In intermediate water depths, an array of floating point-absorbing Wave Energy Converters (WECs) may be employed for extracting efficiently ocean wave energy. In such case, it may be more feasible to connect the array with a submerged bottom-moored plate, whose function is to act as the seabed. An array of identical vertical axis floating symmetrically distributed cylinders over a coaxial slack-moored submerged plate is proposed in this study. The Power Take-Off (PTO) system is assumed to be composed of a linear damper and spring activated by the buoys heaving motion. Linear hydrodynamic analysis of the examined floating system is implemented in frequency domain. Hydrodynamic interferences between the oscillating bodies are accounted for in the corresponding coupled equations. The optimal reactive and resistive loads and the corresponding oscillation amplitudes and energy absorption capture width ratios are determined analytically and numerically. Numerical results with regular waves are presented and discussed for the axisymmetric system utilizing heave mode, in terms of a specific numbers of cylinders and expected power production.
Wave Energy Converters (WECs) used to harvest clean marine renewable energy has motivated a wide variety of investigations. The power take off (PTO) mechanism is usually regarded as the control devices of WECs, since it aims to the transformation of the kinetic energy of the oscillating body into electrical energy. So the advent of PTO system has a significant impact on the WEC in optimizing and maximizing the extraction of wave energy from ocean waves.
It is well known that the three main research approaches corresponding to analytical equations, numerical models and experimental models have been employed to solve any engineering problem, such as the conversion of wave energy into electricity. A lot of effort has been devoted to improve the geometries and the conversion ability of a single-point absorber WEC by various investigators. The pioneer work of this issue can be traced to Maccormick (1981) who explores the potential and possibility of converting the ocean's energy from waves into useful work. Lately, Falnes (2002) expounded systematically a thorough consideration of the interaction between waves and oscillating systems under the linear wave conditions. Based upon this principle, some classical devices such as the IPS buoy (Cleason et al. 1982), the Aquabuoy (Weinstein et al. 2004), the Wavebob (Weber et al. 2009) and the PowerBuoy (Eder et al. 2013) have attained the stage of prototype tested in the sea. Falcão (2010) described the development of wave energy utilization since 1970s and he discussed several topics such as the conception design, the hydrodynamics of WEC, the mooring system and so on. The design of a mooring system for WECs has been considered in the last few years by several authors (Johanning, Smith and Wolfram, 2006; Waters, Stalberg and Danielsson, 2007; Elwood, Schacher, Rhinefrank and Prudell, 2009; Fonseca, Pascoal and Morais, 2009; Fitzgerald and Bergdahl, 2008; Bachynski, Young and Yeung, 2012). Although, the mooring system has a little effect on the wave energy conversion, it has a great effect on the device safety. For example, Bachynski, Young and Yeung (2012) considered a cylinder moored to the seabed and found that the mooring can introduces a lowfrequency coupled pitch-surge resonance. Although various types of WECs have been designed, there is no standard technology that has been recognized to been super to the others.