Long term wave load trends against offshore monopile structures: A case study in the Bay of Biscay

Abstract

This study examines the trend in wave parameters over available annual records in the Bay of Biscay, where EWTEC
2023 is being hosted. There have been various renewable offshore energy projects in the 21st century in this region,
such as the OWC (Oscillating Water Column) plant in Mutriku [1], or BiMEP (Biscay Marine Energy Platform)[2],
the infrastructure for testing ocean devices in Armintza, where better characterization of the wave resource could help
to provide design information to developing wave energy technology. Other studies [3] have shown that wave height
has increased in recent decades, as well as the frequency at which extreme waves occur, which affects the fatigue
experienced by deployed devices. The aim is to study the effect of the maximal wave height, its frequency, and loads
on monopile cylindrical structures, which are basic component structures for wave energy converters and offshore
wind turbines. The effect of this evolution, against these generic structures in offshore wind and wave energy devices,
is studied using the 20th century reanalysis ERA20 (1900-2010) of ECMWF (European Centre for Medium-Range
Weather Forecasts) [3]. A significant increase in two forces, drag forces and inertial forces, of up to 15%, is computed
over 110 years at a gridpoint near the Western Basque coast, which constitutes a strong positive slope that can be also
associated with climate change, and has strong implications for the design of new marine renewable energy technology.