Prof. Claire De Marco and Ms Diane Scicluna attended the International Conference in Naval Architecture and Marine Engineering (MARTECH2022) conference in Lisbon, Portugal 24 – 26 May 2022. Ms Scicluna presented her paper entitled “Modelling the Hydrostatic Stability Characteristics of a Self-Aligning Floating Offshore Wind Turbine” as part of her M.Sc. by Research in Mechanical Engineering at the University of Malta. The research project, MedFOWT (A versatile Floating Offshore Wind Turbine platform concept for central Mediterranean conditions), was funded by the Maritime Seed Award 2020 and the collaborative programme of the VENTuRE (Project no. 856887) EU funded H2020 project. The conference covered engineering topics including:
- Ship Design (structures, hydrodynamics, machinery)
- Ship Building and Repair
- Maritime Transportation and Ports
- Fishing and Aquaculture
- Energy Resources
- Military and Surveillance Vessels
- Recreational Craft and Maritime Tourism
Paper abstract: There has been an increased interest in renewable energy due to the rising energy demands, the shortage of fossil fuels, and environmental issues. Through wind energy there is an opportunity to overcome these issues while using clean energy. For islands such as Malta, which are limited in terms of spatial availability and possess deep near-shore waters, wind energy is only possible through the use of floating substructure technology. The proposed design must take into consideration the spatial limitations and deep nearshore waters present in the Maltese archipelago as well as include innovative features. Therefore the design supports an 8 MW turbine, has a dual-pontoon floating substructure and four symmetrical aerofoil shaped columns which promote the self-alignment characteristics of the structure. The design also has a deck included for on-board energy storage and is suitable for manufacturing in the ship-building dock in the Maltese harbour.
In order to test the stability of the structure, the DNV ST-0119 standard requirements were used which required that the area under the righting-moment curve to the second intercept or downflooding angle in excess of the area under the wind heeling moment curve ≥ 130% and that the righting-moment curve should be positive over range of angles from upright to the second intercept. The structure was tested under no wind conditions and under rated wind conditions and ballasted equally from 0 – 100% capacity.
The structure exhibited good stability characteristics and passed all standard requirements both in the pitching axis and in the heeling axis. The proposed concept exhibited more favourable stability characteristics in the heeling axis than in the pitching axis which is synonymous with dual-pontoon structures. Through the analysis carried out it was revealed that the structure experiences a large trim angle from 80% – 100% capacity which is caused due to the sudden decrease in waterplane area caused by the total submersion of the pontoons.