Research on Support Structures in the German Offshore Wind Farm alpha ventus (original) (raw)
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Support Structures for Offshore Wind Turbines–A Holistic Design Concept–
Within the optimisation process for offshore wind energy converters (OWEC) one essential part comprises the support structure. At the German test field "alpha ventus" twelve turbines shall be installed in 30 meter water depth where all loads of wind, turbine and waves have to be carried into load-bearing ground. In particular these aspects become more important since thousands of OWECs are planned in the North and Baltic Sea. The German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) is funding "alpha ventus" with the research initiative RAVE. Priority objective of the RAVE project GIGAWIND alpha ventus, which is presented here, is cost reduction for OWEC support structures, which means towers, different types of substructures and foundations. This can be divided in designing lighter support structures on the one hand (material cost) and in optimising the design process on the other hand (personnel cost). Because of the interdisciplinary orientation of the project coverage of all civil engineering problems is intended.
Uncertainties in the design of support structures and foundations for offshore wind turbines
Renewable Energy, 2014
sector, some uncertainties have not been identified yet; these will be discussed in the paper with the aim of achieving an adequate and sustainable growth of the offshore wind technology. 2. Design requirements The design of foundations and support structures of a wind turbine generator is very complex (Fig. 2 clarifies the meaning of "foundation" and "support structure" to be used along the paper). This implies taking into account numerous factors. Firstly, the different loads to consider for the structural design: wind turbine generator weight and loads due to the wind action, wave and current loads, operation and maintenance loads, etc. Also it is essential to consider terrain conditions and its main properties, construction and operation issues, and so on. The effect of all these issues, among others, makes the design of these structures very complex the design. However, there are some international recommendations and standards focused on this. In force and current recommendations and standards for support structures and foundations design, with more relevance and use in the offshore wind industry, are the following ones:
Structural engineering & mechanics, 2010
Offshore wind turbines are relatively complex structural and mechanical systems located in a highly demanding environment. In the present paper the fundamental aspects and the major issues related to the design of these special structures are outlined. Particularly, a systemic approach is proposed for a global design of such structures, in order to handle coherently their different parts: the decomposition of these structural systems, the required performance and the acting loads are all considered under this philosophy. According to this strategy, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessments in various sub-problems, which can be solved by means of sub-models at different levels of detail, for both structural behavior and loads simulation. Specifically, numerical models are developed to assess the safety performances under aerodynamic and hydrodynamic actions. In order to face the problems of the actual design of a wind farm in the Mediterranean Sea, in this paper, three schemes of turbines support structures have been considered and compared: the mono pile, the tripod and the jacket support structure typologies.
Design of a new foundation for Offshore Wind Turbines
2004
The gravitation platform and the monopile have in the previous major offshore wind turbine projects been dominating. A four-year research and development project has proven the bucket foundation to be feasible in suitable soil condition in water depth from near shore to app. 40 meters. A prototype was installed at the test field in Frederikshavn in late 2003, with a 3 MW wind turbine in normal operation. The R&D work is continued the complete the bucket concept and having the design standards for the construction and installation methodologies recognised. The design saves about half of the steel weight as compared to a traditional pile foundation, it is much easier to install and it can easily be removed when the wind turbine is taken down. However, the new design is suffering from uncertainties in the accumulated fatigue in the both the steel structure and the surrounding earth material. Therefore an on-line monitoring system has been utilized on the 80 m high operating test 3 MW wind turbine. It is explained how the system is being used to obtain mode shapes and modal parameters during different operating conditions, and how the response measurements are being used to improve the estimation of fatigue.
REDWIN –REDucing cost in offshoreWINd by integrated structural and geotechnical design
Journal of Physics: Conference Series
The cost of offshore wind energy production has to be reduced continuously to improve its competitiveness compared to other energy sources. To contribute to this goal, a 4year research project REDWIN-REDucing cost of offshore WINd by structural and geotechnical integrated design-is currently ongoing, addressing the challenge of integrating the geotechnical discipline in the design process. The project aims to develop foundation and soil models to be used in dynamic time-domain analyses of offshore wind turbine structures. A library of models has been developed for representation of the most common foundation types. The models can be applied to different ground conditions by site-specific model input. To make the models applicable for practical usage, it has been important to balance the need for computational effectiveness against the need for accuracy. Studies so far indicate that the foundation models improve the accuracy in the integrated analyses.
