CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is based on provisional patent application Ser. No. 62/887,122 filed Aug. 15, 2019.

FIELD OF THE INVENTION

The present invention relates generally to thermoelectric devices.

BACKGROUND

Thermoelectric materials may be used in systems that harness electrical power for cooling and for systems that generate electrical power in response to a temperature difference between a heat source and a heat sink.

Cooling in response to an electrical current passed through a thermoelectric device is a manifestation of the Peltier effect. A basic device that manifests the Peltier effect and hence may be used for cooling includes two dissimilar materials having a junction thermally coupled to a thermal load to be cooled. The Peltier effect is described by equation 1 below:
{dot over (Q)}=(ΠA−ΠB)·IEQU. 1where {dot over (Q)} is a net quantify of heat flow to the junction;ΠAand ΠBare respectively the Peltier coefficient of the aforementioned two dissimilar materials; andI is a current passed through the junction.Selection between heating and cooling of the junction can be achieved by changing the direction of the current I through the junction;

The generation of electricity in response to the establishment of a thermal gradient across a thermoelectric device is a manifestation of the Seebeck effect. The construction of a basic device that manifests the Seebeck effect parallels the construction of a basic device that manifests the Peltier effect. The two devices do differ however in the manner of use. In the case of the Seebeck effect electrical output is obtained in response to subjecting the device to a thermal gradient whereas in the case of the Peltier effect heat is transferred in response to application of electrical power from a separate external power source. The Seebeck effect for a single conductor is described by equation 2 below.
J=σ·(−∇V+EPeltier)  EQU. 2

where,J is a current generated due to the Seebeck effect;σ is an electrical conductivity of the device;∇V is an externally measured voltage; and
EPeltier=S·ΔTWhere,S is the Seebeck coefficient; andΔT is the temperature gradient across the device.

By forming a junction between a P-doped semiconductor and N-doped semiconductor, both of which manifest the Seebeck effect and exposing the junction to a heat source, a continuous current can be induced to flow between proximal ends of the two semiconductors which are situated at a position removed from the heat source.

FIG.1shows a prior art thermoelectric generator100. The thermoelectric generator100includes n-doped block102and a p-doped block104. A first end102aof the n-doped block102, and a first end104aof the p-doped block104are contact a common hot side electrical contact106which also serves as a heat source contact for coupling to a heat source (not shown) such as an exhaust manifold of an internal combustion engine. A second end102bof the n-doped block102is coupled to first cold side electrical contact (cathode)108and a second end104bof the p-doped block is coupled to a second cold side electrical contact (anode)110. The cold side electrical contact electrical contacts108,110are supported on a heat sink thermal contact112which in use may be connected to a heat sink (not shown). Common thermoelectric materials are brittle material and hence cannot be bent near the hot side to form a direct junction between the n-doped block102and the p-doped block104. Aside from the low compliance issue, methods of forming a PN junction from blocks of p-doped and n-doped materials may not be available. Hence the hot side electrical contact106is provided to connect the n-doped block102and the p-doped block104. Now generally speaking the efficiency of the thermoelectric effect and the amount of electrical power that can be extracted from a thermoelectric device depends on the magnitude of the temperature difference between the heat source (hot side) temperature and the heat sink (cold side) temperature. The cold side temperature is tied to the ambient temperature and differs therefrom by an amount proportional to the thermal resistance of the heat sink, so the best that can be done in respect to the cold side temperature is to approach the ambient temperature. A limiting factor in the temperature difference that may be achieved is then dependent on the maximum temperature that the hot side of the thermoelectric generator can withstand. In the prior art thermoelectric generator100the limiting factor may be the temperature limit of the common hot side electric contact106which may be made of metal. In certain applications it would be desirable to eliminate the common hot side electrical contact, so as to allow a higher hot side temperature and greater electrical output. The maximum service temperature of the P and or N thermoelectric materials may also limit the hot-cold side temperature difference that may be achieved. It would be desirable to provide a thermoelectric generator that includes thermoelectric materials that are able to sustain high temperature operation and are also unfettered by the temperature limits typically associated with hot side interconnect metallization.

