Tham khảo tài liệu 'wind turbines part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Genetic Optimal Micrositing of Wind Farms by Equilateral-Triangle Mesh 429 An intuitive idea is to locate the wind turbines at the center of some circular cells which are tangent to each other as illustrated in Figure 4 a . When the centers of the cells are connected we obtain intertwined equilateral hexagons shown in Figure 4 b seemingly a honeycomb mesh. If further analyzed the hexagons can be decomposed into six equilateral triangles and the triangle vertices represent the possible positions of turbines as shown in Figure 4 c . Therefore the mesh is called the equilateral-triangle mesh. a Tangent circles Fig. 4. Equilateral-triangle mesh As recommended in Troen Petersen 1989 for a flat farm with unidirectional wind turbines should be place about 3 5 times of rotor diameter apart in columns and about 5 9 times in rows. In this paper we follow Mosetti et al. 1994 Grady et al. 2005 and Marmidis et al. 2008 and set the side length of the triangle as five times of the turbine rotor diameter. Definition 1 ETM orientation . Pick up any equilateral triangle in a mesh construct a vector from the center of the triangle to the vertex and obtain the angle f in degrees of this vector from the north-direction vector . y-axis clockwise as illustrated in Figure 5. The orientation of the mesh is defined as f mod f 60 where mod stands for the modulo operation. For convenience an ETM with an orientation angle f is denoted as ETM-f. Then the orientation of the traditional SM can be similarly defined as follows. Definition 2 SM orientation . Pick up any square in the mesh and construct a vector from the center of the square towards one of its vertices. The clockwise angle from the north-direction vector towards it is f in degrees . The orientation of the traditional SM is defined as f mod f 90 Under this definition the orientation of the square meshes used in Mosetti et al. 1994 Grady et al. 2005 and Marmidis et al. 2008 were 45 which can be denoted as ETM-45 in short. .
