Turbine Tower Research Articles

Load identification of a 2.5 MW wind turbine tower using Kalman filtering techniques and BDS data

The rapid increase in the number of wind turbine installations and operations, is increasing the importance of the health monitoring of these wind turbines. To assess the remaining service life of a wind turbine, continuous monitoring of the internal forces acting on the critical locations of fatigue in the structure is required. However, a large number of sensors are usually required for the comprehensive determination of the internal force at a site-specific location; additionally, these sensors cannot be placed in locations with strong stress or strain gradients. Therefore, in this paper, a strategy for estimating the thrust at the tower top and the bending moment at any position of the wind turbine tower is proposed, which only requires a limited number of acceleration sensors and the BeiDou Navigation Satellite System (BDS). The estimated load includes static and dynamic components. The former is calculated by fitting the derived function and the BDS data, and the latter is estimated by the time-domain inverse method using the Kalman filter and with acceleration sensors. The performance of the proposed strategy is validated in two case studies, including simulated data and recorded data from a 2.5 MW onshore wind turbine located in China. The results show that the strategy can produce an estimation of thrust and bending moment, with good accuracy.

Experimental investigation on anisotropic fatigue crack growth characteristics of Q420C steel

The hot-rolled steel sheets often exhibit anisotropy in their mechanical characteristics due to the grain’s elongation along the rolling orientation. The anisotropy characteristic also appears in the fatigue crack growth behaviour. However, it has not been thoroughly studied for some types of steel materials although they have been widely used for wind turbine towers. In this study, the longitudinal fatigue crack growth behaviour of the hot-rolled steel sheet (Q420C) is investigated by an experimental programme. A total of six specimens were tested under constant amplitude loading cases with different load ratios. It was found that longitudinal cracks are approximately 15% faster than transverse cracks at the load ratio of 0.1; at the load ratio of 0.3, they are approximately 22% faster. The anisotropy of crack growth rates is attributed to differences in the microstructure of the material. A comparison of the crack growth rate is carried out for Q420C steel and some widely used American-made steel materials. Furthermore, the applicability of design curves in the British Standard BS 7910 is explored, the crack closure phenomenon is analysed and the fatigue crack growth mechanism is discussed.

Designing sustainable innovations in manufacturing: A systems engineering approach

Innovating manufacturing systems can substantially support a sustainable transformation of value creation across the industry towards higher sustainability maturity levels. The research presents a novel systems engineering approach for innovating manufacturing systems with a focus on sustainability. The systems engineering approach aims at supporting manufacturing companies in realizing sustainable innovations. It allows companies to cope with current and future global challenges while maintaining and improving their competitiveness. The concepts of integrated values and global innovation pathways set the research's scope and practical relevance. A narrative literature review of the earlier and later phase of the sustainable-oriented innovation process is presented. The systems engineering approach for creating sustainable manufacturing innovations with a defined macro and micro cycle is introduced. The macro cycle determines the important design phases for the life cycle of the innovation while the micro cycle provides a process for finding sustainable solutions. A case study grounded on a start-up that developed an innovative wind turbine tower system is introduced for verifying, validating, and evaluating the proposed systems engineering approach within the application field of manufacturing large-scale products.

Study on fatigue performance of double cover plate through-core bolted joint of rectangular concrete-filled steel tube bundle wind turbine towers

Rectangular steel tube concrete bundle wind turbine towers is a new type of tower structure with high prefabrication, convenient installation, convenient transportation and good integrity.Based on the uniaxial tensile test and fatigue loading test of the double cover plate through-core bolted joint, the stress condition of the key connection parts of the structure is analyzed, the S-N curve of the joint under parameter expansion is summarized, and the Weibull distribution test is carried out for the fatigue life of the concrete inside the joint. Finally, the fatigue damage of the joint are analyzed. The results show that the failure mode of the double cover plate through-core bolted joint under fatigue loading is bolt shear; Through S-N curve fitting, the S-N curve expression and fatigue limit value of different types of joints are obtained. It is found that under the shear failure mode, the fatigue limit of different types of joints is higher than the limit value specified in GB50017–2017, EC3 and AISC-360; The fatigue life of concrete at different loading factors conforms to the two parameter Weibull distribution.The damage analysis of the joint through the high cycle fatigue damage model shows that the trend of a sharp increase in the damage rate of the joints in the late loading period can better explain the phenomenon of instantaneous fracture. The research results of this paper can provide reference for the analysis, research and application of wind turbine towers.

