Computational fluid dynamic analysis of roof-mounted vertical-axis wind turbine with diffuser shroud, flange, and vanes

2018 ◽  
Vol 42 (4) ◽  
pp. 404-415
Author(s):  
H. Abu-Thuraia ◽  
C. Aygun ◽  
M. Paraschivoiu ◽  
M.A. Allard
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Guide Vane ◽  
Fluid Dynamic ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Guide Vanes ◽  
Turbine Design

Advances in wind power and tidal power have matured considerably to offer clean and sustainable energy alternatives. Nevertheless, distributed small-scale energy production from wind in urban areas has been disappointing because of very low efficiencies of the turbines. A novel wind turbine design — a seven-bladed Savonius vertical-axis wind turbine (VAWT) that is horizontally oriented inside a diffuser shroud and mounted on top of a building — has been shown to overcome the drawback of low efficiency. The objective this study was to analyze the performance of this novel wind turbine design for different wind directions and for different guide vanes placed at the entrance of the diffuser shroud. The flow field over the turbine and guide vanes was analyzed using computational fluid dynamics (CFD) on a 3D grid for multiple tip-speed ratios (TSRs). Four wind directions and three guide-vane angles were analyzed. The wind-direction analysis indicates that the power coefficient decreases to about half when the wind is oriented at 45° to the main axis of the turbine. The analysis of the guide vanes indicates a maximum power coefficient of 0.33 at a vane angle of 55°.

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.

Reduction in the torque ripple of a vertical axis wind turbine through foil pitching optimization

2019 ◽  
Vol 44 (2) ◽  
pp. 115-124 ◽  
Author(s):  
Gareth Erfort ◽  
Theodor W. von Backström ◽  
Gerhard Venter
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Vertical Axis ◽  
Torque Ripple ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Similar Reduction ◽  
Vertical Axis Wind Turbines ◽  
Gradient Based

Vertical axis wind turbines have a place in the small scale renewable energy market. They are not currently implemented on a commercial scale but have found a niche space in urban areas. Here, the turbulent wind conditions and limited space are more easily tapped into with a vertical axis wind turbine. However, the challenges facing these types of turbines have hampered deployment. One of these issues is the fluctuating torque experienced during operation, which can lead to over-designed power trains. Genetic- and gradient-based optimization is applied to an analytical model of a vertical axis wind turbine, in order to reduce the torque fluctuation while attempting to maintain a high power coefficient. The reduction in torque ripple is achieved through a sinusoidal pitching motion of the blades. The torque ripple can be reduced by 10% with a similar reduction in power coefficient.

Aerodynamic and aeroacoustic performance investigations on modified H-rotor Darrieus wind turbine

2021 ◽  
pp. 0309524X2110039
Author(s):  
Amgad Dessoky ◽  
Thorsten Lutz ◽  
Ewald Krämer
Keyword(s):  
Wind Turbine ◽  
High Speed ◽  
Cfd Simulation ◽  
Vertical Axis ◽  
3D Models ◽  
Power Coefficient ◽  
Design Parameters ◽  
Second Phase ◽  
Vertical Axis Wind Turbine ◽  
Guide Vanes

The present paper investigates the aerodynamic and aeroacoustic characteristics of the H-rotor Darrieus vertical axis wind turbine (VAWT) combined with very promising energy conversion and steering technology; a fixed guide-vanes. The main scope of the current work is to enhance the aerodynamic performance and assess the noise production accomplished with such enhancement. The studies are carried out in two phases; the first phase is a parametric 2D CFD simulation employing the unsteady Reynolds-averaged Navier-Stokes (URANS) approach to optimize the design parameters of the guide-vanes. The second phase is a 3D CFD simulation of the full turbine using a higher-order numerical scheme and a hybrid RANS/LES (DDES) method. The guide-vanes show a superior power augmentation, about 42% increase in the power coefficient at λ = 2.75, with a slightly noisy operation and completely change the signal directivity. A remarkable difference in power coefficient is observed between 2D and 3D models at the high-speed ratios stems from the 3D effect. As a result, a 3D simulation of the capped Darrieus turbine is carried out, and then a noise assessment of such configuration is assessed. The results show a 20% increase in power coefficient by using the cap, without significant change in the noise signal.

