NIR-Selective Glazing & Light-to-Heat

Solar NIR occupies about 50% solar energy in most weather situations, which gives a spectrally selective glazing design opportunity for solar infrared modulation that operates without the need to compensate for visible transmittance. Incorporating nanoscale plasmonic photothermal effects into the design of complex building fenestrations, this research conducted a comprehensive analysis to better understand the light-to-heat conversion of such nanoscale plasmonic photothermal effects and their associated conductive, convective, and radiative heat exchanges between windowpane surfaces and the surrounding indoor and outdoor environments. This study developed a numerical model to incorporate the unique surface plasmon-diced light-to-heat conversion that creates strong localized heating effects with a much smaller fraction resulting in the heating of the substrate, into a whole building energy analysis.

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Photothermal experiment under solar simulator
conducted in our collaborative research group - Dr. Shi at Univ. of Cincinnati

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A hypothesized interfacial insulation (Rh) between the nanoscale plasmonic NPs coating and the glazing was incorporated into the conventional heat transfer model. In the stable boundary situations and same ambient temperature conditions, the absorbed solar energy equals the sum of the heat dissipated from the NP-coated surface and the conductive heat transfer away from the NP-coated layer to the glass through the interfacial layer.  

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Measured vs. Calculated temp. rise via traditional models         Mathematical expression of heat dissipation

Findings

The results show the photothermal coating can be used as new energy-efficient retrofit technology for single-pane windows, with an energy saving potential 16.2–20.8%, which appears very close to the thermal performance of the double-pane windows in winter seasons under typical solar radiation. 

Model validation by the experimental data

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SHGC data distribution                                                                Annual heating loads and associated saving percentages