Offshore Turbines Research Articles

Advanced methodology for screening of novel adsorption materials for cost-efficient CO2 capture

Adsorption is a promising technology to develop cost-effective carbon capture solutions for the energy and industrial sectors. The PrISMa project aims to develop a technology platform to allow translating specific carbon abatement requirements for CO2 source-sink combinations into key performance indicators (KPIs) that will further translate into property targets for the design of novel materials. This is possible by using materials such as metal organic frameworks (MOFs) which can be tailor-made according to the requirements of the separation process. This work presents the progress on the development of one of the main building blocks for the PrISMa technology platform: a computer-based techno-economic screening tool for the screening of novel adsorption materials. The developed screening tool provides the user with a suite of fit-for-purpose models of adsorption processes that allow to co-optimize the material and process domains. The techno-economic screening tool utilizes the effective carbon price (ECP) as the ultimate metric for the identification of the most promising adsorbent materials, either readily existing, or still to be synthesized. This work presents a preliminary screening of novel adsorption materials for cost-effective CO2 capture for two different applications – a waste to energy plant and an offshore gas turbine combined cycle.

Modelling and Analysis of Offshore Energy Hubs

Clean, multi-carrier Offshore Energy Hubs (OEHs) may become pivotal for efficient offshore wind power generation and distribution. In addition, OEHs may provide decarbonised energy supply for maritime transport, oil and gas recovery, and offshore farming while also enabling conversion and temporary storage of liquefied decarbonised energy carriers for export. Here, we investigate the role of OEHs in the transition of the Norwegian continental shelf energy system towards zero-emission energy supply. We develop a mixed-integer linear programming model for investment planning and operational optimisation to achieve decarbonisation at minimum costs. We consider clean technologies, including offshore wind, offshore solar, OEHs and subsea cables. We conduct sensitivity analysis on CO$_2$ tax, CO$_2$ budget and the capacity of power from shore. The results show that (a) a hard carbon cap is necessary for stimulating a zero-emission offshore energy system; (b) offshore wind integration and power from shore can more than halve current emissions, but OEHs with storage are necessary for zero-emission production and (c) at certain CO$_2$ tax levels, the system with OEHs can potentially reduce CO$_2$ emissions by 50% and energy losses by 10%, compared to a system with only offshore renewables, gas turbines and power from shore.

Resource and waste quantification scenarios for wind turbine decommissioning in the United Kingdom

Wind power produces more electricity than any other form of renewable energy in the United Kingdom (UK) and plays a key role in decarbonisation of the grid. Although wind energy is seen as a sustainable alternative to fossil fuels, there are still several environmental impacts associated with all stages of the lifecycle of a wind farm. This study determined the material composition for wind turbines for various sizes and designs and the prevalence of such turbines over time, to accurately quantify waste generation following wind turbine decommissioning in the UK. The end of life stage is becoming increasingly important as a rapid rise in installation rates suggests an equally rapid rise in decommissioning rates can be expected as wind turbines reach the end of their 20–25-year operational lifetime. Waste data analytics were applied in this study for the UK in 5-year intervals, stemming from 2000 to 2039. Current practices for end of life waste management procedures have been analysed to create baseline scenarios. These scenarios have been used to explore potential waste management mitigation options for various materials and components such as reuse, remanufacture, recycling, and heat recovery from incineration. Six scenarios were then developed based on these waste management options, which have demonstrated the significant environmental benefits of such practices through quantification of waste reduction and greenhouse gas (GHG) emissions savings. For the 2015–2019 time period, over 35 kilotonnes of waste are expected to be generated annually. Overall waste is expected to increase over time to more than 1200 kilotonnes annually by 2039. Concrete is expected to account for the majority of waste associated with wind turbine decommissioning initially due to foundations for onshore turbines accounting for approximately 80% of their total weight. By 2035–2039, steel waste is expected to account for almost 50% of overall waste due to the emergence of offshore turbines, the foundations of which are predominantly made of steel.

