An experimental study on ice accretion characteristics and icing-induced aerodynamic penalties to offshore wind turbines

An experimental study was conducted to characterize the dynamic ice accretion process and icing-induced aerodynamic penalties to offshore wind turbines under highly wetted icing environments during sea spray icing events. A turbine blade model was exposed to frozen-cold airflows with the Liquid Water Content levels up to 10.0 g/m3 and ambient temperatures down to −15.0 °C. Ice accretion characteristics under highly wetted icing environments were found to be significantly different from those of the onshore turbine icing scenarios with much lower Liquid Water Content levels. While a typical rime icing process was found to be experienced by onshore wind turbines at the cold temperature of −15.0 °C, mixed or even glaze icing processes occurred over the blade surfaces of offshore wind turbines due to the much higher wetted icing environments. The aerodynamic penalties induced by the mixed and glaze ice accretion were found to be significantly greater (i.e., up to 15 % more accreted ice mass, 85 % less lift, and 150 % more drag) than the rime icing scenario. However, at a “warmer” icing temperature of −5.0 °C, the glaze icing process over blade surfaces under highly wetted icing environments was accompanied by significant runback of unfrozen water, causing smaller aerodynamic penalties to offshore wind turbines.