Power optimization for a unit cell metamaterial energy harvester

• US 10,694,466 B2
• Filed: 06/20/2017
• Issued: 06/23/2020
• Est. Priority Date: 06/20/2017
• Status: Active Grant

• Current Assignee: University of South Carolina
• Original Assignee: University of South Carolina
• Inventors: Banerjee, Sourav, Ahmed, Riaz
• Primary Examiner(s): Dougherty, Thomas M
• Application Number:
  US15/627,817
• Publication Number:
  US 20180368071A1
• Time in Patent Office: 1,099 Days
• Field of Search: 310339
• CPC Class Codes: F03G 7/08 recovering energy derived from swinging, rolling, pitching or like movements, e.g. from the vibrations of a machine
• CPC Class Codes: H02K 7/18 Structural association of electric generators with mechanical driving motors, e.g. with turbines
• CPC Class Codes: H02K 7/1892 Generators with parts oscillating or vibrating about an axis
• CPC Class Codes: H02N 11/002 Generators
• CPC Class Codes: H02N 2/00 Electric machines in general using piezoelectric effect, electrostriction or magnetostriction generating mechanical vibrations in general B06B; piezoelectric, electrostrictive or magnetostrictive devices in general H10N30/00
• CPC Class Codes: H02N 2/188 adapted for resonant operation
• CPC Class Codes: H04W 52/0261 managing power supply demand, e.g. depending on battery level
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Modern living involves using a significant amount of energy, much of which may be wasted or not used efficiently. This apparatus and methodology focuses on potentially wasted energy that is being produced by ambient vibration. Bi-modal broad band energy and/or specific frequency harvester/scavengers utilize the physics of local resonance in acousto-elastic metamaterials (AEMM structures). Frequency selectivity of a harvester depends on the mass of a core resonator, soft material that houses the central mass/resonator, and the base material which is used to manufacture the metamaterial. Piezoelectric materials are known to produce electrical current when they are deformed mechanically. Ambient energy is available in the form of vibration and noise, e.g. car vibration, acoustic noise from heavy machineries, vibration from rails, which is lost, if not otherwise harvested. A smart metamaterial can scavenge/harvest ambient low frequency vibration for charging batteries such that the ambient energy may become a renewable source of energy to power low power electronic gadgets on the go. Power output for a unit cell AEMM embodiment is optimized through one or more of multi-frequency/multi-modal harvesting, geometric optimization, and PZT position optimization.

Claims

1. An energy harvesting apparatus for harvesting of energy from ambient sound sources in a given environment, so that said apparatus is capable of providing electrical energy to a load, said apparatus comprising:

an acousto-elastic metamaterial unit cell having a matrix which receives a core mass resonator for movement in said unit cell in response to ambient sound in the environment of said unit cell; and

at least one piezoelectric member embedded in said unit cell, for outputting electrical energy in response to strain created in said unit cell by movement of said resonator in said unit cell;

wherein said apparatus is tuned for harvesting energy in at least two modes, for optimization of electrical energy generation.

2. Apparatus as in claim 1, wherein said at least two modes comprise at least two respective local resonance modes of said unit cell.

3. Apparatus as in claim 1, wherein said at least two modes comprise at least two piezoelectric wafers respectively embedded in said unit cell, for respectively outputting electrical energy in response to strain created by movement of said resonator in said unit cell.

4. Apparatus as in claim 3, wherein said wafers are embedded in said unit cell in predetermined locations based on the desired axes of vibration for harvesting energy from said unit cell.

5. Apparatus as in claim 1, wherein said piezoelectric member comprises at least one lead zirconate titanate (“

PZT”

) wafer.

6. Apparatus as in claim 1, wherein:

said unit cell further includes a relatively stiff frame enclosing said unit cell matrix;

said unit cell matrix is relatively soft; and

said unit cell core mass resonator is relatively heavy.

7. Apparatus as in claim 6, wherein said unit cell frame comprises aluminum, said unit cell matrix comprises rubber, and said unit cell core mass resonator comprises lead.

8. Apparatus as in claim 1, wherein:

said unit cell matrix comprises a flexible membrane; and

said piezoelectric member comprises a piezoelectric polymer.

9. Apparatus as in claim 8, wherein:

said unit cell matrix comprises a relatively thin section of silicon;

said unit cell core mass resonator comprises steel; and

said piezoelectric polymer comprises polyvinylidene fluoride (PVDF).

