Performance Of Vertical Axis Wind Turbine Research Articles

Study of Pivot Panel Mechanism on the Self Start-Ability of a Darrieus Wind Turbine

In South East Asia countries such Malaysia, wind turbine is generally not suitable to be used in large scale to generate electricity due to inconsistent wind speed and suitable land site availability. However, a small scale application is of preference as the wind speed in the region lies within the low speed range of approximately 2-5 ms−1 with intermittent highs up to 8 ms−1. The performance of Vertical Axis Wind Turbines (VAWTs) is known to be better compared to Horizontal Axis Wind Turbines (HAWTs) in urban conditions due to its omnidirectionality, which allows it to operate in fluctuating turbulent wind conditions. However, the major drawback of VAWTs is the inability to self-start under low wind speed conditions. Hence, the objective of this work is to investigate the Pivoting Panel Mechanism (PPM) which aims to assist VAWT models to self-start at low wind speed condition. Three sets of PPM width configurations (70mm, 80mm, 90mm) are used to study the effect of increasing the pivot panel surface area on the VAWT performance. Performance test showed that the PPM model improved the power coefficient values at the tip wind speed range of TSR<0.75 (PPM 70mm>80mm>90mm). Further investigation revealed that the larger PPM surface area (90mm) was able to assist the VAWT model to achieve a shorter RPM response time at wind speed of v = 2.5ms−1 and 2.9ms−1. These findings have considerable implications for future researches for the optimization of PPM design parameters and its adaptations in VAWT turbine design.

Study on benefit of guide vane for vertical axis wind

Guide vane was introduced to overcome the problem of high turbulence intensity due to the high rise building in the urban area. The guide vane is a fixed aerofoil that directs air into the moving wind turbine. Guide vane borders the Vertical Axis Wind Turbine (VAWT) and improves the VAWT performance by increasing the wind velocity, decreasing turbulence intensity and increasing torque because it acts as wind concentrator and wind shielding to an optimum angle before it interacts with turbines. This project is based on the VAWT on the College of Engineering (COE) building in Universiti Tenaga Nasional (UNITEN). This VAWT had been fabricated in CREO software to study the benefit of guide vane onto it and the design of guide vane also was constructed by using similar software. SOLIDWORKS Flow simulation was used to analyze the performance of the VAWT. The simulation had been done by simulation of VAWT without and with guide vane to study the benefit and analyze the flow characteristic of the guide vane towards wind turbine. The simulation result shows that the presence of guide vane increase wind speed by maximum 0.0051 m/s and torque increment is about seven times from VAWT without guide vane. Other than that, decreasing of turbulence intensity value also detected in flow simulation result. To sum up, guide vane had the potential to be installed in the urban area because it improves the power output of the wind turbine.

Investigation of Blade Tip Shape for Improving VAWT Performance

Vertical axis wind turbine (VAWT) is a competitive power generation device due to structural simplicity, wind direction independence, no yaw mechanism required, easier maintenance, and lower noise emission. However, blade tip vortex will be generated at both ends of the blade during the rotation, resulting in torque loss and efficiency reduction. In this paper, computational fluid dynamics is used to study blade tip vortex and its reduction technique of a single-blade VAWT rotor in real scale. By monitoring the force and flow field at different heights of the blade, the influence ranges of tip vortex are obtained. The reduction effect of the bulkhead obtained from the blade profile curve is studied, and the size of the bulkhead is optimized. On the basis of adding the optimal bulkhead, the influence of the supporting strut is also explored. The joint action is obtained by changing the location of the supporting strut. The results show that the top supporting strut-bulkhead structure is the optimal position. The power-extraction efficiency of the rotor with this integrated structure is significantly improved at optimal tip speed ratios (TSRs) and higher TSRs.

Kesan Kepaduan Rotor Terhadap Prestasi Kuasa Turbin Angin Paksi Menegak

Wind energy is one of the potential renewable energy sources and a great alternative to replace conventional power generation using coal and fossil fuel that heavily contribute to climate change. Recently, small scale vertical axis wind turbine (VAWT) has received growing interest as wind energy converter due to its suitability to be used in low wind speed area. Hence, this paper is intended to evaluate numerically the effect of solidity, by varying turbine diameter, on power performance of VAWT using computational fluid dynamic (CFD) technology. A series of two-dimensional CFD simulations was performed on a three-bladed H-type Darrieus rotor equipped with symmetrical NACA0018 blades. Performance evaluation on 3 turbine configurations with different diameter; i.e. 1.0 m, 0.6 m and 0.43 m were performed over a range of tip speed ratio, λ with an incoming velocity of 8.0 m/s. The simulation results clearly show that low solidity turbine performed better at high values of λ and has wider operating range while turbine with low solidity performed better at low λ and has better self-starting capability. The results lend substantially to our understanding of solidity effect on performance of VAWT in order to develop an ideal design of VAWT that can operate optimally in complex wind condition.

