Power Coefficient Of Wind Turbine Research Articles

PENGARUH KONTROLER MAXIMUM POWER POINT TRACKING (MPPT) TERHADAP EFISIENSI DAYA VERTICAL AXIS WIND TURBINE (VAWT) TIPE SAVONIUS DUA SUDU

The purpose of this research is to determine the effect of Maximum Power Point Tracking (MPPT) controller on the power efficiency of a two-bladed Savonius vertical axis wind turbine (VAWT) with a dimensional diameter of 0.9 m and a height of 1 meter, using 1 mm thick stainless steel plate blades. The MPPT controller is applied to the two-bladed Savonius wind turbine to maintain its operation at the maximum power point. The Perturb & Observe type MPPT controller is used in the study to compare the power output of the Savonius wind turbine when the MPPT system is inactive and when it is active, with three variations of load using resistors of 470 ohm, 560 ohm, and 1000 ohm. The research is conducted by subjecting the turbine blades to three variations of wind thrust at speeds of 4.9 m/s, 5.8 m/s, and 6.4 m/s. The testing without using MPPT resulted in an average power of 0.199 Watt, while using MPPT resulted in an average power of 0.620 Watt. The research findings indicate an average power difference of 0.421 Watt, representing an increase of 317.713%. The average power efficiency of the turbine increased by 2.331% compared to the calculated maximum power of the two-bladed Savonius wind turbine. The average power coefficient (Cp) of the two-bladed Savonius wind turbine without MPPT and with MPPT is 0.159% and 0.509%, respectively, indicating a positive effect of MPPT as it led to an average increase in power coefficient of 0.350%.

Verification of the self-starting problem of a Vertical Axis Wind Turbine with Inclined Blades

In this paper, a theoretical investigation of the impact of varying the blade inclination angle b on the power coefficient of vertical-axis wind turbines equipped with straight blades has been demonstration, where the inclination angle was modified from twenty-five degrees to eighty-five degrees. Within the framework of this study, the term SS-VAWT was assigned to refer to the rotor which is the subject of the research. The "Multi Stream Tube-MST" mathematical model was used after some of its equations were modified to be consistent with the geometrical shape of the SS-VAWT rotor. A computer program was designed using the "Microsoft Visual Basic" programming language as an application of the mathematical model used, which led to the effectiveness of this program and compared its final results with previous experimental results from other studies, this work was carried out on twelve obligatory SS-VAWT, which are classified into four namely H group which is characterized by rotor high change effect, R group which is characterized by diameter effect, N group which is characterized by number of blades effect and C group influenced by the length of blade chord line. The results are represented by power curves as a function of tip speed ratio. The behavior of the curves for each case was verified and compared to determine the optimum case. All results were taken in the small range of tip speed ratio λ0 extending from 0 to 2.8. Since the Cp coefficient and the λ0 coefficient are dimensionless values, the results can be applied to large-sized air rotors, provided that there is geometric similarity. Because they found that the feather's 45-degree tilt and location reduce the problem of starting self-motion.

Performance Improvement of a Savonius Wind Turbine using Wavy Concave Blades

As the best replacement for fossil fuels, green energy resources have established their significance on a worldwide basis. The availability of wind energy makes it the best promising form of green energy. For transforming wind kinetic energy into mechanical energy at low wind speeds, the Savonius wind rotor is regarded as the best choice. The main goal of the current study is to improve the power coefficient (Cp) and torque coefficient (Ct) of the Conventional Savonius wind turbine (SWT) by modifying the inner surface of the blade using a wavy profile. The aerodynamic performance of the wavy turbine is then compared with the conventional turbine in terms of Cp and Ct. The study is conducted using numerical simulation with the assistance of the ANSYS software. The flow characteristics around the turbines are solved utilizing the SST k-ω turbulence model. The simulation outcomes confirmed that the Cp of the wavy rotor increased by about 14.5% at a tip speed ratio of λ= 0.4. Additionally, outcomes showed the peak Cp is 0.18 at λ=0.7 which is 12.5% greater than the conventional SWT

Single-objective optimization design of convergent-divergent ducts of ducted wind turbine using RSM and GA, to increase power coefficient of a small-scale horizontal axis wind turbine

