Experimental Investigation of Performance Characteristics for Savonius-Style VAWTs: A Comparative Study

2021 ◽  
Author(s):  
Diplina Paul ◽  
Abhisek Banerjee
Keyword(s):  
Wind Turbines ◽  
Coefficient Of Performance ◽  
Total Power ◽  
Speed Ratio ◽  
Mechanical Loads ◽  
Tip Speed Ratio ◽  
Ac Motor ◽  
Different Types ◽  
Laminar Air Flow ◽  
Rotor Profiles

Abstract Savonius-style wind turbines are mainly gauged by two types of coefficients namely: (i) coefficient of power (CP) and (ii) coefficient of torques (CT). Coefficient of power is defined as the ratio of power generated by the turbine to the total power available to the turbine from the free-flowing wind. This is synonymous to the operational efficiency of the wind turbine. Coefficient of torque reflects the torque generating ability of the turbine. In this manuscript, experiments have been performed using three different types of rotor profiles for Savonius-style wind turbines (SSWTs) namely, classical SSWT, Benesh type SSWT and elliptical shaped SSWT using oriented jets. Using deflector plates the orientation of jets have been varied from 20° to 70°. Addition of deflector plates to the wind turbines, assists in maximizing the utilization of wind energy. Experiments have been performed in the laminar air flow. Mechanical loads have been used to study Coefficient of performance (CP) and coefficient of torque (CT) as a function of tip speed ratio (TSRs). The velocity of the wind is adjusted by varying the rheostat that controls the AC motor for the wind tunnel systems. Experimental results indicated that optimum performance could be achieved from all three types of SSWT variants at TSR ∼ 0.70. Out of the three designs studied in this manuscript, elliptic shaped SWT yielded best coefficient of performance equal to 0.39 at TSR = 0.70.

Performance Characteristics of a Horizontal Axis Model Wind Turbine

1981 ◽  
Vol 195 (1) ◽  
pp. 223-229 ◽  
Author(s):  
A T Sayers ◽  
A F Christopher Bsc
Keyword(s):  
Low Power ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Horizontal Axis ◽  
Performance Characteristics ◽  
Coefficient Of Performance ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
And Performance ◽  
Prototype Design

The performance characteristics of wind turbines should be thoroughly investigated prior to expending large amounts of capital on a prototype design. A low power dynamometer is described for measuring the power and torque output from a two-bladed model wind turbine, and performance characteristics relating coefficient of performance to tip speed ratio and blade geometric pitch are presented for three designs of blade.

scholarly journals Wake Expansion and the Finite Blade Functions for Horizontal-Axis Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7653
Author(s):  
David Wood
Keyword(s):  
Radial Velocity ◽  
Wind Turbines ◽  
Loss Factor ◽  
Axial Direction ◽  
Horizontal Axis ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Constant Pitch ◽  
Horizontal Axis Wind Turbines ◽  
Blade Element

This paper considers the effect of wake expansion on the finite blade functions in blade element/momentum theory for horizontal-axis wind turbines. For any velocity component, the function is the ratio of the streamtube average to that at the blade elements. In most cases, the functions are set by the trailing vorticity only and Prandtl’s tip loss factor can be a reasonable approximation to the axial and circumferential functions at sufficiently high tip speed ratio. Nevertheless, important cases like coned or swept rotors or shrouded turbines involve more complex blade functions than provided by the tip loss factor or its recent modifications. Even in the presence of significant wake expansion, the functions derived from the exact solution for the flow due to constant pitch and radius helical vortices provide accurate estimates for the axial and circumferential blade functions. Modifying the vortex pitch in response to the expansion improves the accuracy of the latter. The modified functions are more accurate than the tip loss factor for the test cases at high tip speed ratio that are studied here. The radial velocity is important for expanding flow as it has the magnitude of the induced axial velocity near the edge of the rotor. It is shown that the resulting angle of the flow to the axial direction is small even with significant expansion, as long is the tip speed ratio is high. This means that blade element theory does not have account for the effective blade sweep due to the radial velocity. Further, the circumferential variation of the radial velocity is lower than of the other components.

