Concepedia

Radiative Heat Pumping from the Earth Using Surface Phonon Resonant Nanoparticles

Nano Letters · 2010 · 463 citations · 10 references

TL;DR

Nanoparticles with narrow absorption bands inside the atmosphere’s 7.9–13 µm transparent window can radiatively cool below ambient, and dopants in infrared‑transmitting polymers or coatings on low‑emittance substrates reduce heating from the rest of the Planck spectrum; crystalline SiC nanoparticles exhibit a surface phonon resonance from 10.5 to 13 µm, while resonant SiO₂ nanoparticles absorb from 8 to 10 µm, making SiC useful in space dust studies and SiO₂ complementary for atmospheric ozone emissions. The authors present optical properties and analyze subambient cooling performance for doped polyethylene on aluminum. A mixture of SiC and SiO₂ nanoparticles achieves high‑performance, low‑cost cooling in a practical rig.

Abstract

Nanoparticles that have narrow absorption bands that lie entirely within the atmosphere's transparent window from 7.9 to 13 μm can be used to radiatively cool to temperatures that are well below ambient. Heating from incoming atmospheric radiation in the remainder of the Planck radiation spectrum, where the atmosphere is nearly "black", is reduced if the particles are dopants in infrared transmitting polymers, or in transmitting coatings on low emittance substrates. Crystalline SiC nanoparticles stand out with a surface phonon resonance from 10.5 to 13 μm clear of the atmospheric ozone band. Resonant SiO2 nanoparticles are complementary, absorbing from 8 to 10 μm, which includes atmospheric ozone emissions. Their spectral location has made SiC nanoparticles in space dust a feature in ground-based IR astronomy. Optical properties are presented and subambient cooling performance analyzed for doped polyethylene on aluminum. A mixture of SiC and SiO2 nanoparticles yields high performance cooling at low cost within a practical cooling rig.