Posters

Abstract

Offshore wind is moving towards deeper waters. While Monopiles are a proven and cost-effective turbine foundation concept in waters up to ~60m, jackets, and in particular floating, foundations remain expensive in deeper waters. Wood Thilsted and Copenhagen Offshore Partners have teamed up to develop a new foundation concept for water depths between 60m and 150m, the Buoyant Guyed Column (BGC). The BGC consists of a buoyant vertical column held in position by moorings and anchors. The buoyancy and mooring systems allow for the column to be material efficient, even in water depths of up to 150m. The BGC concept is currently the object of a patent application.  We carried out an internal Light Integrated Load Analysis (LILA) using the HAWC model and WT's internal Morpheus software, for ground and metocean conditions representative of example sites and water depths.  A combination of mooring line tension and the shear capacity of the BGC pile provide support for the moment produced by the interacting WTG, wave and current forces, driving down the required pile can thickness and diameter.   As a result, a BGC pile (i.e. excluding anchors) for a water depth of 90m in an onerous environment such as the North Sea off the northern coast of Scotland may have a structural weight of only ~2200 MT. Key WTG performance criteria, such as tower top acceleration and displacement at MSL are kept within typical WTG OEM limits.  This work demonstrates that the BGC is a lightweight foundation, resistant to environmental loading. In addition, it is monopile-like, for both design and fabrication, and therefore the supply chain is ready for it. The secondary structures and J-tube arrangement are also the same as they would be for a monopile.