Load Reductions And Optimizations On Tension-Leg-Buoy Offshore Wind Turbine Platforms

The stiffness-controlled Tension-Leg-Buoy (TLB) platform potentially has low steel mass and limited dynamic response compared to other deep water wind turbine platforms. The higher anchor loads, however, may offset the potential cost advantage of the TLB. The aim of this paper is to address important aspects of this issue, such as the Excess Buoyancy (EB) of the platform and the mooring line layout. The EB is required to keep the mooring lines taut throughout all events, and is therefore strongly influenced by the wave loads. An attempt to reduce the wave loads with a space-frame section in the wave action zone is presented. Optimization routines are utilized to adjust the geometry and mooring line layout for lower cost. The tools and procedures used for the optimizations and the resulting TLB conceptual design improvements are presented. As the trade-offs between different conceptual designs are studied closer, optimization should be helpful to enable more detailed comparisons under similar site specific conditions.