The overall objective of this proposed research is to gain fundamental understanding of ground-tethered wind energy (GTE) systems through modeling, advanced numerical simulation, and physical experiments on GTE system components. GTE systems are a scalable, next-generation concept for wind energy, where a rigid-wing glider or kite is held aloft by the wind and controlled in flight by an automatic control system. The glider or kite is connected to a flexible tether that transmits generated aerodynamic forces to a power generation system on the ground. The main advantage of GTE systems is that they may be able to generate energy in locations where wind speeds are too low to make wind turbines cost-effective.
Although GTE systems are attracting attention from the US wind industry, relatively little work has been done to assess the technical challenges that must be overcome to provide cost-effective power. The work proposed here will lay the foundation for understanding how such systems behave though integration of analytical models and robust control solutions with numerical simulations of sufficient accuracy suitable for system design, wind tunnel testing on gliders and kite components, and evaluation of a GTE demonstration system. Specifically, the proposed numerical simulations would constitute the first computational fluid dynamics (CFD) study of ground tethered energy systems, fully accounting for the flexibility of the kite/wing and the influence of the tethers. The coupling of CFD simulations with developed analytical models and control analyses will predict the behavior and robustness of the GTE system under different conditions and control solutions. Robust control solutions that can control the kite to ensure optimal cross-wind motions when exposed to wind gusts and turbulence are the enabling technology for GTE systems. Overall, this integrated approach will seek to understand the control and aerodynamic properties of kite systems, and propose actuators, sensors and tracking controllers to yield optimal periodic trajectories in the presence of modeling errors and wind disturbances. Concurrently, the proposed work also seeks to advance fundamental knowledge in aerodynamics of flexible structures, novel control system applications, and numerical simulation of complex systems.
The education and outreach plan will provide a variety of experiences that will integrate the research outcomes with student learning. The proposed work will provide significant research experiences for undergraduate students at Worchester Polytechnic Institute (WPI) through design projects in existing courses, and the creation of an undergraduate course in renewable energy that will use the developed GTE simulations and experiments in course laboratories. The PI will also incorporate wind energy topics such as ground tethered energy systems and floating offshore wind turbines into the aerospace engineering segment of the WPI Summer Frontiers Program for high school juniors and seniors, which provides over 200 students per year with a two-week long college experience in various STEM disciplines. Finally, the PI team will prepare a book titled Ground Tethered Energy Systems for Power Generation.