Search Results (169)

Floating Offshore Wind (FOW) enables offshore wind deployment in deeper waters not suitable for bottom-fixed turbines, unlocking new areas for renewable energy generation. Most major cost contributors to FOW have clear pathways for cost reduction however mooring systems are the exception due to the pre-existing market maturity. Solutions to lower mooring costs include Mechanical Compliance Devices (MCDs) aimed at reducing the high peak and snatch loads in mooring lines and thus driving down the capital, operations and maintenance costs. In this paper, a comparison of a physical tank testing campaign and corresponding numerical analysis, for an MCD is described and analysed. The objective of the testing campaign was to validate the component-only tank results with the modelling of an MCD, namely Dublin Offshore’s Load Reduction Device (LRD) using a multi-body dynamics (MBD) approach. The paper presents analysis of the experimental testing and numerical modelling and compares the results with the validated Load–Extension Curve (LEC). Experimental testing was carried out at 1:38.5 scale using bespoke mooring test apparatus at Lír, Ireland’s National Ocean Test Facility. The results of testing are presented for all of the MCD model scales tested and compared with the modelled LEC. The correlation between the experimental and numerical data and with the LEC, characterised by Pearson Correlation Coefficient (R) in the range of 0.952 to 0.999, demonstrates the ability to model the LRD using the MBD approach. Full article

This paper presents WSMAQ (WEC-Sim-MoorDyn-AeroelasticQ), a coupled aero-hydro-elastic-mooring simulation framework for floating offshore multi-rotor wind turbines. The framework integrates WEC-Sim for platform hydrodynamics; MoorDyn-C for mooring-line dynamics; and in-house aeroelastic code, AeroelasticQ, for rotor-level aerodynamic and blade structural calculations. These modules are coupled within MATLAB/Simulink/Simscape 2023a. The novelty of WSMAQ lies in three coupling-oriented methodological extensions. First, for deep-draft spar platforms, the WEC-Sim body is configured using the physical mass and inertia at the true center of gravity, the full unadjusted added-mass matrix is retained in the radiation-load calculation, and a three-block integrator filter is used to break the added-mass–acceleration algebraic loop. Second, the WEC-Sim mooring class is extended to pass the non-zero initial platform orientation to MoorDyn-C. Third, AeroelasticQ is integrated with the multibody wind turbine model through a rotor-count-parameterized Level-2 C++ MEX S-function. The framework was benchmarked against OpenFAST through aeroelastic, platform-mooring, and full-wind-turbine tests on the OC3 spar with the 5 MW reference turbine developed by the National Renewable Energy Laboratory. Across the primary response channels, the mean relative error remained below 2% in most cases. Multi-rotor capacity was demonstrated using three NREL WindPACT 1.5 MW turbines mounted on the OC3 spar. In this case study, an asymmetric rotor-parked condition generated a mean yaw offset of approximately 4°, which did not appear in the symmetric-load cases. Full article

The energy transition and global decarbonization goals have accelerated the development of offshore renewable energy technologies, particularly in deep-water regions, where fixed foundations are limited by technical and economic constraints. Floating structures offer new opportunities for harnessing marine renewable resources, allowing them to be deployed in areas with favorable wind, wave, and oceanographic conditions. This paper presents a comprehensive analysis of European floating structures intended for hybrid renewable energy applications, combining environmental assessment, structural characteristics, hydrodynamic behavior, and energy integration aspects. Unlike previous analyses, which focused primarily on individual technologies, this study offers an integrated perspective on floating platform concepts—including spar, semi-submersible, tension-leg, barge, and FPSO-based solutions—as well as their potential for hybrid energy systems. The analysis shows that platform stability, motion response, and structural adaptability are critical factors affecting energy performance and operational reliability. Furthermore, the analysis highlights that hybrid configurations combining offshore wind, wave, and solar energy with energy storage technologies represent promising pathways toward more autonomous and sustainable offshore infrastructure. Key challenges related to design optimization, environmental loads, and system integration are also identified to support future developments in European offshore renewable energy. Full article

