Impact of Separation Distance on the Performance and Annual Energy Production of a Dual-Flap Oscillating Surge Wave Energy Converter

TL;DR

This study examines how the separation distance between two flaps in a dual-flap OSWEC influences individual flap performance and annual energy production, using inviscid Euler-based simulations validated against a 1:10 scale experiment and applied to PacWave South conditions. It employs torque-forced and wave-forced analyses to dissect inter-flap coupling and wave-field effects, and constructs a partial power matrix to assess AEP across representative separations. The results show that short distances produce phase-sensitive but largely canceling interactions, while longer distances yield constructive interference, with annual energy production largely insensitive to distance but with practical spacing favoring 45 m when considering mooring and surge constraints. The findings inform array design by clarifying how separation distance and wave direction influence energy capture and structural loading in a two-flap OSWEC configuration.

Abstract

Among the different concepts for wave energy conversion, oscillating surge wave energy converters have been shown to have a high capture width ratio. The primary wave capture structure consists of a flap hinged at the seabed or to a floating platform. Different flap configurations, including single and dual-flap, have been investigated. The separation distance between the oscillating surge wave energy converters can have an impact on their response when deployed in arrays. We consider the case of a dual-flap oscillating surge wave energy converter and investigate the impact of the separation distance between them on the performance of each flap. We estimate the absorbed wave energy and the annual energy production by the two flaps when deployed at the PacWave South site. Inviscid numerical simulations were conducted to predict the response of the oscillating surge wave energy converters. The simulations are validated with experimental measurements of a 1:10 scaled model in a wave tank. The results show that for a short separation distance, the interaction between the oscillating surge wave energy converters has a destructive and constructive effect depending on the wave frequency. However, these effects tend to balance each other out when considering the broad range of wave excitations. For longer separation distances, the interaction always results in a constructive effect. The results reveal that the separation distance has an insignificant impact on annual energy production when considering all wave frequencies and amplitudes.

Figures (9)

• Figure 1: Schematic of full-scale dual-flap OSWEC
• Figure 2: The RMS values of the rotation of the right flap under regular forcing with excitation torque amplitudes of (a) 0.6 MN.m and (b) 0.8 MN.m (c) 1 MN.m (d) 1.2 MN.m with the left flap fixed
• Figure 3: The RMS values of the rotation of the left flap (left) and right flap (right) with single flap under regular forcing with excitation torque amplitude of (a) 0.6 MN.m (b) 0.8 MN.m (c)1 MN.m (d) 1.2 MN.m applied on the right flap
• Figure 4: The RMS values of the rotation of the flaps separated by (a) 10 m (b) 45m (c) 70 m under regular forcing with excitation torque amplitude of 0.6 MN.m (left) and 1.0 MN.m (right) amplitudes when the two flaps are in-phase and out-of-phase
• Figure 5: The RMS values of the rotation of the flaps separated by (a) 10 m (b) 45m (c) 70 m under regular forcing with excitation torque amplitude of 0.6 MN.m (left) and 1.0 MN.m (right) amplitudes when the two flaps have arbitrary phase difference ($\phi=\frac{d}{\lambda}2\pi$)