Assimilating a Time-Domain Representation of a Wave Energy Converter Into a Spectral Wave Model

Abstract

To accommodate future power demands, wave energy converters (WECs) will be deployed in arrays, but largely unanswered questions of the annual energy production and environmental impact of such installations present regulatory dilemmas. In recent years, Sandia National Laboratories (SNL) has developed a modified version of the Simulating Waves Nearshore (SWAN) wave model to simulate WEC energy extraction in a propagating wave field. The SNL source code modifications to SWAN have facilitated a way to characterize the frequency dependent power absorption of a device in a spectral model using standard WEC parameterizations. The work presented in this paper seeks to build on source code modifications previously made by SNL. A new WEC meta-model, alters the incident wave spectrum based on power extracted from the sea and dissipated by hydrodynamic losses experienced at the WEC. These losses are calculated in an external six degree of freedom (DOF) time domain WEC simulation. The two WEC models were compared in terms of significant wave height reduction in the WEC’s lee and annual power production. The new model reduced the estimated distance required for the waves to recover 95% of the incident wave height by 50% for the same sea state. A 4.5% difference in annual power production was observed for a WEC operating in the lee of another device when deployed off the west coast of Canada.