Offshore Wind Energy Industry Research Articles

Lifetime assessment of semi-submersible wind turbines by Gaidai risk evaluation method

As the global agenda turns more towards the so-called challenge of climate change and lowering carbon emissions, research into green, renewable energy sources becoming nowadays more and more popular. Offshore wind power, produced by FOWTs (i.e., Floating Offshore Wind Turbines), is one such substitute. It is a significant industrial part of the contemporary offshore wind energy industry and produces clean, renewable electricity. Accurate operational lifetime assessment for FOWTs is an important technical safety issue, as environmental in situ loads can lead to fatigue damage as well as extreme structural dynamics, which can cause structural damage. In this study, in situ environmental hydro and aerodynamic environmental loads, that act on FOWT, given actual local sea conditions have been numerically assessed, using the FAST coupled nonlinear aero-hydro-servo-elastic software package. FAST combines aerodynamics and hydrodynamics models for FOWTs, control and electrical system dynamics models, along with structural dynamics models, enabling coupled nonlinear MC simulation in the real time. The FAST software tool enables analysis of a range of FOWT configurations, including 2- or 3-bladed horizontal-axis rotor, pitch and stall regulation, rigid and teetering hub, upwind and downwind rotors. FAST relies on advanced engineering models—derived from the fundamental laws, however with appropriate assumptions and simplifications, supplemented where applicable with experimental data. Recently developed Gaidai reliability lifetime assessment method, being well suitable for risks evaluation of a variety of sustainable energy systems, experiencing nonlinear, potentially extreme in situ environmental loads, throughout their designed service life. The main advantage of the advocated Gaidai risks evaluation methodology being its ability to tackle simultaneously a large number of dynamic systems' degrees of freedom, corresponding to the system's critical components.

Analysing the cost impact of failure rates for the next generation of offshore wind turbines

AbstractOffshore wind turbines have rapidly scaled up in recent years, with plans to construct turbines up to 22 MW in the next decade. However, the operations and maintenance (O&M) requirements for these ‘next‐generation turbines’ remain largely unknown. In this study, the total O&M costs are calculated, using a bench‐marked O&M model, for a hypothetical 10 MW turbine scenario using two drive train configurations, based on known failure rates of smaller turbines. The O&M costs of the 10 MW turbines are compared with those of existing 3 MW turbines in two case studies: a North Sea wind farm and an East Coast US wind farm. Overall, direct drive 10 MW turbines performed better depending on the site's climate conditions. The study indicated that the two‐stage drive train configuration may be more suitable for the US site than the North Sea, depending on the turbine's failure rate. The US site benefited from increased availability due to more favourable weather windows, resulting in lower lost revenue for the two‐stage configuration despite high transport costs. The study found that the failure rate of 10 MW offshore wind turbines in the North Sea with a two‐stage gearbox can increase by as much as 30% compared to the 3 MW failure rates without increasing direct O&M costs. These findings are crucial for the offshore wind energy industry, particularly for OEMs, developers and maintenance providers, as they provide insights into the required reliability for next generation turbines to reduce O&M costs compared to existing 3 MW turbines.

Nautilus: An autonomous surface vehicle with a multilayer software architecture for offshore inspection

AbstractThe increasing adoption of robotic solutions for inspection tasks in challenging environments is becoming increasingly prevalent, particularly in the offshore wind energy industry. This trend is driven by the critical need to safeguard the integrity and operational efficiency of offshore infrastructure. Consequently, the design of inspection vehicles must comply with rigorous requirements established by the offshore Operation and Maintenance (O&M) industry. This work presents the design of an autonomous surface vehicle (ASV), named Nautilus, specifically tailored to withstand the demanding conditions of offshore O&M scenarios. The design encompasses both hardware and software architectures, ensuring Nautilus's robustness and adaptability to the harsh maritime environment. It presents a compact hull capable of operating in moderate sea states (wave height up to 2.5 m), with a modular hardware and software architecture that is easily adapted to the mission requirements. It has a perception payload and communication system for edge and real‐time computing, communicates with a Shore Control Center and allows beyond visual line‐of‐sight operations. The Nautilus software architecture aims to provide the necessary flexibility for different mission requirements to offer a unified software architecture for O&M operations. Nautilus's capabilities were validated through the professional testing process of the ATLANTIS Test Center, involving operations in both near‐real and real‐world environments. This validation process culminated in Nautilus's reaching a Technology Readiness Level 8 and became the first ASV to execute autonomous tasks at a floating offshore wind farm located in the Atlantic.

