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Reporting period: 2019-11-01 to 2021-04-30

The problem:
The mooring system of a floating offshore wind turbines (FOWT) is composed by several lines anchored to the seabed that keep the platform in the desired location. Mooring systems are critical components due to their impact in the stability, structural design and dynamics of the platform and the associated risk of collapse of the whole system in case of failure. Oil&Gas (O&G) has a long track record and experience in mooring systems design and operation. However, despite mooring components are designed for a typical lifetime of 20 years, high safety factors are applied and integrity management plans are implemented (including monitoring and inspection) failure do happen. Between 2000 and 2013, at least 42 mooring failures occurred in permanent Floating Production Units in the UK, resulting in partial or total replacements, or pre-emptive remedial interventions.
Mooring systems’ design principles and integrity management plans used in FOW so far have been based on O&G recommended practices. Since a Floating Offshore Wind (FOW) farm of 500MW is assumed to have more than 150 mooring lines, the situation suggests that FOW industry will need to take action to mitigate the probability of failure in a much more efficient way.
Consequently, there is a need to develop a more efficient integrity management approach based on accurate and reliable monitoring technologies and appropriate risk-based inspection approaches specific to FOW to reduce operational costs and increase annual energy production (reduce losses).

The need:
Wind energy development will contribute with a 40% reduction of the CO2 emissions in the European Union by 2030, the decarbonisation of the economy being part of the Energy Union Strategy. The SET-Plan Declaration on Strategic Targets in the Context of an Initiative for Global Leadership in Offshore Wind states: “Wind energy is the renewable energy technology expected to provide the largest contribution to the targets for 2020 and beyond.” It is expected that by 2030 21-24% of electricity supply will come from wind. In this context, “Offshore wind (OW) represents a significant future opportunity”. However, floating offshore costs are still substantially above grid parity, and significant innovation is needed. In particular, the SET-Plan Declaration targets for offshore floating wind energy an objective for Levelised Cost of Energy (LCOE) of 12 ct€/kWh by 2025 and 9ct€/kWh by 2030, while these values are far away from the LCOE achieved for prototype (20.1ct€/kWh) and pre-commercial (16.6ct€/kWh) projects like Hywind Scotland.

MooringSense aims at reducing FOW operational costs by 10-15% and increasing operational efficiency by means of an increase of Annual Energy Production by 2-3%, through the development of more efficient strategies and tools for mooring system integrity management and control. MooringSense will take advantage of mooring systems’ updated condition information, provided by a Digital Twin (DT) and innovative monitoring technologies, to allow the implementation risk-based integrity management plans and more holistic control strategies to reduce OPEX and increase energy production of FOW farms.
The work carried out during the first 18 months of project execution has been mainly focused on WP1 (Project Management), WP2 (Analysis and Definition of the Reference Case), WP3 (Development of Mooring System – Digital Twin), WP4 (Development of the Smart Sensor) and WP8 (Communication, Dissemination & Exploitation). However, some progress has been achieved in rest of WPs that started also within this period. This is the case of WP5 (Developmento of the Structural Health Monitoring Solution), WP6 (Integrity Management and Control Strategies), WP7 (Integration and Validation of the Solution), and WP9 (Ethics requirements).

During this project execution period, the technical work has mainly consisted in:
- State-of-the-art revision and update of mooring systems’ integrity management technologies and degradation mechanisms modelling.
- Definition of the reference case and the baseline to be used in the project development for the MooringSense concept implementation and impact assessment
- Definition of the MooringSense Digital Twin (DT) architecture.
- Definition of functional specifications and validation procedures for the components of MooringSense.
- Development of first version of GNSS algorithms for smart sensor.
- Definition of the numerical modelling techniques to assess the degradation, failure and remaining Useful Life of mooring lines.
- Definition of SHM Solution and Big data approach.
- Development of the initial coupled model, including a baseline controller for the reference case.
- Improvement of TNO’s cost modelling tool.
Additionally, the consortium has paid an important effort related to the communication and dissemination of the project. At this regard, the activity consisted in:
- Definition of communication and dissemination plans, including the elaboration of procedures and tools for coordination and monitoring.
- Development of communication and dissemination materials
- Implementation of communication and dissemination activities.
Moreover, it is also significant the effort paid to the definition and set up of project coordination measures, including the elaboration of procedures and tools, identification of roles, etc.
1) DT of the Mooring System: To develop a DT technology for FOW that will integrate a detailed digital replica of the mooring system.
2) Smart Motion Sensor: To develop a very low-cost and robust smart motion sensor to provide highly accurate Attitude, Position, Velocity and Time information, as well as, statistical distinguishing motion features that are representative of mooring system performance.
3) SHM system: Development of early fault detection algorithms under a data-driven approach that are able to exploit motion GNSS measurements and the predictive operation capabilities provided by the DT to detect and classify damages in the mooring systems.
4) FOWT Control: To develop control strategies to optimize operation at wind farm level by making use of floating platform motion and mooring system condition information.
5) Integrity Management Strategy: To develop a mooring integrity management strategy to leverage the MooringSense developments intended to reduce operational costs and to increase efficiency while keeping risks in acceptable levels.
Conceptual representation of MooringSense
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