Operational Strategies for a Large-Scale Horizontal-Axis Wind Turbine During Icing Conditions

The global wind energy capacity installed in mountainous and subarctic regions is predicted to be 26% of the total 711.8 GW of cumulative power, which is expected to be installed by the end of 2020. Power losses due to ice deposition on wind turbine blades can reach up to 25% during severe icing conditions, and ice buildup poses risks because of ice throw and component wear.

The impact of ice accretion on wind turbines strongly depends on the rate of accumulation and the time duration of an icing event. There is a significant amount of research on modelling ice-induced power losses accounting for either the accumulation of ice on blades or the analysis of power production data.

However, there is limited work on identifying the best operational strategies during icing periods. This paper shows how the operation of a large-scale horizontal-axis wind turbine is affected by different icing events and investigates different operational strategies for reducing ice-induced power losses.

The considered operational strategies include utilisation of anti-icing, operation shutdown and rotor rotational speed modifications. The NREL (National Renewable Energy Laboratory) 5 MW reference turbine is used for simulating a large-scale horizontal-axis wind turbine. Ice accretion, aerodynamic analysis and anti-icing power demand calculations have been simulated using lewINT and JavaFoil.

Blade element momentum theory is used to evaluate wind turbine power performance. Ice shapes have been created for temperatures of −5 and −20 °C, considering wind speed of 15 ms−1, liquid water contents of 0.2–0.36 gm−3 and a median volume diameter of 36.10−6 m. The ice-induced losses are calculated and compared to the power required for anti-icing, thus identifying when it is preferable in comparison to an alternative strategy such as shutting down the turbine.

Choosing a suitable strategy for a particular icing condition will help wind turbines to be operated more efficiently in Cold Climates.