Life cycle cost analysis of a floating wind farm in the Norwegian Sea

The offshore wind energy industry has witnessed rapid growth in the past decade. Still, there is a lack of commercial floating wind projects due to the relatively high development costs and other factors. To facilitate the holistic evaluation of floating wind farms in Norway, this article investigates the levelized cost of energy of a floating offshore wind farm and its economic feasibility. The Troll field west of Bergen, Norway, is assumed to be the target offshore site, and a farm size of 50 wind turbines with a lifespan of 25 years are considered. Each floating wind turbine has a 15-megawatt turbine mounted on a semi-submersible floater. Based on detailed analysis, the levelized cost of energy of the wind farm is estimated to be approximately 100.7 $/MWh. The capital expenditure is the most prominent cost and constitutes 63.1% of the total cost, and the operational expenditure constitutes the remaining 36.9%. Further, sensitivity analyses show the influence of the lifespan, capacity factor, and project discount rate on the levelized cost of energy. The present study contributes to techno-economic evaluation of floating wind projects at an early phase.

Development of a high-energy centrifuge model impact hammer for pile-driving

The offshore wind energy industry continues to expand rapidly around the world in response to the demand for clean energy. Research to investigate monopile performance under cyclic lateral loading needs to replicate the installation process as well as the cyclic loading regimes. This has provided the impetus for the development of model pile driving hammers for use in geotechnical centrifuges. This paper presents a new model-scale centrifuge impact hammer that is capable of in-flight driving of large-diameter piles into dense sediments with the flexibility of varying the energy during a test for a more controlled installation. The new hammer is activated by a pair of rotating cams, improving on the pneumatically activated hammer developed in the 1980s, giving greater energy and much better reliability. This paper provides full details of the hammer, together with data obtained at 80g acceleration, driving prototype 4 m wide (50 mm in model scale) piles into dense, dry sand to depths of over 20 m (over 5D) in <1000 blows.

Machine Learning Solutions for Offshore Wind Farms: A Review of Applications and Impacts

The continuous advancement within the offshore wind energy industry is propelled by the imperatives of renewable energy generation, climate change policies, and the zero-emission targets established by governments and communities. Increasing the dimensions of offshore wind turbines to augment energy production, enhancing the power generation efficiency of existing systems, mitigating the environmental impacts of these installations, venturing into deeper waters for turbine deployment in regions with optimal wind conditions, and the drive to develop floating offshore turbines stand out as significant challenges in the domains of development, installation, operation, and maintenance of these systems. This work specifically centers on providing a comprehensive review of the research undertaken to tackle several of these challenges using machine learning and artificial intelligence. These machine learning-based techniques have been effectively applied to structural health monitoring and maintenance, facilitating the more accurate identification of potential failures and enabling the implementation of precision maintenance strategies. Furthermore, machine learning has played a pivotal role in optimizing wind farm layouts, improving power production forecasting, and mitigating wake effects, thereby leading to heightened energy generation efficiency. Additionally, the integration of machine learning-driven control systems has showcased considerable potential for enhancing the operational strategies of offshore wind farms, thereby augmenting their overall performance and energy output. Climatic data prediction and environmental studies have also benefited from the predictive capabilities of machine learning, resulting in the optimization of power generation and the comprehensive assessment of environmental impacts. The scope of this review primarily includes published articles spanning from 2005 to March 2023.

