IN-OCEAN EXPERIMENTS OF A WAVE ENERGY CONVERSION DEVICE WHEN MOORED TO AN ANCHOR AND TO A DROGUE

摘要

We present the results of in-ocean testing of a heaving point source wave energy converter (WEC) off the coast of Honolulu, Hawai'i. The principle of operation of the WEC device is to convert 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 a 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 single-body case consists of the WEC system being held in place via a taut mooring line connected to an anchor. The double-body case consists of the WEC system being held by a sea anchor or drogue. This allows the system to partially float free and drift, but still have adequate vertical resistance to extract power as waves pass. 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, the generated power output, and the surface elevation. To accurately measure the WEC system's heave displacement, a rotary sensor was used to measure angular displacement the WEC system's spool rotated for each wave. An Aquadopp measured the total pressure from the sea floor up-wave from the WEC system. A voltage logger was used to measure the voltage across a resistive load to calculate the power the WEC system generated. The realtime 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.