Abstract
Wind turbine icing has been found to cause a variety of problems to the safe and efficient operations of wind turbines. Ice accretion on turbine blades would result in decreasing lift and increasing drag, thereby, leading to power reduction. The annual power loss due to icing was found to be 20 ~ 50% at harsh sites. Ice accretion and irregular ice shedding during wind turbine operation would lead to load imbalances and excessive turbine vibrations, which may cause structural failures, especially when coupled with strong wind loads. Icing issues can also directly impact personnel safety due to falling and projected large ice chunks.By leveraging the Icing Research Tunnel of Iowa State University (ISU-IRT), a series of experimental investigations were conducted to investigate the dynamic ice accretion process over the surfaces of typical wind turbine blade models and to explore the effective and robust anti-/de-icing strategies for wind turbines icing mitigation. More specifically, a comprehensive experimental study was conducted to quantify the transient surface water transport behavior over the ice accreting surface of typical wind turbine blade models by using a Digital Image Projection (DIP) technique. The aerodynamic performance degradation of the turbine blade models was characterized in the course of the ice accreting process by using two sets of high-sensitive multi-axis force/moment systems and a digital Particle Image Velocimetry (PIV) system. A novel hybrid anti-icing strategy that combines minimized electro-heating near the turbine blade leading edge and bio-inspired icephobic coatings to cover the blade surface was proposed. In comparison to conventional thermal-based anti-/de-icing methods to brutally heat the entire blade surface, the proposed hybrid strategy was demonstrated to be able to prevent the ice formation and accretion over the surfaces of the wind turbine blades effectively with only ~10% of the required power consumption. In addition to conducting wind tunnel experiments, a field campaign was also conducted in a mountainous wind farm to investigate the ice-induced performance degradation of multi-megawatt wind turbines by correlating the acquired images of ice accretion over the rotating wind turbine blades with an unmanned aerial vehicle (UAV) with the turbine operational data recorded by wind turbine supervisory control and data acquisition (SCADA) systems. The new findings derived from the present studies would lead to a better understanding of the underlying physics pertinent to the wind turbine icing phenomena, which could be used to improve current ice accretion models for more accurate prediction of ice accretion on wind turbine blades as well as to develop innovative anti-/de-icing strategies for safer and more efficient operation of wind turbines in cold weathers.