Piezo-pyroelectric energy converter and method

• US 5,644,184 A
• Filed: 02/15/1996
• Issued: 07/01/1997
• Est. Priority Date: 02/15/1996
• Status: Expired due to Term

• Current Assignee: MicroPower Global Ltd.
• Original Assignee: Thermodyne, Inc.
• Inventors: Kucherov, Yan R.
• Primary Examiner(s): LaBalle, Clayton E.
• Application Number:
  US08/602,159
• Time in Patent Office: 502 Days
• Field of Search: 310/306, 310/308, 322/2 R
• US Class Current: 310/306
• CPC Class Codes: F25B 21/00 Machines, plants or systems, using electric or magnetic effects
• CPC Class Codes: F25B 2321/001 by using electro-caloric effects
• CPC Class Codes: G01J 5/34 using capacitors, e.g. pyroelectric capacitors
• CPC Class Codes: H10N 15/10 Thermoelectric devices using thermal change of the dielectric constant, e.g. working above and below the Curie point
• CPC Class Codes: H10N 15/15 Thermoelectric active materials
• CPC Class Codes: Y02B 30/00 Energy efficient heating, ventilation or air conditioning [HVAC]

Abstract

The present invention embodies a piezo-pyroelectric energy converter and is directed to a method and apparatus for conversion of thermal energy to electrical energy and refrigeration. The present invention utilizes one or more piezo-pyroelectric materials with thermally conductive metal electrodes, which resonate at a high frequency and are in thermal communication with hot and cold heat sinks to create a thermal gradient and heat flow along the metal electrodes and the piezo-pyroelectric material.

Claims

1. An energy conversion device, comprising:

one or more plates formed of piezo-pyroelectric material;

thermally conductive electrodes interleaved with said one or more plates forming a capacitor;

hot and cold heat sinks in thermal communication with said electrodes;

means for holding said one or more plates together;

means coupled to said capacitor for applying voltage and resonant frequency thereto; and

means coupled to said capacitor for removing electrical charge therefrom created from piezo-pyroelectric effects.

2. A device defined in claim 1, wherein said one or more plates comprises PZT, BaNaNb₅ O₁₅, PVDF, BaTiO₃, LiNbO₃, LiTaO₃, PbScTaO_x, YMnO₃, or PZST.

3. A device defined in claim 1, wherein said electrodes comprise electrically and thermally conductive materials.

4. A device defined in claim 1, wherein said electrodes comprise Au, Au--Ni, Ag, Pd, Ni, Cu, Al, Mg, Ag--Pd, or combinations or alloys thereof.

5. A device defined in claim 1, wherein said electrodes comprise C, TiN, ZiN, HfN, TiC, ZrC, WC, or combinations or alloys thereof.

6. A device defined in claim 1, wherein said electrodes comprise Pt or Ir.

7. A device defined in claim 1, further comprising diffusion barriers disposed between said one or more plates and said electrodes.

8. A device defined in claim 7, wherein said diffusion barriers comprise SiC or SiN.

9. A device defined in claim 7, wherein said diffusion barriers comprise doped-diamond electrically conductive coatings.

10. A device defined in claim 7, wherein said diffusion barriers comprise W, Re, Os, Ir, Pt, Au, or combinations thereof.

11. A device defined in claim 1, wherein said hot and cold heat sinks comprise metal or metal alloys.

12. A device defined in claim 11, further comprising thermally conductive graphite lubrication disposed on said metal or metal alloys.

13. A device defined in claim 1, further comprising an electric insulator disposed between the capacitor and the heat sinks.

14. A device defined in claim 13, wherein said electric insulator comprises TEFLON, KAPTON, Al₂ O₃, AlN, MgO, NiO₂, SiO₂, or BeO.

15. A device defined in claim 1, wherein said hot and cold heat sinks comprise ceramic material.

16. A device defined in claim 15, wherein said ceramic material comprises BeO, AlN, SiO₂, SiC, MgO₂, NiO₂, TiB₂, W₂ B₅, or SiN.

17. A device defined in claim 1, wherein said hot and cold heat sinks comprise a thermally conductive dielectric material coated on the one or more plates.