Offshore floating photovoltaics (OFPVs) offer a promising route for expanding solar energy development from land and inland waters to marine space, particularly in China’s coastal regions where electricity demand, land-use constraints, offshore wind infrastructure, and photovoltaic manufacturing capacity are highly concentrated. This review examines the development status, structural concepts, hydrodynamic challenges, research methodologies, reliability issues, and future pathways of OFPV systems in China from the perspective of marine engineering. Demonstration projects, representative platform concepts, and recent studies on environmental loading, platform motion, multi-body interaction, connector and mooring responses, and hydroelastic behavior are systematically synthesized. The review shows that Chinese OFPV technology has progressed from conceptual exploration to prototype testing and sea-based validation, with flexible membrane, steel-frame, semi-submersible, tensioned floating-island, HDPE modular, and composite-material concepts under active investigation. However, mature and replicable engineering solutions remain limited. Key barriers include survivability under extreme sea states, fatigue reliability of large arrays, corrosion, biofouling, material degradation, insufficient long-term field data, and the lack of dedicated design standards. Future development should emphasize array-level hydrodynamic design, coupled connector–mooring optimization, life-cycle reliability assessment, full-scale monitoring, and integration with offshore wind, wave energy, floating breakwaters, aquaculture, and other marine energy systems. Full article

This paper analyzes the fatigue loads of wind turbines in a floating offshore wind farm (FOWF) whose layout can be reconfigured. Such wind farm reconfiguration will be useful for wake effect mitigation in varying wind conditions. As an example FOWF, a farm with three 5 MW floating offshore wind turbine (FOWT) models on semi-submersible platforms, developed by the National Laboratory of the Rockies (NLR) (formerly the National Renewable Energy Laboratory (NREL)), is considered. Simulations for the example FOWF are conducted with various realistic turbulent wind and irregular wave conditions in the medium-fidelity wind farm simulator FAST.Farm. Using the simulation data, fatigue analysis is conducted by calculating the damage equivalent loads (DELs) using the computational tool MLife at critical components of the three FOWTs. The analysis results demonstrate the potential of reconfigurable FOWFs in not only increasing power outputs but also reducing fatigue loads for many critical components of turbines. Full article

Offshore renewable energy is widely recognised as a critical pathway for decarbonising electricity systems, but the integration of floating offshore wind turbines with wave energy converters remains technically challenging. This paper presents a structured literature review of hybrid wave–wind offshore energy platforms, drawing on 114 reviewed sources published between 2000 and 2026. The review classifies hybrid concepts using a three-axis framework based on floating platform type, wave energy converter (WEC) integration approach, and energy-dominance category. It then compares representative configurations, including point absorbers, oscillating water columns, flap-type devices, and heaving torus concepts, with emphasis on hydrodynamic response, energy contribution, structural complexity, mooring implications, validation status, and optimization suitability. The findings show that no single hybrid configuration can be ranked as universally superior because reported performance depends strongly on platform geometry, WEC scale, site wave climate, modelling assumptions, and validation maturity. Point absorber systems offer modularity and lower integration complexity, oscillating water column (OWC)-based systems provide protected power take-off (PTO) integration and moderate hydrodynamic interaction, flap-type systems can provide stronger motion-control potential but impose higher structural and mooring demands, and spar–torus concepts remain geometrically compatible with spar platforms but are generally wind-dominated. The review further shows that optimization method selection should depend on problem class: gradient-based methods are most suitable for local PTO tuning, evolutionary methods for non-convex multi-objective layout problems, surrogate-based methods for high-cost coupled simulations, and data-driven methods for adaptive control. The paper concludes that future progress requires standardized benchmark models, transparent evidence-level reporting, multi-physics co-optimization, techno-economic assessment, and systematic experimental or field validation before definitive concept ranking or commercial-readiness claims can be made. For decision-makers, industry stakeholders, and policymakers, the framework supports early-stage concept screening, identification of technology-specific risk factors, prioritisation of validation and investment pathways, and alignment of hybrid-platform development with site conditions, infrastructure constraints, and policy objectives. Full article

