Onshore Counterparts Research Articles

A Damping Modification Factor Prediction Model for Horizontal Pseudoacceleration Spectrum for Subduction Slab Earthquakes Using Offshore Ground Motions in the Japan Trench Area

ABSTRACT This study develops a damping modification factor (DMF) model for offshore ground motion from subduction slab earthquakes that is a function of the damping ratio, spectral period, moment magnitude, focal depth, and rupture distance. The DMF values for 10 damping ratios between 1% and 30% and 34 spectral periods ranging from 0.03 to 5.0 s are calculated using 2803 offshore ground-motion records obtained from the S-net in Japan. An examination of the residuals from a median model, which considers deployment methods, indicates that DMF is influenced by parameters such as magnitude, depth, and distance. The DMF model includes the following components: a median model considering deployment method, a magnitude linear term, a magnitude square term, a focal depth term, an ln(R) scaling, and a constant term. The influence of damping ratio on model coefficients can be simulated by a quadratic function of the damping ratio. In addition, we established a DMF standard deviation model, for which the influence of damping ratio and spectral period on the standard deviation can be simulated by a quadratic function of the damping ratio and a quartic polynomial of the spectral period, respectively. The uncertainty related to the path and site effects is the main source of the deviation of the DMF model. We have conducted a comparison between the offshore DMF model and onshore model proposed by Rezaeian, Al Atik, et al. (2021), revealing that for lower damping ratios, the offshore DMF is generally lower at periods less than 0.2 s and larger at periods greater than 2.0 s compared to its onshore counterparts. The offshore DMF model adjusts the acceleration spectrum proposed by Tan and Hu (2024) to generate smooth pseudoacceleration spectra for most spectral periods.

Seismic responses and vibration control of offshore wind turbines considering hydrodynamic effects based on underwater shaking table tests

AbstractThe recent construction of numerous offshore wind turbines (OWTs) in seismically active areas worldwide has stimulated research on seismic evaluation and vibration control design for OWTs. Unlike the onshore counterparts, the hydrodynamic effects on the seismic responses of OWTs need to be studied. Besides, the equipment in the nacelle of an OWT is highly sensitive to acceleration. Significant dynamic amplification on the nacelle under horizontal earthquake excitation can cause the malfunction of power generation and even seriously threaten the safety of OWTs. As a promising solution, tuned mass dampers (TMDs) based on the first mode of OWTs need to be tested by various earthquake excitations. In this paper, the seismic amplification effect, the hydrodynamic effects, and the vibration control by a single TMD are investigated through a series of underwater shaking table tests based on a 1:20 scaled model of a 5 MW OWT. The “no water”, “with water”, and “with water and TMD” tests are evaluated and compared. The accelerations of OWTs can be amplified or reduced by the hydrodynamic effects, depending on the natural frequencies and vibration modes of the OWT and the frequency spectrum of the seismic excitation. The earthquake‐induced hydrodynamic damping ratio and hydrodynamic added mass are carefully measured. For the TMD's effect, the single TMD performs reasonably well in seismic vibration control in most cases. Finally, the interaction between hydrodynamic effects and TMD's effect is discussed, and the hydrodynamic damping effect is suggested to be ignored when designing TMDs for OWTs.

The GHG Intensities of Wind Power Plants in China from a Life-Cycle Perspective: The Impacts of Geographical Location, Turbine Technology and Management Level

Presented in this study is a comparative life cycle assessment of 60 wind plant systems’ GHG intensities (49 of onshore and 11 of offshore) in China with regard to different geographical location, turbine technology and management level. As expected, geographical location and turbine technology affect the results marginally. The result shows that the life-cycle GHG intensities of onshore and offshore cases are 5.84–16.71 g CO2eq/kWh and 13.30–29.45 g CO2eq/kWh, respectively, which could be decreased by 36.41% and 41.30% when recycling materials are considered. With wind power density increasing, the GHG intensities of onshore cases tend to decline, but for offshore cases, the larger GHG intensity is as the offshore distance increases. The GHG intensities of onshore cases present a decreasing trend along with the technical advancement, and offshore counterparts is around 65% higher than the onshore cases in terms of wind turbines rated at more than 3 MW. The enlarging of offshore turbine size does not necessarily bring marginal benefit as onshore counterparts due to the increasing cost from construction and maintenance. After changing the functional unit to 1 kWh on-grid electricity (practical), the highest GHG intensities of Gansu province increase to 17.94 g CO2eq/kWh, same as other wind resource rich provinces, which significantly offsets their wind resource endowment. The results obtained in this study also highlight the necessity for policy interventions in China to enhance resource exploration efficiency and promote robust and sustainable development of the wind power industry.

