In-ocean experiments of a wave energy conversion device with a drogue and wave power calculations

Abstract

This research describes the experimental and numerical modeling of a heaving point source wave energy conversion (WEC) device developed by Trex Enterprises of Maui and tested by the University of Hawaii at Manoa. The principle of operation of the WEC device is to convert the vertical heave displacement into a rotational action, which generates electrical power. The heave displacement is created by the WEC system riding incoming waves relative to an anchoring system. Two deployment cases of the single WEC device were ocean tested with the goal of collecting power data based on the type of the anchoring method. The anchoring methods are referred to as the single-body case (moored system) and double-body case (drogue anchored system). The experiments were carried out on the South shore of Oahu during the summer of 2012. The WEC system was equipped with sensors to measure and record the heave displacements of the WEC system, the generated power output, and the surface elevation. The real time experimental data were collected and analyzed to determine the power generation profile, the WEC system's heave displacements, surface elevation, and heave response amplitude operator (RAO) for both cases. A numerical modeling program was built to perform hydrodynamic analysis in the time domain in irregular seas for the single-body or double-body case. The program solves for the individual body motion. It is used to predict the WEC device's power production over the time series.