Renewable energy transition and the local economic development of lagging-behind regions: Evidence from the offshore wind energy industry in the UK

Renewable energy transition and the local economic development of lagging-behind regions: Evidence from the offshore wind energy industry in the UK

Longfin squid reproductive behaviours and spawning withstand wind farm pile driving noise

Abstract Pile driving noise is an intense, repetitive, far-reaching sound that is increasing in many coastal habitats as the offshore wind energy industry expands globally. There is concern for its impacts on keystone species and vital fisheries taxa such as squids. In controlled laboratory conditions, we investigated whether exposure to pile driving noise from offshore wind farm construction altered reproductive behaviours in the short-lived semelparous species Doryteuthis pealeii. Pile driving noise had no significant effects on the occurrence rates of agonistic behaviours, mate guarding, mating, and egg laying, compared with silent control trials. The results contrast starkly with behavioural response rates of the same squid species during feeding and shoaling. The data suggest that squid reproductive behaviours may be resilient to this increasingly pervasive environmental stressor, and that behavioural context guides responses to windfarm noise for this invertebrate taxon. While some non-reproductive behaviours can clearly be disturbed, the results show that species with limited opportunity to reproduce can tolerate intense stressors to secure reproductive success.

Hardly seen, often heard: acoustic presence of harbour porpoises (Phocoena phocoena) in one of the most urbanised estuaries in the world

The New York-New Jersey (NY-NJ) Harbour Estuary and surrounding waters support the largest port along the U.S. East Coast, commercial and recreational fishing, and a burgeoning offshore wind energy industry. Despite the high level of anthropogenic use, cetacean sightings have increased in recent years. Here, we investigated the spatiotemporal distribution of harbour porpoise in the NY-NJ Harbour Estuary from 2018–2020 using six archival acoustic recorders. Generalised additive mixed models were used to explore the relationship between weekly harbour porpoise presence and environmental variables. Harbour porpoises were detected at low levels year-round, with seasonal peaks in presence in winter to spring (February to June). Sea surface temperature and chlorophyll-a concentration were significant predictors of harbour porpoise presence, although the relationship warrants further investigation. Our results provide valuable insight into harbour porpoise distribution in the NY-NJ Harbour Estuary, which is likely related to oceanographic processes affecting prey availability. This information is timely for informing mitigation and management actions for forthcoming offshore wind energy development. Harbour porpoises are vulnerable to a range of anthropogenic impacts that have led to population declines in other regions, and therefore further research efforts are recommended for the NY-NJ Harbour Estuary and greater New York Bight.

Deconvolution approach for floating wind turbines

AbstractGreen renewable energy is produced by floating offshore wind turbines (FOWT), a crucial component of the modern offshore wind energy industry. It is a safety concern to accurately evaluate excessive weights while the FOWT operates in adverse weather conditions. Under certain water conditions, dangerous structural bending moments may result in operational concerns. Using commercial FAST software, the study's hydrodynamic ambient wave loads were calculated and converted into FOWT structural loads. This article suggests a Monte Carlo‐based engineering technique that, depending on simulations or observations, is computationally effective for predicting extreme statistics of either the load or the response process. The innovative deconvolution technique has been thoroughly explained. The suggested approach effectively uses the entire set of data to produce a clear but accurate estimate for severe response values and fatigue life. In this study, estimated extreme values obtained using a novel deconvolution approach were compared to identical values produced using the modified Weibull technique. It is expected that the enhanced new de‐convolution methodology may offer a dependable and correct forecast of severe structural loads based on the overall performance of the advised de‐convolution approach due to environmental wave loading.