The Sensitivity of 5MW Wind Turbine Blade Sections to the Existence of Damage

Due to the large size of offshore wind turbine blades (OWTBs) and the corrosive nature of salt water, OWTs need to be safer and more reliable that their onshore counterparts. To ensure blade reliability, an accurate and computationally efficient structural dynamic model is an essential ingredient. If damage occurs to the structure, the intrinsic properties will change, e.g., stiffness reduction. Therefore, the blade’s dynamic characteristics will differ from those of the intact ones. Hence, symptoms of the damage are reflected in the dynamic characteristics that can be extracted from the damaged blade. Thus, damage identification in OWTBs has become a significant research focus. In this study, modal model characteristics were used for developing an effective damage detection method for WTBs. The technique was used to identify the performance of the blade’s sections and discover the warning signs of damage. The method was based on a vibration-based technique. It was adopted by investigating the influence of reduced blade element rigidity and its effect on the other blade elements. A computational structural dynamics model using Rayleigh beam theory was employed to investigate the behaviour of each blade section. The National Renewable Energy Laboratory (NREL) 5MW blade benchmark was used to demonstrate the behaviour of different blade elements. Compared to previous studies in the literature, where only the simple structures were used, the present study offers a more comprehensive method to identify damage and determine the performance of complicated WTB sections. This technique can be implemented to identify the damage’s existence, and for diagnosis and decision support. The element most sensitive to damage was element number 14, which is NACA_64_618.

Study of Centrifugal Stiffening on the Free Vibrations and Dynamic Response of Offshore Wind Turbine Blades

Due to their large and increasing size and the corrosive nature of salt water and high wind speeds, offshore wind turbines are required to be more robust, more rugged and more reliable than their onshore counterparts. The dynamic characteristics of the blade and its response to applied forces may be influenced dramatically by rotor rotational speed, which may even threaten the stability of the wind turbine. An accurate and computationally efficient structural dynamics model is essential for offshore wind turbines. A comprehensive model that takes the centrifugal stiffening effect into consideration could make rapid and accurate decisions with live data sensed from the structure. Moreover, this can enhance both the performance and reliability of wind turbines. When a rotating blade deflects in its plane of rotation or perpendicular to it, the centrifugal force exerts an inertia force that increases the natural frequencies and changes the mode shapes, leading to changes in the dynamic response of the blade. However, in the previous literature, studies of centrifugal stiffening are rarely found. This study investigates the influence of centrifugal stiffening on the free vibrations and dynamic response of offshore wind turbine blades. The National Renewable Energy Laboratory (NREL) 5 MW blade benchmark was considered to study the effect of angular speed in the flap-wise and edge-wise directions. The results demonstrate that the angular speed directly affects the modal features, which directly impacts the dynamic response. The results also show that the angular velocity effect in the flap-wise direction is more significant than its effect in the edge-wise direction.

Intra-basement structures and their implications for rifting of the northeastern South China Sea margin

• Intra-basement structures in the northeastern South China Sea margin are imaged by reflection seismic data . • A group of intra-basement reflectors are shear zones inherited from the former Andean-type orogeny . • Offshore shear zones are similar to onshore counterparts in the footwall of extensional detachments. • Late Mesozoic orogenic collapse reactivated basement structures and changed basement rheology. The present-day passive northern South China Sea (SCS) margin has evolved from an Andean-type margin since the Late Cretaceous and subsequently undergone multiple rifting events. However, few studies focused on the role of pre-existing basement structures and their influence on the Early Cenozoic SCS rifting. This paper addresses the nature and tectonic significance of intra-basement structures in outer northeastern SCS margin, based on 2D seismic reflection, well data and onshore geological studies. We identified three subunits (SF1, SF2 and SF3) of intra-basement reflections by their seismic amplitude and geometrical characteristics. By correlating to drilling and waveform modelling results, we interpret that these subunits represent magmatic and/or metamorphic rocks, residual Mesozoic strata, and layered deformation zone in the basement, respectively. The SF3 shows various spatial contacts with the rift-related faults and has influences on rifting fillings. For faults merging downwards with SF3 shear zones, obvious syn -rift depocenters are located in their hanging walls, while faults with higher dip angles above SF3 almost kept inactive during the rifting. The SF3 extend and rise upward to the shallow level, and form a preferential zone for fault activity. In analogy to the onshore extensional structures, structures in SF3 are most likely mylonitized shear zones in the footwall of detachment faults. The interaction of SF3 with the faults produces antiformal structures in the footwall of extensional detachments, recording ductile to brittle transition of the basement. The intra-basement structures inherited from the Early Mesozoic subduction were probably reactivated with significant rheological change following the Late Cretaceous orogenic collapse.

