Influence of Time and Frequency Domain Wave Forcing on the Power Estimation of a Wave Energy Converter Array

Abstract

Industry-specific tools for analyzing and optimizing the design of wave energy converters (WECs) and associated power systems are essential to advancing marine renewable energy. This study aims to quantify the influence of phase information on the device power output of a virtual WEC array. We run the phase-resolving wave model FUNWAVE-TVD (Total Variation Diminishing) to generate directional waves at the PacWave South site offshore from Newport, Oregon, where future WECs are expected to be installed for testing. The two broad cases presented correspond to mean wave climates during warm months (March–August) and cold months (September–February). FUNWAVE-TVD time series of sea-surface elevation are then used in WEC-Sim, a time domain numerical model, to simulate the hydrodynamic response of each device in the array and estimate their power output. For comparison, WEC-Sim is also run with wave energy spectra calculated from the FUNWAVE-TVD simulations, which do not retain phase information, and with wave spectra computed using the phase-averaged model Simulating WAves Nearshore (SWAN). The use of spectral data in WEC-Sim requires a conversion from frequency to time domain by means of random superposition of wave components, which are not necessarily consistent because of the linear assumption implicit in this method. Thus, power response is characterized by multiple realizations of the wave climates.

Numerical Investigation of the Scaling Effects for a Point Absorber

“…The hydrodynamic development and optimisation of WECs is typically achieved through a combination of physical (i.e., in the laboratory) and numerical modelling. Numerical approaches operating in the time and/or frequency domain [4] include mesh based solvers [5,6] and Smoothed-particle hydrodynamics (SPH) [7,8]. Numerical modelling is especially useful for the investigation of interaction of multiple devices [9][10][11], but requires specific validation data provided by nature or laboratory experimental investigations.…”

Storage Minimization of Marine Energy Grids Using Polyphase Power

“…The physical nature of oceanic waves entails phase offsets in the wave elevations received at individual members of a WEC array as a function of array layout. Rollano et al quantified the effect of phase information on the power output of a virtual WEC array [13]. They compared the power output performance of a WEC array in a phase-averaging wave model using Simulating WAves Nearshore (SWAN) against a phase-resolving wave model FUNWAVE-TVD [14,15].…”

“…They compared the power output performance of a WEC array in a phase-averaging wave model using Simulating WAves Nearshore (SWAN) against a phase-resolving wave model FUNWAVE-TVD [14,15]. A phase-averaging wave environment can be used for a WEC array with a large number of WECs because each WEC at a different location in the array has the opportunity to sample a different phase of the incoming wave to reduce the variability in the aggregate power [13]. However, they point out that power systems are vulnerable to large wave amplitudes, making a phase-resolved wave environment crucial in avoiding underestimating such wave events.…”