Semi-floating Offshore Foundation with Restoring Element
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Solution Overview
Problem
Offshore wind turbines in shallow coastal waters face challenges in finding a cost-effective foundation solution that can withstand extreme loads and large deflections due to limited water depth and soft seabed conditions, which often require complex and costly floating foundations or dispense with foundations altogether.
Innovation Solution
A semi-floating foundation design that incorporates a monopile with a reduced anchoring depth and a restoring element, such as buoyancy bodies or flexible anchorages, to allow for significant deflection and tilting stability, shifting the natural frequency below the 1P frequency band and incorporating materials like reinforced concrete or composite materials for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a floating foundation is used to accommodate offshore wind turbines in shallow coastal waters, then the structure can withstand extreme loads and large deflections, but the cost increases significantly and complex anchoring systems are required
Solution Approach 1:
The foundation is divided into two distinct parts: a monopile component embedded in the seabed providing anchoring, and a floating component providing buoyancy and deformability. This segmentation allows each part to perform its specialized function, reducing overall system complexity while maintaining reliability
Solution Approach 2:
The patent combines ground-based foundation (monopile) and floating foundation elements into a hybrid semi-floating foundation. This merging integrates the stability of embedded structures with the deformability of floating structures, achieving cost-effectiveness without sacrificing load-bearing capacity
2Reliability
If a ground foundation with natural frequency above 1P frequency band is used, then resonance vibrations are avoided, but the foundation cannot tolerate large deflections and extreme loads in shallow coastal waters
Solution Approach 1:
The foundation transitions from a static, rigid ground-based structure to a dynamic semi-floating structure that can adapt its natural frequency. By adjusting the buoyancy force and anchoring depth, the natural frequency can be tuned to avoid resonance while accommodating large deflections through controlled flexibility
3Adaptability or versatility
If the natural frequency of the offshore structure is adjusted below the 1P frequency band, then the structure can tolerate large deflections, but resonance vibrations may occur
Solution Approach 1:
The patent employs parameter changes in the buoyancy force and anchoring depth to dynamically adjust the natural frequency of the structure. This allows optimization of both deflection tolerance and resonance avoidance by tuning the system parameters to match specific operational conditions and environmental loads
4Device complexity
If a monopile with reduced anchoring depth is used, then cost is reduced and adaptability to shallow waters is improved, but stability against tipping is compromised
Solution Approach 1:
The floating component acts as a counterweight system, using buoyancy forces to compensate for the reduced anchoring depth. This counterbalancing mechanism provides tilt resistance without requiring deep embedding, maintaining stability while reducing cost and improving adaptability to shallow coastal waters
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
This design provides a cost-effective, tilt-resistant foundation that can withstand extreme loads and large deflections, maintaining stability and reducing the risk of resonance vibrations, while allowing for natural frequency adjustment through varying anchoring depth and buoyancy forces.
Implementation Method 1
the at least one restoring element being designed (e.g. geometrically) in such a way that in the event of an skewed position of the tower, in which the longitudinal extending axis of the tower ends outside of a vertically extending axis, tensile and/or compressive forces can be transferred to the tower by the at least one restoring element
Data Source
AI summary
A foundation for an offshore structure is disclosed. The foundation includes a tower having an anchoring portion anchored in the seabed and a connecting portion arranged at the opposite end. The foundation also includes a power generation system arranged above the water surface connected to the connecting portion of the tower. A natural frequency of the offshore structure lies below an excitation component one times the rotational frequency 1P of at least one exciting component. The foundation also includes at least one restoring element connected to the tower via one or more transition pieces. The restoring element is designed such that, in a skewed position of the tower, tensile and/or compressive forces can be transferred to the tower by means of the restoring element such that the tower can be straightened up.