Carbon taxes and credits (CT&C) accelerate global deployment of carbon capture, utilization and storage (CCUS) technologies to enable energy transition. This study investigates the economic performance and resilience of floating gas-to-wire with CCUS (f-GTW-CCUS), deployed at the wellhead of stranded CO₂-rich offshore oil and gas reservoirs. The f-GTW-CCUS platform integrates a natural gas combined cycle power plant with monoethanolamine post-combustion capture (PCC-MEA), producing low-carbon electricity (23 kgCO_2e/MWh, competitive with renewables) while monetizing captured CO₂ via enhanced oil recovery (EOR). The mass and energy balance data from the proposed process configuration were obtained in the literature. Critically, f-GTW-CCUS operates on wellhead-sourced in situ-associated gas, eliminating exposure to volatile natural gas markets, and achieves a levelized cost of electricity (LCOE) of USD 67.15/MWh. Monte Carlo analysis (10,000 Gaussian iterations, 30-year lifetime, 10% discount rate, three CT&C scenarios, namely, low/medium/high) is used to quantify economic feasibility across three stochastic variables: oil, natural gas, and electricity prices, starting in the 5th year. The results demonstrate the following: (1) Case A (f-GTW without CCUS) remains economically infeasible (NPV < 0) under all price volatility scenarios due to insufficient electricity-only revenue and carbon taxation penalties; (2) Case B (f-GTW-CCUS with immediate CCUS deployment) maintains positive NPV across all scenarios, with EOR monetization contributing 43% of total revenue; (3) the critical CCUS deployment-delay threshold is 6 years under high carbon taxation, extending to 10 years when carbon credits are included. Gate-to-gate environmental assessment (carbon intensity, water footprint, land transformation) shows f-GTW-CCUS superiority versus alternative power systems, with minimal water–land nexuses due to offshore desalination. An empirical consistency assessment based on the 2026 geopolitical energy crisis demonstrates the structural resilience of the f-GTW-CCUS plant: the wellhead sourcing provides resilience to global natural gas price shocks, while the concurrent crude price escalation amplifies EOR revenues by 43–57%, improving project feasibility during commodity disruptions. These findings position f-GTW-CCUS as a critical decarbonization pathway for O&G producers exploiting stranded gas reserves. The technology combines carbon intensity reduction with economic resilience under volatile energy market conditions and mandatory climate policies. Full article

Offshore floating photovoltaic (OFPV) is an important renewable energy technology, and assessing the reliability of mooring systems is of great significance for promoting the large-scale commercial deployment of OFPV. However, owing to the complexity of the system structure, relevant reliability research has not been extensively carried out. With this in view, this work focuses on the systematic reliability analysis of a novel parallel mooring system composed of elastic ropes and anchor chains under the ultimate limit state (ULS), accidental limit state (ALS) and fatigue limit state (FLS), considering both long-term cyclic and extreme environmental conditions. The first-order second moment (FOSM), first-order reliability method (FORM) and Monte Carlo simulation have been employed to calculate the failure probabilities. By applying the series-parallel model to integrate multimode failures, it is confirmed that the failure probability of the entire mooring system is significantly greater than that under any single limit state. The results indicate that anchor chain is the main fatigue-critical component, and the Monte Carlo simulation based on extensive random sampling data is more conservative in reliability estimation than FOSM and FORM which cannot fully capture all distribution characteristics. This work could provide essential theoretical support for the safe design of subsequent OFPV mooring systems. Full article

