Wind Turbine Tower

Figure 8. Simulation of the side-side translational deflections of the NREL 5-MW baseline monopile wind turbine tower stabilized by a side-side TMD under a wind input with mean speed of 10 m/s and turbulence intensity of 15%, obtained from Σ d (3.48) - (3.49) (red dotted lines) and FAST-SC (blue dash lines) respectively. The upper, middle and lower diagrams show results at 100 s, 200 s and 300 s, respectively. The horizontal axis denotes the translational tower deflections (in meters) with positive value meaning “right” and negative value meaning “left”, while the vertical axis describes the height of the tower (in meters).

We have obtained a strongly stabilizing static output feedback for a wind turbine tower model in the plane of the turbine blades, comprising the drive train and generator, using electrical torque control and measurements of the angular velocities of the nacelle and the electrical generator. The proposed feedback signal should be high-pass filtered to avoid interference with the main electric torque controller. We have reformulated the wind turbine model with our chosen output in the abstract form (4.3) with B being bounded and with A being m-dissipative with compact resolvents. Our proof is based on a stabilization theorem of Batty and Phong and an observability result for the SCOLE system due to Guo and Ivanov.

Abstract. The use of wind energy resources is developing rapidly in recent decades. There is an increasing number of wind farms in high wind-velocity areas such as the Pacific Rim regions. Wind turbine towers are vulnerable to tropical cyclones and tower failures have been reported in an increasing number in these regions. Existing post-disaster failure case studies were mostly performed through forensic investigations and there are few numerical studies that address the collapse mode simulation of wind turbine towers under strong wind loads. In this paper, the wind-induced failure analysis of a conventional 65 m hub high 1.5-MW wind turbine was carried out by means of nonlinear response time-history analyses in a detailed finite element model of the structure. The wind loading was generated based on the wind field parameters adapted from the cyclone boundary layer flow. The analysis results indicate that this particular tower fails due to the formation of a full-section plastic hinge at locations that are consistent with those reported from field investigations, which suggests the validity of the proposed numerical analysis in the assessment of the performance of wind-farms under cyclonic winds. Furthermore, the numerical simulation allows to distinguish different failure stages before the dynamic collapse occurs in the proposed wind turbine tower, opening the door to future research on the control of these intermediate collapse phases.

Abstract—This research introduces an advanced forging method to produce the door frame of the wind turbine tower. The advantage of the new forging method is the increase of raw material utilization ratio and the energy saving. In the conventional method, the door frame is hot forged with a hydraulic press and machined out lots of material because of the big difference between forging shape and final machined shape. But the proposed forging method is composed of forging and rolling process to get near shaped forgings to machined product. The ring rolled blank size is predicted based on the neutral line constancy of the ring and final forgings. On the decision of the ring rolled blank dimension, repeated finite element analyses were applied to increase the material utilization ratio. The new forging method enables raw material to be reduced 28% and heat cost to be cut down 6%.

GL Wind 2003 (Europe), the maximum wind speed verifying the fatigue strength of high-strength bolts of wind turbines is set to 0.7 time of the design wind speed and the frequency of appearance of high wind speed is extremely low. Fatigue damages due to high wind speed can be ignored. On the other hand, the frequency of appearance of high wind speed in Japan is much higher. It is very important to understand the responses of wind turbines and the fatigue behaviors throughout the operation periods. The loading conditions of tower's flange - joints during high wind speed have not been clarified yet. So it is necessary to evaluate the fatigue strength in a strong wind condition up to the design wind speed and the response of wind turbine tower with the consideration of joint separation for establishing the design methods. In this study, we evaluate it in two steps. Firstly, a model of a tower that uses high-strength bolts at flange joints is created and FEM analyses are performed. Then, stiffness of the flange joint is determined in order to model variable stiffness of the flange joints with considering the whole wind turbine tower.

A typical 1.5-MW three-bladed horizontal-axis WT tower constructed widely on the southeast coast of China was chosen for this study. It was designed as Class Ⅱ a in IEC 61400 [2 IEC 61400], without explicit considerations about its seismic performance. The tower is a near-cylindrical steel hollow tube. The outer diameter ranges from 4035mm at the base to 2955mm at the top, with the shell thickness (t) varying from 25mm to 10mm, respectively. The position of the hub is 64.65m above the foundation and this height is divided into 22 segments that are welded together, as shown in Figure 1. The mass of the tower is about 91 tonnes and the rotor diameter is approximately 70m. At the top, the mass of the blades and the nacelle is 30 tonnes and 60 tonnes, respectively. Generally, the WT is in parked condition under extreme conditions, which are the only ones considered in this work. The fore-aft direction refers to the one that is perpendicular to the rotor plane (X direction in the FE model) and the side-to-side direction is the one parallel to the rotor plane (Z direction).

