Evaluating the value of information of inspection strategies for a FOSS

Abstract

Many future commercially exploitable sites of marine renewable energies (MRE) are located in transitional to large water depths if compared to already deployed bottom-fixed offshore wind farms. Some constraints such as visual aspects force the whole MRE sector to consider the implementation of innovative Floating Offshore Sub-Stations (FOSS).

Since a FOSS is exposed to a more sever environment, a higher level of uncertainty and, therefore, a higher failure rate is expected for the system which can increase its life cycle cost. Moreover, performing maintenance operations to avoid failures is also costly due to the distance from the coast and the environment. Therefore, optimal maintenance planning is required to minimize the life cycle cost. A reliability-based maintenance planning can be helpful in order to take into account the associated uncertainties in the problem.

Structural health monitoring (SHM) and inspections can be used to reduce the uncertainty level in order to provide a better maintenance planning. They provide information about the real environmental conditions and the systemﾒs current state, which can be very advantageous during the decision-making process.

Selecting the best SHM or inspection strategy is important for a systemﾒs life cycle management. A proper SHM or inspection should bring the maximum information at a reasonable cost. With this respect, the concept of value of information (VoI) can be of a great help to confirm if a SHM solution is worthy to apply or to rank competitive SHM solutions under given conditions.

Accordingly, the main goal of our work is reducing the life cycle cost of an innovative FOSS. With this respect, the concept of VoI will be used to find the best SHM and inspection methods to monitor the system. The information provided by SHM and inspection can then be employed to update for instance, the reliability or availability level of the system which are main indicators for systemﾒs maintenance planning.

The objective of this study, therefore, is to provide some of our primary results regarding the evaluation of the VoI for different inspection techniques for a FOSS. Moreover, a simple cost analysis has been performed in order to illustrate the importance of maintenance actions during the service life of a FOSS.