scholarly journals Numerical Investigation of the Savonius Vertical Axis Wind Turbine and Evaluation of the Effect of the Overlap Parameter in Both Horizontal and Vertical Directions on Its Performance

Symmetry ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 821 ◽  
Author(s):  
Mohammad Ebrahimpour ◽  
Rouzbeh Shafaghat ◽  
Rezvan Alamian ◽  
Mostafa Safdari Shadloo
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Weather Conditions ◽  
Vertical Axis ◽  
Power Coefficient ◽  
External Diameter ◽  
Vertical Axis Wind Turbine ◽  
Complex Process ◽  
Overlap Ratio ◽  
Volume Method

Exploiting wind energy, which is a complex process in urban areas, requires turbines suitable for unfavorable weather conditions, in order to trap the wind from different directions; Savonius turbines are suitable for these conditions. In this paper, the effect of overlap ratios and the position of blades on a vertical axis wind turbine is comprehensively investigated and analyzed. For this purpose, two positive and negative overlap situations are first defined along the X-axis and examined at the different tip speed ratios of the blade, while maintaining the size of the external diameter of the rotor, to find the optimum point; then, the same procedure is done along the Y-axis. The finite volume method is used to solve the computational fluid dynamics. Two-dimensional numerical simulations are performed using URANS equations and the sliding mesh method. The turbulence model employed is a realizable K-ε model. According to the values of the dynamic torque and power coefficient, while investigating horizontal and vertical overlaps along the X- and Y-axis, the blades with overlap ratios of HOLR = +0.15 and VOLR = +0.1 show better performances when compared to other corresponding overlaps. Accordingly, the average Cm and Cp improvements are 16% and 7.5%, respectively, compared to the base with a zero overlap ratio.

Development of the Dual Vertical Axis Wind Turbine Using Computational Fluid Dynamics

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Gabriel Naccache ◽  
Marius Paraschivoiu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Turbine ◽  
Urban Areas ◽  
High Efficiency ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Circular Path ◽  
Vertical Axis Wind Turbine

Small vertical axis wind turbines (VAWTs) are good candidates to extract energy from wind in urban areas because they are easy to install, service, and do not generate much noise; however, the efficiency of small turbines is low. Here-in a new turbine, with high efficiency, is proposed. The novel design is based on the classical H-Darrieus VAWT. VAWTs produce the highest power when the blade chord is perpendicular to the incoming wind direction. The basic idea behind the proposed turbine is to extend that said region of maximum power by having the blades continue straight instead of following a circular path. This motion can be performed if the blades turn along two axes; hence, it was named dual vertical axis wind turbine (D-VAWT). The analysis of this new turbine is done through the use of computational fluid dynamics (CFD) with two-dimensional (2D) and three-dimensional (3D) simulations. While 2D is used to validate the methodology, 3D is used to get an accurate estimate of the turbine performance. The analysis of a single blade is performed and the turbine shows that a power coefficient of 0.4 can be achieved, reaching performance levels high enough to compete with the most efficient VAWTs. The D-VAWT is still far from full optimization, but the analysis presented here shows the hidden potential and serves as proof of concept.

scholarly journals Design of Rotor Blades for Vertical Axis Wind Turbine with Wind Flow Modifier for Low Wind Profile Areas

2020 ◽  
Vol 12 (19) ◽  
pp. 8050 ◽  
Author(s):  
Mohanasundaram Anthony ◽  
Valsalal Prasad ◽  
Kannadasan Raju ◽  
Mohammed H. Alsharif ◽  
Zong Woo Geem ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Urban Areas ◽  
Wind Profile ◽  
Vertical Axis ◽  
Maximum Power ◽  
Power Coefficient ◽  
Wind Flow ◽  
Efficient Design ◽  
Vertical Axis Wind Turbine ◽  
Flow Modifier

