A Reference Tension-Leg Platform for a 15-MW Floating Wind Turbine

Abstract We have developed a tension-leg platform (TLP) design for the IEA Wind 15-MW reference turbine to facilitate TLP research. The design is representative of existing TLP platform topologies, and the tendons are high-modulus polyethylene rope, which is already prominent in the floating wind industry. The design is sized separately for water depths from 200 m to 1500 m in 100-m increments, allowing use in a range of applications. The TLP has a central column with three radial pontoons, each with two tendons at the end. Diagonal braces between the pontoons and central column reduce bending moments. Vertical cans at the pontoon ends provide hydrostatic stability at port and during tow-out. We explored the effects of a variety of platform geometry parameters using the RAFT frequency-domain model and considered common design constraints, including limits on natural frequencies, motions, and strength safety factors. After identifying which design parameters are most important to vary with depth, we performed a simplified optimization over the range of depths, using RAFT in the loop to model the TLP response. The resulting designs meet the specified constraints and approximately minimize the substructure and tendon cost. The constraints on maximum pitch natural period, pontoon bending strength, and tow-out stability were dominant. Platform surge and pitch motions stayed well within their limits. A brief comparison with the time-domain model OpenFAST suggests the dynamic response can be explored further but the basic constraints are reliably met. These initial designs should be refined while accounting for nonlinear hydrodynamic effects, substructure flexibility, and more load cases.