No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Pitch Angle Control for Small-Scale Darrieus Vertical Axis Wind Turbine with Straight Blades (H-type VAWT)
Abstract
Unlike the Horizontal Axis Wind Turbines (HAWTs), only a few studies have been conducted recently to improve the self-starting capability and/or aerodynamic performance of a Darrieus Vertical Axis Wind Turbine (H-type VAWT). Pitch angle control technique is used to improve the performance of an H-type VAWT. This paper presents an intelligent blade pitch control to enhance the performance of H-type VAWTs in terms of power output. ANSYS FLUENT Computational Fluid Dynamics (CFD) software is used to study the aerodynamic performance of a 2D variable pitch angle H-type VAWT at different Tip Speed Ratios (TSRs) and determine the optimum pitch angles. For each case, the power coefficient Cp is calculated and compared to the published experimental and CFD results. The results obtained from the CFD model are used to construct the aerodynamic model of the H-type VAWT rotor, which is required to design the intelligent pitch angle controller using Multi-Layer Perceptron Artificial Neural Networks (MLP-ANN) method. The performance of the blade pitch controller using MLP-ANN is compared to a conventional controller (PID). Results demonstrate that for an H-type VAWT MLP-ANN has superior performance in terms of power output by comparison to a conventional PID controller.
... According to the energy progress report by the world bank, about 800 million people have no access to electricity [1]. Stand-alone power supply systems, such as wind turbines and solar cells, are not only suitable solutions for producing the electricity needed for rural and remote areas, but also economical alternatives because they can contribute to a reduction in the cost of grid extensions [2]. Wind turbine blade design plays an important role in determining the aerodynamic efficiency of wind turbines by increasing lift-drag ratio of airfoils [3]. ...
... The power coefficient of wind turbines can be calculated by the following equation [2]: ...
... A domain should be large enough to avoid a solid blockage effect of the lateral boundaries and describe a development of the wake. Therefore, the dimensions of the domain are 6 chord length upstream, 12.5 chord length downstream, and 12.5 chord length width [2]. Structured C-type mesh is generated for a 2D NACA 0015 airfoil type using ANSYS Workbench and the mesh is characterized with 200,000 quadrilateral elements. ...
... The usefulness of blade pitch control mechanism is already illustrated in HAWTs and was proved to be very effective in enhancing performance [42]. The above studies [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] also show that the performance enhancement was achieved mostly by understanding the initial blade pitch angle using either the numerical or the computational approach. Due to complex aerodynamics behavior of VAWT blades as it rotates in 3D space, limited research has been conducted on power enhancement using active blade pitching mechanism in the low wind regions considering sensitive parameters. ...
... In contrast, blade element theory provides the force analysis for a small blade element. This combined approach is called strip theory or blade element momentum (BEM) theory [4,34]. DMST model also combines the MST model with the double actuator disk theory to estimate the turbine's performance. ...
In this thesis, the role of active blade pitching on vertical axis wind turbine (VAWTs) technology is investigated under several turbine design parameters, i.e., geometrical (different number and aerofoil thickness, solidity) and operational conditions like Reynolds number (𝑅𝑒), tip speed ratio (TSR). This research mainly focuses towards identifying the flow-sensitive design parameters that can eliminate the dead band issue of wind turbines operating in low wind speed regions. The performance was evaluated utilizing high fidelity computational and low fidelity numerical approach. An analytical model was developed using the double multiple stream tube (DMST) method by integrating blade element with momentum theories. In addition, a high-fidelity URANS CFD model was set up to study the performance of H-rotor VAWTs. Active blade pitching was integrated in both models. The results were initially compared well with experimental literature data. The results indicate that the local widening of the angle of attack as function of azimuth position was very effective in performance enhancement as it minimizes boundary layer separation and maximizes the lift/torque force during the complete cyclic operation. The dead band issue of wind turbines at low TSR (1-3) can be eliminated by either adding a number of blades, increasing blade chord length, and reducing the rotor radius. Moreover, the investigation also shows that the pitching algorithm was very effective for three and four bladed rotor design to achieve maximum possible torque. The effect of varying aerofoil profiles, aspect ratio, solidity, and the number of aerofoil was also investigated, targeting the improvement in the self-starting of VAWTs for regions with low wind speed. The results obtained from soap film provided high-resolution information of boundary layer formation around variable pitching aerofoil that demonstrated the physics of flow behind the blades of VAWTs experiencing low performance
... However, such However, computationally inefficient algorithms implemented in the solvers may cause significant CPU overhead, for example, the sliding mesh algorithm widely used in the unsteady rotor simulations [5]. Moreover, the usage of open-source flow solvers for a VAWT is highly limited in the literature, as the vast majority of the studies [6][7][8][9][10][11][12][13][14] has preferred commercial solvers so far. ...
... In this work, a widely studied [6,7,13,19] 3-bladed H-type Darrieus wind turbine is selected as a VAWT test case. The main features of the 3-bladed rotor with rectangular planform blades are given in Table 2. ...
With rapid advancements in computer hardware and numerical modeling methods, Computational Fluid Dynamics (CFD) has gained prominence in simulating complex flows. As parallel computation becomes an industry standard, the computational efficiency of simulations has become critical. The flow around a Vertical Axis Wind Turbine (VAWT), characterized by complex dynamics and challenging rotating geometry, serves as an intriguing case for CFD studies. This study employs the open‐source CFD solvers SU2 and OpenFOAM to simulate the incompressible, unsteady, and turbulent flow around an H‐type Darrieus VAWT in two dimensions. Spatial and temporal discretization parameters are examined to balance computational cost and accuracy, revealing notable effects on power predictions. Simulations conducted under identical conditions allow for a comparison of the predictions and parallel performances of SU2 and OpenFOAM across three distinct tip speed ratios (TSRs). The findings show that discretization parameters behave differently at various TSRs. While power predictions from SU2 and OpenFOAM generally align with experimental data and with each other, discrepancies arise at lower TSRs, with thrust predictions showing better consistency. Although OpenFOAM provides a faster solution across all parallel configurations, SU2 demonstrates superior parallel scalability, achieving higher speedup and efficiency.
... Several researchers (Paraschivoiu et al., 2009;Sheng et al., 2013;Jakubowski et al., 2017;Zhao et al., 2018;Manfrida and Talluri, 2020;Zhang L. et al., 2021;Guevara et al., 2021) have propose various mathematical approaches to optimize pitch angles. Numerical tools such as artificial neural networks (ANN) (Abdalrahman et al., 2017) and genetic algorithm (GA) De Tavernier et al., 2019) are used for optimising variable pitch settings. However, these approaches are only simulated results, and experimental validation is yet to be conducted . ...
... Many unforeseen weaknesses can be rooted out during this process that may influence final costings and sustainability. • The use of artificial intelligence can be implemented to shorten the duration of studies in improving and optimising the variable design factors like pitch control (Abdalrahman et al., 2017), design of a Savonius VAWT (Teksin et al., 2022) and pattern trends of blade designs on VAWT (Noman et al., 2022). ...
Omnidirectionality and simple design make VAWTs more attractive compared to HAWTs in highly turbulent and harsh operational environments including low wind speed conditions where this technology shines more. However, the performance of VAWTs is lacking compared to HAWTs due to low turbine efficiency at downstream caused by large wake vortices generated by advancing blades in the upstream position. Introducing variable design methods on VAWT provides better adaptability to the various oncoming wind conditions. This paper presents state-of-the-art variable methods for performance enhancement of VAWTs to provide better direction for the wind industry. The variable VAWT design can increase the lift and torque, especially at the downstream regions by managing the blade-to-wake interaction and blade angle of attack (AoA) well, hence contributing to the performance enhancement of VAWTs. In addition, the self-starting capabilities have also been found to improve by employing variable methods with a better angle of attack on the turbine blades. Nevertheless, the complexity of varying mechanisms and structural rigidity are the main challenges in adopting this idea. Yet, it possesses great potential to develop higher-efficiency VAWT systems that can operate in a wide range of wind speeds.
... The dimensions of the simulation domain are constructed based on the previous work , which are sufficient to simulate the flow around the VAWT and ensure the space around the turbines in the leeward region is enough to characterize the flow behaviors within the VAWT system. Such a 2D model has been widely employed in the literature to simulate the VAWT performance instead of a complicated 3D model without loss of generality in the accuracy of numerical simulation (Sun, 2021;Rezaeiha et al., 2017;Abdalrahman et al., 2017). ...
... The upper, right, and bottom boundaries are designated as the outlets with constant atmospheric pressure, and the no-slip condition is applied on the blade surfaces. The power coefficient (C p ) indicates the VAWT performance, which represents the ratio of power output from the VAWT to the power received from the wind (Abdalrahman et al., 2017) and is written as: ...
The present study aims to optimize the design of a vertical axis wind turbine (VAWT) and analyze how the design factors affect the power coefficient of VAWT. The considered factors include the number of blades, angle of attack, airfoil type, tip speed ratio, and wind speed. Computational fluid dynamics (CFD) is used to analyze the flow characteristics and determine the power coefficient. Then the Taguchi method and the modified additive model (MAM) are employed to analyze each factor's influence. As a result, the optimal combination of these factors to give the highest power coefficient is determined. The implementation of MAM analysis is found to enhance the prediction accuracy for the optimal case by exploring the interaction between the factors. The contribution of each factor is evaluated further by the variance analysis method (ANOVA) to examine which factor would be the most crucial one that produces the most significant impact on the VAWT performance. It is found that for a VAWT using NACA 0015 airfoil with 3 blades, the maximum mean power coefficient is 0.421 at an angle of attack 4⁰, tip speed ratio 2, and wind speed 10 m/s. The factors can be ranked in sequence of significance as wind speed, tip speed ratio, angle of attack, airfoil type, and number of blades, in which both the wind speed and tip speed ratio almost exhibit the same impact on the VAWT performance.
