A Novel Construction Method for Deployment of Offshore Wind Spars Using Existing Port Infrastructure

Abstract: With the rapid advancement of the floating offshore wind turbine (FOWT) industry, construction of FOWT systems for utility scale deployment will require rapid construction and technologies with port-friendly attributes. In the U.S. currently, only a handful of ports or fabrication yards on the East, Gulf and West Coasts have capabilities and the capacity to be scaled for mass production of floating wind systems. While the industry’s supply chain struggles to increase capacity, technologies amendable to efficient and novel construction or fabrication methods can accelerate the achievement of utility-scale deployments. This paper demonstrates and discusses one of such potential construction methods: the application of steel-concrete-steel construction to a floating wind spar concept developed by the authors.

A recent OTC paper authored by our team introduced a novel spar concept for floating wind turbines, proposing implementation of structural steel-concrete-steel composite wall system (SC) for offshore wind spars. This construction method has already been successfully used onshore for high rise building and nuclear power plant applications. The SC system utilizes a layer of concrete placed between steel plates, which act in lieu of reinforcing bars. There is composite action between the steel plates and the concrete layer between them, with use of tie bars as required, and with the SC wall essentially acting as a shear wall. Use of this system has resulted in considerable savings in building construction time and the system has been proven safe and reliable through years of research and testing. Another major advantage of this construction method is that existing ports can implement it without extensive investment towards obtaining deeper drafts for the dock. Rather, spatial expansions or modifications to existing space may be required to accommodate the serial production of multiple units concurrently, to meet installation targets.

Our study envisions ports where SC spar production lines would be efficiently operating, resulting in a streamlined spar production assembly that would enable rapid deployment of hull systems. Such an assembly would satisfy the high demand for a quick turnaround in the production of offshore wind turbines leveraging local workforce and materials. This is especially important, considering that very few nations are currently on track to achieve offshore wind energy goals by 2030, with most nations around the world already falling behind on these carbon emission reduction plans. More specifically, and according to COP28, the operational offshore wind capacity is estimated to reach 250 GW worldwide by 2030, which is about half the target of 494 GW set by the International Renewable Energy Agency (IRENA), in order to keep global warming under control.

Our paper presents assembly options for mass production of SC spars at ports, as well as the associated port structures or port adaptations to support these production assemblies. Such streamlined construction and assembly would substantially obviate supply chain constraints in the deployment of offshore wind farms, thereby accelerating the industry’s efforts towards reducing carbon emissions and ramping up green energy gigawatt-scale production. Additionally, this production approach will benefit local communities and ports without requiring a large investment.

How does this project / topic contribute to the advancement of the industry and profession?: The SC spar concept for offshore wind turbines has been presented in a recent OTC paper. Among its many advantages is that it does not require a deep draft dry dock construction, thereby lowering any port infrastructure development costs. To accommodate its successful deployment, existing ports may have to be upgraded, and new ports may need to be constructed. In that regard, a review of the port infrastructure and fabrication aspects of this newly proposed SC spar concept for offshore wind turbines will further contribute to advancement of the port industry.

Does the project / topic implement new and innovative techniques, materials, technologies, and delivery methods?: SC is a novel steel-concrete-steel composite structural wall system that that has been developed over the past two decades and has seen successful implementation for onshore applications. A recent OTC paper has introduced the SC spar concept, i.e. an adaptation of the SC wall system to offshore wind turbine applications. This paper presents a review of the newly proposed SC spar system from the perspective of port infrastructure and fabrication. It contains elements of innovation regarding method of construction, technology, and delivery using existing port infrastructure across the US.

What was the most challenging aspect of your project / topic and how did you handle it to ensure success?: The topic presented in this paper is not a single-area topic but called for the engagement, coordination, and collaboration of experts from several disciplines including structural engineering, naval architecture, onshore structural research, marine and offshore engineering.

Who is the target audience for this paper?: The audience targeted by this paper includes offshore wind developers, port officials, marine engineers, offshore structural engineers, coastal engineers, and offshore energy professionals in general, especially those engaged in offshore wind farm design and deployment. Steel fabricators and professionals engaged in composite steel-concrete construction are also part of the target audience for this paper.