Single-objective optimization design of convergent-divergent ducts of ducted wind turbine using RSM and GA, to increase power coefficient of a small-scale horizontal axis wind turbine

Influence of drivetrain efficiency determination on the torque control of wind turbines

Decreasing the levelized cost of energy is a major design objective for wind turbines. Accordingly, the control is generally optimized to achieve a high energy production and a high-power coefficient. In partial load range, speed and torque are controlled via the generator torque but the rotor torque determines the power coefficient of the turbine. High uncertainties for the uncalibrated low-speed shaft torque measurement and varying drivetrain efficiencies which depend on the speed, load and temperature lead to a torque control error that reduces the power coefficient of the wind turbine. In this paper the rotor torque control error and the impact on the power coefficient of wind turbines is quantified. For this purpose, the variation of drivetrain efficiency is analyzed. An efficiency model for the wind turbine drivetrain is build and validated on the test bench. Then, the influence of the drivetrain speed, torque loads, non-torque loads, and temperature on the efficiency is quantified. Finally, the influence of the rotor torque control error on the power coefficient was simulated with an aerodynamic model. The results show that of all examined influences only torque and temperature significantly impacting the efficiency leading to rotor torque control errors that reduce the power coefficient and consequently increase the levelized cost of energy. Improved efficiency measurement on WT test benches or drivetrain efficiency modelling can reduce the rotor torque control error and therefore decrease the LCOE.

A new similarity criterion and design method for wind tunnel model tests of floating offshore wind turbines

Floating offshore wind turbines (FOWTs) have received strong attention in recent years, and numerous experimental studies have been conducted on them. However, the small-scaled wind turbine models designed by the criterion of traditional thrust coefficient similarity are unable to obtain similar power coefficients with the prototype, and they are not able to reflect the expected dynamic aerodynamics induced by the platform motions. To this end, this paper presents a new criterion for wind tunnel model tests based on the mapping of the optimal tip speed ratio (TSR) and the similarity of the changing rate of the relative TSR. The National Renewable Energy Laboratory's offshore 5-MW wind turbine is selected as the prototype wind turbine. The blade of the model wind turbine is generated by NACA 4412 airfoil, and the chord and twist are optimized by the genetic algorithm. The objective is to keep the thrust and power coefficients of the model wind turbine around the optimal TSR consistent with that of the prototype through a linear mapping relationship. Dynamic simulations with the Unsteady Blade-Element Momentum method are performed to verify the new similarity criterion at different surge frequencies. Compared with those of the model wind turbine designed by the traditional method, fluctuations of the mapped thrust and power coefficients of the new model are in better agreement with the prototype. Hysteresis effects with respect to the relative TSR are newly captured, and loops of the new model are also closer to that of the prototype. This paper provides a more reasonable criterion for wind tunnel model tests of FOWTs, and the dynamic aerodynamics of the prototype can be reflected more accurately compared with the traditional method, which is important for the performance evaluation and optimization design of large-scale FOWTs.

Investigation of the turbine performances in the case of dual usage of Savonius wind turbines

In this study, the turbine performances of Savonius wind turbines were investigated in the case of dual usage. While implementing the dual use of the Savonius wind turbine, a flat plate deflector was placed in front of the turbines to increase the turbine performance. The effects of design parameters such as the geometric dimensions of this flat plate placed in front of the turbines and the geometrical placement position on the turbine performance were investigated. In this direction, the flat plate prevented the negative torque that occurs during the operation of the turbines. Hence, the plate guided the wind to the turbine blade, which generated positive torque. The numerical analyses made in this study were confirmed by the previous literature study. The performance values of single, dual, and flat plate dual Savonius wind turbines were analyzed using the numerical analysis method, the accuracy of which was proven by the experimental data. It was determined that the similarity between the experimental result and the numerical result was approximately 0.3%, especially in the maximum power coefficient values. The computational fluid dynamics (CFD) program ANSYS Fluent was used for turbine performance analysis. With this design study, the maximum power coefficient ( Cp) was obtained around 0.17 with a single Savonius wind turbine, while the maximum power coefficient ( Cp) was obtained around 0.24 with a flat plate dual Savonius wind turbine. As a result, the power coefficient obtained with a single Savonius wind turbine increased by 42% in the flat plate dual Savonius turbine system when compared to the power coefficient of the single Savonius wind turbine. Thus, it was determined that the power coefficient obtained with a single Savonius wind turbine in the flat plate dual Savonius turbine system increased by 42% compared to the power coefficient of the single Savonius wind turbine.

