Wind energy technology is one of the fastest growing alternative energy technologies. However, conventional turbines commercially available in some countries are designed to operate at relatively high speeds to be appropriately efficient, limiting the use of wind turbines in areas with low wind speeds, such as urban areas. Therefore, a technique to enhance the possibility of wind energy use within the range of low speeds is needed. The techniques of augmenting wind by the concept of Diffuser Augmented Wind Turbine (DAWT) have been used to improve the efficiency of the wind turbines by increasing the wind speed upstream of the turbine. In this paper, a comprehensive review of previous studies on improving or augmentation power of horizontal axis wind turbines (HAWT) have been reviewed in two categories, first related with relative improvement of energy by improving the aerodynamic forces that affecting on HAWT in some different modifications for blades. Second, reviews different techniques to the augment the largest possible amount of power from HAWT focusing on DAWTs to gather information, helping researchers understand the research efforts undertaken so far and identify knowledge gaps in this area. DAWTs are studied in terms of diffuser shape design, sizing of investigation and geometry features which involved diffuser length, diffuser angle, and flange height. The conclusions in this work show that the use of DAWT achieves a quantum leap in increasing the production of wind power, especially in small turbines in urban areas if it properly designed. On the other hand, shrouding the wind turbine by the diffuser reduces the noise and protects the rotor blades from possible damage.

Small-scale vertical-axis wind power generation technologies such as Savonius wind turbines are gaining popularity in suburban and urban settings. Although vertical-axis wind turbines (VAWTs) may not be as efficient as their horizontal-axis counterparts, they often present better opportunities for integration within building structures. The main issue stems from the suboptimal aerodynamic design of Savonius turbine blades, resulting in lower efficiency and power output. To address this, modern turbine designs focus on optimizing various geometric aspects of the turbine to improve aerodynamic performance, efficiency, and overall effectiveness. This study developed a unique optimization method, incorporating a new blade geometry with guide gap flow for Savonius wind turbine blade design. The aerodynamic characteristics of the Savonius wind turbine blade were extensively analyzed using 3D ANSYS CFX software. The optimization process emphasized the power coefficient as the objective function while considering blade profiles, overlap ratio, and blade number as crucial design parameters. This objective was accomplished using the design of experiments (DOE) method with the Minitab statistical software. The research findings revealed that the novel turbine design “OR0.109BS2BN2” outperformed the reference turbine with a 22.8% higher power coefficient. Furthermore, the results indicated a trade-off between the flow (swirling flow) through the gap guide flow and the impact blockage ratio, which resulted from the reduced channel width caused by the extended blade tip length.

Renewable energy sources are preferred for many power generation applications. Energy from the wind is one of the fastest-expanding kinds of sustainable energy, and it is essential in preventing potential energy issues in the foreseeable future. One pertinent issue is the many geometrical alterations that the scientific community has suggested to enhance rotor performance features. Hence, to address the challenge of developing a model that resolves these problems, the purpose of this investigation was to determine how well a scaled-down version of a Savonius turbine performed in terms of power output using a wind tunnel. Subsequently, the effect of the blockage ratio produced in the wind tunnel during the chamber test on the scaled model was evaluated. This study discusses the influences of various modified configurations on the turbine blades’ torque and power coefficients (Cp) at various tip speed ratios (TSRs) using three-dimensional (3D) unsteady computational fluid dynamics. The findings showed that the scaled model successfully achieved tunnel blockage corrections, and the experimental results obtained can be used in order to estimate how the same turbine would perform in real conditions. Furthermore, numerically, the new models achieved improvements in Cp of 19.5%, 16.8%, and 12.2%, respectively, for the flow-guiding channel (FGC at Ⴔ = 30°), wavy area at tip and end (WTE), and wavy area on the convex blade (WCB) models in comparison to the benchmark S-ORM model and under identical wind speed conditions. This investigation can provide guidance for improvements of the aerodynamic characteristics of Savonius wind turbines.

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