Offshore Wind Turbine Farm Research Articles

Performance assessment of buoyancy work energy storage system with various buoy materials, coatings, and gasses

This study investigates the performance of a buoyancy work energy storage system. The sought operational and efficiency enhancements were examined by coupling various permutations of buoy material, working gasses, buoy surface coatings, and applied loads. A plastic buoy and a polyvinyl chloride (PVC) float are used as they are common materials for buoy construction. Both buoys are filled with different gasses, namely air and helium and examined with and without a lubricating exterior silicon coating. The air and helium-filled PVC floats exhibited the best energy output performance across the different loads, whereas the original plastic buoy performed the poorest. The inclusion of the silicon coating on the external surface of the PVC floats resulted in an energy output performance enhancement of 15.44 % and 5.01 % for air and helium-filled PVC floats, respectively, and a 4 % efficiency enhancement overall. However, the greater required input energy to descend (system charge) the silicon coated helium-filled PVC floats caused efficiency losses, with peak efficiency reaching 24.18 %. However, the silicon coated air-filled PVC float reached a higher maximum of 29.61 %. Moreover, Analysis of Variance (ANOVA) test was carried out to investigate the system performance dependence on the presented variables. Consequently, a scaled-up version of the proposed buoyancy energy storage system was presented to be utilized in the London Array offshore wind turbine farm, with a LCOE of 0.978 ¢/kWh.

Potential biological impacts of very low frequency acoustical energy produced by offshore wind turbine energy generation

Offshore wind turbine farms are being planned and installed around the US Outer Continental Shelf. These will be introducing a panoply of noises into the environment, from siting, through installation, to operations, and eventually decommissioning. Noise concerns from these activities are typically framed within frequency bands of concern defined by governmental regulatory agencies. A less considered noise is the very low frequency thump generated by the motion of the turbine blades as they intersect the “stagnate wind area” on the windward side of the mast. This “infrasonic” thump contains a lot of energy and is in the perceptual range of migratory birds and baleen whales. Given that whales and birds use “infrasonic” sound and barometric pressure signals for navigation and migration cues, the installation of thousands of turbines off the Atlantic Outer Continental Shelf, and hundreds off the Pacific OCS, may impose significant impacts on migratory passerine birds along the “Atlantic Flyway,” Procellariiformes on both the Atlantic and Pacific OCS, and all baleen whales within the infrasonic energy propagation reach of the turbines.

Integrated Dynamics Response Analysis for IEA 10-MW Spar Floating Offshore Wind Turbine

Wind energy in the deep-sea area is more abundant and the capacity of wind turbines can be made larger. Therefore, the research on deep-sea floating offshore wind turbines will be the primary strategy for wind energy exploitation in the future. The spar-type platform depends on the characteristics of a small water plane, deep draft, and good stability, which has been applied to the commercial development of deep-sea wind energy. In the next ten years, the 10-MW wind turbine will become the mainstream class installed in the floating offshore wind turbine farm. Thus, it is very necessary to conduct a comprehensive and in-depth study on the 10-MW spar type floating offshore wind turbine. The direct-drive 10-MW offshore wind turbine was proposed by the International Energy Agency (IEA) in Wind Task 37 in 2019. In this paper, a spar-type platform is designed to support the IEA 10-MW reference wind turbines, and a nonlinear aero-hydro-servo-elastic numerical model is established using the FAST tool (which is developed by the National Renewable Energy Laboratory, NREL). Then, the accuracy of the wind turbine and the sensitivity of the controller are verified, and the natural periods of the floating offshore wind turbine are obtained by free-decay tests. The natural periods of the platform in six degrees-of-freedom are found to be within the range recommended by the design standard. The measured wind and wave data of the target site close to Fujian Province of China are used to evaluate the performance of the floating offshore wind turbine under the 100-, 50-, 5-, and 2-year-return stochastic weather conditions. The results indicate that the design of the spar platform is reasonable and has excellent hydrodynamic performance.

