Developing a holistic operation and maintenance simulation tool for emerging offshore wind projects

Abstract

Offshore fixed and floating wind deployment is growing globally every year. According to the ORE Catapult projections there will be over 4000 turbines installed in 2030 in the UK alone. The number of offshore cables and substations will increase proportionally. Operation and maintenance of these offshore assets contributes to a significant portion of project costs. This is particularly due to the growing demand for resources: vessels, ports and personnel. Operation and maintenance simulation tools can support the industry by modelling various scenarios and predicting the cost and downtime difference. This thesis introduces a simulation tool for operation and maintenance, an extension of the pre-existing COMPASS tool, incorporating innovative features.

Existing tools rely solely on the user input which can be problematic considering the lack of public data, the complexity of operation and maintenance and the fact that not all users are familiar with it. This thesis reviews information and data collected from several sources, enhances it with expert knowledge and presents an assembled operation-and-maintenanceinputs guide that can be reliably used in operation and maintenance simulations. Data analysis of over 2000 major operations presented in this thesis showed that maintenance duration is highly variable but it is modelled as fixed in existing tools. A novel function was developed to capture this variability in COMPASS and the impact of it is demonstrated via a case study. This thesis also presents the variation of major operation rates throughout the lifetime of a wind farm.

Existing operation and maintenance simulation tools either cannot model cable topology impact, floating wind turbine maintenance and multi-rotor turbine maintenance or model these technologies with significant limitations. This thesis presents a function that is able to capture the impact of cable failures in complex array cable networks that existing tools cannot model. Its application is then demonstrated in this thesis via a case study showing how the choice of cable topology can impact the revenue losses.

This research project developed the computational logic for modelling floating turbines, multirotor turbines and personnel movement and limitations. These developments are then demonstrated in novel case studies. One compares a service operation vessel with an offshore maintenance base accommodating three crew transfer vessels and finds that the scenario with service operation vessels results in higher energy availability and lower operational expenditure. Another case compares multi-rotor turbines with single-rotor turbines and finds that despite the more frequent tow-to-port operations, the case with twin turbines results in lower operational expenditure primarily due to a smaller number of array cables and hence fewer cable repairs.

This thesis presents a cross-model benchmarking study that includes tow-to-port scenarios that have not been considered in previous model verification studies. This thesis benchmarks COMPASS outputs against the outputs of two other simulation tools, WOMBAT v0.8.1 (developed by the NREL) and the operation and maintenance analysis tool developed byWavEC. The findings from this benchmarking study highlight that the differences in methodology can have a significant impact on the simulation outcomes. In particular the main differences occurred from modelling maintenance activity interruption and towing to port. The key outcome of this work is the operation and maintenance simulation tool that can guide the industry to finding the best operation and maintenance strategies for emerging wind farm projects.