Developments in the design of wind turbines with augmentation are advancing around the globe with the goal of generating electricity close to the user in built-up areas. This is certain to help lessen the power generation load as well as distribution and transmission network costs by reducing the distance between the user and the power source. The main objectives driving the development and advancement of vertical-axis wind turbines are increasing the power coefficient and the torque coefficient by optimizing the upstream wind striking on the rotor blades. Unlike horizontal-axis wind turbines, vertical axis turbines generate not only positive torque but also negative torque during operation. The negative torque generated by the returning blade is a key issue for vertical-axis wind turbines (VAWTs) that is counterproductive. Installation of wind deflectors for flow augmentation helps to reduce the negative torque generated by the returning blades as well as enhance the positive torque by creating a diversion in the upstream wind towards the forwarding blade during operation. This paper reviews various designs, experiments, and CFD simulations of wind deflectors reported to date. Optimization techniques for VAWTs incorporating wind deflectors are discussed in detail. The main focus of the review was on the installation position and orientation of the deflectors and their potential contribution to increasing the power coefficient. Topics for future study are suggested in the conclusion section of the paper.

https://www.mdpi.com/1996-1073/14/16/5140/pdf

Recent Development in the Design of Wind Deflectors for Vertical Axis Wind Turbine: A Review

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Numerical simulation of Savonius rotors used for low wind speed application

This paper proposes a new augmentation device to improve the coefficient of power (Cp) of a Savonius turbine using a Computational Fluid Dynamics (CFD) method. The device is a rotating cylinder synchronized with a rotating turbine using a timing belt mechanism without needing any external power source. Unlike conventional flow deflectors, the device is not placed in front of the turbine. Instead, it is placed parallel to the turbine position. The optimum device diameter and position are determined using the Taguchi optimization method. The device diameter and its position (Lateral distance, Longitudinal distance, and Location; left and right) are selected as controllable process parameters, and the Cp as the performance output. The Taguchi L16 orthogonal array is selected as the Design of the Experiment (DOE). From the Taguchi analysis, the optimum device parameter improves the Cp by up to 0.3877 at TSR 0.9, a 55.64% improvement relative to the case without the device. The highest Cp achieved is 0.4450 at TSR 1.1, with an 83.73% improvement relative to the case without the device. ANOVA results suggest that the Cp is greatly influenced by both the device diameter and lateral distance. The proposed device improves the overall performance of the Savonius turbine over a wide range of TSR.

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Shrouded wind turbines are emerging as a promising approach for integrating wind energy into residential areas. A wind turbine’s shrouding plays a key role in strengthening the wind speed in low-wind areas, thereby maximizing power generation. The wind speed is improved by various novel geometries, airfoils, and positioning of the turbines at various locations. In this research, further improvement in wind speed is attained by optimizing the shrouded profile using the Taguchi approach. A modified INVELOX is attached at the exit of the shroud for harnessing wind power at multi-stages using the shrouded turbine. A high turbulence environment at two distinct locations was chosen based on the standards of the International Wind Agency to validate the performance of the shrouded INVELOX small-scale wind turbines. The wind turbulence characteristics based on the urban atmospheric boundary layer inflow situation over the above locations are analyzed using computational fluid dynamics and validated with experimental results. The shrouded INVELOX increases the wind speed by 1.52 times the actual wind speed when located at low-rise buildings and increases by 1.68 times when located at the top of the tallest building. The shrouded INVELOX performs better in comparison with the shroud and INVELOX when operated separately.

Performance analysis of shrouded invelox wind collector in the built environment

This work presents an innovative technique to enhance the performance of the Savonius wind turbine. The new technique is based on introducing an upstream deflector and downstream baffle. The shape ...

Ahmed M El Kholy

Papers

An innovative augmentation technique of savonius wind turbine performance