Energies

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24 pages, 7399 KiB

Open AccessArticle

Design Features and Numerical Investigation of Counter-Rotating VAWT with Co-Axial Rotors Displaced from Each Other along the Axis of Rotation

by Ihor Shchur, Volodymyr Klymko, Shengbai Xie and David Schmidt

Energies 2023, 16(11), 4493; https://doi.org/10.3390/en16114493 - 2 Jun 2023

Cited by 6 | Viewed by 1630

Abstract

In this paper, dual-rotor counter-rotating (CR) configurations of vertical axis wind turbines (VAWTs) are briefly inspected and divided into three types. This investigation was focused on one of these types—the CR-VAWT with co-axial rotors, in which two equal rotors are placed on the [...] Read more.

In this paper, dual-rotor counter-rotating (CR) configurations of vertical axis wind turbines (VAWTs) are briefly inspected and divided into three types. This investigation was focused on one of these types—the CR-VAWT with co-axial rotors, in which two equal rotors are placed on the same shaft, displaced from each other along it and rotated in opposite directions. For this CR-VAWT with three-blade H-Darrieus rotors, the properties of the design in terms of aerodynamics, mechanical transmission and electric generator, as well as control system, are analyzed. A new direct-driven dual-rotor permanent magnet synchronous generator was proposed, in which two built-in low-power PM electric machines have been added. They perform two functions—starting-up and overclocking of the rotors to the angular velocity at which the lifting force of the blades is generated, and stabilizing the CR-VAWT work as wind gusts act on the two rotors. Detailed in this paper is the evaluation of the aerodynamic performance of the CR-VAWT via 3D computational fluid dynamics simulations. The evaluation was conducted using the CONVERGE CFD software with the inclusion of the actuator line model for the rotor aerodynamics, which significantly reduces the computational effort. Obtained results show that both rotors, while they rotate in opposite directions, had a positive impact on each other. At the optimal distance between the rotors of 0.3 from a rotor height, the power coefficients of the upper and lower rotors in the CR-VAWT increased, respectively, by 5.5% and 13.3% simultaneously with some increase in their optimal tip-speed ratio compared to the single-rotor VAWT. Full article

(This article belongs to the Special Issue Wind Turbine Advances)

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15 pages, 1800 KiB

Open AccessArticle

Multi-Horizon Wind Power Forecasting Using Multi-Modal Spatio-Temporal Neural Networks

by Eric Stefan Miele, Nicole Ludwig and Alessandro Corsini

Energies 2023, 16(8), 3522; https://doi.org/10.3390/en16083522 - 18 Apr 2023

Cited by 2 | Viewed by 1372

Abstract

Wind energy represents one of the leading renewable energy sectors and is considered instrumental in the ongoing decarbonization process. Accurate forecasts are essential for a reliable large-scale wind power integration, allowing efficient operation and maintenance, planning of unit commitment, and scheduling by system [...] Read more.

Wind energy represents one of the leading renewable energy sectors and is considered instrumental in the ongoing decarbonization process. Accurate forecasts are essential for a reliable large-scale wind power integration, allowing efficient operation and maintenance, planning of unit commitment, and scheduling by system operators. However, due to non-stationarity, randomness, and intermittency, forecasting wind power is challenging. This work investigates a multi-modal approach for wind power forecasting by considering turbine-level time series collected from SCADA systems and high-resolution Numerical Weather Prediction maps. A neural architecture based on stacked Recurrent Neural Networks is proposed to process and combine different data sources containing spatio-temporal patterns. This architecture allows combining the local information from the turbine’s internal operating conditions with future meteorological data from the surrounding area. Specifically, this work focuses on multi-horizon turbine-level hourly forecasts for an entire wind farm with a lead time of 90 h. This work explores the impact of meteorological variables on different spatial scales, from full grids to cardinal point features, on wind power forecasts. Results show that a subset of features associated with all wind directions, even when spatially distant, can produce more accurate forecasts with respect to full grids and reduce computation times. The proposed model outperforms the linear regression baseline and the XGBoost regressor achieving an average skill score of 25%. Finally, the integration of SCADA data in the training process improved the predictions allowing the multi-modal neural network to model not only the meteorological patterns but also the turbine’s internal behavior. Full article

(This article belongs to the Special Issue Wind Turbine Advances)

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16 pages, 3370 KiB

Open AccessArticle

Vertical Axis Wind Turbine Layout Optimization

by Davide Cazzaro, Gabriele Bedon and David Pisinger

Energies 2023, 16(6), 2697; https://doi.org/10.3390/en16062697 - 14 Mar 2023

Cited by 1 | Viewed by 3981

Abstract

Vertical Axis Wind Turbines (VAWTs) are not mature enough yet for offshore wind farms, but they offer benefits compared to conventional Horizontal Axis Wind Turbines (HAWTs). Higher power densities, reduced wakes, lower center of mass, and different power and thrust curves make VAWTs [...] Read more.

