Abstract
Theoretical studies have demonstrated that the energy transfer between a hot an cold body at close spacing (on the order of the radiation wavelength) can greatly exceed the limit for black body radiation (i.e. Power=σT4). This effect, due to the coupling of evanescent fields, presents an attractive option for thermo-photovoltaic (TPV) applications (assuming the considerable technical challenges can be overcome). The magnitude of the enhanced energy transfer depends on the optical properties of the hot and cold bodies as characterized by the dielectric functions of the respective materials. The present study considers five different situations as specified by the materials choices for the hot/cold sides: metal/metal, metal/insulator, metal/semiconductor, insulator/insulator, and semiconductor/semiconductor. For each situation, the dielectric functions are specified by typical models. An increase in energy transfer (relative to the black body law) is found for all situations considered, for separations less...
Highlights
Enhanced energy transfer at close spacingThe enhancement at close spacing can be described within the framework of statistical mechanics and classical electromagnetism
This report was prepared as an account of work sponsortd by au agency of the United States Government Neither the United States Government nor any agency thereof, nor any of their employe# maices any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, mmpieteness, or usefulness of any information, apparatus, produn, or process disclosed or rrprrsents that its use would not infringe privately owned rightt
Theoretical studies have demonstrated that the energy transfer between a hot an cold body at close spacing can greatly exceed the limit for black body radiation @.e.Power = oT4).[1,2,3,4,5,6,7,8,9]
Summary
The enhancement at close spacing can be described within the framework of statistical mechanics and classical electromagnetism. There is a component of the electromagnetic field near the surface of a radiating body which has a fluctuating time dependence, but does not propagate. This so-called “evanescent” field decays exponentially with a characteristicdistance on the order of the wavelength. The evanescent fields produced in one body interact directly with the electric charges in the other body; and, act as sources of electromagnetic waves. These new waves are transmitted or absorbed depending on the properties of the second body. The radiation “tunnels” across the gap and represents a net energy transfer
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