Method and structure for providing a uniform micron/sub-micron gap separation within micro-gap thermophotovoltaic devices for the generation of electrical power
A near-field energy conversion method, utilizing a sub-micrometer “near-field” gap between juxtaposed infrared radiation receiver and emitter surfaces, wherein compliant membrane structures, preferably fluid-filled, are interposed in the structure for maintaining uniform gap separation. Thermally resistant gap spacers are also used to maintain uniform gap separation. Means are provided for cooling a receiver substrate structure and for conducting heat to an emitter substrate structure. The gap may also be evacuated for more effective operation.
1. A method for near-field energy conversion, comprising:
juxtaposing a relatively hot inner surface of a thermal emitter substrate and an adjacent relatively cool inner surface of a radiation receiver substrate;
separating the juxtaposed relatively hot inner surface of the thermal emitter substrate and the adjacent relatively cool inner surface of the radiation receiver substrate by a gap of less than one micron;
covering an outer surface of the thermal emitter substrate opposite the hot inner surface with an emitter membrane structure of pressure-compliant thermally conductive material and covering an outer surface of the radiation receiver substrate opposite the cool inner surface with a receiver membrane structure of pressure-compliant thermally conductive material;
setting and maintaining uniformity of the gap, and providing thermal conductivity between impinging radiation and the outer surface of the thermal emitter substrate by the emitter membrane structure; and
setting and maintaining uniformity of the gap, and providing cooling to the outer surface of radiation receiver substrate by the receiver membrane structure.
2. The method of claim 1 , further comprising assembling the receiver membrane structure and the outer surface of the radiation receiver substrate in a frame secured along the periphery of the radiation receiver substrate.
3. The method of claim 2 , wherein the frame includes an internal cavity chamber extending along the receiver membrane structure.
4. The method of claim 3 , wherein a coolant is passed through the internal cavity chamber.
5. The method of claim 1 , further comprising positioning an array of thermally resistant gap spacers in the gap between the relatively hot inner surface of the thermal emitter substrate and the relatively cool inner surface of the radiation receiver substrate.
6. The method of claim 1 , further comprising evacuating the gap between the relatively hot inner surface of the thermal emitter substrate and the relatively cool inner surface of the radiation receiver substrate.
7. The method of claim 1 , further comprising positioning a single emitter compression support layer on the outer surface of the thermal emitter substrate.
8. The method of claim 7 , further comprising maintaining gap uniformity by the single emitter compression support layer by applying a rigid external pressure to the outer surface of the thermal emitter substrate.
9. The method of claim 1 , further comprising positioning a single receiver compression support layer on the outer surface of the radiation receiver substrate.
10. The method of claim 9 , further comprising maintaining gap uniformity by the single receiver compression support layer by applying a rigid external pressure to the outer surface of the radiation receiver substrate.
11. The method of claim 1 , further comprising enclosing a pressure-exerting fluid by a wall comprising the emitter membrane structure and the receiver membrane.
12. The method of claim 11 , further comprising exerting a pressure by the emitter membrane structure on the outer surface of the thermal emitter substrate that is a function of a coolant flow rate in the emitter membrane structure resulting in a compressive force through the gap.
13. The method of claim 11 , further comprising exerting a pressure by the receiver membrane structure on the outer surface of the radiation receiver substrate that is a function of a coolant flow rate in the receiver membrane structure resulting in a compressive force through the gap.
14. The method of claim 1 , further comprising positioning a cool side compliant layer between the outer surface of the radiation receiver substrate and the receiver membrane structure to ensure efficient cooling of the radiation receiver substrate, and positioning a hot side compliant layer between the outer surface of the thermal emitter substrate and the membrane structure to ensure efficient heat transfer to the thermal emitter substrate.
15. The method of claim 1 , further comprising positioning a hot side compliant layer between the outer surface of the thermal emitter substrate and the membrane structure to ensure efficient heat transfer to the thermal emitter substrate.
16. The method of claim 7 , further comprising positioning a hot side compliant layer between the emitter compression support layer and the outer surface of the thermal emitter substrate to ensure efficient heat transfer to the thermal emitter substrate.
17. The method of claim 9 , further comprising positioning a cool side compliant layer between the receiver compression support layer and the outer surface of the radiation receiver substrate to ensure efficient cooling of the radiation receiver substrate.
18. The method of claim 1 , further comprising positioning an emitter stress-compensating layer of substantially the same material as the thermal emitter substrate, within the emitter membrane structure to ensure that a pressure exerted by the emitter membrane structure does not result in deformation of the thermal emitter substrate.
19. The method of claim 1 , further comprising positioning a stress-compensating layer of substantially the same material as the radiation receiver substrate, within the receiver membrane structure to ensure that a pressure exerted by the receiver membrane structure does not result in deformation of the radiation receiver substrate.
20. The method of claim 1 , further comprising adjusting a thickness of the emitter membrane structure to provide a flexing compliance to compensate for mechanical deformation of the thermal emitter and radiation receiver substrates.
21. The method of claim 1 , further comprising adjusting a thickness of the receiver membrane structure to provide a flexing compliance to compensate for mechanical deformation of the thermal emitter and radiation receiver substrates.
22. The method of claim 1 , wherein the radiation receiver comprises a PV cell.
23. The method of claim 1 , wherein the thermal emitter comprises an array of quantum dots.
24. The method of claim 1 , wherein the radiation receiver and thermal emitter comprise an MTPV system.