Darrieus-type Vertical Axis Wind Turbine Research Articles

Self-starting and performance improvement of a Darrieus type wind turbine using the plasma actuator

Although the popularity of Darrieus-type vertical axis wind turbines is growing for small-scale electricity generation, these turbines have severe challenges in self-starting. This paper proposes a flow control method, namely, the plasma actuator, to solve the self-starting problem besides enhancing the turbine performance. The Darrieus turbine is numerically investigated using a pressure-based finite volume method to solve the unsteady Reynolds-averaged Navier–Stokes and the γ–Reθt transitional model equations. Simulation of the blade rotation is performed using the sliding mesh technique accompanied by the turbine equation of motion to enable the blade rotational degree of freedom. Furthermore, the body forces associated with the plasma actuator are determined by calibrating the Shyy plasma model parameters. The plasma actuator is assessed at both the constant and free rotational speeds. The constant rotational speed results in plasma off condition show negative torque generation for tip speed ratios lower than 1.5, known as the origin of turbine self-starting challenges. The plasma actuator improves the negative torque by 128% in the tip speed ratio of 0.5 and turns it positive. Also, at larger tip speed ratios, it reduces the negative torque generation and enhances the turbine power production by up to 260%. Furthermore, the plasma actuator in free rotational speed improves the tip speed ratio increment by up to 8%, reducing the total time of turbine self-starting.

Computational fluid dynamics analysis on performance assessment of Darrieus-type vertical axis wind turbine using NACA0016, NACA0019 and NACA0020 airfoil sections

The efficiency of a vertical-axis wind turbine is remarkably less than a horizontal-axis wind turbine and consequently, the most important challenge of the former one is to enhance its aerodynamic performance. An earlier study shows that the selection of an efficient airfoil shape is an important criterion for enhancing the overall performance of a wind turbine. The objective of the present work is to perform the two-dimensional Computational Fluid Dynamics simulation of Darrieus Vertical axis wind turbine using NACA0016, NACA0019 and NACA0020 airfoils which are neither too thick nor too thin. Furthermore, the performance of these three airfoils is compared with two established airfoils, namely NACA0015 and NACA0018. The result reveals that the overall power coefficient of NACA0019 airfoils resulting from the CFD simulation is significantly higher than that of NACA0015. Therefore, the NACA0019 airfoil may be considered one of the effective alternative airfoils for the Darrieus VAWT. Highlights Simulation of vertical axis wind turbine using NACA0016, NACA0019 and NACA0020 airfoils Unsteady URANS studies are carried out to investigate the performance of the airfoils Among the blade profiles studied in this work, NACA 0019 offers superior fluid mechanical performance

Computational study of the effect of building height on the performance of roof-mounted VAWT

The power of a Vertical Axis Wind Turbine (VAWT) placed at the frontal corner of a roof-top of a building is significantly higher compared to the same turbine in a uniform wind without a surrounding building. Due to the importance of this configuration's benefits, it is crucial to study its effect for different building heights. To investigate the impact of building height on the power performance of VAWTs, three buildings with heights of 30.48 m (100 ft), 60.96 m (200 ft), and 91.44 m (300 ft) are considered. A two-blade Darrieus-type VAWT is placed on the roof-top, with the wind flow directed straight towards the corner of the building. Computational Fluid Dynamics (CFD) is utilized to simulate the entire flow over the building and the rotating turbine. Different atmospheric boundary wind velocity profiles are considered. Firstly, the same velocity profile is applied to all three buildings, with taller buildings experiencing higher velocities. Secondly, three distinct velocity profiles are used over the buildings, ensuring that the wind velocity at the middle of the turbine for each case remains at 9.3 m/s. The results demonstrate that placing the VAWT on the roof-top of a 30.48 m (100 ft) building increases the maximum Power Coefficient (CP) by 36% compared to the turbine operating in a uniform flow. Moreover, in the case of one velocity profile applied to buildings with different heights, it was observed that the maximum CP increased by 84% for a building with a height of 91.44 m compared to the turbine operating in uniform flow. On the other hand, in the second scenario with three different velocity profiles over the buildings, it was found that the maximum CP increased by 18% and 22% when the turbine was placed in the 60.96 m and 91.44 m buildings, respectively, compared to the 30.48 m building.

