ABSTRACT The demand for renewable energy is growing, and offshore renewable energy plays a crucial role among the available alternatives. In this regard, the identification of suitable Offshore Renewable Energy Resource Areas (ORERA) and the implementation of effective marine spatial planning are essential for efficient and safe resource utilization. This study focuses on ORERA from the perspective of navigational safety. Factors affecting navigational safety for ORERA were identified through a literature review using academic studies and publications of the International Maritime Organisation (IMO) and the Maritime and Coast Guard Agency (MCA). The cause-and-effect relationships between these factors were analyzed using the Fuzzy Decision-Making Trial and Evaluation Laboratory (DEMATEL) method. The research aims to clarify factors affecting navigational safety within or near ORERA and explore their interrelationships. The analysis highlights weather conditions, water depth, tidal streams and local currents as the most influential factors. This research provides insights ORERA planning and nearby navigation.

European states have set ambitious targets to meet their climate goals and decarbonize their energy sector. These included development plans for the marine environment, knowing its potential in harnessing Offshore Renewable Energy (ORE) through wind, wave and tidal resources. The latter is becoming highly attractive due to its predictability, reliability and potential to answer communities' energy needs, but it is still associated with several challenges that are often overlooked. This paper aims to identify the barriers and drivers for tidal energy development in Ireland following the recent policy changes. This is done through semi-structured interviews with key local and regional stakeholders in the ORE field, which are analysed following Braun and Clarke's Thematic Analysis approach. The main challenges for tidal energy development revolve around the uncertainties and dynamic nature surrounding the existing regulatory framework in terms of marine spatial planning and planning processes, in addition to the technology's high cost, limited competitiveness and lack of resources in state agencies and departments. Moreover, community objections, socio-economic interests and supply chains issues play a key role in project delays. Nevertheless, the technology offers undervalued advantages in terms of its predictability and reliability, particularly in remote and island communities. Interviews revealed the need to provide better clarity and faster action at all levels of the ORE value chain. This cannot happen without providing incentives, enhancing awareness and community participation, and ensuring environmental sustainability. As the identified barriers represent typical challenges encountered in other country-cases, Ireland can learn from leading EU and international countries to enable projects’ commercialization, and can also lead by example for similar island nations. • This paper examines the barriers and drivers for tidal energy development using the Republic of Ireland as a case study following the Government decision to shift from a developer-led to a plan-led approach. • A thematic analysis approach through semi-structured interviews with key public and private stakeholders in the ORE field was followed. • Tidal Energy offers undervalued advantages such as predictability and reliability, particularly in remote and island communities. • Qualitative interviews highlighted the need for more clarity at all levels of ORE development in future years, and underscored the dynamic and interconnected nature of ORE policies in Ireland. • Ireland is well positioned to learn from EU and international experience to enhance tidal and ORE potential and lead as an example for other island nations.

Space–time regression and interpolation of metocean measurements: A focus on satellite data for the offshore energy sector

Predicting the dynamics of floating offshore wind turbines (FOWTs) in realistic extreme conditions is important for their effective design and operation. This includes realistic extremes involving combined wave-current conditions and breaking-wave conditions, which are highly prevalent yet seldom accurately incorporated into design due to modelling challenges. Here, a smoothed particle hydrodynamics (SPH) based wave-current flume with open boundaries is employed to model the dynamics of a semi-submersible FOWT. First, FOWT motions are validated against experimental measurements in regular waves. Second, focused waves on vertically sheared currents and spilling breaking waves are replicated in the numerical flume. Following these validations, the FOWT response is examined under these conditions. For the present mooring configuration, surge and heave are primarily governed by wave excitation but are also influenced by current through the modification of wave-induced kinematics and altered mean position. Pitch exhibits a distinct two-stage response under waves on a following sheared current and under spilling breaking waves, with pitch angles reaching about 14.5° in the former, revealing potential consequences for aerodynamic and drivetrain loads and underscoring the importance of capturing these phenomena for design. Mooring design refinement shows that increasing the line length (initially 1 m) by 0.4 m reduces observed extreme pitch angle from 14.5° to 4.6°, and mooring tension from 533.7 N to 58.7 N, respectively. This study therefore develops and demonstrates a novel SPH-based framework with open boundaries to model FOWTs and other offshore renewable energy (ORE) systems in realistic extreme conditions, with the capability of refining their design. • An SPH framework with open boundaries is developed for FOWTs in realistic extremes. • Realistic extremes are generated using waves on sheared currents and breaking waves. • The FOWT dynamics in these realistic extremes exhibit a distinct two-stage response. • The ability to model any offshore system in realistic ocean extremes is demonstrated.

