A SELF-REACTIVE OCEAN WAVE ENERGY CONVERTER WITH WINCH-BASED POWER TAKE-OFF: DESIGN, PROTOTYPE, AND EXPERIMENTAL EVALUATION

Abstract

Agriculture provides a large amount of the world's fish supply. Remote ocean farms need electric power, but most of them are not covered by the electric power grid. Ocean wave energy has the potential to provide power and enable fully autonomous farms. However, the lack of solid mounting structure makes it very challenging to harvest ocean power efficiently; the small-scale application makes high-efficiency conversion hard to achieve. To address these issues, we proposed a self-reactive ocean wave converter (WEC) and winch-based Power Take-Off (PTO) to enable a decent capture width ratio (CWR) and high power conversion efficiency. Two flaps are installed on a fish feed buoy and can move along linear guides. Ocean wave in both heave and surge directions drive the flaps to move and hence both wave potential energy and wave kinetic energy are harvested. The motion is transmitted by a winch to rotation motion to drive an electric generator, and power is harvested. Dynamic modeling is done by considering the harvester structure, the added mass, the damping, and the excitation force from ocean wave. The proposed WEC is simulated in ANSYS AQWA with excitations from regular wave and results in a gross CWR of 13%. A 1:3.5 scaled-down PTO is designed and prototyped. Bench-top experiment with Instron is done and the results show that the mechanical efficiency can reach up to 83% and has potential for real applications.