Simulation of two in-line wind turbines using an incompressible Finite Volume solver coupled with a Blade Element Model

The present study addresses the first steps of development and validation of a coupled Finite Volume-Blade Element Model (FV-BEM) simulation tool dedicated to offshore wind turbine farm modeling. The fluid domain is solved using the incompressible formulation of the CFD solver Grid-flow [40]. The turbines are taken into account using FAST (from NREL) [23] and their effects are imposed into the fluid domain through an actuator line model (ALM) for which specific enhancements are proposed. The Grid-flow solver and its two-way coupling with the aero-elastic modules from FAST are introduced and detailed. The present two-way coupling is built on a parallel framework using the MPI library. The ALM force coefficient values are deduced by FAST from the incident local velocity interpolated from the CFD solver grid at each timestep. In return, the ALM forces computed by FAST are projected from its cylindrical support to the Cartesian grid of the CFD solver. This force projection is made through a specific kernel interpolation technique inspired from meshless methods such as Smoothed Particle Hydrodynamics (SPH). The simulation of the case of two in-line wind turbines using the FV-BEM coupling proposed is presented, together with comparisons against experimental results for validation purposes. Coarse and refined grid results are compared and discussed. Finally, a discussion on performances, advantages and limitations of the formulation proposed is provided.

Simulation of Two In-Line Wind Turbines Using an Incompressible Finite Volume Solver Coupled with a Blade Element Model

The present study addresses the first steps of development and validation of a coupled Finite Volume-Blade Element Model (FV-BEM) simulation tool dedicated to offshore wind turbine farm modeling. The fluid domain is solved using the incompressible formulation of the CFD solver Grid-flow. The turbines are taken into account using FAST (from NREL) and their effects are imposed into the fluid domain through an actuator line model (ALM) for which specific enhancements are proposed. The Grid-flow solver and its two-way coupling with the aero-elastic modules from FAST is introduced and detailed. The simulation of the case of two in-line wind turbines using the FV-BEM coupling proposed is presented, together with comparisons against experimental results for validation purposes. Finally, a discussion on performances, advantages and limitations of the formulation proposed is provided.

Risk-based maintenance planning of offshore wind turbine farms

A risk-based maintenance planning for offshore wind farm installations is developed. Initially, the optimal number of monopile offshore wind turbines to be installed in an offshore wind farm is estimated, targeting a minimum levelised cost of energy. To this end, a sufficient number of design combinations for monopile support structure is generated by the design of experiment technique and then analysed based on the fatigue limit state. Following the fatigue reliability analysis performed for the monopile designs, an analytical relation between manufacturing cost and the structural safety regarding fatigue is developed to be used in the life-cycle cost analysis. The offshore wind farm is considered here as a system consisting of correlated components. The system reliability is estimated by using Ditlevsen bounding technique, which uses a time-variant correlation matrix of offshore wind turbines. The event tree method is employed to assess the expected cost of failure to be included in the capital investment as the structural risk premium, and the total expected cost to be included in the operational cost. Furthermore, different inspection policies are studied, and the most cost-effective inspection and maintenance policy is found for each studied wind farm. The present study also develops a novel framework for inspection and maintenance planning that maximises the benefits of performing inspections for a multi-unit system. Finally, the developed framework is applied to an offshore wind farm with sixty installations, and the detailed description of the planned inspections are discussed.

GIS-based multi-criteria analysis for offshore wind turbine deployment in Hong Kong

ABSTRACTThe search for suitable marine areas is a prerequisite at an early stage of any offshore renewable energy system project. This paper introduces a methodological framework for identifying the maritime areas the most appropriate to implement an offshore wind turbine farm in the Hong Kong bay. The framework is based on the combined use of Multi-Criteria Decision Analysis (MCDA) and Geographical Information Systems (GIS). At the first stage of the analysis, unsuitable areas for the deployment of an offshore wind turbine have been first identified. At the second stage of the analysis, eligible marine areas have been ranked using a MCDA and different scenarios. Finally, a cost analysis has been performed to refine the whole approach as well as a comparison to previous studies in the Hong Kong bay.

