Large-scale Offshore Wind Farms Research Articles

Time-domain fatigue damage assessment for wind turbine tower bolts under yaw optimization control at offshore wind farm

Yaw optimization control is recognized as the most effective active wake control strategy for enhancing the overall power generation of wind farms. However, the potential adverse effects of yaw optimization control on the fatigue life of wind turbines remain unclear. This study examined the effect of yaw optimization control on the fatigue life of offshore wind turbines using tower bolts. Initially, the yaw misalignment of the wind turbines was optimized using the open-source FLORIS package to maximize wind farm power generation. Subsequently, the time-varying load of the wind turbines was obtained through the OpenFAST software, using the optimal yaw misalignment, wind speed, and turbulence intensity at the hub height as inputs. The fatigue life of the wind turbines was then calculated by integrating the Schmidt–Neuper engineering stress algorithm, rain flow counting method, and Miner-Palmgren fatigue damage accumulation theory. Finally, a case study of the Horns Rev I large-scale offshore wind farm, comprising 80 wind turbines, revealed that yaw optimization control could significantly enhance the annual power generation of the wind farm by approximately 1.818%. However, optimization comes at the cost of reducing the fatigue life of wind turbine tower bolts by approximately 3–9 years.

Life cycle environmental analysis of offshore wind power: A case study of the large-scale offshore wind farm in China

China's decarbonization is indispensable for the large-scale utilization of renewable energy. In this process, the development of offshore wind energy has become an important support, because in the eastern region of China, especially the coastal areas, there's the most load requirements but limited onshore renewable resources. Under the goals of both carbon neutral and sustainable development, however, there's still a research gap in evaluating the environmental impacts of large-scale offshore wind plants in China. In this study, the research performed a comprehensive process-based life cycle environmental analysis of a large-scale (400 MW) offshore wind farm with large wind turbine units (5 MW) in China. Global Warming Potential is 25.73 g CO2-eq/kWh and greenhouse gas payback time is calculated as 12.05 months. Fossil fuel consumption amounts to 0.31 MJ/kWh with an energy payback period of 25.56 months. Material resources and ecotoxicity to freshwater need more attention with the values of 1.68 CTUe/kWh and 3.32 10−6 kg Sb-eq/kWh, respectively. The manufacturing stage contributes most to all the impacts examined. The disposal and recycling process shows significant environmental benefits for most impacts but exerts burdens on the particulate matter. Focusing on Global Warming Potential, the wind turbine generation set has the highest effect, among which the blades contribute 73.2% of it. Further, the evolution of electricity and heating mix of China and use of biomass-based precursors could decrease 57% of the blades' greenhouse gas emissions in 2050. This study could provide guidance on the sustainable design and policy-making of offshore wind farms.

Sub-Synchronous Oscillation Constrained Communication-Free Grid Frequency Control of Offshore Wind Farm Linked HVDC System

This paper proposes a frequency control method of a voltage source converter (VSC) high-voltage direct current (HVDC) system for large-scale offshore wind farms (OWFs) integration into an AC grid. Without frequency control, power output of OWFs varies with the wind velocity and it causes a grid frequency fluctuation. This fluctuation on the AC grid is becoming more severe as the level of wind power penetration increases. The previously suggested communication-free controls are vulnerable to continuously changing frequency fluctuations owing to concerns about its excessive energy releases. Therefore, our proposed control enables OWFs with HVDC to participate in grid frequency regulation continuously by considering its energy state when AC grid frequency fluctuates. In addition, there is a concern about sub-synchronous oscillation (SSO) instability owing to its cascading frequency control structure. A simplified small-signal model is developed to reveal out the existence of these SSO problems and its main factors in the frequency control scheme. Using developed model, overall system stability is comprehensively investigated. Also, a damping controller to mitigate SSO instability is also suggested and validated through simulation. To demonstrate the effectiveness of overall proposed frequency control, time-domain simulations were also carried out utilizing PSCAD/EMTDC under varying wind velocity condition.

Acoustic presence and demographics of sperm whales (Physeter macrocephalus) off southern New England and near a US offshore wind energy area

Abstract Construction in the southern New England wind energy area (WEA), a large-scale offshore wind farm on the east coast of the United States, started in June 2023. Baseline data was collected from 2020 to 2022, with six passive acoustic recorders (SoundTraps) deployed at shallow (<60 m) sites in the vicinity of Nantucket Shoals and Cox’s Ledge. Data were analysed for sperm whale presence, and demographic composition was assessed using interclick intervals. Presence varied by site, season, and year. Sperm whales were detected year-round but the majority (78%) of days with acoustic occurrences were between May and August. Three demographic classes (putative social groups, adult males, and midsize animals) were detected across multiple seasons, with social groups detected most frequently. Sound propagation tests were conducted at two sites and predicted detection ranges within 20–40 km indicate that sperm whales were likely in proximity to the WEA. These results provide a baseline that will be used to assess ongoing sperm whale presence, especially that of social groups which may be more sensitive to disturbance. This study highlights why sperm whales, classed as endangered in US waters, should be considered in mitigation plans and permitting efforts for offshore wind energy.

