scholarly journals The Effect of a Flexible Blade for Load Alleviation in Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4988
Author(s):  
Azael Duran Castillo ◽  
Juan C. Jauregui-Correa ◽  
Francisco Herbert ◽  
Krystel K. Castillo-Villar ◽  
Jesus Alejandro Franco ◽  
...  
Keyword(s):  
Wind Turbines ◽  
Simulation Analysis ◽  
Bending Moment ◽  
Turbine Rotor ◽  
Aerodynamic Coefficients ◽  
Cam Mechanism ◽  
Wind Speeds ◽  
Flexible Surface ◽  
Fiberglass Composite ◽  
Internal Mechanism

This article presents the analysis of the performance of a flexible wind turbine blade. The simulation analysis is based on a 3 m span blade prototype. The blade has a flexible surface and a cam mechanism that modifies the aerodynamic profile and adapts the surface to different configurations. The blade surface was built with a flexible fiberglass composite, and the internal mechanism consists of a flexible structure actuated with an eccentric cam. The cam mechanism deforms five sections of the blade, and the airfoil geometry for each section was measured from zero cam displacement to full cam displacement. The measured data were interpolated to obtain the aerodynamic profiles of the five sections to model the flexible blade in the simulation process. The simulation analysis consisted of determining the different aerodynamic coefficients for different deformed surfaces and a range of wind speeds. The aerodynamic coefficients were calculated with the BEM method (QBlade®); as a result, the data performance of the flexible blade was compared for the different deformation configurations. Finally, a decrease of up to approximately 6% in the mean bending moment suggests that the flexible turbine rotor presented in this article can be used to reduce extreme and fatigue loads on wind turbines.

Design and Evaluation of a Rooftop Wind Turbine Rotor With Untwisted Blades

2013 ◽  
Author(s):  
Sayem Zafar ◽  
Mohamed Gadalla
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Low Cost ◽  
Turbine Blades ◽  
Angle Of Attack ◽  
Turbine Rotor ◽  
Wind Turbine Blades ◽  
Wind Speeds ◽  
Small Wind Turbines ◽  
Wind Turbine Rotor

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.

scholarly journals Assessment of Two-Equation Turbulence Models and Validation of the Performance Characteristics of an Experimental Wind Turbine by CFD

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Ece Sagol ◽  
Marcelo Reggio ◽  
Adrian Ilinca
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Wind Turbine ◽  
Flow Simulation ◽  
Turbulence Models ◽  
Bending Moment ◽  
Mesh Size ◽  
Turbine Rotor ◽  
Cross Sectional ◽  
Wind Speeds

The very first step in the simulation of ice accretion on a wind turbine blade is the accurate prediction of the flow field around it and the performance of the turbine rotor. The paper addresses this prediction using RANS equations with a proper turbulence model. The numerical computation is performed using a commercial CFD code, and the results are validated using experimental data for the 3D flow field around the NREL Phase VI HAWT rotor. For the flow simulation, a rotating reference frame method, which calculates the flow properties as time-averaged quantities, has been used to reduce the time spent on the analysis. A basic grid convergence study is carried out to select the adequate mesh size. The two-equation turbulence models available in ANSYS FLUENT are compared for a 7 m/s wind speed, and the one that best represents the flow features is then used to determine moments on the turbine rotor at five wind speeds (7 m/s, 10 m/s, 15 m/s, 20 m/s, and 25 m/s). The results are validated against experimental data, in terms of shaft torque, bending moment, and pressure coefficients at certain spanwise locations. Streamlines over the cross-sectional airfoils have also been provided for the stall speed to illustrate the separation locations. In general, results have shown good agreement with the experimental data for prestall speeds.

scholarly journals Pengaruh Jumlah Bilah dan Sudut Pasang terhadap Daya Turbin Angin Poros Vertikal Tipe H-Darrieus Termodifikasi sebagai Energi Alternatif Pembangkit Tenaga Listrik Skala Rumah Tangga