Vertical Axis Wind Turbines (VAWTs) are not mature enough yet for offshore wind farms, but they offer benefits compared to conventional Horizontal Axis Wind Turbines (HAWTs). Higher power densities, reduced wakes, lower center of mass, and different power and thrust curves make VAWTs an interesting option to complement existing wind farms. The optimization of wind farm layouts—finding the optimal positions of wind turbines in a park—has proven crucial to extract more energy from conventional wind farms. In this study, we build an optimizer for VAWTs that can consider arbitrarily shaped layouts as well as obstacles in the area. We adapt a recent model for the wakes of VAWTs considering a Troposkien design. We can then model and optimize a large VAWT park in a real wind scenario and assess for the first time its performance operating Troposkien VAWTs. In addition, we present a novel model for wind farm optimization that considers the clockwise and counterclockwise rotation of turbines. This optimization exploits the asymmetric wakes of VAWTs, thus increasing the total energy production. We benchmark our optimization on realistic instances and compare VAWTs and HAWTs wind farm layouts, showing that VAWTs can achieve higher density and power production than HAWTs in the same area. Finally, the wake loss reduction is compared to the literature. Full article

(This article belongs to the Special Issue Wind Turbine Advances)

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14 pages, 761 KiB

Open AccessArticle

Generation of Surface Maps of Erosion Resistance for Wind Turbine Blades under Rain Flows

by Alessio Castorrini, Paolo Venturini and Aldo Bonfiglioli

Energies 2022, 15(15), 5593; https://doi.org/10.3390/en15155593 - 2 Aug 2022

Cited by 4 | Viewed by 1511

Abstract

Rain erosion on wind turbine blades raises considerable interest in wind energy industry and research, and the definition of accurate erosion prediction systems can facilitate a rapid development of solutions for blade protection. We propose here the application of a novel methodology able [...] Read more.

Rain erosion on wind turbine blades raises considerable interest in wind energy industry and research, and the definition of accurate erosion prediction systems can facilitate a rapid development of solutions for blade protection. We propose here the application of a novel methodology able to integrate a multibody aeroelastic simulation of the whole wind turbine, based on engineering models, with high-fidelity simulations of aerodynamics and particle transport and with semi-empirical models for the prediction of the damage incubation time. This methodology is applied to generate a parametric map of the blade regions potentially affected by erosion in terms of the fatigue life of the coating surface. This map can represent an important reference for the evaluation of the sustainability of maintenance, control and mitigation interventions. Full article

(This article belongs to the Special Issue Wind Turbine Advances)

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24 pages, 15866 KiB

Open AccessArticle

Power and Energy Management of a DC Microgrid for a Renewable Curtailment Case Due to the Integration of a Small-Scale Wind Turbine

by Jamila Aourir, Fabrice Locment and Manuela Sechilariu

Energies 2022, 15(9), 3421; https://doi.org/10.3390/en15093421 - 7 May 2022

Cited by 2 | Viewed by 3245

Abstract

Economic dispatch optimization and power management are the main concerns for a microgrid (MG). They are always studied and are considered to achieve an efficient operation of the MG by simplifying the control process and decreasing losses. The integration of a small-scale wind [...] Read more.

Economic dispatch optimization and power management are the main concerns for a microgrid (MG). They are always studied and are considered to achieve an efficient operation of the MG by simplifying the control process and decreasing losses. The integration of a small-scale wind turbine (SSWD) into a direct current (DC) MG has an impact on its power and energy management. Excess power produced by renewable energy sources (RESs) is one of the problems that face the reliability of the MG and should be resolved. For this reason, a supervisory system is suggested to manage the excess of power. During the supervision process, some criteria, such as the physical limits and tariffs of the components are taken into account. Then, the suggested power management strategy aims to achieve an instantaneous power balance considering a rule-based power and depends on the above-mentioned criteria. To better meet the power balance, it is necessary to explore the constraints related to the control and supervision of the studied DC MG. Performance measures include the overall system energy cost and renewable curtailment (renewable energy that cannot be utilized and should be limited). Thus, the power limitation strategy consists of using two types of “shedding coefficients”,

α

and

γ

, to calculate the power that should be limited from each RES in the case of energy surplus. Simulation tests are carried out using two power management strategies: optimization and without optimization (i.e., storage priority). The results reveal that the coefficient

γ

reduces the overall energy cost and whatever the applied coefficient, optimization still provides good performances and significantly reduces the global energy cost. Full article

(This article belongs to the Special Issue Wind Turbine Advances)

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17 pages, 6691 KiB

Open AccessArticle

Technologies of Wind Turbine Blade Repair: Practical Comparison

by Leon Mishnaevsky, Jr., Nicolai Frost-Jensen Johansen, Anthony Fraisse, Søren Fæster, Thomas Jensen and Brian Bendixen

Energies 2022, 15(5), 1767; https://doi.org/10.3390/en15051767 - 27 Feb 2022

Cited by 10 | Viewed by 3506

Abstract

Maintenance and repair of wind turbines contribute to the higher costs of wind energy. In this paper, various technologies of structural repair of damaged and broken wind turbine blades are compared. The composite plates, mimicking damaged blade parts, were damaged and repaired, using [...] Read more.

