World - Innovation in floating wind will be crucial to the future of offshore energy
With offshore floating wind as a proven commercial reality, the challenges associated with the industry are now focused on delivering at scale, but there are still key innovation issues to be resolved across the industry.
The global floating offshore wind industry is expected to reach 126 MW by the end of 2021 and to grow to 70 GW by 2040. As well as powering electricity grids around the world, floating wind will help decarbonize offshore oil and gas production and play a critical role in green hydrogen production.
Developers, insurers, financers and all stakeholders serious about making the significant advances needed to upscale floating offshore wind capacity to meet these expectations will be interested in reducing project risk, improving installation time and building robust supply chains that will function throughout their asset’s lifecycle.
Operational efficiency and technology options will continue to evolve over time. The challenge for developers is to remain open to innovation and look for continued improvement without impeding progress.
Foundation pros and cons
Choosing the best foundation technology is critical to delivering the best levelized cost of energy (LCOE) for floating offshore wind projects. The decision should be based on assessment of available port infrastructure and supply chains as much as water depth and environmental conditions.
As much as economies of scale based on consistency and repeatability are appealing, the choice of foundation type should not be made before site analysis. The physical attributes of foundations will influence where they can be fabricated and the ease with which they can be towed and moored, and detailed motion response should be compared on a case-by-case basis for any specific location. A foundation perfectly suited to the Mediterranean may not be viable in the Pacific.
There are currently four main types to choose from, with multiple options for each type and still several more innovative concepts under development. Firstly, spar buoys are cylindrical in shape and very stable given their deep draft with ballast creating a low center of gravity. They require a deep water area for fabrication and also for maintenance if towed to shore. They can be made from steel or concrete, and are conventionally catenary moored.
The other option is semi-submersible platforms which consist of typically three connected vertical columns. Considered suitable for most locations given that relatively shallow water required at fabrication site, stable for tow during installation and O&M, their biggest disadvantage is being prone to heave motion which is difficult to prevent without increased fabrication complexity. Semi-submersibles are generally fabricated from steel and conventionally catenary moored.
Tension leg platforms typically have a central column and arms connected to tensioned tendons. They can be assembled onshore or in a dry dock, but they can be harder to keep stable during transport and installation than other concepts. Their biggest advantage is that the taught mooring lines significantly reduce the length of mooring lines for deep water locations in comparison to a catenary moored structure.
Damping pool structures have a square barge structure which contains a damping pool that has been tuned to reduce the foundation motion. They can be made from concrete or steel — a factor that can increase flexibility of the fabrication location.
Understanding the installation methodology and defining the developments and operations and maintenance strategy up front is also critical to determining which solutions are feasible and where the challenges lie. Initial findings from UK Offshore Renewable Energy Catapult (ORE) for a select set of scenarios suggest that it is cheaper to tow turbines to shore where crane operations are simpler and there is ready access to onshore services and personnel.