隨著人們對能源的重視，全球能源需求發生了重大變化。無論是因為空氣污染日趨嚴重，還是台灣政府的大力推導和民眾的教育，台灣在離岸風電的努力都被世界關注，這也是本論文的研究動機。本論文修改及利用美國能源局的軟體及朱聖浩團隊的軟體，進行浮式離岸風機的有限元素分析及鋼結構最佳化設計，並以15MW風機為設計案例。首先使用軟件中的自動建模程序進行有限元網格劃分，再將數據文件中每個設計外力的結構網格生成到計算機的目錄中。其中有限元素網格包含浮筒、二次構件和纜繩系統。本論文進行了半潛式離岸風機的模擬與鋼結構最佳化設計，利用靜力分析的外力可以得到模擬的平衡結果，包括內外力的平衡和結構在該狀態下的平衡位置，然後再進行動力分析，最後程式從所有結構分析結果中找出每個構件的合適厚度，並進行浮式離岸風機的最佳化設計。本論文在理論上和數值上都做了詳盡的規劃，亦包含有限元素在浮力分析的驗證。然而，在採用有限元素模型設計半潛浮式離岸風機時，必須特別注意程式收斂性的問題。由於浮式離岸風機的支撐結構僅由纜繩系統控制，與固定式離岸風機完全不同，海浪和風造成的位移很大，整體結構比較不穩定。因此，在設計浮式離岸風機時，纜繩系統將是一個關鍵因素。一旦纜繩斷裂時，整體系統的行為將會難以預測，為此，本論文提供了多種的纜繩配置，供讀者參考。然而，控制浮式離岸風機的垂直位置也是個重要因素，當浮筒的位置過高時，底層直徑較大的浮桶則會受到很大的波浪力；如果浮筒的位置過低時，上層的二次構件則會受到很大的波浪力。這兩種狀況都會導致程式難以設計。本論文中使用的程式皆由朱聖浩教授及其團隊開發，分析程式與研究成果皆屬於公開資源。

With people's emphasis on energy, major changes have taken place in global energy demand. Whether it is because of the increasingly serious air pollution, or the vigorous derivation of the Taiwan government and the education of the public, Taiwan's efforts in offshore wind power have attracted the attention of the world, which is also the research motivation of this thesis. This thesis modifies and uses the software of the US Department of Energy and the software of Ju, Shen-Haw' s team to carry out the finite element analysis and steel structure optimization design of floating offshore wind turbines, and takes the 15MW wind turbine as a design case. First, use the automatic modeling program in the software to divide the finite element mesh, and then generate the structural mesh of each designed external force in the data file to the directory of the computer. The finite element mesh includes buoys, secondary members, and cable systems. In this thesis, the simulation of the semi-submersible offshore wind turbine and the optimal design of the steel structure are carried out. The external force of the static analysis can be used to obtain the simulated balance results, including the balance of internal and external forces and the equilibrium position of the structure in this state, and then perform dynamic analysis, and finally, the program finds out the appropriate thickness of each component from all structural analysis results and performs the optimal design of the floating offshore wind turbine. This thesis has made a detailed plan theoretically and numerically, and also includes the validation of finite elements in buoyancy analysis. However, when using the finite element model to design semi-submersible floating offshore wind turbines, special attention must be paid to the problem of program convergence. Since the supporting structure of the floating offshore wind turbine is only controlled by the cable system, which is completely different from the fixed offshore wind turbine, the displacement caused by waves and wind is large, and the overall structure is relatively unstable. Therefore, the mooring system will be a key factor when designing a floating offshore wind turbine. Once the mooring line breaks, the behavior of the overall system will be unpredictable. Therefore, this thesis provides a variety of cable configurations for readers' reference. However, controlling the vertical position of the floating offshore wind turbine is also an important factor. When the position of the buoy is too high, the buoy with a larger diameter at the bottom will be subjected to a large wave force; Secondary components will be subject to a large wave force. Both of these situations can make the computer program difficult to design. The programs used in this thesis were developed by Prof. Ju, Shen-Haw, and his team. The analysis programs and research results are all public resources.

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