The DEL (Damage Equivalent Load) method facilitates to determine the steel tower preliminary dimensions in any circumstances which fatigue load histogram data does not exist. The SN curve for the DEL method can be expressed in the following [2]:

The advantages of utilization of taller hub heights have long been understood, where the wind-turbine tower heights have constantly increased from below 131 ft (40 m) in the 1990s to 263 ft (80 m) for the utility-scale turbines employed today. Currently, three steel tubular sections built off-site and shipped via specialized trailers are applied to develop the 263 ft (80 m) tall towers. The base diameter of this tower is about 13.5 ft (4.1 m), which is just under the vertical clearance permitted on state highway routes. Developing the hub height of steel tubular sections will considerably raise the cost of taller towers. The reason is that the tower base required for taller towers (above 100 m [328 ft]) should be designed by higher-strength steel or segmented base sections, necessitating field assembly.

The effectiveness of the BVA is studied through a series of shake table tests on a 1/13 scaled wind turbine model under wind-wave equivalent loads and ground motions. The control device was installed on the top of the nacelle. Cases of the wind turbine in parked and operational con- ditions are investigated and the dynamic responses of the structure with or without control are compared. Based on the experimental study, the following concluding re- marks can be made: 1) The BVA is consistently effect- tive in mitigating the top displacement, top acceleration, platform stress and bottom stress of the wind turbine tower both under wind-wave equivalent loads and ground motions. The response reduction varies from 15% - 53% in different cases. But the damping device can inhibit a better performance when the structure is subjected to wind-wave equivalent loads. 2) When the turbine is in operational condition, the performance of the damping device is slightly different from the cases when the tur- bine is parked. For wind-wave equivalent loads, the op- eration of the turbine will weaken the effectiveness of the control device whereas it is opposite for ground motions.

Figure 1 describes the methodology adopted for the study. Mode of installation [5], Wind Turbine, Tower [1] and environmental factors like site, wind, wave and depth are fixed as the primary inputs. From the design considerations like mechanics of TLP and performance requirements, a design step was formulated to obtain primary design proportions of tension-leg support. Natural frequencies of the system analogous to six degrees of freedom were calculated. Support parameters were adjusted using parametric study [4- 7], to control natural frequency to requisite limits. Model corresponding to refined dimensions was analysed in DNV Sesam to obtain natural frequencies and RAOs, which were compared with a well investigated tension leg model developed at Massachusetts Institute of Technology (MIT), the NREL/MIT Model [2] to affirm the strength of proposed design procedure.

The detrimental effect of geometric imperfections on the behaviour of thin cylindrical shells under fundamental static loads, and axial compression in particular, is well known in the shells literature [17-19]. However, studies within earthquake engineering that explicitly account for imperfections in shell structures are rare. Known to the authors is only the study of Guo et al. [20] who performed a geometrically and materially nonlinear pushover analysis on an example 53 m high steel wind turbine tower with tapering d/t ratio ranging from 121 to 184. They introduced a single localised ‘dent’ imperfection of up to 5% of the diameter, intended to simulate the effects of an accidental impact, in the upper segments of the tower. However, this choice of imperfection form did not show any significant decrease in the predicted buckling strength, possibly because the most critical region for buckling under their assumed load distribution was at the base of the tower away from the position of the imperfection. This is not thought to be a representative result, and it is more likely that imperfections will be at least as deleterious to the seismic response of hollow metal wind turbine towers as to the static response [4].

The wind turbine tower finite element (FE) model is used for tower dynamic response analysis under wind turbine loads, which is then followed by tower stress analysis for fatigue damage estimation. The tower loads are the power production turbine hub loads in different wind speeds, taking into account the tower door opening and wind directionality through rotation of hub load around tower vertical axis. The full-scale FE model of the wind turbine tower with the height of 71m is developed in ANSYS [14] , based on the partially available information Figure 3. The door opening and its stiffener flange are modelled according to the detailed dimensions obtained from in situ measurements. There are some uncertainties with regard to tower FE modelling, since precise values for some parameters including rotor and nacelle mass properties, tower wall radius and tower wall thickness variations and actual mechanical properties of tower material are due to data protection policy of the manufacturers unavailable.

energy utilisation. The execution of building integrated wind turbines contributes positively to the environment as a climate change mitigation option. Built in environment wind turbines are those located in an urban or suburban environment. They can be integrated into a building and included in the building design from architectural, structural, and economic perspectives. The wind power is gaining more importance due to its low price and it’s friendly to environment and the wind energy and building integration also becomes a very important mode to develop new energy sources. The application of BEWT systems to high-rise buildings can be done in different ways. Five different ways by which turbine can be installed to buildings are discussed in this paper. Both Static and dynamic analysis are done for this models. And the behavior of the buildings are studied. The feasibility of these structures was verified preliminarily by comparing analysis results. Using ANSYS 19.1, both static and dynamic structural analyses were performed. A simplified finite element model that represents the wind turbine tower was created, an ultimate load condition was applied to check the stress level of the tower in the static analysis and for dynamic analysis the rotational velocity of turbine is considered and seismic analysis is also performed along with it. CFD FLUENT is used for the analysis of the building under the action of wind. Key Words: Seismic analysis, computational fluid dynamics