Dynamic failure analysis of renewable energy systems in the remote offshore environments

AbstractFor effective integrity management of marine renewable energy systems in the dynamic and uncertain ocean environments, understanding the failure dynamics is crucial. The cost of investment in marine/offshore renewable energy infrastructures and the associated cost due to failure and loss of energy production necessitate a predictive monitoring methodology that is dynamic and adaptive. This paper presents an integrated multi‐state pure‐birth‐pure‐death Markovian‐net profit value model for the offshore turbine subsystem failure analysis and its cost‐based consequences. The integrated model captures the offshore turbine subsystem's dynamic failure states and its economic implications due to the cost of energy loss and downtime for the period under consideration. The model applies a phase‐type exponential distribution to describe the monotonic state of failure. The methodology is demonstrated with an offshore wind turbine gearbox, and it captures the dynamic state of the system and its failure mechanisms. The cumulative effect of the subelements deterioration decreases the gearbox performance by over 35% within the first 2 years of operation.

An Integrated Framework of Drivetrain Degradation Assessment and Fault Localization for Offshore Wind Turbines

As wind energy proliferates in onshore and offshore applications, it has become significantly important to predict wind turbine downtime and maintain operation uptime to ensure maximal yield. Two types of data systems have been widely adopted for monitoring turbine health condition: supervisory control and data acquisition (SCADA) and condition monitoring system (CMS). Provided that research and development have focused on advancing analytical techniques based on these systems independently, an intelligent model that associates information from both systems is necessary and beneficial. In this paper, a systematic framework is designed to integrate CMS and SCADA data and assess drivetrain degradation over itslifecycle. Information reference and advanced feature extraction techniques are employed to procure heterogeneous health indicators. A pattern recognition algorithm is used to model baseline behavior and measure deviation of current behavior, where a Self-organizing Map (SOM) and minimum quantization error (MQE) method is selected to achieve degradation assessment. Eventually, the computation and ranking of component contribution to the detected degradation offers component-level fault localization. When validated and automated by various applications, the approach is able to incorporate diverse data resources and output actionable information to advise predictive maintenance with precise fault information. Theapproach is validated on a 3 MW offshore turbine, where an incipient fault is detected well before existing system shuts down the unit. A radar chart is used to illustrate the fault localization result.

Platform Optimization and Cost Analysis in a Floating Offshore Wind Farm

Floating offshore wind represents a new frontier of renewable energies. The absence of a fixed structure allows exploiting wind potential in deep seas, like the Atlantic Ocean and Mediterranean Sea, characterized by high availability and wind potential. However, a floating offshore wind system, which includes an offshore turbine, floating platform, moorings, anchors, and electrical system, requires very high capital investments: one of the most relevant cost items is the floating substructure. This work focuses on the choice of a floating platform that minimizes the global weight, in order to reduce the material cost, but ensuring buoyancy and static stability. Subsequently, the optimized platform is used to define a wind farm located near the island of Pantelleria, Italy in order to meet the island’s electricity needs. A sensitivity analysis to estimate the Levelized Cost Of Energy is presented, analyzing the parameters that influence it most, like Capacity Factor, Weighted Average Capital Cost (WACC) and number of wind turbines.

Short Review and 3-D FEM Analysis of Basic Types of Foundation for Offshore Wind Turbines

Abstract Some problems of the foundations of offshore wind turbines are considered in this paper. A short review is presented on the two basic types of foundations, i.e. monopiles and gravity foundations, including their basic features and applications as well as general design considerations. Also, some issues regarding analysis are discussed, including geotechnical problems and modelling techniques. A numerical model of offshores turbine and some preliminary computations are presented. Finite element analysis was carried out for wind turbines supported on both gravity and monopile foundations. The wind turbine tower, blades (simplified model), gravity foundation and part of the surrounding soil are included in the model. The turbine was loaded by wind and loads induced by waves, inertia and gravity. Both non-linear static and dynamic analysis of the wind turbine was performed. The displacements and stresses under the tower foundations were calculated and a comparison analysis carried out.

