Wind turbine performance in natural icing environments: A field characterization

Over 30% worldwide installations of wind turbines in cold climate regions are threatened with icing risks. The current study presents a systematic characterization of the turbine operation, power production, and blade/ tower structural responses of a utility-scale wind turbine (2.5 MW, variable-speed variable-pitch regulated) under natural icing environments, by leveraging the unique facilities at the Eolos Wind Energy Research Field Station. A representative icing event that lasts 51 h is selected and divided into pre-icing, operational-icing, stopped-icing, and post-icing phases based on the variation of turbine operational conditions (i.e., power, rotor speed, and pitch angle) for the detailed evaluation. The results show that ice accretion can lead to appreciable reductions in the rotor speed and pitch angle before the turbine reaches its operational limits. Such reductions increase correspondingly as the inflow wind speed increases, which may accelerate the airfoil stall process and result in more severe power loss. The 51-h icing event yields a total energy loss of similar to 25 MWh, and the post-icing phase contributes a second-largest share of 17%, on the heel of the stopped-icing phase of 71%, associated with the long duration of natural ice melting process. Besides, blade structural response is highly sensitive to the ice accretion due to its fast reaction to the ice-induced lift penalties. The tower response also provides concrete evidence for the increase of the structural imbalance with ice accretion. Our findings can provide insights into the development of advanced control strategies for a more efficient and safer operation of wind turbines in natural icing environments.