... 13,14 In VAWTs, the pitch control mechanism has been studied in terms of fixed or variable pitch control [15][16][17] as a means to improve starting torque, 18 increase power production, 19 and protect against overspeeding instead of relying on stalling. 20 Abdalrahman et al. (2017) 21 studied the effect of variable pitch control compared with conventional pitch control, which resulted in a 25% increase in power production for variable pitch control for H-type VAWTs. Pitch control also has been shown to be an effective VAWT control strategy by raising the annual energy production (AEP) of H-type VAWTs by at least 30%. ...
... 33 Similar methods have already been developed in terms of intracycle pitch control, whereby varying the pitch of the blades as a function of azimuth, one can effectively modify the nominal angle of attack of the blades and improve the power production. 21 As for intracycle RPM control, which is the focus of this paper, it has been demonstrated experimentally for a small-scale hydrokinetic cross-flow turbine to increase C P by 59% over standard control methods. 26 The present study presents for the first time the application of intracycle RPM to a large-scale 5 MW Darrieus VAWT. ...
The wind energy market is currently dominated by horizontal axis wind turbines (HAWTs); however, vertical axis wind turbines (VAWTs) are emerging as a design alternative, especially for deep‐water offshore siting due to their low center of gravity, ease of access to drivetrain components, and overall simplicity. Due to the absence of a pitch mechanism in large‐scale Darrieus VAWTs, stall control has often been used to manage power and loads. Introducing a pitching mechanism in H‐type VAWTs has been studied, but this diminishes the mechanical simplicity advantage, and the use of a pitching mechanism in a large‐scale Darrieus‐type VAWT is not practical. This work examines an innovative, alternative method to control the rotor dynamics of a large‐scale 5 MW VAWT to maximize power while constraining loads without introducing any new or complex mechanical elements. This control strategy is termed intracycle revolution per minute (RPM) control, where the rotational speed of the turbine is allowed to vary in an optimal fashion with the azimuthal location of blades as opposed to typical constant RPM operation. An optimization framework is formulated for an open‐loop optimal control problem and solved to maximize power subject to constraints on aerodynamic design loads. Results are presented to demonstrate the benefits and the performance limits of intracycle RPM control for large‐scale 5 MW Darrieus VAWTs, namely, (1) power production (quantified in terms of AEP) that can be increased subject to baseline load limits and (2) opportunities to significantly increase AEP or decrease loads via intracycle RPM control that are examined for both two‐bladed and three‐bladed VAWTs.
... Incorrect patterns of production and consumption of energy, water and resources are the main cause of environmental problems (Matiolli & Lunkes, 2022). Due to the growing energy demand, alternative and renewable energies, such as hydro, wind, solar, and geothermal among others, have become an important source to supply this demand (Abdalrahman, Melek, & Lien, 2017). Giving way to the development of devices capable of transforming this type of energy, such as hydrokinetic turbines, which have been arousing interest in researchers, seeking to achieve higher yields with lower implementation costs (Patel, Eldho, & Prabhu, 2017). ...
... The meshing of the stationary part the same for the twelve turbine models that were evaluated. To ensure an appropriate density of elements, the elements were placed in such a way that by increasing the number of nodes a proximity between the stationary and rotational domain was guaranteed, achieving a faster convergence (Abdalrahman et al., 2017). The second part was the meshing of the rotational domain, adopting an unstructured mesh of rectangular elements. ...
Purpose: In the present work, the 2D design of H-Darrieus turbines with a diameter of 900 mm and NACA blades 0018, 0025, 2415, and 4415 has been carried out for the solidity values of 0,5; 1 and 1,5. In order to know its maximum performance. Method/design/approach: The 2D simulations were developed with the ANSYS® FLUENT package in the transient state, varying the angular velocity (ω) for a peak velocity ratio (TSR) of 1 to 7 and the SST K-ω turbulence model, for a constant water flow rate of 1 m/s. This in order to know the results of the torque (Nm) generated and thus calculate the power coefficient (Cp). Results and conclusion: The NACA 0018 blade reached a power coefficient of 0,604 for a solidity of 0,5, followed by NACA 2415 blade at the same solidity with a maximum Cp of 0,594. On the other hand, the NACA 0025 blade for solidity of 1 reached a maximum Cp value of 0,570, while the NACA 4415 profile with a solidity of 1,5 obtained a maximum value of 0.495. Research implications: These results of maximum Cp values were given in a TSR range of 2 to 4 with a mean value of 3,5 for NACA profiles 0018 and 2415. Thus, evidencing the behavior of this type of turbine reaching maximum values to then begin to decrease. Originality/value: The present work contributes to the understanding of the impact of geometrical parameters on the operating coefficient of H-Darrieus.
... To mitigate challenges associated with natural behavior, such as dynamic stall and flow separation, and to enhance overall performance, the optimization of the VAHT blade is imperative. A direct solution from a non-modification blade is to orient the blade passively to achieve independence AoA from the incoming flow using passive pitch [22]- [24]. This approach could improve performance by 81% at TSR 1.5, while the suggested pitch angle is between 5 and 8 degrees for very low incoming flow [25]- [26]. ...
... The blade pitch angle, which determines the position of the blade's leading edge and directly affects the attack angle, is considered to be an important design parameter. Based on the results of a previous study, the best performance was achieved with a negative blade pitch angle, and as it increased, the Cp power factor values decreased [28]. ...
In this study, we conducted experimental and numerical investigations of a Darrieus rotor with asymmetrical blades, which has two structural configurations—with and without horizontal parallel plates. Experimental tests were conducted in a wind tunnel at various air flow velocities (ranging from 3 m/s to 15 m/s), measuring rotor rotation frequency, torque, and thrust force. The computational simulation used the ANSYS 2022 R2 Fluent software package, where CFD simulations of air flow around both rotor configurations were performed. The calculations employed the Realizable k-ε turbulence model, while an unstructured mesh with local refinement in the blade–flow interaction zones was used for grid generation. The study results showed that the rotor with horizontal parallel plates exhibits higher aerodynamic efficiency at low wind velocities compared to the no-plates rotor. The experimental findings indicated that at wind speeds of 3–6 m/s, the rotor with plates demonstrates 18–22% higher torque, which facilitates the self-start process and stabilizes turbine operation. The numerical simulations confirmed that horizontal plates contribute to stabilizing the air flow by reducing the intensity of vortex structures behind the blades, thereby decreasing aerodynamic drag and minimizing energy losses. It was also found that the presence of plates creates a directed flow effect, increasing the lift force on the blades and improving the power coefficient (Cp). In the case of the rotor without plates, the CFD simulations identified significant low-pressure zones and high turbulence regions behind the blades, leading to increased aerodynamic losses and reduced efficiency. Thus, the experimental and numerical modeling results confirm that the Darrieus rotor with horizontal parallel plates is a more efficient solution for operation under low and variable wind conditions. The optimized design with plates ensures more stable flow, reduces energy losses, and increases the turbine’s power coefficient. These findings may be useful for designing small-scale wind energy systems intended for areas with low wind speeds.
... Zhang et al. [40] reported a 15 % improvement through blade pitching adjustments; however, their study focused on a single-blade design at specific TSR values, utilizing computationally intensive optimization methods. Similarly, Abdalrahman et al. [41] combined artificial neural networks (ANN) with CFD simulations to model blade pitching, achieving a 22 % performance increase, though the approach was computationally demanding. ...
This research delves into the performance enhancement of Vertical Axis Wind Turbines (VAWTs) through the innovative
approach of variable blade pitching based on Double Multiple Stream Tube theory principles. VAWTs, known for their
potential in urban and low-wind environment, often face efficiency and energy yield challenges. This study addresses
these challenges by proposing a novel variable blade pitching mechanism that dynamically adapts to changing wind
conditions, optimizing the aerodynamic performance, and enhancing the torque and overall performance of VAWT rotor.
The efficiency of two pitching models is investigated on 3-bladed NACA0015 rotors, where the blade's local angle of
attack is cyclically adjusted below the stall angle to maximize the lift force and torque throughout full revolution. In
Model 1, the angle of attack experiences cyclic variation as a sinusoidal function providing smooth pitching, whereas in
Model 2, the peak value of angle of attack was fixed below the stall condition forming linear function. The investigation
showed substantial improvement in the VAWT performance using both pitching models. The variable blade pitching
strategy significantly enhances the lift-to-drag ratio and thus improving the torque output across diverse wind scenarios/tip
speed ratios, demonstrating its effectiveness in maximizing the operational efficiency of VAWTs. Blade pitching model
1 and 2 were found to be effective across all lower Tip Speed Ratio (TSR) values, suggesting its robustness in variable
wind conditions. A peak average coefficient of performance (Cp) of 0.568 was achieved at TSR = 5 using pitching Model
1 with a maximum angle of attack of 8.5 degrees, compared to a Cp of 0.48 for the fixed blade configuration, near to
Betz’s limit (Cp = 0.593). The findings confirm that integrating variable blade pitching would substantially improve
VAWT performance and offer a clear direction for revolutionary future wind turbine aerodynamic design enhancements.
... The flow angle is the summation of the angle of attack, AOA or α; the angle between the relative wind and the chord line of the blade's airfoil; and the pitch angle, β, the angle between the chord line of the airfoil and tangential velocity vector [31]. ...
This study introduces a novel approach to wind energy by investigating a novel Active Axis Wind Turbine design. The turbine is neither a horizontal nor vertical axis wind turbine but has an axis of operation that can actively change during operation. The design features a rotor with a single blade capable of dynamic pitch and tilt control during a single rotor rotation. This study examines the potential to balance the centrifugal and aerodynamic lift forces acting on the rotor blade assembly, significantly reducing blade, tower, foundation and infrastructure costs in larger-scale devices and decreasing the levelised cost of energy for wind energy. The design of a laboratory prototype rotor assembly is optimised by varying the masses and lengths in a lumped mass model to achieve equilibrium between centrifugal and lift forces acting on the turbine’s rotor assembly. The method involves an investigation of the variation of blade pitch angle to provide a balance between centrifugal and aerodynamic forces, thereby facilitating the cost advantages and opening the opportunity to improve the turbine efficiency across a range of operation conditions. The implication of this study extends to different applications of wind turbines, both onshore and offshore, introducing insight into innovation for sustainable energy and cost-effective solutions.
