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In recent years, Hybrid Wind-Solar Energy  Systems (HWSES) comprised of  Photovoltaic (PV) and wind turbines have been utilized to reduce the intermittent issue of renewable energy generation units. The proposed research work provides optimized modeling and control strategies for a grid-connected HWSES. To enhance the efficiency of the maximum power tracking of a grid-connected wind-driven Doubly Fed Induction Generator (DFIG) integrated with solar Photovoltaic (PV) system, connected to the DC link of the back-to-back converters of the Hybrid Wind-Solar Energy System (HWSES). Stator Flux-Oriented control is utilized to regulate the Grid Side Converter and Rotor Side Converter. The main objective of this paper is to apply the  Maximum Power Point Tracking (MPPT) strategy to wind and solar PV systems to maximize the power extraction and to provide better integration of the hybrid systems into the electrical grids. Perturb and Observe (P&O) and Incremental Conductance (IC) MPPT algorithms are implemented to the solar PV system with varying solar insolation and their performances and efficiencies are compared. For varying wind speeds, Tip Speed Ratio (TSR) and Optimal Torque (OT) MPPT algorithms are implemented and their performances and efficiencies are compared for the hybrid system considering and integrating solar PV system. The optimal torque MPPT algorithm shows better responses when compared to the TSR method. A 2MW simulation model of the HWSES is developed and its performance is analyzed using MATLAB/Simulink environment. The implemented schemes have the advantage of tracking the optimal power output of the HWSES rapidly and precisely. Additionally, the provided schemes effectively control the power flowing through the HWSES and the utility grid, resulting in a quick transient response and enhanced stability performance.

Multi‐bladed windmills usually pump water for agriculture and domestic consumption, often in remote locations. Although they have been around for over 150 years, their aerodynamic performance is still poorly understood. This paper describes the use of helical vortex theory (HVT) and blade element momentum (BEM) analysis to predict windmill thrust, torque, and extracted power. We emphasize the unusual features of windmills: low Reynolds numbers and tip speed ratios and high solidity, all related to the generation of high torque at low wind speeds. Wind tunnel tests on a model rotor with 3, 6, 12, and 24 circular‐arc, constant‐chord blades determined the thrust, torque, and extracted power over a range of tip speed ratio that extended to runaway. For comparison, BEM was implemented with a correction for finite blade number derived from HVT, as well as the classical Prandtl tip loss factor. The HVT correction predicted the rotor power coefficient to within 3% of the test data on the average. At low tip speed ratios and smaller blade numbers, HVT was consistently more accurate than the Prandtl factor. At all blade numbers, the measured rotor torque exceeded the BEM predictions at the lowest tip speed ratios indicating stall delay which became more important (and more beneficial for windmill performance) as the blade number increased. The Prandtl formulation predicted the thrust to within a mean accuracy of 13% and was more accurate than the HVT method.

This study aims to develop a comprehensive CFD methodology to accurately predict the Power Coefficient ( C P ) across a wide range of rotor solidities ( σ ) and Tip Speed Ratios ( TSR ) for small-size H-Darrieus wind turbines. The methodology involved delineating the characteristic curve by simulating only three key operating points based on useful power-producing operating condition limits: TSR in , TSR r , and TSR out , for five case studies from the literature, covering solidities from 0.12 to 0.75. The TSR r , representing the TSR of the turbine’s rated operating point, is estimated by using an empirical correlation from the literature which provides the TSR r magnitude solely based on σ. TSR in and TSR out are then calculated as defined percentages of TSR r . The methodology was validated against experimental data from the literature, yielding root-mean-square errors below 0.05 for C P at any TSR within the key operating points. Additionally, a minimum number of revolutions required for simulation convergence of each σ at each TSR were established, as well as, by using dimensionless parameters to assess spatio-temporal discretization, general recommendations for mesh and time step resolutions, for rotors with 0.12 ≤  σ  ≤ 0.75, operating within TSR in  <  TSR  <  TSR out . Finally, a CFD workflow has been developed to provide reliable H-Darrieus simulations, achieving reductions of up to threefold in total simulation time.

The need for clean, sustainable and cost-effective energy sources leads to the installation of wind turbines with advanced technologies. One of the main parameters which govern the productivity of any wind turbine is its power generation capacity. The higher the incoming wind speed, the more the power generation, but the challenges faced by wind turbine is in low wind speeds. Hence, it becomes important to boost the efficiency of wind turbine with modified designs for lower wind urban regions. The prime objective is to boost the power production of a conventional two-bladed VAWT with the application of convergent-divergent type wind lens. Ansys CFX is employed for numerical analysis of flow around the rotor of straight bladed H-Darrieus turbine. Different turbulence models are analysed and SST k-ω model is well validated with experimental result. Power coefficient values are evaluated at a range of 0.5 to 3 tip speed ratios in both cases. Simulation result is validated with experimental results in terms of power coefficient. Computational result is validated with 4% error and 2% error for simple VAWT and VAWT with wind lens respectively. The results show an enhancement of 2.6 times the power coefficient values of conventional VAWT.

