A Flexible Wind Turbine Blade With an Actively Variable Twist Distribution to Increase Region 2 Efficiency: Design and Control

2017 ◽  
Author(s):  
Hamid Khakpour Nejadkhaki ◽  
John F. Hall
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Wind Turbine Blade ◽  
Design Solution ◽  
Angle Distribution ◽  
Stiffness Ratio ◽  
Aerodynamic Efficiency ◽  
Simulation Results ◽  
And Control

A method for designing and controlling a novel wind turbine blade is presented. The blade is modular, flexible, and additively manufactured. Conventional blades are monolithic and relatively stiff. The conventional method for improving aerodynamic efficiency is through generator torque control. The anisotropic nature of the additive manufacturing (AM) process has the potential to create a flexible blade with a low torsional-to-longitudinal-stiffness ratio. This enables new design and control capabilities that could be applied to the twist angle distribution (TAD). Simulation results suggest this can increase the aerodynamic efficiency during Region 2 operation. The suggested blade design includes a rigid spar with flexible AM segments that form the surrounding shells. The stiffness of each individual segment and the actuator placement define the TAD. In practice, the degree of flexibility for each segment will be established through the design and AM processes. These variations in compliance allow the blade to conform to the desired set of TAD geometries. The proposed design process first determines the TAD that maximizes the aerodynamic efficiency in Region 2. A mechanical design algorithm subsequently locates a series of actuators and defines the stiffness ratio between the blade segments. The procedure is optimized to minimize the amount of variation between the theoretical TAD and that which is obtained in practice. The free-shape TAD is also determined in the final design step. The geometry is chosen to minimize the amount of deflection needed to shape the TAD as it changes with Region 2 wind speed. A control framework is also developed to set the TAD in relation to wind speed. A case study demonstrates the capability of the proposed method. The simulation results suggest that a TAD controlled through five actuators can achieve the full range of required motion. Moreover, the design solution can increase the efficiency at cut-in and rated speeds up to 3.8% and 3.3%, respectively.

Integrative Control and Design Framework for an Actively Variable Twist Wind Turbine Blade to Increase Efficiency

2018 ◽  
Author(s):  
Hamid Khakpour Nejadkhaki ◽  
John F. Hall
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Mechanical Design ◽  
Wind Turbine Blade ◽  
Angle Distribution ◽  
Stiffness Ratio ◽  
Aerodynamic Efficiency ◽  
And Control ◽  
Actuator Placement

A methodology for the design and control of a variable twist wind turbine blade is presented. The blade is, modular, flexible, and additively manufactured (AM). The AM capabilities have the potential to create a flexible blade with a low torsional-to-longitudinal-stiffness ratio. This enables new design and control capabilities that could be applied to the twist angle distribution. The variable twist distribution can increase the aerodynamic efficiency during Region 2 operation. The suggested blade design includes a rigid spar and flexible AM segments that form the surrounding shells. The stiffness of each segment and the actuator placement define the twist distribution. These values are used to find the optimum free shape for the blade. Given the optimum twist distributions, actuator placement, and free shape, the required amount of actuation could be determined. The proposed design process first determines the twist distribution that maximizes the aerodynamic efficiency in Region 2. A mechanical design algorithm subsequently locates a series of actuators and defines the stiffness ratio between the blade segments. The free shape twist distribution is selected in the next step. It is chosen to minimize the amount of actuation energy required to shape the twist distribution as it changes with Region 2 wind speed. Wind profiles of 20 different sites, gathered over a three-year period, are used to get the free shape. A control framework is then developed to set the twist distribution in relation to wind speed. A case study is performed to demonstrate the suggested procedure. The aerodynamic results show up to 3.8 and 3.3% increase in the efficiency at cut-in and rated speeds, respectively. The cumulative produced energy within three years, improved by up to 1.7%. The mechanical design suggests that the required twist distribution could be achieved by five actuators. Finally, the optimum free shape is selected based on the simulations for the studied sites.

A Design Methodology for a Flexible Wind Turbine Blade With an Actively Variable Twist Distribution to Increase Region 2 Efficiency

2017 ◽  
Author(s):  
Hamid Khakpour Nejadkhaki ◽  
John F. Hall
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Twist Angle ◽  
Full Range ◽  
Wind Turbine Blade ◽  
Design Solution ◽  
Angle Distribution ◽  
Design Algorithm ◽  
Aerodynamic Efficiency

