Offshore wind turbines are becoming increasingly popular due to their higher wind energy harnessing capabilities and lower visual pollution. Researchers around the globe have been reporting significant scientific advancements in offshore wind turbines technology, addressing key issues, such as aerodynamic characteristics of turbine blades, dynamic response of the turbine, structural integrity of the turbine foundation, design of the mooring cables, ground scouring and cost modelling for commercial viability. These investigations range from component-level design and analysis to system-level response and optimization using a multitude of analytical, empirical and numerical techniques. With such wide-ranging studies available in the public domain, there is a need to carry out an extensive yet critical literature review on the recent advancements in offshore wind turbine technology. Offshore wind turbine blades’ aerodynamics and the structural integrity of offshore wind turbines are of particular importance, which can lead towards system’s optimal design and operation, leading to reduced maintenance costs. Thus, in this study, our focus is to highlight key knowledge gaps in the scientific investigations on offshore wind turbines’ aerodynamic and structural response. It is envisaged that this study will pave the way for future concentrated efforts in better understanding the complex behavior of these machines.

Optimization of the vibro-impact capsule system for the best progression is considered in this paper focusing on the choice of the excitation parameters and the shape of the capsule. Firstly, the fastest and the most efficient progressions are obtained through experimental investigations on a novel test bed. Control parameters, the amplitude and the frequency of harmonic excitation, and one of the system parameter, namely the stiffness ratio, are optimized. The experimental results confirm that the control parameters for the fastest progression are not the same as those for the most efficient progression from the energy consumption point of view. Therefore, the capsule system can be controlled either in a speedy mode or in an energy-saving mode depending on the operational requirements. In the second part of the paper, optimization of the capsule shape is studied using computational fluid dynamics (CFD) simulations. Here the aim of achieving the best progression is addressed through minimizing the drag and the lift forces acting on a stationary capsule positioned in the pipe within a fluid flow. The CFD results indicate that both drag and lift forces are dependent on capsule and arc lengths, and finally, an optimized shape of the capsule is obtained

Recently, wind turbine research has switched focus to vertical axis wind turbines due to the extensive research that has been performed on horizontal axis wind turbines and the potential of vertical axis wind turbines in built-up areas. This study aims to analyse the performance of a small-scale hybrid vertical axis wind turbine that can switch from functioning as a Darrieus (lift) turbine to a Savonius (drag) turbine by rotating the blades. The turbine was analysed using 3D computational fluid dynamics (CFD) simulations in ANSYS Fluent as the primary method, and the findings were verified using wind tunnel experiments. During the analysis, design parameters such as the blade length, diameter, and number of blades were varied to determine if the design had room for improvement. It was found that the current design of the turbine has an optimal efficiency of 12.5% in the Darrieus configuration, which was found to increase when the diameter or blade length was increased. The Savonius configuration was found to be more efficient at low tip-speed ratios (<0.14), and its efficiency could be increased by adding more blades. The experiments found similar trends to the simulations; however, the efficiencies obtained were on average a tenfold increase from the simulation. Implementing the changes that increased efficiency leads to an increased wake recovery distance, making it less suitable for use in a wind farm.