Analysis of Induced Turbulence and Simulation of a Vertical Axis Wind Turbine Optimised for Thika Superhighway at Juja

Abstract

The expansion of highways occasioned by increase in traffic has led to the rise in electricity consumption for street lighting. To offset the increasing energy demand, induced wind speed along highways can be harnessed to produce electricity to reduce the cost of powering the streetlights via the grid. However, there is insufficient documented data concerning induced wind speeds along highways in Kenya to help characterise the wind regime and understand wind power density for investment purposes. Therefore, this research collected data on the wind speeds and used the data to design, through simulations, an optimised vertical axis wind turbine (VAWT) for electricity generation. The wind speed data was gathered using a Young wind sentry anemometer and vane, namely the 03002V model. The data was then analyzed using statistical software on an hourly basis. Weibull distribution was subsequently employed to assess the parameters of the Weibull distribution, yielding values of k=3.0883 and c=4.689 m/s. The characteristics were utilized to evaluate the wind power density along the highway, resulting in a measurement of 50.4 W/m2, with a maximum extractable power of 29.8 W/m2. The air density was determined to be 0.9896 kg/m3, and it had a kinematic viscosity of 1.86755×10-5 kg/m.s. The average wind speed was 4.1883 m/s, and the turbulence intensity was found to be 33.8% These parameters, along with air density and dynamic viscosity, were used to design and simulate an optimized vertical axis wind turbine (VAWT) using ANSYS® Fluent®. A 2D airfoil analysis, employing the Spalart-Allmaras turbulence model, determined the optimal angle of attack (AoA) for the NACA 0025 airfoil to be 7°. Subsequently, a 3D VAWT simulation, using the SST k-ω model, resulted in an optimized design with a 0.75-meter diameter and 1.5 aspect ratio. This optimized turbine design demonstrated the capability of harnessing 10 W/m2 of power. The research provides valuable insights into the feasibility of utilizing highway-induced wind energy for sustainable street lighting in Kenya.