scholarly journals Effect of Helix Angle on the Performance of Helical Vertical Axis Wind Turbine

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 393
Author(s):  
Unnikrishnan Divakaran ◽  
Ajith Ramesh ◽  
Akram Mohammad ◽  
Ratna Kishore Velamati
Keyword(s):  
Standard Deviation ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Helix Angle ◽  
Vertical Axis Wind Turbine ◽  
Ansys Fluent ◽  
Entire Study ◽  
Moment Coefficient ◽  
Deviation Plot ◽  
The Moment

The energy crisis has forced researchers to look for various non-conventional energy sources. Wind energy is one of the potential sources, and researchers have invested resources in developing different kinds of wind turbines. Vertical axis wind turbines (VAWT) have received less attention than their horizontal-axis counterparts. A helical-bladed VAWT is preferred because it makes perfect sense as an improvement in design, as they have higher azimuth angles of power generation capabilities. This paper studies the effects of the helix angle of blades in the aerodynamic performance of VAWT using 3D numerical simulations. Three different helix angles of 60°, 90°, and 120° of a three-bladed VAWT operating across different tip speed ratios were studied. Turbulence is modelled using a four-equation transition SST k-ω model (shear stress transport). The 60° helical-bladed VAWT was found to be better performing in comparison with all other helical-bladed and straight-bladed VAWT. The ripple effects on the shaft are also analysed using a standard deviation plot of the moment coefficient generated by a single blade over one complete cycle of its rotation. It was observed that the greater the helix angle, the lower the standard deviation. The paper also tries to analyse the percentage of power generated by each quartile of flow and the contribution of each section of the blade. Ansys FLUENT was employed for the entire study. A comparative study between different helical-bladed VAWT and straight-bladed VAWT was carried out along with wake structure analysis and flow contours for a better understanding of the flow field.

scholarly journals Effect of Helix Angle on the Performance of Helical Vertical Axis Wind Turbine

2020 ◽  
Author(s):  
Unnikrishnan Divakaran ◽  
Ajith Ramesh ◽  
Akram Mohammad ◽  
Ratna Kishore Velamati
Keyword(s):  
Standard Deviation ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Helix Angle ◽  
Speed Ratio ◽  
Small Scale ◽  
Ripple Effect ◽  
Vertical Axis Wind Turbine ◽  
Moment Coefficient ◽  
Helical Blade

The global energy crisis has lead researchers explore other sources of energy like wind, resulting in a wide acceptance of wind turbines. Vertical axis wind turbines (VAWT) more suitable for small scale application in urban conditions than their horizontal-axis counterparts. A Helical bladed VAWT would reduce the ripple effect when compared to Straight bladed VAWT. The effect of the blade helix angle on the aerodynamic performance of VAWT using 3D numerical simulations is studied. Turbulence modelled using 4-Equation transition SST k-w model. Three different helix angles of 60, 90 and 120 of a 3 bladed VAWT operating across different tip speed ratios were studied. The 60 helical bladed VAWT was found to perform better than all other helical bladed and straight bladed VAWT. Standard deviation of the moment coefficient generated by a blade plotted against 360 of azimuth rotation revealed that the ripple effect on the shaft produced by cyclic loading of the straight blade is considerably reduced upon introduction of helix angle, with 120 helical blade giving lowest standard deviation. The analysis has been done for the percentage of power generated by each quartile of flow and the contribution of each section of the blade. A comparative study was also conducted between different helical bladed VAWT and straight bladed VAWT. Flow feature analysis also revealed the reasons behind secondary peaks and the performance improvement when tip speed ratio increases. Wake structure analysis and flow contours were also studied for a better understanding of the flow field.

Simulation on Performances of Vertical Axis Wind Turbine

2010 ◽  
Author(s):  
Chien-Chang Chen ◽  
Cheng-Hsiung Kuo
Keyword(s):  
Wind Turbine ◽  
Pitch Angle ◽  
Vertical Axis ◽  
Flow Structures ◽  
Vertical Axis Wind Turbine ◽  
Ansys Fluent ◽  
Moment Coefficient ◽  
Pressure Distributions ◽  
The Moment ◽  
Starting Torque

This study employs the commercialized computational fluid dynamics software (Ansys/Fluent), with the user’s defined technique, to simulate the unsteady flow structures around the small-size vertical axis wind turbines (VAWT) with three straight blades. This study addresses the effects of the collective variations of the pitch angle (within ± 10°) on the performance of the VAWT system. The results of the transient (acceleration) stage will be employed to evaluate the self-starting ability. While the vertical axis wind turbine (VAWT) reaches a steady rotating stage, the detailed flow structures, the vorticity fields, the pressure distributions around, and the forces on the airfoils at various azimuthal positions will be addressed. For the blades with a negative pitch angle (θ = −10°), has the peak value of the moment coefficient within one revolution is the largest which will provide the largest starting torque to drive the VAWT system more easily. However, in this case, the moment coefficients are negative within some part of the period. This cancels part of the positive moment within one revolution, thus the efficiency is reduced at this pitch angle. For the case with positive pitch angle (θ = 10°), the area under the moment coefficient curve is the smallest and the time elapse of large moment coefficient is relatively short. Thus the efficiency and the starting torque are the lowest among thee pitch angles.