Mesh-Free Analysis of a Vertical Axis Wind Turbine Using Lattice Boltzmann Method and Various Turbulence Models

This study aims to investigate the aerodynamic analysis of a Darrieus-type vertical axis wind turbine (VAWT) using the Lattice Boltzmann Method (LBM). The objective is to assess the accuracy and performance of the meshless LBM approach in predicting torque coefficients, velocity, turbulence intensity, and vorticity distributions for VAWT aerodynamic analysis. Two turbulence modelling approaches, Large Eddy Simulation (LES) and Reynolds-Averaged Navier-Stokes (RANS), are employed to model the flow domain. The central problem revolves around comparing the performance of different turbulence models based on their agreement with experimental results for power and torque coefficients. The findings demonstrate the effectiveness of the WALE turbulence model in achieving the best agreement with experimental data. Overall, the study provides valuable insights into applying LBM in VAWT aerodynamic analysis and highlights the advantages of the meshless approach compared to traditional CFD methods.

PIV measurements over a double bladed Darrieus-type vertical axis wind turbine: A validation benchmark

Vertical axis wind turbines (VAWTs) are very attractive for in-home power generation since they can be adopted even at low wind speeds and highly variable wind direction. Even if significant experimental research activity has been carried out to improve VAWTs performance, the ability to accurately reproduce flow field characteristics around turbine blades by CFD (computational fluid dynamics) techniques represents a powerful approach to further enhance wind turbines performance. Thanks to CFD, in fact, it is possible to reproduce flow characteristics with a detail level impossible to achieve by experiments. Nevertheless, in order to appropriately analyze the flow structure by CFD application, an accurate validation is essential, and high-quality measurements of some main flow characteristics are required. In recent publications the authors investigated, both experimentally and numerically, the performance of an innovative double bladed Darrieus-type VAWT, with the aim to define an optimal configuration also focusing on self-starting ability of the prototype by employing CFD technique. Nevertheless, comparison between experiments and numerical results was made only in terms of power and torque coefficients. To overcome such limitation, in this paper the authors propose an experimental benchmark case for CFD results validation, describing detailed flow field in correspondence of one pair of blades of the innovative Darrieus-type VAWT in static conditions. Measurements were performed employing Particle Image Velocimetry (PIV) technique on a scaled model of the turbine blades realized by 3D printing. An uncertainty analysis was also performed which showed a high accuracy of the obtained experimental results. The measurements of the main flow characteristics (bi-dimensional velocity components) were then used for a test case CFD validation of two different turbulence models.

Design and fabrication of NACA 0018 straight bladed vertical axis wind turbine

The most important advantage in generation of electric power using renewable sources of energy, like wind, are the non availability of toxic exhaust emission products, highly uncluttered and the infinite presence of wind that is finally transformed into electricity. The generation and utilization of wind has been considered as one of the mature and cost effective resources among the various available renewable energy technologies. A wind turbine is a rotating machine that is converting the winds kinetic energy initially to mechanical energy, which finally getting converted into electric power. The wind turbines basically are of two types, i.e. Horizontal Axis Wind Turbine (HAWT) and Vertical Axis Wind Turbine (VAWT). The main point of difference between the two is the position of their axis of rotation. When wind blows over the VAWT, only a fractional part of the blades generates the torque whereas the remaining parts simply rotate. The end result of this is a comparably reduced efficiency in power generation. Here, a miniature Darrieus type VAWT with straight blade - NACA 0018 Airfoil, is designed and fabricated so as to develop maximum possible power output. The blades are designed in way were majority of the air covers majority of blade surface area and thus rotating it at its maximum possible speed. The results shows that the system we developed could produce power of 23.45 watts, with blades designed for aspect ratio of 0.24. This is the maximum possible result that can be attained for this dimension. The entire system is made of strong material so that it could also withstand high wind speed and high energetic wind possible.

Numerical Analysis of Exhaust Air Energy Extractor for Cooling Tower Applications

Over the years, the need of renewable energy has been accelerated to minimise the reliance on using the fast depleting fossil fuel. Research on wind turbines to harness wind power is widely increasing especially with the progression of vertical axis wind turbines (VAWT) for the locations, where conventional horizontal axis wind turbines are not effective. The ability to provide renewable energy by generating efficient power is vital in combatting climate change due to increase in global energy demand thus, leading to this present study of extracting wind energy from a cooling tower. In this paper, a three dimensional numerical investigation has been conducted on the straight bladed Darrieus type VAWTs with S1046 airfoils. The implicit unsteady Reynolds-Averaged Navier-Stokes equations are solved using shear stress transport k-? turbulent model. The VAWT model is placed at the outlet of the cooling tower to calculate power output with an aspect ratio of 0.88. The results show that a maximum power coefficient of 0.36 is obtained at a tip speed ratio of 3.0.

