The Effect of Number of Blades on the Performance of Helical-Savonius Vertical-Axis Wind Turbines

2012 ◽  
Author(s):  
Majid Rashidi ◽  
Jaikrishnan R. Kadambi ◽  
Asuquo Ebiana ◽  
Ali Ameri ◽  
James Reeher
Keyword(s):  
Wind Turbines ◽  
Three Dimensional ◽  
Vertical Axis ◽  
3D Models ◽  
Test Results ◽  
Rotor Design ◽  
Vertical Axis Wind Turbines ◽  
3D Geometry ◽  
Bladed Rotor ◽  
Series Of Experiments

This work presents the results of a series of experiments conducted on three different scaled-down Helical-Savonius vertical axis wind turbines (VAWT) systems. The work was aimed at investigating how the number of blades may affect the performance of the Helical-Savonius VAWTs. The first turbine consisted of two helical blades, the second turbine had three blades, and the third turbines had four blades. The work included a design phase in which the three dimensional (3D) geometry of each of three VAWTs were developed using a 3D drawing software. The 3D models were then uploaded to a rapid-prototyping machine to fabricate the VAWTs. The projected areas of each of the VAWTs were that of a rectangle of 4″ × 6″. A test setup was designed and developed to examine the performance of the scaled-down turbines. A 1.1 KW floor fan was used to simulate wind flow in the laboratory for testing of the turbines. A flow straightener was also designed and developed in order to minimize the turbulent flow of the air at the discharge opening of the floor fan. The test results show that the 3-bladed rotor design performs better than the two and four bladed turbines. Under the same wind speed conditions the 3-bladed turbine produced 18% more power compared to the 2-bladed turbine, whereas the 3-bladed turbine produced 30% more power compared to the 4-bladed turbine.

FloVAWT: Progress on the Development of a Coupled Model of Dynamics for Floating Offshore Vertical Axis Wind Turbines

2013 ◽  
Author(s):  
Maurizio Collu ◽  
Michael Borg ◽  
Andrew Shires ◽  
Feargal P. Brennan
Keyword(s):  
Experimental Data ◽  
Wind Turbines ◽  
Three Dimensional ◽  
Coupled Model ◽  
Vertical Axis ◽  
Potential Method ◽  
Vertical Axis Wind Turbine ◽  
Vertical Axis Wind Turbines ◽  
Wind Profiles ◽  
Gyroscopic Effects

In the present article, progress on the development of an aero-hydro-servo-elastic coupled model of dynamics for floating Vertical Axis Wind Turbines (VAWTs) is presented, called FloVAWT (Floating Vertical Axis Wind Turbine). Aerodynamics is based on Paraschivoiu’s Double-Multiple Streamtube (DMST) model [1] [2], relying on blade element momentum (BEM) theory, but also taking into account three-dimensional effects, dynamic stall, and unsteady wind profiles and platform motions. Hydrodynamics is modelled with a time domain seakeeping model [3], based on hydrodynamic coefficients estimated with a frequency analysis potential method. In this first phase of the research program, the system is considered a rigid body. The mooring system is represented through a user defined force-displacement relationship. Due to the lack of experimental data on offshore floating VAWTs, the model has initially been validated by taking each module separately and comparing it against known experimental data, showing good agreement. The capabilities of the program are illustrated through a case study, giving an insight on the relative importance of aerodynamics loads and gyroscopic effects with respect to hydrodynamic load effects.

Time-Resolved Experimental Characterization of the Wakes Shed by H-Shaped and Troposkien Vertical Axis Wind Turbines

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
Giacomo Persico ◽  
Vincenzo Dossena ◽  
Berardo Paradiso ◽  
Lorenzo Battisti ◽  
Alessandra Brighenti ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Large Scale ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Local Dynamic ◽  
Performance Measurements ◽  
Time Resolved ◽  
Vertical Axis Wind Turbines ◽  
Blade Section

