Fraunhofer-Institut für Windenergiesysteme IWES

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  • Publication
    Influence of rotor blade flexibility on the near-wake behavior of the NREL 5 MW wind turbine
    ( 2024-01-22)
    Höning, Leo
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    Lukassen, Laura
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    Stoevesandt, Bernhard
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    Herráez, Iván
    High-fidelity computational fluid dynamics (CFD) simulations of the National Renewable Energy Laboratory (NREL) 5 MW wind turbine rotor are performed, comparing the aerodynamic behavior of flexible and rigid blades with respect to local blade quantities as well as the wake properties. The main focus has been set on rotational periodic quantities of blade loading and fluid velocity magnitudes in relation with the blade tip vortex trajectories describing the development of those quantities in the near wake. The results show that the turbine loading in a quasi-steady flow field is mainly influenced by blade deflections due to gravitation. Deforming blades change the aerodynamic behavior, which in turn influences the surrounding flow field, leading to non-uniform wake characteristics with respect to speed and shape.
  • Publication
    Deep Learning Enabled Data-Driven Detection of Wind Turbine Operating Conditions Using Transformer Networks
    ( 2024-01-17)
    Sultan, Rubbiya
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    Ahmed, Nourhan
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    Faller, Luca
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    Lichtenstein, Timo
    Test data (1min) Test data (10min) Test data (30min) Training data (1min) Training data (10min) Training data (30min) Precision Recall F1 (calibrated) Prevalence
  • Publication
    Model-Based Analysis of Cure-Induced Stresses for a Short Fiber-Reinforced Epoxy Adhesive Used in Wind Turbine Rotor Blades
    (Fraunhofer Verlag, 2024)
    Holst, Tobias
    As a climate-neutral energy source, wind energy plays a key role in the global energy transition to mitigate climate change. Ensuring a reliable and affordable supply of wind energy requires a deep understanding of materials, structures, and processes both for existing wind turbines and for the future development of ever larger turbines. Bond line cracks in rotor blades often initiate structural blade damage as they propagate into the surrounding laminate. Adhesive shrinkage during cure results in a pre-stressed bond line due to residual stresses which affects the mechanical performance by promoting adhesive cracking. This work generates comprehensive insights into the formation mechanisms of residual stresses in bond lines during cure and their effects on the bond line strength. An analytical residual stress model is developed on an experimental basis, taking into account the relevant adhesive properties and manufacturing boundary conditions. The findings contribute to an improved understanding of the curing process of adhesives and its influence on the mechanical strength of bond lines. The application of this knowledge improves the reliability of wind turbine rotor blades.
  • Publication
    From wind conditions to operational strategy: optimal planning of wind turbine damage progression over its lifetime
    ( 2023-11-20)
    Requate, Niklas
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    Meyer, Tobias orcid-logo
    ;
    Hofmann, René
    Renewable energies have an entirely different cost structure than fossil-fuel-based electricity generation. This is mainly due to the operation at zero marginal cost, whereas for fossil fuel plants the fuel itself is a major driver of the entire cost of energy. For a wind turbine, most of the materials and resources are spent up front. Over its lifetime, this initial capital and material investment is converted into usable energy. Therefore, it is desirable to gain the maximum benefit from the utilized materials for each individual turbine over its entire operating lifetime. Material usage is closely linked to individual damage progression of various turbine components and their respective failure modes. In this work, we present a novel approach for an optimal long-term planning of the operation of wind energy systems over their entire lifetime. It is based on a process for setting up a mathematical optimization problem that optimally distributes the available damage budget of a given failure mode over the entire lifetime. The complete process ranges from an adaptation of real-time wind turbine control to the evaluation of long-term goals and requirements. During this process, relevant deterministic external conditions and real-time controller setpoints influence the damage progression with equal importance. Finally, the selection of optimal planning strategies is based on an economic evaluation. The method is applied to an example for demonstration. It shows the high potential of the approach for an effective damage reduction in different use cases. The focus of the example is to effectively reduce power of a turbine under conditions where high loads are induced from wake-induced turbulence of neighbouring turbines. Through the optimization approach, the damage budget can be saved or spent under conditions where it pays off most in the long term. This way, it is possible to gain more energy from a given system and thus to reduce cost and ecological impact by a better usage of materials.
  • Publication
    Wind turbine nacelle testing: State-of-the-art and development trends
    ( 2023-10-07)
    Siddiqui, Muhammad Omer
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    Feja, Paul Robert
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    Borowski, Philipp
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    Kyling, Hans
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    Nejad, Amir R.
