Subsurface Mooring Buoy Swivel for Offshore Renewable Energy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mooring systems for offshore renewable energy systems, particularly those involving single-point moorings, are exposed to surface damage and fatigue due to wind, waves, and tides, and often require multiple mooring lines, which complicate installation and maintenance.
Innovation Solution
A sub-surface buoyant element with a swivel system that allows a floating unit to rotate around a fixed seabed component, using a tether system kept in tension by upthrust, reducing the number of mooring lines and minimizing surface exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-point mooring buoy is used at the surface, then the number of mooring lines is reduced to one, but the buoy is exposed to damage and fatigue from wind, waves and tides
Solution Approach 1:
The patent moves the mooring buoy from the traditional surface location to a sub-surface position, changing the spatial dimension of operation. The buoy operates at a depth where it is not directly exposed to wind and wave action, while still maintaining effective mooring control through the single line connection to the seabed anchor.
Solution Approach 2:
The patent introduces a swivel mechanism as an intermediary component between the mooring line and the buoy. This swivel allows the buoy to rotate and move freely while maintaining the tension in the mooring line, enabling the buoy to respond to currents and waves without direct surface exposure while still providing effective mooring control.
2Stability of the object's composition
If multiple mooring lines are used to anchor the buoy, then the buoy is stable and resistant to surface forces, but installation and maintenance become more complex
Solution Approach 1:
The patent divides the mooring system into distinct functional segments: a single mooring line for tension control, a swivel mechanism for rotational freedom, and a sub-surface buoy for positioning. This segmentation allows each component to be optimized independently and simplifies installation and maintenance compared to a multi-line system.
Solution Approach 2:
The patent employs a dynamic swivel mechanism that allows the buoy to rotate and adjust its orientation freely while maintaining mooring line tension. This dynamic capability provides stability against surface forces without requiring multiple fixed mooring lines, thereby reducing installation and maintenance complexity.
3Ease of repair
If the buoy is positioned at the surface for easy access, then maintenance is simplified, but the buoy is exposed to damaging environmental conditions
Solution Approach 1:
The patent positions the buoy in the sub-surface dimension rather than at the surface, creating a compromise location that is accessible enough for maintenance while being protected from the most damaging environmental conditions. The single line connection and swivel mechanism maintain effectiveness at this intermediate depth.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enables reduced mooring line loads and stress, allowing for greater freedom of movement and stability of floating units, while minimizing damage from surface conditions and simplifying installation and maintenance.
Implementation Method 1
A tensioned member extends between a sub-surface buoyant element and a fixed component on the seabed and is kept in tension by upthrust of the buoyant element
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A mooring system for a floating electric power producing unit such as a wind turbine or a wave energy converter comprises a buoyant element held beneath the surface and a swivel supported by the buoyant element. The swivel comprises a static part that is held against angular movement about an upright axis and a rotating part that is movable angularly relative to the static part about the upright axis. A mooring link extends between the power producing unit and a mooring point supported by the buoyant element. A conductor link extends between the power producing unit and a connector supported by the buoyant element. The mooring point and the conductor link are movable angularly about the upright axis together with the rotating part of the swivel. Angular movement of the mooring link about the upright axis drives corresponding angular movement of the conductor link about the upright axis.