This work focuses on the design and analysis of wind flow modifier (WFM) modeling of a vertical axis wind turbine (VAWT) for low wind profile urban areas. A simulation is carried out to examine the performance of an efficient low aspect ratio C-shaped rotor and a proposed involute-type rotor. Further, the WFM model is adapted with a stack of decreased diameter tubes from wind inlet to outlet. It accelerates the wind velocity, and its effectiveness is examined on the involute turbine. Numerical analysis is performed with a realizable K-ε model to monitor the rotor blade performance in the computational fluid dynamics (CFD) ANSYS Fluent software tool. This viscous model with an optimal three-blade rotor with 0.96 m2 rotor swept area is simulated between the turbine rotational speeds ranging from 50 to 250 rpm. The parameters, such as lift–drag coefficient, lift–drag forces, torque, power coefficient, and power at various turbine speeds, are observed. It results in a maximum power coefficient of 0.071 for the drag force rotor and 0.22 for the lift force involute rotor. Moreover, the proposed WFM with an involute rotor extensively improves the maximum power coefficient to an appreciable value of 0.397 at 5 m/s wind speed, and this facilitates efficient design in the low wind profile area.

Numerical Investigation of a Vertical Axis Wind Turbine Performance Characterization Using New Variable Pitch Control Scheme

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Amin A. Mohammed ◽  
Ahmet Z. Sahin ◽  
Hassen M. Ouakad
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Numerical Study ◽  
Average Power ◽  
Vertical Axis ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Variable Pitch ◽  
De Algorithm

Abstract A double multiple streamtube model coupled with variable pitch methodology is used to analyze the performance characteristics of a small-scale straight-bladed Darrieus type vertical axis wind turbine (SB-VAWT). The numerical study revealed that a fixed pitch of −2.5 deg could greatly enhance the performance of the wind turbine. However, no improvement is observed in the starting torque capacity. Furthermore, the performance of upwind and downwind zones has been investigated, and it is found that the VAWT starting capacity is improved by increasing/decreasing the pitch angle upwind/downwind of the turbine. To optimize the performance, four cases of variable pitch angle schemes of sinusoidal nature were examined. The parameters of the sinusoidal functions were optimized using differential evolution (DE) algorithm with different cost functions. The results showed improvement in the power coefficient, yet with low starting capacity enhancement. Among the objective functions used in DE algorithm, the negative of the average power coefficient is found to lead to the best starting capacity with moderate peak power coefficient.

Experimental Test of Multi-Stage Vertical-Axis Turbines for Cellular Communication Applications

2012 ◽  
Author(s):  
John Abraham ◽  
Brian Plourde ◽  
Greg Mowry ◽  
Ephraim Sparrow
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Fluid Dynamic ◽  
Turbine Blades ◽  
Vertical Axis ◽  
Power Production ◽  
Cellular Communication ◽  
Vertical Axis Wind Turbine ◽  
Rotating Shaft ◽  
Turbine Design