Hybrid Model Predictive Control of Floating Offshore Wind Turbines With Artificial Muscle Actuated Mooring Lines

Abstract Floating offshore wind turbines (FOWTs) are subject to undesirable platform motion and a significant increases in fatigue loads compared to their onshore counterparts. We have recently proposed using the fishing line artificial muscle (FLAM) actuators to realize active mooring line force control (AMLFC) for platform stabilization and thus load reduction, which features a compact design and no need for turbine redesign. However, as for the thermally activated FLAM actuators, a major control challenge lies in the asymmetric dynamics for the heating and the cooling half cycle of operation. In this paper, for a tension-leg platform (TLP) based FOWT with FLAM actuator based AMLFC, a hybrid dynamic model is obtained with platform pitch and roll degrees-of-freedom included. Then a hybrid model predictive control (HMPC) strategy is proposed for platform motion stabilization, with preview information on incoming wind and wave. A move blocking scheme is used to achieve reasonable computational efficiency. Fatigue, aerodynamics, structures, and turbulence (FAST) based simulation study is performed using the National Renewable Energy Laboratory (NREL) 5 MW wind turbine model. Under different combinations of wind speed, wave height and wind directions, simulation results show that the proposed control strategy can significantly reduce the platform roll and tower-base side-to-side bending moment, with a mild level of actuator power consumption.

Inherently safer design in offshore oil and gas projects

Like all hazardous installations, inherently safer design (ISD) is one of the key tools in offshore oil and gas projects to minimize risks in offshore facilities. As the life cycle of offshore facilities is relatively short compared with onshore counterparts and there are many projects running every year, the potential is high for raising inherent safety standards and lowering safety risks throughout the offshore industry as old facilities are phased out. This paper gives an overview of offshore facilities and examples of implementation of ISD. Good examples of ISD are numerous. Industry guidance on ISD implementation abound. Yet, the systematic implementation of it in the industry is patchy. There are many reasons for factors which impede the effective, efficient and consistent implementation of ISD in projects. This paper describes some of them and proposes solution to address them. They include (a) the effective integration of ISD into hazard management systems with appropriate language to engage all disciplines in projects, (b) the phasing of resources to enable the project to capture ISD measures which are only available during early phases, (c) application of appropriate ISD goals and ISD performance metrics at various stages and (d) the appropriate use of quantified risk assessment to support ISD.

Temporal and spectral characteristics of seismic ground motions: Offshore versus onshore

To distinguish offshore and onshore seismic ground motions, conventional analyses in terms of peak ground acceleration (PGA) and earthquake response spectrum (ERS) have been carried out in a recent work by authors and other papers in literature. In the present study, distinct temporal and spectral characteristics between onshore and offshore earthquake ground motions are further investigated in time-domain and frequency-domain. The data used is 69 pairs of concurrent onshore and offshore ground motions collected from the Kyoshin Network (K-NET). Each pair of data are of approximately identical epicenter distances. Comparisons are made on zero-up-crossing period (Tz), peak-to-trough acceleration range (Apt) and period (Tpt), duration of ground motion (Td), predominant frequency (fp) and the spectral bandwidth parameter (ε). The results indicate that for offshore horizontal and vertical seismic signals, statistics of Tz, Tpt, Td and predominant period Tp tend to be larger than the onshore counterparts. Meanwhile, ε of the offshore vertical ground motions is also greater. Through the proposed energy ratio (ER) analysis, the spectral energy of offshore ground motion is found to shift to moderate and low frequency bands. The time-frequency analysis conducted by Hilbert-Huang transform (HHT) shows that the Hilbert spectra of offshore accelerations contain larger spectral energy than the onshore counterpart but the corresponding instantaneous frequencies at peak energy are smaller, especially for horizontal recordings. Therefore, larger dynamic response of offshore structures is prone to be induced by the offshore ground excitation. This is further validated through the dynamic analysis of a marine pipeline in case study.

