Effects of turbine damping and wave conditions on OWC performances for optimal wave energy conversion

The oscillating water column (OWC) devices constitute the most widely used systems for the wave energy conversion. Optimizing the performances of such devices mainly composed with a bidirectional air turbine and a water–air chamber still remains of great interest. The present investigations focus on the numerical analysis of an OWC system, the air turbine damping, and on its coupling with the OWC chamber. A validated 2D RANS-VoF numerical model was implemented to determine the optimum induced damping of the OWC device in case of an impulse turbine. The model is based on the concept of the Numerical Wave Tank (NWT). In the present model, the turbine quadratic behavior was simulated with an orifice. Simulations have been conducted in typical cases located on the central zone of the Moroccan Atlantic coast. All the simulated cases are of intermediate water waves which are in compliance with the use of the Stokes’ second-order wave generation. The pneumatic power corresponding to the various values of turbine-induced damping is computed, and the optimum damping accounting for the wave climate variability is identified. It was found that the damping induced by the air turbine is the factor that influence most the OWC chamber efficiency, followed by the climate conditions.