Optimisation of monopiles supporting offshore wind turbines through advanced numerical modelling of cyclic loading

Abstract

The European Union (EU) has established ambitious renewable energy targets in order to de-carbonise the energy sector. In Ireland, it is estimated that 2.3GW of offshore wind capacity will be installed by 2030 at an estimated cost of €6 billion. The foundations for offshore wind turbines (OWTs) can represent up to 30% of the overall cost of development. Among all components of an OWT structure, the foundations offer the greatest scope for optimisation. Monopile foundations, which are large diameter (typically 4 – 8m) steel tubes driven into the ground, represent around 80% of all offshore wind turbine foundations installed to date and will continue to be the most common foundation solution for offshore wind for at least the next 15 years. As larger wind turbines are being developed, XL monopiles from 8 – 12m in diameter are needed to support these. These larger diameter piles typically have a lower slenderness (length to diameter ratio) than standard monopiles and are therefore significantly more susceptible to the effects of cyclic loading. Because of an inadequate understanding of the effects of cyclic loading, XL monopiles are currently over-designed, causing excessive manufacturing, transportation, and installation costs. This project aims to improve design methods for cyclic loading effects on XL monopiles through state-of-the-art numerical modelling and calibration against new field test data and will lead to significant advances in scientific knowledge and improvements in the design efficiency of OWTs. Specifically, this will build upon recent advances in the state of the art in numerical modelling of monopiles and will be validated against recent and new monopile field test data. The ultimate goal is to reduce cost and improve the viability of offshore energy, leading to a more rapid reduction in carbon emissions and reliance on fossil fuels.