Deeply Embedded Ring Anchor System for Floating Offshore Wind Turbines

Floating offshore wind turbines comprise a floating unit, typically a semi-submersible or spar structure, attached to anchors in the seabed using catenary, taut, or tension-leg moorings that, respectively, impose horizontal, inclined or vertical loads on the anchor. However, existing anchor types are often not optimal for certain combinations of load angle, load duration, and seabed soils, which can limit the number of viable anchor solutions and increase project costs. A deeply embedded ring anchor developed in this research is intended to achieve major reductions in anchor costs. The key to reducing anchor costs is increased efficiency (load capacity/anchor weight). Arrays of wind turbines offer a second primary source of anchor cost reduction: shared anchors. This project will develop: high anchor efficiency through deep embedment, effective installation-follower- keying systems to achieve this embedment, and anchors amenable to shared systems. A project goal is to reduce single anchor costs by 75% relative to conventional anchors through improved efficiency, with an additional 75% reduction when shared anchors are possible. The deeply embedded ring anchor has several attractive features, including its high geotechnical efficiency, which leads to a compact anchor. This small size provides benefits such as requiring less demand on port facility marshaling areas, smaller handling equipment, and smaller vessels for transport and anchor installation. The applicability of the proposed anchor to various mooring systems and its shared-anchor potential can mitigate the steel mooring supply chain issues by reducing the required mooring chains or utilizing alternative synthetic materials. Thus, the high geotechnical efficiency and multiline potential of the suggested anchor system can be key features that reduce the nation’s CO2 emissions by reducing the demand for material, fabrication, and transport vessels.