10. Apparatus as in claim 8, wherein:

said flexible membrane is attached to a surface of an associated electronic device; and

said piezoelectric member electrical energy output is configured for at least one of powering and charging such electronic device.

11. Apparatus as in claim 10, wherein such associated electronic device comprises an implantable medical device.

12. Apparatus as in claim 11, wherein:

said implantable medical device comprises a pacemaker; and

said apparatus is tuned for having at least one local resonance mode of said unit cell resulting in an energy harvestable frequency of about 39 Hz.

13. Apparatus as in claim 8, wherein said flexible membrane is attached to a plate of a mobile associated electronic device.

14. Apparatus as in claim 13, further including:

a plurality of said acousto-elastic metamaterial unit cells, each respectively having a matrix which receives a core mass resonator for movement in each of said unit cells in response to ambient sound in the environment of said unit cells; and

with at least one piezoelectric member embedded in each of said unit cells, for outputting electrical energy in response to strain created in said unit cells by movement of said resonators in said unit cells; and

wherein said piezoelectric members having respective electrical energy outputs configured for at least one of powering and charging such mobile associated electronic device.

15. Apparatus as in claim 14, wherein said plurality of said acousto-elastic metamaterial unit cells comprise generally circular unit cells having respective diameters in a range in respective increments.

16. Apparatus as in claim 1, wherein said apparatus is tuned for harvesting energy from relatively low frequency ambient sound sources.

17. Apparatus as in claim 1, wherein said at least two modes comprise at least three respective piezoelectric wafers respectively embedded at different locations in said unit cell, for respectively outputting electrical energy in response to strains created by vibrations relative respectively to the x-, y- and z-directions of said resonator in said unit cell.

18. Apparatus as in claim 1, wherein

said unit cell further includes a relatively stiff frame having a cavity wall enclosing said unit cell matrix;

said at least one piezoelectric member comprises a piezoelectric wafer selectively embedded in a selected mode Q in said unit cell, for outputting electrical energy in response to strain created in said unit cell by movement of said resonator in said unit cell; and

the distance between the outside diameter of said core mass resonator and said cavity wall is about 3.5 times the distance of the wafer from the outside diameter of said core mass resonator.

19. Apparatus as in claim 1, wherein:

said unit cell further includes a relatively stiff frame enclosing said unit cell matrix;

said apparatus further includes a plurality of said acousto-elastic metamaterial unit cells, having at least one piezoelectric member embedded in each of said unit cells, for outputting electrical energy in response to strain created in said unit cells by movement of said resonators in said unit cells; and

said plurality of unit cells are collectively arranged in a sound barrier for reducing ambient noise from ambient sound sources in a given environment while also collectively electrically connected for outputting electrical energy from said barrier for being stored in an energy storage mechanism or concurrently used as harvested energy output from said barrier.

20. Methodology for harvesting of energy from ambient sound sources in a given environment, for providing electrical energy to a load, such methodology comprising:

providing an acousto-elastic metamaterial unit cell having a matrix which receives a core mass resonator for movement in such unit cell in response to ambient sound in the environment of such unit cell;

embedding at least one piezoelectric member in such unit cell, for outputting electrical energy in response to strain created in such unit cell by movement of such resonator in such unit cell; and

tuning the unit cell and piezoelectric member for harvesting energy in at least two modes, for optimization of electrical energy generation.

21. Methodology as in claim 20, wherein such tuning includes configuring such unit cell for at least two respective local resonance modes of performance.

22. Methodology as in claim 20, wherein such tuning includes providing at least two piezoelectric wafers respectively embedded in such unit cell, for respectively outputting electrical energy in response to strain created by movement of such resonator in such unit cell.

23. Methodology as in claim 22, further including embedding such wafers in such unit cell in predetermined locations based on the desired axes of vibration for harvesting energy from such unit cell.

24. Methodology as in claim 20, wherein such piezoelectric member comprises at least one lead zirconate titanate (“

PZT”

) wafer.

25. Methodology as in claim 20, further including:

providing such unit cell with a relatively stiff frame enclosing such unit cell matrix; and

wherein such unit cell matrix is relatively soft; and

such unit cell core mass resonator is relatively heavy.

26. Methodology as in claim 25, wherein such unit cell frame comprises aluminum, such unit cell matrix comprises rubber, and such unit cell core mass resonator comprises lead.

27. Methodology as in claim 20, wherein:

such unit cell matrix comprises a flexible membrane; and

such piezoelectric member comprises a piezoelectric polymer.

