Suspended cable model for layout optimisation purposes in floating offshore wind farms

Abstract

The cable layout optimisation for floating offshore wind farms is a complex task due to the number of elements involved and their nature, such as dynamic cables with buoyant sections. The first step is defining a model of the suspended cables that connect wind turbines between them or to cables on the seabed (risers). A lumped mass model and the finite element method are used to find the static position and mechanical stresses of the cables, keeping a balance between computational time and the quality of the results. The model allows the inclusion of standard ancillary equipment such as bend stiffeners, buoyancy modules, clamps and tethers in order to simulate multiple configurations: double hanging, single hanging (catenary), lazy wave, steep wave and tethered wave. The external actions considered are marine growth and currents and the main cable properties are taken into account to calculate its weight, buoyancy, tensions, moments and drag forces. The information obtained after the simulation includes cable tensions, curvature, laid and suspended lengths and tether tension, when applicable. Next steps include the optimisation of the suspended cables and the full network in the farm.