Megawatt Wind Turbine Research Articles

Technical and Economic Feasibility study on Repowering of Wind Farms

Objectives: The main objective of the paper is to perform a repowering assessment of an old wind farm consisting of 2 bladed turbines located at Gudimangalam near Coimbatore in Tamil Nadu which is a good wind potential site. Methods/Statistical Analysis: Repowering refers to the replacement of first generation small capacity wind turbines with modern multi megawatt wind turbines that can produce more energy than before from the same site. Technical analysis of the site is done using WAsP software with the help of wind data collected from a met mast at the site and includes the calculation of Net Annual Energy Production and Wake losses. Net Annual Energy Production and Wake losses are the primary indicators for selecting the best options for repowering. The option selected is further supported by calculating the economic performance indices. The total repowering has been accomplished through partial repowering executed in three stages. Partial repowering refers to the replacement of only few of the turbines from the existing wind farm rather than replacing the whole farm. The economic feasibility of every repowering option has been studied based on the calculation of the economic performance indices like ALCoG, Payback Period and IRR. Findings: The study mainly results in framing a procedure for performing total repowering for any site through the optimization of best possible partial repowering options. The existing site comprises 18 turbines of 450 kW rating and is having a net AEP of 14.5 GWh with a wake loss of 3.82%. The Plant Load Factor (PLF) is obtained to be 20.44%. The best possible total repowering option is found to be producing a net AEP of 65.287 GWh with a wake loss of 2.36% and included 9 Suzlon S95 2.1 MW turbines which are four times the AEP of the existing farm. The three stages of partial repowering also include replacement of 6 old turbines by 3 new turbines in each stage. Finally the total repowering is reached through the execution of partial repowering options in three stages and it results in close proximity to the best possible total repowering option in both technical and economic aspects. The final repowering eventually attained results in a net AEP of 65.28 GWh with a wake loss of 2.36% which is the exact match of the best possible total repowering option found in the beginning. The total repowering also leads to an improvement in PLF i.e. almost doubles the PLF to 39.42%. Application/Improvements: This procedure can be very useful where the initial investment is an important factor. The study infers that performing total repowering through optimization process is more beneficial than performing partial repowering randomly.

CFD simulation of a 2 bladed multi megawatt wind turbine with flexible rotor connection

An innovative passive load reduction concept for a two bladed 3.4 MW wind turbine is investigated by a conjoint CFD and MBS - BEM methodology. The concept consists of a flexible hub mount which allows a tumbling motion of the rotor. First, the system is simulated with a MBS tool coupled to a BEM code. Then, the resulting motion of the rotor is extracted from the simulation and applied on the CFD simulation as prescribed motion. The aerodynamic results show a significant load reduction on the support structure. Hub pitching and yawing moment amplitudes are reduced by more than 50% in a vertically sheared inflow. Furthermore, the suitability of the MBS - BEM approach for the simulation of the load reduction system is shown.

Aerodynamic Numerical Testing of Megawatt Wind Turbine Blade to Find Optimum Angle of Attack

Wind energy is one of the oldest kinds of energy source used by mankind and it is dating back to thousand years. At the beginning of twentieth century, multi blades wind turbines were improved and used for charging in USA. After oil crisis in in the seventies, there was a surge of alternative energy sources in USA, Denmark and Germany. In terms of installed capacity, Germany had the leadership until 2007, then it passed to USA and finally China becomes the leader. Today, 6 MW capacity wind turbine are available in the market. The majority of the airfoils in use on horizontal-axis wind turbines today were originally developed for aircraft but it has been begun to design airfoil especially for wind turbine for 20 years. S series airfoil poses the most significant examples designed by NREL. In this study, S809 airfoil was simulated using the SST turbulence model and compared with experimental data to validate simulation accuracy of the computational fluid dynamics and this calculation. After verifying the consistency of the simulation model, S830 airfoil was simulated with different Reynolds numbers or velocities. Lift and drag coefficient, lift to drag ratio and pressure coefficient were calculated and compared