Examination of the Effect of Triangular Plate on the Performances of Reverse Rotating Dual Savonius Wind Turbines

In the present study, the performance of the Savonius wind turbine in designs with dual turbines rotating opposite to each other was examined. To improve the performance of the Savonius wind turbine in the dual turbine design, a triangular plate was placed in front of the turbines. The effects of the geometric parameters of this triangular plate which was placed on the turbine performance were studied. The numerical analyses performed were confirmed by the experimental data of a previous study in the literature. The performance values of Savonius wind turbines were analyzed by numerical analysis, the accuracy of which was proven by experimental data. ANSYS Fluent, a computational fluid dynamics (CFD) program, was used for the performance analysis. In the first stage, the maximum power coefficient (Cp) of the conventional Savonius wind turbine was obtained around 0.17. With the optimum geometric parameter studies, the maximum power coefficient of the Savonius wind turbine in the triangular plate dual turbine design was determined to be around 0.22. Thus, it was found that the power coefficient obtained by a single Savonius wind turbine in a triangular plate dual turbine design was around 30% higher compared to the power coefficient of the conventional Savonius wind turbine.

Increasing power coefficient of small wind turbine over a wide tip speed range by determining proper design tip speed ratio and number of blades

This paper proposes a design strategy based on an understanding of basic rotor aerodynamics principles to achieve aerodynamically efficient small wind turbine rotor by determining proper design tip speed ratio (TSR) and number of blades. In the design and performance analyses of rotors, the blade element momentum (BEM) method was employed in conjunction with the Viterna-Corrigan post-stall model and Buhl’s wake state model. BEM simulations use the Re number dependent airfoil aerodynamic coefficients derived through Xfoil panel code. Reduced design tip speed ratio increased rotor solidity and hence blade Reynolds number. The width of the optimum TSR range, on the other hand, was found to decrease when the design TSR was less than a certain threshold. At high tip speeds, rotors with optimum design TSR were able to maintain an almost constant and near-ideal axial induction factor, resulting widest optimum TSR range for high aerodynamic efficiency. Increasing number of blades ( B) increased CP,max, but further increase in B lowered rotor efficiency due to reduced blade Re number. Based on CFD results, 5-blade SD7032 rotor with a design TSR of 4 achieved 12.3% higher CP,max compared to 0.9 m diameter 3-blade experimental reference rotor. Maximum achievable power coefficient of infinitely many-bladed ideal rotor with design TSR of 4 is 0.559, while CP,max of 5-blade SD7032 rotor is 0.492.

Investigating the effects of wind concentrator on power performance improvement of crossflow wind turbine

Small wind turbines are efficient for solving power supply problems in remote off-grid regions. A crossflow wind turbine is a drag-based small vertical axis wind turbine, which is suitable for small-scale power generation in the built environment because of its low aerodynamic noise. However, the power performance of a crossflow wind turbine is generally lower than that of a Savonius wind turbine. Aiming at improving the performance of a crossflow wind turbine, this study develops a wind concentrator by adding two parallel plates with flanges, which is based on the “wind lens” concept, to an arc-shaped windshield, which is based on an existing concept of a flow deflection device for a crossflow wind turbine. The effects of adding two parallel plates with flanges to the windshield (i.e., the effects of the wind concentrator) on the performance of the crossflow wind turbine are quantified with wind tunnel experiments and analyzed based on the flow field characteristics obtained by computational fluid dynamics simulations. The experimental results show that the wind concentrator enhances the maximum power coefficient of the crossflow wind turbine by 108% from 0.12 (without wind concentrator/windshield) to 0.25 (with the wind concentrator), whereas the arc-shaped windshield improves it by 48% from 0.12 to 0.17 (with the windshield). The numerical simulations reveal that the main cause for the power performance enhancement is a downward deflection of the approaching flow to the upper part of the rotor because of a significant increase in the pressure level on the upwind side of the upper flange and an overall decrease in the pressure level in the wake of the wind concentrator. In conclusion, adding two parallel plates with flanges to an arc-shaped windshield is effective for significantly enhancing the power performance of a crossflow wind turbine.

