ABSTRACT: An Oscillating Water Column wave-energy device is simulated in a 2D numerical wave tank. The fluid flow modelization is fully nonlinear. A new wave generation by spinning dipole is proposed; when coupled to a robust wave absorption technique, it permits long time simulations without energy accumulation in the tank. The turbine power take off mechanism is driven by a self-adaptive controller. The technique initially developed for active piston wave absorbers is applied successfully to OWC power plants. It is based on a Kalman filter frequency tracking algorithm. This control compares favourably with more conventional open loop systems.
INTRODUCTION It has been shown in several previously published studies that tile overall efficiency of wave power plants can be improved in a large proportion by a suitable on-line control of the power take-off mechanism (see e.g. Perdigao and Sarmento 1993). In the case of Oscillating Water Colunm (OWC) devices, the maximum power is recovered when the inner pressure can be kept in phase with the diffraction flow. In the present study, we assume that we are able to control the air flow rate across tile turbine according to a feedback of the pressure in the chamber. For simple 2D devices, the transfer function of such an ideal controller can be derived in the frequency domain, under the usual assumptions of the linear potential flow theory (Evans and Porter 1995). Unfortunately, the time domain counterpart of the ideal controller is m, t causal, making it practically unrealizable. Tiffs problem is not specific of OWC devices, but is a general property of ideal (i.e : perfect) wave absorbers (Naito and Nakamura 1985). It has been also encountered when we devised a control law for the regulation of a piston wave absorber (Cldment and Maisondieu 1993).