Feasibility study on suspended inter-array power cables between two spar-type offshore wind turbines

Abstract

The present study investigates the feasibility of suspended inter-array cabling between two floating offshore wind turbines. In these cable configurations, the power cables do not touch the seabed and are kept afloat midwater below the sea surface using buoyancy modules. The floating offshore wind turbine (FOWT) used is the OC3-Hywind. The present study considers power cables of different sizes having cores with different materials, copper and aluminium. Lightweight cables have been found to be generally better suited for suspended configurations than heavy cables. Furthermore, suspended configurations using buoys show significantly lower maximum effective tensions than configurations with buoyancy modules attached. The minimum bending radius is low for configurations with buoys, whereas it is high for configurations with buoyancy modules. Power cable excursions can be significant but never exceed the mooring line anchor positions of the FOWTs. The standard deviation of the hang-off angles of the power cables from the FOWTs is more significant for load cases (LCs) at rated wind velocities than for extreme LCs where the turbine rotor stands still. It indicates that the motions of the FOWTs influence the power cable. Cost reductions can be achieved compared with a configuration where the power cable lies on the seabed.