18. A device defined in claim 17, wherein said dielectric material comprises aluminum nitride, non-doped diamond coatings, aluminum oxide, zirconium oxide, titanium oxide, yttrium oxide, magnesium oxide, beryllium oxide, silicon oxide, nickel dioxide, scandium oxide, hafnium oxide, lanthanoid oxides, thorium oxide, or uranium oxide.

19. A device defined in claim 1, wherein said hot and cold heat sinks comprise graphite.

20. A device defined in claim 1, wherein said holding means comprises a compressing frame internal to said one or more plates.

21. A device defined in claim 20, wherein said compressing frame comprises:

a rod centrally disposed to said one or more plates, said rod having first and second ends; and

compressing elements disposed on the first and second ends for applying a compressive force to the one or more plates.

22. A device defined in claim 21, wherein said first and second ends include threads and the compressing elements comprise threaded nuts.

23. A device defined in claim 22, further comprising compression washers disposed between the one or more plates and the threaded nuts.

24. A device defined in claim 23, wherein said compressing washers are disposed on a dielectric tube.

25. A device defined in claim 20, wherein said compressing frame comprises:

one or more supporting elements rigidly secured to the hot or cold heat sink; and

a rod disposed internal to the one or more plates and having a first and second end, said first end being rigidly affixed to said one or more supporting elements and the second end having a compressing element for applying a compressive force to the one or more plates.

26. A device defined in claim 25, wherein said second end includes threads and the compressing element comprises a threaded nut.

27. A device defined in claim 26, further comprising dielectric washers disposed between the one or more supporting elements, the one or more plates, and the threaded nut.

28. A device defined in claim 1, wherein said holding means comprises a compressing frame external to said one or more plates.

29. A device defined in claim 28, wherein said compressing frame comprises:

first and second supporting elements rigidly secured to the hot or cold heat sink; and

a compressing element threadably engaged with said first supporting element for applying force to said one or more plates.

30. A device defined in claim 29, further comprising thermal insulator washers disposed between the one or more plates and said compressing frame and said compressing element.

31. A device defined in claim 30, further comprising a spring disposed between said compressing element and said washer.

32. A device defined in claim 31, wherein said compressing frame is formed with the hot or cold heat sinks.

33. A device defined in claim 1, wherein said means for applying voltage and resonant frequency ω

_o comprises a function generator, and resonant voltage being governed by the equation V(t)=V_o sin(ω

t), and said resonant frequency ω

_o being governed by capacitor internal acoustic resonance and related to the resonant circuit by the equation ##EQU23## where L is the inductance and C is the capacitance of the capacitor.

34. A device defined in claim 1, further comprising frequency adjusting means for varying the resonant frequency due to acoustic resonance frequency variation.

35. A device defined in claim 34, wherein said frequency adjusting means comprises a variable inductance device.

36. A device defined in claim 34, wherein said frequency adjusting means comprises a variable capacitance device connected in series or in parallel with said capacitor.

37. A device defined in claim 1, further comprising means for controlling hot or cold heat sink temperature or a combination thereof.

38. A device defined in claim 1, further comprising means for controlling hot sink temperature and resonant circuit frequency.

39. A device defined in claim 1, wherein said charge removal means comprises a switch comprising a resonant contour formed of said capacitor and an inductance, said contour being driven by a pulse/sine or function generator.

40. A device defined in claim 39, wherein said generator has an output impedance of at least about 1 kΩ

and is connected directly across said resonant contour.

41. A device defined in claim 39, wherein said inductance comprises a first winding of a transformer having a frequency of at least said capacitor resonant frequency and a second winding being connected to said generator.

42. A device defined in claim 1, wherein said charge removal means comprises a switch comprising:

a resonant contour formed of said capacitor, said contour being driven by a pulse/sine or function generator;

an inductance, said inductance being a first winding of a transformer having a frequency of at least said capacitor resonant frequency, said transformer having a second winding connected to said generator; and

an extracting circuit connected in parallel to said contour, said extracting circuit comprising a Zener diode and a first winding of a transformer having a frequency of at least said capacitor resonant frequency, said transformer having a second winding connected to a useful load through a rectifier.

