Wind energy is one of the most promising renewable energy resources for power generation, and rapid growth has been seen in its acceptance since 2000. The most acceptable classification for wind ...turbines is by its axis of orientation: Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT). HAWTs are used in many countries for medium-to-large scale power projects, and most commercial installations around the globe are solely based on these turbines. On the other hand, HAWTs are not recognized as a viable option to harness the energy of the wind in urban areas, where the wind is less intense, much more chaotic and turbulent. VAWTs are suggested as a better choice for cities and isolated semi-urban areas. Several attributes have been suggested for the large-scale deployment of VAWTs, e.g., good performance under the weak and unstable wind, no noise and safety concerns, and aesthetically sound for integration in urban areas. Significant research has been published on wind turbine technology and resources assessment methodologies, and this review paper is a modest attempt to highlight some of the major developments of VAWTs, with a focus on the integration with urban infrastructure. Several recommendations have been drawn based on the state-of-the-art information on the subject for future studies and acceptance of wind turbines in the urban areas. It was concluded that further research is critical in making VAWTs a viable, dependable, and affordable power generation technology for many low and decentralized power applications.
This paper presents the stability augmentation of pitch angle control for a permanent magnet synchronous generator (PMSG)-based wind turbine system (WTS) with pitch actuator uncertainty via L1 ...adaptive scheme. To do this, a novel L1 adaptive scheme is firstly proposed to regulate the pitch angle at above-rated wind speed conditions and maintain the rated rotor speed in the presence of pitch actuator uncertainties in the obtained pitch system. Next, a non-affine PMSG system with uncertainties is utilized to represent the pitch regulated variable-speed WTS. Then, the L1 adaptive scheme is proposed as a stability augmentation system. At this time, the bound conditions are presented to prove the stability and performance evaluation of the proposed L1 adaptive scheme. Finally, through the simulation of the 20−MW PMSG-based WTS, the proposed algorithm proves its efficiency and applicability compared to the existing control methods.
•This study is to effectively regulate the pitch angle and extract the maximum power from the 20MW WTS.•The proposed adaptive control scheme introduces the SAS method to improve the transient and steady-state performance of the system.•The proposed stability augmentation scheme minimizes the frequency of adaptation estimations and gain values required.•The proposed scheme is evaluated under various environmental conditions, such as gust wind, step wind, and varying wind speed.•The proposed algorithm is provided to prove its efficiency and applicability compared to existing control methods through MATLAB/SIMULINK simulation of the 20−MW PMSG-based WTS.
Savonius wind turbine (SWT) is one of the popular vertical axis wind turbines (VAWT) used for energy harvesting applications. In this study, the aerodynamic performance of the SWT is numerically ...investigated by coupling an efficiency two-dimension (2D) unsteady Reynolds-Averaged Navier-Stokes (URANS) simulation with a generalized k-ω (GEKO) turbulence model. The numerical method is first validated against the available experimental data before further carrying out to examine the applicability of the GEKO model for various flow scenarios and rotor configurations, including the overlap and non-overlap geometries. The analysis reveals high sensitivity of the computed torque (CT) and power (Cp) coefficients to the model empirical constants such as the separation parameter Csep, the near wall parameter Cnw, and the jet flow parameter Cjet. Although showing a good agreement in Cp with the measured data of the non-overlap configuration, an excessive prediction of Cp with a maximum error of 39% is produced at the tips speed ratio over 0.8 in the overlap one by the default GEKO model. Meanwhile, a satisfactory prediction with the experimental data with a maximum deviation of 6.7% can be achieved with the new set of model empirical constants, resulting in a better capturing of the flow-induced rotor such as the flow separation-attaching, vortex, and turbulent quantities.
•Investigating the performance of the Savonius rotor by the GEKO turbulent model.•Optimized model empirical parameters are introduced.•A superior agreement with experimental data is obtained with an optimized GEKO model.•Clarify the cause of the improvement by analyzing flow physics around the rotors.
