Size Of Wind Turbines Research Articles

Study on composite bend-twist coupled wind turbine blade for passive load mitigation

The wind turbine size is nowadays becoming increasingly larger as an effective approach to reduce cost of energy. Passive load control technique is introduced to alleviate the increasing loads on an upscaling wind turbine blade to improve its fatigue life. In this paper, the composite bend-twist coupled blade is investigated and utilized to mitigate the cyclic fluctuating loads in shear wind. The NREL 5-MW blade is firstly inversely redesigned of its composite layup configuration. The fiber on the spar cap is rotated away from the blade axis to implement the bend-twist coupling (BTC). An advanced aeroelastic model of the wind turbine blade is developed to conduct the study. The geometrically exact beam theory is used to account for the large deformation effects, while the tool VABS is utilized to generate the cross-section stiffness matrices. Meanwhile, the free wake lifting surface model is adopted to calculate the aerodynamic loads, which is physically more realistic than the traditionally used BEM method. Based the established model, the influences of BTC on the rotor aerodynamic performance are investigated. Load mitigation effects of the blades with various spar cap fiber angles are evaluated. The influences of coupling region and different wind speeds are also discussed.

Parametric Study of a Gurney Flap Implementation in a DU91W(2)250 Airfoil

The growth in size and weight of wind turbines over the last years has led to the development of flow control devices, such as Gurney flaps (GFs). In the current work, a parametric study is presented to find the optimal GF length to improve the airfoil aerodynamic performance. Therefore, the influence of GF lengths from 0.25% to 3% of the airfoil chord c on a widely used DU91W(2)250 airfoil has been investigated by means of RANS based numerical simulations at Re = 2 × 106. The numerical results showed that, for positive angles of attack, highest values of the lift-to-drag ratio CL/CD are obtained with GF lengths between 0.25% c and 0.75% c. Particularly, an increase of 21.57 in CL/CD ratio has been obtained with a GF length of 0.5% c at 2° of angle of attack AoA. The influence of GFs decreased at AoAs larger than 5°, where only a GF length of 0.25% c provides a slight improvement in terms of CL/CD ratio enhancement. Additionally, an ANN has been developed to predict the aerodynamic efficiency of the airfoil in terms of CL/CD ratio. This tool allows to obtain an accurate prediction model of the aerodynamic behavior of the airfoil with GFs.

An evaluation of wind turbine waste heat recovery using organic Rankine cycle

Wind turbine size has increased to megawatt capacity, and the related technologies and facilities have improved, including the cooling systems. Currently, all of the heat generated by wind turbine components is wasted to the environment. This study presents a conceptual design of a novel method for waste heat recovery of a wind turbine using an organic Rankine cycle (ORC). An organic Rankine cycle is implemented to the wind turbine as a part of the cooling system. The proposed system is thermodynamically modeled to evaluate the amount of recovered energy. Seven working fluids are chosen and investigated in the simulations to estimate the working fluid effect. The results revealed that the organic Rankine cycle can be a suitable choice for cooling wind turbines while simultaneously produce the power. Both exergy and energy analysis are conducted. A maximum power of 7.1 kW is provided by the proposed system using R134 when 20 K superheat is utilized. While R600a and SE36 stand on the next place. Furthermore, a minimum of 6.25 kW power is achievable. The generated work can be used as pump driving or electricity generation. In the next step, the thermal efficiency and total annual cost are optimized simultaneously using a multi-objective optimization for R134a as best working fluid in the thermodynamic viewpoint. It is found that the ideal efficiency of the system is obtained to be 14.7% with the total price of 7050 $/year. Finally, the effects of design parameters on the efficiency are obtained.

Integrated sizing of hybrid PV-wind-battery system for remote island considering the saturation of each renewable energy resource

The proliferation of renewable energy particularly the combination of solar-wind power and storage bank, is likely to be occupied throughout the world, to mitigate the local energy concerns, improve the energy supply opportunities for off-grid communities and vitiate environmental pollution concerns as well as ease the intensity of energy consumption. To mitigate the disharmony between renewable energy (RE) generation and supply, a cost-optimal autonomous hybrid renewable energy system is developed and comparatively analyzed, considering the saturation level of each involved RE source based on various technical and economic key indicators. This study proposes a mathematical model to comprehensively analyze the effect of varying saturation, i.e. increasing the saturation of one resource meanwhile decreasing the ratio of other resource, on battery bank size, state of charge (SOC), loss of power supply, excess energy, net present cost, levelized cost of energy (COE) and payback time. A saturation factor is introduced, from 0 to 1 value with step size 0.02, where zero represents the wind-only system and one represents the solar-only system. Three different systems are considered, with different wind turbine sizes (total 150 configurations), to comparatively analyze the different energy systems and the result reveals that smaller wind turbine size (2 kW) with 90% saturation of wind energy is the most cost-effective system for the proposed remote island. In addition, the solar-alone and wind-alone systems are compared, showing that the wind-only system can provide good performance as compare to solar-only. Furthermore, the effects of the saturation factor on COE, battery bank size, SOC, excess energy, system reliability and different load demands are analyzed. Energy balance analysis of whole year and simulation performance of the system is accomplished to verify the system reliability. Sensitivity analysis reveals that wind energy, battery cost and load has a significant impact on COE than other factors.