Experimental and Computational Investigation on Gyromill Wind Turbines Focusing on Wing Camber

2015 ◽  
Author(s):  
Eiji Ejiri ◽  
Tomoya Iwadate
Keyword(s):  
Wind Turbines ◽  
Flow Analysis ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Computational Investigation ◽  
Tip Speed Ratio ◽  
Maximum Value ◽  
Commercial Code ◽  
Volume Method ◽  
Turbine Impeller

Gyromill wind turbines with three different blade profiles were investigated experimentally and numerically in order to verify the effect of the direction of camber on aerodynamic performance. Experiments were carried out using a model turbine impeller with an axial length of 200 mm and a diameter of 200 mm. The results showed that the maximum power coefficient was higher for blades with negative camber than for ones with positive camber. On the other hand, the operating range of the tip speed ratio tended to be narrower for the blades with negative camber than for the ones with positive camber. An unsteady numerical flow analysis around the wind turbines was conducted using a commercial code employing the finite volume method. The results showed that the power coefficient of one blade had a maximum value in the second quadrant and that the blades with negative camber were advantageous for obtaining high rotational force in the position, compared with the blades with positive camber and a symmetrical blade.

Performance of a High Tip Speed Ratio H-Darrieus in the Skewed Flow on a Roof

2003 ◽  
Author(s):  
Sander Mertens ◽  
Gijs van Kuik ◽  
Gerard van Bussel
Keyword(s):  
Wind Turbines ◽  
Power Output ◽  
Energy Demand ◽  
Leading Edge ◽  
Spatial Dimension ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Blade Element Theory ◽  
Excess Power ◽  
Flat Roof

Small wind turbines sited on a flat roof have good opportunities to become widespread. They operate in the accelerated wind above the roof and deliver the power where it is needed. Since the power produced offsets that which would otherwise be bought from the utility, they reduce energy demand and bills from the utility. Furthermore excess power can be sold back to the utility, thus producing income as well. Flow over a building separates at the roof leading edge at a certain angle. Wind turbines sited well above the roof thus operate in skewed flow. H-Darrieus operating at (flat) roofs just recently start to be at public interest, operation of an H-Darrieus in skewed flow is thus not discussed in literature until now. To examine this, a model of an H-Darrieus with high Tip Speed Ratio (λ) in skewed flow is developed. The model is based on multiple stream-tube theory: a combination of axial momentum and blade element theory on an actuator plate representation of the rotor, which is divided into multiple stream-tubes. The model shows that, for an H-Darrieus designed for skewed flow, the optimal power output in skewed flow can be up to two times the power output in normal - perpendicular to the H-Darrieus axis- flow. The spatial dimension of the H-Darrieus is responsible for this.

Aerodynamic Design and Wind Tunnel Tests of Small-scale Horizontal-axis Wind Turbines for Low Tip Speed Ratio Applications

2022 ◽  
pp. 1-34
Author(s):  
Ojing Siram ◽  
Neha Kesharwani ◽  
Niranjan Sahoo ◽  
Ujjwal K. Saha
Keyword(s):  
Wind Tunnel ◽  
Wind Turbines ◽  
Pitch Angle ◽  
Horizontal Axis ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Small Scale ◽  
Wind Tunnel Tests ◽  
Tip Speed Ratio ◽  
Horizontal Axis Wind Turbines

Abstract In recent times, the application of small-scale horizontal axis wind turbines (SHAWTs) has drawn interest in certain areas where the energy demand is minimal. These turbines, operating mostly at low Reynolds number (Re) and low tip speed ratio (λ) applications, can be used as stand-alone systems. The present study aims at the design, development, and testing of a series of SHAWT models. On the basis of aerodynamic characteristics, four SHAWT models viz., M1, M2, M3, and M4 composed of E216, SG6043, NACA63415, and NACA0012 airfoils, respectively have been developed. Initially, the rotors are designed through blade element momentum theory (BEMT), and their power coefficient have been evaluated. Thence, the developed rotors are tested in a low-speed wind tunnel to find their rotational frequency, power and power coefficient at design and off-design conditions. From BEMT analysis, M1 shows a maximum power coefficient (Cpmax) of 0.37 at λ = 2.5. The subsequent wind tunnel tests on M1, M2, M3, and M4 at 9 m/s show the Cpmax values to be 0.34, 0.30, 0.28, and 0.156, respectively. Thus, from the experiments, the M1 rotor is found to be favourable than the other three rotors, and its Cpmax value is found to be about 92% of BEMT prediction. Further, the effect of pitch angle (θp) on Cp of the model rotors is also examined, where M1 is found to produce a satisfactory performance within ±5° from the design pitch angle (θp, design).

