Wind, Volume 2, Issue 3 (September 2022) – 10 articles

Wind turbines (WT) are complex multidisciplinary systems containing a large number of mechanical, control, and electrical components. Model-Based Systems Engineering (MBSE) provides an approach for cross-discipline development to address the system complexity and focuses on creating and utilizing domain models as the primary means of information exchange. The domain models predict system behaviors and can support system validation through virtual testing at an early stage of system development. However, the further the WT development proceeds, the more system parameters are set, and the more domain models and virtual tests are involved. Therefore, it is necessary to design a framework of virtual testing workflows of WTs to support virtual validation processes as well as to automate those workflows. To achieve this goal, this contribution shows how standardized virtual testing workflows can be designed and linked to hierarchical and functional system architectures modeled in the Systems Modeling Language (SysML). The virtual testing workflows enable to trigger simulations of domain models and handle system parameters participating in the simulations, thus ensuring data consistency. Furthermore, to facilitate modular management and reuse of domain models, the domain models are classified according to model purposes, model fidelities, and system scopes. The virtual testing workflows are structured corresponding to the classification of the domain model, thereby forming a nested framework. To verify the feasibility of the proposed workflows, a virtual testing process of WT components (i.e., bearings) inside the system context with different model purposes and different model fidelities is demonstrated. It is shown that virtual testing workflows are systematically organized so that engineers can easily virtually (re-)validate the systems. Full article

This study aims to evaluate wind speed and significant wave height data from the Copernicus Marine Environment Monitoring Service (CMEMS) reanalysis using buoy measurements for offshore energy application off the east coast of Brazil. Such analysis has become important, since reanalysis datasets can be fundamental tools in identifying regions with wind energy potential that are suitable for the installation of offshore farms. Two sets of reanalysis were used: wind speed (with spatial resolution of 0.25° and temporal resolution of 6 h) and significant wave height (with spatial resolution of 0.2° and temporal resolution of 3 h). For validation, seven MetOcean buoys were selected. In the statistical validation, Pearson’s correlation, coefficient of determination (R²), slope of the straight line, root mean square error (RMSE), mean square error (MSE), probability density function (PDF), mean and standard deviation were calculated. In the evaluation of offshore wind energy resources, the calculation of energy density was performed. The results showed correlations above 0.70 for wind speed and above 0.91 for significant wave height, and additionally, the RMSE values showed maximums of 2.31 m/s for wind speed and 0.28 cm for significant wave height. In the PDF comparison of buoy data and reanalysis, similarities were observed, mainly in the PDF parameters. The energy density presented values consistent with other studies (352–461 W/m²). The results show that the reanalysis data can be applicable in studies focusing on offshore wind potential. Full article

Wind energy in Europe is expected to grow at a steady, high pace, but opposition from residents to local wind farm plans is one of the obstacles to further growth. A large body of evidence shows that local populations want to be involved and respected for their concerns, but in practice, this is a complex process that cannot be solved with simple measures, such as financial compensation. The visual presence and the acoustic impact of a wind farm is an important concern for residents. Generally, environmental noise management aims to reduce the exposure of the population, usually based on acoustics and restricted to a limited number of sources (such as transportation or industry) and sound descriptors (such as L_den). Individual perceptions are taken into account only at an aggregate, statistical level (such as percentage of exposed, annoyed or sleep-disturbed persons in the population). Individual perceptions and reactions to sound vary in intensity and over different dimensions (such as pleasure/fear or distraction). Sound level is a predictor of the perceived health effects of sound, but explains only part of the reaction. The positive or negative perception of and attitude to the source of the sound is a better predictor of its effects. This article aims to show how the two perspectives (based on acoustics and on perception) can lead to a combined approach in the management of a wind farm aimed to reduce annoyance, not only on a sound level. An important aspect in this approach is what the sound means to people, leading to the following questions: is it associated with the experience of having no say in plans, does it lead to anxiety or worry and is it appropriate? The available knowledge will be applied to wind farm management, including planning as well as operation. Full article

