Electrocaloric device and thermal transfer systems employing the same

• US 6,877,325 B1
• Filed: 06/03/2003
• Issued: 04/12/2005
• Est. Priority Date: 06/27/2002
• Status: Expired due to Fees

• Current Assignee: Ceramphysics, Inc.
• Original Assignee: Ceramphysics, Inc.
• Inventors: Lawless, William N.
• Primary Examiner(s): Esquivel, Denise L.
• Assistant Examiner(s): Drake, Malik N.
• Application Number:
  US10/453,450
• Time in Patent Office: 679 Days
• Field of Search: 62/31, 62/37, 623/30, 624/67, 252/518.1, 252/521.1
• US Class Current: 62/3.1
• CPC Class Codes: F25B 21/00 Machines, plants or systems, using electric or magnetic effects
• CPC Class Codes: F25B 2309/003 characterised by construction or composition of the regenerator
• CPC Class Codes: F25B 2321/001 by using electro-caloric effects
• CPC Class Codes: F25B 25/00 Machines, plants or systems, using a combination of modes of operation covered by two or more of the groups F25B1/00 - F25B23/00
• CPC Class Codes: F25B 9/14 characterised by the cycle used, e.g. Stirling cycle
• CPC Class Codes: Y02B 30/00 Energy efficient heating, ventilation or air conditioning [HVAC]

Abstract

Thermal transfer devices according to the present invention comprise electrocaloric materials that increase in temperature upon application of an applied voltage thereto and decrease in temperature upon removal of the applied voltage. In specific embodiments of the present invention, the electrocaloric materials, described in further detail below, are configured such that the respective increases and decreases in temperature of the electrocaloric material extend from about −10° C. to about 50° C. As a result, thermal transfer devices according to the present invention are suitable for use in a wide variety of practical refrigeration applications. In accordance with 37 CFR 1.72(b), the purpose of this abstract is to enable the United States Patent and Trademark Office and the public generally to determine quickly from a cursory inspection the nature and gist of the technical disclosure. The abstract will not be used for interpreting the scope of the claims.

Claims

1. A device comprising:

an electrocaloric device; and

a power supply configured to apply a voltage to said electrocaloric device, wherein

said electrocaloric device comprises the following electrocaloric material

x(PbMg_0.33Nb_0.67O₃)+y(PbSc_0.5Nb_0.5O₃)

where x and y represent respective mol percentages of respective portions of said electrocaloric material, and

said electrocaloric material increases in temperature upon application of an applied voltage thereto and decrease in temperature upon removal of said applied voltage.

2. A device as claimed in claim 1 where x represents a mol percentage of between about 45 and about 70 and y represents a mol percentage of between about 30 and about 55.

3. A device as claimed in claim 1 where said respective increases and decreases in temperature of said electrocaloric material extend from about −

10°

C. to about 50°

C.

4. A device as claimed in claim 1 wherein said electrocaloric device comprises a ceramic capacitor.

5. A device as claimed in claim 4 wherein said ceramic capacitor defines a circular cross section.

6. A device as claimed in claim 5 wherein said ceramic capacitor comprises gas vias extending across said ceramic capacitor.

7. A device as claimed in claim 6 wherein said gas vias are located on one or more concentric circles of said cross section.

8. A device as claimed in claim 1 wherein said device comprises a plurality of said electrocaloric devices arranged in one or more capacitor banks.

9. A device as claimed in claim 1 wherein said power supply is configured to apply said voltage to said electrocaloric device according to a predetermined driving cycle.

10. A device as claimed in claim 9 wherein said electrocaloric device is characterized by a thermal time constant and said power supply is configured such that said driving cycle defines an cooling period sufficient to account for said thermal time constant.

11. A device as claimed in claim 1 wherein said device further comprises circuitry coupling a pair of said electrocaloric devices such that electrical discharge of one of said electrocaloric devices contributes to charging of the other of said pair of electrocaloric devices.

12. A device as claimed in claim 1 wherein said circuitry is configured to resonantly couple said pair of electrocaloric devices to establish a continuous cycle where discharge of one of said electrocaloric devices partially charges the other of said electrocaloric devices.

13. A device as claimed in claim 1 wherein:

said device comprises a thermal load and a thermal sink; and

said electrocaloric device is configured to enable transfer of heat from said thermal load to said thermal sink.

14. A device as claimed in claim 13 wherein said thermal load comprises an enclosed compartment of a refrigerator.

15. A device as claimed in claim 13 wherein said device further comprises a heat exchanger coupled thermally between said electrocaloric device and said thermal load.

16. A device as claimed in claim 13 wherein said device further comprises a heat exchanger coupled thermally between said electrocaloric device and said thermal sink.

17. A device as claimed in claim 13 wherein said electrocaloric device defines a heat exchanger coupled thermally between said thermal load and said thermal sink.

18. A device as claimed in claim 1 wherein said electrocaloric device includes interior vias defining a thermal flow passages across said electrocaloric device.

19. A device as claimed in claim 1 wherein said device comprises a plurality of electrocaloric devices.

20. A device as claimed in claim 19 wherein said plurality of electrocaloric devices define a cascading thermal coupling.

21. A device as claimed in claim 1 wherein said device further comprises components of a refrigeration system configured to cooperate with said electrocaloric device.

22. A device as claimed in claim 21 wherein said refrigeration system comprises a Stirling cycle refrigeration system.

24. A device as claimed in claim 21 wherein said refrigeration system comprises a split cycle refrigeration system.

25. A device as claimed in claim 21 wherein said refrigeration system comprises a cascading regenerator refrigeration system.

23. 22 wherein said electrocaloric device is configured to serve as an active regenerator of said Stirling cycle refrigeration system.

26. A device comprising:

an electrocaloric device; and

a power supply configured to apply a voltage to said electrocaloric device, wherein

said electrocaloric device comprises the following electrocaloric material

x(PbMg_0.33Nb_0.67O₃)+y(PbTiO₃)+z(SrTiO₃)

where x, y, and z are each greater than zero and represent respective mol percentages of respective portions of said electrocaloric material, and

said electrocaloric material increases in temperature upon application of an applied voltage thereto and decrease in temperature upon removal of said applied voltage.

27. A device comprising:

an electrocaloric device; and

a power supply configured to apply a voltage to said electrocaloric device, wherein

said electrocaloric device comprises the following electrocaloric material

x(PbMg_0.33Nb_0.67O₃)+y(PbTiO₃)+z(C)

where x, y, and z are each greater than zero and represent respective mol percentages of respective portions of said electrocaloric material and C represents a ceramic oxide configured to offset substantially an increase in a dielectric transition temperature attributable to inclusion of PbTiO₃ in said electrocaloric material, and

said electrocaloric material increases in temperature upon application of an applied voltage thereto and decrease in temperature upon removal of said applied voltage.

28. A device comprising:

an electrocaloric device; and

a power supply configured to apply a voltage to said electrocaloric device, wherein said electrocaloric device comprises the following electrocaloric material that increases in temperature upon application of an applied voltage thereto and decrease in temperature upon removal of said applied voltage

x(A)+y(B)+z(C)

where

A represents a ceramic oxide of Pb, Mg, and Nb,

B represents a ceramic oxide of Pb and at least one additional metal selected from Sc, Nb, and Ti,

C represents a ceramic oxide of Sr and Ti,

x represents a mol percentage of between about 45 and about 90,

y represents a mol percentage of between about 10 and about 55, and

z represents a mol percentage of about 0 where B represents a ceramic oxide of Pb, Sc and Nb, and a mol percentage greater than 0 and less than about 10 where B represents a ceramic oxide of Pb and Ti.