Kinetic energy recovery system for sailing yachts: preliminary experimental results

SEAKERS (SEA Kinetic Energy Recovery System) is a research project, funded within the 7th EU Framework Program, whose goal is to develop an innovative device consisting in a model of a kinetic energy recovery system for sailing yachts, based on the conversion of wave-induced boat oscillations (heave, pitch and roll) into electric energy by means of a linear generator. The device aims at recovering as much kinetic energy as possible from the natural movements of a sailing yacht on the sea, therefore taking the view of a boat as a moving wave energy converter with energy harvesting capability. The boat's motions can be vertical oscillations due to the buoyancy in the presence of sea waves and rolling and pitching motions originated both by sailing in wavy waters and by the normal boat dynamics due to the sails' propulsion. This paper presents a brief description of the prototype of linear generator, which has been developed in the SEAKERS project, and reports about the first experimental tests carried out on the prototype. Two kind of tests have been performed on the generator, which can be classified as a linear permanent magnet switched reluctance generator: first, the possibility to use the prototype like an actuator has been investigated, in order to force the cursor to have a motion in phase with the external forcing, so as to recover more energy when the machine acts as generator. The behaviour of the actuator was examined in a static way, measuring the forces between cursor and stator, varying relative position of cursor and current in the coils. The second kind of tests has been performed to analyse the efficiency of the generator, for different external loads and translational velocities. The trend shown in these tests are then explained by an analytical model based on an electromagnetic circuit.