Optimization design of prestressed concrete wind-turbine tower

Wind energy is a clean and renewable energy for which technology has developed rapidly in recent years.Wind turbines are commonly supported on tubular steel towers.As the turbine size is growing and the towers are rising in height,steel towers are required to be sufficiently strong and stiff,consequently leading to high construction costs.To tackle this problem,a new type of prestressed concrete tower was designed employing a novel tower concept having a regular octagon cross section with interior ribs on each side,which was optimized by comparing the natural frequency and stress difference under the same lateral load in different directions of the tower.The designed tower features a tapered profile that reduces the area subjected to wind;the tapered profile reduces the total weight,applied moment and the capital cost.An optimization method was developed employing ABAQUS software and a genetic algorithm.A target function was defined on the basis of the minimum cost of the concrete and prestressed tendon used,and constraints were applied by accounting for the stress,displacements and natural frequency of the tower.Employing the method,a 100 m prestressed concrete tower system for a 5 MW turbine was optimized and designed under wind and earthquake loads.The paper also reports a systematic design procedure incorporating the finite element method and the optimization method for the prestressed concrete wind-turbine towers.

Automatic Discontinuity Classification of Wind-turbine Blades Using A-scan-based Convolutional Neural Network

Recent development trends in wind power generation have increased the importance of the safe operation of wind-turbine blades(WTBs). To realize this objective, it is essential to inspect WTBs for any defects before they are placed into operation. However, conventional methods of fault inspection in WTBs can be rather difficult to implement, since complex curvatures that characterize the WTB structures must ensure accurate and reliable inspection. Moreover, it is considered useful if inspection results can be objectively and consistently classified and analyzed by an automated system and not by the subjective judgment of an inspector. To address this concern,the construction of a pressure-and shape-adaptive phased-array ultrasonic testing platform, which is controlled by a nanoengine operation system to inspect WTBs for internal defects, has been presented in this paper. An automatic classifier has been designed to detect discontinuities in WTBs by using an A-scanimaging-based convolutional neural network(CNN). The proposed CNN classifier design demonstrates a classification accuracy of nearly 99%. Results of the study demonstrate that the proposed CNN classifier is capable of automatically classifying the discontinuities of WTB with high accuracy, all of which could be considered as defect candidates.

Effects of a rooftop wind turbine on the dispersion of air pollutant behind a cube-shaped building

The concentration distribution of urban air pollutants is closely related to people’s health.As an important utilization form of urban wind power,rooftop wind turbines have been widely used in cities.The wake effect of the rooftop wind turbines will change the flow behind buildings and then affect the pollutant dispersion.To this end,the pollutant dispersion behind the building is studied via the computational fluid dynamics method.The actuator disk model and idealized cube are adopted to model the wind turbine and the building,respectively.The study shows that the rooftop wind turbine can reduce the pollutant mass fraction near the ground and the pedestrian level.Due to the wake effect of the rooftop wind turbine,the turbulent fluctuation behind the building is weakened,and the spanwise pollutant dispersion is suppressed.Besides,the rooftop wind turbine weakens the downwash movement of the building,which enhances the vertical pollutant dispersion.

Development of a Fast Fluid-Structure Coupling Technique for Wind Turbine Computations

Fluid-structure interaction simulations are routinely used in the wind energy industry to evaluate the aerodynamic and structural dynamic performance of wind turbines. Most aero-elastic codes in modern times implement a blade element momentum technique to model the rotor aerodynamics and a modal, multi-body, or finite-element approach to model the turbine structural dynamics. The present paper describes a novel fluid-structure coupling technique which combines a three- dimensional viscous-inviscid solver for horizontal-axis wind-turbine aerodynamics, called MIRAS, and the structural dynamics model used in the aero-elastic code FLEX5. The new code, MIRAS- FLEX, in general shows good agreement with the standard aero-elastic codes FLEX5 and FAST for various test cases. The structural model in MIRAS-FLEX acts to reduce the aerodynamic load computed by MIRAS, particularly near the tip and at high wind speeds.

Dynamic Modeling and Analysis ofWind Turbine Blade of Piezoelectric Plate Shell

This paper presents a theoretical analysis of vibration control technology of wind turbine blades made of piezoelectric intelligent structures.The design of the blade structure,which is made from piezoelectric material,is approximately equivalent to a flat shell structure.The differential equations of piezoelectric shallow shells for vibration control are derived based on piezoelectric laminated shell theory.On this basis,wind turbine blades are simplified as elastic piezoelectric laminated shells.We establish the electromechanical coupling system dynamic model of intelligent structures and the dynamic equation of composite piezoelectric flat shell structures by analyzing simulations of active vibration control.Simulation results show that,under wind load,blade vibration is reduced upon applying the control voltage.