Rain erosion-resistant coatings for wind turbine blades: A review

Wind blades are the most expensive parts of wind turbines made from fibre-reinforced polymer composites. The blades play a critical role on the energy production, but they are prone to damage like any other composite components. Leading edge (LE) erosion of the wind turbine blades is one of the common damages, causing a reduction in the annual energy production especially in offshore wind turbine farms. This erosion can be caused by rain, sand and flying solid particles. Coating the blade against erosion using appropriate materials can drastically reduce these losses and hence is of great interest. The sol–gel technique is a convenient method to manufacture thin film coatings, which can protect the blades against the rain erosion, while having negligible effect on the weight of the blades. This article provides an extensive review of the liquid erosion mechanism, water erosion testing procedures and the contributing factors to the erosion of the LE of wind turbine blades. Techniques for improving the erosion resistance of the LE using carbon nanotubes and graphene nano-additives are also discussed.

Satellite-Based Offshore Wind Energy Resource Mapping in Malaysia

Development and application of offshore wind turbine farms have been increasing, particularly in the developed countries, because of their high power rating, high yield energy, high offshore wind, and unlimited space in the offshore. However, the poor data and simplistic methodologies of the previous assessments result in insufficient estimates of the wind energy potential. Thus, this study provides an assessment of the offshore wind energy resources in Malaysia using multi-mission satellite altimetry data. The satellite altimetry data was extracted from Radar Altimeter Database Systems located at GNSS and Geodynamics Laboratory, Universiti Teknologi Malaysia. The data were validated by buoy measurements from two offshore sites, as indicated by the high correlation coefficient of 0.88. Further, the offshore wind energy resource mapping data in Malaysia identified three areas in Peninsular Malaysia and Borneo as potential areas for offshore wind energy development.

Seismic performance assessment of monopile-supported offshore wind turbines using unscaled natural earthquake records

The number of offshore wind turbine farms in seismic regions has been increasing globally. The seismic performance of steel monopile-supported wind turbines, which are the most popular among viable structural systems, has not been investigated thoroughly and more studies are needed to understand the potential vulnerability of these structures during extreme seismic events and to develop more reliable design and assessment procedures. This study investigates the structural performance assessment of a typical offshore wind turbine subjected to strong ground motions. Finite element models of an offshore wind turbine are developed and subjected to unscaled natural seismic records. For the first time, the sensitivity to earthquake types (i.e. crustal, inslab, and interface) and the influence of soil deformability and modeling details are investigated through cloud-based seismic fragility analysis. It is observed that monopile-supported offshore wind turbines are particularly vulnerable to extreme crustal and interface earthquakes, and the vulnerability increases when the structure is supported by soft soils. Moreover, a refined structural modeling is generally necessary to avoid overestimation of the seismic capacity of offshore wind turbines.

The impact of on-shore and off-shore wind turbine farms on property prices

We present the results of a large-scale analysis on how on-shore and off-shore wind turbines affect the property prices of nearby single family residential and vacation homes in Denmark. We find that on-shore wind turbines negatively affect the price of surrounding properties to a distance of three kilometers. The negative impact increases with the number of wind turbines at a declining marginal rate but declines with distance. In the case of off-shore wind turbine farms, we do not find a significant effect of having an off-shore wind farm in view from a property itself or from the nearest beach, likely because the closest off-shore turbine is 9 km from the closest traded home. We illustrate the policy relevance of our findings by providing maps showing how the marginal impact of a wind turbine varies across the landscape according to the spatial distribution of home density and homes values in the proximity of a wind turbine site. The results suggest that ceteris paribus, wind turbine farms should be built quite far away from residential areas with turbines gathered in larger wind farms rather than installed as single turbines.

