Nowadays, with respect to trend of Kyoto protocol, many producers turn to renewable energy resources. That leads to a fact that more than 75% of new power capacity installations in EU in the year 2015 are renewables. The leading among the... more
Nowadays, with respect to trend of Kyoto protocol, many producers turn to renewable energy resources. That leads to a fact that more than 75% of new power capacity installations in EU in the year 2015 are renewables. The leading among the new renewable energy resources is wind energy. In the last decades, even more wind energy is accommodated by moving offshore. That brings up a problem of more complicated design, which includes new loads to be investigated and modelled. For offshore wind turbines, dominant loads are wave and wind loads. For the substructure itself, the highest impacts have wave-induced loads, as it is submerged at most of its height. As the waves are stochastic and irregular loads, this paper investigates appropriate methods for modelling of the wave loads, in order to achieve a very realistic load model and results. This is only some of the numerous challenges in this area of expertise, which are more accurately investigated in a research plan within the framework of the Innovative Training Network (ITN) AEOLUS4FUTURE, related to reliability of offshore wind energy structures.
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The fatigue limit state (FLS) of fixed offshore wind turbine structures is critical and difficult to handle. As it is the most common design driving criteria for offshore structures, the simulation and calculation of this phenomenon must... more
The fatigue limit state (FLS) of fixed offshore wind turbine structures is critical and difficult to handle. As it is the most common design driving criteria for offshore structures, the simulation and calculation of this phenomenon must be as accurate as possible. Research is needed to improve the current design. There are mainly two design approaches available: Integrated design approach (IDA) and Sequential design approach (SDA). The IDA, described in this paper, considers the coupled structural analysis of a whole wind turbine system exposed to windand wave-induced loads in an aero-hydro-elastic solver. The results given by solver are loads series, which are afterwards used for obtaining the stress series with stress concentration factors (SCF) included. The stresses are processed in terms of rainflow counting and finally, fatigue damage of a critical K-joint is obtained externally, to avoid the use of damage equivalent loads (DEL) as by default in the solver, but to calculate i...
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Nowadays, much attention is payed to the development of renewable energy resources. Wind energy plays a major role in this issue. That is why there is a growing interest for improving the design process of wind turbines at many aspects.... more
Nowadays, much attention is payed to the development of renewable energy resources. Wind energy plays a major role in this issue. That is why there is a growing interest for improving the design process of wind turbines at many aspects. This study compares two types of offshore wind turbines structures, the monopile and the jacket structure, in their dependency on wave load characteristics’ variations. The examined wave characteristics are significant wave height and wave peak period. The jacket structure showed lower influence of increase of wave height to stresses in the cross section at the bottom of the structure compared to the monopile structure. The monopile structure showed slight dependency of stresses on increasing wave frequency, while the jacket structure showed nearly no dependency, due to its more complex geometry and higher stiffness.
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The scientific community is devoting more attention to the wide scope of offshore wind turbine structures. Since such structures are subjected to high level of fatigue loads as well as a large number of load cycles caused by wind, waves... more
The scientific community is devoting more attention to the wide scope of offshore wind turbine structures. Since such structures are subjected to high level of fatigue loads as well as a large number of load cycles caused by wind, waves and turbine operation, the fatigue performance of welded connections is usually a design driving criteria. In this paper, a brief review on experimental fatigue analysis of circular hollow section joints for jacket structures is presented. Special emphasis is given to full-scale experimental testing. In order to face some of the challenges in this area of expertise, an experimental research plan within the framework of the Innovative Training Network (ITN) AEOLUS4FUTURE is introduced, aiming to understand and validate the fatigue performance of circular hollow section joints produced by an automated process, using Tandem MIG/MAG welding.