Influence of the wave spectrum representation on production estimations from point absorbers WEC farms

Abstract

To date the use of the JONSWAP parametric spectrum is still widely accepted in many engineering applications, including the wave energy sector. Nevertheless, in the last 15 years many studies have progressively shown the necessity to implement more detailed and realistic spectral information in order to reduce the errors (or differences) introduced when the JONSWAP spectrum fails to describe more complex sea states. In the present study, the changes in produced power estimations, related to different spectral representations, are analysed. All power production estimates are obtained through 30 years simulations of point-absorber Wave Energy Converter (WEC) arrays, using the HAMS-MREL Boundary Element Method (BEM) solver. To assess the effects of the wave energy distribution on power production, 3 different spectral forcing are considered. Two based on the JONSWAP spectrum, and 1 using spectra time series from the ECHOWAVE hindcast specially developed for wave energy applications. For comparison purposes, the hindcast spectra is used as reference, since it can accurately represent the sea states evolution in time including the occurrence of multimodal conditions, which are not considered by the JONSWAP formulation. Additionally, 3 locations with different wave climates are analysed within European coastal waters. Recent results, focused on the response of a single (point-absorber) WEC, show that the differences in the mean yearly production can be > 12% when compared to reference hindcast data. The generalised analysis presented here, including the hydrodynamic interactions between multiple WECs within an array, is an important step forward in the understanding and quantification of the uncertainties present in power production assessments.