43. A device defined in claim 42, wherein part of said useful load feeds the generator.

44. A device defined in claim 42, wherein said generator is powered by a start-up battery having a timer which is part of the useful load.

45. A device defined in claim 1, wherein said hot and cold heat sinks are at a temperature differential when said voltage is applied.

46. A device defined in claim 1, wherein said hot and cold heat sinks are at equal temperatures when said voltage is applied.

47. A device defined in claim 1, wherein said one or more plates and said electrodes are wedge-shaped, said electrodes having a widest cross-section adjacent said cold heat sink.

48. A device defined in claim 1, wherein said one or more plates are wedge-shaped and said electrodes are planar-shaped.

49. A device defined in claim 48, further comprising a passive wedge-shaped material.

50. A device defined in claim 49, wherein said passive wedge-shaped material comprises mica or KAPTON™

.

51. An energy conversion device, comprising:

one or more plates comprising lead scandium tantalate;

thermally conductive electrodes interleaved with said one or more plates forming a capacitor;

electric insulators being adjacent to said electrodes;

hot and cold heat sinks in thermal communication with said electric insulators, said electric insulators disposed between said hot and cold heat sinks and said electrodes;

means coupled to said capacitor for applying voltage thereto; and

means coupled to said capacitor for removing electrical charge therefrom created from pyroelectric effects.

52. A device defined in claim 51, wherein said electrodes are U-shaped, having left and right legs and a bottom whereby the left and right legs are in thermal communication with the electric insulators and the bottom being adjacent to said plate.

53. A device defined in claim 51, wherein a gap is disposed between the plate and the hot heat sink.

54. A device defined in claim 53, wherein said gap comprises air, gas, or vacuum.

55. A device defined in claim 51, wherein a gap is disposed between the plate and the cold heat sink.

56. A device defined in claim 55, wherein said gap comprises air, gas, or vacuum.

57. A device defined in claim 51, wherein said voltage means comprises a pulse generator.

58. A device defined in claim 51, wherein said voltage means comprises a sine wave generator.

59. A device defined in claim 51, wherein said charge removal means comprises a switch comprising a resonant contour formed of said capacitor and an inductance, said contour being driven by a pulse/sine or function generator.

60. A device defined in claim 59, wherein said inductance comprises a first winding of a transformer having a frequency of at least said capacitor resonant frequency and a second winding being connected to said generator.

61. A device defined in claim 51, wherein said charge removal means comprises a switch comprising:

a resonant contour formed of said capacitor, said contour being driven by a pulse/sine or function generator;

an inductance, said inductance being a first winding of a transformer having a frequency of at least said capacitor resonant frequency, said transformer having a second winding connected to said generator; and

an extracting circuit connected in parallel to said contour, said extracting circuit comprising a Zener diode and a first winding of a transformer having a frequency of at least said capacitor resonant frequency, said transformer having a second winding connected to a useful load through a rectifier.

62. A device defined in claim 61, wherein part of said useful load feeds the generator.

63. A device defined in claim 61, wherein said generator is powered by a start-up battery having a timer which is part of the useful load.

64. A device defined in claim 51, wherein said hot and cold heat sinks are at a temperature differential when said voltage is applied.

65. A device defined in claim 51, wherein said hot and cold heat sinks are at equal temperatures when said voltage is applied.

66. An energy conversion device, comprising:

a capacitor, said capacitor including a U-shaped electrode, a plate comprising lead scandium tantalate adjacent said U-shaped electrode, a second electrode in the form of a plate adjacent said plate comprising lead scandium tantalate, an electric insulator adjacent said second electrode, a plate comprising PZT-5A adjacent said electric insulator, and a third electrode in the form of a plate adjacent said plate comprising PZT-5A;

a means for holding said capacitor together;

electric insulators, said U-shaped electrodes having first and second legs and a bottom, said electric insulators being adjacent to said first and second legs and said bottom being adjacent to said plate comprising lead scandium tantalate;

hot and cold heat sinks in thermal communication with said electric insulators, said electric insulators disposed between said hot and cold heat sinks and said first and second legs of said U-shaped electrode;

means coupled to said capacitor for applying voltage thereto; and

means coupled to said capacitor for removing electrical charge therefrom created from piezo-pyroelectric effects.