Cumulative effects of offshore wind farms on common guillemots (Uria aalge) in the southern North Sea - climate versus biodiversity?

Governments are under increasing pressure to reduce greenhouse gas emissions, and large-scale wind farms are being developed in marine environments worldwide. However, top predators are strongly affected by environmental change and anthropogenic activities. Common guillemots (Uria aalge, hereafter guillemots), as one of the world’s most numerous seabird species, are prone to interference with offshore wind farms (OWFs). This study assessed the cumulative impacts of all operating OWFs on guillemots in the German North Sea. These estimates were applied to quantify the possible conflicts between guillemot occurrence and current German government plans to implement large-scale OWFs. If OWFs were implemented according to the current maritime spatial plan for the German Exclusive Economic zone, they would cover 13% of the German North Sea. Guillemot numbers peak during autumn, with German North Sea offshore waters hosting approximately 90,000 individuals. Guillemot density in autumn was significantly reduced within a radius of 19.5 km around operating OWFs. Applying this disturbance distance to current installation plans, about 70% of the German North Sea would be affected, and an estimated 68% of guillemots in the German North Sea would experience habitat loss. This highlights the possible threat to guillemots in the southern North Sea if the current German government plans are implemented. The current estimates are highly relevant to decisions regarding marine spatial planning and management recommendations. Such evaluations are essential for developing sustainable scenarios including reducing the human CO2 footprint, whilst also conserving biodiversity.

Grouping-Based Optimal Design of Collector System Topology for a Large-Scale Offshore Wind Farm by Improved Simulated Annealing

Grouping-Based Optimal Design of Collector System Topology for a Large-Scale Offshore Wind Farm by Improved Simulated Annealing

The impact of platform motion phase differences on the power and load performance of tandem floating offshore wind turbines

The interactions between tandem floating offshore wind turbines remain an essential research topic with a view to optimizing future large-scale offshore wind farms. The focus of past floating offshore wind turbine aerodynamic research was centred on platform motion impact on rotor aerodynamics for standalone or in-phase tandem turbines. The question of how the differences in the surge motion phase of tandem turbines influence the performance of the downstream turbine remains open. Recent investigations reveal that these motions might not invariably be in-phase. This study seeks to determine the repercussions of platform motion phase differences on power, thrust, and wake recovery. Notably, it postulates that phase differences could detrimentally affect fatigue. Using a validated Navier–Stokes actuator line model rooted in the OpenFOAM® toolbox, the study aims to address this hypothesis. It was found that the out-of-plane root bending moment amplitude increase by 100% when the rotors are out of phase. A 72% increase in amplitude was also observed for CT. Both of these observations have also been linked to an increase in angle of attack amplitude over the blade span. This work stimulates future research in floating offshore turbine control strategies and provides guidance to minimize turbine failures and downtime.

Study on a Boat-Assisted Drone Inspection Scheme for the Modern Large-Scale Offshore Wind Farm

This study proposes a novel and comprehensive boat-assisted drone inspection scheme for offshore wind farms. Specifically, we develop a unique wireless communication model, a detailed wind turbine blade detection model, and a route planning scheme for the drone and boat to formulate the minimum energy consumption problem for drone inspection. Then, we demonstrate that this problem is a combinatorial optimization mixed-integer nonlinear programming problem, which we solve by decomposing the optimization problem into four subproblems. Moreover, an improved heuristic algorithm is constructed to solve the optimum energy consumption problem, exploiting these subproblems. The simulation results indicate that the proposed scheme achieves optimal energy consumption for boat-assisted drone inspection. Furthermore, compared with the existing methods, the proposed algorithm obtains the lowest total energy consumption and provides a higher route planning performance for the unmanned aerial vehicle and boat when utilized for offshore wind farm inspection.

Environmental life cycle assessment of a novel offshore wind energy design project: A United States based case study

Renewable energy resources, particularly offshore wind energy, and their role in combating global climate change have gained significant interest in recent years. Considering the potential life cycle impacts of such systems is essential to support effective policy and decision making. This study used life cycle assessment to compare the environmental sustainability of an offshore wind farm case study employing a novel foundation design to one employing a conventional foundation design. Literature has not yet examined the life cycle environmental sustainability of large-scale United States based facilities using a detailed data inventory from a real case study. The life cycle environmental single score of the novel design was 18% lower than that of the conventional design, highlighting that alternative foundation materials like concrete can help reduce the overall life cycle environmental impact of a large scale offshore wind farm. In general, the proposed novel design is favorable from a life cycle perspective compared to the conventional design, particularly in the impact categories of ecotoxicity, eutrophication, carcinogenics, noncarcinogenics, and respiratory effects. The energy payback time was found to be less than one year for both designs. Additional benefits of the novel design concept include lower costs, easier installation, domestic job opportunities, decreased reliance on foreign supply chains, ability to expand the design to deeper and disaster prone waters globally, and increased support for current political goals. Scenario sensitivity analyses showed that the environmental impact of wind energy systems may decrease with domestic sourcing of foundation materials and foundation reuse after decommissioning.