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    Wenske, Jan
    Wind turbine nacelles are complex machines that are designed to operate under extreme loads and harsh environments. Extensive tests are performed throughout their development process to ensure that they can operate with high reliability. As both onshore and offshore wind turbine systems have rapidly evolved, so have the methods for testing the nacelle systems and subsystems. This paper presents the state of the art in wind turbine nacelle testing and the development trends in this field. It discusses the existing test requirements for certification and the different levels of testing that form part of a nacelle system’s development. The latest changes to the nacelle certification requirements are highlighted, along with several important research activities related to drivetrain testing. Future challenges for nacelle testing are identified and their potential solutions are proposed.
  • Publication
  • Patent
    Wälzlager mit einer Ultraschallsensoranordnung zur Überwachung von Laufbahnschäden
    ( 2023-09-28)
    Menck, Oliver
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    Graßmann, Matthis
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    Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
    Die Erfindung bezieht sich auf ein Wälzlager sowie auf eine Windenergieanlage, die ein solches Wälzlager umfasst und auf ein Verfahren zum Überwachen einer Windenergieanlage. Das Wälzlager umfasst einen Innenring (3) mit einer Innenringlaufbahn (3a), einen Außenring (4) mit einer zu der Innenringlaufbahn (3a) opponierenden Außenringlaufbahn (4a) und zwischen dem Innenring (3) und dem Außenring (4) angeordnete Wälzkörper (5a), die auf der Innenringlaufbahn (3a) und der dazu opponierenden Außenringlaufbahn (4a) abrollen. Das Wälzlager umfasst außerdem mindestens eine Ultraschallsensoranordnung (1, 1'), wobei die mindestens eine Ultraschallsensoranordnung (1, 1') eine oder mehrere Ultraschallsensoranordnungen (1') umfasst, die an dem Innenring (3) angeordnet sind, eingerichtet zum Emittieren von Schallwellen durch ein Volumen des Innenrings (3) in Richtung der Innenringlaufbahn (3a) und zum Empfangen von an der Innenringlaufbahn (3a) reflektierten Schallwellen und/oder wobei die mindestens eine Ultraschallsensoranordnung (1, 1') eine oder mehrere Ultraschallsensoranordnungen (1) umfasst, die an dem Außenring (4) angeordnet sind, eingerichtet zum Emittieren von Schallwellen durch ein Volumen des Außenrings (4) in Richtung der Außenringlaufbahn (4a) und zum Empfangen von an der Außenringlaufbahn (4a) reflektierten Schallwellen.
  • Publication
    Database of Short Term Damage Equivalent Loads (DEL) of IWT7.5MW wind turbine depending on wind, TI, yaw and derating
    ( 2023-09-28)
    Requate, Niklas
    ;
    Meyer, Tobias orcid-logo
    Two datasets for short term damage equivalent loads (DEL) and energy production of the IWT7.5 MW research wind turbine (https://doi.org/10.24406/IWES-N-518562) are provided. dataset_Derating is a subset of dataSet_Derating_withYaw. The damage equivalent loads are computed with the rainflow counting algorithm applied to time series loads. They are based on Miner's rule. Further details can be found in: Requate, N., Meyer, T., and Hofmann, R.: From wind conditions to operational strategy: Optimal planning of wind turbine damage progression over its lifetime, Wind Energ. Sci., accepted for publication, 2023. In the paper, the dataset_Derating was used to create surrogate models. A fullfactorial approach to simulate different parameter-combination was applied. Information about the signals and units is provided in the yml files. The range of parameters is given by python code in the yml file. For each set of parameters, 6 different 10 minute-realizations of a turbulent wind field ("seeds") were created. The turbine was then simulated separately for each turbulent wind field. Each folder contains the short term DELs for each 10 minute simulation and the aggregated short term DELs over all 6 wind realizations. Outliers from simulation error were removed. The data was originally intended to create surrogate models of the variation of outputs values throughout the parameter space. Further usage is possible and encouraged.
  • Publication
    Field-Data based Lab Testing of a Wind-Energy Power Converter System: Insights into Cabinet and IGBT-Module Microclimates
    ( 2023-09)
    Zorn, Christian
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    Peters, Jan-Hendrik
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    Hanf, Michael
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    Adler, Johannes
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    Holzke, Wilfried
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    Pelka, Karoline
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    Broer, Christian
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    Fröhling, Sören
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    Kostka, Benedikt
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    Wenzel, Johannes Christian
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    Mertens, Axel
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    Dehning, Kirsten Jonna
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    Zimmermann, Stefan
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    Fischer, Katharina orcid-logo
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    Kaminski, Nando
    IGBT power modules have been equipped with temperature/humidity sensors and integrated into a power converter system from the wind-power application. While exposed to climatic cycles, the power converter has been tested power-in-the-loop in a climate chamber. The test profile is a sequence of actual stress conditions recorded in a wind turbine converter operating in the field. During the tests, the internal conditions of the power modules and the power cabinet have been monitored. The resulting microclimates are examined when varying electrical loads coincide with climatic cycles.