Search Results (1,312)

Wind energy is one of the clean and sustainable energy sources that can be used to meet global energy demand. However, although wind turbines are used to harness energy in coastal and offshore areas, the extreme environmental conditions make it difficult to utilize these structures optimally and also negatively impact their safety. Therefore, in this study, the yaw angles of the National Renewable Energy Laboratory (NREL) 5 MW wind turbine mounted on a monopile platform were controlled using a Long Short-Term Memory (LSTM) artificial intelligence (AI) architecture to optimize power output and ensure structural stability against dynamic responses under irregular wave and Izmir–Samos tsunami conditions. First, the İzmir–Samos tsunami, the NREL 5 MW wind turbine mounted on a monopile platform, the analytical methods employed, the LSTM architecture, and the parameters used in the study were described. The results of the wind direction time series prediction and the aerodynamic, hydrodynamic, and structural responses of the LSTM-based yaw angle control strategy on the wind turbines were investigated and discussed. According to the results, the increase in aerodynamic power achieved using the LSTM-based strategy was approximately $5.18\%$ under a scenario with constant wind speed and variable wind direction in two different sea conditions and $5.29\%$ under conditions of irregular waves with fully variable wind speed and direction. In addition, more stable responses were observed for most of the parameters examined. The primary goal of this study is to serve as a reference for researchers working on AI-optimized power output and response analysis resulting from varying the yaw angles of wind turbines. Full article

The development of offshore wind energy in tropical cyclone-prone regions requires analytical frameworks that capture non-stationary climate dynamics. This study presents a multi-scale spectral approach to characterize Atlantic tropical cyclone variability and assess implications for offshore wind resilience in the Caribbean Basin. The methodology integrates Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) to resolve temporal variability in sea surface temperature, cyclone frequency, and intensity, complemented by two-dimensional kernel density estimation (KDE) and non-stationarity analysis. Using NOAA and National Hurricane Center datasets, results identify dominant periodicities at annual and ENSO (2–7 year) scales, a post-1995 spectral energy shift associated with the positive AMO phase, and a thermodynamically consistent energy corridor along 12–16° N. A statistically significant change point in 1987 (Pettitt test, p < 0.05) is detected, although spatial displacement is not significant. An integrated Wind Risk Index highlights the central-western Caribbean as a high-exposure zone overlapping offshore wind development areas. Exceedance analysis shows that 39.8% of observations surpass 25 m/s, 6.0% exceed 50 m/s, and 1.3% approach 70 m/s, indicating relevant design considerations. These findings support the need for non-stationary, multi-scale approaches in offshore wind risk assessment under tropical cyclone influence. Full article

Accurate spatiotemporal forecasting of sea surface temperature (SST) makes a great difference to offshore wind power development, since SST is a crucial factor influencing wind field patterns. In this work, a remote sensing-driven, multi-parameter field-coupled co-forecasting approach is proposed to utilize the cross-field interaction mechanisms among different physical fields to enhance forecasting performance. With this approach, more than one physical field can be simultaneously forecasted, thus improving forecasting efficiency. Compared with pure SST forecasting cases, the advanced enhancement of SST forecasting performance based on this approach is achieved by coupling SST with geostrophic current (GC) in data-driven forecasting. Also, both the spatiotemporal SST and GC fields are demonstrated to be accurately forecasted simultaneously. In addition, the causal effects between SST and GC are demonstrated as a reliable factor for evaluating the coupling scheme. To further improve co-forecasting performance, an exponential cross-entropy loss function is proposed for multi-physical field co-forecasting scenes, and shows more satisfying performance than a classical cross-entropy loss function. The results demonstrate that the data-driven multi-physical field-coupled co-forecasting approach is an advanced, highly efficient method that can accurately forecast more than one physical field at the same time. Full article

Offshore wind and wave energy have emerged as promising alternatives due to their abundant availability and substantial energy potential. This research explores a V-shaped semi-submersible platform designed to support both wind turbines and wave energy converters (WECs). The V-shaped configuration is selected for its ability to enhance hydrodynamic performance by reducing wave-induced loads and improving motion characteristics, while also providing increased structural stability through a wider effective footprint. In addition, the geometry creates a favourable layout for integrating WECs between the pontoons, enabling efficient wave energy capture without significantly interfering with the aerodynamic performance of the wind turbine. The study assesses the performance of different V-shaped platform configurations, ensuring their motion responses meet the operational limits required for wind turbines. It also examines whether interactions between the platform and coexisting WECs can lead to an improvement in wave energy absorption efficiency. Numerical hydrodynamic diffraction was conducted using the boundary element method in ANSYS AQWA, based on 3D potential flow theory and considering viscous damping effects, to calculate platform motion and the wave power output of WECs with a linear power take-off system. Preliminary analyses revealed that optimising the placement of WECs on a V-shaped semi-submersible can significantly improve energy generation while maintaining acceptable platform motion. This research demonstrates the additional potential of integrated wind-wave energy systems in delivering efficient and sustainable offshore energy solutions. The study also highlights the advantages of a turret mooring system for passive alignment with environmental forces, prolonging platform structure longevity and enhancing energy efficiency. Full article