Defining Capacity Factor by Weibull Shape Parameter and Mean Wind Speed

This workmodels capacity factor in terms of wind turbine operating characteristics, mean wind speed, and shape parameter of Weibull probability density function. The methodology used involves fewer parameters than have been used by other workers. We have used a nondimensional speed parameter ( x) as the ratio of the wind speed ( V) to the mean wind speed ( Vm). The operating characteritics of a megawatt wind turbine cut-in ( Vin), rated ( Vr) and cut-out ( Vout) speeds are divided by Vm, resulting into nondimensional speeds: xin, xr, and xout, respectively. Similarly, the Weibull scale parameter is also transformed by the Vm. The final model of the capacity factor constitutes four variables: xin, xr, xout and k. The analysis of model shows that, in general, low values of nondimensional speed xr results into higher values of capacity factor. The shape parameter also influences the value of capacity factor. High values of shape parameter provides, in general, low value of capacity factor. For example, a turbine designed for shape parameter of about 2 if installed at a site where the shape parameter is about 4 or more than the value of capacity factor may reduce by almost 10%. The analysis also shows that if one wishes to achieve higher values of capacity factor for a turbine desined for k = 2 to k = 4 would necessitate increase in the mean wind speed of the new site ( k = 4).

Dynamic analysis of a megawatt wind turbine drive train

The dynamic performance of a wind turbine drive train significantly influences the operation of an entire machine. In this work, a megawatt wind turbine drive train is subject to theoretical and experimental dynamic analysis. The method of rigid-flexible coupling multibody dynamics was applied to develop a dynamic model of the entire drive train. This model was then used to study the natural characteristics of the system. The blades, hub, main shaft, and speed-up gearbox in the dynamic model were modeled as flexible bodies. The potential resonances of the system were detected through Campbell and modal energy distribution analyses. Theoretical results show that the first-order natural frequency of the system is approximately 1.72 Hz. This frequency represents a torsional vibration mode, Moreover, resonances are not observed within the normal operating speed range of the drive train. An experimental remote real-time system was developed to monitor the torsional vibration of the drive train. This vibration was used to measure the torsional vibration of the system overall. The experimental results are consistent with the theoretical results.

Separated Pitch Control at Tip: Innovative Blade Design Explorations for Large MW Wind Turbine Blades

This paper focuses on the deployment and evaluation of a separated pitch control at blade tip (SePCaT) control strategy for large megawatt (MW) wind turbine blade and explorations of innovative blade designs as a result of such deployment. SePCaT configurations varied from five to thirty percent of the blade length in 5 percentage increments (SePCaT5, SePCaT10, SePCaT15, SePCaT20, SePCaT25, and SePCaT30) are evaluated by comparing them to aerodynamical responses of the traditional blade. For low, moderate, high, and extreme wind speed variations treated as 10, 20, 30, and 40 percent of reference wind speeds, rotor power abatement in region 3 of the wind speed power curve is realized by feathering full length blade by 6, 9, 12, and 14 degrees, respectively. Feathering SePCaT30, SePCaT25, SePCaT20, and SePCaT15 by 14, 16, 26, and 30 degrees, respectively, achieves the same power abatement results when compared to traditional blade at low wind speeds. Feathering SePCaT30, SePCaT25, and SePCaT20 by 18, 26, and 30 degrees on the other hand has the same effect at high wind speeds. SePCaT30 feathered to 26 and 30 degrees has the same abatement effects when compared to traditional blade at high and extreme wind speeds.

J0530405 AIST-RAMによるティータ式2枚翼風車の動的荷重評価

Two-bladed wind turbines are noticed because of reducing nacelle's weight on multi megawatt wind turbine size. However, two-bladed wind turbines have some issues such as increasing fatigue load and noise. Increasing noise is not so important when installing wind turbines in a sea area. So, to implement larger size of off-shore wind turbines, reducing fatigue load is important. As one of the methods that reduce fatigue load, a teetered-hub is noticed. A teetered-hub enables blades to rotate on a central axis of the hub like a seesaw. By this movement, the difference of aerodynamic load between two blades is balanced. In this study, blades behavior of teeter axis circumference and a blade root bending moment are analyzed by AIST-Realtime Aeroelastic Model (AIST-RAM). AIST-RAM is derived by Lagrange's method on Euler's coordinate system and is coded by The National Institute of Advanced Industrial Science and Technology using MATLAB/Simulink. By comparing AIST-RAM result with wind tunnel test result, confirming the validity of AIST-RAM.

