Performance Analysis of Savonius-Style Wind Turbines Under Concentrated and Oriented Jets

Concave Part ◽

Open Test ◽

Horizontal Axis Wind Turbines

With the rapid growth of renewable energy sector, vertical axis wind turbines are finding their applications in the small-scale distributed wind energy system, particularly in rural areas. These turbines are simple in construction and easy to install with comparatively lower cost. However, the efficiency of these turbines is not competitive to that of horizontal axis wind turbines. In this paper, an attempt has been made to improve the efficiency of a Savonius-style vertical axis wind turbine under concentrated and oriented jets through installation of deflectors at different positions ahead of the turbine. The aim is to make the major portion of the flow to be incident on the concave part of the blades. Experiments are conducted in a low speed wind tunnel with an open test section facility. For all the experiments, the wind speed in the tunnel is kept constant at 6.2 m/s. The mechanical loads are varied to analyze the performance of the turbine at various tip speed ratios. In each case, both power and torque coefficients are calculated in order to estimate the performance indices of the turbine. Moreover, a suitable operating range of this turbine is specified. The present investigation demonstrates that with the installation of deflectors, the performance of the Savonius-style wind turbines can be sufficiently improved under concentrated and oriented jets. The peak power coefficient of 0.32 is achieved with an optimized position of the deflectors in front of both the advancing and returning blades.

The Straight-Bladed Morphing Vertical Axis Wind Turbine

ASME 2016 Power Conference ◽

10.1115/power2016-59192 ◽

2016 ◽

Author(s):

David MacPhee ◽

Asfaw Beyene

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Low Cost ◽

Vertical Axis ◽

Power Coefficient ◽

Pitch Control ◽

Control Schemes ◽

Novel Concept

Blade pitch control has been extremely important for the development of Horizontal-Axis Wind Turbines (HAWTs), allowing for greater efficiency over a wider range of operational regimes when compared to rigid-bladed designs. For Vertical-Axis Wind Turbines (VAWTs), blade pitching is inherently more difficult due to a dependence of attack angle on turbine armature location, shaft speed, and wind speed. As a result, there have been very few practical pitch control schemes put forward for VAWTs, which may be a major reason why this wind turbine type enjoys a much lower market share as compared to HAWTs. To alleviate this issue, the flexible, straight-bladed vertical-axis turbine is presented, which can passively adapt its geometry to local aerodynamic loadings and serves as a low-cost blade pitch control strategy increasing efficiency and startup capabilities. Using two-dimensional fluid-structure action simulations, this novel concept is compared to an identical rigid one and is proven to be superior in terms of power coefficient due to decreased torque minima. Moreover, due to the flexible nature of the blades, the morphing turbine achieves less severe oscillatory loadings. As a result, the morphing blade design is expected to not only increase efficiency but also system longevity without additional system costs usually associated with active pitch control schemes.

Recent Development in the Design of Wind Deflectors for Vertical Axis Wind Turbine: A Review

Energies ◽

10.3390/en14165140 ◽

2021 ◽

Vol 14 (16) ◽

pp. 5140

Author(s):

Altaf Hussain Rajpar ◽

Imran Ali ◽

Ahmad E. Eladwi ◽

Mohamed Bashir Ali Bashir

Keyword(s):