As offshore wind energy advances into deeper waters, the dynamic response and safety assessment of tension leg platform (TLP) wind turbines under complex marine conditions have become focal research points. This study investigates a 15 MW TLP wind turbine, acquiring data on motion responses, mooring tensions, and tower-base loads through time-domain analysis, with extreme value estimation conducted using the mean up-crossing rate method. The results indicate that under normal operating conditions, second-order wave forces significantly influence extreme response estimation. At an exceedance probability of 0.01, the second-order sum-frequency force increases the extreme tower base shear by 4.28% and the bending moment by 10.11% compared to the first-order-only case, while the difference-frequency force has a minor effect. Different wind-wave incidence angles cause distinct variations in turbine motion, with head-on incidence exciting the largest wave-frequency responses and lateral incidence producing relatively weaker excitation effects. Furthermore, the coupling effect between incident direction and second-order wave forces further amplifies extreme response risks. Therefore, it is essential to fully assess the prevailing wind-wave directions in the target sea area and consider the effects of second-order wave forces, especially the sum-frequency component, to ensure the long-term safe operation of TLP wind turbines under complex sea conditions. Full article

The development of offshore wind energy has increased the demand for reliable submarine transmission systems. In South Africa, research remains constrained due to the lack of operational offshore wind farms, despite favorable geographical conditions and persistent energy challenges such as load-shedding. Submarine cable faults, primarily caused by manufacturing deficiencies, environmental factors, and human activities, contribute significantly to system downtime while accounting for only a small portion of overall installation costs. This study reviews submarine cable fault identification, classification, pre-determination, and localization techniques. Conventional methods, including time-domain reflectometry, the Murray loop, the Varley loop, and impulse-based techniques, are reviewed alongside artificial neural network models, such as convolutional and deep learning architectures. Findings imply that traditional techniques offer low error margins but lack the accuracy needed for pinpointing exact faults, as faults may extend over several kilometers. In contrast, neural network-based methods, particularly when integrated with signal processing methods, significantly improve fault classification and localization accuracy. The study concludes that hybrid approaches combining conventional diagnostic techniques with neural networks offer a robust framework for submarine cable fault analysis, providing real-world solutions to enhance reliability and efficiency in future offshore wind transmission systems. Full article

The stability and functionality of offshore wind energy systems depend critically on how offshore platforms interact with the geotechnical features of the seabed. This review describes developments in five areas: (i) offshore geotechnical site investigation and strength assessment; (ii) seabed geohazard causes and deep-water mooring challenges; (iii) frameworks for seabed modeling; (iv) sediment behavior influencing anchor and mooring performance; and (v) selection of anchors based on their interactions with various soils. The review emphasizes developments in seabed assessment and modeling using field, lab, and numerical methods. It discusses how the new advances in analytical and simulation frameworks have enhanced our knowledge of anchor–mooring responses, cyclic loading behaviors, and soil–structure interactions under changing seabed conditions. The key findings reveal that: (1) cyclic loadings considerably change anchor holding capacity and evolution of seabed trenching, yet most existing design methods still use quasi-static loads; (2) site-specific data from integrated geophysical–geotechnical surveys are vital to reduce uncertainty in anchor penetration and the frictional resistance of chains; (3) geohazards, such as shallow gas, marine landslides, and seabed erosion, pose under-recognized risks to long-term anchor reliability. The lack of knowledge on the coupled, long-term evolution of the seabed–anchor–mooring line system is identified as another gap in the literature. Major gaps exist in validating the life cycle of anchor performance under real-scale storm–wave sequences for offshore geotechnical risk management in layered soils. At the end of the discussion, the current study also highlights the need for flexible, data-driven frameworks that integrate geotechnical, hydrodynamic, and structural analyses in a coupled framework to improve reliability in next-generation offshore wind energy systems. Full article

The addition of renewable energy sources (RES), including photovoltaic (PV) and wind generation technology, has introduced new challenges and opportunities for modern power systems. This paper examines the functionality and reliability of a hybrid PV–-wind-integrated 9-bus power system evaluated in DIgSILENT PowerFactory. The system has been designed with two solar PV plants, two offshore wind farms, multiple loads, and transformer interconnections, and aims to evaluate steady-state, dynamic, and contingency behavior. The system was evaluated using load-flow, quasi-dynamic, and RMS simulations to assess power balance, voltage stability, and fault recovery. The outcomes indicated convergence, balanced power flow, and system resilience under single-contingency conditions. This paper shows the effectiveness of the power system simulation tool for analyzing hybrid renewable power systems. Full article