Investigation of the maximum load alleviation potential using trailing edge flaps controlled by inflow data

The maximum fatigue load reduction potential when using trailing edge flaps on mega-watt wind turbines was explored. For this purpose an ideal feed forward control algorithm using the relative velocity and angle of attack at the blade to control the loads was implemented. The algorithm was applied to time series from computations with the aeroelastic code HAWC2 and to measured time series. The fatigue loads could be reduced by 36% in the computations if the inflow sensor was at the same position as the blade load. The decrease of the load reduction potential when the sensor was at a distance from the blade load location was investigated. When the algorithm was applied to measured time series a load reduction of 23% was achieved which is still promissing, but significantly lower than the value achieved in computations.

Design of a family of new advanced airfoils for low wind class turbines

In order to maximize the ratio of energy capture and reduce the cost of energy, the selection of the airfoils to be used along the blade plays a crucial role. Despite the general usage of existing airfoils, more and more, families of airfoils specially tailored for specific applications are developed. The present research is focused on the design of a new family of airfoils to be used for the blade of one megawatt wind turbine working in low wind conditions. A hybrid optimization scheme has been implemented, combining together genetic and gradient based algorithms. Large part of the work is dedicated to present and discuss the requirements that needed to be satisfied in order to have a consistent family of geometries with high efficiency, high lift and good structural characteristics. For each airfoil, these characteristics are presented and compared to the ones of existing airfoils. Finally, the aerodynamic design of a new blade for low wind class turbine is illustrated and compared to a reference shape developed by using existing geometries. Due to higher lift performance, the results show a sensitive saving in chords, wetted area and so in loads in idling position.

The Design of Valve Block of Megawatt Wind Turbine Hydraulic Yaw System and AMESim Simulation Model

In view of the current 1.5 megawatt wind turbine,this paper designs a set of corresponding hydraulic system,mainly including the system of pumping station valve block the main part by UG 3D software,the AMESim software is used to establish the yaw hydraulic system model and the analysis of the simulation.

Megawatt Wind Turbine Hydraulic Brake System Locking Device Modeling and Research Based on AMESim

As a megawatt-class wind turbine braking system, in addition to brake, it should also be in place with a wind wheel locking device to ensure that the failure of the braking system in the normal case fan will not burst start again.To solve the problem the article has designed a hydraulic locking device, and USES the AMESim software on the research and analysis.

Dynamic analysis of the drive train of a wind turbine based upon the measured load spectrum

A dynamic model of the drive train of a megawatt wind turbine is proposed in which the blades, the hub, the main shaft, and the speedup gearbox are assumed as flexibilities. The external excitation due to the measured load spectrum and the internal excitations due to the time-varying mesh stiffness, the transmission errors, and the meshing impacts within the gearbox are considered to predict the dynamic response of the system. Results show that the most vibration energy occurs at the speed-up gearbox, followed by the generator, and then the main shaft. An experimental remote real-time system is developed to monitor vibration performance of the drive train, with which the accelerations of components are detected. The experimental results are in accordance with the theoretical results.

Study on Casting Instead of Traditional Forging for Main Shaft of Megawatt Wind Turbine

Turbine main shaft is one of the most important components for wind turbines. Nowadays, the main shafts of megawatt wind turbine have been mainly manufactured by forging technology. Although forged spindle has good performance, forging process is so complicated that it generally takes long production cycle and high cost. This paper has been undertaken in an attempt to describing a novel method of gravity casting to manufacture wind turbine. It has been found that some performances such as the tensile strength and the yield strength of the casted main shaft are higher than those of the forging standard ones, while other performances dependent on various positions of the sampling present different performance distribution.

Coupled vibration study of the blade of the flexible wind wheel with the low-speed shafting

Movement and deformation of flexible wind wheel has a profound effect on dynamics of the low-speed shafting in Megawatt wind turbine. The paper is based on the power production1.2 MW wind turbine, vibration characteristics of elastic wind wheel with the low-speed shafting were studied. In order to obtain the finite element model, the author created a physical model of this coupled system and used the minimum energy principle to simplify the model. While its single blade simplified as cantilever. Using modal superposition method for solving the coupled system model. Structural mechanics equations were used to solve the simple blade finite element model. Analyzing the natural frequency of the coupled system and the stress diagram, the results indicate that in the coupling system, low frequency vibration occurs in the low-speed shaft bearing, while the high-frequency vibration happens on wind turbine blades. In the low-frequency vibration process, blades vibration and low-speed shaft vibration there is a strong correlation. Contrast inherent frequency of the wind wheel with natural frequency of a single blade, the results show that the frequency of the wind wheel slightly less than it in the single blade.