Development and multi-objective optimization of a novel power-to-ice system for offshore renewable energy penetration

An integrated spatiotemporal techno-economic assessment of offshore renewable energy complementarity: A case study in China's maritime zones

iSeaPower: An interactive decision-support digital twin platform for offshore renewable energy managements

For offshore renewable energy planning and intelligent power management, access to long-term, high-resolution, and physically consistent meteorological and power generation records is essential. Such data supports a wide range of tasks, including resource assessment, hybrid system capacity sizing, grid operation planning, and data-driven forecasting model development. This article presents the construction of a 10-year continuous hourly dataset for 16 deep-sea grid sites in the Beibu Gulf, China, spanning from January 2016 to December 2025. The raw meteorological variables, including 10 m wind speed, wind direction, solar irradiance, and 2 m air temperature, were retrieved from the NASA POWER satellite database and subsequently cleaned using a 24 h periodic substitution algorithm designed to preserve the physical integrity of daily weather cycles. The dataset is organized into two sub-datasets, the Historical Weather Dataset and the Normalized Power Yield Dataset, with the latter providing normalized wind and solar power outputs on a 1.0 per-unit (p.u.) basis derived from a wind turbine power curve model and a PV thermodynamic model. All 32 CSV files are freely accessible online with UTF-8 encoding. The utility of the dataset is illustrated through two representative application cases including offshore site selection with hybrid capacity sizing and physics-informed deep learning forecasting, demonstrating its suitability for both engineering analysis and machine learning model development.

Energy transportation and storage systems are becoming increasingly economically viable as maritime and offshore renewable energy generation technologies advance, thereby diversifying both hydrocarbon and green energy sources. Offshore Compressed Air Energy Storage (OCAES) comprises flexible energy storage and transportation technologies. It is frequently utilized by Floating Production, Storage and Offloading (FPSO) units, offshore wind farms, and marine green renewable energy systems. Currently, marine risers being widely used to connect floating platforms to subsea equipment during offshore operations. Therefore, understanding the dynamic characteristics of marine risers is critical to ensure the overall operational safety and stability of various offshore OCAES systems. Due to frequent use in the offshore industrial sector, marine risers are often susceptible to excessive dynamic environmental stresses. For various offshore installations, an accurate assessment of the dynamic response of deep-sea risers to subsurface currents is essential, given that VIV are critical to design and operational safety. This case study examined the effects of hydrodynamic sea-current loads on marine risers under actual in situ environmental conditions, using an accurate experimental dataset. This case study demonstrated that, under excessive sea/ocean wave/current loads, it is possible to accurately assess the risk of damage or failure for the riser system.

Submarine power cables (SPCs) associated with offshore renewable energy developments emit electromagnetic fields (EMFs) that can influence aquatic biota. Although research on this topic has increased, a comprehensive, systematic synthesis of observed effects across taxa and life stages, and biological contexts has been lacking. Following PRISMA 2020 guidelines (PROSPERO ID: 1138188), we systematically reviewed peer-reviewed and grey literature published between 1990 and 2024. Of 1637 records screened, 67 eligible field and laboratory studies were included. Significant behavioural and physiological responses to EMF exposure were reported in 66% of studies, with early life stages (embryos, larvae, juveniles) and magnetosensitive taxa, particularly fishes and crustaceans being most frequently affected. Effects occurred even at environmentally relevant intensities (<250μT). Laboratory experiments more frequently detected effects than field studies, which were generally fewer, shorter in duration, and methodologically heterogeneous. Sensitivity heatmaps identified developmental stages and freshwater species as particularly sensitive, with notable taxonomic disparities. EMFs from SPCs can elicit ecologically relevant responses in aquatic biota, particularly during sensitive developmental windows and in magnetically responsive taxa. Emerging evidence further indicates that sex specific responses represent an important and previously under recognised dimension of EMF sensitivity. However, major uncertainties persist regarding chronic, population and ecosystem level impacts. Future research should prioritise standardisation of exposure characterisation and reporting, routine inclusion of sex and life stage as biological variables and coordinated laboratory to field validation. Integrating EMF considerations into marine spatial planning, environmental regulation, and biodiversity conservation frameworks will be essential to support proportionate ecological risk assessment and management of offshore renewable energy infrastructure.

