Frequency multiplying piezoelectric generators

• US 5,814,921 A
• Filed: 03/13/1995
• Issued: 09/29/1998
• Est. Priority Date: 03/13/1995
• Status: Expired due to Term

• Current Assignee: Ocean Power Technologies, Inc.
• Original Assignee: Ocean Power Technologies, Inc.
• Inventors: Carroll, Charles B.
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US08/404,186
• Time in Patent Office: 1,296 Days
• Field of Search: 310/338, 310/339, 322/2 R, 290/53, 60/497
• US Class Current: 310/339
• CPC Class Codes: F03B 13/16 using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
• CPC Class Codes: H02N 2/18 producing electrical output from mechanical input, e.g. generators for measurement devices G01
• CPC Class Codes: Y02E 10/30 Energy from the sea, e.g. using wave energy or salinity gradient

Abstract

Piezoelectric electrical generators comprise cantilevered beams of piezoelectric material, cross sections of the beams preferably being triangular and of increasing area from free end to fixed end. Arrays of spaced apart beams are disposed in overlapping, interdigitated relationships with arrays of cams, and the cam arrays are moved relative to the beam arrays for causing engagement and deflection of the beams by the cams for the generation of electrical energy. One system comprises a raft floating on the surface of an ocean. Cam arrays are suspended from the raft for interaction with vertically extending beam arrays mounted on the ocean floor beneath the raft. Relative vertical movements are caused by passing surface waves. In another system, beam arrays are suspended from an above surface structure, e.g., an oil drilling ocean platform, and the beam arrays extend towards and interact with cam arrays mounted on the upper surface of a floating raft.

Claims

1. A system for generating electrical energy comprising a first array of piezoelectric power generating elements spaced apart along a first direction, a second array of spaced apart engaging means, means for supporting said arrays in operative relationship to one another, means for causing relative movements between said arrays for causing said engaging means to move relative to said elements along said first direction for causing successive engagements of each of said engaging means with successive ones of said elements along said first direction for causing straining of and the generation of electrical energy by said elements, means for providing synchronous engagements of said engaging means with said elements, said first array of elements including first and second groups of elements, said second array of engaging means including first and second groups of engaging means, and said synchronous means causing all the engaging means of said first group of, engaging means to simultaneously engage respective ones of said first group of elements during a first time period and causing all the engaging means of said second group of engaging means to simultaneously engage respective ones of said group of elements during a second time period different from said first time period.

2. A system for generating electrical energy comprising a raft for floating on a surface of a body of water, a first piezoelectric power generator for converting straining of said generator to electrical energy, a support means for supporting a plurality of spaced apart cams for movement along a path intersecting said generator for causing deflection of said generator, means connected to said raft for causing movements of said cams relative to said generator along said path for causing successive cams to cause successive deflections of said generator, and the spacings between said cams being such that, with waves on said surface of preselected parameters, said generator, after each deflection thereof, freely vibrates at the natural frequency of oscillation of said generator for a period of time before the next, successive deflection of said generator.

3. A system according to claim 2 including a second power generator disposed relative to said first generator for being engaged and deflected by a cam during said period of time when said first generator is freely vibrating.

4. A system for generating electrical energy comprising a first array of spaced apart first elements, a second array of spaced apart second elements, means for supporting said arrays in operative relationship to each other, means for causing relative movements between said arrays for causing simultaneous engagement of each of said first elements with a respective one of said elements, said first elements being piezoelectric power generating elements the engagement of which by said second elements causing straining of and the generation of electrical energy by said first elements, and a third array of spaced apart first elements mounted in operative relationship to said second array, said movements causing means causing simultaneous engagement of all of said first elements of said first array with respective ones of said second elements during a first time period and causing simultaneous engagement of all of said first elements of said third array with respective ones of said second elements during a second time period different from said first time period.

5. A system according to claim 4 wherein said second elements are fixedly mounted relative to one another for common movements relative to said first and third arrays.

6. A system for generating electrical energy comprising first and second operatively associated support members subject to relative movements therebetween, first and second arrays of piezoelectric generators attached to said first support member for being strained in response to relative movements between said first and second members, said relative movements causing in-phase straining of all the generators of said first array of generators and in-phase straining of all the generators of said second array of generators, but out-of-phase straining of the generators of said first array relative to the generators of said second array.

7. A system according to claim 6 wherein each of said generators comprises a cantilevered beam of piezoelectric material having a first, free end and a second end secured to first said support member, and deflection means mounted on said second support member for causing deflections of said beams for causing said in-phase and out-of-phase strainings of said beams in response to said relative movements between said support members.

8. A system according to claim 7 wherein each of said beams has a cross-sectional area which increases from said free end towards said second end.

9. A system according to claim 7 wherein one of said support members is a float for floating on a body of water for vertical movements in response to passing surface waves, and the other of said support members is for being anchored to the floor of the water body at a position underlying said one support member.

10. A system according to claim 7 wherein one of said support members is a float for floating on a body of water for first vertical movements in response to passing surface waves, and the other of said support members is suspended from said float for second vertical movements different from said first vertical movements in response to passing waves causing said first vertical movements, the differences between said first and second vertical movements causing said relative movements between said support members.

11. A system according to claim 7 wherein one of said support members is a first float for floating on a body of water for first vertical movements in response to passing surface waves, and the other of said support members is a second float for floating on a body of water for second vertical movements different from said first vertical movements in response to passing waves causing said first vertical movements, the differences between said first and second vertical movements causing said relative movements between said support members.