DESIGN AND MODELING OF STRAIGHT-BLADE VERTICAL AXIS WIND TURBINE IN PAKISTAN

2021 ◽  
Author(s):  
S M Nazmuz Sakib
Keyword(s):  
Wind Turbines ◽  
Renewable Energy Sources ◽  
Vertical Axis ◽  
Energy Harvest ◽  
Vertical Axis Wind Turbine ◽  
Ansys Fluent ◽  
Straight Blade ◽  
The World ◽  
Horizontal Axis Wind Turbines ◽  
Radial Arrangement

Pakistan is one of those countries which has large potential of energy harvest from renewable energy sources and specially from wind. With the surge of global warming, the world is moving towards cleaner and viable sources of energy. Horizontal Axis Wind Turbines (HAWT) currently dominates the most of the wind power farm markets in the world but Vertical Axis Wind Turbines (VAWT) are also capable of harvesting large amounts of energy with benefits over the HAWTS. VAWTS do not need a control system to be pointed in the direction of wind because with its blade in radial arrangement, wind from any direction is useful. In this report, a Straight-Blade VAWT is designed for low speeds and its performance parameters are also identified for which the improvement of the VAWT will be obtained. Self-starting ability of VAWT is also analyzed and stress and vibration analysis will be investigated in ANSYS Fluent.

Numerical Analysis of the Overlap Effect Between Blades at Four-Bladed Rooftop VAWT

2012 ◽  
Author(s):  
H. Flores-Saldaña ◽  
A. Gallegos-Muñoz ◽  
N. C. Uzarraga-Rodriguez ◽  
V. H. Rangel-Hernandez
Keyword(s):  
Numerical Analysis ◽  
Wind Turbine ◽  
Fluid Dynamic ◽  
Vertical Axis ◽  
Rotor Blades ◽  
Power Coefficient ◽  
Vertical Axis Wind Turbine ◽  
Moment Coefficient ◽  
Mesh Model ◽  
The Moment

This work presents a numerical analysis of a four-bladed Rooftop vertical axis wind turbine (VAWT). The effects generated on the performance of turbine by the overlap variation between blades of wind rotor were analyzed. The numerical simulations were developed using commercial software based on Computational Fluid Dynamic (CFD). Each one of the models generated was built in a 3D computational model. A sliding mesh model (SMM) capability was used to present in dimensionless form the moment coefficient and power coefficient of the wind turbine based on the relationship between wind speed and rotor rotational speed. The results show that the aerodynamic performance is better with overlap between rotor blades, resulting in a significant increase in the moment coefficient and power coefficient. Having that in the cases of four-bladed Rooftop rotor with overlap both coefficients increase about 29% comparing with four-bladed Rooftop rotor without overlap between blades.

Dimple Shape Effect on the Aerodynamic Performance of H-Rotor Darrieus Vertical Axis Wind Turbine

2021 ◽  
Author(s):  
Kabita Naik ◽  
Niranjan Sahoo
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Speed Ratio ◽  
Shape Effect ◽  
Vertical Axis Wind Turbine ◽  
Ansys Fluent

Abstract Nowadays, the vertical axis wind turbines (VAWTs) have gained significant attention among the small wind turbine (WT) due to their omnidirectional ability, low costs, low noise, and robustness, mainly for urban and off-shore applications. The H-rotor Darrieus is one of the class of VAWT that is mostly suitable for low-speed wind and low tip speed ratio (TSR) conditions. These VAWTs have relatively lesser performance than horizontal axis wind turbines (HAWTs). Therefore, to improve the performance of the H-rotor Darrieus VAWT, a dimple/cavity of different shapes is created into the surface of the blade airfoil as a power augmentation technique. The current study presents several two-dimensional numerical simulations on the H-rotor Darrieus VAWT in the turbulent flow. The performance of the VAWT has been examined through ANSYS Fluent solver with different turbulence models, and it is found that the Shear stress transport (SST) k–ω turbulence model shows better results. The study primarily focuses on the effect of the dimple location, diameter and shape to enhance the aerodynamic performance of the H-rotor Darrieus VAWT. It is found that the rotor performance is increased by about 13% with a quadral/rectangular dimple in comparison to without dimple. Further, with the inclusion of a dimple on the rotor blade airfoil, its performance is not only enhanced but also able to maintain it for a broad range of TSR. Thus, the present study suggests the implication of a dimple/cavity to be very promising in improving H-rotor Darrieus VAWT.