Optimization of the erosion-safe operation of the IEA Wind 15 MW Reference Wind Turbine

The work describes modelling of erosion of the IEA 15 MW Reference Wind Turbine. Five-year worth of historical time series including wind speed, rain intensity and price of energy was used in the modelling. The work included erosion-safe operation of the turbine where the tip speed was limited during rain events to prevent erosion. The tip-speed limit was defined as a function of rain intensity and price of energy, the distribution of which was subject to an optimization. The objective for the optimization was to maximize the profit. The factors taken into account in the modelling and optimization were: the loss in power curve due to erosion, and the cost of repair and associated downtime. The results indicated that for this particular turbine it would be sufficient to define the tip-speed limit as a function of rain intensity alone. The model showed that 88% of the overall profit loss due to erosion could be saved by running the turbine in the erosion-safe operation. Although some inaccuracy may be associated with the modelling, the results strongly indicate that a significant amount of money could be saved by utilizing the erosion-safe operation on offshore turbines.

A control cost criterion for controller tuning of two- and three-bladed 20 MW offshore wind turbines

When wind turbine concepts are modified, the difference in characteristic behavior and the impact on the cost of energy are of great interest. However, before comparing it is mandatory to re-adapt controller gains or weights to altered turbine dynamics in order to guarantee a still suitable overall system design. As an expenditure-based solution, the proposed control cost criterion could help to assess changes of turbine concepts better due to a clear and objective controller tuning. Conflicting design objectives are therefore assessed on their approximated influence on the cost of energy in order to result in the most cost-beneficial trade-off. These objectives are variations of component loads, actuator usage, and energy production. The criterion is applied to three- and two-bladed 20 MW offshore turbines with turbulent wind for full load operation, exemplarily. This provides insight into the benefits and limitations of low controller integral pitch gains and results in potential cost reductions for all turbines.

Preliminary design of a hydraulic wind turbine drive train for integrated electricity production and seawater desalination

The integration of wind energy to desalinate seawater can address the freshwater scarcity issue and alleviate the environmental impact of desalination. This paper presents the use of the Delft Offshore Turbine, an unconventional wind turbine with hydraulic transmission which can be used to directly drive a seawater reverse osmosis desalination process and to produce electricity with a Pelton turbine. A steady-state model is used to identify the potential regions at which it is possible to operate the system and to propose a system settings for maximising water production. The results show that the proposed system provides up to 300 kW of electricity and can desalinate up to 25 m3/h, at rated operating conditions.

Rapid Estimate of Wind Turbine Energy Loss Due to Blade Leading Edge Delamination Using Artificial Neural Networks

Abstract Estimating reliably and rapidly the losses of wind turbine annual energy production due to blade surface damage is essential for optimizing maintenance planning and, in the case of leading edge erosion, assessing the need for protective coatings. These requirements prompted the development of the prototype system presented herein, using machine learning, wind turbine engineering codes, and computational fluid dynamics to estimate annual energy production losses due to blade leading edge delamination. The power curve of a turbine with nominal and damaged blade surfaces is determined, respectively, with the open-source FAST and AeroDyn codes of the National Renewable Energy Laboratory, both using the blade element momentum theory for turbine aerodynamics. The loss prediction system is designed to map a given three-dimensional geometry of a damaged blade onto a damaged airfoil database, which, in this study, features 6000+ airfoil geometries, each analyzed with Navier–Stokes computational fluid dynamics over the working range of angles of attack. To avoid lengthy aerodynamic analyses to assess losses due to damages monitored during turbine operation, the airfoil force data of a damaged turbine required by AeroDyn are rapidly obtained using a machine learning method trained using the pre-existing airfoil database. Presented results demonstrate that realistic estimates of the annual energy production loss of a utility-scale offshore turbine due to leading edge delamination are obtained in just a few seconds using a standard desktop computer. This highlights viability and industrial impact of this new technology for managing wind farm energy losses due to blade erosion.

Coupled Motion Prediction of a Floating Tidal Current Power Station with Vertical Axis Twin-rotor Turbine

Hu, C.; Ma, Y.; Li, L., and Li, T., 2020. Coupled motion prediction of a floating tidal current power station with vertical axis twin-rotor turbine. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 784–788. Coconut Creek (Florida), ISSN 0749-0208.Floating offshore tidal current turbines are usually moored in the sea, which will endure the wind-wave-current load in a long term. Power production of the tidal current turbine will result in extra excitation force acting on the platform, which will make the motion prediction and positioning system design of the floating platform more complicated. In order to predict the motion response of a floating tidal current power station, a coupled motion prediction method is established to explore the coupled interaction among the platform, the turbine and the mooring system. The turbine influence is considered as added mass and damping acting on the platform. Results shows that the fitted hydrodynamics agree well with numerical simulation results. The operation of the tidal turbine can increase the surge amplitude and pitch angle of catamaran, and the mooring line tension will increase as well. The research can provide some reference for motion response prediction and mooring positioning of a floating tidal current power station.