Performance Evaluation of H-Type Darrieus Vertical Axis Wind Turbine with Different Turbine Solidity

Among renewable energy resources, wind energy is one of the best alternative for power generation. Recently, vertical axis wind turbine (VAWT) received renewed interest as small-scale wind energy converter due to its suitability for urban application, where the wind condition is known to be unsteady and turbulence. Amongst various type of VAWTs, H-type Darrieus rotor has become more popular, thanks to its simple construction features, resulting to low manufacturing and installation cost. The aim of this paper is to evaluate numerically the power performance of straight-bladed Darrieus VAWT with different turbine solidity using computational fluid dynamic (CFD) technology. A series of two-dimensional CFD simulations of a three-bladed H-type Darrieus rotor were performed with 3 different solidities, σ (0.3, 0.5 and 0.7) to evaluate their power performance. Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations were used to calculate the instantaneous moment coefficient, Cm and power coefficient, Cp over a range of tip speed ratio, λ (0.5–4.5) with a free stream velocity of 8.0 m/s. The simulation results show that high solidity turbine performed well at low values of λ while turbine with low solidity has a wider operating range of λ and performed better at λ &gt; 3.0 due to less blade-wake interactions between upstream and downstream halves of the turbine and lower blockage effect. The findings lend substantially to our understanding of physics flow around blades and turbine in order to optimize the power performance of small scale straight-bladed Darrieus VAWT operating in unsteady and turbulence wind condition.

An experimental test of the effect of cup diameter on the power performance of novel design HC-type VAWT

Wind energy is one solution to overcome the energy problem in Indonesia. This study aimed to analyze the effect of cup diameter on the power performance of an HC-type vertical axis wind turbine (VAWT). The wind turbine used a combination of an H-type Darrieus wind turbine and a type-C rotor VAWT. The Darrieus HC-rotor wind turbine blade has a height H = 800 mm and diameter D = 800 mm with C-rotor variations on the tip with diameters of 76,2, 101,6, and 152,4 mm. The wind tunnel used an electric motor with a power of 1 HP (740 Watt) and 1400 rpm connected to a fan. The variation of wind speed was set to 2, 3, 4, 5, 6 and 7 m/s. The results showed that: (a) the highest rotation speedal speed was achieved by the HC-rotor diameter of 76,2 on 105 rpm with a wind speed of 7 m/s; (b) the highest value of the coefficient of power (Cp) is achieved by the HC-rotor diameter of 101,6mm (c) the highest value of the coefficient of torque (Ct) is achieved with the HC-rotor diameter of 152,4mm (d) the Darrieus HC-rotor wind turbine is suitable to be used in tropical regions that have low wind speeds. This result provides important information about the effect of the C rotor radius on the performance of HC-rotor Darrieus wind turbine blade vertical axis.

Vertical Axis Wind Turbine Improvement using DC-DC Boost Converter

Vertical axis wind turbine (VAWT) can be operated in any direction of wind speed, but it has low rotation. To improve the performance of VAWT in which low rotation, this paper presents a simple control strategy of VAWT using a DC-DC boost converter to tap constant voltage in a standalone application. The main objective of this research is to maintain a constant output voltage of converter despite variation input voltage affected by variable wind speed. A simple proportional-integral (PI) controller has been used for a DC-DC boost converter and tested in MATLAB-Simulink environment, with the closed-loop system of the converter maintain constant output voltage although the wind speed is kept changing. The PI controller obtains the feedback from the output voltage of the boost converter to produce the correct pulse width modulation (PWM) duty cycle and trigger the metal oxide semiconductor field effect transistor (MOSFET) following the reference voltage of the turbine. This system has suppressed the value of overshoot and increased the efficiency of wind turbines as 34 %.