Floating offshore wind turbines are a promising technology for addressing energy needs by utilizing wind resources offshore. The current state of the art is based on heavy, expensive platforms to survive the ocean environment. Typical design techniques do not involve optimization because of the computationally expensive time domain solvers used to model motions and loads in the ocean environment. However, this design uses an efficient frequency domain solver with a genetic algorithm to rapidly optimize the design of a novel floating wind turbine concept. The concept utilizes a liquid ballast mass to mitigate motions on a lightweight post-tensioned concrete platform. The simple cruciform-shaped design of the platform made of post-tensioned concrete is less expensive than steel, reducing the raw material and manufacturing cost. The use of ballast water to behave as a tuned mass damper allows a smaller platform to achieve the same motions as a much larger platform, thus reducing the mass and cost. The optimization techniques applied with these design innovations resulted in a design with a levelized cost of energy of USD 0.0753/kWh, roughly half the cost of the current state of the art. Full article

In this work, the ERA5 reanalysis dataset, with its fine spatial and temporal resolution, is used to study the wind speed and direction characteristics in the Mediterranean basin from 1979 to 2020. Their variability, trend and mean values, as well as their association, are examined in the monthly, annual and interannual/decadal time scales. The long-term variability of the wind direction is assessed using the angular variance, while the mean annual and interannual variability are used for the wind speed. The most characteristic and constant flow systems appear in the Gulf of Lion (Mistral) and the Aegean Sea during the summer (Etesian winds). The mean annual variability maximizes in the northern part of the basin, while the western part appears to have the most variable wind directions, while the fastest increasing wind speeds appear in the southwestern Levantine sub-basin. The long-term linear trend for the mean, the 95th and 99th quantiles of annual wind speed and the number of occurrences of extreme wind events have been also assessed. For particular areas, there is an increasing tendency in both intensity and frequency of occurrence of extreme wind events. Τhe linear-circular correlation coefficient has been implemented in order to quantify the linear association between the wind direction and the wind speed. This parameter demonstrates higher annual values for the Mistral wind in the Gulf of Lion and the Etesian winds in the Aegean Sea during the summer. Finally, the comparison of the results of ERA5 with the results of ERA-Interim highlighted significant differences in the Mediterranean wind speed and direction characteristics. Full article

Brazil is currently witnessing the dawn of its offshore wind industry, and companies, government, investors, and society must understand the risks and possible environmental impacts this technology can generate. This paper aims to partially fill this need by presenting an analysis of the environmental impacts that would be caused by a 5 MW floating offshore wind turbine to be installed on the Brazilian continental shelf through an Environmental Impact Assessment (EIA) and a Life Cycle Assessment (LCA). We assumed that the wind turbine would supply electrical power to a floating oil and gas extraction platform, with the intention of reducing the amount of energy produced with fossil fuels in these platforms, in order to decrease the carbon footprint of this economic activity. The turbine would be mounted on a semi-submersible platform with a high mass of steel, and a battery system for energy storage. We considered two different sites for the turbine installation, Campos Basin and Santos Basin, which are the most important areas of oil and gas extraction in Brazil. The EIA examines the effects caused by the turbine in the ecosystems around it, showing that the fauna suffers from various impacts such as sedimentation, electromagnetic fields, and others, but few species are seriously affected, except for birds, which can have a risk of mortality. The LCA makes an assessment on the carbon dioxide (CO₂) emissions and energy consumption for each part of the life cycle of the project, finding a total 21.61 g of CO₂ emitted per kWh of energy produced by the turbine. The total energy consumed was 89,131.31 GJ, which causes an Energy Payback Ratio (EPR) of 16.28 and Energy Payback Time (EPT) of 1.23 years. Several sensitivity analyses were performed to understand the effect of the variation of several parameters related to recycling, maintenance and failures, and the capacity factor, on the values of CO₂ emission and energy consumption. These analyses showed that variations in the amount of steel recycled and in the capacity factor of the system cause the most significant changes in EPR and EPT. Full article