... Where R is the rotor radius, ω is the rotational speed of the turbine, and V in is the incoming wind speed The Cp parameter represents the ratio of a turbine's highest power output to the kinetic energy flow through its front section [40,41]: ...
... The output of the lth fully connected layer can be defined as follows 67 [Eqs. (7) and (8)]: ...
The Venturi reactor, widely used in process intensification through hydrodynamic cavitation technology, has proven highly effective in various chemical and environmental applications. The cavitation intensity of a Venturi is primarily influenced by shape parameters such as the convergent angle (β1), throat diameter (dth), throat length (lth), and divergent angle (β2). However, the impact of these parameters on cavitation intensity has not been sufficiently clarified. In this study, the structural optimization of a Venturi reactor was accomplished by integrating deep neural networks with particle swarm optimization. The Cavitation Intensity Prediction Network model, which combines artificial neural networks and numerical simulation, was used to establish the nonlinear relationship between shape parameters and cavitation intensity. Partial dependence plots and individual conditional expectation plots were utilized to clarify the influence of each parameter. The findings reveal that the cavitation intensity of the optimal Venturi is 2.76 times greater than that of the original design. Reducing β1 resulted in a swift conversion of static pressure into dynamic pressure, but it also caused an uneven distribution of fluid velocity. To reduce this unevenness and allow the dynamic pressure in the throat to reach its peak, which is advantageous for cavitation generation, lth should be extended. dth directly influenced the efficiency of converting static pressure into dynamic pressure and was a key factor in determining cavitation intensity. β2 indirectly impacted cavitation intensity by modulating the space available for cavitation development. The insights gained from this study may provide valuable guidance for designing Venturis in process intensification applications.
... The flow angle is the summation of the angle of attack, AOA or α, the angle between the relative wind and the chord line of the blade's airfoil, and the pitch angle, β, the angle between the chord line of the airfoil and tangential velocity vector [25]. ...
This research introduces a novel approach to improving wind energy's LCOE (Levelised Cost of Energy). Specifically, this research aims to reduce the LCOE from wind turbines by investigating a novel Active Axis Wind Turbine (AAWT) design. The turbine is neither a horizontal nor vertical axis wind turbine but has an axis of operation that can actively change during operation. The design features a rotor with a single blade capable of dynamic pitch and tilt control during a single rotor rotation. This study examines the potential to balance the centrifugal and aerodynamic lift forces acting on the rotor blade assembly, significantly reducing blade, tower, foundation and infrastructure costs in larger-scale devices and decreasing the LCOE for wind. The design of a laboratory prototype rotor assembly is optimised by varying the masses and lengths in a lumped mass model to achieve equilibrium between centrifugal and lift forces acting on the turbine's rotor assembly. The method involves an investigation of the variation of blade pitch angle to provide a balance between centrifugal and aerodynamic forces, thereby facilitating the cost advantages and opening the opportunity to improve the turbine efficiency across a range of operation conditions. The implication of this study extends to different applications of wind turbines, both onshore and offshore, introducing insight into innovation for sustainable energy and cost-effective solutions.
... Among the diverse technologies under consideration for urban wind energy applications, it appears that small VAWTs may present the most promising solution [9]. To enhance the overall performance of wind turbines, Lulu Ni [10] investigated the impacts of Gurney flaps and solidity on VAWTs within a three-turbine array. ...
Examining dual vertical-axis wind turbines (VAWTs) across various turbulence scenarios is crucial for advancing the efficiency of urban energy generation and promoting sustainable development. This study introduces a novel approach by employing two-dimensional numerical analysis through computational fluid dynamics (CFD) software to investigate the performance of VAWTs under varying turbulence intensity conditions, a topic that has been relatively unexplored in existing research. The analysis focuses on the self-starting capabilities and the effective utilization of wind energy, which are key factors in urban wind turbine deployment. The results reveal that while the impact of increased turbulence intensity on the self-starting performance of VAWTs is modest, there is a significant improvement in wind energy utilization within a specific turbulence range, leading to an average power increase of 1.41%. This phenomenon is attributed to the more complex flow field induced by heightened turbulence intensity, which delays the onset of dynamic stall through non-uniform aerodynamic excitation of the blade boundary layer. Additionally, the inherent interaction among VAWTs contributes to enhanced turbine output power. However, this study also highlights the trade-off between increased power and the potential for significant fatigue issues in the turbine rotor. These findings provide new insights into the optimal deployment of VAWTs in urban environments, offering practical recommendations for maximizing energy efficiency while mitigating fatigue-related risks.
... With all stated advantages of VP systems, the complexity of these systems raises some disadvantages. The need for powerful control systems, mechanical mechanisms, actuators, and sensors increases the operational cost and the initial investment price [24][25][26]. These extra components must be engineered precisely and maintained regularly to ensure a reliable performance [6]. ...
Blade pitch angle regulation is an effective approach to enhance the performance of H-type Darrieus Vertical Axis Wind Turbines (VAWTs). Improving the blade interaction with the wind for this type of rotor is a challenging task, especially in unsteady wind conditions. This paper presents a novel hybrid approach that integrates fixed and variable blade pitch angle regulation techniques, aiming to enhance the wind turbine efficiency across various operational stages and wind speeds. The proposed blade pitch angle regulation method targets a less complicated, mechanically feasible, and cost-effective pitching technique. This study uses the Double Multiple Streamtube (DMST) model to analyze the aerodynamic performance and calculate the power output generated at different pitch angles. MATLAB Simulink was utilized to implement the DMST model, and experimental validation was conducted to confirm the results. The findings indicate that the blade pitch angle regulation has significantly enhanced the self-starting ability of H-type Darrieus VAWT by 80%. Additionally, the maximum rotational speed and power coefficient are achieved at a zero pitch angle. Furthermore, regulating the blade pitch angle allows for the effective control of excessive rotational speeds during high wind conditions.
... The R-L load model in the Park frame is [26]: ...
The objective of this article is to compare the effectiveness between the optimal TSR MPPT regulation strategy and the neuro-fuzzy MPPT one to control the column of turbines of a vertical axis tidal turbine facing the impact of its oscillated torque on the electromechanical quantities output of the PMSG such as rotational speed, currents and voltages. In this study, the turbine torque is determined by the DMST method. And, the Park model of the PMSG is used. In addition, the methods of regulating the turbine by the optimal TSR MPPT and by the neuro-fuzzy MPPT are studied. Each control strategy includes PI correctors and a PWM rectifier in the electrical chain. Three turbines mounted in a column with the same radius of 455mm and height of 824mm were considered. The simulation was carried out with operation at maximum average efficiency of the column of three turbines and a flow of 1.5 m/s. Without a control system, the rotational speed of the PMSG with the three non-offset turbines, when feeding a resistive and inductive load, has the amplitude more wavy compared to if they are offset. The output quantities of PMSG are improved by both regulation strategies. The MPPT neuro-fuzzy regulation mode is more effective than the MPPT one at optimal TSR. Due to the fact that the turbine produces the oscillating speed and that, unlike the MPPT strategy at optimal TSR, the MPPT neuro regulation mode-Fuzzy provides instant reference speed. A comparative study with other regulation strategies using instantaneous reference rotation speeds can be undertaken.
... These turbines harness the kinetic energy of river or marine currents, the equivalent of wind turbines. To produce energy, they require a water current speed of more than 1m/s on average [1], [2]. Horizontal-axis tidal current turbines have higher efficiency and have been developed by many renewable energy companies around the world. ...
This article aims to improve the output voltage efficiency of a Permanent Magnet Synchronous Generator (PMSG) with the benefit combination of Neural Networks and Fuzzy Logic. The previous both give a Neuro-fuzzy system tool. The PMSG is associated with a vertical-axis tidal turbine to produce electrical energy. PMSG and the vertical tidal turbine make up the studied system. Regarding the regulation and control of the Pulse Wave Modulation (PWM) rectifier at the output of the system, two controllers are explained and their performance is tested and compared: Maximum Power Point Tracking (MPPT) at Tip Speed Ratio (TSR) and MPPT Neuro-fuzzy. The two control algorithms were simulated for a turbine operating at maximum mean efficiency with a flow of 1.5 m/s. It is shown that when an unregulated generator feeds a resistive and inductive load, the amplitude of the output voltages is more undulating compared with a tidal turbine equipped with MPPT-TSR and MPPT Neuro-fuzzy control systems. It shows that the optimal MPPT-TSR improves and stabilizes voltages by seeking the reference rotational speed as a variable to minimize the error between the measured and reference rotational speeds. The MPPT Neuro-fuzzy controller, on the other hand, offers a clear improvement and better stabilization of voltages by providing the reference rotational speed as instantaneous to minimize the error between the measured and reference rotational speeds. As for the MPPT Neuro-fuzzy controller, it offers a clear improvement and better stabilization of voltages by providing the reference speed of rotation as instantaneous to minimize the error between the recorded rotational speed and the specified reference speed.
... In this work, a widely studied [6], [7], [11], [12] 3-bladed H-type Darrieus wind turbine is selected as a VAWT test case. The main features of the 3-bladed rotor with rectangular planform blades are given in Table I. ...
This study presents an analysis of the parallel computing performance of the Vertical-Axis Wind Turbine CFD simulations on a HPC cluster. The efficiency and scalability of flow simulations are evaluated in the parallel computing environment , thereby providing valuable insights into their suitability for complex rotor aerodynamic simulations. 2D unsteady CFD simulations are performed by using OpenFOAM with the Sliding Mesh Interface methodology. The unsteady flow around the VAWT rotor test case is solved and presented as the velocity and vorticity contours, and the flow and wake development are observed. Each blade's power production over time is investigated showing that each blade has its own unique torque pattern and an uneven contribution to the total power production. Finally, the parallel speedup and efficiency of the simulations are assessed and the parallel computing performance is evaluated and discussed.
