Potential improvement of wind turbine array efficiency by active wakecontrol (AWC)

摘要

Wind energy is of increasing importance in electrical power production. The key for even further enhancing its role is to make the cost per produced energy unit competitive with other sources. Common approaches to control and therefore to optimize the power output include tip speed variation, stall, variable blade pitch, and yaw. The aerodynamic efficiency is one side of the problem, the other being the interaction between two or more turbines. This paper focuses on the possible increase in power output from a wind farm using an Active Wake Control (AWC) method. Comprehensive studies on the wake characteristics of single turbines are available in the literature. Comparisons between tunnel tests and full-scale turbines [1] [2] are a typical example. Near wake measurements [3] [4] have been performed using, for example, hot wire and laser techniques. The airflow behind wind turbines has also been investigated [5] [6]. Studies of wakes [7] visualised the wake deflection when the turbine was yawed. Smoke was injected in the airflow at two positions at hub height such that the smoke trails touched the blade tip paths on both sides of the turbine. A photo taken from the test is presented in Figure 1. The two-bladed turbine was yawed 30 degrees and operated close to maximum power. The vortices emerging from each blade passage are clearly visible. Note the vortex core path on each side. Both the sides of the wake are deflected upward, although the lower side more noticeably.