Investigation of V-shaped blade for the performance improvement of vertical axis wind turbines

The vertical axis wind turbine (VAWT) is regarded as an important device to utilize the renewable offshore wind energy to supplement the existing power systems. Hence, the demand for higher wind energy conversion makes the research focus on the blade optimization of wind turbines. This paper attempts to propose a novel VAWT structure with V-shaped blade to improve the power outputs at moderate tip speed ratios. The feasibility of the Reynolds-Averaged Navier-Stokes SST k-ω turbulence model applied on the VAWT was verified against available experiments at first. Then a comprehensive investigation on the aerodynamic performance of such V-shaped VAWT was carried out using the SST k-ω model. The results indicated that the maximum enhancement in power coefficient obtained in the optimal V-shaped blade was about 24.1%. In addition to the great improvement of the power efficiency, the V-shaped blade was proven to alleviate the damage caused by lateral loads to the wind turbine. Besides, the flow structures over the blade surface were studied to reveal the mechanism of dynamic stall with the reason of power increase explained. Moreover, it was found that the V-shaped blade could effectively suppress the flow separation and delay the dynamic stall in the middle of the blade, and the undesirable blade tip effect would not be more serious comparing to that of the conventional straight blade. It was finally concluded that the current work could be practically applied to the design and optimization of the VAWT blades.

Developed DMST model for performance analysis and parametric evaluation of Gorlov vertical axis wind turbines

Vertical axis wind turbines (VAWTs) are appropriate for operating under low wind speeds. However, many VAWT designs have been developed. The aim of this paper is to develop a low-cost model to evaluate and compare the aerodynamic performance of Gorlov and Darrieus-type straight-bladed VAWTs. For this purpose, a double multiple stream tube (DMST) model has been developed for Darrieus and Gorlov VAWTs. Subsequent to the validation of the developed models with the available results in the literature, a comparison has been performed between the Darrieus and Gorlov VAWTs. Then, the role of geometrical and operational parameters on the aerodynamic performance and the torque coefficient curves of Gorlov VAWT has been evaluated. It has been found that the performance of Gorlov rotor is better from the effectiveness and fluctuation standpoints. The results of parametrical evaluation of the studied Gorlov turbine show that maximum power coefficient (CP) is obtained for NACA 0018 airfoil. In addition, the number of blades and the helical angle variation are significant parameters in reducing the oscillation of aerodynamic loads and rotor stability. Moreover, self-starting behavior has been improved with increasing the blade chord length or free wind velocity and deteriorated by the usage of thinner airfoils.

NUMERICAL AND EXPERIMENTAL STUDY OF A TWO-STAGE SAVONIUS WIND TURBINE

This article presents a numerical and experimental study of vertical axis wind turbine performance comparison involving a two-stage Savonius rotor with similar parameters. The experimental study is conducted in the aerodynamic tunnel at the Fluid Mechanics Laboratory of the Federal University of Rio Grande do Sul. The aerodynamics rotors are manufactured by 3D prototyping technique. Numerical simulations are performed using the Finite Volumes Method performed by the solution of the Reynolds Averaged Navier-Stokes (RANS) and continuity equations using the SST k-ω turbulence model. The numerical domain is modeled in order to maintain the same characteristics of the experimental model. The mesh quality is evaluated through the GCI (Grid Convergence Index) method. The static and dynamic torque coefficients and the power coefficients are compared. The tests are made without blockage corrections due to the small blockage ratio from 7.5%. Results show that the turbine has a positive static torque coefficient for any rotor angles. The dynamic torque reaches the maximum value for a tip speed ratio (λ) of 0.2 for the experimental and numerical cases. The relative difference between the numerical simulations and the experimental results are between 3.8% and 13.4%.

Effect of vortices on power output of vertical axis wind turbine (VAWT)

Performance of a vertical axis wind turbines (VAWTs) is a major focus of research these days. The present research focuses on numerical investigate the performance of a VAWT in the presence of upstream bluff bodies and investigate the impact of vortices shed on the VAWT performance. Designing of wind turbine is performed using Multiple Stream Tube Model which uses turbine power, number of turbine blades, aspect ratio and wind speed as parameter. Simulations are done using Reynolds averaged Navier-Stokes equation. Furthermore, VAWT equipped with three NACA 0018 airfoils is used. In this study, single and two upstream bluff bodies are used and the distance of the VAWT relative to a bluff body is changed to 1D, 2D and 3D (where D is the length and width of bluff body) both along and perpendicular to flow direction in order to find an optimal location for maximum power. This study shows that the deflected wind from the bluff body possess high wind velocity which is 12% higher for single bluff body and 25% higher for two bluff bodies than the free stream wind velocity. Moreover the VAWTs can be deployed downstream of tall urban structures for enhancement of wind turbine power generation.

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

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.

