In an oscillating water column (OWC)-type wave energy conversion system, the performance of the OWC chamber depends on the chamber shape, as well as the incident wave direction and pressure drop produced by the turbine. Although the previous studies on OWC chambers have focused on wave absorbing performance in ideal operating conditions, incident waves do not always arrive normally to the OWC chamber in real sea conditions, especially in fixed devices. The present study deals with experiments and numerical calculations to investigate the effects of wave direction on the performance of the OWC chamber. The experiments were carried out in a three-dimensional wave basin for five different wave directions, including the effect of turbine using the corresponding orifice. The wave elevation inside the chamber was measured at the center point under various incident wave conditions. The numerical study was conducted by using a numerical wave tank-based volume-of-fluid model to compare the results with experimental data and to reveal the detailed flows around the chamber.
Wave energy is one of the most promising ocean renewable resources. The oscillating water column (OWC) device has been widely employed in wave energy conversion. An OWC wave energy converting system includes three energy converting stages:
the OWC inside a chamber forces air alternately into and out of the atmosphere through the duct.
a turbine with symmetric blades transforms the bi-directional air flow energy into a torque.
an electricity generator linked to the turbine transforms the torque into electrical power.
This third stage is not considered in the present study. There have been several researches on the efficiency and operating performance of OWC wave energy conversion systems. A number of efforts have been put into the research of wave energy converting efficiency and operating performance of the oscillating water column system. Wang et. al (2002) constructed and tested physical models with different bottom slopes in a wave tank under regular wave.