A wave-resource characterization along the coast of Vietnam was performed based on the 12-year period from 2007 to 2018, using the structured-grid Simulating WAves Nearshore (SWAN) model with a ~2.3 km spatial resolution. Extensive model validations were performed using an observed nearshore dataset and ERA5 offshore datasets. The wave parameters, significant wave height, wave period, total wave energy and omnidirectional wave power varied both spatially and temporally, with a strong seasonal pattern influenced by the northeast and southwest monsoons, with the impact of the northeast monsoon being stronger. Wave energy resources were highest in winter and lowest in summer, making the southcentral coast of Vietnam a prime location for wave energy harvesting. However, further feasibility and design studies are needed before wave farms can be established. The Gulf of Tonkin and the Gulf of Thailand had lower wave energy due to wind distribution, shadowing effects and changes in water depth. This study also noted the impact of ENSO phases on wave conditions. Year-round, El Niño generally weakened winds, leading to smaller waves and reduced wave energy, while La Niña had the opposite effect. Additionally, tropical cyclones can further amplify significant wave height, especially during both ENSO phases in July, thereby increasing wave energy. Full article

Land availability is a critical dimension in high-renewable power generation strategies, as renewable technologies typically require substantially more area for infrastructure deployment and operational spacing than incumbent fossil-fuel-powered technologies. Land use has mainly been considered in energy system modeling studies as a post-processing evaluation, at a sub-national scale, or in non-Mediterranean regions. Consequently, there remains a gap in endogenizing land requirements within an energy planning optimization model for a Mediterranean country with high renewable potential, thereby allowing examination of the trade-offs between land use, mitigation and economic efficiency. In this study, we address this gap by focusing on the Greek power system, developing alternative land supply curves, and integrating them into an optimization model for the Greek power sector (OSeMOSYS-Greece). This approach generates a large ensemble of mitigation scenarios with varying land intensities and cost requirements. The results highlight strong substitution effects between land-intensive and less-land-intensive renewable technologies. Notably, onshore wind power generation is found to decline by up to approximately 70% by 2050 between the land-unconstrained case and the most stringent land-constrained scenario, chiefly substituted by offshore wind and, to a lesser extent, solar PV. Furthermore, under integrated energy-land planning, land occupation for power generation can be reduced to 3% of Greece’s total land area by 2050, compared to around 11% under a land-unconstrained pathway. Full article

Spar-type floating offshore wind turbines (FOWTs) operating in deep-sea environments are subjected to coupled wind and wave excitations spanning a wide frequency range, rendering single-frequency passive damping solutions inadequate. A folded-beam nonlinear energy sink (FB-NES) is proposed for broadband vibration suppression of spar-type FOWTs. The device employs pre-buckled elastic beam arms integrated with constrained layer damping patches, and a closed-form analytical relationship between the beam geometric parameters and the nonlinear stiffness coefficients is derived, enabling direct parameter design without iterative calibration. The pre-buckled geometry introduces a negative-stiffness mechanism that substantially lowers the targeted energy transfer (TET) threshold, ensuring device engagement under all normal operational sea states. A 14-degree-of-freedom aero-hydro-elastic model of the NREL 5 MW OC3-Hywind FOWT with the FB-NES is established via the Euler–Lagrange formulation and validated against OpenFAST. Based on the numerical results under operational and extreme parked load cases, the FB-NES achieves substantial broadband vibration reductions that grow monotonically with wave severity, consistently and substantially surpassing both the optimally tuned mass damper (TMD) and a conventional cubic nonlinear energy sink of equal mass. Wavelet analysis confirms that targeted energy transfer, rather than direct viscous damping, is the dominant energy dissipation mechanism. The FB-NES also maintains effective control over a wide frequency detuning range, demonstrating superior robustness compared to the TMD. Full article