A wind turbine and its robust control using the CRONE method

Abstract This paper presents the identification, development and simulation of a complex order, third generation CRONE (Commande Robuste d’Ordre Non Entier) controller for a new Darrieus type vertical-axis wind turbine design. A prototype of this wind turbine was developed and tested in a wind tunnel. Data acquired in the tests were used to develop and validate an accurate model. The CRONE control system design methodology was then used to develop a robust controller, which was tested in simulation. Simulations allow for parameter uncertainty in different wind conditions, with and without the presence of turbulence. This control system can be easily implemented using a micro-controller.

Numerical performance assessment of a novel Darrieus-style VAWT with auxiliary straight blades

Domestic Vertical Axis Wind Turbines (VAWT) are able to operate also when the wind speed is low and can be installed in the open spaces of housing areas. The Darrieus turbine is the most promising since it is characterized by higher efficiency, even if for applications at higher wind speeds with respect to Savonius VAWTs. Several researchers try to optimize the aerodynamics of the Darrieus rotors, allowing wind turbines to start rotation even in the presence of low wind speeds. In this paper the authors propose a numerical investigation of the flow field around a 1:4 scaled model of a pair of blades installed on an innovative Darrieus-type VAWT. A Reynolds Averaged Navier-Stokes-based CFD model was validated on the basis of the wind tunnel data, and the scaled turbine performance was analysed by numerically evaluating the effect of different geometric configurations and rotation angles on the turbine torque coefficients. The results of the simulations confirmed the capabilities of the proposed configuration to give valuable performance even for low wind speeds.

INVESTIGATE THE EFFECT OF DIFFERENT DESIGN PARAMETER ON PERFORMANCE EVALUATION OF STRAIGHT BLADEVERTICAL AXIS WIND TURBINE (SB-VAWT)

Energy is an essential ingredient for socioeconomic development and economic growth country. Energy is available in two different forms, fast depleting or non-renewable (coal, fuel, natural gas) and renewable (solar, wind, hydro etc.). In fact, one of the biggest sources of energy is all around us all of the time, the wind. Every year the number of installed wind power plants in the world increases. Vertical axis wind turbines (VAWT) are capable of producing a lot of power, and offer many advantages for small-scale and domestic applications. One drawback of Darrieus Type VAWT is their inability to reliably self-start at a low tip speed ratio [1]. The main purpose of the study described here is to investigate the effect of different designparameter on performance evaluation of SB-VAWTs.

Computational Optimization of Adaptive Hybrid Darrieus Turbine: Part 1

Darrieus-type Vertical Axis Wind Turbines (VAWT) are promising for small scale decentralized power generation because of their unique advantages such as simple design, insensitive to wind direction, reliability, and ease of maintenance. Despite these positive aspects, poor self-starting capability and low efficiency in weak and unsteady winds deteriorate further development. Adaptive Hybrid Darrieus Turbine (AHDT) was proposed by the author in the past study as a potential solution to enhance low wind speed characteristics. The objective of the current research is to optimize the parameters of AHDT. AHDT integrates a dynamically varying Savonius rotor with a Darrieus rotor. A fully detailed 2D numerical study employing Reynold-Averaged Navier Stokes (RANS) is carried out to investigate the impact of the Darrieus rotor diameter (DR) on the Savonius rotor (DT) with regard to hybrid turbine performance. The power coefficient of the Darrieus rotor is evaluated when the Savonius rotor is in the closed condition (cylinder) of various diameters. The influence of Reynolds number (Re) on the torque coefficient is examined. Power loss of 58.3% and 25% is reported for DR/DT ratio of 1.5 and 2 respectively for AHDT with solidity 0.5 at 9 m/s. The flow interaction between the Savonius rotor in closed configuration reveals the formation of von Karman vortices that interact with Darrieus blades resulting in flow detachment. An optimum diametrical ratio (DR/DT) of 3 is found to yield the maximum power coefficient of the Darrieus rotor.