In this paper, the aerodynamics of two vertical axis wind turbines (VAWTs) are discussed, on the basis of a wide set of experiments performed at Politecnico di Milano, Milan, Italy. A H-shaped and a Troposkien Darrieus turbine for microgeneration, featuring the same swept area and blade section, are tested at full-scale. Performance measurements show that the Troposkien rotor outperforms the H-shaped turbine, thanks to the larger midspan section of the Troposkien rotor and to the nonaerodynamic struts of the H-shaped rotor. These features are consistent with the character of the wakes shed by the turbines, measured by means of hot wire anemometry on several surfaces downstream of the models. The H-shape and Troposkien turbine wakes exhibit relevant differences in the three-dimensional morphology and unsteady evolution. In particular, large-scale vortices dominate the tip region of the wake shed by the H-shape turbine; these vortices pulsate significantly during the period, due to the periodic fluctuation of the blade aerodynamic loading. Conversely, the highly tapered shape of the Troposkien rotor not only prevents the onset of tip vortices, but also induces a dramatic spanwise reduction of tip speed ratio (TSR), promoting the onset of local dynamic stall marked by high periodic and turbulent unsteadiness in the tip region of the wake. The way in which these mechanisms affect the wake evolution and mixing process for the two classes of turbines is investigated for different tip speed ratios, highlighting some relevant implications in the framework of wind energy exploitation.

scholarly journals Parked and Operating Loads Analysis in the Aerodynamic Design of Multi-megawatt-scale Floating Vertical Axis Wind Turbines

2021 ◽  
Author(s):  
Mohammad Sadman Sakib ◽  
D. Todd Griffith
Keyword(s):  
Aspect Ratio ◽  
Wind Turbines ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Lateral Force ◽  
Aerodynamic Design ◽  
Power Performance ◽  
Vertical Axis Wind Turbines ◽  
Design Variables ◽  
Loads Analysis

Abstract. A good understanding of aerodynamic loading is essential in the design of vertical axis wind turbines (VAWTs) to properly capture design loads and to estimate the power production. This paper presents a comprehensive aerodynamic design study for a 5 MW Darrieus offshore VAWT in the context of multi-megawatt floating VAWTs. This study systematically analyzes the effect of different, important design variables including the number of blades (N), aspect ratio (AR) and blade tapering in a comprehensive loads analysis of both the parked and operating aerodynamic loads including turbine power performance analysis. Number of blades (N) is studied for 2- and 3-bladed turbines, aspect ratio is defined as ratio of rotor height (H) and rotor diameter (D) and studied for values from 0.5 to 1.5, and blade tapering is applied by means of adding solidity to the blades towards blade root ends, which affects aerodynamic and structural performance. Analyses were carried out using a three-dimensional vortex model named CACTUS (Code for Axial and Crossflow TUrbine Simulation) to evaluate both instantaneous azimuthal parameters as well as integral parameters, such as loads (thrust force, lateral force, and torque loading) and power. Parked loading is a major concern for VAWTs, thus this work presents a broad evaluation of parked loads for the design variables noted above. This study also illustrates that during the operation of a turbine, lateral loads are on par with thrust loads, which will significantly affect the structural sizing of rotor and platform & mooring components.

scholarly journals Actuator cylinder theory for multiple vertical axis wind turbines

2016 ◽  
Vol 1 (2) ◽  
pp. 327-340 ◽  
Author(s):  
Andrew Ning
Keyword(s):  
Conceptual Design ◽  
Wind Turbines ◽  
Power Loss ◽  
Wind Farm ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Navier Stokes ◽  
Vertical Axis Wind Turbines ◽  
Wide Range ◽  
Wake Interactions

Abstract. Actuator cylinder theory is an effective approach for analyzing the aerodynamic performance of vertical axis wind turbines at a conceptual design level. Existing actuator cylinder theory can analyze single turbines, but analysis of multiple turbines is often desirable because turbines may operate in near proximity within a wind farm. For vertical axis wind turbines, which tend to operate in closer proximity than do horizontal axis turbines, aerodynamic interactions may not be strictly confined to wake interactions. We modified actuator cylinder theory to permit the simultaneous solution of aerodynamic loading for any number of turbines. We also extended the theory to handle thrust coefficients outside of the momentum region and explicitly defined the additional terms needed for curved or swept blades. While the focus of this paper is a derivation of an extended methodology, an application of this theory was explored involving two turbines operating in close proximity. Comparisons were made against two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) simulations, across a full 360° of inflow, with excellent agreement. The counter-rotating turbines produced a 5–10 % increase in power across a wide range of inflow conditions. A second comparison was made to a three-dimensional RANS simulation with a different turbine under different conditions. While only one data point was available, the agreement was reasonable, with the computational fluid dynamics (CFD) predicting a 12 % power loss, as compared to a 15 % power loss for the actuator cylinder method. This extended theory appears promising for conceptual design studies of closely spaced vertical axis wind turbines (VAWTs), but further development and validation is needed.