This paper discusses the wind loads for designing vaulted free roofs based on a wind tunnel experiment, in which the wind force coefficients for the main wind force resisting system and the peak wind force coefficients for cladding are considered. The focus is on the dynamic load effects of fluctuating wind pressures on the wind force coefficients. Wind pressure distributions on the top and bottom surfaces were measured in a turbulent boundary layer. The results indicated that the distributions of wind force coefficients changed significantly with wind direction. Then, the wind direction providing the maximum load effect on the structural frame was detected from a dynamic response analysis using the time histories of wind pressure coefficients. In the analysis, the focus was on the bending moment at the windward column base and the axial force in the leeward column as the most important load effects. The LRC method proposed by Kasperski was employed for evaluating the equivalent static wind force coefficients providing the maximum load effects. Based on the results, a model of design wind force coefficient was proposed in the framework of the conventional gust effect factor approach. Finally, positive and negative peak wind force coefficients for designing the cladding were proposed based on the most critical maximum and minimum peak wind force coefficients among all wind directions. Full article

This paper analyzes one of the most important power capture challenges of the DC series–parallel collection system, called the power curtailment losses. The wind speed difference between the series-connected turbines causes over- and under-voltage conditions in the output voltage of the MVDC (medium-voltage DC) converters of the wind turbine. The power curtailment losses caused by the upper-voltage tolerance levels of the MVDC converters of the wind turbines are analyzed considering a redundancy-based upper-voltage limiting condition. This analysis emphasizes the importance of choosing suitable voltage tolerance levels for the MVDC converters of wind turbines based on the wind farm configuration. The annual energy curtailment losses are quantified and evaluated by a comparative case study performed on a DC series–parallel-connected wind farm rated at 200 MW with the redundancy-based upper-voltage limiting condition. Full article

The transition of nations to renewable energy sources is a fact, and the deployment of renewable energy (RE) projects has increased in the last decades. The deployment of energy projects in uninhabited islets (islands) provides a promising opportunity for low-carbon energy transition. Considering the importance of the spatial dimension of RE projects, in this research, we identified and ranked uninhabited islets (UIs) for wind farm deployment in the South Aegean Sea, Greece. The proposed methodology combines geographic information systems (GIS) and two multicriteria analysis methods (AHP and TOPSIS) using some restrictions found in Greek law as well as assessment criteria considering environmental, economic, and technical aspects. The appropriate UIs were then ranked under four different policy scenarios (baseline, equal criteria weights, a policy scenario oriented to technical/economic criteria, and a policy scenario focusing on environmental criteria). The results indicated the existence of three UIs for siting wind farms in the region of the South Aegean, with the same ranking of these UIs under different scenarios. The proposed methodology provides useful guidelines for selecting UIs as wind farm sites in Greece and could be applied in other countries worldwide. Full article

Global industrialization, population explosion and the advent of a technology-enabled society have placed dire constraints on energy resources. Furthermore, evident climatic concerns have placed boundaries on deployable energy options, compounding an already regrettable situation. It becomes apparent for modern renewable energy technologies, including wind generators, to possess qualities of robustness, high efficiency, and cost effectiveness. To this end, direct-drive permanent magnet (PM) wind generators, which eliminate the need for gearboxes and improve wind turbine drivetrain reliability, are trending. Though rare-earth PM-based wind generators possess the highly sought qualities of high-power density and high efficiency for direct-drive wind systems, the limited supply chain and expensive pricing of the vital raw materials, as well as existent demagnetization risks, make them unsustainable. This paper is used to provide an overview on alternative and viable non-conventional wind generators based on the so-called non-PM (wound-field) stator-mounted flux modulation machines, with prospects for competing with PM machine variants currently being used in the niche direct-drive wind power generation industry. Full article