Wind Turbines ◽

Vertical Axis ◽

Optimization Techniques ◽

Rotor Blades ◽

Power Coefficient ◽

Potential Contribution ◽

Vertical Axis Wind Turbines ◽

Network Costs

Developments in the design of wind turbines with augmentation are advancing around the globe with the goal of generating electricity close to the user in built-up areas. This is certain to help lessen the power generation load as well as distribution and transmission network costs by reducing the distance between the user and the power source. The main objectives driving the development and advancement of vertical-axis wind turbines are increasing the power coefficient and the torque coefficient by optimizing the upstream wind striking on the rotor blades. Unlike horizontal-axis wind turbines, vertical axis turbines generate not only positive torque but also negative torque during operation. The negative torque generated by the returning blade is a key issue for vertical-axis wind turbines (VAWTs) that is counterproductive. Installation of wind deflectors for flow augmentation helps to reduce the negative torque generated by the returning blades as well as enhance the positive torque by creating a diversion in the upstream wind towards the forwarding blade during operation. This paper reviews various designs, experiments, and CFD simulations of wind deflectors reported to date. Optimization techniques for VAWTs incorporating wind deflectors are discussed in detail. The main focus of the review was on the installation position and orientation of the deflectors and their potential contribution to increasing the power coefficient. Topics for future study are suggested in the conclusion section of the paper.

Experimental Investigation of Overlap and Blockage Effects on Three-Bucket Savonius Rotors

Wind Engineering ◽

10.1260/030952407783418702 ◽

2007 ◽

Vol 31 (5) ◽

pp. 363-368 ◽

Cited By ~ 26

Author(s):

A. Biswas ◽

R. Gupta ◽

K.K. Sharma

Keyword(s):

Wind Turbines ◽

Vertical Axis ◽

Power Coefficient ◽

Experimental Investigations ◽

Small Scale ◽

Correction Factors ◽

Vertical Axis Wind Turbines ◽

Blockage Correction ◽

Model Rotor

Savonius vertical axis wind turbines (VAWT) have advantages over horizontal axis wind turbines (HAWT), such as simple construction, acceptance of wind from any direction without orientation, self-starting, inexpensive etc. These advantages make it a viable proposition for small-scale applications in developing countries. In spite of the above advantages, VAWT are not gaining popularity mainly because of their poor efficiency. Hence, a three-bucket Savonius model rotor, having 8 cm bucket diameter and 20 cm height, was designed, fabricated, and tested in a sub-sonic wind tunnel. Provisions for variations of ‘blade’ overlap were included. Experiments were conducted for overlap conditions in the range of 16% to 35%. From the experimental investigations, power-coefficients (Cp) were calculated with and without blockage correction factors for tunnel interference. In both analyses, the power-coefficient increased if there was overlap, with an optimum value at 20% overlap of 47% without blockage correction, and 38% with blockage correction.

Double-Multiple Streamtube Analysis of a Flexible Vertical Axis Wind Turbine

Fluids ◽

10.3390/fluids6030118 ◽

2021 ◽

Vol 6 (3) ◽

pp. 118

Author(s):

Lalit Roy ◽

Kellis Kincaid ◽

Roohany Mahmud ◽

David W. MacPhee

Keyword(s):

Wind Turbines ◽

Vertical Axis ◽

Power Coefficient ◽

Speed Ratio ◽

Lower Efficiency ◽

Major Disadvantage ◽

Operational Range ◽

Naca 0012

Vertical-axis wind turbines (VAWTs) have drawn increased attention for off-grid and off-shore power generation due to inherent advantages over the more popular horizontal-axis wind turbines (HAWTs). Among these advantages are generator locale, omni-directionality and simplistic design. However, one major disadvantage is lower efficiency, which can be alleviated through blade pitching. Since each blade must transit both up- and down-stream each revolution, VAWT blade pitching techniques are not yet commonplace due to increased complexity and cost. Utilizing passively-morphing flexible blades can offer similar results as active pitching, requiring no sensors or actuators, and has shown promise in increasing VAWT performance in select cases. In this study, wind tunnel tests have been conducted with flexible and rigid-bladed NACA 0012 airfoils, in order to provide necessary input data for a Double-Multiple Stream-Tube (DMST) model. The results from this study indicate that a passively-morphing VAWT can achieve a maximum power coefficient (Cp) far exceeding that for a rigid-bladed VAWT CP (18.9% vs. 10%) with reduced normal force fluctuations as much as 6.9%. Operational range of tip-speed ratio also is observed to increase by a maximum of 40.3%.