Energy Balance Analysis and Turbulence Profile of a Darrieus-type Vertical Axis Wind Turbine

Vertical axis wind turbines (VAWTs) extract energy through reduction of the kinetic and turbulent kinetic energies, and the vertical momentum flux. Detailed turbulence profiling and energy balance analysis were attempted through direct turbulence quantification using the Eddy Covariance method. A high-frequency sonic anemometer was employed to measure flow and turbulence upwind and downwind of a Darrieus-type VAWT at different positions that cover the entire windswept area. The data was processed and analysed using a custom Matlab script. Energy balance analysis showed that there was a significant drop in kinetic energy before and after the VAWT (72% to 42%) but a small increase in turbulent kinetic energy (28% to 31%). The results also showed that the rotational direction of VAWT contributed to a higher value of longitudinal turbulence at the windward edge of the VAWT. The VAWT affected the flow field upwind by generating reverse flows. The largest vertical momentum flux transfer occurred downwind of the windward side of the VAWT. Spectral analysis shows that the VAWT produced smaller but faster momentum flux vortices due to the rotating rotors in the 1 Hz to 5 Hz range. This data and results have important applications to accurately model complex flows around VAWTs.

Effect of number of blades on the dynamic behavior of a Darrieus turbine geared transmission system

Abstract Dynamic behavior of a Darrieus-type vertical axis wind turbine geared transmission system taking into account variable gear mesh stiffness and the external aerodynamic torque excitation is carried out in the present paper. The aerodynamic torque is obtained by a complete campaign of simulations based on Reynolds Averaged Navier-Stokes unsteady calculations for two, three and four-bladed rotor architectures. A three-dimensional model of a one-stage bevel spur gear system is developed. For each proposed rotor configuration, the effect of the number of blades on both aerodynamic performance and dynamic vibration of the Darrieus turbine geared transmission system is discussed at several tip speed ratios in non-stationary operation. The main originality of the present paper is to establish a correlation between the aerodynamic parts and the dynamic vibration of the gearing system by studying the effect of some design parameters on the dynamic vibration of the Darrieus turbine gearing system in non-stationary regime. This new methodology of simulation makes considerable progress in the understanding of the wind turbine dynamic vibration, which is an important issue. The number of the blades is the core problem of wind turbine engineering. In this paper, the numerical results show that the number of blades significantly affects the turbine efficiency and the dynamic response of the studied wind turbine gearing system in non-stationary regime.

Performance assessment of Darrieus wind turbines with symmetric and cambered airfoils

During the operation of a Darrieus type vertical axis wind turbine (VAWT), the blade sections are subjected to different flow velocities and incidences that can be converted to mechanical power with varying efficiency depending on the airfoil. The goal of the present study is to emphasize the advantages and the drawbacks of the use of symmetrical, cambered, and laminar airfoil for a typical Darrieus type VAWT. The NACA 0018, FX63-137 and SNLA 18/50 airfoils were selected for this study.

Comparison of horizontal axis wind turbine (HAWT) and vertical axis wind turbine (VAWT)

As the demand for green technology is rising rapidly worldwide, it is important that Malaysian researchers take advantage of Malaysia’s windy climates and areas to initiate more power generation projects using wind. The main objectives of this study are to build a functional wind turbine and to compare the performance of two types of design for wind turbine under different speeds and behaviours of the wind. A three-blade horizontal axis wind turbine (HAWT) and a Darrieus-type vertical axis wind turbine (VAWT) have been designed with CATIA software and constructed using a 3D-printing method. Both wind turbines have undergone series of tests before the voltage and current output from the wind turbines are collected. The result of the test is used to compare the performance of both wind turbines that will imply which design has the best efficiency and performance for Malaysia’s tropical climate. While HAWT can generate higher voltage (up to 8.99 V at one point), it decreases back to 0 V when the wind angle changes. VAWT, however, can generate lower voltage (1.4 V) but changes in the wind angle does not affect its voltage output at all. The analysis has proven that VAWT is significantly more efficient to be built and utilized for Malaysia’s tropical and windy climates. This is also an initiative project to gauge the possibility of building wind turbines, which could be built on the extensive and windy areas surrounding Malaysian airports. Â