MIMO-SAR Interferometric Measurements for Wind Turbine Tower Deformation Monitoring

Deformations affect the structural integrity of wind turbine towers. The health of such structures is thus assessed by monitoring. The majority of sensors used for this purpose are costly and require in situ installations. We investigated whether Multiple-Input Multiple-Output Synthetic Aperture Radar (MIMO-SAR) sensors can be used to monitor wind turbine towers. We used an automotive-grade, low-cost, off-the-shelf MIMO-SAR sensor operating in the W-band with an acquisition frequency of 100 Hz to derive Line-Of-Sight (LOS) deformation measurements in ranges up to about 175 m. Time series of displacement measurements for areas at different heights of the tower were analyzed and compared to reference measurements acquired by processing video camera recordings and total station measurements. The results showed movements in the range of up to 1 m at the top of the tower. We were able to detect the deformations also with the W-band MIMO-SAR sensor; for areas with sufficient radar backscattering, the results suggest a sub-mm noise level of the radar measurements and agreement with the reference measurements at the mm- to sub-mm level. We further applied Fourier transformation to detect the dominant vibration frequencies and identified values ranging from 0.17 to 24 Hz. The outcomes confirmed the potential of MIMO-SAR sensors for highly precise, cost-efficient, and time-efficient structural monitoring of wind turbine towers. The sensors are likely also applicable for monitoring other high-rise structures such as skyscrapers or chimneys.

Design optimisation of wind turbine towers with reliability-based calibration of partial safety factors

Having an optimal design of the wind turbine tower, with a minimum mass (cost) while fulfilling multiple design constraints, plays an important role in ensuring an economic and safe design of the wind turbine. During the design of wind turbine towers, partial safety factors (PSFs) are currently commonly used to account for the uncertainties in the loads and material properties due to its easy implementation. The values of PSFs given in design standard are generic and are not derived for a specific design. For a site-specific design of wind turbine towers, the details of the load parameters, such as the type of distributions and the coefficient of variation, can be obtained through the condition monitoring system. With these information, the PSFs can be calibrated based on the reliability method, meeting the target reliability index and avoiding over or under engineering of wind turbine tower structures. In this work, a parametric finite element analysis model is integrated with a genetic algorithm to develop a structural optimisation model of wind turbine towers. The optimisation framework minimises the tower mass under multiple design constraints. The optimisation model has been applied to a representative 2.0 MW onshore wind turbine tower. PSFs are calibrated on the basis of reliability. The optimal tower design with calibrated PSFs is compared against the design with un-calibrated PSFs. Results indicate that the tower design with calibrated PSFs achieves a mass reduction of 2.9% in comparison to the design with un-calibrated PSFs.

The Flexible Cable Deformation Effect of a Prestressed Tuned Mass Damper on Vibration Control for Wind Turbine Towers

Larger megawatt wind turbines are of significant height. The wind turbine tower (WTT) can suffer excessive vibration under external dynamic excitation, so an additional vibration control device is needed. Taking a novel prestressed tuned mass damper (PS-TMD) as the research object, its nonlinear vibration control performance induced by a flexible cable deformation effect was investigated. The dynamic coefficient amplitudes at two fixed points were derived based on the principle of virtual work, and results showed that the vibration amplitude considering flexible cable deformation is smaller than that of the linear PS-TMD system. For harmonic response, the numerical simulation of a 3.2 MW WTT indicated that vibration migration performance of the nonlinear PS-TMD is better than that of the linear PS-TMD. The Wilson-[Formula: see text] method was applied to analyze the vibration control effect under three fatigue and two ultimate wind loads. Results showed that the nonlinear PS-TMD can decrease the vibration amplitude more than the linear PS-TMD, and the vibration mitigation performance under the fatigue wind loads is slightly better than ultimate wind loads.

