Numerical investigation on the aerodynamics of vertical axis hydrokinetic turbines with semi-empirical data
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Date
2018-06
Authors
Foong Xipeng
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Abstract
Renewable energy sources provide a sustainable power production for the future.
Hydropower is one of the optimum choices for renewable energy extraction.
Predictability, regularity and reliability make hydropower the most attractive choices for
energy production. Hydrokinetic energy is harnessed from flowing streams, tidal currents
and other water channels. Compared to conventional hydropower, construction of a dam
or reservoir is not required due to its nature of extracting energy via water motion.
Hydrokinetic turbines can be divided into two main categories: horizontal axis turbines
and vertical axis turbines. For this project, attention is given to vertical axis hydrokinetic
turbines (VAHTs), due to the prominence in research of horizontal axis turbines and lack
thereof for vertical axis ones. VAHTs are further classified according to their different
arrangements: squirrel-cage Darrieus, H-Darrieus, Curved Darrieus, Gorlov and
Savonius. In this project, the H-Darrieus turbine is chosen as the model to be investigated
due to its utilization of airfoil-shaped blades, thus easing the calculation of forces. For
the sake of creating a mathematical model, new theories related to VAHTs are learned.
Some computational models are introduced briefly, but they are not used in this
investigation. Also, some previous studies which are related to the project are highlighted.
Next, design methodology is prepared to aid the mathematical modelling process. The
airfoil data is extracted from a previous study (s1210, NACA-0015 airfoil). The
mathematical model required to compute turbine performance is formulated and shown
in steps. The initial parameters are also listed. Then, details regarding the modification v
of initial parameters, the in-depth study of tip speed ratio and turbine solidity, and the
investigation of self-starting physics are outlined. In the end, all data acquired are
displayed and plotted according to the requirements of the project. First, a baseline plot
of one-blade configuration is introduced to provide a basis for comparing results. Then,
plots of two-blade and three-blade turbines are made and compared to the one-blade
turbine results. An in-depth look into the tip speed ratio and turbine solidity reveals that
they affect the turbine similarly in outcomes but differs a little in the process. A brief
insight into the self-starting physics and issues of VAHT is provided and suggestions on
improving the self-starting of turbines are given. The project is then concluded with the
summarization of previously covered stuff, the drawing of conclusions based on the
observations and inferences, as well as suggestions provided to improve the current
project and ideas for new advanced projects that can be taken in the future.