Editorial

4 pages, 172 KiB

Open AccessEditorial

Editorial on Special Issue “Wind Turbine Power Optimization Technology”

by Francesco Castellani and Davide Astolfi

Energies 2020, 13(7), 1796; https://doi.org/10.3390/en13071796 - 08 Apr 2020

Cited by 1 | Viewed by 1742

This Special Issue collects innovative contributions in the field of wind turbine optimization technology. The general motivation of the present Special Issue is given by the fact that there has recently been a considerable boost of the quest for wind turbine efficiency optimization [...] Read more.

This Special Issue collects innovative contributions in the field of wind turbine optimization technology. The general motivation of the present Special Issue is given by the fact that there has recently been a considerable boost of the quest for wind turbine efficiency optimization in the academia and in the wind energy practitioners communities. The optimization can be focused on technology and operation of single turbine or a group of machines within a wind farm. This perspective is evidently multi-faced and the seven papers composing this Special Issue provide a representative picture of the most ground-breaking state of the art about the subject. Wind turbine power optimization means scientific research about the design of innovative aerodynamic solutions for wind turbine blades and of wind turbine single or collective control, especially for increasing rotor size and exploitation in offshore environment. It should be noticed that some recently developed aerodynamic and control solutions have become available in the industry practice and therefore an interesting line of development is the assessment of the actual impact of optimization technology for wind turbines operating in field: this calls for non-trivial data analysis and statistical methods. The optimization approach must be 360 degrees; for this reason also offshore resource should be addressed with the most up to date technologies such as floating wind turbines, in particular as regards support structures and platforms to be employed in ocean environment. Finally, wind turbine power optimization means as well improving wind farm efficiency through innovative uses of pre-existent control techniques: this is employed, for example, for active control of wake interactions in order to maximize the energy yield and minimize the fatigue loads. Full article

(This article belongs to the Special Issue Wind Turbine Power Optimization Technology)

Research

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21 pages, 7582 KiB

Open AccessArticle

Wind Turbine Control Using Nonlinear Economic Model Predictive Control over All Operating Regions

by Xiaobing Kong, Lele Ma, Xiangjie Liu, Mohamed Abdelkarim Abdelbaky and Qian Wu

Energies 2020, 13(1), 184; https://doi.org/10.3390/en13010184 - 01 Jan 2020

Cited by 46 | Viewed by 3948

Abstract

With the gradual increase in the installed capacity of wind turbines, more and more attention has been paid to the economy of wind power. Economic model-predictive control (EMPC) has been developed as an effective advanced control strategy, which can improve the dynamic economy [...] Read more.

With the gradual increase in the installed capacity of wind turbines, more and more attention has been paid to the economy of wind power. Economic model-predictive control (EMPC) has been developed as an effective advanced control strategy, which can improve the dynamic economy performance of the system. However, the variable-speed wind turbine (VSWT) system widely used is generally nonlinear and highly coupled nonaffine systems, containing multiple economic terms. Therefore, a nonlinear EMPC strategy considering power maximization and mechanical load minimization is proposed based on the comprehensive VSWT model, including the dynamics of the tower and the gearbox in this paper. Three groups of simulations verify the effectiveness and reliability/practicability of the proposed nonlinear EMPC strategy. Full article

(This article belongs to the Special Issue Wind Turbine Power Optimization Technology)

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18 pages, 9218 KiB

Open AccessEditor’s ChoiceArticle

Dynamic Stall of a Vertical-Axis Wind Turbine and Its Control Using Plasma Actuation

by Lu Ma, Xiaodong Wang, Jian Zhu and Shun Kang

Energies 2019, 12(19), 3738; https://doi.org/10.3390/en12193738 - 30 Sep 2019

Cited by 32 | Viewed by 3536

Abstract

In this paper, a dynamic stall control scheme for vertical-axis wind turbine (VAWT) based on pulsed dielectric-barrier-discharge (DBD) plasma actuation is proposed using computational fluid dynamics (CFD). The trend of the wind turbine power coefficient with the tip speed ratio is verified, and [...] Read more.