Seismic dynamics of offshore wind turbine-seabed foundation: Insights from a numerical study

In the past 10 years, the offshore wind energy harvest industry has developed rapidly worldwide. However, seismic waves would bring a great threat to the safety and stability of offshore wind turbines (OWTs). In this study, taking the marine geotechnics numerical software FssiCAS as the computational platform, adopting the generalized elastoplastic soil model Pastor-Zienkiewicz-Mark III (PZIII) to describe the complex mechanical behavior of seabed soil, the seismic dynamics, as well as the stability of a thin-walled monopile OWT with an equipped capacity of 1.5 MW and its seabed foundation are comprehensively investigated, by the way of finely modeling and meshing for the important components of the OWT, i.e., the blades, nacelle, and tower. The numerical results indicate that OWT and its seabed foundation strongly respond to the excitation of seismic waves, and there is intensive interaction between OWT and its seabed foundation. In the case of this study, the horizontal oscillation amplitude at the top of the turbine tower reaches 2m, the superficial seabed soil at the far field is liquefied with a depth of 3–4 m, and the liquefaction depth of the seabed soil surrounding the monopile reaches 5–6 m. Even so, the OWT involved in this study has no cumulative displacement, there is only vibration displacement. It is indicated that the OWT has good seismic stability. It is indicated by the comparative study that the complex mechanical behavior of seabed soil, the complex geometry and mass distribution of OWTs, and the consideration of the pore water in seabed foundations have a radical influence on the seismic dynamics of OWTs. The work presented could be a valuable reference for the evaluation of the seismic dynamics and stability of OWTs in the future.

Experimental and two-scale numerical studies on the behavior of prestressed concrete-steel hybrid wind turbine tower models

Prestressed concrete-steel hybrid (PCSH) wind turbine tower has been recognized as an efficient alternative to traditional steel tube supporting towers for wind farms in harsh sites such as mountain regions. To investigate the global and local mechanical behavior including failure patterns of a full scale PCSH wind turbine towers, an experimental study on a substructure of a scaled PCSH tower is carried out firstly. Then, a material subroutine for three-dimensional (3D) fiber beam elements suitable for implicit analysis on the mechanical behavior of the substructure of the scaled PCSH tower is developed. A two-scale numerical model of the substructure of the scaled PCSH wind turbine tower employing the developed 3D fiber beam elements and solid elements is developed. The accuracy and efficiency of the developed two-scale numerical model for the behavior simulation of the substructure of the scaled PCSH wind turbine tower is illustrated by comparing the numerical results with the experimental measurements. Additional comparison of the simulation results using the developed two-scale numerical model is made with them of a model using sole 3D fiber beam elements and a model using sole solid elements, respectively. Results show that the force–displacement curve determined with the developed two-scale model is close to the test result and coincident well with that of the two models using 3D fiber beam elements and the solid elements. The developed two-scale model can describe the global behavior, the local failure patterns and the stress distribution of the tested specimen accurately with improved simulation efficiency. Finally, the validated two-scale modelling approach is employed to analyze the static behavior, modal parameter, and fatigue of the optimized full-scale PCSH wind turbine tower previously developed by the authors. The simulation results show that the two-scale model can reflect the stress of the PCSH wind turbine tower at the critical position as well as the global mechanical behavior with higher computational efficiency. The fiber beam model can be used for predicting only global, but not local, behavior.

A Wind-Turbine-Tower-Climbing Robot Prototype Operating at Various Speeds and Payload Capacity: Development and Validation

The development of control technology on wind turbine application robots has played an integral role in facilitating the digitization of inspection and maintenance in the wind energy industry. This paper presents a wind-turbine-climbing robot that determines the service lifespan of the wind turbine components subject to its payload capacity. The model has four rubber wheels, as the driving mechanism for its locomotion is being supported by a Bowden cable as a winding mechanism for its adhesion. The design further incorporates an Arduino microcontroller, distance sensors, motors, and a step motor to form its electromechanical structure. The overall capability of the robot has been analyzed through its kinematics and dynamics. Practical indoor experiments using a wind turbine tower mockup have been conducted for the validation of the various speeds and payload capacity of the prototype. The results indicate the effectiveness of its driving and winding mechanism to climb at the various speeds and with or without a payload. The advantage of the operations of its mechanism conformed with the wind turbine application robots.

Estimation of probability distribution of long-term fatigue damage on wind turbine tower using residual neural network