With the rapidly growing global demand for clean energy, offshore wind power has become an important renewable energy source. To clarify how the principal dimensions affect the performance of a 15 MW-class floating wind turbine platform in 100 m water depth, this paper proposes a steel-concrete hybrid semi-submersible platform and systematically performs a parametric sensitivity analysis. The platform adopts a three-column configuration with heave tanks. The upper columns and cross braces are made of steel, while the lower hexagonal columns, pontoons, and heave tanks are constructed from concrete, significantly reducing steel consumption while satisfying structural and stability requirements. Focusing on three key design variables—draft, column spacing, and column diameter—this study establishes a unified normalized sensitivity analysis framework. It quantitatively evaluates their influence on platform mass, intact stability, natural periods, and fully coupled dynamic responses (including surge, heave, pitch motions, and mooring line tensions) under both operational and extreme conditions. The results reveal distinct roles of the principal dimensions in governing the platform dynamics: column spacing is the most sensitive parameter for tuning pitch response, restoring stiffness, and stability; increasing draft effectively suppresses heave and pitch responses but has only a limited effect on low-frequency surge motions; and column diameter strongly affects the natural periods of heave and pitch. Notably, dynamic responses exhibit significant nonlinear characteristics with variations in column diameter. When the diameter exceeds 110–120% of the baseline value, the peak pitch response under extreme sea states shows a deteriorating inflection point, accompanied by an accelerated surge in peak mooring loads. This indicates that excessive increases in column diameter may cause wave excitation forces to become dominant, thereby compromising the overall dynamic safety of the system. This paper identifies the governing geometric parameters for different motion modes and their control boundaries, providing a quantifiable and generalizable basis for the multi-objective collaborative design and cost reduction optimization of 15 MW steel-concrete hybrid semi-submersible floating wind turbine platforms. Full article

Stable wind resources in far-reaching sea areas are important direction for the development of renewable energy, making floating offshore wind turbine (FOWT) a focus of current research. However, the working environment of FOWT is severe. Under the condition of changeable wind and waves, the floating platform exhibits various motion responses, which may reduce power generation efficiency and even lead to structural damage with unpredictable consequences. In this paper, the National Renewable Energy Laboratory (NREL) 5 MW OC4-DeepCwind semi-submersible wind turbine is considered, and a multi-degree-of-freedom (M-DOF) tuned mass damper (TMD) system is designed to simultaneously suppress its roll and pitch motion responses. A multi-objective optimization problem is formulated to unify the frequency tuning accuracy, damping ratio constraints, and mass ratio limits through penalty functions. Then an improved Particle Swarm Optimization algorithm with time-varying acceleration coefficients (TVAC-PSO) is employed to determine the optimal TMD parameters, which dynamically adjusts exploration and exploitation capabilities to overcome the limitations of standard PSO in handling the strongly coupled parameter space. A high-fidelity aero-hydro-servo-elastic simulation model is established using OpenFAST to verify the vibration suppression performance under various sea state conditions. Simulation results demonstrate that the proposed M-DOF TMD system can effectively reduce the roll and pitch motion responses and significantly suppress the resonant peak energy, substantially improving the dynamic performance of FOWT. Full article

Following successful applications in inland water bodies, floating photovoltaics (FPV) developers are now targeting offshore sites. This advancement requires numerical tools that can quantify the hydrodynamic performance of large-scale FPV farms. The existing wave-diffraction solver DIFFRAC was extended to simulate the response of a large number of interconnected floating objects on a supercomputer. The applicability is demonstrated by simulating a 2 MWp offshore solar farm, consisting of 3660 FPV modules moored inside a protective ring of 32 interconnected floating breakwaters (FBWs). The FPV motions and loads on FPV connectors in regular and irregular waves are compared to a reference case without FBW protection. Results show an average reduction in axial FPV connector loads in the setup with FBW ring, but local load enhancements occur due to dynamic amplifications of horizontal FPV module motions. Vertical loads and overturning moments onto FPV connectors are globally reduced by up to 50% in steep irregular seas but are locally enhanced due to standing waves that develop inside the ring. The insights of the hydrodynamic behaviour lead to recommendations for improving the farm configuration to further reduce fatigue and survival loads onto FPV modules and connectors. Full article