2019 ◽  
Vol 12 (2) ◽  
pp. 92
Author(s):  
Susilo Susilo ◽  
Bambang Widodo ◽  
Eva Magdalena Silalahi ◽  
Atmadi Priyono
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Output Power ◽  
Wind Turbines ◽  
Output Voltage ◽  
Turbine Rotor ◽  
Wind Speeds ◽  
Blade Shape ◽  
Low Wind Speeds ◽  
Wind Turbine Rotor

Bentuk sudu taper linier merupakan bentuk sudu yang paling optimal untuk kecepatan angin yang rendah. Jumlah sudu yang baik untuk kecepatan angin rendah berkisar antara 3-7 buah sudu, namun desain sudu dengan menggunakan airfoil dan profil pada sudut pasang sudu yang bagaimana memberikan daya keluaran dan tegangan keluaran yang optimal. Turbin angin didesain dengan 2 bilah dan 4 bilah dengan sudut pasang yang bisa diatur untuk mendapatkan perbedaan daya optimal masing-masing desain. Pengujian dilakukan di 3 area berbeda untuk mendapatkan gambaran geografis kondisi angin yang berbeda khususnya masalah kecepatan angin di ksiaran 2 m/s - 7 m/s. Pengujian dilakukan dengan luas penampang turbin angin (A) sebesar 3m2 Hasil penelitian menunjukkan bahwa nilai terbaik diperoleh pada kecepatan angin maksimal 4 m/s dan jumlah blade 4  sedangkan untuk nilai terkecil diperoleh pada kecepatan angin 3 m/s dan jumlah blade 2 yaitu. Untuk nilai TSR maksimal pada kecepatan maksimal 4 m/s terjadi pada jumlah blade 4, sedangkan untuk nilai terendah pada kecepatan angin 3 m/s dihasilkan pada jumlah blade 2. Melalui pengukuran berbasis teknologi smart monitoring system, dari penelitian diperoleh semakin tinggi kecepatan angin maka tegangan keluaran semakin tinggi. Semakin tinggi tegangan keluaran, semakin tinggi daya keluaran pada generator. Sudut pasang ? dan jumlah sudu mempengaruhi kecepatan putaran rotor turbin angin. Kecepatan putaran rotor turbin angin berelasi dengan tegangan keluaran generator. pada sudut pasang ? dan jumlah sudu 4, diperoleh daya keluaran yang sebesar 150 watt namun pada kecepatan angin 7 m/s daya turbin yang dihasilkan mencapai 600 watt. Dengan kondisi ini cukup memenuhi untuk alternatif cadangan listrik skala rumah tangga khusunya di pedesaan dan daerah terpencil (rural area). The linear taper blade shape is the most optimal blade shape for low wind speeds. The number of blades that are good for low wind speeds ranges from 3-7 blades, but the blade design uses an airfoil and profile on the blade mounting angle which is how to provide optimal output power and output voltage. Wind turbines are designed with 2 blades and 4 blades with adjustable tide angles to get the difference in the optimal power of each design. Tests were carried out in 3 different areas to obtain a geographical description of different wind conditions, especially the problem of wind speed in the range of 2 m / s - 7 m / s. Tests carried out with a cross section area of  wind turbines (A) of 3m2 The results showed that the best value was obtained at a maximum wind speed of 4 m / s and number 4 blade while the smallest value was obtained at wind speeds of 3 m / s and number 2 blades namely. For the maximum TSR value at a maximum speed of 4 m / s occurs in the number of 4 blades, while for the lowest value at 3 m / s wind speed is produced on the number of blades 2. From the research, the higher the wind speed, the higher the output voltage. The higher the output voltage, the higher the output power at the generator. The ? tide angle and number of blades affect the speed of the wind turbine rotor rotation. The rotational speed of the wind turbine rotor is related to the generator output voltage. at the tide angle ? and number of blades 4, the output power of 150 watts is obtained but with wind speed 7 m/s turbine power 600 watt achieved. With this condition, it is sufficient for alternative household electricity reserves, especially in rural and remote areas (rural areas).

