Upwind Horizontal Axis Wind Turbine Research Articles

Upwind Horizontal Axis Wind Turbine Output Power Optimization via Artificial Intelligent Control System

Power capturing capacity is one of the key performance indicators of wind turbines. This article presents a study done on the optimization of output power of upwind horizontal axis wind turbine using artificially intelligent control system. The study shows how blade tip speed ratio (λ) and pitch angle (β) are optimized to increase wind turbines power conversion coefficient (C_p) which increases the output power. An artificial intelligence system named Mandani fuzzy inference system (MFIS) was applied to optimize the power conversion coefficient in combination with blade pitch actuator control. To this end, a novel optimization technique is designed that maximizes the power harvesting ability of wind turbines by updating the parameters of the membership functions of fuzzy logic found in the MFIS. With the application of this optimization method, a power conversion coefficient C_p of 0.5608 value is achieved at optimal values of λ and β. As a result, the energy harvesting ability of the wind turbine considered is improved by 16.74%. This study clearly shows that the wind energy harvesting capacity of wind turbines can be enhanced via optimization techniques that could be further implemented in wind turbine blade pitch drive system. Thus, this novel optimization method creates further insights for the wind energy industry in reducing the cost of energy generation.

Determination of the angle of attack on a research wind turbine rotor blade using surface pressure measurements

Abstract. In this paper, a method to determine the angle of attack on a wind turbine rotor blade using a chordwise pressure distribution measurement was applied. The approach used a reduced number of pressure tap data located close to the blade leading edge. The results were compared with the measurements from three external probes mounted on the blade at different radial positions and with analytical calculations. Both experimental approaches used in this study are based on the 2-D flow assumption; the pressure tap method is an application of the thin airfoil theory, while the probe method applies geometrical and induction corrections to the measurement data. The experiments were conducted in the wind tunnel at the Hermann Föttinger Institut of the Technische Universität Berlin. The research turbine is a three-bladed upwind horizontal axis wind turbine model with a rotor diameter of 3 m. The measurements were carried out at rated conditions with a tip speed ratio of 4.35, and different yaw and pitch angles were tested in order to compare the approaches over a wide range of conditions. Results show that the pressure tap method is suitable and provides a similar angle of attack to the external probe measurements as well as the analytical calculations. This is a significant step for the experimental determination of the local angle of attack, as it eliminates the need for external probes, which affect the flow over the blade and require additional calibration.

Wind Turbine Tip Vortices under the influence of Wind Tunnel Blockage Effects

The current paper describes the characteristics of the tip vortex in the near wake of a three-bladed upwind horizontal axis wind turbine with a rotor diameter of 3 m. Phase-locked stereo particle image velocimetry measurements were carried out under the influence of the wind tunnel walls that create a high blockage ratio. The location of the vortex, convection velocity, core radius, and strength were investigated and compared with similar investigations, including different blockages cases. Additionally, the same performance of the wind turbine model was simulated in the open source wind turbine tool QBlade, using the lifting line free vortex wake module in the absence of the walls.The results showed that the location of the tip vortices was more inboard the tip and more downstream the tunnel compared to the simulations and similar experiments. The convection velocity remained similar in the axial direction and changed in the lateral direction, contributing to the delay of the movement of the tip vortex outboard the tip. The strength, based on the circulation, was found with a difference of 4% between simulation and experiment.

Aeroelastic response of a multi-megawatt upwind horizontal axis wind turbine (HAWT) based on fluid–structure interaction simulation

Abstract. With the increasing demand for greener, sustainable, and economical energy sources, wind energy has proven to be a potential sustainable source of energy. The trend development of wind turbines tends to increase rotor diameter and tower height to capture more energy. The bigger, lighter, and more flexible structure is more sensitive to smaller excitations. To make sure that the dynamic behavior of the wind turbine structure will not influence the stability of the system and to further optimize the structure, a fully detailed analysis of the entire wind turbine structure is crucial. Since the fatigue and the excitation of the structure are highly depending on the aerodynamic forces, it is important to take blade–tower interactions into consideration in the design of large-scale wind turbines. In this work, an aeroelastic model that describes the interaction between the blade and the tower of a horizontal axis wind turbine (HAWT) is presented. The high-fidelity fluid–structure interaction (FSI) model is developed by coupling a computational fluid dynamics (CFD) solver with a finite element (FE) solver to investigate the response of a multi-megawatt wind turbine structure. The results of the computational simulation showed that the dynamic response of the tower is highly dependent on the rotor azimuthal position. Furthermore, rotation of the blades in front of the tower causes not only aerodynamic forces on the blades but also a sudden reduction in the rotor aerodynamic torque by 2.3 % three times per revolution.

The effect of blade-tower interaction on the structure loading of multi megawatt horizontal axis wind turbine

The aim of this work is to investigate the blade-tower interaction of multi megawatts upwind horizontal axis wind turbine (HAWT). With the increasing of the tower height, tower base becomes bigger and transportation problems appear. Nowadays, the tower dimensions are almost reached roads limits. To optimize tower dimensions there is the need to get a better understanding of what loads act on the tower.In this work, a CFD simulation of a 3MW upwind HAWT is performed to predict tower load for nominal operation conditions considering blade-tower interaction. It was found that blade-tower interaction induces significant dynamic load. The tower suffers pressure fluctuation called 3P oscillation (for three blades rotor) leading to cyclic fatigue and influences rotor stability. Moreover, because of blade passage in front of the tower, the stagnation point position changes and displacement of separation points on tower sides occur. The tower suffers different shedding frequencies on the upper and lower parts and side forces are resulted.

