benefit from the wind velocity increasing and streamlining effects that may occur around small hills, roof tops and tall buildings. The MVAWT system concentrates, collects and utilizes the available energy in the wind by way of a naturally yawed, downwind seeking, vertical axis orientated flow tube and integrated air turbine assembly with adjustable inlet air scoop and outlet drag sections mounted on the flow tube. The MVAWT system’s air turbine is a combination radial or mixed out-flow and reaction cross-flow type centrifugal fan design as mounted on the discharge end of the flow tube. This air turbine, being more of a radial instead of an axial flow or propeller type design, can potentially exceed the Betz limit of 59.26% energy recovery or effectiveness from the maximum energy available from the wind flowing through the inlet flow tube. A low pressure drop screen can be provided at the inlet and outlet to protect flying birds and mammals from being drawn into the integrated flow tube and air turbine assembly. Additionally, access to the rotating components for inspection and maintenance purposes is much safer, easier and less costly than with conventional propeller type wind turbine systems mounted on tall towers. No multiple staged wind turbine system as described herein has as yet been researched as to its technical feasibility and developed to the point of a prototype demonstration at a commercial size. Such parameters as overall performance, energy conversion efficiency, costs (installed, operating and maintenance), system reliability, public acceptance and environmental impacts have not yet been truly assessed. A Phase I - technical feasibility assessment and Phase II - prototype demonstration program for a nominal 10 kWe sized Multi-Phased Vertical Axis Wind Turbine system with an average power output in a 16 mph wind of as much as 2 kWe (kW-hr / hr) and as much as 10 kWe (kW-hr / hr) at a 28 mph wind velocity is suggested to provide this essential information to both the authors and the public at large.

scholarly journals The Array Optimization of Vertical Axis Wind Turbine Based on a New Asymmetric Wake Model

2021 ◽  
Vol 9 (8) ◽  
pp. 820
Author(s):  
Zheng Yuan ◽  
Qihu Sheng ◽  
Ke Sun ◽  
Jun Zang ◽  
Xuewei Zhang ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Goal Function ◽  
Mean Amplitude ◽  
Vertical Axis ◽  
Good Choice ◽  
Vertical Axis Wind Turbine ◽  
Gaussian Functions ◽  
Array Optimization ◽  
Wake Model ◽  
Increasing Demand

With the increasing demand for wind energy, the vertical axis wind turbine (VAWT) is attracting more and more attention. In order to design the VAWT array for better performance, the VAWT wake model needs to reflect the wake characteristics well. Based on the asymmetric wake characteristic, a new VAWT wake model is proposed in this paper, which is a combination of two semi Gaussian functions with different deviations, and can be called the “double semi Gaussian functions wake model”. The model is simple and has only four parameters (mean, amplitude, left deviation and right deviation). Compared with the traditional Gaussian and Top-hat model, this model can better reflect the asymmetric characteristic of the VAWT wake. In particular, it can describe the behavior of wake merging in the case of counter-rotating twin turbines. Based on this wake model, the velocity field of VAWT array can be reproduced accurately. The goal function is mainly based on the performance of a basic array unit, and it can ensure the rapidity of the optimization process. The optimal arrangements under two different criteria are analyzed. Moreover, the truncation ratio is introduced to ensure that the downstream turbine works at the rated condition, and the optimal arrangements under different truncation ratios are analyzed. In this paper, the proposed wake model provides a good choice for the preliminary design of the VAWT array, and some relevant suggestions on the array arrangement have been put forward.

scholarly journals Analysis on the aerodynamic performance of vertical axis wind turbine subjected to the change of wind velocity

2012 ◽  
Vol 31 ◽  
pp. 213-219 ◽  
Author(s):  
Huimin Wang ◽  
Jianliang Wang ◽  
Ji Yao ◽  
Weibin Yuan ◽  
Liang Cao
Keyword(s):  
Wind Turbine ◽  
Wind Velocity ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Vertical Axis Wind Turbine

scholarly journals Optimization of Symmetrical Airfoils of the Darrieus Vertical Axis Wind Turbine

2020 ◽  
Vol 55 (3) ◽  
Author(s):  
Hadi Sutanto ◽  
Chin-Tu Lu ◽  
Hodik Chaiyadi
Keyword(s):  
Wind Turbine ◽  
Wind Velocity ◽  
Angle Of Attack ◽  
Vertical Axis ◽  
Coefficient Of Performance ◽  
Vertical Axis Wind Turbine ◽  
Horizontal Axis Wind Turbine ◽  
Lift And Drag ◽  
Lift And Drag Coefficient ◽  
The Impact

