Wave-to-wire models of wells and impulse turbines for oscillating water column wave energy converters operating in the Mediterranean Sea

Abstract

Despite the huge potential, energy harnessing from sea waves is often still at a demonstrative stage. Oscillating water column (OWC) wave energy converters have proven to be one of the few suitable solutions to this end. A wave-to-wire analytical code modelling an entire wave energy converter based on the OWC technology, operating with either a Wells or an impulse turbine, was developed. The hydrodynamics, thermodynamics, and aerodynamics of the caisson were determined with a rigid piston approach. Two original low-order aerodynamic models were created for the two turbines, providing an interesting compromise between accuracy and computational cost. Finally, a control strategy was applied to monitor the instant rotor angular velocity and torque in both design and off-design conditions. The simulation tool was applied to screen the geometry of two typologies of air turbines for a specific chamber under the wave conditions of a selected Mediterranean site located in Sardinia (Italy). In particular, annual and seasonal scatter matrices were utilised to define the wave conditions of the site, providing an overview of the seasonal performance variation. The designed Wells and impulse turbines are capable of converting 47.67 and 41.14 MWh/year and operate with an overall efficiency of 5.77% and 4.98%, respectively.