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Dynamic Analysis of Fixed Bottom Offshore Wind Turbines
Throumoulopoulosv, Amfilochios G. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Loukogeorgakiv, Eva (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Dimitriou, Aristarchos C. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Angelides, Demos C. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh))
ABSTRACT In this paper, a numerical tool (MicroSAS-OWT) for the integrated analysis of Offshore Wind Turbines (OWTs) with fixed-bottom support structure of arbitrary shape is presented. MicroSAS-OWT is developed through the coupling of FAST with MicroSAS. FAST is used for modeling the rotor nacelle assembly, while the tower and the support structure are modeled in MicroSAS. The interface of the two codes is ensured at the tower top. The tool is applied for the case of the NREL 5MW OWT that consists of a monopile support structure with rigid foundation, and is preliminary assessed through comparison of results with the corresponding ones obtained using FAST. Stress analysis of the tower and the support structure is also performed. INTRODUCTION Offshore wind energy represents a very promising kind of renewable energy source. Offshore Wind Turbines (OWTs) are considered nowadays as an attractive alternative solution to the onshore ones offering multiple benefits and addressing effectively the well-known obstacles and problems associated with the latter ones (Henderson et al., 2003; Breton and Moe, 2009; Esteban et al., 2011). The efficient exploitation of offshore wind energy necessitates the successful handling of several challenges related to developmental, economical and technological issues (Musial et al., 2006). Among these challenges, one of the most crucial is the development, investigation, assessment and adoption of new design concepts, especially for the support structure. These new design concepts will allow the placement of OWTs in deeper water and therefore, the operation of larger capacity OWTs. Considering the high complexity characterizing any OWT system, resulting from its inherent characteristics (e.g. variability and intense interaction of components) and from its operation in a complex environment, where different loading sources exist, the development/application of suitable numerical tools is critical for addressing efficiently the previously mentioned challenge.
- North America > United States (1.00)
- Europe (1.00)
A Numerical Tool For the Integrated Analysis of Fixed-Bottom Offshore Wind Turbines
Loukogeorgaki, Eva (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Angelides, Demos C. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Llorente, Carlos (McDermott Inc.)
ABSTRACT In this paper, a numerical tool (MicroSAS-OWT) for the integrated analysis of Offshore Wind Turbines (OWTs) with fixed-bottom support structure of arbitrary shape is presented. MicroSAS-OWT is developed through the coupling of FAST with MicroSAS. FAST is used for modeling the rotor nacelle assembly, while the tower and the support structure are modeled in MicroSAS. The interface of the two codes is ensured at the tower top. The tool is applied for the case of the NREL 5MW OWT that consists of a monopile support structure with rigid foundation, and is preliminary assessed through comparison of results with the corresponding ones obtained using FAST. Stress analysis of the tower and the support structure is also performed. INTRODUCTION Offshore wind energy represents a very promising kind of renewable energy source. Offshore Wind Turbines (OWTs) are considered nowadays as an attractive alternative solution to the onshore ones offering multiple benefits and addressing effectively the well-known obstacles and problems associated with the latter ones (Henderson et al., 2003; Breton and Moe, 2009; Esteban et al., 2011). The efficient exploitation of offshore wind energy necessitates the successful handling of several challenges related to developmental, economical and technological issues (Musial et al., 2006). Among these challenges, one of the most crucial is the development, investigation, assessment and adoption of new design concepts, especially for the support structure. These new design concepts will allow the placement of OWTs in deeper water and therefore, the operation of larger capacity OWTs. Considering the high complexity characterizing any OWT system, resulting from its inherent characteristics (e.g. variability and intense interaction of components) and from its operation in a complex environment, where different loading sources exist, the development/application of suitable numerical tools is critical for addressing efficiently the previously mentioned challenge.
- North America > United States (1.00)
- Europe (1.00)
- Reservoir Description and Dynamics > Reservoir Simulation (1.00)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (1.00)
- Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (0.91)
ABSTRACT In the present paper a multi objective optimization mathematical model of a Floating Flexible System (FFS) subjected to regular incident waves is developed and presented. FFS is considered as a system for both wave energy production and protection. The performance criteria considered for the optimum design of the FFS are the produced power, the protection effectiveness of the area behind the FFS, and the structural integrity of system parts. A mathematical approach is developed, based on genetic algorithms and global criterion method, in order to properly address FFS's design variables towards a most preferable (optimum) design. INTRODUCTION FFS present nowadays one of the most characteristic types of offshore and coastal structures that can be utilized in the sea environment in order to develop modern and sophisticated projects that address new trends and needs and satisfy new requirements. Floating island cities, floating entertainment facilities, floating emergency bases, floating storage bases of oil or water, floating wave energy devices, floating offshore wind turbines and/or sea water desalination plants, floating bridges and breakwaters represent characteristic current and future potential FFSs. The design of an effective FFS in terms of desired performance, properly defined, is the key element for their successful implementation. Performance should include the structural integrity of system parts that compose the FFS and more specifically the avoidance of any structural failure of the connectors of the modules of the FFS. Meanwhile, significant opportunities and benefits have been identified in the area of ocean wave energy due to extremely abundant and promising resource of alternative, renewable and clean energy in the world's ocean (Falnes, 2007). FFS present a major category of wave energy converters that up to now numerate a very large number of proposed and developed energy devices (Drew et al., 2009, Falnes, 2007 and Falcao, 2010).
