Ocean Power Technologies, Inc.

Michael Y Epstein

George W Taylor

Charles B Carroll

A flexible layer of piezoelectric material, e.g., a known PVDF polymer, is used for generating electrical energy for use on a water craft. In one arrangement, the sheet is laminated within a craft hull of fiberglass. Electrodes are provided for the major opposite surfaces of the layer, and an encapsulating material, e.g., fiberglass or a layer of the polymer itself, comprises the water contacting, exterior surface of the hull. In salt water, the water is one electrode, and an outer encapsulating layer is omitted. Spaced apart air pockets are optionally provided along the polymer sheet for increasing the flexing thereof in response to passing water and for inducing turbulence in the passing water. Elongated, flexible and electroded sheets, optionally including air pockets, are towed behind or beneath the craft, or are flown from a mast on the craft.

Water craft using piezoelectric materials

A system for converting the mechanical energy of ocean waves to electrical energy comprises a weighted member supported from a piezoelectric element for applying a preselected strain to the element. In one embodiment, the element is supported by a float floating on the surface of the water. In another embodiment, the element is supported above the surface of the water and the weighted member, of negative buoyancy, is immersed in the water. The system functions, in use, as an oscillating, weighted spring and, for tuning the system to cause it to enter into mechanical resonance in response to passing waves, means are provided for tuning the natural frequency of the oscillating system.

Piezoelectric generation of electrical power from surface waves on

Disposed within a float on the surface of a body of water is a vertically suspended, resilient piezoelectric element provided with a preselected strain by a hanging weight. The piezoelectric system functions as a weighted coiled spring which is driven into oscillation in response to movements of the float in response to passing surface waves. Preferably, the natural frequency of the system is selected in correspondence with the frequency of the passing waves for causing the system to oscillate in resonance with the passing waves. Additionally, a mechanism is provided for automatically adjusting the natural frequency of the system in response to changing wave conditions for maintaining the system in resonance with the waves.

Generation of electrical energy by weighted, resilient piezoelectric

An electrical energy generator comprises a cylindrical stator, a cylindrical liner of a piezoelectric material in concentric contact with the stator, and an armature rotatable about the liner. In one embodiment, as the armature rotates, the armature squeezes successive portions of the liner against the stator for alternately compressing and decompressing the liner portions for causing them to generate electrical energy. In another embodiment, the armature causes alternating stretching and destretching of successive portions of the liner between spaced apart portions of the stator for causing the liner portions to generate electricity.

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Belle Mead, NJ, United States of America

Michael Y Epstein