Miniature Thermoelectric Power Generator

• US 20110155202A1
• Filed: 09/11/2009
• Published: 06/30/2011
• Est. Priority Date: 09/18/2008
• Status: Active Grant

• Current Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Original Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Inventors: Boniche, Israel, Masilamani, Sivaraman, Meyer, Christopher David, Arnold, David Patrick
• Granted Patent: US 9,214,618 B2
• Time in Patent Office: Days
• US Class Current: 136/224
• CPC Class Codes: H10N 10/17 characterised by the structure or configuration of the cell or thermocouple forming the device

Abstract

The subject invention pertains to thermoelectric power generation. According to certain embodiments, a stack of silicon-micromachined chips can be connected to form a cylindrical heat exchanger that enables a large, uniform temperature difference across a radially-oriented thermopile. Each layer in the stack can comprise two thermally-isolated concentric silicon rings connected by a polyimide membrane that supports patterned thermoelectric thin films. The polyimide membrane can be formed by selectively etching away the supporting silicon, resulting in thermally-isolated inner and outer rings. In operation, hot gas can flow through a finned central channel, and an external cross flow can enhance heat transfer to ambient to keep the outer surfaces cool. The resulting temperature gradient across the thermopile generates a voltage potential across the open ends due to the Seebeck effect. When connected to a load, current flows, and electrical power is supplied by the generated voltage potential caused by the temperature gradient.

Claims

1. A thermoelectric device, comprising:

a stack of thermoelectric modules, each thermoelectric module comprising;

an inner thermally conductive ring, the inner thermally conductive ring providing a channel for hot gas to pass therethrough;

an outer thermally conductive ring, an outer surface of the outer thermally conductive ring remaining cooler than the inner thermally conductive ring; and

a radially-oriented thermopile in connection with the inner thermally conductive ring and the outer thermally conductive ring, wherein the radially-oriented thermopile has alternating regions of thermoelectric material.

2. The thermoelectric device according to claim 1, wherein the outer surface of the outer thermally conductive ring remains cool through exposure to an external environment by passive exposure or by convective flow.

3. The thermoelectric device according to claim 1, wherein each thermoelectric module further comprises:

inner fins on an inner surface of the inner conductive ring.

4. The thermoelectric device according to claim 3, wherein the inner fins extend longitudinally along the inner surface.

5. The thermoelectric device according to claim 3, wherein the inner fins comprise pin shapes extending perpendicular to the inner surface.

6. The thermoelectric device according to claim 1, wherein certain ones of the thermoelectric modules of the stack comprise a fin extension at the outer conductive ring.

7. The thermoelectric device according to claim 1, wherein the inner thermally conductive ring and the outer thermally conductive ring comprise silicon.

8. The thermoelectric device according to claim 1, wherein the alternating regions of thermoelectric material comprise a first metal as one thermoelectric material and a second metal different than the first metal as another thermoelectric material.

9. The thermoelectric device according to claim 1, wherein the alternating regions of thermoelectric material comprise a metal as one thermoelectric material and polysilicon as another thermoelectric material.

10. The thermoelectric device according to claim 1, wherein the alternating regions of thermoelectric material comprise at least one of bismuth telluride alloy, lead telluride alloy, silicon germanium alloy, TAGS, and LAST.

11. The thermoelectric device according to claim 1, further comprising resistive temperature sensors on the inner thermally conductive ring and the outer thermally conductive ring.

12. The thermoelectric device according to claim 1, wherein each thermoelectric module further comprises:

an annular supporting membrane on a top surface of the inner and outer thermally conductive rings, wherein the radially-oriented thermopile is disposed on the annular supporting membrane.

13. The thermoelectric device according to claim 12, wherein the annular supporting membrane comprises a thermally insulating material.

14. The thermoelectric device according to claim 12, wherein the inner and outer thermally conductive rings comprise silicon;

and wherein the annular supporting membrane comprises;

a silicon dioxide pattern on a top surface of the silicon inner and outer thermally conductive rings; and

an annular polyimide membrane on the silicon dioxide pattern, wherein the radially-oriented thermopile is disposed on the annular polyimide membrane.

15. A method for fabricating a thermoelectric device, the method comprising:

providing a semiconductor substrate comprising a front-side oxide layer and a back-side oxide layer;

forming an annular thermally insulating membrane on the front-side oxide layer;

forming a set of first thermoelements on the annular thermally insulating membrane;

forming a set of second thermoelements on the annular thermally insulating membrane;

removing portions of the front-side oxide layer exposed at an inner region of the annular thermally insulating membrane and at an outer region of the annular thermally insulating membrane;

removing the back-side oxide layer;

forming a protective coating on the set of first thermoelements and the set of second thermoelements; and

performing an etching process with respect to the back-side of the semiconductor substrate such that the semiconductor substrate is completely removed in a region corresponding to the inner region of the annular thermally insulating membrane while defining a finned inner channel, and the semiconductor substrate is completely removed to expose a bottom surface of the front-side oxide layer.

16. The method according to claim 15, wherein a portion of a material for the second thermoelements is formed to overlap a region of at least one first thermoelement.

17. The method according to claim 15, wherein performing the etching process with respect to the back-side of the semiconductor substrate further comprises etching the semiconductor substrate through a region surrounding the annular thermally insulating membrane, releasing the resulting structure from the semiconductor substrate.

18. The method according to claim 17, wherein the resulting structures are formed in plurality, the method further comprising:

stacking each resulting structure in alignment; and

bonding the stacked resulting structures to each other.

19. The method according to claim 15, wherein the annular thermally insulating membrane comprises an annular polyimide ring.

20. A method for fabricating a thermoelectric device, comprising:

fabricating a plurality of thermoelectric modules using a silicon wafer, wherein each thermoelectric module comprises two thermally-isolated concentric silicon rings connected by a thermally insulating membrane that supports patterned thermoelectric thin films; and

stacking two or more of the thermoelectric modules to form a tubular or cylindrical structure.