System for converting electromagnetic radiation to electrical energy using metamaterials
Spectral tuning of heat source to emit radiation at a desired frequency or frequency band is accomplished using metamaterials. The metamaterials include a structured geometry having holes with dimensions and spacing chosen such that the resulting surface will emit radiation in the desired spectrum. A collector can be made of a similar metamaterial or antenna array to detect the emitted radiation and transfer it to a converter device that converts the detected radiation to electricity. Embodiments also provide efficient coupling to the converter device for energy harvesting. Cooling of the converter devices can be accomplished using a cooling sink or deep space.
1. A system to convert heat into electricity, comprising:
a metamaterial having a surface that is tuned to generate an enhanced electric field at a desired frequency; and
a rectenna placed over the enhanced electric field, at a distance to interact with the generated electric field, and to produce electricity from the generated electric field.
2. The system of claim 1 , wherein the surface of the metamaterial comprises a plurality of holes with dimensions and spacing to cause the surface to generate the enhanced electric field at the desired frequency, and wherein a rectenna is placed over each hole.
3. The system recited in claim 2 , wherein each rectenna is placed in the near field over the holes at less than 0.5 wavelengths of the desired frequency.
4. The system recited in claim 1 , wherein the rectenna comprises:
an antenna tuned to the desired frequency to interact with the generated electric field to generate an electric current in an antenna element; and
a transfer structure to convert the electric current into direct current.
5. The system recited in claim 1 , further comprising at least one lead to carry the direct current to power another device or to an electricity storage device.
6. The system recited in claim 1 , further comprising a cold source to act as a cold sink to cool the rectenna.
7. The system recited in claim 1 , further comprising a thermally insulating and radiation transparent material placed between the surface of the metamaterial and the rectenna.
8. The system recited in claim 7 , wherein the rectenna comprises an antenna element, further comprising a thermally conductive material to couple the antenna element to a cold source.
9. The system recited in claim 8 , further comprising a thermally insulating material on either side of the thermally conductive material to prevent heat loss from a heat source.
10. The system recited in claim 2 , wherein the hole dimensions and spacing form a periodic pattern on the surface of the metamaterial.
11. The system of claim 1 , wherein the surface of the metamaterial comprises a plurality of posts with dimensions and spacing to cause the surface to generate the enhanced electric field at the desired frequency.
12. The system recited in claim 11 , wherein deep space is used as a cold sink for the rectenna.
13. The system recited in claim 11 , wherein the rectenna is placed in the near-field over each post at less than 0.5 wavelengths of the desired frequency.
14. The system recited in claim 11 , wherein the post is has a height greater than one quarter of the wavelength of the desired frequency.
15. The system recited in claim 11 , further comprising a thermally insulating and radiation transparent material surrounding each post.
16. The system recited in claim 11 , further comprising an environmental overcoat to reflect away out-of-band energy.
17. The system recited in claim 11 , wherein the desired frequency has a wavelength in the bands of one of 3 μm to 5 μm and 8 μm to 12 μm.