A review of improved machine learning-based reliability analysis methods applied to floating renewable energy structures

Abstract Erosion at the base of submarine landslides remains poorly understood, despite being a critical threat for the stability of valuable seabed infrastructures such as communication cables and offshore renewable energy installations. Clues about its genesis are often preserved at the basal surface of landslides in the form of elongated scours aligned in the direction of landslide transport. However, these features are commonly concealed by the overlying landslide mass, and when visible, the overprint of slope gradient often masks their structural complexity. This research applies detrending algorithms to remove slope-induced overprint from exceptionally well-imaged landslide basal surfaces mapped using high-quality 3D seismic reflection data. Detrending revealed the morphological characteristics of prominent scour fields, providing new insights into the erosional mechanisms operating at the base of submarine landslides. The results indicate that distinct basal erosion processes create morphometrically diagnostic scour features. For example, basal block tooling produces steep and symmetric scours with increased erosion depth at their downslope termination, suggesting enhanced material removal at the base of blocks as these progressively sink within a decelerating landslide. Erosion might also occur by the action of longitudinal flow vortices at the boundary layer of gravity flows, with the latter generated from the disaggregation of landslides evacuating further upslope. These scours are spatially detached from landslide headscarps and initiate where seabed irregularities ignite secondary flow vorticity. The termination of this type of scours where bathymetric breaks occur suggests changes in flow dynamics and suppression of vorticity at those locations. Recognising different scour morphologies is key to reconstructing failure dynamics and better assessing hazards posed by submarine landslides. The detrending method presented here offers a powerful tool able to unravel complex geomorphic features, with potential applications across marine, terrestrial, and planetary environments.

The European Green Deal (EGD) sets an ambitious, cross-sectoral agenda with direct implications for the sea. Yet methods to systematically assess how national Maritime Spatial Plans contribute to EGD objectives remain scarce. The article proposes an EGD–MSP nomenclature that translates the EGD's complexity into a practical, adaptable framework for practical application in Maritime Spatial Planning. The framework clusters EGD ambitions into seven topics—climate change mitigation, climate change adaptation, sustainable seafood production, biodiversity and ecosystem protection and restoration, blue circular economy, zero pollution, and fair and just transition—and organises them hierarchically into sub-topics and operational elements. The nomenclature was tested across seven EU countries (Bulgaria, Finland, France, Germany, Italy, Latvia, Spain) using desk analysis of MSP plans and related documents, targeted interviews, and a workshop to examine aspects common to the participating countries. A semi-quantitative synthesis (YES/PARTIALLY/NO) enabled consistent comparison of how EGD elements appear in MSP visions, objectives, and measures. Results show that climate change mitigation is widely and explicitly addressed—primarily via offshore renewable energy—while adaptation is present but often indirect. Biodiversity protection is common, whereas restoration remains limited. Blue circular economy and zero-pollution objectives are referenced more often in objectives than in concrete measures. Approaches to a fair and just transition are emerging, with participation and transparency improving, yet institutional, financial and technical knowledge capacities remain uneven. The nomenclature balances harmonisation and interpretative flexibility, enabling robust cross-national comparisons without imposing uniformity. Beyond analysis, it provides a practical scaffold for implementation, monitoring, and iterative plan revision, and can be extended into an indicator-based system to track MSP contributions to the EGD over time.

Submarine cable systems are essential for intercontinental connectivity and the integration of offshore renewable energy into onshore grids. The reliability of these systems depends on a well-coordinated life cycle process that integrates installation, monitoring, and maintenance technologies. This review synthesizes the key components of submarine communication and power cables, highlighting the processes involved in route survey, cable laying, and burial under complex seabed conditions. The major factors contributing to damage are typically classified into natural hazards and human activities. Particular attention is given to fault diagnosis techniques, including optical time domain reflectometry (OTDR) and time domain reflectometry (TDR). Additionally, practical workflows and processes for fault location and cable repair are outlined. By structuring advancements across installation, monitoring, and maintenance processes, this review offers a comprehensive technical reference for researchers and practitioners, while emphasizing emerging trends aimed at enhancing system resilience, real-time situational awareness, and rapid response, thus supporting global digitalization and the transition to clean energy.

