L-Shaped Offshore Rack Structure for Motion-Free Barge Transfer
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Solution Overview
Problem
The offshore wind turbine installation industry faces challenges in safely and cost-effectively transporting and installing wind turbine components using feeder transport vessels that comply with the U.S. Jones Act, as existing systems require expensive customized vessels or complex motion compensating equipment, and there is a need for a method that eliminates relative movement between the jack-up and barge to enhance operational efficiency and reduce costs.
Innovation Solution
A rack structure system is fitted to the transom of a self-elevating vessel to lift feeder transport barges out of the sea, using a rack and pinion jacking system to vertically lower and raise the rack structure, allowing the barge and its cargo to be secured over the submerged rack, and then elevated by the jack-up's onboard leg jacking system, enabling direct installation of components onto the seabed foundation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a feeder transport vessel is used to transport wind turbine components from mainland dockside to an offshore jack-up, then transportation capability is improved, but relative movement between the vessel and jack-up causes operational inefficiency and increased wear
Solution Approach 1:
A motion compensation system with actuators and sensors is introduced as an intermediary between the feeder transport vessel and the jack-up. The system actively counteracts relative movements by adjusting the position of the vessel or the jack-up's receiving structure, thereby eliminating the harmful relative motion while maintaining the transportation capability
Solution Approach 2:
The system dynamically changes operational parameters (position, orientation) of the vessel or jack-up structure in response to environmental conditions and operational requirements. By continuously adjusting these parameters, the system maintains optimal alignment and eliminates relative movement during component transfer operations
2Productivity
If expensive customized vessels or motion compensating equipment are used to eliminate relative movement, then operational efficiency is improved, but construction and equipment costs increase to $600 million
Solution Approach 1:
The motion compensation system is divided into modular components (sensors, actuators, control systems) that can be selectively deployed based on operational needs. This segmentation allows for a more cost-effective solution compared to fully customized vessels, as standard components can be used and only the necessary level of compensation is implemented
Solution Approach 2:
The motion compensation system is designed to be multi-functional, serving both to eliminate relative movement during operations and to provide stabilization during various operational phases. This universality reduces the need for separate specialized equipment, thereby reducing overall costs while maintaining operational efficiency
3Ease of operation
If the jack-up remains in the water during component installation, then accessibility is improved, but relative movement with the barge increases wear and reduces uptime
Solution Approach 1:
The jack-up structure dynamically adjusts its elevation, transitioning between submerged and elevated positions based on operational requirements. During component transfer, the jack-up elevates to eliminate relative movement and wear. This dynamic positioning maintains accessibility while reducing harmful effects during critical operations
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 system eliminates relative motion between the jack-up and barge, reducing wear on the jack-up, increasing operational uptime, and lowering construction costs to approximately $300 million for a U.S. Jones Act compliant offshore jack-up, compared to $600 million for existing solutions, while ensuring safe and efficient installation of wind turbine components.
Implementation Method 1
using a rack and pinion jacking system to vertically lower and raise the rack structure
Implementation Method 2
elevated by the jack-up's onboard leg jacking system
Data Source
AI summary
A deployed L-shaped rack structure interengaged with a self-elevating vessel is used for supporting a feeder transport vessel, such as an ocean or sea barge, to eliminate relative motion or movement between the vessels. Some of the proposed rack structures are movable between a stowed position and a deployed position. The method of use for the movable rack structures includes the self-elevating vessel arriving at a predetermined location, elevating the hull of the self-elevating to a suitable height above the sea surface at a desired still water line (SWL) to create an air gap, and then deploying the rack structure. A feeder transport vessel, with its cargo and/or components, can then be floated over the deployed rack structure. The self-elevating vessel then uses its jacking system including a plurality of legs supported on the seabed to raise the feeder transport vessel and its cargo and/or components to a desired height above the SWL. From this position relative motion between the self-elevating vessel and transport vessel is eliminated so that the self-elevating vessel lifting device, such as a crane, can be more safely used to install energy components, such as wind turbine components. A bottom supported tower/column section could also be assembled and installed in seabed using the self-elevating vessel and rack structure along with the lifting device. A fixed rack structure system and its method can also be advantageously used with a self-elevating vessel. The systems and methods could be used in reversing the method or steps for deinstallation of the energy components installed in the sea.