FFATA: Floating Offshore Wind Turbines: Conceptual Assessment of Highly Compliant Platforms Using Theory, Design and Simulation
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The objective of this project is to develop new theory and numerical tools to accurately simulate the behavior of floating offshore wind turbines subject to large angular displacements, and use those results to assess the economic and technical feasibility of potential next-generation structures. Intellectual Merit: The potential for a change in design philosophy from highly rigid wind turbine support structures to highly compliant ones will be investigated. New designs and operational control systems will be developed that allow the tower to lean significantly in response to the wind force, and the technical and economic merits of these new designs will be assessed. A shift to highly compliant structures would be a major shift in design philosophy paralleling that of the offshore oil business as drilling and production moved into very deep water. A family of new designs will be developed with rotational restoring properties ranging from very stiff (very small lean of the tower due to wind) to very compliant (leans easily). These designs will be completed in sufficient detail to identify all challenges to existing technology. Computing the dynamics of these highly compliant structures is both difficult and important, in part because of the gyroscopic effect of the huge whirling blades. This challenge will be met through theoretical development and practical implementation of a new dynamic simulation methodology that could prove useful beyond the field of wind energy to other rotating equipment subject to large angular displacements. The new method will be based on conservation of angular momentum in Euler-space for a cloud of rigid bodies representing a floating wind turbine. Development of this new theory and simulation methodology is necessary because conventional wind turbine design tools do not consider the order of rotation of angular deflections and so are inadequate for large angular motions. Additionally, the overall system is extremely nonlinear: the environmental forcing, hydrostatic restoring moments, time-domain control system, and gyroscopic effects are all nonlinear; accurate simulation in the time domain is necessary to assess the viability of the any design concept. Proof that highly compliant support structures have both technical and economic value could begin a technical revolution that enables economic development of wind farms in very challenging deepwater offshore locations. Broader Impacts: As the US continues to work towards ``greener?? sources of alternative energy, there is increasing interest in installing wind turbines offshore, where good winds and adequate space are both available. Public pressure continues to push for having these structures beyond sight of land, and new technologies are needed for more cost-effective generation of wind-powered electricity in very deep waters. This proposal explores for the first time the viability of highly compliant structures for that purpose, the result of which could be a dramatic shift in the design philosophy for floating wind turbines. The education and outreach components include course development, education of graduate and undergraduate students and outreach to K-12 students and teachers as well as to at-risk college students. The teaching will include development of innovative course curricula on off-shore wind energy to teach about design of both bottom-founded and floating offshore wind turbines, and will include education of graduate and undergraduate students in the rapidly advancing area of offshore wind turbine design. Outreach to K?12 students and teachers will be include presentations on offshore energy by the PI and his graduate students in the well-established ``Sea Camp?? program at Texas A&M at Galveston; outreach to at-risk college students, who include many historically underrepresented and financially disadvantaged students, will be through an established program.