A polydimethylsiloxane-coated metal structure for all-day radiative cooling

Abstract

Radiative cooling is a passive cooling strategy with zero consumption of electricity that can be used to radiate heat from buildings to reduce air-conditioning requirements. Although this technology can work well during optimal atmospheric conditions at night, it is essential to achieve efficient cooling during the daytime when peak cooling demand actually occurs. Here we report an inexpensive planar polydimethylsiloxane (PDMS)/metal thermal emitter thin film structure, which was fabricated using a fast solution coating process that is scalable for large-area manufacturing. By performing tests under different environmental conditions, temperature reductions of 9.5 °C and 11.0 °C were demonstrated in the laboratory and an outside environment, respectively, with an average cooling power of ~120 W m2 for the thin film thermal emitter. In addition, a spectral-selective structure was designed and implemented to suppress the solar input and control the divergence of the thermal emission beam. This enhanced the directionality of the thermal emissions, so the emitter’s cooling performance was less dependent on the surrounding environment. Outside experiments were performed in Buffalo, New York, realizing continuous all-day cooling of ~2–9 °C on a typical clear sunny day at Northern United States latitudes. This practical strategy that cools without electricity input could have a significant impact on global energy consumption.

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Fig. 1: PDMS/metal thin film thermal emitter.
Fig. 2: Indoor radiative cooling characterization using liquid nitrogen as the cold source.
Fig. 3: Outdoor radiative cooling test over different emission angles.
Fig. 4: Beaming effect and solar shelter for daytime cooling.
Fig. 5: All-day continuous radiative cooling.

Data availability

The data that support the findings of this study are available from the corresponding authors on request.

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Acknowledgements

This work was partially supported by the National Science Foundation (grant nos. IIP-1745846, ECCS-1507312, CBET-1445934 and ECCS-1425648).

Author information

Q.G., B.O. and Z.Y conceived the idea and supervised the project. L.Z., H.S., J.L., E.S. and T.N. executed the experiments. All authors contributed to the analysis of the experimental results and modelling. L.Z., H.S., Z.Y., B.O. and Q.G. wrote the manuscript. All authors reviewed the manuscript.

Correspondence to Zongfu Yu or Boon Ooi or Qiaoqiang Gan.

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Competing interests

Q.G. and Z.Y. have founded a company, Sunny Clean Water LLC, seeking to commercialize the results reported in this paper.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–9, Notes 1–6 and Refs. 1–3

Supplementary Video 1

Short clip showing application of PDMS coating to metal.

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