Sensitivity of Risk-Based Maintenance Planning of Offshore Wind Turbine Farms

Inspection and maintenance expenses cover a considerable part of the cost of energy from offshore wind turbines. Risk-based maintenance planning approaches are a powerful tool to optimize maintenance and inspection actions and decrease the total maintenance expenses. Risk-based planning is based on many input parameters, which are in reality often not completely known. This paper will assess the cost impact of this incomplete knowledge based on a case study following risk-based maintenance planning. The sensitivity study focuses on weather forecast uncertainties, incomplete knowledge about the needed repair time on the site as well as uncertainties about the operational range of the boat and helicopter used to access the broken wind turbine. The cost saving potential is estimated by running Crude Monte Carlo simulations. Furthermore, corrective and preventive (scheduled and condition-based) maintenance strategies are implemented. The considered case study focuses on a wind farm consisting of ten 6 MW turbines placed 30 km off the Danish North Sea coast. The results show that the weather forecast is the uncertainty source dominating the maintenance expenses increase when considering risk-based decision-making uncertainties. The overall maintenance expenses increased by 70% to 140% when considering uncertainties directly related with risk-based maintenance planning.

Economic cost evaluation on the viability of offshore wind turbine farms in Nigeria

Abstract The paper presents an economic cost evaluation on the feasibility of offshore wind turbine (OWT) farms development in Nigeria, using a 500 MW OWT farm as an incident study. A developed model was used to evaluate the economic cost of the OWTs at different phases of the project. Additionally, the effect of the cost drivers at the changed phases of the OWTs was studied correspondingly. Results obtained showed that over 50% of the OWT project cost emanated from CAPEX while a value less than 50% came from OPEX. However, further analysis indicates at maximum power of 4 MW a 4.95% diminution in LCOE. For comparable power rating (PR) between 5 ⩽ PR ⩽ 6 MW , a 2.7% reduction in LCOE exists. Cost stability was apparent at a growth of WTs between 300 ⩽ WT ⩽ 500 MW. The study also observed a decrease in LCOE for all development stages of the OWT while a decrease in the CMS detectability was considered marginal. Subsequently, it can be inferred that Nigeria has the potential for OWT farm expansion. However, the demonstrated model was appropriate for handling preliminary variations in OWT studies.

Reliability analysis of laterally loaded piles for an offshore wind turbine support structure using response surface methodology

With an increasing demand of a renewable energy, new offshore wind turbine farms are being planned in some parts of the world. Foundation installation asks a significant cost of the total budget of offshore wind turbine (OWT) projects. Hence, a cost reduction from foundation parts is a key element when a cost-efficient designing of OWT budget. Mono-piles have been largely used, accounting about 78% of existing OWT foundations, because they are considered as a most economical alternative with a relatively shallow-water, less than 30 m of seawater depth. OWT design standards such as IEC, GL, DNV, API, and Eurocode are being developed in a form of reliability based limit state design method. In this paper, reliability analysis using the response surface method (RSM) and numerical simulation technique for an OWT mono-pile foundation were performed to investigate the sensitivities of mono-pile design parameters, and to find practical implications of RSM reliability analysis.

Transmission of wave energy through an offshore wind turbine farm

The transmission of wave energy passing an offshore wind farm is studied. Three effects that can change the wave field are analysed, which is the A) energy dissipation due to drag resistance, B) wave reflection/diffraction from structures, and C) the effect of a modified wind field inside and on the lee side of the wind farm. The drag dissipation, A), is quantified by a quadratic resistance law. The effect of B) is parameterised based on 1st order potential theory. A method to find the amount of reflected and transmitted wave energy is developed based on the panel method WAMIT™ and a radiation condition at infinity. From airborne and Satellite SAR (Synthetic Aperture Radar) a model has been derived for the change of the water surface friction C) inside and on the lee side of the offshore wind farm. The effects have been implemented in a spectral wind wave model, MIKE21 SW, and a parametric study to compare the 3 different processes has been carried out. The method to study reflection/diffraction can be used for any type of offshore structure, vessel or a number of structures, as long as the assumptions for the use of potential wave theory are valid, and the effect of the modified wind field on the water surface friction is known.