Vertical axis wind turbine operation in icing conditions: A review study

Wind Engineering ◽

10.1177/0309524x211061828 ◽

2021 ◽

pp. 0309524X2110618

Author(s):

Syed Abdur Rahman Tahir ◽

Muhammad Shakeel Virk

Keyword(s):

Wind Turbine ◽

Wind Turbines ◽

Vertical Axis ◽

Electricity Production ◽

Vertical Axis Wind Turbines ◽

Promising Solution ◽

Review Study ◽

Accretion Physics

Vertical Axis Wind Turbine (VAWT) can be a promising solution for electricity production in remote ice prone territories of high north, where good wind resources are available, but icing is a challenge that can affect its optimum operation. A lot of research has been made to study the icing effects on the conventional horizontal axis wind turbines, but the literature about vertical axis wind turbines operating in icing conditions is still scarce, despite the importance of this topic. This paper presents a review study about existing knowledge of VAWT operation in icing condition. Focus has been made in better understanding of ice accretion physics along VAWT blades and methods to detect and mitigate icing effects.

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

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-2017-0093 ◽

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 ◽

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°.

Optimized Small Vertical Axis Wind Turbine (VAWT), Phase I

10.1115/gtindia2021-74879 ◽

2021 ◽

Author(s):

Moshe Zilberman ◽

Abdelaziz Abu Sbaih ◽

Ibrahim Hadad

Keyword(s):

Wind Energy ◽

Wind Turbine ◽

Wind Turbines ◽

Cost Effective ◽

Clean Energy ◽

Vertical Axis ◽

Low Noise ◽

Power Coefficient ◽

Different Types

Abstract Wind energy has become an important resource for the growing demand for clean energy. In 2020 wind energy provided more than 6% of the global electricity demand. It is expected to reach 7% at the end of 2021. The installation growth rate of small wind turbines, though, is relatively slow. The reasons we are interested in the small vertical axis wind turbines are their low noise, environmentally friendly, low installation cost, and capable of being rooftop-mounted. The main goal of the present study is an optimization process towards achieving the optimal cost-effective vertical wind turbine. Thirty wind turbine models were tested under the same conditions in an Azrieli 30 × 30 × 90 cm low-speed wind tunnel at 107,000 Reynolds number. The different types of models were obtained by parametric variations of five basic models, maintaining the same aspect ratio but varying the number of bucket phases, the orientation angles, and the gaps between the vanes. The best performing turbine model was made of one phase with two vanes of non-symmetric bipolynomial profiles that exhibited 0.2 power coefficient, relative to 0.16 and 0.13 that were obtained for symmetrical polynomial and the original Savonius type turbines, respectively. Free rotation, static forces and moments, and dynamic moments and power were measured for the sake of comparison and explanation for the variations in performances of different types of turbines. CFD calculations were used to understand the forces and moment behaviors of the optimized turbine.

An experimental study of the optimal design parameters of a wind power tower used to improve the performance of vertical axis wind turbines

Advances in Mechanical Engineering ◽

10.1177/1687814018799543 ◽

2018 ◽

Vol 10 (9) ◽

pp. 168781401879954

Author(s):

Soo-Yong Cho ◽

Sang-Kyu Choi ◽

Jin-Gyun Kim ◽

Chong-Hyun Cho

Keyword(s):

