Session: 09-02-04 WEC Numerical Modeling

Paper Number: 81070

81070 - Three-Dimensional Simulations for Geometric Optimization of a Shoreline Hybrid Wave Energy Converter 

Hybridisation of different wave energy conversion (WEC) technologies appears to be a promising approach to harness the available energy most efficiently over a wide range of metocean conditions and overcome some of the challenges facing the roll out of a competitive wave energy industry. This underlying idea, hybridisation, is in the genesis of a novel device being further developed in the OCEANERA-NET project WEC4PORTS, concept which had been proved under the SE@PORTS project.

Said novel hybrid wave energy converter (HWEC) combines two well-known wave energy conversion principles, an oscillating water column (OWC) and a multi-reservoir (4 reservoirs) overtopping device (OTD), and has been developed for installation in multi-purpose breakwaters.

Within WEC4PORTS, different geometrical configurations of the HWEC are being tested through a composite modelling approach, defined here as the combination of numerical and physical model testing, with respect to their hydraulic and energy performances. Furthermore, components of the turbines will be tested in real sea conditions in BIMEP testing facility in Mutriku, Spain.

In this paper focus is given to the three dimensional numerical model developed with OpenFoam for comparing alternative configurations of this breakwater-integrated HWEC, by studying the hydrodynamic efficiency. The three dimensional Navier-Stokes equations for two incompressible, immiscible fluids were employed while for turbulence closure the Shear-Stress Transport (SST) k-w model was selected. Finally, the ‘Volume of Fluid’ method was used for the free surface tracking.

In total, five alternative geometries were compared. All tested geometries shared the same multi-reservoir OTD device geometry except for the ramp that leads the incidents waves to overtop into the reservoirs and differed either in the configuration of the oscillating water column inlet or in the number of oscillating water columns. These differences in the OWCs inlet were responsible for the different ramps in the OTD device.

Different regular wave conditions were tested with various wave periods. The results included mean wave amplification coefficients in the OWCs, head-discharge characteristics in the air outlets (turbines’ inlets) of the OWCs, overtopping discharges in all four reservoirs of the OTDs,  volumetric flow rates in the water outlets (turbines’ inlets) of the different reservoirs, head-discharge characteristics in the water outlets and the corresponding hydraulic and pneumatic efficiencies of the OTD device and OWC components.

With respect to mean wave amplification coefficients in the OWCs, the results indicate that the most effective geometry amongst the ones tested is always the same irrespective of the wave period. In addition, the results concerning the overtopping discharges in the reservoirs and the volumetric flow rates in the water outlets of the OTD device showed overall small differences across the alternative geometries that can be attributed to the configuration of the OTD device ramp, as well as the performance of the OWC component of the HWEC device. Finally, from the hydraulic and pneumatic efficiencies it can be confirmed that the optimum breakwater-integrated HWEC is one that must consider the performances of the OWC and OTD devices concurrently.

Presenting Author: Theofano Koutrouveli IMDC nv

Authors:

Theofano Koutrouveli IMDC nv
Luciana Das Neves IMDC nv