Abstract
Wind energy has become a very interesting option regarding the replacement of fossil-based energy sources by renewable options. Despite its eco-friendly character, some challenges remain across the whole lifecycle of wind turbines. These are mainly related to the use of more sustainable materials and processes in the construction phase, to lifetime extension for the structures currently installed and to waste management at the end-of-life phase, the disassembly or decommissioning phase. Following worldwide concerns about sustainability, the circular economy and decarbonization, several projects have been addressing the themes identified, proposing alternatives that are more suitable and contribute to the body of knowledge in the sector towards enhanced environmental and technical performance. This work presents the state of the art of the European wind energy sector, reflecting on the main drivers, barriers and challenges for circularity, while identifying knowledge gaps and strategic opportunities to develop new potential approaches. A compilation of key projects and main wind energy sites in Europe is shown, as well as a collection of lifecycle extension strategies and reported environmental impacts. Approaches to sustainability are highlighted, such as recyclability, ecodesign and eco-efficiency of the turbine blades. Furthermore, the associated potential environmental, economic and societal impacts are put forward to support the implementation of more circular solutions, which can also contribute to reducing EU energy dependency and more integration of in what relates to potential circular solutions and strategies towards a higher level of sustainability.

Abstract
A 2D numerical investigation of the power absorption of a constrained wave energy hyperbaric converter (WEHC) under full-scale sea wave conditions is presented. A fully non-linear numerical model DualSPHysics, based on the coupling of a smoothed particle hydrodynamics (SPH) fluid solver with a multibody dynamics solver, is used to model the interaction between wave and WEHC sub-systems. The numerical model was first validated against experimental data for a similar device, with a good accordance between PTO position and velocity. The model is then employed to study the hydrodynamics of a constrained WEHC considering several sea states, different hydraulic power take-off (PTO) damping and breakwater geometries. It is observed that the capture width ratio (CWR) is particularly sensitive to variations in the PTO damping, although the CWR absolute maximum is less sensitive considering mild variations applied to the PTO damping. Both wave height and wave period have an important effect on the CWR. The breakwater geometry is also essential for the performance of the WEHC, with a decrease in maximum CWR of about 15% for porous breakwater. These results are necessary to understand the full-scale behaviour of WEHC.

Abstract
Techniques based on artificial neural networks (ANNs) have been increasingly applied to predict emergency situations, such as extreme wave conditions, wave overtopping or flooding, and damage to maritime structures, in coastal and port areas. In this work, a fuzzy adaptive resonance theory with mapping (FAM) ANN was trained to predict the wave regime both inside and at the entrance to the Port of Sines, one of the major trade and economic gateways of the Iberian Peninsula, located on the Portuguese west coast. In situ measurements using pressure sensors, wave buoy data, and results from two numerical wave propagation models simulating waves nearshore (SWAN) and diffraction refraction elliptic approximation mild slope (DREAMS) were used to train and validate the ANN. The wave regime was calculated for different points outside and inside the port. In general, the FAM predictions outside the port showed a satisfactory fit to the wave parameters (significant wave height, peak wave period, and mean wave direction) from the numerical model SWAN. Inside the port, differences from the DREAMS model were greater, because the optimized FAM parameters were obtained only for outside the port and the FAM network showed some difficulties in accounting for the complex phenomena of wave refraction, diffraction, and reflection within the port. Consequently, it is of paramount importance to obtain the FAM results based on fully optimized parameters to use the FAM output in place of the numerical models of wave propagation. Nevertheless, this methodology proved capable of providing a fast and satisfactory response that is especially useful in the scope of risk management, particularly in wave forecasting and warning systems.