Performance degradation and vibration response of Wells-type turbines due to marine salt fouling: A full-scale study at the Mutriku Wave Power Plant

This study investigates the impact of marine salt accumulation on the Wells-type turbines of the Mutriku Wave Power Plant (MWPP). During the first half of 2020, a failure of the automatic freshwater washing system, combined with COVID-19-related mobility restrictions, resulted in an extended period without turbine cleaning. The information recorded by the data acquisition system (SCADA) in the MWPP (power provided by the turbines as well as vibrations) and ocean-state data were analysed to quantify the associated operational degradation. The results show that salt accumulation reduced the power relative difference of the affected turbine by an average of 46% (ranging from 31% to 59%) during the three-month failure period, and significantly altered the vibration response. For the sea-state conditions observed in 19th March 2020 ( s w h = 2.0 m and m w p = 13.4 s), the healthy-state vibration baseline ranged from 1.68 to 1.86 mm/s, whereas the measured average vibration on that day reached 4.25 mm/s. After manual cleaning, turbine performance rapidly returned to normal operating levels. These findings demonstrate that salt accumulation was the dominant factor affecting both turbine power output and vibration behaviour, highlighting the importance of effective cleaning strategies in Oscillating Water Column (OWC) energy converters.