8. Monitoring Ice Accumulation and Active De-icing Control of Wind Turbine Blades

Ice accumulation on wind turbines operating in cold regions reduces power generation by degrading aerodynamic efficiency and causes mass imbalance and fatigue loads on the blades. Due to blade rotation and variation of the pitch angle, different locations on the blade experience large variation of Reynolds number, Nusselt number, heat loss, and nonuniform ice distribution. Hence, applying different amounts of heat flux in different blade locations can provide more effective de-icing for the same total power consumption. This large variation of required heat flux highly motivates using distributed resistive heating with the capability of locally adjusting thermal power as a function of location on the blade. Under medium/severe icing conditions, active de-icing with accurate direct ice detection is more energy efficient and effective in keeping the blade ice-free. This chapter includes: (1) A literature study on different methods of ice detection and a review on passive and active anti/de-icing techniques on wind turbines, (2) Development of an optical ice sensing method for direct detection of ice on the blade, including experimental results, (3) Development of an aero/thermodynamic model, which predicts how much heat flux is needed locally for de-icing under variable atmospheric conditions, (4) Experimental results showing a proof of concept of closed-loop de-icing using distributed optical ice sensing and resistive heating, and (5) Numerical modeling of ice melting on a blade for different distributed heater layouts and geometries in order to optimize thermal actuation strategy, improve de-icing efficiency, and reduce power consumption. We conclude with discussions of future directions on distributed ice sensing and thermal actuation for the next generation of de-icing systems on wind turbines.