Abstract
This study aims to improve the applicability of Vertical Axis Wind Turbines (VAWTs) by investigating their feasibility in a novel planetary cluster configuration by observing its effect on efficiency and overall power density. Computational Fluid Dynamics (CFD) simulations were carried out using a two-dimensional vertical axis wind turbine model in ANSYS Fluent 2020 R1. This software was used to solve the transient k-omega (SST) turbulence model. For the isolated VAWT the wind velocity, rotor radius and tip speed ratio were varied to find the optimum turbine performance at a given parameter. A peak efficiency of 34.05% was attained and equivalent configuration used as the “sun” turbine in the novel planetary design. The parametric study of the novel set up was conducted with the PCD (Pitch Circle Diameter) and oblique angular (ϕ) position of the smaller “planet” turbines being varied in relation to the “sun” turbine. The planetary system was then evaluated in terms of efficiency improvements against the isolated VAWT model. Use of the “planet” turbines resulted in power extraction from the free stream which in turn creates varying wind velocities and improved the efficiency of the central “sun” turbine. The optimal PCD was found to be 5D (3.75 m) and the optimum angular position of the “planets” was discovered at 30°. Ultimately this gave a percentage increase of 1.01% from 33.04% to 34.05% when comparing the “sun” turbine of the planetary arrangement to the optimum isolated respectively. An average improvement of 4% over the range of tip speed ratios (TSR) was found. Lastly, a scale model of the isolated VAWT was constructed and tested through wind tunnel experiments. The characteristic curve correlation was found between the CFD and experimental results which allowed validation of the CFD models.
Highlights
IntroductionWith fossil fuels being one of the main contributors to the destruction of the environment and combined with the finite capacity of oil and gas reserves, the world is looking for a sustainable alternative energy source to help
The majority of the research has currently been invested into horizontal axis wind turbines (HAWTs) due to the large power output and increased efficiencies when compared against Vertical Axis Wind Turbines (VAWTs)
VAWTs do have a number of advantages over the HAWT and have in recent times become subject to interest as more options for sustainable power generation are required
Summary
With fossil fuels being one of the main contributors to the destruction of the environment and combined with the finite capacity of oil and gas reserves, the world is looking for a sustainable alternative energy source to help. Field tests indicate that arranging VAWTs in this layout may allow significant improvement of the power density when compared to the current HAWT range of 2 to 3 W/m2. This was found to be due to the VAWTs extracting energy from adjacent wakes and wind flowing above the farm. The purpose of this study is to investigate the fluid flow around a planetary VAWT cluster arrangement to analyse the impact of the smaller “planet” turbines on the “sun” turbine efficiency and overall power density. Pitch Circle Diameter (m) Planetary Oblique Angles (◦) Inlet velocity (m/s) Angular Velocity (rad/s) Solver Type Turbulence model Inlet: turbulence Intensity Inlet: Turbulence Length Scale (m) Outlet: Backflow Turbulent Intensity Outlet: Backflow Turbulent Viscosity Ratio
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