28. Methodology as in claim 27, wherein:

such unit cell matrix comprises a relatively thin section of silicon;

such unit cell core mass resonator comprises steel; and

such piezoelectric polymer comprises polyvinylidene fluoride (PVDF).

29. Methodology as in claim 27, further including:

attaching such flexible membrane to a surface of an associated electronic device; and

configuring such piezoelectric member electrical energy output for at least one of powering and charging such electronic device.

30. Methodology as in claim 29, wherein such associated electronic device comprises an implantable medical device.

31. Methodology as in claim 30, wherein:

such implantable medical device comprises a pacemaker; and

such unit cell is tuned for having at least one local resonance mode resulting in an energy harvestable frequency of about 39 Hz.

32. Methodology as in claim 27, further including attaching such flexible membrane to a plate of a mobile associated electronic device.

33. Methodology as in claim 32, further including:

providing a plurality of such acousto-elastic metamaterial unit cells, each respectively having a matrix which receives a core mass resonator for movement in each of such unit cells in response to ambient sound in the environment of such unit cells; and

with at least one piezoelectric member embedded in each of such unit cells, for outputting electrical energy in response to strain created in such unit cells by movement of such resonators in such unit cells; and

configuring respective electrical energy outputs of such piezoelectric members for at least one of powering and charging such mobile associated electronic device.

34. Methodology as in claim 33, wherein such plurality of such acousto-elastic metamaterial unit cells comprise generally circular unit cells having respective diameters in a range in respective increments.

35. Methodology as in claim 20, wherein such unit cell is tuned for harvesting energy from relatively low frequency ambient sound sources.

36. Methodology as in claim 20, further including providing at least three respective piezoelectric wafers respectively embedded at different locations in such unit cell, for respectively outputting electrical energy in response to strains created by vibrations relative respectively to the x-, y- and z-directions of such resonator in such unit cell.

37. Methodology as in claim 20, further including:

providing such unit cell with a relatively stiff frame having a cavity wall enclosing such unit cell matrix; and

wherein such at least one piezoelectric member comprises a piezoelectric wafer selectively embedded in a selected mode Q in such unit cell, for outputting electrical energy in response to strain created in such unit cell by movement of such resonator in such unit cell; and

the distance between the outside diameter of such core mass resonator and such cavity wall is about 3.5 times the distance of the wafer from the outside diameter of such core mass resonator.

38. Methodology as in claim 20, further including:

providing such unit cell with a relatively stiff frame enclosing such unit cell matrix;

providing a plurality of such acousto-elastic metamaterial unit cells, having at least one piezoelectric member embedded in each of such unit cells, for outputting electrical energy in response to strain created in such unit cells by movement of such resonators in such unit cells; and

collectively arranging such plurality of unit cells in a sound barrier for reducing ambient noise from ambient sound sources in a given environment while also collectively electrically connecting such unit cells for outputting electrical energy from such barrier for being stored in an energy storage mechanism or concurrently used as harvested energy output from such barrier.

39. Methodology for harvesting of electric potential from ambient low frequency vibrations having multiple acoustic low frequencies, using a smart unit cell metamaterial, for providing electrical energy to an electrical load, such methodology comprising:

providing an energy harvesting unit comprising an acousto-elastic metamaterial unit cell having a matrix which receives a core mass resonator for movement in such unit cell in response to ambient sound in the environment of such unit cell, and having at least one embedded piezoelectric member in such unit cell, for outputting electrical energy in response to strain created in such unit cell by movement of such resonator in such unit cell;

providing a plurality of such energy harvesting units together in an environment having ambient low frequency vibrations; and

electrically connecting such plurality of energy harvesting units, for providing electrical energy therefrom for one of charging or driving a load.

40. Methodology as in claim 39, further including:

providing each of such energy harvesting units with respective frames surrounding their respective matrices; and

supporting such plurality of such energy harvesting units in a barrier wall so that such wall functions both for noise control and energy harvesting.

41. Methodology as in claim 39, further including:

providing each of such energy harvesting units with planar cell structures; and

supporting such plurality of such energy harvesting units on a plate of an associated electronic device so that such plurality of energy harvesting units provide electrical energy therefrom for one of charging or driving such associated electronic device.

42. Methodology as in claim 39, wherein at least some of such plurality of such energy harvesting units include respective, different structures or materials designed for having different energy harvestable frequencies from at least one other of such energy harvesting units having different structures or materials therefrom.