Fatigue is one of the most significant failure modes in structural and mechanical design. As for wind engineering, the fatigue issue on wind turbine towers is more critical since it concerns not only the structural safety but also the power production of the wind turbine. On the one hand, due to the complex fluid–solid interaction and the sophisticated control system of the wind turbine, it is impossible to predict the probability of fatigue-induced failure on wind turbine towers by analytical method. On the other hand, the structural reliability methods based on a numerical approach are usually time-consuming. To overcome these drawbacks, this work firstly proposes a probabilistic fatigue analysis framework to estimate the fatigue damage of wind turbine tower based on numerical simulations. Then, to reduce the computational cost of numerical approach, a residual neural network (ResNet)-assisted fatigue estimation approach is designed for the assessment of long-term fatigue loads under the proposed probabilistic fatigue analysis framework. The proposed probabilistic fatigue analysis framework estimates the cumulative fatigue damage on the cross-section of wind towers in a probabilistic pattern. The designed surrogate-assisted approach learns a model to approximate the relationship between wind speed and the fatigue damage. Then, this surrogate model can be used to predict fatigue damage under different wind speed so that a large number of simulation can be replaced by model prediction. Consequently, the efficiency of the proposed probabilistic fatigue analysis method can be significantly improved. Our proposed method is validated by numerical studies with a state-of-the-art wind turbine and has been applied in a wind turbine design with real-world wind loads.

Optimization of extraction tower structure and extraction conditions for lincomycin separation

Lincomycin is a widely used aminoglycoside antibiotic. For its separation from fermentation broth in production, solvent extraction is usually applied because of its low cost and high capacity compared to other bioseparation methods. The multistage mixer-settler is a common extraction equipment in commercial production, but it occupies a large area and causes pollution. In this study, a fully enclosed turbine tower was designed and applied in order to replace the mixer-settler. Its structure parameters (turbine diameter, tray porosity) were optimized on the basis of the extraction effect of lincomycin. The results showed that with 35% tray porosity and 28/26 mm turbine diameter of the tower, the extraction rate was kept above 99.0% steadily under 375 rpm/min rotating speed and 60 °C temperature. The extraction effect is much better than mixer-settler and such turbine tower is expected to be applied in the commercial production of lincomycin.

Modeling Cyclic Crack Propagation in Concrete Using the Scaled Boundary Finite Element Method Coupled with the Cumulative Damage-Plasticity Constitutive Law.

Many concrete structures, such as bridges and wind turbine towers, fail mostly due to the fatigue rapture and bending, where the cracks are initiated and propagate under cyclic loading. Modeling the fracture process zone (FPZ) is essential to understanding the cracking behavior of heterogeneous, quasi-brittle materials such as concrete under monotonic and cyclic actions. The paper aims to present a numerical modeling approach for simulating crack growth using a scaled boundary finite element model (SBFEM). The cohesive traction law is explored to model the stress field under monotonic and cyclic loading conditions. In doing so, a new constitutive law is applied within the cohesive response. The cyclic damage accumulation during loading and unloading is formulated within the thermodynamic framework of the constitutive concrete model. We consider two common problems of three-point bending of a single-edge-notched concrete beam subjected to different loading conditions to validate the developed method. The simulation results show good agreement with experimental test measurements from the literature. The presented analysis can provide a further understanding of crack growth and damage accumulation within the cohesive response, and the SBFEM makes it possible to identify the fracture behavior of cyclic crack propagation in concrete members.

Research of Turbine Tower Optimization Based on Criterion Method

Tower cost makes up an important part in the whole wind turbine construction especially for offshore wind farms. The main method to reduce tower cost is to reduce tower weight by optimum design. This paper proposes a two-level optimization criterion method for the optimal design of steel conical tower considering different structural reliability and uncertainty, along with the discreteness of design variables such as tower thickness and bolt type. In the first level, the tower shell geometry can be obtained by section design method; in the second level, bolted connections and flanges are designed based on the results of the first level. Then, summarized analysis and iterative calculation is performed to obtain optimum tower design with constant strength and rigidness. This method will play an important role in offshore customized turbine design.

Gap height prediction for bolted ring flange connections based on measurements

AbstractWind turbine towers and their flange connections are highly fatigue loaded structures. Previous investigations have shown that initial parallel gaps between L‐flange connections, which are resulting from their respective flatness of the contact surfaces, can increase fatigue loads of the connecting fasteners significantly. Flange flatness and/or gap sizes in between flanges must comply with limitations given in relevant standards and therefore must be measured after the manufacturing process and/or during installation. More than 1900 flatness measurements of several offshore wind projects were collected and used to determine initial gaps between flanges analytically. A statistical evaluation allows to determine the distribution of expected gap sizes. The increase of gap height with increasing gap length can be described with linear correlations. Furthermore, the distributions of gap heights are approximated with log‐normal distributions. Parameters for generic log‐normal distributions are derived considering all performed mating simulations. Following the described methodology, gaps can be determined from any large number of flatness measurements. It is proposed to consider the results for flange design.