This study aimed to analyze the effect of turbulence intensity and wind shear on the power characteristics of a Horizontal Axis Wind Turbine (HAWT). For this purpose, the blade pitch angle and yaw ...were compared by using a two-bladed HAWT in the wind tunnel experiments. In this study, the turbulence intensities were generated by active turbulence grids and wind shears were obtained by an atmospheric boundary layer generation device. Through measurement of the power and thrust coefficients for each rotor configuration, the aerodynamic feasibility of this wind turbine was discussed. As a result, it was clarified that the power coefficient was strongly dependent on the blade pitch angle and yaw angle. The optimum power coefficients were 0.308, 0.321, 0.298 at the blade pitch angle of β = 4°, for the turbulence intensities of TI = 1.4%, 8.0% and 13.5%. Moreover, thrust coefficient decreased with the increase of pitch angle. For the optimum pitch angle, the maximum power and thrust coefficients obtained at as = 0.0558, showing smaller values than the results of wind shear as = 0.1447. From this study, these results were very important for developing HAWT suitable for turbulence environment.
•Power performance was measured at different turbulence intensities and wind shears.•Effects of blade pitch angle and yaw angle were compared.•Peak of the power coefficient decreased with the increase of yaw angle.•Thrust coefficient decreased with the increase of pitch angle.•Wind shear had a significant effect on the power and thrust coefficients.
This paper examines the effects of applying three Savonius wind turbines with different mounting positions, including lateral spacing, on power coefficients by conducting high-fidelity ...three-dimensional numerical simulations, i.e., based on the Reynolds-Averaged Navier-Stokes (RANS) method. The first validation case of the single Savonius wind turbine located on the fixed step height, and a flat surface is found to be in good agreement with that reported in the literature. Then the model is expanded to study the performances of three laterally aligned Savonius wind turbines by placing them above a flat surface and a forward facing step. When the three laterally placed turbines are on a flat surface, an increase of approximately 5% of the maximum mean power coefficient is observed compared to that of a single turbine. Next, the effect of implementing the three turbines at different positions on a fixed step is investigated, where the maximum mean power coefficient improvement for the three turbines can be as high as 230%. Finally, the effect of the lateral spacing distance between the two adjacent turbines is examined. It has been shown that there is an optimal spacing if the maximum mean power coefficient is concerned.
•Savonius wind turbine is numerically investigated by the three-dimensional aerodynamics simulations.•Installation of such a turbine on a step significantly increases its aerodynamics power coefficient.•Laterally aligned turbines offer further power coefficient gains over an isolated turbine.•Arrayed turbines have an optimal spacing considering the maximum mean power coefficient.
A VAWT is the one turbine which rotor and shaft are kept in transverse direction to the direction of the wind. Due to this the motor or generator is kept on the ground. There are Darrieus, Savonius ...and Giromill types of VAWT are there. This type of turbine has many problems like the effect of turbulence, flow separation to eddies, and stress generation in the blade. All these things have been discussed in this review paper and conclusions are given. Different methods like FEM and CFD are used to find the performance of VAWT.
Savonius hydrokinetic turbine is a vertical axis turbine suitable for generating electrical power used in rivers and canals. The performance of the turbine is described in terms of power coefficient. ...The power coefficient (CP) depends on input variables such as aspect ratio, overlap ratio, blockage ratio, number of blades, blade arc angle, blade shape factor, twist angle, Reynolds number, and Tip Speed Ratio (TSR). In this study, different soft computing methods, namely CatBoost, Artificial Neural Network (ANN), Random Forests (RF), Multivariate Adaptive Regression Splines (MARS), Adaptive Neuro-Fuzzy Inference System (ANFIS), ANFIS-Genetic algorithm (ANFIS-GA), ANFIS-Slime Mold Algorithm (ANFIS-SMA), ANFIS-Marine Predators Algorithm (ANFIS-MPA) along with Linear Regression (LR) were used to predict the power coefficient of Savonius hydrokinetic turbines for the first time. In order to obtain appropriate data, experimental tests were conducted in an open water channel for different design configurations of Savonius turbines. Further, more data were collected from different references. These data were used for the training and testing process of the models. The precision of the methods was evaluated using multiple statistical indices. Three different training-testing scenarios were prepared to provide a reliable predictive model, and in all scenarios, the CatBoost method was superior. Sensitive analysis showed that aspect ratio is the most important design parameter among all effective parameters. As a result, the CatBoost is recommended to predict a Savonius hydrokinetic turbine's performance considering multi-input variables.
