半潛式浮台水下基礎之陰極防蝕設計與評估

Abstract

台灣西部沿海擁有開發離岸發電之潛能，位處於亞熱帶的台灣，高溫高濕度高鹽分形成高腐蝕環境，海上結構物受腐蝕影響程度大，故腐蝕防治為離岸風電中相當重要的一環。因台灣西部沿海近岸淺水區開發逐漸飽和，未來將往近海深水區作為離岸風場開發區域，離岸風機平台也由結構較為簡單之固定式水下基礎轉變至幾何形狀較為複雜之浮動式平台，如半潛式平台(Semi- submersible)。離岸風機腐蝕防治方法主要有腐蝕餘裕量設計、塗層系統及陰極防蝕。其中，陰極保護受海水溫度、鹽度及溶氧量等因素影響，此設計較其他防蝕方法困難和複雜。故為了解浸沒於水下結構物是否能受到完整的陰極防蝕保護，本實驗採用邊界元素法（Boundary element method）為基礎的模擬軟體- Beasy CP來模擬浮動式平台水下基礎受陰極防蝕系統的保護情形，並透過模擬來找出其保護效力最佳之設計。研究結果可得出陰極及陽極之間的距離在0.5公尺處且陽極塊交錯擺放可獲得較好的防蝕效果。而陰極防蝕系統中陽極塊的擺放恐會造成干擾的情形發生，而降低防蝕效果。於任何結構物下的陽極塊之間擺放距離小於3公尺將會抑制陽極塊保護電流的釋放。而陽極干擾情形又會隨著陰極結構物大小改變發生位置也會有所不同。

The western coast of Taiwan has the potential to develop offshore wind power. However, Taiwan is located in subtropical which is a highly corrosive environment caused by high temperature, high humidity and high salinity. Offshore structures are greatly affected by corrosion without question. Therefore, corrosion prevention is an important part of offshore wind turbine. The development of offshore wind turbines has gradually transferred from shallow-water areas to deep-water areas. The supported structure of offshore floating wind turbine is more complicated than fixed structure, such as jacket. Offshore wind turbine corrosion prevention methods mainly include corrosion allowance design, coating system and cathodic corrosion protection. Among them, cathodic protection is affected by factors such as seawater temperature, salinity and dissolved oxygen, and its design is more difficult than other methods. In order to know whether the submerged underwater structure is completely protected by cathodic protection, this research uses the simulation software Beasy CP based on the boundary element method to simulate the cathodic protection situation of the floating platform and design the most suitable corrosion protection. The research results indicated that when the distance between the cathode and the anode is 0.5 m and the anode blocks are staggered placed could achieve better protection. The placement of the anode in the cathodic protection system may cause anode interference and reduce the cathodic protection effect. Placing the anode blocks less than 3 meters apart under any structure will inhibit the release of the anode block protection current. The anode interference situation will also vary as the size of the cathode structure changes.