Numerical analysis in vertical axis wind turbines and wind farm layout optimization

Renewable energy sources play a very important role in providing the energy needs of the modern world with environmentally friendly approaches. One of the most important renewable energy sources is wind energy. Wind turbines can capture the kinetic energy of the wind and convert it to useful energy. The most common types of wind turbines are 3-bladed horizontal axis wind turbines. Moreover, there is a growing interest in vertical axis wind turbines due to the fact that they have many advantages, such as low cost, suitability for individual usage and a simple design. A straight-bladed H-Darrieus wind turbine is numerically investigated in this thesis. The Computational Fluid Dynamics (CFD) analyses are considered under two-dimensional, incompressible, and unsteady flow conditions. First, the effect of turbulence on the performance of the wind turbine is studied in a range of turbulence intensity from \%0 to \%29.2. Results show that the performance of the wind turbine increased with increasing turbulence intensity until the tip speed ratio of 2.64. It is observed that there is a slight negative effect of turbulence when the tip speed ratio is greater than 2.64. Secondly, the effect of solidity on the performance of the wind turbine is assessed for solidity values ranging from 0.25 to 3.00. It is concluded that there is a critical decrease in the performance of the wind turbine with an increase in solidity. On the other hand, wind turbines with high solidity values produce more energy at low tip speed ratios (λ ≤ 1.0). Additionally, the exergy efficiency analyses are performed for both turbulence and solidity cases. Results show that the trend of the exergy efficiency - tip speed ratio relation is similar to that of the power coefficient - tip speed ratio. The second main objective of this thesis is the investigation of the effect of solidity on the self-starting performance of the wind turbine. The range of solidity is considered from 0.10 to 3.00. It is noticed that the self-starting performance of the wind turbine is enhanced by increasing the solidity up to 1.40. Furthermore, it is suggested that the solidity of the wind turbine should be σ ≤ 1.0 to achieve both better self-starting and power generation performance. The optimization of the wind farm with vertical axis wind turbines is conducted in the final part of the thesis. A two-stage optimization is performed to realize better self-starting of the wind turbine cluster. Results reveal that the optimum wind farm configuration is achieved at the following parameters: the solidity of each turbine is 1.00, horizontal (X1, X2) and vertical (Y) distances between the turbines are 1.1D, 1.1D, and 1.5D, respectively.