#Case study floating foundation wind turbine code#
The following year, the Offshore Code Comparison (OC3) project was established to verify the accuracy and correctness of the most commonly used numerical codes for coupled analysis of offshore wind turbines. This wind turbine is a conventional three-bladed upwind variable-speed variable blade-pitch-to-feather-controlled turbine. In 2009 the US National Renewable Energy Laboratory (NREL) developed the specifications of a representative utility-scale multimegawatt turbine now known as the “NREL offshore 5-MW baseline wind turbine” to support concept studies aimed at assessing offshore wind technology. The experimental data showed relatively good agreement with the numerical results obtained in well-known models, but, again, some key information concerning the detailed characteristics of the exact model was not released. The model was tested in irregular waves and turbulent wind speed and various control strategies were adopted. In 2006, a 1:47 scale model of a 5-MW spar floating wind turbine was tested at the Ocean Basin Laboratory of Marintek, in Trondheim (Norway). The project, called “Hywind Demo”, has proved the technical feasibility of the spar configuration for floating offshore wind turbines, but neither the detailed design characteristics of the offshore wind turbine, nor the recorded field data are the property of the company and confidential. For example, a full-scale prototype of a 2.3MW spar floating offshore wind turbine was installed in 2009 by Statoil, off the coast of Norway, on a water depth of about 200 m. But not all the data are freely available. Up to now, several small-scale and large-scale experimental activities have been conducted on spar support structures for offshore wind turbines, aimed to prove the feasibility of the concept and validate the corresponding numerical models. Clearly, such projects are even more expensive and usually represent pilot activities, which are carried out by big companies and/or public bodies for demonstration and commercial purposes, and whose results are rarely publicly available. On the other hand, large-scale activities (1:1–1:10) are carried out in open sea and allow to represent all the relevant features of the offshore wind turbines, including turbine-support interaction, mooring system and grid connection, in relevant operational conditions. The good news is that this kind of setting, a controlled environment, allows to achieve very precise and reliable data, but at the cost of being relatively expensive (high rental fees of the basins is a main cost), a key factor for the duration of the experiments, and still limited in representing all the relevant physical phenomena at scale level, which may alter significantly the dynamic behaviour of the model with respect to the full-scale structure. Traditional small-scale activities (1:50–1:100) are carried out in a controlled environment such as wave tanks and ocean basins, where the desired wind-wave conditions can be reproduced, to measure the dynamic response of the structure and to calibrate the numerical model.
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How do you get experimental data for a huge off-shore wind turbine? Do you actually build one?Broadly speaking, there are two kind of experiments, namely small-scale and large-scale ones and, in some cases, yes, you build a full-scale wind turbine. While such models are usually basically numerical codes, experimental activities play a crucial role for their validation. The implementation of such concepts requires a significant amount of research in the development of reliable dynamic models, able to represent the coupled behaviour of the floating wind turbines. In the case of the offshore wind industry, as there are several advantages in moving offshore wind energy production towards deep waters, including the availability of larger areas, stronger and steadier winds, and the reduction of visual and acoustic impact, some new challenges appear. They are used by several industries, some have been in business for decades, like those dedicated to oil and gas, some are newer, like renewables (wind, wave, tidal), and there are still some other uses, like ports, while there is a constant flow of new ideas that imply their use in a near future. Floating structures are becoming increasingly popular.