A comprehensive analysis of blade tip for vertical axis wind turbine: Aerodynamics and the tip loss effect

Vertical axis wind turbines are receiving renewed attention due to the challenges faced by horizontal axis wind turbines in recent years. To achieve commercial applications, a key aspect is to improve the relatively low power coefficient of vertical axis wind turbines. Among several factors that affects output efficiency, the three-dimensional tip loss effect is essential because each vertical axis wind turbine blade has two tops (e.g., the H-type wind turbine). Although several blade tips have been designed, a comprehensive and fair analysis is necessary to find a suitable one. Therefore, in this paper, a total of 20 blade tips have been analyzed using the three-dimensional computational fluid dynamic method. The results indicate that the improved winglet and endplate we proposed are relatively optimal when the synthetic performance of aerodynamic efficiency, structural loads and start-up torque is considered. However, the improvement mechanisms of these two tips are different. Based on the performance curves and the fluid fields at specific tip speed ratios, we find that the endplate increases the blade torque in the upwind region by reducing the spanwise flow, but its negative effect in the downwind region partially counteracts the improvement. For the improved winglet, it reduces the tip loss in the upwind region and suppress separation in the downwind region at the appropriate tip speed ratio, thus significantly improving its performance in one rotor revolution. The winglet also contributes to the reduction of rotor thrust. In addition, the influence of the blade tip on wake is not remarkable and is mainly concentrated in the tip area affected by the tip vortex.

A new method for prediction of power coefficient and wake length of a horizontal axis wind turbine based on energy analysis

Power coefficient and wake length are important indexes for wind farm design and operational control. Accurate estimation of this coefficient is of great significance for the design of wind energy conversion system. In the present study, new methods for estimating rotor power coefficient (Cp) and wake length (WL) of wind turbine from an energy-based perspective are proposed, and the corresponding prediction models are established. Large eddy simulation (LES) coupled with the Actuator Line Method (ALM) are used to simulate the flow field around the wind turbine, and then transient snapshot Proper Orthogonal Decomposition (POD) method is adopted to analyze the energy contained in each plane of the velocity field. Results show that the new model for power coefficient Cp prediction is effective and the maximum error between the estimated value and that obtained with the conventional method is 1.7%. Meanwhile, the wake lengths predicted with the new model are all about 28.5D for the studied tip speed ratios, and the velocity contours perpendicular to the center of wind turbine verify the good accuracy of the model. The POD analysis results also show that the first-order POD mode characterizing the large-scale turbulence structures maintains more than 99.5% energy of the inflow plane, and offers primarily the energy extracted by the wind turbine. This method can be used in the conditions of the transient velocity field easily obtained, and will rich the method of rotor power coefficient and wake length estimation.

Bionic coupling design and aerodynamic analysis of horizontal axis wind turbine blades

AbstractWith millions of years of evolution, owls have developed many excellent characteristics in terms of their flight. The speed of an owl in flight is similar to the relative speed of the blade of a small wind turbine with respect to air. Therefore, the owl wing airfoil is selected as the design airfoil of the wind turbine blade to reduce the flow separation under low Reynolds number. In this study, we analyze an owl wing‐section airfoil and the non‐smooth leading‐edge shape of an owl's wing, and implement an orthogonal optimum design to optimize the wavelength and amplitude of the non‐smooth leading edge. We extract the cross‐sectional features of the airfoil and the non‐smooth leading‐edge shape of the wing. Based on the orthogonal optimum design results, we determine the optimal combination of the wavelength, amplitude, and airfoil, and then design a horizontal‐axis wind turbine blade through bionic coupling. The flow field at different tip speed ratios (TSRs) is simulated using the turbulence model at the rated wind speed. The results show that the power coefficient () of the bionic wind turbine at a high tip speed ratio is 17.7% higher than that of the standard type. Furthermore, we analyze the operation of the turbine at TSRs of 2 and 5. At a high TSR, the leading edge bulge of the bionic wind turbine blade can change the flow direction distribution of the airflow on the blade surface, make the airflow to adhere to the suction surface, and then reduce the stall area on the suction surface of the blade. Thus, the wind turbine produces higher torque, thereby generating higher power.