Fast Adaptive Fault Accommodation in Floating Offshore Wind Turbines via Model-Based Fault Diagnosis and Subspace Predictive Repetitive Control

As Floating Offshore Wind Turbines (FOWTs) operate in deep waters and are subjected to stressful wind and wave induced loads, they are more prone than onshore counterparts to experience faults and failure. In particular, the pitch system may experience Pitch Actuator Stuck (PAS) type of faults, which will result in a complete loss of control authority. In this paper, a novel fast and adaptive solution is developed by integrating a model-based Fault Diagnosis (FD) scheme and the Subspace Predictive Repetitive Control (SPRC). The FD role is to quickly detect and isolate the failed pitch actuator. Based on the fault isolation results, a pre-tuned adaptive SPRC is switched online in place of the existing one, whose initial values of the parameters has been tuned offline to match the specific faulty case. After that, SPRC employs subspace identification to continuously identify a linear model of the wind turbine over a moving time window, and thereby formulate an adaptive control law to alleviate the PAS-induced loads. Results show that the developed architecture allows to achieve a considerable reduction of the PAS-induced blade loads. More importantly, the time needed to reduce the PAS-induced loads are significantly shortened, thus avoiding further damage to other components during the adaption time and allowing continued power generation.

An implementation of standardization for telecom systems on ships and offshore plants based on the TMS

Telecom systems for ships and offshore plants used to be tools for long-distance communication in the past. Today, telecom systems combined with evolving IT ensure safety, accident prevention and cost saving for ships and offshore plants. In the future, all systems will be managed and controlled by telecom systems. Yet, the IMO and Classification Societies have neither revised nor amended the requirements and certification concerning telecom systems for decades. The failure to establish a standardized scheme applicable to telecom systems hinders ships and offshore plants from adopting advanced next-generation technologies widely used on land. Thus, unstandardized telecom systems are manufactured and installed for different user demands. Consequently, complicated interfaces impede the scalability and compatibility between telecom systems. Ships and offshore plants require advanced stability and diversity compared to their onshore counterparts. Unless the communication systems for ships and offshore plants are duly verified before use, serious adverse effects including marine accidents may ensue. This paper proposes a method of standardization to implement safe, scalable and general-purpose telecom systems for ships and offshore plants. The standardization of communication systems for ships and offshore plants facilitates the simplification and systematization of interfaces, and thus maximizes system inter-operability. Also, ships and offshore plants should adopt the standardized communication systems to enhance data reliability. This paper demonstrates the superior stability and performance of the proposed standardized communication system compared to the existing systems. Moreover, it proves the proposed system ensures the stable performance and fast data processing even in emergency. The standardized system for ships and offshore plants is a requisite for quality improvement, cost saving and stable performance. The findings of this paper are applied to the Smart Ship Solution for standardized integrated communication systems for containers, VLCC and LNG. Also, this paper analyzes the strengths and weaknesses of telecom systems configuration in TMS for offshore plants. In addition, it experimentally demonstrates the advantages of the proposed standardization of telecom systems in light of processing time and system operation cost.

Spatial probabilistic evaluation of offshore/nearshore sea bottom soils based on cone penetration tests

The inherent variability of soil has a crucial role in reliability-based design, especially for offshore foundations where the variability and uncertainty are more critical due to high costs as compared to the onshore counterparts. In this study, spatial probabilistic evaluation of the characteristics of offshore/nearshore sea bottom soils is performed based on data of 65 cone penetration tests (CPTs), reaching to 200-m depths in seabed soils, in up to 64 m of water. The types and typical characteristics of sea bottom soils are reported, together with statistical evaluation. A key parameter for random field theory, the spatial correlation length, based on CPT data is obtained for different soil types, using four different autocovariance functions (exponential, squared exponential, cosine exponential and second-order autoregressive). For these purposes, a MATLAB code is developed to take the CPT data, identify individual soil layers, carry out statistical evaluation of the properties of soils and report the vertical spatial correlation length of each layer using four different autocovariance functions. The undrained shear strength of clays in nearshore and offshore soils increases with depth, at rates of 1 to 3 kPa/m. Sands nearshore and offshore have similar relative density that is generally less than 50% (i.e. in loose to medium-dense state). The vertical spatial correlation length based on CPT of all soils is in the range of 0.11 m to 0.27 m, for all four different autocovariance functions, for all CPT cone tip resistances, sleeve friction and friction ratio, and for all shallow- and deep-water soils. The vertical spatial correlation length of nearshore soils is slightly larger than offshore soils. The results add to the scarce data on the spatial correlation length of offshore soils and can be useful for future studies on reliability and risk assessment of nearshore/offshore foundations.