scholarly journals Effect of Pitch Parameters on Aerodynamic Forces of a Straight-Bladed Vertical Axis Wind Turbine with Inclined Pitch Axes

2021 ◽  
Vol 11 (3) ◽  
pp. 1033
Author(s):  
Jia Guo ◽  
Timing Qu ◽  
Liping Lei
Keyword(s):  
Wind Turbine ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Incline Angle ◽  
Asymmetric Distribution ◽  
Vertical Axis Wind Turbine ◽  
Power Performance ◽  
Aerodynamic Forces ◽  
Ansys Fluent ◽  
Pitch Regulation

Pitch regulation plays a significant role in improving power performance and achieving output control in wind turbines. The present study focuses on a novel, pitch-regulated vertical axis wind turbine (VAWT) with inclined pitch axes. The effect of two pitch parameters (the fold angle and the incline angle) on the instantaneous aerodynamic forces and overall performance of a straight-bladed VAWT under a tip-speed ratio of 4 is investigated using an actuator line model, achieved in ANSYS Fluent software and validated by previous experimental results. The results demonstrate that the fold angle has an apparent influence on the angles of attack and forces of the blades, as well as the power output of the wind turbine. It is helpful to further study the dynamic pitch regulation and adaptable passive pitch regulation of VAWTs. Incline angles away from 90° lead to the asymmetric distribution of aerodynamic forces along the blade span, which results in an expected reduction of loads on the main shaft and the tower of VAWTs.

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

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 Turbine ◽  
Vertical Axis Wind Turbines ◽  
Horizontal 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.

scholarly journals Aerodynamic improvement of Darrieus wind turbine

2021 ◽  
Vol 897 (1) ◽  
pp. 012001
Author(s):  
Oleg Goman ◽  
Andrii Dreus ◽  
Anton Rozhkevych ◽  
Krystyna Heti
Keyword(s):  
Reynolds Number ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Structural Reliability ◽  
Vertical Axis ◽  
Vertical Wind ◽  
Integral Approach ◽  
Vertical Axis Wind Turbine ◽  
Calculation Algorithm ◽  
Vertical Axis Wind Turbines

Abstract Until recently, vertical-axis wind turbines are less extensively developed in wind energetics. At the same time, there are a number of advantages in turbines of such type like their independence from the change of wind direction, lower levels of aerodynamic and infrasound noises, higher structural reliability (compared to horizontal engines), etc. With these advantages, vertical-axis wind turbines demonstrate promising capacities. Inter alia, the productiveness of such turbines can be refined through the aerodynamic improvement of the structure and comprehensive optimization of the rotor geometry. The main purpose of the presented paper is to aerodynamically improve vertical wind turbine in order to increase the efficiency of wind energy conversion into electricity. Within the framework of the classical theory of impulses, this article presents a study of the effect of variation in Reynolds number on the general energy characteristics of a vertical-axis wind turbine with two blades. The integral approach makes it possible to use a single-disk impulse model to determine the main specific indicators of the system. The power factor was calculated based on the obtained value of the shaft torque factor, which in turn was determined by numerically integrating the total torque generated by the wind turbine. To calculate the test problem, we used the classic NACA airfoils: 0012, 0015, 0018 and 0021. The proposed calculation algorithm makes it possible not to indicate the Reynolds number and corresponding aerodynamic coefficients at the beginning of the calculation, but to recalculate it depending on the relative speed, position of the airfoil and the linear speed of the airfoil around the circumference. Proposed modern design techniques can be helpful for optimization of vertical wind turbines.

scholarly journals CFD for Helical Type Vertical Axis Wind Turbine

2019 ◽  
Vol 9 (2S4) ◽  
pp. 474-476
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Computer Aided Design ◽  
Flow Characteristics ◽  
Vertical Axis ◽  
Urban Environments ◽  
Vertical Axis Wind Turbine ◽  
Wind Turbine System ◽  
Twisted Blade ◽  
Aided Design

Vertical axis wind turbines are most effective for home energy generation especially in urban environments. Wind energy creates a stand-alone energy source that is relied on any place. The main criteria for this work is the design of micro wind turbines for all kinds of applications. Design of Twisted Blade Micro-Wind Turbine system is accomplished using computer aided design with Computational Fluid Dynamics (CFD). The flow characteristics in the wind turbine blade were analyzed by varying its twist ratio. The wind turbines with vertical axis utilize the wind from any direction with no yaw mechanism. The risk of blade ejection besides catching wind from all the directions is avoided by using the helical tye vertical axis wind turbine.

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

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 ◽  
Vertical Axis Wind Turbine ◽  
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.

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