Credit: Beridi Maritime.
We are excited to be part of Beridi’s Maritime team to bring this innovative hybrid concept to reality.
FWTC has been supporting Beridi with control design, fully-coupled loads analyses, ultimate and fatigue limit state design of tower and tower-floater interface, and structural design of the tower-Archime3 connection and floater.
Cannot wait to see the demo in open waters! Go Beridi!
Phase I of ARPA-E's ATLANTIS has come to an end. A lot of progress has been made in the Control-Co-Design (CCD) of the USFLOWT. FWTC has been working with Colorado School of Mines (CSM) to support this project that had been initiated in 2019 by one of our very own principals (Rick Damiani) while at NREL, and that NREL's Senu Sirnivas still leads today together with CSM, the University Colorado at Boulder, the University of Virginia, and the American Bureau of Shipping. Recently, USFLOWT was showcased at the ARPA-E Summit 2022 in Denver, and Secretary of Energy Jennifer Granholm paid a nice visit to the USFLOWT booth.
We hope USFLOWT will continue efforts toward a new testing phase, with a subscale demonstration project that would see us involved as aero-hydro-structural designers. Whatever the outcome of ATLANTIS's Phase II will be, we have had a great pleasure working with the USFLOWT team, a talented group of individuals that are truly passionate about making this concept a reality.
A moment from ARPA-E Summit 2022. USFLOWT PI Team with Dr. Mario Garcia-Sanz of ARPA-E. Photo credit: Dr. Lucy Pao (CU).
Views and Cross-sections of the Designed Concrete Suction Anchor
We have submitted our final report, and this concludes our feasibility study on the applicability of a new concrete suction anchor for floating wind. In the course of this project, FWTC devised innovative solutions encompassing buoyancy chamber, spiral post-tensioning, and padeye connection, that are now all patent-pending. We believe that there is ample potential for further exploitation of these technologies that lower LCOE for floating offshore wind. We want to thank the entire team for their contributions, and particularly Ramboll and Cathie for helping FWTC with design basis, load assessments, and steel suction anchor designs. Please reach out to us to know more about how we can help your floating offshore wind project make use of these new technologies.
We are grateful for working with Colorado School of Mines (CSM) on this project that Dr. Rick Damiani had led while at NREL.
With CSM, we are optimizing the structural design of the SpiderFLOAT, an innovative substructure invented by Dr. R. Damiani (FWTC), Mr. S. Sirnivas (NREL), and Mr. F. Wendt (Ramboll).
The project is part of ARPA-e's ATLANTIS program, is led by NREL and Colorado School of Mines, and seeks to use control-co-design techniques to minimize costs in the OWT floating substructure. Other partners include the University of Colorado at Boulder, the University of Virginia, and the American Bureau of Shipping.
Tasks include optimization of concrete structures and aero-hydro-servo-elastic simulations of the entire OWT.
Mooring accounts for around 15-20% of total floating wind costs. We have optimized an anchoring system for floating offshore wind by combining the versatility and low-cost of concrete materials with the efficiency of a suction anchor. Concrete can be cast in many forms and can leverage the existing local supply chain. Moving away from heavy steel-use for offshore wind structures is a trend that other experienced players in this field, e.g., Equinor and Ideol, have already embraced. Additionally we envisioned adding flotation capabilities to the anchor to allow for wet-towing. With this new design, we propose to cut costs by 80% in the anchoring systems CaPEx while maintaining all the advantages of a suction-assisted installation anchor (omni-directional loading capacity, installation accuracy, and environmentally friendly instillation and removal).
The suction anchor is made of two chambers. The main suction chamber sits at the bottom. At the top of the anchor, a special buoyancy chamber (FWTC, patent pending) is realized via a pair of dome-shape walls. The domes and the hatches are designed to keep the domes at rest or under compression at all times during installation, operation, and removal. This structural arrangement allows for the minimization of the necessary reinforcement and for the creation of additional buoyancy. With an air bag creating a water-tight seal at the bottom, and with the buoyancy chamber evacuated, the anchor can be wet-towed to the installation site with inexpensive vessels.
This new, patent-pending, three-dimensional post-tensioning arrangement allows us to mitigate longitudinal, radial, and circumferential tensile stresses that would otherwise arise in the suction skirt under certain loading conditions. This system allows for an efficient use of concrete and reduced use of steel reinforcement in the anchor, making it very economically attractive.
At the padeye, loads from the mooring line fairlead give rise to stress concentration and localized shear and bending in the concrete walls that must be overcome with an ad-hoc structural design. FWTC conceived three patent-pending solutions: an external steel fascia with load-transferring pins fastened to a recess in the suction skirt; a tendon assisted load distribution strategy; an integrated plate that uses existing tendons.
Ultimate horizontal capacity vs. outer anchor diameter for different clay undrained shear strengths.
We designed the anchor for both a 10-MW and a 15-MW OWT system at sites offshore Scotland. We have also carried out a sensitivity analysis showing a wide range of soil and water conditions for this new anchor applicability. From a design standpoint, the anchor is structurally efficient and reliable; from an economic standpoint, the new anchor shows a great cost-cutting advantage for developers of floating offshore wind.
The next steps in the anchor design will require structural testing, sea-trials, and 3rd-party certification.
If interested in this technology, please contact us.
