A new semi type floating offshore wind turbine platform called Y-Wind is developed to support a 5MW wind turbine, considering various design aspects from engineering through to installation, which can reduce the CAPEX. The platform is designed to achieve the integration of the tower and rotor to the platform at quayside in a US shipyard. Also a proper lightship draft is considered in the early platform design phase to enable wet-tow from the yard to the installation site with no dedicated extra equipment, as the majority of shipyards in US east and west coasts may not be able to accommodate floating wind platforms with deep lightship draft.
The Y-Wind platform with damping plates consists of four columns having the same diameter. No deck structures and braces are used. Center column supports a 5MW wind turbine and three other offset columns connected to the center column by respective pontoon are optimally placed such that the hydrostatic stability and minimal static heeling angle by wind turbine peak thrust are ensured. The platform is moored with three catenary lines with a sufficient length to avoid the uplift at the anchor.
Time domain coupled simulations under typical US offshore metocean conditions are conducted to assess the platform dynamic responses including motions, accelerations, and mooring tensions for the design load cases of the power production, 50-yr extreme and 500-yr survival conditions in accordance with ABS floating offshore wind turbine guide. The present design is checked against the ABS design criteria and confirmed to comply with the design requirements. Also significant reductions of motions are observed due to the damping plates, which also results in reducing the mooring line tensions. Preliminary global structural analysis was performed to assess the stress ratios of the primary structures.