High-Frequency (HF) radar remote sensing offers a unique capability to detect mesoscale air-sea interactions under strong monsoon conditions. This study leveraged HF radar-derived surface currents, buoy observations, and reanalysis data to systematically investigate the driving mechanism of the sea–land breeze (SLB) on surface currents in the Taiwan Strait during the strong winter monsoon. To address the challenge of extracting weak signals from a dominant background flow, we employed the Separation of the Regional Wind Field (SRWF) method and the complex demodulation spectrum shifting technique. The results demonstrate that HF radar observations confirm the presence of regular SLB activity even under the strong monsoon, with its intensity modulated by the land–sea temperature difference influenced by cloud cover. Spatial correlation analysis reveals that the SLB significantly drives diurnal variations in the surface current, with its impact extending up to 110 km offshore and a maximum amplitude of approximately 2.2 cm/s. Additionally, the analysis reveals that the duration of SLB events critically influences the current response: events lasting 7 days produce a stronger and more spatially coherent correlation with the diurnal currents than shorter 5-day events. Furthermore, harmonic analysis indicates that the SLB’s energy primarily affects the non-tidal residual current, with no significant impact on the principal diurnal tidal constituents ($O_1$, $K_1$). This work not only quantifies the SLB-current coupling during sustained SLB events in a strong monsoon regime but, more importantly, demonstrates the capability of HF radar remote sensing for resolving weak signals in complex, high-energy environments, providing a robust methodological framework and valuable insights for regional marine environmental forecasting. Full article

Maritime transport is energy-efficient but remains heavily dependent on fossil fuels. Renewable electricity-based ammonia (e-NH₃) has emerged as a promising alternative, particularly through small-scale, modular production. Assessing its economic viability is essential for future adoption, and techno-economic analysis offers a structured way to evaluate its feasibility. This study investigates the cost performance of a small-scale offshore e-NH₃ plant of 2.4 tons per day (tpd) at the Port of Santander, Spain, based on nitrogen obtained via membrane separation and hydrogen from electrolysis of pretreated seawater. The results are based on process simulation outcomes obtained using ASPEN v14, and the detailed cost breakdown is derived from modular costing methodologies applied to preliminary process designs and sensitivity analyses of the levelized cost of ammonia (LCOA) with respect to the main variables. A comparative review of LCOA values reported in the literature for offshore and onshore e-NH₃ plants is provided. An estimated CAPEX of 5.99 M EUR (equivalent to 0.53 M EUR/y), OPEX of 1.58 M EUR/y, and an LCOA of 2408 EUR/tNH₃ are obtained, with equipment investment and operating costs identified as the most influential parameters. The results highlight the need for supraregional techno-economic studies considering optimal offshore wind availability within a collaborative interregional framework. Full article

The Gulf of Mexico and the Caribbean Sea are key regions of the western Atlantic, where sea-state conditions are critical for coastal safety and offshore operations. This study analyzes wave climate trends (1981–2022) using WAVEWATCH III simulations validated against buoy observations. The Mann–Kendall test and Theil–Sen estimator were employed to quantify trends in significant wave height (Hs), energy period (Te), and wave power (P), while correlation analysis was performed to explore teleconnections with the Oceanic Niño Index (ONI), Atlantic Multidecadal Oscillation (AMO), and North Atlantic Oscillation (NAO). The results reveal basin-wide increases in mean Hs and P, characterized by pronounced spatial and seasonal heterogeneity. The most robust positive trends occur during winter and spring; in summer and fall, the weaker or negative tendencies, particularly in Te, suggest an intensification of seasonal contrasts rather than uniform change. Teleconnection analysis demonstrates that, among the climate indices considered in this study, ENSO is the primary driver of interannual wave variability in the Caribbean, particularly modulating wave power through remotely generated swell. While the NAO exerts regionally dependent control associated with storm-track modulation, the AMO plays a secondary role, affecting swell-dominated sectors. In contrast, the Gulf of Mexico shows limited sensitivity to large-scale climate modes, with wave variability largely governed by local wind–sea processes. These findings highlight the contrasting wave dynamics between these two basins, providing critical insights for coastal hazard assessments, maritime traffic along major shipping routes, oil spill management, and regional wave energy planning. Full article

With the rapid development of offshore wind power, the fractional frequency offshore wind power system based on the modular multilevel matrix converter (M3C) faces severe frequency stability challenges due to the reduced inertia under high wind power penetration. This paper focuses on its frequency control and proposes a set of coordinated strategies. Modified frequency regulation schemes for wind turbines (WTs) under different operating states avoid secondary frequency drop (SFD) and accelerate rotor speed recovery. A coordinated power allocation strategy combining energy storage (ES) and automatic generation control (AGC) suppresses wind-induced power fluctuations, with a reducing pitch angle variation method to extend WTs’ life. Meanwhile, an adaptive virtual inertia control strategy for M3C enhances sustained inertia support. A coordinated frequency control scheme between wind farm, M3C, and ES is further constructed to achieve faster and better frequency stabilization under wind and load variations. Simulation results under a 10.5 MW load disturbance show that, compared with the uncontrolled scheme, the proposed scheme raises the frequency nadir from 49.01 Hz to 49.67 Hz, limits the maximum rate of change of frequency (ROCOF) to 0.583 Hz/s with a 49.8% reduction, fully eliminates SFD, and provides theoretical support for the stable grid integration of fractional frequency offshore wind power. Full article