- North America > United States (0.46)
- Asia (0.46)
- Europe > Greece (0.28)
- South America > Brazil (0.28)
- Energy > Renewable > Ocean Energy (1.00)
- Energy > Renewable > Wind (0.88)
Investigation of the Accuracy of "Time Snapshot" Based Structural Analysis And Design of Jacket Type Platforms
Farmakis, George E. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh)) | Angelides, Demos C. (Department of Civil Engineering, Aristotle University of Thessaloniki (AUTh))
ABSTRACT The focus of this article is the evaluation of the traditional method of time domain analysis regarding its assumption that the maximum stresses of the structural members appear at the same time and specifically, at the time of the base shear maximization. Two procedures are followed for the analysis of identical offshore jacket type models in order to gain adequate data for performing comparisons between them. The first, is the generally used method mentioned above, while the second examines every member independently during time domain simulation and reveals the maximum values of their internal forces and moments whenever they appear. Various comparisons between the two groups of results are performed, and the final conclusions are presented. INTRODUCTION The society's needs for energy often leads to the construction of offshore structures; traditionally for oil exploration and production, and for most recently for wind energy exploitation. According to EWEA (European Wind Energy Association, 2012), 235 new Offshore Wind Turbines in nine wind farms were fully grid connected in the year 2011. Offshore structures are subjected to the wave load, which is dynamic and thus, a need for dynamic analysis arise for their safe design. For the dynamic analysis two main approaches are used, frequency domain analysis and time domain analysis. In the case of Offshore Wind Turbines, a time domain approach is preferable primarily due to the nature of the wind load. Several investigators have dealt with time domain simulation. Kurian et al. (2010) worked on the dynamic behavior of semi submergible platforms. Pollio et al. (2006) investigated the non linear dynamic behavior of risers in the time domain, using an implementation of the Runge-Kutta algorithm. Morooka et al. (2006) demonstrated that time domain can address better riser nonlinearities, while frequency domain analysis makes easier the handling of the solution obtained and requires less computational efforts, in general.
Fatigue Analysis of a Tripod Supporting Structure of an Offshore Wind Turbine
Zacharioudaki-Apelidou, Fotini (Department of Civil Engineering, Aristotle University of Thessaloniki) | Dedonakis, Fotios (Department of Civil Engineering, Aristotle University of Thessaloniki) | Angelides, Demos C. (Department of Civil Engineering, Aristotle University of Thessaloniki)
ABSTRACT Offshore Wind Turbines (OWT) are exposed to loads varying both in time and in amplitude, designating fatigue damage as a main concern. In this paper, an analysis is presented for assessing the total fatigue damage of an OWT tripod supporting structure. The combined effect of wind and wave loading is computed and different loading scenarios are examined to determine the dominating load on the final result. Further investigation is done to assess the influence of different welding profiles of the tubular joints of the structure on the final fatigue resistance. Results are presented and conclusions are drawn, indicating the importance of the combined analysis. INTRODUCTION The geography of Greece consists of numerous inhabited smaller and bigger islands, with energy needs varying throughout the year. This decentralized demand for energy can be addressed by providing the islands with an autonomous source of energy production. Offshore Wind Turbines (OWT) are an appealing alternative to satisfy this need. A solution like this would allow the islands to use their own resources and produce their own energy in an environmentally friendly way. The realization of OWT is a complicated task and an engineering challenge. Several design scenarios have to be taken into account, including extreme load and fatigue load cases. OWT are exposed to critical environmental loads, which designate this kind of analysis essential. Contrary to common offshore structures- such as oil and gas platforms, OWT are not only exposed to dynamic wave loads but also to dynamic loads from the turning rotor of the Wind Turbine. These loads make OWT susceptible to fatigue damage. Loads varying in amplitude, direction and time act on the structure throughout its lifetime, progressively reducing the fatigue resistance. Deeper water depths for installation and turbines of larger size used nowadays, lead to increased loadings upon the supporting structure.
- Europe (1.00)
- North America > United States (0.69)
- Facilities Design, Construction and Operation > Offshore Facilities and Subsea Systems > Platform design (0.92)
- Facilities Design, Construction and Operation > Facilities and Construction Project Management > Offshore projects planning and execution (0.82)
- Health, Safety, Environment & Sustainability > Environment (0.67)