Ice formation on wind turbines in cold climates

Ice accretion on wind turbine blades operating in cold climates can lead to significant aerodynamic degradation, increased structural loading, and reduced energy yield. While numerical icing prediction tools provide valuable insight, uncertainties in environmental inputs, aerodynamic modelling, and ice morphology can lead to substantial discrepancies between predicted and actual ice shapes. This thesis addresses the need for a systematic, quantitative framework to compare and evaluate ice shapes and their aerodynamic impact, with the aim of bridging the gap between academic modelling approaches and industry requirements for rapid, high-confidence assessments.

A comprehensive aerodynamic foundation is first established, progressing from two-dimensional aerofoil theory to three-dimensional blade aerodynamics, and applying the Blade Element Momentum (BEM) method to predict spanwise aerodynamic conditions under a range of realistic meteorological inputs. These outputs, including effective angle of attack and relative velocity, are then used to drive high-fidelity icing simulations with ANSYS FENSAP-ICE at multiple spanwise stations. The parametric analysis explores the influence of wind speed, temperature, median volumetric diameter (MVD), liquid water content (LWC), and icing duration across representative glaze, rime, and mixed icing conditions, resulting in a dataset of 105 simulations that capture both individual and combined parameter effects.

The second phase of the research investigates iced aerofoil performance using an experimentally derived reference ice shape, which is systematically modified to alter key geometric features, including impingement limits, horn dimensions, horn angle, leading-edge ice thickness, and total ice area. A total of 119 iced aerofoil simulations are performed, covering 17 geometric modifications tested at seven angles of attack (0°, 1°, 5°, 6°, 9°, 14°, and 20°), enabling a detailed examination of how specific ice shape characteristics influence aerodynamic performance.

The principal contribution of this research is the development of an integrated, quantitative framework that links ice morphology to aerodynamic degradation. The thesis culminates in the development of the Geometric Ice Severity Index (GISI) and Aerodynamic Influence Factor (AIF). Applied together, these provide a transferable and computationally efficient method for consistent severity assessment across varied icing scenarios. This framework offers industry a practical tool for rapid early-stage design and operational decision-making, providing predictive confidence in the evaluation of icing impacts on wind turbine performance.