Fault Diagnosis of Wind Turbine Power Converter Considering Wavelet Transform, Feature Analysis, Judgment and BP Neural Network

The larger capacity of power converters increases with the size of wind turbines over the years, which implies more failures occur in the components of power converter. Meanwhile, the strategies of fault diagnosis of power converter in wind turbine are still under discussion and research. The main purpose of this paper is proposing a strategy containing wavelet transform, feature analysis, judgment and back propagation neural network (BPNN) classification (WT-FA-JD-BP) to identify the single and double power components open-circuit faults accurately, happen in grid-side converter (GSC) of permanent magnet synchronous generator (PMSG) wind turbine systems. First, as the original signals, the three-phase bridge legs voltage of the GSC are collected under different faults. Second, wavelet transform is used to decompose and reconstruct the signals. Third, a new method includes feature analysis and judgment is conducted to amplify the divergence of data obtained by wavelet transform. Finally, the data are used as the inputs of BPNN for decision-making and classification. The simulation and experimental results show that the proposed strategy can classify the single and double open-circuit faults, and the accuracy is higher than that without data feature analysis and judgment.

Optimal sizing of hybrid renewable energy system via artificial immune system under frequency stability constraints

An efficient sizing procedure for renewable energy resources (RESs) is a mandatory requirement for the implementation phase. The sizing procedure is mainly demand curve dependent, and the proper sizing certainly optimizes system components and hence reduces the cost. This article proposes an innovative optimal sizing procedure for wind/solar/battery hybrid renewable power systems (HRPSs) using the Artificial Immune System (AIS) technique. The optimal sizes of photovoltaic arrays, wind turbines, and batteries which fulfil the demand requirement with the least percent of load interruptions are identified. HRPSs usually suffer from the uncertainty of RESs and the absence of synchronous inertia. Energy storage systems (ESSs) could successively remedy these deficiencies. This article advises the application of ESS for providing the primary frequency control during any contingency/fall of frequency out of its normal limits. Accordingly, ESS acts as virtual synchronous inertia that balances between demand and generation during disturbance. The proposed sizing procedure is analysed as a constrained optimization problem. The constraints ensure high reliability power supply along with the frequency stability constraints. Therefore, the proposed sizing procedure has the advantages of minimized HRPS cost, improved system security, and regulated frequency. The uncertainty of RESs is considered in the proposed sizing procedure, to improve the applicability of the obtained results. The proposed procedure algorithm is correlated via comparison with Practical Swarm Optimization, a fertile optimization method. A case study for evaluating the proposed sizing approach is Qena AL-Gadida city, Qena province, Egypt. The power supply of this city is considered as a Microgrid. MATLAB is used for coding AIS and systems under concern. Numerous operating scenarios are considered to test the functionality of the proposed sizing and primary function regulation ability of its ESS. The results reveal the reliability and applicability of the advised sizing procedure. Moreover, adopting primary frequency regulation of ESS resulted only in a slight increase in the overall costs.

Power quality enhancement in electricity grids with wind energy using multicell converters and energy storage

In recent years, the wind power industry is experiencing a rapid growth and more wind farms with larger size wind turbines are being connected to the power system. While this contributes to the overall security of electricity supply, large-scale deployment of wind energy into the grid also presents many technical challenges. Most of these challenges are one way or another, related to the variability and intermittent nature of wind and affect the power quality of the distribution grid. Power quality relates to factors that cause variations in the voltage level and frequency as well as distortion in the voltage and current waveforms due to wind variability which produces both harmonics and inter-harmonics. The main motivation behind work is to propose a new topology of the static AC/DC/AC multicell converter to improve the power quality in grid-connected wind energy conversion systems. Serial switching cells have the ability to achieve a high power with lower-size components and improve the voltage waveforms at the input and output of the converter by increasing the number of cells. Furthermore, a battery energy storage system is included and a power management strategy is designed to ensure the continuity of power supply and consequently the autonomy of the proposed system. The simulation results are presented for a 149.2 kW wind turbine induction generator system and the results obtained demonstrate the reduced harmonics, improved transient response, and reference tracking of the voltage output of the wind energy conversion system.