This research emphasizes designing a straight-bladed Double-Darrieus hybrid vertical axis wind turbine (VAWT) with a high power coefficient as well as self-starting capability. Computational fluid ...dynamics analysis was performed using the sliding and dynamic meshing techniques. Various datasets were employed in the design of experiments to determine optimal configurations. A quadratic equation based on a regression model was established, and response surface methodology was applied to determine the accuracy of the model by analysis of variance, goodness of fit, investigation of residuals, and R-squared values. The optimized chord length, number of blades, pitch angle, distance of blades from the central rotating shaft, and rotor height were obtained as 0.547 m, 03, -3.41 deg, 0.789 m, and 1.605 m, respectively. A standard H-rotor Darrieus configuration, comprising symmetric airfoils and existing Darrieus-Savonius hybrid VAWTs were also analyzed for comparison. The positive static torque coefficient at all azimuth angles indicates that the proposed hybrid wind turbine is completely self-starting. The output power of the standard Darrieus configuration is substantially zero below a wind speed of 3.65 m/s, indicating that it is not capable of converting the kinetic energy of the airflow into electrical power below this specified value. On the contrary, the self-starting speed of the proposed hybrid wind turbine is as low as 2.81 m/s with a rated power of 1.522 kW at a wind speed of 7.5 m/s. The capability of the proposed hybrid wind turbine with a better power coefficient and transforming wind energy, even at low wind speeds, extends its utilization for various small to large-scale power projects. The proposed approach enables the determination of the optimum design configuration of a hybrid vertical axis wind turbine, along with a high-fidelity analysis in the early design phase.
•An innovative straight-bladed Double-Darrieus hybrid VAWT has been explored.•We emphasize designing a VAWT with a high power coefficient as well as improved self-starting capability.•Geometric parameters of hybrid VAWT have been optimized using DOE techniques.•Computational fluid dynamic analysis was performed by using k-ɛ turbulence model.•The proposed methodology enables to obtain optimum design configuration of hybrid VAWT, along with the high fidelity analysis in the early design phase.
•This paper proposes a new deflector system around Helical Savonius rotor.•Six deflector system configurations had been studied numerically.•The deflector system affects the hydrodynamic ...characteristics of the flow.•The rotor power coefficient was found dependent on the deflection angle.•The power coefficient of the rotor reaches 0.14 using the optimal configuration.
The use of renewable energy sources has becoming a necessity to generate electricity. Helical Savonius rotors have been preferred for small-scale hydropower generation. Numerous studies were carried out to improve the performance of the Helical Savonius rotor which has not been fully explored. In this paper, an experimental study was carried out to evaluate the performance of a Helical Savonius water rotor in an irrigation channel. In order to enhance the performance of the studied water rotor, a new deflector system design was proposed. Different configurations of the proposed deflector system were tested numerically using the commercial software ANSYS FLUENT 17.0. Without a deflector system, the maximum power coefficient is found to be equal to 0.125 at tip-speed ratio of 0.7. Using the optimal configuration of the new deflector system, the maximum power coefficient reaches 0.14. The utilization of this new design system is predicted to contribute towards a more efficient use of flows in rivers and channels for electricity production in rural areas.