scholarly journals Optimal relationship between power and design driving loads for wind turbine rotors using 1D models

2019 ◽  
Author(s):  
Kenneth Loenbaek ◽  
Christian Bak ◽  
Jens I. Madsen ◽  
Bjarke Dam
Keyword(s):  
Wind Turbine ◽  
Optimal Solution ◽  
Bending Moment ◽  
Turbine Rotor ◽  
Aerodynamic Load ◽  
Thrust Coefficient ◽  
Wind Speeds ◽  
Rotor Design ◽  
Power Capture ◽  
Thrust Characteristics

Abstract. We investigate the optimal relationship between the aerodynamic power, thrust loading, and size of a wind turbine rotor when its design is constrained by a static aerodynamic load. Based on 1D-axial momentum theory, the captured power P~ for a uniformly loaded rotor can be expressed in terms of the rotor radius R and the rotor thrust coefficient CT. Common types of static Design Driving Load Constraints (DDLC), e.g. limits on permissible root-bending moment or tip deflection, may be generalized into a form that also depends on CT and R. Using these relationships to maximize P~ subject to a DDLC, shows that operating the rotor at the Betz limit (maximum CP) does not lead to the highest power capture. Rather, it is possible to improve performance with a larger rotor radius and lower CT without violating the DDLC. As an example, a rotor design driven by a tip-deflection constraints, may achieve 1.9 % extra power capture P~ compared to the baseline (Betz limit) rotor. The method is extended for optimization of rotors with respect to Annual Energy Production (AEP), where the thrust characteristics CT(V) needs to be determined together with R. This results in much higher relative potential for improvements, since the constraint limit can be met over a larger range of wind speeds. For example, a relative gain in AEP of +5.7 % is possible for a rotor design constrained by tip deflections compared with a rotor designed for optimal CP. The optimal solution for AEP leads to a thrust curve with three distinct operational regimes and so called thrust-clipping.

scholarly journals Optimal relationship between power and design-driving loads for wind turbine rotors using 1-D models

2020 ◽  
Vol 5 (1) ◽  
pp. 155-170
Author(s):  
Kenneth Loenbaek ◽  
Christian Bak ◽  
Jens I. Madsen ◽  
Bjarke Dam
Keyword(s):  
Wind Turbine ◽  
Early Stage ◽  
Optimal Solution ◽  
Bending Moment ◽  
Turbine Rotor ◽  
Aerodynamic Load ◽  
Thrust Coefficient ◽  
Wind Speeds ◽  
Rotor Design ◽  
Power Capture

Abstract. We investigate the optimal relationship between the aerodynamic power, thrust loading and size of a wind turbine rotor when its design is constrained by a static aerodynamic load. Based on 1-D axial momentum theory, the captured power P̃ for a uniformly loaded rotor can be expressed in terms of the rotor radius R and the rotor thrust coefficient CT. Common types of static design-driving load constraints (DDLCs), e.g., limits on the permissible root-bending moment or tip deflection, may be generalized into a form that also depends on CT and R. The developed model is based on simple relations and makes explorations of overall parameters possible in the early stage of the rotor design process. Using these relationships to maximize P̃ subject to a DDLC shows that operating the rotor at the Betz limit (maximum CP) does not lead to the highest power capture. Rather, it is possible to improve performance with a larger rotor radius and lower CT without violating the DDLC. As an example, a rotor design driven by a tip-deflection constraint may achieve 1.9 % extra power capture P̃ compared to the baseline (Betz limit) rotor. This method is extended to the optimization of rotors with respect to annual energy production (AEP), in which the thrust characteristics CT(V) need to be determined together with R. This results in a much higher relative potential for improvement since the constraint limit can be met over a larger range of wind speeds. For example, a relative gain in AEP of +5.7 % is possible for a rotor design constrained by tip deflections, compared to a rotor designed for optimal CP. The optimal solution for AEP leads to a thrust curve with three distinct operational regimes and so-called thrust clipping.

