Direct Drive Wave Energy Buoy ? Intermediate scale experiment

Abstract

Columbia Power Technologies deployed a scaled prototype wave energy converter (WEC) in the Puget Sound in February 2011. Other than a brief period (10 days) in which the WEC was removed for repair, it was in the water from Feb. 15, 2011 until Mar. 21, 2012. The SeaRay, as this WEC is known, consists of three rigid bodies which are constrained to move in a total of eight degrees of freedom (DOF). The SeaRay is kept on station with a spread, three-point mooring system. This prototype WEC is heavily instrumented, including but not limited to torque transducers and encoders reporting generator torque applied to and relative pitch of the floats, an inertial measurement unit (IMU) reporting translational acceleration and rotational position of the spar/nacelle, a GPS sensor reporting position, load cells reporting mooring loads at the WEC connection points and a number of strain gauges embedded in the fiberglass reinforced plastic (FRP) hull. Additionally, wave and current data are collected using an Acoustic Wave And Current Profiler (AWAC), allowing performance and design data to be correlated to environmental input conditions. This data – quality controlled, processed and analyzed – is used to characterize the metocean conditions (i.e. sea states). The WEC response will be correlated to the metocean conditions. These results will primarily be used to validate numerical models. The validated numerical models will be used optimize the commercial scale WEC and inform the design process. This document details the SeaRay experiment, including the quality control, processing and subsequent analysis of the data. Furthermore, the methodology and the results of numerical model validation will be described.