A design methodology for a monolithic composite spar-buoy platform supporting a 15~MW floating offshore wind turbine is developed and demonstrated. The concept originates from the need to explore composite alternatives to steel structures, with geometry and material choices initially informed by literature on comparable designs and the WindCrete reference model. The structural layout was parametrized in Grasshopper and coupled to a Python-based workflow integrating aero-hydro-servo-elastic simulations (OpenFAST, BModes, HAMS), post-processing (MExtremes, MLife), and optimization (OpenMDAO), enabling automated updates of simulation inputs from parametric geometry changes.

Extreme and fatigue design load cases (DLC6.1, DLC6.3, DLC1.2) following IEC~61400-3 were simulated to assess yielding, buckling, and fatigue performance. Due to the high computational cost of flexible spar simulations, a rigid spar approach was employed, focusing on the tower base as the critical section. Initial assessments revealed that the filament-wound layer was insufficient under extreme loads, which was addressed by increasing its thickness.

An optimization using 10{,}000 sampled designs identified a configuration with reduced composite thicknesses and an increased tower base diameter, lowering capital expenditure (CAPEX) to 22.67~million~\texteuro{} while meeting structural and stability constraints. The optimized CAPEX lies within the reported range for steel spar and tower designs, indicating economic competitiveness. Further improvements, such as a tapered thickness distribution, are expected to enhance cost-effectiveness. The results demonstrate the technical feasibility and economic potential of composite spar-buoy platforms for large-scale FOWTs.

With the European Commission’s ambitious goals for reducing greenhouse gas emissions and increasing renewable energy usage, marine renewables, including wave energy, have gained attention as a promising source of clean and predictable energy. Despite its potential, wave energy has lagged behind other renewable technologies like wind and solar, primarily due to higher costs and slower commercialization. This thesis investigates the impact of power output capping on the levelized cost of electricity (LCOE) of wave energy converters (WECs), a crucial metric for assessing their commercial viability. The research uses numerical modeling to calculate the theoretical LCOE/kg, considering both uncapped and capped power outputs. Using a cylindrical point absorber WEC, the study employs a boundary element method (BEM) solver to model hydrodynamic parameters, such as response amplitude operators and excitation forces. By constructing power matrices, the research analyzes the effects of two capping strategies on the AEP and capacity factor in both medium and high energy regions.
Results indicate that capping significantly influences the LCOE, with small variations observed between medium- and high-energy regions. The study highlights that specifically PTO damping capping has the most negative economic implication, with similar changes in LCOE in terms of percentage observed in high-energy regions and medium-energy regions. These findings contribute to the broader goal of advancing the commercialization of wave energy, supporting the transition towards a more sustainable and climate-neutral energy future.

Array design of a wave farm composed of multiple WECs is an essential issue during the design phase of an offshore wave energy farm. Although various research has looked into the optimal array design, the optimization process usually takes a lot of time.

The objective of this thesis is to reduce the time required during the WEC design phase. The study focuses on performing a hydrodynamic analysis of a wave farm consisting of four single-point absorbers, examining the relationship between excitation force and array spacing, and determining the average total power production of the wave farm.

This thesis employs the Boundary Element Method (BEM) to analyze the hydrodynamic interactions of waves and oscillatory motions in WECs. Using the open-source software Capytaine, it estimates key hydrodynamic coefficients and solves the system of equations via Green's theorem to evaluate added mass and excitation forces. By selecting excitation force as a design parameter, a linear regression model is established. Furthermore, a machine learning model based on the Random Forest algorithm is developed to capture the complex relationship between total power output and the design parameter. After the machine learning model is created, the optimal array spacing for a specific site can be estimated quickly by combining results with a wave scatter diagram.

These findings aim to contribute to wave energy systems design by providing a reliable link between hydrodynamic results and design parameters and accelerating development in the wave energy sector.

Ocean waves being considered to have huge potential on providing renewable energy resources. While significant research and application of wave energy converters have been conducted in many seas, exploration on low-energy seas is still an ongoing endeavour. In this study, a point absorber array is being studied in the scenario of implementing at low-energy site within Caspian Sea.
The primary objective of this study is to give an optimal layout for a point absorber array with five devices. Firstly, hydrodynamic analysis is conducted by Boundary Element Method using a frequency domain model in NEMOH and WEC-Sim. Layouts with different spacing factor are examined to obtain the power matrices for each case. The q-factor, a measure that quantifies the WEC array’s power absorption efficiency, and annual power production are readily calculated. Furthermore, given the annual energy production, an economic model is built to assess the CapEx, OpEx and LCOE, the Levelized Cost of Energy of the WEC array with different layouts. The final optimization phase finds a solution that simultaneously maximizes the q-factor and minimizes the LCOE by executing a multi-objective algorithm. The best layout configuration for the point absorbers array in the Caspian Sea site is determined, taking into account both high energy output and economic viability.