The effects of aerofoil profile modification on a vertical axis wind turbine performance

Significance Statement

There are increasing concerns regarding the conventional sources of energy’s contributions to global climate change and ocean acidification. Of the renewable sources of energy, wind energy possess considerable future potential and it is anticipated that renewable source will account for 69-74% of global power capacity addition by 2030, with wind accounting for 30% [1]. Current state-of-the-art wind turbines can be classified into horizontal axis wind turbine (HAWT) and vertical axis wind turbine (VAWT) [2]. HAWTs consist of a turbine mounted on tall towers rotating about a horizontal axis [2] and are more suitable for large scale energy generation. VAWTs consist of blades mounted about a vertical rotating shaft at its center and can be mounted at lower heights with considerably less effort. VAWTs are particularly suited for local micro power generation and off-the-grid power generation. Hence Dr. Vijayaraghavan’s research focuses on VAWTs. The profile of the blade used in wind-turbines plays a crucial role in determining the performance of the wind-turbine. This paper proposes a new optimization of VAWTs blade profile using a combination of semi-circular dimple and Gurney flap at the lower surface of the blade. With HAWTs, the axis of rotation of the is parallel to the wind direction. The angle of attach (AOA), which measures the relative angle between the blade orientation and the wind direction, remains constant in HAWTs. Hence profile optimization is significantly simpler on HAWTs. With VAWTs, the AOA continuously changes as the blades rotate about their axis. Hence we need to optimize the blade profile to maximize the tangential torque over the entire duration of the cycle rather than just a single AOA. This paper develops a fully automated optimization of the wind-turbine blade and the final optimal shape is shown to outperform the standard blade profiles.

The effects of aerofoil profile modification on a vertical axis wind turbine performance. Renewable Energy Global Innovations 2

The effects of aerofoil profile modification on a vertical axis wind turbine performance. Renewable Energy Global Innovations

Journal Reference

Md Farhad Ismail, Krishna Vijayaraghavan. Energy, Volume 80, 2015, Pages 20-31.

Mechatronic Systems Engineering, Simon Fraser University, Surrey, BC, Canada.

Abstract

This paper investigates the effect of profile-modifications on a NACA-0015 aerofoil used in VAWTs (vertical axis wind turbines). The profile-modifications being investigated consist of a combination of inward semi-circular dimple and Gurney flap at the lower surface of the NACA-0015 aerofoil. Rather than maximize the lift-coefficient or the ratio of the lift to drag coefficients, this paper choose to maximize the average (or effective) torque of the VAWT as this is a much better measure of the power produced. A fully automated optimization using RSA (Response Surface Approximation) is utilized here to maximize the average torque produced by the wind turbine blade. The data-set used in the optimization is generated using CFD (computational fluid dynamics) simulations. In order to ensure reliability, the computational domain and the turbulence model used in the CFD simulations are validated against previous experimental results. The optimized shape of the modified aerofoil is shown to improve the aerodynamics of the wind turbine blade.

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