The vertical-axis wind turbine has an advantage over the horizontal-axis wind turbine because of its structural simplicity due to the independence of motion in wind direction. This article describes a new idea on how to develop the Darrieus vertical-axis wind turbine by modifying the angle of attack and adding airfoils on the wind turbine. The wind turbine has a symmetrical airfoil of NACA 0012 with three-double blade configurations to optimize the performance of the vertical shaft wind turbine. A computational fluid dynamics technique was used to understand the impact of variations of wind velocity on the angle of attack and additional distance of airfoil in turbulence intensity based on the contour of wind velocity passing the wind turbine. Using this method, the authors showed that the results of the study in turn with the variation of wind velocity, different angle of attack and additional distance of airfoil have an effect on the values of lift and drag coefficient. The highest value of the coefficient of lift is 4.1, followed by the coefficient of drag which is 0.79 at 0.3 m with the angle of attack at -4o, the wind velocity is 9.428 m/s and the result of the highest torque is 0.57 Nm which has a coefficient of performance of 1.3%.

scholarly journals Performance Analysis of Highway Wind Turbine Enhanced with Wind Guide Vanes Using the Taguchi Method

CFD letters ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 25-42
Author(s):  
Mohamad Zahid Mazlan ◽  
Fazila Mohd Zawawi ◽  
Teeab Tahzib ◽  
Kamarulafizam Ismail ◽  
Syahrullail Samion
Keyword(s):  
Taguchi Method ◽  
Wind Turbine ◽  
Wind Velocity ◽  
Guide Vane ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Guide Vanes ◽  
Moving Vehicle ◽  
Low Wind Speed

Considerable efforts have been made by researchers to study the interaction between moving vehicles and wind turbines. The Savonius vertical-axis wind turbine was chosen due to its effectiveness in low-wind speed conditions. Speeding vehicles produce a scattered and non-uniform wind flow with disturbances. Hence, to prevent a negative torque, a row of wind guide vane panels was arranged in front of the blades of a wind turbine. The wind guide vane had the shape of an NACA4412 aerofoil to reduce the loss of wind energy, and to further increase wind velocity. A number of CFD simulations were designed using the Taguchi method to determine the optimum conditions for the power coefficient of the wind turbine in terms of the effects of three factors, namely, the distance between the guide vanes (d), the angle of the guide vanes (?), and the speed of the moving car (VC). An orthogonal array of L9(33) was designed. In addition, to observe the effects of the wind velocity induced by the moving vehicle, the wind turbine was incorporated with one degree of freedom (1DOF). The results showed that the speed of the moving car played a major role in determining the power coefficient. The order of influence of each factor was ranked as VC > ? > d. The performance of the wind turbine was sensitive to the speed of the car and the angle of the guide vanes, whereas it was insensitive to the distance between the guide vanes. Furthermore, the analysis of the signal-to-noise (S/N) ratio suggested that the optimal combination of factors for a maximum power coefficient were d = 0.4m, ? = 30°, and VC =30m/s. The optimum setting increased the Cp to 26% compared to the Cp that was produced without the installation of the guide vanes.

scholarly journals THE EFFECT OF DARRIEUS AND SAVONIUS WIND TURBINES POSITION ON THE PERFORMANCE OF THE HYBRID WIND TURBINE AT LOW WIND SPEED

2020 ◽  
Author(s):  
Nawfal M. Ali ◽  
Abdul Hassan A. K ◽  
Sattar Aljabair
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Velocity ◽  
Vertical Axis ◽  
Aerodynamic Characteristics ◽  
The Other ◽  
Vertical Axis Wind Turbine ◽  
Low Wind Speed ◽  
Turbine Model ◽  
Better Than

This paper presents an experimental and numerical simulation to investigate a hybrid vertical axis wind turbine model highly efficient which can be worked at low wind speed by studying the aerodynamic characteristics of four models of hybrid VAWTs. The hybrid WT consists of the SWT having two blades and the DWT type straight having two blades. Four models were constructed to study experimentally and numerically to choose the best model. Two models were DWT in the upper and SWT in the lower, also two models were SWT in the upper and DWT in the lower. The phase stage angle between the turbines is 0o and 90o . The experimental and numerical results showed that the performance of hybrid WT where DWT in the upper and SWT in the lower with phase stage 90o is better than in the other models, it can be started to work at a wind velocity of 2.2 m/s. At the wind velocity 3 m/s, the values of the parameters are the rotational speed (198 rpm), the CP (0.3195), the CT (0.2003), the TSR (1.6) and self-starting rotation at this value of wind velocity (3 m/s). The efficiency of extracting the wind power by hybrid WT is (51.2 %).

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