Recent Advances in Rotor Design of Vertical Axis Wind Turbines

2012 ◽  
Vol 36 (6) ◽  
pp. 647-665 ◽  
Author(s):  
David MacPhee ◽  
Asfaw Beyene
Keyword(s):  
Power Generation ◽  
Wind Power ◽  
Recent Work ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Wind Power Generation ◽  
Small Scale ◽  
Rotor Design ◽  
Vertical Axis Wind Turbines ◽  
Design And Testing

The following work represents the most recent advances in design and testing of vertical axis wind turbines (VAWT) rotors. VAWTs have received much attention as of late due to proposed advantages in small scale and off grid wind power generation. Thus, many recent works have surfaced involving analysis, design and optimization of VAWT rotors in order to more efficiently convert wind energy to electricity or other readily usable means. This paper is a collection of most of the recent literature works involving VAWT rotor design and testing, the majority of which published after 2005. We discuss research in the designing of various lift based rotors as well as some drag based rotors, hybrids, and various others. The recent work in this area suggests VAWT capacity could dramatically increase in the near future, and play a vital role in obtaining cleaner, more sustainable energy when global energy demand is increasing at an unprecedented rate. HIGHLIGHTS A review of various works involving rotor design and testing of both lift and drag Vertical Axis Wind Turbines (VAWTs) is presented; Benefits of vertical axis wind turbines in small scale and off grid wind power generation is summarized; Much of the recent work, published after 2005, has been directed towards analyzing, designing, and optimizing rotor shapes. The body of this recent work suggests that research on VAWT rotor design continues to flourish and could make VAWTs a viable competitor to more traditional Horizontal Axis Wind Turbines (HAWTs) worldwide.

scholarly journals Formulation, Validation, and Application of a Novel 3D BEM Tool for Vertical Axis Wind Turbines of General Shape and Size

2021 ◽  
Vol 11 (13) ◽  
pp. 5874
Author(s):  
Andrea G. Sanvito ◽  
Vincenzo Dossena ◽  
Giacomo Persico
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Three Dimensional ◽  
Vertical Axis ◽  
Small Scale ◽  
Engineering Practice ◽  
Blade Profile ◽  
General Shape ◽  
Vertical Axis Wind Turbines ◽  
Shape And Size

Low order models based on the Blade Element Momentum (BEM) theory exhibit modeling issues in the performance prediction of Vertical Axis Wind Turbines (VAWT) compared to Computational Fluid Dynamics, despite the widespread engineering practice of such methods. The present study shows that the capability of BEM codes applied to VAWTs can be greatly improved by implementing a novel three-dimensional set of high-order corrections and demonstrates this by comparing the BEM predictions against wind-tunnel experiments conducted on three small-scale VAWT models featuring different rotor design (H-shaped and Troposkein), blade profile (NACA0021 and DU-06-W200), and Reynolds number (from 0.8×105 to 2.5×105). Though based on the conventional Double Multiple Stream Tube (DMST) model, the here-presented in-house BEM code incorporates several two-dimensional and three-dimensional corrections including: accurate extended polar data, flow curvature, dynamic stall, a spanwise-distributed formulation of the tip losses, a fully 3D approach in the modeling of rotors featuring general shape (such as but not only, the Troposkein one), and accounting for the passive effects of supporting struts and pole. The detailed comparison with experimental data of the same models, tested in the large-scale wind tunnel of the Politecnico di Milano, suggests the very good predictive capability of the code in terms of power exchange, torque coefficient, and loads, on both time-mean and time-resolved basis. The peculiar formulation of the code allows including in a straightforward way the usual spanwise non-uniformity of the incoming wind and the effects of skew, thus allowing predicting the turbine operation in a realistic open-field in presence of the environmental boundary layer. A systematic study on the operation of VAWTs in multiple environments, such as in coastal regions or off-shore, and highlighting the sensitivity of VAWT performance to blade profile selection, rotor shape and size, wind shear, and rotor tilt concludes the paper.

