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The Science of Making Torque from Wind (TORQUE 2018)

20 June  |  21 June  |  22 June  |  Events View
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Room: BL.27 Building
Topic: DSE. Poster Session
Form of presentation: Poster
Duration: 75 minutes

Authors:
Fernando Echeverria, Fermin Mallor, Unai San-Miguel

Abstract:
The approach of designing blades as a multi-disciplinar holistic optimization implies important challenges due to the high complexity and diversity of involved engineering fields (aerodynamics, elasticity, controller, loads, etc.). This paper presents a design exploration and statistical analysis, prior to blade optimization, which is crucial to understand the importance of the design variables and the form of the response surface. Furthermore, the combinations of design variables leading to aeroelastic instabilities in the response should be avoided. Logistic regression and innovative Fast and Frugal decision Trees are applied to identify the conditions that cause the undesirable phenomenon.

Authors:
Oğuz Atalay, Altan Kayran

Abstract:
Usage of composite materials in wind turbine blades is a passive mechanism to alleviate fatigue loads besides the reduction in the mass of the wind turbine system. Off-axis plies in bend-twist coupled blades accounts for the passive fatigue load reduction by reducing the effective angle of attack of blade sections. Reduction in fatigue loads is generally represented by damage equivalent load ratios. In the present study, multibody aeroelastic analyses are performed for wind turbine systems for underrated, rated and overrated turbulent wind speeds. It is shown that load reduction can be achieved for the whole range of wind speeds with the usage of bend-twist coupled blades at the cost of power loss at underrated wind speeds which is unacceptable. Thus, the main concern of the present study is first to make performance study of wind turbines with bend-twist coupled blades at underrated wind speeds and then to overcome the power loss while still achieving reduction in damage equivalent loads by the proper modification of the pre-twist schedule of the bend-twist coupled blades together with the generator torque curve across whole range of wind speeds.

Authors:
Matthias Stammler, Sebastian Baust, Andreas Reuter, Gerhard Poll

Abstract:
Blade bearings of wind turbines are large, grease-lubricated rolling bearings that connect the rotor blades with the rotor hub. Rolling bearings are the standard bearing type for this application. Most blade bearings are four-point bearings with one or two rows. Three-row roller bearings with two axial rows and one radial row have higher costs, but are an increasingly used alternative. In this paper, we evaluate the load sharing of such a three-row bearing for a fictive wind turbine of the 3 MW-class, taking account of the stiffness of the interface parts hub and rotor blade. A set of finite-element simulations with varying loads, load angles and pitch angles has been executed to determine the influence of said parameters on the loads of the individual rollers. Curve fits of these discrete load points allow the determination of roller loads for any given parameter combination. One application of the results is the determination of the overall bearing load PEA which is used for fatigue lifetime calculations.

Authors:
Rahmi Erdem Yildiz, Abdurrahman Ekinci

Abstract:
This work presents design and analysis of a shrouded small-scale wind turbine optimized for low wind speeds. In-house FORTRAN codes based on algebraic models are used for preliminary design. QBlade and CFD is used for iterative optimization. Results show that power output can be increased 1.5-2.5 times by using shroud. Additionally, using shroud concept and optimizing for low wind speed solves starting problem of small-scaled wind turbines considerably and increases sustainability of power production.

Authors:
Matias Sessarego, Wen Zhong Shen

Abstract:
Modern wind turbine aero-structural blade design codes generally use a smaller fraction of the full design load base (DLB) or neglect turbulent inflow as defined by the International Electrotechnical Commission standards. The current article describes an automated blade design optimization method based on surrogate modeling that includes a very large number of design load cases (DLCs) including turbulence. In the present work, 325 DLCs representative of the full DLB are selected based on the message-passing-interface (MPI) limitations in Matlab. Other methods are currently being investigated, e.g. a Python MPI implementation, to overcome the limitations in Matlab MPI and ultimately achieve a full DLB optimization framework. The reduced DLB and the annual energy production are computed using the state-of-the-art aero-servo-elastic tool HAWC2. Furthermore, some of the interior dimensions of the blade structure are optimized using the finite-element based cross-sectional analysis tool BECAS. The optimization framework is applied to redesign the NREL 5 MW wind turbine blade to obtain improvements in rotor performance and blade weight.

Authors:
Tonio Sant, D. Buhagiar, R. N. Farrugia, D. Farrugia, F. M. Strati

Abstract:
This paper will compare the hardware costs of the two different concepts that integrate hydro-pneumatic energy storage into floating wind turbine support structures for deep offshore sites.  The analysis is based on a 6 MW wind turbine supported on a tension leg platform. Open source wind measurements for typical North Sea meteorological conditions are used to determine the energy storage capacity requirements to transform the intermittent power output from the turbine into scheduled stepped output at different intervals. A simplified model for sizing the accumulators for both concepts, as well as for the floating platform required to support compressed air, is presented.  The numerical model determines the wall thickness required for the cylindrical vessels housing the compressed air.  Sub-models are integrated to determine the costs of steel and concrete required as well as the costs for ancillary systems.  It is shown that the cost Euro per Kilo-watt hour of storage capacity of both platform concepts decreases for larger accumulator volumes.  Yet one of the two concepts will require a smaller accumulator on the sea bed for a given energy storage capacity and operating compressed air pressure ratio.  This makes this concept a more favourable option for intermediate deep waters.