To address stringent reliability demands of offshore renewable energy systems, particularly wind power, this paper proposes an NPC three-level rectifier based on relay-driven topology and control scheme, featuring excellent fault-tolerant capability. The proposed strategy enables real-time identification of fault locations and types, followed by relay-actuated topological reconfiguration for effective isolation of faulty phases. By redefining modulation sectors and vector sequences, and generating pulse-width modulation (PWM) signals through duty-cycle calculation combined with triangular carrier comparison, the system realizes two-level modulation control and maintains stable operation even in case of IGBT failures. This approach not only enables rapid post-fault recovery while ensuring balanced three-phase currents, but also stabilizes neutral-point voltage, significantly improving system robustness under harsh offshore conditions. Relay-centric topology eliminates need for additional power switches, further enhancing cost-effectiveness and structural simplicity of offshore wind power conversion systems.

In the real-time energy management of offshore islanded microgrids, determining the optimal operating points of storage systems, particularly in hydrogen-based storage, poses significant challenges. These arise from the stochastic nature of offshore Renewable Energy Sources (RES), variable power demand, and the volatility of hydrogen systems. To address these, a novel objective function has been developed that integrates electrolyzer system efficiency into the Energy Management Strategy (EMS) of a DC microgrid. Unlike most existing literature, which considers electrolyzer efficiency as a constant, this work treats efficiency as a dynamic variable that depends on operating current, temperature, and pressure. The behavior of the electrolyzer efficiency with respect to these parameters is modeled, verified, and subsequently incorporated into the EMS. A MINLP based EMS is developed to implement the proposed formulation, and its effectiveness is validated by demonstrating optimal microgrid performance under the above scenario. Notably, the impact of optimal temperature and pressure control is evidenced by electrolyzer efficiency improvements of 1.7% and 3.1% in the efficiency-focused and multi-objective scenarios, respectively. The proposed EMS is evaluated against a rule-based and heuristic (PSO) methods. In the cost-based case, the developed method shows 36.5% and 0.04% cost reductions relative to the rule-based approaches, and a 0.39% reduction relative to PSO. In the efficiency-based scheme, it attains 0.10% efficiency gain over PSO for the optimal temperature-pressure method, and in the multi-objective case, it delivers 7.40% efficiency gain versus PSO. • Novel optimization with electrolyzer efficiency for offshore islanded DC microgrids. • Electrolyzer efficiency modeled dynamically via current, temperature, and pressure. • Multi-objective framework balances cost and efficiency in flexible microgrid EMS. • Sensitivity to electrolyzer operating conditions is analyzed. • EMS validated against rule-based and metaheuristic approaches.

The present study aims to provide a comprehensive and integrated analysis of the potential of offshore renewable energy resources in the maritime sector located at the Danube mouth area in the Black Sea, one of the most complex and dynamic hydrological and climatic systems in Eastern Europe. In the current context of climate change, the Danube mouths are of strategic importance due to the specific morphology of the area and the high potential for harnessing multiple renewable sources such as wind, wave, and solar energy. Therefore, this research supports sustainable development and adaptation to climate change. At the same time, predicted climate change may increase the frequency of extreme events, such as storms, sudden changes in water levels, and increased wave heights, which can affect navigational safety, ecosystem integrity, and coastal infrastructure. Thus, this research seeks not only to identify the energy potential of renewable resources but also to assess their risks and vulnerabilities. Using a wide range of data types, three time periods were studied for the main Danube mouth: Sulina and St. George. Both Sulina and St. George present future wind and wave intensification trends, especially in high-emission scenarios, without significant changes in the dominant direction. St. George remains the area with the more intense regime, while Sulina has more moderate episodes, but with a slightly more evident increase in the frequency of 6–12 m/s winds. At the same time, solar radiation shows a slight increase in recent years, especially in the summer season. Harnessing these resources has the potential to, for example, power coastal communities and offshore installations, providing clean and reliable energy while reducing greenhouse gas emissions.

