Experimental Study of the Wake Regions in Wind Farms

It is desired, through this work, to investigate in detail the scenario that takes place behind a single wind turbine unit by focusing on three parameters; average axial wind velocity component, velocity deficit, and total turbulence intensity. The testing was done at mainstream velocity, U_∞, of 5.2 m/s, u and v velocity components were captured by x-probe dual-sensor hot wire anemometer. A massive amount of point data was obtained, which then processed by a matlab script to plot the desired contours through the successive transverse sections along the entire length of the test section. By monitoring the previously mentioned flow parameters, the regions of low velocity and high turbulence can be avoided, while the location of the subsequent wind turbine is selected. The estimation of the distance, at which the inlet flow field will restore its original characteristics after being mixed through the rotor blades, is very important as this is the distance that should separate two successive turbines in an inline configuration wind farm to guarantee the optimum performance and to extract the maximum power out of the subsequent array of turbines. It is found that the hub height axial velocity recovery at six rotor diameters downstream distance is only 82%. This fact means that the power extraction out of the downstream turbine in an inline configuration wind farm is only 55% of the upstream turbine if the same free stream velocity and blade design are adopted.