Abstract
A field study was conducted to examine ice accretion on 50-m-long turbine blades and icing-induced power production losses to multi-megawatt wind turbines. An unmanned-aerial-system equipped with a digital camera was deployed to take images of the ice structures on turbine blades after undergoing a 30-hour-long icing event to quantify the ice thickness accreted along blade leading edges. While ice accreted over entire blade spans, more ice was found to accrete on outboard blades with the ice thickness reaching up to 0.3 m near blade tips. Based on the icing similarity concept and blade element momentum theory, a theoretical analysis was performed to predict the ice thickness distributions on turbine blades. The theoretical predictions were found to agree with the field measurements well in general. Turbine operation status during the icing event was monitored by using turbine supervisory control and data acquisition (SCADA) systems. Despite the high wind, iced wind turbines were found to rotate much slower and even shut down frequently during the icing event, with the icing-induced power loss being up to 80%. The present study aims to fill in the knowledge gaps between the fundamental icing physics studies conducted under idealized lab conditions and complex wind turbine icing phenomena under realistic, natural icing conditions.
•A field study to quantify the ice accretion on utility-scale wind turbines for the first time.•An UAS-based imaging system is used to characterize ice accretion over 50-m-long blades.•A theoretical analysis is performed to predict the ice accretion on turbine blades.•Icing-induced power losses of the turbines are evaluated based on SCADA measurement data.•The study fills in the gaps between the simplified icing lab studies and turbine icing phenomena.