In order to improve the static start-up problem of Savonius wind turbines, a Savonius wind turbine with a modified blade is proposed. It was obtained by twisting the half-cylindrical blades of the basic Savonius wind turbine by 70°. The aerodynamic performance of the wind turbine before and after the modification was compared. Firstly, the static torque coefficient of two wind turbines at different azimuth angles were obtained by means of three-dimensional numerical simulation. The static flow field around the wind turbine was analyzed. Then, the output power and speed characteristics of a spiral Savonius wind turbine under different incoming wind speeds were evaluated in the wind tunnel. The results show that, compared with the Savonius wind turbine with half-cylindrical blades, the spiral wind turbine could start at any azimuths in one rotation cycle. The reverse torque was eliminated. The static torque coefficient fluctuation range was reduced by 10%. The start-up performance was effectively improved. This investigation could provide guidance for the improvement of start-up characteristics of Savonius wind turbines.

When wind turbines work in a cold and humid environment, especially offshore condition, ice accretion on the blade surfaces has a negative effect on the aerodynamic performance. In order to remove the ice from the wind turbine blade, the adhesive characteristics of atmospheric icing on the blade surface should be mastered under various conditions. The objective of this study is to evaluate the effects of offshore atmospheric conditions, including wind speeds, ambient temperatures and, especially, the salt contents on ice adhesion strength for wind turbine blades. The experiments were conducted on a NACA0018 blade airfoil under conditions including an ambient temperature of −3 °C~−15 °C, wind speed of 6 m/s~15 m/s and salt content of 1~20 mg/m3. The results showed that salt content was the most important factor affecting the ice adhesion strength, followed by ambient temperature and wind speed. The interactive effect of wind speed and salt content, ambient temperature and salt content were extremely significant. The research can provide a reference for the anti-icing for offshore wind turbines.

Wind turbines operating in cold regions are prone to freezing in winter, which can affect their performance and safety. To resolve this situation, the development of blade anti-icing technology has attracted widespread attention. In this study, a type of biochar/polypyrrole coating was obtained through synthesis on the surface of biochar. After characterization, it was found that the porous structure, irregular dents, and bumps on the surface of biochar/polypyrrole material contributed to the formation of a nanoscale roughness structure with a typical super-hydrophobic nanostructure. Additionally, it had a sufficient surface area. The wetting characteristics of the coating were analyzed with the assistance of a contact angle measurement instrument. The contact angle of the coating was determined as 151°, which indicates the excellent hydrophobic properties of the coating. Icing wind tunnel tests were carried out to evaluate the anti-icing effect of biochar coating and biochar/polypyrrole coating at different ambient temperatures and wind speeds. Compared with uncoated leaves, the icing area of biochar/polypyrrole coating was reduced. Additionally, the anti-icing effect of biochar/polypyrrole coating was most significant. This study provides a practical reference for the research of anti-icing coating on wind turbine blades.

No abstract

As clean and renewable energy, wind energy has been widely used in the world. The wind turbine is a kind of rotating machinery, which can convert wind energy into mechanical energy and electrical energy. Wind turbines sometimes face a variety of extreme weather conditions, such as icing, heavy snow, lightning, sand storm, and so on, which affect the safety operation of wind turbines. In the present study, icing events on the blade surfaces of wind turbines are focused, and the wind tunnel test of icing was carried out on a 2D blade with NACA0018 airfoil used in wind turbines. In the icing tests, three kinds of ambient temperatures were selected, including −5 °C, −10 °C, and −15 °C, and two kinds of wind speeds were decided, including 5m/s and 10m/s. The icing distributions on the blade surface at the different attack angles were tested and recorded by a high-speed camera for several minutes. The ice accretion and distribution characteristics at the leading edge of the 2D blade airfoil were acquired and analyzed. The findings can provide a reference for the research on the icing mechanism and the de- and anti-icing of wind turbines.