A dual-objective optimization study was carried out to illuminate how the tip speed ratio of a small wind turbine affects the aerodynamic noise as well as the blade geometry. A 0.75 kW three-bladed small horizontal axis wind turbine was selected as the case study. Two important goals were considered in the study: maximization of the output power and the minimization of the aerodynamic noise. The former was calculated by the well-known blade-element momentum theory while a validated semi-empirical model was adopted for the computation of the latter. A combination of these goals defined the objective function and the weighted-sum approach was employed to find the optimal values for the design variables of the optimization including the distributions of the chord and the twist angle along the blade together with the tip speed ratio. The extracted power was calculated at the rated wind speed of 10 m/s while the noise was computed at lower wind speeds of 5 and 7.5 m/s. The genetic algorithm technique was adopted for the muti-objective optimization. The results revealed the importance of the blade tip region in producing the emitted aerodynamic noise. Specifically, an increase in the chord and twist values near the tip results in the reduction in the emitted noise. Results also show that a good compromise between the two goals is achievable such that a noticeable reduction in the emitted aerodynamic noise is attainable in exchange for a very small drop in the power coefficient. The optimization results also indicated that the noise could be adequately reduced at the smaller value of the tip speed ratio without a large reduction in output power which is due to the decrease in the rotational speed of the turbine.

Hydrokinetic energy sources are considered as strong alternative to provide clean, affordable and green energy to future generation. There are different types of turbines available to harness this kind of energy resource. Among all the turbines, Savonius hydrokinetic turbines are acknowledged as the most suitable rotor for generating power from flowing water streams such as rivers and canal. The objective of this research paper is to improve the performance of Savonius hydrokinetic turbine using slotted blades. Under the present study, four different slot parameters, i.e. slot shapes, slot position, slot gaps and slot shape factor, are considered. The water velocity was kept constant as 1 m/s in this study. The fluid flow distributions that occur all around the rotor have been studied and discussed. Based on the investigations, Savonius hydrokinetic turbine having divergent slot has outperformed the all other shapes of slots for the entire range of tip speed ratio considered. The highest power coefficient of 0.2942 corresponds to the tip speed ratio value of 0.9 has been achieved for divergent slot Savonius rotor at slot position of 5% having slot gap of 3 mm and slot shape factor of 0.2.

There is a significant contribution of the wind energy to total renewable energy consumption. In vertical axis wind turbines (VAWTs), most of the experimental works are done on the Darrieus VAWT or Savonius VAWT alone. However, the experimental results cannot capture all the aerodynamic characteristics of the turbine. Therefore, computational analysis is the most powerful tool for reducing the time and cost of experimental analysis in this type of research. Recently, research on hybrid wind turbines is attaining popularity because such coaxial arrangements exhibit the improved efficiency and the better self-starting capability as compared to individual Darrieus or Savonius turbines. In this present study, firstly, a wind dataset was collected for different seasons and heights (above ground level) to get the average wind speed as an inlet boundary condition. Then two-dimensional simulation was performed on the considered hybrid VAWT using ANSYS Fluent. The steady analysis shows that the static torque is low at 90° azimuthal angle for the hybrid VAWT at different heights in all cases. For various tip speed ratios, flow visualization through a hybrid turbine showed that vortex generation is lower at the high tip speed ratio (TSR) as compared to the low TSR. At TSR = 2.5, all attachment angles achieve the highest power coefficients, which decline with increase in the attachment angles. Among all the operating conditions, the TSR = 2.5 and the 0° attachment angle revealed the optimal power coefficient value of 0.33.

The Savonius Vertical Axis Wind Turbine (VAWT) has gained significant attention as a wind energy solution due to its simple design, cost-effectiveness, and ability to perform well in urban and low-wind-speed environments. However, despite their advantages, these turbines face challenges, including lower efficiency compared to Horizontal Axis Wind Turbines (HAWTs) and performance limitations under high wind conditions. Therefore, this present review provides an in-depth examination of its design and aerodynamic performance, highlighting how various blade configurations and modifications, such as overlap ratios, helical blade structures, and hybrid designs, can enhance its efficiency. Additionally, key operational factors, such as tip speed ratio, Reynolds number, and turbulence effects, are explored in terms of their impact on power output. Different computational and experimental studies are also reported here, which address the influence of varying augmentation techniques. Moreover, the effects of different blade materials, artificial intelligence-based optimization, and innovative blade geometries are also investigated here to gain insight into several performance improvement approaches for Savonius turbines. Therefore, this present review can serve as a valuable resource for researchers and engineers working towards more efficient and sustainable Savonius wind turbines.

The two-dimensional (2D) computational analysis is done on a newly proposed parabolic blade profile of a Savonius wind rotor that is specifically designed for the small-scale power generation. The geometry of the blade profile is obtained by optimizing the section cut angle ( θ ) of a parabola that varies from 27.5° to 45°. The simulations are performed using ANSYS Fluent software to solve the Reynolds averaged Navier–Stokes (RANS) equations. The two-equation eddy viscosity shear stress transport (SST) k–ω model is solved to find the torque and power coefficients ( C T , C p ) of the blade profile. The effects of tip speed ratio (TSR) and Reynolds number (Re) on the performance are also investigated. The blade profile generated at θ  = 32.5° has showcased an increment of performance coefficient ( C pmax ) by 20% against the conventional semicircular blade profile. The parabolic profile has shown an improvement of drag coefficient ( C Dmax ) by 18.18% over its semicircular counterpart. The best performance of the parabolic profile is obtained at TSR of 0.8 and at Re of 0.97 × 10 5 .

In order to make the ocean energy generator system realize the maximum power under various conditions, this paper proposes a control strategy based on linear active disturbance rejection control algorithm. The output power is mainly affected by the spin-speed of the generator in a nonlinear manner, and this phenomenon is originated from the tip speed ratio state of the turbine blades. This tip speed ratio associated maximum power can be achieved through a coupled control system that adjusts the spin-speed of generator elaborately. The state equations of ocean power generation system are transformed into a standard form to fit the linear active disturbance rejection control. Finally, the simulation model of the system is established by using Matlab/Simulink platform, with a series of input signals for different working conditions. The results verify that the maximum power under control can be effectively attained by a quick tracking of the target speed.