scholarly journals Comparative Fatigue Life Assessment of Wind Turbine Blades Operating with Different Regulation Schemes

2019 ◽  
Vol 9 (21) ◽  
pp. 4632 ◽  
Author(s):  
Brian Loza ◽  
Josué Pacheco-Chérrez ◽  
Diego Cárdenas ◽  
Luis I. Minchala ◽  
Oliver Probst

A comparative evaluation of the fatigue damage occurring in the blades of small wind turbines, with different power regulation schemes, has been conducted for the first time. Three representative test cases were built, one based on stall regulation and two using pitch regulation. The power curves were tuned to be identical in all cases, in order to allow for a direct comparison of fatigue damage. A methodology combining a dynamic simulation of a wind turbine forced by stochastic wind speed time series, with the application of the IEC 61400-2 standard, was designed and applied for two levels of turbulence intensity. The effect of the wind regime was studied by considering Weibull-distributed wind speeds with a variety of parameter sets. Not unexpectedly, in typical wind regimes, stall regulation led to a generally higher fatigue damage than pitch regulation, for similar structural blade design, but the practical implications were smaller than thought previously. Given the need for cost-effective designs for small wind turbines, stall regulation may be a viable alternative for off-grid applications.

Author(s):  
Sayem Zafar ◽  
Mohamed Gadalla

A small horizontal axis wind turbine rotor was designed and tested with aerodynamically efficient, economical and easy to manufacture blades. Basic blade aerodynamic analysis was conducted using commercially available software. The blade span was constrained such that the complete wind turbine can be rooftop mountable with the envisioned wind turbine height of around 8 m. The blade was designed without any taper or twist to comply with the low cost and ease of manufacturing requirements. The aerodynamic analysis suggested laminar flow airfoils to be the most efficient airfoils for such use. Using NACA 63-418 airfoil, a rectangular blade geometry was selected with chord length of 0.27[m] and span of 1.52[m]. Glass reinforced plastic was used as the blade material for low cost and favorable strength to weight ratio with a skin thickness of 1[mm]. Because of the resultant velocity changes with respect to the blade span, while the blade is rotating, an optimal installed angle of attack was to be determined. The installed angle of attack was required to produce the highest possible rotation under usual wind speeds while start at relatively low speed. Tests were conducted at multiple wind speeds with blades mounted on free rotating shaft. The turbine was tested for three different installed angles and rotational speeds were recorded. The result showed increase in rotational speed with the increase in blade angle away from the free-stream velocity direction while the start-up speeds were found to be within close range of each other. At the optimal angle was found to be 22° from the plane of rotation. The results seem very promising for a low cost small wind turbine with no twist and taper in the blade. The tests established that non-twisted wind turbine blades, when used for rooftop small wind turbines, can generate useable electrical power for domestic consumption. It also established that, for small wind turbines, non-twisted, non-tapered blades provide an economical yet productive alternative to the existing complex wind turbine blades.


Author(s):  
Sandip Kale ◽  
S. N. Sapali

Micro wind turbines installed in various applications, experience average wind speed for most of the time during operations. Power produced by the wind turbine is proportional to the cubic power of the wind velocity and a small increase in wind velocity results increases power output significantly. The approach wind velocity can be increased by covering traditional wind turbine with a diffuser. Researchers are continuously working to develop a compact, lightweight, cost effective and feasible diffuser for wind turbines. The present work carried out to develop a diffuser with these stated objectives. A compact, lightweight inclined flanged diffuser developed for a micro wind turbine. Bare micro wind turbine and wind turbine covered with developed efficient inclined flanged diffuser tested in the field as per International Electrotechnical Commission (IEC) standards and results presented in the form of power curves. The prediction of annual energy production for both wind turbines determined as per IEC standards.


2019 ◽  
Vol 12 (5) ◽  
pp. 84
Author(s):  
Wongsakorn Wisatesajja ◽  
Wirachai Roynarin ◽  
Decha Intholo

