Experimental Modelling of Point-Absorber Wave Energy Converter Arrays: A Comprehensive Review, Identification of Research Gaps and Design of the WECfarm Setup

Abstract

Commercial wave energy exploitation will be realised by placing multiple wave energy converters (WECs) in an array configuration. A point-absorber WEC consists of a floating or submerged body to capture wave energy from different wave directions. This point-absorber WEC acts as an efficient wave absorber that is also an efficient wave generator. Optimising the WEC array layout to obtain constructive interference within the WEC array is theoretically beneficial, whereas for wind farms, it is only important to avoid destructive interference within an array of wind turbines due to wake effects. Moreover, the WEC array layout should be optimised simultaneously with the applied control strategy. This article provides a literature review on the state of the art in physical modelling of point-absorber WEC arrays and the identification of research gaps. To cover the scientific gap of experimental data necessary for the validation of recently developed (nonlinear) numerical models for WEC arrays, Ghent University has introduced the “WECfarm” project. The identified research gaps are translated into design requirements for the “WECfarm” WEC array setup and test matrix. This article presents the design of the “WECfarm” experimental setup, consisting of an array of five generic heaving point-absorber WECs. The WECs are equipped with a permanent magnet synchronous motor (PMSM), addressing the need for WEC array tests with an accurate and actively controllable power take-off (PTO). The WEC array control and data acquisition are realised with a Speedgoat Performance real-time target machine, offering the possibility to implement advanced WEC array control strategies in the MATLAB-Simulink model. Wave basin testing includes long- and short-crested waves and extreme wave conditions, representing real sea conditions. Within the “WECfarm” project, two experimental campaigns were performed at the Aalborg University wave basin: (a) a testing of the first WEC in April 2021 and (b) a testing of a two-WEC array in February 2022. An experimental campaign with a five-WEC array is under preparation at the moment of writing.

A spectral-domain wave-to-wire model of wave energy converters

“…One such factor is the hydrodynamic interaction between multiple WECs, which can impact the power capture efficiency of individual devices. This effect becomes particularly significant when WECs are arranged in the configuration of a closely-located array or farm (Vervaet et al, 2022). It is important to note that this study focuses only on one single point absorber.…”

Physical Modelling Of A Centralized Controlled Array Of Five Wecfarm Wave Energy Converters

“…The 'WECfarm' point absorbers have a truncated cylindrical buoy with radius 0.30 m and draft 0.16 m. The motion is restricted to the heave direction, and the PTO system of each WEC is designed as a rotary permanent magnet synchronous motor (PMSM) connected to a gearbox, which drives a linear rack and pinion system (Vervaet et al, 2022). Figure 1 (left) shows the planview of the five-WEC array, with dimensions in m. A staggered five-WEC array layout is considered for which each of the outer WECs has an identical distance of 1.41 m to the inner WEC.…”

“…Therefore, the PTO control should be optimized taking all these interactions into account, referred to as centralized control. The 'WECfarm' project has been initiated to study WEC arrays, and to address the research gap on available realistic and reliable data on WEC array tests to validate numerical models (Vervaet et al, 2022). This work discusses the experimental design, implementation and testing of a centralized controlled array of five 'WECfarm' heaving point absorber WECs, tested at the Coastal and Ocean Basin Ostend.…”

Modelling the far-field effect of drag-induced dissipation in wave–structure interaction: a numerical and experimental study

“…from the wave field. To our knowledge, this effect has not been taken into account in the numerical modelling of wave energy arrays (Folley 2016;Verbrugghe et al 2017;Vervaet et al 2022).…”