A multi-year research program has generated a working prototype for a vertical-axis wind turbine that is capable of powering cellular communication equipment. The turbine is designed to be affixed to already existing communication towers and thereby has a reduced cost of installation. The turbine is driven by air drag forces rather than by lift. It has a number of novel features including venting slots that are created to reduce the thrust loading on the communication tower. In addition, contoured caps are affixed to the upper and lower edges of the turbine blades to increase power production. As previously mentioned, the turbine design itself is a drag-based concept rather than the more typical lift-driven devices. The advantages of the drag-based design are: 1. lower startup wind speed, 2. slower rotation and a lessened vibrational load on the tower, 3. less sensitive to wind direction, and 4. it can be aligned with the tower. The design of the device was carried out through a combination of numerical simulation and experimentation. The simulations have evolved from preliminary two-dimensional calculations to a fully three dimensional, unsteady, computational fluid dynamic analysis. Simultaneously, the experiments have included both in-field and wind-tunnel tests of various stages of the turbine design. An outcome of the effort is a third-generation working vertical-axis wind turbine (VAWT) that is currently being evaluated with in-field tests. The results of the tests are positive and confirm the expectations that were developed during the product design phase. The turbine, which can be constructed with various rotor stages, has the capability of producing approximately 2–3 kW of power in wind-speed environments of 12–16 m/s. These power production levels are greatly in excess of that required to fully power the electronics equipment on a typical cellular communication tower. Unfortunately, subsequent tests showed that the turbine production dropped approximately sevenfold. The cause of the decrease in performance was friction in the mechanical components which coupled the rotating shaft to the support structure. This recognition reinforces the importance of low-resistance mechanical design for VAWTs. Another aspect of the turbine design is the specialized electronics which allow the electronics to adapt to local wind speeds and consequently increase the efficiency of the power production.

A Straight-Bladed Vertical Axis Wind Turbine With a Directed Guide Vane: Mechanism of Performance Improvement

2008 ◽  
Author(s):  
Hideki Kuma ◽  
Manabu Takao ◽  
Toshiyuki Beppu ◽  
Takao Maeda ◽  
Yasunari Kamada ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Performance Improvement ◽  
Aerodynamic Force ◽  
Guide Vane ◽  
Vortex Method ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Lagrangian Simulation

A straight-bladed vertical axis wind turbine with a directed guide vane has been proposed in order to enhance its torque. The experimental study of the proposed wind turbine was carried out by a wind tunnel with an outlet diameter of 1.8m. The tested rotor has 3 straight rotor blades with a profile of NACA0018, a radius of 0.35 m and a height of 0.7 m. The guide vane which consists of an arc plate rotates around the rotor and is directed to the wind by aerodynamic force generated by tail vanes, so as to put the guide vane in upstream of the rotor. As a result, the performance of the straight-bladed vertical axis turbine was improved by means of the directed guide vane and the power coefficient of the proposed wind turbine was approximately 1.2 times higher than that of the original wind turbine which has no guide vane. Further, flows around the proposed wind turbine have been investigated by use of the vortex method which provides a Lagrangian simulation of unsteady and vortical flows.

scholarly journals Numerical evaluation of aerodynamic performances of vertical-axis wind turbine rotor with flow concentrator

2020 ◽  
Author(s):  
Jelena Svorcan ◽  
◽  
Ognjen Peković ◽  
Toni Ivanov ◽  
Miloš Vorkapić ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Operating Conditions ◽  
Power Coefficient ◽  
Small Scale ◽  
Vertical Axis Wind Turbine ◽  
Flow Simulations ◽  
Wind Speeds

With wind energy extraction constantly increasing, the interest in small-scale urban wind turbines is also expanding. Given that these machines often work in adverse operating conditions (Earth’s boundary layer, vortex trails of surrounding objects, small and changeable wind speeds), additional elements that locally augment wind velocity and facilitate turbine start may be installed. This paper investigates possible benefits of adding an optimized flow concentrator to a vertical-axis wind turbine (VAWT) rotor. Three-dimensional, unsteady, turbulent, incompressible flow simulations of both isolated rotor consisting of three straight blades and a rotor with flow concentrator have been performed in ANSYS FLUENT by finite volume method for several different operational regimes. This type of flow simulations is challenging since flow angles are high, numerous flow phenomena and instabilities are present and the interaction between the blades and detached vortices can be significant. The rotational motion of the blades is solved by the unsteady Sliding Mesh (SM) approach. Flow field is modeled by Unsteady Reynolds Averaged Navier-Stokes (URANS) equations with k-ω SST turbulence model used for closure. Both quantitative and qualitative examinations of the obtained numerical results are presented. In particular, the two computed power coefficient curves are compared and the advantages of installing a flow concentrator are accentuated.

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