Design procedures and experimental verification of an electro-thermal deicing system for wind turbines

Abstract

Abstract. There has been a substantial growth in the wind energy power capacity worldwide, and icing difficulties have been encountered in cold climate locations. Rotor blade icing has been recognized as an issue, and solutions to mitigate accretion effects have been identified. Wind turbines are adapting helicopter rotor and propeller ice protection approaches to reduce aerodynamic performance degradation related to ice formation. Electro-thermal heating is one of the main technologies used to protect rotors from ice accretion, and it is one of the main technologies being considered to protect wind turbines. In this research, the design process required to develop an ice protection system for wind turbines is discussed. The design approach relies on modeling and experimental testing. Electro-thermal heater system testing was conducted at the Adverse Environment Rotor Test Stand at Penn State, where wind turbine representative airfoils protected with electro-thermal deicing were tested at representative centrifugal loads and flow speeds. The wind turbine sections tested were half-scale models of the 80 % span region of a generic 1.5 MW wind turbine blade. The icing cloud impact velocity was matched to that of a 1.5 MW wind turbine at full power production. Ice accretion modeling was performed to provide an initial estimate of the power density required to de-bond accreted ice at a set of icing conditions. Varying icing conditions were considered at −8 ∘C with liquid water contents of the cloud varying from 0.2 to 0.9 g/m3 and water droplets from 20 µm median volumetric diameter to 35 µm. Then, ice accretion thickness gradients along the span of the rotor blade for the icing conditions were collected experimentally. Given a pre-determined maximum power allocated for the deicing system, heating the entire blade was not possible. Heating zones were introduced along the span and the chord of the blade to provide the required power density needed to remove the accreted ice. The heating sequence for the zones started at the tip of the blade, to allow de-bonded ice to shed off along the span of the rotor blade. The continuity of the accreted ice along the blade span means that when using a portioned heating zone, ice could de-bond over that specific zone, but the ice formation could remain attached cohesively as it is connected to the ice on the adjacent inboard zone. To prevent such cohesive retention of de-bonded ice sections, the research determined the minimum ice thickness required to shed the accreted ice mass with the given amount of power availability. The experimentally determined minimum ice thickness for the varying types of ice accreted creates sufficient tensile forces due to centrifugal loads to break the cohesive ice forces between two adjacent heating zones. The experimental data were critical in the design of a time sequence controller that allows consecutive deicing of heating zones along the span of the wind turbine blade. Based on the experimental and modeling efforts, deicing a representative 1.5 MW wind turbine with a 100 kW power allocation required four sections along the blade span, with each heater section covering 17.8 % span and delivering a 2.48 W/in.2 (0.385 W/cm2) power density.

An Experimental Study on Blade Surface De-Icing Characteristics for Wind Turbines in Rime Ice Condition by Electro-Thermal Heating

“…Anti-icing was identified as the preferred strategy when ambient temperatures were above −5 • C, and the system cost was no higher than 2% of the turbine's capital. Gezt et al [32] designed an efficient anti-icing system for wind turbines by combining modeling and experimental testing. Experimental tests showed that accumulated ice needs to reach a certain minimum thickness to break away at a given available power.…”

Trifolium repens L.-Like Periodic Micronano Structured Superhydrophobic Surface with Ultralow Ice Adhesion for Efficient Anti-Icing/Deicing

“…As a renewable energy with great development potential, wind energy plays a key role in global energy. − Wind turbines are mostly built in high altitudes and cold regions to maximize the energy utilization degree, which makes it inevitable that wind turbine blades will face the problem of ice coverage. − The formation and accumulation of ice seriously affect the efficiency and lifetime of wind turbines and may even pose a potential threat to the safety of surrounding buildings and residents. , Therefore, how to efficiently and quickly remove accumulated ice on wind turbine blades has become a critical issue. The existing active deicing technologies mainly include chemical deicing, , mechanical deicing, thermal deicing, , etc., but these deicing technologies generally suffer from the disadvantages of environment pollution, low efficiency, and high energy consumption …”

“…8,9 Therefore, how to efficiently and quickly remove accumulated ice on wind turbine blades has become a critical issue. The existing active deicing technologies mainly include chemical deicing, 10,11 mechanical deicing, 12 thermal deicing, 13,14 etc., but these deicing technologies generally suffer from the disadvantages of environment pollution, low efficiency, and high energy consumption. With the development of anti-icing/deicing technology, passive anti-icing surfaces quickly entered the vision of scholars, such as a superhydrophobic surface, 15−18 a slippery liquidinfused porous surface, 19−21 and an icephobic polymer with low interfacial toughness.…”