Generation of electrical energy by weighted, resilient piezoelectric elements

• US 5,552,657 A
• Filed: 02/14/1995
• Issued: 09/03/1996
• Est. Priority Date: 02/14/1995
• Status: Expired due to Term

• Current Assignee: Ocean Power Technologies, Inc.
• Original Assignee: Ocean Power Technologies, Inc.
• Inventors: Taylor, George W., Epstein, Michael Y.
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US08/388,557
• Time in Patent Office: 567 Days
• Field of Search: 310/328, 310/329, 310/338, 310/339, 310/800, 310/367, 290/42, 290/53, 60/495, 60/497
• US Class Current: 310/339
• CPC Class Codes: F03B 13/20 wherein both members , i.e. wom and rem are movable relative to the sea bed or shore
• CPC Class Codes: F05B 2250/44 one element moving inside another one, e.g. wave-operated member (wom) moving inside another member (rem)
• CPC Class Codes: H02N 2/18 producing electrical output from mechanical input, e.g. generators for measurement devices G01
• CPC Class Codes: H10N 30/60 having a coaxial cable structure
• CPC Class Codes: Y02E 10/30 Energy from the sea, e.g. using wave energy or salinity gradient
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

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.

Claims

1. A power generating system comprising a hollow float for floating on a surface of a body of water and being movable in response to movements of the surface of the water, a resilient piezoelectric power generating element in the form of a coiled spring for being suspended within said float for oscillations of said element in response to float movements, and a weight member for being suspended from said element within said float for driving said element into said oscillations.

2. A system according to claim 1 wherein said spring is formed from a cable comprising an elongated, central electrode surrounded by a layer of piezoelectric material surrounded, in turn, by an outer electrode.

3. A power generating system comprising a hollow float for floating on a surface of a body of water and being movable in response to movements of the surface of the water, a resilient piezoelectric power generating element for being suspended within said float for oscillations of said element in response to float movements, a hollow weight member for being suspended from said element within said float for driving said element into said oscillations, and means for passing a weighting substance into and out of said weight member for varying the weight thereof.

4. A system according to claim 3 including a pump for pumping water from the body of water into and out of said weight.

5. A power generating system comprising a hollow float for floating on a surface of a body of water and being movable in response to movements of the surface of the water, a resilient piezoelectric power generating element for being suspended within said float for oscillations of said element in response to float movements, a weight member for being suspended from said element within said float for driving said element into said oscillations, and magnetic means for controlling the rate of oscillation of said element.