Effective Stakeholder Engagement for Offshore Wind Energy Development: The State of New York's Fisheries and Environmental Technical Working Groups

AbstractThe offshore wind (OSW) energy industry is rapidly developing in the United States. New federal mandates require at least 30 GW of OSW by 2030. With the largest goal in the eastern United States, the state of New York seeks to advance OSW in a way that is both environmentally and socially responsible as well as cost‐effective. To achieve this, New York developed technical working groups (TWGs) in 2017 focused on critical topics relating to OSW energy development, including the Fisheries Technical Working Group and Environment Technical Working Group (F‐TWG and E‐TWG; collectively, “the TWGs”). The TWGs are composed of OSW developers, fishing industry (F‐TWG) or environmental nongovernmental organizations (E‐TWG), federal agency representatives, and state representatives from Maine to North Carolina. These groups advise the state of New York on OSW issues by emphasizing the use of science and technical expertise to inform decision making. The effectiveness of TWG collaborations is due to a variety of reasons, including the regional scale of stakeholder involvement, which allows the groups to develop guidance at an appropriate geographic scale relative to OSW and fishing activities and wildlife populations. The regional collaboration and communication fostered by the TWGs are essential for building trust among stakeholder groups and working collectively to minimize fisheries and environmental impacts as the OSW industry progresses. This paper highlights the OSW stakeholder engagement process and approach implemented by New York through the development of TWGs, as a means of identifying needs for environmental and fisheries resources to inform responsible OSW development within New York and regionally across the eastern United States. The lessons learned from the TWG process can be used to inform stakeholder engagement efforts in other locations.

Assessing the performance of winged caisson foundations for offshore wind turbines

The foundation of an offshore wind turbine (OWT) accounts for up to 20% of the total cost; therefore, investigations into reliable and efficient foundations are important for the offshore wind energy industry. This article describes an innovative winged caisson foundation for OWTs, which adapts the conventional caisson foundation to produce higher overturning capacities. The behaviour of this proposed novel foundation in the sand was investigated through experimental and numerical modelling using a series of 1 tests (1/70th scale), centrifuge model tests (70), and finite element (FE) simulations. Models with various wing sizes installed in different sand densities were tested in the laboratory by applying an overturning load. In this article, the moment–rotation performance of the foundation under monotonic loading is compared against that of conventional caissons to assess the potential benefits of adding wings to caisson foundations. Results show that there is a significant increase in overturning capacity provided by the novel foundation. FE models were first validated against experimental results, then, used to conduct a parametric study to better understand the behaviour of the winged caissons beyond the scaled model tests. In addition, the FE models were used to evaluate the drained response of the proposed foundation under combined loading.

DSS tests on marine clays for offshore windfarm foundation design

This technical note presents results of a series of monotonic and cyclic DSS laboratory tests performed on five intact marine clays offshore China. The laboratory program aimed to determine the cyclic shear strength and soil deformation properties for offshore foundation design. Various cyclic contour diagrams are provided, including cyclic shear strength and average and cyclic shear strains for different number of cycles. Results of the five clays are discussed and compared with an existing database on static and cyclic strengths of clays. In general, the test data fits well with the database and OCR plays an important role in the cyclic behaviour of the marine clays. The provided cyclic strength parameters for the tested clays can be used as references for similar clays offshore. The purpose of this study is to provide a realistic reference for research and practice offshore China where very few cyclic test results are available for offshore wind energy industry.

Immersion matters: The medium is the message for wind energy

The U.S. offshore wind energy industry is projected to experience a thousand-fold growth from less than 45 MW today to the target of 110 GW by 2050. The industry's modus operandi of presenting the public with 2D photos or 2D videos is inadequate as it does not resolve concerns about projects' visibility and noisiness, but rather perpetuates pre-existing erroneous beliefs. In the present study, we exposed respondents in Massachusetts to either photos, videos (2D, 360°), or immersive cinematic virtual reality displays depicting a real wind turbine. We tracked attitude shifts in a pre-post survey about the respondents' views on wind energy, including their perceptions of the wind turbine and the expected impact of a hypothetical wind project in their community. Exposure to more immersive media resulted in more positive perceptions, as well as larger and more positive changes in support for wind projects. We also found large changes in expectations about the soundscape of wind turbines, including when volume levels were not controlled in a lab. These findings suggest that traditional media (2D photos, videos) may be counterproductive for informing the public about proposed wind projects. Immersive, multimodal media (VR, 360° video) provide more accurate audiovisual information in a format that is easily understood by audiences less familiar with wind technology, leading to more positive attitudes toward wind projects.

