ABSTRACT

At present, the research related arrays of wave energy converters (WECs) have gradually emerged as one of the hotspots in the field of wave energy. In this study, the multiple wave energy converters coupled with a floating octagonal platform (FOP-WECs) were proposed. Firstly, a three-dimensional numerical wave tank was developed to investigate multi-body hydrodynamic interaction between a floating octagonal platform and absorber-type wave energy converters utilizing a computational fluid dynamics (CFD) tool. Then the convergence studies of meshes and time steps for the numerical model were carried out to evaluate its accuracy and efficiency. Finally, considering the multi-body interaction, the hydrodynamic performance and absorbed power of the FOP-WECs under different degrees of freedom (DOF) of platform were studied. The numerical results demonstrated that the multi-body interaction and DOFs of the platform have a remarkable influence on the absorption power and hydrodynamic performance of FOP-WECs, therefore, they cannot be neglected when evaluating the performance of the whole system.

INTRODUCTION

Ocean wave energy represents one of the most common, clean, reliable, sustainable, regular, and repeatable types of energy on the planet. The wave energy converter (WEC) is a device that can harness the kinetic energy of waves and transform it into usable electricity (Muetze et al., 2006). However, high power generation costs are impeding the growth of wave energy because of the high cost of construction and low wave energy extraction performance of WECs. One common method of addressing these issues with point-absorber wave energy converters (PA-WECs) involves forming a coupled multi-body WECs-platform system by placing multiple-WECs on a floating platform. As a rule, a multi-body WECs platform system will have a central platform that floats in midair, multiple oscillating bodies, and a number of actuating arms (Yang et al., 2017).

This type of system places the point-absorbing WECs on a floating platform in an attempt to optimize absorption power via interaction between the WECs and the platform. Generally speaking, the dimension of PA-WEC is smaller than the incident wavelength, and it can take in energy from any direction of wave (Budar et al., 1975; Falnes et al., 2003). Given these benefits, the PA-WEC is well-suited for array development and can generate more continuous power, which in turn leads to higher energy converter efficiencies and lower costs (Yang et al., 2020). Because of the remarkable effect that arrays of PA-WECs in a wave farm have on the transformation of incident waves (Carballo and Iglesias, 2013), incident waves will diffract and refract among devices in the array.

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