Introduction
Floating offshore wind turbines present an opportunity to access vast wind resources located far from shore in deeper waters. Designing and implementing floating wind solutions requires extensive research and testing to verify performance and address technical challenges. This research paper provides an in-depth overview of various studies that have been conducted related to floating windmill technology.
Floating Wind Turbine Design Concepts
Several floating turbine concepts have been proposed and tested at various technology readiness levels. The three main floating designs that have received the most attention are spar buoys, tension leg platforms (TLP), and semi-submersibles. Spar buoys resemble long cylindrical structures with ballast at the bottom for stability. TLP designs use taught vertical tendons to keep the platform vertically moored. Semi-submersibles have submerged pontoons to provide buoyancy and an above water central pod to house turbine components.
Each design concept has relative advantages and disadvantages related to fabrication complexity, motion response, installation/maintenance feasibility, and costs. Spar buoys have simpler fabrication but may be more sensitive to waves. TLPs are stable but installation/decommissioning of tendons poses challenges. Semi-submersibles have more complex structures but provide greater stability. Research studies have explored the performance differences between these concepts through numerical modeling, wave tank testing, and full-scale prototype deployments.
Modeling Floating Wind Turbine Dynamics
Accurately predicting the dynamic response of floating wind turbines to environmental conditions like wind and waves is critical for design validation. Researchers have developed sophisticated numerical models and simulation tools to analyze loads and motions. Early studies focused on modeling floating foundations as rigid or multi-body systems. More advanced models now consider flexible blades, towers, and mooring/tendon lines.
Factors influencing modeling complexity include the environmental conditions being simulated, turbine/foundation design parameters, coupled/uncoupled analysis methods, model discretization, and computational resources. Verification and validation against measurement data is needed, but full-scale data remains limited. Simulation tools allow design tradeoffs to be explored cost-effectively before building prototypes. Ongoing model development work aims to better capture nonlinear and viscoelastic influences on floating turbine dynamics.
Prototype Design, Testing and Field Operations
After numerical modeling, floating wind turbine concepts must undergo physical testing to prove performance in realistic conditions. Earlier studies featured small-scale wave tank tests to examine foundation concepts. Larger 1:50 and 1:100 scaled moored floater prototypes were also dynamically tested. More recently, researchers have conducted full-scale field testing of floating wind prototypes up to multi-megawatt sizes.
Full-scale prototype deployments have provided invaluable data for design validation and de-risking floating wind technology. Sensors monitor environmental conditions, structural loads, motions, power production, and system integrity over extended operating periods. Measurements are used to refine numerical models, operation and maintenance procedures, electrical integration strategies, and other critical aspects. Key full-scale prototype projects that have greatly contributed to floating wind research include Hywind Scotland (5 MW), WindFloat Atlantic (2.4 MW), and the Fukushima Forward project (7 MW).
Challenges and Future Research Needs
While significant progress has been made, more research and testing is still needed before floating offshore wind reaches industrialization and scalable deployment. Key ongoing research priorities relate to reducing costs, improving reliability, and verifying technology in various sea states and water depths. Challenges include optimizing mooring/tendon systems, developing standardization, addressing environmental and ecological impacts, advancing installation/O&M methods, grid integration, and lifecycle performance/durability. Further research on coupled dynamics, aero-hydro-elasticity, and system identification using advanced sensor technologies also holds promise.
International collaborations are driving technology advancements through demonstrations of larger prototype arrays. Research hubs like the National Renewable Energy Laboratory (NREL) and the MaREI Center in Ireland continue working to validate new floating concepts. With further innovations, floating offshore wind has potential to play a major role in the transition to renewable energy on a global scale. Sustained research efforts will be needed to fully prove and optimize this emerging technology.
Conclusion
This research paper provided an overview of the extensive studies conducted related to advancing floating windmill technology. Key findings from modeling, testing, and full-scale prototype deployments were discussed. While promising progress has been made in designing and proving various floating concepts, further research and development is still required before floating offshore wind achieves maturity and widespread industrial deployment. Areas needing additional focus were identified, such as reducing costs, optimizing technical and operational aspects, quantifying environmental impacts, and validating larger prototype arrays in diverse sea states. With continued innovations and testing, floating offshore wind holds vast potential to access wind resources globally in deeper offshore waters.
Andrew Stroud