Experimental Study ◽

Optimal Design ◽

Wind Turbine ◽

Wind Power ◽

Wind Turbines ◽

Vertical Axis ◽

Power Coefficient ◽

Design Parameters ◽

Vertical Axis Wind Turbines

In order to augment the performance of vertical axis wind turbines, wind power towers have been used because they increase the frontal area. Typically, the wind power tower is installed as a circular column around a vertical axis wind turbine because the vertical axis wind turbine should be operated in an omnidirectional wind. As a result, the performance of the vertical axis wind turbine depends on the design parameters of the wind power tower. An experimental study was conducted in a wind tunnel to investigate the optimal design parameters of the wind power tower. Three different sizes of guide walls were applied to test with various wind power tower design parameters. The tested vertical axis wind turbine consisted of three blades of the NACA0018 profile and its solidity was 0.5. In order to simulate the operation in omnidirectional winds, the wind power tower was fabricated to be rotated. The performance of the vertical axis wind turbine was severely varied depending on the azimuthal location of the wind power tower. Comparison of the performance of the vertical axis wind turbine was performed based on the power coefficient obtained by averaging for the one periodic azimuth angle. The optimal design parameters were estimated using the results obtained under equal experimental conditions. When the non-dimensional inner gap was 0.3, the performance of the vertical axis wind turbine was better than any other gaps.

CFD Investigation of the Multiple Rotors Darrieus Type Turbine Performance

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy ◽

10.1115/gt2019-91491 ◽

2019 ◽

Cited By ~ 1

Author(s):

Omar Sherif Mohamed ◽

Ahmed Ibrahim ◽

Ahmed M. R. El Baz

Keyword(s):

Urban Areas ◽

Low Cost ◽

Vertical Axis ◽

Power Coefficient ◽

Cfd Simulations ◽

Close Proximity ◽

Computational Fluid Dynamics Cfd ◽

Overall Performance

Abstract The last few years have witnessed researches concerned by vertical axis wind turbine (VAWT) performance considering its advantages compared to the horizontal axis wind turbines, as it can be operated in urban areas without producing noise, ease of maintenance and simple construction, in addition to its low cost. More interest is growing in developing efficient clusters of VAWT in order to increase power generation at specific sites by using multiple turbines. In the present work, the performance of various configurations of Darrieus type VAWT clusters is examined using computational fluid dynamics (CFD) simulations. The objective of this work is to increase the overall power coefficient of the turbines cluster compared to single rotor performance. This objective shall be achieved by examining mutual interactions between rotors arranged in close proximity and examining the effect of oblique angle between rotors on overall performance of the cluster of rotors. The performance is assessed by observing the overall power coefficient of the cluster. Also, the velocity wake of the simulated three rotors turbine cases was analyzed and compared to the that of the single rotor.

Experimental Vibration Analysis of a Small Scale Vertical Wind Energy System for Residential Use

Machines ◽

10.3390/machines7020035 ◽

2019 ◽

Vol 7 (2) ◽

pp. 35 ◽

Cited By ~ 1

Author(s):

Francesco Castellani ◽

Davide Astolfi ◽

Mauro Peppoloni ◽

Francesco Natili ◽

Daniele Buttà ◽

...

Keyword(s):

Wind Turbines ◽

Urban Areas ◽

Wind Farm ◽

Vertical Axis ◽

Energy System ◽

Small Scale ◽

Main Research ◽

Small Wind Turbines ◽

Low Sensitivity ◽

A Minor

In the recent years, distributed energy production has been one of the main research topics about renewable energies. The decentralization of electric production from wind resources raises the issues of reducing the size of generators, from the MW scale of industrial wind farm turbines to the kW scale, and possibly employing them in urban areas, where the wind flow is complex and extremely turbulent because of the presence of buildings and obstacles. On these grounds, the use of small-scale vertical axis small wind turbines (VASWT) is a valid choice for on-site generation (OSG), considering their low sensitivity with respect to turbulent flow and that there is no need to align the turbine with wind direction, as occurs with horizontal axis small wind turbines (HASWT). In addition, VASWTs have a minor acoustic impact with respect to HASWTs. The aim of this paper is to study the interactions that take place between a 1.2 kW, vertical axis, Darrieus VASWT turbine and a small, experimental building, in order to analyze the noise and the vibrations transmitted to the structure. One method to damp the vibrations is then assessed through spectral analysis of data acquired through accelerometers located both in the mast of the wind turbine and at the building walls. The results confirm the usefulness of dampers to increase the building comfort regarding vibrations.