Effect of the external beveled tip angle of the bucket foundation in clay on its penetration resistance considering soil large deformation and strain softening

In offshore wind energy industry, the bucket foundation in clay has been considered as an alternative to conventional foundations due to their unique features such as high overturning resistance. However, it cannot be installed to the pre-determined depth due to the soil plug generated during the penetration, which will significantly affect its bearing capacity. By setting the external beveled tip at the bottom of the bucket, the height of the soil plug can be reduced effectively. In order to study the influence of external beveled tip on the soil plug, soil softening and penetration resistance, the Coupled Eulerian-Lagrangian approach is used in this study to establish the bucket foundation penetration resistance models in correlation with different angles of external beveled tip considering soil large deformation and strain softening. It was found that as the angle increases, more soil are directed and flows out of the bucket, and the height of soil surface inside the bucket obviously decreases. When the angle increases to 60°, the soil plug inside the bucket is very small and hardly changes. As the angle increases from 0° to 60°, the degree of softening and amount of soil inside the bucket decreases, while that the trend is opposite for the soil outside the bucket. In addition, due to the influence of soil flow and strength degradation, the end bearing capacity factor and the frictional coefficient of inner side wall decrease as the angle increases, while the coefficient of outer side wall increases due to the reduction of softening effect. However, the total penetration resistance of the bucket foundation does not obviously change with the external beveled tip angle. 60° is recommended as the optimal angle for the external beveled tip in order to avoid the soil plug inside the bucket.

A novel multi-dimensional reliability approach for floating wind turbines under power production conditions

Floating offshore wind turbines (FOWT) generate green renewable energy and are a vital part of the modern offshore wind energy industry. Robust predicting extreme offshore loads during FOWT operations is an important safety concern. Excessive structural bending moments may occur during certain sea conditions, posing an operational risk of structural damage. This paper uses the FAST code to analyze offshore wind turbine structural loads due to environmental loads acting on a specific FOWT under actual local environmental conditions. The work proposes a unique Gaidai-Fu-Xing structural reliability approach that is probably best suited for multi-dimensional structural responses that have been simulated or measured over a long period to produce relatively large ergodic time series. In the context of numerical simulation, unlike existing reliability approaches, the novel methodology does not need to re-start simulation again each time the system fails. As shown in this work, an accurate forecast of the probability of system failure can be made using measured structural response. Furthermore, traditional reliability techniques cannot effectively deal with large dimensionality systems and cross-correction across multiple dimensions. The paper aims to establish a state-of-the-art method for extracting essential information concerning extreme responses of the FOWT through simulated time-history data. Three key components of structural loads are analyzed, including the blade-root out-of-plane bending moment, tower fore-aft bending moment, and mooring line tension. The approach suggested in this study allows predicting failure probability efficiently for a non-linear multi-dimensional dynamic system as a whole.

Bivariate statistics of floating offshore wind turbine dynamic response under operational conditions

FOWT (Floating offshore wind turbines) belong to the modern offshore wind energy industry generating green renewable energy. Accurate extreme loads and response prediction during power generation is an important design concern. More accurate and reliable estimations of extreme responses are significant for the offshore wind industry as it advances the design, manufacturing and deployment of large FOWTs in the coming decade. In this study, the OpenFAST code was used to model offshore wind turbine mooring line tension force and blade bending moment due to environmental loads, acting on a site-specific FOWT under realistic local environmental conditions. This paper presents an efficient Monte Carlo based method to study bivariate extreme dynamic response statistics. The ACER2D (bivariate average conditional exceedance rate) method is briefly discussed. The ACER2D method enables robust estimation of bivariate statistics, efficiently utilizing available data. Large return period 2D (two-dimensional) probability contours were obtained using the ACER2D method. Based on the studied performance of the presented methodology, it was seen that ACER2D provides accurate and efficient predictions of extreme return period contours.The described approach may be utilized at the design stage, defining optimal FOWT design values to minimize potential structural damage due to extreme environmental loads. It should be noted that the bivariate design point is less conservative than the classic univariate one; therefore, this study advocates a design method leading to lower structural production costs.

