High temperature selective emitters via critical coupling of weak absorbers

Patent metadata

Field	Value
Publication number	US-2019288636-A1
Application number	US-201815923909-A
Country	US
Kind code	A1
Filing date	Mar 16, 2018
Priority date	Mar 16, 2018
Publication date	Sep 19, 2019
Grant date	—

Abstract

Tailoring the emission spectra of a solar thermophotovoltaic emitter away from that of a blackbody, thereby minimizing transmission and thermalization loss in the energy receiver, is a viable approach to circumventing the Shockley-Queisser limit to single junction solar energy conversion. Embodiments allow for radically tuned selective thermal emission that leverages the interplay between two resonant phenomena in a simple planar structure—absorption in weakly-absorbing thin films and reflection in multi-layer dielectric stacks. A virtual screening approach is employed based on Pareto optimality to identify a small number of promising structures for a selective thermal emitter from a search space of millions, several of which approach the ideal values of a step-function selective thermal emitter

First claim

What is claimed is:

1 . A method of identifying thermophotovoltaic structures comprising:
determining parameters P i in a parameter space P for candidate emitter structures; for each parameter P i , solve transfer matrix equations for the emissivity spectrum of each candidate emitter structure; for each parameter P i compute thermal emission spectrum of each candidate emitter structure; computing figures of merit for each candidate emitter structure; identifying whether a parameter P i is Pareto optimal and, if so, add to a Pareto Front; and displaying a Pareto front for the parameter space P for the candidate emitter structures.

2 . The method of claim 1 , wherein the figures of merit are spectral conversion efficiency (η s ) and useful power(P).

3 . The method of claim 2 , wherein prior to identifying if a parameter is Pareto optimal, determining absorption spectrum for an alloy layer of the candidate emitter structure.

4 . The method of claim 3 , wherein prior to identifying if a parameter is Pareto optimal, determining stored energy spectrum of a Bragg reflector of the candidate emitter structure.

5 . The method of claim 4 , wherein the parameters are selected from the group consisting of Bragg reflector dielectric layer thicknesses, Bragg reflector refractive indices, Bragg reflector number of such pair layers, Λ BR , and the alloy layer composition, operating temperature, bandgap of an associated photovoltaic.

6 . The method of claim 4 , wherein the candidate emitter comprises a refractory metal, the Bragg reflector and the alloy layer.

7 . The method of claim 6 , wherein the refractory metal is tungsten and the alloy layer is W—Al 2 O 3 alloy.

8 . A computer implemented system for identifying photonic crystals comprising
a processor; and a tangible computer-readable medium operatively connected to the processor and including computer code configured to:
determine emissivity for candidate emitter structures;
select an absorber to pair with the candidate structures;
determine spectral conversion efficiency (η s ) and useful power(P) as figures of merit;
perform a Pareto optimization using the figures of merit; and
determine the degree of critical coupling of at least a portion of the structures and the selected absorber.

9 . The computer implemented system of claim 8 , further comprise computer code configured to:
select an operating temperature for the photovoltaic.

10 . A photonic system comprising:
an absorber in thermal contact with an emitter; the emitter paired with a photovoltaic cell, the emitter configured to have a controllable temperature, the emitter having a first substrate, a Bragg reflector, and an optically tunable layer where the optically tunable layer and the Bragg reflector are critically coupled; further wherein the emitter generates useful power (P) by

P
=

∫
0

λ
bg



λ

λ
bg



ρ


(

λ
,
T

)



ϵ


(
λ
)


d



λ

where p(λ, T) is the blackbody spectral density and ϵ(λ) is the emissivity spectrum of the emitter
and further wherein pair emitter and photovoltaic cell have a conversion efficiency (η s ) of

η
s

=

P

P
inc

=

∫
0

λ
bg



λ

λ
bg



ρ


(

λ
,
T

)



ϵ


(
λ
)


d



λ

∫
0
∞



ρ


(

λ
,
T

)



ϵ


(
λ
)


d



λ

.

11 . The photonic system of claim 9 wherein neither η s or P can be increased without decreasing the other.

12 . The photonic system of claim 10 wherein the Bragg reflector consists of alternating layers of SiO 2 and TiO 2 .

13

Assignees

• Uchicago Argonne Llc

Inventors

• Martinson Alex B
• Jeon Nari
• Gray Stephen K
• Foley Iv Jonathan J

Classifications

• G06F30/00

  Computer-aided design [CAD] · CPC title

• G06F30/20

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title

• G06F30/367

  Design verification, e.g. using simulation, simulation program with integrated circuit emphasis [SPICE], direct methods or relaxation methods · CPC title

• G06F2119/06

  Power analysis or power optimisation · CPC title

• H02S10/30 Primary

  Thermophotovoltaic systems (photovoltaic cells specially adapted for conversion or sensing of infrared [IR] radiation H10F10/00; thermoelectric devices H10N10/00) · CPC title