In this paper, a dynamic stall control scheme for vertical-axis wind turbine (VAWT) based on pulsed dielectric-barrier-discharge (DBD) plasma actuation is proposed using computational fluid dynamics (CFD). The trend of the wind turbine power coefficient with the tip speed ratio is verified, and the numerical simulation can describe the typical dynamic stall process of the H-type VAWT. The tangential force coefficient and vorticity contours of the blade are compared, and the regular pattern of the VAWT dynamic stall under different tip speed ratios is obtained. Based on the understanding the dynamic stall phenomenon in flow field, the effect of the azimuth of the plasma actuation on the VAWT power is studied. The results show that the azimuth interval of the dynamic stall is approximately 60° or 80° by the different tip speed ratio. The pulsed plasma actuation can suppress dynamic stall. The actuation is optimally applied for the azimuthal position of 60° to 120°. Full article

(This article belongs to the Special Issue Wind Turbine Power Optimization Technology)

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18 pages, 7494 KiB

Open AccessArticle

Investigation on Optimization Design of Offshore Wind Turbine Blades based on Particle Swarm Optimization

by Yong Ma, Aiming Zhang, Lele Yang, Chao Hu and Yue Bai

Energies 2019, 12(10), 1972; https://doi.org/10.3390/en12101972 - 23 May 2019

Cited by 17 | Viewed by 2961

Abstract

Offshore wind power has become an important trend in global renewable energy development. Based on a particle swarm optimization (PSO) algorithm and FAST program, a time-domain coupled calculation model for a floating wind turbine is established, and a combined optimization design method for [...] Read more.

Offshore wind power has become an important trend in global renewable energy development. Based on a particle swarm optimization (PSO) algorithm and FAST program, a time-domain coupled calculation model for a floating wind turbine is established, and a combined optimization design method for the wind turbine’s blade is developed in this paper. The influence of waves on the power of the floating wind turbine is studied in this paper. The results show that, with the increase of wave height, the power fluctuation of the wind turbine increases and the average power of the wind turbine decreases. With the increase of wave period, the power oscillation amplitude of the wind turbine increases, and the power of the wind turbine at equilibrium position decreases. The optimal design of the offshore floating wind turbine blade under different wind speeds is carried out. The results show that the optimum effect of the blades is more obvious at low and mid-low wind speeds than at rated wind speeds. Considering the actual wind direction distribution in the sea area, the maximum power of the wind turbine can be increased by 3.8% after weighted optimization, and the chord length and the twist angle of the blade are reduced. Full article

(This article belongs to the Special Issue Wind Turbine Power Optimization Technology)

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20 pages, 2384 KiB

Open AccessArticle

Wind Turbine Power Curve Upgrades: Part II

by Davide Astolfi and Francesco Castellani

Energies 2019, 12(8), 1503; https://doi.org/10.3390/en12081503 - 20 Apr 2019

Cited by 11 | Viewed by 2856

Abstract

Wind turbine power upgrades have recently become a debated topic in wind energy research. Their assessment poses some challenges and calls for devoted techniques: some reasons are the stochastic nature of the wind and the multivariate dependency of wind turbine power. In this [...] Read more.

Wind turbine power upgrades have recently become a debated topic in wind energy research. Their assessment poses some challenges and calls for devoted techniques: some reasons are the stochastic nature of the wind and the multivariate dependency of wind turbine power. In this work, two test cases were studied. The former is the yaw management optimization on a 2 MW wind turbine; the latter is a comprehensive control upgrade (pitch, yaw, and cut-out) for 850 kW wind turbines. The upgrade impact was estimated by analyzing the difference between the post-upgrade power and a data-driven simulation of the power if the upgrade did not take place. Therefore, a reliable model for the pre-upgrade power of the wind turbines of interest was needed and, in this work, a principal component regression was employed. The yaw control optimization was shown to provide a 1.3% of production improvement and the control re-powering provided 2.5%. Another qualifying point was that, for the 850 kW wind turbine re-powering, the data quality was sufficient for an upgrade estimate based on power curve analysis and a good agreement with the model result was obtained. Summarizing, evidence of the profitability of wind turbine power upgrades was collected and data-driven methods were elaborated for power upgrade assessment and, in general, for wind turbine performance control and monitoring. Full article

(This article belongs to the Special Issue Wind Turbine Power Optimization Technology)

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18 pages, 2857 KiB

Open AccessArticle

Study of Floating Wind Turbine with Modified Tension Leg Platform Placed in Regular Waves

by Juhun Song and Hee-Chang Lim

Energies 2019, 12(4), 703; https://doi.org/10.3390/en12040703 - 21 Feb 2019

Cited by 10 | Viewed by 3635

Abstract

In this study, the typical ocean environment was simulated with the aim to investigate the dynamic response under various environmental conditions of a Tension Leg Platform (TLP) type floating offshore wind turbine system. By applying Froude scaling, a scale model with a scale [...] Read more.