... • pitch control (angle of attack control): In this method, the angle of attack of blades is adjusted in response to changing wind conditions. If the wind is too strong, the angle of attack can be reduced to limit the speed and avoid overloading the turbine [14]. • aerodynamic control: In this method, by using different shapes or additional elements on blades, the aerodynamics of the turbine can be adjusted, which affects the power generated [15,16]. ...
... The two types of wind turbines are categorised according to their rotational axes: vertical axis wind turbines (VAWTs) and horizontal axis wind turbines (HAWTs) (Torres et al. 2022;Whittlesey 2017). VAWTs can capture wind energy from all directions and allow energy to be harvested under diverse wind conditions, especially in low-wind regions (Abdalrahman, Melek, and Lien 2017). ...
... In this case, the use of the Savonius type Vertical Axis Wind Turbine (VAWT) technology has the potential as a cooling medium when integrated in a hybrid manner with solar PV because it has a large enough cross-sectional area and can utilize wind energy in various directions (omnidirectional) so that it can optimally circulate air to cool the solar PV panels [24], [25]. By utilizing the drag force of the coming wind [26], The airflow that passes through the turbine blades can be manipulated and then directed to the solar PV panels to improve the cooling process of the system. In addition to the advantages previously described, this solar PV-wind turbine hybrid system still requires identification of placement or additional configuration of each component of the system. ...
The harnessing of clean energy from solar and wind constitutes the foremost renewable energy source in Indonesia. The amalgamation of these energy modalities holds the promise of heightened energy efficiency coupled with reduced maintenance expenditures. This investigation endeavors to synergize wind turbines with photovoltaic (PV) solar panels in a hybrid configuration, capitalizing on the turbulent effluent from the wind turbine system as a cooling medium for the solar PV panels. Further studies are needed regarding the Solar PV-Wind Turbine hybrid cooling system, as a system needs to be designed to optimize the direction of airflow from the turbine as a cooling medium for the solar PV panels without compromising the turbine's performance. Experimental-scale modeling is implemented in this study, introducing a flat winglet deflector configuration to refine and optimize the airflow dynamics traversing the turbine, directed towards enhancing the performance of the integrated solar PV-Wind Turbine hybrid system. The results showed that the installation of solar PV panels and the addition of a flat winglet deflector configuration could improve the performance of the turbine. The highest Cp and Ct values obtained were 0.18476 and 0.66404 with an increased value of 21.74% and 20.56% respectively. Using the Taguchi method, the most optimal configuration for Cp is obtained for installing a PV solar panel with a height of 10cm with AoA for installing a flat winglet deflector of 5°. In the ANOVA analysis conducted, it is known that AoA has an effect of up to 71.57%, while the panel height has an effect of 24.69% with an error percentage of 3.73%.
... Using vortex method and some assumptions like neglecting the aerodynamic stall, Vandenberghe and Dick [34] conducted a parametric study to estimate the optimal blade pitch sinusoidal function to enhance the overall turbine performance. Abdalrahman et al. [35] illustrated the implementation of active blade pitching through an artificial neural network (ANN), which was computationally intensive. Their research was limited to a 3-bladed NACA0018 rotor for a few TSR ranges, and a performance enhancement of 25% was achieved using their model. ...
The general frame of the present study falls under the umbrella of ongoing research and innovation in wind energy technology to improve the efficiency and reliability of vertical-axis wind turbines (VAWTs) in terms of design and control. While blade pitching is foreseen as a solution to minimize boundary layer separation and maximize the lift force during the entire cyclic blade operation (effectively enhancing the performances of VAWTs), conclusive research on active blade pitching mechanisms in low wind speed regions is limited because of the 3D complex aerodynamic around VAWT blades. The paper reports a holistic study on active blade pitching solutions to enhance the performance of H-rotor Darrieus VAWTs for different turbine design parameters, i.e., geometrical (different number and airfoil thickness, and solidity) under several operational conditions (Reynolds number (Re), and tip speed ratio (TSR)). In this study, a variable blade pitching technique, adapted for periodic variation of the angle of attack, is incorporated in a high-fidelity two-dimensional VAWTs transient Computational Fluid Dynamics (CFD) model to eliminate the dead band of small-scale wind turbines operating at low wind speed regions and increase the performance coefficient Cp) at different TSRs. Sliding mesh and remeshing to capture the blade pitching are used to manage the rotor rotation. The CFD model is validated against experimental data from the literature. The results indicate that the local widening of the angle of attack (AoA) for each NACA0015 airfoil produces a Cp) of 0.44, which represents 81% enhancement in the Cp) at TSR of 1.5. Moreover, the study shows that increasing the number of blades or extending the blade chord length can eliminate the dead band of wind turbines. Furthermore, the maximum possible torque for 3- and 4-bladed rotor designs is achieved using the variable pitching mechanism.
... It constitutes the optimal operating point of the turbine. This result confirms the work carried out by Bossard [23] which shows that the optimal specific speed of tidal turbines is of the order of 2. We note that this power coefficient curve ( figure 10-a ) has the same appearance predicted in the section 2.2.1 ( Figure 2 ). According to Figure 10-b, we see the different levels of average power as a function of rotation speed which increase following the increase U ∞ . ...
The objective of this article is to observe the effect of the torque provided by a column of turbines offset or not with vertical axis of a tidal turbine on its electromechanical output quantities such as the rotation speed, the currents and the voltages of the PMSG when the tidal turbine is equipped or not with the regulation system. In this study, this torque is determined by the DMST method. And, the PMSG Park model is used. In addition, the chosen control system includes a PWM rectifier, PI correctors and an optimal TSR MPPT control. The latter considers the fixed reference rotation speed at each flow speed. Three turbines mounted in a column with the same radius of 455mm and height of 824mm were considered. The simulation was carried out with operation at maximum average efficiency of the column of three turbines and a flow of 1.5 m/s. Without a control system, the tidal turbine output quantities with a column of non-offset turbines have more undulating amplitudes compared to if they are offset. These output quantities are improved in the presence of regulation. They can be further improved by seeking the reference rotation speed as a variable in order to minimize the error between the measured rotation speed and the reference speed.
... Teknik penentuan ukuran diameter poros mengikuti penentuan diameter poros yang dilakukan oleh Viktus K Koten et al [23], [24], and [25]. Mekipun pitch angle 0 o tidak dianjurkan oleh Viktus K. Koten et al [26], J. J. Miau et al [27], Gebreel Abdalrahman et al [28], Abdolrahim Rezaeiha et al [29], and Bill Gutierrez [30], pemilihan pitch angle ini berdasarkan kemudahan pemasangan blade pada lengan turbin. Pada poros, selain dipasang bantalan untuk mengurangi gesekan antara poros dengan penyanggah juga dipasang flens sebagai tempat pemberian beban. ...
Wind energy is one type of renewable energy which is not only clean and environmentally friendly but also has abundant and is obtained free of charge in the natural. The process of converting kinetic energy in the wind into mechanical energy requires a turbine. Darrieus turbine is a device that converts wind energy that moves from various directions into mechanical energy on a shaft that moves in one direction. This study aims to determine the performance of a two-blade Darrieus turbine with the NACA 0028 profile experimentally. The wind tunnel, Darreus turbine, and load-bearing construction were designed and manufactured by researchers. Data collection of wind velocity, load, and rotation using standard equipment. The results of the study show that the turbine power coefficients are 35.57%, 23.55%, 23.2%, and 20.05% at wind velocity of 6.04, 7.08, 7.25, and 7.59 m/s, respectively.
... The MLP-ANN control system was employed for the uniform wind speed scenario to minimize pitch angle variations that occurred due to minor differences between the real and reference power waveforms [97]. The power output was boosted by 29 % compared to fixed-pitch VAWT [98]. Rezaeiha et al. [99] observed that the AoA, shed vorticity, and transition of laminar to turbulent as a function of pitch angle. ...
The decline of fossil fuel reserves and stringent environmental regulations demands an extensive use of renewable energy sources. Wind turbine power generation is rapidly increasing, and researchers oversee new challenges and solutions every day. This paper critically reviews the flow control techniques and strategies for improving the wind turbine efficiency. The development of controlling and mitigation strategies for dynamic stall requires an understanding of flow mechanisms such as wake formation, downstream vortex, flow separation , and vortex shedding. The aforesaid phenomena significantly lead to the formation of dynamic stall (Tip speed ratio < 4). This review paper extensively discusses the mechanism of dynamic stall formation and its effects on the performance of vertical axis wind turbines along with the recent developments in mitigation techniques (enhances power coefficient by 50-60 %). It highlights the main aspects involved in performance and stability enhancement of vertical axis wind turbines such as objective functions, design constraints, airfoil dynamics , models, flow control, and optimization techniques. The results of various mitigation approaches are critically analysed, and the most effective techniques are identified. Hence, this review article provides a complete information on the constraints and solution strategies involved in vertical axis wind turbine and opens new possibilities for further research for enhancing the aerodynamic performance. Introduction The wind turbine is a leading technology for extracting energy from wind. It has been extensively studied with the dwindling fossil fuel reserves and the growing awareness on building environmental friendly energy supplies. The sustainability metric assessment on the lowest relative emissions of greenhouse gases, lower use of water, and the most favourable social impacts showed the dominance of wind power on hydropower, photovoltaic and geothermal energy [1]. With an addition of 77.6 GW in the year 2022, the projected global wind power capacity is 906 GW, as shown in Fig. 1 [2]. The Indian government recently set a target of 450 GW of overall renewable energy by 2030, with wind energy and solar photovoltaic estimated to account for 36 % of total installed capacity [3]. The future of wind power is mainly dependent on the development of vertical axis wind turbines (VAWTs) because of their applicability in low wind regions, especially urban areas [4-9]. The VAWTs can be classified into two main categories, i.e., drag and lift-based [10,11]. The Savonius rotor is driven by the aerodynamic drag force acting in the direction of the wind, whereas lift-based turbines (Darrieus and H-type) experience the force acting in the perpendicular direction of wind flow. Savonius rotors work at lower wind speeds than Darrieus rotors, resulting in better self-start capabilities. In contrast, the performance of Savonius rotors in terms of power coefficient is lower than that of the other VAWTs due to the limitation of a lower tip speed ratio [12-18]. VAWTs possess omnidirectional behaviour, higher scalability, and better performance in chaotic, unstable, and turbulent flow conditions [16,19-22]. VAWTs also exhibit a higher degree of sustainability than horizontal axis wind turbines (HAWTs) because of its simplified design layout and low maintenance with no yaw or pitch mechanics, lower noise pollution, better safety, lower operational tip ratio, lower centre of mass, and the generator not being limited to the top of the tower [14,23-30]. Over the last decade, on-site implications of the VAWTs have been observed to gain more attention with the increase in its self-starting abilities [14,31-36]. The VAWT is also proven to be a more feasible technology because of its lower installation, operation, and maintenance costs. In general, VAWTs (>10 MW), which are larger in size, provide a lower cost of energy (COE) when compared to HAWTs [16]. There are also certain challenges associated with VAWTs, such as the formation of a wake on the VAWTs blade, which is one of the most
... Moreover, Peng [8] proposed an optimal variable pitch law and confirmed that the tangential force was increased almost in the entire rotational cycle with the blade normal force amplitude reduced by 15.7%. However, as the alternating variation of the AoA in VAWTs determines that the variable pitch mechanism has to act reciprocally with the blades' rotation, it tends to bring fatigue or wear problems to the mechanism [9]. In addition, the optimal variable pitch law is generally difficult to be obtained and realized as the aerodynamic characteristics of VAWTs are complex [10]. ...
