Enhanced radiative energy tunneling with dielectric optical resonators and its usage in harvesting thermal energy inside a solid

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

Far-field thermal radiation is a type of broadband energy transfer among surfaces. When the separation distances among surfaces are less than tens to hundreds of nanometers, the radiation spectrum can be confined to a very narrow band, where the radiation intensity can be orders of magnitude higher than the blackbody limit. This microscale phenomenon is called near-field thermal radiation. The high-intensity energy transport in near-field radiation can be valuable in constructing high efficiency, high power density thermal engines for thermal to electric energy conversion such as thermophotovoltaics, thereby reducing the fuel consumption in transportation and electricity generation. However, implementing near-field thermal radiation can be challenging in practical applications because the required tens to hundreds of nanometer separation distance between hot and cold surfaces are difficult to maintain. This study will extend the useful range of near-field thermal radiation to micron-levels by amplifying the non-radiative thermal electric field and the resulting tunneling distance between hot and cold surfaces. The proposed project is built upon the investigator's expertise in near-field energy transport and the design/fabrication of nano-optical resonators that can amplify the thermal electric field with ultra-thin metasurface structures. The project tasks are to first integrate dielectric optical antenna theory with Wiener Chaotic expansion to understand resonance, amplification, and radiative energy tunneling between two lossy solids across a vacuum gap with appropriate high-quality factors dielectric optical resonators (DORs) under different temperatures. This will allow for the determination of the tunneling frequencies, efficiencies, and distances between two solids as functions of DOR designs. Theoretical thermal efficiencies of energy harvest systems using the enhanced long-distance tunneled radiative heat transfer scheme with a consideration of parasitic heat conduction and quantum efficiencies of photovoltaic devices will then be studied as a function of radiation intensities and output voltages. The knowledge gained will be valuable in constructing high-efficiency, high-power density, lightweight thermal engines using currently available engineering techniques, which can have the potential to reduce greenhouse gas emissions and the associated environmental impacts and increase the nation's energy security. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.