A Feasibility Study to Reduce Infrasound Emissions from Existing Wind Turbine Blades Using a Biomimetic Technique

Infrasound, i.e., low-frequency noise in the frequency range of 10–200 Hz, produced by rotating wind turbine blades has become a matter of concern because it is harmful to human health. Today, with the rapid increase of wind turbine size, this kind of noise is more worrying than ever. Although much effort has been made to design quiet wind turbine blades, today there is still a lack of effective techniques to reduce infrasound emissions from existing blades. To fill this gap in technology, a biomimetic technique that can be readily applied to reduce infrasound emissions of existing wind turbine blades is studied in this paper using both numerical simulation and experimental testing approaches. The numerical study of the technique is based on the analysis of the sound field distribution near the blade, which is derived by performing both aerodynamic and acoustic simulations of the blade. The experimental study of the technique is based on laboratory tests of two scale models of the blade. Both numerical and experimental studies have shown that the shedding vortices behind the blade can be successfully suppressed by semi-cylindrical rings wrapped on the blade. Consequently, both infrasound and the overall sound pressure level of the noise produced by the blade are significantly reduced. Although the rings fail to show good performance in reducing high-frequency noise, it is not a problem for human health because high-frequency noise is weak and moreover it attenuates rapidly as distance increases. The research also showed that the proposed technique can, not only reduce the infrasound produced by the blade, but can also improve the power coefficient of wind turbines.

Maximal power per device area of a ducted turbine

Abstract. The aerodynamic design of a ducted wind turbine for maximum total power coefficient was studied numerically using the axisymmetric Reynolds-averaged Navier–Stokes equations and an actuator disc model. The total power coefficient characterizes the rotor power per total device area rather than the rotor area. This is a useful metric to compare the performance of a ducted wind turbine with an open rotor and can be an important design objective in certain applications. The design variables included the duct length, the rotor thrust coefficient, the angle of attack of the duct cross section, the rotor gap, and the axial location of the rotor. The results indicated that there exists an upper limit for the total power coefficient of ducted wind turbines. Using an Eppler E423 airfoil as the duct cross section, an optimal total power coefficient of 0.70 was achieved at a duct length of about 15 % of the rotor diameter. The optimal thrust coefficient was approximately 0.9, independent of the duct length and in agreement with the axial momentum analysis. Similarly independent of duct length, the optimal normal rotor gap was found to be approximately the duct boundary layer thickness at the rotor. The optimal axial position of the rotor was near the rear of the duct but moved upstream with increasing duct length, while the optimal angle of attack of the duct cross section decreased.

Improving the power coefficient of the Darrieus vertical axis wind turbine with the aid of morphing airfoils

With the advent of smart materials in recent years, the aviation industry and airfoils have undergone many changes. Research into the use of smart materials in aircraft wings to increase their performance and then the use of smart materials in wind turbine airfoils has begun. In this study, computational fluid dynamics and URANS equations for a three-bladed Darrieus wind turbine equipped with a morphing airfoil was used to determine the optimum blade cross-section. 250 airfoils were generated by random control points, in Gambit software, they were unstructured and generated as a sliding mesh then they were simulated in 2D Ansys using the k-ω SST turbulence model and PISO algorithm. Control points and power coefficient were used for Artificial Neural Network (ANN)training and the Genetic Algorithm(GA) was used to optimize the power coefficient. In this study, the base airfoil is NACA0015. The results of that have been very effective. For the first case (Determine the optimal cross-section of the turbine at a full round) the power coefficient of Darrieus wind turbine with the optimal cross-section increased by 42%, and the blade section(airfoil) was also drawn. For the second case(Determine the optimal cross-section in each of the four zones of the rotor), the most efficient sections(airfoils) in four-zone were obtained, increasing the turbine power coefficient by 60% was the result of this optimization.

