Genetic based optimisation of the design parameters for an array-on-device orbital motion wave energy converter

Optimisation of Wave Energy Converters (WECs) is a very important topic to obtain competitive devices in the energy market. Wave energy is a renewable resource that could contribute significantly to a future sustainable world. Research is on-going to reduce costs and increase the amount of energy captured. This work aims to optimise a WaveSub device made up of multiple floats in a line by investigating the influence of 6 different design parameters such as the number of floats. Here we show that a multi-float configuration of 6 floats is more competitive in terms of Levelised Cost Of Energy (LCOE) compared to a single float configuration with a LCOE reduction of around 21%. We demonstrate that multi-float configurations of this device reduce the LCOE especially because of the reduction of grid connection, installation, control and mooring costs. From the power capture perspective, optimized multi-float configurations still have similar capacity factors to the single float configuration. This research gives important indications for further development of the WECs from an optimisation perspective. These promising results show that more complex, optimized, multi-float configurations could be investigated in future

Design and Techno-Economic Analysis of a Novel Hybrid Offshore Wind and Wave Energy System

In the past few years, advanced technologies such as floating offshore wind turbines (FOWT) and wave energy converters (WECs) have been developed. As demonstrated by the innovative hybrid platform Poseidon, the feasibility of combining floating wind turbines and wave energy converters has already been explored. Furthermore, diversification of offshore renewable energy technologies reduces power fluctuations and lowers investment costs. This paper focuses on the development of an integrated wind and wave platform and the creation of a numerical model to evaluate the system performance for the Belmullet site. The novel concept consists of the semi-submersible Nautilus platform, integrated with four-point absorbers. A hydro-servo-aero time-domain model, combining WEC-Sim with an in-house wind turbine model, simulated the device motion and estimated the power generated. The performance of the Wave Energy Converters (WECs) was optimised based on their Power Take Off (PTO) damping. Finally, the hybrid concept was compared with the simple FOWT concerning the energy produced, Levelized Cost of Energy (LCOE) and hydrodynamic stability. The hybrid configuration proved to be a promising solution with 10% lower LCOE and improved hydrodynamic stability evaluated in terms of nacelle acceleration and platform pitch motion. These results show that wind and wave could be one of the best solutions for the future of the marine energy sector and the energy transition

A review of numerical modelling and optimisation of the floating support structure for offshore wind turbines

AbstractCompared to onshore wind power, floating offshore wind power is a promising renewable energy source due to higher wind speeds and larger suitable available areas. However, costs are still too high compared to onshore wind power. In general, the economic viability of offshore wind technology decreases with greater water depth and distance from shore. Floating wind platforms are more competitive compared to fixed offshore structures above a certain water depth, but there is still great variety and no clear design convergence. Therefore, optimisation of the floating support structure in the preliminary phase of the design process is still of great importance, often up to personal experience and sensibility. It is fundamental that a suitable optimisation approach is chosen to obtain meaningful results at early development stages. This review provides a comparative overview of the methods, numerical tools and optimisation approaches that can be used with respect to the conceptual design of the support structure for Floating offshore wind turbines (FOWT) attempting to detail the limitations preventing the convergence to an optimal floating support structure. This work is intended to be as a reference for any researcher and developer that would like to optimise the support platform for FOWT

Investigation and Optimisation of an Array-on-device configuration for a Novel Wave Energy Converter

Wave energy has a huge potential to satisfy the global electricity demand from a renewable source. Many Wave Energy Converters (WECs) have been designed to harvest energy from sea waves but, to date, they cannot compete on the commercial energy market. However, the WaveSub, which is a point absorber developed by Marine power Systems Ltd, has a great potential to become one of the most promising future ways of wave energy extraction. This research project aims to develop and validate a numerical model of a multi-float configuration of the WaveSub device, followed by an optimisation of the design parameters to minimize the Levelized Cost Of Energy (LCOE). Hydrodynamic modelling of the device is based on a linear potential flow theory while a time domain simulation is used to estimate the power produced from the device. Then the drag force, the weakest point of the hydrodynamic forces calculation, has been investigated while the numerical model has been extended to include multi-directional waves. A benchmarking of the numerical model with tank testing of a 3 float WaveSub linear configuration against different regular wave cases demonstrated a good agreement with a relative mean total power difference between tank and model of around 10%. A genetic algorithm combined with the Kriging surrogate model was mainly used to optimise the LCOE. The 6 float configuration was found to operate at 21% lower LCOE compared to a single one. Finally, linear, rectangular, triangular and circular 6 float configurations were investigated. The circular configuration performed best with a LCOE reduction around 12% relative to the worst configuration. This work is a starting point for a more extended study of multi-float configurations, which can include more floats and complex geometries. Our results will help to develop a future multi-float WaveSub design, which can harvest renewable energy competitively

Design and Analysis of a Floating Photovoltaic System for Offshore Installation: The Case Study of Lampedusa

In recent years, numerous projects for floating PV systems have been developed. These plants of various sizes have mainly been installed on enclosed lakes or basins characterised by the absence of external forcing related to waves and currents. However, offshore installation would allow the development of such plants in areas where land is not available, such as islands. This paper analyses the state of the art of floating PV, describes the design of a floating PV platform and the development of a numerical model to evaluate the system performance in an offshore environment. The case study of the island of Lampedusa is then analyzed: starting from a single floating foundation with its mooring system, a floating PV system is designed to meet the island’s electricity needs. In order to provide the competitiveness of the system, a techno-economic analysis is carried out, evaluating the main cost items of Capex, Opex and LCOE. Although the LCOE obtained is significantly higher than a traditional solar plant installed on land, this technology is competitive compared to other offshore marine technologies such as offshore wind and wave energy

Optimization of hydraulic power take-off system settings for point absorber wave energy converter

Ocean wave renewable energy is becoming a key part of the renewable energy industry over the recent decades. By developing wave energy converters (WECs), their power take-off (PTO) systems have been investigated to enhance the power extraction from the ocean. Adjusting PTO parameters is a challenging optimization problem because there is a complex and nonlinear relationship between these parameters and the absorbed power output. In this regard, this study aims to optimize the PTO system parameters of a point absorber wave energy converter in the wave data-set in Perth, on the Western Australian coasts. The converter is numerically designed to oscillate against irregular and multi-dimensional waves and sensitivity analysis for PTO settings. Then, to find the optimal PTO system parameters which lead to the highest power output, ten optimization approaches are incorporated to solve the nonlinear problem, including the Nelder-Mead search method, Active-set method, Sequential quadratic Programming method (SQP), Multi-Verse Optimizer (MVO), and six modified combination of Genetic, Surrogate and fminsearch techniques. After a feasibility landscape analysis, the optimization outcome is carried out and gives us the best answer in terms of PTO system settings. Finally, the investigation shows that the modified combinations of Genetic, Surrogate, and fminsearch approaches can outperform the others in the selected wave scenario, as well as with regard to the interaction between PTO system variables. (c) 2022 Elsevier Ltd. All rights reserved