Extreme wave analysis for marine renewable energies in Ireland

The characterization of extreme wave climates and future projection analyses are essential for offshore renewable energy planning and coastal protection. This study examines the maximum individual wave height ( H m a x ) around Ireland, using ERA5 reanalysis data from 1991 to 2020, validated against H m a x observations from Irish moored buoys. Extreme wave climate regions are defined, employing a model-based clustering technique, which relies on the wave height distribution of each area. The probability of rogue waves – defined as waves where the maximum wave height is at least twice the significant wave height – is assessed for each region. The results suggest that, while extreme waves are more likely to occur far offshore on the west coast of Ireland, the likelihood of rogue waves is higher on the east coast and closer to shore. The Gumbel distribution is employed to estimate the 50-year return period H m a x values; these projections are compared to the National Renewable Energy Laboratory’s threshold of 30 m, representing the maximum 50-year return period wave height offshore wind turbines must withstand. This threshold is exceeded in areas far offshore from Ireland’s west coast, particularly near the M6 buoy location. Additional analyses of thresholds, at 29 and 28 m, suggest a broader area may be impacted by these high waves. The findings provide valuable insights into the spatial variability of extreme wave events, informing risk assessments for offshore renewable energy developments. • Characterization of extreme wave climate around Ireland using ERA5 data. • Definition of climatic regions for extreme wave climate in Ireland. • Assessment of 50-year return period H max via Gumbel distribution. • Identification of areas exceeding the 30-m H max limit, as specified by NREL. • Higher probability of rogue waves found closer to shore.