Analysis and Suppression of High-Frequency Resonance for Offshore Wind Power Grid-Connected Converter Considering Cable Capacitance Effect

Large-scale offshore wind farms have become the development trend in wind power generation. Long submarine cables are used to collect electrical energy in the collection networks of offshore wind farms. However, the distributed capacitance of cables cannot be ignored, which makes the impedance of the collection network complex and changeable. It is common to encounter high-frequency harmonic resonance (HFHR) problems when cables interact with wind turbine generators (WTGs). The HFHR may threaten the safe and stable operation of wind turbines. In order to solve this problem, firstly, the impedance of a collection network was constructed. Furthermore, the wind farm collection network was divided into the equivalent wind turbine subsystem (EWTS) and the remaining equivalent wind farm subsystem (REWFS). Then, the mechanism of HFHR was revealed based on the impedance stability analysis method. The effects of cable parameters, the number of connected WTG, and the grid impedance on the HFHR of the interconnected system were also analyzed. Finally, the hybrid damping control method, combining active damping control (ADC) and passive damping control (PDC), was proposed to suppress the resonance. A simulation and experiment were performed to verify the effectiveness of the analysis results and proposed control method.

Impact of frequency control from wind turbine generator linked to HVDC system on sub-synchronous oscillation

With global trends of carbon neutrality, offshore wind energy is considered as the most promising resource. However, as large-scale renewable energy resources replace the existing synchronous generators (SG), concerns about the system stability are growing. Owing to the absence of system supports provided by the SG. Therefore, operators require the wind generators to participate in frequency control. In addition, controls have been devised to perform frequency support even when large-scale offshore wind farm (OWF) linked to High Voltage Direct Current (HVDC). However, this frequency support control’s impacts on the overall system stability are not investigated in deeply yet. Therefore, in this study, the impacts of frequency control from OWF-linked HVDC system using communication-less scheme on the system instability were investigated using small-signal stability analysis. Its results revealed that this frequency support control caused instability. Modal analysis and simulations support these interpretations and improve the understanding its mechanism and dynamics.

Multi-Stage Sequential Network Energy Control for offshore AC asymmetric fault ride-through of MMC-HVDC system integrated offshore wind farms

Modular Multilevel Converter based High Voltage Direct Current (MMC-HVDC) is the preferred solution to the problem of long-distance transmission from large-scale offshore wind farms (OWFs). When an offshore AC asymmetric fault occurs, OWFs and MMC-HVDC will face the challenge of fault ride-through with power electronic converters on both sides of the fault location. In this paper, a Multi-stage Sequential Network Energy Control (MSNEC) is proposed for offshore AC asymmetric fault ride-through (FRT). Firstly, the constraint relationship among the sequence networks under AC asymmetric faults is revealed. Secondly, the energy control potential of WFMMC is fully explored from the perspective of energy transformation and transfer. Energy control reduces the fault phase current amplitude by putting in submodules at the fault phase. Additional sub-modules are put in the non-faulted phase to realize series voltage dividing effect to actively prevent non-faulted phase fault overvoltage. The MSNEC considers the FRT requirements for multiple stages of fault occurrence, fault steady state, and fault recovery. It combines sequential network control, energy control, and voltage support of the converter station. It realizes AC asymmetric FRT from four aspects: power equivalence, negative sequence suppression, energy control, and voltage stabilization. Finally, a simulation model of OWFs connected to the onshore grid via MMC-HVDC is established in PSCAD/EMTDC. Simulation results verify MSNEC not only improves the AC asymmetric FRT capability of the OWFs and WFMMC, but also promotes the efficient consumption of renewable energy and improves the economics of the OWFs grid-connected system.