The global transition of offshore wind energy into deep-water environments necessitates precise modeling of the complex, nonlinear dynamic responses of floating offshore wind turbines (FOWTs) to stochastic loads. Traditional industry-standard simulation tools often rely on potential flow theory, which neglects critical viscous effects and requires manual, empirical tuning of damping coefficients, reducing model reliability, while CFD modeling demands large computational resources. This paper introduces an application of advanced neural network techniques to model the coupled dynamic response of FOWTs under varied ocean conditions, reducing the simulation time required for training high-fidelity models. The architecture was trained using experimental data from the OC5 semi-submersible platform under the LC4.1 load case and further validated across a matrix of heterogeneous conditions, encompassing steady, turbulent, and irregular wind and wave environments. Results demonstrate exceptional predictive accuracy across coupled degrees of freedom (Heave, Pitch, and Surge), with the model achieving a coefficient of determination (${\mathrm{R}}^2>0.9$) and maintaining superior phase coherence without discernible time lag. Power spectral density analysis confirms the model’s robust ability to capture resonant frequencies and hydrodynamic restoration across varied sea states. This data-driven framework provides a robust, near-instantaneous alternative for simulating FOWTs global dynamics. By successfully capturing complex nonlinear interactions and inertial effects, the methodology enables rapid decision-making in preliminary design, real-time digital twinning, and accelerated long-term fatigue analysis for safety-critical offshore applications. Full article

The global demand for renewable energy is rapidly increasing in response to efforts to reduce greenhouse gas emissions, driving the development of novel technologies. Offshore solar energy is an emerging renewable technology with the potential to contribute to the energy transition and decarbonization of electricity generation. Although offshore solar projects are developing at an increasing pace, their ecological implications are not yet well-understood, including interactions with marine megafauna. Given the central ecological roles of birds and marine mammals, assessing and monitoring these interactions is essential before large-scale deployment. Despite extensive research on marine megafauna interactions with offshore wind farms, no studies have yet examined offshore interactions with solar installations. This study uses year-round time-lapse imagery and bird pellet analyses to record species presence, abundance, juvenile occurrence, and behavioral use of these structures in the southern North Sea. Seagulls, as well as grey and harbor seals, were frequently observed resting on the floating solar installations. Bird occurrence showed seasonal variation, likely reflecting breeding and migration patterns. The results indicate offshore solar structures may serve as temporary resting grounds for marine megafauna. These findings emphasize the importance of long-term ecological monitoring to ensure the sustainable co-existence of offshore renewable energy and marine biodiversity. Full article

Floating offshore wind turbines (FOWTs) are essential for expanding renewable energy capacity into deep-water regions. However, the deployment of semi-submersible FOWTs faces significant operational and financial hurdles, primarily driven by the high costs and logistical complexity of towing these structures to site. This perspective paper critiques current transportation processes, noting that existing offshore guidelines typically fail to account for the hydrodynamic drag generated by the unique bluff-body geometries of these hulls. The substantial pressure drag inherent in these structures leads to excessive fuel consumption and elevated carbon emissions during long-distance transit. Consequently, potential drag-reduction strategies must be explored to address these hydrodynamic inefficiencies. Among various technologies, fairings attached to the FOWT structure emerge as a promising solution, with potential drag reductions of around 40%. However, extensive research is required to ensure these designs do not compromise system stability, while also providing a net carbon emission reduction that justifies their production for large-scale deployment. Ultimately, integrating effective drag-reduction technologies is a vital step towards improving both the economic viability and the environmental footprint of the FOWT industry, ensuring its long-term sustainability in the global energy transition. Full article

Far offshore wind resources are important for reaching the global renewable energy and decarbonization objectives, but great distances to shore and deep waters preclude underwater electricity lines or traditional turbine or platform foundations. At these distances, converting the produced electricity to hydrogen via electrolysis of purified seawater is attracting interest. This hydrogen can then be transferred with fewer losses via undersea pipelines or transported to shore via ships. The difficulties of storing and transporting hydrogen over large distances can also be remedied by converting it into easily transported “e-fuels”, such as methanol and ammonia. The paper summarizes the current literature in terms of technologies and strategies involved in these renewable fuel production processes and highlights power consumption, efficiency, and levelized cost figures. These renewable e-fuels promise an environmentally friendly method of tapping into vast overseas resources that can be utilized on shore or provided to sea vessels for refueling. However, electrolyzer, synthesis reactor, and deep-water foundation or floating platform costs need to be brought down significantly by research and development before they can become commercially feasible in the coming decades. Full article