To reduce the cost of offshore wind and wave power, an innovative combined wind–wave energy generation system constituting of a 15 MW semi-submersible floating offshore wind turbine (FOWT) and four torus-type wave energy converters (WECs) is proposed. A wholly coupled numerical model of aero-hydro-elastic-servo-mooring was built to evaluate the mooring line and motion dynamics of this novel combined system. Additionally, a practical mooring optimization framework is proposed with the Latin Hypercube sampling method, Kriging model, and the combined optimization techniques of the Genetic Algorithm and Gradient Algorithm. The optimization results demonstrate that the optimized mooring scheme satisfies all the strict constraints, validating the effectiveness of the optimization method. Moreover, the hydrodynamic characteristics of the combined system and the effects of the WECs on the mooring system under both rated and extreme conditions are discussed, including changes in time-series mooring tension, power spectral density, and statistical characteristics. The research findings provide a reference for the further development and optimization of this novel combined system, contributing to the efficient utilization of offshore renewable energy.

Extreme wave loading on a marine structure, consisting of a quasi-static and a dynamically slamming component, often drives the design of such a structure. Their accurate predictions remain challenging tasks. This paper examines the slamming contribution to the force–time histories from a series of experiments in which the crest of a wave is forced to hit a truncated cylinder suspended from above. A range of inundation levels, representing the breaker heights, are considered. The work also provides insights into nonlinear load characteristics on a vertical truncated cylinder. A simple analytical model based on the Newtonian momentum analysis is extended to describe the scaling of the horizontal peak force with the inundation level, i.e., the relationship between the wave slamming loads and the breaker height. More specially, it is found that the peak horizontal impact force is proportional to the inundation level and the square of the linear wave amplitude. In addition, the horizontal and the vertical impact forces on a truncated cylinder are found to increase with the increasing inundation level, while the effect from the wave steepness is relatively small. Furthermore, the higher-order wave components driving nonlinear (quasi-static) loading on a structure are separated by applying a phase-based separation method assuming a Stokes-like approximation. The separation method is found to work well even for long shallow-water waves that have strong nonlinearities. The results suggested that the relative contribution from the fundamental linear wave and higher-order wave components decreases and increases with the increasing nonlinearity of long waves, respectively, characterized by the Ursell number. Finally, this increase in the higher-order wave components is found to be saturated at large Ursell numbers.

Subjected to the relentless impacts of typhoons and rough seas, offshore wind turbines’ structures, particularly the tower, foundation, and blade, are at constant risk of damage. Full-field strain monitoring helps to discover potential structural defects, thereby reducing disasters caused by overall structural failure. This study introduces a novel method for assessing strain and temperature fields on these kinds of 3D surfaces of cylindrical structures. The method harnesses the capabilities of a high spatial resolution (0.65 mm) Optical Frequency Domain Reflectometer (OFDR)-based Distributed Optical Fiber Sensor (DOFS) in conjunction with a unique helical wiring layout. The core process begins with mapping the fiber optic path onto a plane corresponding to the unfolded cylinder. Fiber optic signals are then differentiated on this plane, deriving a two-dimensional strain distribution. The plane strain field is subsequently projected onto the 3D side of the cylinder. An experiment was carried out in which a 3.5 m long optical fiber was helically wound with a 10 mm pitch on the surface of a cantilever beam of a cylinder shell with a diameter of 36 mm and a length of 300 mm. The experiment collected about 5400 measurement points on the cylindrical surface of 340 cm², approximately 15.9 measurement points per square centimeter. The reconstructed results successfully reveal the strain field of the pipe cantilever beam under bending and torsional loads, as well as the palm-shaped temperature field. This experimental validation of the method’s efficacy lays the theoretical groundwork for its application to real wind turbines.

To facilitate both the installation and the removal of floating offshore wind turbines (FOWTs), a novel tension-leg dual-module offshore wind turbine system has been proposed. This system primarily consists of a DTU 10 MW wind turbine (WT) module and a supporting tension-leg platform (TLP) module. Considering both mechanical and hydrodynamic coupling effects of the dual-module system, this study focuses on its dynamic responses during both the installation and the removal of the WT module under typical sea states. The effect of different installation vessel positions and key parameters of the clamping device on the dynamic response of the system during the WT module removal has been clarified. Based on the findings, preliminary recommendations are provided regarding the optimal positioning of the installation vessel and the optimal design parameters of the clamping device. Furthermore, an auxiliary sleeve has been proposed to facilitate the WT module removal. The results indicate that the application of the auxiliary sleeve can significantly improve the dynamic response of the system. The results of this study can serve as a reference for the design, installation, and removal of floating offshore wind turbines.

Power allocation in wind-powered multi-stack proton exchange membrane (PEM) electrolysis depends on both load-dependent efficiency and thermal response. This study evaluates coordinated allocation, stack rotation and temperature control for four parallel 200 kW stacks. A control-oriented model couples electrochemical and thermal dynamics with rectifier losses and hydrogen compression power. Particle swarm optimisation determines the allocation, an equivalent health index guides stack rotation, and model predictive control (MPC) tracks temperature references from an offline stack-efficiency map. Predicted polarisation voltages differ from experimental data by no more than 1.4% at 313 and 333 K. In annual simulations, rotation reduces the cross-stack index standard deviation from 725.10 to 2.92 h. MPC achieves a simulated temperature-tracking root mean square error of 0.019 K, 91.12% below that of fuzzy proportional–integral–derivative control. Across three representative wind power scenarios, the probability-weighted daily hydrogen production is 199.85 kg, 0.59% above optimal allocation at 333 K. The corresponding increases over equal and sequential allocation are 1.26% and 2.43%, respectively. These results quantify the additional hydrogen yield from load-dependent temperature control and the operating-load balance obtained through stack rotation under the evaluated conditions.

This study proposes a novel pneumatically driven mechanically prestressed rhombic bistable composite laminate with asymmetric cylindrical curvature, which exhibits two weakly-coupled cylindrical shapes where each shape is influenced by planform and geometry parameters. A reduced-order analytical model is developed to predict the laminate’s quasi-static equilibrium shapes and snap-through transitions of the laminate under pneumatic work loading, which is triggered by the internal pressure applied to the fluidic channels. A sensitivity study based on the model investigates the influence of key planform and geometric parameters (the internal angle α and aspect ratio E) on the laminate’s out-of-plane deflection and snap-through pressure. The results show that increasing α reduces the critical prestrain required to achieve bistability and amplifies the out-of-plane deflection, while excessive α may lead to monostable curvature. Variations in aspect ratio modify the coupling stiffness between orthogonal PEMC layers, thereby influencing the bistable domain and critical snap-through pressure. These findings provide methods for the design of bistable composite structures.