# US 10,374,524 B2 · System for converting electromagnetic radiation to electrical energy using metamaterials

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- Number: US 10,374,524 B2
- Document ID: US10374524B2
- Status: Granted
- Kind: B2
- Application number: 14/745,299
- Filed: 2015-06-19
- Published: 2015-12-24
- Granted: 2019-08-06
- Earliest claimed: 2014-06-20
- Assignees: Redwave Energy, Inc.
- Applicants: Patrick K Brady; Dale K. Kotter; Wounjhang Park
- Inventors: Patrick K Brady; Dale K. Kotter; Wounjhang Park
- Web page: https://patentgrep.com/patent/US10374524B2

## CPC

- H02N 11/002: {Generators}
- G02B 1/002: {made of materials engineered to provide properties not available in nature, e.g. metamaterials}
- H01Q 1/248: {provided with an AC/DC converting device, e.g. rectennas}
- H10F 10/00: Individual photovoltaic cells, e.g. solar cells (electrolytic light-sensitive devices, e.g. dye-sensitised solar cells, H01G9/20)
- H10F 77/12: Active materials
- Y02E 10/52: PV systems with concentrators
- H02N: ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72)
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

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.

## Claims

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 2)

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.

### Claim 4 (depends on 1)

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.

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 1)

The system recited in claim 1, further comprising a cold source to act as a cold sink to cool the rectenna.

### Claim 7 (depends on 1)

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.

### Claim 8 (depends on 7)

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.

### Claim 9 (depends on 8)

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.

### Claim 10 (depends on 2)

The system recited in claim 2, wherein the hole dimensions and spacing form a periodic pattern on the surface of the metamaterial.

### Claim 11 (depends on 1)

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.

### Claim 12 (depends on 11)

The system recited in claim 11, wherein deep space is used as a cold sink for the rectenna.

### Claim 13 (depends on 11)

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.

### Claim 14 (depends on 11)

The system recited in claim 11, wherein the post is has a height greater than one quarter of the wavelength of the desired frequency.

### Claim 15 (depends on 11)

The system recited in claim 11, further comprising a thermally insulating and radiation transparent material surrounding each post.

### Claim 16 (depends on 11)

The system recited in claim 11, further comprising an environmental overcoat to reflect away out-of-band energy.

### Claim 17 (depends on 11)

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.