J. Marine Sci. Appl. (2016) 15: 41-49 DOI: 10.1007/s11804-016-1342-1 Parametric Study of Two-Body Floating-Point Wave Absorber Atena Amiri, Roozbeh Panahi * and Soheil Radfar Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Tehran 14115-143, Iran Abstract: In this paper, we present a comprehensive numerical simulation of a point wave absorber in deep water. Analyses are performed in both the frequency and time domains. The converter is a two-body floating-point absorber (FPA) with one degree of freedom in the heave direction. Its two parts are connected by a linear mass-spring-damper system. The commercial ANSYS-AQWA software used in this study performs well in considering validations. The velocity potential is obtained by assuming incompressible and irrotational flow. As such, we investigated the effects of wave characteristics on energy conversion and device efficiency, including wave height and wave period, as well as the device diameter, draft, geometry, and damping coefficient. To validate the model, we compared our numerical results with those from similar experiments. Our study results can clearly help to maximize the converter’s efficiency when considering specific conditions. Keywords: floating-point absorber, wave energy, energy absorption, Wave Energy Converter (WEC), Power Take Off (PTO), numerical simulation Article ID: 1671-9433(2016)01-0041-09 1 Introduction 1 In order to meet increased energy demands while also reducing CO2 emissions, the development of renewable energy sources is currently a priority for many industrialized countries. Wave power is an extremely promising renewable resource that could provide a substantial supply of clean energy (Bozzi et al., 2013). Using waves as a renewable energy source offers significant advantages over other energy generation methods, including the following (Drew et al., 2009): 1) Sea waves offer the highest energy density among the renewable energy sources. 2) There are few negative environmental impacts associated with their use. 3) There is a natural seasonal variability in wave energy, which follows electricity demand in temperate climates. 4) Waves can travel great distances with little energy loss. 5) Wave power devices can reportedly generate power up to 90 percent of the time, compared to 20–30 percent for wind and solar power devices. Due to the high density of water, sea wave power is one Received date: 2015-10-01 Accepted date: 2015-12-14 *Corresponding author Email: rpanahi@modares.ac.ir © Harbin Engineering University and Springer-Verlag Berlin Heidelberg 2016 of the most powerful sources of renewable energy. In recent years, wave energy extraction has been a popular field of study among researchers and examples of wave-energy converters are found throughout the literature (Antonio, 2009; Drew et al., 2009; Falnes, 2002). These converters are generally divided into categories based on their distance from the shoreline and the type of technology used. In another category type, there are three groups of devices that are classified based on their horizontal dimension with respect to sea waves. When the horizontal dimension of a converter is much smaller than the wavelength of an incident wave, it is known as a point absorber; otherwise, it is called a line absorber. A line absorber that is parallel with the waves is called an attenuator and one that is perpendicular to the waves is called a terminator. In this study, we focus on the point absorber. Point absorbers (floating or submerged) convert the vertical motion of ocean waves into linear or rotational motion to drive electrical generators by means of a power take off (PTO) system (Bozzi et al., 2013). While they have a low energy absorbtion rate, if the size of the device is taken into account, its energy absorption capacity seems favorable (Iglesias et al., 2010). In addition, active and/or passive controls, as well as an optimized wave farm arrangement, can result in an increase in total energy absorption (Babarit et al., 2004; Fusco et al., 2011). The Folating Point Absorber (FPA) concept was first introduced by Budal and Falnes (1978), and the mathematical FPA relationships were presented by McCormick (2013). It is an incontestable fact that a good wave absorber must be a good wave maker. Hence, in order to absorb wave energy, it is necessary to displace water in an oscillatory manner and with the correct phase (timing) (Cruz, 2008; Falnes, 1995). FPAs can heave up and down on the surface of the water. Because of their small size, wave direction is not an important consideration for these devices. There are numerous examples of FPAs, one of which is Ocean Power Technology (OPT)’s Powerbuoy. Fig. 1 shows an photo of a wave farm using Powerbuoys (Drew et al., 2009). Eriksson et al. (2005) conducted numerical wave interaction studies using a cylindrical point absorber connected to a seabed-based linear generator. In that study, the generator was modeled as a viscous damper. By writing the equation of motion and considering different diameters, as well as the spring and damper coefficients, it is possible to calculate the energy absorption. Downloaded from http://iranpaper.ir