Potential scour for marine current turbines based on experience of offshore wind turbine

The oceans have tremendous untapped natural resources. These sources are capable to make significant contribution to our future energy demands. Marine current energy offers sustainable and renewable alternative to conventional sources. Survival problems of Marine Current Turbines (MCTs) need to be addressed due to the harsh marine environment. The analogous researches in wind turbine have been conducted. Some of the results and knowledge are transferable to marine current energy industry. There still exist some gaps in the state of knowledge. Scour around marine structures have been well recognised as an engineering issue as scour is likely to cause structural instability. This paper aims to review different types of foundation of MCTs and potential scour and scour protection around these foundations based on the experience of offshore wind turbine farm.

Ice loading on Danish wind turbines: Part 1: Dynamic model tests

An extensive model test program has been carried out to investigate the key ice load issues on offshore wind turbines in Danish waters. Tests were performed using a compliant structure that had scaled structural characteristics. The test program investigated seven configurations of model structures and dynamic characteristics. Both first- and second-mode vibration issues were investigated. Forty-one ice sheets were used giving information on 144 different experimental set-ups. The parameters that were changed in the tests included the ice velocity, ice thickness, shape of the structure, water level on the structure, structure stiffness and the natural frequency of the structure. Measurements were made of forces, accelerations and displacement of the model during the interaction with ice. Four different ice failure modes were identified—flexure, crushing, mixed mode, and lock-in. The results gave information on the anticipated ice loads and the likelihood of ice-induced vibrations for both the first-mode and second-mode vibration frequencies. They also provided guidance on the optimum angle and cone-size for a protective ice collar for the wind turbines. This paper provides the results of the model tests. A companion paper [Cold Reg. Sci. Technol., (2004)], provides information on the application of the results to the design of an offshore wind turbine farm.

Life cycle assessment of a 150 MW offshore wind turbine farm at Nysted/Roedsand, Denmark : Properzi, S. and Herk-Hansen, H. Int. J. Environment and Sustainable Development, 2002, 1, (2), 113–121

Life cycle assessment of a 150 MW offshore wind turbine farm at Nysted/Roedsand, Denmark : Properzi, S. and Herk-Hansen, H. Int. J. Environment and Sustainable Development, 2002, 1, (2), 113–121

Life cycle assessment of a 150 MW offshore wind turbine farm at Nysted/Roedsand, Denmark

The purpose of this life cycle assessment (LCA) was to illuminate and describe the potential environmental impacts caused by an offshore wind turbine farm (WTF) throughout its lifetime and use this knowledge in the planning and improvement of future WTFs. The LCA was based on experience from the LCA on Danish electricity and district heating [1] as well as the offshore WTF project at Middelgrunden which is in operation. LCA of a wind turbine is not new. However, development in the area of wind turbines at sea and transmission of the electricity from the offshore WTF is new, and therefore, focus on the advantages and disadvantages in comparison with wind turbines on land is necessary. Data from the current wind turbine project, Middelgrunden, near Copenhagen, was collected from SEAS' wind energy centre and the other participating organisations and extrapolated in order to reflect the offshore WTF at Nysted/Roedsand. Nysted/Roedsand is expected to be in operation by the year 2003. All of the components of the WTF and transmission facilities have been examined and areas of environmental improvement have been identified. It was found that Nysted/Roedsand's offshore WTF and associated transmission facilities per produced kilowatt-hour have an improved environmental profile in comparison with a land wind turbine. Areas of improvement of an offshore WTF include the recycling of metals, recycling of the wings, minimising resource consumption and increasing the life expectancy of the entire wind turbine. The ISO 14040 standard on LCA was followed and the EDIP (Environmental Design of Industrial Products) method and modelling tool were used [2].