Analysis of a Concept for a Low Wind Speed Tolerant Axial Wind Turbine

2011 ◽  
Author(s):  
Ali A. Ameri ◽  
Majid Rashidi
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Power Output ◽  
Turbine Rotor ◽  
Navier Stokes ◽  
Ambient Wind ◽  
Wind Speeds ◽  
Low Wind Speed ◽  
Low Wind Speeds

In this paper, the authors analyze a design for a wind tower intended for areas of low wind speeds. The wind tower consists of a combination of several rooftop size turbines arranged alongside a cylindrical structure that acts as a Wind Deflecting Structure (WDS). The WDS amplifies the effective wind speed thus allowing the turbine rotors to operate under lower ambient wind speeds. Analyses were performed using simple models as well as more sophisticated CFD methods employing Steady and Unsteady Reynolds Averaged Navier-Stokes methodology. The effect of the wind amplification was shown on a commercial small wind turbine power output map. Also, a wind turbine rotor flow was computed as operating alongside the WDS and compared to the computed operation of isolated turbines at equal effective and ambient wind velocities. The computational analyses of this work suggest that the power output of isolated rooftop wind turbines deployed at low to moderate wind speed may be matched by installing wind turbines alongside a cylindrical wind deflecting structure operating at lower wind speeds. Other benefits of the arrangement are also enumerated.

EXPERIMENTAL AND ANALYTICAL STUDIES OF VERTICAL AXIS WIND TURBINES

2018 ◽  
pp. 51-58
Author(s):  
B. P. Khozyainov
Keyword(s):  
Wind Turbine ◽  
Flow Velocity ◽  
Wind Power ◽  
Wind Turbines ◽  
Power Efficiency ◽  
Air Flow ◽  
Geometrical Parameters ◽  
Wind Speeds ◽  
Analytical Studies ◽  
Air Flow Velocity

The article carries out the experimental and analytical studies of three-blade wind power installation and gives the technique for measurements of angular rate of wind turbine rotation depending on the wind speeds, the rotating moment and its power. We have made the comparison of the calculation results according to the formulas offered with the indicators of the wind turbine tests executed in natural conditions. The tests were carried out at wind speeds from 0.709 m/s to 6.427 m/s. The wind power efficiency (WPE) for ideal traditional installation is known to be 0.45. According to the analytical calculations, wind power efficiency of the wind turbine with 3-bladed and 6 wind guide screens at wind speedsfrom 0.709 to 6.427 is equal to 0.317, and in the range of speed from 0.709 to 4.5 m/s – 0.351, but the experimental coefficient is much higher. The analysis of WPE variations shows that the work with the wind guide screens at insignificant average air flow velocity during the set period of time appears to be more effective, than the work without them. If the air flow velocity increases, the wind power efficiency gradually decreases. Such a good fit between experimental data and analytical calculations is confirmed by comparison of F-test design criterion with its tabular values. In the design of wind turbines, it allows determining the wind turbine power, setting the geometrical parameters and mass of all details for their efficient performance.

SHAPING OF AN AUTONOMOUS POWER SYSTEM FOR GUARANTEED POWER SUPPLY WITH THE PREDOMINANCE WIND ENERGY

2018 ◽  
pp. 28-50
Author(s):  
S. G. Ignatiev ◽  
S. V. Kiseleva
Keyword(s):  
Energy Storage ◽  
Wind Speed ◽  
Wind Energy ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Energy Demand ◽  
Diesel Generator ◽  
Average Wind Speed ◽  
Wind Speeds ◽  
Average Wind