Anticipating in-use stocks of carbon fibre reinforced polymers and related waste generated by the wind power sector until 2050

The rapid development of the wind power sector with a steady increase in wind turbine size has led to a rising utilization of the carbon fibres used in their blades. This trend is expected to continue and as a result, the amount of carbon fibre reinforced plastic (CFRP) waste generated by the wind power sector will grow quickly in the future due to production waste and wind turbines reaching the end of their product life cycle. This prospective study quantifies and localizes the evolution of the worldwide in-use stocks of CFRP and related waste and until 2050. A bottom-up approach has been used enabling the assessment of CFRP in-use stocks, by country and globally. By then, most of the cumulative amount of waste will be located in Europe and Asia with approximately 190,000 and 149,000 tons, respectively, if not recycled beforehand. To illustrate, it would represent 34,821 and 27,307 wind turbines of 5 MW to recycle in Europe and Asia. Thus, this study estimates the in-use stocks of CFRP and the related waste generation by geographical area including time references. Also, results could serve as a useful guide for the establishment of a waste management programme for the upcoming CFRP waste generated by the wind power sector until 2050.

Wind field reconstruction from lidar measurements at high-frequency using machine learning

The increase in wind turbine size during recent years has led to a situation where the wind speed measured at hub height is no longer a sufficient representation of the power available to be extracted by a turbine. Light Detection and Ranging (“Lidar”) wind sensing devices can measure wind speeds in a volume in front of the sensor, offering affordable and improved estimation of wind turbine power performance and loading. However, a Lidar can only measure the component of the wind velocity in the direction of the beam. This makes reconstruction of the wind velocity field from raw Lidar measurements a challenge, and current methods contain assumptions which cause inaccuracies in complex terrain and in wind turbine wakes. In addition, data availability is reduced in specific weather conditions, such as very cold climates and dense fog. A novel Machine Learning method is developed here, based on Gaussian Process regression, to remove these assumptions when producing full 3D wind fields from Lidar measurements. This approach is naturally robust to overfitting and predicts uncertainty derived from data density and machine error, without needing physical information about the local terrain. Initial validation by comparison of a Windcube Lidar with a meteorological mast, on a site with simple conditions, shows excellent performance which meets the threshold for commercial use. The method also infers data during measurement gaps, offering the potential for 100% data availability. Instantaneous 2D wake measurements in a plane can be made, which when validated and further developed will offer a breakthrough in understanding of wind farm interactions and turbine loading.

Research sized wind turbine blade modal tests: comparison of the impact excitation with shaker excitation

Modern wind turbine blades are being tested for certification purposes in accordance to the IEC-64100 standard. Part 23 of the norm details the requirements for the full scale structural testing of rotor blades. As a minimum, it requires measurement of the first and second flap wise and first edge wise natural frequencies. It lists damping and mode shapes as other blade properties which may be of interest and optionally measured. The paper presents the modal model parameters estimation based on the experimental modal analysis. In two tests performed, the input force has been introduced through impact hammer and two electrodynamic shakers excitation. Several first modes had been identified for both excitation methods, including first torsional mode of the investigated blade. Results of the modal tests can be used to (a) provide more detailed information about the structural dynamics characteristics of the blade and (b) improve the design by adjusting the dynamic properties of the blade to some desired condition.

Numerical investigation of modeling frameworks and geometric approximations on NREL 5 MW wind turbine

Abstract The key to the better design of an industrial scale wind turbine is to understand the influence of blade geometry and its dynamics on the complicated flow-structures. An industrial-scale wind turbine can be numerically represented using various approaches (from simpler 2 D steady flow to complex 3 D with moving mesh, with and without the inclusion of hubs) that can alter the results substantially. At the same time, to standardize and test methodologies, the reference industrial-scale NREL 5 MW wind turbine is gaining popularity. The wind energy community will learn through an improved understanding of the aerodynamics of this NREL 5 MW reference mega-watt size wind turbine by taking into consideration the various levels of geometric approximations. Hence, in this work the NREL 5 MW reference wind turbine is used for both: (a) understanding the associated flow-complexities due to various geometric approximation, and (b) comparison and validation of the performance of different numerical approaches for flow-simulation. The various geometric approximations considered here are related to simulating the influence of the shape of turbines structure (blade, an inclusion of hub, tower) and motions of blades. It involves (a) influence of 2D, 2.5D and 3D turbine blade geometry to highlight the impact of section bluntness, (b) influence of steady frozen rotor and rotating rotor simulations and (c) influence of inclusion of hub through a full-scale geometry of the complete reference turbine. Furthermore, the key features of the flow dynamics of a rotor and full machine are identified and parametric studies are conducted to evaluate overall performance prediction under variable Tip Speed Ratios (TSR = 6, 6.5, 7, 7.5, 8, 8.5, 9) and variable level of geometric and flow modeling approximations.