A Glance at Offshore Wind Turbine Foundation Structures
Brodogradnja, 2016
Energy poverty and climate change are crucial issues we face in our societies. Offshore wind energy has been a reliable solution to both of these problems-solving our growing energy problems while reducing CO2 emission. Innovative foundation design is one of the setbacks faced by this industry. Designing and constructing a cost effective offshore wind farm is greatly hampered by technical and infrastructural challenges, especially in foundation structures. This paper provides a detailed overview of issues related to this problem, with the aim of eliminating the frequent misunderstandings which can arise among engineers and investors working in the offshore wind energy sector. It begins by investigating the latest data and recommendations regarding the design and deployment of various kinds of offshore wind turbine (OWT) foundations. It provides a framework which enables us to study the different OWT foundations, including prototypes and their limitations. Various structural failure modes are highlighted and corrosion measures are presented. Moreover, various removal methods of support structures are put forward. Finally, this paper presents the setbacks preventing the spread of offshore wind energy and the future works for offshore wind energy applications.
Wind Engineering, 2010
Offshore wind turbines are relatively complex structural and mechanical systems located in a highly demanding environment. In this study, the fundamental aspects and major issues related to the design of such structures are inquired. The system approach is proposed to carry out the design of the structural parts: in accordance with this philosophy, a decomposition of the system (environment, structure, actions/loads) and of the structural performance is carried out, in order to organize the qualitative and quantitative assessment in various sub-problems. These can be faced by sub-models of different complexity both for the structural behavior and for the load models. Numerical models are developed to assess the safety performance under aerodynamic and hydrodynamic actions. In the structural analyses, three types of turbine support structures have been considered and compared: a monopile, a tripod and a jacket.
Structural Evaluation of the DeepCWind Offshore Wind Foundation
Frattura ed Integrità Strutturale, 2019
Wind power technologies are being used as a mean of harvesting the energy from the wind with low carbon impact and with great potential to contribute to a new energy paradigm. Great benefits may arise from the use of offshore turbines, such as having a reduced visual impact, if far enough from the coast, or being able to produce more energy due to the use of bigger turbines. Current challenges for these technologies include producing a stable and profitable platform that allow turbines to be installed in deep waters, meaning that these solutions need to be of floating type. An example of such structure is the foundation developed by the DeepCWind consortium, which is evaluated for its structural integrity on this document. The evaluation consists of modal and static/transient analyses, according to a selected Design Loading Case, which is defined for the certification of wind turbines' offshore foundations. The objective is to observe how this structure would perform when subjected to a simulated real life loading. The DeepCWind foundation exhibited great difficulties enduring the applied loads. Therefore, the structure was reinforced in order to safely undergo the required design loading case.
Journal of Coastal Research, 2018
The structural typologies used nowadays in offshore power generation mainly depend on the bearing capacity of the foundation, the sea depth and wave conditions, the characteristics of the offshore wind farm and the impact on the landscape. The use of gravity base structures (GBS) or other type of structures is subject to these input data. The aim of this paper is to ease the decision-making related with the GBS design, by applying different calculation schemes in the two different hydrodynamic domains, D/L<0.20 (Morison) and D/L>0.20 (Diffraction); observing how the models may be complemented in the previous design, by means of dynamic pressure schemes derived from the mechanic of waves. For that purpose, three case studies are raise; the first one, assuming that the structure is a vertical seawall submitted to a quasi-stationary diagram of hydrodynamic pressures and applying the Goda´s theory; the second one, assuming a model of inertial and drag forces, applying the Morison´s theory; and finally, the third case propose the use of the Goda´s theory in the section near foundation, and the Morison theory in the section of shaft, observing the level of trust and the adjustment of this typology of structures. This innovative approach can be used as an advanced guideline to ensure a suitable design of GBS for locations with sea depths between 20 to 40 meters in which it is expected the implementation of this structural typology, and on the other hand, to identify if those locations are suitable for the implementation of GBS.
Structural evaluation of the DeepCWind offshore wind platform
Frattura ed Integrità Strutturale, 2020
Wind power technologies are being used as a mean of harvesting the energy from the wind with low carbon impact and with great potential to contribute to a new energy paradigm. Great benefits may arise from the use of offshore turbines, such as having a reduced visual impact, if far enough from the coast, or being able to produce more energy due to the use of bigger turbines. Current challenges for these technologies include producing a stable and profitable platform that allow turbines to be installed in deep waters, meaning that these solutions need to be of floating type. An example of such structure is the foundation developed by the DeepCWind consortium, which is evaluated for its structural integrity on this document. The evaluation consists of modal and static/transient analyses, according to a selected Design Loading Case, which is defined for the certification of wind turbines' offshore foundations. The objective is to observe how this structure would perform when subjected to a simulated real life loading. The DeepCWind foundation exhibited great difficulties enduring the applied loads. Therefore, the structure was reinforced in order to safely undergo the required design loading case.