Design and Analysis of HTS Rotor-Field Coils of a 10-MW-Class HTS Generator Considering Various Electric Insulation Techniques

This paper presents the results of an electromagnetic design and numerical analysis conducted on a 10-MW-class second-generation high-temperature superconducting generator (2G HTSG) used in an offshore wind power turbine. To report the operation reliability of 10-MW-class HTSGs employed in offshore environment, various electric insulation techniques (EITs) for HTS field coils (FCs), such as no-insulation, metal insulation, and metal-insulator transition insulation, are considered in this study. Using the time-transient solver of the three-dimensional (3D) electromagnetic finite element analysis (FEA), we investigated the electromagnetic characteristics of the HTSG with the three EITs in terms of the electrical output of the HTSG and the critical current of the FCs. To analyze the charging characteristic of the HTS FCs with the three EITs in steady-state operation as well as the electrical in transient-state operation, electric equivalent circuit models are built with key parameters based on the electromagnetic FEA results. Finally, the performances of the HTS FCs are discussed and evaluated in terms of the electromagnetic response and stability characteristics.

Comparison of Prediction Methods for Axial Strength of Grouted Connections with Shear Keys

Grouted connections are commonly used in marine engineering, especially on oil platforms, cross-sea bridges, and offshore wind power turbines. The prediction methods for axial carrying capacity of grouted connections with shear keys and their application ranges in current codes were analyzed in this paper. The calculated results by using different codes were compared based on a practical grouted connection between steel piles and the jacket foundation of a wind turbine. The research team conducted axial compression tests on seven specimens, collected a wide range of experimental results to establish a database, and finally compared the standard calculation results with the experimental results. The study indicates that the axial strength of grouted connections predicted by different methods is distinct. The calculation formula of the British Health and Safety Executive (HSE, 2002) has obvious limitations; specifically, with increased shear keys, strength is overestimated, resulting in insecure design outcome of structures. The results calculated by the Norwegian Det Norske Veritas (DNV, 2013) are generally consistent with the experimental results, in which the reduction effect of multiple shear keys was considered. The prediction method of the American Petroleum Institute (API, 2007), which undervalues the bearing performance of connections, is excessively conservative. The method of the combined Norwegian and German Det Norske Veritas–Germanischer Lloyd (DNV-GL, 2016) has wider applicability and is safe, reliable, and economical.

Investigating the potential impact of wind farms on Lake Erie

Power generation is a leading cause of air pollution and major source of global warming emissions. Renewable energy resources, like wind and solar power, generate electricity with little to no global warming emissions and are reliable, affordable and beneficial for health, economy and climate. There are two sectors in wind energy: offshore and onshore. Offshore wind speeds are faster and steadier and coastal areas often exhibit a high energy demand. Offshore wind farms are coming to the Great Lakes. We therefore investigate the potential impact of wind farms on Lake Erie’s dynamic and thermal structure using the COHERENS (a Coupled Hydrodynamical-Ecological model for Regional and Shelf Seas) and simulate a large wind farm with 432 offshore turbines located in the shallow southern waters of the central basin. The simulation is run twice to compare physical parameters such as temperature and circulation pattern and velocity results in the absence and presence of a large wind farm. In the case of no wind farm, model results are validated with data from buoys located in Lake Erie, while with the wind farm, the results show that the central basin is impacted by the wind turbines. This occurs because the reduced wind speed and stress leads to less mixing, lower current speeds and higher surface water temperature. There is no significant impact, however, in the eastern and western basins. This research examines Lake Erie, since this lake has a high potential for offshore wind turbine installation due to its proximity to population centers and its shallow depth.