Offshore earthquake ground motions: Distinct features and influence on the seismic design of marine structures

Offshore earthquake ground motions have not been fully characterized due to a lack of measured data. This study has collected more than 1,000 offshore and concurrent onshore site records from the K-NET and SEMS projects. These data are compared statistically in terms of the peak ground accelerations (PGA), the vertical-to-horizontal (V/H) PGA ratios, the normalized earthquake response spectra of the horizontal and vertical components and the corresponding vertical-to-horizontal (V/H) ratios. The analysis indicates that in the same earthquake event and with identical epicenter distances, the offshore horizontal PGA has greater amplification than the onshore. Meanwhile, the V/H PGA ratio of the offshore ground motions is much smaller than that of the onshore counterparts due to the effects of seafloor soft sediments and water layer. For offshore earthquake response spectra (both H & V), the peak spectral plateau occurs at longer periods than for the onshore records. Also, the offshore response spectra at moderate and long periods gain greater amplifications, which is critical to bottom fixed offshore structures. The V/H ratios of earthquake response spectra, offshore versus onshore, exhibit different trends varying with periods. Finally, to fill up the gap of current seismic design of offshore structures, two reference design response spectra (both H & V) by spectral fitting have been proposed for the engineering use. The offshore design spectrum is shown to have distinct features compared to land based design spectra in three codes.

Condition monitoring for the safe operation of offshore cranes

Offshore cranes work in harsher conditions than their onshore counterparts, with exposure to a highly corrosive environment and dynamic loading when conducting lifts from floating vessels. These degradation mechanisms can significantly reduce equipment life expectancy and increase maintenance/replacement costs without adequate mitigation programs in place. A systematic process must be followed to identify the potential for loss of integrity of components that could lead to failure, and strategies should be defined/implemented to ensure safe operation. Study outcomes feed into the maintenance and sparing philosophy, and cascade to site personnel as maintenance and operating procedures. The implementation of a robust condition-monitoring program prior to degradation occurring is a key factor in the success of this program, examples of which include the following. Slew bearing condition monitoring: in addition to regular visual inspection and recording of measurable readings, a well-structured grease sampling and analysis protocol provides early detection of moisture ingress, deterioration of lubrication and bearing failure. Structural integrity: reporting on integrity by exception does not provide confidence that an area may have been left out, or consistency in ongoing reporting. End of useful life definition: some components aren’t available for inspection; others can be inspected however they are susceptible to failures that are not practically detectable. These potential hidden failures can be prevented if a process is followed where the critical component’s operating life is defined, with appropriate supporting justification, and it is renewed accordingly regardless of visual appearance. An effective condition-monitoring program allows the operator to ascertain if the strategies in place are effective, pick up early detection of potential failure, and arrest the degradation while still inside a safe operating envelope.

Enhancing Wave Energy Competitiveness through Co-Located Wind and Wave Energy Farms. A Review on the Shadow Effect

Wave energy is one of the most promising alternatives to fossil fuels due to the enormous available resource; however, its development may be slowed as it is often regarded as uneconomical. The largest cost reductions are expected to be obtained through economies of scale and technological progress. In this sense, the incorporation of wave energy systems into offshore wind energy farms is an opportunity to foster the development of wave energy. The synergies between both renewables can be realised through these co-located energy farms and, thus, some challenges of offshore wind energy can be met. Among them, this paper focuses on the longer non-operational periods of offshore wind turbines—relative to their onshore counterparts—typically caused by delays in maintenance due to the harsh marine conditions. Co-located wave energy converters would act as a barrier extracting energy from the waves and resulting in a shielding effect over the wind farm. On this basis, the aim of this paper is to analyse wave energy economics in a holistic way, as well as the synergies between wave and offshore wind energy, focusing on the shadow effect and the associated increase in the accessibility to the wind turbines.

