Mathematical Framework for Hydromechanical Time-Domain Simulation of Wave Energy Converters

Abstract

Efficient design of wave energy converters based on floating body motion heavily depends on the capacity of the designer to accurately predict the device's dynamics, which ultimately leads to the power extraction. We present a (quasi-nonlinear) time-domain hydromechanical dynamic model to simulate a particular type of pitch-resonant WEC which uses gyroscopes for power extraction. The dynamic model consists of a time-domain three-dimensional Rankine panel method coupled, during time integration, with a MATLAB algorithm that solves for the equations of the gyroscope and Power Take-Off (PTO). The former acts as a force block, calculating the forces due to the waves on the hull, which is then sent to the latter through TCP/IP, which couples the external dynamics and performs the time integration using a 4th-order Runge-Kutta method. The panel method, accounting for the gyroscope and PTO dynamics, is then used for the calculation of the optimal flywheel spin, PTO damping, and average power extracted, completing the basic design cycle of the WEC. The proposed numerical method framework is capable of considering virtually any type of nonlinear force (e.g., nonlinear wave loads) and it is applied and verified in the paper against the traditional frequency domain linear model. It proved to be a versatile tool to verify performance in resonant conditions.

Modeling and Analysis of an Inertia Wave Energy Converter and Its Optimal Design

“…In view of the nonlinear phenomena for solving the radiation force convolution integral, calibrated BEM models and compressible Navier-Stokes (NS) equations are applied to optimize and refine the accuracy of the hydro-dynamical model. The study of these nonlinear effects is important, especially when considering the gyroscope operating in a nonlinear state, which will provide some guidelines for further improving the design of the WEC system [13]. Another research focus of WEC design and development is to ensure the resonance between the WEC and the sea wave.…”

The inertial sea wave energy converter (ISWEC) technology: device-physics, multiphase modeling and simulations

“…[3,6,7,8,9], their design and performance has been of much interest to the greater research community in the past few years. Medeiros and Brizzolara [10] used the boundary element method (BEM) based on linear potential flow equations to simulate the ISWEC and evaluate its power generation capabilities as a function of flywheel speed and derivative control of the PTO torque. They also demonstrated that the spinning gyroscopes can induce yaw torque on the hull.…”