دانلود رایگان مقاله انگلیسی طراحی تک ستون برای توربین های بادی دریایی در 10 مرحله - الزویر 2017

ABSTRACT

A simplified design procedure for foundations of offshore wind turbines is often useful as it can provide the types and sizes of foundation required to carry out financial viability analysis of a project and can also be used for tender design. This paper presents a simplified way of carrying out the design of monopiles based on necessary data (i.e. the least amount of data), namely site characteristics (wind speed at reference height, wind turbulence intensity, water depth, wave height and wave period), turbine characteristics (rated power, rated wind speed, rotor diameter, cut-in and cut-out speed, mass of the rotor-nacelle-assembly) and ground profile (soil stiffness variation with depth and soil stiffness at one diameter depth). Other data that may be required for final detailed design are also discussed. A flowchart of the design process is also presented for visualisation of the rather complex multi-disciplinary analysis. Where possible, validation of the proposed method is carried out based on field data and references/guidance are also drawn from codes of practice and certification bodies. The calculation procedures that are required can be easily carried out either through a series of spreadsheets or simple hand calculations. An example problem emulating the design of foundations for London Array wind farm is taken to demonstrate the proposed calculation procedure. The data used for the calculations are obtained from publicly available sources and the example shows that the simplified method arrives at a similar foundation to the one actually used in the project.

 Conclusions

Offshore Wind Turbines are dynamically sensitive structures as their natural frequency is close to the forcing frequencies imposed by wind, wave, and mechanical and aerodynamic loads at the frequency of rotation (1P) and blade passing frequency (2P/3P). Therefore the design of foundation needs careful consideration not only from strength consideration but also from stiffness consideration as the deformation (SLS criteria) and dynamics are mainly governed by the stiffness. The load acting on the wind turbine is complex due to variable operation of the rotor during the 20–30 years of design life and uncertainties related to wind and wave misalignment. Load cases have been proposed to obtain foundation design loads. It has been shown that the loads are a functions of the site characteristics (wind, wave and the water depth) and the type of the turbine. The design of monopiles requires iteration and involves knowledge from many disciplines and therefore a flowchart is presented to capture the interdependency of the parameters and the many disciplines. All the procedure can be implemented through a series of spreadsheets. An example problem is taken to show the application of the simplified method taking an example in similar conditions than those at the London Array wind farm. The resulting pile design is similar to the actual design at the site.