For vertical axis wind turbines (VAWTs), the increase of the incoming wind speed higher than the rated value will make the tip speed ratio (TSR) lower and lower, resulting in the blade fatigue load becoming more and more severe and the power coefficient weakening gradually. This paper explores whether varying the pitch with the TSR decrease is necessary for improving the power coefficient and reducing the fatigue load. Specifically, the pitch angle effect on the power coefficient and fatigue load of a VAWT at different TSRs was studied by the computational fluid dynamics method. The results show that the optimal pitch angle in terms of the power coefficient varies with the TSR, which means that varying the pitch with the TSR decrease can improve the power coefficient. Meanwhile, the principle to guide the pitch variation is to avoid flow separation in the downwind zone and minimize the angles of attack (AoAs) in the upwind zone. At the lowest TSR of 1.7 in the present work, varying the pitch from the optimal one in terms of the power coefficient reduced the blade normal force amplitude significantly, which is mainly attributed to avoiding the vortex–blade encounter and minimizing the AoAs in the downwind zone. The vortex–blade encounter at the lowest TSR is an important phenomenon related to the variation of the blade torque and blade normal force and will weaken and disappear with the pitch angle increase.
... Therefore, active control of the degrees of freedom for wind turbines in arrays may further improve the overall power output of the array. For VAWT, pitch angle is one of the most important degrees of freedom, and pitch control method have been proven to effectively improve the performance of a single VAWT [23][24][25]. ...
... The dynamic stall phenomenon makes VAWTs have the power generation capacity and great potential for power generation. Although some studies (Abdalrahman et al., 2017) pointed out that suppressing the dynamic stall phenomenon would improve the power coefficient (Jain and Abhishek, 2016), such as pitch control (Miau et al., 2012), winglet (tian Zhang et al., 2019), V-shape blade (Su et al., 2020a) and double-layer rotors (Xu et al., 2019b), the operation conditions corresponding to the optimal tip speed ratio always have a typical dynamic stall phenomenon. The parameter that directly affects the strength of dynamic stall is the reduced frequency, which corresponds to tip speed ratio , solidity (Peng et al., 2019), pitch angle (Rezaeiha et al., 2017), and chord length. ...
With the continuously increasing installed capacity of offshore wind turbines, highly adaptable vertical axis wind turbines (VAWTs) are facing new opportunities. Large-scale offshore platforms need a megawatt installed capacity, at least 1∼2 MW, which requires the feasibility analysis of aerodynamic characteristics for large-scale VAWTs. Due to the unsteady aerodynamic phenomenon, i.e. the dynamic stall phenomenon, the power output of VAWTs is very sensitive to the variations of Reynolds number and reduced frequency, which are closely related to the scale of wind turbines. In order to explore the large-scale VAWTs for offshore platforms, three design methods are proposed: Increasing the Reynolds number; Decreasing reduced frequency; Forming an array. Their feasibility and economies are verified by a high-resolution numerical method, and the results show that increasing the Reynolds number could improve their power coefficients to 0.259 for a one-blade VAWT, while an excessive decrease of reduced frequency would lead to power losses. The form of installing one or more levels of VAWT arrays on a single platform is a better design scheme with averaged power coefficient of 0.326 and a blade weighing 2.7 tons per 10 MW, and for large offshore platforms, it could reach the lowest levelized cost of energy.
... The study found that the suitable amplitude of sinusoidal blade pitch was around 10 • when TSRs were higher than 2.0 and increased to 35 • when the TSRs were less than 0.5. There were also some new optimization methods for pitch control with the help of machine learning techniques [22,23]. ...
... The main problem attributed to the Darrieus rotor during the literature survey is the inability to start the rotor during the initial starting of the turbine (Batista et al., 2015). Many investigations have suggested the inclusion of variable-pitch blades (Abdalrahman et al., 2017;Lazauskas and Kirke, 2012;Paillard et al., 2015;Zeiner-Gundersen, 2014), which makes the system complex. ...
Darrieus rotor is a promising technology for hydrokinetic and wind energy harvesting applications. However, the Darrieus rotor suffers from the problem of poor starting performance. The present research highlights solutions to improve the poor starting performance of the Darrieus rotor by introducing the hybrid rotor. Further, a comparative performance evaluation of conventional vertical axis Darrieus and hybrid rotors has been investigated numerically. The most widely used S-series S-1046 hydrofoil has been utilized by hybrid and Darrieus rotors. Further, two semicircular blades are used for the Savonius part of the hybrid rotor. The size of the Savonius part is optimized to obtain maximum performance from the hybrid rotor. Analyzing the flow field distributions across the turbine vicinity has highlighted various possible reasons. The study results have demonstrated that the hybrid rotor yields an exceptional increment of about 159.41% in the torque coefficient under low tip speed ratio (TSR) regimes (during initial starting) compared to the Darrieus rotor. However, due to the Savonius rotor's presence, the hybrid rotor's maximum power coefficient is reduced slightly compared to the maximum operating point of the Darrieus rotor. Further, the hybrid rotor yields a wider operating range than the single maximum operating point by the Darrieus rotor. The present investigations will assist the designers in selecting the site-specific hydrokinetic technology suitable for efficient and optimum use of hydrokinetic potential.
... However, CFD can be used to determine approximate computer-based solutions to solve the governing equations [12]. The CFD simulation results of a 2-D Darrieus VAWT were conducted in [13] which were obtained by ANSYS FLUENT 15.0 as one of the computational fluid dynamics (CFD) commercial software package. These CFD results are used in this research. ...
ABSTRACT Wind turbines are mainly divided into horizontal and vertical axis wind turbines. The quality and performance of wind turbines have been extensively investigated by researchers. A pitch angle controller is one of the most common techniques used to improve wind turbines' aerodynamic performance. Unlike horizontal axis wind turbines, only a few studies being conducted recently to improve the self-starting capability and aerodynamic performance of H-type Vertical Axis Wind Turbines with straight blades (Darrieus VAWT). This study aims to process the issue of VAWT performance using the pitch angle controller technique. Due to the mathematical complexity associated with addressing the behavior of VAWT, numerical results extracted from a Computational Fluid Dynamics (CFD) model are used to design a system identification model, neural networks (ANNs) based, that can identify the behavior of the VAWT model. In addition, two controllers based on both neural networks (MLP-network) and fuzzy logic (FLC) techniques were designed to control Darrieus VAWT pitch angle. Moreover, comparisons between the two intelligent controllers were provided. Results show that both controllers (ANNs and FLC) can achieve better control performance in terms of VAWT power regulations.
Plain flaps (PFs) significantly increase camber, enhancing lift and aerodynamic performance when deployed. In Darrieus Vertical Axis Wind Turbines (VAWTs), which perform efficiently in low-speed, turbulent wind conditions, structural modifications like PFs can improve efficiency. This study explores plain flaps with 10-20-degree deflections at different chord lengths to enhance the NACA 2412 aerofoil’s performance. Using Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations and the Shear Stress Transport (SST) k-ω turbulence model, simulations were conducted across high (Re ≈ 2.71 × 10⁵), medium (Re ≈ 1.35 × 10⁵), and low (Re ≈ 5.4 × 10⁴) Reynolds numbers (Re). The 0.7–10 and 0.8–10 configurations significantly improved torque and Cp. At a Tip Speed Ratio (TSR) of 2.5, the 0.8–10 configuration increased the Cp by 19.51% over the flapless NACA 2412 without PF. The 0.7–10 configuration achieved the highest Cp across all TSRs, while a three-blade setup improved Cp by 43% compared to four- and five-blade configurations. The modified blades demonstrated consistent torque gains across all Re, proving the effectiveness of blade shape modifications in enhancing VAWT efficiency, particularly under fluctuating wind conditions, indicating the potential of PF-modified blades in improving small-scale wind turbine performance in varied urban environments.
In this study, we developed active physics-informed turbine blade pitch control methods to conquer the inconsistent energy harvesting efficiency challenges encountered by the vertical-axis turbines (VATs) technology. Specifically, individual turbine blades were pitched by actuators following commands from the physics-informed controllers, and the turbine performance improvements as a result of the blade pitch control mechanism and the associated flow physics were studied. The aim of the blade pitch control was to maintain constant effective angles of attack (AoAs) experienced by turbine blades through active blade pitch, and the constant AoA function was designed to facilitate control mechanism implementation into real-world VATs. To gain in-depth understanding of the capability of the control, flow physics was studied for different constant AoA control strategies across a wide range of tip speed ratios and wind speeds and was compared with that from the corresponding baselines without control, and that from the sinusoidal AoA control strategy. The comparison between the turbine performance with constant AoA control and that without control showed a consistent increase in the time-averaged net power coefficient, a measure of energy harvesting efficiency taking out of the actuator loss, ranging from 27.4% to 704.0% across a wide spread of wind speeds. The superior turbine performance with constant AoA control was largely attributed to blade dynamic stall management during the blade upstream and downstream cycles and the transition between the two cycles.