A novel real-time feedback pitch angle control system for vertical-axis wind turbines

Modern horizontal-axis wind turbines improve their performance by controlling the blade pitch, which is a well-developed technique in practical use. However, the application of this method in vertical-axis wind turbines (VAWTs) is restricted, due to continuous changes in both the relative wind velocity and angle of attack of the blade. In the study, through an in-depth aerodynamic analysis between the blade pitch and performance of VAWTs, a real-time feedback blade pitch control system is developed, which is based on the real-time flow velocity around the blade. Subsequently, a computational fluid dynamics method with FLUENT is constructed to evaluate the performance of the pitch control system on improving VAWT performance. The calculation method is verified via wind tunnel experimental data. Results indicate that real-time feedback control of the pitch angle increases the average power coefficient in a wide range of tip speed ratios (TSRs). At low TSRs, it significantly improves the starting performance by decreasing the occurrence of vortex shedding and flow separation on the blade surface. At high TSRs, it effectively increases the power coefficient of VAWTs. Additionally, at high TSRs, the power coefficient generally exceeds 0.3 and the maximal power coefficients of the VAWTs corresponds to 0.441. At high TSRs, when compared to the zero pitch, the power coefficient relatively increases by at least 12.7%.

Effects of trailing-edge movable flap on aerodynamic performance and noise characteristics of VAWT

Efficiency enhancement and noise reduction are the two critical factors in the wind turbine design. In this paper, the effects of trailing-edge flap on the aerodynamic performance and noise characteristics of NACA0018 airfoil and vertical axis wind turbine (VAWT) were investigated, and the geometric parameters including flap angle, flap position and flap length were considered. The aerodynamic performance was simulated with the Detached-Eddy Simulation (DES) based on Spalart-Allmaras turbulence model and noise characteristics is calculated by CFD combined with Ffowcs-Williams and Hawkings (FW-H) acoustic analogy method. The research results indicate that the trailing-edge flap could effectively suppress flow separation and reduce the airfoil noise at high angle of attack (AOA). The optimum flap parameters obtained by orthogonal experimental design (OED) method were applied in VAWT, and it was observed that the trailing-edge flap could significantly improve the power coefficient at high tip-speed ratio (TSR) and reduce the VAWT noise. The research in this paper provided a comprehensive reference for improving the dynamic stall characteristics and reducing the noise of VAWT in practical engineering applications.

Effects of inward and outward overlap ratios on the two-blade Savonius type of vertical axis wind turbine performance

ABSTRACTIn this paper, using numerical simulation, the effects of inward and outward overlaps on the performance of a conventional two-blade Savonius wind turbine and the complete analysis of the events caused by the rotation of the blades have been investigated. Computations have been carried out at several nondimensional overlap ratios such as G/d = 0, ±0.1, ±0.2, and ±0.3 for three wind speeds of 3, 5, and 7 m/s. On the other hand, in the present study, the values of the tip speed ratio (TSR) are considered in the range from 0.2 to 1.2. The obtained results are validated against the available data in the open literature and found excellent agreements between them. Several results such as the instantaneous velocity and pressure fields in the rotating zone, variation of torque coefficients in one complete cycle of the rotor, and mean power coefficient distributions as a function of TSR and wind speed have been presented in this numerical investigation. The results show that, regardless of the overlap ratio, the maximum power coefficient occurs at a tip speed ratio (TSR) of 0.8. Additionally, the maximum power coefficient is observed in the inwards overlap ratio of 0.2 and an increasing or decreasing the overlap ratio reduces the maximum value of the power coefficient in all wind speeds under consideration. Finally, it was concluded that at each TSR and G/D value, increasing the wind speed enhances the power coefficient of two-blade Savonius VAWT. It was hoped the obtained results arouse interest among the VAWT designers.

Numerical investigations of a novel vertical axis wind turbine using Blade Element Theory‐Vortex Filament Method (BET‐VFM)

AbstractThe aerodynamic performance of three different configurations of vertical axis wind turbines (VAWT), namely: (a) conventional Darrieus troposkein VAWT (based on turbines designed by Sandia National Laboratories), (b) novel 50% STS‐VAWT (50% shifted‐troposkein‐shaped STS‐VAWT), and (c) novel 100% STS‐VAWT were investigated numerically. An in‐house code, which combined the blade element theory (BET) and the vortex filament method (VFM), was used. The main purpose of this work was to develop an aerodynamic code to predict the performance of conventional VAWT as well as assess the novel 50% and 100% STS‐VAWT configurations. Simulation results (power coefficients) were verified and then validated against experimental data available from the literature (2‐, 5‐, and 17‐m conventional troposkein VAWT measured by Sandia National Laboratories). Additional numerical results showed that the 50% STS‐VAWT outperformed both the conventional VAWT and the 100% STS‐VAWT by up to 14% (peak power), within the range of rotation and turbine sizes that were investigated in the present work.