Control of MW-Scale Wind Turbines for Fatigue Load Reduction and Performance Improvement

As the size of wind turbines are continuously increasing, fatigue loads must be reduced to obtain a more reliable condition for main components. Independent pitch control (IPC) strategy, based on the collective pitch control (CPC) strategy, provides an effective solution to load reduction on WT’s components caused by asymmetry loads. Meanwhile, IPC can also improve the performance of MW-scale wind turbine. This paper presents a dynamic model for 5 MW wind turbines of CSIC (Chongqing) Haizhuang Windpower Equipment Co., Ltd. Based on the dynamic model, an independent variable pitch controller has been investigated. Non-linear dynamic analysis has been conducted on wind turbine structures. During the turbine linearization, the blade flap-wise and tower F–A bending modes are considered. The tower, main shaft and blade are regarded as rigid bodies. Based on the dynamic model, the IPC controller is designed through d–q conversion. The results suggest that the IPC technique not only works well in stabilizing the output power, but may also effectively reduce the fatigue loads on the blades, main shaft, tower and hub. Under the identical conditions, the IPC presented in this paper has more advantages than a collective pitch controller, and can further reduce loads on key components. The IPC is of greater significance in control of wind turbines, and can lead to lower maintenance costs. However, IPC will raise the pitch-regulating speed, and further increase the fatigue load on the pitch mechanism. This problem requires further studies for a solution.

An Opportunistic MAC Protocol for Energy-Efficient Wireless Communication in a Dynamic, Cyclical Channel

As wind energy continues to expand to new frontiers in terms of the location, number, and size of wind turbines, the industry has begun to seek smarter operations and management solutions. Low-cost wireless sensing nodes could be used to support data-driven techniques for optimizing production and reducing maintenance costs, among other benefits. Wireless instrumentation makes particular sense for wind turbine blades; however, traditional wireless sensor network deployment approaches are not suitable for blades, due to physical constraints and the resulting extremely limited energy supply. Alternatively, a sensor node attached to a rotating blade could opportunistically and efficiently offload its data to a sink node, attached to the turbine tower, as the blade passes the tower. This approach results in a channel with a cyclical signal strength pattern that existing medium access control (MAC) protocols are not designed to handle. We thus present BladeMAC, a MAC-layer protocol that efficiently handles the cyclical channel problem by dynamically identifying duty-cycling opportunities based on received signal strength. In this paper, we describe the details of BladeMAC’s design and our implementation and evaluation in Contiki OS and the Cooja simulation tool. We also discuss practical considerations for our deployment scenario.

Aerodynamic effects of compressibility for wind turbines at high tip speeds

In the present work two dimensional airfoil computations are used to investigate the effects of compressibility in the tip region of large scale wind turbines of 20 MW+ size. In the past application of incompressible CFD solvers have been wide spread for wind turbine aerodynamics, due to their efficiency and robustness at the near incompressible conditions experienced near the rotor center. With the increasing size of modern wind turbines and the desire to approach high tip speeds, the incompressible assumption might be violated in the tip region of the turbine.To investigate the effects of compressibility and the possibility of correcting incompressible flow solutions using explicit compressibility corrections, a CFD study of 2D airfoil aerodynamics at conditions of a large scale wind turbine is performed. The present study show that classical compressibility corrections can be successfully applied as a post-processing step to incompressible solutions, reducing the error in the predicted lift and drag to within a few percent for attached flow conditions where viscous effects are limited at Mach numbers upto 0.3.

Design of a two-bladed 10 MW rotor with teetering hub

Two-bladed rotors are emerging as a viable alternative to classic three-bladed ones for driving down the cost of energy of large sized wind turbines. By eliminating a blade one could easily reduce the cost of the rotor. However, design challenges arise due to the reduced power output and the resonance typically occurring between the frequency of the tower and the two-per-revolution. In this work, we perform a dedicated design of a two-bladed configuration for a 10 MW wind turbine: the solution is upwind and equipped with a teeter hinge at the hub in order to alleviate the loads on the fixed infrastructure. The rotor and the tower are then optimized by using a holistic design algorithm, and a complete technical and economic assessment of the optimal design is conducted against a reference three-bladed one in order to compare the main performance including loads, energy yielding and the cost of energy.