Numerical simulation of tower shadow effect of upwind horizontal axis wind turbine

The tower-blade interaction is one of key reasons that would seriously affect the wind turbine aerodynamic performance. Simulation of tower shadow effect for a three-bladed, upwind offshore wind turbine using STAR-CCM+ software is researched. The model of national renewable energy laboratory (NREL) 5 MW baseline wind turbine is used in this simulation by computational fluid dynamics (CFD) method. Based on the reynolds averaged navier-stokes (RANS) equations and the shear-stress transport (SST) k - ω turbulence model, aerodynamic simulations for NREL 5 MW turbine have been studied. Model validation and grid-independence verification are conducted in order to have more accurate results. The aerodynamic simulations of wind turbine model with tower and rotor model without tower are carried out separately. The impacts of tower shadow effect on aerodynamic performance are obtained by comparison of two models. The method of blade element momentum (BEM) is also used to study tower shadow effect, and two research methods are compared. Simulation results demonstrate that the tower shadow effect is remarkable. Mutation caused by tower shadow effect of aerodynamic performance is emerged and it will cause some adverse results for blades and tower. Impact of tower shadow effect on average value of wind turbine aerodynamic load is not significant. As is shown by simulation results, average thrust of wind turbine is declined by 0.46% and average power is declined by 0.87%. This paper could also provide some references for further research about the influence of tower shadow effect on aerodynamic performance.

Prediction and analysis of infra and low-frequency noise of upwind horizontal axis wind turbine using statistical wind speed model

Despite increasing concern about low-frequency noise of modern large horizontal-axis wind turbines (HAWTs), few studies have focused on its origin or its prediction methods. In this paper, infra- and low-frequency (the ILF) wind turbine noise are closely examined and an efficient method is developed for its prediction. Although most previous studies have assumed that the ILF noise consists primarily of blade passing frequency (BPF) noise components, these tonal noise components are seldom identified in the measured noise spectrum, except for the case of downwind wind turbines. In reality, since modern HAWTs are very large, during rotation, a single blade of the turbine experiences inflow with variation in wind speed in time as well as in space, breaking periodic perturbations of the BPF. Consequently, this transforms acoustic contributions at the BPF harmonics into broadband noise components. In this study, the ILF noise of wind turbines is predicted by combining Lowson’s acoustic analogy with the stochastic wind model, which is employed to reproduce realistic wind speed conditions. In order to predict the effects of these wind conditions on pressure variation on the blade surface, unsteadiness in the incident wind speed is incorporated into the XFOIL code by varying incident flow velocities on each blade section, which depend on the azimuthal locations of the rotating blade. The calculated surface pressure distribution is subsequently used to predict acoustic pressure at an observing location by using Lowson’s analogy. These predictions are compared with measured data, which ensures that the present method can reproduce the broadband characteristics of the measured low-frequency noise spectrum. Further investigations are carried out to characterize the IFL noise in terms of pressure loading on blade surface, narrow-band noise spectrum and noise maps around the turbine.

Reduction of Wind Turbine Torque Fluctuation Using Individual Pitch Control Based on Edgewise Moment

In order to eliminate the nonuniform force on the wind rotor caused by wind shear, tower shadow and turbulence and smooth the torque fluctuation of the wind turbine and the unbalanced loads on the wind turbine, a new individual pitch control strategy based on edgewise moment using single neuron PID controller is proposed. That is, the presented control strategy directly controls the blade edgewise moment generated by aerodynamic force. At the same time, to simulate the wind turbine loads, a dynamic model of three-bladed upwind horizontal axis wind turbine is built. Thus, the influence rules of the wind turbine torque fluctuation are deduced at length. Finally, to verify the effectiveness of the proposed individual pitch control system with the single neuron PID controller, the 2MW wind turbine generator system is modeled and simulated. The performance of the controller is illustrated its capability of not only reducing the wind turbine fluctuation, but also smoothing the fluctuation of the flapwise moment, the yaw moment and the tilt moment.

Unsteady Blade Element-Momentum Method Including Returning Wake Effects

The wind energy research has grown substantially in the past few years, considerably fostered by the pursuit for a clean and sustainable energy source. Improvements on the design methods are increasingly needed. The purpose of this research is to investigate the use of the Loewys lift deficiency function (LDF), also named Returning Wake Model, coupled with a non-stationary Blade Element-Momentum Method (BEM). The LDF simulates the influence of the wake behind the wind turbine on its capacity to generate power. It is expected that this model reduce the dependency of the several empirical parameters necessary in other wake models which are currently used. Aiming to validate the results obtained in this new approach they are compared with those provided by commercial computational software and they have proven to be very consistent. It is concluded that the method is feasible to be used as an efficient design and optimization tool of upwind horizontal axis wind turbine blades.

Hydraulic Variable Pitch Control and Aerodynamic Load Analysis for Wind Turbine Blades

This paper reviews the principle of power production, and analyses the influnece on aerodynamic load and output power due to the variation of pitch angle. For three-bladed upwind horizontal axis wind turbine, the blade pitch control is used primarily to adjust the power coefficient and obtain the optimal power at high wind speed, but it also make aerodynamic load, such as edgewise, flapwise and torsion moment, change during variable pitch control. Hydraulic mechanism is used in a process requiring large driving forces and torques, fast response and high stiffness. Therefore, the variable pitch mechanism is operated using electro-hydraulic proportional technology in this paper. Simulation results are presented and analysed to show that aerodynamic load and output power are sensitivity to pitch angle for wind turbine blade. These works lay foundation for the further studying of individual pitch, power control, fatigue and dynamical stability for wind turbine.