Risk-based life-cycle assessment of offshore wind turbine support structures accounting for economic constraints

The objective of the present study is to perform a risk-based life-cycle assessment of monopile offshore wind turbine support structures. The design of the structure is based on the optimised levelised cost of energy so that the offshore wind energy can compete with the other energy resources. Both optimal design solutions for a monopile support structure and the optimal inspection planning are addressed here. The structural assessment of the monopile support structures is carried out using the finite element method accounting for the pile-soil interactions. The risk-based assessment is performed for the design solutions aiming to achieve the minimum of the levelised cost of energy and the total expected cost conditional to the implemented inspection strategy and the structural risk. Furthermore, the optimal inspection interval is investigated. Finally, the sensitivity of the parameters influencing the risk life-cycle assessment is also studied. The present study analyses a multi-dimensional framework, which integrates structural configuration of the support structure, manufacturing, detailed structural risk assessment, inspection and repair planning, and economic conditions into a coupled dynamic system accounting for the feedback loops resulted from the introduction of the probabilistic structural state to the life cost expenditure such as CAPEX, OPEX, and DECEX.