Thesis
Dynamics of mooring system for floating offshore wind turbine (FOWT)
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2025
- Thesis identifier
- T17535
- Person Identifier (Local)
- 201886767
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This study introduces a novel concept for a Tension Leg Buoy (TLB) floating offshore wind turbine (FOWT) system intended to support a 10 MW wind turbine and anchored by an innovative taut mooring system for deployment in water depths of 110 meters in the challenging environmental conditions of the Northern North Sea. The unique design of this system underwent a thorough iterative development process to attain an optimal configuration, followed by a detailed analysis that adheres to the recognized principles and criteria for the design of floating wind turbines. Frequency domain and hydro-aero-servo-elastic time domain analysis carried out by considering wave drift and second order effect. The performance of the 10 MW TLB FOWT utilizing synthetic fibre materials was evaluated in comparison to that using steel wire rope. Furthermore, a benchmarking study was conducted by scaling the current leading technology types FOWT platforms to verify an innovative TLB design. Finally, an examination was conducted to assess the practicality of anchor sharing in the suggested TLB system by analysing the system dynamics within a wind farm. The results of the study indicate that the integration of second-order effects plays a significant role in influencing outcomes. It is imperative to consider second-order effects in order to enhance conceptual design and attain more accurate predictions of forces and responses during the early phases of a project, thus preventing unnecessary overdesign. The optimal design utilizing steel, polyester, and nylon mooring materials effectively demonstrated stability with limited motion responses and satisfied the rule-based limitations including the design criterion for ultimate limit state (ULS) and accidental limit state (ALS). Increased motion responses were found to be associated with decreased dynamic tension in mooring lines that have higher elasticity, while higher dynamic tension was observed in mooring lines made of more rigid materials. This highlights the significance of high stress on steel mooring line. The effect of the wind turbulence on the system responses utilized higher elasticity mooring material was significant. TLB systems with steel and polyester are suitable for applications requiring consistent behaviour due to minimal variability, while TLB systems with nylon may be less reliable for applications necessitating consistent performance. Platforms utilizing catenary mooring systems exhibit more responses when contrasted with those utilizing tensioned mooring systems and show different low-frequency motion behaviour compared to the high-frequency motions experienced by the stiff-mooring stabilised platforms. The environmental forces exerted on motion responses, particularly pitch motion, are more pronounced on the Semi-Submersible platform, leading to decreased power production. Analysing the motion and tension responses that apply loads on common anchors, while considering specific assumptions, can offer valuable insights into the feasibility of anchor sharing for a designed TLB utilizing semi-taut mooring lines.
- Advisor / supervisor
- Tao, Longbin
- Resource Type
- DOI
- Date Created
- 2024
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