The development of Floating Offshore Wind Turbines (FOWTs) aims to improve the potential performance of the wind turbine. However, a problem arises due to the angle of tilt from the wind flow and the floating platform, which leads to a vertical misalignment of the turbine axis, thereby reducing the available blade area and lowering the capacity to capture energy. To address this problem, this paper seeks to compare the influence of the rotor tilt angle on wind turbine performance between fixed tower wind turbines and FOWTs. The models used in the experiments have R1235 airfoil blades of diameter 84 cm. The experiment was analyzed using a wind tunnel and mathematical modelling techniques. Measurements were obtained using an angle meter, anemometer and tachometer. Testing involved wind speeds ranging from 2 m/s to 5.5 m/s, and the rotational speeds of the two turbine designs were compared. The study found that the rotational speeds of the FOWTs were lower than those of the fixed tower turbines. Moreover, at tilt angles from 3.5° – 6.1° there was a loss in performance which varied between 22% and 32% at different wind speeds. The tilt angle had a significant effect upon FOWTs due to the angle of attack was continuously changing, thus altering the optimal position of the turbine blades. This changing angle of attack caused the effective area of the rotor blade to change, leading to a reduction in power output at suboptimal angles. The study finally makes recommendations for future studies.


Author(s):  
Kishor Sontakke ◽  
Samir Deshmukh ◽  
Sandip Patil

The growing demand for electrical energy for industrial and domestic use, coupled with the limited amount of available fossil fuel reserves and its negative effects on the environment, have made it necessary to seek alternative and renewable energy sources. The use of renewable energy is promoted worldwide to be less dependent on conventional fuels and nuclear energy. Therefore research in the field is motivated to increase efficiency of renewable energy systems. This study aimed to study potential of micro wind turbine and velocity profile through shroud for low wind speeds. Although there is a greater inclination to use solar panels because of the local weather conditions, there are some practical implications that have place the use of solar panels in certain areas to an end. The biggest problem is panel stealing. Also, in some parts of the country the weather is more appropriate to apply wind turbines. Thus, this study paying attention on the design of a new concept to improve wind turbines to be appropriate for the low wind speeds in India. The concept involves the implementation of a concentrator and diffuser to a wind turbine, to increase the power coefficient. Although the wind turbine was not tested for starting speeds, the realization of the shroud should contribute to improved starting of the wind turbine at lower wind speeds. The configuration were not manufactured, but simulated with the use of a program to obtain the power production of the wind turbine over a range of wind speeds. These values were compared to measured results of an open wind turbine developed. The most important topic at hand when dealing with a shrouded wind turbine is to find out if the overall diameter or the blade diameter of the turbine should be the point of reference. As the wind turbine is situated in a shroud that has a larger diameter than the turbine blades, some researchers believe that the overall diameter should be used to calculate the efficiency. The benefits of shrouded wind turbines are discussed.


2020 ◽  
Author(s):  
Francesco Papi ◽  
Lorenzo Cappugi ◽  
Alessandro Bianchini ◽  
Sebastian Perez-Becker

Abstract Wind turbines often operate in challenging environmental conditions. In hot and dusty climates, wind turbine blades are constantly exposed to abrasive particles that, according to many field reports, cause significant damages to the blade’s leading edge. On the other hand, in cold climates similar effects can be caused by prolonged exposure to hail and rain. Quantifying the effects of airfoil deterioration on modern multi-MW wind turbines is crucial to correctly schedule maintenance and to forecast the potential impact on productivity. Analyzing the impact of airfoil damage on fatigue and extreme loading is also important to improve the reliability and longevity of wind turbines. However, this is a topic that has not yet been extensively investigated. In this work, a blade erosion model is developed and calibrated using Computational Fluid Dynamics (CFD). The DTU 10MW Reference Wind Turbine (RWT) is selected as the case study for the analysis, as it is representative of the typical size of the future generation wind turbines. Lift and Drag polars are generated using the developed model and a CFD numerical set-up. Power and torque coefficients are compared in idealized conditions at two wind speeds, i.e. the rated speed and one below it. Full aero-servo-elastic simulations of the turbine are conducted with the eroded polars using NREL’s BEM-based code OpenFAST. Sixty-six ten-minute simulations are performed for each stage of airfoil damage, reproducing operating conditions specified by the IEC 61400-1 power production DLC-group, including wind shear, yaw misalignment and turbulence. Performance data, fatigue and extreme loads are compared for the aeroelastic simulations, showing maximum decreases in CP of about 12% as well as reductions in fatigue and extreme loading.


2019 ◽  
Vol 44 (4) ◽  
pp. 434-451
Author(s):  
Karthikeyan Ravikumar ◽  
Rajkumar Subbiah ◽  
Nalini Ranganathan ◽  
Joseph Bensingh ◽  
Abdul Kader ◽  
...  

