Analytical modelling of an U-Oscillating Water Column and performance in random waves

Abstract

The oscillating water column (OWC) technology is recognized as one of the most effective solutions for exploiting sea wave energy in a scenario including hundreds of promising devices. In this context, the novel U-OWC device has been recently introduced as a further development of the OWC. This device differs from the conventional OWC as it utilizes a small vertical U-duct for connecting the air pocket to the open wave field. The objective of this paper is to propose a consistent representation of the wave field interacting with the U-OWC in the context of a linearized theory of water waves and, then, an analytical description of the U-OWC dynamics. Such a representation overcomes the drawbacks of the analytical models proposed, at the present time, in the open literature. Moreover, it allows including memory effects previously neglected.Next, the performance of the U-OWC is investigated by Monte Carlo simulations. In this regard, several simulations are produced for testing the efficiency of the device in sea waves compatible with power spectral density of wind-generated waves and of swells. The efficiency is evaluated according to a number of parameters, that allow highlighting the remarkable amount of energy absorbed by the system. The influence of the turbine is investigated, as well, by comparing the performance of monoplane (with and without guide vanes), biplane and contra-rotating turbines.