重力式安裝錨於臺灣海峽之可行性評估

Abstract

近年來，風電開發商將重心轉向深海域發展離岸風電，為考量其成本及發電效率，考慮採用浮動式風機。浮動式風機主要以繫泊系統中之錨碇固定於海上，相關可行之錨碇技術眾多，其中重力式安裝錨中魚雷錨最為常見，除了經濟及安裝快速，還有易導入本土化產業鏈的優勢。如今魚雷錨的應用案例皆於超過100公尺水深及海床為黏土之環境條件下安裝，而在臺灣海峽70公尺水深及海床為粉土質砂土之環境條件下是否達到其安裝仍需進行討論。 本研究先行透過計算流體力學軟體STAR-CCM+，基於有限體積法之數值模擬，針對大型魚雷錨進行水動力分析，除此之外將錨鍊及傾斜情形納入考量，探討魚雷錨在自由落體時的距離與速度之變化。在海床貫入行為的分析中，藉由模型錨試驗以輔助文獻整合之結果，推估出經驗公式，試驗將模型錨的直徑及長度固定，以四種不同幾何形狀(圓錐、子彈、拋物線、橢圓)之頭部分別進行投放試驗，比較模型錨於砂層中的貫入行為。 結果得到在長徑比於15-17範圍中，魚雷錨的其餘設計參數差異對其在50公尺落距中，能達到的速度並不會有過大差異，其中，錨鍊及傾斜行為造成相當程度之影響，不可忽略；而模型錨之室內貫入試驗顯示，當頭部形狀為30度圓錐時具有相當優良的貫入行為。綜合以上分析結果，魚雷錨具有價格經濟、安裝迅速等優勢，在臺灣海峽以砂或粉土質砂為主的環境條件下，魚雷錨能夠達到足夠的動能完全貫入海床，故初步評估魚雷錨能夠應用於臺灣海峽，但對於鰭片在貫入深度的影響，以及其在砂質或粉土質砂海床中的錨碇力估計方法，應進一步投入研究建立。

In recent years, offshore wind power developers have been exploring the use of floating offshore wind turbines (FOWT). These turbines are anchored to the seabed using various technologies. One common type of gravity installed anchor is the torpedo anchor, which is cost-effective, easy to install, and can be integrated into the local industry. However, previous applications of torpedo anchors have been limited to water depths of over 100 meters with the seabed is silty sand. It is necessary to study whether these anchors can be used in the Taiwan Strait where the water depth is 70 meters and the seabed consists of sandy soil. This study conducted hydrodynamic analysis using computational fluid mechanics software to investigate large torpedo anchors. The analytical method is based on the calculation of the finite volume method. The velocity and distance of the anchor during free fall were also considered. Empirical formulas were derived from actual tests and existing literature. The results showed that the design parameters of a typical torpedo anchor did not significantly affect the achieved velocity, but did affect the behavior of the anchor chain and tilting. The model anchor tests revealed excellent penetration behavior when the head shape was conical at a 30-degree angle. Torpedo anchors offer advantages in terms of cost-effectiveness and quick installation. Furthermore, considering the environmental conditions in the Taiwan Strait, torpedo anchors can attain sufficient kinetic energy to fully penetrate the seabed. Therefore, torpedo anchors can be applied to the Taiwan Strait.