The wind energy has been recognised as one of the rising sustainable energies in the world. The wind turbines are subjected to high aerodynamic loads and they cause vibrations due to the wake formation. The magnitude of the applied loads has significant effects on the crack propagation. The fatigue loads have been identified as one of the key sources of damage, with delamination as the main cause for the failure of the turbine blades. The article presents a review of fatigue damages that have been experienced in the wind turbine blades, and factors that are influenced due to the fatigue loads are discussed. The causes and effects of the fatigue loads have been highlighted, and the ways for preventing the fatigue damage by improving the design lifetime are mainly concentrated in review. The overall review gives an idea for determining and reducing the crack growth in wind turbine blades.


2019 ◽  
Vol 6 (1) ◽  
pp. 64
Author(s):  
Jamal Jamal

Savonius wind turbines are wind turbines that canoperate at low wind speeds, this type of turbine is very suitable tobe used in several places in Indonesia. The research aims toimprove the performance of the Savonius wind turbine withvariations in the number of turbine blades as well as variations inthe velocity of wind speed. The research method wasexperimental where wind turbine testing was carried out withvariations in the number of turbine blades with number of 2, 3and 4 blades, other variations carried out were wind speed at 3.5;4,5; 5.5 and 6.5 m/s. The study results show that the 2-bladeturbine produces greater rotation, but the torque moment islower than the 3 and 4 blade turbines, this can be seen in the lowefficiency of the 2 blade turbine at low wind speeds with highloading. At 3.5 m / s wind turbines 2 blade turbines haveefficiency that tends to be the same as 3 and 4 blade turbines upto 0.5 N but at loads of 0.6 - 1.2 N 2 blade turbines have lowerefficiency, while at wind speeds of 4.5 - 6.5 m / s 2 blade turbineshave greater efficiency than turbines 3 and 4 blades up to a loadof 1.2 N but if the load is added then the efficiency of 2-bladeturbines can be smaller than efficiency 3 and 4-blade.


Author(s):  
Timothy A. Burdett ◽  
Kenneth W. Van Treuren

A crucial step in evaluating a potential location for a wind turbine, especially small-scale wind turbines, is a proper wind site survey. Eventually the wind site survey is used to calculate the annual energy production (AEP) of the wind turbine and determine if this location will be profitable. Generally, a wind classification of 3 or above is recommended for any wind turbine site, according to the U.S. Department of Energy. Wind Classes of 1–2 are not considered suitable; however, data suggests that a wind site with Class of 2 wind has the potential to be more cost effective than even the least expensive offshore wind and deserves consideration. Wind data usually exists at locations such as local airports; however, the height at which this data are taken is not representative of the heights at which wind turbines will be installed and thus, airport wind data should not be used. Also, with the variability in wind from location to location, the airport data are generally not near the potential site for the wind turbine and thus, are not useful. A local wind site survey generally entails a two year study of the site using a meteorological (MET) tower. Waco, TX is being studied for the application of small-scale wind turbines. Waco is in a Class 2 wind area; however, no proper wind survey had ever been accomplished. Such a study was undertaken using a MET tower of 100 ft with two anemometers at 100 ft, one anemometer at 75 ft and one anemometer at 50 ft. This paper will describe the potential of Class 2 wind as an energy source, the erection of the MET tower, collection of the data and analysis of the data for the potential of locating a small-scale wind turbine at the site. Techniques for analyzing data when two anemometers are present will be discussed. Focus will be on identifying invalid data with an emphasis on correcting this invalid data. The data from two anemometers was then used in a novel way to identify and correct the invalid data found at both the 75 ft and 50 ft elevations. A filtering technique has also been developed to help identify invalid data. Based on the results of the wind survey, it will be shown that it is feasible to purposely design wind turbine blades for Class 2 wind which will perform better than commercially available small-scale wind turbines.