Authors:
Jone Torsvik, Amir R. Nejad, Eilif Pedersen

Abstract:
This paper discusses analysis requirements for design and operation of main bearings in modern multi-megawatt offshore wind turbines. Through a survey of existing research, offshore wind turbine design trends, design codes, industry practices and standards, we take a systems approach perspective, describing interaction and interfaces between industry stakeholders, as well as a life-cycle perspective, distinguishing between the designer and operator use-cases.

Authors:
Nikolay Dimitrov

Abstract:
This study provides a risk-based, quantitative interpretation of damage severity categories used in wind turbine blade inspection practices. The paper presents a quantitative definition of damage severity categories in terms of a risk matrix, defines procedures for model-based estimation of probability of consequences for specific failure modes, and outlines a decision model for cost-optimal intervention based on assessed damage severity. The workflow and example categorization are demonstrated on two specific faults in wind turbine blades: leading edge erosion damage, and trailing edge crack.

Authors:
Atsushi Yamaguchi, Takeshi Ishihara

Abstract:
In this study, wave hindcasting was performed for one year at Fukushima floating offshore wind turbine demonstration site by using Wave Watch III, and the simulation results were validated by using measurement data. It was found that the use of the computational domain which covers whole the Pacific Ocean improves the prediction accuracy of significant wave height and wave period. By applying correction factors to the extreme value of the significant wave height results in the accurate estimation of the average value and the frequency distribution of the significant wave height. The long term variations of the annual average significant wave height and period as well as the extreme value distribution of the annual maximum wave height are estimated from 10 years of hindcasting data. The estimated extreme wave height with 50 years recurrence period is consistent with the value specified in the national design code for port facilities. A model to describe the joint probability distribution of wind speed, wave height and wave period is proposed. The predicted joint probability distribution based on this model shows good agreement with measurement.

Authors:
Langbein Max, Maja Ruby

Abstract:
To generate power from high-altitude winds, concepts using kites or planes linked to the ground with tether are in development.The most popular high-altitude wind generation concept is one using a flying wing attached to a single tether whose movement generates power by turning a winch. The usual trajectories for power generation consist of a period where the kite distance is increased, and the pulling force enlarged by figure-of-eight movements,  interrupted by a pull-back phase where power is consumed. We compare that with a new concept we introduce here. It uses a triplet of tethers whose length sum is kept more or less constant using differential gears, resulting in a trajectory surface. It does not have a pull-back phase and allows to have similar power output in a closed trajectory. Moreover, starting and landing can be achieved without additional equipment when using a soft kite as wing, and keeping the wing flying without any wind is easier.Also the control can be easier, as one has more degrees of freedom in the force direction and the movement of the kite.Its disadvantages are an increased effort for the ground stations and more restrictions on the location. Also the tether’s air drag is increased.Optimal power generation is compared using an example configuration and state with given wind speed under the assumption of an optimal steering of the generators and the kites. This is done for state snapshots, for example trajectories, wind speeds, and kites.

Authors:
Andreas Schulze, Jànos Zierath, Sven-Erik Rosenow, Reik Bockhahn, Roman Rachholz, Christoph Woernle

Abstract:
This study investigates the performance of passive tuned mass damper (TMD) on the W2E 120/3.0fc wind turbine designed by W2E Wind to Energy. Two different TMD concepts are approached. A TMD is implemented at the tower top to mitigate fore-aft vibrations of the turbine. Further a TMD is mounted on each turbine blade to mitigate out-of-plane vibrations of the blades. The performance of the TMDs is evaluated by means of a detailedvalidated multibody model of the turbine prototype.

Authors:
Burcu Tasdemir, Demirkan Coker

Abstract:
Curved composite geometries which are commonly found in spars and shear webs of wind turbine blades undergo cyclic loading during their whole life. Therefore, fatigue behaviour of these components is a vital phenomenon for a safe design and durability of the structure. These laminated composite components may experience three types of failure: delamination, matrix cracking and fiber breakage. In curved composite parts, delamination and matrix cracking are dominant. In order to obtain an understanding of these failure types, curved composite beam tests are conducted under combined moment/axial loading. The main aim of this study is to investigate the difference between static and fatigue failure of these curved composite structures.  The overall goal of the project, is to contribute to development of design techniques or reinforcement methods to increase fatigue life and durability of these structures.

Authors:
Michael Pagitsch, Georg Jacobs, Dennis Bosse, Stefan Kock

Abstract:
The “Internet of Things” has become more and more common. All kinds of facilities are connected to the world wide web and exchange vast amounts of information. The interconnection of wind turbines and their operators is already state of the art. However, independent and overarching platforms can become providers for additional smart services – information generated from available datasets and action plans derived from it. The present paper lists key requirements for the design of such platforms and proposes solutions to meet the requirements.

Authors:
Meltem Ozyildiz, Can Muyan, Demirkan Coker

Abstract:
The strength analysis of an existing 5-meter composite wind turbine blade using Tsai-Wu and Puck failure criteria is presented. Finite element analysis is performed on the blade under static flap wise loading. ANSYS APDL scripting language is used to implement Puck failure criteria and degradation rules for the progressive failure analysis of the blade. Evaluation and visualization of Tsai-Wu inverse reserve factors and Puck failure exposures in the blade is done with the help of the Ansys ACP/Post module. The results of this study indicate that the blade is not able to resist extreme load case and needs to be redesigned. Root and trailing edge of the blade have the highest risk of failure initiation. Linear analysis using Tsai-Wu and Puck failure criteria is compared with the  nonlinear  analysis using progressive Puck failure criteria. It is concluded  that progressive analysis is necessary for a more realistic simulation of blade failure mechanisms. Results of the analysis will be used to calibrate structural test set-up of the blade.

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