Nacelle and tower effect on a stand-alone wind turbine energy output—A discussion on field measurements of a small wind turbine

Abstract

Nowadays, small wind turbines (i.e., those less than 100 kW) have unique advantages in remote and underdeveloped areas with low and distributed electricity demand. With this consideration, expert committees are established for small wind turbine under various international scientific communities such as International Electrotechnical Committee and International Energy Agency. The major research question is the wake effect from the nacelle and tower, which significantly affect the turbine performance because it is relatively large compared with megawatt turbine. To answer this question, a four-month field test campaign was conducted by using anemometers to measure the incoming and wake flow of a 33 kW horizontal axis wind turbine in a remote area in Gansu, China. The results show that nacelle and tower significantly affect the turbulent kinetic energy, flow angles and velocity deficit. Particularly, the distributing range of flow angles of wake is increased significantly and the horizontal flow angle has an asymmetric bimodal probability distribution. Furthermore, the spectral analysis reveals a strong interaction between the tower and nacelle as well as blade-generated structures. This interaction leads to distortion at low-frequency of the power spectrum, and then a frequency band with relatively stable energy is generated. Overall, this study is expected to provide guidance for small wind turbine development in rural area.