Evaluation of the MPPT performance in small wind turbines by estimating the tip-speed ratio

2013 ◽  
Author(s):  
Louis F. M. Gevaert ◽  
Jeroen D. M. De Kooning ◽  
Tine L. Vandoorn ◽  
Jan Van de Vyver ◽  
Lieven Vandevelde
Keyword(s):  
Wind Turbines ◽  
Speed Ratio ◽  
Tip Speed Ratio ◽  
Small Wind Turbines

scholarly journals Numerical Analysis and Parameter Optimization of J-Shaped Blade on Offshore Vertical Axis Wind Turbine

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6426
Author(s):  
Lin Pan ◽  
Ze Zhu ◽  
Haodong Xiao ◽  
Leichong Wang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Vertical Axis ◽  
Offshore Wind ◽  
Speed Ratio ◽  
Offshore Wind Turbine ◽  
Offshore Wind Turbines ◽  
Tip Speed Ratio ◽  
Turbulence Effect ◽  
Dimensional Simulation

In this study, the performance of offshore wind turbines at low tip speed ratio (TSR) is studied using computational fluid dynamics (CFD), and the performance of offshore wind turbines at low tip speed ratio (TSR) is improved by revising the blade structure. First, the parameters of vertical axis offshore wind turbine are designed based on the compactness iteration, a CFD simulation model is established, and the turbulence model is selected through simulation analysis to verify the independence of grid and time step. Compared with previous experimental results, it is shown that the two-dimensional simulation only considers the plane turbulence effect, and the simulation turbulence effect performs more obviously at a high tip ratio, while the three-dimensional simulation turbulence effect has well-fitting performance at high tip ratio. Second, a J-shaped blade with optimized lower surface is proposed. The study showed that the optimized J-shaped blade significantly improved its upwind torque and wind energy capture rate. Finally, the performance of the optimized J-blade offshore wind turbine is analyzed.

scholarly journals A design and performance prediction method for small horizontal axis wind turbines and its application

AIMS Energy ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 1043-1066
Author(s):  
Stephen K. Musau ◽  
◽  
Kathrin Stahl ◽  
Kevin Volkmer ◽  
Nicholas Kaufmann ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Performance Prediction ◽  
Prediction Method ◽  
Drive Train ◽  
Performance Characteristics ◽  
Speed Ratio ◽  
Battery Charger ◽  
Tip Speed Ratio ◽  
And Performance

<abstract> <p>The paper deals with small wind turbines for grid-independent or small smart grid wind turbine systems. Not all small turbine manufacturers worldwide have access to the engineering capacity for designing an efficient turbine. The objective of this work is to provide an easy-to-handle integrated design and performance prediction method for wind turbines and to show exemplary applications.</p> <p>The underlying model for the design and performance prediction method is based on an advanced version of the well-established blade-element-momentum theory, encoded in MATLAB™. Results are (i) the full geometry of the aerodynamically profiled and twisted blades which are designed to yield maximum power output at a given wind speed and (ii) the non-dimensional performance characteristics of the turbine in terms of power, torque and thrust coefficient as a function of tip speed ratio. The non-dimensional performance characteristics are the basis for the dimensional characteristics and the synthesis of the rotor to the electric generator with its load.</p> <p>Two parametric studies illustrate typical outcomes of the design and performance prediction method: A variation of the design tip speed ratio and a variation of the number of blades. The predicted impact of those parameters on the non-dimensional performance characteristics agrees well with common knowledge and experience.</p> <p>Eventually, an interplay of various designed turbine rotors and the given drive train/battery charger is simulated. Criterions for selection of the rotor are the annual energy output, the rotor speed at design wind speed as well as high winds, and the axial thrust exerted on the rotor by the wind. The complete rotor/drive train//battery charger assembly is tested successfully in the University of Siegen wind tunnel.</p> </abstract>

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