Parametrisation Scheme for Multidisciplinary Design Analysis and Optimisation of a Floating Offshore Wind Turbine Substructure – OC3 5MW Case Study

Abstract

The development of novel energy technologies is considered imperative in the provision of solutions to meet an increasing global demand for clean energy. Floating Offshore Wind Turbine (FOWT) is one of the emerging technologies to exploit the vast wind resources available in deeper waters. To lower the levelized cost of energy (LCOE) or optimise the performance response associated with a FOWT system, a detailed understanding of the different disciplines (Aero-Hydro-Servo-Elastic) within the system and the relationship between the FOWT system and the dynamics of the marine environment is required. This requires an efficient Multidisciplinary Design, Analysis and Optimisation (MDAO) framework for FOWT systems to reduce the capital cost and increase dynamic performance. A key component of any MDAO framework is the shape parameterisation scheme, as it enables the modelling of a large array of platform designs with different geometric shapes using limited number of parameters. This work focuses on the B-Spline parameterisation modelling technique of OC3 spar-buoy and the use pattern search optimization algorithm to select the optimal design variants. The parametrisation technique is implemented in an analysis framework, where a B-spline library from Sesam GeniE is used to model each design representation, and a potential flow frequency domain analysis solver (HydroD/Wadam) is used for the hydrodynamic analysis. Validation of the selected designs within the design space is conducted with a benchmark NREL5MW spar-buoy hydrodynamic response results in literature with the hydrodynamic response of the frequency domain modelling approach using Sesam GeniE and HydroD/Wadam. This analysis process shows a high accuracy in response results between the OC3 spar-buoy in literature and the OC3 spar-buoy model design using B-Spline parametrization technique. Key performance metrics like the cost of materials and root mean square (RMS) of the nacelle acceleration also show improvement with the design variants compared to estimation from OC3 design in literature.

Parametric Curve Comparison for Modeling Floating Offshore Wind Turbine Substructures

“…Integrate the parametric curves in the MDAO framework developed by Ojo et al [12] using the DNV suite software (Sesam GeniE 64 V8.4-06 and HydroD 64 v6.1-02) and the derivative free pattern search optimization algorithm; 2.…”

“…1. Integrate the parametric curves in the MDAO framework developed by Ojo et al [12] using the DNV suite software (Sesam GeniE 64 V8.4-06 and HydroD 64 v6.1-02) and the derivative free pattern search optimization algorithm; 2. Adopt a multi-criteria decision making (MCDM) process, more specifically a TOPSIS approach, to rank the parametric curve techniques against established marking criteria.…”

“…The MDAO framework involves an integration of all the multi-disciplines within the FOWT system coupled together, analyzed and benchmarked against the objective function and a set of design and analysis constraints to select the optimal model. The MDAO framework used for this work is detailed in the study conducted by Ojo et al [12] and summarized in this section.…”

“…The baseline substructure is the OC3 5 MW substructure. This work is based on the MDAO framework developed in Ojo et al [12]. However, in Ojo et al [12], a B-spline free-form curve was used to model the OC3 5 MW spar with a total of 13 control points and 12 curve segments.…”

“…This work is based on the MDAO framework developed in Ojo et al [12]. However, in Ojo et al [12], a B-spline free-form curve was used to model the OC3 5 MW spar with a total of 13 control points and 12 curve segments. For this study, a reduced number of control points (6 control points and 5 curve segments), with different parametric free-form curves, is used.…”