Experimental investigation of the power performance of a minimal wind turbine array in an atmospheric boundary layer wind tunnel

Layout optimization is a critical step in constructing and operating wind power plants. The layout optimization strongly depends on the wake spatial evolution and on wake interactions within the wind farm. In this study, the power performance of a minimal wind turbine array was investigated in an atmospheric boundary layer wind tunnel. Five turbine configurations were tested in site-specific experiments: a single turbine, two aligned turbines, two misaligned turbines, three aligned turbines, and three misaligned turbines. Along with angular velocity and power measurements, a Constant Temperature Anemometer (CTA) cross-wire probe collected the downstream wake velocity data. The results show that the operating configuration of the upstream turbine significantly affects the power of the total wind turbine array, inducing the optimal tip speed ratios of the downstream turbines in the wake to decrease. To improve the power performance of the turbine array, introducing a spanwise offset is more beneficial than increasing the streamwise distance between turbines. The wake interaction between upstream turbines results in a larger wake expansion, leading to a reduction in the power produced by downstream turbines in the array. In addition, the most downstream turbine can be observed to have a better performance than its upstream turbine in an aligned three-turbine array. Balancing these effects is critical in the optimization strategy of wind farm layout.