Studi Numerik Pengaruh Sudut Kemiringan Sudu Terhadap Performa Turbin Angin Vertikal Tipe Savonius

AbstractWind energy is a renewable energy source that can be felt in everyday life. To convert wind energy into electrical energy, a tool is needed that is a wind turbine. Horizontal Axis Wind Turbine is more widely used and developed today than the vertical type wind turbine. However, the vertical turbine has several advantages compared to the horizontal wind turbine, which is that it can move without depending on the direction of the wind. This study aims to determine the effect of tilt angel of savonius turbine with blades angle 30°, 60° and 90° the turbine power coefficient and determine the optimal turbine blade results in designing a Vertical wind turbine  by simulation  using Computational  Fluid Dynamics  (CFD). The variations used are tilt angel turbine blades is 30°, 60°, 90°. The results showed that the value of Cp (Power Coefficient) of wind turbines with the addition of the blade angel 30°, 60° and 90° had a different increase. The variation the addition of turbine blade tilt angle with 90° tilt angle can increase the efficiency of the turbine blade when compared 30°, 60° blade inclination this is evidenced by wind turbine speed contour analysis, wind vortex contour analysis and turbulence intensity contour analysis shows that the turbine blade simulation results with a slope of 90° has an efficient turbine blade that is very good and effective and get optimal results.Keywords:  Wind  turbine,  VAWT,  CFD,  Efficiency,  Contour,  Optimal,  TSR, power

Numerical investigation of the power and self-start performance of a folding-blade horizontal axis wind turbine with a downwind configuration

ABSTRACT This study proposes an oblique folding mechanism design inspired by the wings of Borneo camphor seeds to enable the blades of wind turbines to pitch and cone. The blade pitching increases the power output, while the blade coning reduces the blade root stress and increases the yaw stability of the wind turbine. Numerical predictions of the power and self-start performance of a downwind folding-blade horizontal axis wind turbine were conducted. For comparison, a benchmark wind turbine with a constant chord blade section with an SD8000 airfoil and zero blade twist was also modeled. The maximum power coefficient (CP ) of the folding-blade wind turbine is 0.404 which is 28.22% higher than that of the benchmark wind turbine, when the fold axis angle is 50° and the pitch angle is 3.834°. The maximum starting torque of the folding-blade wind turbine is 0.720 Nm at a pitch angle of 64.59°, which is 1153.97% higher than that of the benchmark wind turbine. This finding confirms that a folding blade can increase the power output, start-up capability and passive yaw capability of a wind turbine. In conclusion, the proposed folding design can be adopted as an alternative for pitching and coning wind turbine blades.

Study on aerodynamic performance of a combined vertical axis wind turbine based on blade element momentum theorem

The vertical axis wind turbine is mainly divided into lift type and drag type. The lift-type wind turbine has high-power coefficient, but it is difficult to start. The drag-type wind turbine is easy to start, but the power coefficient is low. Combined with the advantages of the two, a combined wind turbine with the lift blade and the drag blade is designed in this paper, which is expected to obtain higher power coefficient and better starting ability. For the combined wind turbine, based on the blade element momentum theorem, the analytical model of multiple-disk-multiple-streamtube is established. By solving the model with the program code, a method of analyzing the aerodynamic characteristics of the combined vertical axis wind turbine is given. The characteristics of attack angle, normal force, tangential force, and power coefficient of the combined wind turbine with different tip speed ratio are obtained by using the analytical model. The Navier–Stokes equation is solved by SST(Shear Stress Transfer) k–w turbulence model (four equations) in fluent 16.0 software. The tangential force coefficient, power coefficient and starting ability of the combined wind turbine are obtained by computational fluid dynamic method. The accuracy of the analytical model in solving the aerodynamic performance of the combined wind turbine is verified by comparing the solution results of the analytical model with the simulation results.

Evaluating wind turbine power coefficient—An undergraduate experiment

We devise an undergraduate experiment to evaluate the wind turbine power coefficient. The apparatus features a commercial miniature rotor hub that allows both blade replacement and adjustment of the pitch angle. The blades are 3D printed. Three pedagogical objectives are emphasized: (1) the demonstration of a practical application of rotational mechanics, (2) the illustration of wind harvesting by parameter optimization, and (3) the appreciation of where the unharvested wind energy goes. Analysis of the student performance shows that the three objectives are partially achieved.