Small Wind Turbine Rotor Research Articles

A Comparison of a Three Blade and Five Blade Wind Turbine in Terms of the Mechanical Properties Using the Q-Blade Software

يمكن لتوربينات الرياح المنتشرة في مزارع الرياح على نطاق المرافق أن تدعم تلبية رغبات الطاقة المستقبلية وتقليل انبعاثات ثاني أكسيد الكربون عن طريق تقليل متطلبات الطاقة من الوقود الأحفوري. مع ارتفاع درجة حرارة الهواء على مدار اليوم، تزداد سرعة الرياح بسبب تدرجات درجة الحرارة، والتي تنتج تدرجًا في الكثافة / الضغط، مما يؤدي إلى حركة الهواء التي تواجهها توربينات الرياح. اعتمادًا على تضاريس الأرض، يمكن أن تواجه الرياح وتوجه في الوديان بين التلال وفوقها حيث تتدفق وتتبع منحنيات الأرض. تنتج هذه التضاريس زيادة في سرعة الرياح في القمم والتلال. في هذا العمل، تم تصميم شفرة دوار توربينات الرياح الأفقية الصغيرة للعمل في ظل سرعة الرياح المنخفضة، باستخدام برنامج (Q-Blade). استنادًا إلى نظرية عنصر الشفرة (BEM). مع الجنيح NACA3712. تم استخدام دوار ثلاثي الشفرات ودوار بخمس شفرات بناءً على نوع التوربين وحجم الدوار لتوليد الطاقة الميكانيكية من طاقة الرياح. تم إجراء مقارنة وتحليل قوة التوربين ومعامل القدرة ومعامل عزم الدوران عند سرعة رياح منخفضة ((1m/s-8m/s وتم الحصول على نتائج دقيقة للغاية. وجد أن أفضل أداء يمكن أن يعمل فيه دوار توربيني ثلاثي الشفرات بقدرة توربينية تبلغ (955W) كما تم الحصول على قدرة التوربين ((582W للدوار خماسي الشفرات. وجد أن تصميم توربينة رياح أفقية صغيرة بخمس ريش أفضل من التوربين بثلاث ريش ومناسب للعمل في المناطق ذات سرعة الرياح المنخفضة وبكفاءة عالية مقارنة بحجم التوربين.

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.

Performance analysis of two different sizes of wind turbine rotors based on Nigerian low wind regime

Nigeria can reduce its level of dependency on fossil fuel by making use of wind energy which is an indigenous renewable energy source for electricity generation. For large energy generation, large wind turbine is more preferable over a wind farm of smaller wind turbine units that will generate the equivalent amount of energy because, there will be loss of energy due to transmission and generation system of every turbine unit of the wind farm while the larger turbine has only one transmission and generation units. However, smaller wind turbines are generally more efficient than the bigger ones in terms of wind energy conversion and they are therefore good for small power generation. In this research work the performance of two different sizes of small wind turbine rotors, a 4-metre rotor (D4-Rotor) and a 4/5-metre one (D4/5-Rotor) were studied at 6m/s wind speed using numerical method. The POINTWISE software is used for modelling the rotor blade and meshing the flow domain. The software used for the simulation is ANSYS 20 which uses finite volume method (FVM) of analysis for solving governing flow equations. From the result of performances, the D4/5-Rotor has higher power coefficient (0.2995) than that of D4-Rotor (0.237), and this indicate about 26 per cent performance improvement of the smaller rotor. Conclusively, smaller wind turbines are more efficient than the bigger ones in terms of wind energy conversion and they are therefore good for small power generation especially in low wind regime.

3D printed rotor blades for a research wind turbine: Aerodynamic and structural design and testing

This study combines the design, the 3D printing and the testing of a small 3-bladed wind turbine rotor for research and teaching purposes. The objective is the additive manufacturing of a rotor with a radius of one meter, as an alternative to subtractive methods, such as computerized milling. The blade design is developed using freely available software packages. The aerodynamic considerations include the airfoil selection, the calculation of the blade geometry and the simulation of the ultimate load cases. The structural considerations are focussed on the printable materials, the infill structures and the retrofit of a load-carrying spar. The rotor blades are 3D printed with the BigRep One at the maker space of the TH Wildau. The structural integrity of the prototype blade is tested in terms of the ultimate root bending moments and the centrifugal forces at the HTW Berlin. The aerodynamic run-up tests are performed at the large wind tunnel of the TU Berlin measuring the power curves. The successful prototype paves the way for follow-up projects, such as open field tests and the 3D printing of larger rotor blades.

