City Research Online

Abstract

Locating wind turbines on floating platforms offshore would allow tapping an immense wind resource available in a deep sea. A realisation of this potential, however, requires cost effective floating platform designs that can compete with other energy sources. To reduce the large capital cost associated with construction, the design of such platforms will need a reliable and sophisticated design tool that can perform load and response analysis in a comprehensive and fully integrated manner. This thesis presents an integrated nonlinear model for performing load and response analysis of a tension-leg-platform wind turbine that is being considered as a most promising concept to harness wind energy in a moderately deep sea (80m to 200m). It presents the formulation for evaluating various external loads acting on each component of a floating wind turbine considering nonlinear interaction among them. The formulations for various external loads and the motions are developed and solved, and the results are used to demonstrate the significance of the hybrid hydrodynamic model suggested in this thesis as the main contribution. The most discerning feature of the hybrid hydrodynamic model is, it employs fully nonlinear potential theory for wave kinematic prediction and non-diffracting potential theory for wave force calculation. This feature enables to study the nonlinear loads and responses of the floating wind turbine subjected to extreme waves resulting from the nonlinear evolution in a random sea environment which linear and second order wave theories fail to predict, as evidenced by many experimental studies. The model predicts the responses of a floating wind turbine for the given environmental condition which could be time history of wind speed and wave surface derived either from existing site-specific spectra or record of an actual arriving storm event. Therefore, the model can be used to analyse structure during both pre and post construction stage. During the pre-construction stage, the model can be used to optimize the structure's geometry whereas, during the post construction stage, the model can be used for predicting costly wind turbine's performance under actual storm event, to issue warning for planning its evacuation or arranging precautionary measures, to minimize damages to it and its supporting structure including stationkeeping system. Thus, the model can be used for optimizing CAPEX as well as OPEX and hence the LCOE for the concerned floating wind turbine system.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > Q Science (General) Q Science > QA Mathematics T Technology > TJ Mechanical engineering and machinery
Departments:	Doctoral Theses School of Science & Technology > School of Science & Technology Doctoral Theses School of Science & Technology > Engineering

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