Assessment and optimization of the power performance of twin vertical axis wind turbines via numerical simulations

The power performance of twin vertical axis wind turbines (VAWTs) is believed to surpass that of their individual counterparts. In this study, the power performance of twin VAWTs was investigated via computational fluid dynamics (CFD) simulations by changing their configuration parameters, including the airfoil section (NACA), solidity ratio (σ), pitch angle (β), rotational direction (φ), and turbine spacing (S/D). The CFD model was validated against wind tunnel test data from the literature. An L16 (45) orthogonal table was adopted to optimize the power performance using the Taguchi method. The rated power coefficient (CP) and rated tip speed ratio (TSR) were calculated for the 16 cases in the table. The extent of impact of the five parameters on the rated TSR ranked as σ ˃ β ˃ NACA ˃ φ ˃ S/D. In comparison, the extent of impact of these parameters on CP ranked as β ˃ S/D ˃ σ ˃ NACA ˃ φ. The optimal and worst configurations of the twin VAWTs were determined and their CP values increased by 13% and 8%, respectively, from that of their standalone counterparts. Moreover, the rated TSRs of the twin VAWTs differed from those of their standalone counterparts.

Airfoil parameterization evaluation based on a modified PARASEC method for a H-Darrious rotor

The airfoil research is one of the most essential issue which has great influence on the vertical axis wind turbine (VAWT) performance. Thus, a comprehensive research was conducted in this study with the objective of evaluating the effect of the twelve airfoils' controlling parameters on a Darrieus rotor's performance. The airfoil parameterization method, orthogonal algorithm and computational fluid dynamic (CFD) prediction were intergtated to fulfill this objective. A modification was conducted for the airfoil parameterization method to avoid trailing edge crossing and make controlling parameter's geometrical meaning more explicitly. The analysis results sorted the effect of design parameters by impact weight or contribution ratio. A remarkable finding was that the design parameters on the lower surface have greater influence than those on the upper surface. Orthogonal analysis gained a best airfoil whose power coefficient (CP) is 13.26% larger than that of NACA 0015. Flow field analysis found that a tiny positive vortex was enlarged intensively with the increasing of the azimuth angle, which degrades the rotor's performance.

Improved double-multiple-streamtube approach for H-Darrieus vertical axis wind turbine computations

Accurate predictions on vertical axis wind turbine performance are important for the design process but also challenging because the flow is highly unsteady involving a strong variation of the angle of incidence. In the present work, a double-multiple-streamtube (DMS) approach is improved by analytical corrections. First, two-dimensional and three-dimensional computational fluid dynamics (CFD) simulations are performed for wind turbines at various tip speed ratios. The CFD results are used as a database to investigate the velocity field of the turbines and to derive reasonable physical basis for the modelling approach. Second, new analytical models are introduced to correct the angle of incidence seen by the airfoil section together with correction models for the streamtube expansion and dynamic stall effects. DMS simulations are then carried out and compared with experimental data for turbines with different rotor solidity and various operating ranges. The prediction accuracy is significantly improved by the new model not only for the power coefficient but also for the azimuthal variations of the blade loads.

Blade shape effect on the behavior of the H-rotor Darrieus wind turbine: Performance investigation and force analysis

This work introduces a numerical analysis of three-bladed Darrieus vertical axis wind turbine performance using 25 different sectional profile airfoils from different families. This investigation is to optimize and maximize torque output coefficient and output power coefficient as well as studying force analysis for the optimum airfoil. Aerodynamic simulations were used depending on finite volume analysis using computational fluid dynamic (CFD) methodology. These CFD simulations used the unsteady (transient) Reynolds-Averaged-Navier-Stokes (URANS) calculations to solve and analysis the flow field around the turbine. Quantitative and qualitative validations were presented in this work, it is found that an acceptable agreement between the current CFD calculations and the published experimental work in the calculations of the power output coefficient. The results presented that the optimal configuration is LS (1)-0413 airfoil. The power coefficient of the turbine consists of LS (1)-0413 airfoil has been increased by 16% compared to NACA 0021 performance. Furthermore, in the current study, the different forces on the different elements of the Darrieus turbine were analyzed during the rotation as well as in stationary conditions for the best blade profile.