Thermophotovoltaic energy generation
Inventive systems and methods for the generation of energy using thermophotovoltaic cells are described. Also described are systems and methods for selectively emitting electromagnetic radiation from an emitter for use in thermophotovoltaic energy generation systems. In at least some of the inventive energy generation systems and methods, a voltage applied to the thermophotovoltaic cell (e.g., to enhance the power produced by the cell) can be adjusted to enhance system performance. Certain embodiments of the systems and methods described herein can be used to generate energy relatively efficiently.
1. An energy generation system, comprising:
an emitter constructed and arranged to emit electromagnetic radiation, wherein the emitter comprises a photonic crystal comprising 1-dimensional or 2-dimensional periodicity;
a thermophotovoltaic cell constructed and arranged to convert at least a portion of the electromagnetic radiation emitted by the emitter into electricity; and
a filter positioned between the emitter and the thermophotovoltaic cell, the filter comprising:
a first material having a first index of refraction,
a second material having a second index of refraction different from the first index of refraction positioned between the first material and the emitter and in direct contact with the first material,
a third material having a third index of refraction different from the first and second indices of refraction positioned between the second material and the emitter and in direct contact with the second material, and
a fourth material having a fourth index of refraction different from the first, second, and third indices of refraction positioned between the third material and the emitter and in direct contact with the third material,
wherein the indices of refraction of the first, second, third, and fourth materials increase along a path directed toward the emitter.
2. The energy generation system of claim 1 , wherein the emitter is constructed and arranged to emit electromagnetic radiation within one or more predetermined ranges of wavelengths.
3. The energy generation system of claim 1 , wherein the filter is in physical contact with the emitter.
4. The energy generation system of claim 1 , wherein the filter is spaced apart from the emitter and the thermophotovoltaic cell.
5. The energy generation system of claim 1 , wherein the filter is in physical contact with the thermophotovoltaic cell.
6. The energy generation system of claim 1 , wherein the filter comprises a photonic crystal comprising 1-dimensional periodicity.
7. The energy generation system of claim 1 , wherein the emitter is constructed and arranged to emit electromagnetic radiation when it is heated.
8. The energy generation system of claim 1 , wherein the emitter comprises a chemical reactor.
9. The energy generation system of claim 8 , wherein the chemical reactor comprises a combustor.
10. The energy generation system of claim 1 , wherein the emitter comprises a radioactive isotope.
11. The energy generation system of claim 1 , wherein the photonic crystal comprises a fifth material having a fifth index of refraction and a sixth material having a sixth index of refraction that is different from the fifth index of refraction.
12. The energy generation system of claim 1 , wherein the photonic crystal comprises a plurality of bi-layers, each bi-layer comprising a first layer of a fifth material having a fifth index of refraction and a second layer of a sixth material having a sixth index of refraction.
13. The energy generation system of claim 12 , wherein the thicknesses of the bi-layers are arranged such that they have a chirping of between about 0.5 and about 1.0.
14. The energy generation system of claim 11 , wherein the photonic crystal further comprises a seventh material having a seventh index of refraction that is different from at least one of the fifth index of refraction and the sixth index of refraction.
15. The energy generation system of claim 11 , wherein the photonic crystal comprises a seventh material having a seventh index of refraction that is different from both the fifth index of refraction and the sixth index of refraction.
16. The energy generation system of claim 15 , wherein the indices of refraction of the fifth, sixth, and seventh materials increase substantially exponentially from the material closest to the emission surface to the material farthest from the emission surface.
17. The energy generation system of claim 1 , wherein the photonic crystal comprises 2-dimensional periodicity.
18. The energy generation system of claim 17 , wherein the photonic crystal comprises a material in which a 2-dimensional pattern of openings are formed.
19. The energy generation system of claim 18 , wherein the openings have an aspect ratio of at least about 0.75:1.
20. The energy generation system of claim 18 , wherein the openings have an aspect ratio of between about 0.75:1 and about 10:1.
21. The energy generation system of claim 18 , wherein the openings comprise substantially cylindrical holes with ratios of depth to diameter of between about 0.75:1 and about 10:1.
22. The energy generation system of claim 1 , wherein the indices of refraction of the first, second, third, and fourth materials increase substantially exponentially along a path directed toward the emitter.
23. The energy generation system of claim 1 , wherein:
the filter comprises m total materials,
the filter material closest to the emitter has an index of refraction of n, and
an i th filter material, wherein i is an integer within a range of 0 to m and refers to the index of the materials in order from the material closest to the emitter to the material farthest from the emitter, has an index of refraction of about n^((m+1−i)/(m+1)).
24. The energy generation system of claim 1 , wherein the filter is constructed and arranged to reflect at least about 90% of electromagnetic radiation with a wavelength of between about 4.5 microns and about 7 microns.