Advanced Concept Offshore Wind Turbine Development

Development of novel offshore wind turbine designs and technologies are necessary to reduce the cost of offshore wind energy since offshore wind turbines need to withstand ice and waves in addition to wind, a markedly different environment from their onshore counterparts. This paper focuses on major design challenges of offshore wind turbines and offers an advanced concept wind turbine that can significantly reduce the cost of offshore wind energy as an alternative to the current popular designs. The design consists of a two-blade, downwind rotor configuration fitted to a fixed bottom or floating foundation. Preliminary results indicate that cost savings of nearly 25% are possible compared with the conventional upwind wind turbine designs.

The Windy Domain — A Challenging Real-World Application of Integrated Planning and Scheduling

Many renewable sources of energy can harness greater uptime and power output when located in remote and potentially hostile locations. One example of this is wind power, wherein turbines positioned at offshore locations can experience higher and more sustained windspeeds than their onshore counterparts. However, these traits also lead to increased load and degradation upon components, which in turn means that regular maintenance is required. While onshore maintenance costs are relatively trivial, the costs associated with offshore maintenance can be several orders-of-magnitude greater.Traditionally, the scheduling of these repairs is performed by hand using a set of pre-determined plans for specific fault-categories (e.g. trivial/minor/major component replacement). This paper formulates this problem as a PDDL domain which encapsulates all of the individual pre-defined plans in a single representation, such that multiple levels of response can be integrated in a single plan. The domain presented is complex in that it contains not only numeric and temporal planning aspects, but that a subset of the domain is heavily geared towards pure scheduling. We include performance results on how a state-of-the-art planner performs on various example scenarios.

Idealized WRF model sensitivity simulations of sea breeze types and their effects on offshore windfields

Abstract. The behaviour and characteristics of the marine component of sea breeze cells have received little attention relative to their onshore counterparts. Yet there is a growing interest and dependence on the offshore wind climate from, for example, a wind energy perspective. Using idealized model experiments, we investigate the sea breeze circulation at scales which approximate to those of the southern North Sea, a region of major ongoing offshore wind farm development. We also contrast the scales and characteristics of the pure and the little known corkscrew and backdoor sea breeze types, where the type is pre-defined by the orientation of the synoptic scale flow relative to the shoreline. We find, crucially, that pure sea breezes, in contrast to corkscrew and backdoor types, can lead to substantial wind speed reductions offshore and that the addition of a second eastern coastline emphasises this effect through generation of offshore "calm zones". The offshore extent of all sea breeze types is found to be sensitive to both the influence of Coriolis acceleration and to the boundary layer scheme selected. These extents range, for example for a pure sea breeze produced in a 2 m s−1 offshore gradient wind, from 0 km to 21 km between the Mellor-Yamada-Nakanishi-Niino and the Yonsei State University schemes respectively. The corkscrew type restricts the development of a backdoor sea breeze on the opposite coast and is also capable of traversing a 100 km offshore domain even under high along-shore gradient wind speed (>15 m s−1) conditions. Realistic variations in sea surface skin temperature and initializing vertical thermodynamic profile do not significantly alter the resulting circulation, though the strengths of the simulated sea breezes are modulated if the effective land-sea thermal contrast is altered. We highlight how sea breeze impacts on circulation need to be considered in order to improve the accuracy of both assessments of the offshore wind energy climate and forecasts of wind energy output.

Shifting towards offshore wind energy—Recent activity and future development

To date, most of the existing wind farms have been built on-land but during the last few years many countries have also invested in offshore applications. The shift towards offshore wind project developments has mainly been driven by European energy policies, especially in north-west countries. In offshore sites the winds are stronger and steadier than on-land, making wind farms more productive with higher capacity factors. On the other hand, although offshore wind energy is not in its infancy period, most of the costs associated with its development are still much higher from onshore counterparts; however some recent technological progress may have the potential to narrow this gap in the years to come. In the present work, an overview of the activity noted in the field of offshore wind energy is carried out, with emphasis being given on the current status and future trends of the technology employed, examining at the same time energy production and availability issues as well as economic considerations.

Offshore reliability

Offshore turbines need to be more reliable than their onshore counterparts. How is this creating divergence in approach as the offshore turbine industry evolves?