Investigation of Flow Interaction Effect between Optimized Airfoils on Small Darrieus-type Vertical Axis Wind Turbine

Investigation of Flow Interaction Effect between Optimized Airfoils on Small Darrieus-type Vertical Axis Wind Turbine

Study on approach of performance improvement of VAWT employing double multiple stream tubes model

On the circular blade path of a Darrieus-type vertical axis wind turbine (VAWT), there are two azimuth positions where torques are small or even negative. These two azimuths have the lowest aerodynamic performance and greatly weaken the overall performance of the VAWT. An approach is proposed to rebuild the flow field of the turbine blades by applying two additional airflows at the two azimuths to enhance the local performance. The aim is to improve the overall power coefficient of the VAWT. A Φ-type VAWT with a diameter of 2 m and a height of 2 m is studied to evaluate the effectiveness of the proposed approach. The effect of additional airflow on the aerodynamic performance of the blade and the turbine is researched using the double multiple streamtube model. The simulation results suggest that the additional airflows are effective in promoting the performance of the rotor blades and the overall rotor; the increase in maximum power coefficient achieved was 6% at an optimum tip speed ratio. Some rules of the effect on the performances of the rotor are obtained in this paper.

A numerical study on the aerodynamic performance and the self-starting characteristics of a Darrieus wind turbine considering its moment of inertia

Self-starting characteristics is a challenging issue in the field of Darrieus-type vertical axis wind turbines. Traditionally, the numerical simulations were performed at several constant rotational velocities for the turbine and the generated torques were reported for each rotational velocity, neglecting the effects of the turbine inertia on the transient start-up motion of the turbine. In the current study, a numerical method is proposed to study the self-starting characteristics of a Darrieus wind turbine, considering the turbine moment of inertia. The simulation starts from the initial stationary state and continues until the final steady-periodic condition. At each time step, the instantaneous rotational velocity of the turbine is computed based on the Newton’s second law, according to the instantaneous aerodynamic and mechanical forces acting on the turbine. Results indicate that as the rotor inertia increases, it takes a longer time for the turbine to reach its final velocity, in a manner that, the turbine might even fail to reach the final condition and the rotation halts. Results also show that as the rotor inertia decreases, the oscillations amplitude of the turbine rotational velocity increases. This can enable the turbine to pass higher resistant torques than those computed based on the traditional method.

Electric Circuit Model for the Aerodynamic Performance Analysis of a Three-Blade Darrieus-Type Vertical Axis Wind Turbine: The Tchakoua Model

The complex and unsteady aerodynamics of vertical axis wind turbines (VAWTs) pose significant challenges for simulation tools. Recently, significant research efforts have focused on the development of new methods for analysing and optimising the aerodynamic performance of VAWTs. This paper presents an electric circuit model for Darrieus-type vertical axis wind turbine (DT-VAWT) rotors. The novel Tchakoua model is based on the mechanical description given by the Paraschivoiu double-multiple streamtube model using a mechanical‑electrical analogy. Model simulations were conducted using MATLAB for a three-bladed rotor architecture, characterized by a NACA0012 profile, an average Reynolds number of 40,000 for the blade and a tip speed ratio of 5. The results obtained show strong agreement with findings from both aerodynamic and computational fluid dynamics (CFD) models in the literature.

Dependency of Torque on Aerofoilcamber Variation in Vertical Axis Wind Turbine

The advancements in the wind turbine technology specially associated with Vertical Axis Wind Turbines (VAWT), has been improved for last couple of years. This is due to extensive use of computational techniques. This paper investigates dependency of torque on aerofoil geometry by performing numerical simulation on Darrieustype VAWT with fix pitch blades. Coordinate points for aerofoil was generated using Java Foil software. Reynolds-Averaged Navier Stokes (RANS) turbulence modelling was used for predicting the flow and efficiency of the three blades VAWT. The unsteady flow condition was considered to make simulation as realistic as possible. In order to visualize high strain flow and separation, we used two equation models i.e. k-e with RNG. NACA 0012 aerofoil was used and camber variations were carried out for developing samples of aerofoil to check the enhancement in performance of VAWT. Results demonstrate the torque and power along with its coefficients. It has been investigated that the performance efficiency was significantly improved by changing the aerofoil camber, demonstrating highest torque with camber (C3) aerofoil and the least performance was observed using camber (C0).