Analysis of the Legal Blind Sectors of the Large-Scale Offshore Wind Farms of Korea and Proposal to Improve Safety Management

Analysis of the Legal Blind Sectors of the Large-Scale Offshore Wind Farms of Korea and Proposal to Improve Safety Management

Projected cross-shore changes in upwelling induced by offshore wind farm development along the California coast

In California offshore waters, sustained northwesterly winds have been identified as a key resource that can contribute substantially to renewable energy goals. However, the development of large-scale offshore wind farms can reduce the wind stress at the sea surface, which could affect wind-driven upwelling, nutrient delivery, and ecosystem dynamics. Here we examine changes to upwelling using atmospheric and ocean circulation numerical models together with a hypothetical upper bound buildout scenario of 877 turbines spread across three areas of interest. Wind speed changes are found to reduce upwelling on the inshore side of windfarms and increase upwelling on the offshore side. These changes, when expressed in terms of widely used metrics for upwelling volume transport and nutrient delivery, show that while the net upwelling in a wide coastal band changes relatively little, the spatial structure of upwelling within this coastal region can be shifted outside the bounds of natural variability.

A fast dimension reduction framework for large-scale topology optimization of grid-layout offshore wind farm collector systems

The construction of large-scale offshore wind farms faces the difficulty of solving the optimization problem of collector systems. Due to its NP-hard feature, this problem cannot be solved straightforwardly. This paper proposes an efficient and precise solution framework suitable for large-scale collector system optimization and raises the main influencing factors of time complexity. First, according to a heuristic idea, an arc selection algorithm is established to tighten the feasible region. Second, an optimization framework based on the greedy algorithm and mixed integer quadratic programming (MIQP) is established with excellent efficiency and accuracy. The overall problem is decomposed into the master problem of topology optimization and the sub-problem of cable selection. A bi-level model that adopts both greedy algorithm and global optimization is proposed, iterating through the master problem and the sub-problem by transferring parameters and updating constraints. Third, a large number of examples are analyzed, and the advantages of the proposed algorithms and model are comprehensively verified. In the end, time complexity analysis is carried out, and the empirical formula of solution time is obtained by fitting. Based on the proposed method, large-scale problems can be solved much faster than traditional methods and reach a balance of both speed and quality.

Electrical System Planning of Large-scale Offshore Wind Farm Based on N+ Design Considering Optimization of Upper Power Limits of Wind Turbines

Electrical System Planning of Large-scale Offshore Wind Farm Based on N+ Design Considering Optimization of Upper Power Limits of Wind Turbines

Integrated Equivalent Model of Permanent Magnet Synchronous Generator Based Wind Turbine for Large-scale Offshore Wind Farm Simulation

Integrated Equivalent Model of Permanent Magnet Synchronous Generator Based Wind Turbine for Large-scale Offshore Wind Farm Simulation

Modeling for large-scale offshore wind farm using multi-thread parallel computing

Large-scale Offshore Wind Farms (OWFs) face difficulty when carrying out microsecond-level Electro-Magnetic Transient (EMT) simulations due to the large number of Wind Turbines (WTs) and electrical nodes. This paper provides an OWF modeling method considering the electrical collection network based on the integrated equivalent modeling method of single WT, which can eliminate the internal nodes and reduce the order of admittance matrix. Meanwhile, the multi-thread parallel computing is integrated into the whole solution procedure, which achieves further simulation speedup. Moreover, simulations are performed in PSCAD/EMTDC to compare the model accuracy and time efficiency of the proposed method with the detailed model. The simulation results show that the proposed method can accurately simulate the dynamic characteristics of large-scale OWFs with large speedup factors.

A case study of offshore wind turbine positioning optimization methodology using a novel multi-stage approach

This investigation maximize the annual energy production (AEP) of a wind farm’s layout at a specific site using a novel multi-stage approach. The downstream wind turbines’ energy production decreases due to the reduced wind speed and turbulence created by the upstream wind turbines’ wakes. The wake interference from wind turbines causes the reduction of overall power efficiency. This paper provides a novel multi-stage strategy for the optimal layouts generated by heuristic algorithms to address this problem. A comparison of the proposed multi-stage approach to previous optimization algorithms is presented to demonstrate its efficiency using three referenced cases and one potential wind farm in the Gulf of Maine. The results demonstrate that applying the proposed multi-stage approach increases AEP and decreases computational time compared to previous research and optimization algorithms, which is crucial for large-scale offshore wind farm layout design and optimization.

GPU simulation of wake effects at the Horns Rev 1 offshore wind farm using the CFD porous disk wake model

To verify the effectiveness of the GPU simulation of wake effects at a large-scale offshore wind farm, we ran an in-house large-eddy simulation (LES) solver with a CFD porous disk wake model for the Horns Rev 1 wind farm. For this numerical research, we prepared the latest workstation equipped with a Xeon W-2265 CPU and an NVIDIA RTX A6000 GPU. We clarified that the calculation speed of the single GPU of the NVIDIA RTX A6000 is approximately 10 times faster than the calculation speed of the Xeon W-2265. Careful data analysis and visualization of the unsteady turbulent flow fields obtained in the current LES study suggest that the mutual interference of the wakes developed by wind turbines may frequently form a local speed-up region around wind turbines, located on the downstream side of large offshore wind farms.