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Towards Game-changer Service Operation Vessels for Offshore Windfarms

Periodic Reporting for period 3 - NEXUS (Towards Game-changer Service Operation Vessels for Offshore Windfarms)

Reporting period: 2020-11-01 to 2021-04-30

Operation and Maintenance (O&M) accounts for 20-30% of life cycle cost of a typical offshore wind farm, and this is forecast to increase as sites move further out to sea with more challenging O&M needs. NEXUS analyses these needs, providing better understanding and tools to improve efficiency and cost.
Carrying technicians, equipment and spares usually relies on service operation vessels (SOVs) and the demand for SOVs will grow as windfarms move further offshore and increase in size and number, the size of the SOV fleet estimated to quadruple in the next decade to meet demand.
NEXUS aims to improve SOV operational efficiency by pursuing a new vessel, including game-changing technologies, advances in O&M, and carrying out a business analysis of the complete O&M services.
•Reduce logistics costs of offshore wind turbine maintenance by 20%, and lower CO2 emission by 30% using a new design of windfarm service vessel
•Enable robust decision-making resulting in reduced costs & effective management of business risk for the service vessel
•Capture robust design requirements for a new design of windfarm service vessel for operation in the North Sea
•Develop a new vessel concept for servicing offshore windfarms to satisfy the set robust design requirements
•Develop specialised safety regulations for windfarm service vessels to improve cost effectiveness and operational flexibility potentially inhibited by the current, generic safety rules
•Compile a business case for a new windfarm service vessel
1. Defining the NEXUS requirements:
•Specifying labour and energy markets
•Understanding the influence of climate, maintenance strategies and fleet logistics on offshore wind energy costs
•Identifying contractual and standardisation practices, and any regulatory barriers
•Collecting data on both the business and technology infrastructure
2. Operational Efficiency and Energy Efficiency models using full-scale measurements with energy efficiency improvements were developed showing significant fuel savings for a variable speed generator set and the direct current grid power plant
A Mission Planner (part of Predictive Power Management (PPM)) containing the SOV path and speed profile. Basic functionality for remote and autonomous vessels is included to enable automatic sailing between turbines pre-planned via the Operational and the Mission Planners, which will allow for the optimal operation of the vessel power plant.
3. Hazard analysis identified the basic safety management aspects that should be applied to a new and existing safety management systems (SMSs) using new safety features for the SOV control systems, also aiding the cyber-security analysis. This has been applied to the PPM, the mission planner, the autonomous navigation system, and the automated resource management system
4. Developing a business risk model to support decisions on SOV solution options through life, involving data collection for model variables and dependencies, the creation of a graphical model showing uncertainties, KPIs and decisions. A robust decision-making model was developed that models several vessel and operational related variables to define operational performance indicators.
5. A vessel feasibility study and robust resign requirements, including:
•Defining design requirements and operational scenarios for a new vessel concept based upon vessel requirements, and logistics and assets making up the O&M fleet
•Integrating business & business performance models developed in the project
•Several high-level concepts developed (Floatel and SOV types) and different hull shapes
•SOV concept selection for basic design verified through model testing and simulations
6. Defining the safety regulations for windfarm vessels:
•Hazard identification of several operational aspects
•Mapping existing safely rules and their influence on the vessel and operational design
•Risk analysis, particularly with respect to new vessel and operational concepts
•Cost-benefit assessment of the impact of new rules
•Assessing and ranking of hazards to guide the decision making
7. A basic design concept for a medium size SOV enabling the use of alternative energy sources with efficiency gains and cost benefits. A review of the performance indicators and the consideration of critical factors was performed
8. Vessel simulation, testing, demonstration and construction:
•Wind and current load analysis of the new concept vessel design
•Studying vessel motions, particularly with respect to vessel to turbine platform personnel transfer
•Testing two representative SOV models in different conditions (different range of waves, speeds, and headings). A second campaign was performed in the last period on an updated model to improve vessel performance, specially in waves
•Development of a simulator and digital test tank (DTT) to allow assessment of operational efficiency, demonstration of the transfer system and the demonstration of the predictive power management concept. The DTT will be completed and demonstrated in the final period of the project
•Advanced hydrodynamic analysis and time-domain simulations of the hull design, the power and propulsion system design, new control system strategies, transfer solutions, and offshore charging
9. The development of a business case for the vessel, with a sensitivity analysis of the vessel performance in-service wind farm maintenance, considering the impact of, e.g. pricing and technology on turbine installation rate, and the extent of technological innovation and standardisation in O&M delivery
A video describing the project and its achievements can be found here: and the final dissemination webinar here:
15 novel vessel efficiency technologies assessed, including:
•Solar Energy: potential for ~3% fuel reduction
•Hydrogen – Zero emission but a huge cost & logistics challenge
•DC-grid/Variable Speed, very beneficial for SOV-operations
•Wind Power for Floatel
A new vessel concept assesses the advantages and disadvantages of novel designs for windfarm application, comprising:
•Novel hull concepts, including advanced mono-hull and multi-hull designs
•The use of different transfer systems including SOV, SOV with daughter craft and Floatel
•Beyond state of art vessel technologies including: semi-autonomy, alternative fuels, energy efficiency measures, advanced propulsion, manoeuvring, advanced transfer systems
An operational Planner (OP) optimised for an offshore wind farm maintenance fleet, providing on-board and onshore capabilities to pre-assess and pre-plan operations, using route planning, positioning, weather and environment, and expected fuel burn and cost. This has been developed for several case studies and operational scenarios including:
•Single & combination of vessels
•Optimal routing & inspection/maintenance effort assigned
•Use of multiple inputs/outputs
A novel model to predict the strategic impact on the business of windfarm maintenance and operation for logistical solution concepts. This model considers the risks to be assessed throughout the concept developments by understanding the effect of uncertainties over the vessel lifetime. By providing a predictive assessment of uncertain elements of future operations and markets, analysis enables optimal choices about the logistical solution concept, including the SOV design, so that they will be robust in future markets.
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