Session: 01-04-01 Renewable Energy

Paper Number: 131510

131510 - Optimization of Kinematic Parameters for Oscillating Foil Energy Harvesting Devices in Simple and Complex Motion 

This paper investigates an iterative optimization method applied to non-dimensional kinematic operating parameters for an oscillating foil energy harvester (OFEH). The goal is to identify optimum cycle parameters to maximize the efficiency of an OFEH using novel kinematic modes. Three separate types of successively more complex motion are investigated, consisting of three, five and eight degrees of freedom (DOF), respectively, in the operational space. The optimization algorithm uses a gradient ascent approach to find a local optimum for a given initial set of kinematic parameters. In an effort to fully explore the operational space, several different sets of initial conditions were implemented for each case. The sets of initial conditions were determined based on a maximin space filling condition for a predetermined range of the operational parameters. The steepest ascent iterative method was then used to find local optima for each set of starting operating points. Efficiency of the OFEH for each operating point was found based on computational fluid dynamics (CFD) simulations using the open-source CFD solver flowPsi. Resulting optima were similar to previously reported values in the open literature for both experimental and numerical investigations. Results garnered for the 3, 5 and 8-DOF parameters show an increase in maximum achievable efficiency as more non-dimensional parameters are defined, and unique kinematic motions were found for the 8-DOF that are qualitatively different than those found for the 3- or 5-DOF cases. Overall, the results demonstrate that the implementation of an iterative optimization method can find successfully determine optimum kinematic parameters for novel operating cycles in OFEHs.

This paper investigates an iterative optimization method applied to non-dimensional kinematic operating parameters for an oscillating foil energy harvester (OFEH). The goal is to identify optimum cycle parameters to maximize the efficiency of an OFEH using novel kinematic modes. Three separate types of successively more complex motion are investigated, consisting of three, five and eight degrees of freedom (DOF), respectively, in the operational space. The optimization algorithm uses a gradient ascent approach to find a local optimum for a given initial set of kinematic parameters. In an effort to fully explore the operational space, several different sets of initial conditions were implemented for each case. The sets of initial conditions were determined based on a maximin space filling condition for a predetermined range of the operational parameters. The steepest ascent iterative method was then used to find local optima for each set of starting operating points. Efficiency of the OFEH for each operating point was found based on computational fluid dynamics (CFD) simulations using the open-source CFD solver flowPsi. Resulting optima were similar to previously reported values in the open literature for both experimental and numerical investigations. Results garnered for the 3, 5 and 8-DOF parameters show an increase in maximum achievable efficiency as more non-dimensional parameters are defined, and unique kinematic motions were found for the 8-DOF that are qualitatively different than those found for the 3- or 5-DOF cases. Overall, the results demonstrate that the implementation of an iterative optimization method can find successfully determine optimum kinematic parameters for novel operating cycles in OFEHs.

Presenting Author: Stuart Fletcher University of Arkansas