Renewable energy sources have gained much attention due to the recent energy crisis and the urge to get clean energy. Among the main options being studied, wind energy is a strong contender because of its reliability due to the maturity of the technology, good infrastructure and relative cost competitiveness. It is also interesting to note that there are physical limits to the potential height of a wind turbine tower since the mechanical structure of wind turbines are thus very flexible and tend to oscillate. This makes the design of wind turbines a demanding task. In this paper, the oscillation of a wind turbine tower due to imbalance in the masses of the blades is modeled in maplesim and the effect of the tower height on its oscillation was simulated. For a wind turbine with three rotor blades, two of which have masses of 10 kg, a mass moment of inertia of approximately 20 kg/m 2 and one of the

Another and equally important advantage of installing a wind turbine on preheater tower top is low cost wind energy. As we know that installing a ducted wind turbine at a high altitude is always favorable, but the fabrica- tion cost of wind turbine tower will increase so much on high altitude that it will not be economical to install. Hence using the r.c.c preheater tower’s height for wind turbine tower installation on its top, will reduce almost 60% - 70% cost of turbine tower fabrication cost. On the other hand since nearly 11% cost of total cost belongs to grid connection cost, hence using wind turbine output for cement production will eliminate this 11% cost of total cost [6]. The cost break up of total installation cost wind turbine is as follows

Energy plays an important role in everyday life to carry out any task. The non-renewable energy resources such as oil, coal and gas are majorly used as energy nowadays. The main problem behind the non-renewable energy resources are not sustainable and create global warming which is hazardous to the environment. The renewable energy resources are best way to solve this issue. The renewable energy resources such as solar, wind, tidal and biogas are available in abundant and sustainable which can be utilized for the requirement. Wind energy is the purest form of renewable energy which is available highly for production of electricity. This project envisions the design and appropriate implementation of 600W electricity producing wind turbine.

In the data analysis “Excel wind analysis tool” is used. The raw data obtained from NREL is used as an input to the Excel wind analysis tool. The purpose of this tool is to analyze wind data to prove a wind resource exists at a specific location. The spreadsheet is a program to create a Wind Rose graph, as well as a folder containing power curves for various wind turbines. Some important items calculated by the spreadsheet are the average wind speed, capacity factor, and estimated annual energy production. A report sheet is also included, formatted for printing, which summarizes results and displays graphs.

Abstract: This paper presents Design & FEM Analysis of Twisted Blade Micro Wind Turbine. Rapid depletion of fossil fuel resources necessitated research on alternative energy sources. A wind system is a reliable alternative energy source because it uses wind energy to create a stand-alone energy source that is both dependable and consistent. The main objective of this project is to investigate the design and development of micro wind turbines for integration into residential, commercial and industrial complexes. This project mainly focuses on Design of Twisted Blade Micro-Wind Turbine system using computer aided design and FEM analysis technology.

Over the last few years, experience has been gained with floating wind technology. It has evolved from being an academic topic to start delivering sustainable, reliable and supply energy to the grid. Equinor’s Hywind project [4] installed their first full- scale spar buoy floating offshore wind turbine (FOWT) back in 2009 in the North Sea, which became in 2018 the world's first floating wind farm producing electricity to the Scottish grid. [5]. Hitherto, different floating foundations have been proposed [6, 7]. Semi-submersibles [8, 9], barges [10], and tension leg platforms [11, 12] have been developed along with spar buoy- based [13] developments like the DTI-F foundation.

An initial design for four-legged articulated support structure for supporting 5 MW offshore wind turbine to construct in Indian ocean. From the preliminary eigen value analysis of the proposed candidate structure it is seen that the structure’s natural frequency lies much above the limiting values in sea conditions as proposed by different researchers, hence the structure was forwarded for the non linear coupled response analysis. From RAO computations, it was seen that although the system is excited by wind and wave only in surge and pitch, it displays motion in the modes of sway, roll, heave and yaw as well. The system’s response in these modes indicates the coupling of wind turbine with platform motions. Considering the surge motion there is no significant difference is seen in RAOs corresponding to different wind speed which means that turbines dynamic property is not affecting the platforms surge movements. But it is seen that when the wind is 25 m/s and at an encounter frequency in between 2 to 6 seconds, there is a peak is seen in surge response. But while considering the sway motion, according to the varying wind speed RAOs show significant variations. This is due to the damping property of turbine. This concludes that turbines sway motion affects platform sway thereby causing damping. In the case of heave motion we may see significant changes in the RAO plot which shows that the platforms heave motion is affected by the turbines heave motion there by damping is seen in plot. Turbine dynamics have significant influence in Roll RAOs also. In the pitch RAO plot, an irregular curve is seen for 25m/s but all other wind speed have similar curves but in the initial ranges we can see the damping but reaching to the end of curve it becomes aligned. In the yaw plot a peak is seen in the 0 to 10 seconds range, which is a crucial observation but with response analysis it is seen that yaw and heave responses are not at all significant and hence this peak in yaw can be neglected. Wind effect on RAO shows that the aero-hydrodynamic coupling to the system is done effectively, the preliminary aim of the study was fulfilled.