Optimization of the autonomous wind-diesel plants composition and of their power for guaranteed energy supply, despite the long history of research, the diversity of approaches and methods, is an urgent problem. In this paper, a detailed analysis of the wind energy characteristics is proposed to shape an autonomous power system for a guaranteed power supply with predominance wind energy. The analysis was carried out on the basis of wind speed measurements in the south of the European part of Russia during 8 months at different heights with a discreteness of 10 minutes. As a result, we have obtained a sequence of average daily wind speeds and the sequences constructed by arbitrary variations in the distribution of average daily wind speeds in this interval. These sequences have been used to calculate energy balances in systems (wind turbines + diesel generator + consumer with constant and limited daily energy demand) and (wind turbines + diesel generator + consumer with constant and limited daily energy demand + energy storage). In order to maximize the use of wind energy, the wind turbine integrally for the period in question is assumed to produce the required amount of energy. For the generality of consideration, we have introduced the relative values of the required energy, relative energy produced by the wind turbine and the diesel generator and relative storage capacity by normalizing them to the swept area of the wind wheel. The paper shows the effect of the average wind speed over the period on the energy characteristics of the system (wind turbine + diesel generator + consumer). It was found that the wind turbine energy produced, wind turbine energy used by the consumer, fuel consumption, and fuel economy depend (close to cubic dependence) upon the specified average wind speed. It was found that, for the same system with a limited amount of required energy and high average wind speed over the period, the wind turbines with lower generator power and smaller wind wheel radius use wind energy more efficiently than the wind turbines with higher generator power and larger wind wheel radius at less average wind speed. For the system (wind turbine + diesel generator + energy storage + consumer) with increasing average speed for a given amount of energy required, which in general is covered by the energy production of wind turbines for the period, the maximum size capacity of the storage device decreases. With decreasing the energy storage capacity, the influence of the random nature of the change in wind speed decreases, and at some values of the relative capacity, it can be neglected.

scholarly journals Numerical Analysis of the Dynamic Interaction between Two Closely Spaced Vertical-Axis Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2286
Author(s):  
Yutaka Hara ◽  
Yoshifumi Jodai ◽  
Tomoyuki Okinaga ◽  
Masaru Furukawa
Keyword(s):  
Wind Turbines ◽  
Power Distribution ◽  
Phase Synchronization ◽  
Average Power ◽  
Vertical Axis ◽  
Turbine Rotor ◽  
Mean Power ◽  
Vertical Axis Wind Turbines ◽  
Fluid Body ◽  
First Time

To investigate the optimum layouts of small vertical-axis wind turbines, a two-dimensional analysis of dynamic fluid body interaction is performed via computational fluid dynamics for a rotor pair in various configurations. The rotational speed of each turbine rotor (diameter: D = 50 mm) varies based on the equation of motion. First, the dependence of rotor performance on the gap distance (gap) between two rotors is investigated. For parallel layouts, counter-down (CD) layouts with blades moving downwind in the gap region yield a higher mean power than counter-up (CU) layouts with blades moving upwind in the gap region. CD layouts with gap/D = 0.5–1.0 yield a maximum average power that is 23% higher than that of an isolated single rotor. Assuming isotropic bidirectional wind speed, co-rotating (CO) layouts with the same rotational direction are superior to the combination of CD and CU layouts regardless of the gap distance. For tandem layouts, the inverse-rotation (IR) configuration shows an earlier wake recovery than the CO configuration. For 16-wind-direction layouts, both the IR and CO configurations indicate similar power distribution at gap/D = 2.0. For the first time, this study demonstrates the phase synchronization of two rotors via numerical simulation.

scholarly journals Effect of Wind Turbine Classes on the Electricity Production of Wind Farms in Cyprus Island

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Yiannis A. Katsigiannis ◽  
George S. Stavrakakis ◽  
Christodoulos Pharconides
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Energy Production ◽  
Wind Farms ◽  
Electricity Production ◽  
Wind Speeds ◽  
Wind Potential

This paper examines the effect of different wind turbine classes on the electricity production of wind farms in two areas of Cyprus Island, which present low and medium wind potentials: Xylofagou and Limassol. Wind turbine classes determine the suitability of installing a wind turbine in a particulate site. Wind turbine data from five different manufacturers have been used. For each manufacturer, two wind turbines with identical rated power (in the range of 1.5 MW–3 MW) and different wind turbine classes (IEC II and IEC III) are compared. The results show the superiority of wind turbines that are designed for lower wind speeds (IEC III class) in both locations, in terms of energy production. This improvement is higher for the location with the lower wind potential and starts from 7%, while it can reach more than 50%.

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