Vertical axis wind turbines present many advantages compared with horizontal axis ones despite their low performance. Thus, mechanisms, which aim to improve VAWT performance, are still in continuous development and investigation. The present paper aims to contribute to this improvement by proposing a mechanism for an H-Darrieus wind turbine and aims to gain insights about this improvement by performing numerical and experimental investigations. The proposed solution is a combined scheme of two existing mechanisms, namely a variable blade-pitch mechanism and the omni-directional-guide-vanes (ODGV). Therefore, an experimental test bench with a wind tunnel was built to measure the different combinations performance. Computational fluid dynamics (CFD) simulations were used to provide local properties and flow patterns that give more insight about the flow behaviour. Among the results, we found that the proposed combined-mechanism increases the maximum power at the optimal tip speed ratio compared to the blade-pitch mechanism alone. Furthermore, this combined-mechanism with non-uniform distribution of ODGV provides better performance and increases the maximum extracted power about 35.16% as the experiments show. On the other hand, CFD simulations show that the maximum power coefficient is obtained with two configurations, the non-uniform configuration and the uniform configuration with 4 guide-vanes at 20° of tilt angle. It is found that the power production of an H-Darrieus VAWT with a variable blade pitch can be improved using a non-uniform ODGV, which can improve considerably the power extraction in the downstream turbine half.
Wind energy is crucial for meeting climate and energy sustainability targets. Small wind turbines (SWTs) have gained significant attention due to their size and adaptability. These turbines have potential for Internet of Things (IoT) applications, particularly in powering large areas and low-power devices. This review examines SWTs for IoT applications, providing an extensive overview of their development, including wind energy rectifiers, power generation mechanisms, and IoT applications. The paper summarizes and compares different types of wind energy rectifiers, explores recent advancements and representative work, and discusses applicable generator systems such as electromagnetic, piezoelectric, and triboelectric nanogenerators. In addition, it thoroughly reviews the latest research on IoT application scenarios, including transportation, urban environments, intelligent agriculture, and self-powered wind sensing. Lastly, the paper identifies future research directions and emphasizes the potential of interdisciplinary technologies in driving SWT development.
A numerical simulation study on the combination of a Darrieus and a Savonius wind turbine is conducted. Hybrid T-II, T-III, and T-IV turbines are suggested with the same Darrieus turbine T-I. In the T-II and T-III, the Savonius turbine is at the center of the Darrieus turbine, whereas in the T-IV, the Savonius turbine is above the Darrieus turbine. The T-III Savonius turbine has half the radius of that of the T-II turbine. Results reveal that variations of the power coefficients, C p with the tip speed ratio, TSR for the hybrid turbines have different slopes. It is observed that C p increases with increasing TSR for the T-II and T-IV and does not decrease for the range of TSRs considered, in contrast with the C p behavior of the T-I. The proposed hybrid T-IV turbine has also a larger C p than the T-I turbine at the highest TSR.
In the present work, human blood is modelled as a non-Newtonian fluid, couple stress fluid with viscosity as a function of Haematocrit, plasma viscosity and shape factor. The artery is considered as the circular pipe which is flexible in nature, and blood flow is described as oscillatory. This model is solved using homotopy analysis method (HAM), for deriving the expressions of the wall shear stress (WSS) and volumetric flow rate (QF). Further, in this study, the data on blood flow is considered from the age groups 19 to 60 for males and females and the developed mathematical model then simulated for healthy, anaemia and Polycythaemia cases with the help of publicly available data. The studies revealed that the Haematocrit parameter is the most potential predictor of WSS and the QF. Further, the results align with Huo and Kassab, who predicted that WSS in arteries increased with Haematocrit.KeywordsNon-Newtonian fluid modelHaematological disordersHomotopy analysis method
In this study, a mathematical model for blood flow in human arteries is examined. Arteries are modelled as tapered elastic pipes, blood as a Newtonian fluid with variable viscosity, and blood flow as an oscillatory function with a single harmonic. We solved the model using the Homotopy analysis method (HAM) and obtained expressions for the volumetric flow rate (QF) and wall shear stress (WSS). Blood flow in the human femoral artery for male and female populations aged 19–60 and above years have been simulated using publicly accessible data for healthy, anaemia, and polycythaemia cases. The outcomes of the analysis of the simulated data are as follows: in anaemic conditions, the model predicted high wall shear stress, whereas in polycythaemia situations, it predicted lower levels. Statistical techniques were used to test the significance of the model parameters on wall shear stress (WSS) and volumetric flow rate (QF).KeywordsNewtonian fluidTapered elastic pipesHomotopy analysis method
Wind energy is a clean and sustainable energy source and has been playing a crucial role in reducing the energy crisis in recent decades, therefore bringing down our reliance on fossil fuel-based energy sources. Vertical axis wind turbines (VAWTs) have been found to be more suitable for small scale power generation applications and at the same time provide a reliable and cost-effective alternative to generate electrical energy even at low wind speeds. The kinetic energy of the wind is converted in to mechanical energy which is further converted in to electrical energy by a dynamo. The power developed is stored in battery bank and then can be used to power street lights, traffic signals, toll plazas and charging e-vehicles. It can also cater to the energy demand of nearby areas and cut down on the use of energy produced by burning fossil fuels. In this research work a novel drag-based VAWT rotor design has been conceptualized, developed and tested. By virtue of the proposed novel rotor design, the developed wind turbine model has been shown to achieve performance gains in terms of increased output and correspondingly increased efficiency. The economic viability and the robustness of the model further render the design particularly suitable for implementing on the sites like highways.KeywordsRenewable energyWind energySavonius wind turbineBlade pitch angleTip speed ratioDrag forceVAWT
The combination of Savonius and Darrieus turbines had been proposed with the aim to overcome the weaknesses and complement the strengths from each design. This paper gathers relevant information and provided an extensive review on the combined Savonius-Darrieus turbine for both wind and hydro applications. The paper initially reviews the experimental and computational methodologies utilized in previous research in design evaluation of the turbines. The self-starting capability and efficiency of both turbines were the main concern. Following this, investigations were conducted on the possibility of combining the advantages on the two turbines with respect on the design compactness, radius ratios, attachment angles and rotational velocities.
An airfoil which can establish flow tunnel is simulated in this study. Y-type flow tunnel is opened inside the airfoil which can produce lift and drag to drive itself under different wind speed and different wind angle. Selecting the NACA low-speed airfoil as standard airfoil and using fluent method, the influence on aerodynamic characteristics can be analyzed according to the results. In this paper, two airfoils are simulated under 3m/s and 8m/s of wind speed, wind angle area 15° to 45° and 150° to 180 ° respectively. The results of simulation show that the areodynamic characteristic of airfoil combined lift and drag is similar to the standard airfoil under the low wind speed up, thus, the airfoil combined lift and drag keeps the characteristic of providing lift; Under the high wind speed, the airflow ejected from Y-type flow tunnel, the thrust reversal is generated; At a specific wind angle area, the airfoil can be driven by the lift and drag. According to the results of simulation, suggestions on the optimization of the wing combined lift and drag are proposed.
A parametric study of vertical axis turbines of the H-Darrieus type is conducted using state-of-the-art Computational Fluid Dynamics (CFD) and the k-ω Shear Stress Transport RANS model in its unsteady form. Although most parameters have previously been investigated individually, the effect of solidity, number of blades, tip speed ratio, Reynolds number, fixed blade pitch angle, and blade thickness on the aerodynamic efficiency of the turbine is evaluated using the same performance evaluation set-up in order to determine what would be the best aerodynamic configuration and operation parameter in a given application. The quantitative impact of 3D effects associated with the blade aspect ratio and the use of end-plates is also investigated. For high-Reynolds applications, optimal radius-based solidity is found to be around σ = 0.2, while higher solidities show a lower maximum efficiency than what was previously published using simpler streamtube based methods. In 3D, a small blade aspect ratio (AR = 7) leads to a relative efficiency drop of nearly 60% compared to the 2D prediction. Longer blades improve the 3D efficiency greatly. End-plates are found to have a positive effect on power extraction performances, as long as their size and thus their drag are limited.
The current work involves a numerical study of the effect of preset pitch angle on the performance of a Vertical Axis Wind Turbine (VAWT). A three bladed H-Darrieus VAWT has been considered for the study. The equations governing the flow are solved using a commercial CFD code ANSYS CFX 13. The turbine with NACA 0015 profile and zero pitch angle as the reference case for comparison. The analysis has been done for three pitch angles -6°, 0°, +6°, tip speed ratios (TSR) from 1 to 2.2 and wind velocities of 6, 8 and 10 m/s. Of the pitch angle considered, the best performance is observed with -6° for all tip speed ratios and wind velocities. This has been explained by studying the instantaneous torque characteristics of the turbine. It is seen that at any given instant, the blade in the upwind region contributes significantly to the positive torque with other blades either contributing less or negating the positive torque. The pressure coefficient distributions over the upwind blade and stream lines at different azimuthal angles have also been analysed to understand the effect of pitch.
The knowledge of unsteady forces is necessary when designing vertical axis wind turbines (VAWTs). Measurement data for turbines operating at an open site are still very limited. The data obtained from wind tunnels or towing tanks can be used, but have limited applicability when designing large-scale VAWTs. This study presents experimental data on the normal forces of a 12-kW straight-bladed VAWT operated at an open site north of Uppsala, Sweden. The normal forces are measured with four single-axis load cells. The data are obtained for a wide range of tip speed ratios: from 1.7 to 4.6. The behavior of the normal forces is analyzed. The presented data can be used in validations of aerodynamic models and the mechanical design for VAWTs.
