A dual de-icing system for wind turbine blades combining high-power ultrasonic guided waves and low-frequency forced vibrations

Wind turbines mounted on cold climate sites are subject to icing which could significantly influence the performance of the turbine blades for harvesting wind energy. In this study, an innovative dual de-icing system under development is described. This either prevents ice accumulation (anti-icing) or removes any ice layer present on the surface of the blade material (de-icing). A modelling study on ultrasonic guided waves propagating in composite blades was used to determine the optimal frequency and location of the transducers for ensuring wave propagation, causing the required level of energy concentration and resulting shear stress across the leading edge of the turbine's blade. In parallel, the effects of low frequency vibrations have been investigated through modal and harmonic analyses. This allowed specification and optimisation of the positioning of shaker(s), together with the magnitude and direction of harmonic forces required to induce sufficient acceleration to the blade surface for ice removal. An appropriate survey was also carried out to evaluate the potential for fatigue failure of the blade due to harmonic forces induced by shakers. The proposed technique configures and presents an active solution for the icing problem, allowing safe and reliable operation of wind turbines in adverse weather conditions. (C) 2015 Elsevier Ltd. All rights reserved.