SUMMARY OF THE INVENTION

One aspect of the invention is a thermoelectric generator including a heat source contact, a heat sink contact, and a plurality of co-axial fibers, each of the co-axial fibers including a core and a cladding disposed about the core, the plurality of co-axial fibers extending from the heat source contact to the heat sink contact. In such a thermoelectric generator the heat sink contact may include a first electrical contact and a second electrical contact, and the core of the co-axial fibers may extend beyond the cladding so as to present an exposed portion of the core, the cladding may be electrically coupled to the first electrical contact and the core may be electrically coupled to the second electrical contact. The heat source contact may include a hole and the plurality of co-axial fibers may have ends inserted in the hole. The plurality of co-axial fibers may have a serpentine shape that meanders back and forth between the heat source contact and the heat sink contact. In relation to the latter option the heat sink contact may further include a first electrical contact and a second electrical contact and in proceeding along a length of a particular co-axial fiber of the plurality co-axial fibers, the particular coaxial fiber includes: a first portion at which the cladding is electrically coupled to the first electrical contact; a second portion thermally coupled to the heat source contact; a third portion at which the core is exposed and is electrically coupled to the second electrical contact.

Another aspect of the invention includes a spinneret for spinning a co-axial fiber with an interrupted cladding. Such a spinneret includes: an inner conduit configured to conduct a flow of a first material for forming a core of the co-axial fiber, the inner conduit having an inner conduit inlet for receiving the first material and an inner conduit outlet for discharging the first material; an outer chamber configured to conduct a flow of a second material for forming a cladding of the co-axial fiber, the outer chamber having an outer chamber inlet for receiving the second material and an outer chamber outlet for discharging the second material, wherein the inner conduit passes through the outer chamber and the inner conduit outlet is disposed in the outer chamber outlet; and a valve mechanism configured for selectively stopping the flow of the second material. The valve mechanism may include a plunger disposed in the outer chamber around the inner conduit and a biasing element for urging the plunger into the outer chamber outlet to interrupt the flow of the second material. A solenoid may be disposed proximate the plunger and configured to counteract the biasing element and withdraw the plunger from the outer chamber outlet so as to allow the flow of the second material.

Another aspect of the invention is a thermoelectric fabric having a first set of conductive threads extending in a first direction, a second set of conductive threads extending in the first direction, and a set of co-axial thermoelectric fibers generally extending in a second direction and woven through the first set of conductive threads and the second set of conductive threads, each of the set of co-axial thermoelectric fibers including a core having a first type doping and a cladding having a second type doping, wherein the cladding contacts the first set of conductive threads, and wherein the core contacts the second set of conductive threads. A portion of the thermoelectric fibers may be looped such that the thermoelectric fabric is a looped fabric.

Another aspect of the invention includes a thermoelectric generator including: a heat source contact, a plurality of N doped hollow fibers having first ends thermally coupled to the heat source contact, a plurality of P doped hollow fibers having first ends thermally coupled to the heat source contact, a first electrical contact electrically coupled to second ends of the plurality of N doped hollow fibers, and a second electrical contact electrically coupled to the second ends of the plurality of P doped hollow fibers.

Another aspect of the invention includes a thermoelectric fiber including: an outer cladding including semiconductor having a first type of doping; an inner core including seeming conductor having a second type of doping; and an inner cladding disposed between the inner core and the outer cladding.

Another aspect of the invention includes a spinneret for forming a doubly clad core co-axial fiber, the spinneret including: an inner conduit configured to conduct a flow of a first material for forming a core of the co-axial fiber, the inner conduit having an inner conduit inlet for receiving the first material and an inner conduit outlet for discharging the first material; an intermediate chamber configured to conduct a flow of a second material for forming an inner cladding of the co-axial fiber, the intermediate chamber having an intermediate chamber inlet for receiving the second material and an intermediate chamber outlet for discharging the second material, wherein the inner conduit passes through the intermediate chamber; and the inner conduit outlet is disposed in the intermediate chamber outlet; and an outer chamber configured to conduct a flow of a third material for forming an outer cladding of the co-axial fiber, the outer chamber having an outer chamber inlet for receiving the third material and an outer chamber outlet for discharging the third material, wherein the intermediate chamber outlet is disposed in the outer chamber outlet.