The desirable performance attributes of a vertical axis wind turbine (VAWT) include high starting torque, high peak efficiency, broad operating range and a reasonable insensitivity to the parameters that define its operation. The theoretical performances of three variable pitch mechanisms for VAWT are compared. Cycloturbines use cam devices or gears to impose a sinusoidal pitch regime. In the mass-stabilized system, pitch is determined by the interplay of two opposing moments on the blades. These two mechanisms are compared with `Aero-pitch', a hypothetical pitch control system in which stabilizing moments are related to the blade relative velocity.
A renewed interest in vertical axis wind turbines (VAWTs) has been seen recently. Computational fluid dynamics (CFD) is regarded as a promising technique for aerodynamic studies of VAWTs. In particular, 20 unsteady Reynolds-averaged Navier-Stokes (URANS) is commonly adopted, although past studies on VAWTs revealed the limited accuracy of 2D URANS. This paper investigated the feasibility and accuracy of three different CFD approaches, namely 2D URANS, 2.5D URANS and 2.5D large eddy simulations (LES), in the aerodynamic characterization of straight-bladed VAWT (SBVAWT), with a focus on the capability of the 2.5D LES approach in CFD simulation of high angle of attack (AOA) flow. The 2.5D model differs from a full 3D model in that only a certain length of blades is modeled with periodic boundaries at the two extremities of the domain. The applications of these three approaches were systematically examined in the aerodynamic simulations of a single static airfoil and a 3-blade SBVAWT at different rotating speeds. Their capabilities to predict the aerodynamic forces were evaluated through a comparison with the wind tunnel results obtained by other researchers, with particular attention to high AOA flow beyond stall. Among the three methods, 2.5D LES yielded the best agreement with the experimental results in both cases. Detailed examinations of simulated flow field revealed that 2.5D LES produces more realistic 3D vortex diffusion after flow separation, resulting in more accurate predictions of aerodynamic coefficients in static or dynamic stall situations. It is noteworthy that 2.5D LES cannot capture the effect of tip vortex and vertical flow divergence in VAWTs, which used to be regarded by some researchers as the major cause of overprediction of VAWT power in 2D URANS. In this study, the considerably improved results achieved by 2.5D LES imply that the poor accuracy of URANS method is mainly due to its inherent limitation in vortex modeling. In general, 2.5D LES showed good agreement with experimental results at a relatively low tip speed ratio (TSR), but only fair agreement at a high TSR. Compared with the other two approaches, 2.5D LES is regarded as a more promising and effective CFD tool for investigating the aerodynamic characteristics of VAWTs, particularly their self-starting features corresponding to very low rotation speeds.
The effect of thickness of the symmetric NACA 4-digit airfoil series on self starting of a 1kW three blades H-type vertical axis wind turbine (VAWT) using computational fluid dynamic (CFD) analysis is the main objective of this study. A sliding interface technique was used to investigate two dimensional unsteady flow around VAWT model by solving the Reynolds Average Navier-Strokes equation with k-e Realizable turbulent model. A novel CFD-dynamic coupling model is proposed to solve the dynamic of VAWT. In this model, while the aerodynamic force acting on the VAWT blades is solved by CFD, the torque of the generator and the dynamic friction force at the bearing applying on the axis ofVAWT are modelled vie their physical characteristics. The during time to rotate an angle of 120° of VAWT is one of the principle parameters to investigate the self starting capability. The effect of the starting azimuth angle of blade, the wind velocity and the geometry of the airfoil (NACA 0012, 0015, 0018, 0021) on self starting capability are analysed. The qualitative result show that the considered VAWT has the highest self starting capability when the starting azimuth angle of blade is in the range of [90°÷100°] and it has the lowest self starting capability when the starting azimuth angle is in the range of [45°÷60°]. By using the CFD-dynamic coupling model and by comparing the aerodynamic moment of the wind on the steady three blades to the static friction moment, the considered VAWT rotate at the starting wind velocity of 4 m/s, 3.5 m/s, 3m/s and 3 m/s for NACA 0012, 0015, 0018 and 0021 respectively. The VAWT has the lowest self starting capability with the configuration of NACA 0012 and has the highest capability with NACA 0021.
Data Mining aims at discovering knowledge out of data and presenting it in a form that is easily
compressible to humans. Data Mining represents a process developed to examine large amounts
of data routinely collected. The term also refers to a collection of tools used to perform the
process. One of the useful applications in the field of medicine is the incurable chronic disease
diabetes. Data Mining algorithm is used for testing the accuracy in predicting diabetic status.
Fuzzy Systems are been used for solving a wide range of problems in different application
domain and Genetic Algorithm for designing. Fuzzy systems allows in introducing the learning
and adaptation capabilities. Neural Networks are efficiently used for learning membership
functions. Diabetes occurs throughout the world, but Type 2 is more common in the most
developed countries. The greater increase in prevalence is however expected in Asia and Africa
where most patients will likely be found by 2030. This paper is proposed on the Levenberg –
Marquardt algorithm which is specifically designed to minimize sum-of-square error functions.
Levernberg-Marquardt algorithm gives the best performance in the prediction of diabetes
compared to any other backpropogation algorithm.
This study characterizes the effects of cyclic blade pitch actuation on the efficiency and
operability of a high-solidity vertical axis wind turbine (VAWT). A VAWT utilizing a cam
and control rod mechanism to prescribe the pitch dynamics is constructed and tested in
MIT's Wright Brothers Wind Tunnel over a wide range of design and operational variables.
The experiment concludes that a tuned �first-order sinusoidal actuation system can achieve
a maximum absolute effi�ciency of 0.436, an increase of 35% over the optimal fixed-blade
baseline configuration, with self starting capabilities and drastically improved performance
at a wide range of suboptimal operating conditions. This performance is comparable to
that which as been previously reported for more structurally demanding variable pitch
VAWT designs of lower solidity and fixed pitch designs operating at higher tip speed ratios
(TSRs). Additionally, a low order computational model is found to accurately predict
the trends and maximum efficiencies of the system.
The concept of pitch control has been implemented in the design of a small vertical-axis wind turbine. Benefits gained can be shown by the experimental and numerical results presented in this paper. As found, the method of variable pitch control outperforms the one of fixed pitch control. The present results show that the former can make remarkable improvement on the starting torque as well as the aerodynamic characteristics at low tip speed ratios.
The purpose of this study is to introduce and demonstrate a fully
automated process for optimizing the airfoil cross-section of a
vertical-axis wind turbine (VAWT). The objective is to maximize
the torque while enforcing typical wind turbine design constraints
such as tip speed ratio, solidity, and blade profile. By fixing
the tip speed ratio of the wind turbine, there exists an airfoil
cross-section and solidity for which the torque can be maximized,
requiring the development of an iterative design system. The
design system required to maximize torque incorporates rapid
geometry generation and automated hybrid mesh generation tools
with viscous, unsteady computational fluid dynamics (CFD)
simulation software. The flexibility and automation of the modular
design and simulation system allows for it to easily be coupled
with a parallel differential evolution algorithm used to obtain an
optimized blade design that maximizes the efficiency of the wind
turbine.
The primary objective of this report was to develop universal manufacturer-independent wind turbine and wind power plant models that can be shared, used, and improved without any restrictions by project developers, manufacturers, and engineers. Manufacturer-specific models of wind turbines are favored for use in wind power interconnection studies. While they are detailed and accurate, their usages are limited to the terms of the non-disclosure agreement, thus stifling model sharing. The primary objective of the work proposed is to develop universal manufacturer-independent wind power plant models that can be shared, used, and improved without any restrictions by project developers, manufacturers, and engineers. Each of these models includes representations of general turbine aerodynamics, the mechanical drive-train, and the electrical characteristics of the generator and converter, as well as the control systems typically used. To determine how realistic model performance is, the performance of one of the models (doubly-fed induction generator model) has been validated using real-world wind power plant data. This work also documents selected applications of these models.
Large-scale wind turbine generator systems have strong nonlinear multivariable characteristics with many uncertain factors
and disturbances. Automatic control is crucial for the efficiency and reliability of wind turbines. On the basis of simplified
and proper model of variable speed variable pitch wind turbines, the effective wind speed is estimated using extended Kaiman
filter. Intelligent control schemes proposed in the paper include two loops which operate in synchronism with each other.
At below-rated wind speed, the inner loop adopts adaptive fuzzy control based on variable universe for generator torque regulation
to realize maximum wind energy capture. At above-rated wind speed, a controller based on least square support vector machine
is proposed to adjust pitch angle and keep rated output power. The simulation shows the effectiveness of the intelligent control.
A procedure for computing the optimal variation of the blades' pitch angle of an H-Darrieus wind turbine that maximizes its torque at given operational conditions is proposed and presented along with the results obtained on a 7 kW prototype. The CARDAAV code, based on the “Double-Multiple Streamtube” model developed by the first author, is used to determine the performances of the straight-bladed vertical axis wind turbine. This was coupled with a genetic algorithm optimizer. The azimuthal variation of the blades' pitch angle is modeled with an analytical function whose coefficients are used as variables in the optimization process. Two types of variations were considered for the pitch angle: a simple sinusoidal one and one which is more general, relating closely the blades' pitch to the local flow conditions along their circular path. A gain of almost 30% in the annual energy production was obtained with the polynomial optimal pitch control.
The design of turbine blades is a critical issue in the performance of vertical-axis wind-turbines (VAWTs). In a previous study, it is discovered that a loss of thrust in VAWT blades with a wave-like leading edge can be attributed primarily to vortex distribution. This finding prompted us to apply the wave-like blade design to the trailing edge rather than the leading edge. In this study, computational fluid dynamics was used to observe the flow field on straight and tubercle blades in order to predict the resulting thrust and power performance. Increasing the amplitude and wavelength of the tubercle was shown to increase the maximum thrust by as much as 2.31% and the power coefficient by 16.4%, compared to a straight blade. Furthermore, the overall and maximum thrust performance of blades with a modified trailing edge was shown to exceed those of blades with a wave-like leading edge, due to a shift in the location of the vortices by the induced flow.
