A Study For Anti-Icing Of Hydrophobic Coatings On Wind Turbine Blades

Wind energy has many advantages such as environmentally friendly, renewable and wide distribution, which will become the trend of clean energy development around the world, and the wind power generation of China has been developing rapidly during the past ten years. But in recent years, since climate is deteriorating gradually, icing becomes a serious threat to power equipment. Due to wind power industry neglected the icing problem during the rapid development period in China, almost all wind farms installed in our country did not take measures for anti-icing, therefore suffered huge losses when icing happened in wind farms. So it is critical to investigate and find out the effective anti-icing methods for wind turbine blades. Particularly the hydrophobic coatings added in object's surface can help the droplets roll off easily, then reduce water resource for icing, and delay icing process or reduce the degree of icing. But the anti-icing performance of coatings applied on wind turbine blades still needs much more research, and according to the current research results, the anti-icing performance of the hydrophobic coating still remains controversial. Therefore, to Fig out the anti-icing performance of hydrophobic coatings on the wind turbine blades, this paper completed follow work:Firstly the motion property on different wind turbine blades with hydrophobic coatings were investigated, and the influence factor on roll of droplets on hydrophobic surfaces were analyzed, then the tests for accumulation and roll of droplets were performed at temperature of-7°C based on NACA7715 model blades with 4 kind different SAR(Silicone Acrylate Resin) hydrophobic coatings, and the bare blade was arranged as contrast group. The test results reveal that it hard for droplets to remain on hydrophobic surfaces, and the better the hydrophobicity is, the more easily for the droplets will roll off. Then the simulation research for frozen process of droplets on different blade surfaces were performed based on the model combined the phase transition, convection heat transfer and solid heat transfer under different airflow velocity conditions through COMSOL Multiphysics software. The results indicate that it takes more time to be frozen fully for droplets on better hydrophobic surfaces, and when the droplets remained on the hydrophobic surfaces, the airflow velocity affects the frozen time less significantly than that on bare blade surface. The reasons for that phenomenon may be that the expansion area of droplets on hydrophobic surfaces aremuch smaller than that on bare surface, and their liquid layers are thicker than that on bare surface.Secondly we established a small wind test tune at the multi-function artificial climate chamber of Chongqing University, and plenty of artificial glaze icing tests were carried out. 5 type of wind velocity and 3 type of AOA(angle of attack) conditions were arranged for icing test. The ice weight of blades were measured and the icing distribution of blades were observed. Then de-icing and ice-melting tests also been carried out, and the icing adhesion force strength and ice-melting time were measured.The results indicate that with the larger CA(contact angle) and smaller CAH(contact angle hysteresis), the icing degree will decrease. And with the better hydrophobicity, the icing adhesion force strength and ice-melting time become lower.Eventually, the natural icing tests for 3 type of different hydrophobic blades were carried out at natural icing station of Xuefeng mountain with different windward side conditions, then the icing distribution and icing weight were obtained. The ice-melting property of blades also been investigated under warm weather. The results indicate with the larger CA, the icing degree will decrease, and the icing melt speed also become faster.According to the icing test and the simulation research, the results can indicate that hydrophobic coatings with the CA not less than 130 ° can help the droplets roll off and delay the frozen time, then delay the icing process on surfaces and reduce the icing degree. Moreover, the coatings also can reduce the de-icing force strength and reduce ice-melting time. The better of the hydrophobicity on blade surface is, the better anti-icing performance and de-icing performance will be.