Seabed response and local scouring around pile groups under combined wave–current loading pose critical threats to the stability and long-term performance of offshore structures, particularly those supporting offshore renewable energy infrastructures. In this study, we present a systematic experimental investigation on the pore-water pressure and local scour around pile groups subjected to regular waves, combined regular wave–current conditions, and irregular waves generated using the JONSWAP spectrum under wave-only conditions. Pore-water pressures and seabed morphology were analyzed for different hydrodynamic conditions, pile spacings, and pile arrangements. The experimental results demonstrate that the presence and magnitude of current are the dominant factors controlling scour development. Increasing the current velocity from 0 to 0.25 m/s leads to a three (3) to five (5) times increase in maximum scour depth, whereas comparable variations in wave height and wave period produce relatively small effects. The direction of a current affects the location of maximum scour, with the wave–forward current condition promoting the development of an interconnected scour area within the pile array and wave–opposing current condition, shifting local scour toward downstream piles. Small-spaced piles (G/D = 1) intensify hydrodynamic interactions and increase scour depth by approximately 30–40% compared with wider spacing. Irregular waves generate more spatially distributed but shallower scour than regular waves of comparable wave characteristics. These findings provide insights into the mechanisms governing seabed instability around pile group foundations and contribute to more sustainable design and operation of offshore infrastructure, such as offshore wind turbine foundations.

Abstract Submarine export cables (SECs) are an essential component of any offshore wind farm (OWF), serving as the primary conduit for energy transmission to the onshore grid. As floating wind technology advances, the increasing distance of OWFs from the shore results in longer and more complex SEC routes, raising costs and potential environmental impacts. This study presents a comprehensive approach to optimising SEC routes, aimed at enhancing the efficiency of site selection and ensuring the long-term reliability of OWFs. By compiling a geospatial repository of publicly available data, the study reviews and evaluates SEC route feasibility using bathymetric, geological, ecological, and human activity data. The Analytical Hierarchical Process was used to establish criteria weights for two anticipated scenarios for Ireland's South and West coasts, classifying regions into zones of suitability based on economic and environmental considerations. In areas designated for offshore wind development, potential offshore substation and cable landfall sites were identified and optimised SEC routes were generated using a Least Cost Path Algorithm. Openly available sub-bottom profile data were analysed in two key regions, providing a novel use case of repurposing publicly accessible data for the planning of offshore infrastructure. Derived sediment thickness profiles further refined cable routing away from areas with outcropping bedrock toward areas with optimal sediment thicknesses for cable burial, thereby minimising the risk to cables from external hazards. The results of the study highlight key areas for offshore wind projects, as well as providing a scalable workflow for policymakers and developers of offshore renewable energy projects.

Abstract Europe and the world are currently in a poly-crisis. Firstly, anthropogenic climate change leads to an increase in extreme weather conditions while increasing the pressure on an already weakened ecosystem. Secondly, the biodiversity crisis as a follow up of pollution and reduction of natural habitats causes unstable eco systems. Thirdly, the geopolitical order and energy security for many (European) countries is getting jeopardised by the Russian attack on Ukraine and the ongoing trade-wars. This work shows how the build-out of offshore renewable energy in multi-source parks combining offshore wind, wave and offshore solar energy can tackle multiple of those crises. A tool, called Multi-Source Offshore Renewable Energy (MultiORE) is used for the layout, energy profile and economics of such a combination of technologies wave, wind and solar energy resources. The MultiORE simulation of a 600 MW wind – 210 MW wave – 900 MW solar park at this North Sea location resulted in an 21% increased energy density compared to the wind-only scenario. The increase in energy density is possible without any delay on site characterisation and grid infrastructure build-out as well as only minor expected impacts on construction time, critical for the climate crisis. The increased energy density requires less areas for offshore renewables leaving more space for natural ecosystems. To achieve the same yearly energy output as the wind-only park, the multi-source park would require about 18% less space helping to mitigate the biodiversity crisis. The model further shows an increase of the capacity factor from 52% (Wind only) to 63% (Wind/Wave/Solar) while also reducing low production hours (&lt;20% of export capacity) by almost 60% compared to wind-only. The longest duration of low production hours was reduced from 144 consecutive hours to 39 hours. This overplanting at the same time did not lead to significant curtailment, as only 5% of the total energy produced could not be exported indicating improved energy security. Even though multi-source parks can have several positive impacts on above described crises they also come with difficulties like varying maturity of different technologies having a higher risk profile and cost . An economic assessment showed that a positive bussiness case, calculated via a net present value (&gt;0), is possible, considering learning rates on the Levelised Cost of Electricity (LCOE) provided by industry as part of the Horizon 2020 EU-SCORES project.