Maintenance and repair of wind turbines contribute to the higher costs of wind energy. In this paper, various technologies of structural repair of damaged and broken wind turbine blades are compared. The composite plates, mimicking damaged blade parts, were damaged and repaired, using various available curing and bonding technologies. Technologies of repair with hand layup lamination, vacuum repair with hand layup and infusion, ultraviolet repair and high temperature thermal curing were compared. The repaired samples were tested under tensile static and fatigue tests, and subject to microscopic X-ray investigations. It was observed that both the strength of the repaired structures and the porosity depend on the repair technology used. Vacuum-based technologies lead to relatively stiff and lower-strength repaired plates, while ultraviolet-curing technologies lead to average stiffness and high strength. High-temperature vacuum curing leads to the highest maximum stress. Hand layup (both vacuum and without vacuum) leads to high post-repair porosity in the adhesive and scarf, while vacuum infusion leads to low porosity. Fatigue lifetime generally follows the trend of porosity. There exist risks of micro-damaging the parent laminate and the formation of residual stresses in the repaired structure. Full article

(This article belongs to the Special Issue Wind Turbine Advances)

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14 pages, 4967 KiB

Open AccessArticle

A Comparative Analysis of the Characteristics of Platform Motion of a Floating Offshore Wind Turbine Based on Pitch Controllers

by Chan Roh, Yoon-Jin Ha, Hyeon-Jeong Ahn and Kyong-Hwan Kim

Energies 2022, 15(3), 716; https://doi.org/10.3390/en15030716 - 19 Jan 2022

Cited by 7 | Viewed by 1890

Abstract

The installation of fixed offshore wind power systems at greater water depths requires a floating body at the foundation of the system. However, this presents various issues. This study analyzes the characteristics of the platform motion of a floating offshore wind turbine system [...] Read more.

The installation of fixed offshore wind power systems at greater water depths requires a floating body at the foundation of the system. However, this presents various issues. This study analyzes the characteristics of the platform motion of a floating offshore wind turbine system based on the performance of the pitch controller. The motion characteristics of the platform in a floating offshore wind power generation system, change according to the response speed of the blade pitch controller since the wind turbine is installed on a floating platform unlike the existing onshore wind power generation system. Therefore, this study analyzes the platform motion characteristics of a floating offshore wind turbine system using various pitch controllers that have been applied in previous studies. Consequently, an appropriate pitch controller is proposed for the floating offshore wind turbine system. The floating offshore wind turbine system developed in this study consists of an NREL 5-MW class wind turbine and an OC4 semi-submersible floating platform; the pitch controller is evaluated using FAST-v8 developed by NREL. The results of this study demonstrate that the pitch controller reduces the platform motion of the floating offshore wind power generation system, considering both the individual pitch control and the negative damping phenomenon. Additionally, it is confirmed that the output increases by approximately 0.42%, while the output variability decreases by 19.3% through the reduction of the platform movement. Full article

(This article belongs to the Special Issue Wind Turbine Advances)

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12 pages, 509 KiB

Open AccessArticle

Wake Expansion and the Finite Blade Functions for Horizontal-Axis Wind Turbines

by David Wood

Energies 2021, 14(22), 7653; https://doi.org/10.3390/en14227653 - 16 Nov 2021

Cited by 5 | Viewed by 1496

Abstract

This paper considers the effect of wake expansion on the finite blade functions in blade element/momentum theory for horizontal-axis wind turbines. For any velocity component, the function is the ratio of the streamtube average to that at the blade elements. In most cases, [...] Read more.

This paper considers the effect of wake expansion on the finite blade functions in blade element/momentum theory for horizontal-axis wind turbines. For any velocity component, the function is the ratio of the streamtube average to that at the blade elements. In most cases, the functions are set by the trailing vorticity only and Prandtl’s tip loss factor can be a reasonable approximation to the axial and circumferential functions at sufficiently high tip speed ratio. Nevertheless, important cases like coned or swept rotors or shrouded turbines involve more complex blade functions than provided by the tip loss factor or its recent modifications. Even in the presence of significant wake expansion, the functions derived from the exact solution for the flow due to constant pitch and radius helical vortices provide accurate estimates for the axial and circumferential blade functions. Modifying the vortex pitch in response to the expansion improves the accuracy of the latter. The modified functions are more accurate than the tip loss factor for the test cases at high tip speed ratio that are studied here. The radial velocity is important for expanding flow as it has the magnitude of the induced axial velocity near the edge of the rotor. It is shown that the resulting angle of the flow to the axial direction is small even with significant expansion, as long is the tip speed ratio is high. This means that blade element theory does not have account for the effective blade sweep due to the radial velocity. Further, the circumferential variation of the radial velocity is lower than of the other components. Full article

(This article belongs to the Special Issue Wind Turbine Advances)

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