Future offshore wind farms will be built in deeper and deeper water, leading to foundation piles that keep increasing in size and weight. Installation of these ‘XL’ monopiles will be challenging and far from optimal unless new installation technologies are developed. Nowadays, most monopiles are installed using purpose built jack-up vessels, however, for XL monopiles, these jack-ups have too little lifting and jacking capacity. Alternatively, monopiles are being installed with floating heavy lift vessels. These vessels have sufficient crane and payload capacity, however, they are sensible to wave motions and have rather limited workability; you cannot keep a monopile still on a moving vessel.
To utilize the ample crane and payload capacity of floating vessels, but to avoid the sensibility to waves of the operation, TWD and Barge Master have developed the Motion Compensated Pile Gripper. The principle function of the Motion Compensated Pile Gripper is to hold a monopile perfectly vertical by counteracting the wave motions of the vessel on which it is fixed.
The impact of this innovative technology on the installation cycle has been investigated for different vessel types, both for existing assets as for new-built floating heavy lift vessels. Due to a higher pay-load, reduced vessel day-rate and time savings related to the jacking process, a reduction of the monopile installation costs up to 40% can be achieved.
Extensive research related to the operational safety and interaction of the gripper with the vessel’s DP-system resulted in a reliable and redundant installation method. Together with certifying bodies, installation contractors and wind farm developers, TWD and Barge Master continuously refine this game changing solution, aiming for a full scale demonstration of the technology in 2018.