Acoustic Sensing Based Operational Monitoring of Wind Turbine Blades

This paper presents a general overview of the different aspects of a novel structural health monitoring technique developed for wind turbine blades. The proposed technique is based upon detecting the changes in acoustic transmission loss due to structural deformation and damage incurred. This acoustics-based damage detection technique consists of two complementary approaches, namely, the active and passive acoustic damage detection approaches. The proposed approaches can be applied to both onshore and offshore turbines and requires minimum number of acoustic sensors positioned internal and external to the blade structure. Both approaches will be detailed from the structural health monitoring, acoustics, aeroacoustics as well as the practical implementation perspective. The potential benefits of using the proposed approaches and the corresponding technology on wind turbine blades is also discussed.

The impact of information sharing on installation processes of offshore wind farms - process modelling and simulation-based analysis

The installation of offshore wind energy turbines is accompanied by great challenges arising from the dynamic environment, which influences logistics processes. Communication plays a major role for cost-efficient installation processes, due to the coordination needed between different partners involved in the offshore wind energy supply chain. A detailed process analysis revealed the importance of shared information about weather conditions, storage capacities and vessel availabilities. By applying a simulation study, which evaluates eight information sharing scenarios, the influence of the following execution time-related performance measures is investigated: average time in manufacturer storage, average time in port, total installation time and average vessel usage time. As a result, the simulation study verifies that sharing information between supply chain partners can contribute to more efficient logistics processes. However, the achievable prediction accuracy and the interdependencies between the information items have a major influence on the quality of results.

Adaptive control design and implementation for collective pitch in wind energy conversion systems

This paper introduces a discrete-time L1 adaptive controller design for collective pitch control for variable speed variable pitch wind turbines. In this control algorithm, the blades’ pitch angles are regulated to manipulate the generator speed and generated power during high speeds wind airflow. The main merits of the proposed controller are its robustness against the wind turbine model uncertainties, guaranteeing the closed loop system stability and performance, and applicability during implementation in real life. Commonly used industrial gain-scheduled PI controller is used to be compared with the proposed controller. The proposed scheme is simulated using a 5-MW offshore turbine model and the obtained results illustrates the superior performance of the proposed controller. Further, a reduced scale wind turbine emulator is used to provide hardware in the loop to test the implementation of the proposed controller. The controller is implemented using laboratory equipment to demonstrate the feasibility of the controller for real time applications. The obtained experimental results validate the closed loop system performance enhancement due to replacing the traditional PI controller with the proposed design.

Structural Evaluation of the DeepCWind Offshore Wind Foundation

Wind power technologies are being used as a mean of harvesting the energy from the wind with low carbon impact and with great potential to contribute to a new energy paradigm. Great benefits may arise from the use of offshore turbines, such as having a reduced visual impact, if far enough from the coast, or being able to produce more energy due to the use of bigger turbines. Current challenges for these technologies include producing a stable and profitable platform that allow turbines to be installed in deep waters, meaning that these solutions need to be of floating type. An example of such structure is the foundation developed by the DeepCWind consortium, which is evaluated for its structural integrity on this document. The evaluation consists of modal and static/transient analyses, according to a selected Design Loading Case, which is defined for the certification of wind turbines’ offshore foundations. The objective is to observe how this structure would perform when subjected to a simulated real life loading. The DeepCWind foundation exhibited great difficulties enduring the applied loads. Therefore, a structurally improved platform was design with the aim of successfully passing the load case.

High fidelity modeling of pile driving acoustic energy

Pile driving for the installation of wind farms has become a recent topic of interest as we seek to learn how to protect the marine environment while energy efficient offshore turbines are installed. For environmental compliance, propagation models for spreading from a point source are sometimes used to evaluate impact volumes. Use of a point source is problematic in that a pile (either hammered or shaken using a vibratory source) fully extends through the water column and cannot be considered a point source. In this paper we present a hybrid model solution to evaluate the sound field at close and far ranges. First, a finite element model, consisting of the hammer, pile, the nearby seawater and the sediment, is used to computed the acoustic pressure field at a short range (∼3 m). The sound pressure field versus depth and frequency at this range is used as the starter field for the Parabolic Equation and the field is then propagated to range, including range dependent environments. Impact volumes, for various marine species hearing groups are computed. [Work supported by BOEM.]