Dynamics of a Kinetic Energy Storage Device for a Translating Hydrokinetic System

Current hydropower is sourced predominately from dams, which have several ecological and societal issues. Despite growing demand for energy, dam construction has recently been at a standstill. Hydrokinetic systems are new methods of harvesting renewable energy from rivers without requiring dams. Hydrokites, a subset of hydrokinetic systems, use a translating hydrofoil to generate electricity. Previous models of hydrokite systems have been promising, but their performance in experimental settings has not been as expected. One possible cause for this discrepancy is a loss in system energy when the hydrofoil reaches the end of its stroke, resulting in significantly less power generation. This thesis proposes an alternative hydrokite model that incorporates a flywheel to store kinetic energy during the cycle. A numerical simulation was created that calculates the average cycle power for a flywheel hydrokite system for given system parameters. The dynamics of this system were studied by optimizing various system parameters to maximize average cycle power. The optimization routine found that 278.1 W of power could be produced in a river flow of 1 m/s for the flywheel hydrofoil model. In order to determine how the flywheel affects the system, the optimized hydrokite with a flywheel was compared to an optimized version of the previous hydrokite without a flywheel. The previous optimized model produced an average cycle power of 24.91 W, which shows the flywheel was able to improve the performance of the system by over 1100%. The parameters found from the optimization schemes are only expected to be optimal for instantaneous hydrofoil flips; therefore, in order to characterize how the hydrofoil flip affects the system, the simulation was modified by setting the hydrofoil angle to 0 degrees for the duration of the flip time. The system was optimized again for various flip times. The simulation predicts that less power will be generated for increasing flip times until a flip time of 0.45 seconds is reached where the system cannot produce any power. Experimental testing on a small-scale system was performed to determine how much electrical energy is required to flip a hydrofoil for various flip times and submerged depth. All hydrofoil flips required less than 1 J, a small fraction of the predicted total cycle energy generated