New Type of Solar Structure Cools Buildings in Full Sunlight

[OKIsItJustMe]

6. It actually does more than that (in theory at least)

It reflects energy, and it also radiates energy.

Imagine a typical roof. It radiates heat, but it is absorbing sunlight, which means it generates heat as well. In full sunlight, it may easily generate more heat than it radiates (as anyone who has walked on a hot roof can tell you.)

So, let’s put a mirror on the roof. Now, it absorbs less sunlight, yet it still radiates heat.

In this case, they’re proposing optimizing both.

http://pubs.acs.org/doi/abs/10.1021/nl4004283

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In conclusion, we have numerically demonstrated for the first time a macroscopically planar structure capable of achieving radiative cooling in the daytime, even in the presence of realistic nonradiative heat transfer. In contrast to previous approaches to radiative cooling, we have used concepts from nanophotonics to design a dielectric reflector, which minimizes solar absorption, and a two-layer 2D photonic crystal of SiC and quartz, which selectively emits thermal radiation in the atmospheric transparency window. These two functionalities are combined into a single device that achieves the ultrabroadband performance needed to radiatively cool in the daytime. Currently, applications of thermal light sources are being explored mainly in the field of thermophotovoltaic power conversion but the demands of high-operating temperatures inevitably leads to nano- and microscopic material degradation, presenting a formidable challenge. In our work, we have presented another application of thermal light emission from microstructured materials, radiative cooling. In contrast to previous applications, using thermal light emission to cool structures does not require high temperature operation. We thus anticipate that radiative cooling will motivate continued interest and research in thermal nanophotonics and metamaterials.