Recent advances in thermophotovoltaic (TPV) power generation have produced notable gains in efficiency, particularly at very high emitter temperatures. However, there remains substantial room for improving TPV conversion of waste, solar, and nuclear heat streams at temperatures below 1,100°C. Here, we demonstrate the concept of transmissive spectral control that enables efficient recuperation of below-bandgap photons by allowing them to transmit through the cell to be absorbed by a secondary emitter. We fabricate a semitransparent TPV cell consisting of a thin InGaAs–InP heterojunction membrane supported by an infrared-transparent heat-conducting substrate. The device absorbs less than 1% of below-bandgap radiation, resulting in a TPV efficiency of 32.5% at an emitter temperature of 1,036°C. To our knowledge, this represents an 8% absolute improvement (~33% relative) in efficiency relative to the best TPV devices at such low temperatures. By enabling near-zero photon loss, the semitransparent architecture facilitates high TPV efficiencies over a wide range of applications.
more »
« less
A Review of Advances in Thermophotovoltaics for Power Generation and Waste Heat Harvesting
ABSTRACT The vast majority of power generation in the United States today is produced through the same processes as it was in the late-1800s: heat is applied to water to generate steam, which turns a turbine, which turns a generator, generating electrical power. Researchers today are developing solid-state power generation processes that are more befitting the 21 st -century. Thermophotovoltaic (TPV) cells directly convert radiated thermal energy into electrical power, through a process similar to how traditional photovoltaics work. These TPV generators, however, include additional system components that solar cells do not incorporate. These components, selective-emitters and filters, shape the way the radiated heat is transferred into the TPV cell for conversion and are critical for its efficiency. Here, we present a review of work performed to improve the components in these systems. These improvements will help enable TPV generators to be used with nearly any thermal source for both primary power generation and waste heat harvesting.
more »
« less
- Award ID(s):
- 1806311
- PAR ID:
- 10152803
- Date Published:
- Journal Name:
- MRS Advances
- Volume:
- 4
- Issue:
- 41-42
- ISSN:
- 2059-8521
- Page Range / eLocation ID:
- 2271 to 2282
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Thermoelectric generators are being used as a successful power sources for space applications since 1960's in radioisotope-thermoelectric generators (RTGs) to supply power to space systems in deep space. RTG’s are capable of directly converting heat energy to uninterrupted electric power with no moving parts involved. The ability of thermoelectric materials to convert heat energy to electrical energy is defined by a dimensionless value known as the thermoelectric figure of merit (ZT) 1. This value quantifies the maximum thermoelectric efficiency of a thermoelectric generator (TEG) and is calculated by ZT= S2σT/κ, where S, σ, T, and κ represent Seebeck coefficient, electrical conductivity, temperature, and thermal conductivity, respectively. Among all of the thermoelectric materials, Bi2Te3 and its alloys have been reported to have high ZT values for low temperature energy harvesting and are highly suitable for powering wearables and self-powering sensors2, 3.more » « less
-
Thermophotovoltaic (TPV) cells generate electricity by converting infrared radiation emitted by a hot thermal source. Air-bridge TPVs have demonstrated enhanced power conversion efficiencies by recuperating a large amount of power carried by below-bandgap (out-of-band) photons. Here, we demonstrate single-junction InGaAs(P) air-bridge TPVs that exhibit up to 44% efficiency under 1435°C blackbody illumination. The air-bridge design leads to near-unity reflectance (97-99%) of out-of-band photons for ternary and quaternary TPVs whose bandgaps range from 0.74 to 1.1 eV. These results suggest the applicability of the air-bridge cells to a range of semiconductor systems suitable for electricity generation from thermal sources found in both consumer and industrial applications, including thermal batteries.more » « less
-
Thermoelectric materials enable the direct conversion of thermal to electrical energy. One application of this is ambient heat energy harvesting where relatively stable temperature gradients existing between the inside and outside of a building could be utilized to produce electricity. Buildings can thus change from energy consumers to energy generators. This could ultimately help reduce the surface temperatures and energy consumption of buildings, especially in urban areas. In this paper, research work carried out on developing and characterizing a cement-based thermoelectric material is presented. Cement-based samples are doped with different metal oxides (Bi2O3 and Fe2O3) to enhance their thermoelectric properties, which are defined through their Seebeck coefficient, electrical conductivity and thermal conductivity. The study also discusses the positive impact of moisture content on the electrical conductivitymore » « less
-
Optical filters with narrow transmission band above the bandgap of thermophotovoltaic (TPV) cells are not restrained by the rigorous thermal reliability as needed for the emitters. In this work, a novel metasurface filter made of an aluminum nanopillar (AlNP) array on a quartz substrate is proposed to achieve spectrally selective transmission above the bandgap of the TPV cell. Optical simulations using Finite-difference time-domain were carefully performed to determine the appropriate AlNP period, diameter, and height such that the resulting nanopillar array will show narrowband transmission at a wavelength of 1.9 μm, which is close to the bandgap of a commercial gallium antimonide (GaSb) TPV cell. The narrow-band transmission enhancement can be attributed to the magnetic polariton (MP) resonance between neighboring Al nanopillars. The MP mechanism is further confirmed by an inductor-capacitor circuit model and the effects of the nanopillars period, diameter, height, as well as incidence angles were discussed. Moreover, open-circuit voltage, short-circuit current density, output electric power, and conversion efficiency were evaluated for the GaSb TPV cell coupled with the AlNP metasurface filter structure with enhanced TPV performance.more » « less
An official website of the United States government