In this study, the typical ocean environment was simulated with the aim to investigate the dynamic response under various environmental conditions of a Tension Leg Platform (TLP) type floating offshore wind turbine system. By applying Froude scaling, a scale model with a scale of 1:200 was designed and model experiments were carried out in a lab-scale wave flume that generated regular periodic waves by means of a piston-type wave generator while a wave absorber dissipated wave energy on the other side of the channel. The model was designed and manufactured based on the standard prototype of the National Renewable Energy Laboratory (NREL) 5 MW offshore wind turbine. In the first half of the study, the motion and structural responses for operational wave conditions of the North Sea near Scotland were considered to investigate the performance of a traditional TLP floating wind turbine compared with that of a newly designed TLP with added mooring lines. The new mooring lines were attached with the objective of increasing the horizontal stiffness of the system and thereby reducing the dominant motion of the TLP platform (i.e., the surge motion). The results of surge translational motions were obtained both in the frequency domain, using the response amplitude operator (RAO), and in the time domain, using the omega arithmetic method for the relative velocity. The results obtained show that our suggested concept improves the stability of the platform and reduces the overall motion of the system in all degrees-of-freedom. Moreover, the modified design was verified to enable operation in extreme wave conditions based on real data for a 100-year return period of the Northern Sea of California. The loads applied by the waves on the structure were also measured experimentally using modified Morison equation—the formula most frequently used to estimate wave-induced forces on offshore floating structures. The corresponding results obtained show that the wave loads applied on the new design TLP had less amplitude than the initial model and confirmed the significant contribution of the mooring lines in improving the performance of the system. Full article

(This article belongs to the Special Issue Wind Turbine Power Optimization Technology)

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14 pages, 4568 KiB

Open AccessArticle

Multiple Wind Turbine Wakes Modeling Considering the Faster Wake Recovery in Overlapped Wakes

by Zhenzhou Shao, Ying Wu, Li Li, Shuang Han and Yongqian Liu

Energies 2019, 12(4), 680; https://doi.org/10.3390/en12040680 - 20 Feb 2019

Cited by 29 | Viewed by 4603

Abstract

In a wind farm some wind turbines may be affected by multiple upwind wakes. The commonly used approach in engineering to simulate the interaction effect of different wakes is to combine the single analytical wake model and the interaction model. The higher turbulence [...] Read more.

In a wind farm some wind turbines may be affected by multiple upwind wakes. The commonly used approach in engineering to simulate the interaction effect of different wakes is to combine the single analytical wake model and the interaction model. The higher turbulence level and shear stress profile generated by upwind turbines in the superposed area leads to faster wake recovery. The existing interaction models are all analytical models based on some simple assumptions of superposition, which cannot characterize this phenomenon. Therefore, in this study, a mixing coefficient is introduced into the classical energy balance interaction model with the aim of reflecting the effect of turbulence intensity on velocity recovery in multiple wakes. An empirical expression is also given to calculate this parameter. The performance of the new model is evaluated using data from the Lillgrund and the Horns Rev I offshore wind farms, and the simulations agree reasonably with the observations. The comparison of different interaction model simulation results with measured data show that the calculation accuracy of this new interaction model is high, and the mean absolute percentage error of wind farm efficiency is reduced by 5.3% and 1.58%, respectively, compared to the most commonly used sum of squares interaction model. Full article

(This article belongs to the Special Issue Wind Turbine Power Optimization Technology)

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14 pages, 5109 KiB

Open AccessEditor’s ChoiceArticle

Parametric Study of a Gurney Flap Implementation in a DU91W(2)250 Airfoil

by Iñigo Aramendia, Unai Fernandez-Gamiz, Ekaitz Zulueta, Aitor Saenz-Aguirre and Daniel Teso-Fz-Betoño

Energies 2019, 12(2), 294; https://doi.org/10.3390/en12020294 - 18 Jan 2019

Cited by 30 | Viewed by 5140

Abstract

The growth in size and weight of wind turbines over the last years has led to the development of flow control devices, such as Gurney flaps (GFs). In the current work, a parametric study is presented to find the optimal GF length to [...] Read more.

The growth in size and weight of wind turbines over the last years has led to the development of flow control devices, such as Gurney flaps (GFs). In the current work, a parametric study is presented to find the optimal GF length to improve the airfoil aerodynamic performance. Therefore, the influence of GF lengths from 0.25% to 3% of the airfoil chord c on a widely used DU91W(2)250 airfoil has been investigated by means of RANS based numerical simulations at Re = 2 × 10⁶. The numerical results showed that, for positive angles of attack, highest values of the lift-to-drag ratio C_L/C_D are obtained with GF lengths between 0.25% c and 0.75% c. Particularly, an increase of 21.57 in C_L/C_D ratio has been obtained with a GF length of 0.5% c at 2° of angle of attack AoA. The influence of GFs decreased at AoAs larger than 5°, where only a GF length of 0.25% c provides a slight improvement in terms of C_L/C_D ratio enhancement. Additionally, an ANN has been developed to predict the aerodynamic efficiency of the airfoil in terms of C_L/C_D ratio. This tool allows to obtain an accurate prediction model of the aerodynamic behavior of the airfoil with GFs. Full article

(This article belongs to the Special Issue Wind Turbine Power Optimization Technology)

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