Fixed Wake Theory for Vertical Axis Wind Turbines

1983 ◽  
Vol 105 (4) ◽  
pp. 389-393 ◽  
Author(s):  
R. E. Wilson ◽  
S. N. Walker
Keyword(s):  
Wind Turbines ◽  
Vertical Axis ◽  
Explicit Calculation ◽  
Speed Ratio ◽  
Test Results ◽  
Vortex Methods ◽  
Tip Speed Ratio ◽  
Vertical Axis Wind Turbines ◽  
Darrieus Rotor ◽  
Good Agreement

A theory for vertical axis wind turbines has been developed using a fixed wake approach. The theory combines some of the best features of vortex and streamtube approaches. This approach accounts for flow differences between fore-and-aft-blade positions that are predicted by vortex methods while retaining the low computation costs associated with streamtube theories. The theory is applied to high tip speed ratio operation of a Darrieus Rotor where the use of linear aerodynamics results in explicit calculation of the induced velocities. Comparison to test results shows good agreement.

scholarly journals Location-Optimized Aerodynamic Rotor Design of Small Wind Turbines and Lightweight Implementation Using Additive Hybrid Material

2020 ◽  
Vol 22 (2) ◽  
pp. 437-446
Author(s):  
Daniel Lehser-Pfeffermann ◽  
Tobias Häfele ◽  
Frank U. Rückert ◽  
Jürgen Griebsch ◽  
Tobias Müller ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Wind Turbines ◽  
Selective Laser Sintering ◽  
Software Tool ◽  
Vertical Axis ◽  
Site Specific ◽  
Rotor Design ◽  
Vertical Axis Wind Turbines ◽  
Small Wind Turbines ◽  
Design Software

AbstractWind power plays a crucial role in supplying cities with renewable energy. Combined with short transport routes, it is essential to establish site-specific small wind turbines in the urban environment. An increasing interest in small, decentralized, vertical-axis wind turbines (VAWT) can be observed here. However, concepts with low visual and auditory effects and economic efficiencies are largely limited. The project part described in this paper enables a specially developed design software tool of rotor geometries optimized for such boundary conditions. By using fiber-reinforced structures in combination with selective laser sintering, it is theoretically possible to economically produce even the smallest quantities of these geometries for a typical service life of wind turbines. The results presented and discussed in this work can serve as a basis for a subsequent feasibility study.

The Influence of Detailed Blade Design on the Aerodynamic Performance of Straight-Bladed Vertical Axis Wind Turbines

1996 ◽  
Vol 210 (1) ◽  
pp. 65-74 ◽  
Author(s):  
F N Coton ◽  
R A McD Galbraith ◽  
D Jiang
Keyword(s):  
Wind Turbines ◽  
Three Dimensional ◽  
Bending Moment ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Speed Ratio ◽  
Blade Design ◽  
Aerodynamic Model ◽  
Vertical Axis Wind Turbines ◽  
Limited Scope

The recent development of an unsteady, three-dimensional aerodynamic model has provided the opportunity to determine the influence of detailed blade geometry on the performance of straight-bladed vertical axis wind turbines. In particular, the present paper examines the effect of blade pitch, twist, taper and aerofoil section by comparison with a simplistic baseline configuration. The study concentrates on the low tip-speed ratio regime where the blade aerodynamics are inherently unsteady and the most severe loadings are experienced. In general, the effects of pitch and twist are similar, with both presenting only limited scope for enhanced design. Moderate taper is shown to improve the overall aerodynamic performance while having the structural benefit of reducing the bending moment at the cross-arm. The potential of a blade with varying cross-section to produce passive stall regulation is also demonstrated. Finally, the influence of unsteady blade stall is considered in more detail for each of the configurations.

Sign in / Sign up

Export Citation Format

Share Document