Using Small Wind Turbine Technology to Design an AntiFrost Fan

Anti-frost fans (AFFs) are widely used in agriculture to reduce the frost damage to crops. The small wind turbine rotor design code (SWRDC) was adapted to design the blades of an anti-frost fan to maximize the mass flow rate through the rotor while minimizing the blade mass and aerodynamic noise. Using a random sample set of 60 baseline designs, the design is iterated using a genetic algorithm to obtain an optimized design with a mass flow rate of 3.11 kg/s, a blade mass of 6.96 kg, and with a noise level of 72.8 dB.

Insight aerodynamic analysis on small‐scale wind turbines airfoils for low Reynolds number applications

AbstractThe selection of low Reynolds number airfoils for the application of small wind turbine rotor that results in greater rotor performance to the given operating condition is monotonous process. The 16 low Reynolds number airfoils specially developed for small‐scale wind turbine applications were shortlisted to determine the optimum set of airfoils for designing the 3 bladed and 2.25 m radius rotor with the tip speed ratio of 7. Numerical studies were conducted using subsonic airfoil design and analysis solver XFOIL. The aforesaid analysis was done for the Reynolds number of 49,637, 72,801, 115,820, 132,366, and 169,869, which are calculated from the velocity triangle for the subsequent free stream wind speed of 3, 4, 5, 6, and 7 m/s that represents the urban wind condition of India. The indispensable characteristics to improve the performance of wind turbines such as maximum lift to drag ratio, insensitivity to optimum angle of attack over a range of Reynolds numbers and linear transition locations are present in SD7037, E193, SD7032, A18, E387, SD7062, E193MOD, S1210, and S1223 airfoils. Detailed investigation on the aerodynamic characteristics and the effect of laminar separation bubble (LSB) on each airfoils would be helpful to identify the airfoils which needed to be studied for the further improvement of performances through grooving and gurney flaps.

Design and Performance Analysis of Composite Airfoil Wind Turbine Blade

Abstract
 Small horizontal axis wind turbine rotors with composite airfoil rotor blades were designed and investigated in the present study in order to improve its performance in low wind speed and low Reynolds number (Re) conditions for standalone system. The geometrical and aerodynamic nature of a single airfoil small horizontal axis wind turbine blade curtails efficient energy harnessing of the rotor blade. The use of composite airfoil rotor blade improves energy production but imposes uncertainty in determining an optimal design angle of attack and the off design aerodynamic behaviour of the rotor. This research investigated the effects of two airfoils used at different sections in a composite blade and determined the blade’s optimal design angle of attack for maximum power generation. The wind turbine rotor blades were designed using blade element momentum (BEM) method and modelled by SolidWorks software. The SG6042 and SG6043 airfoils were used for the composite airfoil blades. Five wind turbines were designed with rotor blades of design angles of attack from 3° to 7°. The five wind turbine blades were simulated in computational fluid dynamics to determine the optimal design angle of attack. The composite airfoil wind turbine blade showed improved performance, whereas, the wind power generated ranged from 4966 W to 5258 W and rotor power coefficients ranged from 0.443 to 0.457. The blade with design angle of attack of 6° showed highest performance.
 Keywords: composite airfoil, lift-to-drag ratio, pressure coefficient, Reynolds number, design angle of attack.