67. A device defined in claim 66, wherein said voltage means comprises a pulse generator.

68. A device defined in claim 66, wherein said voltage means comprises a sine wave generator.

69. A device defined in claim 66, wherein said charge removal means comprises a switch comprising a resonant contour formed of said capacitor and an inductance, said contour being driven by a pulse/sine or function generator.

70. A device defined in claim 69, wherein said inductance comprises a first winding of a transformer having a frequency of at least said capacitor resonant frequency and a second winding being connected to said generator.

71. A device defined in claim 66, wherein said charge removal means comprises a switch comprising:

a resonant contour formed of said capacitor, said contour being driven by a pulse/sine or function generator;

an inductance, said inductance being a first winding of a transformer having a frequency of at least said capacitor resonant frequency, said transformer having a second winding connected to said generator; and

an extracting circuit connected in parallel to said contour, said extracting circuit comprising a Zener diode and a first winding of a transformer having a frequency of at least said capacitor resonant frequency, said transformer having a second winding connected to a useful load through a rectifier.

72. A device defined in claim 71, wherein part of said useful load feeds the generator.

73. A device defined in claim 71, wherein said generator is powered by a start-up battery having a timer which is part of the useful load.

74. A device as defined in claim 66, further comprising a material having a lower thermal conductivity than said one or more plates, said material disposed between said one or more plates and said hot heat sink.

75. A device defined in claim 74, wherein said material comprises pressed fiberglass or mica.

76. A device defined in claim 66, wherein said hot and cold heat sinks are at a temperature differential when said voltage is applied.

77. A device defined in claim 66, wherein said hot and cold heat sinks are at equal temperatures when said voltage is applied.

78. A method of converting energy comprising the steps of:

a) holding together one or more plates formed of piezo-pyroelectric material having thermally and electrically conductive electrodes interleaved with said one or plates forming a capacitor, and said electrodes in thermal communication with hot and cold heat sinks;

b) applying a voltage and resonant frequency to said capacitor; and

c) removing electrical charge created by piezo-pyroelectric effects from said capacitor.

79. A method defined in claim 78, wherein said hot and cold heat sinks are at a temperature differential when said voltage is applied.

80. A method defined in claim 78, wherein said hot and cold heat sinks are at equal temperatures when said voltage is applied.

81. A method of converting energy comprising the steps of:

a) holding together one or more plates formed of lead scandium tantalate having thermally and electrically conductive electrodes interleaved with said one or plates forming a capacitor with electric insulators adjacent to said electrodes, and said electric insulators disposed between hot and cold heat sinks and said electrodes;

b) applying a voltage to said capacitor; and

c) removing electrical charge created by pyroelectric effects from said capacitor.

82. A method defined in claim 81, wherein said hot and cold heat sinks are at a temperature differential when said voltage is applied.

83. A method defined in claim 81, wherein said hot and cold heat sinks are at equal temperatures when said voltage is applied.

84. A method of converting energy comprising the steps of:

a) holding a capacitor together, said capacitor comprising;

a U-shaped electrode;

a plate comprising lead scandium tantalate adjacent said U-shaped electrode;

a second electrode in the form of a plate adjacent said plate comprising lead scandium tantalate;

an electric insulator adjacent said second electrode;

a plate comprising PZT-5A adjacent said electric insulator; and

a third electrode in the form of a plate adjacent said plate comprising PZT-5A;

said capacitor further comprising electric insulators, said U-shaped electrodes having first and second legs and a bottom, said electric insulators being adjacent to said first and second legs and said bottom being adjacent to said plate comprising lead scandium tantalate, and hot and cold heat sinks in thermal communication with said electric insulators, said electric insulators disposed between said hot and cold heat sinks and said first and second legs of said U-shaped electrode;

b) applying a voltage to said capacitor; and

c) removing electrical charge created by piezo-pyroelectric effects from said capacitor.

85. A method defined in claim 84, wherein said hot and cold heat sinks are at a temperature differential when said voltage is applied.

86. A method defined in claim 84, wherein said hot and cold heat sinks are at equal temperatures when said voltage is applied.