Vulnerability and spatial competition: The case of fisheries and offshore wind projects

Professional fishing activities are subject to spatial pressures. The cohabitation between a traditional fishing activity and development of the offshore wind energy industry raises questions about space sharing and rules of use. This paper proposes to adapt the vulnerability methodology developed to deal with global threats of climate change to this example of local, non-climatic change using the case study of a floating wind turbine project between Groix and Belle-Île (France). To understand and compare the potential impact of the different artisanal fishing activities, the method aims to conceptualize vulnerability with the identification of social, economic, and environmental key pressures and address them in a composite index. Although the smallest fishing units appear to be the most vulnerable, this effect is associated with a high sensitivity to the area near the coast. This research also highlights the importance of transparency and clarity during the construction of the composite index to avoid misinterpretation. This case study supports the relevance of applying the vulnerability method on a local scale to facilitate dialogue between stakeholders and reduce negotiation costs.

Floating wind turbines: marine operations challenges and opportunities

Abstract. The global floating offshore wind energy industry is rapidly maturing, with several technologies having been installed at pilot and demonstration scales. As the industry progresses to full array-scale deployments, the optimization of marine activities related to installation, operation and maintenance, and decommissioning presents a significant opportunity for cost reduction. This paper reviews the various marine operations challenges towards the commercialization of floating wind in the context of spar-type, semi-submersible and tension leg platform (TLP) technologies. Knowledge gaps and research trends are identified along with a review of innovations at various stages of development, which are intended to widen weather windows, reduce installation costs, and improve the health and safety of floating-wind-related marine operations.

Use of drones in offshore wind farm inspections

Abstract: With the increase in global investments in offshore wind energy and the rapid implementation of wind technologies in hazardous deep water environments, operational inspection of wind turbines and related infrastructure plays an important role in the safe and efficient operation of offshore wind farms. In recent years, much attention has been paid to the use of unmanned aerial vehicles (UAVs) and remotely piloted unmanned aerial vehicles (RPAs) commonly referred to as "drones" for remote inspection of renewable energy infrastructure, i.e. photovoltaic farms and onshore wind farms. Drones have significant potential also in in offshore wind energy. Inspection with drones allows for to reduce not only the number of flight operations (involvement of aircraft and flight crews) and the transport of personnel carrying out the maintenance and repair of offshore wind turbines. With drones is possible carry the equipment transported for hazardous inspection work. The involvement of UAVs also reduces the plant downtime needed to detect faults and collect diagnostic information from the entire wind farm. The benefits of inspection technology in the offshore wind energy industry based on drones are confirmed by the previous tests, and the prospect of offshore energy development encourages further work with the use of UAVs. At the same time, it should be borne in mind that any unexpected failure of the drone system during its mission may interrupt control works (during inspections), and thus reduce the electricity generated by wind turbines. The article presents the potential of drones in the process of inspecting wind farms, including offshore wind farms, presents examples of UAV models used for inspections, indicates methods of conducting inspections with the use of drones and highlights a significant reduction in the costs of the operation of offshore wind farms as a result of limiting the use of manned aviation (helicopters and flight crews) and the elimination of the risk associated with the involvement of personnel to perform inspections of wind farms at sea. The potential of unmanned floating platforms as part of cooperation with UAV in the process of inspecting offshore wind farms was also indicated. Keywords: wind energy, offshore, drones, wind farms, drone inspections, maritime inspections, marine aviation, offshore, offshore wind energy, safety air operations, risk analysis