Experimental investigations of winglet effects on blade geometry of small horizontal axis wind turbine rotors

In this research work, the investigation and optimization of small horizontal axis wind turbine blade at low wind speed is pursued. The experimental blades were developed using the 3D printing additive manufacturing technique. The airfoils E210, NACA2412, S1223, SG6043, E216, NACA4415, SD7080, SD7033, S1210 and MAF were tested at the wind speed of 2-6 m/s. The airfoils and optimum blade geometry were investigated with the aid of the Xfoil software at Reynolds number of 100,000. The initial investigation range included tip speed ratios from 3 to 10, solidity from 0.0431 – 0.1181 and angle of attacks from 2o to 20o. Later on these parameters were varied in MATLAB and Xfoil software for optimization and investigation of the power coefficient, lift coefficient, drag coefficient and lift to drag ratio. The cut-in wind speed of the rotors was 2 and 2.5 m/s with the winglet-equipped blades and without winglets. It was found that the E210, SG6043, E216 NACA4415 and MAF airfoil displayed better performance than the NACA 2412, S1223, SD7080, S1210 & SD7003 for the geometry optimized for the operating conditions and manufacturing method described.

Structural and Aerodynamic Characteristics Analysis of a Small V-shaped Vertical Axis Wind Turbine Rotor

ABSTRACT A detailed comprehensive study of a proposed V-shaped turbine rotor is performed in order to examine its structural and aerodynamic characteristics. The structural analysis section of this work determined the most structurally sound blade geometry from 3 different blade geometries. Using the chosen blade profile, 8 rotor models are developed and are tested numerically. These rotor models are of different configurations, focusing on an inclination angle of 45 and 60 degrees, blade twist angle of 0 and 5 degrees and number of blades. Four rotor models are taken from the initial tests for further study, 3B45D which is a three-bladed rotor with a 45 degree inclination angle, 5B45D which is a five-bladed rotor with a 45 degree inclination angle, 5B45D (5deg) which is a five-bladed rotor with a 45 degree inclination angle and a 5 degree blade twist angle, and 5B60D which is a five-bladed rotor with a 60 degree inclination angle. From the structural study, blade design 2 held the best structural characteristics. The design showed an excellent Von-Mises at 8.8 MPa for static structural and 22.2 MPa for fatigue stress response which is well below the yield strength of ABS Plastic. Both experimental and numerical data have relatively good agreement that is within 15% difference. Overall, maximum power coefficient achieved in this study is about 0.259 numerically and 0.213 experimentally. The best performance is seen by the 3B45D rotor in both static and dynamic study considering experimental and numerical corroboration of results.

Influence of the Solidity Ratio on the Small Wind Turbine Aerodynamics

Increasing popularity of individualised electricity generation from wind by prosumers creates a strong demand for profitable and highly efficient small wind turbines. This paper investigates the influence of rotor blade solidity parameter on device efficiency in hope of determining its optimal value as a part of the development process of the GUST small wind turbine. The study involved experimental analysis in the wind tunnel and numerical simulations performed in QBlade software. Different solidities of the rotor were achieved by alteration of (1) number of blades and (2) chord distribution along the blade span. The increase of rotor solidity resulted in augmentation of the aerodynamic efficiency in both approaches. The elongation of the chord by 33% in a 3-bladed rotor resulted in a bigger power coefficient increment than addition of a 4th blade with original chord distribution. Even though the solidity was the same, the 3-bladed rotor performed better, possibly due to lower form drag. The results emphasize the importance of the rotor solidity optimization during the small wind turbine rotor development and may significantly influence overall power output.

The design of a small lab-scale wind turbine model with high performance similarity to its utility-scale prototype

This paper discussed the procedure of an optimization design method involving a small lab-scale wind turbine rotor. To simulate the aerodynamic performance of a prototype wind turbine at utility-scale by scaled model experiments (especially, the visualization measurements of wake flow in small wind tunnels), an appropriate similar design of the small lab-scale rotor is needed. However, the similar design of blade performance from a prototype wind turbine for small scaled model is rare. In this paper, using a 2.5 MW utility-scale wind turbine as the prototype, we set up a new optimization process of similar design for a model wind turbine with a 320 mm rotor based on the Lifting-Line Theory (LLT) with wake-induced corrections. Results show a dramatic deviation in performance of the geometric scaled model compared to the objective values, which demonstrates the significance of the Reynolds number effects. With the optimized blade, the distribution of normal thrust force is very similar to the objective values. Geometric characteristics variations along the blade span are similar to the prototype. With the tip speed ratio runs at a roughly matched rated condition, the optimized rotor gives a better performance than other models used in previous wind tunnel studies.