Another aspect of the invention includes a thermoelectric device including: a P doped thermoelectric fiber having a first end and an N doped thermoelectric fiber having a first end wherein the first end of the P doped thermoelectric fiber is directly contacting the first end of the N doped thermoelectric fiber forming a PN junction. The thermoelectric device may include a heat source coupler thermally coupled to the PN junction. The N doped thermoelectric fiber has a second end and the P doped thermoelectric fiber has a second end. The thermoelectric device further includes a first electrical contact and a second electrical contact, the second end of the N doped thermoelectric fiber is electrically coupled to the first electrical contact and the second end of the P doped thermoelectric fiber is electrically coupled to the second electrical contact. A heat sink may be thermally coupled to the first electrical contact and the second electrical contact.

Another aspect of the invention is a method of making a thermoelectric device. The method includes: preparing a first batch of silicon carbide precursor mixed with a first type of dopant species; preparing a second batch of silicon carbide precursor mixed with a second type of dopant species; supplying the first batch of silicon carbide precursor mixed with the first type of dopant species to a first inlet of a co-axial spinneret; suppling the second batch of silicon carbide precursor mixed with the second type of dopant species to a second inlet of a co-axial spinneret; using the co-axial spinneret to spin a co-axial clad core silicon carbide precursor fiber; pyrolizing the co-axial clad core silicon carbide precursor fiber to obtain a co-axial clad core silicon carbide fiber; and assembling the co-axial clad core silicon carbide fiber precursor into the thermoelectric device.

Another aspect of the invention is a method of making a hollow thermoelectric fiber. The method includes; preparing a fugitive core spinning feed stock; preparing a cladding spinning feed stock including silicon carbide precursor and dopant; supplying the cladding feed stock to an outer annular conduit of a spinneret; supplying the fugitive core spinning feed stock to an inner conduit of the spinneret; using the spinneret to spin a fiber having a cladding including the cladding spinning feed stock and a core including the fugitive core spinning feed stock; and heating the fiber to transform the cladding feed stock to doped silicon carbide and to eliminate the core.

Another aspect of the invention is a method of making a PN junction. The method includes: obtaining a first batch of silicon carbide precursor including a first type of dopant; obtaining a second batch of silicon carbide precursor including a second type of dopant; spinning a first precursor fiber from the first batch of silicon carbide precursor including the first type of dopant; pyrolizing the first precursor fiber to obtain a first silicon carbide fiber having the first type of dopant; spinning a second precursor fiber from the second batch of silicon carbide precursor including the second type of dopant; contacting the second precursor fiber with the first silicon carbide fiber; heating the second precursor fiber that is in contact with the first silicon carbide fiber to a temperature sufficient and pyrolize the second precursor fiber to obtain second silicon carbide fiber having the second type of dopant in contact with the first silicon carbide fiber having the first type of dopant forming the PN junction.

Another aspect of the invention is another method of making a PN junction that includes: obtaining a first batch of silicon carbide precursor including an N type dopant; spinning a first precursor fiber from the first batch of silicon carbide precursor; obtaining a second batch of silicon carbide precursor including a P type dopant; spinning a second precursor fiber from the second batch of silicon carbide precursor; contacting the first precursor fiber and the second precursor fiber; subjecting the contacted first and second precursor fibers to heat and pyrolize the first and second precursor fibers to obtain an N doped silicon carbide fiber in contact with a P doped silicon carbide fiber thereby forming a PN junction.

Another aspect of the in invention is a jet engine including an outer housing, a combustion chamber and a thermoelectric generator thermally coupled to the outer housing and to the combustion chamber. The thermoelectric generator may include semiconductor fibers.

Another aspect of the invention is a rocket engine including a double walled nozzle including an inner wall, an outer wall and a thermoelectric generator located between the inner wall and the outer wall and thermally coupled to the inner wall and to the outer wall.

Another aspect of the invention is a method of forming a semiconductor junction including: obtaining silicon carbide semiconductor having a first doping type obtaining a silicon carbide precursor that includes a second doping type species, contacting the silicon carbide precursor with the silicon carbide semiconductor and pyrolyzing the silicon carbide precursor.

Another aspect of the invention is a method of forming a semiconductor junction comprising, the method including: obtaining a first silicon carbide precursor having a first doping type species, obtaining a second silicon carbide precursor having a second doping type species, contacting the first silicon carbide precursor and the second silicon carbide precursor, and pyrolyzing the first silicon carbide precursor and the second silicon carbide precursor.