This paper presents a methodology for designing key features of a flexible wind turbine blade with an actively variable twist distribution. Simulation results suggest this capability can increase the aerodynamic efficiency during Region 2 operation. The concept for the flexible blade consists of a rigid spar with flexible modular segments that form the surrounding shells. The segments are additively manufactured. The associated compliances of the each individual segment and actuator placement determine the Twist Angle Distribution (TAD). It is assumed that the degree of flexibility for each segment will be established through the design and additive manufacturing (AM) processes. Moreover, the variations in compliance make it possible for the blade to conform to the desired set of TAD geometries. The design process first determines the TAD that maximizes the aerodynamic efficiency for discrete points of wind speed in Region 2. The results are obtained using the National Renewable Energy Laboratory (NREL) Aerodyn software and a genetic algorithm. The TAD geometry is then passed to a mechanical design algorithm that locates a series of actuators and defines the stiffness ratio between the blade segments. The process employs a computer cluster to create the TAD for a set of design scenarios. The design selections are found through an objective function. It minimizes the amount of deviation between the actual TAD and that found in the aerodynamic analysis. The free-shape TAD is determined in the final step. The geometry is chosen to minimize the amount of deflection needed to shape the TAD, which changes with Region 2 wind speed. A case study suggests that a blade with only five actuators can achieve the full range of TAD geometry. Moreover, the design solution can increase the efficiency at cut-in and rated speeds up to 3.8% and 3.3%, respectively.

Control Framework and Integrative Design Method for an Adaptive Wind Turbine Blade

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Hamid Khakpour Nejadkhaki ◽  
John F. Hall
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Design Method ◽  
Design Procedure ◽  
Wind Turbine Blade ◽  
Control Technique ◽  
Angle Distribution ◽  
Control Framework ◽  
Integrative Design

Abstract A control framework and integrative design method for an adaptive wind turbine blade is presented. The blade is adapted by actively transforming the twist angle distribution (TAD) along the blade. This can alleviate fatigue loads and improve wind capture. In this paper, we focus on wind capture. The proposed design concept consists of a rigid spar that is surrounded by a series of flexible blade sections. Each section has two zones of stiffness. The sections are actuated at each end to deform the TAD. A quasi-static control technique is proposed for the TAD. The controller sets the position of the blade actuators that shape the TAD during steady-state operation. A design procedure is used to define the required TAD as a function of the wind speed. This is based on an optimization procedure that minimizes the deviation between the actual TAD and that found in the aerodynamic design. The design inputs for this optimization problem include the stiffness for each zone of the section, and the actuator locations along the blade. Given the optimal TAD at each wind speed, the free position of the blade is established using a dynamic programming technique. The position is selected based on minimal actuation energy according to wind conditions at any installation site. The proposed framework is demonstrated using a National Renewable Energy Laboratory (NREL) certified wind turbine model with recorded wind data. An increase in efficiency of 3.8% with only a deviation of 0.34% from the aerodynamic TAD is observed.

scholarly journals Numerical simulation of icing effect on aerodynamic characteristics of a wind turbine blade

2021 ◽  
Vol 25 (6 Part B) ◽  
pp. 4643-4650
Author(s):  
Yan Li ◽  
Lei Shi ◽  
Wen-Feng Guo ◽  
Kotaro Tagawa ◽  
Bin Zhao
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Aerodynamic Characteristics ◽  
Wind Turbine Blade ◽  
Horizontal Axis Wind Turbine ◽  
Ambient Temperatures ◽  
Research Findings ◽  
Simulation Results ◽  
Lift And Drag ◽  
Lift And Drag Coefficient

Icing accretion on wind turbine will degrade its performance, resulting in reduction of output power and even leading to accidents. For solving this problem, it is necessary to predict the icing type and shape on wind turbine blade, and evaluate the variation of aerodynamic characteristics. In this paper the icing types and shapes in presence of airfoil, selected from blade of 1.5 MW horizontal-axis wind turbine, are simulated under different ambient temperatures and icing time lengths. Based on the icing simulation results, the aerodynamic characteristics of icing airfoils are simulated, including lift and drag coefficient, lift-drag ratio, etc. The simulation results show that the glaze ice with two horns presents on airfoil under high ambient temperature such as -5?C. When ambient temperatures are low, such as -10?C and -15?C, the rime ices with streamline profiles present on the airfoil. With increase in icing time the lift forces and coefficients decrease, and the drag ones increase. According to the variations of lift-drag ratios of icing airfoil, the aerodynamic performance of airfoil deteriorates in the presence of icing. The glaze ice has great effect on aerodynamic characteristics of airfoil. The research findings lay theoretical foundation for icing wind tunnel experiment.

scholarly journals Modal Analysis of Vertical Wind Turbine Blade

2018 ◽  
Vol 217 ◽  
pp. 01003 ◽  
Author(s):  
Lee Zhou Yi ◽  
Choe-Yung Teoh
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Modal Analysis ◽  
Turbine Blade ◽  
Wind Turbine Blade ◽  
Flow Induced Vibration ◽  
Low Wind Speed ◽  
Teak Wood ◽  
Blade Failure ◽  
Wind Induced Vibration