The stiffness tailoring of megawatt wind turbine

Wind power has developed rapidly in recently years, the wind turbine's blades determine the performance of the device and the power. In this paper, we used integrated tailoring aimed at institutional characteristics of horizontal axis wind turbine with the composite laminated plate theory, then analyzed the composite blades of wind turbine by combining experimental analysis and finite elements method, and finally studied the influences that composite material properties on stiffness tailoring with changes in the number of different layers.

Vibration Analysis on the Megawatt-Class Wind Turbine Based on the Rigid-Flexible Coupling Model

The rigid-flexible coupling model of wind turbine was established in ADAMS to study the vibration characteristics, which was based on the working principle of megawatt wind turbine. The natural frequencies and vibration modes of the tower have been obtained by dynamic simulation analysis and vibration analysis of the wind turbine. The comparison of the first-order bending natural frequency by raley analysis algorithm and the first-order bending natural frequency by the software, which has validated the correctness of rigid-flexible coupling model of wind turbine, the analysis of vibration characteristic has verified the rationality of the structure of the wind turbine.

Modeling and Simulation of Wind Turbine Driving PMSG with MPPT Control Based on Current Source Converter

This paper elaborates on the analysis and simulation of a megawatt Wind Turbine (WT) driving low speed Permanent Magnet Synchronous Generator (PMSG) based on Current Source Converter (CSC) using PSIM computer simulation program. The system consists of wind turbine, PMSG, maximum power point tracking (MPPT) and three-phase CSC models. In the WT model, the best performance coefficient has been determined according to the variable wind speed with MPPT control. The gear-box has been eliminated by the low speed PMSG to achieve high efficiency. The ac power output from PMSG is fed to a three-phase CSC, which extracts maximum power through closed-loop regulation of generator speed. The current source PWM inverter is used to interface the system with the electrical utility. The available maximum power fed to the grid is adjusted by regulating dc-link output current of CSC according to the variable wind speed.

Guesstimation 2.0: Solving the World's Problems on the Back of a Napkin.

Guesstimation 2.0 reveals the simple and effective techniques needed to estimate virtually anything--quickly--and illustrates them using an eclectic array of problems. A stimulating follow-up to Guesstimation, this is the must-have book for anyone preparing for a job interview in technology or finance, where more and more leading businesses test applicants using estimation questions just like these. The ability to guesstimate on your feet is an essential skill to have in today's world, whether you're trying to distinguish between a billion-dollar subsidy and a trillion-dollar stimulus, a megawatt wind turbine and a gigawatt nuclear plant, or parts-per-million and parts-per-billion contaminants. Lawrence Weinstein begins with a concise tutorial on how to solve these kinds of order of magnitude problems, and then invites readers to have a go themselves. The book features dozens of problems along with helpful hints and easy-to-understand solutions. It also includes appendixes containing useful formulas and more. Guesstimation 2.0 shows how to estimate everything from how closely you can orbit a neutron star without being pulled apart by gravity, to the fuel used to transport your food from the farm to the store, to the total length of all toilet paper used in the United States. It also enables readers to answer, once and for all, the most asked environmental question of our day: paper or plastic?

Application of the multifractal method to the feature extraction of megawatt wind turbine main bearing

Application of the multifractal method to the feature extraction of megawatt wind turbine main bearing

State Recognition for Main Bearing of Wind Turbines Based on Multi-Fractal Theory

The main bearing dynamic characteristics of megawatt wind turbines are complex system with strong non-linearity, strong coupling and time-varying. The vibration signals are mixed with background noise, so it is difficult to extract the characteristics of week signals. Based on the dynamic characteristics, multi-fractal theory is put forward to detect and recognize the working status of the main bearing of megawatt wind turbines. Different working states are recognized intuitively by different dimensions of multi-fractural which are sensitive to variety of working state. The paper justifies the method can detect and recognize different working states of main bearings quickly and accurately through the experiments on the main bearings of 3 WM wind turbines.