Wave-to-wire simulation of a floating oscillating water column wave energy converter

Abstract

A comprehensive time domain numerical simulation has been built for a moored, floating Oscillating Water Column (OWC) Wave Energy Converter (WEC), in order to provide accurate predictions of WEC power production. This novel simulation incorporates fully coupled simulations of the WEC dynamics, mooring lines, hydrodynamics, air chamber thermodynamics, air turbine dynamics and generator. It includes the forces and moments created by incoming irregular waves, moorings, buoyancy, wave radiation effects, viscous drag, and the differential pressure on the OWC hull and water column. The thermodynamics of the air chamber and the nonlinear biradial air turbine are fully coupled within the simulation.Using a biradial air turbine with a radius and angular velocities designed to maximize mechanical power, the rated power of the PTO’s Variable Frequency Drive (VFD) and generator are optimized to maximize annual energy production. Simulations of 36 differing sea states, constituting 71% of the annual wave energy transport for a Canadian Pacific location, provide an annual power production of 530 MWhr, with an overall wave-to-wire efficiency of 11.6%. Simulation variants with no external viscous drag and linearized moorings resulted in a 42% and 16% change in energy recovered while excluding air compressibility and internal viscous drag had limited influence.