Technical potential assessment of offshore wind energy over shallow continent shelf along China coast

Abstract Offshore wind resource assessment seems to be urgently needed due to the rapid development of offshore wind energy in the coming decades. Technical potential of offshore wind energy over the sea area shallower than 250 m along China coast is investigated. To avoid erroneous estimation of wind power density, a statistical model considering sea state effect is proposed. Long-term CCMP wind field data are examined using that model to reduce uncertainties. Further, influential factors including wind power density, water depth, wind turbine size, wind farm layout and various spatial constraints are analyzed on the GIS platform. Technical potential under different scenarios are presented and discussed. It shows that wind resource at Taiwan Strait is particularly abundant, where wind power density at 70 m height can be above 900 W/m2. Technical potential is quite sensitive to the size of wind turbine. Taking the layout S1 (8 × 15 turbines in each farm, 8 rotor diameters apart between wind turbines, 20 km buffer region between neighboring farms) as an example: the total technical potential of the study area is 613 GW for rotor radius 60 m, and that for rotor radius 90 m is 1264 GW; the growth rates of technical potential with rotor radius is 19.3 GW/m roughly. Spatial constraints has significant impact on the region with water depth less than 50 m, where only 48.1% of area is available for developing wind energy and the technical potential there is about 23% of that of the study area.

Minimising the levelised cost of energy and grid impact by multiobjective optimisation of wind turbine sizing

Minimising the levelised cost of energy and grid impact by multiobjective optimisation of wind turbine sizing

An optimization method for sizing a solar/wind/battery hybrid power system based on the artificial immune system

This study proposes a novel technique to obtain the optimum size of a Solar/Wind/Battery hybrid power system (HPS) using Clonal Selection Algorithm (CLONALG). The objective of the proposed method is to find the optimal size of the HPS to utilize its output with small fluctuation rate and minimum cost. The system is designed with the optimal size of PV arrays, wind turbines, and batteries so that it can satisfy the demand requirement with the least percentage of load interruptions. Loss of Power Supply Probability (LPSP) is considered as a reliability index of the HPS, and the optimization process is supposed to get the least LPSP as it could. To verify the proposed algorithm, it is applied to a case study located in Troyes Barbery Station- France and the results are compared with those obtained by Genetic Algorithm (GA). Then the CLONALG is used to get the optimal size of an HPS located in Qena AL-Gadida city-Egypt. The results proved that the proposed method is effective for the sizing process and can achieve the system objectives.

Modal Characteristics of Novel Wind Turbine Rotors with Hinged Structures

The vibration problems of the wind turbine rotors have drawn public attention as the size of wind turbine has increased incredibly. Although various factors may cause the vibration problems, the flexibility is a big threat among them. Therefore, ensuring the high stiffness of the rotors by adopting novel techniques becomes a necessity. The study was a further investigation of several novel designs regarding the dynamic behaviour and the influencing mechanism. The modal testing experiments were conducted on a traditional blade and an isolated blade with the hinged rods mounted close to the root. The results showed that the rod increased both the modal frequency and the damping of the blade. More studies were done on the rods’ impact on the wind turbine rotor with a numerical model, where dimensionless parameters were defined to describe the configuration of the interveined and the bisymmetrical rods. Their influences on the modal frequencies of the rotor were analyzed and discussed.

Lightning strike evaluation on composite and biocomposite vertical-axis wind turbine blade using structural health monitoring approach

Lightning damages to wind turbine blades increase as the size of wind turbine becomes larger. The damages are quite serious since it contributes to high cost of repairs and loss of electric power production. Since natural plant fibres receive attention nowadays due to low density and high specific strength, the usage of natural fibre to replace synthetic fibre in fabricating the turbine blade will promote a green renewable material. As the application of biocomposite for wind turbine blade has been explored, the effect of lightning strike damage has been required for further test investigation. This article explores the comparative results of performing lightning strike damage testing on composite (fibreglass) and biocomposite (flax fibre) wind turbine blades with protective metal mesh materials. The damage assessments were performed using visual non-destructive inspection methods and piezoelectric sensor as part of structural health monitoring. From the result, it is found that fibreglass blade experienced larger damage area compared to flax fibre blade based on the visual test conducted.