Wind turbines cannot simply be installed in Malaysia due to low wind speed condition. the project has analyzed the existing wind turbine blade (Aeolos-V 1k) design based on modal properties using computational approach (ANSYS Workbench) and redesign it. the modal analysis is simulated to observe natural frequency and corresponding mode shaped of the system under free vibration. the flow induced vibration can cause blade failure due to resonance or fatigue. Fluid Structural Interaction (FSI) ANSYS is used to the determined the interaction between the wind flow and the blade. Harmonic Response ANSYS is used to analyze the frequency response of the blade under wind induced vibration. After modification, the first mode has increased from 91.42 Hz to 102.12, since it is more than 50.92 Hz (Turbine maximum operating frequency), resonance would not occur during operating condition. the Aeolos-V’s blade has been modified by using. teak wood material and. redesign the blade for weight. reduction and aim for lower blade cost. the weight of modified blade has reduced 72.8 % after using teak wood and the efficiency of the wind turbine also increased. Modified design has been tested under Malaysia maximum wind speed of 9.44 m/s, the yield stress of teak wood (10.3 MPa) is higher than the maximum stress (4.2 MPa) obtained under force vibration which gives safety factor of 2.4. Hence, modified blade is reliable, efficient and more economic for Malaysia.

Study of Fatigue Test Loading Spectrum for Wind Turbine Blade

2014 ◽  
Vol 889-890 ◽  
pp. 221-224
Author(s):  
Gao Hua Liao ◽  
Jian Zhong Wu ◽  
Yong Jun Yu
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Fatigue Test ◽  
Turbine Blade ◽  
Time History ◽  
Wind Load ◽  
Wind Turbine Blade ◽  
Fatigue Life Analysis ◽  
Test Loading ◽  
Loading Spectrum

According to the principle of equivalent, the approach to draw up the fatigue test loading spectrum of wind turbine blade is presented. Analysis of wind load characteristics, based on ARMA (Autoregressive Moving Average Model) for the simulation of wind speed, wind load simulation example is given. Using Bladed software, the wind speed-time history is converted to a moment-time history that is the equivalent of blade root.Using data compression technology and the rain flow counting algorithm, load represented by a 2D matrix examples is given.The one-dimensional symmetry loading spectrum draw up, the complexity can be simplified, and provides the necessary foundation for fatigue life analysis.

Modeling and Design Method for an Adaptive Wind Turbine Blade With Out-of-Plane Twist

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Hamid Khakpour Nejadkhaki ◽  
John F. Hall
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Energy Production ◽  
Full Range ◽  
Unsteady Aerodynamics ◽  
Wind Turbine Blade ◽  
Torsional Stiffness ◽  
Angle Distribution ◽  
Modeling Framework ◽  
Out Of Plane

A modeling framework to analyze a wind turbine blade subjected to an out-of-plane transformation is presented. The framework combines aerodynamic and mechanical models to support an automated design process. The former combines the National Renewable Energy Lab (NREL) aerodyn software with a genetic algorithm solver. It defines the theoretical twist angle distribution (TAD) as a function of wind speed. The procedure is repeated for a series of points that form a discrete range of wind speeds. This step establishes the full range of blade transformations. The associated theoretical TAD geometry is subsequently passed to the mechanical model. It creates the TAD geometry in the context of a novel wind turbine blade concept. The blade sections are assumed to be made by additive manufacturing, which enables tunable stiffness. An optimization problem minimizes the difference between the practical and theoretical TAD over the full range of transformations. It does so by selecting the actuator locations and the torsional stiffness ratios of consecutive segments. In the final step, the blade free shape (undeformed position) is found. The model and design support out-of-plane twisting, which can increase energy production and mitigate fatigue loads. The proposed framework is demonstrated through a case study based on energy production. It employs data acquired from the NREL Unsteady Aerodynamics Experiment. A set of blade transformations required to improve the efficiency of a fixed-speed system is examined. The results show up to 3.7% and 2.9% increases in the efficiency at cut-in and rated speeds, respectively.

Fatigue Analysis of an Innovative Extensible Wind Turbine Blade

2016 ◽  
Author(s):  
Jiale Li ◽  
Xiong (Bill) Yu
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Fatigue Damage ◽  
Wind Turbine Blade ◽  
Time Interval ◽  
Data Set ◽  
Low Wind Speed ◽  
Wind Turbine Tower ◽  
Utility Scale

This paper describes the feasibility analyses of an innovative, extensible ‘smart’ blade technology aims to significantly improve the wind turbine energy production. This innovative ‘smart’ blade will be extended at low wind speed to harvest more wind energy. It will be retracted to its original shape above rated wind speed, to protect the blade from possible damages under high wind speed. The extended blade, however, will inevitably increase the fatigue damage of the wind turbine blade of which fatigue demand, which often controls the design requirement of wind turbine blade. A rain-flow counting method is used for calculating stress range cycles during turbine blade operation. The analyzes model in the research is built based on a 100 kW utility-scale wind turbine installed on the campus of Case Western Reserve University with a data acquisition system installed on the wind turbine tower to monitor the operation data continuously over the years. In this analyses, the data set consists of four years’ wind speed data at 10-minutes time interval and blade rotational speed from March 2014 to February 2015 have been used. The results show that the fatigue damage of this extensible blade increased is acceptable considering its increased power output.

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