Abstract
Not only the driving for offshore wind energy capacity of 12 GW by Korea’s Renewable Energy 2030 plan but also the need for the rejuvenation of existing world-class shipbuilders’ infrastructures is drawing much attention to offshore wind energy in Korea, especially to the diverse substructures. Considering the deep-sea environment in the East Sea, this paper presents detailed modeling and analysis of spar-type substructure for a 5 MW floating offshore wind turbine (FOWT). This process uses a fully coupled integrated load analysis, which was carried out using FAST, a widely used integrated load analysis software developed by NREL, coupled with an in-house hydrodynamic code (UOU code). The environmental design loads were calculated from data recorded over three years at the Ulsan Marine buoy point according to the ABS and DNVGL standards. The total 12 maximum cases from DLC 6.1 were selected to evaluate the structural integrity of the spar-type substructure under the three co-directional conditions (45°, 135°, and 315°) of wind and wave. A three-dimensional (3D) structural finite element (FE) model incorporating the wind turbine tower and floating structure bolted joint connection was constructed in FEGate (pre/post-structural analysis module based on MSC NASTRAN for ship and offshore structures). The FEM analysis applied the external loads such as the structural loads due to the inertial acceleration, buoyancy, and gravity, and the environmental loads due to the wind, wave, and current. The three-dimensional FE analysis results from the MSC Nastran software showed that the designed spar-type substructure had enough strength to endure the extreme limitation in the East Sea based on the von Mises criteria. The current process of this study would be applicable to the other substructures such as the submersible type.
Highlights
Among the renewable energy resources, wind energy has been growing steadily and securing the competitiveness of price through its lowering levelized cost of energy (LCOE)
Onshore wind has shown large cost reductions over decades with economically large-scaled wind turbine size and wind farms construction in addition to the improvement of the technologies and logistics, which lead to a preferable choice among other alternative renewable energy sources against fossil fuel energy [1,2,3,4]
Finite element modeling was constructed as of possible toand the the conceptu was modeled as the lumped mass element to the centerasofclose gravity the rotor nacelle assembly (RNA), and basic specification of the spar-type substructure, and all structural componen tower component was modeled as shell elements for the wind load application
Summary
Among the renewable energy resources, wind energy has been growing steadily and securing the competitiveness of price through its lowering levelized cost of energy (LCOE). The onshore wind farms have been facing many limitations for large-scale wind turbines installation due to the visibility issue, noise emission, transportation difficulty, and other opposition aroused from residents Due to their surrounding land conditions, onshore wind turbines are more likely to have lower capacity factors which could decrease the overall power performance [5,6,7]. The bottom-fixed offshore wind turbines exclusively dominate todays offshore wind energy market and the substructure types (monopile, gravity, and jacket) shown in Figure 2 are mostly utilized depending on the soil condition and water depth [13]. Type, semi-submersible type including barge type, and TLP type as shown in Figure 1 [24]
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