Integrated structural optimisation of offshore wind turbine support structures based on finite element analysis and genetic algorithm

Abstract

By accounting for almost 25% of the capital cost of an OWT (offshore wind turbine), optimisation of support structures provides an efficient way to reduce the currently high cost of offshore wind energy. In this paper, a structural optimisation model for OWT support structures has been developed based on a coupled parametric FEA (Finite Element Analysis) and GA (Genetic Algorithm), minimising the mass of the support structure under multi-criteria constraints. Contrary to existing optimisation models for OWT support structures, the proposed model is an integrated structural optimisation model, which optimises the components of the support structure (i.e. tower, transition piece, grout and monopile) simultaneously. The outer diameters and section thicknesses along the support structure are chosen as design variables. A set of constraints based on multi-criteria design assessment is applied according to standard requirements, which includes vibration, stress, deformation, buckling, fatigue and design variable constraints. The model has been applied to the NREL (National Renewable Energy Laboratory) 5MW OWT on an OC3 (Offshore Code Comparison Collaboration) monopile. The results of the application of the integrated optimisation methodology show a 19.8% reduction in the global mass of the support structure while satisfying all the design constraints. It is demonstrated that the proposed structural optimisation model is capable of effectively and accurately determining the optimal design of OWT support structures, which significantly improves their design efficiency.

Using Genetic Algorithms with Multi-Objective Optimization to Adjust Finite Element Models of Welded Joints

“…Using GA to adjust FE models is a well-known method that some researchers have used in recent years, especially when these models exhibit highly nonlinear behavior (Lostado et al [3]; Lostado et al [20]; Lostado et al [21]; Gentils et al [22]; Duanm et al [23]). In the field of welded joints, some authors (Bag et al [24]) have used GA to adjust the unknown parameters that define three-dimensional heat transfer FE models when the GTAW process is studied.…”

On gradient‐based optimization of jacket structures for offshore wind turbines

“…Some of the first work in the field of structural optimization of wind turbine support structures was using gradient‐free methods to optimize monopile structures . Since then, much work has been done on optimizing both onshore and offshore monopile structures using gradient‐free methods . As jackets gained in popularity, different gradient‐free methods have also been applied in the design thereof .…”

Comparative Study of Structural Reliability Assessment Methods for Offshore Wind Turbine Jacket Support Structures

“…Calculations and formulations of each load produced by the environment in this study are based on DNV-RP-C205 [73]. The loads relevant to OWT support structures can be roughly classified into six groups, i.e., (1) aerodynamic loads transferred from the rotor, (2) wind loads on the tower, (3) inertia loads, (4) current loads, (5) wave loads, and (6) hydrostatic loads [24]. These loads are illustrated in Figure 2.…”

“…Gravitational and inertia loads are static and dynamic loads which result from seismic activity, the entire structure's weight and imposed equipment on the structure under operation, and the exerted forces on the structure due to operations [74]. The inertia loads, as a result of the support structure and rotor-nacelle assembly (RNA) weight at the tower top, can have a significant impact on buckling and considerably influence the eigen-frequencies of the OWT support structure [24].…”

“…In comparison to the one-dimensional beam model, the three-dimensional finite element model has the capability of examining detailed stress distributions and accurately capturing structural responses within the structure. The three-dimensional finite element analysis model was extensively applied to structural modeling of wind turbine structures due to its high fidelity [1,2,[23][24][25][26][27]. Thus, the 3D FEA model is adopted in this study to determine the structural responses of OWT jacket foundations.…”