Analysis of Aero-hydrodynamic Equations Inside an OWC Device for Wave Energy Conversion

摘要

An Oscillating Water Column device (OWC) is a Wave Energy Converter (WEC) that harvests energy from sea waves, via the oscillation of seawater inside a chamber caused by incoming waves. It consists essentially of two parts: the chamber made of concrete and the turbine generator group used for energy conversion. This paper deals with a one dimensional modeling based on the resolution of the aero-hydrodynamic coupled equations of air and water in the OWC chamber. The objective is to improve the results of an existing linear model by including other physical effects such as: viscosity, friction, isentropic transformation, and the chamber height. In this study we are interested in the water oscillation motion inside the chamber resulting from the water level perturbation inside the chamber. This process similar to a mechanical oscillator system is characterized by its own natural frequency and global damping. Theoretically, the free water surface will oscillate vertically according to the natural frequency and its amplitude will decrease with a ratio relative to the global damping. Analyses are focused on the temporal variation of wave height inside OWC and the effect of parameters on this variation (gravity acceleration, submerged depth, turbine damping, base area, chamber height, viscosity, friction and initial conditions). For practical applications; this aero-hydrodynamic model will improve the characterization of the linear model during the design step, where the objective is to find values of parameters giving maximum efficiency, this scenario corresponds to the resonance domain where the damping is low and the frequency of incoming waves matches with the natural frequency of the OWC.