A multi-stable ultra-low frequency energy harvester using a nonlinear pendulum and piezoelectric transduction for self-powered sensing

This paper presents the design, theoretical modelling and experimental validation of a quad-stable energy harvester for harnessing ultra-low frequency random motions using a nonlinear pendulum and piezoelectric transduction. The multi-stable pendulum is created by the magnetic forces between magnets on the pendulum and a tip magnet on a piezoelectric cantilever beam. Two attractive and one repulsive magnetic forces in combination with the gravitational force of the pendulum create multiple stable positions for the pendulum. The multi-stable dynamics allow the pendulum to effectively convert low-frequency random kinetic motions from the host, e.g. human motion or wind turbine tower oscillation into the pendulum oscillation, enabling effective plucking of the piezoelectric beam with enhanced output power. A theoretical model, including the magnetic interaction, piezoelectric conversion and pendulum dynamics, is established to describe the electromechanical dynamics of the whole harvester. A prototype is fabricated and tested on a linear shaker at ultra-low frequencies (1–3 Hz) to showcase the capability of the harvester and to validate the theoretical results. Around 8 μW Root-Mean-Square output power was obtained at 2.5 Hz and 0.8 g of excitation. Using the experimentally validated theoretical model, a parametric study was carried out to examine the influence of different structural and operating parameters, such as pendulum mass and length, magnetic coupling strength, excitation frequency and amplitude, on the output power and operating frequency range of the energy harvester. The operation frequency range and output power can be effectively adjusted by changing the above-mentioned parameters. The self-powered sensing capability is then illustrated by integrating the harvester with an off-the-shelf power management circuit and a 22 μF storage capacitor. The capacitor was charged from 2.8 V to 4 V in 90 s, showing its capability of implementing battery-free wireless sensing for different Internet of Things (IoT) applications.

Dynamic synthetic inertial control method of wind turbines considering fatigue load

This paper proposes a dynamic synthetic inertia control method, considering the fatigue loads of the wind turbine. The control objectives include reducing the rate of change of frequency and frequency nadir of the power system and the fatigue load of the shaft and tower of the wind turbine. A frequency regulation model of the power system containing the primary operating dynamics of the wind turbine is established. The dynamic synthetic inertia control method is proposed according to the relationship between fatigue load, wind velocity, and frequency. Case studies are conducted with a wind turbine fatigue load under a synthetic inertia control with different weights for different wind velocities and system loads. Therefore, the dynamic weights are obtained. Comparing the rate of change of frequency and frequency nadir and equivalent damage load, the efficacy of the proposed method is verified.

Vibration analysis of tower of onshore wind turbine

Vibration analysis of tower of onshore wind turbine

Fatigue Analysis of Hybrid Wind Turbine Towers

Fatigue analysis of hybrid wind turbine towers between cut in wind speed and cut out wind speed are demonstrated. Nominal stress method and miner liner accumulated damage theory are adopted. Through the analysis of the results, comparative research on effect of parameters of aspect ratio, height ratio and unequal legs for fatigue properties of hybrid wind turbine towers. The results show that the optimal range of aspect ratio of hybrid towers is 1/6~1/4, the optimal range of height ratio of hybrid towers is 0.60~0.67. Fatigue analysis of hybrid towers, should select the right junction of leeward towers and the S-N curve from EN 1993-1-9.The effect of unequal legs for fatigue properties of hybrid towers can be neglected.

A Fused Gaussian Process Modeling and Model Predictive Control Framework for Real-Time Path Adaptation of an Airborne Wind Energy System

This article presents a computationally tractable adaptive control strategy suitable for mobile systems operating in a stochastically and spatiotemporally varying environment by fusing Gaussian process modeling and receding horizon control. This strategy ideally manages the tradeoff between exploration (maintaining an accurate estimate of the stochastic resource) and exploitation (maximizing a performance index, which generally consists of harvesting the resource) subject to partial observability (stochastic resource only measurable at the system’s location) and mobility constraints, which are characteristic of dynamic systems. The case study in this article focuses on a crosswind airborne wind energy (AWE) system where the wind turbine tower is replaced by tethers and a lifting body, allowing the system to adjust its altitude, with the goal of operating at the altitude that maximizes net energy production in a wind environment that is changing in altitude and time. Real wind speed versus altitude data has been used to validate the strategy and results are presented for a variety of control strategies applied to a rigid wing-based AWE system.