Author(s):  
Fardin Khalili ◽  
Pradip Majumdar ◽  
Mehdi Zeyghami

Far-field noise propagation from wind turbines propel development of wind farms to an issue for public acceptance. Airstream contains pressure fluctuations as a result of instability, giving a regular eddy pattern or an irregular turbulent motion which are responsible for the sound produced by wind turbine blades. Aeroacoustic noise emanated from a wind turbine is mainly generated by the interactions of tip and trailing edge of wind turbine blades with the mechanics in wake region such as inflow turbulence structures, boundary layer separation and vortex shedding. Hence, there is a strong necessity for an analytical investigation for noise reducing design and development of the technology in order to further expand wind farms. The objectives of this study are to analyze the far-field aeroacoustics of wind turbines with the purpose of predicting far-field sound pressure levels at different receivers and monitoring total acoustic power captured within wind turbine performance for various wind speeds. Blades are modeled based on NREL S825 airfoil since it has high maximum lift and low profile drag. With the purpose of predicting far-field noise, the Ffowcs Williams-Hawkings (FW-H) acoustics model is the preferred method in order to compute the far-field sound signal which is released from near-field flow. As the key attribute of the research, detached eddy simulation (DES) provides accurate results for the desired simulation since it is a hybrid modeling approach that combines features of Reynolds-averaged Navier-Stokes (RANS) simulation in boundary layers and irrotational flow regions, and large-eddy simulation (LES) in unsteady separation regions. In addition, SST K-Omega detached eddy turbulence model is used due to its good compromise between robustness, computational cost and accuracy. Aerodynamic and aeroacoustic analysis of a wind turbine is performed using a three-dimensional model and a commercial CFD Software, STAR-CCM+. In order to predict far-field sound pressure levels and acoustic powers on different locations, five point receivers are defined downstream of the wind turbine model. Receivers are placed one diameter, D, over the wind turbine rotor blades with 1D, 2D, 5D, 10D and 15D away from the wind turbine that represent receivers 1 to 5. Higher acoustic powers are delivered at closer receivers. It means that acoustic power fades out with larger distances. It is observed that there is a fractional variation of 61%, 17%, 6% and 3% as compared to the receiver 1 for receivers 2, 3, 4 and 5 respectively. Moreover, the results show that variation in total acoustic power is non-linear and higher acoustic powers will be captured for higher velocities. This comparison is done between wind speeds of 10m/s and 15m/s.


2017 ◽  
Vol 22 (2) ◽  
pp. 77
Author(s):  
Salome Gonzáles Chávez ◽  
William Urcuhuaranga Jesús

En este trabajo se realiza el diseño y pruebas de un nuevo dispositivo mecánico acoplado a la Cola-Veleta de un pequeño aerogenerador, tal que autorregula y controla la potencia instantánea de generación durante las sobrevelocidades de viento. La faja costera rural y zonas altoandinas del Perú, poseen gran potencial eólico, pero contrariamente se tienen nulos servicios eléctricos. En este escenario, la dotación de electricidad mediante microaerogeneradores constituye una alternativa estratégica. Una desventaja de los vientos característicos de las zonas de influencia es su alta variación de velocidades, cuyo efecto adverso en el aerogenerador es la destrucción prematura del bobinado del generador de imanes permanentes y rotura de palas. Las pruebas de regulación y control de potencia de aerogeneración se realizaron en el Túnel de Viento del Laboratorio de Energía de la Facultad de Ingeniería Mecánica de la UNI. Los resultados se dan en las curvas de potencia del conjunto aerogenerador de ensayo, donde se demuestra el control del crecimiento de la potencia generada, en el rango de velocidades de viento superiores a la condición nominal de diseño del aerogenerador. También se demuestra la confiabilidad del mecanismo cuando se somete a velocidades extremas de viento hasta alcanzar el bloqueo del aerogenerador, así como la inmediata recuperación continua de operación a medida que la velocidad de viento disminuye hacia condiciones nominales de trabajo. Palabras clave.- Control de potencia, Pequeño aerogenerador, Sobrevelocidad de viento, Dispositivo pivote de cola, Confiabilidad. ABSTRACTIn this work we make the design and testing of a new mechanical element coupled to the vane of a small wind turbine, such that self-regulates and controls the instantaneous power generating wind during overspeed. The rural coast an andean highlands of Peru have high wind potential and on the contrary zero electrical services, in this scenario the provision of electricity by small wind turbines is a strategy solution. One disadvantage of the winds from these areas is its high speed variation, whose adverse effect on the turbine generator is the premature destruction magnet generator winding and turbine blades breakage. Tests were performed on the Wind Tunnel Energy Laboratory- Mechanical Engineering Faculty, Universidad Nacional de Ingeniería-Perú. The results are given in the power curves of the wind turbine prototype. We also demonstrated the reliability of the mechanism when submitting to extreme wind speeds up to the blocking of the turbine generator, as well as the immediate recovery operation when the wind speed returns to nominal turbine generator working conditions. Keywords.- Power control, Small wind turbine, Wind overspeed, Tail pivot mechanism, Reliability.


Sign in / Sign up

Export Citation Format

Share Document