This paper predicts and analyzes the aerodynamic performance of a Vertical Axis Wind Turbine (VAWT) with variable amplitude dynamic blade pitching. This study contributes to the physics based understanding of the dependence of power extracted by the turbine on various design parameters. An aerodynamic model based on double multiple streamtube theory coupled to an airfoil table lookup based blade element theory analysis and attached unsteady aerodynamics is used for performance prediction. A method for calculating virtual camber effect for dynamically pitching blades is proposed and validated. Inclusion of dynamic virtual camber effect and unsteady aerodynamics are critical for accurate performance prediction. The parametric study relates performance of VAWT to rotor solidity, blade airfoil and pitch amplitude. It is concluded that the amplitude of sinusoidal blade pitching must be varied with wind speed and tip speed ratio to maximize the power extracted from the turbine for wide range of wind speeds and tip speed ratios. High (about 35 deg) pitch amplitudes work best for tip speed ratios below 0.5 and the pitch amplitude should be reduced to approximately 10 deg for tip speed ratios greater than 2.0.
As concerns about rising fossil-fuel prices, energy security and climate-change increase, renewable energy plays a vital role in producing local, clean and inexhaustible energy to supply world rising demand for electricity. In this study, hydrodynamic analysis of vertical axis tidal turbine (both fixed pitch and variable pitch) is numerically analyzed. Two-dimensional numerical modeling and simulation of the unsteady flow through the blades of the turbine is performed using ANSYS CFX, hereafter CFX, which is based on a Reynolds-Averaged Navies- Stokes (RANS) model. A transient simulation is done for fixed pitch and variable pitch vertical axis tidal turbine using a Shear Stress Transport turbulence (SST) scheme. Main hydrodynamic parameters like torque T, combined moment CM, coefficients of performance CP and coefficient of torque CT, etc., are investigated. The modeling and meshing of turbine rotor is performed in ICEM-CFD. Moreover, the difference in meshing scheme between fixed pitch and variable pitch is also mentioned. Mesh motion option is employed for variable pitch turbine. This study is the one part of the ongoing research on turbine design and developments. The numerical simulation results are validated with analytical results performed by Edinburgh design Ltd. The study concludes with a parametric study of turbine performance, comparison between fixed pitch and variable pitch operation for a four-bladed turbine. It is found that for variable pitch we get maximum CP and peak power at smaller revolution per minute N and tip sped ratio λ.
Computational Fluid Dynamics is thought to provide in the near future an essential contribution to the development of vertical-axis wind turbines, helping this technology to rise towards a more mature industrial diffusion. The unsteady flow past rotating blades is, however, one of the most challenging applications for a numerical simulation and some critical issues have not been settled yet.
In this work, an extended analysis is presented which has been carried out with the final aim of identifying the most effective simulation settings to ensure a reliable fully-unsteady, two-dimensional simulation of an H-type Darrieus turbine.
Moving from an extended literature survey, the main analysis parameters have been selected and their influence has been analyzed together with the mutual influences between them; the benefits and drawbacks of the proposed approach are also discussed.
The selected settings were applied to simulate the geometry of a real rotor which was tested in the wind tunnel, obtaining notable agreement between numerical estimations and experimental data. Moreover, the proposed approach was further validated by means of two other sets of simulations, based on literature study-cases.
In this paper, an advanced pitch angle control strategy based on the fuzzy logic is proposed for the variable-speed wind turbine systems, in which the generator output power and speed are used as control input variables for the fuzzy logic controller (FLC). The pitch angle reference is produced by the FLC, which can compensate for the nonlinear characteristic of the pitch angle to the wind speed. With the control variables of the generator output power and speed, the wind turbine is smoothly controlled to maintain the aerodynamic power and its speed at the rated values without any fluctuation in the output power and speed in the high-wind-speed regions. The effectiveness of the proposed method is verified by simulation results for a 2-MW permanent-magnet synchronous generator (PMSG) wind turbine system, and experimental results for a reduced-scale PMSG wind turbine simulator.
Despite increasing attention paid by both the industrial and the academic worlds, an effective diffusion of Darrieus wind turbines is still hindered by productivity lower than that of classical HAWTs, mainly connected to the critical behavior of these machines during the transient phases and in particular, during the start-up transitory, which has not been investigated in depth in the past. In this paper, a numerical code for the evaluation of the transient behavior of H-Darrieus turbines is presented. The time-dependent code was based on a theoretical approach derived from the Momentum Models and completed by several sub-models for the evaluation of the main secondary and parasitic effects. The new software was validated with an extended experimental campaign in a wind tunnel on a three-bladed H-Darrieus turbine, obtaining constant agreement with experimental data. A sensitivity analysis was then performed in order to investigate the start-up behavior of a generic small size three-bladed H-Darrieus rotor. In particular, for a fixed turbine layout, the influence of the airfoil type and the blade shape on the startup capabilities of the rotor was investigated as a function of the initial position of the rotor and the oncoming wind velocity.
A numerical investigation of the influence of pitch angle on vertical axis wind turbine (VAWT) aerodynamic performance is carried out using the finite volume method. The attack angle of the wind turbine is studied under a speed ratio lambda = 3D 4, and the pitch angle of the wind turbine is adjusted to optimize the working attack angle and hence the aerodynamic performance of the turbine. The flow is assumed to be 2D fully turbulent and the fluid is incompressible, and turbulence is modeled by the k-w SST. The sliding mesh technique is adopted. The present study shows that an appropriate pitch angle can apparently improve the wind turbine power-coefficient.
The paper describes the design of a neural network based model predictive controller for controlling the interface level in a flotation column. For the system identification, the tailings valve opening is subjected to a pseudo-random ternary signal and response of the interface level is recorded over a period of time. The data so generated is used to develop a dynamic feed forward neural network model. The model uses two past values and one present value of the tailings valve opening as well as interface level as inputs and predicts the future interface level. This model is used for the design of a model predictive controller to control the interface level. The controller was tested both for liquid–gas system as well as liquid–gas–solid system and was found to perform very satisfactorily. The performance of the controller was compared with that of a conventional PI controller for a two-phase system and was found to be better.
This paper presents a combined experimental and computational study into the aerodynamics and performance of a small scale vertical axis wind turbine (VAWT). Wind tunnel tests were carried out to ascertain overall performance of the turbine and two- and three-dimensional unsteady computational fluid dynamics (CFD) models were generated to help understand the aerodynamics of this performance.
Wind tunnel performance results are presented for cases of different wind velocity, tip-speed ratio and solidity as well as rotor blade surface finish. It is shown experimentally that the surface toughness on the turbine rotor blades has a significant effect on performance. Below a critical wind speed (Reynolds number of 30,000) the performance of the turbine is degraded by a smooth rotor surface finish but above the turbine performance is enhanced by a smooth surface finish. Both two bladed and three bladed it, rotors were tested and a significant increase in performance coefficient is observed for the higher solidity rotors (three bladed rotors) over most of the operating range. Dynamic stalling behaviour and the resulting large and rapid changes in force coefficients and the rotor torque are shown to be the likely cause of changes to rotor pitch angle that occurred during early testing. This small change in pitch angle caused significant decreases in performance.
The performance coefficient predicted by the two dimensional computational model is significantly higher than that of the experimental and the three-dimensional CFD model. The predictions show that the presence of the over tip vortices in the 3D simulations is responsible for producing the large difference in efficiency compared to the 2D predictions. The dynamic behaviour of the over tip vortex as a rotor blade rotates through each revolution is also explored in the paper.
Modern wind turbines are capable to work in variable speed operations. These wind turbines are provided with adjustable speed generators, like the double feed induction generator. One of the main advantage of adjustable speed generators is that they improve the system efficiency compared to fixed speed generators because turbine speed is adjusted as a function of wind speed to maximize output power. In this sense, to implement maximum wind power extraction, most controller designs of the variable-speed wind turbine generators employ anemometers to measure wind speed in order to obtain the desired optimal generator speed. In this paper a Neural Network based wind speed estimator for a wind turbine control is proposed. The design uses a feedforward Artificial Neural Network (ANN) to implement a wind speed estimator. In this work, a sliding mode control for variable speed wind turbines is also proposed. The stability analysis of the proposed controller is provided under disturbances and parameter uncertainties by using the Lyapunov stability theory. Finally simulated results show, on the one hand that the proposed control scheme using an ANN estimator provides high-performance dynamic characteristics, and on the other hand that this scheme is robust under uncertainties that usually appear in the real systems and under wind speed variations.
Physics of Solar Cells: from Basic Principles to Advanced Concepts
- W Peter
- W Uli
W. Peter, W. Uli, Physics of Solar Cells: from Basic Principles to Advanced
Concepts, third ed., John Wiley & Sons, 2016.
Self-starting of a Small Urban Darrieus Rotor. Strategies to Boost Performance in Low-Reynolds-number Flows
- R Bos
R. Bos, Self-starting of a Small Urban Darrieus Rotor. Strategies to Boost Performance in Low-Reynolds-number Flows, Master's Thesis, Delft University of
Technology, 2012.
Wind turbine design: with emphasis on Darrieus concept, Presses inter Polytechnique
- I Paraschivoiu
I. Paraschivoiu, Wind turbine design: with emphasis on Darrieus concept,
Presses inter Polytechnique, 2002.
An approach to the performance-oriented model of variable-speed wind turbines
- A Luna
- J Rocabert
- D Aguilar
- G Azquez
A. Rol an,
A. Luna, J. Rocabert, D. Aguilar, G. V azquez, An approach to the
performance-oriented model of variable-speed wind turbines, in: IEEE International Symposium on Industrial Electronics, 2010, pp. 3853e3858.
Backpropagation learning algorithm based on levenberg marquardt algorithm
- S Sapna
- A Tamilarasi
- M Pravin Kumar
S. Sapna, A. Tamilarasi, M. Pravin Kumar, Backpropagation learning algorithm
based on levenberg marquardt algorithm, Comp. Sci. Inf. Technol. (CS IT) 2
(2012) 393e398.