Numerical simulation of transient aerodynamic processes in the vertical axis wind turbine rotor

This paper describes the steps of elaboration of calculation model for dynamic simulation of a small vertical axis wind turbine rotor. The calculation model is based on the finite element analysis ANSYS CFX software. The CFD model is used to determine the performance of the wind turbine rotor for different settings (tip speed ratio, solidity, mesh size etc.). The verification of the proposed model is done by hand calculation of the rotor performance and comparison of the real wind turbines output.

Improvement of aerodynamic performance of a small wind turbine

The aerodynamic performance of horizontal-axis wind turbines is strongly dependent on many parameters, among which the airfoil type and the blade geometry (mainly defined by the chord and the twist distributions) are considered the most critical ones. In this article, an approach giving the appropriate airfoil for a small wind turbine design was conducted by performing an aerodynamic improvement of the blade’s airfoil. First, a preliminary design of the rotor blades of a small wind turbine (11 kW) was conducted using the small wind turbine rotor design code. This preliminary approach was done for different airfoils, and it resulted in a maximum power coefficient of 0.40. Then, the aerodynamic efficiency of the wind turbine was improved by modifying the geometry of the airfoils. This technique targets the optimization of the lift-to-drag ratio (Cl/Cd) of the airfoil within a range of angles of attack. Also, a non-uniform rational B-spline approximation of the airfoil was adopted in order to reduce the number of the design variables of the optimization. This methodology determined the best airfoil for the design of a small wind turbine, and it gave an improved power coefficient of 0.42.

Numerical simulation of flow over an airfoil for small wind turbines using the $$\gamma - {\text{Re}}_{\theta }$$ γ - Re θ model

The mechanism of the laminar separation bubble and the laminar-turbulent transition over the airfoil UBD5494 is simulated in ANSYS-FLUENT using the transition $${\text{gamma}} - {\text{Re}}_{\theta }$$ model at Reynolds number 6 × 104, 1 × 105, 1.5 × 105, 2 × 105 and 3 × 105. Modified constants of the Reynolds momentum thickness are incorporated in the model. The aerodynamic performance of the airfoil is also examined against the flow behaviour. Simulation results show that with the increase in angle of attack, laminar separation bubble moves towards the leading edge and at the same time contracts in size. It starts to expand after reaching the foremost point of the leading edge and then bursts, resulting in flow turbulence and stall. With decreasing Re, the size of the laminar separation bubble is found to be increasing and its progress towards the leading edge is noticed to be slower. The numerical results also indicated that UBD5494 airfoil has enhanced lift-to-drag ratio and desirable stall characteristics which are distinctively advantageous for the better performance of small wind turbine rotors.

Wind tunnel experiments for innovative pitch regulated blade of horizontal axis wind turbine

In current study, innovative pitch regulated blade model with folding outer blade section to control power output was made. A small wind turbine rotor with three innovative blades was tested in a low speed wind tunnel to validate the blade effectiveness. The main objective of current study is to investigate this blade performance in limiting power growth in high wind speed and to discuss its mechanism to control power. All the experiment data are inclusive of wind tunnel blockage correction and blade performance is assessed in terms of power output and power coefficient. It is found that when the outer blade section is folded, decrease of both blade energy conversion efficiency and wind energy contained in the airflow that passes through the rotor leads to power output reduction. The highest power coefficient of tested blade is 0.23 and can be reduced by the maximum of 82.8% through folding control. A constant power output in high wind speed is achieved with the tested blade and corresponding fold angle control rule is acquired.

Wind tunnel experiments to prove a hydraulic passive torque control concept for variable speed wind turbines

In this paper the results are presented of experiments to prove an innovative concept for passive torque control of variable speed wind turbines using fluid power technology. It is demonstrated that by correctly configuring the hydraulic drive train, the wind turbine rotor operates at or near maximum aerodynamic efficiency for below rated wind speeds. The experiments with a small horizontal-axis wind turbine rotor, coupled to a hydraulic circuit, were conducted at the Open Jet Facility of the Delft University of Technology. In theory, the placement of a nozzle at the end of the hydraulic circuit causes the pressure and hence the rotor torque to increase quadratically with flow speed and hence rotation speed. The rotor torque is limited by a pressure relief valve. Results from the experiments proved the functionality of this passive speed control concept. By selecting the correct nozzle outlet area the rotor operates at or near the optimum tip speed ratio.

