Performance Analysis of Multiple Wave Energy Converters due to Rotor Spacing

Abstract

A wave energy converter (WEC) that generates electrical energy from wave energy is a subject of high research interest in academia. Salter's duck, which is a pitch-type WEC positioned on the water surface to primarily convert wave energy into rotational kinetic energy of a floating body (rotor), is one of the oldest WECs and has been researched since the 1970s (Salter et al., 1975). Salter's duck maximizes wave energy absorption by designing the front and rear shapes differently and thus is theoretically known to have nearly 90% energy absorption efficiency (Swift-Hook et al., 1975). Several recent studies in South Korea have designed Salter's duck-type WECs suitable for the western waters of Jeju Island. The design parameters and performance of a rotor have been verified through a parametric study of optimal motion performance using the wave data of the western waters of Jeju Island (Poguluri and Bae, 2018), a study on estimating viscous coefficients of a rotor using computational fluid dynamics (CFD) (Poguluri et al., 2019a), and a numerical and experimental study on the linear behavior of a rotor (Kim et al., 2019a). These previous studies, however, focused on only one WEC rotor, so the effects of hydrodynamic interactions between adjacent modules must be analyzed considering how multiple WECs are simultaneously installed in the seas in general (Kim et al., 2020). Previous studies on analyzing dynamic behavior by arranging multipleWECs include an analysis of multiple cylindrical WECs in a heaving motion in the frequency domain (Lee et al., 2018) and in the time domain (Bae and Lee, 2017) as well as a study on optimal arrangement for improving the overall performance of multiple cylindrical WECs (Kim and Bae, 2019b). In these studies, a multibody analysis was performed for cylindrical WECs in the frequency domain to which a linear potential theory was applied, based on which the motion performance of individual WECs was evaluated by solving the coupled equations of motion in the time domain. An approach for computing performance changes and interactions may be effective for multiple cylindrical WECs with a fairly weak nonlinearity of motions; however, there are limitations in examining performance changes and interactions of arrayed WEC rotors based only on linear potential theory, because asymmetrical WEC rotors applied in this study have a

Two-Way Coupling Simulation of Fluid-Multibody Dynamics for Estimating Power Generation Performance of Point Absorber Wave Energy Converters

“…Figure 26a shows the velocity time series for the relative heave motion between the float and spar/plate. Figure 26b shows the time series of the instantaneous absorbed power calculated according to Equation (12). Similar to the results of single-body cylinder simulation in Section 3.2, the relative heave velocity decreased with an increase in the PTO damping coefficient.…”

“…Reference source not found., in the process of representing a plate thinner than the particle size or the slope of a float by a regular arrangement of particles, distortion may have occurred compared to the actual shape, which may have affected the response characteristics of the object motions in waves. In addition, because the thin plate was expressed with relatively large particle sizes and the mass was increased to adjust for the resulting buoyancy force, this The velocity-based damping force, which is a constraint condition for modeling the PTO system, can be expressed by Equation (11): Based on this equation, the instantaneous absorbed power with time can be calculated, as shown in Equation (12), and the final averaged absorbed power is calculated using Equation (13).…”

“…In addition, various numerical studies [12,13] have been conducted for the efficient design of WEC considering a significantly complex problem requiring multiphysics simulation (hydrodynamics, multibody dynamics, power take-off system analysis, control, etc.) encompassing different fields.…”

Enhancing Wave Energy Conversion Efficiency through Supervised Regression Machine Learning Models

“…These dynamic wave conditions can lead to a notable reduction in efficiency. In response to these challenges, numerous researchers have used nonlinear models to investigate the complex behavior of the asymmetric WEC, uncovering factors that contribute to its suboptimal performance [22,25]. To surmount these limitations, innovative strategies have been explored, including the incorporation of mechanisms such as negative stiffness, which have shown promising results in augmenting the device's efficiency [26,27].…”

Multibody Analysis of Wave Energy Converters and a Floating Platform in the Time Domain

“…Numerous studies have focused on multibody interactions, primarily exploring the hydrodynamic interactions between WECs and floating structures [10][11][12][13][14][15][16]. Konispoliatis et al [17] studied the effect that a fixed vertical breakwater has on the hydrodynamic characteristics of multiple WECs parametrically.…”