Phase II of Stage II of the Floating Wind JIP was delivered from 2018-2019 and focused on technology innovations and challenges for turbine requirements and foundations scaling, heavy lift offshore operations, dynamic export cable development and monitoring and inspection.
The key findings of the first phase of technical projects were published in a summary report.
Phase II technical studies and projects
Turbine requirement and foundation scaling
Turbine size is increasing rapidly, with 13-15MW turbines expected to be on the market by 2025. Floating substructures have specific design requirements compared to turbines for bottom-fixed offshore wind that need to be better understood. Scaling of turbine power output will also be a key driver of cost reduction, so it is critical to define the estimated scaling factors for different floater types. This study was initiated in order to assess the suitability of the next generation of turbines for commercial-scale floating wind farms.
Heavy lift offshore operations
Commercial-scale floating wind farms will require a different approach to fixed offshore wind due to the water depth and likely size of future turbines. Deep waters and large turbines pose challenges to undertaking large lifting operations offshore. For several floating wind concepts, port-side operations are unlikely to be feasible due to draft and/or towing constraints. Even for concepts advocating port-side maintenance operations, there are challenges regarding the economic and technical viability of such an approach. In a large-scale floating wind farm, it is possible that undertaking more operations in-situ at the offshore site could be advantageous, and in some cases, essential. This study investigated the technical feasibility and challenges associated with heavy lift offshore operations in a floating wind farm, during both installation and heavy maintenance.
Dynamic export cables
Early prototypes and first arrays of floating wind turbines have been connected to shore using MV power cables (of 22-66kV). Large commercial-scale floating wind farms at deep-water sites will need floating substations to increase the voltage before exporting power back to shore. The export cables will need to be more robust than conventional static cables to withstand the motions of a floating substation. These cables are known as dynamic export cables, and previous Floating Wind JIP studies have highlighted a lack of suitable dynamic cables currently available on the market for future floating wind projects.
This project assessed the challenges to the development of high voltage dynamic power cables for export purposes in floating offshore wind farms. An international competition was launched for cable manufacturers to support the design, initial testing and development of dynamic cables ranging from 130kV to 250kV. Five cable manufacturers have been supported to develop and test their designs in preparation for product qualification and future manufacturing.
Competition winners were:
- Aker Solutions (Norway)
- Furukawa Electric Co. (Japan)
- Hellenic Cables S.A. (Greece)
- JDR Cable Systems (UK)
- Zhongtian Technology Submarine Cable Co., Ltd [ZTT] (China)
Monitoring and inspection
Monitoring and inspection methods for bottom-fixed offshore wind farms have improved considerably in recent years, however, floating wind farms introduce novel elements that may require alternative approaches and new technologies. These novel elements can result in more conservative monitoring and inspection requirements and higher operation and maintenance costs across a wind farm. There is a need to better understand current and future requirements and identify technology innovations that could reduce requirements and associated costs. This study assessed monitoring and inspections requirements based on national and international guidelines and standards, as well as the technologies available.