A Hybrid Metaheuristic-Based Approach for the Aerodynamic Optimization of Small Hybrid Wind Turbine Rotors

This work presents a novel framework for the aerodynamic design and optimization of blades for small horizontal axis wind turbines (WT). The framework is based on a state-of-the-art blade element momentum model, which is complemented with the XFOIL 6.96 software in order to provide an estimate of the sectional blade aerodynamics. The framework considers an innovative nested-hybrid solution procedure based on two metaheuristics, the virtual gene genetic algorithm and the simulated annealing algorithm, to provide a near-optimal solution to the problem. The objective of the study is to maximize the aerodynamic efficiency of small WT (SWT) rotors for a wide range of operational conditions. The design variables are (1) the airfoil shape at the different blade span positions and the radial variation of the geometrical variables of (2) chord length, (3) twist angle, and (4) thickness along the blade span. A wind tunnel validation study of optimized rotors based on the NACA 4-digit airfoil series is presented. Based on the experimental data, improvements in terms of the aerodynamic efficiency, the cut-in wind speed, and the amount of material used during the manufacturing process were achieved. Recommendations for the aerodynamic design of SWT rotors are provided based on field experience.

BEM Simulation and Performance Analysis of a Small Wind Turbine Rotor

The blade element momentum (BEM) method is a popular tool for predicting the performance of wind turbine rotors. This study investigated the impact of including factors such as tip loss, hub loss and drag coefficients in BEM simulations of a Bergey XL.1 small wind turbine. The Bergey XL.1 has constant chord, untwisted blades that are challenging to simulate owing to the large variation in angle of attack along the blade during operation. Methods of including post-stall airfoil characteristics, and three wake approaches (Buhl, Glauert and Wilson-Walker) were also examined. BEM simulations were consistent with test data from a Bergey XL.1 collected using a vehicle-based platform. Including tip losses, drag coefficients and wake effects in the BEM simulation had a significant impact on predicted performance, while the effect of including hub loss was negligible. The results illustrate that BEM methods can predict the performance of small wind turbine rotors.

Blade design and performance testing of a small wind turbine rotor for low wind speed applications

Small wind turbines operating at low wind speeds regularly face the problem of poor performance due to laminar separation and laminar separation bubbles on the blades. This is due to the low Reynolds number (Re) resulting from low wind speeds and small rotor size. The use of specially designed low Re airfoils permits start up at lower wind speeds, increasing the startup torque and thus improving the overall performance of the turbine. A new airfoil was designed and the performance of a 2-bladed rotor designed for low Re application fitted to an Air-X marine 400 W wind turbine was tested at a wind speed range of 3–6 m/s. The low Re rotor incorporated taper and twist to the low Re AF300 airfoil section. The pitch of the blades was varied over a range of 15°, 18° and 20° to study the performance and the startup wind speed. It was found that the turbine performed best at 18° pitch angle. On an average, the wind turbine yielded a power coefficient (CP) of 0.255 at a height of 8.22 m at a wind speed of 6 m/s at 18° pitch angle. Maximum CP based on 10 s data at the freestream velocity of 6 m/s was 0.291. The cut-in wind speed based on 10 s averaged data at the optimum pitch angle was 3.24 m/s whereas the instantaneous cut-in wind speed was 2.34 m/s. In comparison with the baseline 3-bladed rotor, the new 2-bladed rotor produced more electrical power at the same freestream velocity.

서남권 도서지역에 적합한 1kW급 수평축 풍력터빈 로터 블레이드 설계 및 유동해석

This study is to develop a 1kW-class horizontal axis wind turbine(HAWT) rotor blade which will be applicable to relatively low wind speed regions in southwest islands in Korea. Shape design of 1kW-class small wind turbine rotor blade is carried out using a blade profile with relatively high lift to drag ratio by blade element momentum theory(BEMT). Aerodynamic analysis on the newly designed rotor blade is performed with the variation of tip speed ratio. Power coefficient and pressure coefficient of the designed rotor blade are investigated according to tip speed ratio.<BR><BR><BR>