Abstract
The sea wave energy has a significant potential to be converted in electrical one. However, there are still many difficulties to its harvesting. The most studied device is the Oscillating Water Column (OWC) wave energy converter, in which the majority of researches consider the air inside the chamber as a dry air. This study aims to investigate the influence of the environment humidity on the behavior and the performance of this device equipped with Wells and Impulse turbines. A numerical model, that uses the first law of thermodynamics to analyze a piston movement in a air chamber with a turbine, is developed to compare results of an ideal gas with those of a real gas. The behavior of the real gas inside the chamber is based on empirical parameters. An typical case of an onshore OWC in atmospheric conditions with high level of humidity of the south of the Brazilian cost is studied. Ranges of wave period and height and turbine characteristic relation for Wells and Impulse turbines are tested. Comparison between dry and real air gases inside the chamber for the same conditions of wave period, amplitude of the free surface oscillation inside the chamber and turbine characteristic relation for Wells and Impulse turbines are analyzed. Vapor precipitation is observed in cases where air pressure inside the chamber is higher than 7.17.1 kPa. In general, time-averaged pneumatic powers of real gases are slightly lower (2%2% maximum) to those of ideal ones, which indicates that the influence of air humidity on the performance of the device is practically negligible. However, the definitive conclusion depends on the consideration of the coupling between hydrodynamics and aerodynamics in the process.