Assessment of the surge effects in a heaving point absorber in the Mediterranean Sea

In the present paper, the feasibility of wave electricity production in Italian seas is investigated through the implementation of a variant of the Seabased point absorber WEC. A numerical model of the coupled buoy-generator system is presented, which simulates the behavior of the WEC under different significant wave heights and periods. The WEC scheme is an improvement of the modeling of a three-body device, taking into account several aspects (independence among the bodies, heave and surge) ignored in previous studies for simplification of the scheme. One WEC composed by three bodies is simulated, with two different hydrodynamic numerical model schemes: a floating buoy and a submerged sphere placed at 25 meters below the water surface. The third body is the translator of the linear generator, which is located at the sea bottom and attached to the submerged sphere by a steel wire.. For the hydrodynamic numerical model, the two bodies are allowed to move independently; heave and surge modes have been taken into account. The first scheme consists in the modeling with only three degrees of freedom, one per body only in the vertical direction (heave) and the other with five degrees of freedom, adding the horizontal component of movement for the buoy and the submerged body (surge). The results are compared with previous results of a WEC modeled as a single body system, with only one degree of freedom along the vertical axis. Preliminary results show that the produced energy in a simplified 1 DoF scheme is higher than results produced by the 3 DoF scheme, and is then approximately equal for the 5 DoF. The power matrixes present similar shapes. So the simplification made by neglecting the surge mode, in order to have a simpler dynamic model, doesn't give a significant improvement in the capture width and energy production assessment.